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991.
ZnSe semiconductor hollow microspheres 总被引:9,自引:0,他引:9
992.
Step-wise capacitance increase with voltage (C-switching) effect has been experimentally and theoretically investigated in the case of one-component electrographic developer powder pressed in tablet-shape samples. Peculiarities of capacitance (current)-voltage characteristics as well as frequency dependences of components of complex dielectric constant indicate thatC-switching effect is related to the extent of ferromagnetic carrier capsulation by polymeric compound. The application possibilities of theC-switching effect have been proposed. 相似文献
993.
研究了La^3+,Sr^2+置换对Ca[(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷微观结构与微波介电性能的影响。研究结果表明:La^3+,Sr^2+置换改性Ca[(Mg1/3Nb2/3)0.6Ti0.4]O3系列陶瓷均形成了单一正交系的钙钛矿结构;随着置换量的增加,La^3+改性Ca[(Mg1/3Nb2/3)0.6Ti0.4]O3陶瓷的介电常数、介电损耗下降,同时谐振频率温度系数向正的方向移动,而Sr^2+改性陶瓷则表现出相反的规律,其主要原因在于La^3+,Sr^2+置换所引起Ca[(Mg1/3Nb2/3)0.6TiO4]O3陶瓷内部氧八面体结构变化上的差异。 相似文献
994.
利用量子化学的第一性原理,在自洽场理论水平上对尿素晶体的线性和非线性光学介电性质进行了定量计算,获得了与实验值相符的理论计算结果.提供了一种解决分子晶体量子化学理论计算的新思路. 相似文献
995.
TiO2@Ni(OH)2 core-shell microspheres were synthesized by a facile strategy to obtain a perfect 3D flower-like nanostructure with well-arranged Ni(OH)2 nanoflakes on the surfaces of TiO2 microspheres; this arrangement led to a six-fold enhancement in photocatalytic hydrogen evolution. The unique p-n type heterostructure not only promotes the separation and transfer of photogenerated charge carriers significantly, but also offers more active sites for photocatalytic hydrogen production. A photocatalytic mechanism is proposed based on the results of electrochemical measurements and X-ray photoelectron spectroscopy. 相似文献
996.
HAN Kun XIANG Zheng WANG Zheng WANG Chun-lei LI Min-jie ZHANG Jun-hu YANG Bai 《高等学校化学研究》2006,22(1):76-79
IntroductionSemiconductor nanoparticles show a quantum sizeeffect and have attracted much attention because oftheir unique photochemical and photophysical proper-ties[1—4].In recent years,quantumdots of CdS and in-organic nanoparticles hybrid composites … 相似文献
997.
SHI Qizhen CUI Bin WANG Hui TIAN Jing CHANG Zhuguo & HOU Yudong Department of Chemistry Northwest University Shaanxi Key Laboratory of Physico-lnorganic Chemistry Xi''''an China Key Laboratory of Advanced Functional Materials of China Education Ministry Beijing University of Technology Beijing China 《中国科学B辑(英文版)》2005,48(Z1)
The Nd-doped BaTiO3 nanocrystalline powders and ceramics with different Ti/Ba ratios were prepared by sol-gel method. Phases and microstructures of the Nd-doped BaTiO3 based powders and ceramics were characterized by XRD, SEM and TEM methods. The results revealed that the powders synthesized by sol-gel method were nanometer scale (30-60 nm) and were mainly composed of cubic BaTiO3 with a small amount of BaCO3. After sintering at high temperature, both cubic BaTiO3 and BaCO3 were transformed into tetrahedron BaTiO3 phase. The dielectric properties of the ceramics were also determined and the influence of Ti/Ba ratio on the dielectric properties was discussed. The Tc did not change with the variation of Ti/Ba ratio, while theεmax increased firstly and then decreased. The excess TiO2 is benefit for the modification of ceramics' microstructure and dielectric properties. 相似文献
998.
Permittivity data at frequencies from 0.9 to 12 GHz for propylene carbonate and for the solutions of NaI, NaClO4, Bu4NI, Bu4NClO4, ZnBr2, and Ca(ClO4)2 in propylene carbonate at 25°C are reported and discussed. The contaminating influence of water on the dielectric spectra is shown. Measurements were executed by the method of travelling waves with equipment known to produce data of high precision. Evaluation of the data is performed on the basis of models presupposing one or more relaxation regions. The dielectric spectra of all salts with the exception of ZnBr2 yield relaxation time distributions with a single critical relaxation time or can be analyzed by assuming two critical relaxation times for the solvent. ZnBr2 solutions show a supplementary relaxation region at low frequencies which is attributed to the solute. The variation of permittivities at zero frequency with the salt concentration is discussed in the framework of kinetic depolarization. Solvation numbers are estimated. 相似文献
999.
The technique of asymmetric Fourier transform spectroscopy has been used to determine the complex relative permittivities of undoped GaAs at frequencies near the transverse optic mode. It is demonstrated that the anharmonic damping function calculated from these results is sensitive to two phonon processes excited by the anharmonic decay of the qO transverse optic phonon. Critical-point phonon frequencies are assigned from the structure revealed in damping function. 相似文献
1000.
Ing K. Liedermann 《Colloid and polymer science》1996,274(1):20-26
A simple,five-parameter empirical formula for the temperature dependence of the relaxation frequency is presented. It is shown that this formula reduces to the Arrhenius equation at higher temperatures and to the Vogel-Fulcher-Tamman equation at lower temperatures. Apart from parameters which may be obtained independently from either equation the proposed formula contains an additional parameter describing the sharpness of the transition between the regions of validity of Arrhenius or Vogel-Fulcher-Tamman equation. The applicability of the formula is tested on dielectric relaxation data of acrylic polymers and on other dielectric data available in the literature. The physical meaning of individual parameters is discussed. 相似文献