共查询到19条相似文献,搜索用时 140 毫秒
1.
研究了SiO2介孔组装复合材料的光学性质。对于Ni介孔组装体系,随着组装成分和还原温度的提高,纳米颗粒尺寸增大;由于纳米颗粒的表面效应,光吸收边发生明显的红移。光吸收行为与纳米颗粒和基体之间的相互作用,以及相互之间电子转移有关;纳米金属颗粒介孔组装体系光吸收符合间接带隙半导体光吸收模式。在组装体系中加入稀土元素Ce,还原气氛处理后体系的光吸收增强,随着稀土元素添加量的提高,组装体系的吸收边发生较大红移。 相似文献
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以熔融原位接枝的方式, 制得聚丙烯酸丁酯( PBA) 接枝改性纳米SiO2 / 聚丙烯复合材料, 并利用转矩流变、红外光谱、热重分析、X射线光电子能谱、透射电镜和动态力学分析等技术研究了原位接枝的机理以及相应复合材料的结构。结果表明: 熔融共混过程中PBA 通过化学键的形式接枝到纳米SiO2 的表面, 促使其在聚丙烯基体中得到较好的分散, 而且粒子表面的接枝聚合物分子链和基体大分子链相互缠结, 这样的结构加强了纳米粒子和基体间界面相互作用, 将有利于提高复合材料的机械性能。 相似文献
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为了研究无机刚性颗粒对通用塑料聚丙烯 (PP) 的力学性能的影响, 采用熔融共混方法制备了经硅烷偶联剂A-151处理的SiO2/PP 复合材料, 并通过其缺口冲击、 拉伸、 弯曲试验和冲击断面的形貌观察, 分析研究了微纳米SiO2颗粒大小、 填充量、 表面改性以及不同颗粒大小SiO2混合物对PP复合材料增韧、 增强效果的影响。实验结果表明: 纳米SiO2的加入可以同时改善其韧性、 刚性和强度; 填充量相同, 颗粒越细, SiO2/PP复合材料的力学性能越好。SiO2经改性后填充到PP基体中, 明显改善了颗粒在基体中的分散性及基体与颗粒之间界面结合性能, 使复合材料的综合力学性能得到提高。不同颗粒大小的SiO2混合后填充到PP基体中, 混合SiO2的协同效应使复合材料拉伸、 弯曲性能进一步提高, 对PP基体具有更好的增强效果, 但其冲击性能下降。 相似文献
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利用溶胶-凝胶酸碱二步催化法和常压干燥法制备了掺有不同含量TiO2粉末、 自制SiO2干凝胶纳米粉末和微玻璃纤维的SiO2干凝胶。采用氮气吸附-脱附实验,由经典FHH方程计算得到各掺杂SiO2干凝胶的表面分形维数。比较研究了不同添加物对SiO2干凝胶密度、 孔结构和比表面积等的影响, 并根据de Boer理论判断了孔隙的形状。结果表明, 添加物不仅能够增强SiO2干凝胶的强度, 抑制湿凝胶干燥过程中的收缩, 而且能改变其孔隙结构和颗粒堆积方式。SiO2纳米颗粒能够降低SiO2干凝胶的比表面积, 且使其孔径分布逐渐变宽;而TiO2粉末和短切纤维, 能够提高SiO2干凝胶的比表面积, 最终获得的改性SiO2干凝胶最高比表面积可达1064.96m2/g。各个样品的表面分形维数均在2.4~2.5之间。 相似文献
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综述近年来介孔二氧化硅干凝胶和气凝胶同金属、半导体和其它功能性材料组成纳米复合材料的制备和理化特性研究。介孔二氧化硅纳米复合材料是当前纳米材料研究的热点领域,有广泛的应用前景,对其进行理论和应用研究有着十分重要意义。 相似文献
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用溶胶2凝胶法成功地合成了PI/SiO2 纳米复合材料, 并用紫外-可见光谱、红外光谱、扫描电子显微镜等手段对硅烷偶联剂对其微观形态结构以及密度、溶解性等性能的影响进行了研究。研究结果表明, 偶联剂的加入对两相间起到很好的增容作用, 使得二氧化硅无机粒子的粒径大大减小, 分散更加均匀, 在宏观上表现为透明性提高, 所得P I/SiO2 纳米复合材料的溶解性有明显改善, 而且随偶联剂加入量的增加, 效果更加显著。另外, PI/SiO2 纳米复合材料的密度也随偶联剂量的增加而增大。 相似文献
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通过熔融共混过程中原位接枝的方法制得聚丙烯酸丁酯接枝改性纳米二氧化硅/ 聚丙烯(SiO2-g- PBA/PP) 复合材料, 探讨了材料制备的最佳工艺条件, 研究了复合材料的机械性能、结晶性能、微观形貌以及动态黏弹行为。结果表明, 少量纳米粒子(体积分数≤1.36 %) 的加入即可对PP 起到同时增强增韧的作用, 制备SiO2-g- PBA/PP 的适宜工艺条件为熔融共混温度180 ℃, 共混时间10 min , 转子转速60 r/ min。对复合材料结晶行为的研究表明, 纳米粒子的成核效应使PP 的结晶速率加快。微观形态观察表明, 纳米粒子与聚合物基体间具有良好的界面结合, 这一点从对材料动态黏弹行为的研究中得到进一步证明, 从而阐明了纳米粒子增韧增强聚合物的机理。 相似文献
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FSM-16,MCM-41和SBA-15等具有高规则二维六角晶格的多孔硅可用不同硅源和表面活性剂合成,其孔径可达10,15或30nm,可用具有不同熔基链长的表面活性剂和膨胀剂控制。其结晶规则性随孔径的增大而降低。用层状硅土Kanemite制备的FSM-16和来自水玻璃的MCM-41,其表面阴离子度比用四甲氧基硅烷(TMOS)制备的SBA-15高得多。如将在等电点以下呈阴离子性的生物酶插入硅孔,则由于离子间的相互作用和氢键结合力,可得到结合得十分稳定的生物/无机陶瓷结合体。以此结合体为有机酸化反应的催化剂,反应的活性很高。 相似文献
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Leite ER Carreño NL Longo E Valentini A Probst LF 《Journal of nanoscience and nanotechnology》2002,2(1):89-94
Here we describe a new route for the synthesis of nanometric Ni particles embedded in a mesoporous silica material with excellent potential for catalytic applications. Mesoporous silica with a surface area in the range of 202-280 m2/g, with narrow pore size distribution and Ni nanoparticles (particles in the range of 3-41 nm) were obtained in a direct process. A different approach was adopted to process such a nanocomposite. This new approach is based on the formation of a polymer with the silicon oxianion and nickel cation chelated to the macromolecule structure and on the control of the pyrolysis step. The CO/CO2 atmosphere resulting from the pyrolysis of the organic material promotes the reduction of the Ni citrate. 相似文献
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Y. R. Liu 《Journal of Materials Science》2009,44(13):3600-3607
Mixed amphiphilic block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) and polydimethylsiloxane-poly(ethylene
oxide) (PDMS–PEO) have been successfully used as co-templates to prepare ordered mesoporous polymer–silica and carbon–silica
nanocomposites by using phenolic resol polymer as a carbon precursor via the strategy of evaporation-induced self-assembly
(EISA). The ordered mesoporous materials of 2-D hexagonal (p6m) mesostructures have been achieved, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy
(TEM), and nitrogen-sorption measurements. Experiments show that using PDMS–PEO as co-template can enlarge the pore sizes
and reduce the framework shrinkage of the materials without evident effect on the specific surface areas. Ordered mesoporous
carbons can then be obtained with large pore sizes of 6.7 nm, pore volumes of 0.52 cm3/g, and high surface areas of 578 m2/g. The mixed micelles formed between the hydrophobic PDMS groups and the PPO chains of the F127 molecules should be responsible
for the variation of the pore sizes of the resulting mesoporous materials. Through the study of characteristics of mesoporous
carbon and mesoporous silica derived from mother carbon–silica nanocomposites, we think mesoporous carbon–silica nanocomposites
with the silica-coating mesostructure can be formed after the pyrolysis of the PDMS–PEO diblock copolymer during surfactant
removal process. Such method can be thought as the combination of surfactant removal and silica incorporation into one-step.
This simple one-pot route provides a pathway for large-scale convenient synthesis of ordered mesostructured nanocomposite
materials. 相似文献
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Mesoporous silica nanoparticles carrier for urea: potential applications in agrochemical delivery systems 总被引:1,自引:0,他引:1
Wanyika H Gatebe E Kioni P Tang Z Gao Y 《Journal of nanoscience and nanotechnology》2012,12(3):2221-2228
Nanotechnology-based agrochemical delivery systems would ensure efficient and economical utilization of these very important agricultural inputs. In this study, mesoporous silica nanoparticles with particle diameters of -150 nm and pore sizes of -2.5 nm were synthesized via liquid crystal templating mechanism. Urea, as a model agrochemical molecule, was entrapped in the mesopores of the siliceous material by simple immersion loading using aqueous urea solutions. About 15.5% (w/w) of urea was loaded inside the pores mainly by physisorption while the total adsorption capacity of mesoporous silica nanoparticles could reach up to 80% (w/w). Highly concentrated urea solution was found to be more effective due to high driving concentration gradient generated. Release process of the urea-loaded mesoporous silica nanoparticles in water and soil indicated a two stage sustained slow release-profile. The findings for soil release studies revealed at least fivefold improvement in the release period. By the ability to entrap urea guest molecules into its mesopores and release them in a controlled manner, mesoporous silica nanoparticles demonstrated its great potential as a nanocarrier for agrochemicals. 相似文献
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Irina Ursachi Aurelia Vasile Adelina Ianculescu Eugeniu Vasile Alexandru Stancu 《Materials Chemistry and Physics》2011
Iron oxide nanoparticles were stabilized within the pores of mesoporous silica MCM-41 amino-functionalized by a sonochemical method. Formation of iron oxide nanoparticles inside the mesoporous channels of amino-functionalized MCM-41 was realized by wet impregnation using iron nitrate, followed by calcinations at 550 °C in air. The effect of functionalization level on structural and magnetic properties of obtained nanocomposites was studied. The resulting materials were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy and selected area electron diffraction (HRTEM and SAED), vibrating sample and superconducting quantum interface magnetometers (VSM and SQUID) and nitrogen adsorption–desorption isotherms measurements. The HRTEM images reveal that the most of the iron oxide nanoparticles were dispersed inside the mesopores of silica matrix and the pore diameter of the amino-functionalized MCM-41 matrix dictates the particle size of iron oxide nanoparticles. The obtained material possesses mesoporous structure and interesting magnetic properties. Saturation magnetization value of magnetic iron oxide nanopatricles stabilized in MCM-41 amino-functionalized by in situ sonochemical synthesis was 1.84 emu g−1. An important finding is that obtained magnetic nanocomposite materials exhibit enhanced magnetic properties than those of iron oxide/MCM-41 nanocomposite obtained by conventional method. The described method is providing a rather short preparation time and a narrow size distribution of iron oxide nanoparticles. 相似文献
