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针对Al_2O_3-SiO_2溶胶稳定性差、复合材料结构不稳定等问题,通过溶胶-凝胶和超临界干燥工艺制备出Al_2O_3-SiO_2气凝胶复合材料。采用平板导热仪、SEM、BET等对Al_2O_3-SiO_2气凝胶复合材料在不同工艺参数下的结构和性能进行分析与表征,完成了Al_2O_3-SiO_2溶胶制备工艺参数研究,确定了较佳的Al_2O_3-SiO_2气凝胶复合材料优化工艺参数。结果表明:随着螯合剂与仲丁醇铝物质的量的比增加,气凝胶的孔径分布(30~50 nm)变化不大,复合材料的密度均匀性提高,在微观结构中,气凝胶与纤维的结合程度先增加后减小,其中螯合剂与仲丁醇铝物质的量的比为0. 09时结合较好。 相似文献
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Al2O3-SiO2气凝胶是一种低密度、高比表面积、高孔隙率、低热导率的三维结构纳米多孔材料,在航空航天、建筑保温、石油化工等领域具有广泛的应用前景,是理想的高温隔热基体之一。但纯Al2O3-SiO2气凝胶力学性能和抑制高温辐射传热能力较弱,限制了自身在隔热领域的应用。采用纤维作为增强体,制备的Al2O3-SiO2气凝胶复合材料同时具有较好的力学和隔热性能,是目前国内外高温隔热材料方向的研究热点之一。本文介绍了纤维增强Al2O3-SiO2气凝胶隔热复合材料的制备方法,综述了目前国内外该材料的研究进展,并对其未来发展趋势做了展望。 相似文献
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以硝酸铝、正硅酸乙酯、氧氯化锆、钛酸丁酯为前驱体,水和无水乙醇为溶剂,用溶胶-凝胶法制备适合涂膜的复合溶胶。 相似文献
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Sol-Gel-SPD制备超细Al2O3-SiO2二元粉体材料 总被引:1,自引:0,他引:1
以硝酸铝(Al(NO3)3·9H2O)和正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶(Sol-Gel)技术并结合喷雾干燥(SPD)技术制得超细Al2O3-SiO2二元复合粉体材料,并分别于400℃、800℃、1000℃、1150℃和1200℃煅烧2 h;采用全自动比表面积与孔隙率分析仪、TEM、TG-DSC及XRD等仪器研究了热处理温度、pH值(分别为5.5、7和8)以及干燥方法对粉体材料的表面性能、显微形貌、物相组成及Al2O3-SiO2二元系晶体转变过程的影响.结果表明由Sol-Gel-SPD制备的超细Al2O3-SiO2二元粉体材料的比表面积>448 m2·g-1,而经1200℃煅烧2 h后所得的超细莫来石的比表面积34.05m2·g-1;TG-DSC分析表明采用Sol-Gel-SPD制得的Al2O3-SiO2二元粉体材料的质量损失主要发生在500℃之前;XRD分析表明粉体试样的开始莫来石化温度为1000℃,铝硅尖晶石(6Al2O3·SiO2)与非晶态SiO2在1150~1200℃完全转化为莫来石;比较不同pH值试样经1200℃煅烧后的TEM照片发现,当pH=7时,得到的超细莫来石粉体粒径最小,为50 nm. 相似文献
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Al2O3-SiO2-TiO2复合陶瓷膜的研制 总被引:3,自引:0,他引:3
本文用Sol-Gel法制备了掺杂TiO2、SiO2改性的γ-Al2O3膜,Al2O3-SiO2-TiO2混合溶胶的比例为:Al:Si:Ti=1:4:1(mol比),加入硝酸调节其pH值位1.2-2.5,可得到稳定的Al2O3-SiO2-TiO2溶胶。通过XRD分析,膜的相组成为非晶态SiO2、γ-Al2O3和Al4Ti2SiO12及TiO2,SEM分析膜主要特征为层状表面结构,平铺在支撑体上。研究发现添加剂、pH值、膜与基体之间的应力作用、浸渍时间、热处理过程对膜的形成的影响甚大。 相似文献
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H. Makishima Y. Tanaka Y. Kato S. Kure H. Shimada N Matsubayashi A. Nishijima M. Nomura 《Catalysis Today》1996,29(1-4):267-271
A series of Ni---W/A12O3-SiO2 catalysts with different A12O3/SiO2 ratios were prepared and loaded in a commercial HDS unit for a year. The catalytic properties of the freshly sulfided and spent catalysts were investigated by performing structural analyses and model test reactions. The aggregation of the WS2 slabs in the lateral direction, which was observed by EXAFS and TEM, was a major cause of the catalyst deactivation. The addition of SiO2 into the catalyst support was found to suppress the structural changes of the catalyst. 相似文献
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Wenguang Zhang Weimin Liu Chengtao Wang 《Journal of the European Ceramic Society》2002,22(16):2869-2876
Thin films of Al2O3 and doped Al2O3 were prepared on a glass substrate by dip coating process from specially formulated ethanol sols. The morphologies of the unworn and worn surfaces of the films were observed with atomic force microscope (AFM) and scanning electron microscope (SEM). The chemical compositions of the obtained films were characterized by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of obtained thin films sliding against Si3N4 ball were evaluated and compared with glass slide on