共查询到20条相似文献,搜索用时 169 毫秒
1.
本文利用XRD、SEM和EDAX等方法系统研究了含ZrO_2约33%的ZrO_2-Al_2O_3-SiO_2系耐火材料,从生坯煅烧至1600℃所发生的结晶相变化,显微结构变化及烧结过程中ZrSiO_4的分解温度.结果表胆:ZrSiO_4的分解比莫来石的形成要快,莫来石是由ZrSiO_4分解的非晶SiO_2与Al_2O_3反应形成的.1450~1550℃是锆莫来石耐火材料煅烧过程中物相变化最激烈的温度范围,该反应对致密化产生不利影响.要使结构致密,烧成温度必须大干1600℃. 相似文献
2.
3.
4.
6.
7.
以铝厂污泥和苏州土合成的不同粒径级配的莫来石作为原料,添加少量堇青石作为结合剂,甲基纤维素、水作为添加剂研制优质莫来石耐火材料。通过测定耐火材料的抗折强度、热稳定性、气孔率等性能指标确定出最佳配方。结果表明:No.1配方的0次抗折强度为126.76 kgf/cm^2,1次热震抗折强度为81.07 kgf/cm^2,10次热震抗折强度为45.07 kgf/cm^2。1次热震强度保持率为49.24%,10次热震强度保持率为36.52%,10次热震后气孔率为40.37%,0次热震吸水率为24.76%,0次热震体积密度为1.61g/cm3。 相似文献
8.
9.
10.
11.
Porous Mullite Preforms via Fused Deposition 总被引:1,自引:0,他引:1
Raj Atisivan Susmita Bose Amit Bandyopadhyay 《Journal of the American Ceramic Society》2001,84(1):221-223
Nonrandom porous mullite ceramic preforms were fabricated by the indirect fused deposition process. MgO was added to commercial mullite powders as a sintering aid. The influence of porosity and the amount of MgO on the densification and mechanical properties was studied. The shrinkage and compressive strength of the porous samples were found to increase with increasing MgO content. At constant MgO concentration, shrinkage was found to decrease linearly as the volume fraction of porosity increased. The compressive strength of porous samples decreased with an increase in the volume fraction of porosity at constant MgO content. 相似文献
12.
13.
莫来石/刚玉复相陶瓷热断裂特性研究 总被引:1,自引:0,他引:1
通过调整复相陶瓷中颗粒相的组成与级配,利用引入的热膨胀失配机制,控制莫来石/刚玉复相陶瓷显微结构,改善高温复相陶瓷热稳定性,着重研究了莫来石/刚玉复相陶瓷的热断裂特性.研究表明,全部采用莫来石颗粒相时,由于柱状莫来石颗粒极易发生热冲击穿晶断裂,且热膨胀失配导致的微裂纹较长,密度较小,故复相陶瓷热稳定性较差;全部采用刚玉颗粒相时,虽然基质相裂纹扩展至刚玉颗粒表面时穿晶断裂与沿晶的裂纹扩展同时发生,有利于改善复相陶瓷热稳定性,但由于热膨胀失配过度,未经热冲击时已产生宏观裂纹,故热稳定性最差.而采用莫来石/刚玉复合颗粒相,相比例为75/25制备的复相陶瓷试样,热膨胀失配形成的微裂纹较短,密度较大,其热稳定性最优. 相似文献
14.
15.
Hiroki Fujita George Jefferson Robert M. McMeeking Frank W. Zok 《Journal of the American Ceramic Society》2004,87(2):261-267
Weakly bonded particle mixtures of mullite and alumina are assessed as candidate matrixes for use in porous matrix ceramic composites. Conditions for the deflection of a matrix crack at a fiber-matrix interface are used to identify the combinations of modulus and toughness of the fibers and the matrix for which damage-tolerant behavior is expected to occur in the composite. Accordingly, the present study focuses on the modulus and toughness of the particle mixtures, as well as the changes in these properties following aging at elevated temperature comparable to the targeted upper-use temperature for oxide composites. Models based on bonded particle aggregates are presented, assessed, and calibrated. The experimental and modeling results are combined to predict the critical aging times at which damage tolerance is lost because of sintering at the particle junctions and the associated changes in mechanical properties. For an aging temperature of 1200°C, the critical time exceeds 10 000 h for the mullite-rich mixtures. 相似文献
16.
17.
