金属中氢的分析技术进展

介绍了金属中氢的存在状态及其对材料的影响。总结了近年来金属中氢的检测方法及目前实验室常用的测氢设备以及分析方法。除常规取样、实验室检测方法外,由于工艺的要求,在线检测手段发展越来越快。钢液、铝液中氢的在线测量技术越来越多地应用到实际生产中,并已经研制出可在线同时检测钢液中氧、氮、氢3种气体元素的检测设备。熔敷金属中氢的检测已经逐渐由热导法替代了传统的水银法和甘油法。     

低温球磨制备Mg-4%Ni-1%NiO储氢材料及其性能

采用低温球磨技术制备了Mg-4%Ni-1%NiO储氢材料,主要研究低温球磨时间对材料形貌结构以及储氢性能的影响.采用扫描电子显微镜(SEM)和X射线衍射(XRD)分析材料的形貌和相组成,采用压力-组成-温度(P-C-T)设备研究材料的储氢性能.结果表明:分别经过2、4和7 h球磨后,材料的相组成没有发生明显改变,只有极少量的Mg₂Ni合金相生成.随着球磨时间的延长,材料的平均粒度逐渐下降,作为催化剂的Ni、NiO相逐渐揉进基体内部.伴随着上述变化,材料的活化性能、吸氢性能逐渐提高,球磨到7 h后材料仅需活化1次即可达到最大吸放氢速率,初始吸氢温度降为60℃,在4.0 MPa初始氢压和200℃下吸氢量为6.4%(质量分数),60s即可完成饱和吸氢量的80%,10min内完成饱和吸氢量的90%;材料的放氢性能则在球磨4 h后已经基本保持不变,0.1MPa下初始放氢温度为310℃,在350℃、0.1MPa下材料可在500s内释放饱和储氢量的80%.

     

脉冲加热-红外吸收热导法同时测定钢铁材料中氧和氢

针对钢铁材料中氧和氢的同时测定, 提出了一种新型的气路结构和检测原理, 解决了传统技术中转化效率及后续吸收脱除问题, 并通过研究分析功率、助熔剂等对氧和氢释放的影响, 确定了分析功率2 250 W、加入锡片作助熔剂的最佳分析条件。选用合适的钢中氧和氢标准样品, 建立了方法的校准曲线, 实现了钢铁材料中氧和氢的脉冲加热-红外吸收热导法测定。利用对空白的标准偏差计算得氧和氢的检出限分别为0.000 051%、0.000 024%, 氧和氢的分析范围分别为0.000 05%~0.1%、0.000 03%~0.05%。实验方法避免了中间处理阶段对测定结果的准确性与稳定性的影响, 用于实际样品的测定结果与对照值一致, 完全满足钢铁材料氧和氢快速、准确的分析要求。     

The influence of stirring method on hydrogen removal during ladle treatment

A mathematical model based on fundamental transport equations for vacuum degassing in an Asea‐SKF ladle furnace was developed earlier and predicted hydrogen values from the model were found to agree well with experimental measurements from plant trials. In the present study, the mathematical model was used to predict the hydrogen removal for four different stirring methods: 1–2) combined gas and induction stirring with the inductive stirrer working upwards or downwards and 3–4) gas stirring with two different locations for two porous plugs. Plant data was used as input to the calculations. The hydrogen calculation was validated by simulation of an actual heat and comparison with measured data. After 44 minutes of stirring the predicted and measured hydrogen contents were 1.6 and 1.8 ppm, respectively. This agreement was considered satisfactory and the model was then used to study the effect of different stirring methods on hydrogen refining. A change in the stirring method was found to affect the hydrogen refining. Combined gas and induction stirring using downward stirring was found to result in the lowest final hydrogen content in the steel as it rendered the most favourable kinetic conditions for hydrogen refining.     

氧化钨氢还原动力学的研究进展

超细钨粉是目前制备多种硬质合金和结构材料的重要原料,其主要制备方法为氢还原法.在对大量文献资料进行查阅及分析的基础上,综述了氧化钨氢还原动力学的研究现状,包括氧化钨氢还原的基本原理、不同动力学条件下的还原历程以及物相转换.介绍了国内外学者在不同钨氧化物的氢还原过程中,通过改变动力学参数对产物钨粉的粒度、形貌、结构和性能的影响,以及实际工业生产的现状和存在的问题.重点介绍了目前氢还原动力学的几种模型及其方程,并对可能适用于氧化钨氢还原动力学研究的动力学模型进行了展望.      

降低重轨钢的氢含量

研究重轨钢中氢的来源及控制手段.分析表明,钢水增氢主要是外加材料,尤其是增碳剂带入的水分所引起的.通过控制各工序加入材料的水分,有利于减少重轨钢中的氢含量.通过VD真空脱气处理,能有效地脱去钢液中的氢.     

