Mg17Al12氢化物的水解放氢性能研究

金属Mg和Al都是水解制氢原料的最佳候选之一,但存在制粉难、氢化难、产氢量低等问题.而金属间化合物Mg17Al12易粉化和氢化,并且氢化产物(MHA)的水解产氢量高达13.6%(质量分数).研究了溶液pH值对Mg17Al12氢化物水解放氢性能的影响.结果表明,Mg17Al12氢化物只能在强酸溶液中才能放出理论氢量,在其...     

TiH_2和V_(0.6)Ti_(0.23)Cr_(0.05)Fe_(0.12)H_2复合金属氢化物锂离子电池负极材料的制备及其电化学性能研究

通过氢化和高能球磨的方法制备出TiH_2和V_(0.6)Ti_(0.23)Cr_(0.05)Fe_(0.12)H_2复合金属氢化物,并利用XRD、SEM、BET、拉曼和充放电测试等技术对其结构、形貌、比表面积、导电剂电导率和电化学性能进行了研究。结果表明,金属氢化物经高能球磨未改变其初始的FCC结构;在电流密度为10mA/g条件下,添加导电剂乙炔黑和石墨烯时复合金属氢化物的首次放电比容量分别为248.2和580.6mAh/g。     

Li以及Li化合物的添加对17Mg/12Al复合材料储氢性能影响的研究

通过粉末烧结制备17Mg/12Al复合材料,然后再添加Li,LiH以及LiAlH_4混合球磨制备17Mg/12Al+10M(M=0,Li,LiH,LiAlH_4)复合材料。经研究发现,烧结后的17Mg/12Al复合储氢材料主要由Mg17Al12和Mg2Al3组成,经过20h机械球磨后,Mg17Al12和Mg2Al3转变为具有FCC结构的Mg-Al固溶体。Li以及Li化合物的添加能提高Mg-Al固溶体的储氢容量和改善Mg-Al固溶体的热力学性能,如17Mg/12Al复合材料的储氢容量为1.73%(质量分数),添加Li以及Li化合物后,17Mg/12Al+10M(M=Li,LiH,LiAlH_4)的吸氢量则分别上升到2.23%,2.36%和1.81%(质量分数),且脱氢活化能从194.5kJ/mol分别降低到172.8,146.3和155.4kJ/mol。     

Mg95Ni5-30wt%La0.7Mg0.3Ni2.8Co0.5复合物的吸放氢性能研究

先采用氢化燃烧合成法制备Mg95Ni5,然后将氢化燃烧合成产物与30%(质量分数)La0.7Mg0.3Ni2.8Co0.5合金进行机械球磨复合,球磨时间分别为5、10、15和20h;将Mg95Ni5的氢化燃烧合成产物直接球磨10h用于对比研究.采用X射线衍射仪、扫描电镜、能谱仪及气体反应控制器研究了材料的相组成、微观形貌、颗粒化学成分以及吸放氢性能.研究表明,球磨10h的Mg95Ni5/La0.7Mg0.3Ni2.8Co0.5复合物具有最佳的吸放氢性能,在373K,50s内基本达到饱和吸氢量3.78%(质量分数);在523K,1800s内放氢量为3.83%(质量分数);其起始放氢温度为425K,与Mg95Ni5相比降低了35K,吸放氢性能的改善与复合物的组织结构密切相关.此外,La0.7Mg0.36Ni2.8Co0.5的加入改善了复合物的放氢动力学性能.     

球磨CeMg12+100%Ni合金热力学及电化学贮氢性能

用球磨工艺制备CeMg12+100%Ni电极合金,研究了球磨工艺对合金结构及电化学性能的影响。结果表明球磨CeMg12+100%Ni合金具有非晶纳米晶结构,由Mg2Ni相以及Ni相组成,其含量随球磨时间的延长而增加,这在一定程度上改善了合金的电化学放电性能。球磨非晶纳米晶具有较好的结构稳定性,在吸氢后形成的氢化物相仍保持非晶纳米晶尺度,这有利于降低氢化物的热稳定性,改善电化学放电性能。     

