Synthesis and Characterization of Rare Earth Composite Oxides Luminescent Nanofibers by Electrospinning Technique
Nanofibers have attracted much attention of the people due to their superior optical, acoustic, electrical, magnetic, thermal and mechanical properties, they have become one of the popular subject in the field of nanoscience and nanotechnology. Rare earth oxide luminescent materials have been used in many high-tech fields. Preparation, properties and applications of these compounds have become an important research subject.In this dissertation, electrospinning technique was successfully used to fabricate PVP/[Y(NO3)3+Eu(NO3)3], PVA/ [Gd(NO3)3+Eu(NO3)3] and PVP/ [Y(NO3)3+Tb(NO3)3] composite nanofibers. Y2O3:Eu3+, Gd2O3:Eu3+ and Y2O3:Tb3+ crystalline rare earth oxides luminescent nanofibers were obtained by calcination of the relative composite nanofibers.
The technique offered a new route to preparation of Ring neodymium magnet one-dimensional nanoscaled luminescent materials.The morphology of fibers was discussed by adjusting all the important parameters such as concentration of polymer, voltage, distance between tip and collector, the mass of metallic salts added to the sol. The optimum preparation technological parameters of the polymer/inorganic salts composite fibers were acquired. The samples were characterized by scanning electron microscope(SEM), X-ray diffraction(XRD), thermal analysis(TG-DTA), Fourier transform infrared spectrometer(FTIR) and fluorescence spectrophotometer. All the results http://www.chinamagnets.biz/ show that the prepared polymer/inorganic salts composite fibers and Y2O3:Eu3+, Gd2O3:Eu3+ and Y2O3:Tb3+ luminescent nanofibers were good one-dimensional nanofibers. The diameters of the luminescent nanofibers were ca. 50nm, and these luminescent nanofibers possessed excellent emission spectra. Some new meaningful results have been achieved, and laid a foundation for further study of luminescent nanofibers.
2012年5月31日星期四
Preparation and Characterization of Fluorphosphate Glasses Doped with Ho～(3+)/Tm～(3+)/Yb～(3+) Ions
Preparation and Characterization of Fluorphosphate Glasses Doped with Ho～(3+)/Tm～(3+)/Yb～(3+) Ions
In this thesis, fluoride, fluorphosphate and phosphate glass doped with rare earth ions were studied in order to gain 2 micrometer emission laser amplified material for the high-power solid-state laser. The rare earth ions and their concentrations were also researched.The orthogonal design was introduced in order to contrive the basic glass compositions. The host glass, the rare earth magnets maximal rare-earth doped concentration, the best doped rate and the laser activities of the Ho3+/Tm3+ doped fluorphosphate glass has been researched and discussed systematically. But the Ho3+/Tm3+doped laser system is less used ,in the result of the 790nm pumping source,
which wave-length does not belong to the commercial LD laser. In order to increase the laser amplified materials practicability, Ho3+/Tm3+/Yb3+ doped system had been introduced, for using the 980nm commercial LD laser as the pumping source in this way.At present, few research on the microcrystalline treatment of laser glass has been carried out. The advantages of the laser crystal and glass can be combined with together in this way. Furthermore the laser http://www.chinamagnets.biz/ amplified material, gained by this method, has the higher pumping efficiency, lower phonon coupled level and better machine-shaping capability. Experiment results indicated that the best microcrystalline treatment conditions were found to be 520℃ for 6h and the workable cooling process was annealed to 200℃ at the rate 0.35℃/min and then lowed to the room temperature naturally.
In this thesis, fluoride, fluorphosphate and phosphate glass doped with rare earth ions were studied in order to gain 2 micrometer emission laser amplified material for the high-power solid-state laser. The rare earth ions and their concentrations were also researched.The orthogonal design was introduced in order to contrive the basic glass compositions. The host glass, the rare earth magnets maximal rare-earth doped concentration, the best doped rate and the laser activities of the Ho3+/Tm3+ doped fluorphosphate glass has been researched and discussed systematically. But the Ho3+/Tm3+doped laser system is less used ,in the result of the 790nm pumping source,
which wave-length does not belong to the commercial LD laser. In order to increase the laser amplified materials practicability, Ho3+/Tm3+/Yb3+ doped system had been introduced, for using the 980nm commercial LD laser as the pumping source in this way.At present, few research on the microcrystalline treatment of laser glass has been carried out. The advantages of the laser crystal and glass can be combined with together in this way. Furthermore the laser http://www.chinamagnets.biz/ amplified material, gained by this method, has the higher pumping efficiency, lower phonon coupled level and better machine-shaping capability. Experiment results indicated that the best microcrystalline treatment conditions were found to be 520℃ for 6h and the workable cooling process was annealed to 200℃ at the rate 0.35℃/min and then lowed to the room temperature naturally.
Energy Transmission and Charge Transfer between Rare Earth Ions of Nanometer Fluorides
Energy Transmission and Charge Transfer between Rare Earth Ions of Nanometer Fluorides
Nanoparticles of doped and co-doped KMgF3 with rare earth ions were prepared from the quaternary microemulsions of CTAB, n-butanol, http://www.chinamagnets.biz/ n-octane and water based on the pseudo-ternary phase diagrams.The X-ray diffraction (XRD) patterns were indexed to a pure KMgF3 cubic phase. The fluorescent spectra were studied and compared with their powder crystal. Energy transmission and charge transfer between rare earth ions of nanometer fluorides were discussed.The emission of prepared KMgF3: Eu nanoparticles peaked at 360 nm. The excitation band strong magnets was observed at 250 nm, blue shifted separately about 62 nm and 80 nm comparing with KMgF3: Eu multicrystal powders and single crystal. The maximum peak of KMgF3: Gd nanoparticles located at 311nm attributed to the transition of 6P7/2→8S7/2We can conclude there is charge transfer process of Ce3+→Yb3+ in KMgF3: Ce, Yb nanoparticles. The energy transmission Ce3+→Tb3+, Ce3+→Gd3+ and Ce3+→Eu2+exist in KMgF3: Ce, Tb and KMgF3: Ce, Gd and KMgF3: Ce, Eu nanoparticles.
Nanoparticles of doped and co-doped KMgF3 with rare earth ions were prepared from the quaternary microemulsions of CTAB, n-butanol, http://www.chinamagnets.biz/ n-octane and water based on the pseudo-ternary phase diagrams.The X-ray diffraction (XRD) patterns were indexed to a pure KMgF3 cubic phase. The fluorescent spectra were studied and compared with their powder crystal. Energy transmission and charge transfer between rare earth ions of nanometer fluorides were discussed.The emission of prepared KMgF3: Eu nanoparticles peaked at 360 nm. The excitation band strong magnets was observed at 250 nm, blue shifted separately about 62 nm and 80 nm comparing with KMgF3: Eu multicrystal powders and single crystal. The maximum peak of KMgF3: Gd nanoparticles located at 311nm attributed to the transition of 6P7/2→8S7/2We can conclude there is charge transfer process of Ce3+→Yb3+ in KMgF3: Ce, Yb nanoparticles. The energy transmission Ce3+→Tb3+, Ce3+→Gd3+ and Ce3+→Eu2+exist in KMgF3: Ce, Tb and KMgF3: Ce, Gd and KMgF3: Ce, Eu nanoparticles.
Synthesis and Properties of the Fluorescent Complexes of Terbium Adulterated by Lanthanun and Gadolinium
Synthesis and Properties of the Fluorescent Complexes of Terbium Adulterated by Lanthanun and Gadolinium
Rare earth elements possess luminescent, electric and magnetic properties due to their particular electron structure, and can be used to manufacture many hi-tech materials, so they are called the resources of new materials. In this dissertation, a series of new green fluorescence complexes of teribium ion adulterated by cheap non- fluorescence lanthanum or gadolinium ions with the first ligands of the cheap and popular aromatic carboxylic acid (m-chlorobenzoic acid, p-methylbenzoic acid, methoxybenzoic acid, p-hydroxylbenzoic acid, benzoic acid, salicylic acid, p-aminobenzoic acid, sulfosalicylic acid) and 1,10-phenanthroline, and the second ligands of oleic acid and Ball Neodymium Magnets undecenoic acid have been synthesized under the best optimisation synthesis conditions. Their molecular compositions and structures were characterized by means of elemental analysis, EDTA titrimetric method, FT-IR and UV spectroscopies; their thermal properties were studied by thermal analysis instrument; their luminescent properties were investigated by means of fluorescence instrument. The main results are as follows:1. The thermal stability properties of the complexes of teribium adulterated by lanthanum or gadolinium have relationships with the structure of ligands and the adulteration content of lanthanum and gadolinium. The sequence of thermal stability of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium with the aromatic carboxylic acid and undecenoic acid is Tb0.5Y0.5(PABA)2(UA)·3H2O>Tb0.5Y0.5(BA)2(UA)·3H2O > Tb0.5Y0.5(MCBA)2(UA)·3H2O >
Tb0.5Y0.5(PHBA)2(U- A)·3H2O > Tb0.5Y0.5(MBA)2(UA)·3H2O > Tb0.5Y0.5(SA)2(UA)·3H2O > Tb0.5Y0.5(Ph- en)(UA)3·H2O>Tb0.5Y0.5(SSA)(UA)·2H2O. The sequence of thermal stability of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium with the aromatic carboxylic acid and oleic acid is Tb0.5Y0.5(SA)2(OA)·3H2O >Tb0.5Y0.5(PMBA)2(OA)·3H2O > Tb0.5Y0.5(Phen)(UA)3·H2O > Tb0.5Y0.5(PABA)2(O- A)·3H2O > Tb0.5Y0.5(MCBA)2(OA)·3H2O > Tb0.5Y0.5(BA)2(OA)·3H2O > Tb0.5Y0.5(SS- A)(OA)·2H2O>Tb0.5Y0.5(MBA)2(UA)·3H2O.2. The adulteration of the non-fluorescence lanthanum or gadolinium ions can enhance the fluorescence intensity of the complexes of terbium. The sensitization of the non-fluorescence lanthanum or gadolinium ions to the terbium ion increased in the first and then decreased with the increment of adulteration content of lanthanum or gadolinium ions. The basic order of the fluorescence intensity http://www.chinamagnets.biz/ of the complexes of terbium adulterated by lanthanum or gadolinium is that of 50% adulteration content >that of 75% adulteration content > that of 25% adulteration content > that of 100% adulteration content. The results indicate that the emission peaks of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium ions changes little compared with that of corresponding fluorescence complexes, which means that the addition of lanthanum or gadolinium ions does not affect the characteristic emission peaks of the rare earth, but affect their fluorescence intensity very much.3. The fluorescence intensity of the complexes of terbium adulterated by lanthanum or gadolinium has relationships with the structure of ligands and complexes. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkLa1-k(X)2(UA)·3H2O was that of salicylic acid > m-chlorobenzoic acid > p-aminobenzoic acid > p-methylbenzoic acid > methoxybenzoic acid > sulfosalicylic acid > 1,10-phenanthroline > p-hydroxylbenzoic acid > benzoic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkGd1-k(X)2(UA)·3H2O was that of m-chlorobenzoic acid >
p-methylbenzoic acid > p-hydroxylbenzoic acid > salicylic acid > p-aminobenzoic acid > benzoic acid > methoxybenzoic acid > 1,10-phenanthroline > sulfosalicylic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkLa1-k(X)2(OA)·3H2O was that of salicylic acid > p-aminobenzoic acid > benzoic acid > methoxybenzoic acid > 1,10-phenanthroline > p-hydroxylbenzoic acid > sulfosalicylic acid > m-chlorobenzoic acid > p-methylbenzoic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkGd1-k(X)2(OA)·3H2O was that of p-aminobenzoic acid > salicylic acid > p-hydroxylbenzoic acid > 1,10-phenanthroline > benzoic acid > methoxybenzoic acid > m-chlorobenzoic acid > sulfosalicylic acid > p-methylbenzoic acid.4. The relationships between the luminescent intensity of the Ball Neodymium Magnets complexes of terbium adulterated by lanthanum or gadolinium and the adulteration content of lanthanum or gadolinium were studied by means of chart and table. The results indicate that the luminescent properties of title complexes are affected by the change of content of lanthanum or gadolinium ions, but there are not apparent change rule. The fluorescence enhancement factor R was introduced for the further investigation of the effect of lanthanum or gadolinium ions and content on the luminescent properties of title complexes. The adulteration of lanthanum or gadolinium ions cause the sensitization effect if R value is greater than 1, however, they cause quenching effect if R value is less than 1. The greater the value R deviate 1, the greater the effect of sensitization or quenching. The results indicate that the value R of the most of title complexes is greater than 1, and increases with the increment of the adulterationcontent of lanthanum or gadolinium ion, it demonstrates the sensitization of lanthanum or gadolinium ions to terbium ion increase with the increment of the adulteration content of lanthanum or gadolinium ions.