脉冲熔融-飞行时间质谱法同时测定钨和钽中氧氮氢

在对仪器测定条件优化的基础上, 以0.15 g镍箔作助熔剂, 采用自行设计的由套坩埚和内坩埚组成的新型石墨坩埚, 建立了同时测定难熔金属钨、钽中氧、氮和氢的脉冲熔融-飞行时间质谱法。选择与钨、钽产品中氧和氮含量较匹配的钢标准样品建立测定氧和氮的校准曲线, 和与钨、钽产品中氢含量较匹配的钛标准样品建立测定氢的校准曲线。方法中氧、氮、氢的检出限分别为0.5 μg、0.5 μg、0.4 μg, 测定下限分别为1.7 μg、1.7 μg、1.2 μg。方法用于钨条和钽片样品中氧、氮、氢的测定, 对于钨条样品氧、氮、氢测定结果的相对标准偏差分别为5.5%、11.5%、8.9%(n=11), 对于钽片样品氧、氮、氢测定结果的相对标准偏差分别为12%、24%、22%(n=11), 并且氧、氢和氮的测定结果分别与红外吸收法和热导法基本一致。     

Mechanisms of hydrogen embrittlement and fracture of nanocrystalline materials

The physical mechanisms of hydrogen embrittlement and fracture of nanocrystalline materials due to the molecular hydrogen pressure in cavities and the formation of hydride phases are proposed and justified mathematically.     

基于惰气熔融-红外法的镍助熔剂法和锡浴法测定钛及钛合金中氢的方法对比

氢含量对钛及钛合金的组织形貌与物理机械性能有显著影响。分别采用镍(简称镍助熔剂法)与锡(简称锡浴法)为助熔剂,用惰气熔融-红外法对钛及钛合金中氢含量进行测定,从氢释放率、空白值、校准方式、检出限、定量限、精密度、正确度等方面对这两种方法进行了对比。结果表明,锡浴法相对于镍助熔剂法氢释放率高且空白值低,两种方法在测定过程中不能使用同一校准曲线。锡浴法在3.8 μg/g≤w(H)≤200 μg/g范围内有良好的线性关系,相关系数大于0.999;镍助熔剂法宜采取分段校准方式,在8.2 μg/g≤w(H)<90 μg/g和90 μg/g≤w(H)≤200 μg/g分析范围内分别建立校准曲线,各分段校准曲线的相关系数均不小于0.999。锡浴法测定氢的检出限和定量限(分别为1.2 μg/g和3.8 μg/g)相对镍助熔剂法均较低(分别为2.5 μg/g和8.2 μg/g)。采用镍助熔剂法和锡浴法对钛合金标准样品中氢含量平行测定6次,结果表明,两种方法测定结果与认定值均保持一致。将这两种方法应用于样品分析,镍助熔剂法测定结果的相对标准偏差(RSD,n=6)为1.9%~8.6%,锡浴法为1.6%~4.3%。采用镍助熔剂法和锡浴法对多种牌号的钛及钛合金中氢含量分别进行单次测量,用其中一种分析方法精密度参数中的重复性限r和再现性限R检验两种分析方法测量结果的一致性,结果表明,镍助熔剂法的测定结果与锡浴法具有良好的一致性。锡浴法的氢释放率、空白值、检出限、定量限、精密度均优于镍助熔剂法,适用于单独测定钛及钛合金中氢含量,常作为标准方法使用。因镍助熔剂法测定条件可用于测定氧和氮,适用于钛及钛合金中氧、氮、氢的同时测定。     

晶粒尺寸对高锰奥氏体TWIP钢氢脆行为的影响

主要研究了晶粒尺寸对Fe- 17Mn- 1Al- 0.6C TWIP钢的氢脆行为的影响。原始材料经过不同的热处理制度,得到晶粒尺寸为17和45μm的材料。通过慢拉伸试验研究氢质量分数在0～0.001%材料的氢脆敏感性。试验结果表明,充氢后的试验材料比未充氢试验材料易发生氢脆,充氢后的试验材料断裂强度和断裂应变均降低。随着晶粒尺寸的增大,试验材料的氢脆敏感性增强。在氢质量分数为0.001%,晶粒尺寸增加到45μm时,应变损失率为17%,随着晶粒尺寸的增大,氢脆敏感性增加的原因是晶粒尺寸较大的材料孪晶较早出现,孪晶密度较大,同时单位晶界氢质量分数增加。     

