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991.
Anion exchange membranes (AEMs) are one of the core components of AEM fuel cells. A series of poly(vinyl alcohol)/polyquaternium-10 (PVA/PQ-10) AEMs with semi-interpenetrating networks (s-IPNs) are prepared by a simple solution-casting method using glutaraldehyde (GA) as a cross-linking agent. Subsequently, the prepared PVA/PQ-10 cross-linked membranes are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, mechanical analysis, water uptake and swelling ratio tests, ion exchange capacity (IEC) tests, ionic conductivity measurements, and oxidative/alkaline stability tests. The effects of the mass ratio of PVA and PQ-10 and the amount of cross-linking agent GA on the performance of the PVA/PQ-10 cross-linked membranes are systematically explored. The results show that the cross-linked PVA/PQ-10 AEMs have high IEC and low water uptake and swelling ratio, and its maximum ionic conductivity can reach 79.37 mS cm–1 at 80 °C. In addition, the PVA/PQ-10 cross-linked membrane has good oxidative and alkaline stability under optimal preparation conditions. These results may provide valuable insights toward more effective scheme designs and new, simple preparation methods for AEMs with s-IPN structures. 相似文献
992.
Yangyang Xu Zhaofu Ding Haibin Zhu Yijun Zhang Stephan Knopf Pu Xiao Jacques Lalevée 《大分子材料与工程》2021,306(3):2000720
The introduction of metallic fillers to polymers via the photopolymerization approach can endow the composite materials with some unique properties, but the relevant research is still scarce due to the issue of light penetration and inner filter effect. Herein, for the first time the fabrication of photocomposites based on fine iron powder (i.e., a typical kind of metallic filler) is reported in this work. The free radical polymerization of two different acrylate monomers, poly(ethylene glycol) diacrylate and trimethylolpropane triacrylate, is performed in the presence of iron filler under mild conditions (i.e., light emitting diode (LED)@405 nm irradiation at room temperature under air). And the real-time Fourier transform infrared spectroscopy reveals remarkable photopolymerization kinetics of acrylates with high final conversions and fast polymerization rates despite the increasing contents of iron filler in the composites. Interestingly, the 3D printing technique is applied to the iron filler-based composites to produce tridimensional patterns with excellent spatial resolution. This work not only paves the way for the investigation of photocomposites based on metallic fillers through photochemical methods, but also broadens the potential application prospects. 相似文献
993.
Wenlong Zheng Xiao Chen Chunyang Liu Shiping Ren Li Zhang 《International Journal of Applied Ceramic Technology》2021,18(4):1244-1254
Silica-based ceramic cores are extensively used in investment casting process, during which they must exhibit sufficient flexural strength and deformation resistance. In this study, micro-sized mullite was used as an additive to silica-based ceramic cores to optimize their high temperature properties. To investigate the effects of micro-sized mullite on cristobalite crystallization, mechanical and thermal properties of silica-based ceramic cores, ceramic cores with different amounts of micro-sized mullite were fabricated. The XRD results showed that additional micro-sized mullite diminished the crystallization of cristobalite at high temperatures, primarily caused by the mullite related compressive stresses on the surface regions of fused silica particles. Three-point bending tests and SEM results showed that micro-sized mullite had a more significant effect on the flexural strength of ceramic cores compared with conventional additives. Particularly, the fracture mechanism of silica-based ceramic cores had been changed from intergranular fracture into a mixed fracture consisting of both intergranular and transgranular fracture. The mechanical and thermal properties of ceramic cores were all reduced slightly as the mullite content exceed 4.6 wt%. Hence, to optimize the properties of silica-based ceramic cores, the micro-sized mullite content should not exceed 4.6 wt%. 相似文献
994.
采用常规水溶液法合成了一种新型的有机-无机杂化多金属氧酸盐(C5H7N2O2)4(SiMo12O40)(简称SiMo-12)。采用红外光谱(IR)、热重分析(TG)、单晶和粉末X射线衍射(XRD)、元素分析等对SiMo-12进行了表征。以过氧化氢为氧化剂,运用SiMo-12催化碘离子氧化,考察了催化剂用量、氧化剂用量、pH、温度等因素对反应速率的影响。结果表明:该化合物属三斜晶系,P-1空间群,晶胞参数a=1.097 58(4) nm、b=1.144 88(4) nm、c=1.252 66(4) nm、α=64.665(1)°、β=64.804(1)°、γ=83.441(1)°、V=1.282 89(8) nm3、Z=1、R=0.034 0、wR2=0.079 9。化合物由4个1-咪唑乙酸和一个经典的Keggin型[SiMo12O40]4-单元组成,有机配体和多金属氧酸阴离子之间通过静电作用、质子转移以及氢键作用沿x轴形成一维链,链与链之间相互平行形成平行于xy面的二维层,层与层之间再通过氢键连接而得到三维网状结构。SiMo-12在催化碘离子氧化中表现出较为优异的催化活性,在c(SiMo-12)=2.0×10-4 mol/L、c(过氧化氢)=2.0×10-3 mol/L、pH=1.4、50 ℃条件下反应速率达到2.641 6×10-5 mol/(L·s),比未加催化剂时的反应速率提高了1 565倍。 相似文献
995.
997.
不同制备工艺对ZnS光学性能的影响 总被引:1,自引:0,他引:1
分别用真空热压、H2S模式的化学气相沉积以及S模式的化学气相沉积3种工艺方法制备了红外透过性能良好的ZnS材料.比较了不同的工艺过程对ZnS显微结构的影响,并且分析了不同制备方法形成的缺陷对光学性能的影响.探讨了热等静压工艺改善光学性能的原因和机理.透过谱图的测试表明,S模式的化学气相沉积法制备的ZnS具有最高的可见光至远红外的透过率.对3种方法制备的ZnS分别进行了热等静压后处理,发现对材料的光学透过性能都有不同程度的提高. 相似文献
998.
999.
我公司采用实型铸造方法,铸造了毛坯质量达42t的大型磨床床身。用冷硬呋喃树脂砂造型、导轨部位加外冷铁、合理布置排气口等方法,成功铸造出了磨床床身。经检测,铸件几何尺寸、力学性能、化学成分、导轨硬度均达到图纸的技术要求,为铸造生产大型和特大型铸铁机床床身提供了经验。 相似文献
1000.