Rare earth elements possess luminescent, electric and magnetic properties due to their particular electron structure, and can be used to manufacture many hi-tech materials, so they are called the resources of new materials. In this dissertation, a series of new green fluorescence complexes of teribium ion adulterated by cheap non- fluorescence lanthanum or gadolinium ions with the first ligands of the cheap and popular aromatic carboxylic acid (m-chlorobenzoic acid, p-methylbenzoic acid, methoxybenzoic acid, p-hydroxylbenzoic acid, benzoic acid, salicylic acid, p-aminobenzoic acid, sulfosalicylic acid) and 1,10-phenanthroline, and the second ligands of oleic acid and Ball Neodymium Magnets undecenoic acid have been synthesized under the best optimisation synthesis conditions. Their molecular compositions and structures were characterized by means of elemental analysis, EDTA titrimetric method, FT-IR and UV spectroscopies; their thermal properties were studied by thermal analysis instrument; their luminescent properties were investigated by means of fluorescence instrument. The main results are as follows:1. The thermal stability properties of the complexes of teribium adulterated by lanthanum or gadolinium have relationships with the structure of ligands and the adulteration content of lanthanum and gadolinium. The sequence of thermal stability of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium with the aromatic carboxylic acid and undecenoic acid is Tb0.5Y0.5(PABA)2(UA)·3H2O>Tb0.5Y0.5(BA)2(UA)·3H2O > Tb0.5Y0.5(MCBA)2(UA)·3H2O >
Tb0.5Y0.5(PHBA)2(U- A)·3H2O > Tb0.5Y0.5(MBA)2(UA)·3H2O > Tb0.5Y0.5(SA)2(UA)·3H2O > Tb0.5Y0.5(Ph- en)(UA)3·H2O>Tb0.5Y0.5(SSA)(UA)·2H2O. The sequence of thermal stability of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium with the aromatic carboxylic acid and oleic acid is Tb0.5Y0.5(SA)2(OA)·3H2O >Tb0.5Y0.5(PMBA)2(OA)·3H2O > Tb0.5Y0.5(Phen)(UA)3·H2O > Tb0.5Y0.5(PABA)2(O- A)·3H2O > Tb0.5Y0.5(MCBA)2(OA)·3H2O > Tb0.5Y0.5(BA)2(OA)·3H2O > Tb0.5Y0.5(SS- A)(OA)·2H2O>Tb0.5Y0.5(MBA)2(UA)·3H2O.2. The adulteration of the non-fluorescence lanthanum or gadolinium ions can enhance the fluorescence intensity of the complexes of terbium. The sensitization of the non-fluorescence lanthanum or gadolinium ions to the terbium ion increased in the first and then decreased with the increment of adulteration content of lanthanum or gadolinium ions. The basic order of the fluorescence intensity http://www.chinamagnets.biz/ of the complexes of terbium adulterated by lanthanum or gadolinium is that of 50% adulteration content >that of 75% adulteration content > that of 25% adulteration content > that of 100% adulteration content. The results indicate that the emission peaks of the fluorescence complexes of terbium adulterated by lanthanum or gadolinium ions changes little compared with that of corresponding fluorescence complexes, which means that the addition of lanthanum or gadolinium ions does not affect the characteristic emission peaks of the rare earth, but affect their fluorescence intensity very much.3. The fluorescence intensity of the complexes of terbium adulterated by lanthanum or gadolinium has relationships with the structure of ligands and complexes. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkLa1-k(X)2(UA)·3H2O was that of salicylic acid > m-chlorobenzoic acid > p-aminobenzoic acid > p-methylbenzoic acid > methoxybenzoic acid > sulfosalicylic acid > 1,10-phenanthroline > p-hydroxylbenzoic acid > benzoic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkGd1-k(X)2(UA)·3H2O was that of m-chlorobenzoic acid >
p-methylbenzoic acid > p-hydroxylbenzoic acid > salicylic acid > p-aminobenzoic acid > benzoic acid > methoxybenzoic acid > 1,10-phenanthroline > sulfosalicylic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkLa1-k(X)2(OA)·3H2O was that of salicylic acid > p-aminobenzoic acid > benzoic acid > methoxybenzoic acid > 1,10-phenanthroline > p-hydroxylbenzoic acid > sulfosalicylic acid > m-chlorobenzoic acid > p-methylbenzoic acid. The ability order of the first ligand transferring light energy to the central terbium ion for the TbkGd1-k(X)2(OA)·3H2O was that of p-aminobenzoic acid > salicylic acid > p-hydroxylbenzoic acid > 1,10-phenanthroline > benzoic acid > methoxybenzoic acid > m-chlorobenzoic acid > sulfosalicylic acid > p-methylbenzoic acid.4. The relationships between the luminescent intensity of the Ball Neodymium Magnets complexes of terbium adulterated by lanthanum or gadolinium and the adulteration content of lanthanum or gadolinium were studied by means of chart and table. The results indicate that the luminescent properties of title complexes are affected by the change of content of lanthanum or gadolinium ions, but there are not apparent change rule. The fluorescence enhancement factor R was introduced for the further investigation of the effect of lanthanum or gadolinium ions and content on the luminescent properties of title complexes. The adulteration of lanthanum or gadolinium ions cause the sensitization effect if R value is greater than 1, however, they cause quenching effect if R value is less than 1. The greater the value R deviate 1, the greater the effect of sensitization or quenching. The results indicate that the value R of the most of title complexes is greater than 1, and increases with the increment of the adulterationcontent of lanthanum or gadolinium ion, it demonstrates the sensitization of lanthanum or gadolinium ions to terbium ion increase with the increment of the adulteration content of lanthanum or gadolinium ions.
The Study of the Tissue Feature of the Rare Earth Oxide Passivated Magnesium Powder and Its Ignition Proof and Desulphurization Performance
The Study of the Tissue Feature of the Rare Earth Oxide Passivated Magnesium Powder and Its Ignition Proof and Desulphurization Performance
In the present dissertation, a new type of rare earth oxide passivated magnesium powders as desuifurizer in molten iron was prepared by the combinative method of physics and chemistry(labeled as P-C sample). It was tested and analyzed compared to two Ball Neodymium Magnets present passivated magnesium powders(one was prepared by physical method, labeled as P sample; another one was prepared by chemical method, labeled as C sample).
The ignition-proof time, burning point and surface topography as well as the composition and structure of the surface layers of the three kinds of passivated magnesium powders were determined by means of TG/DTA,SEM,XRD,EDS line scan and AES.The mechanical properties of the surface layer of the passivated magnesium were studied by nanoindentation method and tensile test to simulate that of the new passivated magnesium powder. The feasibility of desulphurization by passivated magnesium powder in molten iron is expounded through calculation in http://www.chinamagnets.biz/ thermodynamics and dynamics in this article and the industrialized desulphurization trial of the rare earth oxide passivated magnesium was processed in the Bao-steel Co.Ltd. The main results after
In the present dissertation, a new type of rare earth oxide passivated magnesium powders as desuifurizer in molten iron was prepared by the combinative method of physics and chemistry(labeled as P-C sample). It was tested and analyzed compared to two Ball Neodymium Magnets present passivated magnesium powders(one was prepared by physical method, labeled as P sample; another one was prepared by chemical method, labeled as C sample).
The ignition-proof time, burning point and surface topography as well as the composition and structure of the surface layers of the three kinds of passivated magnesium powders were determined by means of TG/DTA,SEM,XRD,EDS line scan and AES.The mechanical properties of the surface layer of the passivated magnesium were studied by nanoindentation method and tensile test to simulate that of the new passivated magnesium powder. The feasibility of desulphurization by passivated magnesium powder in molten iron is expounded through calculation in http://www.chinamagnets.biz/ thermodynamics and dynamics in this article and the industrialized desulphurization trial of the rare earth oxide passivated magnesium was processed in the Bao-steel Co.Ltd. The main results after
2012年5月23日星期三
Up-conversion Fluorescence Properties of Rare Earth Doped Sample Based on Bi2O3 and SrF2 Compounds
Up-conversion Fluorescence Properties of Rare Earth Doped Sample Based on Bi2O3 and SrF2 Compounds
With the rapid development of techniques, rare-earth doped up-conversion materials have became valuable in the fields of display devices, lighting storage, optical materials, anti- faker industry, solid-state lasers and so on. At present, the most important task is to improve the efficiency of up-conversion. In this paper, a series of samples have been prepared by rare earth single-doped or co-doped to hosts according to the fundamental principles of up- conversion materials. The influences of the microstructures, the compositions of host materials and the rare earth concentrations on the up-conversion luminous efficiency were studied by metalography, XRD and SEM.
And the up-conversion spectrum was measured by R-500. The results are shown as follows:1. Er3+-doped Bi2O3 glasses have been fabricated through the high temperature solid-state reaction method. Under exitation of 980 nm LD, the glass emits strong red Magnetic lifter emission (4F9/2→4I15/2) and green emission (2H11/2→4I15/2, 4S3/2→4I15/2). But the red emission becomes too weak to be detected under excitation of 808 nm LD which shows that the electron population of 4F9/2 level is mainly achieved by energy transfer..2. The Judd–Oflet intensity parametersΩt (t =2,4,6), were found to beΩ2 =3.35×10-20cm2,Ω4 =1.34×10-20cm2 ,Ω6 =0.67×10-20cm2 calculated basing on the measured absorption spectrum according to the Judd-Oflet theory The stimulated emission cross-section of 4I13/2→4I15/2 transition was calculated by Mc- Cumber theory. The value of FWHM×σepeak is found to be 6.0×10-21cm2, which accounts for that the band-width property of the Bi2O3 glasses is better than those of silicate, phosphate and germinate glasses.
3. A set of SrF2:Yb3+/Er3+ co-doped samples were also prepared by high temperature solid- state reaction method. Under the excitation of 980 nm LD, The ratio of blue emissionⅠ(480 nm) to blue emission bandⅡ(449nm) and the ratio of red to green reduced with increasing the Yb3+/Er3+ ions ratio, this is due to that the blue emissionⅠwas originated from the co- operative sensitization of Yb3+- Yb3+ pair, while the blue emissionⅡwas originated from the co- http://www.999magnet.com/
operative sensitization of Er3+- Yb3+ pairs. The ratio of blue emissionⅠtoⅡdecreases with the decreasing of the Er3+ concentration. The red/green ratio becomes smaller due to the increase of Yb3+ ions, which lead to the increasing of the electron population of 4F9/2 and the electron population in 4S3/2/2H11/2 increasing faster than in4F9/2,4. According to the XRD and SEM, with the increasing of SrF2 concentration, the volume of phase of SrF2 crystal has increased and the fluorescence intensity of the samples has became stronger. It can be concluded that SrF2 are the fairly good choice as a host for up-conversion materials because cubic phase SrF2 is beneficiary to hence the fluorescence efficiency.
With the rapid development of techniques, rare-earth doped up-conversion materials have became valuable in the fields of display devices, lighting storage, optical materials, anti- faker industry, solid-state lasers and so on. At present, the most important task is to improve the efficiency of up-conversion. In this paper, a series of samples have been prepared by rare earth single-doped or co-doped to hosts according to the fundamental principles of up- conversion materials. The influences of the microstructures, the compositions of host materials and the rare earth concentrations on the up-conversion luminous efficiency were studied by metalography, XRD and SEM.
And the up-conversion spectrum was measured by R-500. The results are shown as follows:1. Er3+-doped Bi2O3 glasses have been fabricated through the high temperature solid-state reaction method. Under exitation of 980 nm LD, the glass emits strong red Magnetic lifter emission (4F9/2→4I15/2) and green emission (2H11/2→4I15/2, 4S3/2→4I15/2). But the red emission becomes too weak to be detected under excitation of 808 nm LD which shows that the electron population of 4F9/2 level is mainly achieved by energy transfer..2. The Judd–Oflet intensity parametersΩt (t =2,4,6), were found to beΩ2 =3.35×10-20cm2,Ω4 =1.34×10-20cm2 ,Ω6 =0.67×10-20cm2 calculated basing on the measured absorption spectrum according to the Judd-Oflet theory The stimulated emission cross-section of 4I13/2→4I15/2 transition was calculated by Mc- Cumber theory. The value of FWHM×σepeak is found to be 6.0×10-21cm2, which accounts for that the band-width property of the Bi2O3 glasses is better than those of silicate, phosphate and germinate glasses.
