N. Li 1)
,
Y.H. Wen 1)
,
Y.G. Xu 1)
,
M.J. Tu 1)
,
P.Q. Li 2)
,
Y.L. Liu 2) and Y.L.Ma 2) 1) Department of Materials Shaping and Controlling Engineering
,
Sichuan University
,
Chengdu 610065
,
China 2) Xi'an Petroleum Pipe Research Institute
,
Xi'an 710065
,
China
金属学报(英文版)
The effect of quenching temperature on the recovery stress of Fe 18Mn 5Si 8Cr 4Ni shape memory alloy has been studied. The results show that both the maximum recovery stress σ h in heating and the recovery stress σ c at room temperature after heating increased as increasing quenching temperature increased, both σ h and σ c reached maximum at 650℃, and then decreased rapidly with the further increase in quenching temperature,but the descent degree of σ c was far bigger than that of σ h; When the quenching temperature is higher than 850℃, the further increase in quenching temperature had little effect on them; At random quenching temperature, σ c was far bigger than σ h.
关键词:
shape memory alloy
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null
,
null
Journal of Physical Chemistry C
The Li-Mg-N-H system was prepared by reacting magnesium amide [Mg(NH(2))(2)] with lithium nitride (Li(3)N) and investigated with regard to the hydrogen storage properties. Our study shows that the present method is superior to the conventional route in enhancing the reversible dehydrogenation properties. Through optimizing the Li(3)N:Mg(NH(2))(2) ratio in the starting materials, the reversible capacity of U-Mg-N-H system increases to 4.9 wt %, 18% higher than that typically obtained from the Mg(NH(2))(2) + 2LiH mixture at 200 degrees C. Furthermore, increasing the Li(3)N:Mg(NH(2))(2) ratio is effective for mitigating the ammonia release from thus-prepared samples. Combined property/structure investigations indicate that the obtained enhancements should be ascribed to the effects of LiNH(2) and LiH that were in situ generated from the excess Li(3)N. LiNH(2) may promote the dehydrogenation reaction via seeding the reaction intermediate. The concurrently generated LiH acts as an effective ammonia trapping agent. These findings highlight the potential of "intermediate seeding" as a strategy to enhance the reversible hydrogen storage properties of metal-N-H systems.
关键词:
complex hydrides;ultrafast reaction;amide;improvement;desorption;linh2;destabilization;mechanism;mixtures;imides
Journal of Materials Research
The effect of Li(3)N additive on the Li-Mg-N-H system was examined with respect to the reversible dehydrogenation performance. Screening Study with varying Li(3)N additions (5, 10, 20, and 30 mol%) demonstrates that all are effective for improving the hydrogen desorption capacity. Optimally, incorporation of 10 mol% Li(3)N improves the practical capacity from 3.9 wt% to approximately 4.7 wt% hydrogen at 200 degrees C, which drives the dehydrogenation reaction toward completion. Moreover, the capacity enhancement persists well over 10 de-/rehydrogenation cycles. Systematic x-ray diffraction examinations indicate that Li(3)N additive transforms into LiNH(2) and LiH phases and remains during hydrogen cycling. Combined structure/property investigations suggest that the LiNH(2) "seeding" should be responsible for the capacity enhancement, which reduces the kinetic barrier associated with the nucleation of intermediate LiNH(2). In addition, the concurrent incorporation of LiH is effective for mitigating the ammonia release.
关键词:
complex hydrides;improvement;mixtures;imides;amide;h-2
Molecular Physics
The ab initio method based on density functional theory at the B3PW91 level has been applied to study the geometric, electronic, and magnetic properties of neutral and anionic Au(n)Pd (n = 1-9) clusters. The results show that the most stable geometric structures adopt a three-dimensional structure for neutral Au(7)Pd and Au(8)Pd clusters, but for anionic clusters, no three-dimensional lowest-energy structures were obtained. The relative stabilities of neutral and anionic Au(n)Pd clusters were analysed by means of the dependent relationships between the binding energies per atom, the dissociation energies, the second-order difference of energies, the HOMO-LUMO energy gaps and the cluster size n, and a local odd-even alternation phenomenon was found. Natural population analysis indicates the sequential transfer from the Pd atom to the Au(n) frame in Au(1,2,3,5)Pd and Au(2,3)Pd(-) clusters, and from the Au(n) frame to the Pd atom in other clusters. Much to our surprise, irrespective of whether it is the total magnetic moment or the local magnetic moment, the magnetic moment presents an odd-even alternation phenomenon as a function of the cluster size n. The magnetic effects are mainly localized on the various atoms (Au or Pd) for different cluster size n.
