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
周秋香
,
王荷芳
,
赵新强
,
岳琳
,
王延吉
机械工程材料
doi:10.3969/j.issn.1000-3738.2004.04.012
以Cd(CH3COO)2·2H2O和3-(3-吡啶基)丙烯酸(pda)为原料,在水热合成反应条件下,合成了一种新型多纳米孔道的二维配位聚合物[Cd(pda)2]n.对其进行了元素分析、红外光谱表征、差热热重分析和X射线衍射测定.结果表明:该配位聚合物属三斜晶系,P-1空间群,它为一个二维结构,在220℃下呈稳定结构.
关键词:
多纳米孔道配位聚合物
,
合成
,
晶体结构
余迎新
,
张少峰
,
宋海斌
人工晶体学报
doi:10.3969/j.issn.1000-985X.2004.03.025
在中温水热条件下,利用醋酸镉和3-(3-吡啶基)丙烯酸反应,合成了一种新型的二维配位聚合物[Cd(C8H7NO2)2]n.对其进行了元素分析、红外光谱表征和X射线单晶衍射测定.该配位聚合物属三斜晶系,P-1空间群,晶胞参数为:a=0.5031(2)nm,b=0.8109(3)nm,c=0.9531(4)nm,α=69.411(6)°,β=80.554(6)°,γ=76.020(7)°,V=0.3519(2)nm3,Z=1,dc=1.929g/cm3,μ=1.575 mm-1,F(000)=202,R1=0.0313,wR2=0.0641.
关键词:
二维配位聚合物
,
水热合成
,
晶体结构
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 Alloys and Compounds
Cr(N)-beta-Cr2N nanoparticles were prepared by arc-discharge process in a mixture of argon, hydrogen and nitrogen gases. The nanoparticles are composed of the two components, i,e. Cr(N) solid-solution nanoparticles (polyhedral shape) and beta-Cr2N nitrogen-deficiency nanoparticles (cuboidal shape). Both the nanoparticles share a similar shell-core structure: the shell consists of chromium oxide Cr-2(CrO4)(3) or Cr-O (20 at% Cr), and the complex of Cr and N-O, as well as the core of Cr(N) solid-solution or beta-Cr2N. Moreover, the nanoparticles have a blocking temperature of 29 K and a narrow size distribution. The weak ferromagnetism can be interpreted in terms of the presence of non-compensated surface spins. For the field-cooled (FC) magnetization with the field of 0.01 T, a perfect Curie-Weiss fit of the data above 50 K indicates paramagnetic characteristics of the nanoparticles. This is supported by the hysteresis loops at 5 and 295 K. The paramagnetic Curie temperature of -124 K suggests the type of dominant interaction is antiferromagnetic. (c) 2006 Published by Elsevier B.V.
关键词:
arc-discharge;nanoparticles;blocking temperature;Curie-Weiss law;fe-co(c) nanocapsules;chromium;temperature;fabrication;particles;oxidation;diborane;nitrides;coatings;metals
裴雨辰
,
李嘉禄
,
于长清
,
李淑琴
材料工程
doi:10.3969/j.issn.1001-4381.2008.05.002
以Y2O3和Al2O3陶瓷粉体作为烧结助剂,原位无压液相烧结制备Si3N4-Si2N2O复相陶瓷,Si2N2O相通过SiO2+Si3N4 2Si2N2O反应生成.生坯采用注凝成型制备,然后在1780℃保温2h烧结,烧结体基本由板条状的Si2N2O及长柱状的β-Si3N4晶粒构成.Si2N2O陶瓷相对于Si3N4陶瓷而言,具有优异的抗氧化性能,低的弹性模量,以及低的热膨胀系数,因此,Si2N2O-Si3N4复相陶瓷结合了两者的优异性能,并大大提高了材料的热冲击性,材料的热冲击温差即使达到1200℃,其残余强度基本上没有变化.
关键词:
原位无压
,
Si2N2O
,
Si3N4
,
复相陶瓷