3. A set of SrF2:Yb3+/Er3+ co-doped samples were also prepared by high temperature solid- state reaction method. Under the excitation of 980 nm LD, The ratio of blue emissionⅠ(480 nm) to blue emission bandⅡ(449nm) and the ratio of red to green reduced with increasing the Yb3+/Er3+ ions ratio, this is due to that the blue emissionⅠwas originated from the co- operative sensitization of Yb3+- Yb3+ pair, while the blue emissionⅡwas originated from the co- http://www.999magnet.com/
operative sensitization of Er3+- Yb3+ pairs. The ratio of blue emissionⅠtoⅡdecreases with the decreasing of the Er3+ concentration. The red/green ratio becomes smaller due to the increase of Yb3+ ions, which lead to the increasing of the electron population of 4F9/2 and the electron population in 4S3/2/2H11/2 increasing faster than in4F9/2,4. According to the XRD and SEM, with the increasing of SrF2 concentration, the volume of phase of SrF2 crystal has increased and the fluorescence intensity of the samples has became stronger. It can be concluded that SrF2 are the fairly good choice as a host for up-conversion materials because cubic phase SrF2 is beneficiary to hence the fluorescence efficiency.
Preparation and Characterization of Fe-Base Catalyst for Reverse-Water-Gas-Shift Reaction
Preparation and Characterization of Fe-Base Catalyst for Reverse-Water-Gas-Shift Reaction
Recycle of CO2 is urgent because of its emission threaten environment fearfully. Reverse Water Gas Shift Reaction(RWGS) is one of the most important approach in the reusing of CO2. Co-precipitation was used to prepare iron manganeses mixed oxides for the RWGS. The catalysts samples were studied by Micro-reactor,XRD,TPR,BET and TEM. The emphasis is to optimize composite and structure of the catalysts with robust activity and thermostability.The activity of catalyst prepared by Fe2+ and Fe3+ starting materials is superior to that of catalyst prepared by individual Fe2+ or Fe3+. Manganese dopant into the iron oxides enhances its activity and thermostability. magnet lifter Fe/Mn based catalyst present higher activity and thermostability than that of Cu/Mn、Zn/Mn based catalyst.. The optimization composition is Fe2+/Fe3+/Mn=42:16:42.Additives rare earths can further improve activity and thermostability no matter Fe or Fe/Mn catalysts. Co adulterant of CeO2 http://www.999magnet.com/ and La2O3 can promote the activity and thermostability of manganeses mixed oxides for the reverse water gas shift reaction.
Recycle of CO2 is urgent because of its emission threaten environment fearfully. Reverse Water Gas Shift Reaction(RWGS) is one of the most important approach in the reusing of CO2. Co-precipitation was used to prepare iron manganeses mixed oxides for the RWGS. The catalysts samples were studied by Micro-reactor,XRD,TPR,BET and TEM. The emphasis is to optimize composite and structure of the catalysts with robust activity and thermostability.The activity of catalyst prepared by Fe2+ and Fe3+ starting materials is superior to that of catalyst prepared by individual Fe2+ or Fe3+. Manganese dopant into the iron oxides enhances its activity and thermostability. magnet lifter Fe/Mn based catalyst present higher activity and thermostability than that of Cu/Mn、Zn/Mn based catalyst.. The optimization composition is Fe2+/Fe3+/Mn=42:16:42.Additives rare earths can further improve activity and thermostability no matter Fe or Fe/Mn catalysts. Co adulterant of CeO2 http://www.999magnet.com/ and La2O3 can promote the activity and thermostability of manganeses mixed oxides for the reverse water gas shift reaction.
2012年5月17日星期四
Research of Preparation and Luminescent Capability on the Nanocrystal
Research of Preparation and Luminescent Capability on the Nanocrystal Y2O3: Eu～(3+) Red Phosphor Powder
In this dissertation,we used precipitation method to prepare rare earths luminescent materials Y2O3:Eu3+ and we added different surfactant dodecamine,tetrabutyl-bromize-ammonium,CTAB and metallic ions such as K+,Mg2+,Ba2+ which were characterized by XRD, IR,granularity,excitation and emission spectra. The effect to rare earths luminescent materials Y2O3:Eu3+ were compared by adding different surfacant and metallic ions.By many experiments, we got the conclusion. 1.In the oxalic acid series, the luminescent properities of rare earths luminescent Block neodymium magnet materials Y2O3:Eu3+ increase by adding surfactant dodecamine,no change by adding CTAB,and decrease by adding tetrabutyl-bromize-ammonium,likewise adding metallic ion K+ can increase luminescent intensity, metallic ion Ba2+ can increase luminescent intensity a little,and no luminescent intensity change when added metallic ion Mg2+. 2.In the urea series, the luminescent intensity of rare earths luminescent materials Y2O3:Eu3+ increase by adding surfactant dodecamine;basically no change by Block neodymium magnet adding CTAB,and decrease by adding tetrabutyl-bromize-ammonium,likewise adding metallic ion K+, Ba2+ and Mg2+ all can increase luminescent intensity.
In this dissertation,we used precipitation method to prepare rare earths luminescent materials Y2O3:Eu3+ and we added different surfactant dodecamine,tetrabutyl-bromize-ammonium,CTAB and metallic ions such as K+,Mg2+,Ba2+ which were characterized by XRD, IR,granularity,excitation and emission spectra. The effect to rare earths luminescent materials Y2O3:Eu3+ were compared by adding different surfacant and metallic ions.By many experiments, we got the conclusion. 1.In the oxalic acid series, the luminescent properities of rare earths luminescent Block neodymium magnet materials Y2O3:Eu3+ increase by adding surfactant dodecamine,no change by adding CTAB,and decrease by adding tetrabutyl-bromize-ammonium,likewise adding metallic ion K+ can increase luminescent intensity, metallic ion Ba2+ can increase luminescent intensity a little,and no luminescent intensity change when added metallic ion Mg2+. 2.In the urea series, the luminescent intensity of rare earths luminescent materials Y2O3:Eu3+ increase by adding surfactant dodecamine;basically no change by Block neodymium magnet adding CTAB,and decrease by adding tetrabutyl-bromize-ammonium,likewise adding metallic ion K+, Ba2+ and Mg2+ all can increase luminescent intensity.
Studies on Rare Earth Doping and Radiated Modification of Magnetic Photocatalyst
Studies on Rare Earth Doping and Radiated Modification of Magnetic Photocatalyst
Photocatalytic technology is a new method and has extensive applied foreground in wastewater treatment. TiO2 is believed to be the most promising material because of its low price, nontoxcity, long term stability in aqueous solution.At present, the research about TiO2 form has two tendencies: one is TiO2 power, another is TiO2 membrane. Because of its limit surface area, the immobilized TiO2 membrane has been demonstrated to lower photocatalytic activity than TiO2 power. But TiO2 power is difficult to be separated from aqueous reactant systerm. It is at big lost rate in separation process due to its small particle diameter. In order to solve separation and reuse of Ball Neodymium Magnets TiO2 power, magnetic photocatalyst has been prepared in our laboratory.
However, the photocatalytic efficiency has been decreased by the addition of magnetic support. In this paper, we do research on rare earth doping and radiation modification of magnetic photocatalyst in order to enhance its activity.By using micro-sized Fe3O4 as support, SiO2 isolated layer is coated on the surface of Fe3O4 via sol-gel method, followed by dryness and pestled treatment. On the surface of SiO2/Fe3O4, TiO2 particles are coated while rare earth nitrate is added, followed by dryness, calcinations, and pestled treatment.Photocatalyst La doped is put into Co-60 radiation equipment (Tianjin Institute of thechnology and physics). Then the radiated modification is investigated. Photocatalyst under different dosage are obtained by changing radiation time.With ezao-dye as object Ball Neodymium Magnets contamination, photocatalytic activity of modificated samples is evaluated. The result showed that photocatalytic activity was enhanced by different degree, when different kinds of rare earth(RE=La、Nd、Gd) were doped. And photocatalytic activity of material changes with different concentration of rare earth.By radiation, photocatalytic activity of material is enhanced. In this paper, the curve of photocatalytic activity, as function of radiation dosage, is obtained. Its theoretical analysis is processed.
Photocatalytic technology is a new method and has extensive applied foreground in wastewater treatment. TiO2 is believed to be the most promising material because of its low price, nontoxcity, long term stability in aqueous solution.At present, the research about TiO2 form has two tendencies: one is TiO2 power, another is TiO2 membrane. Because of its limit surface area, the immobilized TiO2 membrane has been demonstrated to lower photocatalytic activity than TiO2 power. But TiO2 power is difficult to be separated from aqueous reactant systerm. It is at big lost rate in separation process due to its small particle diameter. In order to solve separation and reuse of Ball Neodymium Magnets TiO2 power, magnetic photocatalyst has been prepared in our laboratory.
However, the photocatalytic efficiency has been decreased by the addition of magnetic support. In this paper, we do research on rare earth doping and radiation modification of magnetic photocatalyst in order to enhance its activity.By using micro-sized Fe3O4 as support, SiO2 isolated layer is coated on the surface of Fe3O4 via sol-gel method, followed by dryness and pestled treatment. On the surface of SiO2/Fe3O4, TiO2 particles are coated while rare earth nitrate is added, followed by dryness, calcinations, and pestled treatment.Photocatalyst La doped is put into Co-60 radiation equipment (Tianjin Institute of thechnology and physics). Then the radiated modification is investigated. Photocatalyst under different dosage are obtained by changing radiation time.With ezao-dye as object Ball Neodymium Magnets contamination, photocatalytic activity of modificated samples is evaluated. The result showed that photocatalytic activity was enhanced by different degree, when different kinds of rare earth(RE=La、Nd、Gd) were doped. And photocatalytic activity of material changes with different concentration of rare earth.By radiation, photocatalytic activity of material is enhanced. In this paper, the curve of photocatalytic activity, as function of radiation dosage, is obtained. Its theoretical analysis is processed.
GaN及GaN基薄膜的制备、表征和特性研究
GaN及GaN基薄膜的制备、表征和特性研究
The subject investigated in this thesis is to attempt a method for thin film preparation by using the combination of pulsed laser plasma and electron cyclotron resonance (ECR) plasma, which is ECR plasma assisted pulsed laser deposition (ECR-PLD) and in situ doping via coablation of two targets with two pulsed laser beams. The method is used to synthesize GaN, GaN:Er, GaN:Pr thin films and SiC, AlN thin films as the candidates of buffers between Si substrates and GaN thin films.Pulsed laser deposition (PLD) is a technique using the properties of laser to ablate materials and the ablation plasma deposit on the substrates as the form of thin films, which has been successfully Ball Neodymium Magnets used for the preparation of many kinds of thin films. ECR microwave discharge can produce plasma with high density, high degree of ionization, and high purity at low working pressures. We developed a method for film synthesis named ECR-PLD by combining PLD with ECR microwave plasma. This method colligates the advantages of PLD and ECR plasma at low temperatures. As one of the most promising wide band gap III- V semiconducting materials, GaN has attracted much attention because of its potential applications in optoelectronic devices. GaN is also prospective materials for full-color displays, detectors as well as high-power and high temperature electronics and radiation-resistant devices due to their excellent optical, thermal, mechanical properties. In this work, the GaAs target was ablated by the focused laser beam in the ambience of ECR nitrogen plasma to deposit GaN thin films at low temperatures.
