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排序方式: 共有459条查询结果,搜索用时 15 毫秒
441.
From the results of first principles tight-binding linear muffin-tin orbital (TB-LMTO) calculations, half-metallic ferromagnetism is proposed in Zn(TM)O2 with a chalcopyrite structure. The calculated electronic and magnetic property shows that consistent with the integer value for the total magnetic moment, half metallicity is obtained for ZnCrO2, ZnMnO2, ZnFeO2, ZnCoO2 and ZnNiO2. A careful analysis of the spin density reveals the ferromagnetic coupling between the p–d states and the cation dangling-bond p states, which is believed to be responsible for the stabilization of the ferromagnetic phase. The calculated heat of formation, bulk modulus and cohesive energy are reported. 相似文献
442.
Wei Chen Steen Mørup Mikkel F. Hansen Tobias Banert Urs A. Peuker 《Journal of magnetism and magnetic materials》2008
We have prepared magnetic beads consisting of iron oxide nanoparticles in a polymethyl methacrylate (PMMA) and a polyvinyl butyral (PVB) matrix. High-field Mössbauer studies show that the particles have an almost perfect collinear spin structure and magnetization measurements show that they are superparamagnetic at room temperature at a time scale of seconds. We have followed the oxidation of the particles, which initially have a stoichiometry close to magnetite. The oxidation is fast during the first 2–3 weeks and then continues slowly such that even after 30 weeks the particles have not completely transformed to maghemite. The PVB beads are hydrophilic and biocompatible and are therefore well suited for applications in medicine and biology. 相似文献
443.
Hojin Ryu 《Physica B: Condensed Matter》2008,403(18):3195-3198
CaAl2O4:Eu2+ co-doped with varying concentrations of Er3+ was prepared by solid-state reaction method. Prepared materials with 1 mol% Eu2+ and 2-10 mol% of Er3+ were investigated for their photoluminescence properties. Phase, morphology and crystalline structure were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Broad band UV-excited luminescence was observed for CaAl2O4:Eu2+, Er3+ in the blue region (λmax=440 nm) due to transitions from 4f65d1 to the 4f7 configuration of the Eu2+ ion. The Er3+ ion co-doping generates deep traps, which results in longer decay time for phosphorescence. 相似文献
444.
Gong-Yi Li Xiao-Dong Li Hao Wang Zhong-Quan Li 《Applied Physics A: Materials Science & Processing》2008,93(2):471-475
Long silicon nitride (Si3N4) nanowires with high purity were synthesized by heating mixtures of SiO2 powders and short carbon fibers at 1430°C for 2 h in a flowing N2 atmosphere. The nanowires had the length of 1–2 millimeters and the diameters of 70–300 nm, and were mainly composed of ⍺-Si3N4, growing along the [001] direction. The vapor–solid (VS) mechanism was employed to interpret the nanowires growth. 相似文献
445.
M.S.F. da Rocha T.E.A. Santos V.R. Hering J.H. Vuolo V.P. Mammana 《Applied Surface Science》2008,254(6):1859-1869
A statistical data analysis methodology was developed to evaluate the field emission properties of many samples of copper oxide nanostructured field emitters. This analysis was largely done in terms of Seppen-Katamuki (SK) charts, field strength and emission current. Some physical and mathematical models were derived to describe the effect of small electric field perturbations in the Fowler-Nordheim (F-N) equation, and then to explain the trend of the data represented in the SK charts. The field enhancement factor and the emission area parameters showed to be very sensitive to variations in the electric field for most of the samples. We have found that the anode-cathode distance is critical in the field emission characterization of samples having a non-rigid nanostructure. 相似文献
446.
ZHANG Jian-Fu RUAN Xi-Chao HOU Long LI Xia BAO Jie ZHANG Guo-Guang HUANG Han-Xiong SONG Chao-Hong 《中国物理C(英文版)》2010,34(7)
The light output functions for protons of ST-401 and BC-408 plastic scintillators were measured using white neutron source produced by the 9Be(d,n)10B reaction at the HI-13 Tandem Accelerator at China Institute of Atomic Energy(CIAE).The LOFs of plastic scintillators for protons in the energy range of 0.516.5 MeV were obtained by the time-of-flight(TOF)technique and an iterative procedure.Two parameters(kB and C)were deduced by fitting the experimental data. 相似文献
447.
An efficient pulsed CH3OH terahertz (THz) laser pumped by a TEA CO2 laser is investigated experimentally. To improve photon conversion efficiency and THz laser energy, two cavity configurations of the TEA CO2 laser, which is external and semi-external, are evaluated. The pump intensities are about 4.7 MW/cm2 and 1.2 MW/cm2, respectively. Higher pump intensity and more stable single lines are obtained in the external cavity. For the 3.8 J pump energy of the 9P(16) transition in the external cavity, the maximum terahertz output energy with 570.5 μm wavelength at 160 Pa is 431 μJ. With a 6 J energy pulse in terms of a semi-external cavity, a 353 μJ terahertz emission (570.5 μm) is produced. The corresponding photon conversion efficiencies are 1.36% and 0.705%, increasing by a factor of about 2. 相似文献
448.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
449.
450.