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941.
Yiming Zeng Yanqing Zheng Haikuan Kong Jun Xin Hui Chen Xiaoniu Tu Pan Gao Erwei Shi 《Crystal Research and Technology》2011,46(5):459-462
Single crystals of Sr3NbAl1.5Ga1.5Si2O14 (SNAGS) with langasite structure have been successfully grown by Czochralski method. The X‐ray diffraction (XRD) verified that the as‐grown crystal was isostructural with A3BC3D2O14 structure and the lattice parameters were calculated as follows: a = 8.242 Å, c = 5.041 Å, V = 296.6 Å3. The piezoelectric coefficient d11 was 5.7pC/N, which was 2.47 times of α‐quartz (d11=2.31pC/N). The electric resistivity was up to 3.04×106 Ωcm at 700 °C for X‐cut sample. In addition, the transmission spectrum of the SNAGS crystal showed that it had a high transmittance (>80%) in the range of 350‐800 nm and exceeded 90% above 520 nm. These results suggest that the SNAGS crystals have potential applications in high‐temperature piezoelectric sensors and optical techniques. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
942.
Abstract
The synthesis and single-crystal structure of a Na-salt compound Na10[Co4(OH2)2(AsW9O34)2]·32H2O (1) was reported. Compound 1 crystallizes in triclinic system, space group P−1, with the lattice parameters: a = 11.6040(10) ?, b = 12.9361(13) ?, c = 17.396(2) ?, α = 97.4120(10)°, β = 106.8590(10)°, γ = 111.867(2)° and Z = 1. Compound 1 consists of a pure inorganic network based on tetra-sodium capped sandwich-type anionic clusters [Co4(OH2)2(AsW9O34)2]10− bridged through Na–OH2 subunits. The thermogravimetric and electrochemistry measurements had also been studied. 相似文献943.
Xihong Hao Jiwei Zhai Zhenxing Yue Jing Zhou Jichun Yang Shengli An 《Journal of Crystal Growth》2011,314(1):151-156
In the present work, the effects of oxide buffer layers, such as ZrO2, CeO2 and TiO2, on the microstructure and electrical properties of (Pb0.97La0.02)(Zr0.87Sn0.10Ti0.03)O3 (PLZST 2/87/10/3) antiferroelectric (AFE) thin films were investigated systematically. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) pictures illustrated that the crystalline orientation and surface microstructure of PLZST 2/87/10/3 AFE thin films had a close relation with these oxide buffer layers. As a result, the final electrical properties of AFE films were tuned by these buffer layers. Electrical measurements result showed that the dielectric properties, polarization characteristic and current–field curves of AFE thin films could be tailored by selecting a proper oxide buffer layer. 相似文献
944.
A sol-gel method was used to prepare CaO-B2O3-SiO2 (CBS) glass powder for making low-temperature cofired ceramics. This paper was focused on the mechanism of hydrolysis and polymerization and also on the structural evolution of xerogel at various temperatures. The xerogel was transformed into glass ceramics containing CaSiO3 and CaB2O4 crystalline phases through nucleation and crystallization processes. The results indicated that the xerogel exhibits [BO4] or [SiO4] based three-dimensional network structure whose interstices Ca ions fill in, which becomes more orderly and stable after heat treatments. The CBS glass ceramics through controlled crystallization have a potential as electronic packaging materials. 相似文献
945.
Hailong Li Lei Wang Junfeng Zhai Yingwei Zhang Jingqi Tian Xuping Sun 《Macromolecular rapid communications》2011,32(12):899-904
In this communication, the application of coordination polymer nanobelts (CPNs) assembled from H2PtCl6 and 3,3′,5,5′‐tetramethylbenzidine (TMB) are explored as an effective fluorescent sensing platform for nucleic acid detection for the first time. The suggested method has a high selectivity down to single‐base mismatch. DNA detection is accomplished by the following two steps: (1) CPN binds fluorecent dye‐labeled single‐stranded DNA (ssDNA) probe via both electrostatic attraction and π‐π stacking interactions between unpaired DNA bases and CPN. As a result, the fluorescent dye is brought into close proximity to CPN and substantial fluorescence quenching occurs due to photoinduced electron transfer from the nitrogen atom in CPN to the excited fluorophore. (2) The hybridization of adsorbed ssDNA probe with its target generates a double stranded DNA (dsDNA). The duplex cannot be adsorbed by CPN due to its rigid conformation and the absence of unpaired DNA bases, leading to an obvious fluorescence enhancement.
946.
