小型低温空气源热泵用转子和涡旋压缩机对比

空气源热泵是一种利用高位能使能量从低位热源空气流向高位热源的节能装置。阐述了小型低环境温度空气源热泵（输入功率在1～4 kW,工作环境温度可达−20 ℃）的概念和用能效率评定方式。介绍了适用于小型低环境温度空气源热泵的两种全封闭压缩机：转子压缩机和涡旋压缩机。对比了两类压缩机的压缩原理;通过技术分析和产品调研,对两类压缩机的基本特性、喷气增焓和喷液增焓技术、变频技术和适用工况等方面进行了分析,并对其变压比特性进行阐述;对其制造工艺进行比较。得出了两种压缩机的适用性对比。     

An eco-friendly and high shear strength adhesive from catechol-modified polyethyleneimine

Conventional adhesives often emit volatile organic compounds (VOCs), which have a negative impact on human health. In this paper, an environmentally-friendly supramolecular adhesive PD which has high adhesive and low VOCs emission is prepared by the reaction between polyethyleneimine (PEI) and 3,4-dihydroxybenzaldehyde (DBA). PD containing abundant catechol groups exhibit excellent adhesion to wood substrates and is able to reach a maximum shear strength of 5.20 ± 0.39 MPa. One factor is attributed to multiple reactions between PEI, and DBA and oxidation of DBA. These reactions construct a complex three-dimensional cross-linked structure which is very helpful to improve the bonding performance of the adhesive. Another reason refers to the fact that a large number of catechol groups in PD can form a lot of hydrogen bonds with the amino group in PEI and the hydroxyl group in the wood substrate. These hydrogen bonds play an important role in enhancing shear strength. PD adhesives have a stronger bond strength than commercial chloroprene rubber (CR, Pattex-PXL) and polyvinyl acetate adhesives (PVAc, JUJU-8708) and have lower emissions of VOCs. As an environmentally-friendly adhesive for wood-based substrates, this adhesive may have potential applications in the wood processing industry.     

Sintering behavior and morphology control of porous Al2O3-SiO2 ceramics for radome applications

Ceramics from porous Si₃N₄ and its derivatives SiAlON and Si₂N₂O were once considered the most promising high-temperature wave-transmitting materials. However, their large-scale application in the field of radomes is greatly restricted due to their poor oxidation resistance, high preparation costs, and expensive raw materials. Therefore, the development of low-cost porous oxide ceramics remains of significant interest to the field of high-temperature wave transmission. Surprisingly, mullite ceramics, which are representative of the Al₂O₃-SiO₂-system of ceramics, are ultra-low-cost materials with the potential to replace ceramics from Si₃N₄ and its derivatives. In this paper, integrated porous Al₂O₃-SiO₂-system ceramics were successfully prepared for load-bearing/wave-transmitting applications, using inexpensive calcined kaolin and alumina powder as the main raw materials. Calcined kaolin can provide seeds for the growth and development of mullite crystals in the ceramic system. High-strength and high-porosity ceramics were obtained with the mullite morphology controlled through the molar ratio of Al₂O₃ to SiO₂ and the resulting content of mullite seeds. With increasing of mullite seed content, the length and radial width of mullite whiskers with “interlocking structure” gradually change from rod-shaped “long and thick” to needle-like “short and thin.” The prepared porous Al₂O₃-SiO₂ ceramics have high flexural strength, fracture toughness, and good dielectric properties.     

纳米氧化锌微乳液制备方法研究进展

微乳液法具有操作简单、粒径可控、生成粒子的尺寸比较均匀等优点.采用微乳液法制备的纳米氧化锌具有普通氧化锌所无法比拟的光、电、磁等性能.结合国内外的研究进展,主要介绍了微乳液法制备纳米氧化锌的各反应条件的影响.表面活性剂的种类和用量、反应温度、反应物浓度比、后处理温度及时间对产物的形貌和粒径具有重要的影响,通过改变各反应参数可以实现产物从零维向一维方向的转变.     