Mullite for Structural, Electronic, and Optical Applications 总被引:2,自引:0,他引:2
Ilhan A. Aksay Daniel M. Dabbs Mehmet Sarikaya 《Journal of the American Ceramic Society》1991,74(10):2343-2358
Mullite (3Al2 O3 ·2SiO2 ) is becoming increasingly important in electronic, optical, and high-temperature structural applications. This paper reviews the current state of mullite-related research at a fundamental level, within the framework of phase equilibria, crystal structure, synthesis, processing, and properties. Phase equilibria are discussed in terms of the problems associated with the nucleation kinetics of mullite and the large variations observed in the solid-solution range. The incongruent melting behavior of mullite is now widely accepted. Large variations in the solid solubility from 58 to 76 mol% alumina are related to the ordering/disordering of oxygen vacancies and are strongly coupled with the method of synthesis used to form mullite. Similarly, reaction sequences which lead to the formation of mullite upon heating depend on the spatial scale at which the components are mixed. Mixing at the atomic level is useful for low-temperature (<1000°C) synthesis of mullite but not for low-temperature sintering. In contrast, precursors that are segregated are better suited for low-temperature (1250° to 1500°C) densification through viscous deformation. Flexural strength and creep resistance at elevated temperatures are significantly affected by the presence of glassy boundary inclusions; in the absence of glassy inclusions, polycrystalline mullite retains >90% of its room-temperature strength to 1500°C and displays very high creep resistance. Because of its low dielectric constant, mullite has now emerged as a substrate material in high-performance packaging applications. Interest in optical applications mainly centers on its applicability as a window material within the mid-infrared range. 相似文献
18.
Mullite whiskers were synthesized by heating a mixture of SiO2 and silicon in an alumina tube reactor under a flow of H2 and CF4 . The length and diameter of the whiskers were several hundred micrometers and >15 μm, respectively. It was postulated that a vapor phase reaction between SiF4 and AlF3 made possible the synthesis of the large mullite whiskers. 相似文献
19.
Fabrication and Property of Mullite Whiskers Frameworks with an Ultrahigh Porosity by Expandable Mesocarbon Microbeads 下载免费PDF全文
De‐Jun Zeng Ya‐Ming Zhang Jian‐Feng Yang Bo Wang Junichi Matsushita 《Journal of the American Ceramic Society》2016,99(7):2226-2228
Mullite whiskers frameworks with an ultrahigh porosity were fabricated by the vapor‐phase reaction of AlF3, Al2O3, and SiO2 and adding expandable mesocarbon microbeads (MCMB) as a pore‐forming agent. A large volume expansion of 122% for MCMB due to its layered structure occurred during the formation of mullite whiskers, resulting in the expansion of samples and high porosities of 87.7%–98.2% at 50–90 wt% MCMB contents. Perfect whiskers and a lap‐joint structure formed due to the formation of mullites through the vapor‐phase reaction. A bimodal pore structure was achieved from the spaces of the whiskers framework and burning of the expanded MCMB. High compressive strengths of 1.7 to 5.4 MPa were obtained for the porous mullite at porosities of 94.2%–87.7%, which suggested a rigid structure; these strengths at the ultrahigh porosities are attributed to the merit of the framework with high strength whiskers and their strong bonding. 相似文献
20.
Claus H. Rüscher Shiro Shimada Hartmut Schneider 《Journal of the American Ceramic Society》2002,85(6):1616-1618
A plane-parallel, polished, 0.9 mm thick, single-crystal (001) plate of 2:1 mullite was treated for 6 h at 1600°C in an Ar/H2 O (90/10) gas mixture at 100 kPa. Optical microscopy studies and infrared (IR) reflection spectroscopy studies of the lattice vibrations yielded no evidence for change with respect to the untreated reference crystal. However, IR absorption spectroscopy showed that structurally bound OH groups were formed by the heat treatment in the Ar/H2 O gas mixture. IR absorption depth profile analysis showed a rather homogeneous OH distribution through the crystal. Five different hydroxyl groups were separated according to dipole orientations and peak positions: E ‖ a , ω a 1 = 3447 cm−1 , ω a 2 = 3579 cm−1 ; E ‖ b , ω b 1 = 3456 cm−1 , ω b 2 = 3544 cm−1 ; and E ‖ c , ω c 1 = 3498 cm−1 . All IR peaks were strongly broadened (between 90 and 150 cm−1 ) because of a distribution in O-H binding distances caused by the real structure of mullite. 相似文献