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TiB2的自蔓延高温合成过程研究 总被引:15,自引:3,他引:12
研究了原料组成、稀释剂含量和颗粒尺寸、性质等对TiB2的自蔓延高温合成过程的影响。随着原料颗粒尺寸的增大,燃烧温度和燃烧波速度都减小;随着稀释剂含量的增加,燃烧温度、燃烧波速度和合成样品孔隙率都呈递减趋势,最终出现不稳定燃烧波,在垂直蔓延波方向形成穿透样品的片状裂纹,以燃烧温度3050K为分界点,在高燃烧温度区和低燃烧温度区里,过程激活能分别为140kj/mol和355KJ/mon,预示着不同的反 相似文献
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前言
自蔓延高温合成技术(Self—propagating High-temperatuer Synthesis)即SHS,它是许多金属和非金属难熔化合物在燃烧合成时依靠自身放热,来合成材料的技术。某些物质在合成时自身可以放热并利用此热量可以使合成反应继续下去的这种现象在19世纪中、后期被一些科学工作者发现,经过一个多世纪的努力,直到20世纪的五、六十年代人们才开始使其在受控的状态下和冶金机械等技术结合起来,发展成为具有普遍意义的制备材料新技术并应用于工业生产。 相似文献
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以废钽粉为原料,通过自蔓延高温合成技术制备TaC粉末,阐明了稀释剂加入量、压制压力等因素对燃烧波蔓延速率的影响,得到了合格的TaC粉末。 相似文献
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以废钽粉为原料,通过自蔓延高温合成技术制备TaC粉末,阐明了稀释剂加入量,压制压力等因素地燃烧波等蔓延速率的影响,得到了合格的TeC粉末。 相似文献
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Synthesis, Sintering, Microstructure, and Mechanical Properties of Ceramics Made by Exothermic Reactions 总被引:6,自引:0,他引:6
Raymond A. Cutler Kevin M. Rigtrup Anil V. Virkar 《Journal of the American Ceramic Society》1992,75(1):36-43
Al2 O3 -TiC, Al2 O3 -TiC0.5 N0.5 , Al2 O3 -WC, Al2 O3 -SiC, and Al2 O3 -HfB2 powders were synthesized by the aluminothermic reduction of oxides in the presence of carbon or boron. The reacted powders were milled to reduce the size of agglomerates and subsequently densified without applied pressure to near-theoretical density. Microstructures and mechanical properties of composites made from exothermically reacted powders were compared with similar ceramics made from commercially available powders. In situ sintering was possible in the Al2 O3 -TiC system using a closed graphite crucible to contain reaction gases. The synthesis of β -SiC at temperatures above 1400°C via the direct reaction of the elements (SHS) was compared with SiC made by the magnesiothermic reduction of SiO2 in the presence of C after removing the MgO by leaching. 相似文献
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ZrB2纤维或含ZrB2纤维复合粉的制备对于发展纤维增强超高温结构陶瓷基复合材料具有重要的意义.以ZrO2纤维、B2O3和Al粉为原料,通过自蔓延高温合成法制备了含ZrB2纤维的ZrB2/Al2O3复合粉.通过X射线衍射、场发射扫描电子显微镜、X射线能谱,对产物的相组成、微观形貌及化学组成进行了分析表征,用差示扫描量热-热重分析研究了原料混合粉在加热过程中的反应过程.研究了氩气压力对燃烧合成产物的物相组成及ZrB2纤维结构的影响,重点分析了产物中ZrB2的存在状态.结果表明:氩气压力为1.5 MPa下,产物相组成为ZrB2和Al2O3.部分ZrB2以ZrO2纤维为模板形成ZrB2纤维;部分ZrB2以颗粒形式分散在ZrB2/Al2O3复合粉中.生成的ZrB2纤维,表面粗糙,结构较为完整,直径约为10 μm. 相似文献
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Suman Kumari Mishra Swapan Kumar Das Ajoy Kumar Ray P. Ramachandrarao 《Journal of the American Ceramic Society》2002,85(11):2846-2848
An investigation of the sintering behavior of ZrB2 powder with Fe and Cr (0 to 20 wt%) addition was conducted. It was observed that Fe addition helps to enhance the density of ZrB2 only up to 10 wt%. Further addition of Fe degrades the sintering by segregation of Fe-rich phases. Formation of a eutectic phase containing a Fe:Zr ratio of 92.57:7.43 was also found in Fe-added samples. The addition of Cr to a ZrB2 matrix was found to result in swelling of the samples, leading to several cracks. 相似文献
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Synthesis of Ternary Titanium Aluminum Carbides Using Self-Propagating High-Temperature Synthesis Technique 总被引:6,自引:0,他引:6
Micha opaciski Jan Puszynski Jerzy Lis 《Journal of the American Ceramic Society》2001,84(12):3051-3053
Different ternary carbide phases, namely Ti3 AlC2 , Ti3 AlC, and Ti2 AlC, were successfully synthesized in a self-sustaining regime. Direct reactions among elemental powders of titanium, aluminum, and carbon are strongly exothermic, and the resulting reaction products consist of binary carbides and they are partially molten. The use of TiAl, instead of elemental titanium and aluminum, significantly reduces the combustion temperature. As a result, ternary titanium aluminum carbide phases are formed. In addition, the combustion-synthesized products are not sintered and easy to deagglomerate. Reaction conditions and X-ray diffraction patterns of different ternary phases formed in a self-sustaining regime are presented. 相似文献
