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1.
Cordierite-bonded porous SiC ceramics were prepared by air sintering of cordierite sol infiltrated porous powder compacts of SiC with graphite and polymer microbeads as pore-forming agents. The effect of sintering temperature, type of pore former and its morphology on microstructure, mechanical strength, phase composition, porosity and pore size distribution pattern of porous SiC ceramics were investigated. Depending on type and size of pore former, the average pore diameter, porosities and flexural strength of the final ceramics sintered at 1400 °C varied in the range of ~ 7.6 to 10.1 µm, 34–49 vol% and 34–15 MPa, respectively. The strength–porosity relationship was explained by the minimum solid area (MSA) model. After mechanical stress was applied to the porous SiC ceramics, microstructures of fracture surface appeared without affecting dense struts of thickness ~ 2 to 10 µm showing restriction in crack propagation through interfacial zone of SiC particles. The effect of corrosion on oxide bond phases was investigated in strong acid and basic salt medium at 90 °C. The residual mechanical strength, SEM micrographs and EDX analyses were conducted on the corroded samples and explained the corrosion mechanisms. 相似文献
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A powder compact of α-SiC and α-Al2O3 was infiltrated with a liquid precursor of SiO2, which on subsequent heat treatment at 1500 °C produced a mullite bonded porous SiC ceramics. Results showed that infiltration
rate could be estimated by using weight gain measurements and theoretical analysis. The bond phase was composed of needle-shaped
mullite which was observed to be grown from a siliceous melt formed during the process of oxide bonding. The porous SiC ceramics
exhibited a density and porosity of 2 g cm−3 and 30 vol%, respectively, and also a pore size distribution in a range of 2–15 μm with an average pore size of 5 μm. No
appreciable degradation of room temperature flexural strength (51 MPa) was observed at high temperatures (1100 °C). 相似文献
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Yoshio Sakka Fengqiu Tang Hiroshi Fudouzi Tetsuo Uchikoshi 《Science and Technology of Advanced Materials》2005,6(8):915-920
Well-defined macroporous ceramics consisting of TiO2 and ZrO2 have been fabricated by two methods. One is via a template-assisted colloidal processing technique and the other is via a hetero-coagulation of template/ceramic particle colloidal processing. The former technique is as follows. Close-packed polymer spheres were first prepared as a template using centrifugation or gravitational sedimentation, followed by infiltration with alkoxide precursors. Then the removal of the template beads was achieved by calcination of the organic–inorganic hybrids at appropriate temperatures, yielding well-ordered macroporous ceramics. The latter technique is as follows. Core–shell composites of polymer/ceramic were obtained by mixing the oppositely charged two suspensions via electrostatic attraction following by filtration and calcination to produce macroporous ceramic materials. SEM images revealed that macroporous TiO2 and ZrO2 with ordered and uniform macropores have been obtained by both procedures. 相似文献
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Kiyoshi Itatani Takayasu Kubozono F. Scott Howell Akira Kishioka Makio Kinoshita 《Journal of Materials Science》1995,30(5):1196-1202
The sinterability of mullite (3Al2O3·2SiO2) powder prepared by chemical vapour deposition was examined to improve the conditions for fabricating dense mullite ceramics. The starting powder contained not only mullite, but also a small amount of -Al2O3 (Al-Si spinel) and amorphous material. Although the compressed powder was fired at a temperature between 1550 and 1700 °C for 1, 3 and 5 h, the relative densities of the sintered compacts were limited to 90%: (i) due to the creation of pores/microcracks during the solid state reaction (1100–1350 °C), and (ii) due to restriction on the rearrangement of grains because the amount of liquid phase (1550–1700 °C) was insufficient. Calcination of the starting powder was effective for preparation of easily sinterable powder with homogeneous composition. When the compact formed by compressing the calcined powder at 1400 °C for 1 h was fired at 1650 °C for 3 h, the relative density was raised up to 97.2%; moreover, mullite was the only phase detected from the sintered compact. The sintered compact was composed of polyhedral grains with sizes of 1–2 m and elongated grains with long axes of 6 m. 相似文献
