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Suche nach „[S.] [Liu]“ hat 12 Publikationen gefunden
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    NachhaltigElektrotechnik und Medientechnik

    Zeitschriftenartikel

    J. Michalicka, S. Li, Z. Bi, Y. Zhang, Ondrej Man, Y. Hong, Y. Wu, W. Ni, H. Fan, Günther Benstetter, L. Liu, Q. Yang, D. Liu

    The effect of O2 impurity on surface morphology of polycrystalline W during low-energy and high-flux He+ irradiation

    Fusion Engineering and Design, vol. 139, pp. 96-103

    2019

    DOI: 10.1016/j.fusengdes.2019.01.003

    Abstract anzeigen

    The interaction between the impurities (such as carbon, nitrogen, oxygen) and the plasma-facing materials (PFMs) can profoundly influence the performance and service of the PFMs. In this paper, we investigated the influence of oxygen (O2) impurity in the helium radio frequency (RF) plasma on the surface morphology of polycrystalline tungsten (W) irradiated at the surface temperature of 1450 ± 50 K and the ion energy of 100 eV. The pressure ratio of O2 to He (R) in RF source varied from 4.0 × 10−6 to 9.0 × 10-2. The total irradiation flux and fluence were ˜1.2 × 1022 ions·m-2·s-1 and ˜1.0 × 1026 ions·m-2, respectively. After He+ irradiation, the specimen surface morphology was observed by scanning electron microscopy. It was found that with increasing R from 4.0 × 10−6 to 9.0 × 10-2 the thickness of nano-fuzz layer at the W surface was thinner and thinner, accompanied by the formation of rod-like structures. The erosion yield increased from 5.2 × 10-4 to 2.3 × 10-2 W/ion when R varied from 4.0 × 10-6 to 9.0 × 10-2. The X-ray diffraction analysis shows that tungsten oxides were formed at the near surface of specimens when R exceeded 1.8 × 10-2. The erosion yield measurements revealed that in addition to surface physical sputtering process, the chemical erosion process could occur due to the interaction between oxygen-containing species and W at the surface. The results indicated that the presence of O2 impurity in He plasma can obviously affect the surface microstructure of W. The study suggested that O2 impurity can effectively reduce the growth of nano-fuzz structures.

    NachhaltigElektrotechnik und Medientechnik

    Zeitschriftenartikel

    S. Li, Z. Bi, Y. Zhang, D. Liu, Y. Hong, Y. Wu, W. Ni, H. Fan, Günther Benstetter, L. Liu, Q. Yang

    Surface damages of polycrystalline W and La2O3-doped W induced by high-flux He plasma irradiation

    Journal of Nuclear Materials, vol. 501, no. April, pp. 275-281

    2018

    Abstract anzeigen

    In this study, polycrystalline tungsten (W) and three oxide dispersed strengthened W with 0.1 vol %, 1.0 vol % and 5.0 vol % lanthanum trioxide (La2O3) were irradiated with low-energy (200 eV) and high-flux (5.8 × 1021 or 1.4 × 1022 ions/m2⋅s) He+ ions at elevated temperature. After He+ irradiation at a fluence of 3.0 × 1025/m2, their surface damages were observed by scanning electron microscopy, energy dispersive spectroscopy, scanning electron microscopy-electron backscatter diffraction, and conductive atomic force microscopy. Micron-sized holes were formed on the surface of W alloys after He+ irradiation at 1100 K. Analysis shows that the La2O3 grains doped in W were sputtered preferentially by the high-flux He+ ions when compared with the W grains. For irradiation at 1550 K, W nano-fuzz was formed at the surfaces of both polycrystalline W and La2O3-doped W. The thickness of the fuzz layers formed at the surface of La2O3-doped W is 40% lower than the one of polycrystalline W. The presence of La2O3 could suppress the diffusion and coalescence of He atoms inside W, which plays an important role in the growth of nanostructures fuzz.