a one-way reciprocating friction tester. XPS results confirm that the target films were obtained successfully. The doped elements distribute in the film evenly and exist in different kinds of forms, such as oxide and silicate. AFM results show that the addition of the doped elements changes the structure of the Al2O3 films, i.e., a rougher and smoother surface is obtained. The wear mechanisms of the films are discussed based on SEM observation of the worn surface morphologies. As the results, the doped films exhibit better tribological properties due to the improved toughness. Sever brittle fracture is avoided in the doped films. The wear of glass is characteristic of brittle fracture and severe abrasion. The wear of Al2O3 is characteristic of brittle fracture and delamination. And the wear of doped Al2O3 is characteristic of micro-fracture, deformation and slight abrasive wear. The introduction of ZnO is recommended to improve the tribological property of Al2O3 film. 相似文献
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Ni/Al_2O_3催化剂是甲烷二氧化碳重整反应制取合成气研究最多、最具应用潜力的一种催化剂。通过对催化剂进行CO_2-TPD研究,考察还原态Ni/Al_2O_3催化剂的CO_2脱附特性。结果表明,浸渍法制备的Ni/Al_2O_3催化剂CO_2脱附曲线呈现双峰,分别在(60~65)℃和(350~380)℃出现高低温两个活性位;高温CO_2吸附量为3.0 cm~3·g~(-1),低温CO_2吸附量为24.0 cm~3·g~(-1)。催化剂的CO_2吸附量与其Ni含量无关。考察选用不同载体的CO_2脱附行为,发现以Al_2O_3为载体的催化剂CO_2吸附量是MgO和SiO_2为载体催化剂的2~4倍,以TiO_2为载体的催化剂几乎不吸附CO_2。 相似文献
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The effect of Al2O3 on mechanical properties of Ti3SiC2/Al2O3 composite fabricated by SPS was studied systematically. The results show that the hardness of the Ti3SiC2/Al2O3 composite can reach 10.28 GPa, 50% higher than that of pure Ti3SiC2. However, slight decrease in the other mechanical properties was observed with Al2O3 addition higher than 5–10 vol.%, which is believed to be due to the agglomeration of Al2O3 in the composite. 相似文献
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Mechanical properties of Al2O3/ZrO2 composites 总被引:1,自引:0,他引:1
W. H. Tuan R. Z. Chen T. C. Wang C. H. Cheng P. S. Kuo 《Journal of the European Ceramic Society》2002,22(16):2827-2833
In the present study, both t-phase zirconia and m-phase zirconia particles are incorporated into an alumina matrix. Dense Al2O3/(t-ZrO2+m-ZrO2) composites were prepared by sintering pressurelessly at 1600 °C. The microstructure of the composites are characterized, the elastic modulus, strength and toughness determined. Because the ZrO2 inclusions are close to each other in the Al2O3 matrix, the yttrium ion originally in t-ZrO2 particles can diffuse to nearby m-ZrO2 particles during sintering, and the m-phase zirconia is thus stabilized after sintering. The strength of the Al2O3/(t-ZrO2+m-ZrO2) composites after surface grinding can reach values as high as 940 MPa, which is roughly three times that of Al2O3 alone. The strengthening effect is contributed by microstructural refinement together with the surface compressive stresses induced by grinding. The toughness of alumina is also enhanced by adding both t-phase and m-phase zirconia, which can reach values as high as two times that of Al2O3 alone. The toughening effect is attributed mainly to the zirconia t–m phase transformation. 相似文献
