共查询到19条相似文献,搜索用时 171 毫秒
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高温处理对渗硅碳化硅性能的影响 总被引:1,自引:0,他引:1
研究了全碳粉反应渗硅碳化硅(PCRBSC)材料在1700℃高温氩气氛中4h的处理,研究结果表明,RCPBSC材料的结构对高温处理后的强度有很大的影响,特别是游离硅sfi,游离碳fc的含量明显影响高温处理后PCRBSC材料的抗折强度。 相似文献
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渗硅碳化硅材料结构与性能关系的研究 总被引:6,自引:1,他引:6
采用低廉石油焦碳分为原料制造全碳粉生坯,通过有机添加剂来调配生坯中碳的比例,以控制烧结体中游离硅(fsi)、游离碳(fC)含量(其中fs,fc为烧结中未反应的硅和碳),研究了全碳粉反应硅碳化硅(PCRSC)材料的结构与力学性能的关系,分析了渗硅碳化硅材料中游离硅、游了碳含量对抗弯强度的影响。结果表明:渗硅碳化硅材料中随游离硅含量的增加,其抗弯速度下降,并且二者呈直线关系,符合线性复合规则,另一方面,游离碳含量较高的渗硅碳化硅材料,尽管游离硅含量低,但其抗弯强度低于等量或较多游了硅含量的渗硅碳化硅材料的抗弯强度。 相似文献
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为提高钢纤维混凝土耐久性能,采用复掺的方式,选择高品质的硅灰掺入到钢纤维的混凝土结构中。在保证基准配合比相同的情况下,通过不同的硅灰与钢纤维配合比,探讨硅灰对钢纤维混凝土耐久性能的影响。通过实验结果表明,随着硅灰掺入钢纤维混凝土量的增加,混凝土的抗折强度、抗压强度和劈裂强度、抗冻性能都明显提高,并在12%硅灰+1.2%钢纤维时达到最大。 相似文献
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开发了湿式氧化分解和电量测定法,该分析法不受含有的杂质的影响,可以定量分析碳化硅原料和碳化硼原料中的游离碳量,精确地求出碳化硅的纯度. 相似文献
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选用四种不同孔隙结构的石墨进行熔融渗硅(简称熔渗)反应,采用扫描电镜、X-射线衍射、压汞、CT等方法表征了熔渗前后材料的微观形貌、物相及孔隙结构。结果表明,熔渗后的材料由石墨、硅及碳化硅三种物相组成,且硅及碳化硅的分布与石墨孔隙结构相关。熔渗后样品孔隙率均<1%,体积密度提高21.08%~35.94%。熔渗后材料强度及模量均有明显提高,强度是原石墨样品的1.7~6.2倍,模量是原石墨样品的2.4~7倍,提高幅度与石墨孔隙结构及晶粒尺寸相关。理论计算结果表明,石墨样品熔渗过程主要受扩散-反应控制。 相似文献
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采用碳化硅、烧高岭土、氢氧化铝、滑石为主要原料,石墨为造孔剂制备了碳化硅/堇青石复相多孔陶瓷.研究了烧结温度和烧结助剂二氧化铈对碳化硅/堇青石复相多孔陶瓷气孔率和强度的影响,并分别用XRD和SEM分析晶相组成和断面显微结构表明:制备出的SiC多孔陶瓷的主相是SiC,结合相是堇青石与方石英,多孔陶瓷具有相互连通的开孔结构;在1350℃烧结,并保温3h,当造孔剂含量为15%时,碳化硅/堇青石复合多孔陶瓷性能最佳,其气孔率31.80%,相应的弯曲强度为63.74 MPa.在1200℃下,添加不同含量的CeO2,对烧结样品的相组成有影响,能够降低生成堇青石的温度,在CeO2含量为3%的样品中,堇青石的峰最明显,但是过量的氧化铈会抑制了堇青石的生成;随着CeO2加入量的增加,其气孔率和弯曲强度也会随之变化,1200℃下,在CeO2加入量为4%时其弯曲强度最优.但随着CeO2的含量的增加,其气孔率逐渐下降. 相似文献
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Yoshio Akimune Yasushi Katano Kazuo Matoba 《Journal of the American Ceramic Society》1989,72(5):791-798
The silicon carbide (SiC) whisker reinforcement of silicon nitride (Si3 N4 ) improves fracture strength and toughness, hardness, and Young's modulus, resulting in higher resistance of the composites to sphere penetration and crack initiation at spherical impact. Sintered Si3 N4 shows an elastic/plastic response and initiates median/radial cracks at 100 m/s impact velocity. SiC-whisker/Si3 N4 composites, on the other hand, demonstrate an elastic response, with Hertzian cone crack initiation, only when impact velocity exceeds 280 m/s. The SiC-whisker/Si3 N4 composites thus exhibit improved strength degradation versus critical impact velocity characteristics because of improved mechanical properties provided by the SiC whiskers. 相似文献
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Strength of Nicalon Silicon Carbide Fibers Exposed to High-Temperature Gaseous Environments 总被引:1,自引:0,他引:1
The effects of exposures to high-temperature gaseous atmospheres on the strength of Nicalon SiC fibers were investigated. The exposure conditions were as follows: (1) H2 with various P H2O for 10 h at 1000° and 1200°C, and (2) air for 2 to 100 h at 800° to 1400°C. Individual fibers were tested in tension following each exposure. The strengths of the fibers were strongly influenced by the exposure atmosphere and temperature, but less affected by time at temperature. When exposed in air, a SiO2 layer was formed on the surface, minimizing the degradation of strength. However, this beneficial effect was negated under conditions in which the SiO2 layer became too thick. The most severe degradation resulted from exposure to a reducing atmosphere, presumably due to the reduction of SiO2 inherent in the fibers. 相似文献
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Hironori Kodama Hiroshi Sakamoto Tadahiko Miyoshi 《Journal of the American Ceramic Society》1989,72(4):551-558
