One-step to prepare high-performance gas diffusion layer (GDL) with three different functional layers for proton exchange membrane fuel cells (PEMFCs)

Gas diffusion layer (GDL) is one of the most important components of fuel cells. In order to improve the fuel cell performance, GDL has developed from single layer to dual layers, and then to multiple layers. However, dual or multi layers in GDL are usually prepared by layer-by-layer methods, which cost too much time, energy, and resources. In this work, we successfully developed a facile one-step method to prepare a GDL with three functional layers by utilizing the different sedimentation rates and filtration rates of short carbon fiber (CF) and carbon nanotube (CNT). The treatment temperature for this GDL is much lower than that of traditional method. The thickness of the GDL can be effectively controlled from as thin as 50 μm to more than 200 μm by simply adjusting the content of CF. The GDL with high flexibility is suitable to develop high performance flexible electronics. The fuel cell with the GDL has the maximum power density 1021 mW cm^?2, which shows 19% improvement comparing to the conventional one. Therefore, this work breaks the traditional concept that GDL for fuel cells only can be prepared by very complex and high-cost procedure.     

The impact of the thermal treatment during ink preparation on the ionomer-supported catalyst interactions in the catalyst layers

Catalyst slurries (inks) were prepared with and without thermal treatment to determine the support/ionomer structures and interactions in the catalyst layer (CL) which impact on membrane electrode performance and durability. The thermal treatment of the ink has a nominal effect on the ionomer/support structure in which the carbon support is non-graphitised. The agglomerate/aggregate structures have a high degree of support/ionomer interface and sufficient macroporosity for water movement in the CL. This improves the membrane electrode assembly (MEA) performance, but also accelerates electrochemical carbon degradation. Thermal treatment of graphitised support-containing inks resulted in increased performance facilitated by a larger support/ionomer interface. Without thermal treatment, the more hydrophobic support would form aggregate structures in which water contact was restricted, limiting proton transfer, isolating catalyst, decreasing performance. The water limited access, would however, prolong stability during accelerates carbon degradation. The electrochemical properties were studied using full and half MEA cells.     

超高分子量聚乙烯纤维增强中空蜂窝模压复合材料性能研究

为研制车船等壳体所用的轻质、高强复合板材,选用超高分子量聚乙烯(UHMWPE)短纤维纱,制备成单层经纬为120根/(10 cm)的平纹组织,采用多组经纱持续更替交织层的方法制成2L(1+0)型、4L(2+1)型、6L(3+2)型3种多层角联锁结构织物,采用扦插芯棒、模压成型方法制成菱形蜂窝状的热固性环氧树脂基中空板,并与2块真空吸液法制成的面板组成“三合一”复合板,同时测定了复合板材的结构特征及其平拉、平压和弯曲性能。结果表明:3种类型复合板的密度均远小于水的密度,其中6L(3+2)型最小,为0.48 g/cm³;复合板层数越多,环氧树脂越难渗透尤其是在中空板菱形交叉点处,复合板平拉、平压、抗弯曲强度则呈现递增,制成的6L(3+2)型复合板试样平压强度可达到1.03 MPa。     

Establishment of a color tolerance for yarn-dyed fabrics from different color-depth yarns

Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔE_CMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns.     

The origin of interfacial delamination in Au/ceramic cofired LTCC structure

The interfacial delamination of electrode/ceramic multilayer structure will seriously damage the reliability of low temperature co-fired ceramic (LTCC) module in practical applications. In this work, three kinds of glasses employed in Au electrode are designed and prepared to study the abnormal expansion and delamination process in the Au/ceramic LTCC multilayer structure. The interfacial delamination in the co-fired structure is found to be attributed to the abnormal expansion of glass in respect to Au electrode at high temperature, which is originated from the enlarged closed pores during the co-firing process. This conclusion is further confirmed by co-firing the sample in a low-pressure condition. The mechanism and elimination of interfacial delamination here provides a feasible solution for the design of novel glasses in Au electrode for LTCC applications.     

