Ecological system for water treatment in fine chemicals industry enterprises

Clean Technologies and Environmental Policy - The issues of water management in chemical enterprises are considered to be very challenging and important at present. There are a significant number...     

用途广泛的精细化工新原料──金刚烷

本文介绍了金刚烷的结构、性质、用途及其制备方法     

Polycrystalline silicon films with nanometer-sized dense fine grains formed by flash-lamp-induced crystallization

Flash lamp annealing (FLA) with millisecond-order pulse duration can crystallize microm-order-thick a-Si films on glass substrates through explosive crystallization (EC), and flash-lamp-crystallized (FLC) poly-Si films consist of densely-packed nanometer-sized fine grains. We investigate the impact of the hydrogen concentration and the defect density of precursor a-Si films on crystallization mechanism and the microstructures of FLC poly-Si films, by comparing chemical-vapor-deposited (CVD) and sputtered precursor a-Si films. Transmission electron microscopy (TEM) observation reveals that FLC poly-Si films with similar periodic microstructures are formed by the FLA of the two kinds of precursor films, meaning no significant influence of hydrogen atoms and defect density on crystallization mechanism. This high flexibility of the properties of precursor a-Si films would contribute to a wide process window to reproducibly form FLC poly-Si films with the particular periodic microstructures.     

Effect of crystal growth on the effectiveness of fine purification through counterflow melt crystallization

A method is proposed for calculating the axial impurity profile in a crystallization column and assessing the effectiveness of the purification of a substance via counterflow melt crystallization. The method takes into account the combined effect of diffusion and crystallization processes. An approximate equation for the separation factor is derived. The results obtained for a few systems agree well with experiment.     

Two-stage crystallization kinetics equation and nonisothermal crystallization analyses for PTEG and filled PTEG

A novel modified Avrami model considering both primary and secondary crystallization has been presented to extract the kinetic behavior of these two crystallization stages in nonisothermal crystallization process of polymers. Nonisothermal crystallization kinetics of poly(trimethylene terephthalate)–poly(ethylene glycol) segmented copolyesters (PTEG) has been investigated by differential scanning calorimetry. The crystallization rate constants and Avrami exponents at various cooling rates were obtained from the analyses for neat PTEG and multiwalled carbon nanotube (MWNT) filled PTEG. Secondary crystallization displays a lower-dimensional crystal growth compared with primary crystallization and the results of kinetics analyses are consistent with morphology study. The MWNTs introduced into PTEG matrix take the role of effective nucleating agents during composites crystallization and can expedite the process of crystallization of the matrix by providing more nucleation sites to the crystallizing phase.     

Hazard evaluation of chemicals for bulk marine shipment

For economic reasons most chemicals used in large quantities by industry are transported in tank vessels. These chemicals range in properties from essentially harmless to highly dangerous. Although the United States and IMCO require certain minimum data before classifying a new chemical to be transported in bulk, no formal system exists to correlate these data with specific shipboard requirements such as the location of the tank within the vessel, gauging and venting systems, or cargo overfill protection.Developing guidelines for the evaluation of chemicals is a two part problem. First, the inherent hazards of a chemical (the hazards of a product when it is released, without regard to its cargo containment system) must be investigated. In the second part of the evaluation, these hazards are then correlated with specific shipboards requirements as mentioned above. This paper outlines the essential elements for developing a comprehensive system of hazard evaluation for bulk liquid chemicals.     

Incompatibilities of chemicals

Chemical incompatibilities are potentially significant problems where hazardous chemicals are found. A number of chemical segregation systems have been developed which provide recommendations for the separation of incompatible chemicals. Three segregation systems were identified in this study: the UN Dangerous Goods system (which uses physical hazard as the main reason for segregation and has 14 categories), the US CHRIS system (which uses chemical reactivity and has 24 categories) and a third system which uses environmental risks (and has 25 categories). These systems were combined. Merging of each system was initially problematic, but became considerably easier once certain characteristics had been defined (such as flammability or water incompatibility). This gave a final merged incompatibility table containing 100 different segregation groups. This research study showed that it was possible to combine different segregation systems based on different criteria and that more comprehensive segregation systems can be developed. These can be of use in the decision-making process about where groups of chemicals may be used, and during the use of chemicals, where chemicals should not be combined. The use of more comprehensive segregation systems will also assist in developing proper measures for their control.     

铝诱导对磁控溅射制备CdZnTe薄膜结晶的影响

选用Cd0.9Zn0.1Te晶体和纯度为99.999%的铝为靶材,结合Al诱导晶化技术,采用磁控溅射法在普通玻璃衬底上制备了CdZnTe薄膜。研究了铝诱导CdZnTe薄膜的结构和形核机理。研究表明,铝诱导的CZT薄膜为闪锌矿结构,且为(111)晶面的取向生长;在薄膜生长过程中,覆盖在CdZnTe表面的铝首先与ZnTe结合,形成了ZnAl2Te4相,并以此为核心,诱导CdZnTe异质形核结晶,重新形成了小晶粒团簇的较致密颗粒状薄膜,提高了薄膜(111)面的优势取向结晶,提高了CdZnTe薄膜的结晶质量。讨论了薄膜的光学性能。     

Quantitative risk analysis for toxic chemicals in the environment

An overview and basic framework is presented for quantification of human health risks associated with toxic chemicals in the environment. The presentation is designed for program managers who require an introduction to the principles of risk analysis and an understanding of the current state-of-the-art. The basic terminology is explained, the methodological components are reviewed, and a series of procedures is discussed for estimating ambient concentrations, effect potency, and human exposure and risk levels for a chemical substance. Practical considerations are discussed, including the uncertainties introduced by data gaps and modelling assumptions. Finally, a simple numerical illustration of the calculation procedures is presented.