Behaviour of Hydrogen in Nano-transition Metals

Nanocrystalline transition metals were prepared with Ar+H2 arc plasma method. The hydrogenmust be used during preparation to get a special nanrvparticles. The hydrogen plays an importantrole in the structure and state of nanocrystalline transition metals. The state of hydrogen andthe change of the nanocrystalline metal structure caused by hydrogen are called the behaviour ofhydrogen in nano-transition metals which includes the ability and function of storing hydrogenin the metals.     

Hydrogen Degradation of High-Strength Weldable Steels in Seawater

Hydrogen degradation of high-strength weldable steels was evaluated under monotonic static tensile loading in seawater at room temperature. Two types of quenched and tempered steels and their submerged-arc welded and shielded-metal-arc welded joints were examined. The slow-strain-rate tests were carried out on cylindrical smooth specimens in air and in artificial seawater. The tests in seawater were performed under cathodic polarization for various current densities. The relative values of fracture energy, time to failure, elongation, reduction in area, and tensile strength were used as measures of hydrogen degradation. The permeation of hydrogen through the base metal, the heat-affected zone, and the weld metal were analyzed by using the conventional Devanathan-Stachurski method. The hydrogen diffusivity and the content of diffusible hydrogen were established. The observed decrease in the relative values of the degradation parameters with the increase in the current density exhibits a certain minimum. The loss of plasticity was as high as 70–90% for the base metals and welded joints. The subsequent increase in the current density does not cause higher degradation. Good correlation was obtained between the relative parameters of degradation (except tensile strength) and the concentration of diffusible hydrogen.__________Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 6, pp. 101–104, November–December, 2004.     

A New Analysis of Hydrogen Diffusion in Metals with Trapping

A new model of hydrogen diffusion in metalshas been developed,it is more efficient todescribe the hydrogen diffusion with trappingin metals.In the model newly developed an impli-cit dependence on time of hydrogen diffusioncoefficient in metals with trapping was firstlybuilt and it is shown that hydrogen diffusioncoefficient will be different at different posi-tions in a dynamic process of hydrogen diffusionin a metal.Numerical solutions of the present modelwere obtained by finite difference method.Bychanging the parameters in the model the diffusionof hydrogen in a metal and the effect of trappingwere described and discussed.And the comparisonbetween the well known McNabb and Foster's modeland the present model was also made.     

Influence of Cyclic Preloading on the Hydrogen Degradation of Materials

We present the results of numerical analysis of the influence of the mode of preliminary cyclic loading on hydrogen-induced crack growth in high-strength steel with regard for the stress-strain state and diffusion of hydrogen. The elastoplastic stress-strain state at the crack tip under cyclic loading followed by monotonic loading is simulated for the case of high strains. The diffusion of hydrogen at the crack tip is modeled by taking into account the evolution of the stress-strain state from postcyclic compression to tension in the course of hydrogenation. It is shown that the accumulation of hydrogen in the process zone depends on the distribution of residual stresses induced by cyclic preloading.     

Carbon-based Electrocatalysts for Hydrogen Evolution Reaction Modulated by Embedded Metals

正Development of effective technologies for clean and sustainable hydrogen energy has been attracting great attention lately,as hydrogen is hailed as a promising energy source to reduce our dependence on fossil fuels and benefit the environment by reducing the emissions of greenhouse and other toxic gases.Toward this end,an effective and promising approach is based on the electrolysis of water for     

Analysis of Hydrogen Diffusion in Metals with Trapping under Local Equilibrium Assumption

The assumption of the local equilibrium ofhydrogen distribution in metals[1]was used in themodel formerly developed[2]to describe the diffu-sion of hydrogen in metals.From the assumption adirect relationship between the hydrogen diffusivityand the hydrogen concentration in metals is estab-lished asD=D_o/{1+N_x(k/p)/[1+C(k/p)]}The comparison between the two results drawnfrom the assumption of equilibrium and the dynam-ics of hydrogen trapping[3]was also presented.Thecomputation results well explained the scatteringphenomenon existed in hydrogen diffusion data andsuggested that the experimental conditions shouldbe identical for the study of hydrogen permeation inmetals.     

The Effect of Hydrogen on Fatigue Properties of Metals used for Fuel Cell System

The effect of hydrogen on the fatigue properties of alloys which are used in fuel cell (FC) systems has been investigated. In a typical FC system, various alloys are used in hydrogen environments and are subjected to cyclic loading due to pressurization, mechanical vibrations, etc. The materials investigated were three austenitic stainless steels (SUS304, SUS316 and SUS316L), one ferritic stainless steel (SUS405), one martensitic stainless steel (0.7C-13Cr), a Cr-Mo martensitic steel (SCM435) and two annealed medium-carbon steels (0.47 and 0.45%C). In order to simulate the pick-up of hydrogen in service, the specimens were charged with hydrogen. The fatigue crack growth behaviour of charged specimens of SUS304, SUS316, SUS316L and SUS405 was compared with that of specimens which had not been hydrogen-charged. The comparison showed that there was a degradation in fatigue crack growth resistance due to hydrogen in the case of SUS304 and SUS316 austenitic stainless steels. However, SUS316L and SUS405 showed little degradation due to hydrogen. A marked increase in the amount of martensitic transformation occurred in the hydrogen-charged SUS304 specimens compared to specimens without hydrogen charge. In case of SUS316L, little martensitic transformation occurred in either specimens with and without hydrogen charge. The results of S-N testing showed that in the case of the 0.7C–13Cr stainless steel and the Cr–Mo steel a marked decrease in fatigue resistance due to hydrogen occurred. In the case of the medium carbon steels hydrogen did not cause a reduction in fatigue behaviour. Examination of the slip band characteristics of a number of the alloys showed that slip was more localized in the case of hydrogen-charged specimens. Thus, it is presumed that a synergetic effect of hydrogen and martensitic structure enhances degradation of fatigue crack resistance.     