Pattern design and optimization of yarn-dyed plaid fabric using isolation niche genetic algorithm and rough set theory

Under the circumstance of perceptual consumption, it is still challenging to grasp consumer's emotions and demands due to the large search space, diversified preferences, and easy fatigue of consumers. To reduce user fatigue and enlarge search space, a novel method was presented to design and optimize the pattern of yarn-dyed plaid fabric using the isolation niche genetic algorithm and rough set theory. Each pattern was encoded as a chromosome based on the real number code. The population was initialized and evolved using INGA to maintain the diversity. The rough set theory was adopted as the fitness function of isolation niche genetic algorithm to extract the consumer's demands. After multiple evolutions, a large set of practical patterns of the yarn-dyed plaid fabric are obtained. Experiments were carried out by 24 testers of different ages and genders. The results prove that the proposed method based on the isolation niche genetic algorithm and rough set theory is feasible and effective, supplying references to the designer.     

High ultraviolet transparent conducting electrodes formed using tantalum oxide/Ag multilayer

We investigated the optical and electrical properties of Ta₂O₅/Ag/Ta₂O₅ films as functions of the thicknesses of the Ta₂O₅ and Ag layers. It was found that with an increase in the thicknesses of the Ta₂O₅ and Ag layers from 10 to 40 nm and from 12 to 24 nm, respectively, the sheet resistance, carrier concentration, electron mobility, and resistivity of the Ta₂O₅/Ag/Ta₂O₅ film varied from 2.02 to 8.95 Ω/sq, 5.74 × 10²¹ to 2.92 × 10²² cm^–3, from 13.21 to 24.07 cm²/V·s, and from 8.89 × 10^-6 to 8.24 × 10^-5 Ω cm, respectively. The average transmittance (T_av) of the multilayer samples ranged from 57.18% to 93.99%, and it depended on the Ta₂O₅ and Ag layer thicknesses. The highest T_av of 93.99% was observed for the film with 35 nm thick Ta₂O₅ and 18 nm thick Ag layers, and the peak Haacke's figure of merit (157.04 × 10^–3 Ω^–1) was obtained for 20 nm thick Ta₂O₅ and 21 nm thick Ag layers. Ta₂O₅ (100 nm) and Ta₂O₅/Ag/Ta₂O₅ (20 nm/21 nm/20 nm) samples had optical bandgaps of 4.70 and 4.45 eV, respectively. Film Wizard simulations were conducted to understand the dependence of the transmittance of the multilayer on the thicknesses of the Ta₂O₅ and Ag layers, and phasor analyses were performed to determine how the transmittance of the Ta₂O₅/Ag/Ta₂O₅ (20 nm/21 nm/20 nm) film depended on the Ta₂O₅ layer's thickness.     

织物结构参数对热传递性能影响的模拟分析

为方便快捷构建出接近三原组织织物真实结构的三维几何模型,应用图像处理技术对织物截面提取特征点,基于Newton插值公式拟合纱线中心线方程进而建立织物模型,而后在有限元软件中设置材料取向、定义边界条件,对三原组织织物的热传递性能进行数值模拟,通过实验验证了有限元方法及模型的有效性。之后预测了织物紧度对织物热传递性能的影响。结果表明:在相同织物紧度的条件下,平纹织物的热传递性能最好,其次是斜纹织物,最后是缎纹织物;在一定范围内,随着织物紧度的增加,织物的导热性能逐渐增加。     

微纳米气泡在棉织物碱退浆工艺中的适用性

研究了微纳米气泡对棉织物碱退浆的作用,分析了不同碱用量条件下,微纳米气泡作用时间、加工温度等对碱退浆效果的影响,优化了处理工艺。结果表明,微纳米气泡对棉织物碱退浆促进作用明显,在微纳米气泡条件下碱退浆的优化工艺为:碱液用量2 g/L,时间40 min,温度80℃。     

Kevlar织物软壁包容环抗冲击数值仿真分析研究

针对机匣包容性问题,提出Kevlar平纹织物本构模型的拟合方法,分别采用单层壳、多层壳、层合壳三种有限元建模方式对Kevlar织物软壁包容环弹道冲击过程进行模拟,发展了机匣包容性仿真分析模型。结果表明,多层壳模型和层合壳模型的计算结果更准确,并且可以通过调节摩擦因子使仿真结果与试验结果更接近。在此基础上研究了撞击点位置和弹体入射姿态对弹体剩余速度的影响。结果表明:在较小偏移距离内,撞击点的位置对剩余速度的影响可以忽略不计;滚转角和俯仰角对剩余速度影响较小,而对于偏航角,当角度大于30°时,剩余速度会随着角度的增大明显呈下降趋势,且弹体出射姿态也会发生明显变化。