Mg2Ni纳米材料的电化学性能初步研究

时机械合金化制备的Mg2Ni纳米材料进行了循环伏安测试,获得了样品随扫描速度和温度变化的循环伏安曲线.测试结果表明:氧化峰的电位随扫描速度的加快有所正移;机械合金化制备的样品在室温下的吸氢性能显著增强,吸放氢速度随温度的升高而加快.X射线小角散射结果表明高能球磨制备的Mg2Ni粉末具有1～5nm以及5～10nm范围内的粒度分布,较小的粒度使得吸/放氢反应的活性位置增多和放氢的扩散路径降低,这可能是机械合金化制备的Mg2Ni纳米材料贮氢性能显著提高的原因.     

Mg2Ni纳米晶储氢材料的机械合金化制备工艺研究

利用机械合金化方法制备了Mg2Ni纳米晶粉末,根据不同球磨参数下样品的X射线衍射结果,分析了球磨过程中相组成、粉末晶粒度等的变化,研究了球磨时间、球磨转速、过程控制剂等工艺条件对粉末晶粒度、机械合金化程度的影响.结果表明:在较高的转速下进行循环变速运行并加入合适的过程控制剂可以使生成Mg2Ni的时间提前,完全合金化的过程缩短,得到的Mg2Ni晶粒度为10nm左右.对Mg2Ni纳米晶粉末进行了初步的贮氢性能研究,结果表明:机械合金化制备的样品在室温下即可吸氢,贮氢性能较之传统材料有较大改善.     

机械合金化制备的Mg-Al-Ni系储氢合金及其性能

在机械合金化的过程中不断增加球料比,在24h内制得性能较好的Mg-Al-Ni系储氢材料.用P-C-T曲线测试仪进行测试,并利用X射线衍射和扫描电镜对材料吸放氢前后的变化进行了表征.研究表明,Mg1.8Al0.2Ni合金的吸氢相为Mg2Ni和由Mg、Al、Ni元素组成三元化合物.球磨26h Mg1.8Al0.2Ni粉末试样在150℃下开始吸氢.     

快淬纳米晶Mg_2Ni型合金的贮氢性能

为了改善Mg2Ni合金的贮氢性能,用Cu部分替代合金中的Ni,用快淬工艺制备了纳米晶Mg2Ni型Mg20Ni10-xCux(x=0、1、2、3、4)合金。用XRD、SEM、HRTEM分析了铸态及快淬态合金的微观结构;用自动控制的Sieverts设备测试了合金的吸放氢动力学性能;用程控电池测试仪测试了合金电极的电化学贮氢性能。结果表明,所有的快淬态合金具有纳米晶结构,Cu替代Ni及快淬处理没有改变合金的Mg2Ni型主相。合金的吸放氢容量及动力学随淬速的增加而增加。此外,快淬处理显著地提高了合金的电化学贮氢容量,但使循环稳定性下降。     

机械球磨制备La2Mg17/Ni复合材料的微观结构及气态吸放氢性能

为提高La2Mg17贮氢合金的吸放氢性能,以机械球磨La2Mg17+Ni+NbF5在氩气为保护气氛围下制备复合材料。采用XRD分析了球磨后复合材料的微观结构,用SEM观察了其形貌。通过自动控制的Sieverts设备测试了材料的吸放氢动力学性能。研究表明混合球磨后复合材料的吸放氢性能有了显著的提高,进一步说明Ni粉、NbF5促使了材料纳米晶/非晶结构的形成,而该结构的形成是材料吸放氢性能提高的主要原因。     

Cu的添加对Mg2Ni合金储氢性能的影响

采用机械合金化法,制备了Mg2Ni1-xCux(x=0、0.1、0. 3)合金,研究了Cu对Mg2Ni储氢合金储氢性能的影响.XRD和SEM研究表明Cu的加入使合金中产生了Cu11Mg10Ni9新相.利用PCT测试仪测定了合金的储氢性能,结果表明,添加Cu元素会降低合金的吸氢量,但能有效地提高放电容量和循环稳定性.制备出的Mg2Ni0.9Cu0.1与Mg2Ni0.7Cu0.3相比,前者具有较大的吸氢量,后者的放电容量较大,循环稳定性较好.     