Mg2Ni纳米储氢合金结构及电化学性能研究

利用高能球磨方法制备纳米Mg2Ni储氢合金,用于高容量MH／Ni电池氢化物电极电化学性能研究。XRD和TEM测试结果表明,机械合金化方法制备Mg2Ni合金的历程为合金化——非晶化——纳米晶化,球磨时间直接影响Mg2Ni合金的结构。高能球磨20h可以制备非晶态Mg2Ni合金,比普通的机械合金化方法制备非晶态Mg2Ni合金的时间减少了约5倍之多;高能球磨30h可以制备纳米晶态Mg2Ni合金,粒径在10nm以下,有团聚现象。研究了Mg2Ni纳米氢化物电极在不同温度下的电化学性能,并从热力学角度就Mg2Ni纳米氢化物电极的某些高温电化学性能进行了解释和推测。实验结果表明：在30～70℃范围内,随着温度增加,氢化物电极的电化学容量逐渐增加,在70℃时电化学容量可达530．5mAh／g,约为30℃放电容量273．2mAh／g的2倍,Mg2Ni纳米氢化物电极具有较好的高倍率放电性能及大电流充放电性能,这表明机械合金化方法制备的Mg2Ni纳米氢化物电极具备电动车用大型MH／Ni电池负极材料的初步条件,但容量衰减严重。     

球磨法超细化的V_(60)Ti_(25)Cr_3Fe_(12)合金微观应变与吸放氢性能的关系

钒基储氢合金在球磨制粉过程中会造成晶格缺陷,这些缺陷会使吸放氢性能恶化。采用XRD、TEM、SEM和PCT研究了球磨法制备的平均粒径100nm~2μm的V_(60)Ti_(25)Cr_3Fe_(12)合金粉微观应变与吸放氢性能的关系。结果显示,球磨过程引入了非晶化、晶格畸变、位错和微观应变。400℃热处理后合金的微观应变(y1)随球磨时间(x1)的函数关系为y1=0.313+0.170x1-0.00695x12,微观应变变化速率的函数y'1=0.170-0.0139x1。球磨时间增加,微观应变的变化速率(y'1)线性减小;球磨初始y'1为最大值,y'1(0)(max)=0.170(%h-1),此时微观应变快速积累;球磨12h后,y'1(12)=0.0032(%h-1),此时微观应变的积累趋于饱和。球磨时间从0h增加到12h,微观应变从0.313%增加到1.354%。微观应变的增加使高平台的二氢化物(γ相)的含量从65.2%减少到13.2%,低平台的一氢化物(β相)的含量从32.5%增加到80.3%,导致有效放氢量从1.81%(质量分数)减小到0.58%(质量分数)。微观应变(x2)与放氢量(y2)负相关,函数关系为y2=1.999-1.124x2。     

球磨时间对TiB_2-Ni(Al)复合粉末组织结构影响研究

在不同球磨时间条件下,采用机械球磨方法制备TiB_2-Ni(Al)复合粉末,其中Ni粉和Al粉的物质的量比为1∶1,TiB_2陶瓷相含量为40%(体积分数)。采用扫描电子显微镜(SEM)以及X射线衍射仪(XRD)分析球磨后粉末的显微组织结构及物相,研究不同球磨时间对制备TiB_2-Ni(Al)复合粉末物相演变、组织结构的影响。研究结果表明,随着球磨时间的延长,延性金属Ni和Al变形程度逐渐增大,粉末中呈现Ni/Al交替混合组织结构,此种结构有利于金属在球磨过程中扩散形成Ni(Al)固溶体,且逐渐细化的TiB_2相嵌入至金属Ni和Al颗粒中。通过物相分析发现,随着球磨时间的延长,Al衍射峰强度逐渐降低,并发现在球磨时间为36h时形成Ni(Al)固溶体。     

Mg_(17)Al_(12)相在AZ61镁合金半连续铸锭中的分布特性

通过图像分析技术定量分析Mg17Al12相的大小和面积密度,并采用光学显微镜和扫描电镜观察Mg17Al12相在AZ61镁合金半连续铸锭的边部与心部形貌及分布上的差异。结果表明:枝晶形态可以控制Mg17Al12相的大小和分布,枝晶越发达Mg17Al12相形态越细小分布越弥散。铸锭心部的Mg17Al12比边部的细小弥散并且主要分布于枝晶间而边部的Mg17Al12相主要群聚分布在晶界处,这与普通的永久模铸的结果相反。随着冷却速率增加,Mg17Al12相在共晶中所占比例增加,铸锭边部Mg17Al12相的面积密度比心部的高。另外固相反扩散对心部的Mg17Al12相的面积密度也有影响。     

Cu合金化Mg2NiH4储氢体系的组织结构与解氢性能

基于机械反应球磨技术在氢气气氛下成功合成了Mg2NiH4及Cu掺杂Mg2NiH4储氢体系,并采用XRD、SEM、DSC及TGA检测手段对其组织结构与解氢性能进行表征。结果显示,适当提高氢压、延长球磨时间均有助于2Mg-Ni混合物氢化反应的完全化及产物结构的纳米化;Cu掺杂可进一步加快混合物的氢化反应速率,但其产物结构的团聚现象却因MgCu2相的出现而趋于严重;综合热分析表明Cu掺杂不仅降低了Mg2NiH4的解氢温度,还加快了体系的解氢速率;研究结果很好地证实Cu元素是改善Mg2NiH4储氢体系解氢性能最理想的合金化元素之一。     

