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1.
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
2.
Yongsheng Liu Litong Zhang Laifei Cheng Yongdong Xu Yi Liu 《International Journal of Applied Ceramic Technology》2010,7(1):63-70
Silicon nitride particle-reinforced silicon nitride matrix composites were fabricated by chemical vapor infiltration (CVI). The particle preforms with a bimodal pore size distribution were favorable for the subsequent CVI process, which included intraagglomerate pores (0.1–4 μm) and interagglomerate pores (20–300 μm). X-ray fluorescence results showed that the main elements of the composites are Si, N, and O. The composite is composed of α-Si3 N4 , amorphous Si3 N4 , amorphous SiO2 , and a small amount of β-Si3 N4 and free silicon. The α-Si3 N4 transformed into β-Si3 N4 after heat treatment at 1600°C for 2 h. The flexural strength, dielectric constant, and dielectric loss of the Si3 N4(p) /Si3 N4 composites increased with increasing infiltration time; however, the pore ratios decreased with increasing infiltration time. The maximum value of the flexural strength was 114.07 MPa. The dielectric constant and dielectric loss of the composites were 4.47 and 4.25 × 10−3 , respectively. The present Si3 N4(p) /Si3 N4 composite is a good candidate for high-temperature radomes. 相似文献
3.
Si3 N4 /MoSi2 and Si3 N4 /WSi2 composites were prepared by reaction-bonding processes using as starting materials powder mixtures of Si-Mo and Si-W, respectively. A presintering step in an At-base atmosphere was used before nitriding for the formation of MoSi2 and WSi2 ; the nitridation in a N2 -base atmosphere was followed after presintering with the total stepwise cycle of 1350°C × 20 h +1400°C × 20 h +1450°C × 2 h. The final phases obtained in the two different composites were Si3 N4 and MoSi2 or WSi2 ; no free elemental Si and Mo or W were detected by X-ray diffraction. 相似文献
4.
The rate of dissolution of β-Si3 N4 into an Mg-Si-O-N glass was measured by working with a composition in the ternary system Si3 N4 -SiO2 -MgO such that Si2 N2 O rather than β-Si3 N4 was the equilibrium phase. Dissolution was driven by the chemical reaction Si3 N4 (c)+SiO2 ( l )→Si2 N2 O(c). Analysis of the kinetic data, in view of the morphology of the dissolving phase (Si3 N4 ) and the precipitating phase (Si2 N2 O), led to the conclusion that the dissolution rate was controlled by reaction at the crystal/glass interface of the Si3 N4 , crystals. The process appears to have a fairly constant activation energy, equal to 621 ±40 kJ-mol−1 , at T=1573 to 1723 K. This large activation energy is believed to reflect the sum of two quantities: the heat of solution of β-Si3 N4 hi the glass and the activation enthalpy for jumps of the slower-moving species across the crystal/glass interface. The data reported should be useful for interpreting creep and densification experiments with MgO-fluxed Si3 N4 . 相似文献
5.
The compressive creep behavior and oxidation resistance of an Si3 N4 /Y2 Si2 O7 material (0.85Si3 N4 +0.10SiO2 +0.05Y2 O3 ) were determined at 1400°C. Creep re sistance was superior to that of other Si3 N4 materials and was significantly in creased by a preoxidation treatment (1600°C /120 h). An apparent parabolic rate constant of 4.2 × 10−11 kg2 ·m-4 ·s−1 indicates excellent oxidation resistance. 相似文献
6.
Densification and Mechanical Properties of Titanium Diboride with Silicon Nitride as a Sintering Aid 总被引:3,自引:0,他引:3
June-Ho Park Young-Hag Koh Hyoun-Ee Kim † Cheol Seong Hwang Eul Son Kang 《Journal of the American Ceramic Society》1999,82(11):3037-3042
Titanium diboride (TiB2 ) was hot-pressed at a temperature of 1800°C, and silicon nitride (Si3 N4 ) was added as a sintering aid. The amount of Si3 N4 that was added had a significant influence on the sinterability and mechanical properties of the TiB2 . When a small amount (2.5 wt%) of Si3 N4 was added, the Si3 N4 reacted with titania (TiO2 ) that was present on the surface of the TiB2 powder to form titanium nitride (TiN), boron nitride (BN), and amorphous silica (SiO2 ). The elimination of TiO2 suppressed the grain growth effectively, which led to an improvement in the densification of TiB2 . The formation of SiO2 also was deemed beneficial for densification. The mechanical properties-especially, the flexural strength-were enhanced remarkably through these improvements in the sinterability and microstructure. On the other hand, when a large amount (greaterthan equal to5 wt%) of Si3 N4 was added, the mechanical properties were not improved much, presumably because of the extensive formation of a glassy Si-Ti-O-N phase at the grain boundaries. 相似文献
7.
