Studies on waterline corrosion processes and corrosion product characteristics of carbon steel in 3.5 wt% NaCl solution

The waterline corrosion behaviors of carbon steel partially immersed in a 3.5 wt% NaCl solution were investigated using the wire beam electrode technique, and the effects of corrosion products on the processes of waterline corrosion were analyzed. The results demonstrated that the initial stage and development stage of waterline corrosion were mainly controlled by the concentration and diffusion of dissolved oxygen, respectively, and the deceleration stage of waterline corrosion was mainly affected by corrosion products. The main component of the yellow corrosion products was γ-FeOOH, and γ-FeOOH that exhibited a high reduction reactivity could be involved in the cathodic reaction. The black corrosion products were mainly composed of Fe₃O₄ with strong thermodynamic stability and the processes of dissolved oxygen diffusion and ion transports were obviously affected due to the continuous accumulation of Fe₃O₄ on the surface of the electrodes. Polarity reversals were observed on the single electrodes below the waterline, but the reasons for the phenomena were different from each other.     

瞬变电磁井间勘探的全空间几何因子

井间是剩余油的主要分布区域,为探测井间剩余油,提高采收率,提出了基于全空间几何因子的瞬变电磁井间勘探方法。在本井使用线圈发射、邻井使用线圈接收,根据瞬变电磁场理论,在阶跃信号的激励下发射线圈在地层中激发出沿圆周方向的闭合瞬变电场,该电场在导电地层中产生与地层电导率呈正比的涡流。由Doll地层环模型可知,地层中的涡流在空间任意点激发得到与地层电导率成正比的二次场响应信号(有用信号),并可表示为空间各点电导率的加权平均值,其权重即为井间瞬变电磁勘探的全空间几何因子;全空间几何因子集中分布在发射线圈和接收线圈附近,其它区域分布较少,在发射线圈和接收线圈两侧呈现不同的极性;对瞬变电磁响应与地层电导率、井间距和源距的变化规律研究可知,瞬变电磁井间勘探有用信号随着地层电导率的增大而增大,随着井间距的增加单调减小,在发射线圈和接收线圈处于同一深度时该响应信号幅度最大。     

Effect of anode iridium oxide content on the electrochemical performance and resistance to cell reversal potential of polymer electrolyte membrane fuel cells

An ideal polymer electrolyte membrane fuel cell (PEMFC) is one that continuously generates electricity as long as hydrogen and oxygen (or air) are supplied to its anode and cathode, respectively. However, internal and/or external conditions could bring about the degradation of its electrodes, which are composed of nanoparticle catalysts. Particularly, when the hydrogen supply to the anode is disrupted, a reverse voltage is generated. This phenomenon, which seriously degrades the anode catalyst, is referred to as cell reversal. To prevent its occurrence, iridium oxide (IrO₂) particles were added to the anode in the membrane-electrode assembly of the PEMFC single-cells. After 100 cell reversal cycles, the single-cell voltage profiles of the anode with Pt/C only and the anodes with Pt/C and various IrO₂ contents were obtained. Additionally, the cell reversal-induced degradation phenomenon was also confirmed electrochemically and physically, and the use of anodes with various IrO₂ contents was also discussed.     

铍材料精密电火花加工工艺研究

针对铍材料机械加工性能较差的缺点,进行了电火花精密加工工艺的探索;通过负极性和以较低放电能量的加工方式,突破了机械加工极限,得到了厚度为0.05mm左右的铍薄膜。     

Effect of electric field polarity on inter-poly dielectric during cell operation for the retention characteristics

Retention characteristic represents a capability to maintain the storage data and it is related with the reliability of memory device. The retention characteristic is degraded by the leakage of charges from a floating gate to a control gate, and thus the leakage current at low and moderate electric field of inter-poly dielectric (IPD) is one of the important characteristic for floating gate type flash memories. In addition, it is necessary to investigate the effects of the electric field polarity on the electric characteristics of IPD because the electric field polarity is changed as the cell operations such as the programming and erasing. Therefore, in this paper, the variation of the leakage current of IPD at moderate electric field region is measured with varying the previously applied electric field polarity. Based on the result, the effect of sequential change of an applied electric field polarity on the electrical characteristics is analyzed.     