By analyzing the samples’ components and structure, such as HEIBS, XPS, FTIR, we demonstrated the feasibility of the presented method for GaN thin films preparation through thin films synthesis mentioned above.Rare earth (RE) ions have been received wide attention because of its prominent light emission properties for applications on optical emission and full color display devices. People mostly use the method of MBE and MOCVD to synthesize III-V nitrides doped with Rare earth ions implantation and in situ doping during thin film growth. But there still exist many disadvantages such as damage to the host and ununiformity of the dopant in the former as well as difficult to Ball Neodymium Magnets increase doping concentration in the latter. In this work, a novel method for compound thin film synthesis and in situ doping based on plasma assisted pulsed laser deposition by coablating two targets by two laser beams through the preparation of Er-doped GaN and Pr-doped GaN thin films was demonstrated. With the assistance of ECR nitrogen plasma, the ablation of a polycrystalline GaAs target resulted in the reactive deposition of host GaN film, while the ablation of a metallic RE (Er, Pr) target provided with RE atoms for doping in the growing GaN film.The growth of GaN is on silicon due to the advantages of this substrate, which is low cost, large scale availability, good thermal and electrical conductivities. However, there exist large lattice mismatch and difference in thermal expansion coefficients between GaN and silicon. Buffer layer is one of useful methods; we prepare SiC using coablation of two targets with two pulsed laser beams and AlN using ECR-PLD as the candidates of buffer materials. We select AlN as the buffer materials by analyzing the samples’ properties.Post-annealing is an effective way to improve Ball Neodymium Magnets prepared thin films’ structures and qualities. We do some work about it to analyze the effect of anneal toward GaN thin films.Through synthesis of these thin films above, with some assistant ways containing buffer layer and anneal, we demonstrated a purpose of laser and ECR plasma on material preparation in the thesis at one hand and studied the properties of GaN related thin films at the other hand.
The subject investigated in this thesis is to attempt a method for thin film preparation by using the combination of pulsed laser plasma and electron cyclotron resonance (ECR) plasma, which is ECR plasma assisted pulsed laser deposition (ECR-PLD) and in situ doping via coablation of two targets with two pulsed laser beams. The method is used to synthesize GaN, GaN:Er, GaN:Pr thin films and SiC, AlN thin films as the candidates of buffers between Si substrates and GaN thin films.Pulsed laser deposition (PLD) is a technique using the properties of laser to ablate materials and the ablation plasma deposit on the substrates as the form of thin films, which has been successfully Ball Neodymium Magnets used for the preparation of many kinds of thin films. ECR microwave discharge can produce plasma with high density, high degree of ionization, and high purity at low working pressures. We developed a method for film synthesis named ECR-PLD by combining PLD with ECR microwave plasma. This method colligates the advantages of PLD and ECR plasma at low temperatures. As one of the most promising wide band gap III- V semiconducting materials, GaN has attracted much attention because of its potential applications in optoelectronic devices. GaN is also prospective materials for full-color displays, detectors as well as high-power and high temperature electronics and radiation-resistant devices due to their excellent optical, thermal, mechanical properties. In this work, the GaAs target was ablated by the focused laser beam in the ambience of ECR nitrogen plasma to deposit GaN thin films at low temperatures.
By analyzing the samples’ components and structure, such as HEIBS, XPS, FTIR, we demonstrated the feasibility of the presented method for GaN thin films preparation through thin films synthesis mentioned above.Rare earth (RE) ions have been received wide attention because of its prominent light emission properties for applications on optical emission and full color display devices. People mostly use the method of MBE and MOCVD to synthesize III-V nitrides doped with Rare earth ions implantation and in situ doping during thin film growth. But there still exist many disadvantages such as damage to the host and ununiformity of the dopant in the former as well as difficult to Ball Neodymium Magnets increase doping concentration in the latter. In this work, a novel method for compound thin film synthesis and in situ doping based on plasma assisted pulsed laser deposition by coablating two targets by two laser beams through the preparation of Er-doped GaN and Pr-doped GaN thin films was demonstrated. With the assistance of ECR nitrogen plasma, the ablation of a polycrystalline GaAs target resulted in the reactive deposition of host GaN film, while the ablation of a metallic RE (Er, Pr) target provided with RE atoms for doping in the growing GaN film.The growth of GaN is on silicon due to the advantages of this substrate, which is low cost, large scale availability, good thermal and electrical conductivities. However, there exist large lattice mismatch and difference in thermal expansion coefficients between GaN and silicon. Buffer layer is one of useful methods; we prepare SiC using coablation of two targets with two pulsed laser beams and AlN using ECR-PLD as the candidates of buffer materials. We select AlN as the buffer materials by analyzing the samples’ properties.Post-annealing is an effective way to improve Ball Neodymium Magnets prepared thin films’ structures and qualities. We do some work about it to analyze the effect of anneal toward GaN thin films.Through synthesis of these thin films above, with some assistant ways containing buffer layer and anneal, we demonstrated a purpose of laser and ECR plasma on material preparation in the thesis at one hand and studied the properties of GaN related thin films at the other hand.
Study on Synthesis and Properties of Complexes Eu
Study on Synthesis and Properties of Complexes Eu(Ⅲ)
The rare earth polymer materials have attracted considerable interests for they assume both good luminescent characteristics and high color purity of rare earths and the excellent machinability of polymers. Rare earth ions, having abundant emission spectrum, have been extensively used in inorganic and organic luminophores as an effective luminescent sources.However, rare earth inorganic materials have some problems such as poor processibility and high costing.The synthesis, characterization and properties of the Eu(Ⅲ) complexes of acetaacetone-polymethacrylic neodymium magnets acid,benzoylacetone-polyacetamide, acetaacetone -acrylic acid-acrylonitrile, have been studied in this thesis.
Three kinds of typical polymer ligands of polymethacrylic acid(PMAA) and polyacetamide(PAM) and benzoylacetone (BA) have been synthesized, and a detailed investigation on the formed coordination compounds with rare earth metals has been carried out as well.This paper consists of three parts as follow:(1) A brief review of the study for macromolecular metal complexes compounds and low temperature solid phase reaction have been given.(2) Polymethacrylic acid(PMAA) ligand was synthesized ,their compounds with rare earth nitrates and acetaacetone have been synthesized and characterized. The scheme of polymethacrylic acid(PMAA) ligand are showed as follow: The component and the scheme of PMAA-Eu-acac are showed respectively as follow: The carboxylates maybe are in the same chain or not.(3) Benzoylacetone(BA) ligand、polymer polyacetamide(PAM) ligands and their compounds with Eu (Ⅲ) have been synthesized and characterized. The component of the PAM and PAM -Eu-BA are:(4) A quarternary complex is synthesized by the reaction of neodymium magnets metallorganic complex (NaEu(acac)4 ) with acrylic acid and acrylonitrile. The scheme of quarternary complex is showed as follow: The compound has been characterized by elemental ,UV spectra, IR spectra, conductance fluorescent. The result shows that the production has fixation compose when add Eu (Ⅲ) and small molecule into polymers after all these have reaction. The production is a good irradiance material.The outcome shows that the rare earth cordination polymers which have been synthesized have steady compose , are unsolvable in most organic solvent and have high decomposed http://www.chinamagnets.biz/ temperature and excellent fluorescence property.(5) conclusion and constructionIntroduce the thesis’content and provide some construction.
The rare earth polymer materials have attracted considerable interests for they assume both good luminescent characteristics and high color purity of rare earths and the excellent machinability of polymers. Rare earth ions, having abundant emission spectrum, have been extensively used in inorganic and organic luminophores as an effective luminescent sources.However, rare earth inorganic materials have some problems such as poor processibility and high costing.The synthesis, characterization and properties of the Eu(Ⅲ) complexes of acetaacetone-polymethacrylic neodymium magnets acid,benzoylacetone-polyacetamide, acetaacetone -acrylic acid-acrylonitrile, have been studied in this thesis.
Three kinds of typical polymer ligands of polymethacrylic acid(PMAA) and polyacetamide(PAM) and benzoylacetone (BA) have been synthesized, and a detailed investigation on the formed coordination compounds with rare earth metals has been carried out as well.This paper consists of three parts as follow:(1) A brief review of the study for macromolecular metal complexes compounds and low temperature solid phase reaction have been given.(2) Polymethacrylic acid(PMAA) ligand was synthesized ,their compounds with rare earth nitrates and acetaacetone have been synthesized and characterized. The scheme of polymethacrylic acid(PMAA) ligand are showed as follow: The component and the scheme of PMAA-Eu-acac are showed respectively as follow: The carboxylates maybe are in the same chain or not.(3) Benzoylacetone(BA) ligand、polymer polyacetamide(PAM) ligands and their compounds with Eu (Ⅲ) have been synthesized and characterized. The component of the PAM and PAM -Eu-BA are:(4) A quarternary complex is synthesized by the reaction of neodymium magnets metallorganic complex (NaEu(acac)4 ) with acrylic acid and acrylonitrile. The scheme of quarternary complex is showed as follow: The compound has been characterized by elemental ,UV spectra, IR spectra, conductance fluorescent. The result shows that the production has fixation compose when add Eu (Ⅲ) and small molecule into polymers after all these have reaction. The production is a good irradiance material.The outcome shows that the rare earth cordination polymers which have been synthesized have steady compose , are unsolvable in most organic solvent and have high decomposed http://www.chinamagnets.biz/ temperature and excellent fluorescence property.(5) conclusion and constructionIntroduce the thesis’content and provide some construction.
2012年5月14日星期一
Studies on Treatment of Wastewater with High Concentration of Ammonia Nitrogen in the Process of Rear Earth Metallurgy
Studies on Treatment of Wastewater with High Concentration of Ammonia Nitrogen in the Process of Rear Earth Metallurgy
This is according to the subject: The study of removing ammonia nitrogen which comes from waste water in the Process of rear earth metallurgy, through to expound the rare earth smelting craft, and inspected the process flow of sour law metallurgy and alkali law metallurgy of rare earth the two kinds of types. Combined the process flow, had further understood the way, type and essential component of smelting waste water. The main pollutant of rare earth smelting waste water is ammonia nitrogen, and the concentration is very high. According to the present of rare earth smelting waste water pollution situation, introduced the harm of ammonia nitrogen waste water, then introduced home and abroad disposal of ammonia nitrogen waste water. Synthesizes each kind of e Block Neodymium magnets xisting processing technology, this article decide to use blow-off method and the ion exchange technique unify to carry on the experiment. The ammonia nitrogen waste water is from the laboratory simulation. The concentration of ammonia nitrogen in original water is approximately 10000mg/L, according to influence factor research of the two methods processing for ammonia nitrogen waste water, has made certain the best experimental condition.The main influence factors of removing ammonia nitrogen with blow-off method are temperature, pH, aeration quantity and blows escapes the time, considered the economic factor, the experiment carries on under the room temperature, Through the theory research of pH which influence the removing of the ammonia nitrogen, Adjust the pH to 9, 10.5, 11, 12, finally determined the best pH is 10.5,The other two important factors are aeration quantity and http://www.999magnet.com/ aeration time, the experiment determined the best aeration quantity is 1.5L/min, the aeration time is 48h (namely gas/ liquid = 8640).The ionic exchange craft uses the zeolite, porcelain stone and crockery to carry on the adsorption. According to the experiment result, it had bad effort of using porcelain stone and crockery to carry on the adsorption, but used the zeolite can obtain the good effect. The waste water of disposal by zeoliteadsorption Block Neodymium magnets is which comed from the former step. The concentration of NH4-N is 1770mg per litre, pH is 8.0, after the first adsorption, it can make the ammonia nitrogen removing rate achieved 85.9%, the zeolite regeneration uses the the muffle furnace to drying, drying 1h under the temperature of 200℃, the second adsorption can make the adsorption capacitance achieved 5.73mg/g, When the ammonia nitrogen concentration of original water is 1770mg/L, removing rate is 69.18%. After several times regeneration, the adsorption capacitance also can achieve 5.39mg/g. After the second adsorption, the waste water from blow-off can achieve the discharges the standard. 更多还原
