Low pressure synthesis of boron nitride with(C2H5)2O·BF3 and Li3N precursor

Cubic boron nitride(c-BN) was synthesized through benzene thermal method at a lower temperature of 300 ℃ by selecting liquid(C2H5)2O·BF3 and Li3N as reactants. Hexagonal boron nitride(h-BN) and orthorhombic boron nitride(o-BN) were also obtained. The samples were characterized by X-ray powder diffractometry and Fourier transformation infrared spectroscopy. The results show that all the BF3, BCl3 and BBr3 in the same family compounds can react with Li3N to synthesize BN since the strongest bond of B-F can be broken. Compared with BBr3, liquid (C2H5)2O·BF3 is cheaper, less toxic and more convenient to operate. Li3N not only provides nitrogen source but also has catalytic effect on accelerating the formation of c-BN at low temperature and pressure.     

Structure and Properties of B4C - SiC Composites

We have investigated how the composition, grain morphology, and method of preparing the starting mixture affect the processes that form the structure and phase composition of B₄C - SiC composites during hot pressing. We found that, depending on the composition of the initial powder mixtures, which is responsible for different mechanisms of consolidation of ceramic materials during hot pressing, the grain size of the main B₄C phase and its defect content as well as the nature of the SiC phase distribution within the material differ significantly. When B₄C - SiC composites with a low SiC content are made from initial B₄C - B₄Si - B - C powder mixtures those composites have a high cracking resistance because of their fine grain structure.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 112–119, March–April, 2005.     

The electronic structure and grain boundary segregation by boron addition

The electronic structure and grain boundary segregation caused by boron addition to Ni₃Al have been studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy, respectively. The obtained results show that the Ni2p_3/2 electron binding energy rises gradually in the sequence of pure Ni<Ni₇₆Al₂₄<Ni₇₄Al₂₆<Ni₇₅Al₂₅, while it reduces monotonously with an increase in boron addition to Ni₃Al. Besides, it is found that the grain boundary segregation of boron occurring in Ni₃Al is a combined equilibrium and non-equilibrium type in nature. Based on the concept of the bonding environmental inhomogeneity, measured by the shift in Ni2p_3/2 electron binding energy from the nickel atoms in the simple substance nickel to those in the intermetallic compound Ni₃Al (ΔE _B), being responsible for the brittle behavior of the alloy, a binding energy shifting criterion for the brittle-ductile fracture transition in Ni₃Al is presented; when ΔE _B>0, the brittle failure occurs in Ni₃Al; when δE _B<0, the ductile one appears. Combined with the above experimental rules, the criterion predicts that pure Ni₃Al is brittle, and there exist the stoichiometric effect and concentration effect in the ductilization process for Ni₃Al by boron addition. Hence the criterion can be taken as a theoretical guide to alloy design in developing ductile intermetallics. Project supported by the National Natural Science Foundation of China.     

硼胺络合物／环氧树脂体系的固化反应

应用ＤＳＣ和ＩＲ分析技术，研究了含有恶硼杂环的硼胺络合物与环氧树脂体系的固化反应机理和固化反应动力学。结果表明，固化反应主要是硼胺络合物与体系中羟基化合物形成含氢质子的配位络合物，然后由此引发体系的环氧基进行的阳离子开环聚醚反应，整个固化反应过程遵循一级动力学方程。     

Thermodynamic evaluation of the phase equilibria and glass-forming ability of the Fe–Si–B system

A thermodynamic study has been carried out on the Fe–Si–B ternary system, which is important in the development of transformer core materials and Ni-based filler metals. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by combining the experimental results from differential scanning calorimetry with literature data. The evaluated parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams. Furthermore, the glass-forming ability of this ternary alloy was evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies–Uhlmann kinetic formulations. In this evaluation, the time–temperature-transformation (TTT) curves were obtained, which are a measure of the time required to transform to the minimum detectable mass of crystal as a function of temperature. The critical cooling rates calculated on the basis of the TTT curves enabled us to evaluate the glass-forming ability of this ternary alloy. The results show good agreement with the experimental data in the compositional amorphization range.     

