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高温等静压后处理液相烧结SiC陶瓷的结构与性能表征 总被引:3,自引:0,他引:3
本文研究了高温等静压(HIP)后处理工艺对液相烧结SiC陶瓷的显微结构及力学性能的影响.实验表明,HIP后处理的效果随烧结助剂的不同及液相烧结温度的变化而改变.Ar气氛条件下的HIP后处理可以提高液相烧结SiC的密度,减少或消除内部气孔等结构缺陷,但不引起晶粒的长大.N2条件下的HIP后处理除了具有Ar-HIP后处理的优点外,由于表面SiC与N2之间的反应生成的Si3N4可以有效地改善表面状态,从而达到表面改性,提高SiC陶瓷的力学性能.结构分析表明,经N2-HIP后处理,表面氮化层中晶粒细小,结构致密.同时,HIP后处理的效果还受液相烧结SiC陶瓷显微结构的影响,当液相烧结SiC的烧结温度较低,晶粒较细时,经HIP后处理,尤其是N2-HIP后处理,强度和韧性均有较大幅度的提高. 相似文献
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Y和YF3掺杂钛酸钡系PTCR材料的结构及性能 总被引:1,自引:0,他引:1
在不同烧结气氛下制备了Y和YF3掺杂钛酸钡材料,借助于XRD、SEM、XRF和阻温测试分析仪,研究了烧结气氛对Y和YF3掺杂钛酸钡材料结构和性能的影响.研究结果表明,低氧分压气氛可促进Y和YF3掺杂钛酸钡材料的烧结,晶粒长大,而且这二种掺杂钛酸钡材料都是n型半导体.经过氩气气氛烧结的Y掺杂钛酸钡材料PTCR效应较弱;而对在氩气气氛中烧结的0.3mol%YF3掺杂钛酸钡材料却观察到了较好的PTCR效应,这种效应的产生可能与F元素取代O位而导致材料的价控半导有关. 相似文献
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碳化硅晶须补强氧化铝复合材料的制备及其力学性能 总被引:5,自引:0,他引:5
本论文利用商用γ-Al2O3粉体和上海硅酸盐所制备的碳化硅晶须,通过热压工艺来制备碳化硅晶须补强氧化铝复合材料.当晶须含量为30vol%时,室温下复合材料的抗弯强度为812±38MPa,断裂韧性为8.8±0.1MPa·m1/2;在1200℃、Ar气氛下,分别为560±61MPa和6.1±0.4MPam1/2.在氮气氛下,由于晶须的损伤易导致材料的力学性能下降.添加剂可降低复合材料的烧结温度,但不利于其力学性能.显微结构观察发现,不同温度下,AS复合材料的增韧机理有变化. 相似文献
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Single-wall carbon nanotubes as attractive toughening agents in alumina-based nanocomposites 总被引:3,自引:0,他引:3
The extraordinary mechanical, thermal and electrical properties of carbon nanotubes have prompted intense research into a wide range of applications in structural materials, electronics, chemical processing and energy management. Attempts have been made to develop advanced engineering materials with improved or novel properties through the incorporation of carbon nanotubes in selected matrices (polymers, metals and ceramics). But the use of carbon nanotubes to reinforce ceramic composites has not been very successful; for example, in alumina-based systems only a 24% increase in toughness has been obtained so far. Here we demonstrate their potential use in reinforcing nanocrystalline ceramics. We have fabricated fully dense nanocomposites of single-wall carbon nanotubes with nanocrystalline alumina (Al2O3) matrix at sintering temperatures as low as 1,150 degrees C by spark-plasma sintering. A fracture toughness of 9.7 MPa m 1/2, nearly three times that of pure nanocrystalline alumina, can be achieved. 相似文献
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采用浆料喷涂与高温熔渗结合的方法,以γ-Y_2Si_2O_7和Y_2O_3-Al_2O_3-SiO_2三元氧化物粉体为原料,在多孔Si_3N_4表面制备致密γ-Y_2Si_2O_7陶瓷涂层,采用XRD和SEM测试方法系统研究原料配比及烧结温度对涂层结构、组织和抗热震性能的影响。结果表明:SiO2与Al2O3物质的量之比较高时,涂层为致密γ-Y_2Si_2O_7层和过渡层的双层结构;SiO_2与Al_2O_3物质的量之比较低时,只能形成单层结构;双层结构涂层的抗热震性能优于单层结构涂层。 相似文献
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W. Acchar M. Diniz Y. A. A. Fonseca C. R. C. Sousa E. S. Lima 《Journal of Materials Science》2008,43(2):597-601
Recently, studies have been developed in order to obtain Al2O3-NbC composite materials. The reinforced materials have shown good potential to be used as cutting tool materials at high-speed
cutting and high temperature as a substitute to WC-Co material. The main disadvantage to produce these alumina-reinforced
materials is the necessity to use pressure assisted sintering or high sintering temperatures to produce dense bodies. Manufacturing
of composite ceramic materials derived from polymer reactive filler has been intensively investigated. Polymer pyrolysis is
a relatively new and very promising method for obtaining ceramic material in complex shapes and lower sintering temperatures.
