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1.
CdS/TiO2复合纳米粒子的光学性质 总被引:5,自引:0,他引:5
在Brij35/正己醇/环己烷/水构成的反相微乳体系中,分别合成了CdS、TiO2纳米粒子和TiO2包覆CdS(CdS/TiO2)的复合纳米粒子.测定了它们的紫外-可见吸收和荧光光谱.结果表明, CdS/TiO2复合纳米粒子在可见光区的吸收比相应的两组分的吸收之和更强.纳米CdS和纳米TiO2均有较强的荧光.而且在相同浓度时纳米TiO2的荧光比纳米CdS的荧光更强.但在CdS/TiO2复合纳米粒子中,TiO2的荧光被淬灭,而CdS的荧光稍有降低. 相似文献
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TiO2纳米微粒对聚苯胺性能的影响 总被引:26,自引:0,他引:26
纳米微粒具有量子尺寸效应, 其光、电、声及磁等方面的性能与常规材料有显著的不同, 其中以TiO2纳米微粒的电荷载体、光电活性中心、光学微腔和光电特性等特征[1,2]尤为引人注目. 导电聚合物的纳米复合材料是纳米材料的研究热点之一, 在导电材料、电流体和高密度信息存储材料等方面具有良好的应用前景[3]. 在导电聚合物中, 聚苯胺(PANI)因其具有较高的电导率, 原料便宜, 稳定性好而成为目前最有希望获得实际应用的导电聚合物[4~6]. 将纳米微粒和PANI制成复合材料, 其光电性能等与PANI相比均有所改变. 目前已相继有PANI-ZrO2, PANI-MnO2, PANI-SiO2纳米复合材料的报道[7,8], 而有关PANI-TiO2研究工作尚少见报道. 本文制备了PANI-TiO2纳米复合材料, 通过红外光谱、紫外可见光谱及透射电镜等探讨了复合材料的微结构及性能. 相似文献
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表面接枝改性纳米二氧化硅填充聚丙烯的结晶行为 总被引:13,自引:0,他引:13
应用差示扫描量热方法研究了纳米二氧化硅 (SiO2 )及其表面接枝改性对聚丙烯 (PP)结晶过程、等温与非等温结晶动力学的影响 ,并研究了上述等温结晶的熔融行为和平衡熔点 .研究发现纳米SiO2 具有明显的异相成核效应 ,能够提高PP的结晶温度、熔融温度、结晶度和结晶速率 ,但降低聚丙烯结晶的完善程度 .粒子的表面接枝处理 ,因改善了粒子与基体的亲和性而有利于粒子成核效应的提高 ,而且此效应尚与粒子的分散相关 相似文献
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掺杂过渡金属离子的TiO2复合纳米粒子光催化剂──罗丹明B的光催化降解 总被引:64,自引:0,他引:64
在悬浮液体系中进行的半导体光催化降解反应中,催化剂的导带电子(或被俘获到半导体表面的电子)还原电解质溶液的O2分子(受主)是反应的决速步骤,O2分子接受电子后形成的超氧自由基O2-或羟基自由基HO·具有很强的氧化能力,能将污梁物氧化降解[13]. 相似文献
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纳米碳酸钙微粒填充改性聚丙烯复合材料的力学性能和结晶行为研究 总被引:5,自引:0,他引:5
研究了两种不同粒径的纳米碳酸钙(Nano-CaCO3)熔融共混改性均聚聚丙烯(PP)材料的力学性能和结晶行为,结果表明,两种纳米CaCO3填料对PP的B晶形成均有不同程度的诱导作用,并可提高基体结晶温度和结晶速率,从而提高材料的冲击韧性. 相似文献
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聚丙烯/纳米蒙脱土复合材料的结晶动力学研究 总被引:5,自引:1,他引:5
徐笑非 《分析测试技术与仪器》2002,8(1):26-30
采用热分析方法,研究了聚丙烯/纳米蒙脱土复合材料(PP/CLAY)的等温结晶行为,并分别用Avrami方程和赵志英方法对所得数据进行了分析,研究结果表明,纳米蒙脱土微粒对聚丙烯等温和非等温结晶行为均有不同程度的影响,可提高聚丙烯的结晶速率并改善结晶结构。 相似文献
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Wenjing Li József Karger‐Kocsis Ralf Thomann 《Journal of Polymer Science.Polymer Physics》2009,47(16):1616-1624
Polyethylene terephthalate (PET)/Polypropylene (PP)/TiO2 nanocomposites were prepared by compounding a PP/TiO2 nanocomposite premix with PET in absence and presence (up to 6 vol %) of maleic anhydride grafted polypropylene (PP‐g‐MA). In absence of PP‐g‐MA, the TiO2 nanoparticles were mainly located at the PET/PP interface and to a lesser extent in the dispersed PET droplets. As the TiO2 nanoparticles were coated by polyalcohol their surface could react with PP‐g‐MA and thus improving the compatibilization with PP. Therefore in presence of PP‐g‐MA the TiO2 nanoparticles were preferentially located in the PP. The incorporated TiO2 nanoparticles exerted a compatibilization effect on the PET/PP blend. Depending on the location of TiO2 three different compatibilization mechanisms were proposed to be at work: (1) Locating at the interface, the TiO2 nanoparticles decrease the free energy of mixing, and thus increase the thermodynamic stability of the nanocomposites; (2) The TiO2 nanoparticles at the interface also prevent the coalescence of PET droplets; (3) Preferentially located in the PP matrix, the TiO2 nanoparticles decreased the viscosity ratio which facilitated the droplet breakup of PET. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1616–1624, 2009 相似文献
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Enis S. Džunuzović Jasna V. Džunuzović Aleksandar D. Marinković Milena T. Marinović-Cincović Katarina B. Jeremić Jovan M. Nedeljković 《European Polymer Journal》2012,48(8):1385-1393
Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO2 nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO2 nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO2 was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO2 nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO2 nanocomposites in nitrogen and air was investigated. The influence of content of TiO2 nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO2 nanocomposites revealed that degree of TiO2 aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO2 content, indicating that used TiO2 nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO2 nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO2 nanoparticles modified with gallates. 相似文献
