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纳米颗粒悬浮液池内泡状沸腾的实验研究 总被引:7,自引:0,他引:7
本文对纳米颗粒悬浮液在平壁面上池内沸腾进行了实验研究。实验用的纳米粒子为26 nm的铁粉和13 nm的三氧化二铝纳米粉末,基液为去离子水。分别配成体积浓度为0.1%, 1%和2%的悬浮液。实验结果表明,纳米悬浮颗粒对液体沸腾换热过程的影响会随着纳米颗粒性质,颗粒浓度及热流密度大小的不同而出现不同的效果;加入纳米颗粒后, 对基液沸腾换热的影响存在着两个相反的作用机制,它们分别为:纳米颗粒增强了液体内部的热量迁移能力(热物性的影响)和改变了加热面的表面结构特性(加热面特性的影响)。 相似文献
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本文使用有限元方法迎风格式数值研究了热显著性血管影响下的纳米低温手术过程,重点分析了热显著性血管和纳米颗粒的存在对于低温手术过程的影响。结果表明:热显著性血管在纳米低温手术过程中依然表现出显著的加热效果,但相对于不使用纳米颗粒的传统低温手术而言,其加热作用有所降低。基于此,拟深入研究纳米低温手术过程血管网的热效应,并对血管网存在条件下的纳米低温手术过程进行优化。 相似文献
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HA纳米微粒对PEG-600低温保护剂反玻璃化结晶的影响 总被引:1,自引:0,他引:1
为了研究羟基磷灰石HA纳米微粒对低温保护剂反玻璃化结晶的影响,本文利用DSC和低温显微镜研究了含有不同粒径(20nm、40nm、60nm)和不同质量浓度(0.1%、0.2%、0.4%、0.8%)HA纳米微粒的PEG-600(50%,w/w)溶液反玻璃化过程中的结晶现象.试验结果表明:与未添加纳米微粒的PEG-600溶液相比,加入40nm、0.4%纳米微粒的HA-PEG600溶液的反玻璃化温度升高了7℃;加入20nm、0.4%和40nm、0.8%纳米微粒的HA-PEG600溶液的冰晶生长速率分别降低了35%和提高了50%;纳米低温保护剂溶液的冰晶形貌从大圆形变成了小圆形、枝晶或小圆形中夹带枝晶. 相似文献
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Weathering performance of the polyurethane nanocomposite coatings containing silane treated TiO2 nanoparticles 总被引:1,自引:0,他引:1
S.M. Mirabedini M. SabziJ. Zohuriaan-Mehr M. AtaiM. Behzadnasab 《Applied Surface Science》2011,257(9):4196-4203
Nano-filled polyurethane coatings were prepared by incorporation of various amounts of untreated and amino propyltrimethoxy silane (APS) treated TiO2 nanoparticles. TEM and AFM techniques were employed to evaluate dispersion of nanoparticles and surface morphology of the coating, respectively. TEM observations revealed that the APS treated nanoparticles have a better dispersion and smaller agglomeration, compared with their untreated counterparts. AFM images revealed that, surface roughness of the coatings increased with increasing of nanoparticles content, however, at equal level of loadings; coatings containing untreated nanoparticles showed a higher surface roughness.Colour changes (colour coordinates data measurements), mechanical properties and surface morphology of the PU nanocomposite coatings, before and after being exposed to a QUV chamber for 1000 h were studied using various techniques. The results revealed that addition of 0.5 to 1.0 wt.% APS treated TiO2 nanoparticles reduces photocatalytic activity, and improves the weathering performance PU nanocomposite coatings. Tensile strength measurements showed significant improvement of mechanical properties of PU coatings containing modified TiO2 nanoparticles. Results also revealed that the colour measurement is a useful technique and non destructive method for evaluation of coating's performance against weathering conditions. The experimental results showed a good correlation between different techniques findings. 相似文献
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This study presents a new method for classifying the sizes of colloidal nanoparticles of below 100 nm in diameter in liquid dispersion using a microchannel size exclusion chromatography (SEC) chip. This chip can classify polydisperse colloidal nanoparticles containing a mix of two monodisperse nanoparticles into several monodisperse particle populations. The particles classified by the SEC chip are then sequentially analyzed by a photon correlation spectroscopy (PCS) method in combination with a flow cell. Two different pillar patterns of such SEC chips were used in experiments to investigate the effects of these patterns on the nanoparticle classification performance. The results obtained were compared with those from a numerical simulation. Standard polystyrene latex particles with diameters of 20 nm and 100 nm were used in this study. The usefulness of this methodology was verified since the simulation and measurement results were in good agreement with each other. 相似文献
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I-Hsiang Tseng Stephanie S. Watson Li-Piin Sung 《Journal of nanoparticle research》2011,13(5):2195-2204
Metal oxide nanoparticles are small but easily form agglomerates in suspension, depending on the strength of particle–particle
and particle–media interactions. To understand the agglomeration behavior of nanoparticles in media and relate to it to product
performance testing, measurement methods are desired to characterize highly scattering metal oxide nanoparticle suspensions