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CoMo on Al2O3 catalyst prepared by spray pyrolysis method was found in the form of spheres of 0.5–1.2 μm, which consisted of tiny primary particles of ca. 10–20 nm diameter. The materials shows comparable activity to those of commercial catalysts in HDS of straight run gas oil, in particular, refractory 4,6-dimethyldibenzothiophene (4,6-DMDBT). Weaker interactions between CoMo and Al2O3 are suggested by temperature-programmed reduction (TPR), Raman spectroscopy, to give more active species than those over the impregnated catalysts. This accounts for its comparable activity in spite of its smaller surface area. 相似文献
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The phase diagram of the Al2O3–ZrO2–Nd2O3 system was constructed in the temperature range 1250–2800 °C. The liquidus surface of the phase diagram reflects the preferentially eutectic interaction in the system. Two new ternary and one new binary eutectics were found. The minimum melting temperature is 1675 °C and it corresponds to the ternary eutectic Nd2O3·11Al2O3 + F-ZrO2 + NdAlO3. The solidus surface projection and the schematic of the alloy crystallization path confirm the preferentially congruent character of phase interaction in the ternary system. The polythermal sections present the complete phase diagram of the Al2O3–ZrO2–Nd2O3 system. No ternary compounds or regions of remarkable solid solution were found in the components or binaries in this ternary system. 相似文献
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Motonobu Kobayashi Ryoji Kuma Sinyuki Masaki Noboru Sugishima 《Applied catalysis. B, Environmental》2005,60(3-4):173-179
TiO2-SiO2 with various compositions prepared by the coprecipitation method and vanadia loaded on TiO2-SiO2 were investigated with respect to their physico-chemical characteristics and catalytic behavior in SCR of NO by NH3 and in the undesired oxidation of SO2 to SO3, using BET, XRD, XPS, NH3-TPD, acidity measurement by the titration method and activity test. TiO2-SiO2, compared with pure TiO2, exhibits a remarkably stronger acidity, a higher BET surface area, a lower crystallinity of anatase titania and results in allowing a good thermal stability and a higher vanadia dispersion on the support up to high loadings of 15 wt% V2O5. The SCR activity and N2 selectivity are found to be more excellent over vanadia loaded on TiO2-SiO2 with 10–20 mol% of SiO2 than over that on pure TiO2, and this is considered to be associated with highly dispersed vanadia on the supports and large amounts of NH3 adsorbed on the catalysts. With increasing SiO2 content, the remarkable activity decrease in the oxidation of SO2 to SO3, favorable for industrial SCR catalysts, was also observed, strongly depending on the existence of vanadium species of the oxidation state close to V4+ on TiO2-SiO2, while V5+ exists on TiO2, according to XPS. It is concluded that vanadia loaded on Ti-rich TiO2-SiO2 with low SiO2 content is suitable as SCR catalysts for sulfur-containing exhaust gases due to showing not only the excellent de-NOx activity but also the low SO2 oxidation performance. 相似文献