Effects of La~(3 ) doping on MnZn ferrite nanoscale particles synthesized by hydrothermal method

1　INTRODUCTIONMnZnferritesarewidelyusedinelectronicappli cationsbecauseoftheirhigh permeabilityandlowmagneticlossesathighfrequencies[1,2 ] .Theproper tiesofferritesdependlargelyontheirmicrostructure ,sothenano techniqueisintroducedtocontroltheirultramicrostructure ,insteadofthetraditionalceramicway .Additionally ,aprecisesmallamountofcationicsubstitutionisusedusually .ThemagneticlossofMnZn ferritesdopedwithCaO SiO2 athighfrequencyisdiminishedforincreasesofresistivitylayersatgrainbound…     

Mechanical properties and structure of zirconia-mullite ceramics prepared by in-situ controlled crystallization of Si-A1-Zr-O amorphous bulk

Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-A1-Zr-O amorphous bulk, which were first treated at 900-1 000℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150℃. This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m^1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.     

非晶晶化法制备高性能ZTM微纳米复相陶瓷

采用非晶晶化法制备了Si-Al-Zr-O系氧化锆增韧莫来石(ZTM)微纳米复相陶瓷.分析了不同热处理温度和氧化锆含量对材料微观结构及其力学性能的影响.锆含量为15%(质量分数)的样品在1150℃热处理后能得到较好的力学性能,断裂韧性和抗弯强度分别达到了5.13 MPa·m1/2,520 MPa.比用传统方法制各的ZTM陶瓷性能提高约40%.     

PIM充填过程计算机模拟

在Hele-Shaw近似下,采用有限元和有限差分混合法求解粉末注射成型充填过程,有限元法处理中面离散,厚度方向使用有限差分,运用控制体积法追踪运动边界,压力方程和能量方程顺序求解,实现了复杂型腔不同流率多种浇口下充填过程温度场、压力场和速度场以及运动前沿的数值仿真分析,得到了较有价值的数值实验结果。     

PVDF-HFP黏结剂用于高性能锌锰电池（英文）

为了优化和选择合适的黏结剂提高水系锌锰电池的电化学性能,系统地研究水溶性黏结剂和油性黏结剂对锰基正极材料储锌性能的影响。结果表明,含有大量羟基和羧基官能团的水溶性黏结剂易溶于水系电解液,导致较差的电化学性能。幸运的是,采用聚偏氟乙烯-六氟丙烯(PVDF-HFP)黏结剂制备的正极材料在电流密度为100 mA/g下循环90周后表现出264.9 mA·h/g的高比容量,容量保持率达到92%。与此同时,含有大量疏水性官能团的PVDF-HFP黏结剂在抑制电极表面裂纹、降低电压极化和电荷转移电阻、保持电极完整性方面表现出优异的能力。     

粉末注射成型充填过程数值模拟

基于Hele-Shaw流动的近似描述, 采用有限元／有限差分混合法求解粉末注射成型充填过程, 有限元法处理中面离散求解, 厚度方向则使用有限差分法, 运用控制体积法追踪运动边界, 压力方程和能量方程顺序求解, 实现了复杂型腔多种浇口充填过程温度场、压力场和速度场以及运动前沿的数值仿真分析, 得到了较有价值的流场数值分析结果。     

高锆Si-Al-Zr-O系非晶晶化过程

采用差示扫描量热分析(DSC)、X射线衍射(XRD)分析、红外光谱(IR)分析和扫描电镜(SEM)观察等方法,对Si-Al-Zr-O系非晶晶化过程、晶核剂对晶化过程的影响进行了研究.结果表明:Si-Al-Zr-O系非晶在935～970℃和1 100～1 200℃分别发生了四方氧化锆和莫来石的析出反应;TiO2和ZrO2作为晶核剂引入对四方氧化锆和莫来石的析出有一定影响;TiO2含量的增加可使四方氧化锆晶相的析出能力显著提高,而ZrO2含量的增加可提高莫来石晶相的析出能力.根据晶化过程的研究结果制定了合理的晶化热处理工艺,并获得晶粒大小均匀、结构致密的微米晶、纳米晶、莫来石/SiO2-t-ZrO2复相陶瓷.     

Chemistry principles for thermoplastic polymer binder formula selection for powder injection molding

The polymer binder selection is one of the very important aspects for the powder injection molding.However, even nowadays the binder selection is still mainly performed by try and error method, Six commercial or intensive studied binder formulas were analyzed according to state diagram and chemical characteristics of ingredients in each binder formula. In addition, the interactions between the binder components and additives were also taken into account. Based on the analysis, the optimum binder formula was selected and some selection criterions were put forward for the binder and additives.     

New development of Einstein′s viscose law for powder suspension systems

Through the analysis of the present situation of the rheology of suspension disperse systems, the classical Einstein′s viscosity law was developed into the generalized Einstein′s viscosity law which can be further developed into universalized form, called the universalized Einstein′s viscosity law by introducing modification function f(φ). Some rational forms of the function f(φ) were discussed according to functional approximation method, and were consequently developed into a few suspension disperse system rheological equations suitable for high particle concentration. These equations all keep good consistence with the models acquired in experiments or other mathematical physics analysis.     

金属粉末注射成形模具浇口对成形性能的影响规律

根据金属粉末注射成形原理，在材料、模具温度等试验条件一致的前提下，将螺旋测试模与0．5～2．1mm之间的6个不同深度尺寸的侧浇口相结合，通过改变注射料熔体温度、注射压力、注射速率等工艺参数，描绘出在不同工艺参数时的侧浇口深度尺寸与阿基米德螺旋线长度的关系曲线，从而研究得到金属粉末注射成形的浇口尺寸与注射料熔体注射成形性能的关系规律：浇口尺寸对金属粉末螺旋线流动长度的影响较大，且不成比例；浇口尺寸与螺旋线流动长度关系曲线(L—H曲线)的变化不是单调的递增或递减，曲线形状呈较为明显的“波浪”形；在一定试验条件下粉末注射成形的理想浇口尺寸值为1．8mm，要偏大于注塑成形的浇口尺寸值；相对注射压力变化时浇口尺寸对L—H曲线关系的影响而言，注射料熔体温度和注射速率的影响相对较小，波动方向一致且较平坦，曲线有微小的上升趋势；当浇口尺寸一定时，工艺参数对流动长度的影响规律与注塑成形中工艺参数的影响规律类似。