This is according to the subject: The study of removing ammonia nitrogen which comes from waste water in the Process of rear earth metallurgy, through to expound the rare earth smelting craft, and inspected the process flow of sour law metallurgy and alkali law metallurgy of rare earth the two kinds of types. Combined the process flow, had further understood the way, type and essential component of smelting waste water. The main pollutant of rare earth smelting waste water is ammonia nitrogen, and the concentration is very high. According to the present of rare earth smelting waste water pollution situation, introduced the harm of ammonia nitrogen waste water, then introduced home and abroad disposal of ammonia nitrogen waste water. Synthesizes each kind of e Block Neodymium magnets xisting processing technology, this article decide to use blow-off method and the ion exchange technique unify to carry on the experiment. The ammonia nitrogen waste water is from the laboratory simulation. The concentration of ammonia nitrogen in original water is approximately 10000mg/L, according to influence factor research of the two methods processing for ammonia nitrogen waste water, has made certain the best experimental condition.The main influence factors of removing ammonia nitrogen with blow-off method are temperature, pH, aeration quantity and blows escapes the time, considered the economic factor, the experiment carries on under the room temperature, Through the theory research of pH which influence the removing of the ammonia nitrogen, Adjust the pH to 9, 10.5, 11, 12, finally determined the best pH is 10.5,The other two important factors are aeration quantity and http://www.999magnet.com/ aeration time, the experiment determined the best aeration quantity is 1.5L/min, the aeration time is 48h (namely gas/ liquid = 8640).The ionic exchange craft uses the zeolite, porcelain stone and crockery to carry on the adsorption. According to the experiment result, it had bad effort of using porcelain stone and crockery to carry on the adsorption, but used the zeolite can obtain the good effect. The waste water of disposal by zeoliteadsorption Block Neodymium magnets is which comed from the former step. The concentration of NH4-N is 1770mg per litre, pH is 8.0, after the first adsorption, it can make the ammonia nitrogen removing rate achieved 85.9%, the zeolite regeneration uses the the muffle furnace to drying, drying 1h under the temperature of 200℃, the second adsorption can make the adsorption capacitance achieved 5.73mg/g, When the ammonia nitrogen concentration of original water is 1770mg/L, removing rate is 69.18%. After several times regeneration, the adsorption capacitance also can achieve 5.39mg/g. After the second adsorption, the waste water from blow-off can achieve the discharges the standard. 更多还原
Study on Forming and Alloying of Mg-Cu-Tb Bulk Amorphous Alloy
Study on Forming and Alloying of Mg-Cu-Tb Bulk Amorphous Alloy
Mg-based alloys have great potential as engineering materials for automobile, aircraft and computer industries due to their high specific strength and abundance. In the papers, the Mg65Cu25Tb10 bulk with high oxygen resistances was firstly prepared by the copper mold casting technique. The Mg65Cu25-xTb10-yNixREy bulk amorphous alloys were prepared by the copper mold casting technique. And the effect of Ni addition and the rare earth (RE) addition on the glass forming ability (GFA) and mechanical properties were studied according to X-ray diffractrometry (XRD), differential scanning calorimeter (DSC) , compression tests and scaning electron microscopy (SEM). The main Special shape NdFeB magnets conclusions as follows:The Mg65Cu25Tb10 bulk amorphous alloy rods with 3 mm diameters were prepared by the copper mold casting technique. From the endothermal signal of the melting, one can deduce that the composition of the alloy is very close to the eutectic point with highly glass froming ability and thermal stability. The compressive fracture strength and Young’s modulus at room temperature are 756MPa and 54GPa, respectively.The effect of Ni http://www.999magnet.com/ addition and on the glass forming ability (GFA) and mechanical properties of Mg-Cu-Tb alloys were studied. With the increase of substitution of Ni for, the glass forming ability and thermal stability of the Mg65Cu25-xNixTb10(x=0, 5, 10) alloys decreased. The Cu substitution by Ni (10%) will result in the detrimental impact on the GFA and decreasing the mechanical property. But after substitution of Ni for Cu from (5%) , the compressive fracture strength, increase clearly from 756 MPa to 867 MPa.The effect of rare earth (RE) addition on Mg based Special shape NdFeB magnets metallic glass was studied. After substitution of rare-earth element (Ce(3%)) and their admixtures (Ce(3%)+Y(3 %)) for Tb, the reduced glass transition temperature (Trg) of the Mg65Cu20Ni5Tb7Ce3 and Mg65Cu20Ni5Tb4Ce3Y3 alloys were increased orderly, and the supercooled liquid region, ΔTx, increased. The new multielement Mg based metallic glasses with highly GFA and thermal stability are successfully fabricated owing to multielement -compounded principles and high oxidation resistance of rare-earth admixtures. But, these samples were very frail and their compressive fracture strengths were below 300 MPa, considerably less than that of Mg65Cu20Ni5Tb10. 更多还原
Mg-based alloys have great potential as engineering materials for automobile, aircraft and computer industries due to their high specific strength and abundance. In the papers, the Mg65Cu25Tb10 bulk with high oxygen resistances was firstly prepared by the copper mold casting technique. The Mg65Cu25-xTb10-yNixREy bulk amorphous alloys were prepared by the copper mold casting technique. And the effect of Ni addition and the rare earth (RE) addition on the glass forming ability (GFA) and mechanical properties were studied according to X-ray diffractrometry (XRD), differential scanning calorimeter (DSC) , compression tests and scaning electron microscopy (SEM). The main Special shape NdFeB magnets conclusions as follows:The Mg65Cu25Tb10 bulk amorphous alloy rods with 3 mm diameters were prepared by the copper mold casting technique. From the endothermal signal of the melting, one can deduce that the composition of the alloy is very close to the eutectic point with highly glass froming ability and thermal stability. The compressive fracture strength and Young’s modulus at room temperature are 756MPa and 54GPa, respectively.The effect of Ni http://www.999magnet.com/ addition and on the glass forming ability (GFA) and mechanical properties of Mg-Cu-Tb alloys were studied. With the increase of substitution of Ni for, the glass forming ability and thermal stability of the Mg65Cu25-xNixTb10(x=0, 5, 10) alloys decreased. The Cu substitution by Ni (10%) will result in the detrimental impact on the GFA and decreasing the mechanical property. But after substitution of Ni for Cu from (5%) , the compressive fracture strength, increase clearly from 756 MPa to 867 MPa.The effect of rare earth (RE) addition on Mg based Special shape NdFeB magnets metallic glass was studied. After substitution of rare-earth element (Ce(3%)) and their admixtures (Ce(3%)+Y(3 %)) for Tb, the reduced glass transition temperature (Trg) of the Mg65Cu20Ni5Tb7Ce3 and Mg65Cu20Ni5Tb4Ce3Y3 alloys were increased orderly, and the supercooled liquid region, ΔTx, increased. The new multielement Mg based metallic glasses with highly GFA and thermal stability are successfully fabricated owing to multielement -compounded principles and high oxidation resistance of rare-earth admixtures. But, these samples were very frail and their compressive fracture strengths were below 300 MPa, considerably less than that of Mg65Cu20Ni5Tb10. 更多还原
2012年5月11日星期五
Study on Preparation and Properties of Nanoscale Rare Earth Eu～(3+) Luminescent Materials
Study on Preparation and Properties of Nanoscale Rare Earth Eu～(3+) Luminescent Materials
Rare-earth ions luminescence materials have attracted of interest because of its low wastage in communication wavelength and its application in the field of fiber communication and photoelectron integration technology. In the dissertation, nano-meter Y2-xSiO5:Eux material was synthesized by sol-gel method, preparation of ordered mesoporous silicon basic luminescence materials doped by Eu was explored. The contents of this thesis consist of the following main points.(1) Nano-meter Y2-xSiO5:Eux material was synthesized by sol-gel method, and its structure and morphology were characterized by XRD, FTIR and TEM. The influence of phase structure, Block neodymium magnet calcination temperature and Eu3+ doping concentration on luminescence properties was investigated. The results show that the materials obtained at calcination temperature below 900℃mainly present non-crystal state, while the materials mainly exhibit crystal state structure when calcined over 900℃. The particle size increased with the calcination temperature.
The particle size was 15-45 nm and 60-80 nm for amorphous and crystal forms, respectively. The excitation and emission spectra of materials are both affected by phase structure, calcining temperature and Eu3+ doping concentration and Y2-xSiO5:Eux in crystalline state shows finer excitation and emission spectrum band than that in amorphous state and Y1.6SiO5:Eu0.4 shows the largest luminescence intensity.(2) The ordered Eu3+ doped silicon mesoporous materials were synthesized by using a triblock copolymer as a molecular template under strongly acidic condition. Its structure were characterized by XRD, FTIR, TEM and BET. The results show that the pore size http://www.chinamagnets.biz/ distribution is affected by Eu3+ doping concentration and change wider in high doping concentration. It is found in the material preparation process that the hydrothermal treatment will make crystallization degree of materials increase and result in finer luminescence spectrum bands. Simultaneously, it is found that the fluorescence lifetimes of 5D0 energy level of Eu3+ obviously become short(only 0.36～0.37 ms) in contrast to bulk materials(1.7 ms). 更多还原
Rare-earth ions luminescence materials have attracted of interest because of its low wastage in communication wavelength and its application in the field of fiber communication and photoelectron integration technology. In the dissertation, nano-meter Y2-xSiO5:Eux material was synthesized by sol-gel method, preparation of ordered mesoporous silicon basic luminescence materials doped by Eu was explored. The contents of this thesis consist of the following main points.(1) Nano-meter Y2-xSiO5:Eux material was synthesized by sol-gel method, and its structure and morphology were characterized by XRD, FTIR and TEM. The influence of phase structure, Block neodymium magnet calcination temperature and Eu3+ doping concentration on luminescence properties was investigated. The results show that the materials obtained at calcination temperature below 900℃mainly present non-crystal state, while the materials mainly exhibit crystal state structure when calcined over 900℃. The particle size increased with the calcination temperature.
The particle size was 15-45 nm and 60-80 nm for amorphous and crystal forms, respectively. The excitation and emission spectra of materials are both affected by phase structure, calcining temperature and Eu3+ doping concentration and Y2-xSiO5:Eux in crystalline state shows finer excitation and emission spectrum band than that in amorphous state and Y1.6SiO5:Eu0.4 shows the largest luminescence intensity.(2) The ordered Eu3+ doped silicon mesoporous materials were synthesized by using a triblock copolymer as a molecular template under strongly acidic condition. Its structure were characterized by XRD, FTIR, TEM and BET. The results show that the pore size http://www.chinamagnets.biz/ distribution is affected by Eu3+ doping concentration and change wider in high doping concentration. It is found in the material preparation process that the hydrothermal treatment will make crystallization degree of materials increase and result in finer luminescence spectrum bands. Simultaneously, it is found that the fluorescence lifetimes of 5D0 energy level of Eu3+ obviously become short(only 0.36～0.37 ms) in contrast to bulk materials(1.7 ms). 更多还原
Research on the Preparation and Mechanical Property of SIALON Ceramics
Research on the Preparation and Mechanical Property of SIALON Ceramics
In this paper, the property and the structure of Sialon ceramics are introduced. Simultaneously the study and application of present condition about Sialon ceramics at home and abroad are also discussed. In addition, this paper put forward the existent problem and expectation on study and application of Sialon ceramics. This subject studied the influence of different additives on the microstructure and mechanical property of Sialon ceramics systemicly.For Sialon is sosoloid of Si3N4-SiO2-Al2O3-AlN system, some a concrete phase can be synthesized according to the mixture ratio of phase diagram and choosing appropriate conditions. Sialon ceramics have been Ball Neodymium Magnets studied by pressureless sintering with the components of Si3N4, Al2O3, AlN at 1750℃. Because of the different components, different mechanical properties and microstructure can be found in different samples.
The morphologies and the mechanical properties of Sialon ceramics prepared by pressureless sintering were investigated. According to the result, the optimal composition was confirmed: the sample A3 which is composed with 56%α-Si3N4, 34%Al2O3 and 10%AlN has the relative better mechanical property and the flexure strength and the fracture toughness are up to 362.5MPa and 3.31MPa·m1/2 respectively. Choosing Y2O3、La2O3、Ce2O3、Nd2O3 and Sm2O3 as different fluxing agents and Sialon ceramics prepared above as parent materials, we studied the influence of the fluxing agents contents of different on the morphologies and the mechanical properties of Sialon Ball Neodymium Magnets ceramics. The microstructure were analyzed by deferent analysis methods such as X-ray Diffraction(XRD) and scanning electron microscope(SEM) and the mechanical properties were tested by three-point bending method and single edge notched beam method. Results showed that the mechanical property of the sample which used Y2O3 as the fluxing agent was best of all. And when the amount of Y2O3 is 6wt%, the flexure strength and the fracture toughness is as high as 390.28MPa and 4.4MPa·m1/2. It can be found that the amount of columnar crystal grains increased and slenderness ratio enlarged.
It is feasible that the additive Y2O3 can be taken the place partly by light-rare-earth oxide and when the Y2O3 was substituted by Nd2O3 partly, the mechanical property of C3 is better than the others: the flexure strength is 483MPa and the fracture toughness is 4.9MPa·m1/2. Because of the additional compound rare-earth oxide additives, more long columnarβ-Sialon grains were formed in the sintering body. The toughness of the material was improved as a result of the http://www.chinamagnets.biz/ grains full development and mutual zigzag. Liquid phase was filled into the interstice between the grains, which makes the density of the materials improve. Otherwise, the form ability of lightweight compound rare-earth for Sialon is different. With the increment of rare-earth atomic, the radius of rare-earth ionic decreases and the solid solubility of Sialon become augment, at the same time the amounts of rare-earth ions in the solid solubility of Sialon become larger. 更多还原
In this paper, the property and the structure of Sialon ceramics are introduced. Simultaneously the study and application of present condition about Sialon ceramics at home and abroad are also discussed. In addition, this paper put forward the existent problem and expectation on study and application of Sialon ceramics. This subject studied the influence of different additives on the microstructure and mechanical property of Sialon ceramics systemicly.For Sialon is sosoloid of Si3N4-SiO2-Al2O3-AlN system, some a concrete phase can be synthesized according to the mixture ratio of phase diagram and choosing appropriate conditions. Sialon ceramics have been Ball Neodymium Magnets studied by pressureless sintering with the components of Si3N4, Al2O3, AlN at 1750℃. Because of the different components, different mechanical properties and microstructure can be found in different samples.
