氮化硅结合碳化硅耐火材料的氧化

氮化硅结合碳化硅耐火材料高温氧化后，其抗折强度有所提高，但经扫描电镜观察，材料断面结构已发生了明显的变化。该材料长时间在氧化气氛中使用，可靠性将下降。     

加入碳化硅对硅质耐火材料性能的影响

进行了通过加入碳化硅的方法来改善硅质耐火材料热机械性能的试验,并评估了该种耐火材料的物理性能和热机械性能。     

氮化硅结合碳化硅耐火材料在钢水中的腐蚀行为

运用扫描电镜（ＳＥＭ）技术，研究了氮化硅结合碳化硅耐火材料在钢水中的腐蚀行为。结果表明，金属与氮化硅结合碳化硅材料之间的界面清晰，基体内部无任何金属渗入，但氧化的材料表面有氧化物粘附。     

Pressureless sintering of silicon carbide ceramics containing zirconium diboride

SiC-5 wt.% ZrB₂ composite ceramics with 10 wt.% Al₂O₃ and Y₂O₃ as sintering aids were prepared by presureless liquid-phase sintering at temperature ranging from 1850 to 1950 °C. The effect of sintering temperature on phase composition, sintering behavior, microstructure and mechanical properties of SiC/ZrB₂ ceramic was investigated. Main phases of SiC/ZrB₂ composite ceramics are all 6H-SiC, 4H-SiC, ZrB₂ and YAG. The grain size, densification and mechanical properties of the composite ceramic all increase with the increase of sintering temperatures. The values of flexural strength, hardness and fracture toughness were 565.70 MPa, 19.94 GPa and 6.68 MPa m^1/2 at 1950 °C, respectively. The addition of ZrB₂ proves to enhance the properties of SiC ceramic by crack deflection and bridging.     

Characterization of alumina-magnesia-carbon refractory bricks containing aluminium and silicon

The present paper is a continuation of previous ones focused on the characterization of alumina-magnesia-carbon refractories (AMC) bricks. Unlike those characterised materials which only have aluminium as an antioxidant, a brick also containing silicon is comparatively analysed in this paper. Along with metallic aluminium, silicon is among the most commonly used antioxidant additives in oxide-C refractories, but the studies on the incorporation of this metal into AMC bricks are rather limited.In this work, several complementary techniques were used in combination to achieve a detailed characterization in relation to the physical and chemical characteristics and thermal evolution of the Si-containing AMC refractory: X-ray fluorescence, plasma emission spectroscopy, gravimetry, granulometry, X-ray diffraction, differential thermal and thermogravimetric analyses, reflection optical and scanning electron microscopies, mercury intrusion porosimetry, and density, porosity, permanent linear change and permeability measurements. In addition, the characterization was completed by evaluating the chemical resistance to air and to a basic slag and calculating the equilibrium composition of the brick when it is subjected to high temperatures (up to 1400?°C). A comparison with the results obtained for previously characterised AMC bricks with similar MgO contents and metallic aluminium as an antioxidant was also made. The presence of silicon was related to finer open porosity and higher oxidation resistance at high temperature (1400?°C).     

Corrosion behavior of silicon nitride bonded silicon carbide refractory material by molten copper and copper slag

Silicon Carbide refractories may be used in contact with copper and copper slags. The object for the investigation of corrosion by the melt of copper and the copper slag was SiC siphon block of the slag collector in the runner of the cathode shaft furnace. It is exposed to the permanent flow of copper with small amount of slag. Slag on the surface of the melt is stopped by siphon block and it suffers the most extensive corrosion wear, but the same time it is a good object for investigation, because different parts of this plate are exposed to intensive corrosion by different corrosive agents.General observations show, that the corrosion of Si₃N₄-SiC by slag is sufficiently more extensive and the wear is about 3 mm per month, while the wear by the flowing copper is below 1 mm per month.The observation of the cross section of the exposed Si₃N₄-SiC plate on macro level shows 4–5 zones of different color. Microstructural observations show almost no changes of the material in direct contact with molten copper without exposure of air, that suggests slow dissolution of Silicon Carbide and Silicon Nitride in the flowing melt of copper (physical dissolution in case of permanent removal of reactants). The most severe wear of Si₃N₄-SiC refractory is by slag, because the chemical erosion takes place.     