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Wave-transparent porous Si3N4 ceramics were prepared by gel-casting and gas pressure sintering, and the effects of solid loading on microstructure, mechanical and dielectric properties were investigated. Microstructures with interlocked elongated β-Si3N4 grains and uniformly distributed pores were observed, while both the β-Si3N4 phase content and grain aspect ratio reduced as the solid loading increased due to the restrained anisotropic growth of β-Si3N4 grains. As the solid loading increased from 30 to 45 vol.%, the porosity of ceramics declined from 57.6% to 36.4%. The flexural strength increased linearly from 108.3 to 235.1 MPa, and the dielectric constant and loss tangent of ceramics increased from 2.63 and 2.85 × 10−3 to 3.68 and 3.56 × 10−3 (10 GHz), respectively. 相似文献
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Synthesis and properties of spodumene-modified mullite ceramics formed by sol-gel processing 总被引:1,自引:0,他引:1
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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Yoshimi Ohzawa Xingun Cheng Takashi Achiha Tsuyoshi Nakajima Henri Groult 《Journal of Materials Science》2008,43(8):2812-2817
Using pressure-pulsed chemical vapor infiltration (PCVI) method, TiN was partially infiltrated at 850 °C from gas system of
TiCl4 (1%)–N2 (10%)–H2 into the highly porous carbon substrates prepared by the carbonization of cotton-wool, filter paper, and wood at 1,000 °C
in Ar for 4 h. After 10,000 pulses of PCVI, electro-conductive porous ceramics having the three-dimensionally continuous current
paths were obtained, which had the porosity of 80% and more, the resistivity of 10−5–10−6 Ω m, and the average pore sizes of 10–40 μm. The geometric surface area per unit volume of the sample was higher than that
of the conventional foil-type current collector for lithium-ion battery. The surface area showed the highest value for the
sample obtained from carbonized wood substrate. 相似文献
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孔径可控的多孔羟基磷灰石的制备工艺研究 总被引:14,自引:0,他引:14
采用添加造孔剂法,选择合适的造孔剂聚甲基丙烯酸甲酯(PMMA),通过严格筛分,可烧结制得孔径可控的多孔基磷灰石陶瓷,气孔率可从20%到50%变化。并对烧结多孔体中孔的结构、孔径分布与特征,影响气孔率和力学性能的因素进行了研究与讨论。 相似文献
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T.B. KimM. Tane S. Suzuki H. UtsunomiyaT. Ide H. Nakajima 《Materials Science and Engineering: A》2011,528(6):2363-2369
Porous aluminum with a porosity of 17.6% and porous copper with a porosity of 39.7% (the pores of both aluminum and copper were cylindrical and oriented in one direction) were deformed by equal channel angular extrusion using a 150° die with sequential 180° rotations (route C), and the mechanical strength and pore morphology after the extrusions were investigated. In the case of porous aluminum with low porosity, the pores were collapsed by the extrusions that were both parallel and perpendicular to the orientation direction of the pores. In contrast, the porosity of porous copper decreased slightly after extrusions that were parallel to the orientation direction of the pores, and the pores thus remained even after four extrusions. The yield strength after the second extrusion was 7.3 times greater than it was before the extrusion, even though there was a decrease in porosity of only 8%. On the other hand, almost all the pores of the porous copper collapsed after the fourth extrusion, when the extrusion direction was perpendicular to the orientation direction of the pores. Thus, the yield stress cannot be enhanced without being accompanied by progressive densification. 相似文献
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《Materials Research Bulletin》2006,41(7):1259-1265
ZnO bulk porous nanosolids were prepared by a novel solvothermal hot press (STHP) method with different pore-forming agents using ZnO nanoparticles. The samples were characterized with SEM, XRD, FTIR, a mercury intrusion porosimeter and N2 adsorption–desorption method. Experimental results showed that pore size of the nanosolids was between 20–32 and 20–100 nm when de-ionized water and CTAB solution were used as pore-forming agents, respectively. There was no obvious morphological change in the samples when all pore-forming agents were removed from the autoclave. 相似文献
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以SiC为主要原料,以羧甲基纤维素(CMC)为造孔剂,分别以Al2O3-Y2O3和Al2O3-高岭土为烧结助剂,在1550℃真空烧结制备出孔洞均匀的SiC多孔陶瓷,研究了造孔剂和烧结助剂对其抗折强度和抗弯强度的影响.结果表明:随着造孔剂用量的增加,气孔率和线收缩率提高,抗折强度下降.对于经预氧化处理以Al2O3-Y2O3为助烧剂的样品,因发生低温液相反应烧结,其结构致密,气孔率较小,线收缩率和抗折强度较高;而在以Al2O3-高岭土为助烧剂的样品中发生固-固反应,其结构疏松,因而线收缩率和抗折强度较低.但是这种疏松结构有利于热应力的释放,使样品具有较高的抗热震性能. 相似文献
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Yttria-stabilized zirconia (YSZ) fiber was introduced as the reinforcement for porous YSZ ceramics fabricated by tert-butyl alcohol-based gel-casting process and pressureless sintering. Effect of YSZ fiber addition on the microstructure and
properties of porous YSZ ceramics was studied systematically. Results showed that YSZ fiber obviously obstructed densification
during the sintering process and therefore higher porosity could be achieved with the same solid loading of the initial slurry.
