Preparation of Nd-Fe-B based magnetic materials by soft chemistry and reduction-diffusion process

Lin, Jianhua; Liu, S.F.; Cheng, Qiang; Qian, Xin; Yang, Lihua; Su, Mian-Zeng

doi:10.1016/s0925-8388(96)02741-7

Cited by 37 publications

(15 citation statements)

References 11 publications

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“…The compact was used for Ca reduction and diffusion, which was proceeded under a flowing Ar atmosphere at 1000°C for 2 h. All constituents were reduced and transformed into alloy particles by the solid-state diffusion. 14,19,21 The recovered Nd 2 Fe 14 B particles are sphere shaped with mean particle size of <1 micron [ Fig. 2(d)], which was in a loose state interspersed with fine particles of the by-product CaO.…”

Section: Resultsmentioning

confidence: 99%

“…[11][12][13][14][15][16] It has been proven that the R/D process has many advantages in energy consumption and the production cost due to use of inexpensive rare-earth oxides as raw materials. In an attempt to fabricate the Nd-Fe-B magnets, all components may be added in the forms of Nd 2 O 3 , [17][18][19] 19 Granular calcium or CaH 2 was used as a reduction agent, while CaCl 2 was also added to improve the disintegration of compacts. 10,18,22 Lin et al 19 developed a novel route to prepare alloy particles by using both soft chemistry and R/D processes.…”

Section: Introductionmentioning

confidence: 99%

“…In an attempt to fabricate the Nd-Fe-B magnets, all components may be added in the forms of Nd 2 O 3 , [17][18][19] 19 Granular calcium or CaH 2 was used as a reduction agent, while CaCl 2 was also added to improve the disintegration of compacts. 10,18,22 Lin et al 19 developed a novel route to prepare alloy particles by using both soft chemistry and R/D processes. The basic idea of this preparation strategy was that, to avoid the use of mechanical milling, superfine precursors, such as rare-earth oxides and transition metals, were used in the R/D reactions.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

et al. 2001

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The magnetic Nd-Fe-B powders were prepared by a mechanochemical method, including the processes of spray drying, debinding, milling, H 2 reduction, Ca reduction, and washing. The liquid solution dissolved with various metal salts was first spray-dried to prepare the precursor powders having uniformly dispersed Nd, Fe, and B components. The precursor powders in turn were subjected to the subsequent processes. The particle size of the resultant Nd-Fe-B powders was about 1 m. Effects of the process parameters on phases, morphologies, microstructures, compositions, and thermal properties of the powders were investigated.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

et al. 2001

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“…Researchers have attempted to use the wet chemical approach to synthesize Nd2Fe14B [86][87][88]. Haik and others synthesized Nd-Fe-B NPs by this method [88].…”

Section: Solution Based Chemical Processingmentioning

confidence: 99%

“…Inspired by the chemical synthesis of Sm-Co magnets, researchers attempted to employ the wet chemical approaches to synthesize Nd2Fe14B nanoparticles [86][87][88] [91].…”

Section: Reduction Diffusionmentioning

confidence: 99%

Microwave processing of Nd-Fe-Co-B magnetic materials

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Numerous studies have been performed in the field of Nd-Fe-B based permanent magnets since they possess excellent hard magnetic properties. The magnetic properties are closely related to the structure, phases present, processing route etc. High performance hard magnets can obtain their desired large energy product by interaction of magnetic moments at the nanoscale. Therefore, developing nanostructured Nd-Fe-B based magnets requires the study of novel synthesis techniques, microstructure and properties. Conventional physical techniques have limitations of inhomogeneity, contamination, poor control of microstructure and high cost due to the use of elemental rare earth metals. On the other hand, bottom-up chemical methods offer better control of structure at the nanoscale. The use of metal salts as precursors significantly reduces the cost. Hence, a cost-effective, bottom-up, microwave synthesis method is promising to produce homogenous particles by uniform microwave heating. The main objective of this project is the study of the microwave synthesis of Nd-Fe-B based magnets. The processing parameters, reaction mechanisms, characterization and property evaluation of these materials were carried out. Nanostructured Nd-Fe-B particles were prepared by microwave combustion and reduction diffusion. Microwave combustion resulted in a transformation from metal salts to mixed metal oxides consisting of CoFe2O4, NdFeO3, Nd3FeO6 and Fe2O3. Nd2(Fe,Co)14B nanoparticles were obtained by the reduction diffusion process, in which the mixed metal oxide was reduced by CaH2. The effects of processing parameters on properties and structure were studied. It was found that the structure and magnetic properties can be controlled by the microwave power. Higher microwave power resulted in larger grain size. The coercivity of the particles increased from ~ 6 kOe to ~9 kOe when the grain size increased from ~ 20 nm to ~ 60 nm. A range of reduction-diffusion annealing times was also tested. The highest energy product was obtained for reduction diffusion at 800 °C for 2 h. The CaO byproduct was removed by different chemicals. The optimum chemical was found to be NH4Cl (dissolved in methanol), which eliminated the use of water, thus avoiding the vigorous reaction between CaO and water.

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ChemInform Abstract: Preparation of Nd‐Fe‐B Based Magnetic Materials by Soft Chemistry and Reduction‐Diffusion Process.

et al. 1997

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Preparation of Nd-Fe-B Based Magnetic Materials by Soft Chemistry and Reduction-Diffusion Process.-Crystalline powders of the alloys Nd2Fe14B and Nd2Fe12Co2B exhibiting strong magnetic anisotropy are prepared by reduction-diffusion reactions at 930 • C for 2-4 h under Ar of Fe10B0.25 and Co2.0B1. 2 alloy powders, resp., Fe metal, and Nd2O3 powders. Superfine powders of the precursors Nd2O3 and Fe2O3 are prepared by a polymer-network gel method and Fe2O3 is reduced 2 h at 700 • C under Ar-H2 to the metallic state. By this method the particle size of the magnetic materials can be controlled to a few microns. -(LIN, J. H.; LIU, S. F.; CHENG, Q. M.; QIAN, X. L.; YANG, L. Q.; SU, M. Z.; J.

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Preparation of Nd-Fe-B based magnetic materials by soft chemistry and reduction-diffusion process

Cited by 37 publications

References 11 publications

Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

Microwave processing of Nd-Fe-Co-B magnetic materials

ChemInform Abstract: Preparation of Nd‐Fe‐B Based Magnetic Materials by Soft Chemistry and Reduction‐Diffusion Process.

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Preparation of Nd-Fe-B based magnetic materials by soft chemistry and reduction-diffusion process

Cited by 37 publications

References 11 publications

Synthesis of Nd2Fe14B powders by spray-drying and reduction–diffusion processes

Synthesis of Nd2Fe14B powders by spray-drying and reduction–diffusion processes

Microwave processing of Nd-Fe-Co-B magnetic materials

ChemInform Abstract: Preparation of Nd‐Fe‐B Based Magnetic Materials by Soft Chemistry and Reduction‐Diffusion Process.

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Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes