Al_2O_3－SiC－C耐火材料在熔融还原熔体中的侵蚀

讨论了Ａｌ２Ｏ３－ＳｉＣ－Ｃ耐火材料在熔融还原熔体中的侵蚀机理．分析了铁浴式熔融还原熔体的性质、组成及种类和熔体的温度、熔体与耐火材料的相对运动速度以及ＳｉＣ加入量等因素对Ａｌ２Ｏ３－ＳｉＣ－Ｃ耐火材料在熔融还原熔体中侵蚀的影响，阐明了Ａｌ２Ｏ３－ＳｉＣ－Ｃ耐火材料在熔融还原熔体中的侵蚀特征及侵蚀机制。     

SiC晶须的形成及对Al_2O_3－C制品强度的影响

Ａｌ２Ｃ３－Ｃ制品中添加硅粉时，经１１００℃－１５００℃热处理后有ＳｉＣ晶须生成。ＳｉＣ晶须是由硅粉和炭发生反应而生成，其生成量随硅粉含量的增加而增多。实验表明，ＳｉＣ晶须生成后能明显提高制品的强度。     

铝电解烟道灰在Al_2O_3－SiC－C系耐火材料中的应用

以铝电解烟道灰代替Ａｌ２Ｏ３－ＳｉＣ－Ｃ系耐火材料中的工业氧化铝和石墨，采用正交实验的方法，探讨了各种物料加入量对耐火材料性能的影响。实验表明：烟道灰、ＳｉＣ．抗氧化剂的加入量（％）分别为１３～１４、９～１０、４左右。     

混铁车用Al_2O_3－SiC－C砖的研制与使用

采用矾土、电熔刚玉、ＳｉＣ粉及石墨为主要原料研制的Ａｌ２Ｏ３－ＳｉＣ－Ｃ砖，集多种原料的特点于一体，使之具有优异的高温性能，满足了温铁车三脱的使用要求。该砖在宝钢混铁车上与国外进口砖进行使用对比试验表明，其使用寿命接近日本进口砖，优于德国进口砖。     

Al_2O_3基质做模板制备Ag_2S/Al_2O_3纳米复合物及表征

采用无污染的水热合成技术,对滴涂AgNO3的Al_2O_3模板煅烧相同时间不同温度、同一温度煅烧不同时间,制备了Ag_2S/Al_2O_3纳米复合物。用X-射线粉末衍射仪及扫描电镜对复合物的形貌进行了测试和表征,得出制备Ag_2S/Al_2O_3纳米复合物的优良条件。     

Al_2O_3－SiC－C质浇注料抗热震性和抗渣铁侵蚀性的研究

对新研制的Ａｌ２Ｏ３－ＳｉＣ－Ｃ质浇注料和现用出铁沟料的抗热震性和抗渣铁侵蚀性进行了研究、结果表明，该材料具有较高的抗渣铁侵蚀能力和较好的抗热震稳定性。调节Ｓｉ与Ｃ的比例可生成高强度、耐渣蚀的纤维状ＳｉＣ。     

NiO－RE_2O_3／α－Al_2O_3催化剂制备过程中稀土的流失

用浸渍法考察先浸硝酸稀土、后浸硝酸镍制备ＮＩＯ－ＲＥ２Ｏ３／α－Ａｌ２Ｏ３催化剂过程中浸渍液的酸度、温度等因素对催化剂上稀土（ＲＥ２Ｏ３）流失的影响，并讨论了抑制稀土流失的方法。     

添加Si、Al、Si_3N_4对Al_2O_3－SiC－C质浇注料性能的影响

通过对Ａｌ２Ｏ３－ＳｉＣ－Ｃ质浇注料的力学性能、抗氧化性和抗渣蚀性的研究，表明添加Ｓｉ、Ａｌ、Ｓｉ３Ｎ４可提高材料的抗氧化性和抗法侵蚀性，并对烧后力学性能有一定改善。     

B_4C添加物对Al_2O_3-C和Al_2O_3-SiC-C耐火材料抗氧化性能的影响

在大气中1400℃下对添加标题提及的B_4C耐火材料的氧化特性进行了动力学研究。氧化率可以通过测量随氧化时间而变化的脱碳面积的比例来确定,也可以用一个圆柱体试样的局部化学反应模型进行分析。研究的结果表明,Al_2O_3-C耐火材料的氧化率由化学反应控制,Al_2O_3-SiC-C耐火材料的氧化率由质量转换控制。在Al_2O_3-SiC-C耐火材料的氧化区可观察到氧化铝颗粒表面有莫来石和9Al_2O_3·2B_2O_3,含SiO_2和B_2O_3的融体填充于气孔中。添加1.5％(质量百分比,下同)的B_4C,可以提高Al_2O_3-SiC-C耐火材料在空气中抗氧化性能。     

Al_2O_3微粉性能的研究

对国产的十余种陶瓷及耐火材料用Ａｌ２Ｏ３微粉做了形貌、粒度分布、水化增重率及烧结性能的研究。结果表明，Ａｌ２Ｏ３微粉的加入能明显促进烧结。微粉加入的粒度以１～５ｕｍ为宜，加入量以１５％～２０％最好。     

Fabrication and characterization of random chopped fiber reinforced reaction bonded silicon carbide composite

This paper deals with the microstructure and mechanical properties of reaction bonded silicon carbide reinforced with random chopped carbon fibers of 3 mm length. The composites were fabricated by dispersing chopped carbon fibers into bimodal SiC/C suspension, forming green body through slip casting, and then reaction sintering at 1700 °C. The effect of the chopped fiber fraction on microstructure and mechanical properties was evaluated. A significant increase of fracture toughness was obtained as the carbon fiber fraction approaches 30 vol.%. The chopped fibers had reacted with liquid silicon during reaction sintering, so little fiber pullout was observed. Crack deflection and bridging is the predominant mechanism for the composite toughening.     

Review of ballistic performance of alumina: Comparison of alumina with silicon carbide and boron carbide

Ceramic armour materials are designated to protect personnel and vehicles against ballistic damage. The main effort is now focused on developing ceramics with difficult-to-obtain properties, such as high ballistic performance and light weight. Over the past 30 years, the development of ceramic materials has led to a sustained improvement in their properties and structural homogeneity. Nevertheless, the relation of these properties with the ballistic performance of ceramics remains unclear.This paper reviews the current understanding regarding the failure stages of ceramic armour and the methods used to evaluate ballistic performance. A comparison of alumina with silicon carbide and boron carbide was performed.     

氧化铝纤维增强红柱石基复合材料的制备与性能

在南非进口红柱石细粉中分别加入 5 %、10 %、15 %和 2 0 %的氧化铝纤维 ,研究了纤维加入量对材料显气孔率、体积密度、力学性能及显微结构的影响。结果表明 :当氧化铝纤维加入量为 5 %～ 10 %时 ,材料的体积密度大 ,力学性能好 ,超过 10 %后材料的性能显著下降     

Toughening enhanced at elevated temperatures in an alumina/zirconia dual-phase matrix composite reinforced with silicon carbide whiskers

A unique temperature dependence of toughening is observed in an alumina/zirconia dual-phase matrix composite reinforced with silicon carbide whiskers. The work of fracture (WOF) of the composite is maximized at 400 °C to 130 J/m², which is about 6.5 times larger than that of monolithic alumina at room temperature. The WOF decreases sharply with an increase in temperature above 400 °C. The enhanced toughening at elevated temperatures is described by the stress-induced transformation toughening of tetragonal zirconia, which is affected by the internal thermal stress owing to thermoelastic mismatch between the matrix and the whiskers. The maximum WOF is not given only by the stress-induced transformation but also by the crack-face bridging of the whiskers. The WOF was optimized at a specific zirconia volume fraction of 0.7 in the matrix, which was essentially due to the maximized tensile internal stress on zirconia in the dual-phase matrix.     

Excellent ablation resistance and reusability of silicon carbide fiber reinforced silicon carbide composite in dissociated air plasmas

This work explores the potentials of SiC fiber reinforced SiC matrix composites (SiC_f/SiC) with SiC coating to resist aerodynamic ablations for thermal protection purpose. A plasma wind tunnel is employed to evaluate their anti-ablation property in dissociated air plasmas. The results suggest a critical ablation temperature of SiC coated SiC_f/SiC, ≈ 1910 °C, which is the highest ever reported in literatures. Benefited by ‘all-SiC’ microstructures and relative flat ablated surfaces, the SiC_f/SiC is still ablation-resistant up to ≈ 1820 °C after the occurrence of ablation. This implies an excellent ablation resistance and reusability property of SiC_f/SiC, which surpasses that of traditional carbon fiber reinforced composites. Finally, an ablation mechanism dominated by surface characteristic is proposed. For the SiC coated SiC_f/SiC, ablation is prone to take place at surface cracks formed by thermal mismatch; while for the ablated SiC_f/SiC, ablation is triggered at the exposed fiber bundles which is over-heated in the plasmas.     