without dilution. In this article, we describe the advantages of using photocorrelation spectroscopy (PCS) in a backscattering
detection configuration to carry out a realistic agglomerate size measurement in multiple scattering media found in most metal
oxide nanoparticle suspensions. The dynamic behavior of nano-titanium dioxide (TiO2) particles in buffer solutions of different chemical composition and pH values was investigated as a sample system using
PCS. The resulting autocorrelation functions (AFs) at different time intervals, particle concentrations, and pH values were
measured at several detection angles. The AF exhibits a multi-mode relaxation time feature and the calculated hydrodynamic
diameters strongly depended on media composition and detection angle. This result indicates that the size and dispersion of
nano-TiO2 agglomerates are significantly affected by solution media. A measurement protocol for determining size and dispersion of
metal oxide particles in media is proposed and related to a performance test found in industry. 相似文献
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A facile way for preparing tin nanoparticles from bulk tin via ultrasound dispersion 总被引:3,自引:0,他引:3
In this paper, we reported a facile and rapid process to prepare tin nanoparticles from bulk tin via ultrasound dispersion. The morphology and structure of synthesized tin nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) and thermogravimetric analysis (TGA). The results show that the morphology of tin nanoparticles is spherical and the structure of tin nanoparticles has the same crystal structure as the bulk tin. In addition, the tribological property of tin nanoparticles as additives in oil is evaluated on a four-ball tester and the results show that tin nanoparticles exhibit good performance in wear. 相似文献
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An amorphous acrylic acid (AA) polymer coating was generated on TiO2 nanoparticles through pulse radio frequency (RF) plasma polymerization. The AA plasma synthesis mechanism was studied by its optical emission spectrum. The chemical structures of AA–plasma‐polymer were carefully investigated by Fourier transform infrared spectroscopy (FTIR). The dispersion behaviors of AA‐coated and uncoated TiO2 nanoparticles in glycol solution were characterized by ultraviolet absorbency and particle size distribution measurements. The results showed that the aggregation of TiO2 nanoparticles in glycol solution was effectively lowered and the dispersion was improved a lot after AA–plasma‐polymer coating. The pulse plasma coating parameters played an important role in the dispersion enhancement of TiO2 nanoparticles. By properly regulating the pulse discharge parameters, the system could gain the highest radical–monomer reactions rate, the most compatible functional groups on the nanoparticles, and the best dispersion in the background media. 相似文献
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V. Goodarzi S. ALI Monemian F. Maleki M. Torabi Angaji 《Journal of Macromolecular Science: Physics》2013,52(3):472-484
In the preparation of nanocomposites, there is competition between the dispersion of nanoparticles and the formation of agglomerates. In this study, radical copolymerization of ethyl acrylate and methyl methacrylate initiated by 2,2‐azobis (isobutyro) nitrile (AIBN) was performed, in the presence of titanium oxide (TiO2) nanoparticles modified in a new approach; a good dispersion of the nanoparticles in the unsaturated polyester (UP) matrix was obtained. The TiO2 nanoparticles were exposed to 3‐(methacryloxy) propyl trimethoxy silane as the coupling agent. The presence of coupling agent‐grafted TiO2 nanoparticles in the copolymerization process resulted in the formation of a polymeric layer on the surface of the TiO2 nanoparticles (doubly modified‐TiO2). The grafting of coupling agent molecules and consequently copolymer macromolecular chains onto the surface of TiO2 nanoparticles was investigated using Fourier transform infrared (FTIR) analysis. It found that the formation of an acrylate layer on the surface of nanoparticles was successful. Then, unsaturated polyester (UP)/TiO2 nanocomposites were prepared. The morphology was studied using transmission electron microscopy (TEM). Mechanical properties and ultraviolet visible (UV/VIS) spectroscopy of various samples, including the doubly modified‐TiO2 nanoparticles, with different nanoparticle inclusions and the unmodified‐TiO2 nanoparticles, were also investigated. The results showed the doubly modified‐TiO2 nanoparticles, compared to those of unmodified‐TiO2, had better nanoparticle dispersion causing improvement in the mechanical properties and UV shielding. 相似文献