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Zeta potential is a physico-chemical parameter of particular importance in describing ion adsorption and electrostatic interactions between charged particles. Nevertheless, this fundamental parameter is ill-constrained, because its experimental interpretation is complex, particularly for very small and charged TiO(2) nanoparticles. The excess of electrical charge at the interface is responsible for surface conductance, which can significantly lower the electrophoretic measurements, and hence the apparent zeta potential. Consequently, the intrinsic zeta potential can have a larger amplitude, even in the case of simple 1:1 electrolytes like NaCl and KCl. Surface conductance of TiO(2) nanoparticles immersed in a NaCl solution is estimated using a surface complexation model, and this parameter and particle size are incorporated into Henry's model in order to determine a constrained value of the zeta potential from electrophoresis. Interior conductivity of the agglomerates is calculated using a differential self-consistent model. The amplitude of estimated zeta potential is greater than that derived from the von Smoluchowski equation and corresponds to the electric potential at the outer Helmholtz plane calculated by our surface complexation model. Consequently, the shear plane may be located close to the OHP, contradicting the assumption of the presence of a stagnant diffuse layer at the TiO(2)/water interface. 相似文献
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Slawomir Borysiak 《Journal of Thermal Analysis and Calorimetry》2012,109(2):595-603
Mercerization process is very significant because the alkali treatment facilitates reactivity of lignocellulosic fillers, thus allowing better response to chemical modification. In the present study, the effect of mercerization of pine wood on the nucleation ability of polypropylene was investigated by means of differential scanning calorimetry. We discovered that for the composites with wood containing cellulose II, the decrease in the crystal conversion of the polymer matrix and increase in the half-time of crystallization values are significant. It can be concluded that the amount of cellulose II formed upon alkalization of lignocellulosic fillers determines their nucleation ability. To evaluate the transcrystalline effects caused by various woods, which were untreated or treated with sodium hydroxide, the polarized optical microscopy was also performed. The nucleation of polypropylene on the surface of wood was investigated by induction time measurement. It was found that surfaces of the unmodified wood generate epitaxial nucleation, whereas the mercerized wood generates nonepitaxial nucleation. The differences in the type of nucleation suggest that the effectiveness of formation of transcrystalline structures depends on the contribution of cellulose I and cellulose II. Moreover, the presence of epitaxy is not necessary for the appearance of transcrystalline structures. The results showed that the transcrystalline structures appeared in each system, even with wood containing significant contribution of cellulose II. The only difference noted was the change in the nucleation abilities of the wood surface. Results of this study imply the necessity of quantitative determination of the contributions of cellulose I and cellulose II, whose presence determine the type of nucleation and nucleation ability of the filler surface. 相似文献
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We report on the synthesis of ZnO and TiO2 nanoparticles by solution-phase methods, with a particular focus on the influence of experimental parameters on the kinetics
of nucleation and coarsening. The nucleation rate of ZnO from the reaction between ZnCl2 and NaOH in ethanol was found to increase with increasing precursor concentration, while the coarsening rate is independent
of precursor concentration up to a threshold concentration. The nucleation rate of ZnO from Zn(OOC-CH3)2 and NaOH in n-alkanols was found to decrease with decreasing chain length, which is explained by the increase of the dielectric
constant of the solvent. Due to the larger solubility of ZnO, nucleation is significantly slower than that observed in the
case of TiO2. TiO2 nanoparticles coarsen according to the Lifshitz-Slyozov-Wagner model for Ostwald ripening. We also show that using amorphous
