The influence of deuterium exposures on subsequent outgassing rate of an UHV system

The accuracy of results in experiments where a well-processed UHV system is exposed to hydrogen depends on the hydrogen absorption rate and kinetics of subsequent spontaneous release from the system itself. In experiments to date, the sensitivity required to detect very low rates has been achieved only when tritium has been used as a tracer gas. Unfortunately, tritiated water from the surface prevails among released gas species which is not expected for well-outgassed surfaces. In the present studies, UHV system behaviour at 303 K during three deuterium exposures of duration 92 and 72 h at an initial pressure of 1 mbar was explored. The rate of decrease of pressure was constant during the whole of these periods as monitored by non-ionizing vacuum gauges. It corresponded to an effective sticking probability of the order of 1×10^-12 and resulted in absorption of 5×10¹⁴ D atoms/cm². The release kinetics were observed for several days starting immediately after deuterium had been pumped from the system. Initially, the deuterium release rate exceeded the background hydrogen outgassing by more than three orders of magnitude. These results demonstrate that extremely high sensitivity for deuterium absorption and release can be achieved with a precise pressure measuring technique otherwise attributed exclusively to tritium scintillation methods.     

Gas absorption and outgassing of metals

The solution of the diffusion equation is taken as a foundation of the theory of gas-metal interaction in high vacuum. The boundary conditions are formulated from the analysis of the gas balance equations on a metal surface and in a gas volume. The boundary conditions are generally non-linear but in some important cases linearization is permissible. In this way it is possible to obtain analytical expressions for the instantaneous gas flow on electron- and photon-induced desorption, low temperature thermal desorption and gettering at a constant pressure. By means of these formulae one can generalize the experimental data of various authors and calculate the kinetics of such processes as the outgassing of an electron collector, the gas desorption by synchrotron radiation in a vacuum chamber of electron or positron colliding-beam storage-rings, the degassing of an ultra-high vacuum system, the gas sorption by barium and titanium, etc.     

An overview of methods to suppress hydrogen outgassing rate from austenitic stainless steel with reference to UHV and EXV

The present review of methods reveals some new theoretical aspects and findings concerning suppression of the hydrogen outgassing rate q_out from austenitic stainless steels in relation to the ultrahigh vacuum and extreme high vacuum.The review includes work on thermal treatment and modelling, permeation rate and the role of surfaces, diffusion barriers and coatings.     

一种可用于材料在低温环境下放气的测试系统

总结了材料放气测试的各种方法：压力上升率法、收集法、称重法和气体流量法。开发了一种基于气体流量法的新法,不仅可以用于常温和较高温度,而且可以用于材料在低温环境下放气的测试,最低测试温度可以达到100K左右。此系统方便实用,具备较高的测试精度。     

格栅式摩擦阻尼器的试验研究与数值模拟

位移型阻尼器具有较小的屈服后刚度,在大震下会出现刚度的突然减小,出现明显的损伤集中现象,造成修复成本较高。提出了一种由多种耗能单元组成的新型格栅式摩擦阻尼器,该装置具有屈服后硬化刚度、双重耗能机制、多节点耗能等特点。对耗能单元设计了含6组试件的系数比测定试验和2组试件的耗能单元拟静力试验,并建立了数值模型。系数比测定试验表明:与黄铜摩擦材料相比,无石棉树脂摩擦材料性能更稳定、摩擦出力大;无石棉树脂材料系数比逐渐减小至恒定值,而黄铜材料系数比先增后降至恒定值。通过耗能单元的拟静力试验发现,平动摩擦和转动摩擦行为协同工作良好,耗能单元具有预期的屈服后刚度硬化行为,表现了多阶段耗能特性;其出力中各组分比例可通过控制试件设计参数(如截面尺寸、杆件数量和施加扭矩)进行调整。最后建立了实体单元数值模型,表明数值模拟结果与试验值吻合较好。     

An experimental approach to estimate damage and remaining life of metals under uniaxial fatigue loading

An experimental procedure to estimate damage evolution and remaining fatigue life of metals associated with fatigue loading is presented. Experimental phase involves uniaxial tension–compression fatigue tests performed with solid API 5L X52 and tubular carbon steel 1018 specimens subjected to both constant and variable amplitude loading. A correlation between the so-called damage parameter and the thermal response of a material at different damage levels is proposed. Results demonstrate that the correlation can estimate damage evolution with reasonable accuracy in both constant and variable amplitude fatigue processes. It is shown that under the conditions tested the evolution of damage parameter with respect to the normalized fatigue life is independent of the load amplitude, load ratio, loading sequence, material properties, and specimen geometry. The proposed correlation and the relationship between the damage parameter and the normalized fatigue life are employed to develop a non-destructive method to predict the remaining fatigue life of metallic specimens with prior fatigue damage. The method is applied to both constant and variable amplitude loading and the predicted results are found to be in good agreement with those obtained from the experiments.     

