共查询到20条相似文献,搜索用时 31 毫秒
1.
Young Sik Yoon Sang Woong Na Jaehyung Lee † Myeong-Woo Cho Eun-Sang Lee Won-Seung Cho 《Journal of the American Ceramic Society》2004,87(7):1374-1377
R -curve behavior of Si3 N4 –BN composites and monolithic Si3 N4 for comparison was investigated. Si3 N4 –BN composites showed a slowly rising R -curve behavior in contrast with a steep R -curve of monolithic Si3 N4 . BN platelets in the composites seem to decrease the crack bridging effects of rod-shaped Si3 N4 grains for small cracks, but enhanced the toughness for long cracks as they increased the crack bridging scale. Therefore, fracture toughness of the composites was relatively low for the small cracks, but it increased significantly to ∼8 MPa·m1/2 when the crack grew longer than 700 μm, becoming even higher than that of the monolithic Si3 N4 . 相似文献
2.
Jian-Feng Yang Tohro Sekino Yong-Ho Choa Koichi Niihara Tatsuki Ohji 《Journal of the American Ceramic Society》2001,84(2):406-12
The microstructural evolution and mechanical properties of Si3 N4 –SiC composites obtained by the sinter–post-HIP process were investigated. SiC addition prohibited β-Si3 N4 grain growth; however, the grain growth followed the empirical growth law, with exponents of 3 and 5 for the c - and the a -axis directions, respectively. Mechanical properties were strongly influenced by SiC addition and sintering conditions. Short-crack propagation behavior was measured and analyzed by the indentation-strength in-bending (ISB) method. The present composites had high short-crack toughness, compared with the values for monolithic Si3 N4 . The enhanced short-crack toughness was attributed to crack-tip bridging by the SiC particles. 相似文献
3.
Composites containing 30 vol%β-Si3 N4 whiskers in a Si3 N4 matrix were fabricated by hot-pressing. The composites exhibited fracture toughness values between 7.6 and 8.6 MPa · m1/2 , compared to 4.0 MPa · m1/2 for unreinforced polycrystalline Si3 N4 . The improvements in fracture toughness were attributed to crack wake effects, i.e., whisker bridging and pullout mechanisms. 相似文献
4.
Giuseppe Pezzotti Isao Tanaka Taira Okamoto 《Journal of the American Ceramic Society》1991,74(2):326-332
The fracture behavior at high temperature of a Si3 N4 -based SiC-whisker composite fabricated by hot isostatic pressing without sintering aids is compared with that of other highly refractory materials. Particular attention is directed toward evaluating the slow-crack-growth resistance of the composite up to 1440°C and relating this resistance to the microfracture behavior of Si3 N4 grains, SiC whiskers, and the intergranular, glassy SiO2 phase. Only thick whiskers operate to bridge the wake of the crack; these whiskers may make a positive contribution to the slow-crack-growth resistance. Impurities detected by EDX microanalysis at the grain boundary, however, apparently degrade the high-temperature properties, a finding supported by internal-friction measurements. Nevertheless, the high potential of the system without sintering aids for high-temperature structural applications has been demonstrated by the time to failure estimated from the measured slow-crack-growth resistance for a fixed flaw size. 相似文献
5.
Cha-Yang Chu Jitendra P. Singh Jules L. Routbort 《Journal of the American Ceramic Society》1993,76(5):1349-1353
The high-temperature flexural strength of hot-pressed silicon nitride (Si3 N4 ) and Si3 N4 -whisker-reinforced Si3 N4 -matrix composites has been measured at a crosshead speed of 1.27 mm/min and temperatures up to 1400°C in a nitrogen atmosphere. Load–displacement curves for whisker-reinforced composites showed nonelastic fracture behavior at 1400°C. In contrast, such behavior was not observed for monolithic Si3 N4 . Microstructures of both materials have been examined by scanning and transmission electron microscopy. The results indicate that grain-boundary sliding could be responsible for strength degradation in both monolithic Si3 N4 and its whisker composites. The origin of the nonelastic failure behavior of Si3 N4 -whisker composite at 1400°C was not positively identified but several possibilities are discussed. 相似文献
6.
