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碳化硅陶瓷及其复合材料的热等静压氮化 总被引:2,自引:0,他引:2
通过对SiC陶瓷,SiC-TiC复相陶瓷以及SiC晶须补强SiC基复合材料在氮气氛中进行高温的氮化处理,成功地实现了这些材料的开口气孔与表面裂纹的愈合。有关研究表明:热等静压氮化工艺可以显著提高SiC陶瓷及其复合材料的抗强度,对断裂韧性也有较大的改善作用。 相似文献
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氮化烧结制备Si3 N4 -SiC复相陶瓷 总被引:4,自引:0,他引:4
以酚醛树脂作为结合剂,以冷等静压方法成型制备氮化烧结Si3N4-SiC复相陶瓷,研究了结合剂对坯体强度和生成材料物相组成的影响。坯体强度随酚醛树脂含量增加而提高,最高强度达到23MPa,实现坯体可直接机械加工。经过氮化烧结,生成材料物相中含有SiC,含量达到7.1%~15.7%,并观察到细小的等轴颗粒αSi3N4、棒状晶粒βSi3N4以及少量针状和晶须状Si3N4。SiC颗粒与Si3N4结合在一起,被Si3N4包裹。Si3N4-SiC复相材料的生成机理:300~600℃,酚醛树脂发生裂解,形成单质C,残碳率为50%;1000~1100℃,C开始与Si发生固相反应,形成SiC;1100℃后,Si开始发生氮化反应,生成Si3N4。 相似文献
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通过研究影响95氧化铝陶瓷高温金属化性能指标的主要因素,确定了生产工艺易操作且稳定、适应干规模化大生产的等静压成型氧化铝陶瓷金属化生产技术,产品质量好、可靠性高。 相似文献
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为了进一步了解Ti3SiC2/nSiC复合材料优良的综合性能,特别是其高温力学性能,本文以热等静压原位合成技术制备的Ti3SiC2/4SiC复相陶瓷为试验材料,对其高温拉伸和高温弯曲行为进行研究。结果表明:Ti3SiC2/4SiC复相陶瓷的高温抗拉强度比室温抗拉强度高;Ti3SiC2/4SiC复相陶瓷的高温抗弯强度在900℃出现一极大值,1000℃后具有好的高温塑性。 相似文献
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利用热等静压原位合成技术制备了Ti3SiC2/SiC复相陶瓷,对其高温氧化行为进行了研究.结果表明,Ti3SiC2/SiC复相陶瓷在空气中静态氧化时的氧化增重符合抛物线规律,有比纯Ti3SiC2更好的抗氧化性能,并且在1400℃的长时抗氧化性能优于1200℃. 相似文献
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Jiang Dongliang She Jihong Tan Shouhong Peter Greil 《Journal of the American Ceramic Society》1992,75(9):2586-2589
Surface strengthening of SiC by in situ surface nitridation during post-hot isostatic pressing (post-HIPing) in N2 was investigated. The formation of a thin (5–15 μm) layer of submicrometer β-Si3 N4 on the surface of SiC was obtained at 1850°C and 200 MPa. While SiC HIPed in Ar attained a mean bending strength of 660 MPa, a significant increase in strength (with a maximum fracture stress above 1000 MPa) was observed for the SiC/Si3 N4 -layer composite material. Generation of residual compressive stresses on the surface layer caused by the differences in thermal expansion may account for the observed strengthening. Thus, in situ surface nitridation by post-HIPing in N2 may offer an attractive way to improve surface-sensitive mechanical properties of complex-shaped SiC components. 相似文献
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Alena Bartek Thommy Ekström Harald Herbertsson Thomas Johansson 《Journal of the American Ceramic Society》1992,75(2):432-439
Dense α-sialon materials were produced by hot isostatic pressing (HIP) and post-hot isostatic pressing (post-HIP) using compositions with the formula Y x (Si12–4.5 x , Al4.5 x )-(O1.5 x ,N16–1.5 x ) with 0.1 ≤ x ≤ 0.9 and with the same compositions with extra additions of yttria and aluminum nitride. X-ray diffraction analyses show how the phase content changes from large amounts of β-sialon ( x = 0.1) to large amounts of α-sialon ( x = 0.4) and increasing amounts of mellilite and sialon polytypoids ( x = 0.8). Samples HIPed at 1600°C for 2 h contained unreacted α-silicon nitride, while those HIPed at 1750°C for 1 h did not. This could be due to the fact that the time is to short to achieve equilibrium or that the high pressure (200 MPa) prohibits α-sialon formation. Sintering at atmospheric pressure leads to open porosity for all compositions except those with excess yttria. Therefore, only samples with excess yttria were post-HIPed. Microstructrual analyses showed that the post-HIPed samples had the highest α-sialon content. A higher amount of α-sialon and subsequently a lower amount of intergranular phase were detected at x = 0.3 and x = 0.4 in the post-HIPed samples in comparison to the HIPed. The hardness (HV10) and fracture toughness ( K IC ) did not differ significantly between HIPed and post-HIPed materials but vary with different x values due to different phase contents. Measurements of cell parameters for all compositions show a continuous increase with increasing x value which is enhanced by high pressure at high x values. 相似文献
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Masanori Hirano Michio Inagaki Yasunobu Mizutani Kazuhiro Nomura Masayuki Kawai Yasuhisa Nakamura 《Journal of the American Ceramic Society》2000,83(10):2619-2621
