Electron-cyclotron-resonance plasma heating with broadband microwave radiation: Anomalous effects

Affects of microwave bandwidth on the high-charge-states of ion beams extracted from a conventional minimum-B-geometry ECR ion source are first demonstrated. The high-charge-state intensities, produced with broadband microwave radiation are observed to be factors ?2 than those produced with narrow bandwidth microwave radiation at the same power level.     

Theoretical investigation of Mössbauer hyperfine interactions in ordered FeNi and disordered Fe–Ni alloys

Electronic structure spin-polarized calculations were performed for 79-atoms embedded clusters representing the ordered intermetallic compound FeNi, the fcc Fe-rich disordered alloy Fe₈₅Ni₁₅ in an antiferromagnetic (AFM) configuration, and the ferromagnetic (FM) disordered alloy Fe₅₀Ni₅₀. The spin-polarized discrete variational method (DVM) in Density Functional theory was employed. Spin magnetic moments, as well as the ⁵⁷Fe Mössbauer hyperfine parameters isomer shift and magnetic hyperfine fields, were obtained from the calculations. For FM Fe₅₀Ni₅₀, the effect of pressure on the hyperfine field and on the isomer shift was investigated, for three different local atomic configurations surrounding the ⁵⁷Fe probe atom. In the case of the isomer shift, the calculated values were compared to reported experimental data.     

轴向拉伸对Ni纳米线结构和稳定性的影响

采用推广模拟退火算法和Sutton Chen势, 选取fcc[111]结构的Ni纳米线为初始构型, 研究了轴向拉伸对Ni纳米线的结构和稳定性的影响。 研究结果表明: 拉伸程度的大小对Ni纳米线的结构和稳定性有很大的影响; 随着拉伸强度的变化, 纳米线结构分别为fcc[111]结构、 (6, 0)型管＋中心柱状结构（又为螺旋结构）、 (6, 3) 型管＋中心柱状结构、 fcc[110]结构、 过渡结构（为规则结构）和缺陷结构; 从结合能分布来看, 结合能先减小, 再增大, 结合能最小时对应最稳定结构 (6, 0) 型管＋中心柱状结构（又为螺旋结构）。 Atomic structures and stabilities of Ni nanowires are studied by using the generalized simulated annealing method with Sutton Chen potential. The initial structure is face centered cubic [111] structure. The result shows that the length of the supercell strongly affects the structures and stabilities of Ni nanowires. fcc [111] structure, (6, 0), (6, 3) nanowires, fcc[110], transition structure and defect structure are found for different wire lengths. And from the analyses of the binding energy, it is found that (6, 0) nanowires (helical structure) is the most stable form.     

热压制备(AgSbTe2)100-x-(GeTe)x合金的热电性能

以Pb粉、Te粉、Ag粉、Ge粉为原材料,在真空气氛下合成(AgSbTe₂)_100-x-(GeTe)_x (x=80---90) (TAGS)合金热电材料, X射线衍射(XRD)分析表明,热压烧结后合金具有低温菱形结构. 通过热压烧结法将TAGS粉末制备成块体材料,运用XRD和扫描电子显微镜对材料的物相成分、 晶体结构和形貌进行了表征.采用直流四探针法测定样品的电导率,当样品两端的温差为1---4℃ 的情况下测量Seebeck系数.通过材料热电性能测试,研究了30---500℃温度范围内不同组分 样品性能参数的变化.结果表明,所制备的TAGS热电材料具有纳米结构, 其性能随着组分的变化而变化, TAGS-80具有较好的热电性能,在530℃时具有最高热电优值(ZT=1.80).     

