钨合金的设计窗口研究进展

综述了钨及钨合金制备、热加工及应用等方面的发展。详细分析了改善和提高钨及钨合金的塑性和再结晶温度的方法及钨的固溶强化和弥散强化,从而提出了钨合金的设计和制备的发展方向。     

沿空掘巷工作面防灭火分析及综合治理

随着我矿掘进工作面的沿空掘巷,相邻工作面采空区内的CH4、CO2、CO及高浓度氮气的涌出,将会威胁到工作面内施工人员的安全.为实现我矿第一个综采工作面的顺利回采,以及摸索我矿沿空掘巷及带采煤柱防灭火方面、有害气体的变化方面的经验和规律,为下一步的生产接续和延长矿井服务年限方面从以下情况进行分析和总结,总结出适合我矿特色的防灭火方面的治理方案.     

高居里温度BaTiO3-(Bi0.5Na0.5)TiO3无铅正温度系数电阻陶瓷的制备

用传统的固相反应烧结法制备了(1-xmol%)BaTiO₃-xmol%(Bi_0.5Na_0.5)TiO₃(BBNTx)高温无铅正温度系数电阻( positive temperature coefficient of resistivity, PTCR)陶瓷。X射线衍射表明所有的BBNTx陶瓷形成了单一的四方钙钛矿结构。SEM分析结果显示随着BNT含量的增加, 陶瓷晶粒尺寸减小。空气中烧结的0.2mol% Nb掺杂的BBNT1陶瓷, 室温电阻率为~10² Ω·cm, 电阻突跳为~4.5个数量级, 居里温度为~150℃。氮气中烧结的0.3mol% Nb掺杂的BBNTx(10≤x≤60)陶瓷, 同样具有明显的PTCR效应, 居里温度在180~235℃之间。随着BNT含量的增加, 材料的室温电阻率增大, 同时陶瓷的电阻突跳比下降。     

Nozzle flow behavior of aluminum/polycarbonate composites in the material extrusion printing process

This article investigates the effects of nozzle diameter, resin viscosity, and filler size and volume content on the melt flow properties and clogging of composites in the material extrusion additive manufacturing process. The flow behavior was systematically characterized by a custom nozzle flow test (NOFT) device, thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Results indicated that the viscosity of the material, the particle size, and the diameter of the nozzle were important factors for clogging. TGA results showed deviations from the designed filler volume fraction, which could be due to the buildup of filler material in the nozzle and subsequent partial clogging. SEM observations showed that particle agglomeration tended to be more prevalent in strands with high filler volume content. The agglomeration could be seen near the edge of the strand. A model for the clogging formation in NOFT was summarized into four stages: particle deposition on the wall of the nozzle, creation of dendrites, particle agglomeration, and particle clogging, which explained the clogging mechanism in the NOFT. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47252.     

功能梯度材料的低温挤压成形过程建模与实验研究

使用低温挤压成形方法制造功能梯度材料（FGM）过程中,膏体材料存在气泡、结块和一定程度的液相迁移现象,导致挤压成形过程难以控制。使用系统辨识的方法建立了FGM成形过程的差分模型,运用残差的方差分析方法对系统模型的阶次进行估计,运用递推最小二乘法对参数进行辨识,得到FGM成形的控制模型。设计了自适应控制器,对FGM成形过程进行实时控制。实验验证了控制模型的准确性和控制方法的有效性。     

The effect of membrane pores wettability on CO2 removal from CO2/CH4 gaseous mixture using NaOH,MEA and TEA liquid absorbents in hollow fiber membrane contactor