关键词:
neutral and anionic Au(n)Pd clusters;geometrical configuration;density;function method;generalized gradient approximation;photoelectron-spectroscopy;palladium clusters;gold nanoclusters;metal-clusters;exchange;nanoparticles;molecules;chemistry;au-n(-)
Journal of the European Ceramic Society
Dense Si2N2O was successfully synthesized using 2 mol% Li2O as an additive by a hot-pressing method at 1500 degrees C. Compared to other metal oxide additives, Li2O can significantly decrease the sintering temperature of Si2N2O, which is ascribed to the lower melting point of Li2O-SiO2 and the formation of less viscous liquid phase. Increasing Li2O content has no apparent influence on the mechanical and dielectric properties of dense Si2N2O, which is due to the easy evaporation of Li2O at sintering temperature. The mechanical properties of Si2N2O with Li2O additive are comparable to those of Si2N2O synthesized with other additives. The as-prepared bulk Si2N2O with 2 mol% Li2O additive exhibits both low dielectric constant (6.17 at 1 MHz) and loss tangent (0.0008 at 1 MHz) and combines good mechanical performance, indicating it is a potential high-temperature structural/functional material. (C) 2007 Elsevier Ltd. All rights reserved.
关键词:
Si2N2O;sintering;mechanical properties;dielectric properties;silicon oxynitride ceramics;thermal-conductivity;nitride;densification;toughness;strength;yttria;system
杨昊
,
范广涵
,
李军
材料科学与工程学报
采用基于密度泛函理论的第一性原理赝势法计算了本征ZnO、N掺杂、Li掺杂以及Li、N共掺杂ZnO的能带结构、电子态密度和差分电荷分布.计算结果表明:N掺杂的受主能级局域性较强,导致N溶解度较低,Li替位原子受主能级较浅,但是会受到Li间隙原子的补偿.Li、N共同掺入时,N_o-Li_(Zn)复合受主结构并不是ZnO的主要P型来源,N_o受主可以与间隙原子Li_i形成N_o-Li_i结构,该结构可促进N的掺入,并抑制Li_i施主的补偿效应,因而对实现ZnO的P型非常有利.
关键词:
ZnO
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第一性原理
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密度泛函理论
,
双受主共掺杂
裴增文
,
刘晓鹏
,
黄倬
,
李志念
,
王树茂
,
蒋利军
稀有金属
doi:10.3969/j.issn.0258-7076.2010.04.013
采用等容法研究了机械球磨工艺制备的Li-Mg-N-H材料储氧性能,结果发现,在室温下采用氦气对样品室体积进行标定时,由于Li-Mg-N-H材料对氦气有一定量的物理吸附,造成准确Li-Mg-N-H材料样品体积标定误差,进而造成Li-Mg-N-H储氢材料在503 K下放氢容量随压力的降低而增加异常变化.为准确标定样品体积,通过对Li-Mg-N-H材料室温氮气吸附容量测定,并采用迭代计算方法获得准确的储氢材料样品体积,进而测定Li-Mg-N-H储氢材料503 K下放氢PCT曲线,其表现为放氢容量随压力降低而减小的正常变化规律.Li-Mg-N-H储氢材料503 K,9.6 MPa氢压下的最大储氢容量为4.81%(质量分数),放氢过程表现为单一放氢平台特性.
关键词:
轻质储氢材料
,
Li-Mg-N-H
,
储氢性能
,
等容测试方法
刘奕新
,
杨书全
,
张丹丹
,
黎光旭
,
韦文楼
,
郭进
无机材料学报
doi:10.3724/SP.J.1077.2009.00813
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.
关键词:
Li-N-H络合氢化物
,
储氧性能
,
机械合金化
雷哲锋
,
王发展
,
张立岗
,
王欣
,
陈霞
,
王博
,
尚志新
人工晶体学报
采用基于密度泛函理论的计算方法,系列的研究了锯齿型(9,0) ZnO单壁纳米管、Li,N分别掺杂以及Li-2N共掺杂的ZnO纳米管的能带结构、总体态密度、分波态密度.分析发现虽然Li原子单独掺杂不会对纳米管能带结构产生明显影响,但是Li-2N共掺杂比N单独掺杂ZnO纳米管的结构更加稳定,而且Li-2N共掺杂ZnO纳米管是p型简并半导体.
关键词:
ZnO纳米管
,
第一性原理
,
电子结构
,
Li-N共掺
