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991.
Zong‐Yang Shen Qi‐Guo Hu Yue‐Ming Li Zhu‐Mei Wang Wen‐Qin Luo Yan Hong Zhi‐Xiang Xie Run‐Hua Liao 《Journal of the American Ceramic Society》2013,96(8):2551-2555
Rare–earth‐doped strontium titanate ceramics yielding the formula Re0.02Sr0.97TiO3 (Re–ST, Re = La, Sm, Gd, Er) were prepared by solid‐state reaction route. All Re–ST ceramics had single cubic perovskite structure similar to pure SrTiO3 (ST). The grain size of Re–ST ceramics dramatically decreased to 1–10 μm, depending on different rare‐earth elements, as compared to ~30 μm of pure ST. The relative dielectric constant of Re–ST ceramics (εr = 2750–4530 at 1 kHz) showed about 10–15 times higher than that of pure ST (εr = 300 at 1 kHz), whereas the dielectric loss of Re–ST ceramics still remained lower than 0.03 (at 1 kHz) at room temperature. Under 0–1.63 × 106 V/m bias electric field testing conditions, the εr of Re–ST ceramics at room temperature changed within 14%. The P–E results indicated that the Re–ST ceramics were linear dielectrics. Together with their relatively high breakdown strength (Eb > 1.4 × 107 V/m), the Re–ST ceramics could be very promising for high‐voltage capacitor applications. Meanwhile, the temperature stability of the εr of Re–ST ceramics was evaluated in a temperature range of ?60°C–200°C. 相似文献
992.
Ya‐lei Zhang Min Zhang Zheng Shen Jing‐fei Zhou Xue‐fei Zhou 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(5):829-833
BACKGROUND: Glycerine, a main by‐product of the biodiesel manufacturing process, has potential to be an important biorefinery feedstock with the rapid increase in biodiesel production all over the world. Hydrothermal experiments with glycerine were carried out at 250 °C using H2O2 as an oxidant. RESULTS: Glycerine was converted into formic acid with a yield of 31.0% based on the starting mass of carbon in glycerine. A possible oxidation pathway for the formation of formic acid from glycerine is proposed. In the proposed pathway, glycerine may first be oxidised and then decomposed into formic acid and oxalic acid. Oxalic acid was indirectly attributed to the increase of formic acid production from glycerine, but it instead acts as a retardant to prevent further oxidation of formic acid. However, when an alkali was added to the experimental conditions, the yield of formic acid was not greatly improved, reaching only 34.7%. CONCLUSION: The present work should help to facilitate further studies to develop a new green process for the production of formic acid from renewable biomass. © 2012 Society of Chemical Industry 相似文献
993.
Linghe Cheng Wanjie Wang Jingwu Wang Yanxia Cao Guixun Li Yelong Shen 《应用聚合物科学杂志》2013,127(5):4044-4051
In situ microfibrillar composites (PP/mPA66) of modified polyamide66 (mPA66) with polypropylene (PP) were prepared by using a “post‐compatibilization” technique. The mPA66 was firstly obtained by reactive extrusion of PA66 resin with a specially designed compatibilizer, which was then blended with PP through extrusion combined with a hot stretching and subsequently quenching process. The PP/mPA66 in situ microfibrillar composites were comparatively studied with simply blended samples of PP/PA66 that were prepared by blending PA66 and PP together with (or without) the same compatibilizer through extrusion. PA66‐g‐PP (and/or elastomers) graft copolymer formation in mPA66 was identified by dissolution test and infrared spectroscopy measurement, the compatibilizer is unevenly dispersed with large domains in PA66 as observed by scanning electron microscope (SEM). In PP/mPA66 composites, the in situ generated PA66 microfibrils have a rather nonuniform diameter distribution and a very rough surface. SEM observations for the fractured surface illustrated that PP/mPA66 composites have structural characteristics of stronger adhesion and moderate flexibility of the interface. Enhanced compatibilization between the PA66 microfibrils with the PP matrix resulted in improved mechanical properties of the PP/mPA66 composites. With optimized composition, the PP/mPA66 composite has notched Izod impact strength, flexural modulus, and tensile yield stress of 1.49, 1.16, and 0.99 times as those of the neat PP, respectively. Such enhanced mechanical properties balance and improved interface adhesion were not found in the simply blended samples of PP/PA66 with or without the specially designed compatibilizer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
994.
