Formation of silicon carbide in the reaction of reduction of silica by carbon

Conclusions In the initial stages of heat treatment of H₂SiO₃ and sucrose a mixture of highly dispersed defective SiO₂ particles and carbon material is formed. Then as the result of contact interparticle interaction of a radical character disintegration (activation) of the carbon particles and envelopment of them by a layer of SiO₂ accompanied by deformation of the Si-O-Si bonds occur. Filling of the pores of the carbon material with silicon oxide creates in subsequent higher temperature treatment favorable conditions for formation of SiC. The particles formed as the result of the relatively low-temperature solid-state reaction are non-uniform in composition. Their core consists of uninteracted carbon and after it follow a layer of silicon carbide and an outer layer of SiO₂. A switch to the area of high synthesis temperature makes it possible to approach a stoichiometric composition of the silicon carbide.Translated from Poroshkovaya Metallurgiya, No. 9(321), pp. 57–62, September, 1989.     

Reaction between zirconium carbide and silicon powders

Conclusions A study was made of the reaction of zirconium carbide and silicon powders over the temperature range 800–1700C.Translated from Poroshkovaya Metallurgiya, No. 11(83), pp. 61–65, November, 1969.     

Loss of carbon during plasma-spraying of clad carbide powders

Composition of particles upon atomization of unclad and clad powders is studied. It is estabished that the losses of carbon upon atomization of unclad particles are different for different carbides and increase in the sequence Cr₃C₂-TiC-WC. Upon atomization of clad powders, we observed the highest carbon losses for the particles of tungsten carbide, somewhat smaller losses for titanium carbide, and almost negligible losses for chromium carbide.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 75–78, October, 1992.     

应用红外碳硫仪测定碳化硅中总碳、游离碳及碳化硅

碳化硅是一种常用的脱氧剂,在炼钢过程中主要用于脱氧以提高钢水的内在质量.碳化硅日常分析项目主要有碳化硅、游离碳及总碳,一般采用GB/T3045-89中规定的分析方法,分析过程繁琐、分析时间长,应用于生产过程中批量检验不能很好的满足要求.本文对碳化硅的分析方法进行了试验和探讨,应用红外碳硫分析仪测定碳化硅中的总碳量和碳化硅量进而计算出游离碳的量,其重现性和再现性均较好.     

Structure of zirconium carbide powders subjected to vibratory milling

Conclusions Vibratory milling of zirconium carbide powder can be successfully performed in benzene. Comminution in benzene enables a large specific surface to be attained, with practically no chemical reaction between the medium and the milling products. In milling in trichloroethylene the latter decomposes, with the formation of hydrochloric acid which reacts with the milling products. In a study of the fine structure parameters of zirconium carbide in the <111>, <100>, and <110> directions the smallest crystal lattice strains and block sizes were observed in the <110> direction. This may be taken as evidence that under such disintegration conditions the {110} planes constitute cleavage planes. An evaluation of internal and surface energies established that the strained crystal lattice energy reaches values which must be allowed for in any subsequent uses of the powder.Translated from Poroshkovaya Metallurgiya, No. 4(160), pp. 14–19, April, 1976.     

鱼雷罐用铝碳化硅碳砖中碳化硅的氟硅酸钾滴定法研究

探讨了测定鱼雷罐用铝碳化硅碳砖中碳化硅的氟硅酸钾滴定方法。用KOH和KNO₃混合熔剂在镍坩埚中熔融鱼雷罐用铝碳化硅碳砖,选取熔融温度为700 ℃,熔融时间为15 min的熔融条件,在此条件下进行浸取易于操作,减少了对镍坩埚的损害。采用自制的抽滤装置,即将普通抽滤瓶进行改装,将玻璃砂芯漏斗部分用塑料代替,只需用直径约为40 mm、相当于四分之一张普通滤纸的滤纸进行过滤,过滤时抽滤速度快,滤纸不会穿漏,且吸附的残余酸量很少,易于洗涤和中和。方法用于自制标准样品的测定,回收率在98%～101%之间,相对标准偏差小于5%,能够满足日常分析检测需要。     

Properties of high-dispersion powders of tungsten carbide produced by high-temperature electrochemical synthesis

Translated from Poroshkovaya Metallurgiya, No. 8(344), pp. 1–4, August, 1991.     

Surface of powders of silicon nitride produced by self-propagating high-temperature synthesis

Conclusions The surface of a starting silicon powder used in the production of silicon nitride by the SHS method is covered with an oxide film whose thickness varies, depending on the method of comminution and time of storage of the powder, in the range 1–12 nm. During SHS the Si + SiO₂ reaction results in the formation of gaseous SiO, which becomes adsorbed on the cold walls of the reactor and then experiences disproportionation. This lowers the oxygen content of the resultant silicon nitride, but the overall purification effect achieved is small. After comminution, a 1- to 2-mm-thick layer of powdered silicon nitride produced by SHS consists of a silicon oxynitride with an oxygen content of 5–30 wt.%. Milling conditions do not significantly affect the concentration of oxygen inside the nitride particles, which does not exceed 0.4%. To obtain silicon nitride of low oxygen content, it is necessary to employ starting reactants of high purity.Translated from Poroshkovaya Metallurgiya, No. 1(253), pp. 48–54, January, 1984.     

The interaction of reaction-bonded silicon carbide and inconel 600 with a nickel-based brazing alloy

The objective of the present research was to join reaction-bonded silicon carbide (RBSC) to INCONEL 600 (a nickel-based superalloy) for use in advanced heat engine applications using either direct brazing or composite interlayer joining. Direct brazing experiments employed American Welding Society (AWS) BNi-5, a commercial nickel-based brazing alloy, as a filler material; composite interlayers consisted of intimate mixtures of α-SiC and BNi-5 powders. Both methods resulted in the liquid filler metal forming a Ni-Si liquid with the free Si in the RBSC, which, in turn, reacted vigorously with the SiC component of the RBSC to form low melting point constituents in both starting materials and Cr carbides at the metal-ceramic interface. Using solution thermodynamics, it was shown that a Ni-Si liquid of greater than 60 at. pct Ni will decompose a-SiC at the experimental brazing temperature of 1200 ‡C; these calculations are consistent with the experimentally observed composition profiles and reaction morphology within the ceramic. It was concluded that the joining of RBSC to INCONEL 600 using a nickel-based brazing alloy is not feasible due to the inevitability of the filler metal reacting with the ceramic, degrading the high-temperature properties of the base materials.     

碳化硅侧块在电解过程中的性能分析

本文对碳化硅侧部碳块的性能进行了研究。结果表明:碳化硅侧块的体积密度、耐压强度和电阻率较常规侧块有较大幅度的提高,抗熔盐冲刷性能有较大幅度的提高,抗钠侵蚀性能和抗吸钠膨胀能力较差,原因是碳化硅原料钠含量过高。碳化硅原料铝含量高,可改善碳化硅侧块的散热性。