Mean pore size regularly increased with increasing fiber addition. The reinforcing effect reached its optimum with 10 wt%
YSZ fiber addition, yet decreased with increasing porosity. Fiber addition significantly changed the fracture mode of the
porous ceramics from brittle to quasi-ductile with increasing fiber additions; fiber pull-out and crack deflection play major
roles in the process. Compared with the porous ceramics without fibers, the thermal conductivity decreased a little. With
improved mechanical and thermal properties, YSZ fiber-reinforced porous YSZ ceramics are more applicable in thermal insulation
materials. 相似文献
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Pechini法制备铌酸锂陶瓷的结晶性能研究 总被引:5,自引:1,他引:5
以Li2CO3、Nb2O5、K2CO3为初始原料,采用Pechini法制备了铌酸锂(LiNbO3)陶瓷。用XRD、SEM等分析了LiNbO3陶瓷的结晶特性。分析结果表明Li2O对于铌酸锂陶瓷的烧结及致密度有着重要的影响,经980℃烧结得到的LiNbO3陶瓷晶粒发育良好,当烧结温度>1100℃时,Li2O有较大的损失,所得到的LiNbO3陶瓷组分与化学计量比有一定偏差。因此应采用多种技术方法来减少Li2O的损失以得到致密、结晶性良好的铌酸锂陶瓷。 相似文献
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The purpose of the present work was to investigate and compare the mechanical and tribological behaviors of ceramic-matrix friction material (CMFM) with steel fiber (SF), mullite fiber (MF), and mixing SF and MF. The CMFM was prepared by hot-pressing sintering, and the tribological behaviors were determined using a constant speed friction tester. The worn surfaces and wear debris were observed by a scanning electron microscopy (SEM). Experiment results show that the combination of SF and MF can improve the mechanical properties that each single fiber does not have. The sever fade for the specimen reinforced by single MF during the whole friction testing can be attributed to the poor interface cohesive strength between MF and matrix. Mixing the SF and MF can improve the friction stability, and the friction coefficients for friction material with a mixture of the SF and MF increases with increasing MF content. For all specimens, increasing in the friction temperatures result in the increase of wear rates. 相似文献
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Effect of solid content on pore structure and mechanical properties of porous silicon nitride ceramics produced by freeze casting 总被引:1,自引:0,他引:1
Feng Ye Jingyi ZhangLimeng Liu Haijiao Zhan 《Materials Science and Engineering: A》2011,528(3):1421-1424
Porous Si3N4 ceramics were prepared by freeze casting using liquid N2 as refrigerant. The pore structure, porosity, α → β-Si3N4 transformation and mechanical properties of the obtained materials were strongly affected by the solid contents of the slurries. Increasing the solid content would reduce the porosity, decrease the pore size and change the pore structure from the aligned channels with dendrites to the round pores with decreased pore size. The formation of this round pores impeded the α → β-Si3N4 phase transformation, but was beneficial to the mechanical properties of the obtained porous Si3N4 due to its unique pore structure. 相似文献