共查询到20条相似文献,搜索用时 31 毫秒
1.
Inna G. Talmy James A. Zaykoski Mark M. Opeka 《Journal of the American Ceramic Society》2008,91(7):2250-2257
The effect of Si3 N4 , Ta5 Si3 , and TaSi2 additions on the oxidation behavior of ZrB2 was characterized at 1200°–1500°C and compared with both ZrB2 and ZrB2 /SiC. Significantly improved oxidation resistance of all Si-containing compositions relative to ZrB2 was a result of the formation of a protective layer of borosilicate glass during exposure to the oxidizing environment. Oxidation resistance of the Si3 N4 -modified ceramics increased with increasing Si3 N4 content and was further improved by the addition of Cr and Ta diborides. Chromium and tantalum oxides induced phase separation in the borosilicate glass, which lead to an increase in liquidus temperature and viscosity and to a decrease in oxygen diffusivity and of boria evaporation from the glass. All tantalum silicide-containing compositions demonstrated phase separation in the borosilicate glass and higher oxidation resistance than pure ZrB2 , with the effect increasing with temperature. The most oxidation-resistant ceramics contained 15 vol% Ta5 Si3 , 30 vol% TaSi2 , 35 vol% Si3 N4 , or 20 vol% Si3 N4 with 10 mol% CrB2 . These materials exceeded the oxidation resistance of the ZrB2 /SiC ceramics below 1300°–1400°C. However, the ZrB2 /SiC ceramics showed slightly superior oxidation resistance at 1500°C. 相似文献
2.
Byung-Jin Choi Young-Hag Koh Hyoun-Ee Kim 《Journal of the American Ceramic Society》1998,81(10):2725-2728
The effects of microstructure and residual stress on the mechanical properties of Si3 N4 -based three-layer composite materials were investigated. The microstructure of each layer was controlled by the addition of two differently sized silicon carbides: fine SiC nanoparticles (∼200 nm) or relatively large SiC platelets (∼20 µm). When the SiC nanoparticles were added, the average grain size of Si3 N4 was reduced because of the inhibition of grain growth by the particles. On the other hand, when the SiC platelets were added, the microstructure of Si3 N4 was not much changed because of the large size of the platelets. Three-layer composites were fabricated by placing the Si3 N4 /SiC-nanoparticle layers on the surface of the Si3 N4 /SiC-platelet layer. The residual stress was controlled by varying the amount of SiC added. The mechanical properties of three-layer composites with various combinations of microstructure and residual stress level were investigated. 相似文献
3.
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
4.
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
5.
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
6.
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
7.
Hideki Hyuga Yu-ichi Yoshizawa Kiyoshi Hirao D. Amutha Rani Mark I. Jones 《International Journal of Applied Ceramic Technology》2008,5(2):111-118
The tribological behavior of Si3 N4 ceramics and Si3 N4 /carbon fiber composites sliding against stainless steel under water lubrication was investigated using a thrust-bearing-type test method with normal applied loads varying from 0 to 1000 N in 100 N increments. In the case of the monolithic Si3 N4 , the friction coefficient was found to increase up to 0.4 the first time the applied load was increased from 100 to 200 N, and sudden failure of the ceramic ring specimen occurred. In the case of the Si3 N4 /carbon fiber composite, a low friction coefficient was maintained up to the maximum normal load of 1000 N. The addition of the carbon fibers to the silicon nitride ceramics effectively restricts material transfer from the stainless steel to the Si3 N4 worn surface due to reduction of solid–solid contact through the solid lubricating effect of the carbon fibers. 相似文献
8.
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
9.
Linus U. J. T. Ogbuji 《Journal of the American Ceramic Society》1992,75(11):2995-3000
The results of two-step oxidation experiments on chemically-vapor-deposited Si3 N4 and SiC at 1350°C show that a correlation exists between the presence of a Si2 N2 O interphase and the strong oxidation resistance of Si3 N4 . During normal oxidation, k p for SiC was 15 times higher than that for Si3 N4 , and the oxide scale on Si3 N4 was found by SEM and TEM to contain a prominent Si2 N2 O inner layer. However, when oxidized samples are annealed in Ar for 1.5 h at 1500°C and reoxidized at 1350°C as before, three things happen: the oxidation k p increases over 55-fold for Si3 N4 , and 3.5-fold for SiC; the Si3 N4 and SiC oxidize with nearly equal k p 's; and, most significant, the oxide scale on Si3 N4 is found to be lacking an inner Si2 N2 O layer. The implications of this correlation for the competing models of Si3 N4 oxidation are discussed. 相似文献
10.