The morphologies and the mechanical properties of Sialon ceramics prepared by pressureless sintering were investigated. According to the result, the optimal composition was confirmed: the sample A3 which is composed with 56%α-Si3N4, 34%Al2O3 and 10%AlN has the relative better mechanical property and the flexure strength and the fracture toughness are up to 362.5MPa and 3.31MPa·m1/2 respectively. Choosing Y2O3、La2O3、Ce2O3、Nd2O3 and Sm2O3 as different fluxing agents and Sialon ceramics prepared above as parent materials, we studied the influence of the fluxing agents contents of different on the morphologies and the mechanical properties of Sialon Ball Neodymium Magnets ceramics. The microstructure were analyzed by deferent analysis methods such as X-ray Diffraction(XRD) and scanning electron microscope(SEM) and the mechanical properties were tested by three-point bending method and single edge notched beam method. Results showed that the mechanical property of the sample which used Y2O3 as the fluxing agent was best of all. And when the amount of Y2O3 is 6wt%, the flexure strength and the fracture toughness is as high as 390.28MPa and 4.4MPa·m1/2. It can be found that the amount of columnar crystal grains increased and slenderness ratio enlarged.
It is feasible that the additive Y2O3 can be taken the place partly by light-rare-earth oxide and when the Y2O3 was substituted by Nd2O3 partly, the mechanical property of C3 is better than the others: the flexure strength is 483MPa and the fracture toughness is 4.9MPa·m1/2. Because of the additional compound rare-earth oxide additives, more long columnarβ-Sialon grains were formed in the sintering body. The toughness of the material was improved as a result of the http://www.chinamagnets.biz/ grains full development and mutual zigzag. Liquid phase was filled into the interstice between the grains, which makes the density of the materials improve. Otherwise, the form ability of lightweight compound rare-earth for Sialon is different. With the increment of rare-earth atomic, the radius of rare-earth ionic decreases and the solid solubility of Sialon become augment, at the same time the amounts of rare-earth ions in the solid solubility of Sialon become larger. 更多还原
Study on the Rare Earth Permanent Magnet Synchronous Motor by FEM
Study on the Rare Earth Permanent Magnet Synchronous Motor by FEM
This dissertation develops partial contents of national 863 projects "The High Speed Highly Effective Explosion-proof Rare Earth Permanent Magnet Synchronous Motor". In order to improve the efficiency of rare earth permanent magnet synchronous motor (REPMSM), the paper combined FEM (Finite Element Method) with experiment methods, and studied on the copper losses of rotor of REPMSM in the steady-state, the starting process simulation of REPMSM, neodymium magnets and the harmonic in air-gap magnetic field at no-load of REPMSM.The paper has calculated accurately a 22kW REPMSM in oil field for pumping with the FEM software MagNet. At the fist time, the copper losses of rotor in the steady-state of REPMSM because of the harmonic analyzed thoroughly, the direct and indirect method to measure the efficiency of the 22kW REPMSM is disposed for the harmonic losses.
Compared the simulation and experiment result, the copper losses of rotor in steady-state of REPMSM existed actually. The idea is different from the traditional theory of REPMSM in the steady-state.The starting process simulation for the 22kW of the REPMSM with the FEM software of the MagNet is searched deeply. And the starting process experiment at no-load is completed, the measurement result proved the exactness of the simulation results. Simultaneously, the simulation result by the MagNet provided the reference to optimize REPMSM.The air-gap magnetic field at no-load of 370W REPMSM has simulated by the FEM software MagNet, the http://www.chinamagnets.biz/ simulation results of THD (Total Harmonic Distortion) of back electromotive force at no-load was 6.23%. In order to prove the result of simulation, two 370W REPMSM had towed each other, the measurement results of THD was 3.26%.The damping effect to air gap harmonic was found by the rotor squirrel-cage bar.
This dissertation develops partial contents of national 863 projects "The High Speed Highly Effective Explosion-proof Rare Earth Permanent Magnet Synchronous Motor". In order to improve the efficiency of rare earth permanent magnet synchronous motor (REPMSM), the paper combined FEM (Finite Element Method) with experiment methods, and studied on the copper losses of rotor of REPMSM in the steady-state, the starting process simulation of REPMSM, neodymium magnets and the harmonic in air-gap magnetic field at no-load of REPMSM.The paper has calculated accurately a 22kW REPMSM in oil field for pumping with the FEM software MagNet. At the fist time, the copper losses of rotor in the steady-state of REPMSM because of the harmonic analyzed thoroughly, the direct and indirect method to measure the efficiency of the 22kW REPMSM is disposed for the harmonic losses.
Compared the simulation and experiment result, the copper losses of rotor in steady-state of REPMSM existed actually. The idea is different from the traditional theory of REPMSM in the steady-state.The starting process simulation for the 22kW of the REPMSM with the FEM software of the MagNet is searched deeply. And the starting process experiment at no-load is completed, the measurement result proved the exactness of the simulation results. Simultaneously, the simulation result by the MagNet provided the reference to optimize REPMSM.The air-gap magnetic field at no-load of 370W REPMSM has simulated by the FEM software MagNet, the http://www.chinamagnets.biz/ simulation results of THD (Total Harmonic Distortion) of back electromotive force at no-load was 6.23%. In order to prove the result of simulation, two 370W REPMSM had towed each other, the measurement results of THD was 3.26%.The damping effect to air gap harmonic was found by the rotor squirrel-cage bar.
2012年5月7日星期一
Research on Reverse Osmosis Concentration of Rare-Earth Ammonium Chloride Waste Water
Research on Reverse Osmosis Concentration of Rare-Earth Ammonium Chloride Waste Water
This paper is based on the research of the rare-earth chlorine ammonium wastewater treatment and recycling in Baotou, Inner Mongolia. The Rare-earth chlorine ammonium wastewater, including the mother liquor and cleaning solution, is formed in the production of unitary rare earth carbonate. In practice, many enterprises now directly evaporate and crystallize the mother liquor of high concentration for Ammonium chloride products. However, currently, there is no effective treatment available for the cleaning solution yet. Because of its large liquid volume, low concentration, and high energy consumption,when evaporated and crystallized, it will be too costly for the related enterprises. If untreated before discharged, the cleaning solution will pollute the Yellow River in Baotou. In the Ball Neodymium Magnets project in this paper, the technique of reverse osmosis (RO) concentration is adopted to concentrate and crystallize the cleaning solution.The RO membrane imposes high standards on the quality of the influent water. When it comes to how to prevent the RO membrane from being polluted and being blocked by the scales formed by calcium or magnesium ions in the after-concentration wastewater, it still remains a huge problem in the reverse osmosis concentration of rare-earth Ammonium chloride wastewater. The key to guarantee the long-term stability of RO technique lies in strict pre-cautions.
The RO pretreatment experiment introduced in this paper include mainly the following specific experiments:coagulation sedimentation experiment, oil filtration and removal experiment via oil-absorbing blanket, filtration experiment via dual-media filter feed,activated carbon absorption experiment, and scale inhibition experiment.Coagulation Sedimentation Experiment: The result shows that PFS, as its small but sufficient dosage is concerned, is obviously superior in removing turbidity and COD. Besides, the turbidity of the supernatant liquid is below 2.0 NTU, which meets the requirements of the RO membrane. Since PFS can remove COD and oil to certain degree, it can be used as an assisted treatment.Oil Filtration and Removal Experiment via Oil-Absorbing Blankets: The experiment shows that the oil-absorbing blankets are characterized with a remarkably high removal rate to the oil in the water. And, the oil volume can be reduced to 6.5mg/L.Activated Carbon Absorption Ball Neodymium Magnets Experiment: Activated carbon has been used as adsorbent in the experiment, the result of which shows that after the absorption, oil concentration was reduced below 0.2 mg/L, and that of COD below 10mg/L. It meets entirely the standard of the RO membrane on RO Influent water.Scale Inhibition Experiment: The wastewater concentration quadruples and no scale forms when 3.1mg/L membrane scale inhibitor (MDC220) is added in the wastewater. After the above-mentioned process, the quality of the treated wastewater meets the standard of the RO membrane. It indicates that the application of the cleaning solution in RO concentration of rare-earth ammonium chloride wastewater is feasible.Then, this paper elaborates on the design of the RO concentration system, and the validation of the RO Ball Neodymium Magnets parameter, the type, the number as well as the permutation and combination of the RO membrane.Finally, the RO concentration experiment based on the current ESPA1-4040 system has been conducted. The result shows that the maximum recycling rate of the two-section ESPA1-4040 RO system is 2.36%, which is far below the expected rate. Therefore, it is definitely not suitable for the RO concentration treatment of ammonium chloride wastewater. 更多还原
This paper is based on the research of the rare-earth chlorine ammonium wastewater treatment and recycling in Baotou, Inner Mongolia. The Rare-earth chlorine ammonium wastewater, including the mother liquor and cleaning solution, is formed in the production of unitary rare earth carbonate. In practice, many enterprises now directly evaporate and crystallize the mother liquor of high concentration for Ammonium chloride products. However, currently, there is no effective treatment available for the cleaning solution yet. Because of its large liquid volume, low concentration, and high energy consumption,when evaporated and crystallized, it will be too costly for the related enterprises. If untreated before discharged, the cleaning solution will pollute the Yellow River in Baotou. In the Ball Neodymium Magnets project in this paper, the technique of reverse osmosis (RO) concentration is adopted to concentrate and crystallize the cleaning solution.The RO membrane imposes high standards on the quality of the influent water. When it comes to how to prevent the RO membrane from being polluted and being blocked by the scales formed by calcium or magnesium ions in the after-concentration wastewater, it still remains a huge problem in the reverse osmosis concentration of rare-earth Ammonium chloride wastewater. The key to guarantee the long-term stability of RO technique lies in strict pre-cautions.
