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71.
Griselda A. Eimer Liliana B. Pierella Gustavo A. Monti Oscar A. Anunziata 《Catalysis Letters》2002,78(1-4):65-75
A novel route in the synthesis of Al-MCM-41 and Al-MCM-48, using tetraethoxysilane (TEOS) and sodium aluminate (NaAlO2) as Si and Al source has been obtained. The effect of surfactant nature and the synthesis conditions such as surfactant/Si ratio and hydrothermal treatment time on the formed mesostructure regularity has been studied. Different methods of template removal have also been evaluated. The samples were characterized by X-ray diffraction, nitrogen physisorption, FT-IR, and solid-state MAS NMR spectroscopy. 相似文献
72.
电子陶瓷和器件的低温共烧技术 总被引:1,自引:0,他引:1
较系统地介绍了电子器件用低温共烧陶瓷(low temperature cofired ceramics,LTCCs)材料,探讨了其工艺中的若干问题。电子器件用低温共烧陶瓷材料包括:玻璃/陶瓷复合材料、结晶化玻璃、晶化玻璃/陶瓷复合材料以及液相烧结陶瓷,其中典型的和最为常用的LTCCs为玻璃/陶瓷(特别是氧化铝)复合材料。正在研究的一些陶瓷介质材料中,Bi基介质材料引起了人们的关注。玻璃/陶瓷复合材料的制备工艺中,应当着重关注和加深了解玻璃的流动性和结晶性、玻璃的起泡、玻璃和陶瓷颗粒间的反应、共烧材料的匹配等问题,从优选材料配方和优化工艺着手,从而获得优质可靠的材质和器件。 相似文献
73.
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
74.
Virote Boonamnuayvitaya Chadapa Tayamanon Wiwut Tanthapanichakoon 《Chemical engineering science》2006,61(5):1686-1691
Mesoporous silica materials were synthesized by sol-gel method using tetraethoxysilane (TEOS) as precursors and surfactants i.e., cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene cetyl ether (Brij 56) as templates. Surfactant templates were completely removed by calcination to form mesoporous structure. The effects of type and amount of surfactants on the characteristics of samples were studied. The textural characteristics such as surface area, pore volume, pore size, and pore size distribution were determined by nitrogen sorption isotherms. Fourier transform infrared (FTIR) spectroscopy was employed to qualitatively identify the chemical functionality and to confirm the removal of surfactant template. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to directly observe surface morphology and mesoporous structure, respectively. The adsorption capacity of the synthesized adsorbent for toluene vapor was examined. We found that the pore volume and pore size of mesoporous materials affected the adsorption capacity. The sample prepared with high content of CTAB under basic condition (pH ∼7) yielded large pore volumes and pore sizes and subsequently possessed the high adsorption capacity for toluene vapor. 相似文献
75.
Y.T. Makkawi 《Chemical engineering science》2003,58(10):2035-2051
Here, an experimental investigation on the effective drag force in a conventional fluidized bed is presented. Two beds of different particle size distribution belonging to group B and group B/D powders were fluidized in air in a diameter column. The drag force on a particle has been calculated based on the measurement of particle velocity and concentration during pulse gas tests, using twin-plane electrical capacitance tomography. The validity of the voidage function “correction function”, (1−εs)n, for the reliable estimation of the effective drag force has been investigated. The parameter n shows substantial dependence on the relative particle Reynolds number , and the spatial variation of the effective static and hydrodynamic forces. It is also illustrated that, a simple correlation for the effective drag coefficient as function of the particle Reynolds number (Rep), expressed implicitly in terms of the interstitial gas velocity, can serve in estimating the effective drag force in a real fluidization process. Analysis shows that, the calculated drag force is comparable to the particle weight, which enables a better understanding of the particle dynamics, and the degree of spatial segregation in a multi-sized particle bed mixture. The analogy presented in this paper could be extended to obtain a generalized correlation for the effective drag coefficient in a fluidized bed in terms of Rep and the particle physical properties. 相似文献
76.
77.
Jianfeng Wu Jian Li Xiaohong Xu Lanfang Yang Jufang Wu Fang Zhao Chuanguo Li 《武汉理工大学学报(材料科学英文版)》2009,24(4):651-653
A new type of high temperature energy storage material was obtained through the melt infiltration method, using compounding
SiC ceramic foam as matrix and Na2SO4 as phase change material. The resulting composite material was measured by XRD, SEM, TG-DSC methods. The experimental results
indicate that the composite is composed of silicon carbide, sodium sulfate and square quartz, and no chemical reactions occurs
between Na2SO4 and SiC matrix. Na2SO4 has a good bonding with the SiC ceramic foam matrix. As the composite material is characterized by high thermal energy storage
density and high thermal conductivity, it is suit for energy storage under high temperature.
Funded by the “863” Hi-Tech Research and Development Program of China (2008AA05Z418) 相似文献
78.
数控超声磨削陶瓷叶片型面刀位轨迹计算 总被引:1,自引:0,他引:1
介绍了陶瓷超声磨削加工现状,建立了平行直纹面数学模型.分析了用圆柱磨轮四轴数控超声磨削平行直纹面时原理误差,并提出减小误差的措施,计算出磨轮空间轨迹,并进行陶瓷叶片型面超声磨削加工工艺试验.试验结果表明,超声磨削加工陶瓷叶片型面是可行的,所完成的刀位计算可有效减小原理误差. 相似文献
79.
电网企业物资集约化管理探讨 总被引:2,自引:0,他引:2
吴宗文 《重庆电力高等专科学校学报》2010,15(5):62-65
分析电网企业的物资集约化管理现状,明确物资集约化管理的重要性和必要性,从而探索研究电网企业物资集约化管理的途径. 相似文献
80.
杨从麇 《重庆电力高等专科学校学报》2010,15(4):69-71
分析体育课教学中的主要任务、教材内容、教学方法、成绩考核等几个问题,并对此进行初步的研究和探讨,提出改革意见和措施,以改善体育课的教学效果。 相似文献