Mechanical properties and recrystallization of alumina ceramics reinforced by silicon carbide whisker

The mechanical properties and recrystallization of a material consisting of Al₂O₃ and SiC whisker are considered for different hot pressing regimes. The best properties are obtained at an SiC whisker content of 20% in hot pressing in an argon medium at 1600°C (the ultimate bending strength is 600 MPa, the critical coefficient of stress intensityK _Ic=5.5 MPa · m^1/2). The bending strength measured at 1000°C is at least 400 MPa for the material pressed at 1700°C in air. It is established that the presence of SiC whisker on grain boundaries of Al₂O₃ noticeably impedes the growth of alumina grains in recrystallization for all chosen regimes of hot pressing (1650 – 1900°C, 15 – 45 min). The dominant grain size is 1 –5 µm. A mathematical model is suggested for evaluating the maximum grain size in uniform grain growth, which isD*=0.571 [1++(1+16.151/f)^1/2]d, whered, f are the diameter and the volume fraction of SiC whisker. The material can be recommended for use under conditions of thermomechanical stress and abrasive wear.Translated from Ogneupory, No. 5, pp. 8 – 12, May, 1995.     

Processing and fracture behaviour of hot pressed silicon carbide whisker reinforced alumina

The improvement of mechanical properties of silicon carbide whisker reinforced alumina has been investigated with emphasis on the effects of the whisker type and content, the hot pressing temperature and the influence of an interfacial film between the whisker and the matrix. The introduction of silicon carbide whiskers significantly improves the fracture toughness, flexural strength and creep resistance of polycrystalline alumina.

However, these properties are strongly dependent on the size and morphology of whiskers. Large diameter whiskers generate extensive micro-cracking which leads to a decrease in flexural strength. Also, the presence of carbon-coated SiC whiskers substantially increases the high temperature strain rate by promoting cavitation. A grain boundary glassy phase introduced by the carbon coating was also detected.     

Mechanical and electrical properties of carbon nanotube buckypaper reinforced silicon carbide nanocomposites

The nanocomposite was produced via phenolic resin infiltrating into a carbon nanotube (CNT) buckypaper preform containing B₄C fillers and amorphous Si particles followed by an in-situ reaction between resin-derived carbon and Si to form SiC matrix. The buckypaper preform combined with the in-situ reaction avoided the phase segregation and increased significantly the volume fraction of CNTs. The nanocomposites prepared by this new process were dense with the open porosities less than 6%. A suitable CNT–SiC bonding was achieved by creating a B₄C modified interphase layer between CNTs and SiC. The hardness increased from 2.83 to 8.58 GPa, and the indentation fracture toughness was estimated to increase from 2.80 to 9.96 MPa m^1/2, respectively, by the reinforcing effect of B₄C. These nanocomposites became much more electrically conductive with high loading level of CNTs. The in-plane electrical resistivity decreased from 124 to 74.4 μΩ m by introducing B₄C fillers.     

Crushing behavior of alumina inclusions with different porosity during hot compression

Alumina inclusions in commercial as-cast 2.25Cr1Mo0.25V aluminum deoxidized steel exhibited a feature of porous structure. In order to investigate the crushing characteristics of alumina inclusion during hot working, a series of alumina blocks with different porosity whose properties are similar to the alumina inclusions in ingots were prepared using spark plasma sintering. The crushing behavior of alumina blocks during hot compression with quasi-static load was studied. A prediction model of compressive strength of alumina inclusions considering apparent porosity was established on basis of hyperbolic sine Arrhenius equation. A novel crushing mode diagram for alumina inclusions characterized by Z parameter was proposed. The crushing mechanism of alumina inclusions under different deformation parameters was clarified by fracture characteristics. The results showed that the hot compression process of alumina presented a typical brittle fracture, the compressive strength was more sensitive to deformation conditions at lower apparent porosity as compared with the conditions of higher apparent porosity. With the increase of Z, the crushing mode of alumina inclusions gradually changed from intergranular fracture to transgranular fracture.     

New porous silicon carbide composite reinforced by intact high-strength carbon fibres

A novel processing method to produce a carbon-fibre-reinforced silicon carbide (C/SiC) is presented and the mechanical properties are evaluated. The low-cost process yields a reaction bonded silicon carbide matrix but avoids efficiently reactive damage of the carbon fibres. Thus, the C/SiC-material shows a fibre-dominated behaviour due to high fibre strength and matrix porosity. The characteristics and mechanical properties of this C/SiC are highlighted. The discussion deals with the particular mechanical characteristics of porous-matrix materials relating to similar materials investigated hitherto.