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1.
《Ceramics International》2022,48(8):11031-11042
Polyaniline (PANI) and its composite with sulphur doped reduced graphene oxide (S-RGO) have been successively synthesized via in-situ chemical oxidative polymerization of aniline in presence of 10 wt. % S-RGO nanosheets. Physico-chemical analyses of the synthesized nanomaterial was performed with various characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Atomic Force Microscopy (AFM) and Thermogravimetric analysis/Differential Scanning Calorimetry (TGA/DSC). The results interpreted from the various characterizations confirm the doping of RGO with sulphur as well as strong interaction of PANI nanofibers and S-RGO nanosheets. TG/DSC curves confirm the enhanced thermal stability of polyaniline/sulphur doped reduced graphene oxide (PANI/S-RGO) nanocomposites with heat resistance index (THRI) of 155.2 °C in comparision to pure PANI (THRI = 145.3 °C) at a filler loading of 10 wt. %. TGA validates that thermal stability of PANI/S-RGO nanocomposite improves by 6–7 °C than pure PANI in terms of weight loss percentage at a temperature of 1117 °C. However DSC analysis confirms that PANI/S-RGO retains its structural integrity and conformity to temperatures as high as 900 °C beyond which the polymer composite starts to degrade. The electromagnetic interference shielding effectiveness (EMI SE) of PANI and PANI/S-RGO nanocomposites were measured via open-ended coaxial probe set-up connected to a Vector Network Analyser (VNA) at a broadband frequency range of 1–20 GHz (1000–20000 MHz). For EMI SE measurements the various nanomaterials were incorporated into paraffin wax and made into composite pellets of thickness 5 mm by solution casting technique. The dielectric properties, electrical conductivity and EMI SE were all greatly enhanced for the PANI/S-RGO/Paraffin composite pellets. The as synthesized PANI/S-RGO/Paraffin composite pellets exhibited highest EMI SE of ?22.5 dB (>99%) as compared to ?15.89 dB of PANI/Paraffin composite pellets. The prepared composite pellets revealed an absorption dominant mechanism of shielding with highest SEA of ?14.6 dB for PANI/S-RGO/Paraffin composite pellets.  相似文献   
2.
利用低本底α、β测量仪,通过一系列比较实验和数据获得影响水中总α、总β放射性活度的实验因素。按照现行国标中的标准曲线法进行实验并分析关系曲线的拟合结果;采用^(241)Am和^(40)K标准粉末源进行串道干扰实验;最后利用热释光测量仪分析影响样品源计数值的因素。结果表明:“质量厚度净计数率”关系曲线线性拟合结果良好,可应用在实验计算中;在测量放射性活度较高的水样时,α通道对β通道产生的串道干扰需进行修正;样品源制备完毕后,不宜立刻测量,应贮存在干燥低本底的环境中,贮存后应用红外灯干燥足够长的时间并完全冷却后进行测量。  相似文献   
3.
Melamine–formaldehyde (MF) resins are widely used as adhesives and finishing materials in the wood industry. During resin cure, either methylene ether or methylene bridges are formed, leading to the formation of a three-dimensional resin network. Not only the curing degree, but also the chemical species present in the cured resin determine the quality of the final product. Analytical methods allowing a detailed investigation of network formation are of great benefit to manufacturers. In the present work, resin cure of an MF precondensate is studied at different temperatures (100–200 °C) without considering the initial pH as a factor. Isoconversional kinetic analysis based on exothermal curing enthalpies enables calculation of the crosslinking degree at a given time/temperature regime. A semiquantitative determination of the chemical groups present is performed based on solid-state nuclear magnetic resonance data. Fourier transform infrared spectroscopy has shown to be a fast and reliable analytical tool with high sensitivity toward functional groups and with great potential for at-line process control. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47691.  相似文献   
4.
分析质子交换膜燃料电池(PEMFC)怠速工况衰退机理,确定怠速工况不同衰退机理对燃料电池模型参数的影响,采用所建立的PEMFC二维等温多物理场模型,仿真研究燃料电池在怠速工况衰退前后的性能及各种衰退因素对电压衰减量的贡献和内部反应气体分布变化。研究结果表明,阴极活化损失增大是怠速工况下最重要的衰退因素,其次是开路电压衰退,影响最小的是阴极电化学活性面积衰退;在相同操作条件下,衰退后燃料电池的最低氧气摩尔浓度和最低氢气摩尔浓度上升,电流密度分布不均匀现象加剧。  相似文献   
5.
基于当量的概念(所有合金元素对材料热物理性能的影响可以通过一个参考元素的等效作用来表示),以Zn为参考元素,通过对7XXX系铝合金二元相图富Al端液相线的数值拟合,得到当量算法所需参数,并将其他元素的当量浓度和参考元素的实际浓度之和用于计算材料的液相线温度和潜热。计算结果与差示扫描量热仪(DSC)测得的数据吻合。与Jmatpro软件获得的数值相比,该算法展现出更好的准确性。  相似文献   
6.
7.
为研究圆钢管钢纤维活性粉末混凝土(RPC)短柱的轴压性能,完成了7根外径219~273mm的圆钢管钢纤维RPC短柱轴压性能试验,分析了套箍系数、径厚比对轴压试件荷载-应变曲线和破坏特征的影响。结果表明:套箍系数ξ在0.63~0.88时,荷载-位移曲线在峰值荷载后出现下降段,短柱呈现剪切破坏模式;当ξ≥1时,在到达峰值荷载后,荷载下降幅度明显减小或出现回升趋势,短柱呈现腰鼓形破坏模式。在达到峰值荷载的85%之前,试件处于弹性阶段,钢管纵向应变大于横向应变;弹塑性阶段,钢管横向应变增加较快,其横向变形系数超过钢管的泊松比并逐渐增大,钢管对RPC的约束作用不断增强。随着混凝土抗压强度提高,其横向变形系数减小,钢管对核心区RPC约束效果降低。  相似文献   
8.
针对换流站中换流阀水冷回路PVDF(聚偏氟乙烯)水管损伤导致漏水问题,首先采用红外吸收光谱与差示扫描量热法检测了冷却水管内外侧样品的化学成分,分析换流阀运行条件下老化作用对PVDF水管的影响,相较于低氧环境的内侧,暴露于空气中的外侧样品分子中有含量不高的羰基(C=O)和羟基(-OH);这些极性基团的引入使得内外侧PVDF结晶度与晶片厚度产生差异,但并未对水管机械性能等方面造成明显影响,建议后续对水管材质作进一步质量测评。  相似文献   
9.
Probabilistic risk assessment for bridges under natural hazards is of great interest to engineers for the development of risk mitigation strategies and implementation plans. The present study evaluates risk of an existing highway bridge in California, USA, under the integrated impact of regional seismic and flood hazards. A sensitivity study combining tornado diagram and first-order second moment reliability analyses is conducted to screen significant uncertain parameters to which bridge response is mostly sensitive. A rigorous uncertainty analysis, employing random sampling and Monte Carlo simulation techniques, is performed to obtain variations in fragility and risk curves of the bridge. Observed variations in risk curves at various risk levels are quantified through 90% confidence intervals and coefficients of variation (COV) of risk. It is observed that uncertainty in the estimated risk increases due to the presence of flood hazard at the bridge site, although mean risk does not vary with flood hazard level. Research outcome signifies that the variation in risk due to parameter uncertainty and varied flood hazard level should not be ignored to ensure bridge safety under the stated multi-hazard condition.  相似文献   
10.
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