镁基储氢合金氢化物Mg2NiH4的制备及性能研究

以不经压制的Mg、Ni混合粉末为原料,利用氢化燃烧合成法在合成温度850 K和1.8 MPa初始合成氢压下制备了镁基储氢合金氢化物Mg2NiH4,并利用XRD及PCT仪分析了其物相组成和储氢性能.研究表明,产物由单一物相Mg2NiH4组成,无未反应的Ni和不完全氢化的Mg2NiH0.3;相对于传统熔炼法制备的Mg2Ni,氢化燃烧合成产物具有更高的氢化活性,在没有任何活化处理的前提下,第一次吸氢就能以很快的速度达到饱和吸氢量,同时在任何吸氢温度下均具有较好的吸氢动力学性能,且随温度的降低,最大吸氢量降低幅度较小,平台压和吸放氢温度的关系为:lgP(0.1 MPa)=-3 187.6/ T 6.362 4(吸氢),lgP(0.1 MPa)=-3 468.4/T 6.694 3(放氢).     

合金化对Mg-Ni系合金储氢性能的影响:综述

Mg基合金具有储氢量大、质量轻、资源丰富、价格低廉等特点,但其较高的放氢温度和较慢的吸放氢速率是限制其应用的关键问题.合金化是改善Mg基储氢合金吸放氢热力学和动力学的有效方法,在纯Mg中添加Ni会形成Mg2 Ni,其吸放氢热力学与动力学均会得到明显改善,但仍不够理想,有待进一步提高.本文就合金化对Mg-Ni系合金储氢性能的影响进行了综述,整理了各合金元素的添加对Mg-Ni系合金吸放氢热力学与动力学的影响,最后对Mg-Ni系合金的发展进行了展望.     

Co替代Ni对快淬纳米晶/非晶Mg_2Ni型合金吸放氢动力学的影响

为了改善Mg2Ni型合金的吸放氢动力学性能,用Co部分替代合金中的Ni。用快淬工艺制备了纳米晶和非晶Mg20Ni10-xCox(x=0,1,2,3,4)贮氢合金,分析了铸态及快淬态合金的微观结构,测试了合金的吸放氢动力学性能。研究了Co替代Ni及快淬工艺对合金吸放氢动力学性能的影响。结果表明,在快淬合金(x=0)中没有发现非晶相,但快淬合金(x=4)显示了纳米晶/非晶结构,表明Co替代Ni提高了Mg2Ni型合金的非晶形成能力。Co替代Ni不改变合金的Mg2Ni主相,但形成了第二相MgCo2。随Co替代量的增加,合金的吸氢量先增加而后减少,但其放氢量随Co替代量的增加而单调增加。     

机械合金化(Mg+Mg2 Ni)+TiO2合金的储氢性能

用机械合金化法合成了(Mg Mg2Ni) TiO2储氢合金,借助XRD分析了TiO2的加入对合金的物相结构的影响,SEM考察了合金的形貌.TiO2在合金的吸放氢过程中起到很好的催化作用,降低合金放氢温度并且提高合金储氢量,(Mg Mg2Ni) 10wt%TiO2合金在573K下的储氢量是5.84wt%.     

Mg_(76-x)V_xTi_(12)Ni_(12)(x=4、8、12、16)合金制备与贮氢性能的研究

采用机械合金化制备了Mg76-xVxTi12Ni12(x=4、8、12、16)合金,通过X射线衍射(XRD)、扫描电子显微镜(SEM)和压强-成分-温度(PCT)等分析方法对合金粉末进行分析和表征。结果表明,合金相主要由Mg2Ni相和Ti2Ni相组成,Mg76-xVxTi12Ni12(x=4、8、12、16)合金贮氢量(质量分数,下同)分别为3.71%、3.12%、2.85%和2.33%,随着V含量的增加,合金的贮氢量下降,合金氢化物释氢率分别为95.1%、97.1%、84.9%和94.4%,适量的V能提高合金氢化物的释氢率。     

Synthesis of Nanostructured Mg-Ni Alloy and Its Hydrogen Storage Properties

Nanostructured Mg-Ni alloy with the particle size in the range of 40-50 nm was synthesized by the thermal decomposition of bipyridyl complexes of Mg and Ni metals at 773 K for 24 h under dry argon gas ambient. The as-prepared nano-alloy was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for compositional and structural analysis. The alloy exhibited superior hydrogen absorption and desorption behavior with 3.2 wt% absorption within 1 min at 573 K and about 3 wt% desorption within 5-10 min at 573 K. This favorable behavior of Mg-Ni compound for the hydrogen storage is due to the specific nanostructure of the material. The low activation energy values and favorable thermodynamics indicate that the prepared Mg-Ni alloy is an attracting material for hydrogen storage applications.     

