共查询到20条相似文献,搜索用时 390 毫秒
1.
2.
HL-2A装置的第一壁由石墨构件、Cu偏滤器靶板和AISI 304LN不锈钢真空室内壁组成。石墨构件总重量为44kg,覆盏面积为2.80,覆盖率为2.2%。由于HL-2A装置所用石墨件材料均为历经长期托卡马克实验和长期暴露大气的石墨材料,因此石墨构件的处理效果显得更为重要。介绍了EK98、SMF-800石墨材料、ASDEX装置用CFC、国产CFC的研究结果和HL-2A装置第一壁石墨材料预处理及其结果。 相似文献
3.
钯-抗坏血酸基体改进剂平台石墨炉原子吸收光谱法测定贻贝标样中的砷 总被引:1,自引:0,他引:1
本实验建立了钯-抗坏血酸基体改进剂平台石墨炉原子吸收光谱法测定贻贝中砷的方法。研究了基体改进剂氯化钯、抗坏血酸用量对测定的影响,比较了氯化钯-抗坏血酸、氯化钯、硝酸镍三种基体改进剂及平台石墨管、普通石墨管在测定贻贝中砷的灵敏度。方法的相对标准偏差为3.2%,回收率在97.8%—107.4%之间,检出限为12.0ng/mL。 相似文献
4.
本实验建立了钯-抗坏血酸基体改进剂平台石墨炉原子吸收光谱法测定贻贝中砷的方法。研究了基体改进剂氯化钯、抗坏血酸用量对测定的影响,比较了氯化钯-抗坏血酸、氯化钯、硝酸镍三种基体改进剂及平台石墨管、普通石墨管在测定贻贝中砷的灵敏度。方法的相对标准偏差为3.2%,回收率在97.8%-107.4%之间,检出限为12.0ng/mL。 相似文献
5.
6.
7.
在SMF-800 石墨第一壁化学腐蚀温度特性的实验研究基础上,进一步测试了G3 石墨、SMF-800 高纯石墨和硼化石墨,以及SiC涂层等在1.3μA/3keV 氘离子束轰击下化学腐蚀的温度特性。从中优选出C2B10H12 氦辉光放电法制取的SMF-800 石墨硼化层,它具有最佳的抗化学腐蚀性能。其CD4 产额较SMF-800 高纯石墨的降低一个数量级以上,CD4 产额峰值温度下移至650K附近。用小角度转动样品法,初步观察了氘离子束轰击下石墨释放CD4 的角分布特性,为托卡马克先进偏滤器实验中确立CD4 辐射区的定位及其控制等可行性进行了探索 相似文献
8.
9.
邓运发曹觉先 《原子与分子物理学报》2013,(5):812-818
基于第一性原理计算,研究了单壁锯齿型和扶手型石墨炔管的几何结构、电子结构以及杨氏模量.计算表明:石墨炔管是一类具有一定能隙的直接带隙半导体管,其带隙在0.4~1.3eV的能量范围,且随管径的增大而变小.而石墨炔管的杨氏模量在0.44~0.50Tpa区间变化.对于锯齿型石墨炔管,其杨氏模量随着半径的增大而变小而锯齿型石墨炔管的杨氏模量随其半径的增大而增大. 相似文献
10.
11.
Yongfeng Wang 《Surface science》2006,600(3):729-734
Scanning tunneling microscopy (STM) was used to study the surface structures of dry-prepared and di-chloroethane-treated HOPG samples. Both triangular and honeycomb structures were simultaneously observed with the same tip at room temperature around a strand (grain boundary) on the HOPG surface. This observation did not support the tip effect in STM imaging explanation for HOPG in literature. A general layer-sliding model was utilized to explain the experimental results: sliding of the HOPG topmost layer was used to explain the origins of the triangular and honeycomb structures, and molecule intercalation into inter-layer spacing between the first and second layers of HOPG induced inhomogeneous deformation of the HOPG topmost layer that accordingly generated the Moiré patterns of the HOPG sample in di-chloroethane. 相似文献
12.
13.
Jelena Butikova Boris Polyakov Lauris Dimitrocenko Edgars Butanovs Ivars Tale 《Central European Journal of Physics》2013,11(5):580-583
Highly oriented pyrolytic graphite (HOPG) was scribed by pulsed laser beam to produce square patterns. Patterning of HOPG surface facilitates the detachment of graphene layers during contact printing. Direct HOPG-to-substrate and glue-assisted stamp printing of a few-layers graphene was compared. Printed graphene sheets were visualized by optical and scanning electron microscopy. The number of graphene layers was measured by atomic force microscopy. Glue-assisted stamp printing allows printing relatively large graphene sheets (40×40 μm) onto a silicon wafer. The presented method is easier to implement and is more flexible than the majority of existing ways of placing graphene sheets onto a substrate. 相似文献
14.