John J. Petrovic Maria I. Pena Ivar E. Reimanis Michael S. Sandlin Samuel D. Conzone H. Harriet Kung Darryl P. Butt 《Journal of the American Ceramic Society》1997,80(12):3070-3076
The mechanical behavior of MoSi2 reinforced–Si3 N4 matrix composites was investigated as a function of MoSi2 phase content, MoSi2 phase size, and amount of MgO densification aid for the Si3 N4 phase. Coarse-phase MoSi2 -Si3 N4 composites exhibited higher room-temperature fracture toughness than fine-phase composites, reaching values >8 MP·am1/2 . Composite fracture toughness levels increased at elevated temperature. Fine-phase composites were stronger and more creep resistant than coarse phase composites. Room-temperature strengths >1000 MPa and impression creep rates of ∼10−8 s−1 at 1200°C were observed. Increased MgO levels generally were deleterious to MoSi2 -Si3 N4 mechanical properties. Internal stresses due to MoSi2 and Si3 N4 thermal expansion coefficient mismatch appeared to contribute to fracture toughening in MoSi2 -Si3 N4 composites. 相似文献
7.
Shuichi Kawano Junichi Takahashi Shiro Shimada 《Journal of the American Ceramic Society》2003,86(4):701-705
TiN-coated Si3 N4 particles were prepared by depositing TiO2 on the Si3 N4 surfaces from Ti(O- i -C3 H7 )4 solution, the TiO2 being formed by controlled hydrolysis, then subsequently nitrided with NH3 gas. A homogeneous TiO2 coating was achieved by heating a Si3 N4 suspension containing 1.0 vol% H2 O with the precursor at 40°C. Nitridation successfully produced Si3 N4 particles coated with 10–20 nm TiN particles. Spark plasma sintering of these TiN/Si3 N4 particles at 1600°C yielded composite ceramics with a relative density of 96% at 25 vol% TiN and an electrical resistivity of 10−3 Ω·cm in compositions of 17.5 and 25 vol% TiN/Si3 N4 , making these ceramics suitable for electric discharge machining. 相似文献
8.
Chang-an Wang Yong Huang Qingfeng Zan Linhua Zou Shengyou Cai 《Journal of the American Ceramic Society》2002,85(10):2457-2461
Based on a biomimetic design, Si3 N4 /BN composites with laminated structures have been prepared and investigated through composition control and structure design. To further improve the mechanical properties of the composites, Si3 N4 matrix layers were reinforced by SiC whiskers and BN separating layers were modified by adding Si3 N4 or Al2 O3 . The results showed that the addition of SiC whiskers in the Si3 N4 matrix layers could greatly improve the apparent fracture toughness (reaching 28.1 MPa·m1/2 ), at the same time keeping the higher bending strength (reaching 651.5 MPa) of the composites. Additions of 50 wt% Al2 O3 or 10 wt% Si3 N4 to BN interfacial layers had a beneficial effect on the strength and toughness of the laminated Si3 N4 /BN composites. Through observation of microstructure by SEM, multilevel toughening mechanisms contributing to high toughness of the laminated Si3 N4 /BN composites were present as the first-level toughening mechanisms from BN interfacial layers as crack deflection, bifurcation, and pull-out of matrix sheets, and the secondary toughening mechanism from whiskers in matrix layers. 相似文献
9.
Crack-Healing Behavior of Si3 N4 /SiC Ceramics under Cyclic Stress and Resultant Fatigue Strength at the Healing Temperature 总被引:1,自引:0,他引:1
Kotoji Ando Koji Takahashi Shin Nakayama Shinji Saito 《Journal of the American Ceramic Society》2002,85(9):2268-2272
Si3 N4 /SiC composite ceramics were sintered and subjected to three-point bending. A semi-elliptical surface crack of 100 μm surface length was made on each specimen. The crack-healing behavior under cyclic stress of 5 Hz, and resultant cyclic fatigue strengths at healing temperatures of 1100° and 1200°C, were systematically investigated. The main conclusions are as follows: (1) Si3 N4 /SiC composite ceramics have an excellent ability to heal a crack at 1100° and 1200°C. (2) This sample could heal a crack even under cyclic stress at a frequency of 5 Hz. (3) The crack-healed sample exhibited quite high cyclic fatigue strength at each crack-healing temperature, 1100° and 1200°C. 相似文献
10.
Hideki Hyuga Kiyoshi Hirao Mark I. Jones Yukihiko Yamauchi 《Journal of the American Ceramic Society》2003,86(7):1081-1087
Si3 N4 /carbon fiber composites were fabricated using several types of fiber. All the composites had higher fracture toughness compared with monolithic Si3 N4 ceramics. Tribological properties were investigated by a ball-on-disk method under unlubricated conditions. The composite containing fibers with a high orientation of graphite layers and high graphite content indicated a low friction coefficient. It was identified, by Raman spectroscopy, that graphite was transferred from the composite to the Si3 N4 ball of the counterbody during the wear test. This transferred layer was effective for producing the low friction behavior of the composite. 相似文献
11.
