掺杂NaAlH4放氢性能的研究

采用PCT(pressure-conten-temperature)、XRD等测试方法对掺杂Ag2SO4、SrCO3、TiO2和ZnO的NaAlH4放氢性能进行研究。结果显示,掺杂TiO2的NaAlH4试样具有最大的放氢量,而掺杂SrCO3的试样放氢量最小,并且对比所有掺杂试样在第1阶段的放氢速率发现,掺杂TiO2的NaAlH4试样具有最大的放氢速率,在整个放氢性能的测试过程中,试样表现出了明显的2个分解阶段,并且在第1阶段的分解速率明显大于第2阶段。此外,掺杂TiO2和ZnO试样的XRD结果表明,掺杂试样经过30min的球磨之后,试样的晶体结构没有发生明显变化,并且没有新的物相生成,这说明NaAlH4具有很好的稳定性。     

过渡金属氧化物掺杂NaAlH4放氢性能

采用PCT (Pressure-Content-Temperature)、XRD、SEM等测试方法对掺杂不同过渡金属氧化物(TiO2,ZrO2,Cr2O3,ZnO)的NaAlH4试样的放氢性能进行研究.结果表明,掺杂TiO2和ZrO2的NaAlH14试样的放氢性能较好.此外,所研究球磨工艺明显改善了NaAlH4的放氢性能.SEM结果发现,球磨3h的Zr-NaAlH4试样效果最佳,此时粉体吸附在较大颗粒四周,随球磨时间的延长,NaAlH4粉体颗粒发生团聚.XRD结果表明,NaAlH4球磨后的结构并未发生明显变化,这说明NaAlH4具有良好的稳定性.     

Ti掺杂对NaAlH4储氢性能的影响

采用基于密度泛函理论(DFT)的平面波赝势(PW-PP)方法,分别计算纯净以及掺杂Ti的NaAlH4和Na3AlH6的晶格结构参数、能量变化和电子态密度(DOS),分析比较Ti掺杂对NaAlH4和Na3AlH6储氢性能的影响。结果表明:Ti掺杂后的晶格结构比原纯净的NaAlH4和Na3AlH6稳定,且脱氢所需能量减少。Ti替代Na后,Ti吸引周围的H原子,使Al-H键变弱;Ti替代Al,Ti-H键比原Al-H键明显减弱,使掺杂后脱氢所需能量降低。通过对比分析Ti掺杂对NaAlH4和Na3AlH6结构和态密度的影响,得出Ti的催化作用主要发生在脱氢反应的第一步。     

Ti31Cr15.5V45Fe8.5Ce0.5对CeH2掺杂NaAlH4放氢动力学的影响

采用高能球磨法制备了NaAlH_4(2%CeH_2)+x%Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)(x=0,5,10,20,30)(原子分数)复合体系,通过等温放氢动力学试验研究了该体系在423K下的放氢动力学性能。研究结果表明,随着Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)添加量的增加,NaAlH_4第一步放氢反应的放氢量提高,放氢时间缩短;当Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)添加量达到30%(原子分数)时,第一步放氢反应的放氢量(质量分数)从1.89%提高至提高到2.31%,放氢时间从45min降低至27.6min。X射线衍射结果表明,Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)主要以氢化物形式存在,扫描电子显微镜结果表明,Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)嵌入NaAlH_4颗粒表面。采用三维扩散反应动力学模型研究了NaAlH_4(2%CeH_2)+x%Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)(x=0,5,10,20,30)复合体系样品的放氢动力学曲线,结果表明,添加/未添加Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)的样品均能够符合三维扩散反应动力学模型,氢在产物层的扩散为控制步骤,反应速率常数随Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)添加量增加而增大,揭示了Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)对NaAlH_4第一步放氢反应的影响机制主要是NaAlH_4颗粒表面的Ti_(31)Cr_(15.5)V_(45)Fe_(8.5)Ce_(0.5)氢化物提高了氢在产物层的扩散速率,从而提高NaAlH_4的放氢动力学性能。     

