铁尾矿砂力学特性及再生利用研究进展

铁尾矿砂的储量日趋增加,要减小铁尾矿坝的风险、提高铁尾矿砂的利用率,须明确铁尾矿砂的力学特性.通过对铁尾矿砂静力特性及动力特性的分析发现,尾矿砂的粒径分布是决定尾矿坝稳定及铁尾矿砂再生利用的主要因素之一,细粒含量、干密度、含水率等因素对铁尾矿砂动力特性有一定影响.再生利用铁尾矿砂的主要方式是将铁尾矿砂混凝土、改性铁尾矿砂用作工程材料,水泥、石灰、纤维是改性铁尾矿砂的主要材料.最后指出需进一步研究新型材料取代传统改性材料改善铁尾矿砂的力学特性,从而提高资源利用率.     

铝灰的回收处理及资源化利用研究现状

铝灰是铝工业生产过程中产生的有害固体废物,每年的产生量达到上百万吨。铝灰的大量堆积会引起严重的环境与公共安全问题。铝灰中含有较多的金属铝及其氧化物、氮化物,综合回收利用铝灰对减少环境压力、提升铝行业的经济效益具有重要意义。阐述了铝灰的火法和湿法处理工艺,通过比较得出无盐火法工艺和湿法工艺是值得开发的工艺。介绍了铝灰在耐火材料、陶瓷产品、氢气制备以及工程材料等领域的综合利用现状及研究进展。指出在进一步巩固和发展铝灰原有的高附加值资源化利用的同时,应加强对铝灰处理过程中产生的气体的利用。建议根据铝灰的特性进一步开发新的资源化利用方向。     

Experimental study on the permeability and self-healing capacity of geosynthetic clay liners in heavy metal solutions

Geosynthetic clay liners (GCLs), which have a very low permeability to water and a considerably high self-healing capacity, are widely used in liner systems of landfills. In this study, a series of experimental tests were carried out under complex conditions on typical commercial GCLs from China. In particular, the effects of pH values and lead ions (Pb²⁺) were tested in addition to other factors. The swelling properties of natural bentonite encapsulated between geotextile components in the GCLs were tested first. The swelling capacity was reduced rapidly at pH values < 3 and concentrations of Pb²⁺ >40 mM. Permeability tests on GCLs with different concentrations of lead ions were then performed by using the self-developed multi-link flexible wall permeameter, and data showed that increases in lead ion concentrations greatly improved the permeability. Finally, self-healing capacity tests were conducted on needle-punched GCLs under different levels of damage. Results showed that the GCLs have a good self-healing capacity with small diameter damage holes (2 mm, close to three times the original aperture), but with a damage aperture larger than 15% of the sample area, the self-healing capacity could not prevent leakage; hence, in certain situations it will be necessary to repair the damage to meet the anti-seepage requirement.     

Transparent niobate glass-ceramics for optical limiting

The construction of nonlinear optical materials featuring asymmetric transmission of light is of great technological importance for various applications, including optical switching and optical power limiting. A significant challenge is the scalable fabrication of material candidates with good photochemical stability, high optical transmittance, and excellent optical limiting performance. Here, we present a nanocrystallization avenue for constructing hybrid optical limiting materials that exhibit ultrafast and robust optical limiting performance. The experimental results show that the controllable relaxation of a niobate glass may lead to the clustering of Nb-O units and contracting of the bandgap. It results in the notable improvement in nonlinear optical properties, including the enhanced saturation irradiance (380 GW/cm²), doubly increased nonlinear coefficient, and decreased limiting threshold (200 GW/cm²). Our results suggest a promising material that exhibits promising applications for protecting eyes and sensitive components from laser-induced damage.     

Microwave drying performance of lignite with the assistance of biomass-derived char

Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g^?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading.     

The influence of processing conditions on the mechanical properties of poly(aryl-ether-ketone)/polybenzimidazole blends

Interest in developing high-performance blends for niche applications has grown significantly in efforts to meet ever-increasing harsh environment demands. In this work, four model poly(aryl-ether-ketone)/polybenzimidazole (PAEK/PBI) blends were chosen to study the influence of premixing methods, processing, and matrix polymers, on their mechanical properties. Among the model poly(ether ether ketone) (PEEK) and PBI blends, mechanical properties are greatly enhanced by melt premixing. The molding process mainly affects the matrix crystallinity, which in turn greatly influences fracture toughness of the blend. Poly(ether ketone ketone) (PEKK) and PBI blend exhibits a slightly lower tensile strength and fracture toughness than PEEK/PBI due to the differences in inherent properties of PEEK and PEKK matrices and their interfacial interaction with PBI. The processing−structure–property relationship of PAEK/PBI blends is established to help guide optimal design of high-performance polymer blends for structural applications. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48966.     

文献计量视角下健康人力资本研究动态分析

通过文献计量方法从样本选取、研究动态分析、主题分布三方面对健康人力资本发展现状及热点问题进行总结.研究结果表明,自2004年开始该领域所属学科种类和期刊源日益丰富,并形成合著度较高的核心作者群体,健康人力资本研究成为人力资本领域的研究热点,健康人力资本与经济增长或收入的关系、健康人力资本指标体系的构建和居民健康人力资本收入效应的测算等问题都成为当前和未来的研究重点.     

3-三氟甲基-5,6,7,8-四氢-1,2,4-三唑[4,3-α]吡嗪盐酸盐的合成

乙二胺与氯乙酸乙酯经取代、环合反应制得2-哌嗪酮,2-哌嗪酮与Boc酸酐进行氨基保护反应后,再与五硫化二磷进行硫代反应制得4-(N-叔丁氧羰基)-2-哌嗪硫酮,其与三氟乙酰肼经取代、环合、脱叔丁氧羰基成盐,得标题化合物,总收率为45.7%(以氯乙酸乙酯计)。为磷酸西他列汀中间体的工业化生产提供了一条较理想的工艺路线。