共查询到19条相似文献,搜索用时 62 毫秒
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自蔓延高温技术制备ZrC粉体(英文) 总被引:4,自引:0,他引:4
采用自蔓延高温合成(self-propagating high-temperature synthesis,SHS)技术,以 Zr+C 为反应体系合成了 ZrC 粉末。研究了实验参数对 SHS过程中点火电流、燃烧温度的影响。采用了 3 种碳源,研究了其对最终产物形貌及化学组成的影响。通过添加不同含量的 NaCl 作为 SHS 稀释剂,控制产物粒径及形貌。结果表明:炭黑是高温自蔓延法制备 ZrC 粉体的最佳碳源。由该体系制备的 ZrC 粉末粒径在 0.5~1 μm之间,氧含量为 0.38%。随稀释剂 NaCl 含量增加,体系燃烧温度降低,产物粒径减小。当 NaCl 含量为 30% (质量分数)时,体系燃烧温度下降至 1 810 K,产物 ZrC 粉末的粒径减小至 50 nm。 相似文献
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自蔓延高温合成V3TiNi0.56Al0.2贮氢材料及其电化学性能 总被引:1,自引:0,他引:1
钒基固溶体贮氢合金因其贮氢量大而成为近年来研究的热点,但传统的纯金属熔炼成本高,限制了其应用。文中从理论上计算了V2O5-TiO2-Ni-Al体系的绝热温度Tad=2879 K和单位质量反应热q=-2.80 kJ/g,表明能够进行自蔓延高温反应,且自蔓延高温合成法制备出了钒基固溶体型贮氢合金V3TiNi0.56Al0.2,通过实验研究了V3TiNi0.56Al0.2贮氢合金的组织结构和电化学性能。结果表明,组织结构与真空感应熔炼制备的基本相同,V3TiNi0.56Al0.2合金最大放电容量为350 mA.h/g,活化性能较好,但循环性能和高倍率放电能力差。 相似文献
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自蔓延高温合成(self-propagating high-temperature synthesis,SHS)是一种在数秒~几十秒内即可完成的合成技术,但是直接产物是多孔状的.在SHS产物还处于高温软化状态时立即快速加压(quick pressing,QP),可以一步实现合成和致密化获得致密材料,这一技术被称为SHS/QP技术.传统的高温烧结的致密化过程主要靠原子扩散实现,SHS/QP过程如此之快,其致密化机理尚不明确.为此,探讨了SHS/OP技术制备金属陶瓷和复相陶瓷的致密化机理.研究了SHS/OP技术制备金属陶瓷、复相陶瓷和叠层复合材料的结构和工艺过程,并制备了密实材料.结果表明:基于塑性变形机理,SHS/QP技术能制备出密实、晶粒基本不长大的纳米陶瓷. 相似文献
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用自蔓延高温合成(SHS)在钢管内壁生成Al_2O_3陶瓷涂层,制备了金属/陶瓷复合管。选择合适的添加剂及添加量,可以显著改善陶瓷层的涂覆质量。测试了复合管的抗热冲击性能。 相似文献
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自蔓延高温合成法制备Al2O3-Cr金属陶瓷 总被引:3,自引:0,他引:3
研究了稀释剂Cr2O3对Al-Cr2O3体系自蔓延高温合成(SHS)反应过程及反应产物的影响,并讨论了用自蔓延加压法制备致密的Al2O3-Cr金属陶瓷的可能性。实验结果表明:随稀释剂Cr2O3加入量的增加,Al-Cr2O3体系SHS反应温度和反应产物的孔隙度逐渐降低,激发反应所面的加热时间延长。稀释剂Cr2O3的加入能改善Al2O3与Cr之间的润湿性,避免在反应产物中出现Cr偏聚和分层现象。在一定稀释剂Cr2O3加入量下,通过采用在SHS反应结束后迅速施加-压力将可能制备出致密的Al2O3-Cr金属陶瓷。 相似文献
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《国际智能与纳米材料杂志》2013,4(1):64-71
Half-Heusler (HH) alloys constitute an important class of materials that exhibit promising potential in high-temperature thermoelectric (TE) power generation. In this work, we synthesized Zr1?x Yb x NiSn (x?=?0, 0.01, 0.02, 0.04, 0.06 and 0.10) HH alloys using a time-efficient levitation melting and spark plasma sintering procedure. X-ray diffraction showed that the samples were predominantly single phased, and that the lattice constant increased systematically with increasing Yb doping ratio. The doping effects of Yb on the thermoelectric properties were studied. It was found that Yb doping consistently decreased the electrical and thermal conductivities. On the other hand, the effects of Yb doping on the Seebeck coefficient were found to be non-monotonic. The magnitude of the Seebeck coefficient (n-type) was increased upon Yb doping up to x?=?0.02, above which Yb doping introduced notable p-type conduction. As a result, the room-temperature Seebeck coefficient of the x?=?0.10 sample became positive although the magnitude was not high. The thermoelectric figure of merit, ZT, reached a maximum of ~0.38 at 900 K for the x?=?0.01 sample. Selective doping on the Ni and Sn sites are necessary to further optimize the TE performance of Zr1?x Yb x NiSn alloys. 相似文献
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Microstructure and Mechanical Properties of Silicon Nitride Materials Fabricated from SHS Powders 总被引:1,自引:0,他引:1
Angel De Pablos Joaquin Bermudo Maria Isabel Osendi 《Journal of the American Ceramic Society》2001,84(5):1033-1036
Two different silicon nitride powders, one produced by self-propagating high-temperature synthesis (SHS) and one commercial, have been equally processed to obtain dense materials. Y2 O3 powders as a sintering aid and hot-pressing techniques were used to process the materials. The fracture toughness and strength of the materials prepared have been evaluated and the results comparatively discussed as a function of the microstructure, with special emphasis on the characteristics of the initial powders. 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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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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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
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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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自蔓延高温合成技术研究与应用的新进展 总被引:11,自引:0,他引:11
自蔓延高温合成(SHS)技术是一门新兴的学科,因其独特的优越性而吸引着各国学者进行研究。本文从研究和应用两个方面介绍了SHS的具体特点,重点分析了SHS技术在制备粉体、烧结、催化剂、强化致密化、焊接、颜料和涂层等典型的工业化实践应用的新进展,并进行了综合比较和系统归纳总结,通过分析,认为目前SHS应用存在的主要问题是如何获得高致密度的产品和怎样严格控制燃烧过程。 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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A two-step processing technique was used to make dense, homogeneous intermetallics in the Mo(Al,Si)2 —MoSi2 system. A variation of self-propagating high-temperature synthesis was used, in which starting pellets were nucleated at room temperature to make intermetallic powders from metallic precursors, followed by uniaxial hot pressing at 1600°—1800°C to achieve densification. The samples were held at the hot-pressing temperatures for several hours; therefore, this study also provided qualitative phase-stability information. The solubility limit of Al for Si in MoSi2 was <5% at 1800°C. Samples that had 10% Al substituted for Si yielded approximately equal amounts of MoSi2 and Mo(Al,Si)2 . 相似文献