相间功率控制器过电压及其保护的仿真分析

针对相间功率控制器(interphase power controller,IPC)在潮流控制过程中过电压及其保护的问题,基于相间功率控制器的基本结构原理,建立了电压与元件参数之间关系的数学模型,探讨了IPC过电压出现的原因及其保护系统的组成,并以两电网带IPC 240联络线为例采用Matlab中的Simulink搭建...     

打磨态690TT合金经不同时间浸泡后表面氧化膜结构分析

利用多种分析手段深入分析了打磨处理的690TT合金在模拟压水堆一回路高温高压水环境中经不同时间浸泡后表面生长的氧化膜的微观结构.结果表明,从短期氧化到长期氧化.氧化膜表面形貌变化不明显;氧化膜主要由尖晶石结构的氧化物和单质Ni构成.浸泡96和1440 h后,氧化膜主要由富含Cr的氧化物构成.浸泡720,1440和2160 h后,氧化膜均由外层、中间层和内层构成:外层是分散的富含Ni和Fe的尖晶石结构的大颗粒氧化物;中间层是致密的富含Cr的尖晶石结构的小颗粒氧化物;内层是均匀连续的富含Cr的氧化物.中间层和内层氧化物能对基体起到良好的保护作用;随着氧化时间的延长,保护层的平均生长速率逐渐降低.打磨处理促进了690TT合金表面保护性氧化膜的生长.     

闭塞区中Ni~(2+)对核级304不锈钢高温水氧化行为的影响

核电站服役的高温高压水回路中闭塞区的流动不充分,可能产生异常水化学条件而导致材料服役性能弱化.本文利用国产核级304不锈钢制备了一种简单的模拟闭塞区样品,放入含有Ni~(2+)的高温含氧水中浸泡并对生成的氧化膜进行表征.结果表明:闭塞区从外到内氧化膜外层中的尖晶石结构相的比例逐渐减小,而赤铁矿结构相的比例逐渐增大,模表层的Ni含量逐渐降低.分析表明,Ni~(2+)浓度会显著影响核级不锈钢的氧化行为,闭塞结构会在一定程度上阻碍本体溶液中的Ni~(2+)向闭塞区内扩散,使Ni~(2+)沿闭塞区深度方向形成浓度梯度.导致氧化膜的生长特征沿梯度方向发生明显变化.     

核级不锈钢和铁素体-马氏体耐热钢在400℃/25 MPa超临界水中的腐蚀行为

利用腐蚀增重法,XRD,Raman光谱和SEM研究了核级304不锈钢和铁素体-马氏体耐热钢P92在400℃/25 MPa超临界水中的腐蚀行为.结果表明,2种材料都以均匀腐蚀为主,增重曲线遵循幂指数规律.304不锈钢的腐蚀增重比P92钢低近一个数量级,其氧化膜很薄,局部存在少量的疖状腐蚀.氧化膜主要由Cr_2O_3,α-Fe_2O_3,Fe_3O_4和尖晶石结构氧化物组成.P92钢的氧化膜主要由α-Fe_2O_3,Fe_3O_4和尖晶石结构氧化物组成,表层主要含α-Fe_2O_3.延长腐蚀时间.P92钢表面氧化膜在超临界水中溶解,导致氧化膜形貌由致密的多面体颗粒演化为相互连通的多孔网络结构.     

Sinterability and electrical properties of ZnO-doped Ce0.8Y0.2O1.9 electrolytes prepared by an EDTA-citrate complexing method

The effect of ZnO addition on the sinterability and ionic conductivity of Ce_0.8Y_0.2O_1.9 is investigated. Ce_0.8Y_0.2O_1.9 is prepared using an EDTA-citrate complexing method in order to further improve its electrical properties. Using a ZnO content over 1 mol %, the sinterability of Ce_0.8Y_0.2O_1.9 is significantly improved by reducing the sintering temperature from 1500 to 1350 °C and a relative density of above 95% was achieved. The highest ionic conductivity of 0.0516 S cm⁻¹ was obtained at 750 °C for (YDC)_0.99(ZnO)_0.01 sintered at 1350 °C. Pure YDC sintered at 1500 °C, on the other hand, yielded 0.0289 S cm⁻¹.     