Effects of grain refinement and strength on friction and damage evolution under repeated sliding contact in nanostructured metals

The early stage sliding contact fatigue behavior of nanocrystalline materials, with average and total range of grain sizes well below 100 nm, was studied. The evolution of friction and damage during repeated sliding contact in the nanocrystalline metals and alloys was systematically compared and contrasted with that in ultrafine-crystalline and microcrystalline materials so as to develop a broad perspective on the effects of grain size on sliding contact fatigue. Some critical experiments were performed to separate the effects of material strength and grain size on friction and damage evolution. Over the range of materials examined, strength rather than grain size appeared to dominate the steady-state friction coefficient and damage accumulation, each diminishing with substantial increases in material strength.     

HIRFL-CSR超高真空系统

中国科学院近代物理研究所承担的国家“九·五”重大科学工程项目兰州重离子加速器冷却储存环(HIRFL- CSR)目前正处在建设阶段。为减少真空系统中残余气体分子对粒子束造成的损失 ,要求系统平均真空度达到 6× 10 - 9Pa。在研制和建造过程中 ,我们做了大量的工作以获得所要求的真空度。本文将介绍其中样机的研制 ,超高真空实验室的建立和各项实验工作 ,大型真空处理设备的建造 ,真空烘烤系统研制等。同时对目前的工程进展也做了简要介绍     

An analytical approach for calculating vacuum properties of outgassing tubing systems

A method has been investigated to calculate vacuum properties, such as flow conductance and pressure drop, for complex tubing systems, taking into account the outgassing of the tube walls. The procedure is based on the determination of the pressure drop, Δp_i, of each tube element, starting at the chamber with a given mass flow rate, q_b1. The flow conductance, G, of the system follows from the overall pressure drop, ΔpΣⁿ_i Δp_i as $\text{G\&z.dbnd;q}{}_{\mathrm{b1}}\text{/Δp}$. The results are applied to analysing a vacuum system of the First Spacelab Payload.     

A study of the effects of annealing and outgassing on hydrogenated amorphous silicon

Annealing and outgassing of thin films of hydrogenated amorphous silicon (a-Si:H) are shown to produce major structural changes in the material. Outgassing can occur in three stages with thresholds at 350°C, 450°C and 575°C corresponding to conversion of SiH₃ groups to SiH₂ and SiH; conversion of SiH₂ groups to Si and SiH; and conversion of SiH to Si respectively. Heating to 575°C also appears to remove most of the hydrogen from vacancies and defects in the material. Such heat treatments could be useful for improving the stability of thin film a-Si:H devices.     

Effect of certain hardening treatments on friction and wear of metals

A new method of surface hardening of friction pair components is described. The method consists in the deposition on metal surfaces of finely dispersed composite structures obtained as a result of the formation of liquid eutectics at the metal-hardening phase interface followed by rapid cooling. Tests in vacuum showed that most wear resistant are finely dispersed boride coatings obtained by water quenching liquid eutectics.     

The role of electrical phenomena in friction and cutting of metals

A study is presented of the effect of thermoelectric and electrical phenomena on the process of friction interaction in a three-phase boundary system tool-lubricant-workpiece.     

双生长室超高真空化学气相淀积系统的研制

本文介绍了中国科学院半导体研究所的双生长室超高真空化学气相淀积系统的工作原理、技术参数、结构、性能及特点。该系统具有双生长室、引入准分子激光和多态源等主要优点,是IV族半导体材料生长和研究的强有力工具。     

Factors determining the probability of seizure and oxidation of metals in friction

Based on modern concepts of structural imperfections in crystalline solids, an analysis of the seizing and oxidation of metals was carried out. It was shown that, viewed from this standpoint, both seizing and intense oxidation of metals in friction are based on the activation of contacting surfaces, the extent of which is determined by the degree of interaction between these surfaces. A change-over from one of these processes to the other (seizing to oxidation or vice versa) may take place as a result of only quantitative changes in one of the parameters characterizing the working conditions of a friction pair.     

Investigation of the friction and wear of certain metals in liquid nitrogen

The friction and wear of Fe, Mo, Ti, Al, and a nitrided 38KhMYuA steel in liquid nitrogen were studied and experimental data on the behavior of these metals in low-temperature media were obtained. The effect of the nature of the metal, normal pressure and test duration on the friction coefficients and linear wear was determined.Thanks are due to Corresponding Member AS UkrSSR G. V. Samsonov for his valuable assistance in interpreting the results of this investigation.     

An experimental study on subsequent yield surfaces for metals

In this paper some experimental results on the yield surfaces of metals are presented. The material tested is an aluminium alloy and the experimental technique consists in cutting out flat specimens from a prestrained sheet material. These specimens are then subjected to uniaxial tests. Two specific problems are examined: firstly, the offset influence on the shape of the subsequent yield surfaces, which are then checked for “corners” in the direction of the prestraining path.