制备条件对NiZn铁氧体纳米晶材料磁性能的影响

利用溶胶-凝胶法制备尖晶石结构的Ni1-xZnxFe2O4铁氧体纳米粉体材料,同时系统研究Ni/Zn比、溶液pH值以及煅烧温度对制备的Ni1-xZnxFe2O4铁氧体纳米材料微结构及磁性能影响。结果表明,随着Ni含量的增加,生成物中未反应的氧化铁不断增多。当x=0.3时,NiZn铁氧体的饱和磁化强度(Ms)最大。但随着温度的增加,氧化铁的含量减少,NiZn铁氧体的生成量增加。同时发现溶液pH值对Ni0.7Zn0.3Fe2O4铁氧体微结构及性能影响较大,当溶液的pH=5时,Ni0.7Zn0.3Fe2O4纳米材料的Ms最大。实验得到了NiZn铁氧体的最佳制备条件:Ni/Zn比为0.7/0.3,溶液pH值为5,最佳烧结温度为900℃。     

Preparation and Characterization of Nickel-Zinc Ferrites by a Solvothermal Method

用溶剂热法合成了镍锌铁氧体,并用XRD,SEM,VSM对其进行了性能表征。系统地研究了溶剂热合成条件如镍锌元素比、溶剂热温度、溶剂热时间对样品形貌以及性能的影响。结果表明,当温度为160 ℃时,并未形成镍锌铁氧体,镍锌铁氧体的形成温度为180 ℃;随着溶剂热时间的延长,镍锌铁氧体颗粒变得更加均匀且粒径变大,饱和磁化强度增加;镍锌铁氧体中镍元素的增加不会显著地改变镍锌铁氧体的形貌,却可以使镍锌铁氧体的饱和磁化强度增加。当Ni离子的浓度x=0.30时,饱和磁化强度最高;当Ni离子浓度x=0.20时,饱和磁化强度最低。     

基片温度对Co掺杂ZnO薄膜室温铁磁性的影响

采用磁控共溅射法在Al2O3(0001)基片上沉积了Zn1-xCoxO(x=0.08～0.3%)薄膜,研究了基片温度对Co掺杂ZnO薄膜结构和磁性的影响.结果表明:Al2O3(001)基片很好地诱导了ZnCoO薄膜(002)取向生长,并且所有的薄膜均显示室温铁磁性.较低的基片温度不仅能有效抑制薄膜中Co2O3杂质相的产生,而且薄膜磁矩较大.紫外-可见光谱也表明,薄膜中Co2 取代了ZnO中Zn2 的位置.     

Effect of defect complex on magnetic properties of (Fe,Mn)-doped ZnO thin films

We have observed room temperature ferromagnetism in Mn-doped and (Fe, Mn)-codoped ZnO thin films grown under different oxygen partial pressures by pulsed laser deposition. The X-ray diffraction and optical transmission spectra studies demonstrate the natural incorporation of Fe and Mn cations into wurtzite ZnO lattices. The effects of transition metal doping and defects on the magnetic properties was investigated. It is found that room temperature ferromagnetism is sensitive to oxygen vacancy and Zn vacancy. The absence of ferromagnetism in pure ZnO films grown under different oxygen partial pressures reveals that the transition metal ions should also play an important role in inducing the ferromagnetism.     

Effects of phosphorus addition on the magnetic properties of sintered Fe-50 wt.% Ni alloys

Phosphorus was added to Fe-50 wt.% Ni in the form of a coated composite powder via an electroless plating process. Addition of phosphorus to Fe-50 wt.% Ni facilitated increases in density and grain size, both of which were beneficial to magnetic performance. Because of the homogeneous distribution of phosphorus in the powder, the optimal phosphorus addition was much lower than for those using Fe₃P as the phosphorus precursor. The optimal phosphorus addition was close to its maximum solubility in Fe-50 wt.% Ni (about 0.5 wt.%), above which precipitation of excessive phosphorus in the form of iron nickel phosphide, (Fe,Ni)₃P, effectively degraded the magnetic properties of Fe-50 wt.% Ni. Without the addition of phosphorus, good magnetic properties could be achieved only when the sintering temperature was high enough (>1200 °C) to result in a high sintered density and large grains in the sintered structure.     

