Dispersion and microwave processing of nano-sized ITO powder for the fabrication of transparent conductive oxides

Aqueous dispersions of tin-doped indium oxide (ITO) nanopowder were prepared and the effect of the addition of PEG 400, Tween 80 and β-alanine as dispersants was investigated using zeta potential and particle size distribution measurements. Both PEG 400 and β-alanine were found to produce stable dispersions that were used to deposit ITO thin films on glass substrates by dip and spin coating methods. The ITO thin films were heat-treated using both conventional and microwave heat treatment in order to improve the inter-particle connections and hence the resistivity and transparency of the films. All the films exhibited an average transmittance of >80% over the visible spectrum after being subjected to the heat treatment process. ITO films prepared with no dispersant showed very high resistivity values for both heating methods, however addition of 2 wt% PEG 400 to the dispersion yielded a reduction in the resistivity values to 1.4×10⁻¹ Ω cm and 3.8×10⁻² Ω cm for conventionally and microwave treated films, respectively. The surface morphological studies confirmed that addition of dispersants improved the film uniformity and inter-particle connections of the ITO films considerably.     

W-4Re-0.27HfC合金的1500~1700℃拉伸蠕变性能及损伤机理

本文研究了粉末冶金制备的W-4Re-0.27HfC合金的拉伸蠕变行为,测试环境为真空,蠕变温度为1500~1700℃,蠕变应力为40~60MPa。采用SEM、EBSD和TEM观察其微观组织,表征晶粒尺寸和位错等组织在蠕变过程中的演变规律。结果表明,W-4Re-0.27HfC合金的稳态蠕变速率范围为1′10-7~5′10-6,较纯钨(W)低两个数量级。W-4Re-0.27HfC合金抗蠕变性能优于纯W主要原因是弥散分布的HfC颗粒钉扎位错和Re取代W原子产生晶格畸变阻碍位错运动,降低位错迁移率。蠕变温度为1500℃时,W-4Re-0.27HfC的蠕变机制以位错滑移为主,伴随有晶界滑动。随着温度升高,位错攀移成为主要蠕变机制。HfC颗粒塞积位错,导致HfC/基体界面结合变差,HfC颗粒剥落出现孔洞,合金蠕变性能下降。     

露天矿用汽车尾气排放对大气环境的影响研究

本文根据有关资料和作者所做的分析工作，初步研究了露天矿用汽车尾气排放对大气环境的影响：排放物作为污染线源的源强计算公式；单车排放系数的计算模式；常用线源扩散模式的验证与比较；污染物浓度分布的预测方法。     

Recent advance in research on halloysite nanotubes-polymer nanocomposite

Halloysite nanotubes (HNTs) are novel 1D natural nanomaterials with predominantly hollow tubular nanostructures and high aspect ratios. Due to their high mechanical strength, thermal stability, biocompatibility, and abundance, HNTs have a number of exciting potential applications in polymer nanocomposites. In this article, we review the recent progress toward the development of HNTs-polymer nanocomposites, while paying particular attention to interfacial interactions of the nanocomposites. The characteristics of the HNTs relative to the formation of the polymer nanocomposites are summarized first. The covalent or non-covalent functionalization methods for HNTs and various fabrication approaches for HNTs-polymer nanocomposites are introduced afterward. Polymer nanocomposites reinforced with HNTs possess highly increased tensile and flexural strength, elastic moduli, and improved toughness. HNTs-polymer nanocomposites also exhibit elevated thermal resistance, flame retardance and unique crystallization behavior. Due to the tubular microstructure and the biocompatibility of HNTs, HNTs-polymer nanocomposites have demonstrated good drug encapsulation and sustained release abilities, gaining them extensive use as tissue engineering scaffolds and drug carriers. Finally, we summarize the characteristics of HNTs-polymer nanocomposites and predict for the development of the potential applications in high-performance composites for aircraft/automobile industries, environmental protection, and biomaterials.     

Carbon nanotubes prevent the coagulation at high shear rates of aqueous suspensions of equiaxed ceramic nanoparticles

Equiaxed ceramic nanoparticles and their mixtures are expected to exhibit shear-thinning behaviour when dispersed colloidally in aqueous media, whereas shear-thickening is the expectation for large aspect ratio phases such as, for example, carbon nanotubes (CNTs). Here, contrary experimental evidence is presented demonstrating the occurrence of severe coagulation at high shear rates in colloidally stable, semi-concentrated, aqueous suspensions of equiaxed SiC nanoparticles (major phase) mixed with equiaxed Y₃Al₅O₁₂ nanoparticles (liquid-phase sintering additive), and how CNT addition prevents this coagulation if sufficient sonication is applied. It is also shown that although shear-thinning is the natural behaviour of the ceramic suspension up to moderate shear rates, coagulation is eventually a phenomenon inherent to the aqueous colloidal processing of these suspensions, with the critical shear rate for coagulation increasing and the rheopexy decreasing the better is the initial dispersion state achieved with the sonication. It is also shown that the critical shear rate for coagulation depends on the exact condition of shear rate increase, and that the re-sheared suspensions coagulate more significantly and at lower shear rates than the fresh suspensions. The mechanisms by which this coagulation occurs and is impeded by the CNTs are discussed, together with broader implications of these phenomena for the environmentally friendly processing of nanostructured ceramics and ceramic composites.     

套管螺纹紧密距的测量

对用多只螺纹工作量规测量同一石油套管螺纹紧密距值存在一定离散性的问题进行了分析与研究,找出了引起离散性的各种因素。消除各种引起离散性的因素,不仅可提高螺纹工作量规间的互换性、测量套管螺纹紧密距值的准确性和一致性,确保产品质量,还可提高企业的经济效益。     

悬浮、乳液和分散聚合:工艺的考察(续)

<正> 乳液聚合过程描述在经典的乳液聚合中,单体是不溶(或微溶)于聚合介质的,但在表面活性剂(乳化剂或皂)的帮助下,单体被乳化于其冲,与悬浮聚合不一样,引发剂在是溶解在介质中的,而不是溶解于单体。在这些条件下,根据催化剂的性质和     

The axial dispersion performance of an oscillatory flow meso-reactor with relevance to continuous flow operation

A laboratory scale continuous oscillatory flow meso-reactor was developed and residence time distribution (RTD) studies were carried out in order to establish certain process characteristics of the system. In particular, the dispersion coefficient as a function of the primary variables was established. Using optical probes the axial dispersion was investigated by monitoring the response of a pulse dye tracer at different locations within the meso-reactor. Three cases, net flow without oscillation, oscillation without net flow, and oscillation plus net flow were studied over a range of oscillation frequencies, amplitudes, and net flow rates. Both the imperfect and the perfect pulse injection methods were used to determine the axial dispersion coefficient for the system with and without net flow. The axial dispersion coefficient and the dimensionless dispersion number were analysed in the context of different flow conditions. A correlation was established and demonstrated that the axial dispersion within the meso-reactor could be quantified as a function of flow conditions. The results showed that the laboratory continuous flow meso-reactor was able to produce plug flow with modest axial dispersion over a wide range of parameter space, thereby indicating efficient mixing and effective RTD performance.     

水性双组分聚氨酯的分散混合和成膜

叙述了水性双组分聚氨酯体系的多元醇组分和多异氰酸酯 ,论述了水性双组分体系的分散混合和成膜。