LaNi5-xAlx (x=0~1.2)合金的循环储氢性能研究

通过真空感应熔炼法制备了LaNi5-xAlx (x=0, 0.25, 0.75, 1.2)储氢合金,并对其微观结构、力学性能、循环吸放氢性能及抗粉化性能进行了研究。结果表明,Al元素的加入能够明显改善合金晶体结构稳定性和储氢容量稳定性;随着Al含量的增加,合金的抗粉化性能呈现先减弱后增强的趋势;合金的力学性能和储氢容量共同影响着其抗粉化性能,其中力学性能是最主要的影响因素;在普通高纯氢气氛下,LaNi5-xAlx (x=0~1.2)合金的容量衰减主要是由于材料自身原因造成,很可能是发生了歧化反应     

掺杂稀土类催化剂对LiAlH4放氢性能和相结构的影响

采用球磨的方式在LiAlH4中分别掺入3种稀土催化剂LaCl3、CeCl3和Ce(SO4)2,研究了稀土催化剂对LiAlH4的相结构和放氢性能的影响。结果表明,在球磨过程中,掺杂Ce(SO4)2对LiAlH4的分解基本没有影响,而掺杂LaCl3和CeCl3则造成LiAlH4部分分解,产生了LiCl和Al3RE（RE=La,Ce）相。在LiAlH4放氢反应中,稀土催化剂的加入均使LiAlH4初始放氢温度降低,特别是Ce(SO4)2使第1步的放氢温度降低了约25 ℃。稀土催化剂有助于加快LiAlH4分解反应速率,提高LiAlH4的放氢性能。     

Ce2Mg17及其氢化物添加剂对LiBH4的放氢作用机理研究

为改善LiBH4体系的可逆吸放氢性能,将Ce2Mg17合金(简称为CM)及其氢化物(CeH2.51和MgH2,简称为CMH)分别与LiBH4球磨4 h制得LiBH4-0.02CM和LiBH4-0.02CMH复合储氢体系,采用MS、TPD、XRD和FT-IR等测试手段研究了不同状态Ce-Mg添加剂对复合储氢体系可逆吸放氢性能的影响及其作用机制。结果表明:Ce2Mg17合金本身对改善LiBH4吸放氢性能没有明显作用;而Ce2Mg17氢化物(即MgH2和CeH2.51)可降低复合体系中LiBH4的放氢温度和提高LiBH4的放氢速率,并可明显改善体系的可逆吸放氢性能。进一步分析表明,MgH2和CeH2.51对LiBH4的协同改性作用是有效降低LiBH4热力学稳定性、提高LiBH4-Ce-Mg复合体系可逆吸放氢性能的主要原因。     

Mg2Ni1-xCux (x=0, 0.2, 0.4)合金熔炼法加球磨处理后的储氢性能

采用熔炼法加球磨处理制备Mg2Ni1-xCux(x=0,0.2,0.4)合金。通过XRD和SEM/EDX对合金的相成分和微观组织进行分析。研究表明,3种合金中都有Mg2Ni相形成。随着Cu含量的增加,合金分别形成Mg2Cu相和Cu11Mg10Ni9相。PCT测量结果表明,Cu的添加可以改善合金的吸放氢性能。     

NaAlH4分解后的加氢过程

采用同步X射线衍射、扫描电镜及颗粒度分析研究了NaAlH4分解后的加氢过程.结果表明,催化剂Ti不仅可以降低NaAlH4的分解温度,也可以将Na3AlH6的分解温度从250℃降至160℃左右.NaAlH4分解后的加氢反应理论上是可逆的,但由于分解后的产物NaH和Al相互分离,尤其是由于聚集所形成的Al颗粒过大,造成Na3AlH6不能全部转变成NaAlH4.这也是导致在随后的吸、放氢循环过程中有效贮氢量降低的原因.进一步的实验表明,当聚集的Al颗粒平均尺寸大于2.3 μm时,便不利于加氢过程的完全进行.     