Zhai Jun-Xue Wang He Shi Xin-Yan Zhao Shu-Gao 《Journal of Macromolecular Science: Physics》2013,52(3):496-509
The structure of the bound rubber, the 1H NMR (nuclear magnetic resonance) relaxation time, and the crosslink density of the physical network and the glass transition, were studied for solution polymerized styrene-butadiene rubber (SSBR) filled by carbon black, to investigate the effects of carbon black on the chain mobility and dynamic mechanical properties. It was found by 1H NMR analysis that the rubber chains were adsorbed on the surface of carbon black to form physical crosslinks and restrict the mobility of the chains, especially for some high-mobility units such as chain ends. It was calculated, according to the molecular weight between adjacent crosslinks, that the main motion units of the tightly adsorbed chains appeared to be similar in size to the chain segments. The glass transition temperature (T g) obtained by differential scanning calorimetry (DSC) could not be used to judge the effect of carbon black on chain mobility, while the appearance and change of the loss-tangent (tan δ) peak at high temperature in dynamic mechanical thermal spectrometry (DMTS) test showed that there were three chain states: free chains, loosely adsorbed chains, and tightly adsorbed chains. The dynamic rheology test showed that the unfilled SSBR compound had the rheological characteristics of entangled chain networks; however the nonlinear viscoelasticities of the filled SSBR were related to the gradual disentanglement of adsorbed chains and free chains. The peaks in tan δ vs. temperature curves implied that the motion unit size decreased with the increase of bound rubber content, and the modulus vs. temperature curve showed an apparently lower mobility of adsorbed chains than that of free chains through the very low dependence of modulus on temperature for the highly filled compounds. The extremely high tensile modulus of the vulcanizate with 63.6% carbon black at room temperature also implied that the adsorbed chains were in the glass state due to their restriction by the carbon black. 相似文献
947.
The effect of stress action on pyrite–chalcopyrite galvanic corrosion was investigated using polarization curves and electrochemical impedance spectroscopy (EIS) measurements. When stress increased from 0 to 4?×?105 Pa, the corrosion current density of pyrite–chalcopyrite increased from 5.678 to 6.719 μA cm?2, and the corrosion potential decreased from 281.634 to 270.187 mV, accompanied by a decrease in polarization resistance from 25.09 to 23.79 Ω·cm2. EIS results show there have three time constants in the Nyquist diagrams, which indicated the presence of different steps during the corrosion process. Stress dramatically enhanced pyrite–chalcopyrite galvanic corrosion by affecting the Cu1???x Fe1???y S2 film and the double layer, whereas had little impact on the adsorption species. When the stress changed from 0 to 4?×?105 Pa, the pore resistance and capacitance of the Cu1???x Fe1???y S2 film, R p and Q p, changed by 25.72 and 72.28 %, respectively. The adsorption species resistance, R sl, and capacitance, Q sl, only changed by 9.77 and 2.31 %, respectively. 相似文献
948.
用直径 300 nm的聚苯乙烯微球配制不同浓度的胶体晶体溶液, 将其快速注入内表面镀有导电薄膜的玻璃样品池中, 形成 (111) 晶面平行于玻璃表面的面心立方单晶结构. 通过激光衍射Kossel线方法, 研究了不同体积分数的胶体晶体样品 及它们在均匀电场作用下晶体结构的变化. 实验发现, 随着电场强度的增加, 胶体晶体表现为各向同性的压缩. 胶体晶体在恒定电场下始终保持面心立方结构, 晶格常数随着电场强度的增加逐渐减小. 实验结果可用电场力、电流体力学作用力及颗粒间静电斥力共同解释: 电场力使带电微球克服静电斥力并沿电场反方向运动导致晶体压缩, 而由电场力作用引起的电流体力学液流产生的持续推力使垂直于电场平面上的胶体微球相互靠近. 本实验为天宫一号搭载科学实验的地基实验.
关键词:
胶体晶体
Kossel衍射
结构变化 相似文献
949.
采用传统的固相反应烧结方法制 备BaxSr1-xTiO3(0.40≤ x ≤0.70)陶瓷,借助于Raman散射光谱,研究了陶瓷样品在不同原位电场作用下Raman振动模式的变化,观察到居里温度附近显著的电场诱导的四方–立方相之间的转变. 结果表明A1(TO3)和E(TO4)两种振动模式与晶体的结构存在密切的联系,这两种模式源于O-Ti-O沿晶格中c轴的方向和ab面内的振动. A1(TO3)/E(TO4)之间Raman峰的相对强度比,随外加场强的增加明显升高,顺电相逐渐转变为铁电相,晶格的畸变越来越明显,其宏观性能上表现为介电常数的降低,可调率的增加. 同时对居里温度附近电场诱导的结构相变对顺电相下介电非线性的贡献进行了探讨.
关键词:
钛酸锶钡
Raman散射光谱
结构相变 相似文献
950.
Alex Zhai 《Semigroup Forum》2013,86(3):634-662
We give an asymptotic estimate of the number of numerical semigroups of a given genus. In particular, if n g is the number of numerical semigroups of genus g, we prove that $$\lim_{g \rightarrow \infty} n_g \varphi^{-g} = S $$ where $\varphi = \frac{1 + \sqrt{5}}{2}$ is the golden ratio and S is a constant, resolving several related conjectures concerning the growth of n g . In addition, we show that the proportion of numerical semigroups of genus g satisfying f<3m approaches 1 as g→∞, where m is the multiplicity and f is the Frobenius number. 相似文献