Oxidation Properties of Silver Alloy Powders and Microstructures of Oxidized Powders for Making Electrical Contact Composites

ＯｘｉｄａｔｉｏｎＰｒｏｐｅｒｔｉｅｓｏｆＳｉｌｖｅｒＡｌｏｙＰｏｗｄｅｒｓａｎｄＭｉｃｒｏｓｔｒｕｃｔｕｒｅｓｏｆＯｘｉｄｉｚｅｄＰｏｗｄｅｒｓｆｏｒＭａｋｉｎｇＥｌｅｃｔｒｉｃａｌＣｏｎｔａｃｔＣｏｍｐｏｓｉｔｅｓＺｈｏｕＪｉｋｏｕ（周继扣），Ｍ...     

Magnetic Properties of Nanocrystalline Powder Cores Using Mechanically Crushed Powders

Toroidal shape FeCuNbSiB nanocrystalline alloy powder cores were prepared by cold pressing using me- chanically crushed and ball-milled powders, respectively. The morphologies and their effects on the magnetic proper- ties of the compacted cores were investigated. Compared with ball-milled powders, mechanically crushed ones have more regular shapes and rounder edges, which lead to better inter-particle insulation. FeCuNbSiB nanocrystalline al- loy powder cores fabricated from mechanically crushed powders exhibit remarkably lower core loss of about 248.2 kW/m3 at 100 kHz for maximum flux density Bm 0.1 T, and more stable permeability up to 10 MHz. Moreover, the dc-bias property could be improved significantly using mechanically crushed powders.     

Thermodynamic Properties of FeCN and FeCBN Melts

The saturated solubility of carbon and nitrogen in FeCN and FeCBN melts was measured experimentally at 1 485 ℃ to obtain the activity interaction coefficients between components in these melts. A new method was used to treat experimental results. Using thermodynamic derivation and calculation, some important interaction coefficients between components in these melts were obtained.     

Magnetic Properties of Nd-Fe-B Sintered Magnet Powders Recovered by Yb Metal Vapor Sorption

Fine ground powders of Nd-Fe-B sintered magnet bulks(particle size=46～125 μm in diameter) were coated and alloyed with Yb metal by sorbing them. A significant recovery of the decreased magnetic properties of the ground powders(remanence Br=～0.95 T, coercivity Hcj =～227 kA·m-1 and maximum energy product(BH)max=～48.8 kJ·m-3) was observed in accordance with increasing temperature up to 800 ℃. The sorbing temperature and time for Yb metal vapor were optimized and after heating at 800 ℃ for 90 min and annealing subsequently at 610 ℃ for 60 min, the Br, Hcj and(BH)max values were increased to be 0.98 T, 712 kA·m-1 and 173 kJ·m-3, respectively. From the microstructural characterizations of resulting samples by using X-ray diffraction(XRD), scanning electron microscopy(SEM), and electron probe X-ray microanalyzer(EPMA), it is found that the sorbed Yb metal uniformly covers the surface and diffuses to the Nd-rich grain boundary of fine ground powders of Nd-Fe-B sintered magnet bulks forming a(Nd,Yb)Fe2 phase.     

Thermodynamic Properties of Carbon and Manganese in MnC and MnFeC Melts

Carbon solubility in MnFe melts (xMn=0083-0706, xFe=0034-0715) was measured experimentally at various temperatures. By thermodynamic derivation and calculation, the relationship between activity coefficient of carbon in infinite dilute solution of manganese in MnC system and temperature was obtained. Using GibbsDuhem relationship, the experimental results of this study, and experimental data obtained by strict thermodynamic derivation and calculation in references, the relationships between other thermodynamic properties (εCC, εCCC, εCFe, εCCFe, and εCFeFe) in MnFeC system and temperature were obtained.     

Model of Calculating Activity of Nitrogen and Vanadium in FeCVN Molten Metal

The solubility of nitrogen in the FeCVN system was measured at 1 708 K and the model of calculating activity (action concentration) of nitrogen (N) and vanadium (V) was derived according to the phase diagram and the coexistence theory of the metal melt structure. The solubility expression of nitrogen in the FeCVN system at 1 708 K was wN=0058 194-0010 367wC+0005 543 4wV. Comparing the computing results with the experimental results, a satisfactory conclusion could be obtained. The analysis of the FeCVN system using this model showed that VN was present in a high temperature metal melt, which would reduce the action concentration of nitrogen obviously. It was consequently disadvantageous to the removal of nitrogen from hot metal.     