F-掺杂LiMn2O4的合成及电化学性能

采用溶胶-凝胶法合成掺杂F^-的LiMn2O4。通过XRD、SEM对掺杂F-的LiMn2O4材料的组成、结构、微观形貌等进行分析与表征,测试不同F^-掺杂量的LiMn2O4在常温（20℃）、高温（55℃）下的电化学性能。结果表明：所合成的材料具有良好的尖晶石立方结构,无杂相;F^-的掺杂提高了材料的比容量,增强了材料的稳定性,改善了其在高温下的循环性能。当F^-的掺入量x由0增加到0.1时,材料的比容量由119.7 mA.h/g增加到124.9 mA.h/g,高温下充放电30个循环后容量保持率由79.4%增加到84.4%。     

Hydrogen sorption properties of Ti-Zr hydride doped NaAlH4

The as-prepared Ti-Zr hydride powder is used as dopant to improve hydrogen storage properties of NaAlH4 upon mechanical milling under argon atmosphere. The as-milled sample is investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and Sievert＇s technology test. It is observed that Ti-Zr hydride doped NaAlH4 discharges 2.7% and 4.0% （mass fraction） of hydrogen in 40 min and 11 h at 160℃, respectively, and keeps its reversible dehydrogenation capacity at 4.0% （mass fraction） after 10 hydrogenation/dehydrogenation cycles, These results show the Ti-Zr hydride doped NaAIH4 has good reversible hydrogen storage capacity and kinetics. XRD and SEM investigations also show that the doped Ti-Zr hydride uniformly distributes in NaAIH4 substrate and keeps stable during the hydrogenation/dehydrogenation cycle, indicating that Ti-Zr hydride plays the main surface-catalytic role on improving reversible hydrogen storage properties of NaAlH4,     

基于镍基固溶体催化的氢化镁储氢性能

采用高能球磨制备Ni?25％X(X=Fe,Co,Cu,摩尔分数)固溶体,然后将其掺杂于MgH2体系中.与球磨纯MgH2相比,MgH2/Ni?25％X复合体系初始放氢温度降低近90℃,其中,Ni?25％Co固溶体呈最佳催化效果.球磨MgH2/Ni?25％Co复合体系在300℃、10 min内可释放5.19％(质量分数)氢...     

Hydrogen storage properties of non-stoichiometric AB2-type metal hydride

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉｂａｓｅｄｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｓｂｅｃａｍｅａｔｔｒａｃｔｉｖｅｂｅｃａｕｓｅｏｆｔｈｅｉｒｌａｒｇｅｈｙｄｒｏｇｅｎｃａｐａｃｉｔｉｅｓ.Ｂｅｒｎａｕｅｒｅｔａｌ[1]ａｎｄＬｉｅｔａｌ[2]ｐｏｉｎｔｅｄｏｕｔｔｈａｔｍｕｌｔｉｅｌｅｍｅｎｔＴｉｂａｓｅｄｈｙｄｒｏｇｅｎｓｔｏｒａｇｅａｌｌｏｙｓａｒｅｍｏｒｅｐｒｏｍｉｓｉｎｇｍａｔｅｒｉａｌｓｆｏｒｐｒａｃｔｉｃａｌａｐｐｌｉｃａｔｉｏｎｓ.(ＴｉＺｒ)(ＭｎＣｒＶＦｅ)2ａｌｌｏｙｉｓａｃｏｍｍｏｎ…     

Hydrogen storage properties of Mg(Al) solid solution alloy doped with LaF3 by ball milling

LaF₃ was doped to the Mg(Al) solid solution alloy for enhancing the hydrogen absorption and desorption by ball milling. XRD was used to analyze the phases of the samples and the phase transition induced by hydrogenation and dehydrogenation. The microstructure and phase distribution were investigated by SEM and STEM. The hydrogen storage properties were measured by Sieverts method. For Mg_0.93Al_0.07-5wt.%LaF₃ nanocomposite, the hydrogen storage kinetic properties were significantly improved by reducing the hydriding and dehydriding activation energies to 65 and 78 kJ/mol, respectively, and the dehydriding enthalpy was calculated to be 69.7 kJ/mol. The improved hydrogen storage properties were mainly attributed to the catalytic effects of the in situ formed nanostructure Al₁₁La₃ and MgF₂ together with the dissolving of Al in Mg lattice.     

Hydrogen storage in magnesium-based hydrides and hydride composites

Mg and Mg-based hydrides have attracted much attention because of their high gravimetric hydrogen storage densities and favourable kinetic properties. Due to novel preparation methods and the development of suitable catalysts, hydrogen uptake and desorption is now possible within less than 2 min. However, the hydrogen reaction enthalpy of pure Mg is too high for many applications, for example, for the zero emission car. Therefore, different routes are explored to tailor the hydrogen reaction enthalpy to potential applications. This article summarizes the recent developments concerning sorption properties and thermodynamics of Mg-based hydrides for hydrogen storage applications. In particular, promising strategies to decrease the hydrogen reaction enthalpy by alloying and the use of reactive hydride composites are discussed.     