ICP—AES同时测定钴酸锂中13个杂质元素

利用全谱直读ICP-AES分析技术,对试样处理方法、元素分析谱线、基体干扰、背景校正、仪器分析参数等进行了研究,综合确定了最佳实验条件。将钴酸锂试样用硝酸、高氯酸处理后,再用盐酸与硝酸溶解残渣,ICP-AES同时测定铜、铁、镍、锰、铂、铋、铅、金、铝、镉、钯、锡、砷等13个杂质元素。样品加标回收率为85.2%—113.0%,相对标准偏差为1.0%—7.7%。方法操作简便、快速、准确。     

Facile Construction of 3D Reduced Graphene Oxide Wrapped Ni3S2 Nanoparticles on Ni Foam for High‐Performance Asymmetric Supercapacitor Electrodes

3D reduced graphene oxide (rGO)‐wrapped Ni₃S₂ nanoparticles on Ni foam with porous structure is successfully synthesized via a facile one‐step solvothermal method. This unique structure and the positive synergistic effect between Ni₃S₂ nanoparticles and graphene can greatly improve the electrochemical performance of the NF@rGO/Ni₃S₂ composite. Detailed electrochemical measurements show that the NF@rGO/Ni₃S₂ composite exhibits excellent supercapacitor performance with a high specific capacitance of 4048 mF cm^?2 (816.8 F g^?1) at a current density of 5 mA cm^?2 (0.98 A g^?1), as well as long cycling ability (93.8% capacitance retention after 6000 cycles at a current density of 25 mA cm^?2). A novel aqueous asymmetric supercapacitor is designed using the NF@rGO/Ni₃S₂ composite as positive electrode and nitrogen‐doped graphene as negative electrode. The assembled device displays an energy density of 32.6 W h kg^?1 at a power density of 399.8 W kg^?1, and maintains 16.7 W h kg^?1 at 8000.2 W kg^?1. This outstanding performance promotes the as‐prepared NF@rGO/Ni₃S₂ composite to be ideal electrode materials for supercapacitors.     

Temperature-programmed surface reaction (TPSR) of CH4 synthesis by PdxNi100−x nanoparticles

A series of Pd_xNi_100−x nanoparticles were prepared by the co-precipitation method and analyzed using a temperature-programmed surface reaction (TPSR) of their methanation reactions. ESCA measurement suggested that the as-prepared Pd-Ni alloys had Pd-core/Ni-shell structure. Surface Pd segregation occurred during H₂ reduction and resulted in a surface composition close to the nominal value. The TPSR experiments were performed by pre-adsorption of CO with H₂ to form methane. The peak temperature of methanation increased as Pd content increased, indicating that a methanation reaction is favored on Ni and Ni-rich alloy nanoparticles. For physical mixtures of Pd and Ni nanoparticles, methanation behaviors is similar to those of alloy nanoparticles; but the methanation temperatures of physical mixtures are always higher than those of alloy nanoparticles. This may be due to the formation of a Pd-enriched alloy surface layer during reduction in H₂ at 400 °C, or because the CO molecules adsorbed on the Pd sites spill over onto the Ni sites for methanation. Using TPSR technique and measuring methanation temperature, the top-most surface of such bimetallic nanoparticles can be probed.     

Determination of the Gamow–Teller strength function for the neutron-deficient isotopes In

The Gamow–Teller β decays of the neutron-deficient indium isotopes ^104–107In have been investigated by using total absorption γ-ray spectrometry on mass-separated sources. The experimental Gamow–Teller strength, deduced as a function of the excitation energy in the daughter nuclei ^104–107Cd, is compared to shell-model predictions.     

Energy transfer studies in krypton-xenon mixtures excited in a cooled DC discharge

The VUV spectrum of gaseous mixtures of krypton with a small amount of xenon added was investigated in the range 115-200 nm. The mixtures were excited in a capillary DC discharge where the capillary could be cooled by using liquid nitrogen. The mixed molecule band around the XeI resonance line at nm and the mixed molecule continuum to the long wavelength side from the line were analysed. The band around nm was identified as transitions between a weakly bound excited state and the weakly bound ground state of XeKr molecules. When cooling the capillary wall, the appearance of the Xe₂ continuum was observed. The effect is ascribed to energy transfer between molecular states as a consequence of radiation trapping in the band around nm. The role of the mixed molecule in the formation of the VUV spectrum of the gas mixture is discussed and underlined. Received 12 May 1999 and Received in final form 27 August 1999