共查询到20条相似文献,搜索用时 31 毫秒
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Mina Ahsani Reza Sabouri Mathias Ulbricht Hossein Hazrati Abbas Jafarizad Reza Yegani 《应用聚合物科学杂志》2021,138(38):50977
Hydrophilic antibacterial silver decorated silica-grafted-poly(vinylpyrrolidone) (Ag-SiO2-PVP) nanoparticles were successfully synthesized in multiple steps. In this regard, silanization of the silica nanoparticles was performed with different concentrations of vinyltrimethoxysilane (VTS) to generate vinyl groups onto the nanoparticles surface. Obtained results showed that by increasing the VTS concentration the amount of vinyl groups on the surface of the silica nanoparticles increased while nanoparticles agglomeration did not occur. Then, poly(vinylpyrrolidone) PVP brushes were grafted onto the silanized silica nanoparticles (SiO2-VTS) via grafting-through polymerization method to obtain PVP-grafted silica nanoparticles (SiO2-PVP). Fourier transform infrared spectroscopy, thermal gravimetric analysis, and dynamic light scattering confirmed the successful generation of the vinyl groups and PVP brushes onto the silica nanoparticles. Finally, Ag-SiO2-PVP nanoparticles were prepared by synthesizing silver nanoparticles onto the SiO2-PVP nanoparticles to render them antibacterial. Energy dispersive X-ray spectroscopy showed that highest grafting of silver nanoparticles onto the SiO2-PVP nanoparticles was obtained for the nanoparticles with highest content of vinyl groups. X-ray photoelectron spectroscopy was used to identify the elements and their chemical structure for the synthesized nanoparticles. Plate colony counting method was applied to assess the antibacterial effects of the Ag-SiO2-PVP nanoparticles which revealed outstanding bactericidal properties of them. 相似文献
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Baohe Wang Wenbo Zhang Wei Zhang Caiyuan Yu Gang Wang Lixin Huang 《Drying Technology》2013,31(4):715-721
Magnesium hydroxide precipitate was prepared using magnesium chloride and urea as starting materials via a homogenous precipitation method. Before it was calcined to obtain magnesium oxide nanoparticles, the precipitate was pretreated and dried using different pretreatments and drying methods. The as-prepared magnesium oxide nanoparticles were characterized by transmission electron microscope and X-ray diffraction. The results show that when drying methods (except for supercritical CO2 extraction drying) are the same, grain diameters and agglomeration of magnesium oxide nanoparticles exhibit a similar trend and depend on pretreatment. The agglomeration of magnesium oxide nanoparticles is relevant with drying methods when pretreatments are same. The agglomeration of magnesium hydroxide particles is mostly induced by capillary pressure or surface tension. 相似文献
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D. Stojanovic S.B. Glisic V. Radmilovic R. Aleksic 《The Journal of Supercritical Fluids》2010,52(3):276-24
The objective of this study is to investigate and compare methods of nanosilica coating with γ-methacryloxypropyltrimethoxy (MEMO) silane using supercritical carbon dioxide and carbon dioxide-ethanol mixture. Characterization of grafted silane coupling agent on the nanosilica surface was performed by the infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The d50 value and particle size distribution were determined by laser particle size analyzer (PSA). The operating parameters of silanization process at 40 °C, such as the silica/silane weight ratio, the presence of ethanol, and the pressure, were found to be important for the successful coating of silica particles with minimum agglomeration. The results indicate that presence of ethanol in high-pressure carbon dioxide plays an important role in achieving successful deagglomeration of coated nanoparticles. Dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) revealed that dispersion of the silica particles in the PMMA matrix and interfacial adhesion between silica particles and polymer matrix were enhanced, when silica nanoparticles treated with silane under high pressure of carbon dioxide and ethanol were used for the nanocomposite preparation. 相似文献
