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排序方式: 共有4104条查询结果,搜索用时 68 毫秒
91.
纳米银掺杂二氧化硅复合颗粒的制备及表征 总被引:2,自引:0,他引:2
0引言金属纳米颗粒因其粒子尺寸小(1 ̄100nm),比表面积大,表面原子数多,表面能和表面张力随粒径的下降急剧增大而具有量子尺寸效应[1]、小尺寸效应[2]、表面效应[3]及宏观量子隧道效应[4]等,从而出现了不同于常规固体的新奇特性,如:光学性质、磁性质以及电磁学性质[5],使其在催化、信息存储及非线性光学等领域展示了广阔的应用前景[6]。虽然制备金属纳米颗粒的方法有很多[6],但是由于纳米尺寸的金属颗粒具有较高的表面能,容易发生聚集,所以如何保持其稳定性依旧是比较困难的问题。随着纳米科技的发展,人们正尝试用各种方法来解决这个问题:如… 相似文献
92.
W. Yang H. Inoue T.Y. Chow H. Samura T. Saegusa 《Journal of Sol-Gel Science and Technology》1998,11(1):117-124
Au particles dispersed thin metal oxide films were prepared from precursor films containing HAuCl4 with H2S gas diffusion method. HAuCl4 was uniformly dissolved in the films as promoted by hydroxypropyl cellulose (HPC). The mechanism of the Au particle formation was studied. It was found that HAuCl4 was converted directly to Au metal particles upon contacting with H2S gas. Au particles generated by this method were characterized with small particle size, sharp size distribution and high volume fraction in the films. The surface plasma resonance absorption of Au particles shifted to longer wavelength when TiO2 component was introduced in the matrix. 相似文献
93.
94.
Won Young Jung Seung Hee Baek Seong Soo Park Gun-Dae Lee Euh Duck Jeong Hyun Gyu Kim Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2007,91(2):233-240
The nanosized titania and TiO2/SiO2 particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination
temperature has been investigated. The major phase of the pure TiO2 particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO2/SiO2 particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for
the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO2/SiO2 particles decreases as compared to pure TiO2 at high calcination temperatures. The TiO2/SiO2 particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO2 particles. 相似文献
95.
Equilibrium concentration profiles of non-dilute colloidal suspensions are calculated by means of the Carnahan-Starling expression for the osmotic compressibility of hard sphere liquids. The profiles depend on the average volume fraction of the suspension, , and on the field interaction parameter, 0 (reciprocal of the Péclet number at infinite dilution). Profiles are computed for values of and 0 typical of those encountered in sedimentation field-flow fractionation experiments. It is found that, in most cases, the volume fraction at the depletion wall is negligibly small and that the volume fraction at the accumulation wall 0, depends on the ratio <>0/0 only. An inflexion point is found in the concentration profile if 0 is larger than 0.13 whatever the value of 0. 相似文献
96.
Rong Long Li Cheng You Kan Ze Ping Li Yi Du Yan Nan Cui Department of Chemical Engineering Key Laboratory of Advanced Materials of Ministry of Education Tsinghua University Beijing China 《中国化学快报》2007,18(6):741-743
The effects of ionic emulsifier, sodium dodecylbenzene sulfate (SDBS), on the formation of the multihollow structures in sub-micron sized polymer particles produced by alkali/acid posttreatment were investigated. The original latex particles with narrow size distribution were synthesized by a new sequence emulsifier-free/emulsifier emulsion copolymerization of styrene (St) and methacrylic acid (MAA). Results indicated that the pore size decreased and the pore number increased with the increase of SDBS amount, and the morphology of the posttreated latex particles was also significantly influenced by the introducing time of SDBS in the preparation of the original latex particles, and a suitable introducing time was 3 h of polymerization. 相似文献
97.