Preparation of MgH2–Ni, MgH2–Ni–Si and MgH2–Ni–Ni2Si composites by mechanochemical method and their hydrogen absorption and desorption properties

To improve kinetics for hydrogen absorption of Mg and hydrogen desorption of MgH₂, ternary composites were prepared from MgH₂, Ni and Si or Ni₂Si by a mechanochemical technique. The X-ray diffraction spectra of the resultant ternary composites after the initial hydrogen desorption treatment at 400 °C in vacuum suggested that in all composites the nanocrystalline Mg₂Ni would be formed in the intergrain region between Mg and Ni components, while in the MgH₂–Ni–Si composite the nanocrystalline Mg₂Si would also be formed in the intergrain region between Mg and Si components. However, Ni₂Si did not form any alloys with Mg. The hydrogen absorption rate at 250 °C for the MgH₂–Ni–Ni₂Si composite was comparable to that for the MgH₂–Ni and MgH₂–Ni–Si composites, while the hydrogen desorption rate at 250 °C decreased in the order of MgH₂–Ni > MgH₂–Ni–Ni₂Si > MgH₂–Ni–Si. In contrast, the hydrogen desorption rate at 220 °C for the MgH₂–Ni–Ni₂Si composite was faster than that for the MgH₂–Ni composite, suggesting that Ni₂Si was a key material in the improvement of hydrogen desorbability at lower temperatures. Moreover, the most plausible reaction model and the rate-determining process for hydrogen absorption and desorption at 250 °C were determined.     

B和C对Li-N-H络合氢化物储氢性能的影响

利用机械合金化方法制备了Li-N-H络合氢化物,并研究B、C作为催化剂对其储氢性能的影响. 结果表明：LiNH₂、Li₂NH为Li-N-H络合氢化物的主要储氢相,随B的加入,储氢相的非晶化程度提高. 虽然B、C的添加均使储氢量下降,但n(B)∶n(C)=1∶2的混合添加提高了有效储氢量,同时也提高吸放氢动力学性能;B的添加可有效降低可逆吸放氢温度,适当增加球磨时间,有利于提高可逆吸放氢量.     

Nanostructured electrode materials for Ni-MH x batteries prepared by mechanical alloying

Nanocrystalline TiFe- and Mg₂Ni-type alloys were prepared by mechanical alloying followed by annealing. The structure and electrochemical properties of these materials were studied. The properties of hydrogen host materials can be modified substantially by alloying to obtain the desired storage characteristics. It was found that the respective replacement of Fe in TiFe by Ni and Mn improved not only the discharge capacity but also the cycle life of these electrodes. On the other hand, a partial substitution of Mg by Mn in Mg_2?x M _x Ni alloy leads to an increase in discharge capacity, at room temperature. Furthermore, the effect of the nickel and graphite coating on the structure of the nanocrystalline alloys and the electrodes characteristics were investigated. In Mg₂Ni-type alloy mechanical coating with graphite effectively reduced the degradation rate of the studied electrode materials.     

Ca3-xMg2+xNi13合金的储氢性能

为了弄清Mg含量对Ca3Mg2Ni13型化合物结构参数和储氢性能的影响,利用X射线衍射研究了Ca3-xMg2+x,Ni13(x=0.5,1.0和1.5)合金的相结构,并采用Sieverts型设备测量了其P-C-T曲线.研究表明,Mg在Ca3Mg2Ni13型化合物中的最大固溶度接近于Ca1.5Mg<,3.5>Ni13合金中的Mg含量.固溶的Mg含量增加导致化合物点阵常数减小,这可以有效地改善吸放氢热力学性能,其中Ca2Mg3Ni13吸、放氢的焓变分别为-28,30 kJ/mol H2.此外,Ca2Mg3Ni13在吸放氢循环过程中不发生氢致非晶化和氢致分解,因而具有良好的循环稳定性.     

The reaction of hydrogen with Mg-Cd alloys prepared by mechanical alloying

In this paper, we present the hydrogen storage properties of Mg-Cd alloys prepared by ball milling. Mechanical alloying of a mixture of Mg and Cd elemental powders containing up to 20 at.%Cd leads to a magnesium solid solution. The lattice spacings of the hcp Mg phase shrink with dissolution of cadmium atoms in Mg. The mechanically alloyed pure Mg-Cd alloys are very difficult to activate for hydrogen absorption. However, if vanadium and graphite additives are added, a Mg(Cd)-V-C nanocomposite forms after ball milling and the activation then becomes very easy. The hydrogen absorption/desorption kinetics are very fast. The plateau pressure and slope of hydrogen absorption/desorption increase, while the hydrogen storage capacity decreases with increasing cadmium content.