Dissertation > Excellent graduate degree dissertation topics show

Study on the Corrosion Characteristics and Protection of Nd-Fe-B Sintered Magnets

Author: DuZhouYun
Tutor: JiangLiQiang
School: Zhejiang University of Technology
Course: Materials Science
Keywords: Sintered Nd-Fe-B magnets Remanence Phosphide Pulse plating Layers of sacrificial anode
CLC: TG174.4
Type: Master's thesis
Year: 2009
Downloads: 69
Quote: 0
Read: Download Dissertation

Abstract


The third generation of rare earth permanent magnet alloy Nd-Fe-B with its excellent magnetic properties and relatively low price, is widely used in electrical, instrumentation, and magnetic resonance imaging and other fields. However, Nd-Fe-B alloy chemical stability is poor, in everyday use conditions prone to oxidation, electrochemical corrosion occurs when severe, which have hindered the expansion of its scope of application. This paper reviews recent sintered Nd-Fe-B magnets corrosion mechanism and protective treatment study, based on the study of sintered Nd-Fe-B magnets in common acid Corrosion behavior and sintered Nd- Fe-B magnets coated phosphate coating and electroplating Cu / Ni composite layer, in order to improve the corrosion resistance of the magnet. By scanning electron microscopy, electrochemical methods, corrosion weight loss method, spectrum analyzers, X-ray diffraction, neutral salt spray test other analytical instruments and means, the system of sintering Nd-Fe-B magnets corrosion in acid medium characteristics and mechanisms of phosphate film formation process and mechanism and electroplating system, electroplating method, electroplating layer structure for sintered Nd-Fe-B magnets corrosion effects. The main results are as follows: No magnetized sintered Nd-Fe-B magnets in hydrochloric acid and sulfuric acid corrosion rate of the largest in the phosphoric acid and oxalic acid medium was passivated state, in a variety of acid etched surface of micron scale is more rough, surface cleaning effect of nitric acid which is better, the corrosion rate is moderate, the most suitable sintered Nd-Fe-B magnets pretreatment rust remover. Remanence does not change sintered Nd-Fe-B magnets in various media electrochemical reaction mechanism, the active medium of sulfuric acid and sodium chloride to improve the residual magnetic field of the sintered Nd-Fe-B magnets corrosion rate, which is due to residual Magnetic promote occlusion of a self catalytic corrosion cell formation; phosphoric acid and sodium hydroxide in the medium due to the passivation film is formed, reduces residual magnetic field of the sintered Nd-Fe-B magnets corrosion rate. Residual magnetic field will change the electric double layer structure, resulting in the generation of magneto overpotential, thus affecting the sintered Nd-Fe-B magnets electrochemical corrosion. Temperature phosphating treatment Nd-Fe-B sintered permanent magnet surface, the results showed that: the phosphate film on the sintered Nd-Fe-B permanent magnet and coated on the substrate pores filled, so that the sample after anti-phosphate corrosion has been significantly improved. Intergranular phase Nd phosphide GaP films were significantly greater than the primary crystal phase content; intergranular phase phosphate film thickness thicker than the main phase. HR Pulse pre-plated copper layer optimum process is 15% duty cycle, pulse frequency 5000HZ, this process can be obtained under good corrosion resistance, high (111) preferred orientation of the copper plating. In pulse Cu / dark Ni / DC Cu / Dark Ni / Ni plating bright structure, porosity layers covering each other the best performance, the role of sacrificial anode layers of sintered Nd-Fe-B magnets optimal corrosion: corrosion potential positive shift than the matrix around nearly 1200mV, resistance to neutral salt spray corrosion time reaches 386 hours.

Related Dissertations

  1. Research on High-precision Measurement and Modeling of High Voltage Electric Transformers,TM452
  2. Research and Design of a Security SRAM Testing System Based on FPGA,TP333.8
  3. Role in the regulation of the coupling between the Co / Cu multilayer film,O482.54
  4. Effect of Support Calcination Temperature on Structure and Performance of Al2O3-Supported Nickel Phosphide Catalysts,O643.36
  5. Synthesis, Characterization of Transition Metal Phosphides and Their Applications in Hydrazine Decomposition,O643.36
  6. Control the synthesis and study of the boride , nitride and phosphide nanomaterials,TB383.1
  7. Paleomagnetic study of the upper Devonian and Lower Carboniferous carbonates near JiangYou, Sichuan,South China Block,P318
  8. Synthesis, Modification and Hydrotreating Performances of Nickel Phosphide and Molybdenum Phosphide Catalysts,TE624.93
  9. MOCVD Growth and Characterization of Self-catalyzed InP Nanowires,TB383.1
  10. Panzhihua Iron and Steel cold rolled products in the coating process , the environmental performance of,TG335
  11. The Industrial Pollution of Phosphorus in the Wuyi River Valley and Its Treatment Measures,X522
  12. Development and Application of Compound Corrosion Inhibitor,TG174.42
  13. Monte Carlo Simulation of Electron Transport Properties in Ⅲ-Ⅴ Compound Semiconductors,O472
  14. Analysis of Mounted Resonant Frequency of Piezo-electricAcceleration Sensor and Its Application,TH824.4
  15. Studying of Steel Zn-Fe System Phosphating and Coverage Technology at Room Temperature,TG174
  16. Study on DSP-Controlled Switching No-Load Power Transformer,TM41
  17. Some Researches on Electroplating Grinding Wheel with 3D Controlled Distributing of Multi-layer Abrasives,TG743
  18. Structure and Magnetic Properties of Co and Co-Fe、Co-Cu Nanowire Arrays,TB383
  19. Study on Crystallization Mechanism of Li2O-Al2O3-SiO2 Glass-Ceramic Containing Fluoride and Phosphide,TQ171
  20. Micromagnetic exchange coupled hard / soft magnetic multilayers system,TM271
  21. Study on the Hydrodesulfurization and Hydrodenitrogenation Activities of Supported Tungsten Phosphide Catalysts,O643.32

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology
© 2012 www.DissertationTopic.Net  Mobile