Influence of pH of spray solution on optoelectronic properties of cadmium oxide thin films

Highly conducting transparent cadmium oxide thin films were prepared by the conventional spray pyrolysis technique. The pH of the spray solution is varied by adding ammonia/hydrochloric acid. The effect of pH on the morphology, crystallinity and optoelectronic properties of these films is studied. The structural analysis showed all the films in the cubic phase. For the films with pH < 7(acidic condition), the preferred orientation is along the(111) direction and for those with pH >7(alkaline condition), the preferred orientation is along the(200) direction.A lowest resistivity of 9.9104 cm(with carrier concentration D5.11020cm3, mobility D12.4 cm2/(V s))is observed for pH12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70%. Thus, the electrical conductivity of CdO films could be easily tuned by simply varying the pH of the spray solution without compromising the optical transparency.     

Coil‐Type Asymmetric Supercapacitor Electrical Cables

Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm⁻³), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets.     

A practical Equivalent Electrical Circuit model for Proton Exchange Membrane Fuel Cell (PEMFC) systems

An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H₂ consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H₂ consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis.     

Silver-plated polyamide fabrics with high electromagnetic shielding effectiveness performance prepared by in situ reduction of polydopamine and chemical silvering

In this article, the silver-plated polyamide fabrics (SPPAFs) with high electroconductibility and shielding effectiveness were fabricated by using in situ reduction of polydopamine and chemical silvering. The effects of SPPAFs dopamine (C₈H₁₁O₂N) and silver nitrate (AgNO₃) concentration on surface resistivity and electromagnetic interference shielding effectiveness were studied. The results showed that the surface resistivity of SPPAFs can reach a minimum value of 0.06 ± 0.014 Ω cm⁻¹, when C₈H₁₁O₂N concentration is 4 g L⁻¹ and the AgNO₃ concentration is 120 g L⁻¹. The shielding effectiveness of SPPAFs in the wide frequency range of 10–3000 MHz increases with the increase in the concentration of AgNO₃, and increases first and stabilizes afterward with increasing C₈H₁₁O₂N concentration. When the concentration of C₈H₁₁O₂N and AgNO₃ is 3 and 120 g L⁻¹, respectively, mean shielding effectiveness values in the low-, medium-, and high-frequency bands are 71.3, 73.8, and 76.1 dB, respectively. Moreover, the mean shielding effectiveness values is 83.79 dB in the frequency range of 1.2–2.3 GHz. The dominant shielding mechanism of SPPAFs is the reflected electromagnetic waves and the absorption shielding effectiveness is less than 2 dB. The average electromagnetic shielding values of SPPAFs are above 67 dB after 16 weeks of storage, when C₈H₁₁O₂N concentration is 4 g L⁻¹ and the AgNO₃ concentration is 80 and 100 g L⁻¹. The prepared SPPAFs show promising applications in military textiles and smart wearable clothing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48227.     

Core–shell NTC materials with low thermal constant and high resistivity for wide-temperature thermistor ceramics

Core–shell structures have been proposed to improve the electrical properties of negative-temperature coefficient (NTC) thermistor ceramics. In this work, Al₂O₃-modified Co_1.5Mn_1.2Ni_0.3O₄ NTC thermistor ceramics with adjustable electrical properties were prepared through citrate-chelation followed by conventional sintering. Co_1.5Mn_1.2Ni_0.3O₄ powder was coated with a thin Al₂O₃ shell layer to form a core–shell structure. Resistivity (ρ) increased rapidly with increasing thickness of the Al₂O₃ layer, and the thermal constant (B) varied moderately between 3706 and 3846 K. In particular, Co_1.5Mn_1.2Ni_0.3O₄@Al₂O₃ ceramic with 0.08 wt% Al₂O₃ showed the increase of ρ double, and the change in its B was less than 140 K. The Co_1.5Mn_1.2Ni_0.3O₄@Al₂O₃ NTC ceramics showed high stability, and their grain size was relatively uniform due to the protection offered by the shell. The aging coefficient of the ceramic was less than 0.2% after aging for 500 hours at 125°C. Taken together, the results indicate that as-prepared Co_1.5Mn_1.2Ni_0.3O₄@Al₂O₃ NTC ceramics with a core–shell structure may be promising candidates for application as wide-temperature NTC thermistor ceramics.     

