Dissertation > Excellent graduate degree dissertation topics show

Anisotropy Nd-Fe-B Magnetic Powders Made from SC-HDDR Process

Author: YangWu
Tutor: GaoRuWei
School: Shandong University
Course: Condensed Matter Physics
Keywords: HDDR process anisotropy microstructure magnetic properties Nd-Fe-B
CLC: TM273
Type: Master's thesis
Year: 2009
Downloads: 109
Quote: 0
Read: Download Dissertation

Abstract


Nd-Fe-B magnet is widely used in all fields of modern science and technology, such as computer technology,information technology,communication and transportation technology,aviation and space technology,office automatization,civil appliances and health care technology etc.Based on the different producing processes, the Nd-Fe-B magnet can be classified as sintered magnet and bonded magnet.The investigation and development status of Nd-Fe-B bonded magnet have been synthetically commented in this paper.We adopted new SC-HDDR preparing procedure,regulated process parameters,and greatly improved the hard magnetic property of magnets.Our main studying works are as follows:1.Effect of preparing processes of Strip Casting（SC ） technique on the alignment degree and microstructure of casting flakes.1) The flakes produced by SC technique are mainly composed of 2:14:1 strip grains and exist apparent alignment along[00L].Both the cooling surface and the free surface of flakes prepared at different wheel speeds were analyzed by XRD.The alignment degree changes with the wheel speed.The alignment degree reached maximum when the wheel speed V is 3-4m/s.2) The microstructure of the flakes was investigated by backscattered scanning microscope.The influence of solidification rate（wheel speed） on the microstmcture of flakes was studied.The experimental results show that when the wheel speed is too low,the soft magnetic phaseα-Fe will be appeared in the flakes and apparently decrease the hard magnetic properties.When the wheel speed is too high,the over-small isometric grains are formed on the cooling surface,and the Nd-rich phase distribution are un-homogenous,and also decrease the hard magnetic properties.The best wheel speed is about 3m/s.The Nd2Fe14B main phase strip grains are about 3～5μm in mean width,and Nd-rich phase with thickness of 0.1～0.2μm distributed uniformly along the boundaries of fine strip grains of matrix phase.The grain distributions of main phase and Nd-rich phase are homogeneous.This flake is the ideal starting material for preparing bonded magnet with high hard magnetic:property.2.Effect of HDDR processe parameters on the magnetic properties of magnetic powders.1) The effects of time,temperature and pressure of HD stage on the properties of Nd-Fe-B magnetic powders.HD treatment is the procedure of hydrogenation and decomposition of Nd-Fe-B based phase compounds.HD stage influences hydrogenation and decomposition condition of the main phase and the rich-Nd phase.The different values of time, temperature and pressure in HD stage are carried on.The experiment shows that the optimal HD technology parameters are 40min,820℃and 0.8bar,respectively.The corresponding magnetic properties are as follows,Hcj=645.5 KA/m,Br=1.18T,（BH） max=165 KJ/m3,Br/Bs =0.8022) The effects of time,temperature and pressure of DR stages on the properties of Nd-Fe-B magnetic powders.DR treatment is the procedure of desorption and recombination of materials.The treatment conditions have great impact on the magnetic properties of materials.The different values of time,temperature and pressure in DR stage were carried on.The experiment shows that the optimal DR technology parameters are 1.5h,840℃and (0.3bar + 5×10-3pa),respectively.The corresponding magnetic properties are as follows,Hcj=810kA/m,Br=1.24T,（BH）max= 195 kJ/m3,Br/Bs=0.841.

Related Dissertations

  1. Reactive Hot-Pressing and Mechanical Properties of （ZrB2-ZrO2）/BN Composites,TB332
  2. Microstructure and Mechanical Properties of Mg-Zn-Y-Zr Alloys,TG146.22
  3. Investigation on Microstructure and Properties of Cadmium-Free Silver-Based Intermediate Temperature Filler Metals,TG425.2
  4. Research on Technology and Mechanism of Joining Cemented Carbide to Carbon Steel,TG454
  5. The Investigations on the Characteristics and Mechanism of NIR Emission from Bi-doped Silicophosphate Glasses,TQ171.1
  6. Preliminary Study on Salt-Tolerant Mechanism of the New Pennisetum Purpereum Schumach Variety-Sumu No.2,S543.9
  7. Study on the Fine Structure of Intestine and Intestinal Mucosal Barrier in Zebrfish (Brachydanio Rerio),Q95-33
  8. Study on Characteristics of Morphology Anatomy and Physio-Biochemistry of Two Ecotype Varieties Cucumber Leggy Seedilings,S642.2
  9. Study on the Mechanism of Heat-Induced Gelation of Myofibrillar Proteins,TS251.1
  10. Studies on the Aggregation and Microstructure of Imidazolium Ionic Liquids in Solutions,O645.1
  11. 1,3 - propanediamine shrink o-vanillin 3d-4f heteronuclear bimetallic complexes synthesis, structure and properties of,O627.3
  12. Studies of Luminescence Characteristics of Eu3+-doped Rare Earth Borates REBaB9O16 （RE=rare Earth Ions and Y）,O627.3
  13. The Research on Extrusion Parameters Through the Plate Billet of Magnesium Alloy,TG379
  14. The Study on Strain Distributions and Equilibrium Morphologies of Anisotropic Quantum Dots,O471.1
  15. Study on Stock Price Behavior Around Periodical Reports Based on Asymmetric Information,F832.51
  16. Research on Processings and Microstructure and Properties of HRB400MPa,TG335
  17. Study of Performance of Cordierite Combined Mullite Products,TQ175.71
  18. Effect of Adding ZrO 2 Nanopowder on Microstructure and Mechanical Properties of Carbon Steel,TB383.1
  19. Effect of Cholesterol on Liposome Membrane Bilayer Structure、Liposome Properties and Function,TB383.2
  20. Evaluation of Material Mechanical Properties by Small Punch Test at Low Temperatures,TG115.5
  21. The Broussonetia papyrifera fiber structure and properties of microwave - assisted the degumming process parameters optimization,TS123

CLC: > Industrial Technology > Electrotechnical > Electrical materials > Magnetic materials,ferrite > Permanent magnet materials, permanent magnet
© 2012 www.DissertationTopic.Net  Mobile