The RO pretreatment experiment introduced in this paper include mainly the following specific experiments:coagulation sedimentation experiment, oil filtration and removal experiment via oil-absorbing blanket, filtration experiment via dual-media filter feed,activated carbon absorption experiment, and scale inhibition experiment.Coagulation Sedimentation Experiment: The result shows that PFS, as its small but sufficient dosage is concerned, is obviously superior in removing turbidity and COD. Besides, the turbidity of the supernatant liquid is below 2.0 NTU, which meets the requirements of the RO membrane. Since PFS can remove COD and oil to certain degree, it can be used as an assisted treatment.Oil Filtration and Removal Experiment via Oil-Absorbing Blankets: The experiment shows that the oil-absorbing blankets are characterized with a remarkably high removal rate to the oil in the water. And, the oil volume can be reduced to 6.5mg/L.Activated Carbon Absorption Ball Neodymium Magnets Experiment: Activated carbon has been used as adsorbent in the experiment, the result of which shows that after the absorption, oil concentration was reduced below 0.2 mg/L, and that of COD below 10mg/L. It meets entirely the standard of the RO membrane on RO Influent water.Scale Inhibition Experiment: The wastewater concentration quadruples and no scale forms when 3.1mg/L membrane scale inhibitor (MDC220) is added in the wastewater. After the above-mentioned process, the quality of the treated wastewater meets the standard of the RO membrane. It indicates that the application of the cleaning solution in RO concentration of rare-earth ammonium chloride wastewater is feasible.Then, this paper elaborates on the design of the RO concentration system, and the validation of the RO Ball Neodymium Magnets parameter, the type, the number as well as the permutation and combination of the RO membrane.Finally, the RO concentration experiment based on the current ESPA1-4040 system has been conducted. The result shows that the maximum recycling rate of the two-section ESPA1-4040 RO system is 2.36%, which is far below the expected rate. Therefore, it is definitely not suitable for the RO concentration treatment of ammonium chloride wastewater. 更多还原
Research on High-Performance Wrought Magnesium-Rare Earth Alloys
Research on High-Performance Wrought Magnesium-Rare Earth Alloys
Magnesium alloys, as the lightest structural material in practical application, has achieved rapid development since coming out, attributing to its low density, high specific strength and specific rigidity, excellent damping capacity and electromagnetic shielding capacity, as well as recuperability. However, magnesium alloys are limited to be used at elevated temperature due to its poor mechanical properties. Mg-Al-Zn alloy system wrought magnesium alloys were reported to be the best candidate in practical use till now. Thus, it’s of great significance to research and develop a high Mechanical Properties magnesium alloy, serving for industry.In this dissertation, new magnesium alloys Mg-3Al-0.5Mn-1MM、Mg-3Al-0.5Zn-0.5Mn-1MM、Mg-2Al-0.5Mn-1MM、Mg-2Al-0.5Zn-0.5Mn-1MM、Mg-2Al-0.5Zn-0.5Mn-0.5MM are achieved by adding mischmetal(MM) on the Ball Neodymium Magnets basis of Mg-Al-Zn alloys are melted in electric resistance furnace and poured into steel mould, then select # 2 and # 4 alloys to rolling, extrusion deformation, heat treatment by annealing and aging treatment. This article studies effect of MM on solidification and microstructure, deformation capacities of as-cast alloys, mechanics property and fracture behavior of rolled and extruded alloy.The following are main studying content:(1) Selected alloy consisting of: Mg-2-3Al-0.5Mn-0~0.5Zn-0.5~1.0MM(2) Preparation of alloys, research on organization, structure, the composition of the precipitates, shape and distribution of as-cast, as-rolled, as-extruded and heat treatment states alloys.(3) Mechanical properties of the alloy, tensile fracture morphology observation and fracture mechanism analysis of the alloy for different states.(4) Mechanism of Rare Earth (MM) on the structure and properties of alloys, proposed alloy design. After research above, reach conclusions as fellow:As-cast alloys is composed ofα-Mg, pole-like Al4MM(MM is Ce、La) and grain-like Al10Ce2Mn7, In the Mg-3Al alloy system there are a small number of bone-likeβ-phase precipitates Mg17Al12.α-Mg crystal refines obviously and get coarse grain. Pole-like precipitates major segregate around the grain boundary as discontinuous eutectic structure, and grain-like precipitates are mainly distributed in the grain. Most of Zn dissolved into Ball Neodymium Magnets Mg matrix. The addition of MM, increased alloy solid-liquid phase temperature difference is conducive to the formation of segregation and composition undercooling.,MM enhanced crystallization rate in the process of nucleation, refine microstructure of as-cast alloy. And significantly enhanced mechanical properties of the alloy. The Mg-3Al-0.5Zn-0.5Mn-1MM and Mg-2Al-0.5Zn-0.5Mn-1MM alloy have outstanding performance particularly.In the process of rolling and extrusion deformation dynamic recrystallization phenomenon can be observed, grain size decreases, precipitates broken and uniformly distribute on the grain and the grain boundary.
In the annealing process after rolling, recovery and recrystallization phenomenon can be observed, and then grain grows. In the aging process after extrusion, there is little change on grain size. Aging strengthening is not obvious.After the deformation, the flow http://www.chinamagnets.biz/ stress of the alloy increase, thereby enabling alloy internal dislocation density increased significantly enhanced the strength of the alloy. In addition, at the room temperature, Al4MM and Al10Ce2Mn7 have higher hardness, under high temperature are stable phase, the second phase particles in the matrix surrounding the will bring uneven deformation, For the coordination uneven deformation in the second phase particles around Cypriot plot large dislocation, broken Al4MM and Al10Ce2Mn7 which distribute in the matrix will produce more dislocations, and further enhance the strength of alloy. MM phase can also be effective to inhibit grain growth in the process of crystallization, improve the mechanical properties of heat treatment alloy.After rolling, the max Vickers-hardness of Mg-3Al-0.5Zn-0.5Mn-1Ce(MM) alloy increases from 67HV to 92HV, the max ultimate tensile strength (UTS) and yield tensile strength (YTS) of rolled state alloys at room temperature are 301MPa and 228MPa, respectively, Annealed alloy strength decreased slightly, but a clear enhancement of elongation, reach 21%. For the Mg-2Al-0.5Zn-0.5Mn-1Ce(MM) alloy, the max Vickers-hardness increases from 63HV to 76HV after rolling, The UTS and YTS of rolled state alloys are 290MPa and 202MPa at room temperature, respectively, and the elongation after anneal treatment is 14%. Ball Neodymium Magnets Extruded alloy with higher tensile strength and elongation, but not rolling yield strength alloy state, only 100 MPa at room temperature.Fracture analysis showed that as-cast alloy fracture surface belong to quasi-cleavage fracture, exhibits obvious toughness characteristics. As to as-rolled alloys, its plasticity decreases, and fracture mechanism changes from mix fracture of intergranular fracture and cleavage fracture to quasi-cleavage fracture after annealed. A little number of MM added can increase the strength and plastic deformation of the matrix alloy, the second phase significantly enhanced role. 更多还原
Magnesium alloys, as the lightest structural material in practical application, has achieved rapid development since coming out, attributing to its low density, high specific strength and specific rigidity, excellent damping capacity and electromagnetic shielding capacity, as well as recuperability. However, magnesium alloys are limited to be used at elevated temperature due to its poor mechanical properties. Mg-Al-Zn alloy system wrought magnesium alloys were reported to be the best candidate in practical use till now. Thus, it’s of great significance to research and develop a high Mechanical Properties magnesium alloy, serving for industry.In this dissertation, new magnesium alloys Mg-3Al-0.5Mn-1MM、Mg-3Al-0.5Zn-0.5Mn-1MM、Mg-2Al-0.5Mn-1MM、Mg-2Al-0.5Zn-0.5Mn-1MM、Mg-2Al-0.5Zn-0.5Mn-0.5MM are achieved by adding mischmetal(MM) on the Ball Neodymium Magnets basis of Mg-Al-Zn alloys are melted in electric resistance furnace and poured into steel mould, then select # 2 and # 4 alloys to rolling, extrusion deformation, heat treatment by annealing and aging treatment. This article studies effect of MM on solidification and microstructure, deformation capacities of as-cast alloys, mechanics property and fracture behavior of rolled and extruded alloy.The following are main studying content:(1) Selected alloy consisting of: Mg-2-3Al-0.5Mn-0~0.5Zn-0.5~1.0MM(2) Preparation of alloys, research on organization, structure, the composition of the precipitates, shape and distribution of as-cast, as-rolled, as-extruded and heat treatment states alloys.(3) Mechanical properties of the alloy, tensile fracture morphology observation and fracture mechanism analysis of the alloy for different states.(4) Mechanism of Rare Earth (MM) on the structure and properties of alloys, proposed alloy design. After research above, reach conclusions as fellow:As-cast alloys is composed ofα-Mg, pole-like Al4MM(MM is Ce、La) and grain-like Al10Ce2Mn7, In the Mg-3Al alloy system there are a small number of bone-likeβ-phase precipitates Mg17Al12.α-Mg crystal refines obviously and get coarse grain. Pole-like precipitates major segregate around the grain boundary as discontinuous eutectic structure, and grain-like precipitates are mainly distributed in the grain. Most of Zn dissolved into Ball Neodymium Magnets Mg matrix. The addition of MM, increased alloy solid-liquid phase temperature difference is conducive to the formation of segregation and composition undercooling.,MM enhanced crystallization rate in the process of nucleation, refine microstructure of as-cast alloy. And significantly enhanced mechanical properties of the alloy. The Mg-3Al-0.5Zn-0.5Mn-1MM and Mg-2Al-0.5Zn-0.5Mn-1MM alloy have outstanding performance particularly.In the process of rolling and extrusion deformation dynamic recrystallization phenomenon can be observed, grain size decreases, precipitates broken and uniformly distribute on the grain and the grain boundary.
In the annealing process after rolling, recovery and recrystallization phenomenon can be observed, and then grain grows. In the aging process after extrusion, there is little change on grain size. Aging strengthening is not obvious.After the deformation, the flow http://www.chinamagnets.biz/ stress of the alloy increase, thereby enabling alloy internal dislocation density increased significantly enhanced the strength of the alloy. In addition, at the room temperature, Al4MM and Al10Ce2Mn7 have higher hardness, under high temperature are stable phase, the second phase particles in the matrix surrounding the will bring uneven deformation, For the coordination uneven deformation in the second phase particles around Cypriot plot large dislocation, broken Al4MM and Al10Ce2Mn7 which distribute in the matrix will produce more dislocations, and further enhance the strength of alloy. MM phase can also be effective to inhibit grain growth in the process of crystallization, improve the mechanical properties of heat treatment alloy.After rolling, the max Vickers-hardness of Mg-3Al-0.5Zn-0.5Mn-1Ce(MM) alloy increases from 67HV to 92HV, the max ultimate tensile strength (UTS) and yield tensile strength (YTS) of rolled state alloys at room temperature are 301MPa and 228MPa, respectively, Annealed alloy strength decreased slightly, but a clear enhancement of elongation, reach 21%. For the Mg-2Al-0.5Zn-0.5Mn-1Ce(MM) alloy, the max Vickers-hardness increases from 63HV to 76HV after rolling, The UTS and YTS of rolled state alloys are 290MPa and 202MPa at room temperature, respectively, and the elongation after anneal treatment is 14%. Ball Neodymium Magnets Extruded alloy with higher tensile strength and elongation, but not rolling yield strength alloy state, only 100 MPa at room temperature.Fracture analysis showed that as-cast alloy fracture surface belong to quasi-cleavage fracture, exhibits obvious toughness characteristics. As to as-rolled alloys, its plasticity decreases, and fracture mechanism changes from mix fracture of intergranular fracture and cleavage fracture to quasi-cleavage fracture after annealed. A little number of MM added can increase the strength and plastic deformation of the matrix alloy, the second phase significantly enhanced role. 更多还原
Evaluation of Economic Benefit Rare Earth PM Synchro Linear Motor Project
Evaluation of Economic Benefit Rare Earth PM Synchro Linear Motor Project
In the market economy system , as the principal part of market economy , corporations should not only catch the opportunity of investment and pursue the high profit, but also elusion or reduce the risk of investment , in order to make corporations develop unceasingly. So it is the guarantee of corporations investing project and advancing benefit that analyze economy benefit.This thesis , from the point of investor view, using the theory of project managment and economy benefit analytics , analyzes and studies the Rare Earth PM Synchro Linear motor Project of Harbin Tech.Full Industry Co. Ltd . The thesis analyzes the project’s economy environment , constructer ,Special shape NdFeB magnets manufacture means , finance, investment. The thesis uses the theory of profit and loss balance and economy sensitivity analytical method to quantitative analysze the risk of the Rare Earth PM Synchro Linear motor Project , and put forward the resolve measure.The thesis found the Rare Earth PM Synchro Linear motor Project economic benefit evaluation index system and the fuzzy multiple comprehensive assessment of economic benefit. and the paper use the theory to assesse the Rare Earth PM Synchro Linear motor Project. From the point of view of qualitative analysis and quantitative http://www.999magnet.com/ analysis , the investing decision-making of the project is scientific and exercisable. 更多还原
In the market economy system , as the principal part of market economy , corporations should not only catch the opportunity of investment and pursue the high profit, but also elusion or reduce the risk of investment , in order to make corporations develop unceasingly. So it is the guarantee of corporations investing project and advancing benefit that analyze economy benefit.This thesis , from the point of investor view, using the theory of project managment and economy benefit analytics , analyzes and studies the Rare Earth PM Synchro Linear motor Project of Harbin Tech.Full Industry Co. Ltd . The thesis analyzes the project’s economy environment , constructer ,Special shape NdFeB magnets manufacture means , finance, investment. The thesis uses the theory of profit and loss balance and economy sensitivity analytical method to quantitative analysze the risk of the Rare Earth PM Synchro Linear motor Project , and put forward the resolve measure.The thesis found the Rare Earth PM Synchro Linear motor Project economic benefit evaluation index system and the fuzzy multiple comprehensive assessment of economic benefit. and the paper use the theory to assesse the Rare Earth PM Synchro Linear motor Project. From the point of view of qualitative analysis and quantitative http://www.999magnet.com/ analysis , the investing decision-making of the project is scientific and exercisable. 更多还原
水溶液中电沉积Zn-Ni-RE合金镀层的工艺及机理研究
水溶液中电沉积Zn-Ni-RE合金镀层的工艺及机理研究
In this thesis, the process of electrodeposition of Zn-Ni-RE alloy from aqueous solution and its mechanism of co-deposition have been discussed in detail. It covered the following aspects:The author confirms the electrodeposition technology of Zn-Ni-RE alloy coatings, which is by using Hull trough experiment and rectangle alveus experiment to choose the bright area of the coatings. The technology conditions are: ZnCl2 15-35g/L, NiCl2·6H2O 30～70g/L, LaCl3-7H2O 2～10g/L,NH4Cl 80～120g/L, C6H8O7·H2O 15～35g/L, C6H5Na3O7·2H2O 25～45g/L, H3BO3 25g/L, proper addition, PH is 2.6 to 3.5,30minutes of electroplate time, Dk=2～4A/dm2of electric current density and 15～30℃temperature of electroplating solution.Researches on the process of electrodeposited Zn-Ni-RE alloy coatings indicated that alloy coatings with different contents could be Block Neodymium magnets obtained by means of appropriate parameters. The concentration of main-salt was the primary influence on the content of nickel in the alloy coatings. The adding of NiCl2·6H2O and LaCl3·7H2O could help to increase the content of nickel, while the adding of ZnCl2 helping to reduce the content of nickel. The adding of LaCl3·7H2O could help to increase the content of lanthanum, while the adding of NiCl2·6H2O and ZnCl2 have little effect to the content of lanthanum.
The adding of NH4Cl could help to increase the content of nickel. The adding of C6H8O7·H2O and C6H5Na3O7·2H2O helping to reduce the content of nickel, both of the two influence were weak; When the concentration was 20g/L and 30 g/L, the content of lanthanum was at the highest level. Increasing temperature could help to increase the content of nickel, but helping to reduce the content of lanthanum. Increasing the value of pH could increase the content of nickel, When the value of pH was 2.8 the content of lanthanum was maximal. Current density influenced the component of alloy coatings greatly. Increasing current density could help to increase the content of nickel, When current density was 3A/dm2 the content of lanthanum was maximal.Zn-Ni-RE’s anti-corrosion performance has been studied. The result is that the content of nickel in Zn-Ni(2%)-RE alloy coating’s is http://www.999magnet.com/ lesser than Zn-Ni(13%) alloy coating with equal anti-corrosion performance. The cost will be saved greatly.The cathodic polarization of Zn-Ni-RE alloy coatings obviously lower to the Zn-Ni alloy coatings, the curves of cathodic polarization were determined in the cell of three electrodes, the cathodic polarization of the electrodepositing process is increased due to occurring of LaCl3 special adsorption on electrode surface. Zn-Ni alloy coatings’ codeposition belonged to abnormal codeposition, which is proved by the method of cathodic polarization decomposition. The various characters of cathode polarization curve have been discussed while adding different quantity rare earth salt. The cathodic polarization of Zn-Ni-RE alloy coatings diminishingly when the adding of rare earth at a certain quantity. Mechanisms of Zn-Ni-RE’s co-deposition have been discussed.The mechanism of rare-earth conversion coatings was eondueted to study the corrosive resistance of the coating, as well as polarization resistance and corrosion current of coatings in 5% NaCl solutionhave been determined by electrochemical method, and XRD was used to analyze the products of corrosion.
In this thesis, the process of electrodeposition of Zn-Ni-RE alloy from aqueous solution and its mechanism of co-deposition have been discussed in detail. It covered the following aspects:The author confirms the electrodeposition technology of Zn-Ni-RE alloy coatings, which is by using Hull trough experiment and rectangle alveus experiment to choose the bright area of the coatings. The technology conditions are: ZnCl2 15-35g/L, NiCl2·6H2O 30～70g/L, LaCl3-7H2O 2～10g/L,NH4Cl 80～120g/L, C6H8O7·H2O 15～35g/L, C6H5Na3O7·2H2O 25～45g/L, H3BO3 25g/L, proper addition, PH is 2.6 to 3.5,30minutes of electroplate time, Dk=2～4A/dm2of electric current density and 15～30℃temperature of electroplating solution.Researches on the process of electrodeposited Zn-Ni-RE alloy coatings indicated that alloy coatings with different contents could be Block Neodymium magnets obtained by means of appropriate parameters. The concentration of main-salt was the primary influence on the content of nickel in the alloy coatings. The adding of NiCl2·6H2O and LaCl3·7H2O could help to increase the content of nickel, while the adding of ZnCl2 helping to reduce the content of nickel. The adding of LaCl3·7H2O could help to increase the content of lanthanum, while the adding of NiCl2·6H2O and ZnCl2 have little effect to the content of lanthanum.
The adding of NH4Cl could help to increase the content of nickel. The adding of C6H8O7·H2O and C6H5Na3O7·2H2O helping to reduce the content of nickel, both of the two influence were weak; When the concentration was 20g/L and 30 g/L, the content of lanthanum was at the highest level. Increasing temperature could help to increase the content of nickel, but helping to reduce the content of lanthanum. Increasing the value of pH could increase the content of nickel, When the value of pH was 2.8 the content of lanthanum was maximal. Current density influenced the component of alloy coatings greatly. Increasing current density could help to increase the content of nickel, When current density was 3A/dm2 the content of lanthanum was maximal.Zn-Ni-RE’s anti-corrosion performance has been studied. The result is that the content of nickel in Zn-Ni(2%)-RE alloy coating’s is http://www.999magnet.com/ lesser than Zn-Ni(13%) alloy coating with equal anti-corrosion performance. The cost will be saved greatly.The cathodic polarization of Zn-Ni-RE alloy coatings obviously lower to the Zn-Ni alloy coatings, the curves of cathodic polarization were determined in the cell of three electrodes, the cathodic polarization of the electrodepositing process is increased due to occurring of LaCl3 special adsorption on electrode surface. Zn-Ni alloy coatings’ codeposition belonged to abnormal codeposition, which is proved by the method of cathodic polarization decomposition. The various characters of cathode polarization curve have been discussed while adding different quantity rare earth salt. The cathodic polarization of Zn-Ni-RE alloy coatings diminishingly when the adding of rare earth at a certain quantity. Mechanisms of Zn-Ni-RE’s co-deposition have been discussed.The mechanism of rare-earth conversion coatings was eondueted to study the corrosive resistance of the coating, as well as polarization resistance and corrosion current of coatings in 5% NaCl solutionhave been determined by electrochemical method, and XRD was used to analyze the products of corrosion.
Research on Microstructure and Properties of Mg-Y-Nd Alloys
Research on Microstructure and Properties of Mg-Y-Nd Alloys
Magnesium alloys with high strength and stiffness, damping properties and machinability such advantage as a result of being a focus in the field of material science. However, the development and application has been restricted because of its oxidation easy, poor corrosion resistance, low high-temperature strength and creep resistance. Rare-earth metal is considered to be one of the most effective and valuable elements in the field of improving the high-temperature mechanical properties and corrosion resistance of Magnesium alloys. Therefore, the development of rare earth metal used in magnesium alloys has become the majority of workers interested in the subject.In all the rare earth elements, Y is considered to be most effective elements to improve high-temperature properties of magnesium alloys, and the Nd can be made of magnesium alloys in high temperature and room temperature the same time intensify. This article based on the study of high-performance Mg-Y-Nd Segment neodymium magnets alloys. Systematic study has been done of microstructure, room temperature and high temperature mechanical properties of cast and aging Mg-Y-Nd alloys, and dry sliding friction and wear properties and corrosion of aging Mg-Y-Nd alloys. The most widely used alloys AZ91 are selected as a contrast in performance tests. Come to the following conclusions:⒈Rare earth elements Y, Nd can refine grain. In the solidification process, Y and Nd atoms are concentrated in the crystalα-Mg surface, and will prevent grain from further growing . In the cast Mg-Y-Nd alloy, new phases made up of Mg24Y5 and Mg12Nd precipitate into reticular in grain boundary. And there is a small precipitation within crystal. After solution and aging treatment, there are large granular new phase Mg24Y5 and Mg12Nd2Y precipitated within crystal. Thermodynamic analysis found that the new phase has a higher melting point.⒉Cast and aging Mg-Y-Nd alloys have excellent mechanical properties both at room temperature and high temperature. The ultimate tensile strength and elongation of cast and aging Mg-Y-Nd alloys at room temperature and high temperature of 200°C is higher than AZ91 alloy at room temperature and 150°C. The aging Mg-Y-Nd alloys http://www.999magnet.com/ have higher strength and better plasticity than cast alloys at the same experimental conditions.⒊The fracture surface of cast and aging Mg-Y-Nd alloys is mixed with cleavage fracture and toughness fracture at room temperature. And the fracture mode changes to the toughness fracture with the rising temperature.⒋In experimental conditions, aging Mg-Y-Nd alloys and AZ91 alloys both have occurred changes from minor wear (mainly oxidation wear, abrasive wear and minor delamination wear) to serious wear (mainly serious delamination wear and fusion wear). Rare earth elements Y, Nd increase stability of oxide film covered on the wear surface, and improve the carrying capacity of Magnesium alloys. Segment neodymium magnets All of those delayed changes from minor wear to serious wear effectively. This also proves aging Mg-Y-Nd alloys have superior wear-resistance to AZ91 alloys.⒌Under the same corrosion conditions, aging Mg-Y-Nd alloys have superior corrosion-resistance to AZ91 alloys. On one hand, the corrosion resistance ofα-Mg solid solution with Al is far poor thanα-Mg solid solution with rare earth elements Y, Nd. On the other hand, rare earth phases dispersed within grains prevent corrosion from developing deeply. 更多还原
Magnesium alloys with high strength and stiffness, damping properties and machinability such advantage as a result of being a focus in the field of material science. However, the development and application has been restricted because of its oxidation easy, poor corrosion resistance, low high-temperature strength and creep resistance. Rare-earth metal is considered to be one of the most effective and valuable elements in the field of improving the high-temperature mechanical properties and corrosion resistance of Magnesium alloys. Therefore, the development of rare earth metal used in magnesium alloys has become the majority of workers interested in the subject.In all the rare earth elements, Y is considered to be most effective elements to improve high-temperature properties of magnesium alloys, and the Nd can be made of magnesium alloys in high temperature and room temperature the same time intensify. This article based on the study of high-performance Mg-Y-Nd Segment neodymium magnets alloys. Systematic study has been done of microstructure, room temperature and high temperature mechanical properties of cast and aging Mg-Y-Nd alloys, and dry sliding friction and wear properties and corrosion of aging Mg-Y-Nd alloys. The most widely used alloys AZ91 are selected as a contrast in performance tests. Come to the following conclusions:⒈Rare earth elements Y, Nd can refine grain. In the solidification process, Y and Nd atoms are concentrated in the crystalα-Mg surface, and will prevent grain from further growing . In the cast Mg-Y-Nd alloy, new phases made up of Mg24Y5 and Mg12Nd precipitate into reticular in grain boundary. And there is a small precipitation within crystal. After solution and aging treatment, there are large granular new phase Mg24Y5 and Mg12Nd2Y precipitated within crystal. Thermodynamic analysis found that the new phase has a higher melting point.⒉Cast and aging Mg-Y-Nd alloys have excellent mechanical properties both at room temperature and high temperature. The ultimate tensile strength and elongation of cast and aging Mg-Y-Nd alloys at room temperature and high temperature of 200°C is higher than AZ91 alloy at room temperature and 150°C. The aging Mg-Y-Nd alloys http://www.999magnet.com/ have higher strength and better plasticity than cast alloys at the same experimental conditions.⒊The fracture surface of cast and aging Mg-Y-Nd alloys is mixed with cleavage fracture and toughness fracture at room temperature. And the fracture mode changes to the toughness fracture with the rising temperature.⒋In experimental conditions, aging Mg-Y-Nd alloys and AZ91 alloys both have occurred changes from minor wear (mainly oxidation wear, abrasive wear and minor delamination wear) to serious wear (mainly serious delamination wear and fusion wear). Rare earth elements Y, Nd increase stability of oxide film covered on the wear surface, and improve the carrying capacity of Magnesium alloys. Segment neodymium magnets All of those delayed changes from minor wear to serious wear effectively. This also proves aging Mg-Y-Nd alloys have superior wear-resistance to AZ91 alloys.⒌Under the same corrosion conditions, aging Mg-Y-Nd alloys have superior corrosion-resistance to AZ91 alloys. On one hand, the corrosion resistance ofα-Mg solid solution with Al is far poor thanα-Mg solid solution with rare earth elements Y, Nd. On the other hand, rare earth phases dispersed within grains prevent corrosion from developing deeply. 更多还原
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