Interaction of Boron Carbide with Nickel Oxide

Thermodynamic methods and x-ray analysis have been applied to the chemical interactions in 0.9625 B₄C + 0.05 NiO + 0.0375 C, B₄C + NiO, B₄C + 4 NiO + 3 C mixtures; stages occur in the processes there that correspond to various temperature ranges. It is found that NiB always contains small amounts of lower borides, whose quantity does not exceed 2 mass% when the synthesis conditions are optimal.

     

Secondary Silicon Carbide Formed in the Interaction of Nanosized Silicon Carbide with Iron Oxide

The characteristics of superfine powder composites formed in the interaction of nanosized silicon carbide with iron oxide in vacuum and argon at 1200 and 1400°C, respectively, are analyzed. Silicon carbide (β-SiC), iron silicide and carbide, silicon oxide, and silicon oxynitride are main components of the powder composites. The lattice parameter of SiC in the powder composites synthesized in the SiC–Fe2O3 system is determined. In the interaction in the SiC–Fe2O3 powder mixture in vacuum, secondary SiC is synthesized with a lattice parameter that corresponds to the standard parameter for cubic β-SiC. The interaction in an argon atmosphere is accompanied by the synthesis of secondary SiC with a decreased lattice parameter. The minimum lattice parameter (0.4336 nm) is 0.6% smaller than the standard parameter for cubic β-SiC. The morphology of the powder composite synthesized in the SiC–Fe2O3 system is studied. The average particle size of the powder composite decreases with increasing weight content of secondary SiC.     

多孔碳化硼的力学性能及其微观组织

采用无压烧结法制备得到了多孔的碳化硼,用扫描电镜研究了该材料的微观组织;并测定了不同孔隙率碳化硼的抗弯强度和密度,分析了多孔碳化硼的孔隙率与抗弯强度和密度的关系。研究结果表明:采用无压真空烧结法所制备的多孔碳化硼材料的微观组织烧结良好,烧结颈明显,孔隙大小比较均匀;当空隙率为30%时,所制备的多孔碳化硼密度为1.714 g/cm3,抗弯强度为100.85 MPa。     

B4C材料泊磨擦特性研究

简要地介绍了Ｂ４Ｃ材料的主要制备方法,摩擦特性和获得超低摩擦因数的机理,提出了获得超低摩擦因数的方法,并指出了现在存在的问题和对未来的展望。     

Formation of Polycrystalline Boron Carbide B4C with Elevated Fracture Toughness

We have studied the processes of formation of high-density polycrystalline boron carbide B₄C during sintering under high pressure (5.5 GPa) and at high temperature (2200 K). Study of the structure by transmission electron microscopy showed that under the indicated conditions for sintering B₄C powders with original particle size range 2–80 µm, processes of primary recrystallization occur, as a result of which interlayers of nanodispersed grains (10–50 nm) are formed in the near-surface regions of the original coarse grains. The microhardness of such material is 41 GPa, and the fracture toughness is 7.2 MPa · m^1/2.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 90–101, January–February, 2005.     

碳化硼粉末及其复相陶瓷的研究现状与进展

综述了碳化硼粉末的合成方法、碳化硼复相陶瓷的种类及合成方法，并对其发展方向作了展望。     

碳化钙降低闪速炉渣含镍的研究

闪速熔炼是强氧化熔炼,反应塔的氧势很高,必然产生大量Fe_3O_4及NiO、Cu_2O等并进入渣中,故渣含有价金属高。针对镍闪速炉产生炉渣的过程,分析了炉渣中镍损失的途径,探索了使用碳化钙降低渣含镍的过程。碳化钙加入后炉渣含镍降低0.03个百分点(或～11%)。     

Study on Processing Conditions of Aluminum Matrix Composites Reinforced with Boron Carbide Particles

Different pre-heating of boron carbide particles for reinforcement and different processing conditions were studied in this work. Being one of the most cost-effective industrial methods, conventional melt stir-casting route was utilized.Result showed that the boron carbide particles distributed well for a suitable pre-heating temperature and processed in air.No reaction product was found at the A1-B4C interfaces at the resolution limit of SEM used in that way.     

Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

     

硬质合金中镍和钴的连续测定

利用镍、钴的ＥＤＴＡ络合物在强碱性介质中有效稳定常数的不同，用钙盐返滴定的方法，对硬质合金中的镍、钴两元素进行连续测定。方法快速、准确，相对标准偏差小于２％，测定结果与标准值或经典的分离分别测定法的结果均基本相符。     

Characteristic Features of Boron Carbide Synthesis for Iron Triad Borides

We have studied the characteristic features of synthesis of iron, cobalt, and nickel borides by boron carbide reduction of oxides. We have shown that the reaction of boron carbide with iron triad metal oxides occurs through a stages involving formation of the metals, lower boride phases, carbides and borates of the corresponding metals. A characteristic feature of such a reaction is the higher reactivity of boron carbide compared with carbon in the initial stages, leading to the appearance of B₂O₃ and C which react at higher temperatures to form boron carbide. The method of boron carbide reduction of oxides allows us to obtain rather pure higher borides of iron, cobalt, and nickel.     

Preparation of High-Porosity Permeable Cellular Material Based on Chromium Carbide with Nickel Binder

We have studied the characteristic features of preparation of high-porosity permeable cellular materials with open porosity of 85 to 95%, involving duplication of the structure of polyurethane foam by the method of suspension casting of a powdered mixture based on chromium carbide with nickel binder (KKhN-15). We have optimized the conditions for preparation of the powder, removal of the organic, and sintering. We have studied the structure and properties of the material. We have shown that the material based on KKhN-15 surpasses cellular nichrome in compressive strength and scaling resistance.     

碳热法硼酐还原的热力学

 在相图分析的基础上,根据分子离子共存理论,建立了Fe-C-B三元熔体活度模型。通过对模型求解,可以计算出熔体中Fe、C、B、Fe3C、FeB、FeB2和B4C的组分活度。研究了硼酐碳热还原的热力学条件,分析了CO压力、B2O3含量及炉渣类型对冶炼所需最低温度的影响,常压下冶炼熔体中碳含量较高,温度需高于2000℃才能脱碳保硼。CO气体压力为0.1kPa,CaO的质量分数小于60%时,可使冶炼硼铁的最低温度在1600℃以下。     

The Effect of Twins on the Mechanical Behavior of Boron Carbide

The microstructure and mechanical properties of boron carbide (B₄C) samples processed by slip casting were compared with those processed by the conventional hot-pressing technique. Although the quasi-static and dynamic mechanical experiments showed comparable results between the slip-cast and hot-pressed B₄C, scanning electron microscopy and electron backscattered diffraction of the B₄C samples revealed significant differences in the microstructure. A notable difference was the numerous growth twins in the slip-cast samples. The twin planes were determined to be { 10[`1] 1 } \left\{ { 10\bar{1} 1} \right\} and consisted of 35 pct of the boundary population in the slip-cast B₄C but only 1 pct of the boundary population in the hot-pressed B₄C. It was hypothesized that the presence of twins will cause a different failure mechanism. The effect of the twins on the stress state was examined by finite-element simulations and will also be discussed.     

氧化镍矿处理工艺述评

简述了世界镍的需求和生产概况,对氧化镍矿处理工艺进行评述,指出火湿法结合工艺处理氧化镍矿具有潜力,值得进一步研究开发。     

Oxide Ores of Nickel — The Australian Situation

This review outlines the general features of the oxide nickel ore industry in Australia in terms of type, location, commercial practice and research and development. For oxide nickel ores that occur in the sulphide province of Western Australia, integration of oxide and sulphide processing routes will offer many economic and technological advantages. For other ores, non-metallurgical factors will have a significant influence on their future development.     

氧化镍矿资源开发与利用现状

简单介绍了国内外镍资源现状.阐述了氧化镍矿造锍熔炼、镍铁法和还原焙烧-磁选法处理工艺和氨浸法、微波加热-FeCl3氯化法、高压酸浸法、水热法、硫化焙烧-水浸法、还原焙烧-酸浸湿法处理工艺.结合镍工业发展现状,指出了未来氧化镍矿冶炼发展方向.