Hydrogen absorption behavior of TA15 alloy

The hydrogen absorption kinetics of TA15 titanium alloy at 973-1123 K was studied using a tube-type hydrogen treatment furnace.The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found that only the second hydrogen absorption period exists in the hydrogen absorption process of TA15 alloy between 973 and 1123 K, and the activation energy is 54.889kJ/mol for hydrogen absorption. X-ray diffiaction (XRD) and scanning electron microscopy (SEM) results demonstrate that δ hydride forms between 973 and 1123 K, and β phase decreases with the increase of temperature. Orthorhombic α" martensite is generated at 1073-1123 K,and their amount increases with increasing temperature.     

Study on Kinetics of Hydrogen Absorption by Metal Hydride Slurries Ⅰ. Absorption of Hydrogen by Hydrogen Storage Alloy MlNi_5 Suspended in Benzene

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Hydrogen Absorption of Nd-Fe-B Alloys

The technical parameters of HD process were studied, including the effects of temperature and neodymium contents on the incubation period of hydrogen absorption, hydrogen concentration and the rate of hydrogen absorbed. The results show that the incubation period is shortened and the rate of hydrogen absorbed is accelerated with rising temperature and surface area. These are attributed to the rising rate of hydrogen diffusion at higher temperature. The change of the incubation period and the rate of hydrogen absorbed have the similar trend resulted from the increasing content of the Nd-rich phase owing to the rising temperature. Moreover, the percent of the Nd-rich phase in the ingot can be calculated according to the total hydrogen weight gain.     

氢爆工艺(HD)对钕铁硼磁粉粒度和形状的影响研究

采用热处理态钕铁硼平板铸锭作为母合金,通过氢爆工艺将平板铸锭破碎成磁粉。研究了氢爆工艺过程中温度、氢压对钕铁硼磁粉的破碎程度、粒度和形状的影响。实验发现,随着温度和氢压的提高,吸氢过程活化时间逐渐缩短,当温度为300℃,氢压为0.1 MPa时,活化过程消失,铸锭一旦暴露在氢气中,吸氢过程直接发生。热处理态平板铸锭吸氢之后,破碎得到的磁粉大部分为粒度在178μm下的细粉,且随着氢压的提高,氢爆后细粉所占的质量分数趋势上是单调增加的。磁粉细粉粒度分布对氢压的变化不敏感,但是在相同氢压下,从室温到300℃,随着温度升高,磁粉平均粒度明显变粗。磁粉形状大部分为颗粒状,对应氢爆时富Nd相和Nd₂Fe₁₄B相间的沿晶断裂,少数呈尖角、针棒等不规则形状,可能与Nd₂Fe₁₄B相内穿晶断裂的发生有关。随着实验温度升高,氢爆-脱氢后的磁粉Nd₂Fe₁₄B相的衍射峰峰位向高角度发生偏移,原因是更高温度有利于脱氢,导致含氢量逐渐减少。不同氢压条件下,Nd₂Fe₁₄B相衍射峰位基本不变。     

Mg_(10)Al_((7-x))Li_2Ti_x(x=0,1,2,3)合金的制备及储氢性能研究

在氩气保护下,采用机械合金化法制备Mg_(10)Al_((7-x))Li_2Ti_x(x=0,1,2,3)合金,并通过XRD、SEM以及DSC等手段对合金进行表征。结果表明,适量的Ti替代Al可以提高合金的吸氢量、降低合金的初始氢化/脱氢温度和提高合金氢化/脱氢动力学性能。Mg_(10)Al_((7-x))Li_2Ti_x(x=1,2,3)合金样品比Mg10Al7Li2合金的初始氢化温度都降低了62K,而初始脱氢温度则分别降低了77、98和59K。当Ti的替代量为x=2时,合金的综合储氢性能最好。     

Kinetics of Liquid-Phase Hydrogenation of Toluene Catalyzed by Hydrogen Storage Alloy MlNi_5

Asacleanandhigh efficiencyenergyresource ,hydrogenisthoughttobethemostpromisingsubstituteoffossilfuels .Storingandutilizingtheenergybyus ingthehydrogenasenergycarrieristhemostfavor ablemethodtosolvetheenergycrisis ,whichattractsthefocusoftheworld .Therehavebeenconsiderableprogressesinthetechnologyofhydrogen energyinre centyears .Reillyetal .[1] firstproposedtheconceptofthemetalhydrideslurryin 1 980s ,inwhichthede formationorruptureofthevesselsduetotheparticlepulverizationandthepoorheattransfer…     