Satoshi lio Hitoshi Yokoi Masakazu Watanabe Yasushi Matsuo 《Journal of the American Ceramic Society》1991,74(2):296-300
The mechanical and thermal properties of Si2 N2 O/SiC-whisker composites were studied with emphasis on the effect of matrix composition and of whisker content. The fracture toughness of Si2 N2 O was remarkably improved by 90% with a concomitant 70% strength improvement by addition of SiC whiskers of only 10 vol%. Optimum mechanical and thermal properties of Si2 N2 O/SiC-whisker composites were obtained at an equimolar ratio of Si3 N4 /SiO2 , which is the stoichiometric composition for Si2 N2 O. Additional investigation concerning the Si2 N2 O-matrix/SiC-whisker interface by controlling sintering additives is necessary for further improvement of mechanical and thermal properties of Si2 N2 O/SiC-whisker composites. 相似文献
12.
Hideki Hyuga Mark I. Jones Kiyoshi Hirao Yukihiko Yamauchi 《Journal of the American Ceramic Society》2004,87(4):699-702
The tribological behavior of monolithic Si3 N4 and a Si3 N4 /carbon fiber composite has been assessed under high load and low speeds in an aqueous environment. The results showed that the friction coefficient of the Si3 N4 was not significantly reduced when compared with dry sliding, and this was attributed to the failure to maintain a lubricating layer between the solid–solid surfaces. In the case of the composite, the initial high friction coefficient was reduced shortly after the beginning of the wear test and maintained a low value (about 0.03) throughout. This was attributed to the solid lubricating effect of the composite resulting in lower stress at the contact asperities, preventing the removal of the lubricating layer. 相似文献
13.
Giuseppe Pezzotti 《Journal of the American Ceramic Society》1993,76(5):1313-1320
A dense and isotropic Si3 N4 composite body containing 25 vol% of α-SiC platelets, with average particle size of 24μm and aspect ratio of 8 to 10, was fabricated by hot isostatic pressing without any addition of sintering aids. In this composite, desirable properties for structural ceramics to be used in long-term high-temperature applications are conveniently combined: a fracture resistance comparable with that of Si3 N4 sintered with conspicuous amounts of additives, as well as a superior time-dependent strength and deformation behavior up to 1400°C, was found. The high-temperature reliability in the present composite was improved further than that of the additive-free Si3 N4 , mainly due to mechanisms operating in the wake of the crack. The key to the attainment of a valid synergism between nitride and carbide phase resides both in the presence of pure SiO2 glassy phase at the grain boundary and in the morphology of the reinforcement. 相似文献
14.
Jianren Zeng Yoshinari Miyamoto Osamu Yamada 《Journal of the American Ceramic Society》1991,74(9):2197-2200
Fine Si3 N4 -SiC composite powders were synthesized in various SiC compositions to 46 vol% by nitriding combustion of silicon and carbon. The powders were composed of α-Si3 N4 , β-Si3 N4 , and β-SiC. The reaction analysis suggested that the SiC formation is assisted by the high reaction heat of Si nitridation. The sintered bodies consisted of uniformly dispersed grains of β-Si3 N4 , β-SiC, and a few Si2 N2 O. 相似文献
15.
Jae Young Choi Chong Hee Kim Do Kyung Kim 《Journal of the American Ceramic Society》1999,82(10):2665-2671
The synthesis and structure of a monodispersed spherical Si3 N4 /SiC nanocomposite powder have been studied. The Si3 N4 /SiC nanocomposite powder was synthesized by heating under argon a spherical Si3 N4 /C powder. The spherical Si3 N4 /C powder was prepared by heating a spherical organosilica powder in a nitrogen atmosphere and was composed of a mixture of nanosized Si3 N4 and free carbon particles. During the heat treatment at 1450°C, the Si3 N4 /C powder became a Si3 N4 /SiC composite powder and finally a SiC powder after 8 h, while retaining its spherical shape. The composition of the Si3 N4 /SiC composite powder changed with the duration of the heat treatment. The results of TEM, SEM, and selected area electron diffraction showed that the Si3 N4 /SiC composite powder was composed of homogeneously distributed nanosized Si3 N4 and SiC particles. 相似文献
16.