Preparation and Gas-Sensing Properties of NdFeO_3 Nanocrystalline

H2 Sisakindofdeadlypoisonousgaswhichex istsextensivelyinpetroleumandchemicalengineeringproductionline .Itsmassconcentrationintheairisre strictedbelow 0 .0 1mg·dm- 3inindustry (≈ 7× 10 - 4volumefraction) [1] .AcertainquantityofH2 SintheLPG (liquefiedpetroleumgas)resultsinthecontainerinvalidatingeasily (Nationalstandardisthatthecon tentofH2 SintheLPGcannotexceed 340× 10 - 6 vol umefraction) [2 ] .ThecontentofH2 Sinsomemineraldepositsisinconnectionwiththetypeofmineralde posits[3] ,soitc…     

Preparation and Photocatalytic Activity of Nanocrystalline GdFeO3

Photocatalytic reactions at semiconductor particleshave been the focus of numerous investigations in re-cent years ,since their applicationresults inthe quan-titative degradation of a large number of chemical con-taminants . Of many semiconductor oxides , TiO2hasbeen provento be the benchmark photocatalyst for ef-fective degradation of organic pollutants ,pri marily be-cause of its optical and electronic properties ,lowcost ,chemical stability and non-toxicity .However ,sinceitsband-gapis larg…     

Effect of Additive Cu10Sn Alloy on Sintering Behavior of Elemental Powders in Composition of 465 Stainless Steel

 The addition of Cu 10Sn alloy for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated include the sintering temperature, the sintering time, and the mass percent of Cu 10Sn. For vacuum sintering, effective sintering occurs at temperature between 1 250 ℃ and 1 300 ℃. The maximum sintered density was achieved at 1 300 ℃ for 60 min with 3% (in mass percent) Cu 10Sn alloy. More than 3% (in mass percent) Cu 10Sn content and temperature above 1 300 ℃ caused slumping of the samples. A maximum density of 74 g/cm3 was achieved with 3% (in mass percent) Cu 10Sn content at a sintering temperature of 1 300 ℃ for 60 min. A maximum ultimate tensile strength (UTS) of 517 MPa was achieved with 3% (in mass percent) Cu 10Sn content. With content higher than 2% (in mass percent) Cu 10Sn, a maximum increase in the density was observed. The fracture morphologies of the sintered samples are also reported.     

纳米晶Fe_3B/Nd_2Fe_(14)B粘结永磁体的磁性能研究

本文研究了粘结剂含量和温度－时间变化对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁材料的磁性能影响。结果表明降低粘结剂含量可显著地提高纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能；环境温度对纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁的磁性能具有重要影响，在较高的温度下其磁性能将显著下降，因此纳米晶Ｆｅ３Ｂ／Ｎｄ２Ｆｅ１４Ｂ粘结永磁只能在较低的温度环境下使用     

Effects of Alloying Elements on Microstructure and Magnetic Anisotropy of the HDDR Powder ofNd-Fe-B Alloy

ＥｆｅｃｔｓｏｆＡｌｏｙｉｎｇＥｌｅｍｅｎｔｓｏｎＭｉｃｒｏｓｔｒｕｃｔｕｒｅａｎｄＭａｇｎｅｔｉｃＡｎｉｓｏｔｒｏｐｙｏｆｔｈｅＨＤＤＲＰｏｗｄｅｒｏｆＮｄＦｅＢＡｌｏｙＧａｏＪｉａｎｒｏｎｇ（高建荣），ＳｏｎｇＸｉａｏｐｉｎｇ（宋晓平），Ｗａ...     

Influence of Heat Treatment on Microstructures and Properties of Nd8Fe78B6Co4 Alloy

Melt-spun Nd8Fe78B6Co4 magnetic powders and their bonded magnets were prepared with the optimization of compositions and preparation techniques. The microstructure change of alloy NdFeB and the relation between microstructure and heat-treatment were studied. The heat-treatment temperature is 200～700 ℃. The as-cast structure of the alloy is typically amorphous. Different melt-spun speed and different heat treatment could result in different magnetic properties of NdFeB magnets. Magnetic properties of NdFeB increase with the addition of element Co. The magnetic properties of magnet alloy get the best when the melt-spun speed reaches 23～26 m·s-1, heat treatment temperature is 690 ℃ and time is 30 min.     

