Study of the surfactant role in latex–aerogel systems by scanning transmission electron microscopy on aqueous suspensions

For insulation applications, boards thinner than 2 cm are under design with specific thermal conductivities lower than 15 mW m^?1 K^?1. This requires binding slightly hydrophobic aerogels which are highly nanoporous granular materials. To reach this step and ensure insulation board durability at the building scale, it is compulsory to design, characterise and analyse the microstructure at the nanoscale. It is indeed necessary to understand how the solid material is formed from a liquid suspension. This issue is addressed in this paper through wet‐STEM experiments carried out in an Environmental Scanning Electron Microscope (ESEM). Latex–surfactant binary blends and latex–surfactant–aerogel ternary systems are studied, with two different surfactants of very different chemical structures. Image analysis is used to distinguish the different components and get quantitative morphological parameters which describe the sample architecture. The evolution of such morphological parameters during water evaporation permits a good understanding of the role of the surfactant.     

高庙子膨润土的土水特征曲线

近年来，用于高放废物深地质处置工程屏障的高压密膨润土越来越受到关注。经过全国范围内的比较和筛选，内蒙古兴和县高庙子膨润土矿床被确定为我国高放废物处置库缓冲材料的首选矿床。采用渗析法和水汽平衡法来控制吸力技术，通过上水特征曲线测定试验、环境扫描电镜和乐汞试验，研究高庙子高压密膨润土在不同吸力下的持水特性及其微观结构特征。利用压汞试验结果推算膨润土在恒体积条件下的土水特征曲线，并与实测数据进行比较。研究结果表明：在不同吸力作用下，膨润土的持水特性与其微观结构之间有着密切关系。     

PM_(10)浓度及微观特征季节分布分析——以乌鲁木齐天山区2004年为例

利用2004年乌鲁木齐城区(以天山区为例)PM10日平均浓度和气象要素观测资料,对不同季节PM10浓度变化特征、不同级别污染日数进行统计分析．同时,结合环境扫描电镜／X射线能谱(ESEM-EDX)对不同季节的颗粒物的形貌及来源进行了初步探讨。结果表明2004年PM10浓度变化为:冬季>秋季>春季>夏季;冬季出现4级以上污染日数最多,占39．5％;夏季最为洁净,好于2级的日数占到76．1％．PM10和气象因子的相关分析表明浓度与风速成正比,与降水成反比,与温度,相对湿度和逆温层厚度相关比较复杂,有时成正相关,有时呈负相关。颗粒物的形貌在不同季节特征明显,冬季颗粒物多呈圆球形,春季形貌不规则,夏季既有圆球形又有不规则形貌的颗粒,而秋季颗粒物多呈链状．     

Energy-saving estimation model for hypermarket HVAC systems applications

Energy saving estimation model (ESEM) use normal distribution (Gaussian) probability theory to predict potential savings for previously determined system improvements. Those improvements are low/high cost investments based on data gathered during one year monitoring of typical hypermarket facility HVAC system. The consumption of electrical energy and natural gas has been monitored and system segments with largest amount of energy consumption have been marked. Gathered data pointed out to fan units as the biggest energy consumers and suggested that system energy-saving improvement must be focused on fans energy consumption control. This paper deals with ESEM inputs and outputs in order to provide correct financial estimation of specific investment.     

用ESEM技术研究AP的热分解反应

采用环境扫描电镜(ESEM)技术对AP颗粒在低温(150～240℃)段进行快速和慢速升温试验,研究了整个形貌的变化历程.结果表明,ESEM能够直观地发现AP颗粒在低温下存在气相反应;在150～170℃,AP颗粒表面开始出现微孔;在170～190℃,微孔数量急剧增加;在190～210℃,表面形成多孔结构;在210℃～24...     

