Sushma Bhat and P.N.Kotru(Dept. of Physics
,
Uuiversity of Jammu
,
Jammu -180 001
,
India) M.L.Koul(Dept. of Chemistry
,
Uuiversity of Jammu
,
Jammu
,
India)
材料科学技术（英文）
Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamolybdate crystals are associated with thirty water molecules;the composition being La2Mo7O24.3OH2O. It is shown that all the thirty water molecules associated with lanthanum heptamolybdate crystal are lost during its decomposition, leading to its anhydrous form. Results obtained on application of TG based models, viz. Horowitz-Metzger,Coats-Redfern and Piloyan-Novikova and of DSC based methods viz. Roger-Morris-Smith and Barret, regarding solid state reaction kinetics are also reported. The random nucleation model is shown to be the one that is relevant to the decomposition of lanthanum heptamolybdate. The kinetic parameters, viz.the order of reaction. frquency factor, energy of activation and entropy using above mentioned models are computed and shown to bear reasonably good agreement
关键词:
Sushma Bhat and P.N.Kotru(Dept. of Physics
,
University of Jammu
,
Jammu
,
India)
材料科学技术（英文）
Crystals of mixed NdLa heptamolybdates (max. size0.75×0.75×0.75 mm3) grown by silica gel technique were characterized using EDAX, IR, optical and scanning electron micrscopies.X-ray as well as electrn diffraction. The composition of the crystals was determined as (Nd1/2 La1/2 )2 Mo7O24·35H2O.The crystals exhibit varied morpholgies including square and octagonal platelets, cuboids, multifaceted crystal in coalesced and aggregated forms and spherulites.The XRD results indicate crystallinity of the grown material. Electron diffraction results suggest thermal instability of the material. IR results show the presence of peaks due to water and metal-oxygen bonds
关键词:
杨金瑞
,
余尚先
,
顾江楠
高分子材料科学与工程
通过对resol(羟甲基酚化合物和低分子量羟甲基酚树脂)DEPT135图谱的分析讨论,得到一系列计算resol微细结构参数的经验公式.根据DEPT135图谱可判断是否发生缩聚反应,根据经验公式可计算酚单体各个活性点参与反应百分率或酚羟基导入率、不同类型缩聚所占百分率及低分子量羟甲基酚树脂的平均核体数.
关键词:
羟甲基酚化合物
,
羟甲基酚树脂
,
DEPT135
,
结构参数
Journal of Applied Physics
Two kinds of junctions based on doped graphene nanoribbons (GNRs) are designed and studied in this article. One is the N-doped armchair GNR (AGNR) joined directly by B-doped AGNRs, and another is similar, but there is an undoped AGNR between them. The transport properties are calculated using the full self-consistent ab initio nonequilibrium Green's function and density-functional theory methods under external bias. We find that the I-V curves for both junctions have a striking nonlinear feature and show large negative differential resistance properties, not only at the positive bias but also at the negative one. The results also indicate that the diode-like properties are kept and the rectification coefficient is very high within a wide bias region. Our calculations reveal that the formation of these peculiar transport behaviors is due to the great changes of the transmission spectra and the projected self-consistent Hamiltonian eigenvalues with the applied bias voltage. These findings suggest that the doped AGNRs may offer unique opportunities for the future development of nanoscale electronics. (C) 2011 American Institute of Physics. [doi:10.1063/1.3605489]
关键词:
walled carbon nanotubes;electronic-properties;lithium absorption;edge;ribbons;conductance;defects;states
许小亮
,
杨晓杰
,
付竹西
功能材料
ZnO基注入式发光二极管和激光器件的研究目前仍处于初级阶段,即p型ZnO和ZnOp-n结的制备与特性研究.由于ZnOO薄膜中存在较强的自补偿机制,使得很难有效地施行p型元素的掺杂.本文介绍了目前国际上通用的掺杂方法,对不同方法制备的p型ZnO和ZnOp-n结的特点进行了比较分析,并讨论了目前生长高质量的突变型ZnOp-n结所面临的问题.
关键词:
ZnO
,
同质p-n结
,
激光器件
樊胜
,
阎芳
,
张鸿洲
,
赵志祥
原子核物理评论
doi:10.3969/j.issn.1007-4627.2004.04.037
在En ≤20 MeV的情况下, 忽略了粒子的二次发射过程, 认为复合系统的形成截面是能量相关的, 得到了理论模型清晰、公式形式简单的半经验计算方法. 在靶核23≤A≤209的范围内, 利用大量(n, p) 和(n, α)反应的截面实验数据对可调参数进行了研究, 得到了参数对靶核的N和Z以及入射能量的依赖关系. 对得到的参数做了定性的解释, 利用普适参数对(n, p) 和(n, α)反应的激发函数做了预言, 预言值在其误差范围内与实验数据一致.
关键词:
激发函数
,
半经验计算方法
,
系统学参数