Fischer-Tropsch合成中的CO活化机理

Fischer—Tropsch(F—T)合成是将煤炭、天然气和生物质等含碳资源间接转化为液体燃料的关键工艺步骤,深入了解其反应机理,对于完善F-T合成催化剂设计以及优化其工业操作条件具有重要的理论价值．对近年来有关F—T合成中关键的CO活化机理研究进行了总结和评述,着重介绍了不同过渡金属元素对CO的吸附和活化性质,并就金属晶面与CO的相互作用、催化助剂的影响以及F—T合成反应中与H2的共吸附作用等方面进行分析,为进一步的研究工作提供理     

CaO–ZrO2 Solid Solution: A Highly Stable Catalyst for the Synthesis of Dimethyl Carbonate from Propylene Carbonate and Methanol

CaO–ZrO₂ prepared by co-precipitation showed to be a well-performed catalyst for the transesterification of propylene carbonate (PC) and methanol. The characterization by X-ray powered diffraction (XRD) and Raman spectroscopy indicated that CaO was doped into the lattice of ZrO₂ to form CaO–ZrO₂ solid solution. Such a solid solution was a strong solid base, which was proved by CO₂ temperature program desorption (CO₂-TPD). As a result, the catalyst showed high stability towards the transesterification of propylene carbonate and methanol into dimethyl carbonate with high PC conversion, especially being subjected to the continuous production of dimethyl carbonate at reactive distillation reactor for 250 h without any obvious loss of activity at the PC conversion of 95%.     

Novel sulfonated polyimide ionomers by incorporating pyridine functional group in the polymer backbone

A series of sulfonated polyimides (SPIs) containing pyridine ring in the polymer backbone were synthesized by the polycondensation of 1,4,5,8‐naphthalene‐tetracarboxylic dianhydride (NTDA), 5‐(2,6‐bis(4‐aminophenyl)pyridin‐4‐yl)‐2‐methoxy benzene sulfonic acid (SDAM), and 4,4′‐diaminodiphenyl ether (ODA). Flexible, transparent, and tough membranes were obtained. Property study revealed that all the membranes displayed high thermal stability with the desulfonation and decomposition temperature higher than 290 and 540°C, respectively, as well as good mechanical property with Young's modulus larger than 1.0 GPa, maximum strength (MS) on a scale of 60–80 MPa, and elongation at break (EB) ranged from 41.79 to 75.17%. More importantly, the new materials exhibited small water uptake and excellent dimensional stability with the highest sulfonated SPI‐80 showing the maximum water uptake of 36.1%, and maximum swollen ratio of Δt = 0.038 and Δl = 0.026, respectively (Δt and Δl stands for the thickness and diameter change of the film, respectively). The high water stability exhibited by the SPI films is attributed to the formation of inner salts and/or ionic crosslinking between the sulfonic acid and pyridine functional groups, which suppresses the water uptake ability of sulfonic acid and strengthened the interpolymer chain interactions. Thus, the excellent water stability, good thermal and mechanical properties, and the technologically applicable conductivity of SPI‐80 render this material attractive for proton exchange membrane (PEM) application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

平均天空采光诺谟图

本文在平均天空模式基础上,研制出既反映太阳对天空散射光的影响又考虑了墙厚影响的适合于多种天空类型的采光诺谟图。     

Non-equilibrium model for catalytic distillation process

A new improved tri-diagonal method was developed for the non-equilibrium stage model of the catalytic distillation by coupling consumptive reaction coefficient. The reactions in the distillation column were divided into generative reaction and consumptive reaction. The non-equilibrium stage model was introduced for the catalytic distillation process of the dimethyl carbonate (DMC) synthesis by urea methanolysis over solid based catalyst, and the improved tri-diagonal method was used to solve the model equations. Comparison of predicted results with experiment data shows that the mean relative error of the yield of DMC was 3.78% under different conditions such as different operating pressures and reaction temperatures. The improved tri-diagonal matrix method could avoid the negative values of the liquid compositions during the calculations and restrain the fluctuation of compositions by slowing down the variations of the values in the iteration. The modeling results show that the improved tri-diagonal method was appropriate for system containing a wide range of boiling point components and a different rate of reactions. __________ Translated from Petrochemical Technology, 2007, 36(11): 1128–1133 [译自: 石油化工]     

Correction to: Bismuth Yttrium Oxide (Bi3YO6), A New Electrode Material For Asymmetric Aqueous Supercapacitors

Journal of Inorganic and Organometallic Polymers and Materials - The original version of this article unfortunately contained mistakes. In line 9 of the abstract, 5% should read as 2%. The...