Evaluation of Slow Crack Growth Resistance in Ceramics for High-Temperature Applications 总被引:1,自引:0,他引:1
The slow (subcritical) crack growth (SCG) resistance of Si3 N4 and SiC ceramics has been evaluated by a stepwise loading test on bending bars precracked by Vickers indentation. Three highly refractory materials were selected for the evaluation: i.e., (1) high-purity Si3 N4 sintered by hot isostatic pressing (HIP) without additives and (2,3) α - and β - SiC pressureless sintered with B and C addition. Under the hypothesis of linear elastic behavior at high temperature, which was found satisfied in the present materials, the SCG resistance was expressed in terms of initial stress intensity factor critical for SCG failure within a predetermined lifetime. The present method was found useful in shortening the testing time and consistent with other traditional fatigue tests (e.g., static-fatigue test): It is recommended as a screening test for materials under research and development. Among the materials tested in the present study, the highest SCG resistance up to 1440°C was found in the high-purity Si3 N4 without additives. 相似文献
11.
Giuseppe Pezzotti Isao Tanaka Taira Okamoto 《Journal of the American Ceramic Society》1990,73(10):3039-3045
The fracture behavior of an Si3 N4 /SiC-whisker composite fabricated without sintering aids is investigated using a double approach based on the examination of R -curve behavior and a statistical analysis of crack propagation. In the composite with 20 vol% whisker, a 30% increase in toughness over the matrix value can be attributed to crack-tip phenomena. Strong interfacial bonding prevents any contribution to toughening by mechanisms operating in the wake region of the crack. Based on experimental observations of microfracture in both SiC whiskers and Si3 N4 grains, toughening caused by crack-tip phenomena is quantitatively discussed in terms of fracture energy and whisker-distribution parameters. 相似文献
12.
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
13.
Keith F. Dufrane 《Journal of the American Ceramic Society》1989,72(4):691-695
In support of efforts to apply ceramics to advanced heat engines, a study was performed of the wear mechanisms of ceramics at the ring/cylinder interface. A laboratory apparatus was constructed to reproduce most of the conditions of an actual engine. Ring and cylinder specimens having a simple geometry were used to facilitate their fabrication. Attempts to operate three zirconias, α-SiC, Si3 N4 , and several plasma-sprayed coatings without lubrication were unsuccessful because of high friction and wear rates. The ceramics responded well to liquid lubricants at a temperature of 260°C. Plasma-sprayed coatings of Cr2 O3 and hypersonic flame-sprayed coatings of Co-bonded WC performed particularly well as ring coatings. Similar performance was obtained with these coatings operating against SiC, Si3 N4 , SiC-whisker-reinforced Al2 O3 , and Cr2 O3 coatings. The study demonstrated the critical need for lubrication. 相似文献
14.
Influence of Rare-Earth Additives on Wear Properties of Hot-Pressed Silicon Nitride Ceramics under Dry Sliding Conditions 总被引:2,自引:1,他引:1
Hideki Hyuga Mark I. Jones Kiyoshi Hirao Yukihiko Yamauchi 《Journal of the American Ceramic Society》2004,87(9):1683-1686
The influence of different rare-earth sintering additives (Y, Yb, Lu) on the wear properties of Si3 N4 ceramics was investigated during sliding contact without lubricant. The kind of rare-earth additives was shown to have a significant effect on the wear behavior for contact sliding under the present testing conditions. Samples sintered with Y2 O3 as the sintering additive showed evidence of fracture type wear although this was not observed in samples sintered with Yb2 O3 and Lu2 O3 . These smaller rare earths lead to higher grain boundary bonding strength and superior high-temperature properties and resulted in higher wear resistance. These results showed that the wear properties of Si3 N4 ceramics could be tailored by judicious selection of the sintering additives. 相似文献
15.