Preparation of Cu-Ni alloys through a new chemical route

A copper-nickel alloy has been prepared from an aqueous solution of the nitrates of copper and nickel, through co-formation of their ultrafine mixed oxides, by heating around 650 K followed by reduction with hydrogen at a very low temperature (below 623 K). The effect of temperature (473 to 623 K) on the kinetics of the hydrogen reduction of the co-formed oxides of Ni and Cu has been studied. The activation energy of the reduction reaction has been calculated and found to be 35.8 kJ/mole. A mechanism for the kinetics of the process has been suggested. It has been possible to get high-purity Cu-Ni alloy powder (50 at. pct each) free of any detectable oxygen, from their co-formed oxides, by hydrogen reduction at 623 K in less than 20 minutes. Although the X-ray analysis of the co-formed oxides has shown separate peaks for CuO and NiO, the alloy powder has exhibited a single peak with a d spacing lying in between those of Cu and Ni. It is suggested that the alloying of the two metals has taken place during the H₂ reduction of nanosized oxide particles of copper and nickel, prepared by the aforementioned chemical route. The alloy powder has been sintered at 1273 K. The density and hardness of the consolidated alloy have been measured and found to be close to the theoretical values. The alloy has also been subjected to cold reduction and annealing, in addition to metallograph examination and characterization by a scanning electron microscope (SEM), to confirm the homogeneity of the alloy.     

宽温型AB5储氢合金结构及其电化学性能研究

用高频感应熔炼法制备了Mm(NiCoAlMn)5储氢合金,采用模拟电池法测试了合金在238～323 K温度范围内的活化、放电容量和高倍率放电性能.结果表明:制备合金为典型AB5型储氢合金,303K温度条件下吸氢量达到1.38％(质量分数),氢化物生成焓为32.36 kJ ·mol-1H2.合金电极的活化性能、放电容量和高倍率性能受温度影响显著.室温预活化可有效改善电极的低温性能,经室温预活化后合金电极在238 K最大放电容量达到336 mAh·g -1,明显高于未经室温预活化的最大放电容量25 mAh·g-1.Mm(NiCoMn)5贮氢合金电极的高倍率性能随着温度的升高先升高后降低,273和303 K温度条件下合金保持高倍率性能良好,3C放电电流密度条件下容量保持率均高于80％;238 K温度条件下合金的大电流放电性能急剧降低,1C放电电流密度条件下容量保持率仅为10％; 273 K下合金电极的综合性能最佳,最大放电容量达到340 mAh·g-1,300 mA·g-1放电电流密度下的高倍率放电比率为86％.循环伏安法测试证实,在238～323 K范围内,电极的氧化峰峰值电流(Ip)与扫描速度的平方根(v1/2)之间均存在良好的线性关系,整个电极反应受氢原子扩散控制;随着温度的降低氢扩散系数急剧下降,从而导致该合金电极的低温高倍率放电性能变差.由Arrhenius公式计算出合金中的氢扩散活化能为10.56 kJ·mol -1.     

Hydrogen reduction of a Cu2O-WO3 mixture

In the present work, the reduction kinetics of Cu₂O-WO₃ mixtures by hydrogen gas was studied by thermogravimetric analyses (TGA). The reduction experiments were carried out both isothermally and nonisothermally on shallow powder beds in the temperature interval 673 to 1073 K. During the experiments, the reductant gas flow rate was kept just above the starvation rate for the reaction to ensure that chemical reaction was the rate-controlling step. The composition and microstructures of the reaction products were analyzed after each experiment by X-ray diffraction (XRD) as well as by microprobe analyses. In the temperature interval 673 to 923 K, copper oxide was found to be preferentially reduced in the early stages of the experiment followed by the reduction of tungsten oxide. The reaction mechanism was found to be affected by a reaction/transformation in the starting copper-tungsten oxide mixtures in the temperature interval 923 to 973 K. At temperatures higher than 973 K, the reduction of the complex oxide formed was found to have a strong impact on the reaction kinetics. The activation energy was evaluated, from the isothermal as well as nonisothermal reduction experiments, for the two stages of reduction identified. The XRD and scanning electron microscopy (SEM) studies indicated the formation of a metastable solution of copper in tungsten at about 923 K. The advantage of the hydrogen reduction route toward the bulk production of alloy powders in the nanosize is demonstrated.     

Hydrogen permeation and diffusion in niobium

High temperature hydrogen permeation experiments were performed on niobium using ultra high vacuum techniques in an attempt to maintain clean specimen surfaces. Diffusivities and permeabilities were measured from 700 K to about 1400 K at hydrogen pressures ranging from 4.26 Pa to about 0.013 Pa. The measured diffusivities are in agreement with values extrapolated from the low temperature surface independent measurements. In contrast to low temperature measurements, a trend indicating a classical isotope effect is observed for hydrogen and deuterium diffusivities in niobium at the higher temperatures. The measured hydrogen permeation constants agree with independent solubility and diffusivity measurements and are characterized by a negative enthalpy, as expected from low temperature solubility and diffusivity measurements. These results are contrasted with previous measurements which appear to have been controlled by surface reactions.     

