Effects of CH2F2 and H2 flow rates on process window for infinite etch selectivity of silicon nitride to ArF PR in dual-frequency CH2F2/H2/Ar capacitively coupled plasmas

The process window for the infinite etch selectivity of silicon nitride (Si₃N₄) layers to ArF photoresist (PR) and ArF PR deformation were investigated in a CH₂F₂/H₂/Ar dual-frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters, such as the low frequency power (P_LF), CH₂F₂ flow rate, and H₂ flow rate. It was found that infinitely high etch selectivities of the Si₃N₄ layers to the the ArF PR on both the blanket and patterned wafers could be obtained for certain gas flow conditions. The H₂ and CH₂F₂ flow rates were found to play a critical role in determining the process window for infinite Si₃N₄/ArF PR etch selectivity, due to the change in the degree of polymerization. The preferential chemical reaction of hydrogen with the carbon in the hydrofluorocarbon (CH_xF_y) layer and the nitrogen on the Si₃N₄ surface, leading to the formation of HCN etch by-products, results in a thinner steady-state hydrofluorocarbon layer and, in turn, in continuous Si₃N₄ etching, due to enhanced SiF₄ formation, while the hydrofluorocarbon layer is deposited on the ArF photoresist surface.     

适应高密度化和高速化的FPC新技术开发

概述了适应高密度化和高速化要求的FPC新技术：电沉积聚酰亚胺工艺,半加成法工艺、聚酰亚胺蚀刻工艺。     

一种改进型无速度传感器异步电机直接转矩控制系统

在传统无速度传感器异步电机直接转矩控制系统基础之上进行了改进,引入了变结构控制和无速度传感器技术,设计出电机定子磁链控制器和电磁转矩控制器,并应用Lyapunov第二方法推导出转子转速和定子电阻辨识方程。通过Matlab/Simulink的仿真,验证了改进后的系统比传统系统具有更好的稳态性能,并具有良好的鲁棒性。     

Fabrication of three-dimensional copper nanodomes as anode materials for direct methanol fuel cells

In this study, we demonstrate a novel approach for fabricating copper nanodomes (Cu-NDs) by combining of soft lithography, nanosphere lithography, physical vapor deposition (PVD) and electrochemical deposition methods. The 3D nano structures were characterized using surface microscopic techniques. The methanol oxidation activity of the Cu-NDs anode was tested by electrochemical methods in 0.1 M KOH +1 M CH₃OH solution and the results were compared with that of bulk Cu as a reference point. The results showed that very well-structured, uniformly and homogeneously distributed Cu-NDs could be fabricated using these combined methods. The peak current density related to methanol oxidation reaction increased and charge transfer resistance reduced almost three times at the Cu-NDs electrode with respect to the bulk Cu. Also, the Cu-NDs electrode has good time stability and high tolerance to CO_ads poisoning. The enhanced activity of the nanostructures was related to good intrinsic activity of Cu for this reaction and their larger available electrochemical active sites.     

Performance and long-term durability of direct-methane flat-tube solid oxide fuel cells with symmetric double-sided cathodes

In this work, we investigated the performance and stability of a large flat-tube SOFC with symmetric double-sided cathodes (DSC), which was directly fueled with methane. The effect of steam/carbon (S/C) ratio, temperature, and current density on the performance, and long-term stability of the DSC as well as the catalytic behavior of the anode was investigated in details. The thick anode support and inner channels of the DSC formed an efficient microreactor for steam-reforming of methane, resulting in high conversion rate of methane and CO selectivity. In particular, when the S/C was 2, the conversion of CH₄ at 750 °C achieved 100% in the DSC and no carbon deposition was observed. Moreover, the voltage of DSC with was stable throughout 190 h under a discharge current density of 0.257 A cm⁻².     