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二氧化硅气凝胶因具有低密度、高比表面积、稳定的物理化学性质等特性在吸附分离、隔热保温等领域表现出巨大的应用潜力。但长耗时、高成本的制备工艺限制了它的发展,尤其是湿凝胶向气凝胶转变的干燥工艺。本文介绍了二氧化硅气凝胶在常压干燥的过程中面临的主要难点及解决方法,虽然常压干燥方法工艺简单、过程安全、对设备要求低且可连续制备,成为近年来的研究热点,但也存在制备周期长、体积收缩大、需要消耗大量有机溶剂和改性剂等不足。文中从凝胶基体增强与优化、降低毛细管力与减少不可逆收缩两种角度,介绍了二氧化硅气凝胶常压干燥的改进方法及其发展现状,分析归纳了不同改进方法的优缺点,总结了二氧化硅气凝胶常压干燥目前面临的技术挑战。并且,立足于目前二氧化硅气凝胶基体增强和表面改性技术发展的趋势,对今后二氧化硅气凝胶常压干燥过程中结构可控、成本降低以及产品多功能化的发展路线进行了展望。 相似文献
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Polymer chains were grafted from silica beads (colloidal sol in dimethylacetamide) by atom transfer radical polymerization (ATRP), via the ‘grafting from’ method. The grafting of the initiator onto the silica surface was done in two steps. First, thiol-functionalization of the surface was achieved via silanization with a mercaptopropyl triethoxysilane. Second, we performed an over-grafting of the surface by reacting the thiol with 2-bromoisobutyryl bromide to generate the halogen-functional ATRP initiator. The nanoparticles were kept in solution (in the same solvent) at each stage of the functionalization (even during the purification steps), as this is the only way to avoid irreversible aggregation. Then, the polymerization of styrene was conducted. Control of both the molecular weight and the density of grafted chains can be achieved by this method. Careful characterization such as gel permeation chromatography, 29Si CP/MAS NMR, elemental analysis, infrared spectroscopy and thermo-gravimetric analysis is performed. The state of dispersion of the grafted nanoparticles is followed in details by small angle neutron scattering and results obtained from this technique are presented here as well as the way the SANS data can be treated. Connection is systematically done between the information provided by this technique and the improvement of the synthetic procedure. 相似文献
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The study discussed the synthesis of silica sol using the sol-gel method, doped with two different amounts of Cu nanoparticles. Cotton fabric samples were impregnated by the prepared sols and then dried and cured. To block hydroxyl groups, some samples were also treated with hexadecyltrimethoxysilane. The average particle size of colloidal silica nanoparticles were measured by the particle size analyzer. The morphology, roughness, and hydrophobic properties of the surface fabricated on cotton samples were analyzed and compared via the scanning electron microscopy, the transmission electron microscopy, the scanning probe microscopy, with static water contact angle (SWC), and water shedding angle measurements. Furthermore, the antibacterial efficiency of samples was quantitatively evaluated using AATCC 100 method. The addition of 0.5% (wt/wt) Cu into silica sol caused the silica nanoparticles to agglomerate in more grape-like clusters on cotton fabrics. Such fabricated surface revealed the highest value of SWC (155° for a 10-μl droplet) due to air trapping capability of its inclined structure. However, the presence of higher amounts of Cu nanoparticles (2% wt/wt) in silica sol resulted in the most slippery smooth surface on cotton fabrics. All fabricated surfaces containing Cu nanoparticles showed the perfect antibacterial activity against both of gram-negative and gram-positive bacteria. 相似文献
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《Ceramics International》2021,47(18):25274-25280
Silica aerogels with prominent physical, thermal, optical, and acoustic properties are considered to be highly promising materials. However, owing to the high cost and the complex production processes associated with existing drying technologies, the application of silica aerogels is limited in many fields. In this study, a novel combustion drying method (CDM) was successfully used in the synthesis of superhydrophobic silica aerogels for the first time. It was confirmed that silica aerogel prepared by CDM has a typical aerogel structure with low density, high porosity, high specific surface area, high total pore volume, superhydrophobicity and high thermal stability. Compared with supercritical fluid drying, freeze drying and ambient pressure drying, CDM possesses significant advantages in the drying efficiency and low-cost production due to its active drying mode. Finally, the mechanism of the combustion drying method is proposed based on the combustion of organic solvents. The results will be meaningful for the design and production of aerogel materials in the future. 相似文献
