直流电弧法合成B4C的研究

使用六角氮化硼(h-BN)和石墨作初始原料,在原料里面加入少量的氮化锂(LiN)做催化剂,采用直流电弧等离子体烧结方法,合成出样品,所得样品经过X光衍射(XRD)、描电子显微镜(SEM)和能谱(EDX)分析,结果表明成功地合成出了碳化硼B4C晶体.     

精馏与化学交换法分离硼同位素的数学模型及优化

采用精馏与化学交换法，针对三氟化硼-苯甲醚分离体系，研究了硼同位素分离生产过程的特点，建立了分离过程的稳态数学模型，并利用Matlab程序进行模型求解，同时对操作参量进行优化，得到了不同分离要求的优化参量和操作条件对化学交换过程中理论塔板数的影响以及丰度的分布，该教学模型可以指导工艺设备的改进和优化，为下一步的放大和操作过程提供了理论依据．     

用hBN合成cBN

分别用硼砂和氯化铵、硼砂和尿素为原料,在９５０ ℃下合成出 ２种结晶度相近、平均颗粒度分别为５．６×１０－６和 １．４２×１０－６ｍ的ｈＢＮ．在高温高压条件下,使用锂系催化剂,由前１种ｈＢＮ合成的ｃＢＮ为黄色透明体,由后一种ｈＢＮ合成的ｃＢＮ大部分为黑色半透明体,并且在ｃＢＮ晶体表面上观察到生长台阶．以硼氢化钾和氯化铵为原料合成出的ｈＢＮ为无定形态,平均颗粒度为１２．４３×１０－６ｍ,使用锂系催化剂,该ｈＢＮ未能合成出ｃＢＮ．探讨了ｃＢＮ的形成机制．     

Non-equilibrium segregation of boron on grain boundary in Fe-30%Ni alloy

The moving boundary non-equilibrium segregation during recrystallization and the influence of pre-deformation in Fe-30%Ni Alloy at1000℃ was investigated by the PTA (particle tracking autoradiography) technique, optical and electron microscopy. The results indicated that intensity of boron segregation on moving boundary after different deformation is concerned with the pre-deformation degree and the movingspeed of the boundary. The TEM (transmission electron microscopy) result showed that the dislocation density nearby the moving boundary increase obviously. The phenomena are discussed by the widening grain boundary mechanism.     

Electrical properties of sulfur-implanted cubic boron nitride thin films

Cubic boron nitride(c-BN)thin films were deposited on Si substrates by applying ion beam assisted deposition and then doped by S ion implantation.To produce a uniform depth profile of S ions in c-BN films,the implantation was carried out for the multiple energies.A slight degradation of c-BN crystallinity resulted from ion implantation can be recovered by thermal annealing,keeping the cubic phase content as high as 92%.The resistance reduces from 1010X for the as-deposited c-BN film to 108X after an S implantation of 5 9 1014ions cm-2and annealing at 1,173 K,suggesting an electrical doping effect of S dopant.The electrical resistance of the S-doped c-BN thin film decreases with increasing temperature,indicating semiconductor characteristics.The activation energy of S dopant is estimated to be 0.28±0.01 eV from the temperature dependence of resistance.     

Effects of BN content on the mechanical properties of nanocrystalline 3Y-TZP/Al2O3/BN dental ceramics

3Y-TZP/3wt％ Al2O3 powder was coated with varying amounts of BN using the urea and borate reaction sintering method, and then multiphase ceramics were prepared by hot pressing sintering. The micro-topography and the compositional analysis of synthesized ceramics were conducted through scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A mechanical tester was used to analyze the Vickers hardness, fracture toughness, and bending strength of the synthesized ceramics. The results showed that the ceramic with a BN content of 12wt％ showed the best processability, but had diminished mechanical properties (such as fracture toughness and bending strength). The ceramic with a BN content of 9wt％ showed better processability than those with 3wt％ and 6wt％ BN. However, the fracture toughness was affected by the addition of 9wt％ BN, making this ceramic only usable as a base material for a three-unit fixed bridge. In con-trast, the ceramics with a BN content of 3wt％ or 6wt％ fulfilled the criteria for use in multi-unit restoration, but their low processability made them unsuitable for milling after sintering.