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排序方式: 共有560条查询结果,搜索用时 15 毫秒
1.
Dr. Yanhui Wang Dr. Maroua Bouchneb Rimeh Mighri Dr. Johan G. Alauzun Dr. P. Hubert Mutin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2670-2682
Several non-hydrolytic sol–gel syntheses involving different precursors, oxygen donors, and conditions have been screened aiming to selectively produce mesoporous t-ZrO2 or m-ZrO2 with significant specific surface areas. The in situ water formation was systematically investigated by Karl Fisher titration of the syneresis liquids. XRD and nitrogen physisorption were employed to characterize the structure and texture of the ZrO2 samples. Significant amounts of water were found in several cases, notably in the reactions of Zr(OnPr)4 with ketones (acetone, 2-pentanone, acetophenone), and of ZrCl4 with alcohols (benzyl alcohol, ethanol) or acetone. Conversely, the reactions of Zr(OnPr)4 with acetic anhydride or benzyl alcohol at moderate temperature (200 °C) and of ZrCl4 with diisopropyl ether appear strictly non-hydrolytic. Although reaction time and reaction temperature were also important parameters, the presence of water played a crucial role on the structure of the final zirconia: t-ZrO2 is favored in strictly non-hydrolytic routes, while m-ZrO2 is favored in the presence of significant amounts of water. 1H and 13C NMR analysis of the syneresis liquids allowed us to identify the main reactions responsible for the formation of water and of the oxide network. The morphology of the most interesting ZrO2 samples was further investigated by electron microscopy (SEM, TEM). 相似文献
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采用旋涂法制备了氧化锆介质层薄膜,重点讨论了退火温度以及旋涂转速对薄膜性能的影响及作用机制。研究发现高温后退火一方面使得氧化锆水合物脱水形成氧化锆,另一方面促使氧化锆薄膜结晶。此外,转速较高时,其变化对薄膜厚度及粗糙度无显著影响。当转速为5 000 r/min、退火温度为300℃时,制备的绝缘层厚度具有良好的厚度均匀性,粗糙度为0.7 nm,漏电流为3.13×10-5 A/cm2(电场强度1 MV/cm)。最终,利用ZrO2薄膜作为栅极绝缘层,在玻璃基板上制备了铟镓锌氧化物-薄膜晶体管(IGZO-TFT),其迁移率为6.5 cm2/(V·s),开关比为2×104。 相似文献
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Metal-reinforced sulfonic-acid-modified zirconia catalysts were successfully prepared and used to remove trace olefins from aromatics in a fixed-bed reactor. Catalysts were characterized by ICP-OES, N2 adsorption–desorption, X-ray diffraction, thermogravimetric analysis (TGA), and pyridine-FTIR spectroscopy. Different metals and calcination temperatures had great influence on the catalytic activity. Alumina-reinforced sulfated zirconia exhibited outstanding catalytic performance, stable regeneration activity, and giant surface area, and are promising in industrial catalysis. TGA showed that the decomposition of methyl could be attributed to Brønsted acid sites, and pyridine-FTIR spectroscopy proved the weak Brønsted sites on these synthesized metal-reinforced sulfated zirconia. Also, a relation between the reaction rate and weak Brønsted acid density is proposed. 相似文献
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K. Mohammed Jasim 《Optics and Lasers in Engineering》2011,49(7):785-792
The present paper reports an experimental investigation based on X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and wavelength dispersive spectroscopy (WDS) analyses of phases formed after laser sealing of plasma sprayed coatings of 8.5 wt% yttria partially stabilized zirconia (YPSZ). X-ray diffraction and X-ray step-scanning analyses showed that the plasma sprayed and sealed coatings consisted mainly of t′ phase with a very small amount of monoclinic phase (m phase) in the plasma sprayed coatings. It was also found that the small amounts of m and cubic phases (c phase) present in the sealed coatings were dependent on laser processing specific energies (specific energy is equal to laser power/traverse speed x beam diameter). It was also found that rhombohedral (r) phase formed after laser sealing of coatings at higher specific energies. A direct relationship between c/a ratio of transformable tetragonal phase (t phase) produced by thermal treatment of sealed coatings and nontransformable tetragonal phase (t′ phase) and the amount of Yttria was obtained. A new equation was derived, which describes the relationship between Yttria concentration and the c/a ratio of tetragonal phases (t or t′). 相似文献
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Catalytic dehydration of 2‐propanol and that of 1‐butanol were performed at atmospheric pressure and 150–300°C over ZrO2 and sulfated ZrO2 (S/ZrO2) in a fixed‐bed, tubular reactor. The catalysts were characterized with XRD, elemental analysis, FT‐IR, N2 physisorption, TG/DTA, TPD, and TPR. The main structures of ZrO2 and S/ZrO2 were monoclinic and tetragonal, respectively. As ZrO2 was modified with sulfuric acid, its surface area and acid amount were greatly increased, whereas the pore volume, the pore diameter, and the particle size were reduced. Both samples owned weak basicity. For both reactions, only dehydration products of alkene and ether were obtained. The alcohol conversion enhanced remarkably with the catalyst acid amount and the surface area as well as the reaction temperature. In addition, the ether selectivity on S/ZrO2 decreased with raising the reaction temperature. The activation energy was 81.0 kJ/mol in the propene formation from 2‐propanol over S/ZrO2. The corresponding value was 94.4 kJ/mol for the dehydration of 1‐butanol. 相似文献
9.
蓝宝石晶体因优异的综合性能被广泛用于航空航天等高性能要求领域。泡生法是目前生产大直径蓝宝石单晶的主要方法,热场对生产工艺、产品质量和单晶炉功率具有重要影响;并将影响生产成本。本文对氧化锆及钼金属组合式热屏中氧化锆材料内置、外置及材料不同组合方式对泡生法蓝宝石单晶炉功率的影响进行研究,得到合理的热场结构;并与实际生产结果进行验证。结果表明:相比于传统的15层钼保温结构,加入氧化锆保温层会明显降低单晶炉能耗,其中氧化锆内置的热场结构对单晶炉能耗降低影响更为明显;随着氧化锆层由0增加至15层,单晶炉能耗显著降低,相比传统15层钼保温结构,15层氧化锆保温结构炉体功率降低了38%。 相似文献
10.
硫酸化氧化锆固体超强酸 总被引:1,自引:0,他引:1
硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。 相似文献