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991.
Sea‐Hoon Lee Si‐Young Choi Hai‐Doo Kim 《Journal of the American Ceramic Society》2013,96(4):1051-1054
ZrB2–SiC nano‐powder mixture was synthesized using ZrSi2 source material and a modified spark plasma sintering apparatus. The particle size of ZrB2 and SiC was about 80 and 20 nm, respectively. The molecular‐level homogeneity of Zr/Si source and fast heating/cooling rate by SPS caused the formation of homogeneously intermixed nano‐powders. A strong exothermal reaction occurred at around 860°C, which caused strong agglomeration and growth of the synthesized powder mixture. The rapid reaction could be controlled by adding 20 wt% of NaCl, which acted as an inert filler. 相似文献
992.
The ultraviolet radiation aging behaviors of PVC/CaCO3 and PVC/CaCO3/macromolecular modifier composites were studied through whiteness measurement, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, and mechanical properties test. It was found that nano‐CaCO3 particles used as ultraviolet light screening agents could significantly enhance the antiaging properties of PVC materials. Due to the macromolecular modifier coated on nano‐CaCO3 particles, the compatibility of nano‐CaCO3 and PVC matrix was improved, resulting in uniform dispersion of nano‐CaCO3 in PVC matrix. Therefore, the PVC/CaCO3/MP composite exhibited better antiaging properties than PVC/CaCO3 composite. After 12 h of ultraviolet irradiation, the tensile strength retention, elongation at break retention, and impact strength retention of PVC/CaCO3/MP composite were 79.5%, 74.5%, and 75.3%, which were much higher than that of neat PVC and PVC/CaCO3 composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
993.
Zhang Zhao‐yang Tao Yi‐jie Xu Xiao‐qian Zhou Yong‐jiang Cheng Hai‐feng Zheng Wen‐wei 《应用聚合物科学杂志》2013,129(3):1506-1512
The copolymerization of pyrrole with 3,4‐ethylenedioxythiophene (EDOT) is successfully achieved in boron trifluoride diethyl etherate via direct anodic oxidation of the monomer mixtures on indium‐tin oxide working electrodes. The resultant copolymers are characterized by electrochemical methods, FT‐IR, XPS, SEM, and spectroelectrochemical analysis. The copolymer films present excellent electrochromic properties especially the multicolor electrochromism which can be tuned through the feed ratio of pyrrole and EDOT. The neutral copolymer films exhibit blue‐shift with the increasing feed ratio of pyrrole and EDOT, and the calculated band gaps of the copolymers are as low as that of PEDOT film. Furthermore, the electrochemical and optical stability has been improved by the incorporation of EDOT units into the polymer chains. The copolymer prepared with the changing feed ratio of pyrrole and EDOT at 1/4 retains 71% of its original electroactivity after 500 cycles and 72% of its optical contrast after 500 steps. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
994.
Xia Li Guo‐Jun Zhou Guo‐Hai Chu Xian‐Fu Lin Jun‐Liang Wang Kai Shen Jie Yin 《应用聚合物科学杂志》2013,127(4):3242-3248
Novel size‐controllable mPEG‐decorated polymeric microparticles binding optically active ketoprofen were successfully fabricated based on chemoenzymatic synthesis and self‐assembly of amphiphilic random polymer–ketoprofen conjugates with mPEG and (S)‐ketoprofen as pendants. A series of mPEG350‐ or mPEG1000‐functionalized amphiphilic random polymer–ketoprofen conjugates with drug loading capacity from 16.5% to 73.2% were easily prepared by combining enzymatic resolution with radical polymerization and characterized by Fourier Transform Infrared spectroscopy, 1H‐NMR, and gel permeation chromatography. The formation of aggregates from the amphiphilic random polymer–ketoprofen conjugates was investigated by ultraviolet‐visible absorption spectra using pyrene as the guest molecule. Transmission electron microscopy measurement revealed that the self‐assemblies were well dispersed as spherical microparticles. The size of the self‐assemblies could be widely tuned by varying the length of mPEG chains and the content of ketoprofen in the synthetic polymer–ketoprofen conjugates, and a series of mPEG‐decorated (S)‐ketoprofen‐bound polymeric microparticles with average radius from 70 nm to 1.1 μm were obtained. The successful preparation of the microparticles containing (S)‐ketoprofen provided a new strategy for the design and fabrication of optically active drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
995.
The practical design of GaN-based Schottky barrier diodes(SBDs) incorporating a field plate(FP) structure necessitates an understanding of their working mechanism and optimization criteria.In this work,the influences of the parameters of FPs upon breakdown of the diode are investigated in detail and the design rules of FP structures for GaN-based SBDs are presented for a wide scale of material and device parameters.By comparing three representative dielectric materials(SiO2,Si3N4 and Al2O3) selected for fabricating FPs,it is found that the product of dielectric permittivity and critical field strength of a dielectric material could be used as an index to predict its potential performance for FP applications. 相似文献
996.
大规模风电并网运行会显著影响系统的电压稳定性,为研究风电接入对电压稳定薄弱区域的影响,在电力系统分析综合程序(Power System Analysis Software Package,PSASP)中建立了基于双馈异步风力发电机的风电场模型,以IEEE 39节点系统为例,分析和研究了正常负荷情况下和极限运行状态下风电接入对电压稳定薄弱区域的位置分布和薄弱程度的影响.仿真结果表明,通过对风电场自身的无功补偿及对风电场地址的无功储备进行合理约束,可改善风电接入系统的电压稳定性. 相似文献
997.
998.
Wen-Yi Lin Hai Huang Fang Yang Jerome J. Schmitt Andrew T. Hunt Robert R. Romanofsky 《Integrated ferroelectrics》2013,141(1-2):1-12
Abstract Epitaxial barium strontium titanate and strontium titanate thin films were deposited on (100) MgO single-crystal substrates, utilizing Combustion Chemical Vapor Deposition. The as-deposited films were patterned with gold electrodes to form interdigitated structure to function as electrically tunable devices, namely, coupled microstripline phase shifters (CMPS). Microwave dielectric properties were characterized at 11–20 GHz with an applied electric field up to ±35 V/μm. A maximum figure of merit of 53°/dB at 20 GHz and 23°C was measured. The demonstrated high degree of tunability and relatively low loss showed great potential of these films for the targeted frequency agile device applications. Characterization, using SEM, EDS, and XRD, is presented in addition to microwave performance as a function of dc bias and frequency. 相似文献
999.
1000.