A comparative study of (Ce) and (Gd) doping influence on the superconducting properties of YBCO ceramics

This work is devoted to investigate the structural and electrical properties of the Ce, Gd-doped YBCO superconductors bulk ceramics. YBa_2-xRE_xCu₃O_7−δ (x = 0, 0.01, 0.05, 0.1) (RE = Gd, Ce) samples were prepared by means of conventional solid-state reaction. X-ray diffraction analysis was carried out to identify the present phases in the as-prepared samples followed by the determination of their lattice parameters. Fourier Transform Infrared Spectroscopy (FTIR) was used to identify the functional groups. Furthermore, the morphology and the surface roughness of the studied samples were characterized using Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM). Vickers Micro-hardness of the as-prepared samples was examined. Besides, the electrical resistivity measurements were achieved to determine the critical transition temperature T_C and the critical current density J_C.The effect of Ce and Gd additions is clearly noticed in the obtained results, where all the prepared samples are superconductors with the presence of Y123 as a major polycrystalline phase. From the XRD patterns, the intensities of the Y123 corresponding peaks decrease with further increasing the Ce and Gd contents. In addition, the variation of the cell parameters was significant after additions of both Ce and Gd, which affect the grain size and the oxygen content of the YBa_2-xRE_xCu₃O_7−δ system. An improvement of the structure and surface roughness is observed on SEM and AFM images. Likewise, Vickers micro-hardness has increased after the Ce and Gd additions. Although, the critical transition temperature T_C was not further increased upon Ce or Gd additions compared to the undoped YBCO samples. Nevertheless, an exception has been recorded with an increase of T_C for YBa_2-xRE_xCu₃O_7−δ with (RE = Gd, x=0.01) to reach 88 K. In contrary, an improvement of the deduced critical current density J_C was achieved for all Ce-doped YBCO samples unlike those of Gd-doped samples.     

超级电容器的电性能及其在智能仪表上的应用

超级电容器作为一种新型储能元件,目前应用越来越广泛,但在很多细分市场还处于培育阶段,相关行业标准也不尽完善。文中以超级电容器的等效电路模型引出了电性能的特征参数,对比分析了主要标准中电性能特征参数测试方法的差异,提出了在智能仪表中应用超级电容器的要点,对全面认识超级电容器的电性能,在实际工作中正确的应用超级电容器,有一定的参考价值。     

Electrical resistivity of silicon nitride produced by various methods

It has been shown that the grain growth and amount of the glass phase influence the electrical resistivity of pressureless sintered and spark plasma sintered silicon nitride. Sintering additives strongly affect the impurity conductivity of pressureless sintered silicon nitride and slightly influence the intrinsic conductivity due to the longer sintering process as compared with the spark plasma sintering. It was demonstrated that Al₂O₃-Y₂O₃ lead to decrease in the electrical resistivity of SPSed silicon nitride due to increase in the band gap width as opposed to Al₂O₃-MgO. Effect of the sintering additive on the impurity conductivity is practically absent but there is a strong dependence of the sintering temperature for reported spark plasma sintered silicon nitride. However, intrinsic conductivity of SPSed silicon nitride is affected by both sintering temperature and sintering additive. It was also shown that electrical resistivity of produced ceramics is linearly depends on the content of β-Si₃N₄ and microhardness. Electrical resistivity of manufactured silicon nitride varied from 3.16·10⁹ to 1.73·10¹¹ Ω?m. It has been observed strong influence of the sintering additive and sintering temperature on the electrical properties of SPSed and pressureless sintered silicon nitride.     

焦化厂电气设备常见故障及诊断

焦化厂电气设备更新迅速、功能多样,设备结构和功能趋于复杂化,对故障诊断的精准性提出了更高要求。为保障焦化厂电气设备的正常运行,对电气设备常见故障及影响因素展开分析,探讨了电气设备故障诊断的作用和方法,并对设备维护的要点进行了论述。分析认为,电气设备运行时受诸多因素影响,为保证设备正常使用、延长使用年限,需要以理论为指导,科学制定检修计划,结合设备实际情况合理应用诊断技术。     

信息技术设备电气间隙、爬电距离的设计与测量

电气间隙和爬电距离是信息技术设备的一项重要电气安全指标,由于其涉及的因素较多,导致产品设计人员和检测人员容易出错。本文详细介绍了电气间隙和爬电距离的定义、如何计算不同绝缘的限值,并结合日常检测中遇到的常见问题进行了详细的说明、提出了相应改进建议。