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181.
本文通过对二氧化硫的形成及危害的阐述,以及对我市近几年大气中二氧化硫监测结果的分析,针对发展趋势和存在的问题,根据实际情况提出相应的建议。 相似文献
182.
183.
Wenjun Zhang Fangqing Zhang Yafei Zhang Guanghua Chen Xiangliu Jiang 《Diamond and Related Materials》1994,3(11-12)
Highly purified polycrystalline wafers of Zr and Hf were chosen as substrates for diamond deposition by means of the d.c. arc discharge plasma CVD method. Polycrystalline diamond films were formed on both substrates. Scanning electron microscopy and high resolution X-ray diffraction were used to investigate the surface morphology of the diamond films and the composition of the interface layers between the diamond films and substrates. The experiments showed that the transition layer between the diamond films and Zr substrates was ZrC, ZrH and ZrC0.32H1.2. For Hf substrates, in addition to HfC, it is supposed that there were also some hydrides or carbohydrides in the transition layer, because several X-ray reflections appeared which could not be assigned to Hf, HfC or diamond. 相似文献
184.
Four cocatalysts, referred to as ethylaluminoxanes, were synthesized by the reaction between triethylaluminium (AIEt3) and water under various molar ratios of H2O/Al at ?78°C. Aluminoxanes were used as cocatalysts for a MgCl2‐supported Ziegler–Natta catalyst for propylene polymerization at temperatures ranging from 70 to 100°C. When the polymerization was activated by AlEt3, the activity as well as the molecular weight and isotacticity of the resulting polymer gradually dropped as the temperature varied from 70 to 100°C. When ethylaluminoxane was employed as the cocatalyst, good activity and high molecular weight and isotacticity were obtained at 100°C. Furthermore, when the cocatalyst varied from AlEt3 to ethylaluminoxane, the atactic fraction and polymer fraction with moderate isotacticity decreased and the high isotactic fraction slightly increased, which indicated that the variation of the cocatalyst significantly affects the isospecificity of active sites. It was suggested that the reactivity of the Al‐Et group and the size of the cocatalyst were correlated to the performance of the Ziegler–Natta catalyst at different temperatures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1978–1982, 2006 相似文献
185.
Hao Liang Zhiqiang Zheng Zengchang Li Jie Xu Biao Chen Hui Zhao Qijin Zhang Hai Ming 《应用聚合物科学杂志》2004,93(2):681-685
A step‐index polymer optical fiber (SI POF) containing Rhodamine B in poly(methyl methacrylate) (PMMA) has been fabricated by a preform technique. Fluorescence of different fiber lengths were observed and discussed. A high gain (23 dB) for a SI POF with 60‐cm length, 400‐μm diameter was obtained. The Rhodamine B content of the doped SI POF is 5 ppm‐wt. The signal wavelength providing the highest gain for a 60 cm SI POF is around 630 nm, and the optimum fiber length is about 60 cm at 10 kW launched pump power. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 681–685, 2004 相似文献
186.
Preparation of Titanium Nitride/Alumina Laminate Composites 总被引:2,自引:0,他引:2
Jing-Xian Zhang Zheng-Ren Huang Dong-Liang Jiang Shouhong H. Tan Zhijian Shen Mats Nygren 《Journal of the American Ceramic Society》2002,85(5):1133-1138
A preparation route for TiN/Al2 O3 laminate composites has been described. A water-based process using Al2 O3 and TiN slurries with solids contents of 40 and 35 vol%, respectively, was used to make TiN and Al2 O3 tapes. The removal of the binder was monitored by weight-loss measurements in a thermogravimetry unit. Bodies composed of Al2 O3 and TiN tapes were densified at temperatures of 1400° and 1500°C using the Spark Plasma Sintering® (SPS) technique. Densities of >98% of the theoretical densities were approached. Crack-free and almost fully densified TiN/Al2 O3 compacts were prepared by heating the burned-out green bodies to the final sintering temperature (1500°C) at a rate of 100°C/min, and with a holding time of 5–10 min, under a pressure of 75 MPa. The microstructures of the obtained compacts were studied using scanning electron microscopy. Grain sizes in the sintered Al2 O3 and TiN compacts were similar to those of the precursor powders. Hardness and indentation fracture toughness were measured at room temperature, and the monolithic compacts as well as the laminate composites exhibited anisotropic mechanical behavior; i.e., the cracks propagated much more easily in a direction parallel to the laminas than perpendicular to them. 相似文献
187.
农作物秸秆增强氟石膏复合材料的微观结构研究 总被引:1,自引:0,他引:1
将玉米秸秆加入改性后的氟石膏中,研究改性剂、玉米秸秆对氟石膏复合材料结构性能的影响;并用苯丙乳液对玉米秸秆纤维进行表面处理,用以改善基体材料和增强材料的界面结合状况,由此显著提高制品性能。 相似文献
189.
The surface chemistry of methoxide (CH3O-) on the Ni(111) surface has been studied in the presence of hydrogen pressures up to 2 Torr. During heating in vacuum methoxide decomposes to H2 and CO, which desorb at 380 and 445 K, respectively. The CH3O-decomposition process is rate limited by CH bond breaking and exhibits a strong deuterium kinetic isotope effect in CD3O-. In the presence of ambient hydrogen pressures of 0.02–2.0 Torr both CH3O- and CD3O-are hydrogenated directly to methanol at 310 K. Methoxide is hydrogenated by adsorbed hydrogen, which nearly saturates the surface at these pressures and temperatures. 相似文献
190.
在真空粉末绝热低温贮罐的制造过程中、通过吸附器分子筛的活化、夹层真空系统的处理和充装珠光砂等工艺方法的改进,可较大地缩短产品的制造周期并提高产品的质量。 相似文献