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以羧化多壁碳纳米管为基体、纳米硅溶胶粒为增强相,通过一步液相共混方法制备多壁碳纳米管/二氧化硅纳米复合材料。利用傅里叶变换红外光谱(FTIR)、电子扫描电镜(SEM)、热重(TGA)、孔结构分析(BET/BJH)对其进行了表征。以水中柴油为研究对象考察了该样品对水中柴油的吸附脱除效果,并与纳米二氧化硅胶粒、原生碳纳米管以及活性炭进行对比。结果表明:硅溶胶粒表面修饰后的多壁碳纳米管的聚团行为得以改善,而且材料具有微孔-介孔双孔道结构。对水中直馏柴油的去除率高达97.79%,并于1 h达到吸附平衡。整个吸附过程遵循准二级动力学模型,吸附体系的表观活化能为11.37 kJ·mol-1,吸附等温线与Freundlich模型较为吻合,吸附效果明显强于其他3种吸附剂。 相似文献
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The polymerization of 1‐vinyl‐2‐pyrrolidone (VP) mechanochemically initiated by grinding silica was investigated in a wet stirred media mill. The polymerization itself proceeds from the silica grinding without any additional initiator. We have found that the amount of grafted polymer increases with an increase in total ground silica surface. The suspension of polymer‐modified silica nanoparticles showed high colloidal stability in water because of the appearance of grafted hydrophilic PVP on the surface during the reactive grinding. Because the nanoparticles SiO2‐graft‐PVP are biocompatible, the developed polymer nanocomposite material can be of particular interest for the performance of membranes and for the fabrication of biocompatible hydrogels with enhanced mechanical properties and porosity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3708–3714, 2007 相似文献
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Azin Mazloom Jalali Faramarz Afshar Taromi Laleh Solhi 《Chemical Engineering Communications》2017,204(2):176-181
The purpose of this study is to investigate the effect of reaction conditions on the silanization of montmorillonite nanoparticles using methacryloxypropyltrimethoxysilane (γ–MPS) and to establish relationships between the reaction conditions, the grafting percentage, and the silane arrangement on the particles. The silanization reaction was performed in the following conditions: (i) acidic ethanol-water solution with a pH of 5 and (ii) basic cyclohexane with a pH of 9. To characterize the surface of montmorillonite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), CHN elemental analysis, and X-ray diffraction (XRD) diffraction were utilized. In addition, the dispersion stability of modified particles suspended in different solvents was investigated using a separation analyzer. The results revealed silane grafting in cyclohexane (pH?=?9) achieved higher silanization efficiency, leading to a larger basal spacing in montmorillonite nanoparticles. A parallel arrangement was also suggested for the silane molecules on the surface of the nanoparticles. The higher hydrophobicity of the modified nanoparticles and the decreased overall density of the grafted particles led to a better dispersion in ethanol and toluene. 相似文献
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Andrea Dorigato Alessandro Pegoretti Luca Fambri Miroslav Slouf Jan Kolarik 《应用聚合物科学杂志》2011,119(6):3393-3402
We prepared cycloolefin copolymer (COC)/fumed silica nanocomposites by melt compounding to study the effect of the filler dimensions (filler surface area) on the physical properties, with particular attention to their thermal, mechanical, and optical behaviors. Thermogravimetric analysis revealed a positive contribution of silica nanoparticles to the thermal degradation resistance of COC, as the decomposition temperature of the nanofilled samples increased by 40°C with respect to that of the unfilled matrix. Dynamic mechanical thermal analysis and quasi‐static tensile tests of the nanocomposites evidenced a slight stiffening effect, proportional to the nanofiller surface area, without any reduction in the fracture toughness. Creep resistance of the nanocomposites