钢中氧氮氢同时测定方法中氢空白值的控制

针对钢中氧、氮、氢同时测定方法中氢测定结果较低温测氢法异常偏高的问题,进行了原因分析并提出了解决的办法。通过比较氢含量极低钢样的两种测定方法的氢结果,得出氧、氮、氢同时测定方法中石墨坩埚的氢杂质是造成上述问题的主要原因。为降低石墨坩埚中的氢杂质,实验提出将坩埚于450～480 ℃加热处理48 h用于日常分析,分析系统的氢空白值从0.69 μg/g 降低至0.12 μg/g,同时提高了方法的精密度,11次空白值的标准偏差为0.06 μg/g。按实验提出的方法对氢空白进行控制后,钢中氧、氮、氢同时测定方法中氢的分析结果与低温单独测氢法一致;钢中1.2～6.8 μg/g的氢测定结果,相对标准偏差(RSD,n=5)在1.0%～12.2%,满足炼钢炉前分析的要求。     

Effect of the chemical composition and the structural and phases states of materials on hydrogen retention

The results of investigation of the effect of chemical composition and structural and phase states of reactor steels and vanadium alloys on their capture and retention of hydrogen introduced into the materials in various ways are presented. It is shown that, in the case of identical conditions of hydrogen introduction, the amount of hydrogen captured by austenitic steels is substantially higher than that captured by ferritic/ martensitic steels. At the same time, the EP450 ODS ferritic/martensitic steel dispersion-strengthened with nanosized yttrium oxide particles retains a substantially higher amount of hydrogen as compared to that retained in the EP450 matrix steel. The alloying of vanadium with tungsten, zirconium, and titanium leads to an increase in the amount of retained hydrogen. The effect of titanium content on hydrogen retention is found to be nonmonotonic; the phenomenon is explained from a physical view point.     

Development and Application of Hydrogen Storage

Hydrogen,as a secure,clean,efficient,and available energy source,will be successfully applied to reduce and eliminate greenhouse gas emissions.Hydrogen storage technology,which is one of the key challenges in developing hydrogen economy,will be solved through the unremitting efforts of scientists.The progress on hydrogen storage technology research and recent developments in hydrogen storage materials is reported.Commonly used storage methods,such as high-pressure gas or liquid,cannot satisfy future storage requirement.Hence,relatively advanced storage methods,such as the use of metal-organic framework hydrides and carbon materials,are being developed as promising alternatives.Combining chemical and physical hydrogen storage in certain materials has potential advantages among all storage methods.Intensive research has been conducted on metal hydrides to improve their electrochemical and gaseous hydrogen storage properties,including their hydrogen storage capacity,kinetics,cycle stability,pressure,and thermal response,which are dependent on the composition and structural feature of alloys.Efforts have been exerted on a group of magnesium-based hydrides,as promising candidates for competitive hydrogen storage,to decrease their desorption temperature and enhance their kinetics and cycle life.Further research is necessary to achieve the goal of practical application by adding an appropriate catalyst and through rapid quenching or ball milling.Improving the kinetics and cycle life of complex hydrides is also an important aspect for potential applications of hydrogen energy.     

The hydrogen embrittlement of Fe-Ni martensites

Iron alloys containing 20 and 30 pct Ni and 3 to 4 cu cm H per 100 g metal have been subjected to slow strain-rate tensile tests in a study of hydrogen embrittlement. In the lower nickel massive martensite alloy, embrittlement is manifest as the cracking of prior austenite grain boundaries and is severe at room temperature but less marked at -196°C; while in the higher nickel acicular martensite alloy, the embrittlement observed at 20°C does not occur at —196°C. Hydrogen embrittlement in these materials is believed to be the result of high hydrogen contents in the vicinity of the prior austenite grain boundaries combined with stress concentrations caused by boundary perturbations which result from the impact of the martensite shears. During deformation, microcracks form and propagate in the prior austenite grain boundaries, probably assisted by internal hydrogen pressure and the lowering of crack surface energy by hydrogen adsorption. The temperature dependence and the effect of the type of martensite on the embrittlement can be explained by their effects on the hydrogen content and stress concentrations at prior austenite grain boundaries during deformation.     

脉冲熔融-飞行时间质谱法同时测定钢铁中氧、氮和氢

采用脉冲熔融-飞行时间质谱法同时测定钢铁中氧、氮和氢三种元素,通过对比空白和样品的质谱图,选择C+,N+,H2+作为质谱分析的谱线。对一系列标准样品中的氧、氮和氢进行测定,根据分析谱线的离子数及元素的质量绘制校准曲线。通过对空白的标准偏差计算得氧、氮和氢的检出限分别为0.000 015%,0.000 02%,0.000 003%,测定氧、氮和氢的范围分别为0.000 05%~0.2%,0.000 06~0.2%,0.000 01~0.05%。方法用于标准样品的分析,测定结果与认定值一致,相对标准偏差为1.4%~7.4%。该方法把质谱检测器用于钢铁材料中氧、氮和氢的同时、定量分析,测定结果的允许误差符合国家标准的规定。     