In situ electrodeposition of nickel cobalt selenides on FTO as an efficient counter electrode for dye-sensitized solar cells

Construction of transition metal selenides with high electrocatalytic performance is of significant importance, but it is still a challenge to develop the corresponding counter electrodes (CEs) by an electrodeposition technique. In the present work, nickel cobalt selenide (Ni_xCo_ySe) films are prepared in situ on fluorine-doped tin oxide (FTO) glasses through a potential reversal electrodeposition technique. The morphology and electronic structure of Ni_xCo_ySe films can be tuned by controlling the Ni/Co molar ratio in electroplating solution. Specially, Ni_xCo_ySe-6 film (the Ni/Co molar ratio of 1:1) with the optimized interaction between the Ni and Co elements displays numerous particles composed of sheets attached with nanocrystals, resulting in the more electrocatalytic active sites. Benefiting from the unique morphology and optimized synergistic effect, Ni_xCo_ySe-6 CE exhibits superior electrocatalytic activity for the triiodide reduction. Then, the dye-sensitized solar cell (DSC) fabricated by Ni_xCo_ySe-6 CE has demonstrated a power conversion efficiency (PCE) over 7.40%, which is higher than that of platinum (Pt)-based device (6.32%). Furthermore, Ni_xCo_ySe-6 array CE is also prepared by using polystyrene array as template. The PCE of the DSC with Ni_xCo_ySe-6 array CE reaches its maximum value of 7.64% and 20.9% larger than that of Pt-based device.     

高强铝合金双脉冲VPPA焊缝成形机理

建立双脉冲VPPA(variable polarity plasma arc)焊接系统，进行7A52高强铝合金双脉冲VPPA焊接工艺试验，研究低频脉冲调制叠加高频脉冲对VPPA焊接过程中焊缝成形和焊缝力学性能的影响. 结果表明，低频脉冲周期性振荡液态熔池，可获得表面饱满的鱼鳞纹焊缝；高频脉冲使电弧更为集中，有效地提高了电弧能量密度，穿透力加强；双脉冲耦合振荡加强了对熔池的搅动作用细化了铝合金焊缝晶粒. 焊接接头抗拉强度达到384.13 MPa，相比VPPA焊接接头强度提高了10.21%左右；焊接接头断面收缩率和断后伸长率均有一定程度的提高. 铝合金双脉冲VPPA焊接工艺提高了焊接接头力学性能.     

Ir-Pt/C composite with high metal loading as a high-performance anti-reversal anode catalyst for proton exchange membrane fuel cells

Voltage reversal induced by hydrogen starvation can severely corrode the anode catalyst support and deteriorate the performance of proton exchange membrane fuel cells. A material-based strategy is the inclusion of an oxygen evolution reaction catalyst (e.g., IrO₂) in the anode to promote water electrolysis over harmful carbon corrosion. In this work, an Ir-Pt/C composite catalyst with high metal loading is prepared. The membrane-electrode-assembly (MEA) with 80 wt% Ir-Pt(1:2)/C shows a first reversal time (FRT) of up to 20 hours, which is about ten times that of MEA with 50 wt% Ir-Pt(1:2)/C does. Furthermore, the MEA with 80 wt% Ir-Pt(1:2)/C exhibits a minimum cell voltage loss of 6 mV@1 A/cm² when the FRT is terminated in 2 hours, in which the MEA with 50 wt% Ir-Pt(1:2)/C exhibits a voltage loss of 105 mV@1 A/cm². Further physicochemical and electrochemical characterizations demonstrate that the destruction of anode catalyst layer caused by the voltage reversal process is alleviated by the use of the composite catalyst with high metal loading. Hence, our results reveal that the combination of OER catalyst on the Pt/C with high metal loading is a promising approach to alleviate the degradation of anode catalyst layer during the voltage reversal process for PEMFCs.     

溶剂性质对六硝基六氮杂异伍兹烷晶型的作用

研究稳定地得到e型六硝基六氮杂异伍兹烷( HNIW)的结晶工艺条件,并寻求多晶转变的理论解释。研究发现,非溶剂的物理性质,如偶极矩、分子极性,在结晶过程中对于HNIW的晶型起重要作用。常温下在无晶种时,当利用乙酸乙酯、丙酮作为溶剂,采用偶极矩值小的非溶剂,如环己烷、石油醚、甲苯、异辛烷等均可使HNIW以ε型晶型结晶出来,反之,采用偶极矩值大的非溶剂,如三甘醇则使HNIW以其它晶型结晶出来。在较高温度下,s型HNIW在极性与非极性溶剂中稳定存在时间明显不同。