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《Ultrasonics sonochemistry》2014,21(1):149-153
This work is devoted to a systematic study of nanoparticle dispersion by ultrasonication in different solutions: from organic solvents to polymer solutions. The cluster size of nanoparticles at different concentrations in both organic solvents and polymer solutions were directly characterized by Dynamic Light Scattering to study the effect of solid concentration, surfactant and polymer on the dispersion. It reveals that in stabilized suspensions, the smallest attainable size or aggregate size of nanoparticles is independent of solvent type and solid content over the tested range. Furthermore, nanoparticles in simple solvent and in polymer solutions had the similar evolution of cluster size and almost the same final size, which could be very helpful to optimize the dispersion of nanofillers in polymer solutions and nanocomposites. It is also shown that, with appropriate sonication amplitudes, the dispersion procedure developed for very dilute suspensions could be transferred to higher concentration suspensions or even to polymer suspensions. 相似文献
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Xuelian He Zheng Peng Jingjie Han Puwang Li Haiyan Xu Chifei Wu 《Journal of Macromolecular Science: Physics》2013,52(12):2334-2346
A novel strategy of radical polymerization of sodium 4-styrenesulfonate on the surface of carbon black (CB) in the solid state was developed to prepare hydrophilic carbon nanoparticles (PNASS-CB). A high performance natural rubber latex (NRL)/PNASS-CB composite was produced by the latex compounding technique. Scanning electron microscope shows considerable improvement in the dispersion of PNASS-CB in rubber matrix. The lower degree of filler–filler networks and the stronger filler–rubber interaction of PNASS-CB in rubber matrix were confirmed by dynamic mechanical thermal analysis. Rheometric properties of NRL/PNASS-CB, like scorch time and optimum cure time, decreased. Tensile strength, tear strength, and elongation at break increased due to stronger interaction between the PNASS-CB and rubber matrix. Dynamic mechanical properties of the modified carbon nanoparticles further corroborated a significant contribution from the better dispersion and efficient load transfer of PNASS-CB on the static and dynamic mechanical properties of composites. 相似文献
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CuS/graphene composite has been synthesized by the one-pot hydrothermal method using thiourea as the sulfur source and reducing agent. The formation of CuS nanoparticles and the reduction of graphene oxide occur simultaneously during the hydrothermal process, which enables a uniform dispersion of CuS nanoparticles on the graphene nanosheets. The electrochemical performance of CuS/graphene composite was studied as anode materials for lithium ion batteries. The obtained CuS/graphene composite exhibits a relative high reversible capacity and good cycling stability. The good electrochemical performance of CuS/graphene composite can be attributed to graphene, which improves the electronic conductivity of composite and enhances the interfacial stability of electrode and electrolyte. 相似文献
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Feng Zhu Jing Zhang Zhongxue Yang Ying Guo Hua Li Yafei Zhang 《Physica E: Low-dimensional Systems and Nanostructures》2005,27(4):457-461
In this study, the surface of TiO2 nanoparticles was modified through plasma polymerization, which is a dry coating method at room temperature. The surface morphology of TiO2 nanoparticles was characterized by high-resolution transmission electron microscope (HRTEM). The dispersion behavior of TiO2 nanoparticles in water and ethyl glycol was investigated by laser size distribution and ultraviolet–visible absorption spectrum. TiO2 nanoparticles were coated with a thin film through plasma polymerization, which prevents the agglomeration and improves the dispersion behavior of TiO2 nanoparticles. 相似文献