Characterization of zinc oxide nanoparticles synthesized by polymer assisted deposition method

Zinc oxide nanoparticles (ZNPs) are synthesized onto glass substrates by employing simple and low cost solution based modified polymer assisted deposition (PAD) method. Trionx100 is used as a capping agent and zinc acetate as the zinc source. TritonX100 concentration is varied from 0.02 to 0.45 M for the synthesis of pure ZnO NPs. TG-DTA analysis was employed to determine the decomposition temperature of TritonX100 and zinc acetate, which lead to the formation of ZnO. The films were further characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HR-TEM), Fourier transforms infrared spectroscopy (FT-IR) and room temperature photoluminescence (PL). The results indicate that the synthesized nanoparticles (NPs) exhibits the room temperature PL with two emission peaks, one corresponding to ZnO band edge emission and the other one to point defect states created due to oxygen deficiency. The first peak undergoes blue-shift due to change in NPs size while there is no shift in the second peak. Nevertheless, with increase in TritonX100 concentration the peak intensity of defect peak decreases, indicating that the highly pure NPs have been successfully synthesized by PAD method.     

Effects of oxygen addition on physical properties of ZnO thin film grown by radio frequency reactive magnetron sputtering

We deposited a ZnO thin film on a microslide glass substrate at room temperature by employing the RF reactive magnetron sputtering process. Our results revealed that deposition rate decreases by increasing O₂/(Ar + O₂) ratio that was caused by two mechanisms. The first mechanism was the reduction of plasma density and, thus, argon ion density; caused by the addition of highly electronegative oxygen. While the second mechanism was target poisoning caused by the oxidation of the target. Additionally, at the O₂/(Ar + O₂) ratio of ∼0.3 and the help of XPS analysis the optimum stoichiometry of ZnO thin film (the highest binding energy and content fraction of O^I peak (O-Zn bond)) and the best polycrystallinity (the lowest FWHM with largest grain size) was found.     

Influence of B2O3 additives on microstructure and electrical properties of ZnO-Bi2O3-Sb2O3-based varistors

B₂O₃-doped ZnO-Bi₂O₃-Sb₂O₃-based varistors were fabricated by conventional ceramic technique. The microstructure and electrical properties were investigated by SEM, XRD and electrical measurements. With the addition of B₂O₃, the liquid-assisted sintering based on Bi₂O₃ was improved, and the Bi₂O₃-B₂O₃ glass and Zn₃(BO₃)₂ phase were formed on the grain boundaries. The doping of B₂O₃ markedly improved the varistor performance of the ZnO-Bi₂O₃-Sb₂O₃-based varistors. The nonlinear coefficient of the sample with 3.5 mol% B₂O₃ sintered at 1100 °C reached 56 and the leakage current was only 0.3 μA.     

SmBaCoCuO5+x as cathode material based on GDC electrolyte for intermediate-temperature solid oxide fuel cells

The performance of SmBaCoCuO_5+x (SBCCO) cathode has been investigated for their potential utilization in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction (XRD), thermal expansion and electrochemical performance on Ce_0.9Gd_0.1O_1.95 (GDC) electrolyte are evaluated. XRD results show that there is no chemical reaction between SBCCO cathode and GDC electrolyte when the temperature is below 950 °C. The thermal expansion coefficient (TEC) value of SBCCO is 15.53 × 10⁻⁶ K⁻¹, which is ∼23% lower than the TEC of the SmBaCo₂O_5+x (SBCO) sample. The electrochemical impedance spectra reveals that SBCCO symmetrical half-cells by sintering at 950 °C has the best electrochemical performance and the area specific resistance (ASR) of SBCCO cathode is as low as 0.086 Ω cm² at 800 °C. An electrolyte-supported fuel cell generates good performance with the maximum power density of 517 mW cm⁻² at 800 °C in H₂. Preliminary results indicate that SBCCO is promising as a cathode for IT-SOFCs.     

Electrochemical properties of the carbon-coated lithium vanadium oxide anode for lithium ion batteries

Carbon-coated Li_1.1V_0.9O₂ powder was prepared by dissolving pure crystalline Li_1.1V_0.9O₂ powder in an ethanol solution containing 10 wt% sucrose and sintering it under an argon atmosphere. The structures of the bare and carbon-coated Li_1.1V_0.9O₂ powders were analyzed using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. These powders were used as anode active materials for lithium ion batteries in order to determine the electrochemical properties via cyclic voltammetry (CV) and constant current methods. CV revealed the carbon-coated Li_1.1V_0.9O₂ anode to have better reversibility during cycling than the bare Li_1.1V_0.9O₂ anode. Carbon-coated Li_1.1V_0.9O₂ also showed a higher specific discharge and charge capacities, as well as lower electrolyte and interfacial resistance properties. The observed specific discharge and charge capacities of the carbon-coated Li_1.1V_0.9O₂ anode were 330 mAh/g and 250 mAh/g, respectively, in the first cycle. In addition, the cyclic efficiency of this cell was 75.8% in the first cycle. After 20 cycles, the specific capacity of the Li_1.1V_0.9O₂ anode was reduced to approximately 50% of its initial capacity, irrespective of the presence of a carbon coating.