Zeolite imidazolate framework (ZIF)-based mixed matrix membranes for CO2 separation: A review

Mixed matrix membranes (MMMs), which combine the good separation performance of inorganic materials with the low cost of polymers, have emerged as a research hotspot for gas separation membranes. Zeolite imidazolate frameworks (ZIFs) are widely used as fillers to prepare MMMs owing to their advantageous characteristics, such as adjustable pore channels, unsaturated sites, and easy functionalization. For MMMs, three directions can be employed as criteria for improvement compared with pristine polymeric membranes. In this article, the progress of ZIF-based MMMs is reviewed from the aspects of sole-ZIF-based MMMs and modified ZIF-based MMMs. Both strategies improve the separation performance through different improvement directions and mechanisms. Our analysis shows that the synergistic effect of the modified filler can change the structure of the membranes, such as by improving the filler–polymer interface voids, which provides a foundation to overcome the trade-off effect to a certain extent. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48968.     

A first-principles investigation on mechanical and metallic properties of titanium carbides under pressure

The titanium carbides are potential candidates to achieve both high hardness and refractory property. We carried out a structural search for titanium carbides at three pressures of 0 GPa, 30 GPa and 50 GPa. A phase diagram of the Ti-C system at 0 K was obtained by elucidating formation enthalpies as a function of compositions, and their mechanical and metallic properties of titanium carbides were investigated systematically. We also discussed the relation of titanium concentration to the both mechanical and metallic properties of titanium carbides. It has been found that the average valence electron density and tractility improved at higher concentrations of titanium, while the degree of covalent bonding directionality decreased. To this effect, the hardness of titanium carbide decreases as the content of titanium increases. Our results indicated that the titanium content significantly affected the metallic properties of the Ti-C system.     

Catalytic combustion of methane over a highly active and stable NiO/CeO2 catalyst

In the last decades, many reports dealing with technology for the catalytic combustion of methane (CH₄) have been published. Recently, attention has increasingly focused on the synthesis and catalytic activity of nickel oxides. In this paper, a NiO/CeO₂ catalyst with high catalytic performance in methane combustion was synthesized via a facile impregnation method, and its catalytic activity, stability, and water-resistance during CH₄ combustion were investigated. X-ray diffraction, low-temperature N₂ adsorption, thermogravimetric analysis, Fourier transform infrared spectroscopy, hydrogen temperature programmed reduction, methane temperature programmed surface reaction, Raman spectroscopy, electron paramagnetic resonance, and transmission electron microscope characterization of the catalyst were conducted to determine the origin of its high catalytic activity and stability in detail. The incorporation of NiO was found to enhance the concentration of oxygen vacancies, as well as the activity and amount of surface oxygen. As a result, the mobility of bulk oxygen in CeO₂ was increased. The presence of CeO₂ prevented the aggregation of NiO, enhanced reduction by NiO, and provided more oxygen species for the combustion of CH₄. The results of a kinetics study indicated that the reaction order was about 1.07 for CH₄ and about 0.10 for O₂ over the NiO/CeO₂ catalyst.     

废磺酸的处理技术

废磺酸由于色泽深、酸值高、游离油高等问题,无法正常应用于洗涤剂中,又因其是强的有机酸,属于危化品,无法倾倒、无法储存,日积月累,大量的废磺酸处理成为企业棘手的问题。本文通过中和和漂白工艺,将其应用于工业清洗中,解决了企业难题。     

水热法制备Sr_2FeNiO_6催化剂及其催化性能研究

采用水热法制备双钙钛矿催化剂Sr_2FeNiO_6,考察不同浓度KOH溶液(4 mol·L~(-1)、6 mol·L~(-1)、8 mol·L~(-1)、10 mol·L~(-1)、12 mol·L~(-1)、14 mol·L~(-1))对催化剂性能的影响,利用X射线衍射、比表面积测定、程序升温还原和扫描电镜等对样品进行性能表征,并以催化甲烷燃烧为目标,考察催化剂催化性能。结果表明,矿化剂KOH浓度对样品性能影响较大,当浓度为10 mol·L~(-1)时,起燃温度最低,T_(10%)为430℃;浓度为8 mol·L~(-1)时,样品比表面积最大,为19.0 m~2·g~(-1),完全燃烧温度最低,T_(90%)为610℃。     

基于流固耦合的柱面气膜密封支撑结构性能研究

利用流固耦合分析方法,研究一种波箔结构柔性支撑柱面气膜密封,探讨气膜厚度、浮环与转子的偏心率以及柔性支撑结构的泊松比、弹性模量、波箔数量等参数对支撑结构等效应力及变形量的影响。结果表明:柔性支承结构满足柱面气膜密封的正常运作,不会造成因为气膜刚度过大而使得浮环与波箔发生破坏性变形,并且变形量远小于波箔高度;柔性支撑的等效应力和变形量随平均气膜厚度的增大而减小,随偏心率的增加而增大,随支撑材料泊松比的增大而增大;弹性模量的增加并不影响柔性支撑结构的等效应力,但是会使变形量减小;增加波箔数量,柔性支撑的等效应力略有减小,变形量显著减小。     

Preparation of molecularly imprinted fluorescence sensor based on carbon quantum dots via precipitation polymerization for fluorescence detection of tetracycline

A facile and effective method was proposed to prepare the molecularly imprinted fluorescence sensor with carbon quantum dots, which were modified vinyl groups by acrylic acid on the surface. The obtained fluorescence composite material was investigated by transmission electron microscope and Fourier transform infrared spectra. After the experimental conditions were optimized, a linear range of 1.0–60 μmol L⁻¹ was obtained and the detection limit was 0.17 μmol L⁻¹. The novel fluorescence sensor can be successfully used to detect tetracycline in real samples. This study provides a convenient strategy for selective recognition and rapid detection of tetracycline in the complex environment.     

溶解氧自动分析仪应用中出现的问题及解决办法

本文介绍了霍尼韦尔UDA2182型溶解氧自动分析仪的特点及工作原理。结合多年来的现场应用、维护经验,对其应用过程中出现的故障及存在问题进行分析诊断并提出了较好的解决方案。     

Methodology for dependence-based integrated constitutive modelling: An illustrative application to SiCp/Al composites

In industrial forming and machining process, the large plastic deformation of material takes place in wide loading ranges of strain-rate and forming temperature. A satisfactory modelling of quasi-static and dynamic material behaviors is of great importance for understanding physical process and processes optimization. A dependence-based integrated methodology, together with an improved weighted multi-objective parameter identification strategy is presented for the development of phenomenological constitutive model and the parameter identification using experimental data from quasi-static and dynamic tests with instantaneous strain rate variations and plastic strain-related temperature changes. The improved multi-objective parameter identification model is reformulated by introducing three weighting factors for valuing different measure errors and fit standard errors in individual objective function corresponding to each test, considering the sampling point number and active material parameter number under different loading conditions, and balancing optimization opportunity of quasi-static and dynamic sub-objective functions. The methodology is verified for feasibility through illustrative constitutive identification for SiC_p/Al composites. This may provide a methodology of constitutive modelling for predicting material behaviors in quasi-static and dynamic modes equally well.