Pilot plant manufacture of vanadium carbide

Conclusions A manometric study was carried out of the reduction of vanadium oxide with carbon, and it was found that the pressure vs time curve exhibits three discontinuities, at temperatures of 1200°C (formation of the monoxide VO), 1400°C (formation of VC_X-VO solid solutions), and 1700°C (formation of the carbide VC_X).An investigation of the vacuum reduction of vanadium oxide confirmed that it is impossible to obtain a vanadium carbide with a carbon content in excess of that represented by the formula VC_0.9.It was found that the optimum conditions for the preparation of large, pilot plant scale, batches of a vanadium carbide phase with a composition corresponding to VC_0.9 by the reduction of the oxide V₂O₃ with graphite heating elements and a reducing gas atmosphere are as follows: heating to a temperature of 1900°C in 40 min and subsequent holding for 60 min.Translated from Poroshkovaya Metallurgiya, No. 11(71), pp. 83–88, November, 1968.     

V2O5碳热还原合成碳化钒粉末的反应过程

为了实现小批量连续化制备碳化钒粉末,以工业级V2O5和纳米炭黑为原料,利用碳热还原法,在常压下碳管炉中得到了V8C7。通过X射线衍射仪(XRD)、扫描电镜(SEM),分析了合成过程。结果表明:在较低的温度下,纳米炭黑将V2O5还原为VO2;随着合成温度的升高,还原为更低价的V2O3,但没有VO生成;接着发生碳化反应,生成VC1-x、V8C7,合成的各阶段相互重叠;在合成过程中,试样的显微组织因物相不同而有所不同,生成的钒氧化物为炭黑附着的颗粒状大团聚体,VC1-x粉末颗粒呈类球形,但大小不均匀;随着温度升高,合成的最终产物V8C7粉末颗粒呈球形或类球形,大小均匀,粒度为1μm左右;还原碳化过程中,产生的气体有CO、CO2。     

Sintered ceramics based on boron nitride and carbide

The formation of BN-B₄C composite materials by sintering in nitrogen is investigated. Structural, mechanical, and chemical characteristics of these materials are examined. Excellent dielectric properties, thermal and chemical stability, and erosion resistance in high-intensity laser beams enable high-temperature application of BN-B₄C composite materials. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 58–63, 2007.     

氮化钒制备技术的发展及应用

简要介绍了氮化钒的物理化学性质,详细介绍了国内外氮化钒制备技术的发展历程.氮化钒主要有两种制备方法,即高温真空制备和高温非真空制备,近年来也出现了一些新方法.对氮化钒的应用进行了综述,它不仅成为了微合金钢中重要的合金添加剂,还开拓了催化剂、工具涂层和微电子等应用领域.     

Microwave synthesis of vanadium nitride for industrial applications

Abstract

Microwave carbothermal nitridation was used to prepare vanadium nitride from vanadium pentoxide and carbon black, under flowing nitrogen gas at atmospheric pressure. The effect of synthesis temperature, soaking time and the initial concentration of carbon on the final nitrogen content was studied. The nitrogen content in the products reached 12 to 16 wt-%, well within the current requirements of the steelmaking industry.     

Interaction between vanadium carbide and aluminum and copper melts

The effect of low-frequency vibrations on the interaction between molten metals (Al,Cu) and vanadium carbide is studied. These vibrations are shown to initiate wetting of the V8C7 carbide by a copper melt and a chemical interaction in the Al-V8C7 system, resulting in the formation of vanadium aluminides and aluminum carbide.     

Interaction of vanadium carbide with a nickel-molybdenum alloy

Melting and solidification temperatures for Ni-Mo alloys (the ratio of these elements is 3:1) containing 10% (by weight) of vanadium carbide are determined. Introduction of vanadium carbide into Ni-Mo alloy reduces the melting temperature by 20°C. The alloys consist of two phases: a solid solution based on nickel and a carbide component resembling needle-shaped inclusions of the eutectic type. Traces of eutectic are observed with 1% VC in a sample. Dissolution of vanadium in the Ni-Mo alloy mentioned does not exceed 1% (by weight). The presence of two phases and their approximate composition in the alloys are confirmed by x-ray diffraction analysis. The solid solution based on nickel contains molybdenum (10–20%) and vanadium (1–6%). The carbide component is a vanadium-containing phase based on molybdenum with a crystal lattice of the Mo₂C type.Scientific Research Institute of Refractory Metals and Hard Alloys. Moscow. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 59–62, January–February, 1994.     

Diffusion interaction of vanadium carbide with powdered steels

Conclusions The processes of diffusion interaction of vanadium carbides with cast and powdered steels are largely analogous. Differences are mainly due to unequal diffusional mobility of the components in cast and powdered materials.In cast and powdered steels equal boundary concentration of vanadium are established on the boundary with the carbides, and these concentrations are determined by the carbon content of the steel and by the temperature.The interdiffusion coefficient in ferrite does not depend on the carbon content, and it is the same for cast and powdered steels. The interdiffusion coefficient in austenite increases with increasing carbon content, and it is noticeably larger in powdered steels than in cast steels.The activation energy of interdiffusion in the austenite of powdered steels (220–230 kJ/mole) is noticeably lower than in cast steels (260–270 kJ/mole); this is due to the substantial contribution of the processes of surface diffusion to the overall mass transfer in porous materials.Translated from Poroshkovaya Metallurgiya, No. 11(323), pp. 40–45, November, 1989.     

氮化钒制备技术发展历程及其应用

简要介绍了氮化钒物理化学性质,详细介绍国内外氮化钒制备技术的发展历程.氮化钒主要有两种制备方法,即高温真空制备和高温非真空制备,近年来也出现了一些新方法.同时对氮化钒的应用进行了综述,它不仅成为微合金钢中重要的合金添加剂,还开拓了催化剂、工具涂层和微电子等应用领域.     

Development of nonoxide ceramics based on silicon carbide and nitride

Research on nonoxide ceramics based on silicon carbide and nitride is reviewed along with related technological developments. The role of I. N. Frantsevich in initiating the development of such materials is shown. Three main stages in the development of the ceramics are distinguished. The relationship between the physical properties and applications of ceramics based on SiC and Si₃N₄.Institute of Materials Sciences, Ukranian Academy of Sciences, Kiev. Translated from Poroshkovaya Matallurgiya, Nos. 7/8(380), pp. 24–32, July–August, 1995.     

Wear resistance of silicon carbide and nitride based ceramic materials

Various factors that affect the nature of wear in SiC and Si₃N4₂ based ceramics have been analyzed. It is shown that adhesion, mechanochemical and diffusion interactions in the contact zone and wear due to fatigue, thermal stresses and abrasion are the predominant factors. Ceramics based on SiC and Si₃N₄ are shown to have excellent wear resistance. Poreless silicon nitride materials that have good chemical stability, heat and crack resistance appear promising as ceramic—metal friction couples and for metal machining. Silicon carbide based poreless materials are efficient ceramic—ceramic friction couples and for service under severe hydro and gas abrasive media attack.Translated from Poroshkovaya Metallurgiya, No. 5, pp. 3–8, May, 1993.