Direct Ethanol Fuel Cells: The influence of structural and electronic effects on Pt–Sn/C electrocatalysts

Carbon-supported platinum-tin electrocatalysts (Pt–Sn/C) are known to be the most efficient fuel cell anode material to oxidize ethanol in the so-called Direct Ethanol Fuel Cells (DEFC). However, the platinum-tin binary system presents distinct phases depending on the amount of Sn (i.e., the Pt:Sn ratio) and on the thermal annealing temperatures, as well as the presence of oxides (e.g. SnO₂) whose influence on the performance of DEFCs is not well understood. In this work, Pt–Sn catalysts presenting distinct Pt:Sn ratios were prepared, characterized and tested in a single DEFC. The combined results from DEFC tests and structural characterization techniques showed that increasing the amount of Sn dissolved into the Pt structure enhances DEFC performance but also that Sn content alone does not explain the overall behavior. Microstructural effects on the DEFC response was further investigated by performing a comprehensive study using high intensity X-ray Diffraction and in situ–X-Ray Absorption Spectroscopy provided by synchrotron light on Pt₃Sn₁/C samples subjected to thermal treatments in a reducing H₂ atmosphere at temperatures of 100, 200, 300, 400, and 500 °C. The results showed that best DEFC performance depends on a balance between the amount of Sn dissolved in Pt, the formation of a new phase (PtSn) and also on the presence of tin oxides, yielding a material with an optimized modified 5d-band electronic structure, which was obtained with a thermal treatment at 200 °C.     

Simultaneous thermal and visual imaging of liquid water of the PEM fuel cell flow channels

Water flooding and membrane dry-out are two major issues that could be very detrimental to the performance and/or durability of the proton exchange membrane (PEM) fuel cells. The above two phenomena are well-related to the distributions of and the interaction between the water saturation and temperature within the membrane electrode assembly (MEA). To obtain further insights into the relation between water saturation and temperature, the distributions of liquid water and temperature within a transparent PEM fuel cell have been imaged using high-resolution digital and thermal cameras. A parametric study, in which the air flow rate has been incrementally changed, has been conducted to explore the viability of the proposed experimental procedure to correlate the relation between the distribution of liquid water and temperature along the MEA of the fuel cell. The results have shown that, for the investigated fuel cell, more liquid water and more uniform temperature distribution along MEA at the cathode side are obtained as the air flow rate decreases. Further, the fuel cell performance was found to increase with decreasing air flow rate. All the above results have been discussed.     

自适应变结构永磁同步直线电动机直接推力控制

和矢量控制相比,永磁直线同步电动机直接推力控制具有快速和鲁棒性特点.由于经典直接推力控制在电机参数变化和负载扰动影响下会产生推力波动,严重影响系统性能,为改善系统性能,采用一种新颖的自适应变结构控制器控制动子磁链和推力.计算出动子电压矢量,根据空间矢量调制(SVM)控制逆变器的开关频率.整个控制系统经仿真验证,证明在动子参数变化和负载扰动的影响下,系统具有平滑、快速的动子速度和推力响应.     

双定子/双转子永磁同步电机电压矢量确定方法

首先基于直接转矩控制原理提出了双定子/双转子永磁同步电机双转子运行时,内部电机控制电压矢量的确定方法,然后考虑到内部电机特点与Matlab所提供永磁电机模型的差别,建立了电机等效仿真模型.仿真结果证明本文所提出的方法有效.其结果对在混合动力电动汽车中开发双定子/双转子永磁同步电机的直接转矩控制系统具有意义.     

The long-term effectiveness and failure mechanism of the chemically bonded phosphate ceramic coatings with different thickness

In this study, the chemically bonded phosphate ceramic coatings (CBPCs) with different thickness (100 µm, 200 µm, and 300 µm) are prepared on the mild steel (Q235). Potentiodynamic polarization testing and electrochemical impedance spectroscopy were carried out to study the synthetic effect of coating thickness and etching time (12, 24, 36, and 48 hours) on the corrosion behavior of CBPCs. The surface and cross section microstructure of CBPCs before and after different immersion time in 3.5 wt.% NaCl solution is investigated to better understand the corrosion behavior. Results revealed that the enhanced coating thickness can effectively postpone the corrosive factors infiltration into the substrate and prohibit the corrosion of the mild steel. From the potentiodynamic polarization testing results, the protection efficiency of the coating greatly increases with the increase in etching time. In addition, an increase in 10 000 and 1000 orders of magnitude of impedance value for the CBPCs with 12 hours and 48 hours etching time has been observed, respectively, indicating the CBPCs can effectively protect the mild steel from corrosion damage even with long-term service.