SiC-monofilament-reinforced SiC or Si3 N4 matrix composites were fabricated by hot-pressing, and their mechanical properties and effects of filaments and filament coating layers were studied. Relationships between frictional stress of filament/matrix interface and fracture toughness of SiC monofilament/Si3 N4 matrix composites were also investigated. As a result, it was confirmed experimentally that in the case of composites fractured with filament pullout, the fracture toughness increased as the frictional stress increased. On the other hand, when frictional stress was too large (>about 80 MPa) for the filament to be pulled out, fracture toughnesses of the composites were almost the same and not so much improved over that of Si3 N4 monolithic ceramics. The filament coating layers were found to have a significant effect on the frictional stress of the SiC monofilament/Si3 N4 matrix interface and consequently the fracture toughness of the composites. Also the crack propagation behavior in the SiC monofilament/Si3 N4 matrix composites was observed during flexural loading and cyclic loading tests by an in situ observation apparatus consisting of an SEM and a bending machine. The filament effect which obstructed crack propagation was clearly observed. Fatigue crack growth was not detected after 300 cyclic load applications. 相似文献
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本文提出了一种简单有效的预氧化处理方法,用来强化反应烧结碳化硅(RBSC),研究了800~1 300 ℃预氧化处理对其微观结构和力学性能的影响,探究了含不同尺寸压痕裂纹的材料在氧化前后残余弯曲强度的变化规律。结果表明,随着氧化温度的升高,RBSC的室温强度和Weibull模数均存在先下降后上升,然后再下降的趋势,主要原因是不同温度氧化后的RBSC表面形貌不同。在1 200 ℃下预氧化2 h,RBSC的弯曲强度和Weibull模数都明显变大,强度提升了19.9%,Weibull模数由7.3提升到11.8。然而,800 ℃低温氧化不完全和1 300 ℃高温氧化反应过于强烈均会导致弯曲强度和Weibull模数下降。在最优氧化条件(1 200 ℃氧化2 h)下,含压痕裂纹(载荷20 N)的RBSC试样的残余弯曲强度在氧化后由201.1 MPa提高到324.2 MPa,强化机理是高温氧化生成的SiO2能够消除材料表面缺陷和微裂纹。 相似文献
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Takayuki Narushima Michihisa Kato Shin Murase Chiaki Ouchi Yasutaka Iguchi 《Journal of the American Ceramic Society》2002,85(8):2049-2055
The oxidation behavior of a silicon wafer, chemically vapor-deposited SiC, and single-crystal SiC was investigated in an oxygen—2%–7% ozone gas mixture at 973 K. The thickness of the oxide film that formed during oxidation was measured by ellipsometry. The oxidation rates in the ozone-containing atmosphere were much higher than those in a pure oxygen atmosphere. The parabolic oxidation kinetics were observed for both silicon and SiC. The parabolic rate constants varied linearly with the ozone-gas partial pressure. Inward diffusion of atomic oxygen formed by the dissociation of ozone gas through the SiO2 film apparently was the rate-controlling process. 相似文献
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Tatsuki Ohji Yukihiko Yamauchi Wataru Kanematsu Shoji Ito 《Journal of the American Ceramic Society》1989,72(4):688-690
The tensile strength distribution of sintered silicon carbide was measured at room temperature and 1300°C in air and fracture defects were characterized. The measured strength was compared with strength obtained from flaw characteristics and fracture toughness assuming a peripherally cracked spherical void model. 相似文献
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Conversion of Oak to Cellular Silicon Carbide Ceramic by Gas-Phase Reaction with Silicon Monoxide 总被引:7,自引:0,他引:7
Evelina Vogli Joydeb Mukerji Christiane Hoffman Ralf Kladny Heino Sieber Peter Greil 《Journal of the American Ceramic Society》2001,84(6):1236-1240
Oak has been converted to a porous biocarbon template by annealing in an inert atmosphere above 800°C. Subsequent infiltration with gaseous SiO at 1550–1600°C under flowing argon of atmospheric pressure finally resulted in the formation of a porous, cellular β-SiC ceramic. The conversion retains the biomorphic cellular morphology of oak tissue. While pores in the cell walls with a diameter less than ∼1 μm vanished, two distinct pore channel maxima representing tracheidal cells and large vessels remained in the SiC ceramic. Depending on the cellular morphology of different kinds of wood, e.g., strut thickness and pore size distribution, gas-phase conversion to single-phase β-SiC can be used to manufacture cellular ceramics with a wide range of pore channel diameters. 相似文献