Hydrogen storage properties of Nb-compounds-catalyzed LiBH_4-MgH_2

In order to improve the hydrogen storage properties of LiBH_4-MgH_2 composite, two different kinds of Nb-based catalysts, NbC and NbF_5, were added to LiBH_4-MgH_2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH_4-MgH_2 system was investigated. The experimental results show that LiBH_4-MgH_2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320℃, and there is a long period of incubation time(around 220 min) for the occurrence of the second decomposition step even at high temperature of 450℃. It needs more than 10 h to complete the decomposition process and release around 9 wt% H_2. After addition of 5 mol% NbF_5, the starting decomposition temperature for the first dehydrogenation step is around 150℃, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF_5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.     

Hydrogen storage properties of a Ni,Fe and Ti-added Mg-based alloy

Mg-5wt%Ni-2.5wt%Fe-2.5wt%Ti (referred to as Mg-5Ni-2.5Fe-2.5Ti) hydrogen storage material was prepared by reactive mechanical grinding, after which the hydrogen absorption and desorption kinetics were investigated using a Sievert-type volumetric apparatus. A nanocrystalline Mg-5Ni-2.5Fe-2.5Ti sample was prepared by reactive mechanical grinding and hydriding-dehydriding cycling. Analysis by the Williamson-Hall method from an XRD pattern of this sample after 10 hydriding-dehydriding cycles showed that the crystallite size of Mg was 37.0 nm and that its strain was 0.0407%. The activation of Mg-5Ni-2.5Fe-2.5Ti was completed after three hydriding-dehydriding cycles. The prepared Mg-5Ni-2.5Fe-2.5Ti sample had an effective hydrogen-storage capacity near 5 wt% H. The activated Mg-5Ni-2.5Fe-2.5Ti sample absorbed 4.37 and 4.90 wt% H for 5 and 60 min, respectively, at 593K under 12 bar H₂, and desorbed 1.69, 3.81, and 4.85 wt% H for 5, 10 and 60 min, respectively, at 593K under 1.0 bar H₂.     

苯溶液中球磨La2Mg16Ni合金的储氢性能

对苯溶液中球磨的La2Mg16Ni合金的储氢性能进行了研究。XRD和SEM分析表明：球磨后合金颗粒粒径减小，且有明显的非晶化趋势；由合金和有机苯溶剂在球磨过程中形成的EDA(electron donor-acceptor)体系极大地提高了合金的活化性能；球磨后的合金即使在低温下也具有良好的吸氢速率；延长球磨时间，可改善合金的吸氢性能。     

Effects of Mm(NiCoAlMn)_5 hydrogen storage alloy coated with Ni-Co-P alloy by electroless plating on electrochemical properties of hydride electrodes

1　INTRODUCTIONNickel metalhydride (MH Ni)rechargeablebatterieswithhydrogenstoragealloysasthenegativeelectrodematerialhaveattractedincreasingattentionsbecauseofseveralinherentadvantages[16 ] .Sofar ,manymulti component,mischmetal based ,hydro gen storagealloyshavebeendevelopedtomeetthere quirementofhighcyclinglife ;theseincludesubstitu tionofthenickelbyMn ,CoandAl[7] .Thecomposi tionofthealloyisimportant ,andtheeffectsofsur facecompositionandmorphologyarealsosignificant.Micro encapsulat…     

Effect of F-1 on the Hydrogen Release Properties of NaAlH4 and LiAlH4

使用PCT设备分析了NaF和LiF对NaAlH4和LiAlH4放氢性能的影响。结果显示,除了掺杂0.5 mol%,4 mol%NaF的试样外,掺杂NaF明显提高了NaAlH4的放氢量。此外,掺杂NaF还增加了NaAlH4第1阶段的放氢速率。在所有的掺杂NaF的试样中,掺杂1 mol%NaF的试样的放氢量是最大的,并且放氢速率也是最快的。相比之下,掺杂LiF使得LiAlH4的放氢量明显降低了。