共查询到20条相似文献,搜索用时 390 毫秒
1.
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
2.
Naoki Kondo Yoshikazu Suzuki Tatsuki Ohji 《Journal of the American Ceramic Society》2000,83(7):1816-1818
Silicon nitride–silicon carbide (Si3 N4 –SiC) nanocomposites were fabricated by a process involving reaction bonding followed by superplastic sinter-forging. The nanocomposites exhibited an anisotropic microstructure, in which rod-shaped, micrometer-sized Si3 N4 grains tended to align with their long axes along the material-flow direction. SiC particles, typically measuring several hundred nanometers, were located at the Si3 N4 grain boundaries, and nanosized particles were dispersed inside the Si3 N4 grains. A high bending strength of 1246 ± 119 MPa, as well as a high fracture toughness of 8.2 ± 0.9 MPa·m1/2 , was achieved when a stress was applied along the grain-alignment direction. 相似文献
3.
Layered Silicon Nitride-Based Composites with Discontinuous Boron Nitride Interlayers 总被引:1,自引:0,他引:1
Zoltán Lené Kiyoshi Hirao Manuel E. Brito Motohiro Toriyama Shuzo Kanzaki 《Journal of the American Ceramic Society》2000,83(10):2503-2508
The influence of a strong/weak interface ratio on the mechanical properties of Si3 N4 /BN-based layered composites was studied. The ratio was controlled by the number of BN spots between the adjacent Si3 N4 layers. By increasing the BN interface area from 0% to 72%, fracture toughness increased from 7.7 to 10.9 MPa·m1/2 , and bending strength decreased from 1275 to 982 MPa. Fracture toughness was improved from 8.6 to 10.1 MPa·m1/2 by additional heat treatment of samples containing 2 vol%β-Si3 N4 seed particles. The bending strength of samples with 35% weak BN interfaces, measured perpendicular and parallel to layer alignment, was 1260 and 1240 MPa, respectively. This confirmed the two-directional isotropy of layered samples. 相似文献
4.
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
5.
Rong-Jun Xie Mamoru Mitomo Guo-Dong Zhan Hideyuki Emoto 《Journal of the American Ceramic Society》2000,83(10):2529-2535
Starting with a mixture of ultrafine β-Si3 N4 and a SiO2 -containing additive, a superplastic Si3 N4 -based composite was developed, using the concept of a transient liquid phase. Significant deformation-induced phase and microstructure evolutions occurred in the nonequilibrium, fine-grained Si3 N4 material, which led to the in situ development of a Si3 N4 –22-vol%-Si2 N2 O composite and strong texture formation. The unusual ductility of the composites with elongated Si2 N2 O grains was attributed to the fine-grained microstructure, the presence of a transient liquid phase, and the alignment of the elongated Si2 N2 O grains. The mechanical properties of the resultant composite were enhanced rather than impaired by superplastic deformation and subsequent heat treatment; the resultant composite exhibited both high strength (957 MPa) and high fracture toughness (4.8 MPa·m1/2 ). 相似文献
6.
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
7.
Toughening of Silicon Nitride Matrix Composites by the Addition of Both Silicon Carbide Whiskers and Silicon Carbide Particles 总被引:1,自引:0,他引:1
Hironori Kodama Takaaki Suzuki Hiroshi Sakamoto Tadahiko Miyoshi 《Journal of the American Ceramic Society》1990,73(3):678-683
Si3 N4 matrix composites reinforced by SiC whiskers, SiC particles, or both were fabricated using the hot-pressing technique. The mechanical properties of the composites containing various amounts of these SiC reinforcing materials and different sizes of SiC particles were investigated. Fracture toughness of the composites was significantly improved by introducing SiC whiskers and particles together, compared with that obtained by adding SiC whiskers or SiC particles alone. On increasing the size of the added SiC particles, the fracture toughness of the composites reinforced by both whiskers and particles was increased. Their fracture toughness also showed a strong dependence on the amount of SiC particles (average size 40 μm) and was a maximum at the particle content of 10 vol%. The maximum fracture toughness of these composites was 10.5 MPa·m1/2 and the flexural strength was 550 MPa after addition of 20 vol% of SiC whiskers and 10 vol% of SiC particles having an average particle size of 40 μm. These mechanical properties were almost constant from room temperature to temperatures around 1000°C. Fracture surface observations revealed that the reinforcing mechanisms acting in these composites were crack deflection and crack branching by SiC particles and pullout of SiC whiskers. 相似文献
8.
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
9.
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
10.
