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ZrO2-Y2O3-Al2O3 nanocrystalline powders with different grain sizes have been synthesized using a chemical coprecipitation method. Nano-powders were compacted uniaxially and densified in a vacuum hot-pressing furnace. Density, pore size distribution, grain size and composition of the composites were determined by various techniques, including BET gas absorption, field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). It has been shown that the porosity, grain and pore size of the ceramics can be controlled by the initial powder size and sintering temperature. Fully densified ceramics with narrow grain size distribution in the range of 100 ?? 500 nm could be obtained. 相似文献
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用原位分散聚合法制备了MC尼龙/Dy2O3纳米复合材料,采用SEM、XRD、力学性能测试等对复合材料进行了分析。研究表明,加入少量纳米Dy2O3可明显改善MC尼龙的力学性能和耐磨性,起到同时增强、增韧和耐磨的作用,当纳米Dy2O3的用量为0.5%时,复合材料的拉伸强度和断裂伸长率达到最大值,分别比MC基体提高15.9%和49.3%,当纳米Dy2O3的用量为1.0%时,复合材料的缺口冲击强度达到最大值,比MC尼龙提高26.8%,磨耗体积达到最小值,比MC尼龙降低84.6%。 相似文献
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以凹凸棒土(ATP)为载体, 以Ce(NO3)3·6H2O和La(NO3)3·6H2O为原料, 以C6H12N4(HMT)为沉淀剂, 采用均相沉淀法制备了不同铈镧比的CeO2-La2O3/ATP(Ce:La=9:1~3:7, 摩尔比, 下同)复合材料。用TG-DSC、 TEM、 XRD和FTIR对所制备复合材料的微观结构和形貌进行表征, 并分别考察不同铈镧比和H2O2添加量对酸性品红模拟废水脱色降解的影响。结果表明, 当Ce:La=5:5时, CeO2-La2O3固溶体颗粒均匀分布在ATP表面, 颗粒尺寸为5~10 nm。随着铈镧摩尔比的增加, 酸性品红的降解率呈先增后减的趋势, 且当Ce:La=5:5、 H2O2为10 mL、 酸性品红浓度为100 mg/L时, 降解效果最好, 300 min后的最大降解率达82%。 相似文献
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Qing Yuan Nan Li Wangchang Geng Yue Chi Xiaotian Li 《Materials Research Bulletin》2012,47(9):2396-2402
A simple and efficient method has been developed to fabricate core–shell structured Fe3O4@SiO2@meso-TiO2 nanocomposites with enhanced photocatalytic activity in this paper. The as-made core–shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and an outer layer of TiO2 nanocrystals with mesoporous structure. Fe3O4@SiO2 was obtained through a sol–gel process. To avoid magnetic loss caused by magnetite core phase transition and particle reunion, we adopt a mild synthetic method to get anatase shell instead of traditional high-temperature calcination. The structure of resulting composites was characterized and their photocatalytic activities were also tested. Fe3O4@SiO2@meso-TiO2 composite exhibits higher photocatalytic activities than Fe3O4@SiO2@solid-TiO2 for the degradation of rhodamine B in aqueous suspension. The excellent photocatalytic activities are ascribed to the high surface area and pore volume created by mesoporous anatase shell. 相似文献
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S. Salehi B. Yüksel K. Vanmeensel O. Van der Biest J. Vleugels 《Materials Chemistry and Physics》2009,113(2-3):596-601
Yttria-neodymia double stabilized ZrO2-based nanocomposites with 40 vol% electrical conductive TiCN were fully densified by means of pulsed electric current sintering (PECS) in the 1400–1500 °C range. The Y2O3 stabilizer content was fixed at 1 mol% whereas the Nd2O3 co-stabilizer content was varied between 0.75 and 2 mol% in order to optimise the mechanical properties. The mechanical (Vickers hardness, fracture toughness and bending strength), electrical (electrical resistivity) and microstructural properties were investigated and the hydrothermal stability in steam at 200 °C was assessed.The nanocomposites with 1–1.75 mol% Nd2O3, PECS at 1400 or 1450 °C, have an excellent fracture toughness of 8 MPa m1/2, although the grain size of both ZrO2 and TiCN phases after densification is in the 100 ± 30 nm range. Moreover, the composites combine a hardness of about 13 GPa, a bending strength of 1.1–1.3 GPa with a low electrical resistivity (1.6–2.2 × 10?5 Ω m) allowing electrical discharge machining. The hydrothermal stability of the double stabilizer nanocomposites was higher than for yttria-stabilized ZrO2-based composites with the same overall stabilizer content. 相似文献
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利用光催化材料可以将水体中含有的有机染料有效地降解和去除,因此制备低成本和高效率的光催化材料成为了当今研究的一个热点。通过简单的化学气相沉积法并结合化学液相反应法大量制备了高质量的一维ZnO-Cu2O核壳纳米复合结构材料。利用扫描电子显微镜(SEM)、X射线能量色散谱(EDS)、X射线衍射(XRD)等测试手段对该一维纳米复合材料的形貌和结构进行了表征,并且利用甲基橙作为有机染料,氙灯作为光源对其光催化性能做了研究。结果表明,在纤锌矿结构的一维ZnO纳米线表面成功包覆了立方结构的Cu2O纳米颗粒,形成了平均直径约为35nm的一维纳米复合结构,其在60min内使甲基橙的脱色率超过了91%,光降解速率常数K达到了2.45h-1,在紫外至可见波长光照射下具有非常好的光催化效果。 相似文献
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Sintering additives were prepared from aluminium hydroxide and yttrium hydroxide. These additives were soluble in water and resulted in a binder. A -SiC powder was mixed with the additive solution and sintered at 2150° C without pressure. The oxides formed from the additive promoted sintering. The sintered body contained no pores. Aluminium, silicon, and yttrium oxide were precipitated in the sintered body. 相似文献
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The exchange bias field has been measured in a set of Co-Cr2O3 nanocomposites in order to distinguish between the bulk and interfacial contributions to H(ex). The studies were carried out on a set of samples prepared by the sol gel technique in which the Co concentration was varied between 30 and 80 wt%. The particle sizes in all samples were carefully controlled so as to enable a comparison of their magnetic properties. Using thermal activation measurements we are able to distinguish between contributions to H(ex) arising from the thermal stability of the antiferromagnetic particles (bulk behaviour) and that due to changing interface density with increasing Co concentration. We have interpreted our results in terms of the independent particle volume model. 相似文献
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Lizhu Tong Deming Liu Jianhui Shi Xuwei Yang Hua Yang 《Journal of Materials Science》2012,47(1):132-137
The multifunctional Fe3O4@Y2O3:Eu3+ nanocomposites were prepared by a facile solvothermal method with Fe3O4 nanoparticles as the core and europium-doped yttrium oxide (Y2O3:Eu3+) as the shell. It is shown that Fe3O4@Y2O3:Eu3+ nanocomposites have a strong photoluminescence and special saturation magnetization Ms of 6.1 emu/g at room temperature.