The present paper renders a modeling and a 2D numerical simulation for the removal of CO₂ from CO₂/CH₄ gaseous stream utilizing sodium hydroxide (NaOH), monoethanolamine (MEA) and triethanolamine (TEA) liquid absorbents inside the hollow fiber membrane contactor. Counter-current arrangement of absorbing agents and CO₂/CH₄ gaseous mixture flows are implemented in the modeling and numerical simulation. Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode, CO₂/CH₄ gaseous mixture and liquid absorbents fill the membrane pores. The deteriorated removal of CO₂ in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane. The validation of numerical simulation is done based on the comparison of simulation results of CO₂ removal using NaOH and experimental data under non-wetting mode of operation. The comparison illustrates a desirable agreement with an average deviation of less than 5%. According to the results, MEA provides higher efficiency for CO₂ removal in comparison with the other liquid absorbents. The order for CO₂ removal performance is MEA > NaOH > TEA. The influence of non-wetting and partial wetting modes of operation on CO₂ removal are evaluated in this article as one of the novelties. Besides, the percentage of CO₂ sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0 (non-wetting mode of operation) to 100% (complete wetting mode of operation) is studied in this research paper, which can be proposed as the other novelty. The results indicate that increase in some operational parameters such as module length, membrane porosity and absorbents concentration encourage the removal percentage of CO₂ from CO₂/CH₄ gaseous mixture while increasing in membrane tortuosity, gas velocity and initial CO₂ concentration has unfavorable influence on the separation efficiency of CO₂.     

A computational model for assessing impact of interfacial morphology on polymer electrolyte fuel cell performance

A two-dimensional, non-isothermal, anisotropic numerical model is developed to investigate the impact of the interfacial morphology between the micro-porous layer (MPL) and the catalyst layer (CL) on the polymer electrolyte fuel cell (PEFC) performance. The novel feature of the model is the inclusion of directly measured surface morphological information of the MPL and the CL. The interfacial morphology of the MPL and the CL was experimentally characterized and integrated into the computational framework, as a discrete interfacial layer. To estimate the impact of MPL|CL interfacial surface morphology on local ohmic, thermal and mass transport losses, two different model schemes, one with the interface layer and one with the traditionally used perfect contact are compared. The results show a ∼54 mV decrease in the performance of the cell due to the addition of interface layer at 1 A cm⁻². Local voids present at the MPL|CL interface are found to increase ohmic losses by ∼37 mV. In-plane conductivity adjacent to the interface layer is determined to be the key controlling parameter which governs this additional interfacial ohmic loss. When the interfacial voids are simulated to be filled with liquid water, the overpotential on the cathode side is observed to increase by ∼25 mV. Local temperature variation of up to 1 °C is also observed at the region of contact between the MPL and the CL, but has little impact on predicted voltage.     

Strategic planning on carbon capture from coal fired plants in Malaysia and Indonesia: A review

Malaysia and Indonesia benefit in various ways by participating in CDM and from investments in the GHG emission reduction projects, inter alia, technology transfer such as carbon capture (CC) technology for the existing and future coal fired power plants. Among the fossil fuel resources for energy generation, coal is offering an attractive solution to the increasing fuel cost. The consumption of coal in Malaysia and Indonesia is growing at the fastest rate of 9.7% and 4.7%, respectively, per year since 2002. The total coal consumption for electricity generation in Malaysia is projected to increase from 12.4 million tons in 2005 to 36 million tons in 2020. In Indonesia, the coal consumption for the same cause is projected to increase from 29.4 million tons in 2005 to 75 million tons in 2020. CO₂ emission from coal fired power plants are forecasted to grow at 4.1% per year, reaching 98 million tons and 171 million tons in Malaysia and Indonesia, respectively.     

Uneven gas diffusion layer intrusion in gas channel arrays of proton exchange membrane fuel cell and its effects on flow distribution

Intrusion of the gas diffusion layer (GDL) into gas channels due to fuel cell compression has a major impact on the gas flow distribution, fuel cell performance and durability. In this work, the effect of compression resulting in GDL intrusion in individual parallel PEMFC channels is investigated. The intrusion is determined using two methods: an optical measurement in both the in-plane and through-plane directions of GDL, as well as an analytical fluid flow model based on individual channel flow rate measurements. The intrusion measurements and estimates obtained from these methods agree well with each other. An uneven distribution of GDL intrusion into individual parallel channels is observed. A non-uniform compression force distribution derived from the clamping bolts causes a higher intrusion in the end channels. The heterogeneous GDL structure and physical properties may also contribute to the uneven GDL intrusion. As a result of uneven intrusion distribution, severe flow maldistribution and increased pressure drop have been observed. The intrusion data can be further used to determine the mechanical properties of GDL materials. Using the finite element analysis software program ANSYS, the Young's modulus of the GDL from these measurements is estimated to be 30.9 MPa.