C.H. Zhou
,
K. Yang
,
D.F. Li and Y.X. Lu(Liaoning Key Lab for Hydrogen and Materials
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China)
金属学报(英文版)
The effect of hydrogen on the deformation behavior of three typical kinds of titanium alloys, pure Ti, Ti-6Al-4V and Ti-15V-3Cr-3Al-3Sn (Ti-15-3), at high temperature has been investigated by short time creep test. XRD and TEM techniques are used to examine the changes in their microstructures. The results show that deformation rutes of pure Ti and Ti-6Al-4V alloy can be greatly increased by hydorgen charping due to an increase of β phase volume in their microstructures. β→α transformation is found to occur in unchanged Ti-15-3 alloy during creep process. The addition of 0. 73wt% hydrogen can completely inhibit the deformation-induced transformation and strengthen the metastable β phase in Ti-15-3 alloy, resulting in a dramatic decrease of deformation rate of this alloy at 700° C.
关键词:
titanium
,
null
,
null
孙丹丹
,
潘尚可
,
任国浩
,
吴云涛
,
商珊珊
,
张国庆
无机材料学报
doi:10.3724/SP.J.1077.2013.12735
针对Ce:Li6Lu(BO3)3晶体有效原子序数(zeff)高的问题,采用低原子序数的Y3+离子部分置换晶体中的Lu3+离子.通过固相合成法制备了Ce:Li6Lu1-xYx(BO3)3(0≤x≤1)固溶体.X射线粉末衍射(XRD)分析表明,该系列固溶体结构与Li6Gd(BO3)3晶体相同,空间群为P21/c.其X射线激发发射(XSL)的发光强度随着Y3+的含量增加而降低,当x=0.5时,固溶体的有效原子序数与Li6Gd(BO3)3闪烁体相当,但XSL发光强度是其1.4倍.Ce:Li6Lu0.5Y0.5(BO3)3的XSL光谱和PL光谱都在400 nm附近出现Ce3+离子的特征峰,可拟合出361和419 nm两个发光分量,分别对应于Ce3+离子的激发态电子的5d1→2F5/2和5d1→2F7/2能级跃迁.Ce:Li6Lu0.5Y0.5(BO3)3固溶体的衰减时间比Ce:Li6Lu(BO3)3略长,为19.6 ns.当x=0.50～0.70时,Ce:Li6Lu1-xYx(BO3)3(0≤x≤1)闪烁体比较适合作为中子探测材料.
关键词:
固相合成
,
Ce∶Li6LU1-xYx(BO3)3
,
X射线激发发射谱
,
PL光谱
,
衰减时间
Progress in Chemistry
Hydrogen storage is a key to the utility of hydrogen as a renewable energy source The encapsulation of hydrogen on porous materials has its special advantages In this review, the fundamentals of the encapsulation are briefly introduced The relevant porous materials of zeolites, metal coordination compounds, hollow glass microspheres, fullerenes and their derivative, and their characteristics on encapsulation of hydrogen are addressed in details Recent progresses on the studies of the encapsulation of hydrogen on porous materials are summarized The differences between the encapsulation and physical adsorption of hydrogen on porous materials are analyzed based on their required operation conditions, material specifications and energy barriers Finally, the perspectives of the applications and further studies on the encapsulation of hydrogen are discussed
关键词:
hydrogen storage;encapsulation;porous materials;molecular-orbital calculations;hollow glass microspheres;boron-nitride;fullerene;diffusion;zeolites;carbon;gases;frameworks;sodalite
Acta Physica Sinica
A first-principles plane-wave pseudopotential method based on the density functional theory is used to investigate the dehydrogenation properties and the influence mechanism of Li(4)BN(3)H(10) hydrogen storage materials. The binding energy, the density of states and the Mulliken overlap population are calculated. The results show that the binding energy of crystal has no direct correlation with the dehydrogenation ability of (LiM)(4)BN(3)H(10)(M = Ni, Ti, Al, Mg). The width of band gap and the energy level of impurity are key factors to affect the dehydrogenation properties of (LiM)(4)BN(3)H(10) hydrogen storage materials: the wider the energy gap is, the more strongly the electron is bound to the bond, the more difficulty the bond breaks, and the higher wile the dehydrogenation temperature be. Alloying introduces the impurity energy level in band gap, which leads the Fermi level to enter into the conduction band and the bond to be weakened, thereby resulting in the improvement of the dehydrogenation properties of Li(4)BN(3)H(10). It is found from the charge population analysis that the bond strengths of N-H and B-H are weakened by alloying, which improves the dehydrogenation properties of Li(4)BN(3)H(10).