Phase Structure and Electrochemical Properties of RE-Mg Based Composite Hydrogen Storage Alloys

Rareearth basedAB5 typealloy ,akindofhy drogenstoragealloyusedasnegativeelectrodemateri alsofthenickel/metalhydride (Ni/MH )secondarybattery ,haseasyinitialactivation ,longcyclelifeandlowcost ,butstillasmalldischargecapacity ,poorhigh ratedischargeability(HRD)andpoorpropertiesatlowtemperature[1,2 ] .Therefore ,howtoincreaseitsdischargecapacityandtoimproveotherelectrochemi calpropertiesismeaningfulbothintheoryandinpracticalapplication .Mg basedhydrogenstorageal loysareremarkablebecauseofitsr…     

Hydrogen effects on an amorphous Fe-Si-B alloy

Hydrogen absorption in and desorption from an amorphous Fe₈₀B₁₁Si₉ alloy, hydrogen effects on the microstructure of this alloy, and the possible mechanism of hydrogen embrittlement (HE) in this alloy have been studied. Ribbons were electrochemically charged with hydrogen at room temperature. The interaction of hydrogen with structural defects and the characteristics of hydrogen desorption were studied by means of thermal desorption spectroscopy (TDS). The effects of hydrogen on the microstructure and thermal stability were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), electrical resistivity measurements, and differential scanning calorimetry (DSC). The phenomenon of HE was investigated using scanning electron microscopy (SEM) and various mechanical testing techniques. The absence of hydride-forming elements resulted in low hydrogen solubility and low desorption temperatures. Hydrogenation at room temperature is reported for the first time to lead to either local nanocrystallization of the amorphous phase or transformation of nanocrystalline phases such as Fe_∼3.5B, originally present in the uncharged material, to a new nanocrystalline Fe₂₃B₆ phase. The susceptibility of this alloy to HE is explained in terms of high-pressure bubble formation.     

镀铜压制La-Ni-Al储氢合金改善其抗粉化性能的研究

La-Ni-Al合金吸氢后严重粉化，在使用中对设备产生有害影响，使用范围受到很大限制。由于La-Ni-Al合金粉压制成型后，经过吸放氢后依然粉化，因而先对合金粉表面镀覆铜后再压制成型，通过对成型试样和未进行加工处理的试样进行吸氢性能测试，绘制La-Ni-Al合金化学镀铜压制成型前后的PCT曲线。研究La-Ni-Al镀铜成型试样多次吸放氢后的吸氢量及膨胀数据，对比试验结果，压制成型的La-Ni-Al合金抗粉化性能显著提高，使用方便，有效地消除了对设备的危害。     

TiZrNi准晶电化学储氢性能研究

准晶是一种结构特殊的固态有序相.其特殊的原子排列方式可能会使其具有较高的储氢性能.研究目的是获得Ti系准晶,并对其电化学储氢性能进行研究.采用铸造法炼制合金,准晶难以形成.因此采用首先通过机械合金化获得非平衡态合金,然后对非平衡态合金进行不同温度热处理来获得准晶的技术路线.采用机械合金化制备了Ti42.5 Zr42.5 Ni15非晶.在机械合金化过程中要注意气体保护,否则难以形成非晶.将非晶合金在530℃处理2h后,在基体中出现了准晶,此时的基体为准晶和晶态混合物,准晶占大部分.经750℃处理2h后,合金基体中只有晶态存在.对不同状态合金进行了电化学储氢特性测量.对于非晶、准晶、晶态三状态合金,其电化学储氢均存在一个活化过程.非晶态的容量最高,其次为准晶态,晶态最低.     

Zr-1Nb合金在氢氧化锂溶液中的吸氢性能研究

研究了Zr-1Nb合金管材在氢氧化锂溶液中经350℃,16．5MP条件下渗氢后的吸氢性能。结果表明：Zr-1Nb合金管材的吸氢速率随渗氢时间的增加而加快,验证了Zr-1Nb合金的吸氢动力学曲线也具有其氧化增重类型的特点,即随着渗氢时间的延长,有吸氢速率突增的转折点。对比Zr-4合金的吸氢行为,可以看出Zr-1Nb合金的抗吸氢能力比Zr-4合金要强,这是因为Zr-1Nb合金中的合金元素Nb在一定LiOH溶液浓度和渗氢时间范围内有提高其抗吸氢能力的作用。     

Direct Copper Precipitation from a Loaded Chelating Extractant by Pressure Hydrogen Stripping

The kinetics of direct copper precipitation from a loaded chelating extractant (Kelex 100) using hydrogen in an autoclave (pressure hydrogen stripping) was studied. Copper, in powder form, was found to precipitate rapidly from loaded Kelex 100/decanol/kerosene solvents by reaction with hydrogen at pressures between 520 and 4000 kPa and temperatures from 443 to 488 K. The overall process has heterogeneous nucleation characteristics. Nuclei are provided through slow thermal dissociation of the copper chelate. The freshly produced metallic copper, acting autocatalytically, accelerates the precipitation kinetics. In addition to temperature and pressure, the effects of seeding, agitation, copper concentration, ligand concentration, and copper chelate age were investigated. Some physical and chemical properties of the powder product were also determined.     