Significant improvement in the fracture strength, accompanied by an enhancement in the electrical conductivity, of zirconia polycrystals that were doped with 3–7 mol% Sc2 O3 was obtained by sintering at 1300°C for 1 h in air, followed by hot isostatic pressing (HIP) at 196 MPa at 1300° and 1450°C for 1.5 h in an argon-gas atmosphere. Dense bodies (with an average grain size of <0.5 μm) that were doped with 3.5 mol% of Sc2 O3 showed the highest average fracture strength up to 1770 MPa and an electrical conductivity of 0.08 S/cm at 1000°C. The present zirconia ceramics, which consisted of submicrometer-sized grains of tetragonal phases and were stabilized with 5 and 6 mol% of Sc2 O3 , exhibited high strength (1330 and 1140 MPa, respectively) and good conductivity (0.15 and 0.18 S/cm, respectively); values for both properties were greater than those previously reported. The present HIPed zirconia ceramics, which have excellent properties, are candidates for an electrolyte of planar-type solid oxide fuel cells. 相似文献
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Jing-Feng Li Shinan Wang Katsuhiro Wakabayashi Masayoshi Esashi Ryuzo Watanabe 《Journal of the American Ceramic Society》2000,83(4):955-957
High-density lead zirconate titanate (PZT) ceramics were fabricated for the first time at a temperature as low as 800°C via the hot isostatic pressing (HIP) of a PZT powder with a modified composition of 0.92Pb(Zr0.53 Ti0.47 )O3 —0.05BiFeO3 —0.03Ba(Cu0.5 W0.5 )O3 that contained 0.5 mass% MnO2 . The resultant PZT ceramics exhibited a microstructure that was denser and finer than that of PZT sintered at 935°C, which is the lowest temperature for the densification of the same composition via normal sintering. The relevant dielectric and piezoelectric properties of the HIPed PZT ceramics were as follows: coefficient of electromechanical coupling ( K 31 ), 31.8%; mechanical quality factor ( Q m ), 1364; piezoelectric constant ( d 31 ), −73.7 × 10−12 C/N; relative dielectric constant (ɛ33 T /ɛ0 ), 633; dielectric loss factor (tan δ), 0.5%; Curie temperature ( T c ), 285°C; and density (ρ), 8.06 g/cm3 . In addition to these reasonably good piezoelectric properties, the HIPed PZT exhibited better mechanical properties—particularly, higher fracture strength—than the normally sintered PZT. 相似文献
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采用不同种类的钛酸酯偶联剂和硅烷偶联剂对纳米TiO2进行表面改性试验,利用FTIR红外光谱仪等分析手段,研究发现改性后的纳米TiO2粒子表面已引入有机基团,使纳米TiO2的亲油化度和活化指数分别达到54.34%和99.51%,有效地改善了纳米TiO2与有机介质的相容性,使其在有机相中均匀分散.实验结果表明,在以甲苯为溶剂的体系中,最佳反应条件为:偶联剂用量5%,反应时间120 min,反应温度120℃. 相似文献
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Yutaka Shinoda Michiyuki Yoshida Takashi Akatsu Fumihiro Wakai 《Journal of the American Ceramic Society》2004,87(10):1919-1926
The deformation behavior of boron- and carbon-doped β-silicon carbide (B,C-SiC) with an average grain size of 260 ± 18 nm containing 1 wt% boron was investigated by compression testing at elevated temperatures. Extensive grain growth during deformation was observed. The stress–strain curves were compensated for grain growth by assuming power-law type of dependence on grain size and strain rate. The stress exponent n was ∼1.3 and the grain size exponent p was ∼2.7 at temperatures ranging from 1593° to 1758°C. The apparent activation energy of deformation Q d was ∼760 kJ/mol, which was lower than the activation energy for lattice diffusion of silicon and carbon in SiC and higher than that for grain-boundary diffusion of carbon in SiC. These results suggest that the deformation mechanism of the fine-grained B,C-SiC is grain-boundary sliding accommodated by the grain-boundary diffusion. 相似文献
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Mg(OH)_2阻燃剂的表面改性及其在软质PVC中的应用 总被引:3,自引:1,他引:2
通过TEM、BET、IR对改性前后的Mg(OH)2粉体进行表征和测试,确定了最佳表面改性剂和最佳改性工艺条件。结果表明,改性后的Mg(OH)2比表面积由原来的21.5760m2/g增加到29.8008m2/g,颗粒之间的团聚被打开;红外分析进一步说明,表面改性后Mg(OH)2表面有新的化学键形成;最佳改性工艺条件为:改性温度85℃,改性剂用量5%,改性时间0.5h。改性Mg(OH)2阻燃剂和软质PVC有较好的相容性和分散性。 相似文献
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Si3N4—Al2O3复相陶瓷的抗热震性与晶界脆化 总被引:2,自引:1,他引:2
对Si3N4-Al2O3复相陶瓷的抗热震性能进行了检测和分析。经X射线衍射,SEM和能谱分析表明,材料的热震损伤与晶脆化有关,造成沿晶脆断的主要原因是Ca等杂质元素在晶界的偏聚。采取退火热处理可使非晶相结晶化,提高陶瓷材料的抗热震性。 相似文献