基于SnO2为修饰层的Au-Pt / SnO2 / Au复合电极研究 总被引:1,自引:0,他引:1
用真空镀膜法在Au电极上沉积SnO2薄膜,在HAuCl4和H2PtCl4的混合溶液中利用直接还原法,将Au-Pt双金属纳米颗粒组装在SnO2 / Au电极上,得到Au-Pt / SnO2 / Au复合电极。采用SEM、TEM、XPS及CV曲线测定对Au-Pt / SnO2 / Au复合电极进行了表征。结果表明:复合电极上双金属纳米颗粒分布均匀,粒子粒径约为25 nm左右。SnO2作为修饰层以配位键与双金属纳米粒子结合。Au-Pt / SnO2 / Au复合电极具有良好对甲醇氧化的电化学性能。 相似文献
98.
Synthetic process to control the total size and component distribution of multilayer magnetic composite particles 总被引:5,自引:0,他引:5
A new synthetic process to prepare composite particles with multilayers, comprised of usual polymer latices, ultra-fine magnetic particles, and a polystyrene layer was examined under various solution conditions.First, the synthetic conditions of heterocoagulates, consisted of polystyrene latices (2a=180900 nm) and NiO·ZnO·Fe2O3 particles (2a=20 nm), were investigated as a function of medium pH, particle concentration, and particle size ratio, based on the concept of the heterocoagulation theory as applied by Harding et al. Regular heterocoagulates were generated under suitable medium and mixing conditions, and that their total size can be controlled by selecting the size of the original polymer latices used as the core.Second, the best encapsulation condition of the heterocoagulates via emulsion polymerization with polystyrene monomer was surveyed. The encapsulation of the heterocoagulates was greatly promoted by pretreatment with oleate molecules, although there is no tendency for the encapsulation when the surfactant-free bare heterocoagulates are used as the core. 相似文献
99.
Summary Liquid crystal polysiloxane stationary phases were prepared by coating two different polymers on deactivated porous silica particles (10 m diameter, 80 Å pores). Deactivation of the silica particles before coating was necessary to prepare highly efficient and inert stationary phases for supercritical fluid chromatography (SFC). Fat-soluble vitamins E, A, K1, K2, D2, and D3 were separated on these columns using neat supercritical CO2 as mobile phase. The analyses were completed within 40 min at 70 °C. The results were compared to those obtained using a capillary column packed with less ordered liquid crystalm,m-cyanobiphenyl-substituted polysiloxane coated particles. Reduced shape selectivity was observed with this cyanobiphenyl phase. The response factors of vitamins A, E, K1, K2, D2, and D3 when using the flame ionization detector (FID) were determined to be very similar. 相似文献
100.
The attempt to prepare structurally well-defined polymer/inorganic composite particles, i.e., poly(methyl methacrylate) (PMMA)/CaCO3/SiO2 three-component composite particles, via reverse atom transfer radical polymerization (ATRP), using 2-2′-azo-bis-isobutyronitrile as initiator and Cu(II) bromide as catalyst was reported. CaCO3/SiO2 two-component composite particles were first obtained through sol–gel method, and their morphology and surface element information were determined by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results indicate that the CaCO3 was encapsulated by the obtained SiO2. After being modified by silane coupling agent, the CaCO3/SiO2 composite particles copolymerized with methyl methacrylate (MMA) under standard reverse ATRP conditions to produce PMMA/CaCO3/SiO2 three-component composite particles. In the case concerned, first-order kinetic plots and linear increase of molecular weight (Mn) vs conversion and narrow molecular weight distribution for the graft polymer samples were observed. Furthermore, the gel permeation chromatography results illustrated that both the free PMMA chains from the solvent and the graft PMMA chains from the surface of CaCO3/SiO2 two-component composite particles were growing at the same rate. Characterizations of the PMMA-grafted CaCO3/SiO2 composite particles were done by Fourier transform infrared and thermogravimetric analysis. The results showed that the surface of the modified inorganic particles was grafted by the MMA and that the grafting percentage was about 8.7%. 相似文献