Making reusable reaction-bonded silicon nitride crucibles for silicon casting from kerf-loss silicon waste

Silicon kerf loss during wafer slicing and the broken quartz crucibles after silicon casting are two major solid wastes from photovoltaic (PV) industry. Especially, the recycle of kerf-loss silicon has become an urgent issue because near 100 000 t of solid wastes are generated every year. One of the most meaningful recycle routes of the kerf-loss silicon is to make silicon nitride crucibles to replace the quartz crucibles. In this study, we demonstrated how this is feasible through acid leaching refining, slip casting, and nitridation. The reaction-bonded silicon nitride (RBSN) crucibles after oxidation were found pure enough for silicon ingot growth. More importantly, they could be reused after ingot growth. With the present examples, the potential of using the kerf-loss silicon for fine ceramics is prominent.     

Joining of silicon carbide ceramics using a silicon carbide tape

This paper reports the joining of liquid-phase sintered SiC ceramics using a thin SiC tape with the same composition as base SiC material. The base SiC ceramics were fabricated by hot pressing of submicron SiC powders with 4 wt% Al₂O₃–Y₂O₃–MgO additives. The base SiC ceramics were joined by hot-pressing at 1800-1900°C under a pressure of 10 or 20 MPa in an argon atmosphere. The effects of sintering temperature and pressure were examined carefully in terms of microstructure and strength of the joined samples. The flexural strength of the SiC ceramic which was joined at 1850°C under 20 MPa, was 343 ± 53 MPa, higher than the SiC material (289 ± 53 MPa). The joined SiC ceramics showed no residual stress built up near the joining layer, which was evidenced by indentation cracks with almost the same lengths in four directions.     

Silicon carbide refractory castables

Optimum formulations for castables intended for different service conditions are proposed. Silicon carbide castables containing ultradisperse particles of cement, silica fume, and electrofused corundum are developed. The castables do not weaken on heating and display superior operational properties: the compressive strength is 40–80 MPa at sintering temperature 400°C and 50–85 MPa at 1300°C, the strain onset temperature under a load of 0.2 MPa is 1700–1510°C; thermal stability (1300°C — water) is better than 45 heating/cooling cycles (1300°C — water); no change in linear and volume dimensions was observed on heating. The newly-developed castables can find application in various sectors of industry, in particular, as the refractory material for the lining of Whiting furnaces and porcelain kilns. __________ Translated from Novye Ogneupory, No. 12, pp. 36–39, December, 2005.     

Improved compositions of refractory putties for working surfaces of graphite-containing crucibles

The authors give data on the development of compositions of refractory putties for working surfaces of graphite-containing and silicon carbide — graphite crucibles and their use in the manufacture of crucibles. The experimental crucibles were found to have a substantially higher durability in smelting of bronzes and zinc alloys. The economic efficiency of the application of putties is also considered.Translated from Ogneupory, Vol. 35, No. 1, pp. 29 – 30, January, 1994.     

Evaporation-condensation derived silicon carbide membrane from silicon carbide particles with different sizes

Silicon carbide ceramic is a promising membrane material because of the high corrosive and high temperature resistance, and the excellent hydrophility. Here, a silicon carbide ceramic membrane with both substrate layer and separate layer composed of pure silicon carbide phase was successfully prepared. The effect of particle size on the microstructure and properties was investigated. The substrates were prepared from three silicon carbide particles at 2200 ℃. With the content increase of fine particle, the average pore size increased from 5.6 μm to 14.1 μm; meanwhile, the flexural strength of the substrate increased from 14.1 MPa to 24.6 MPa. The separation layers were made from particles of 3.0 μm and 0.5 μm. When sintered at 1900 ℃, the separation layer formed pore network with homogeneous structure. Such silicon ceramic membrane can be used in harsh conditions, including high temperature wastewater and strongly corrosive wastewater.