Materials problems in large scale production of hydrogen from water and in hydroge storage

Methods for the production of hydrogen from water are discussed with emphasis on thermochemical cycles. These consist of a series of reactions, performed at various temperatures up to about 1000°C, which by their nature involve some compounds that are aggressive toward containment materials. Experience with most such reactions is presently not available in the chemical industry, and a lack of knowledge is thus evident regarding corrosion-resistant materials. The most promising thermochemical cycles are described in terms of the aggressiveness of their reagents. Materials problems associated with the production of hydrogen by water electrolysis and hydrogen storage in the form of metallic hydrides are also reviewed. This paper is based on a presentation made at a symposium on “Materials Requirements for Unconventional Energy Systems” held at the Niagara Falls meeting of The Metallurgical Society of AIME, September 22, 1976, under the sponsorship of Non-Ferrous Metals and Ferrous Metals Committees.     

Diffusion of hydrogen in titanium alloys due to composition,temperature, and stress gradients

A theoretical and experimental study was conducted to determine the combined effects on interstitial diffusion in metals of gradients in interstitial concentration, in solvent composition, in stress, and in temperature. The theory consolidates relationships, some of which have been previously published. It is based on macroscopic irreversible thermodynamics, and is applicable to anisotropic or Isotropic materials. Experiments were conducted and literature analyzed to determine the numerical quantities required to predict the change in hydrogen distribution with time for pure and alloy titanium, where the solvent gradient, stress gradient, and temperature gradient are constant with time. The diffusion driving forces for solute gradient, solvent gradient, and stress gradient are related to the effect of each factor on hydrogen activity. In addition, the material property which determines the diffusion driving force of a stress gradient for anisotropic material is a matter tensor analogous to the scalar partial molal volume used for isotropic material. The experiments, conducted with commercially pure titanium and titanium alloy, 6A1-4V, consist of measuring the effect of alloy additions and stress on the hydrogen activity in solid solution and the dilatation effect of hydrogen. Stress states tested were tension, compression, and torsion. The measurements were made by exposing titanium and the alloy to hydrogen at temperatures from 600° to 800° C, and measuring the equilibrium hydrogen gas pressure at various solid solution hydrogen contents. Both materials were tested with and without stress. Tension decreased the activity, compression increased it, and torsion had no effect. This is consistent with the stress effect theory of Li, Oriani, and Darken. The stress effect corresponds to an apparent partial molal volume of 1.7 to 2.2 cm³/mol, depending on the alloy and hydrogen content.     

MmNi5-x(CoAlMn)x/Mg纳米晶复合储氢合金的吸氢性能

研究了机械合金化制备的ＭｍＮｉ５－ｘ（ＣｏＡｌＭｎ）ｘ／Ｍｇ纳米晶复合储氢合金的吸氢特性。通过测定不同镁含量的ＭｍＮｉ５－ｘ（ＣｏＡｌＭｎ）ｘ／Ｍｇ纳米晶复合储氢合金的吸氢ＰＣＴ曲线,考察了镁含量对其吸氢特性的影响。根据对吸氢速度的测定研究了机械合金化对储氢合金的吸氢动力学特性的影响。机械合金化制备的纳米晶复合储氢合金的活化性能与ＭｍＮｉＭ５－ｘ（ＣｏＡｌＭｎ）ｘ铸态合金相比有较大的提高,不需活化或只需一次活化即可吸氢,吸氢量及吸氢的动力学性能与铸态合金相比也有很大的提高。最后对机械合金化形成的纳米晶吸氢特性进行了分析。     

稀土贮氢电池的发展现状及对策

本文综述了我国稀土贮氢电池的主要发展状况。1990年前我国已能生产作为电池(Ni/MH)负极材料的稀土贮氢合金，1990年初期就开始制造电池（Ni／MH)，且在1995年后逐步走向工业化生产水平。目前我国的这种电池的原料供给能力、电池的生产技术及装备、检测手段、电池的综合技术性能等方面都处于世界先进水平。     

The use of silver decoration technique in the study of hydrogen transport in metallic materials

The silver decoration technique proposed by Schöber and Dieker^[10] for revealing local hydrogen flux in terms of microstructural characteristics is reinterpreted. The results of decoration tests in polycrystalline nickel and palladium with and without hydrogen charging show that hydrogen flux is not solely responsible, nor even a prerequisite, for the deposition of silver crystals on metal surfaces. There is, consequently, no one-to-one correspondence between escaped hydrogen atoms and deposited silver atoms during the decoration process as reported previously. It is the oxidation film formed during electropolishing that prevents silver deposition. Any damage to the film and any factor which reduces its stability may result in spontaneous silver deposition in the absence of hydrogen. With this new interpretation, one can use the silver decoration technique to obtain qualitative information regarding hydrogen transport along grain boundaries in metallic materials.