ESEM investigations for assessment of damage kinetics of short glass fibre reinforced thermoplastics - Results of in situ tensile tests coupled with acoustic emission analysis

The damage mechanisms of short glass fibre reinforced polypropylene (PP) and polybutene-1 (PB-1) materials were investigated. For this purpose, in situ tensile tests were conducted in the environmental scanning electron microscope (ESEM) while simultaneously recording the acoustic emission (AE). To be able to observe damage mechanisms directly during loading, notched specimens were used. This method allows the direct correlation of the recorded load - elongation data with observed damage mechanisms, as well as correlations with acoustic emission data. Hence, it is possible to describe the damage kinetics of short glass fibre composite.It was found that different bonding conditions of the two investigated materials result in different damage mechanisms as well as in different AE behaviour. For fibre reinforced PP with excellent bonding conditions of the fibres in the polymeric matrix, fibre fracture, slipping of fibres in the delamination area, debonding and pull-out with matrix yielding was observed. The determined AE parameter amplitude A_p and energy E_AE for the PB-1 material are lower because of the weak bonding of the fibres to the PB-1-matrix. Hence, energy dissipative damage mechanisms like pull-out with matrix yielding can occur only in a limited part of such materials.     

In Situ Scanning Electron Microscopy Observation of Growth Kinetics and Catalyst Splitting in Vapor–Liquid–Solid Growth of Nanowires

In situ observations during vapor–liquid–solid (VLS) growth of semiconductor nanowires in the chamber of an environmental scanning electron microscope (ESEM) are reported. For nanowire growth, a powder mixture of CdS and ZnS is used as a source material and silver nanoparticles as a metal catalyst. Through tracing growth kinetics of nanowires, it is found that nanowires with a relatively bigger catalyst droplet on the tip grow faster. Intriguingly, it is also found that the growth of nanowires can involve catalyst splitting: while the majority of catalyst remains at the nanowire tip and continues facilitating the growth, a portion of it is removed from the tip due to the splitting. It remains attached to the nanowire at the position where the splitting occurred and subsequently induces the growth of a nanowire branch. As far as it is known, this is the first time that catalyst splitting is revealed experimentally in situ. It is proposed that the instability of catalyst droplet caused by the volume increase is the main reason for the splitting. It is believed that in situ growth inside the ESEM can largely enrich our understanding on the metal‐catalyzed VLS growth kinetics, which may open up more opportunities for morphology‐controlled synthesis of 1D semiconductor nanowires in future study.     

基于响应面法的三元聚合物砂浆力学性能

通过响应面法的Box-behnken试验设计方法构建二次多项式回归方程,对氯乙烯、乙烯和乙烯醚三元聚合物砂浆配合比进行优化,并结合宏观性能与微观形貌进行机理分析.结果 表明:所建模型在试验范围内能较准确地预测结果,响应面法用于三元聚合物砂浆配合比优化具有准确性与科学性;对28 d抗压强度影响强弱顺序依次为水灰比、减水剂掺量、聚合物掺量;对28 d抗折强度和黏结强度影响强弱顺序为聚合物掺量、水灰比、减水剂掺量;将28 d黏结强度最大值、抗折强度最大值和抗压强度最小值(折压比最大)作为目标优化值,得出三元聚合物砂浆的最优配合比为:聚合物掺量为12％,水灰比为0.42,减水剂掺量为1.12％.     

Effect of thermal and mechanical factors on rheological properties of high performance inulin gels and spreads

The aim of this study was analysis of a number of factors affecting the rheological properties of high performance inulin gels and spreads in comparison with commercial products. Inulin gels (20%, 25%, 30%), commercial and inulin model spread (20% canola oil, 20% inulin, 3% emulsifier) were analysed. Inulin particles in water environment absorbed water which caused an increase in viscosity of the inulin suspensions. Different temperatures of preparation, cooling rates and viscosity increase which appeared during the stirring of inulin suspensions did not significantly change the rheological parameters of the final gels in contrast to heating rates (p ? 0.05). In spite of rigid laboratory conditions high standard deviation for hardness and apparent viscosity showed how difficult the process of an inulin crystallization is to control. Rheological properties of inulin model spread exhibited thixotropic and shear thinning behaviour which made it similar to commercial spread. The applied structure destruction step in the manufacturing process should be applied to make inulin model spread comparable to commercial spreads.