辉光放电清洗效果的质谱分析

在辉光放电清洗的实验研究中, 应用质谱技术进行了出气分析,应用其结果对射频辉光放电清洗的效果进行评估.实验结果表明,质谱技术能准确地分析表面吸附气体的分压强,氦离子的轰击可去除以及置换出样品中的气体,氮气、氧气和油蒸气在辉光放电清洗后的出气量下降,有利于超高真空的获得和维持.     

射频驱动频率对托卡马克装置辉光放电清洗特性的影响

HL-2M装置初始放电阶段,分别采用2.1 MHz,13.56 MHz和40.68 MHz三种频率的射频电源开展了射频-直流辉光放电清洗实验,研究射频驱动频率对放电清洗特性的影响。预加载功率1500 W时,2.1 MHz放电的击穿气压为2.0×10^-1 Pa,13.56 MHz放电为5.6×10^-1 Pa;而40.68 MHz叠加直流偏压后在9.2×10^-1 Pa实现击穿。对三种频率辉光放电清洗实验过程中的残余气体成分进行监测,结果表明杂质产额由高到低为：2.1 MHz>40.68 MHz>13.56 MHz。由于低频放电具有较多的加热电子数,所以2.1 MHz放电的杂质产额最高。而虽然40.68 MHz放电的功率耦合效率最低,但由于具有高的等离子体密度,其杂质产额高于13.56 MHz。可见2.1 MHz的射频-直流辉光放电在HL-2M装置初始放电阶段具有最优的清洗特性。然而由于不同频率的功率耦合效率不同,同样会对清洗效率产生影响,因此下一步首先应解决阻抗匹配问题以提高耦合功率。     

HL-1M装置的真空运行与质谱诊断

通过对 HL- 1M装置真空运行模式、真空运行参数、氦辉光放电清洗和硅化壁处理手段等的规范化 ,显著地改善了装置的真空壁出气、本底杂质浓度、托卡马克放电杂质出气比和再循环 ,成功地实现了高参数放电、长脉冲放电和装置暴露大气后快速恢复放电 ,并成功地为演证低混杂电流驱动、离子回旋共振加热、电子回旋共振加热、中性束注入、弹丸注入和分子束注入实验和升级等离子体运行等提供了良好的真空壁条件。描述了 HL- 1M装置真空系统、壁出气和再循环控制、质谱诊断和程序脉冲送气等方面的主要实验成果 ,并为 HL- 2 A装置的真空系统研制和运行提供了有益的参考     

等离子体装置器壁的直流和高频辉光放电清洗

本文描述直流辉光放电、10兆周高频加直流辉光放电原理和实验方法。给出了几种工作气体(H_2,He,Ar,N_2和空气)在30升圆筒形真空室中进行直流辉光放电、直流加高频辉光放电时起辉和灭辉气压随外加电压变化实验结果。实验表明,对于几百伏外加电压下H_2,He,Ar气可在10~(-1)帕气压下起辉;可以维持到10~(-2)帕气压才灭辉。几百伏直流电压附加10兆周高频电源可使起辉气压和灭辉气压下降几倍。空气和氮气比氢更易起辉。对HT-6M托卡马克真空室进行了几十小时常温和100℃中温烘烤条件下辉光放电清洗效果比较,表明边烘烤边辉光放电对水的清洗作用更好。实验由四极质谱仪监测,并用真空传输装置将样品传送到俄歇谱仪中分析放电前后表面成分的变化。对放电有关问题进行了讨论。     

用氧化还原反应气体清洗不锈钢超高真空系统

对粒子加速器和储存环的超高真空系统，消除其表面污染的标准方法是化学清洗、真空炉焙烧、辉光放电清洗及原位烘烤真空系统，本文介绍一种可替代辉光放电的清洗方法；用一氧化氮反应气体进行清洗，它已被用于处理几种不锈钢制作的加速器真空室，用ＮＯ气体处理的效果与其它方法相比，优于普通化学清洗和真空炉焙烧，完全可以和辉光放电清洗相比较，却避免了溅射情况下可能引起的表面损伤。     

HL-2A装置直流辉光自动调节控制系统北大核心CSCD

直流辉光放电清洗的主要作用是去除HL-2A装置内的低Z杂质C、O,以及放电期间所产生的残余气体和杂质。介绍了直流辉光放电自动调节控制系统。在辉光放电过程中,实现了真空室工作气体气压和放电电压的自动调节和信号采集。本文描述了系统的设计原理,控制方案和系统实现后的具体应用效果。直流辉光放电系统的性能得到了提高,放电电流稳定性得到了显著提高,放电电压的控制精度改善为1%FS,系统从启动到稳定运行状态的时间小于40 s,HL-2A装置的清洗效率也明显获得改善。     