Evaluation of Brazed Silicon Nitride Joints: Microstructure and Mechanical Properties 总被引:1,自引:0,他引:1
Stathis D. Peteves Michael G. Nicholas 《Journal of the American Ceramic Society》1996,79(6):1553-1562
Sintered Si3 N4 has been bonded to itself and to AISI 316 steel by the active-metal brazing route. A commercial Ag-35Cu-1.6Ti filler has been used with joining taking place during a 30 min hold at 850°C under vacuum. Si3 N4 / Si3 N4 joints have been produced with strength distribution (average bend strength = 773.5 MPa, Weibull modulus = 11.2) similar to that of the monolithic ceramic. Direct brazing of the Si3 N4 to AISI 316 steel was unsuccessful. However, reliably strong (bend strength of 250–400 MPa) ceramic/ steel joints with 20 × 20 mm2 cross sections were fabricated by using Cu, Mo, or Nb interlayers. The most potent inter-layer used in this work was Mo, whose coefficient of thermal expansion matches best that of the ceramic. 相似文献
8.
Microstructure and Properties of Self-Reinforced Silicon Nitride 总被引:3,自引:0,他引:3
Problems associated with manufacturing Si3 N4 /SiC-whisker composites have been overcome by developing selfreinforced Si3 N4 with elongated β-Si3 N4 grains formed in situ from oxynitride glass. This Si3 N4 –Y2 O3 –MgO–SiO2 –CaO-based material has a flexure strength >1000 MPa and fracture toughness >8 MPa·m½ . The optimum combination of mechanical properties has been obtained with Y2 O3 :MgO ratios ranging from 3:1 to 1:2, CaO contents ranging from 0.1 to 0.5 wt%, and Si3 N4 contents between 90 and 96 wt%. 相似文献
9.
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
10.
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
11.
Brian W Sheldon Janet Rankin John S. Haggerty 《Journal of the American Ceramic Society》1995,78(6):1624-1632
The nucleation and growth of Si3 N4 on silane-derived Si powders was investigated with transmission electron microscopy and FTIR spectroscopy. Thermogravimetric analysis (TGA) was also used to monitor the process through different stages of the reaction. The FTIR and TEM results provide clear evidence that the nucleation of crystalline Si3 N4 coincides with the onset of rapid nitridation. Electron diffraction indicates that Si3 N4 forms heteroepitaxially on the Si powder surfaces, with Si (111) || Si3 N4 (0001) and Si || Si3 N4 . Also, flat interfaces between the Si and Si3 N4 (compared to the initial spherical surface of the Si powders) indicate that a significant rearrangement of the particle surface occurs during the initial stages of nitridation. The results reported here demonstrate that the rapid, low-temperature nitridation observed with silane-derived powders is possible because the Si/vapor surfaces are not covered with a continuous Si3 N4 product layer. The measured nitridation rates are comparable to Si evaporation rates, which suggests that Si vaporization is rate limiting. This is significantly different from conventional RBSN, where nitridation is limited by solid-state diffusion through a Si3 N4 product layer. 相似文献
12.
The abnormal grain growth of β-Si3 N4 was observed in a 70% Si3 N4 –30% barium aluminum silicate (70%-Si3 N4 –30%-BAS) self-reinforced composite that was pressureless-sintered at 1930°C; Si3 N4 starting powders with a wide particle-size distribution were used. The addition of coarse Si3 N4 powder encouraged the abnormal growth of β-Si3 N4 grains, which allowed microstructural modification through control of the content and size distribution of β-Si3 N4 nuclei. The mechanical response of different microstructures was characterized in terms of flexural strength, as well as indentation fracture resistance, at room temperature. The presence of even a small amount of abnormally grown β-Si3 N4 grains improved the fracture toughness and minimized the variability in flexural strength. 相似文献
13.
Influence of Planetary High-Energy Ball Milling on Microstructure and Mechanical Properties of Silicon Nitride Ceramics 总被引:1,自引:0,他引:1
Xue-Jian Liu Zhi-Yong Huang Xi-Peng Pu Xing-Wei Sun Li-Ping Huang 《Journal of the American Ceramic Society》2005,88(5):1323-1326
The influence of ball-milling methods on microstructure and mechanical properties of silicon nitride (Si3 N4 ) ceramics produced by pressureless sintering for a sintering additive from MgO–Al2 O3 –SiO2 system was investigated. For planetary high-energy ball milling, the mechanical properties of Si3 N4 ceramics were evidently improved and a homogeneous microstructure developed. In contrast, some exaggerated elongated grains were developed due to the local enrichment of sintering additives in the specimen prepared by general ball milling. For Si3 N4 ceramics produced by planetary ball milling, flexure strength of 1.06 GPa, Vickers hardness of 14.2 GPa, and fracture toughness of 6.6 MPa·m0.5 were achieved. The differences in the mechanical properties of Si3 N4 ceramics produced by different processing seem to arise mainly from the changes in microstructural homogenization and sinterability. The planetary high-energy ball-milling process provides a good route to mix starting powders for developing ceramics with uniform microstructure and promising mechanical properties. 相似文献
14.