PIII技术在制备c-BN硬化层中的应用

采用一种新型的等离子体浸没式离子注入技术 (PIII)在渗硼后的 5 0Mn钢试样上制备出了厚度为 0 .15～ 0 .2mm的立方氮化硼 (c BN)表面硬化层。经X射线电子能谱 (XPS)和X射线衍射分析 (XRD) ,发现硬化层中的组织有立方氮化硼 (c BN)、六方氮化硼 (h BN)、B2 O3,FeB和Fe2 B。在表层 60nm的深度范围内 ,c BN的含量较高。采用球盘式无润滑滑动摩擦实验和维氏显微硬度实验分别对渗硼 PIII复合处理以及单独渗硼的 5 0Mn钢试样的性能进行了对比实验。结果表明 :与单独渗硼的试样相比 ,经渗硼 PIII复合处理的试样具有高得多的硬度 (高达HV0 .1N44GPa)和耐磨性     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.     

基片温度对纳米金刚石薄膜掺硼的影响

采用微波等离子体化学气相沉积法,以氢气稀释的乙硼烷为硼源进行了纳米金刚石(NCD)薄膜的生长过程掺硼,研究了基片温度对掺硼NCD薄膜晶粒尺寸、表面粗糙度、表面电阻和硼原子浓度的影响.利用扫描电子显微镜和原子力显微镜观察NCD薄膜的表面形貌,并通过Imager软件对原子力显微镜数据进行分析获得薄膜的表面粗糙度及平均晶粒尺寸信息;采用四探针测量掺硼NCD薄膜的表面方块电阻,利用二次离子质谱仪对掺杂后NCD薄膜表面区域的硼原子浓度进行测量.实验结果表明,较高的基片温度有利于提高薄膜的导电能力,但随着基片温度的提高,NCD薄膜的平均晶粒尺寸和表面粗糙度逐渐增大;此外,当反应气体中的乙硼烷浓度一定时,掺杂后NCD薄膜的表面硼原子浓度随基片温度升高存在一个饱和值.在所选乙硼烷浓度为0.01%的条件下,基片温度在700℃左右可以在保证薄膜表面电性能的基础上保持较好的表面形貌.     

钢中硼相分析方法的研究

在弱酸性的氯化钾-柠檬酸电解液中电解提取钢中所有硼的析出相,然后用稀硫酸分离碳硼化物,硫酸-过氧化氢分离合金元素硼化物,硝酸-硫酸分解氧化硼和氮化硼,最后采用ICP-AES光谱法测定各相中硼的含量.通过实验,建立了一整套低硼钢中固溶硼、碳硼化物、合金元素硼化物、氧化硼和氮化硼的分离、测定方法.     

高流速高分辨辉光放电质谱法测定粉末高温合金中26种微量和痕量元素

准确测定粉末高温合金中微量及痕量元素,对粉末高温合金的生产、应用具有重要意义。将样品在放电电流40～45 mA,放电电压1 100～1 200 V,氩气流速400～450 mL/min下进行辉光放电激发,选择合适的同位素和分辨率以消除质谱干扰,使用基体匹配的内控标准样品和标准物质校准各待测元素的相对灵敏度因子(RSF),实现了高流速高分辨辉光放电质谱法(GDMS)对粉末高温合金中硼、钠、镁等26种微量及痕量元素的测定。采用实验方法对粉末高温合金内控样品中26种微量及痕量元素进行测定,各待测元素的测定值与参考值基本一致,测定结果的RSD(n=6)在0.9%～15.4%之间。采用实验方法对粉末高温合金样品进行测定,测定结果分别与电感耦合等离子体原子发射光谱法(ICP-AES)测定硼、铁和锆,高频感应燃烧红外吸收法测定硫,原子荧光光谱法测定硒,高分辨电感耦合等离子体质谱法(HR-ICP-MS)测定其余元素(钠、镁、硅、磷、钙、钒、锰、铜、镓、砷、银、锡、锑、碲、镧、铈、铪、钽、铊、铅和铋)的结果保持一致,测定结果的RSD(n=6)在0.2%～26.6%之间。