HL-2A装置直流辉光自动调节控制系统

直流辉光放电清洗的主要作用是去除HL-2A装置内的低Z杂质C、O,以及放电期间所产生的残余气体和杂质。介绍了直流辉光放电自动调节控制系统。在辉光放电过程中,实现了真空室工作气体气压和放电电压的自动调节和信号采集。本文描述了系统的设计原理,控制方案和系统实现后的具体应用效果。直流辉光放电系统的性能得到了提高,放电电流稳定性得到了显著提高,放电电压的控制精度改善为1%FS,系统从启动到稳定运行状态的时间小于40 s,HL-2A装置的清洗效率也明显获得改善。     

EAST等离子体放电真空室暴露大气后的真空恢复研究

洁净的壁条件和良好的真空环境是托克马克装置运行的基本条件,但是真空室暴露大气后会在器壁表面吸附大量的杂质,如何快速恢复良好的真空环境以及壁条件是关系到托克马克运行效率和成本的一个关键问题。本文深入分析了EAST 2015年夏季实验期间真空室两次暴露大气后的壁处理对真空条件的恢复,结果显示水汽是真空室暴露大气后的主要杂质成分,直流辉光和离子回旋放电清洗与第一壁200℃烘烤同时进行能够有效地恢复真空。研究结果还发现暴露大气前的第一壁涂层处理会增强杂质的吸附,需要更长时间的壁处理才能够恢复较好的真空条件。     

HT-6M装置中频放电清洗实验研究

本文介绍一种用400Hz中频放电清洗HT-6MTokamak装置真空器壁的实验研究。系统经过800min断续中频放电,P_(18)、P_(28)降低两个量级,器壁表面C和O的含量分别降低到26%和5.8%。实验对400Hz中频放电清洗和直流辉光放电清洗效果进行了比较,结果表明400Hz放电对于表面H_2O的清洗效率优先于直流辉光放电清洗。实验中亦探讨了器壁条件的改善对等离子体参数的影响。     

酸掺杂聚苯胺表面接枝丙烯酸的结构与性能

将化学氧化法制备的酸掺杂聚苯胺（ＰＡＮ）压制成片，直接或经过氩气辉光放电等离子体处理后，在溶液中以过硫酸氨为引发剂接枝共聚丙烯酸（ＡＡ）。考察了有关实验条件的诸因素对妆枝共聚的影响。并通过反射ＩＲ、ＳＥＭ和ＸＰＳ分析了拉枝表面的结构和形态。结果表明，在过硫酸氨的引发作用下，ＡＡ能在酸掺杂的ＰＡＮ表面发生接枝共聚反应，而经过氩气辉光放电处理后的而志电率则随之下降。ＳＥＭ照片显示ＰＡＮ表面接枝的ＡＡ呈     

不同处理方法下铁氧体出气性能的研究

为减少加速器束流快引出元件铁氧体材料真空出气量,对铁氧体材料进行真空除气、镀膜以及烘烤工艺处理。采用旁路切换法(SPP)测量不同处理条件下的出气率。结果表明,铁氧体材料经真空除气后镀TiN膜,在测试罩中经烘烤,冷却后充氮气测得的出气率最低。     

Co元素掺杂对CeO_2基固态电解质导电行为的影响

分别采用晶格固溶(Solid Solution,SS)和晶界择优偏聚(Grain Boundary Segregation,GBS)两种方式将Co元素添加至Gd掺杂的CeO_2粉末(GDC)内,研究两种添加方式对GDC电导行为的影响。首先采用共沉淀法制备10%Gd(摩尔分数,下同)掺杂的GDC粉末(10GDC),再分别通过以上两种方式将1%Co元素添加至10GDC粉末中,得到10GDC-1Co(SS)和10GDC-1Co(GBS)粉末样品。上述粉末样品中只含有CeO_2固溶体相,晶粒尺寸范围为10.1~12nm。将Co掺杂前后粉末样品在1000℃下烧结1h,分别得到10GDC,10GDC-1Co(SS)和10GDC-1Co(GBS)片状陶瓷样品。烧结后所有陶瓷样品中均只含有CeO_2固溶体相,晶粒尺寸范围为44.5~59.7nm。10GDC-1Co(SS)和10GDC-1Co(GBS)样品的电导率均高于10GDC样品的电导率,当测试温度低于430℃时,10GDC-1Co(GBS)样品的电导率高于10GDC-1Co(SS)样品;当测试温度高于430℃时,10GDC-1Co(SS)样品的电导率高于10GDC-1Co(GBS)样品。     