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Filippo Maglia Umberto Anselmi-Tamburini Giorgio Spinolo Zuhair A. Munir 《Journal of the American Ceramic Society》2000,83(8):1935-1941
Cubic Zr1− x Me x O y (Me = Fe, Co, Ni, Cu) metastable solid solutions with metal content significantly higher than equilibrium levels have been synthesized by the self-propagating high-temperature synthesis method based on a thermite reaction between metallic zirconium and the transition-metal oxides CoO, Fe2 O3 , CuO, and NiO. Through in situ XRD analysis, it was determined that when heated to 1100°C, the cubic solid solution transformed to the tetragonal phase with the concomitant formation of iron oxide. When cooled to lower temperatures, the tetragonal phase transformed to the monoclinic phase at or below 500°C. Results of auxiliary experiments strongly suggest that the formation of the solid solution takes place behind the combustion front by a reaction between zirconia and the metal. 相似文献
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Jiuxin Jiang Peiling Wang Wanbao He Weiwu Chen Hanrui Zhuang Yibing Cheng Dongsheng Yan 《Journal of the American Ceramic Society》2004,87(4):703-705
Self-propagating high-temperature synthesis (SHS) was applied to synthesize α-SiAlON powders doped by RE (RE = Eu,Pr,Ce) and codoped by RE and yttrium. The results showed that the weight ratio of α-SiAlON to (α-SiAlON +β-SiAlON) decreased from 70%, 55%, and 25% for europium-, praseodymium-, and cerium-doped α-SiAlON compositions, respectively, and the weight percentage of α-SiAlON phase increased to 100% for both (Eu,Y) and (Pr,Y) systems and 94% for the (Ce,Y) system, indicating SHS is a promising approach for synthesizing α-SiAlONs stabilized by the cations that could not be incorporated into the α-SiAlON structure by conventional sintering methods. 相似文献
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Lokesh Chandra Pathak Debajyoti Bandyopadhyay Srinivasan Srikanth Swapan Kumar Das P. Ramachandrarao 《Journal of the American Ceramic Society》2001,84(5):915-920
Various aspects of in situ formation of Al2 O3 –SiC composites by the self-propagating high-temperature synthesis (SHS) technique have been investigated using thermal analyses (TG/DTA) of a powder mixture (4Al, 3SiO2 , 3C) and pellets in an argon atmosphere at different heating rates. Both the reaction initiation and peak temperatures are found to increase with the heating rates. At lower heating rates, the powder samples do not reveal any exothermic peak possibly because of poor reactivity and sluggish exothermic reaction. The appearance of exothermic peaks in the DTA plots after melting of aluminum indicates reduction of silica by liquid aluminum. Conversion of aluminum is found to decrease marginally with an increase in heating rates. The apparent activation energy of the process compares well with the interdiffusion activation energy of silicon and oxygen, indicating that oxygen diffusion in Si formed at the reaction front may be the rate-controlling factor for this SHS process. From SEM studies it appears that the formation of SiC whiskers is through liquid-phase mass transfer. 相似文献
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Ken Hirota Yoshihiko Takano Masaru Yoshinaka Osamu Yamaguchi 《Journal of the American Ceramic Society》2001,84(9):2120-2122
Cr2 N, CrN, and their mixtures (with desired fractions) have been prepared via self-propagating high-temperature synthesis (SHS) under a controlled nitrogen pressure, followed by hot isostatic pressing at 1300°C and 196 MPa under an atmosphere of argon gas. The combustion temperature increased as the nitrogen pressure increased. Single-phase Cr2 N was formed at 1040°C under a pressure of 0.18 MPa, and single-phase CrN was formed at 1730°C under a pressure of 2 MPa. The mechanical properties of the dense nitride ceramics (99.2% of the theoretical density) have been examined; the Vickers hardness (11.2 GPa for CrN and 14.5 GPa for Cr2 N) increased linearly as the fraction of Cr2 N increased, whereas the fracture toughness (∼4.7 MPa·m1/2 ) and bending strength (∼355 MPa) are constant, regardless of the fraction of Cr2 N/CrN. 相似文献