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
15.
Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure
Ya-Li Li Fen Zheng Yong Liang Xian-Feng Ma Suo-Jing Cui Takamasa Ishigaki 《Journal of the American Ceramic Society》2001,84(4):875-877
Oxidized amorphous Si3 N4 and SiO2 powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si2 ON2 ) was observed from amorphous silicon nitride (Si3 N4 ) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si2 ON2 coexisted with β-Si3 N4 with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si2 ON2 . Pressing a mixture of amorphous Si3 N4 of lower oxygen (1.5 wt%) and SiO2 under 1.0–5.0 GPa between 1000° and 1350°C did not give Si2 ON2 phase, but yielded a mixture of α,β-Si3 N4 , quartz, and coesite (a high-pressure form of SiO2 ). The formation of Si2 ON2 from oxidized amorphous Si3 N4 seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure. 相似文献
16.
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
17.
Effect of Sintering Additives on Microstructure and Mechanical Properties of Porous Silicon Nitride Ceramics 总被引:2,自引:0,他引:2
Jun Yang Jian-Feng Yang Shao-Yun Shan Ji-Qiang Gao Tatsuki Ohji 《Journal of the American Ceramic Society》2006,89(12):3843-3845
Porous silicon nitride (Si3 N4 ) ceramics with about 50% porosity were fabricated by pressureless sintering of α-Si3 N4 powder with 5 wt% sintering additive. Four types of sintering aids were chosen to study their effect on the microstructure and mechanical properties of porous Si3 N4 ceramics. XRD analysis proved the complete formation of a single β-Si3 N4 phase. Microstructural evolution and mechanical properties were dependent mostly on the type of sintering additive. SEM analysis revealed the resultant porous Si3 N4 ceramics as having high aspect ratio, a rod-like microstructure, and a uniform pore structure. The sintered sample with Lu2 O3 sintering additive, having a porosity of about 50%, showed a high flexural strength of 188 MPa, a high fracture toughness of 3.1 MPa·m1/2 , due to fine β-Si3 N4 grains, and some large elongated grains. 相似文献
18.
Interface Nanostructure of Brazed Silicon Nitride 总被引:1,自引:0,他引:1
Nanomorphologies and crystallographic orientations of the brazed interface of silicon nitride (Si3 N4 ) were analyzed via high-resolution transmission electron microscopy. When Si3 N4 was brazed using an Ag-Cu-Ti alloy, titanium nitride (TiN) nanoparticles were formed adjacent to the ceramic as reaction products, and these nanoparticles were commonly accompanied by C-phase material. The structure of Si3 N4 /TiN interface was wavy on an atomic scale, which was considered to provide anchoring points that offered high mechanical strength. The TiN nanoparticles extended along the [0001] axis of Si3 N4 . The orientation relationship between TiN and ß-Si3 N4 was, as determined from the observed lattice images, that the [110] direction of TiN was parallel to the [0001] direction of Si3 N4 . The nature of the crystallographic relationships and interface nanomorphologies were also discussed. 相似文献
19.
Junichi Takahashi Hisanori Yamane Masahiko Shimada Yoshinobu Yamamoto Naoto Hirosaki Mamoru Mitomo Kenichi Oikawa Shuki Torii Takashi Kamiyama 《Journal of the American Ceramic Society》2002,85(8):2072-2077
The crystal structure of a lutetium silicon oxynitride (Lu4 Si2 O7 N2 ) was analyzed by the Rietveld method using time-of-flight (TOF) neutron powder diffraction data. The compound crystallizes in a monoclinic cell, space group P 21 / c (No. 14-1) with a = 7.4243(1), b = 10.2728(1), c = 10.6628(1) Å, and β= 109.773(1)° at 297 K. One nitrogen atom in Lu4 Si2 O7 N2 occupies the bridging site between the two Si atoms, and the other one is statistically situated at the terminal sites of Si2 O5 N2 ditetrahedra. In the local structure, Si2 O5 N2 ditetrahedra consist of SiO3 N and SiO2 N2 tetrahedral units sharing the N atom. Lu atoms are in sixfold, sevenfold (×2) and eightfold coordinations of O/N atoms. X-ray powder diffraction data were also analyzed with the model obtained by the neutron diffraction. 相似文献
20.
Corrosion of Si3 N4 under thin films of Na2 CO3 was investigated at 1000°C. Pure Si3 N4 and Si3 N4 with various additives were examined. Thermogravimetric analysis and morphology observations lead to the following detailed reaction mechanism: (I) decomposition of Na2 CO3 and formation of Na2 SiO3 , (II) rapid oxidation, and (III) formation of a protective silica layer below the silicate and a slowing of the reaction. For Si3 N4 with Y2 O3 additions, preferential attack of the grain-boundary phase occurred. The corrosion of pure Si and SiC was also studied for comparison to Si3 N4 . The corrosion mechanism generally applies to all three materials. Silicon reacted substantially faster than Si3 N4 and SiC. 相似文献