This work investigated a ceramic composite matrix based in SiCxOy and Al2O3 and reinforced with NbC obtained by means of the active fillers pyrolysis process. The results obtained in this work demonstrate
that using a mixture of polysiloxanes produces a composite material with better properties when compared to others polymer
materials. 相似文献
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The evolution of nanotechnology provides materials with new properties and over the last years a lot of effort has been put to introduce nano-particles into cement pastes in order to improve their properties and to produce materials of better performance. In the present research work, nano-SiO2 produced by pyrolysis and with specific area of 200 m2/g has been added at different percentages (0%, 0.5%, 1%, 2% and 5%) to high-strength cement pastes. These pastes were tested for their mechanical and structural properties at different ages. Nanoparticles act as nuclei for crystallization and large, idiomorphic crystals of Ca–Si composition were formed assisting, up to a certain percentage, in producing materials with dense structure, reduced porosity and improved strength. 相似文献
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《Materials Letters》1988,6(7):217-221
Heating of YBa2Cu3O7−x compacts above about 930°C is shown to induce liquid formation. Presence of the liquid phase results in excellent densification, but limited superconducting properties. Sintering below 930°C occurs primarily by solid-state diffusion. Although the density of these samples is low, the superconducting properties are similar to those of the dense materials produced via liquid-phase sintering. The highest current densities (≈ 500 A/cm2) have been obtained in these solid-state sintered samples. 相似文献
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In-situ hot pressing/solid-liquid reaction synthesis of dense titanium silicon carbide bulk ceramics
An in-situ hot pressing/solid-liquid reaction process was developed for the synthesis of dense polycrystalline Ti3SiC2 ceramics using Ti, Si, and graphite powders as starting materials. The present work demonstrated that this process was one
of the most effective and simple methods for the preparation of dense bulk Ti3SiC2 materials. Lattice constants of a=3.068 and c=17.645 are calculated for Ti3SiC2 made through this process. The synthesis temperature influenced the phase composition, microstructure and mechanical properties
of Ti3SiC2 prepared at different temperatures. And bulk materials with flexural strength of 480 MPa and fracture toughness of 7.88 MPa.m1/2 were obtained at 1600°C. The high fracture toughness and strength are discussed based on microstructure analysis.
Received: 31 July 1998 / Accepted: 28 August 1998 相似文献
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The controlled nucleation thermochemical deposition (CNTD) process differs from the conventional chemical vapor deposition (CVD) process in that CNTD results in a fine-grained non-columnar deposit with superior mechanical properties. Materials made by this technique include CM 500 (a WC alloy) and CM 4000 (CNTD SiC). These two materials, together with CVD Si3N4, were evaluated for their erosion and sliding wear characteristics and the results were compared with those obtained for conventional refractory and ceramic materials. It is shown that the application of a dense CVD or CNTD coating significantly improves the erosion resistance of substrate materials. 相似文献
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Im SH Kim NJ Kim DH Hwang CW Yoon DK Ryu BK 《Journal of nanoscience and nanotechnology》2012,12(2):1453-1456
Silicon dioxide (SiO2) thin films have gained considerable attention because of their various industrial applications. For example, SiO2 thin films are used in superhydrophilic self-cleaning surface glass, UV protection films, anti-reflection coatings, and insulating materials. Recently, many processes such as vacuum evaporation, sputtering, chemical vapor deposition, and spin coating have been widely applied to prepare thin films of functionally graded materials. However, these processes suffer from several engineering problems. For example, a special apparatus is required for the deposition of films, and conventional wet processes are not suitable for coating the surfaces of substrates with a large surface area and complex morphology. In this study, we investigated the film morphology and optical properties of SiO2 films prepared by a novel technique, namely, liquid phase deposition (LPD). Images of the SiO2 films were obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to study the surface morphology of these films: these images indicate that films deposited with different reaction times were uniform and dense and were composed of pure silica. Optical properties such as refractive index and transmittance were estimated by UV-vis spectroscopy and ellipsometry. SiO2 films with porous structures at the nanometer scale (100-250 nm) were successfully produced by LPD. The deposited film had excellent transmittance in the visible wavelength region. 相似文献
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氧化锆(ZrO2)陶瓷具有出色的机械性能, 但其应用受到低热导率(Thermal Conductivity, TC)的限制。本研究设计并通过微波烧结制备了高热导率氧化锆-氮化铝(AlN)复合陶瓷, 优化制备条件后, 抑制了两种物质之间的反应, 获得了致密的复合陶瓷(相对密度>99%), 详细研究了该复合陶瓷的组织演变、热学性能和力学性能。研究结果表明, 随着AlN含量的增加, 复合陶瓷的室温下热导率、热扩散系数和热容增加, 分别达到41.3 W/(m·K)、15.2 mm2/s和0.6 J/(g·K)。这种具有高热导率和抗热震性的ZrO2-AlN复合复合陶瓷在能源系统的高温热交换材料领域具有广阔的应用前景。 相似文献
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为了提高铜基摩擦材料在高速干摩擦条件下的耐磨性能和具有稳定的摩擦系数,通过粉末冶金方法,制备了铜-SiO2摩擦材料.在摩擦速度为1.6~47.1 m/s条件下,研究了SiO2含量、粒度及摩擦方式对材料摩擦磨损性能的影响.研究表明:材料的摩擦系数和磨损率随着SiO2含量的增加而略有增大;SiO2颗粒尺寸的变化,对摩擦系数影响不显著;摩擦方式对材料的摩擦磨损性能的影响明显.SiO2含量增加有利于提高摩擦系数归因于增加了摩擦面高硬度质点的数量.干摩擦条件下影响材料摩擦磨损性能的一个重要因素是摩擦方式.在高速摩擦条件下,形成的第三体组织致密而连续,这种致密而连续的第三体有利于降低磨损量,并明显降低由于摩擦速度不同而导致的摩擦系数的波动程度. 相似文献