Experimental results are presented on subcritical crack growth under sustained and cyclic loads in a HIPed Si3 N4 at 1450°C and a hot–pressed Si3 N4 –10 vol% SiCw composite in the temperature range 1300°–1400°C. Static and cyclic crack growth rates are obtained from the threshold for the onset of stable fracture with different cyclic frequencies and load ratios. Fatigue crack growth rates for both the monolithic and SiCw -reinforced Si3 N4 are generally higher than the crack growth velocities predicted using static crack growth data. However, the threshold stress intensity factor ranges for the onset of crack growth are always higher under cyclic loads than for sustained load fracture. Electron microscopy of crack wake contact and crack–tip damage illustrate the mechanisms of subcritical crack growth under static and cyclic loading. Critical experiments have been conducted systematically to measure the fracture initiation toughness at room temperature, after advancing the crack subcritically by a controlled amount under static or cyclic loads at elevated temperatures. Results of these experiments quantify the extent of degradation in crack–wake bridging due to cyclically varying loads. The effects of preexisting glass phase on elevated temperature fatigue and fracture are examined, and the creep crack growth behavior of Si3 N4 –based ceramics is compared with that of oxide-based ceramics. 相似文献
17.
Jae-Yuk Kim Takayoshi Iseki Toyohiko Yano 《Journal of the American Ceramic Society》1996,79(10):2744-2746
The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si3 N4 and a Si3 N4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si3 N4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si3 N4 particles milled with oxide additives. Monolithic Si3 N4 could be sintered to 94% of theoretical density (TD) at 1500°C with nitrate additives. The sintering temperature was about 100°C lower than the case with oxide additives. After pressureless sintering at 1750°C for 2 h in N2 , the bulk density of a Si3 N4 /20 wt% SiC composite reached 95% TD with nitrate additives. 相似文献
18.
The tribological behavior of Mo5 Si3 -particle-reinforced silicon nitride (Si3 N4 ) composites was investigated by pin-on-plate wear testing under dry conditions. The friction coefficient of the Mo5 Si3 –Si3 N4 composites and Si3 N4 essentially decreased slowly with the sliding distance, but showed sudden increase for several times during the wear testing. The average friction coefficient of the Si3 N4 decreased with the incorporation of submicrometer-sized Mo5 Si3 particles and also as the content of Mo5 Si3 particles increased. When the Mo5 Si3 –Si3 N4 composites were oxidized at 700°C in air, solid-lubricant MoO3 particles were generated on the surface layer. Oxidized Mo5 Si3 –Si3 N4 composites showed self-lubricating behavior, and the average friction coefficient and wear rate of the oxidized 2.8 wt% Mo5 Si3 –Si3 N4 composite were 0.43 and 0.72 × 10−5 mm3 (N·m)−1 , respectively. Both values were ∼30% lower than those for the Si3 N4 tested in an identical manner. 相似文献
19.
Haiyan Liu Morris E. Fine Herbert S. Cheng Alan L. Geiger 《Journal of the American Ceramic Society》1993,76(1):105-112
Mineral oil lubricated rolling and sliding wear of SiC whisker (SiCw ) reinforced Si3 N4 composite and monolithic Si3 N4 prepared identically against M2 tool steel were investigated using a cylinder-on-cylinder apparatus. Wear of this Si3 N4 was higher than that of the composite. Wear of the steel against Si3 N4 was also higher than that against the composite. Relatively larger scale microfracture occurred in the Si3 N4 than in the composite; more pullout and microchipping of carbide particles were observed in the steel against Si3 N4 than against the composite. Polishing of the worn surfaces of the steel occurred in both sliding and rolling tests. This was attributed to fine, hard wear debris circulating in the contact area. Spalling was observed in the steel sliding against Si3 N4 but not in the steel sliding against the composite. 相似文献
20.
Naoto Hirosaki Yoshinobu Yamamoto Toshiyuki Nishimura Mamoru Mitomo Junichi Takahashi Hisanori Yamane Masahiko Shimada 《Journal of the American Ceramic Society》2002,85(11):2861-2863
Phase relationships in the Si3 N4 –SiO2 –Lu2 O3 system were investigated at 1850°C in 1 MPa N2 . Only J-phase, Lu4 Si2 O7 N2 (monoclinic, space group P 21 / c , a = 0.74235(8) nm, b = 1.02649(10) nm, c = 1.06595(12) nm, and β= 109.793(6)°) exists as a lutetium silicon oxynitride phase in the Si3 N4 –SiO2 –Lu2 O3 system. The Si3 N4 /Lu2 O3 ratio is 1, corresponding to the M-phase composition, resulted in a mixture of Lu–J-phase, β-Si3 N4 , and a new phase of Lu3 Si5 ON9 , having orthorhombic symmetry, space group Pbcm (No. 57), with a = 0.49361(5) nm, b = 1.60622(16) nm, and c = 1.05143(11) nm. The new phase is best represented in the new Si3 N4 –LuN–Lu2 O3 system. The phase diagram suggests that Lu4 Si2 O7 N2 is an excellent grain-boundary phase of silicon nitride ceramics for high-temperature applications. 相似文献