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
11.
Reaction Sintering and Properties of Silicon Oxynitride Densified by Hot Isostatic Pressing 总被引:4,自引:0,他引:4
Richard Larker 《Journal of the American Ceramic Society》1992,75(1):62-66
Silicon oxynitride ceramics were reaction sintered and fully densified by hot isostatic pressing in the temperature range 1700°C to 1950°C from an equimolar mixture of silicon nitride and silica powders without additives. Conversion to Si2 N2 O increases steeply from a level around 5% of the crystalline phases at 1700°C to 80% at 1800°C, and increases a few percent further at higher temperatures. α -Si3 N4 is the major residual crystalline phase below 1900°C. The hardness level for materials containing 85% Si2 N2 O is approximately 19 GPa, comparable with the hardness of Si3 N4 hot isostatically pressed with 2.5 wt% Y2 O3 , while the fracture toughness level is around 3.1 MPa. m1/2 , being approximately 0.8 MPa.m1/2 lower. The three-point bending strength increased with HIP temperature from approximately 300 to 500 MPa. 相似文献
12.
Ming-yuan Kao 《Journal of the American Ceramic Society》1993,76(11):2879-2883
The physical and mechanical properties of hot-pressed Si3 N4 –MoSi2 particulate composites containing 15 and 30 vol% MoSi2 were studied. The average room-temperature four-point bend strength, fracture toughness, and electrical resistivity are 522 MPa, 3.6 MPa·√m, and 6.3 × 105 Χ·cm for the 15 vol% MoSi2 composite, and 487 MPa, 5.3 MPa·√m, and 0.31 Ω·cm for the 30 vol% MoSi2 composite. The mechanical properties of the composites are very close to those of hot-pressed Si3 N4 ceramics. The high electrical conductivity of the 30 vol% MoSi2 composite was attributed to the percolation effect of MoSi2 particles. Parabolic oxidation behaviors were observed for the 30 vol% MoSi2 composite during the 1200°C long-term oxidation experiments. 相似文献
13.
Processing and Mechanical Properties of Zirconium Diboride-Based Ceramics Prepared by Spark Plasma Sintering 总被引:1,自引:0,他引:1
Hailong Wang Chang-An Wang Xuefeng Yao Daining Fang 《Journal of the American Ceramic Society》2007,90(7):1992-1997
Zirconium diboride (ZrB2 ) reinforced by nano-SiC whiskers has been prepared by spark plasma sintering (SPS). Of most interest is the densification of ZrB2 –SiCw composites accomplished by SPS at a temperature as low as 1550°C. The relative density of ZrB2 –SiCw composites could reach to 97% with an average grain size of 2–3 μm. Both flexural strength and fracture toughness of the composites were improved with increasing amount of SiCw. Flexural strengths ranged from 416 MPa for monolithic ZrB2 to over 545 MPa for ZrB2 –15 vol% SiCw composites. Similarly, fracture toughness also increased from 5.46 MPa·m1/2 to more than 6.81 MPa·m1/2 in the same composition range. The relative density of ZrB2 –SiCw composites could be further improved to near 100% by adding some sintering aids such as AlN and Si3 N4 ; however, the effects of different sintering additives on the mechanical properties of the composites were different. 相似文献
14.
Eirik Hagen Tor Grande Mari-Ann Einarsrud 《Journal of the American Ceramic Society》2004,87(7):1200-1204
Microporous two-phase AlN–SiC composites were prepared using Al4 C3 and either Si (N2 atmosphere) or Si3 N4 (Ar atmosphere) as precursors. The reaction mechanisms of the two synthesis routes and the effect of processing conditions on reaction rate and the material microstructures were demonstrated. The exothermic reaction between Si and Al4 C3 under N2 atmosphere was shown to be a simple processing route for the preparation of porous two-phase AlN–SiC materials. The homogeneous two-phase AlN–SiC composites had a grain size in the range of 1–5 μm, and the porosity varied in the range of 36%–45%. The bending strength was 50–60 MPa, in accordance with the high porosity. 相似文献
15.