titania as a base material, pure anatase and brookite nanoparticles can be synthesized. 相似文献
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Colloid and Polymer Science - The kinetics of isothermal and nonisothermal crystallization of polyamide-6 (PA6) containing titania was studied by means of DSC. It was found thatTiO 2 causes an... 相似文献
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Jun Yin Shaohui Wang Yong Zhang Yinxi Zhang 《Journal of Polymer Science.Polymer Physics》2005,43(14):1914-1923
The crystallization and melting behavior of PP/Mg(OH)2 composites was investigated, and the crystallization kinetic parameters and thermal characteristics were investigated according to the Avrami method. Optical polarizing microscope (POM) analysis suggested that the presence of Mg(OH)2 particles gave rise to an increase in the number of nuclei and a decrease in PP spherulitic size. The Avrami exponent n of the PP and composites increased with increasing crystallization temperature, and markedly deceased with the addition of low Mg(OH)2 content. A significant increase in crystallization kinetic constant, and a decrease in crystallization half time of PP were observed in the presence of Mg(OH)2 particles, indicating a heterogeneous nucleating effect of Mg(OH)2 upon crystallization of PP. The melting temperature and equilibrium melting temperature of PP in the composites decreased with increasing the Mg(OH)2 content, which is directly related to the size of the PP crystals. The difference of PP melting enthalpies in the PP and composites demonstrated that the presence of Mg(OH)2 can effectively enhance the crystalline of PP. The crystallization thermodynamics of PP and composites were studied according to the Hoffman theory. Surface free energy of PP chain folding for crystallization of PP/Mg(OH)2 composites was lower than that of PP, confirming the heterogeneous nucleation effect of Mg(OH)2. However, the evaluation of the nucleation activation energy of PP suggested the presence of a large amount of Mg(OH)2 particles in the PP matrix reduced the mobility of PP segments and restricted the development of PP nucleation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1914–1923, 2005 相似文献
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In this report, TiO(2) -SiO(2) composite nanoparticles were prepared by the thermal hydrolysis method using titanium tetrachloride and tetraethylorthosilicate as TiO(2) and SiO(2) precursors, respectively. The prepared nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption/desorption and UV-Vis diffuse reflectance spectroscopy (DRS). The results indicated that, in comparison with pure TiO(2), TiO(2)-SiO(2) composite nanoparticles had a higher thermal stability, which prevents phase transformation from anatase to rutile. In addition, the TiO(2)-SiO(2) nanoparticles had a higher specific surface area, larger pore volume, greater band gap energy and smaller crystallite size. Thus, the surface area of TiO(2)-40% SiO(2) composite nanoparticles was about 17 times higher than that of pure TiO(2) nanoparticles. The photocatalytic activity of TiO(2)-SiO(2) composite nanoparticles in the photodegradation of C.I. Basic Violet 2 was investigated. The photodegradation rate of Basic Violet 2 using TiO(2)-40% SiO(2) nanoparticles calcined at 600°C was much faster than that using pure TiO(2) and Degussa P25 TiO(2) by 10.9 and 4.3 times, respectively. The higher photoactivity of the TiO(2)-SiO(2) composite nanoparticles was attributed to their higher surface area, larger pore volume, greater band-gap energy and smaller crystallite size compared with pure TiO(2). 相似文献
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Li XL Peng Q Yi JX Wang X Li Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(8):2383-2391
Highly crystalline, near monodisperse TiO2 nanoparticles, nanorods and their metal-ion-doped (Sn4+, Fe3+, Co2+, and Ni2+, etc.) derivatives have been prepared by well-controlled solvothermal reactions. Through adjusting the reaction parameters, such as reaction temperature, duration, and concentration of the reactants, the size, shape, and dispersibility of the products can be controlled. A possible reaction mechanism can be proposed based on experimental evidence. 相似文献