The effects of the magnetic field on the luminescence intensities of the nanocomposites are being discussed. The multifunctional
nanocomposites with magnetic resonance response and fluorescence probe properties may be useful in biomedical applications,
such as cell separation and bioimaging. 相似文献
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ZIVAR GHEZELBASH DAVOUD ASHOURI SAMAN MOUSAVIAN AMIR HOSSEIN GHANDI YAGHOUB RAHNAMA 《Bulletin of Materials Science》2012,35(6):925-931
Organic–inorganic hybrid materials consisting of inorganic materials and organic polymers are a new class of materials, which have received much attention in recent years. In the present investigation, at first, the surface of nano-alumina (Al 2 O 3 ) was treated with a silane coupling agent of $\boldsymbol{\gamma} $ -aminopropyltriethoxysilane (KH550), which introduces organic functional groups on the surface of Al 2 O 3 nanoparticles. Then fluorinated polyimide (PI) was synthesized from 4,4 ′ -(hexafluoroisopropylidene) diphthalic anhydride and 4,4 ′ -diaminodiphenylsulfone. Finally, PI/modified Al 2 O 3 nanocomposite films having 3, 5, 7 and 10% of Al 2 O 3 were successfully prepared by an in situ polymerization reaction through thermal imidization. The obtained nanocomposites were characterized by fourier transform infrared spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV-Vis spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The results show that the Al 2 O 3 nanoparticles were dispersed homogeneously in PI matrix. According to thermogravimetry analysis results, the addition of these nanoparticles improved thermal stability of the obtained hybrid materials. 相似文献
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Effects of the fabrication processing on the microstructure and properties of composites were investigated. High-density Ni-Co dispersed-Al2O3 (Al2O3/Ni-Co) composites were obtained by hydrogen reduction and consolidated using hot pressing and pulse electric current sintering (PECS) of Al2O3, Ni(NO3)2·6H2O and Co(NO3)2·6H2O powder mixtures. Microstructural investigations of the hot-pressed composite fabricated using again wet/dry ball-milled powder mixture after calcination revealed that fine Ni-Co particles, about 145 nm in diameter, dispersed homogeneously at the matrix grain boundaries. In particular, fine microstructure of dispersion with the average size of 90 nm was realized for the specimen consolidated by PECS method. High strength of over 1 GPa and hardness of 19 GPa were measured for the nanocomposites prepared from the again ball-milled powder mixture. The ferromagnetism of nano-sized Ni-Co contributes to the magnetic properties of the composites. A change in the coercive force with dispersion size was observed. Also, the extent of magnetic response by an applied stress was strongly influenced by the size of Ni-Co particles. The relations between microstructure and mechanical as well as magnetic properties are discussed. 相似文献
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M. Yoshimura Tatsuki Ohji Mutsuo Sando Koichi Niihara 《Materials Research Innovations》1997,1(1):16-19
Y2O3-based nanocomposites were fabriacted by hot-press and the microstructures and mechanical properties were investigated. Transmission-electron-microscope
observations revealed that the SiC particles were distributed both within Y2O3 matrix grains and at the grain boundaries. Significant mechanical properties improvements were identified particularly at
high temperatures above 1000 oC both in air and inert atmospheres.
Received: 2 January 1997 / Accepted: 27 March 1997 相似文献
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Fabrication and mechanical behaviour of Al2O3/Mo nanocomposites 总被引:3,自引:0,他引:3
Two types of Al2O3/Mo composites were fabricated by hot-pressing a mixture of - or -Al2O3 powder and a fine molybdenum powder. For Al2O3/5 vol% Mo composite using -Al2O3 as a starting powder, the elongated molybdenum layers were observed to surround a part of the Al2O3 grains, which resulted in an apparent high value of fracture toughness (7.1 Mpa m1/2). In the system using -Al2O3 as a starting powder, nanometre sized molybdenum particles were dispersed within the Al2O3 grains and at the grain boundaries. Thus, it was confirmed that ceramic/metal nanocomposite was successfully fabricated in the Al2O3/Mo composite system. With increasing molybdenum content, the elongated molybdenum particles were formed at Al2O3 grain boundaries. Considerable improvements of mechanical properties were observed, such as hardness of 19.2 GPa, fracture strength of 884 MPa and toughness of 7.6 MPa m1/2 in the composites containing 5, 7.5, 20 vol% Mo, respectively; however, they were not enhanced simultaneously. The relationships between microstructure and mechanical properties are also discussed. 相似文献