本文详细讨论了试件在空间六个自由度中产生刚体运动时所形成的云纹图特性,定量地分析了各种刚体运动形式对云纹干涉法的影响。经分析表明:在用云纹干涉法测量变形位移场时,只有当试件绕坐标轴刚体转动时才会影响所测变形位移场。 相似文献
15.
Matsui T Kambara H Niimi Y Tagami K Tsukada M Fukuyama H 《Physical review letters》2005,94(22):226403
Scanning tunneling spectroscopy (STS) measurements were made on surfaces of two different kinds of graphite samples, Kish graphite and highly oriented pyrolytic graphite (HOPG), at very low temperatures and in high magnetic fields. We observed a series of peaks in the tunnel spectra associated with Landau quantization of the quasi-two-dimensional electrons and holes. A comparison with the calculated local density of states at the surface layers allows us to identify Kish graphite as bulk graphite and HOPG as graphite with a finite thickness of 40 layers. This explains the qualitative difference between the two graphites reported in the recent transport measurements which suggested the quantum-Hall effect in HOPG. This work demonstrates how powerful the combined approach between the high quality STS measurement and the first-principles calculation is in material science. 相似文献
16.
The electrochemical reactions of highly oriented pyrolytic graphite (HOPG) bulk and powder electrodes in 1 M LiPF6 1:1 EC/DMC solution were investigated and the results show that the intercalation reaction of lithium ion into HOPG electrode occurs only at the edge plane and SEI formation reaction on the basal plane is negligible in comparison with that on the edge plane. The active surface area of HOPG powder electrode could be deduced by comparing the peak area (consumed charge for SEI formation) at potential of 0.5 V on voltammograms with that of bulk HOPG edge electrode. The diffusion coefficients of lithium ion in HOPG bulk layers and in HOPG powder was for the first time measured by use of electrochemical impedance spectra and potential step chronamperameter methods. It was found that the diffusion coefficients of lithium in HOPG were in the range of 10−11-10−12 cm2 s−1 for the lithium-HOPG intercalation compounds at potentials from 0.2 (vs. Li/Li+) to 0.02 V, decreasing with the increase of lithium intercalation degree. A good agreement was obtained between the results from bulk and powder HOPG electrodes by electrochemical impedance spectra method. 相似文献
17.
《Journal of Physics and Chemistry of Solids》2004,65(2-3):199-203
Superperiodic patterns were observed by STM on two kinds of finite-sized graphene sheets. One is nanographene sheets inclined from a highly oriented pyrolitic graphite (HOPG) substrate and the other is a several-layer-thick graphene sheets with dislocation-network structures against a HOPG substrate. As for the former, the in-plane periodicity increased gradually in the direction of inclination, and it is easily changed by attachment of a nanographite flake on the nanographene sheets. The oscillation pattern can be explained by the interference of electron waves confined in the inclined nanographene sheets. As for the latter, patterns and their corrugation amplitudes depended on the bias voltage and on the terrace height from the HOPG substrate. The interference effect by the perturbed and unperturbed waves in the overlayer is responsible for the patterns whose local density of states varies in space. 相似文献
18.
We have observed high resolution 13C NMR spectra in k-intercalated stages 2, 3, 4 and 6 HOPG compounds. The sample was a block itself or sliced one of HOPG. From T1T of each resolved line we obtained a distribution of density of states N(EF) at the Fermi level among the graphite layers. 相似文献
19.
20.
Magnetic-Field-Induced Semimetal-Insulator-like Transition in Highly Oriented Pyrolitic Graphite 下载免费PDF全文
We report the extraordinarily large positive magnetoresistances (MR, 69400% at 4.5K under a magnetic field of 8.15 T), de Hass-van Alphen oscillations effect at 10 K and the semimetal-Jnsulator-like transition in a wide range of temperature in highly oriented pyrolitic graphite (HOPG). Besides a dominating ordinary MR (OMR) mechanism in the free-electron mode, it is realized from qualitative analysis that the Coulomb interacting quasiparticles within graphite layers play some roles. However it is difficult to associate the transition with the simple OMR theory. In order to investigate the possible origins of the transition, further analysis is carried out. It is revealed that the magnetic-field-induced behaviour is responsible for the semimetal-insulator-like transitions in HOPG. 相似文献