Bonding strength and thermal shock resistance of a novel bilayer (c-AlPO4-SiCw-mullite)/SiC coated carbon fiber reinforced CMCs

Mullite coating, SiC whiskers toughened mullite coating (SiC_w-mullite), and cristobalite aluminum phosphate (c-AlPO₄) particle modified SiC_w-mullite coating (c-AlPO₄-SiC_w-mullite) were prepared on SiC coated C/SiC composites using a novel sol-gel method combined with air spraying. Results show that molten SiO₂ formed by the oxidation of SiC whiskers and molten c-AlPO₄ improved the bonding strength between mullite outer coating and SiC–C/SiC composites due to their high-temperature bonding properties. The bonding strength between mullite, SiC_w-mullite, c-AlPO₄-SiC_w-mullite outer coatings and SiC–C/SiC composites were 2.41, 4.31, and 7.38 MPa, respectively. After 48 thermal cycles between 1773 K and room temperature, the weight loss of mullite/SiC coating coated C/SiC composites was up to 11.61%, while the weight losses of SiC_w-mullite/SiC and c-AlPO₄-SiC_w-mullite/SiC coatings coated C/SiC composites were reduced to 7.40% and 5.12%, respectively. The addition of appropriate SiC whiskers can considerably improve the thermal shock resistance of mullite coating owing to their excellent mechanical properties at high temperature. In addition, c-AlPO₄ particles can further improve the thermal shock resistance of SiC_w-mullite coating due to their high-temperature bonding and sealing properties. No obvious micro-pores and cracks were observed on the surface of c-AlPO₄-SiC_w-mullite coating after 48 thermal cycles due to timely healing effect by formation of secondary mullite.     

密相栓塞水平气力输送压降初步分析

本文应用粉体力学、流体力学原理,建立了可用试验方法测试某些参数的松态密相栓塞水平气力输送理论压降过程.通过1 管路输送及单料栓试验得到理论公式各参数间规律.对基本非粘结性粉体实际应用具有一定的指导意义.     

丙烯酸系列复鞣剂PAAS的研究（II）—合成及合成条件优选

以游离基引发水相共聚方式合成出了系列丙烯酸类新型复鞣剂PAAS—Ⅰ～Ⅳ,讨论了合成PAAS复鞣剂的影响因素。采用正交试验法对PAAS—Ⅲ的合成条件进行了优选。结果表明:引发剂用量、单体配比是合成PAAS复鞣剂的主要影响因素,优选合成条件时应予以优先考虑。     

电模拟平面径向流理论在实际运用中几个问题的探讨

本文探讨了利用水电模拟原理,电模拟平面径向流理论在实际运用中存在的问题。分析了水电两种流动介质的流动特性,通过理论探讨和实验,揭示了存在问题的原因,提出了电模拟和平面径向流中各参数(供给半径,导电液浓度,电源频率)的合理选择原则,以保证理论在实际运用中更加切合实际情况。     

通过多层介质散斑法测量球罐内表面裂纹的应力强度因子K_1

本文介绍了通过多层介质散斑照相退放大技术记录负片,采用逐点分析法测量受内压1?MnR钢制球形容器的内表面半椭圆形裂纹的SCOD及其应力强度因子K_1,并与Schmitt-Kiem解作了比较,两者符合得很好。     

混合电解质溶液热力学——从渗透系数计算溶质活度系数的新型公式和计算方法

从热力学基本关系式出发,应用变量替换,导出从混合电解质溶液的渗透系数计算溶质活度系数的通用热力学方程。分别讨论了在以离子强度I和组分离子强度分数y为变量,或以总离子浓度m和组分离子浓度分数y为变量时方程的各种实用形式。以m和y为变量的方程与C. Pan的方程相同,但不需要两电解质具有相同电价形式的限制。从电解质溶液的理论分析导出渗透系数φ的合适的函数式,使φ的曲面拟合能在较大的浓度区间上进行且有较高的精度。将拟合的φ曲面函数式代入本文的方程能非常简单地求出溶质的活度系数,解决了I=0端点的广义积分问题。四个体系的计算结果与Pitzer方程的结果吻合,本文的公式和计算方法还适用于溶质为非挥发性的非电解质体系。     

Study of stability of high‐temperature polyimides using TG/MS technique

The oxidative stability of the carbon fiber‐reinforced composite of polyimide was examined, in real time, using the evolved gas analysis techniques. Off‐gas degradation products suggested the onset temperature for chain scissions to be fairly low at about 190–220°C. Based on the off‐gas products present and the trend of their release, the composite degradation mechanism appeared to be similar between 190 and 371°C, thereby marking 371°C to be the highest accelerated aging temperature for its long‐term lifetime prediction. Beyond 371°C, different degradation mechanisms would apply. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1219–1227, 2002     

Preparation and characterization of porous carbon beads and their application in dispersing small metal crystallites

Porous carbon beads were prepared by the pyrolysis of poly(vinylidene chloride) beads that were synthesized by suspension polymerization. After prolysis treatment at 180–300 °C under argon stream, the polymeric beads were further carbonized at 1000 °C for 3 h under argon stream to acquire porous carbon beads, of which the specific surface area was about 1000 m²/g, and pore size was mainly in the width range of 0.8–1.2 nm. The carbon structure and surface chemical composition characterized by X-ray diffraction and X-ray photoelectron spectroscopy, depended on the preparation temperature and the relations between them were examined. The characterization of the carbon beads by scanning electron microscopy, atomic force microscopy presented the morphological structure of the carbon beads surface and a global view of pores. The dispersion of nickel crystallites on the carbon beads surface was characterized by electron microprobe analysis. This study reveals that uniform surface morphological structure leads to the fine dispersion of metal crystallites.     

环境监测报告格式规范的探讨

按照GB/T15481-2000《检测和校准实验室能力的通用要求》标准的要求,以环境监测废水监测报告为例,来探讨监测报告设计的格式要求。     

L-肉碱的酶法生产

要L-肉碱是与动物体内脂肪酸代谢有关的化合物,主要功能是作为载体将长链脂肪酸从线粒体膜外输送到膜内促进脂肪酸的β-氧化,将脂肪代谢转变为能量。L-肉碱广泛用于医药、保健食品及饲料等行业。江苏省微生物研究所在成功解决了高转化率微生物酶的选育、肉碱与巴豆甜菜碱的分离技术和巴豆甜菜碱的回收问题后,开发了L-肉碱的微生物酶法生产技术,并与常茂生物化学工程有限公司合作进行了日产1kg规模的中试,用300L发酵罐发酵产酶,150L酶反应器进行酶转化,L-肉碱的发酵水平达15g/L以上,用401L有机玻璃层析柱系统提取精制,提取收率达70％以上,产品质量符合USP23版标准。