Influence of dielectric materials on uniformity of large-area capacitively coupled plasmas for N_2/Ar discharges

The effect of the dielectric ring on the plasma radial uniformity is numerically investigated in the practical 450-mm capacitively coupled plasma reactor by a two-dimensional self-consistent fluid model. The simulations were performed for N2/Ar discharges at the pressure of 300 Pa, and the frequency of 13.56 MHz. In the practical plasma treatment process,the wafer is always surrounded by a dielectric ring, which is less studied. In this paper, the plasma characteristics are systematically investigated by changing the properties of the dielectric ring, i.e., the relative permittivity, the thickness and the length. The results indicate that the plasma parameters strongly depend on the properties of the dielectric ring. As the ratio of the thickness to the relative permittivity of the dielectric ring increases, the electric field at the wafer edge becomes weaker due to the stronger surface charging effect. This gives rise to the lower N_2~+ ion density, flux and N atom density at the wafer edge. Thus the homogeneous plasma density is obtained by selecting optimal dielectric ring relative permittivity and thickness. In addition, we also find that the length of the dielectric ring should be as short as possible to avoid the discontinuity of the dielectric materials, and thus obtain the large area uniform plasma.     

低热固相法制备纳米MnO2/CNT超电容复合电极的循环稳定性

为了改善纳米MnO2超级电容器电极的充放电循环稳定性,以Mn(OAc)2·4H2O、NH4HCO3和碳纳米管(CNT)为原料,采用低热固相反应得到前驱体,再经焙烧和酸处理,制备了一系列CNT含量不同的纳米MnO2/CNT复合电极材料,并用X射线衍射(XRD)、透射电镜(TEM)和Brunauer-Emmett-Teller(BET)比表面积测定方法对其进行了表征.XRD分析结果表明,复合材料中的MnO2为纳米γ-MnO2.研究了复合电极在1 mol·L-1 LiOH电解质中的电化学性能,并与不含CNT的纯纳米MnO2电极进行了比较.结果表明,含CNTs为10%(w,质最分数,下同)和20%的MnO2/CNT复合电极的循环稳定性远优于纯纳米MnO2电极的循环稳定性,其中含10%CNTs的MnO2/CNT复合电极不仪具有良好的循环稳定性,而且在1000 mA·g-1高倍率充放电条件下仍具有200 F·g-1的高比电容.     

Ultra-Wideband Wave Reactances of Capacitive Grids

The accuracy of transmission line models of two-dimensional freestanding capacitive grids is studied on a very wide frequency band. The grids are of infinite extent in the transverse directions and are illuminated by a linearly polarized normally incident plane wave. Comparison with reference results deduced from Finite-Difference Time-Domain (FDTD) simulations allows determining the range of validity of commonly used equivalent circuits It is shown that their accuracy strongly depends on the dimensions of the grids and the operating wavelength. Although very convenient, their implementation for calculating the frequency response of multi-layer systems could lead to unreliable results. Two closed-form new models are thus proposed. The first one results from an optimized expression of the well-known Marcuvitz's impedance, and the second one involves a series resonant LC circuit shunted by an additional capacitance. Both formulations are very accurate for a wide range of grid geometries and over the whole visible region (wavelength > grid constant).     

二氧化锰纳米层的制备及电容性能研究

以Mn(NO3)2、Na OH和H2O2为原料,采用水热技术制备了Na型层状氧化锰(Na-Mn O2)。通过离子交换反应对NaMn O2进行了剥离,得到了氧化锰纳米层胶体分散液。将氧化锰纳米层分散液冷冻干燥后得到了氧化锰重组物(ERMn O2)。通过XRD、SEM和AFM对制备试样进行了分析表征。电化学测试结果表明,在1.0 mol·L-1Na2SO4水溶液中,当电流密度为0.25 A·g-1时,ERMn O2的质量比电容高达117 F·g-1远远高于其前驱物Na-Mn O2的比电容(79 F·g-1),并且表现出相似的循环稳定性。     

The Surge of Metal–Organic-Framework (MOFs)-Based Electrodes as Key Elements in Electrochemically Driven Processes for the Environment

Metal–organic-frameworks (MOFs) are emerging materials used in the environmental electrochemistry community for Faradaic and non-Faradaic water remediation technologies. It has been concluded that MOF-based materials show improvement in performance compared to traditional (non-)faradaic materials. In particular, this review outlines MOF synthesis and their application in the fields of electron- and photoelectron-Fenton degradation reactions, photoelectrocatalytic degradations, and capacitive deionization physical separations. This work overviews the main electrode materials used for the different environmental remediation processes, discusses the main performance enhancements achieved via the utilization of MOFs compared to traditional materials, and provides perspective and insights for the further development of the utilization of MOF-derived materials in electrified water treatment.     

