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991.
协调水泥基材料孔结构与力学性能是制备无机保温材料的关键问题。本实验对比研究了水介质和引气剂作为引孔介质,并与增稠剂羟丙基甲基纤维素HPMC复合方式,探讨了这两种引孔方式对水泥石宏观力学性能、热工性能,以及微观形貌、孔结构等性能的影响。结果表明,当水泥石在相同密度条件下,水介质引孔制备的多孔水泥石抗压强度较引气方式得到的水泥石强度高;水介质引孔对降低水泥石导热系数的效率较引气方式高,相比于水灰比为0.5的水泥石,水灰比为0.9,或者引气剂掺量为0.4%的水泥石降低导热系数的效率分别达58%和50%;水泥石形貌分析结果显示,水介质引入孔隙更均匀,水泥石中产物间的搭接程度降低,且水灰比越大该趋势越明显,而引气剂引入的孔隙分布均匀性较前者差;硬化水泥石孔结构分析表明,水介质引入的孔隙以小于1μm的毛细孔居多,且其中具有墨水瓶结构的孔隙含量明显少于由引气剂引孔时产生的墨水瓶孔含量。引气剂引入的孔隙孔径以大于1μm为主。 相似文献
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993.
Superior temperature‐stable dielectrics for MLCCs based on Bi0.5Na0.5TiO3‐NaNbO3 system modified by CaZrO3 下载免费PDF全文
Wenxu Jia Yudong Hou Mupeng Zheng Yuru Xu Xiaole Yu Mankang Zhu Kuiyong Yang Huarong Cheng Shuying Sun Jie Xing 《Journal of the American Ceramic Society》2018,101(8):3468-3479
An ultra‐wide temperature stable ceramic system based on (1?x) [0.94(0.75Bi0.5Na0.5TiO3?0.25NaNbO3)?0.06BaTiO3]?xCaZrO3 (CZ100x) is developed for capacitor application in this study. All samples exhibit characteristics of pseudocubic structures in XRD patterns. With CaZrO3 addition, the coupling effect of polar nanoregions (PNRs) is weakening, leading to greatly improved temperature stability of dielectric properties. Among all samples, the most attractive properties are obtained in the composition of CZ10 at <15% variation in dielectric permittivity spanning from ?55°C to 400°C and lower than 0.02 of dielectric loss of between ?60°C and 300°C, accompanied by high DC resistivity (107 Ω m at 300°C, calculated by fitting Jonscher's power law). Furthermore, tentative multilayer ceramic capacitors (MLCCs) composed of CZ10 dielectric and Ag:Pd (70:30) internal electrode layers were fabricated by tape casting and cofiring processes. Temperature‐stable dielectric property in formation of MLCC was successfully realized, with small ΔC/C25°C (<15%) and loss factor (≤ 0.02) between ?55°C and 340°C. Meanwhile, CZ10‐based MLCC showed temperature‐insensitive energy storage density of 0.31?0.35 J/cm3 and high‐energy efficiency of above 77% at 120 kV/cm in the range of ?55 to 175°C. All of these exhibit wonderful temperature‐stable dielectric properties and indicate the promising future of CZ10 dielectric as high‐temperature ceramic capacitors. 相似文献
994.
This paper is concerned with an experimental study of the jet diffusion flame characteristics of fuel containing CO2. Using diesel fuel containing dissolved CO2 gas, experiments were performed under atmospheric conditions with a diesel hole-type nozzle of 0.19 mm orifice diameter at constant injection pressure. In this study, four different CO2 mass fraction in diesel fuel such as 3.13%, 7.18%, 12.33% and 17.82% were used to study the effect of CO2 concentration on the jet flame characteristics. Jet flame characteristics were measured by direct photography, meanwhile the image colorimetry is used to assess the qualitative features of jet flame temperature. Experimental results show that the CO2 gas dilution effect and the atomization effect have a great influence on the flame structure and average temperature. When the injection pressure of diesel fuel increased from 4 MPa to 6 MPa, the low temperature flame length increased from 18.4 cm to 21.7 cm and the full temperature flame length decreased from 147.6 cm to 134.7 cm. With the increase of CO2 gas dissolved in the diesel fuel, the jet flame full length decreased for the jet atomization being improved greatly meanwhile the low temperature flame length increased for the CO2 gas dilution effect; with the increase of CO2 gas dissolved in the diesel fuel, the average temperature of flame increases firstly and then falls. Experimental results validate that higher injection pressure will improve jet atomization and then increased the flame average temperature. 相似文献
995.
996.
大白菜施用不同数量腐植酸复混肥试验报告 总被引:3,自引:0,他引:3
腐植酸复混肥作为“绿色环保肥料”被广泛应用于农业生产中,成为我国发展最快的化肥品种,本次试验探讨不同含量腐植酸复混肥品种、施用数量与产量之间的关系,为科研、生产、推广提供依据。 相似文献
997.
Dong‐Jun Wang Chen‐Bin Gu Peng‐Lei Chen Shi‐Xiong Liu Zhen Zhen Jian‐Cheng Zhang Xin‐Hou Liu 《应用聚合物科学杂志》2003,87(2):280-283
Using the interfacial gel polymerization method, a heat‐resistant gradient‐index polymer optical fiber (GI POF) was developed based on the copolymer of methyl methacrylate (MMA) and N‐isopropylmaleimide (IPMI) as the matrix material and bromobenzene (BB) as dopant. The gradient distribution of IPMI in the GI POF rod was determined by element analysis. IPMI had great advantage in improving glass transition temperature (Tg) and forming a gradient‐index profile. There was a significant enhancement in the heat‐resistant property in comparison with a conventional GI POF rod. The combination of high thermal stability and easy fabrication makes the novel BB–IPMI–MMA system very suitable for heat‐resistant GI POF. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 280–283, 2003 相似文献
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