采用纳米SiO2、间苯二甲酸-5-磺酸钠(5-SSIPA)与聚苯硫醚(PPS)共混,利用双螺杆挤出机制备纳米SiO2/5-SSIPA/PPS共混母粒,采用差示扫描量热仪和扫描电子显微镜研究了纯PPS,SiO2/PPS,5-SSIPA/PPS以及SiO2/5-SSIPA/PPS母粒的吸湿性、热性能和分散性。结果表明:SiO2/5-SSIPA的协同作用较单独添加SiO2和5-SSIPA提高PPS母粒的吸湿性更为显著;随着SiO2/5-SSIPA含量的增加,PPS母粒的吸湿性提高,SiO2/5-SSIPA质量分数为9%时,PPS母粒的含水率达2.7%;SiO2/5-SSIP质量分数为6%时,共混体系的分散性最好;SiO2/5-SSIPA的添加改变了PPS母粒的熔融和结晶行为;在制备吸湿性PPS母粒时,添加纳米SiO2/5-SSIPA按质量比3/5混合,SiO2/5-SSIPA质量分数6%为宜。 相似文献
995.
996.
997.
酚类环境激素双酚A(BPA)在各种水体中都有检出,且检出浓度有逐年增大的趋势;酚类有一定的毒性,加之它在水中的溶解度小,常规方法不易去除。本试验研究了NF-270型纳滤膜在不同压强、浓度、温度下对双酚A的去除效果。结果表明:原水中微量双酚A浓度的变化对膜通量基本无影响,截留率会随原水中双酚A浓度的增大而略有增加;随着操作压力的增加,膜通量增加,截留率增大,温度增加,截留率也增大,但超过30℃时,截留率明显下降。 相似文献
998.
提出煤炭地下催化气化新工艺的概念,研究利用高压雾状催化剂-水蒸气带入装置并以钙基化合物为催化剂进行煤炭地下催化气化.在小型模拟地下气化炉中,以大雁褐煤为煤样,选用氢氧化钙水溶液(质量分数为5%,10%,15%)为催化剂进行纯氧气化.结果表明,添加氢氧化钙水溶液气化后的煤气与不加催化剂、添加10%CaCO3气化后的煤气相比,煤气中甲烷组分可以达到7.58%,煤气热值提高到5.43MJ/m3~7.87MJ/m3,产气率提高28%~69%,且可以稳定产气.催化剂组成(质量浓度)以添加Ca(OH)2为10%~15%之间进行气化效果最佳,为提高煤炭地下气化的稳定性开辟了一条全新的路径. 相似文献
999.
Hwee Yoong Felicia Gok Shahram Emami Jianhneg Shen Martin J. T. Reaney 《Journal of the American Oil Chemists' Society》2013,90(2):299-305
Biodiesel, fatty acid methyl ester (FAME), was produced by transesterification of canola oil with methanol in the presence of a series of alkoxide/hydroxide base catalysts produced from glycerol, 1,2-propanediol, 1,3-propanediol, xylitol, or sorbitol produced by dehydration reaction of sodium hydroxide in the presence of polyols. Transesterification reactions proceeded efficiently in the presence of sodium alkoxide catalysts prepared at three different mole ratios of sodium hydroxide to glycerol (1:1, 2:1, and 3:1). The production of methyl ester during the course of the reaction was determined repeatedly and the reaction progress was compared with that achieved in a reaction catalyzed by freshly prepared anhydrous sodium methoxide as a standard catalyst. Sodium alkoxide/hydroxide catalysts activity during the first 2 min of the reaction was in the order of: sorbitol < xylitol < sodium methoxide < 1,2-propanediol < 1,3-propanediol < glycerol regardless of the mole ratio of sodium hydroxide to glycerol. All catalysts showed a higher methyl ester accumulation at higher ratios of sodium hydroxide to polyol and had the following order 1:1 < 2:1 < 3:1 (sodium hydroxide:glycerol). Several of these catalysts were as powerful as sodium methoxide in catalyzing the transesterification reaction at the same mole concentration. All alkoxide/hydroxide catalysts resulted in a high FAME accumulation (>95 wt%) in a single transesterification batch reaction. 相似文献
1000.