磺化石墨烯/活性炭复合电极的制备及其不对称电容器脱盐

在还原剂NaBH₄存在下, 采用对氨基苯磺酸重氮盐与氧化石墨(GO)表面共价键合制备磺化石墨烯(GP-SO₃H). 傅里叶变换红外光谱(FTIR)证明磺酸基团在石墨烯表面接枝. 采用扫描电子显微镜(SEM)研究了磺化石墨烯的表面形貌. 以磺化石墨烯为添加剂, 制备了磺化石墨烯/活性炭(GP-SO₃H/AC)复合电极. 循环伏安及阻抗分析结果表明, 该复合电极的电容特性及导电性有明显改善. 以活性炭电极为对电极组装了不对称电容器(GP-SO₃H/AC|AC), 研究了该不对称电容器的电化学脱盐性能. 与对称电容器(AC|AC)相比, 不对称电容器中由于电极内磺酸基团对反离子的屏蔽作用, 电容器的电流效率达到89.4%以上, 脱盐量提高2.4倍, 单个循环脱盐量达到10.87 mg/g.     

薄层大面积自支撑碳纳米管电极材料的电容脱盐性能

以具有三维开放网络结构的烧结8 μm-Ni金属纤维(SMF-Ni)为基底, 通过乙烯催化化学气相沉积法在金属纤维表面生长碳纳米管(CNTs), 制备了以金属Ni纤维网络为集流极、CNTs为离子存储库, 尺度跨越宏观、介观和纳米的自支撑薄层大面积CNTs/SMF-Ni(CNTs质量分数为50%)复合电极材料. 用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、N₂吸附、脱附等温线和X射线衍射(XRD)等方法对电极材料进行了表征, 并考察了其作为电极对质量分数为0.01%的NaCl水溶液的电容脱盐性能. 自支撑CNTs/SMF-Ni复合电极材料由于具有优异的离子传导和表面电荷传递性能以及较大的介孔表面积, 在1.2 V的工作电压和5 mL/min的水溶液流速下, 对NaCl的电吸附容量和脱盐率分别达159 μmol/g CNTs和57%. 用H₂O₂对CNTs/SMF-Ni电极材料进行氧化处理后, CNTs表面含氧基团的大量增加增大了材料的亲水性, 从而进一步提升了该复合材料的电容脱盐性能.     

气压对于低气压双频容性耦合Ar/O2 等离子体放电特性影响的研究

 研究了气压对双射频氩氧混合等离子体电子温度和电子密度的影响。在13.56MHz低频功率和94.92MHz高频功率固定为60W和氩氧气体比为1:9的情况下,利用发射光谱法分析了气压不同时氩氧混合等离子体的放电光谱中的特征谱线的变化规律。使用一维质点网格法(PIC-MC)静电模型计算了电子温度和电子密度。结果表明：电子温度随着气压的增加先降低后升高,与实验结果趋势相吻合;电子密度随着气压的增加先增大后减小。     

Optimization of a Direct Sample Insertion Into a Stabilized Capacitive Plasma for Optical Emission Spectrometry (SCP-OES)

 A new sample insertion device for the stabilized capacitive plasma (SCP) has been developed, which enables it to analyze dry residues of micro amounts of liquid samples. Insertion was applied into an SCP as plasma source because of its good stability and excitation properties as well as its low instrument and operation costs. The plasma is sustained at a frequency of 27.12 MHz and an RF power of 150 W. For analysis the liquid samples are positioned at the tip of a quartz rod with the aid of a μL syringe. Then the sample is dried and the sampling rod inserted into the plasma. After optimization of the carrier gas flow (5 L/h) and the sample volume (20 μL) the detection limit for Pb with Ar as plasma gas is 200 pg. By further improving the guidance of the insertion detection limits for Pb, Cu, Cd and Mg in the 1 to 30 ng/mL range or 20 to 600 pg range absolute were obtained. It was found that the detection limits in the case of He are better than those obtained with Ar. The matrix interferences caused by changes in the concentration of the easily ionizable element Na were found to be below 10% for Na concentrations of up to 0.45 μg/mL. Ethanol concentrations of up to 14% in the analyte solutions did not cause any interferences. Received December 17, 1998. Revision June 4, 1999.     

一种基于容栅编码器测量炮塔高精度动态转角的方法

容栅编码器是在传统容栅技术上发展起来的新型传感技术,针对目前炮塔相对地盘转角的高精度测试需求,提出了一种基于容栅编码器测量高精度动态转角的方法。结合炮塔环境,设计了容栅测角装置的安装方式,分析了测角装置的工作原理,通过机械结构设计和容栅编码器后续的电路设计,提高了其工作的稳定性与可靠性。对测角装置分别进行了实验室角度标定与某靶场实地试验,结果表明:该测角系统能够满足实际需求,具有断电保护、通电位置识别及零位记忆等功能,测试精度达60。