was increased by the addition of silica nanoparticles, especially when high‐surface‐area nanoparticles were used. The positive effect of the nanoparticles on the viscoelastic and fracture behavior was related to the uniform dispersion of silica aggregates in the matrix. Ultraviolet–visible spectrometry measurements evidenced that the original transparency of neat COC was practically maintained after the addition of silica nanoparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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Quan Shi Narendiran Vitchuli Liwen Ji Joshua Nowak Marian McCord Mohamed Bourham Xiangwu Zhang 《应用聚合物科学杂志》2011,120(1):425-433
Porous Nylon 6 nanofibers were prepared using silica nanoparticles as the template. Firstly, Nylon 6/silica composite nanofibers were prepared as precursors by electrospinning Nylon 6 solutions containing different contents of silica nanoparticles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the surface morphology and the inner structure of composite nanofibers; where it was found that silica nanoparticles were distributed both inside and on the surface of nanofibers. Analytical techniques [Fourier transform infrared (FTIR), differential scanning calorimetry, thermal gravimetric analysis (TGA), and wide‐angle X‐ray diffraction) were used to study the structure and properties of these composite nanofibers. The glass transition, melting, and crystallization processes of the fibers were affected by the addition of silica nanoparticles. Secondly, porous Nylon 6 nanofibers were obtained by removing silica nanoparticles via hydrofluoric acid treatment. The removal of silica nanoparticles was confirmed using FTIR and TGA tests. SEM and TEM observations revealed the formation of the porous structure in these nanofibers. After the formation of the porous structure, Brunauer–Emmett–Teller specific surface areas of nanofibers were increased as compared to solid Nylon 6 and composite nanofibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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Minchae Jang Boyeong Park Hyunseung Lee Tae-Yong Kim Yangsoo Kim 《Korean Journal of Chemical Engineering》2018,35(10):2015-2023
Porous silica supported nanoscale zero-valent iron was prepared by a polymer template method in order to effectively remove a hexavalent chromium ion (Cr(VI)) in an aqueous solution. It did not show a deterioration of Cr(VI) removal efficiency, which could be caused by the surface oxidation and agglomeration of nanoscale zero-valent iron (NZVI) particles. Porous silica by the polymer template method showed quite unique structure, which we named as quasi-inverse opal silica (QIOS), and it showed high surface area (375.4m2/g) and fine pore size (76.5 nm). NZVI immobilized on the surface of QIOS (NZVI@QIOS) was added to an aqueous Cr(VI) solution at 0.025 g/L, and it showed over 96% Cr(VI) removal efficiency. Such a high removal efficiency of Cr(VI) was maintained over two weeks after preparation (92% after 16 days). Morphology of porous silica supported nanoscale zero-valent iron was analyzed by TEM and FE-SEM. Identification of the reaction compounds produced by the reaction of Cr(VI) and zero-valent iron (Fe(0)) was made by the application of XPS. 相似文献
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采用氟化硅烷偶联剂对合成的单分散SiO2纳米颗粒进行表面接枝改性,并通过旋涂法将制备的氟化SiO2颗粒沉积在硅晶基板上.采用粒径分析仪、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TG-DTA)、扫描电镜(SEM)和接触角测量仪对氟化SiO2纳米颗粒涂层的表面形貌、化学组成、接枝密度和润湿性能进行分析表征.结果表明:氟化硅烷偶联剂在SiO2纳米颗粒表面的接枝密度为5.94 nm-2;制备的氟化SiO2纳米颗粒薄膜具备微纳米双重复合网络结构,增加了涂层表面的粗糙程度;氟化SiO2纳米颗粒涂层展现出超疏水和强疏油性能,水和柴油在氟化SiO2纳米颗粒薄膜上的接触角分别为158.4°和125.7°. 相似文献
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粉煤灰酸渣是粉煤灰经酸溶提铝后的副产品,主要化学成分为无定形二氧化硅,其资源化利用不仅解决了粉煤灰酸渣堆存带来的环境问题,还能获得附加值较高的二氧化硅气凝胶。以粉煤灰酸渣制备的水玻璃为原料,通过溶胶-凝胶—溶剂交换/表面改性—常压干燥工艺成功制备了低密度(0.083 g/cm3)、高比表面积(708 m2/g)、高疏水性(接触角为143°)的多孔二氧化硅气凝胶。通过热重-差热分析、红外光谱分析、接触角测试、扫描电镜分析、氮气吸附-脱附测试等手段对热处理前后二氧化硅气凝胶的结构和疏水性进行了表征。结果表明,随着热处理温度升高,二氧化硅气凝胶的比表面积增大、疏水性逐渐减弱直至消失。300 ℃热处理后,二氧化硅气凝胶仍具有较强的疏水性(接触角约为128°),密度为0.080 g/cm3。当热处温度为400~600 ℃时,二氧化硅气凝胶仍具有中孔结构,由疏水性变为亲水性,密度从0.073 g/cm3增加到0.078 g/cm3。 相似文献