J. J. PETROVIC L. A. JACOBSON P. K. TALTY A. K. VASUDEVAN 《Journal of the American Ceramic Society》1975,58(3-4):113-116
Surface flaws of controlled size and shape were produced in high-strength hot-pressed Si3 N4 with a Knoop microhardness indenter. Fracture was initiated at a single suitably oriented flaw on the tensile surface of a 4-point-bend specimen, with attendant reduction in the measured magnitude and scatter of the fracture strength. The stress required to propagate the controlled flaw was used to calculate the critical stress-intensity factor, K IC , from standard fracture-mechanics formulas for semielliptical surface flaws in bending. After the bend specimen had been annealed, the room-temperature K IC values for HS-130 Si3 N4 increased to a level consistent with values obtained from conventional fracture-mechanics tests. It was postulated that annealing reduces the residual stresses produced by the microhardness indentation. The presence of residual stresses may account for the low K IC , values. Elevated-temperature KIC values for HS-130 Si3 N4 were consistent with double-torsion data. Controlled flaws in HS-130 Si3 N4 exhibited slow crack growth at high temperatures. 相似文献
16.
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
17.
Abrasive Wear Behavior of a Si3N4-MoSi2 Composite 总被引:5,自引:0,他引:5
Jeffrey A. Hawk David E. Alman JohnJ. Petrovic 《Journal of the American Ceramic Society》1996,79(5):1297-1302
MoSi2 particles (20 vol%) have been added to Si3 N4 to form ceramic matrix-intermetallic composites. Benefits associated with the addition of the MoSi2 to Si3 N4 include higher strength, higher fracture toughness, no loss in oxidation resistance, and lower electrical resistivity. However, because the hardness of MoSi2 is approximately half that of Si3 N4 , a decrease in the specific wear rate of the Si3 N4 -20 vol% MoSi2 composite is expected to result from the incorporation of the MoSi2 into the Si3 N4 . In this U.S. Bureau of Mines and Los Alamos National Laboratory study, it is found, however, that the specific wear rate of the composite during two-body abrasion by SiC particles is equivalent in magnitude to the specific wear rate of monolithic Si3 N4 . The specific wear rates of both the Si3 N4 -20 vol% MoSi2 composites and monolithic Si3 N4 are four to five times less than that of monolithic MoSi2 . 相似文献
18.
Hiroaki Makino Nobuo Kamiya Shigetaka Wada 《Journal of the American Ceramic Society》1991,74(8):2001-2004
Effects of the grain size of hot-pressed Si3 N4 on contact damage morphology and residual strength were studied using the elastic/plastic indentation method with a spherical indenter. The contact damage, initially formed with increasing indentation load, was Hertzian cracks in the Si3 N4 consisting of fine grains (mean grain size: 0.2 μm). In the coarser-grained Si3 N4 (mean grain size: 0.8 μm), there was a damage texture, consisting of grain-sized microcracks. The residual strength was degraded at a load slightly higher than the critical load for contact damage formation. The strength degradation was not caused by contact damage but the residual stress formed around the impressions. 相似文献
19.
Michael J. Hoffmann Alwin Nagel Peter Greil Günter Petzow 《Journal of the American Ceramic Society》1989,72(5):765-769
Si3 N4 composite materials containing up to 20 vol% SiC whiskers were slip cast and pressureless sintered at 1820°C and 0.13 MPa of N2 . Viscosimetry showed no influence of whisker loading on the rheology of the highly concentrated aqueous slips up to 15 vol% whiskers. During casting the whiskers were preferentially aligned parallel to the mold surfaces. Depending on the whisker loading, green densities of 0.64 to 0.69 fractional density could be achieved. Strong anisotropic shrinkage occurred during sintering with a maximum linear shrinkage of 21% perpendicular but only 7% parallel to the whisker plane. With increasing whisker content from 0 to 20 vol% sintered densities decreased from 0.98 to 0.88, respectively. 相似文献
20.
Edward S. Fisher Murli H. Manghnani Ji-Fan Wang Jules L. Routbort 《Journal of the American Ceramic Society》1992,75(4):908-914
A study of the elastic moduli of Al2 O3 and Si3 N4 ceramics reinforced with 0 to 25 wt% SiC whiskers has been performed. The Young's moduli, shear moduli, and longitudinal modulus are compared with calculated predictions for aligned fiber composites by Hill and Hashin and Rosen, and for fibers randomly oriented in three dimensions by Christensen and Waal. The measured values are in excellent quantitative agreement with those derived for the random orientation of the SiC whiskers. 相似文献