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Yan-Tao Shi Hong-Yun Cheng Yi Geng Hai-Ming Nan Wei Chen Qiang Cai Bao-Hua Chen Xiao-Dan Sun You-Wei Yao Heng-De Li 《Materials Chemistry and Physics》2010
10–60 nm-sized mesoporous silica particles with ordered or worm-like pore structures were controllably synthesized in extremely dilute surfactant solution, and the lowest concentrations of TEOS and CTAB were 12.45 mM, 1.52 mM, respectively. The synthesis of nanometer-sized Al-incorporated mesoporous silica particles (Al-MS) was also performed under the similar conditions. Compared to the mesoporous silica without doping of aluminum, those Al-incorporated silica particles have a certain textural mesoporosity. The results indicate that the size and pore structure of mesoporous silica can be adjusted by changing the concentration of reactants. The mesoporous silica nanoparticles, including Al-MS, were characterized by transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXRD), as well as nitrogen adsorption/desorption techniques. It was suggested that the formation of the mesoporous silica nanoparticles could be attributed to the deposition of self-assembled silicate micelles. 相似文献
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Peiyu Wang 《Materials Research Bulletin》2010,45(2):129-45
Pd nanoparticles supported in functionalized mesoporous silica were prepared. Mesoporous silica support was modified with [3-(2-aminoethyl aminopropyl)] trimethoxysilane. Palladium ions were grafted onto the functionalized mesoporous silica and reduced with hydrazine hydrate to obtain the Pd nanoparticles supported on functionalized mesoporous silica. The Pd loading in the nanocomposite of Pd supported on the functionalized mesoporous silica is 4.30 wt%. CO chemisorption analysis on the nanocomposite shows a Pd dispersion as high as 35% and a Pd surface area of 156 m2/g. The surface area, pore size, and pore volume decrease slightly with the incorporation of the Pd nanoparticles into the functionalized mesoporous silica. Pd supported on the functionalized mesoporous silica with controlled molar ratio of amino groups to palladium exhibits an excellent catalytic activity and low Pd leaching for the Heck carbon-carbon coupling reaction. The catalyst can be reused for at least six recycles in air with only a minor loss of activity. 相似文献
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Huang J Lin YW Fu XW Best SM Brooks RA Rushton N Bonfield W 《Journal of materials science. Materials in medicine》2007,18(11):2151-2157
Nano-sized hydroxyapatite (nanoHA) reinforced composites, mimicking natural bone, were produced. Examination by transmission
electron microscopy revealed that the nanoHA particles had a rod-like morphology, 20–30 nm in width and 50–80 nm in length.
The phase composition of hydroxyapatite was confirmed by X-ray diffraction. The nanoHA particles were incorporated into poly-2-hydroxyethylmethacrylate
(PHEMA)/polycaprolactone (PCL) matrix to make new nanocomposites: nanoHA-PHEMA/PCL. Porous nanocomposite scaffolds were then
produced using a porogen leaching method. The interconnectivity of the porous structure of the scaffolds was revealed by non-destructive
X-ray microtomography. Porosity of 84% was achieved and pore sizes were approximately around 300–400 μm. An in vitro study
found that the nanocomposites were bioactive as indicated by the formation of a bone-like apatite layer after immersion in
simulated body fluid. Furthermore, the nanocomposites were able to support the growth and proliferation of primary human osteoblast
(HOB) cells. HOB cells developed a well organized actin cytoskeletal protein on the nanocomposite surface. The results demonstrate
the potential of the nanocomposite scaffolds for tissue engineering applications for bone repair. 相似文献