XPS and electrochemical impedance spectroscopy studies on effects of the porcelain firing process on surface and corrosion properties of two nickel–chromium dental alloys

The aim of this study was to evaluate the effects of a simulated porcelain firing process on the surface, corrosion behavior and cell culture response of two nickel–chromium (Ni–Cr) dental alloys. A Be-free alloy and a Be-containing alloy were tested. Before porcelain firing, as-cast specimens were examined for surface composition using X-ray photoelectron spectroscopy and metallurgical phases using X-ray diffraction. Corrosion behaviors were evaluated using electrochemical impedance spectroscopy. 3T3 fibroblasts were cultured and exposed indirectly to specimens. MTT assays were counted after 3 and 6 days. The cell culture mediums exposed to specimens were analyzed for metal ion release. After porcelain firing, similar specimens were examined for the same properties. In both as-cast and fired conditions, the Be-free Ni–Cr alloy showed significantly more resistance to corrosion than the Be-containing Ni–Cr alloy, which exhibited BeNi phase. After porcelain firing, the corrosion resistance of the Be-free Ni–Cr alloy decreased statistically, corresponding with evident decreases of Cr and Ni oxides on the alloy surface. Also, the alloy’s MTT assay decreased significantly corresponding with an obvious increase of Ni-ion release after the firing. For the Be-containing Ni–Cr alloy, the firing process led to increases of surface oxides and metallic Be, while its corrosion resistance and cell culture response were not significantly changed after porcelain firing. The results suggested that the corrosion resistance and biocompatibility of the Be-free Ni–Cr alloy decreased after porcelain firing, whereas the firing process had little effect on the same properties of the Be-containing Ni–Cr alloy.     

材料在真空环境下放气的测试技术研究

往真空材料放气率测试装置上对金属材料的放气特性进行了实验研究,实验采用的方法为静态升压法、固定流导法、双通道气路转换法。实验结果表明,测试装置的极限真空度为9．2×10^-9Pa,铜、铝合金2A12、304不锈钢三种材料半小时后的放气率分别为2．34×10^-8a·m^3·s^-1·cm^-2、1．83×10^-9Pa·m^3·s^-1·cm^-2、8．48×10^-11Pa·m^3·s^-1·cm^-2。利用四极质谱计测得装置的本底气体成分主要有H2、N2／CO、H2O和CO2,材料放出的气体成分主要有N2／CO、H2O。三种方法测试得到的铜金属材料的放气率随着温度的升高而小断增大。     

低温与真空条件下1Cr18Ni9Ti钢的疲劳行为

分别在室温大气、室温真空及低温真空几种环境条件下,对1Cr18Ni9Ti钢进行对称载荷拉-压疲劳试验,利用TEM观察疲劳断口附近的显微组织,研究了环境因素对疲劳性能的影响,并对影响的原因进行了分析和讨论.研究表明:1Cr18Ni9Ti钢在低温真空条件下疲劳性能显著提高;疲劳断口附近出现大量板条马氏体;真空与低温显著提高1Cr18Ni9Ti钢疲劳性能的原因与真空对裂纹表面的净化效应,以及低温促进疲劳裂纹前沿形成板条马氏体有关.     

Characterization of electrolyte films deposited by using RF magnetron sputtering a 20 mol% gadolinia-doped ceria target

20 mol% Gd-doped ceria (20GDC) electrolyte films on poly-crystalline Al₂O₃ substrates were prepared by radio frequency (RF) magnetron sputtering from a 20GDC oxide target, which was made by the processes of colloidal dispersion-pressure casting-sintering. Material characteristics of the 20GDC oxide target and the deposited films before and after annealed at 900 °C for 2 h were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and conductivity measurements. Crack-free and dense 20GDC electrolyte films were observed by the deposition conditions of 200 W (RF power). Homogeneity tests revealed the chemical compositions (Ce and Gd) were uniformly distributed through the bulk of the target and the deposited films. 20GDC film with a comparable conductivity of 1.00 × 10^− 3 S/cm at 650 °C is higher than that of bulk yttria-stabilized zirconia (YSZ), but smaller than that of bulk GDCs (10GDC and 20 GDC). Sputtered-GDC films in this study can be also suggested to be used as the electrolyte films for solid oxide fuel cells (SOFCs) systems as compared to the well-known YSZ.     