La-Mg-Ni系A5B19相储氢合金热处理工艺研究

重点研究了热处理工艺对(LaNdPrMg) (NiCoAl)3.8合金相成分和电化学性能的影响.总结发现1323 K保温5h急冷的热处理过程,在改善相成分方面,可以使合金中高容量的A5B19相丰度达到68％(质量分数),电化学性能测试表明,其最大放电容量达到400.9 mAh·g-1,电化学循环100周容量保持率达到82.44％.经分析认为,加热保温过程对改善储氢合金相结构的均匀性起到一定的作用,而急冷过程对改善储氢合金综合性能起到至关重要的作用.     

氢气分离提纯用钯及钯合金膜的研究进展

伴随着煤、石油和天然气等传统化石能源在使用过程中产生的温室效应、能源危机等弊端,更清洁的氢能逐渐受到关注。氢能在能源、交通、工业等领域具有广阔的应用前景,尤其以燃料电池车为代表的交通领域是氢能初期应用的突破口与主要市场。而氢燃料电池对氢气浓度要求较高,氢气中即使微量的H2S和CO杂质也会严重降低电池性能。因此,需要对氢气进行分离纯化去除杂质气体。钯及钯合金膜由于对氢气具有极高的选择渗透性而应用于氢气的分离提纯,然而钯及钯合金膜的化学稳定性问题一直制约其广泛应用。本文介绍了纯Pd膜,Pd-Ag,Pd-Y,Pd-Pt,Pd-Cu和Pd-Au二元合金膜以及Pd-Ag-M,Pd-Cu-M三元合金膜氢渗透与抗杂质气体毒化方面的研究进展及存在问题。纯钯膜在低温下存在氢脆现象且易被杂质气体毒化;与纯钯膜相比,钯基二元合金膜成本较低,Pd-Ag,Pd-Y合金膜透氢性能较好而抗杂质气体毒化性能较差,Pd-Pt,Pd-Cu和Pd-Au合金膜则具有相反的特性;钯基三元合金膜在一定程度上提高了二元合金膜的透氢性能并改善了抗杂质气体毒化的性能,但仍存在合金元素偏析、各组元成分比例不易精确控制等问题,且钯基三元合金膜较之二元合金膜合成工艺更复杂、成本更高。最后,对钯合金膜未来的研究方向进行了展望。     

Hydrogen embrittlement of nickel-titanium alloy in biological environment

A nickel-titanium superelastic alloy is susceptible to environmental embrittlement in a corrosive atmosphere. Because a delayed fracture of the alloy is associated with hydrogen absorption and subsequent formation of brittle hydride phases, the diffusion rate of hydrogen is thought to be one of the factors determining its service life. The Ni-Ti alloys subjected to hydrogen charging of 1 or 10 A/m² for 24 or 120 hours, respectively, were arranged using an electrochemical system. Both the hardness numbers in the cross-sectional area of the alloy and the amount of evolved hydrogen were determined. The fracture surface of the alloys, under tension, was observed using a scanning electron microscope (SEM). Theoretical distributions of the hydrogen concentration were computed for an infinite cylinder model using the differential equation of diffusion. The diffusion constant of hydrogen through the alloy is estimated to be 9×10⁻¹⁵ m²/s, assuming that the hardness is proportional to the concentration of hydride and/or hydrogen. Experimental results of the hardness measurements and fractography support the estimated diffusion constant. The process of fracture formation in a biological corrosive environment was discussed. It was concluded that galvanic currents and fretting corrosion of the alloy might be effective factors in fracture formation during function.     

低温下氢气还原氧化铁的动力学研究

 用热重分析法研究了低温下不同粒度氧化铁的氢还原动力学,得出在同一温度下,铁矿粉粒度从107.5 μm降到2.0 μm后,由于粉体的表面积大幅度增加,提高了粉气接触面积,从而使得化学反应的速度提高了8倍左右,还原反应的表观活化能从78.3 kJ/mol降低到36.9 kJ/mol;当反应速度相同时, 粒度6.5 μm的粉体的反应温度比107.5 μm的降低了80 ℃左右。同时,通过理论推导和实验结果表明,当反应扩散层厚度相同时,铁矿粉粒度越小,反应扩散层厚度越薄,其还原率越高。