关键词:
hydrogen storage materials;first-principles calculation;element;substitution;dehydrogenation;linh2
International Journal of Hydrogen Energy
A systematic investigation on the hydrogen storage properties of Li-Mg-N-H materials with various compositions was performed. Li-Mg-N-H hydrogen storage materials were prepared by mechanically milling LiNH2/MgH2 mixtures with initial molar ratios ranging from 1.5:1 to 3: 1, followed by de/rehydriding at 200 degrees C. It was found that the hydrogen storage capacity of the system was highly dependent on the initial phase ratio of the LiNH2/MgH2 mixture. An optimum hydrogen capacity of about 5 wt% was achieved in the 2.15:1 LiNH2/MgH2 mixture. Different carbon materials, such as the single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes, graphite and activated carbon, were used as additive to improve the hydrogen storage performance. It was found that the dehydriding kinetics of the Li-Mg-N-H material could be markedly improved by adding a small amount of SWNTs, especially in the as-prepared state. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
关键词:
hydrogen storage;dehydriding kinetics;carbon nanotubes;arc-discharge method;system;microstructure;desorption;absorption;behaviors;property;imides
那木吉拉图
,
阮永丰
,
苏小平
,
杨海
,
杨鹏
,
李楠
人工晶体学报
本文在CF4气氛中以提拉法成功地生长出高质量的掺入Tm3+、Ce3+的LiLuF4和LiYF4晶体,对比了Ar和CF4气氛中生长的LiYF4晶体的红外光谱特性,讨论了CF4气氛对LiM(M=Y,Lu)F4晶体生长的影响.同时测试了Tm3+、Ce3+在LiLuF4和LiYF4晶体中的有效分凝系数,从离子半径和晶胞畸变的角度,讨论了Tm3+、Ce3+在LiLuF4和LiYF4晶体中有效分凝系数差别的产生原因.
关键词:
LiYF4
,
LiLuF4
,
晶体生长
,
有效分凝系数
Acta Chimica Sinica
Statistical parameters of the hydrogen bonded network formed in hydrogen bonding solutions were studied on the basis of sol-gel partition theory. With the proposed method, the theoretical and numerical results of these structural parameters were presented under the cases that there exist the activity differences between the proton donors. It was shown that the activity of proton donors has significant effect on the hydrogen bonded networks, and the competition between the proton donors could result in the loose or compact structures, providing a possible clue to control the hydrogen bonded networks.
关键词:
hydrogen bonded network;structural parameters;sol-gel transition;fluids
Acta Physica Sinica
A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the dehydrogenation properties and its influence mechanics on several high-density hydrogen storage materials (MgH(2), LiBH(4), LiNH(2) and NaAlH(4)) and their alloys. The results show that MgH(2), LiBH(4), LiNH(2) and NaAlH(4) high-density hydrogen storage materials are relatively stable and have high dehydrogenation temperature. Alloying can reduce their stability, but the stability of a system is not a key factor to the dehydrogenation properties of high-density hydrogen storage materials. The width of band gap of hydrogen storage materials can characterize the bond strength basically, the wider the energy gap is, the harder the bond breaks, and the higher the dehydrogenation temperature is. The bonding peak of the valence band top of LiNH(2) is attributed mainly to the Li-N bonding, the N-H bond constitutes the low peak, which makes the dehydrogenation temperature of LiNH(2), high, though LiNH(2) has a narrow band gap in respect to LiBH(4) and NaAlH(4), which makes the ammonia release in the dehydrogenation process. Alloying makes the band gap narrow, and the Fermi level goes into the conduction band, which improves the dehydrogenation properties. It was found from the charge population analysis that B-H bond in LiBH(4) is the strongest, H-N bond in LiNH(2) is the weakest, so LiNH(2) is relatively easy to release hydrogen. After alloying, the bond strength of X-H is weakened in every hydrogen storage material, and the N-H bond strength in LiMgNH(2) is the lowest. Therefore, it is perspective to develop LiNH(2) as hydrogen storage from the lowering of dehydrogenation temperature.
关键词:
hydrogen storage material;first-principles calculation;dehydrogenation;ability
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
International Journal of Hydrogen Energy
Hydrogen absorption/desorption properties of La(0.2)Y(0.8)Ni(5-x)Mn(x) (x = 0.2, 0.3, 0.4) alloys for high-pressure hydrogen compression application were investigated systematically. The Pressure Composition isotherms and absorption kinetics were measured at 293, 303 and 313 K by the volumetric method. XRD analyses showed that all the investigated alloys presented CaCu(5) type hexagonal structure and the unit cell volume increased in both a and c lattice axes with Mn substitution. Hydrogen absorption/desorption measurements revealed that Mn could lower the plateau pressure effectively, improve the hydrogen storage capacity and absorption kinetics but slightly increase the slope of the pressure plateau and hysteresis. The study results suggest that La(0.2)Y(0.8)Ni(4.8)Mn(0.2) is suitable for the high-pressure stage compression of the hydrogen compressor and the other two alloys, La(0.2)Y(0.8)Ni(4.7)Mn(0.3) and La(0.2)Y(0.8)Ni(4.6)Mn(0.4), for the preliminary stage. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
关键词:
Hydrogen storage;Metal hydride;Hydrogen compressor;Pulverization;hysteresis;absorption;kinetics;hydrides;systems