Influence of Lithium Oxide Addition on the Sintering Behavior and Electrical Conductivity of Gadolinia Doped Ceria

Ceria-based electrolytes have been widely researched in intermediate-temperature solid oxide fuel cell (SOFC), which might be operated at 500-600?C. Sintering behavior with lithium oxide as sintering additive and electrical conductivity of gadolinia doped ceria (Gd0.1Ce0.9O2δ, GDC10) electrolyte was studied in this paper by X-ray di?raction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). As the results, the fully dense GDC10 electrolytes are obtained at a low temperature of 800?C with 2.5 mol% Li2O as sintering additive (called 5LiGDC800). During sintering process, lithium oxides adsorbed by around GDC10 surface help to sinter at 800?C and are kept at the grain boundary of GDC10 in the end. The fine grains of 100-400 nm and high electrical conductivity of 0.014 S/cm at 6000C in 5LiGDC800 were achieved, which contributed to the lower sintering temperature and enhanced grain boundary conductivity, respectively. Lithium, staying at grain boundary, reduces the depletion of oxygen vacancies in the space charge layers and increases the oxygen vacancy concentration in the grain boundary, which leads to improve the total electrical conductivity of 5LiGDC800.     

Remediation of metal-contaminated aqueous systems by electrochemical peroxidation: an experimental investigation

An innovative technology, electrochemical peroxidation (ECP), was investigated for remediation of mixed metal-contaminated aqueous systems by application of direct electric current to steel electrodes and of dilute H(2)O(2) solution to promote Fenton's reactions, forming sparingly soluble solid hydrous ferric oxides (HFO). Bench scale experiments evaluated the sorption and distribution of As, Be, Cd, Cr, Cs, Cu, Li, Ni, Pb, Se, V, and Zn among the soluble and solid state HFO formed as part of the ECP process. The effects of pH, hydrogen peroxide concentrations and electric current process times on the efficiency of metal removal were studied. The potential of this technology was demonstrated by effective removal at pH 3.5-4.6 and within 3 min of 0.25 A dc+100 mg H(2)O(2) l(-1), of As, Cr, Pb, Se and V with complete removal of As and Cr, >95.0%. On increasing the pH of the solution to 6.0, the retention of Be and Cu by HFO increased from 0.9-1.9% at pH 3.5 to 76.8-80.7% at pH 6.0 while concentrations of other metals, such as Pb, decreased due to precipitation of Pb hydroxy-complexes. Experiments in the absence of H(2)O(2) revealed that metals were adsorbed by HFO with the same order of affinity, As>Cr>Se>V>Be, as in the presence of H(2)O(2), but, with the exception of Cr, to a lesser extent. H(2)O(2) used in the ECP process was fundamental to increase the adsorption capacity of HFO for As, from 79.2 to 99.2%, due to the oxidation of As(III) to As(V), which has a stronger affinity for HFO. The reduced adsorption may be related to the formation of poorly ordered crystalline akaganeite, which has a lower surface area than ferrihydrite formed when H(2)O(2) was used. The optimal operating conditions were pH<6.0, an H(2)O(2) concentration of 100 mg l(-1) and a current process time not exceeding 3 min.     

低温绝热气瓶真空寿命模拟试验研究

提出了对绝热气瓶真空夹层逐次充入模拟气体进行绝热气瓶漏气和材料放气的真空寿命模拟试验评价方法。试验实例表明:低温绝热气瓶静态蒸发率在低温下夹层压力>5×10^-2Pa后迅速上升,即5×10^-2Pa可视为夹层真空寿命终结的拐点(或阈值)。5A分子筛在液氮温度下对氮具有巨大的吸附潜力,对氢表现出弱的吸附能力。真空绝热夹层的材料放气对真空寿命的影响远远大于漏气的影响,提高绝热气瓶真空寿命的技术途径是减小夹层材料的放气率和改善内置吸附剂对氢的吸附能力。模拟试验能直观、实际、准确地研究漏气和放气对真空寿命诸因素的影响,为确定切合实际的设计参数和工艺提供参考数据,进而推广用于各类真空绝热型低温容器的真空寿命评价和应用。     

真空度对MBE GaAs光阴极激活结果的影响

采用分子束外延(MBE)技术生长的GaAs光阴极材料,按照常规方法进行高-低温两步激活时,总是出现低温灵敏度比高温低的反常现象.研究中,当激活时的系统真空度从1×10~(-7)Pa提升到1×10~(-8)Pa时,发现结果能够重新出现低温灵敏度比高温灵敏度高30%的预期规律.此外,在系统真空度为10~(-7)Pa条件下,由于变掺杂材料的表面掺杂浓度较低,其出现光电流时的首次进Cs时间也较均匀掺杂材料长,而在真空度为约10~(-9)Pa条件下,这一情况也不再明显.初步分析造成该现象的原因,是与MBE材料的掺杂元素及其低温处理特性对真空度比较敏感有关.MBE阴极激活结果受系统真空度条件影响较大,因此对MBE变掺杂光阴极的制备工艺应随系统真空度条件不同而调整.