微晶碳对镁粉快速纳米化、储氢体系温度的影响研究

将微晶碳和镁粉在H2气氛中反应球磨复合,球磨时间为3h,制备的镁碳复合材料的平均粒度在20~120nm,说明适量微晶碳的引入,在短时间内,可实现镁粉的纳米化。对其进行吸氢性能研究,70Mg30C材料的储氢密度,在8min内可达5.0%(wt),微晶碳含量越高,储氢时间越短。储氢体系温度瞬间升高200℃,得益于微晶碳在球磨中的助磨作用和镁粉吸氢的催化作用。     

Effect of transition metal on the hydrogen storage properties of Mg–Al alloy

Mg–Al alloys were prepared via sintering combined with ball milling, and the effect of a transition metal (TM = Ti, V, Ni) on the hydrogen storage properties of these alloys was investigated; the alloys were characterized via X-ray diffraction, pressure composition isotherms, and differential scanning calorimetry. The results showed that the alloys were mainly composed of Mg and the Mg₁₇Al₁₂ phase, and the cell volume of these phases decreased after the addition of TM (TM = Ti, V, Ni), which is attributed to the improved hydrogenation kinetics of Mg–Al alloy. Moreover, the hydrogenation/dehydrogenation temperature of the Mg–Al alloy decreased with the addition of TM (TM = Ti, V, Ni). Ti, Ni, and V acted as a catalyst, thereby lowering the reaction barrier for dehydrogenation and promoting the reversible hydrogenation reaction of the Mg–Al alloy. The onset temperature of dehydrogenation of the Mg–Al–V alloy was ~244 °C, which was 66 °C lower than that of the Mg–Al alloy (~310 °C). And the apparent activation energy of the Mg–Al–V alloy was 80.1 kJ mol^?1, where it was 34.6 kJ mol^?1 lower than that of Mg–Al alloy.     

Effect of strain rate and ball milling of reinforcement on the compressive response of magnesium composites

Effect of strain rate change and reinforcement ball milling on the compressive response of Mg composites is investigated in this work. Quasi-static response was determined using a servo hydraulic MTS machine while dynamic response was assessed by Split Hopkinson Pressure Bar. The presence of either as-received or ball milled Al particles significantly assisted in improving compressive response of Mg in both regimes, compared to monolithic Mg. In the quasi-static regime, the Mg/1.626Al composite containing ball milled Al particles exhibits significantly higher compressive yield strength, ultimate compressive strength and work of fracture of (+76, +87% and +58%) compared to monolithic Mg. However, with a fixed amount of Al, composites containing ball milled particles show a higher strength compared to composites containing as-received particles. Results also revealed that the tremendous increase in strain rate led to an increase in flow stress of all synthesized material while the failure strain was marginally compromised.     

多重结构Ti-B4C/Al2024复合材料的组织和力学性能

为了研究多重结构对铝基复合材料力学性能的影响,将气雾化态Al2024合金粉末与球磨不同时间的Ti-10%(质量分数,下同)B_4C复合粉末混合,采用热压烧结和热挤压的方法制备多重结构Ti-B_4C/Al2024复合材料。通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和拉伸试验机对不同材料的显微组织与力学性能进行观察和测试,并对多重结构复合材料的强韧化行为进行讨论。结果表明:Ti-B_4C/Al2024复合材料多重结构包括基体Al2024、核壳结构Ti/Al₁₈Ti_2Mg_3组织和B_4C颗粒。向Al2024中加入5%预先球磨6h后的Ti-B_4C粉末时,其屈服强度从107MPa提高到122MPa,并且表现出与热挤压Al2024合金几乎相同的伸长率。当球磨时间延长至12h时,试样5TB-12h的伸长率可达到16.4%。然而,复合材料的伸长率随着Ti-B_4C添加量的增加而降低。     

储氢材料67Mg29C3Ni1Al的放氢动力学研究

采用氢气反应球磨法,将煤基微晶碳及少量Ni和Al添加到镁粉中在1MPa氢气中球磨3h制得储氢材料67Mg29C3Ni1Al.放氢测试结果表明,温度越高,放氢速度越快,放氢量越大,数据拟舍得出放氢反应为表观一级反应.根据阿伦尼乌斯方程计算得出,在300～350℃范围内,放氢反应表观活化能为(138.0±6)kJ/mol.与储氢材料70Mg30C及纯MgH2相比,微晶碳和催化剂Ni、Al缩短了储氢材料的放氢时间,加快了放氢速度,提高了放氢量,降低了表观活化能,放氢动力学性能得到了改善.     

