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971.
Rohan L. Holmes Jonathan A. Campbell Robert P. Burford 《Polymer Degradation and Stability》2009,94(10):1882-1889
Inorganic-organic hybrid materials are studied due to the unique properties they exhibit. As these materials become more widely applied, particularly as precursor materials for forming inorganic materials, it is essential that the pyrolysis behaviour is understood. Transparent yellow hybrid materials consisting of titanium dioxide and poly(vinyl pyrrolidone) were prepared using sol-gel processing techniques. The hybrids maintained their transparency up to the highest achieved inorganic loading of 57 wt.%. These materials were characterised using thermogravimetric analysis in which the organic component was pyrolysed. The resultant chars were then investigated using optical microscopy, x-ray diffraction, scanning electron microscopy, and atomic force microscopy. The inorganic loading had an effect on char formation, with higher loadings leading to the formation of pyrolysis intermediates which were less apparent in samples of lower inorganic content. The pyrolysis intermediates were found to be carbon-rich. 相似文献
972.
A.A. Al-Ghamdi Nadia Abdel Aal Waleed E. Mahmoud 《Polymer Degradation and Stability》2009,94(6):980-986
Poly(vinyl Chloride)/graphite nanosheet/nickel (PVC/GN) nancomposites are new alternative candidates for electrostatic charge dissipation and electromagnetic interference shielding applications due to their lightweight, ease processing and tunable conductivities. The structures of the nanocomposites were examined by means of scanning electron microscopy (SEM) and X-ray analysis. The mechanical properties such as hardness, modulus of elasticity and elongation at break as a function of GN content were examined. The applicability of the nanocomposites as electrostatic charge dissipation was tested in terms of displaying the variation of decay voltage with time. In addition, the dielectric properties such as real and imaginary permittivity of composites as functions of frequency were investigated. Finally, the electromagnetic properties were measured in the frequency range from 1 to 12 GHz and compared with theoretical modeling. The highest shielding effectiveness at microwave frequency of these nanocomposites was 47 dB which is realistic for defense applications like radar evasion. 相似文献
973.
Xuping Qin Fang Zhao Yingkai Liu Hongyun Wang Shengyu Feng 《Colloid and polymer science》2009,287(5):621-625
HRM (hydrophilic reactive microgels) hydrogels based on acrylamide and 2-acrylamido-2-methylpropane sulfonic acid were prepared
using HRM as a new crosslinking agent. HRM containing double bonds (C=C) were obtained by chemically modifying hydrophilic
microgels (HM) of acrylamide with 2-acrylamido-2-methylpropane sulfonic acid. The resulting HRM hydrogels had high compression
strength, elasticity, and elongation under high water content. The excellent mechanical performance is a main result of the
unique microstructure of the hydrogels that are crosslinked by HRM instead of the conventional crosslinking agents such as
N,N′–methylenebisacrylamide. 相似文献
974.
On the basis of the quantitative relationship among rubber processing, structure and property, the methodology of the integrated processing-structure-property analysis on rubber in-mold vulcanization is presented, and then the temporal evolution and spatial distribution characteristics of silicone rubber hot processing parameters, crosslinking structure parameters and mechanical property parameters are obtained by means of the finite element method. The present work is helpful for optimizing curing conditions, and then the design of rubber vulcanization processes according to certain requirements can be done. 相似文献
975.
Mario Hoyos 《European Polymer Journal》2009,45(4):1322-1327
In this work, the characteristics of the β and γ mechanical relaxations, i.e., temperature and relative intensity, of a series of metallocene iPP samples (MPP) are analysed. The hypothesis that the temperature and the intensity of the glass transition (β relaxation) and local sub-Tg motions (γ relaxation) are related mainly to chain parameters and morphology has been corroborated. On the one hand, it has been found a critical average isotactic length (n1) around 30 propylene units, under which the β and γ dynamics are promoted with respect to the α relaxation. On the other hand, it is apparent that the features which determine the degree of constraint within the inter-lamellar region, i.e., the fraction of low-Tm crystals, drive the relative intensities of the α, β and γ relaxation processes. 相似文献
976.
Synthesis of TiO2 nanoparticles using microorganisms 总被引:1,自引:1,他引:0
A low-cost green and reproducible microbes (Lactobacillus sp. and Sachharomyces cerevisae) mediated biosynthesis of TiO2 nanoparticles is reported. The synthesis is performed akin to room temperature in the laboratory ambience. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of TiO2 nanoparticles. Individual nanoparticles as well as a few aggregate having the size of 8–35 nm are found. Concentric Scherrer rings in the selected area electron diffraction pattern indicated that the nanoparticles are having all possible orientations. A possible involved mechanism for the biosynthesis of nano-TiO2 has also been proposed in which pH as well as partial pressure of gaseous hydrogen (rH2) or redox potential of the culture solution seems to play an important role in the process. 相似文献
977.
Hybrid organic–inorganic nanocomposite coatings were prepared by copolymerizing tetraethylorthosilicate with ethyltriethoxysilane
with an acid catalysis process. Oxygen sensor coatings were fabricated by doping the hybrid sol with platinum meso-tetra(pentfluorophenyl)
porphyrin. Photophysical properties and oxygen sensitivity of the sensor coatings were studied. The microstructure of the
coatings was examined using optical microscopy and scanning electron microscopy. The effect of sol–gel process conditions
like precursor silane molar ratio, acid concentration and stirring time of the sol on the oxygen sensitivity and surface microstructure
of the sensor coating was studied. Oxygen sensitivity and surface morphology of the coatings were dependent on the sol–gel
process parameters. 相似文献
978.
Ming Feng Wen Wang Yu Zhou Dechang Jia 《Journal of Sol-Gel Science and Technology》2009,52(1):120-123
Ferroelectric SrBi2Ta2O9 nanotubes were fabricated by sol–gel dipping template technique and characterized by X-ray diffraction, field emission scanning
electron microscopy, and transmission electron microscopy. They had a single orthorhombic perovskite structure, and most of
SBT nanotubes showed highly preferential crystal growth along the [115] orientation. FE-SEM and TEM investigations showed
that nanotubes have smooth wall morphologies and well-defined diameters corresponding to the diameter of the applied template.
From HRTEM results, the clear lattice fringes indicated that the nanotubes are structurally uniform and well crystallized.
The growth mechanisms of SBT nanotubes into the AAO templates were explored. 相似文献
979.
Thin films of CeO2 and (Ce,Sm)O2 have been prepared by using the SILAR method of deposition in conjunction with hydrothermal and high-temperature annealing. Low-temperature, low-pressure hydrothermal annealing of amorphous Mn:Zn2GeO4 films has lead to the growth of grains having edge lengths near 1 μm. Thick films of crystalline Zn2SiO4 exhibiting limited cracking have been prepared by a doctor-blade method also in conjunction with hydrothermal dehydration and annealing. 相似文献
980.
结合笔者近年来的研究工作,着重论述高乙烯基聚丁二烯的研究进展、聚合动力学与机理、产物的微观结构、分子量及其调节、以及今后的发展动向。 相似文献