Propagation of Cracks in Metals under the Action of Hydrogen and Long-Term Static Loading

We propose a computational model of crack growth caused by the action of hydrogen and long-term static loads. The model is based on the energy criterion of fracture of materials. As a result, we deduce the expression for the crack growth rate as a function of the load, size of the initial crack, and physicochemical and strength characteristics of the material. The theoretical curve reveals satisfactory agreement with the experimental data. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 29–33, May–June, 2005.     

Evaluation of Hydrogen Degradation of Water-Wall Pipes by the Surface-Layer Properties of Magnetite

We propose a simple procedure for the evaluation of the ability of magnetite to protect against the absorption of hydrogen based on measuring the degree of its adhesion to a metal and its permeability. The degree of adhesion was found as the fraction of the area of a part of the surface covered with a layer of magnetite relative to the total surface area of a sample cut out from a pipe and stretched by 20%. The permeability of the layer of magnetite was determined electrochemically according to the value of the stationary potential and the decrease in the corrosion current through the surface covered with magnetite as compared with pure steel. We determine the electrochemical parameters and adhesion of magnetite formed on the inner surfaces of various segments of the pipes of 15Mo3 and 10CrMo910 steels taken from two boilers and analyze the factors affecting the properties and structure of magnetite and, hence, the degree of hydrogenation of the pipes. The proposed method for the electrochemical evaluation of the quality of magnetite can be applied under field conditions for the estimation of the residual service life of the pipes and monitoring of the parameters of technological working media in the boilers affecting the quality of magnetite.     

飞机表面水基清洗剂对金属材料腐蚀及氢脆性能影响研究

研究了AHC-1及AHC-5两种飞机表面水基清洗剂对飞机表面典型金属材料的腐蚀性能及高强度钢氢脆性能的影响,探讨了应用缓蚀剂控制高强度钢氢脆的有效性以及用电化学极化法预测高强度钢在清洗剂中的氢脆倾向性.     

双元活性金属Ni/Al/石墨烯储氢复合材料的研究

通过还原氧化石墨烯法制得了片状石墨烯,并以片状石墨烯为载体,采用原位生成和自组装法结合高温还原工艺负载得到双元活性金属Ni/Al/石墨烯复合材料,分别表征了石墨烯的分子结构、微观形貌和比表面积,并系统研究了Ni/Al/石墨烯复合材料的物相组成、微观结构和储氢性能。结果表明,片状石墨烯具有石墨烯的典型特征,并可以清晰地观察到透明的片层石墨烯,其Brunauer-Emmett-Teller(BET)比表面积达到600m2/g以上。Ni/Al/石墨烯复合材料主要包含Ni、Al和C三相,其中石墨烯对Ni和Al颗粒形成了有效负载,使得Ni/Al/石墨烯复合材料具有较好的储氢性能和吸放氢稳定性,473K时,其最大储氢容量接近5.7%(质量分数)。该材料的释氢效率高达96%~97%(质量分数),且释氢温度低至380K,表现出良好的应用前景。     

Practical Applicability and Limitations of the Elastic Modulus Degradation Technique for Damage Measurements in Ductile Metals

Abstract: The use of damage models require a number of material parameters the identification of which should be made, when possible, based on direct measures of the damage that develops in the material. Among the possible experimental techniques to measure the occurrence of ductile damage in metals, the measure of the damage through the degradation of the material Young’s modulus has been indicated as one of the more effective technique and used by several authors. In this paper, this technique is critically reviewed highlighting the number of issues that may affect the measure of damage. In particular, the attention is focused in the case where damage process initiates at the onset necking and develops in the post‐necking regime where stress, strain and damage are no longer uniform in the gauged section. Since geometry variations alter the reference base length for both stress and strain definition, a procedure based on the use of finite element simulation is proposed in order to account for this effect on the measure of the stiffness loss. The procedure has been applied to two class of metals: a high strength steel and high purity copper.     

燃料电池汽车用加氢站有关问题探讨

作为地面加注系统的加氢站对于燃料电池汽车的发展有着积极的推动作用。简述了国内外加氢站的发展现状,针对我国加氢站建设中的关键问题和车载储罐的研制进行分析,对我国加氢站的自主研发和氢能利用有一定的参考价值。     

非贵金属Co5.47N/N-rGO助催化剂增强TiO2光催化制氢性能

高效稳定的光催化剂或助催化剂研究一直是光催化领域的重要课题之一。本研究以氧化石墨烯、氯化钴和2-甲基咪唑为前驱体, 结合液相法和氨气氮化法制备了负载Co_5.47N的氮掺杂还原氧化石墨烯(Co_5.47N/N-rGO), 其中Co_5.47N高度分散、晶粒尺寸为10~20 nm。Co_5.47N/N-rGO可以作为助催化剂有效地改善商业二氧化钛(P25)的光催化分解水制氢性能, 当其质量分数为25%时, 催化剂的制氢性能可以达到11.71 mmol·h ^-1·g ^-1, 相比于纯P25提升了90倍, 与负载贵金属Pt的性能相当(11.88 mmol·h ^-1·g ^-1), 并且具有良好的稳定性。本研究为高效非贵金属助催化剂的研制提供了新思路。     

Application of Hydrogen in the Production of Sintered Anisotropic Nanostructured Magnets from Alloys of Rare-Earth and Transition Metals

Materials Science - The main stages of the procedure of hydrogen treatment of ferromagnetic materials based on Nd2Fe14B, SmCo5, and Sm2Co17 compounds of rare-earth and transition metals aimed at...