铝对镁碳储氢材料性能的影响

在球磨法制备镁碳储氢材料的过程中添加铝,制备了储氢材料50Mg40C10Al.用透射电子显微镜、X射线衍射和差示扫描量热分析对储氢材料的粒度、结构和教氢温度进行了测定.结果表明,球磨过程中铝不储氢;添加铝能提高铗碳储氢材料的储氢密度并降低其放氢温度,50Mg40C10Al的储氢密度达5.82%(质量分数),初始放氢温度为227.4℃.     

Formation of magnesium nanocomposite via mechanical milling

Nanocomposite Mg5wt%Al has been synthesized via mechanochemical milling of elemental Mg, Al and Ti powders with polyethylene–glycol. TiH₂ phase was formed through the reaction between Ti and polyethylene–glycol during the milling as well as the sintering processes. Formation of ultra-fine particles of a few nanometer in size was observed within the matrix grains. The formation of TiH₂ particles is hypothesized to occur through two stages. In the first stage, Ti is supersaturated in the Mg matrix during high energy milling while polyethylene–glycol decomposes to react with Mg as well as Ti which is not solid solute in the Mg matrix. In the second stage during sintering, the hydrogen and Ti released from the Mg react with each other, thus forming nanoparticles. As a result of the nanoparticles, the nanocomposite manifests improved yield strength and ductility in comparison to it counterpart.     

氢在不同成分和显微组织的Mg-Ni合金电极中的扩散能力研究

采用机械球磨的方法,制备了不同成分和显微组织的MgxNi(x=1%、1.5%、2%(原子分数))合金粉,并采用X射线衍射(XRD)和扫描电子显微镜的方法研究了Mg/Ni比对机械球磨过程中Mg-Ni合金粉末组织结构演变的影响。在不同的电位扫描速度下,对具有不同Mg/Ni比和显微组织结构的Mg-Ni合金电极循环伏安曲线进行了测量,并由此计算出了氢在这些电极中的扩散系数,分析了合金成分和显微组织对Mg-Ni合金电极中氢扩散能力的影响。其结果表明,降低Mg/Ni比,能提高Mg-Ni合金在球磨过程中非晶相的形成能力,Mg-Ni和Mg1.5Ni合金获得完全非晶相的球磨时间分别是120和160h。在由细小、分散并且完全非晶态的Mg-Ni合金颗粒制备的电极中,氢表现出较强的扩散能力,其扩散系数为1.98×10-8cm2/s。     

球磨对碳纳米管增强泡沫铝基复合材料压缩与吸能性能的影响

因碳纳米管（CNTs）具有优异的性能,被认为是金属基复合材料理想的增强体,因此如何制备得到CNTs增强体均匀分散的金属基复合材料一直是本领域的研究热点。本文通过原位化学气相沉积（CVD）、短时球磨和填加造孔剂的工艺成功制备了CNTs增强的泡沫铝基复合材料,着重研究了球磨过程对复合泡沫铝的微观形貌、压缩性能和吸能性能的影响规律。结果表明,随着球磨时间的延长,CNTs的分散性提高并逐步嵌入铝基体中,使复合泡沫铝的组织均匀性得到改善。相对于未球磨的含CNTs 3.0wt%的复合泡沫材料,当球磨时间增加至90 min时,复合泡沫铝的孔壁硬度、屈服强度和吸能能力分别提高了67%、126%和343%。     

Solid state reaction and formation of nano-phase composite hydrogen storage alloy by mechanical alloying of MmNi3.5(CoMnAl)1.5 and Mg

In this work MmNi_3.5(CoMnAl)_1.5 and Mg were mechanically alloyed to prepare composite hydrogen storage alloys. The microstructural variation of the alloy resulted from the mechanical alloying was characterized by X-ray diffraction, SEM and TEM analysis. It was found that solid state reaction occurred between MmNi_3.5(CoMnAl)_1.5 and Mg components, resulting in Mm₂Mg₁₇ phase formation. The alloy obtained by ball milling contains homogeneously distributed Mg, MmNi_3.5(CoMnAl)_1.5 and Mm₂Mg₁₇ phases of nanometer size. It was also found that Mg₂Ni was formed after the mechanically alloyed samples were annealed. The mechanism of the reaction has been proposed based on the estimation of the heat of formation using Miedema's theory and is in accordance with the experiment result of lattice constant measurement of ball milled sample and its structure variation during annealing.