Enhanced sintering of an Fe-Ni-P coated composite powder prepared by electroless nickel plating

An Fe-8.2 % Ni-6.0 % P powder was prepared by electroless nickel plating on a carbonyl iron powder, where phosphorous appeared as a contaminant of the plating process. Because of the high phosphorous concentration, persistent liquid phase sintering was effective at temperatures higher than 1000 °C. The sintered microstructure was dramatically different from the conventional approaches, where a low concentration of phosphorous was added in the form of Fe₃P. Sintering the alloy at a temperature as low as 1050 °C for 30 min yielded a sintered density of 98.6% theoretical and rounded grains having an average grain size of 53 μm. The rounded grains were surrounded by a large volume fraction of intergranular (Fe,Ni)₃P phase, arising from the high phosphorous concentration, which slightly deteriorated the magnetic saturation but significantly increased the electrical resistivity of the alloy. Generally speaking, the magnetic saturation of the sintered alloy was improved with respect to the iron-phosphorus, iron-nickel, or iron-silicon alloys fabricated by powder processing.     

预合金粉对粉末冶金NiFe18.5Al25合金性能的影响

将元素Ni、Fe和Al粉以摩尔比56.5-18.5-25配料,分别按元素粉末高能球磨(300 r/min, 12 h)、元素粉末直接干混、50%元素粉+50%预合金粉末干混3种方式混料;混料在500 MPa的压力下压制成形,1 280 ℃下烧结;对合金烧结态进行相对密度测定、力学性能检测、X射线衍射分析(XRD)和断口形貌观察.结果表明:50%元素粉+50%预合金粉制备的合金性能最好,密度可达到6.61 g/cm3(相对密度94.8%),烧结态抗拉强度可达到868 MPa,说明元素粉末中添加的预合金粉可以控制烧结过程,提高合金的烧结密度,同时增强合金的力学性能.     

镀液组成对碱性体系Zn-Ni合金镀层性能的影响

目的 发现最优工艺条件，了解Zn-Ni电沉积机理。方法 通过场发射电镜分析、能谱分析以及电化学分析等方法，研究以一种胺羧多官能团配体为Ni²⁺络合剂的碱性锌酸盐电解液体系中，锌/镍离子物质的量之比与锌镍离子总浓度对镀层的光泽度、镍含量、耐蚀性、表观质量和微观结构的影响。结果 锌/镍离子物质的量之比增加会使得镀层镍含量降低，最后稳定在15%~19%，镀层微观结构由晶粒细致平滑型转化为粗大疏松型。物质的量之比为1.9时，镀层的腐蚀电流最小。锌镍离子总浓度增加会使得镀层镍含量缓慢减小，镀层微观结构由晶粒细致疏松型转化为细致紧密型，最后又转变为粗大疏松型，镀层的腐蚀电流先减小后急剧增大，即镀层的耐蚀性先增加后急剧降低。结论 在锌/镍离子物质的量之比为1.9、锌镍离子总浓度为0.12 mol/L时，所得镀层的综合性能最好。镀层锌/镍含量变化趋势符合Brenner吸附膜理论。     

Gd、Y含量对烧结钕铁硼永磁体磁性能的影响

本文研究了在不同烧结制度下元素Gd和Y的含量对烧结Nd16Fe78B6永磁材料的磁性能和显微结构的影响。实验中,分别采用Gd、Y等量取代原合金中的部分Nd,实验结果表明,Gd、Y替代Nd含量最佳范围为0～15％（质量）。烧结温度为1120℃回火温度为800℃时（Gd15Nd85）16Fe18B6合金的磁性能最佳。烧结温度为1120℃回火温度为600℃时（Y15Nd85）16Fe78B6合金的磁性能最佳。显微组织研究表明,两种合金样品分别产生新相钆铁钕氧化物相和钇铁钕氧化物相。     

Sintering process and grain growth of Mn-Zn ferrite nanoparticles

The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.