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991.
D. J. Twait W. J. Lackey † Arlynn W. Smith Woo Y. Lee John A. Hanigofsky 《Journal of the American Ceramic Society》1990,73(6):1510-1518
Thermodynamic calculations were performed using a modified solgasmix-pv computer program in order to study the feasibility of codepositing boron nitride (BN) plus aluminum nitride (AIN) by chemical vapor deposition. Reactants considered were AICl3 , BCl3 or B2 H6 , NH3 , and H2 . Deposition diagrams were generated for the BCl3 -AICl3 -NH3 system over a range of processing conditions such as temperature, total system pressure, and reagent concentrations. Codeposition of BN + AIN was predicted by the calculations for temperatures in the range of 900 to 1700 K and pressures of 10.13 to 101.3 kPa. The predicted deposition efficiency at equilibrium was much higher for BN than for AlN at most reagent compositions. The AlN deposition efficiency increased with decreasing temperature and decreasing BCl3 content, with increasing NH3 content, or with the addition of H2 . Aluminum chlorides were found to be the dominant gaseous species. 相似文献
992.
利用醋酸锶与四苯基卟啉反应,合成了四苯基卟啉锶配合物。利用元素分析、红外、核磁共振等对该配合物进行了结构表征。采用紫外-可见吸收光谱、荧光光谱和循环伏安法研究了该配合物的光电性能。四苯基卟啉锶配合物紫外-可见吸收光谱有一个强的吸收峰和一个次强的吸收峰,分别为428、457 nm。荧光光谱有一个强的发射峰和一个弱的发射峰,分别为610、676 nm。循环伏安法测得其氧化峰电位为1.558 V和1.051 V。与四苯基卟啉相比,四苯基卟啉锶紫外吸收发生红移,而荧光发射发生蓝移。 相似文献
993.
994.
The effects of a forming atmosphere on the stability, the sintering and the dielectric properties of Ba5Nb4O15, BaNb2O6, ZnNb2O6 and Zn3Nb2O8 ceramics were investigated, because of the primary importance of the sintering atmosphere in relation to copper sintering. These Nb-based materials were sintered in air and in Ar/H210%. Zn-containing samples are very sensitive to the reductive atmosphere. ZnO volatilises at 800–850 °C and the resulting compound does not exhibit the expected properties. BaNb2O6 and Ba5Nb4O15 are more stable in term of relative weight loss. Nevertheless, the phase analysis reveals a modification of the BaNb2O6 phase, what induces the degradation of the dielectric property stability versus temperature. The properties of Ba5Nb4O15 are not modified by a sintering in reductive atmosphere. A relative permittivity of 38.8, a permittivity temperature coefficient of −150 ppm °C−1 and an insulating resistivity of 1010.9 Ω cm were obtained for this latter. 相似文献
995.
Gina‐Gabriela Bumbu Cornelia Vasile Maria Cristina Popescu Hristea Darie Gabrielle Charlotte Chianu Gheorghe Singurel Adrian Carpov 《应用聚合物科学杂志》2003,88(11):2585-2597
The compatibility of the hydroxypropyl cellulose (HPC) with maleic acid–vinyl acetate copolymer in the solid state was studied by thermogravimetry, thermo‐optical analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and optical microscopy. It was established that physical interactions are prevalent in blends with a high content of HPC, whereas chemical interactions predominate in blends with a medium and low content of HPC. By increasing the temperature, the thermochemical reactions are favored. Thermal properties are dependent on the mixing ratio of the components. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2585–2597, 2003 相似文献
996.
A. Kloczkowski 《Polymer》2002,43(4):1503-1525
This paper examines the application of the statistical mechanics to the analysis of various physical properties of the elastomeric networks. The equilibrium properties of rubber-like networks are discussed, and also some dynamic properties, such as the relaxation spectrum of Gaussian networks. The paper covers a large spectrum of properties of polymer networks such as: fluctuations and chain dimensions in unimodal and bimodal network, effects of entanglements and constraints on the elastic properties of the network, segmental orientation, liquid-crystalline networks, small angle neutron scattering from networks, strain birefringence, elastic properties of filled networks, strain induced crystallization etc. The paper shows that the statistical mechanics can be successfully used to the analysis of almost all physical properties of rubber-like networks. 相似文献
997.
A spout-fluid bed device was developed for dry premixing sand and cement to produce mortar. The goal of the work was to explore the efficacy of a new method for dispersing cement in sand to produce a mortar with better mechanical and physical properties. This strategy was found to work best at high sand/cement ratios, indicating that the dry premixing is more effective as the cement content is reduced and that it may be possible to produce commercially acceptable mortars with a lower cement content. Other properties of the mortar are also positively affected, including a decrease in the shrinkage and an increase in the workability. 相似文献
998.
999.
V. A. Sadykov T. G. Kuznetsova V. P. Doronin E. M. Moroz D. A. Ziuzin D. I. Kochubei B. N. Novgorodov V. N. Kolomiichuk G. M. Alikina R. V. Bunina E. A. Paukshtis V. B. Fenelonov O. B. Lapina I. V. Yudaev N. V. Mezentseva A. M. Volodin V. A. Matyshak V. V. Lunin A. Ya. Rozovskii V. F. Tretyakov T. N. Burdeynaya J. R. H. Ross 《Topics in Catalysis》2005,32(1-2):29-38
Approaches to design of zirconia pillared clays via control of the properties of pillaring species in solutions were elaborated. Structural features of pillars and Pt + Cu active components fixed at these nanoparticles were shown to determine catalytic properties of pillared clays in NOx selective reduction by hydrocarbons in the oxygen excess. 相似文献
1000.
The tensile behavior of polycarbonate was studied at large strains below the glass‐transition temperature. Experiments were carried out at a series of constant temperatures and also under conditions of falling temperatures. The specimens necked with a natural draw ratio of approximately 2, and the study was mainly focused on the necked material. Isothermal experiments revealed an elastic mechanism that initiated beyond the natural draw ratio. A model consisting of an Eyring process and two Gaussian elastic mechanisms was found to be applicable to both the isothermal and anisothermal stress‐relaxation and stress–strain results. The same model also produced reasonable estimates of the stresses generated during the necking process. In addition, a simple relationship between the isothermal and anisothermal stress relaxation was demonstrated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2105–2116, 2005 相似文献