粘结钕铁硼磁环在高性能永磁式步进电动机上的应用

钕铁硼粘结磁体是一种将钕铁硼磁粉与高分子树脂或塑料或低熔点合金及各种添加剂均匀混合,用模压、挤出或注射成形等方法制成的复合永磁材料。国内外对其机理的研究已比较深入,本课题仅就钕铁硼粘结磁体特别是应用于高性能永磁式步进电动机的粘结钕铁硼多极磁环的制备工艺中的关键问题进行了研究,内容包括：（１）专用粘结剂的选择;（２）磁粉选择;（３）薄壁磁环自动压制成形;（４）表面防锈处理方式的选择;（５）多极充磁;（６）磁环转子整体注射成形。结果表明：在解决了上述关键工艺问题后,粘结钕铁硼多极磁环已批量应用于高性能永磁式步进电动机,替代进口或使原有的电机升级换代     

Effect of Multiple Alloying Elements on Microstructure and Magnetic Properties of Nanocomposite Nd2Fe14B／α-Fe Magnets

TheappearanceofnanocompositemagnetsbroketheremanencelimitpredictedbyStoner Wolhfarthmodethattheremanenceofisotropicmagnetwouldnotexceedhalfofitssaturationmagnetization[1] .Accord ingtoSkomski′scalculation[2 ] ,highmaximalenergyproduct (BH) maxof 80 0kJ·m-3 couldbeachievedinNd2 Fe14 B α FenanocompositewhentheaveragegrainsizeofNd2 Fe14 Bisrefinedtoabout 2 0nmandthatofα Fetoabout 10nm ,becauseoftheeffectofrema nenceenhancement (Mr Ms >0 .5 ) .Unfortunately ,thereported (BH) max(185kJ·…     

Nd_(11)Fe_(71)Co_8V_(1.5)Cr_1B_(7.5)合金结构与磁性能的研究

采用熔体快淬及晶化处理工艺制备Nd1 1 Fe71 Co8V1 .5Cr1 B7.5纳米晶合金。运用XRD ,DTA等方法研究了快淬工艺与热处理工艺对该合金纳米晶形成、晶化过程及磁性能的影响。结果表明 ,快淬速度和热处理温度都明显地影响Nd1 1 Fe71 Co8V1 .5Cr1 B7.5纳米晶的形成及其磁性能 ;该合金在晶化过程中先后出现了 3个放热峰 ,分别对应软磁相α Fe ,亚稳相和硬磁相Nd2 Fe1 4B 3个晶化相。快淬速度 2 1m·s- 1 制备快淬薄片经 64 0℃ 4min晶化处理后 ,制成的粘结磁体的最佳磁性能为 :Br=0 64T ,JHc=90 3 5kA·m- 1 ,(BH) max=71kJ·m- 3。     

Changes of Structure and Magnetic Properties during Crystallization in Cast Nd60Fe20Al8Co10B2 Alloy

The Nd60Fe20Al8Co10B2 alloy was prepared by suction casting of the molten alloy into a copper mold under argon atmosphere. The micro-structural and magnetic property changes in the Nd60Fe20Al8Co10B2 alloy during crystallization were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and the vibrating sample magnetometer (VSM). The precipitation and Nd-rich and Fe-rich phases have no significant effect on the intrinsic coercitity for Nd60Fe20Al8Co10B2 alloy annealed below 723 K. However, the growth of Fe-rich phase decreases the saturate magnetization and remanence of the alloy. The hard magnetic behavior is disappeared when the alloy is fullycrystallized.     

A Study of Two-Phase Nanocrystalline Nd_(8.5)Fe_(75)Co_5Cu_1Zr_3Nb_1B_(6.5)Permanent Magnet

Materialswithenhancedremanentmagneticpo larizationwereinitiallypreparedbyCoehoorn[1] frommelt spunNd3.8Fe77B19.2 ribbonsbyheattreatment .Thesimilarbehaviorwasalsoobservedfrommelt spuntwo phasesamplesofNd2 Fe14 Bandα Fe[2 ] .Themag neticpropertiesofisotropicnanocrystallinetwo phasepermanentsdependsensitivelyonmicrostructuralfea tures,suchasdistributionofmagneticallyhardandsoftphases ,meangrainsize ,particleshapeandgrainboundarytype[3] .Inordertoobtainhighmaximumenergyproduct ,itisnecessaryt…