Mode I Fracture Toughness of a Small-Grained Silicon Nitride: Orientation, Temperature, and Crack Length Effects 总被引:1,自引:0,他引:1
The Mode I fracture toughness ( K I C ) of a small-grained Si3 N4 was determined as a function of hot-pressing orientation, temperature, testing atmosphere, and crack length using the single-edge precracked beam method. The diameter of the Si3 N4 grains was <0.4 µm, with aspect ratios of 2–8. K I C at 25°C was 6.6 ± 0.2 and 5.9 ± 0.1 MPa·m1/2 for the T–S and T–L orientations, respectively. This difference was attributed to the amount of elongated grains in the plane of crack growth. For both orientations, a continual decrease in K IC was observed through 1200°C, to ∼4.1 MPa·m1/2 , before increasing rapidly to 7.5–8 MPa·m1/2 at 1300°C. The decrease in K IC through 1200°C was a result of grain-boundary glassy phase softening. At 1300°C, reorientation of elongated grains in the direction of the applied load was suggested to explain the large increase in K IC . Crack healing was observed in specimens annealed in air. No R -curve behavior was observed for crack lengths as short as 300 µm at either 25° or 1000°C. 相似文献
16.
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
17.
Fabrication of Low-Shrinkage, Porous Silicon Nitride Ceramics by Addition of a Small Amount of Carbon 总被引:4,自引:0,他引:4
Jian-Feng Yang Guo-Jun Zhang Tatsuki Ohji 《Journal of the American Ceramic Society》2001,84(7):1639-1641
Successful net-shape sintering offers a significant advantage for producing large or complicated products. Porous Si3 N4 ceramics with very low shrinkage were developed, in the present investigation, by the addition of a small amount of carbon. Carbon powders (1–5 vol%) of two types, with different mean particle sizes (13 nm and 5 μm), were added to α-Si3 N4 −5 wt% Y2 O3 powders. SiC nanoparticles formed through reaction of the added carbon with SiO2 on the Si3 N4 surface or with the Si3 N4 particles themselves. Such reaction-formed SiC nanoparticles apparently had an effective reinforcing effect, as in nanocomposites. Sintered Si3 N4 porous ceramics with a high porosity of 50%–60%, a very small linear shrinkage of ∼2%–3%, and a strength of ∼100 MPa were obtained. 相似文献
18.
Silicon Carbide Whisker Stability During Processing of Silicon Nitride Matrix Composites 总被引:1,自引:0,他引:1
Steven A. Bradley Keith R. Karasek Michael R. Martin Harry C. Yeh James L. Schienle 《Journal of the American Ceramic Society》1989,72(4):628-636
The effects of two different sources of SiC whiskers on the chemistry and microstructure of the SiC-whisker—Si3 N4 composites were evaluated using scanning transmission electron microscopy. Analyses were performed after presintering in N2 and after encapsulated hot isostatic pressing. Significant differences in the porosity, α- to β-Si3 N4 conversion, and whisker degradation were observed after presintering. It was also noted that whiskers containing surface iron impurities were converted to Si3 N4 during processing. Whiskers from the source having low surface iron exhibited little reaction. After hot isostatic pressing, some oxidation of the cleaner whiskers was observed. 相似文献
19.
Gui-hua Peng Guo-jian Jiang Wen-lan Li Bao-lin Zhang Li-dong Chen 《Journal of the American Ceramic Society》2006,89(12):3824-3826
α/β-Si3 N4 composites with various α/β phase ratios were prepared by hot pressing at 1600°–1650°C with MgSiN2 as sintering additives. An excellent combination of mechanical properties (Vickers indentation hardness of 23.1 GPa, fracture strength of about 1000MPa, and toughness of 6.3 MPa·m1/2 ) could be obtained. Compared with conventional Si3 N4 -based ceramics, this new material has obvious advantages. It is as hard as typical in-situ-reinforced α-Sialon, but much stronger than the latter (700 MPa). It has comparable fracture strength and toughness, but is much harder than β-Si3 N4 ceramics (16 GPa). The microstructures and mechanical properties can be tailored by choosing the additive and controlling the heating schedule. 相似文献
20.
The reactivity of AlN powder with water in supernatants obtained from centrifuged Si3 N4 and SiC slurries was studied by monitoring the pH versus time. Various Si3 N4 and SiC powders were used, which were fabricated by different production routes and had surfaces oxidized to different degrees. The reactivity of the AlN powder in the supernatants was found to depend strongly on the concentration of dissolved silica in these slurries relative to the surface area of the AlN powder in the slurry. The hydrolysis of AlN did not occur if the concentration of dissolved silica, with respect to the AlN powder surface, was high enough (1 mg SiO2 /(m2 AlN powder)) to form a layer of aluminosilicates on the AlN powder surface. This assumption was verified by measuring the pH of more concentrated (31 vol%) Si3 N4 and SiC suspensions also including 5 wt% of AlN powder (with respect to the solids). 相似文献