    IQWSonstige

    Zeitschriftenartikel

    D. Stoloff, Andreas Gegenfurtner, A. Naaji, M. Hammond, P.-O. Zander, N. Adedokun-Shittu, J. Foland, A. Al Saif, A. Moreira, L. Sujo-Montes, K. Kinley, M. Coto, K. Charalambous, V. Mbarika, M. Joy, J. Tondeur, S. Gregory, I. Venter, J. Elen, E. Mazzoni, Z. Zhang, López de la Madrid, M.C., M. Rocha Lucas, A. Oni, Y. Al-Saggaf, D. Vlachopoulos, C. Sanga, S. Padilla Partida, A. Gogus, M. Kalz, L. Teixeira Pombo, H. Lee, J. Balaban Sali, K. Oliver, Odeh Helal Jwaifell, M., K. Jordan, V. Padilla Vigil, M. Awshar, M.N.H.M. Said, N. Pinkwart, J. White, Y. Liu, J. Gerstein, B. Sbihi, P. Nleya, C. Tannahill, I. Erguvan, P. Jerry, M. Santally, T. Bushnaq, İ. Umit Yapici, R. Badosek, A. Al Lily, U. Sambuu, S. Schatz, P. Häkkinen, et al., S. Tobgay, S. Schön

    Academic domains as political battlegrounds

    A global enquiry by 99 academics in the fields of education and technology

    Information Development, vol. 33, no. 3, pp. 270-288

    2017

    DOI: 10.1177/0266666916646415

    Abstract anzeigen

    This article theorizes the functional relationship between the human components (i.e., scholars) and non-human components (i.e., structural configurations) of academic domains. It is organized around the following question: in what ways have scholars formed and been formed by the structural configurations of their academic domain? The article uses as a case study the academic domain of education and technology to examine this question. Its authorship approach is innovative, with a worldwide collection of academics (99 authors) collaborating to address the proposed question based on their reflections on daily social and academic practices. This collaboration followed a three-round process of contributions via email. Analysis of these scholars’ reflective accounts was carried out, and a theoretical proposition was established from this analysis. The proposition is of a mutual (yet not necessarily balanced) power (and therefore political) relationship between the human and non-human constituents of an academic realm, with the two shaping one another. One implication of this proposition is that these non-human elements exist as political ‘actors’, just like their human counterparts, having ‘agency’ – which they exercise over humans. This turns academic domains into political (functional or dysfunctional) ‘battlefields’ wherein both humans and non-humans engage in political activities and actions that form the identity of the academic domain.

    NachhaltigElektrotechnik und Medientechnik

    Zeitschriftenartikel

    S. Li, Z. Bi, D. Liu, Y. Hong, W. Ni, H. Fan, Günther Benstetter, L. Liu, Q. Yang

    High-flux He+ irradiation effects on surface damages of tungsten under ITER relevant conditions

    Journal of Nuclear Materials, vol. 471, no. April, pp. 1-7

    2016

    DOI: 10.1016/j.jnucmat.2016.01.001

    Abstract anzeigen

    A large-power inductively coupled plasma source was designed to perform the continuous helium ions (He+) irradiations of polycrystalline tungsten (W) under International Thermonuclear Experimental Reactor (ITER) relevant conditions. He+ irradiations were performed at He+ fluxes of 2.3 × 1021–1.6 × 1022/m2 s and He+ energies of 12–220 eV. Surface damages and microstructures of irradiated W were observed by scanning electron microscopy. This study showed the growth of nano-fuzzes with their lengths of 1.3–2.0 μm at He+ energies of >70 eV or He+ fluxes of >1.3 × 1022/m2 s. Nanometer-sized defects or columnar microstructures were formed in W surface layer due to low-energy He+ irradiations at an elevated temperature (>1300 K). The diffusion and coalescence of He atoms in W surface layers led to the growth and structures of nano-fuzzes. This study indicated that a reduction of He+ energy below 12–30 eV may greatly decrease the surface damage of tungsten diverter in the fusion reactor.

    NachhaltigElektrotechnik und Medientechnik

    Zeitschriftenartikel

    Y. Ji, V. Igelsias, Alexander Hofer, M. Liu, D. Lewis, Y. Shi, S. Long, N. Jiebin, P. McIntyre, Günther Benstetter, A. Scheuermann, H. Fei, M. Lanza, Werner Frammelsberger

    Characterization of the photocurrents generated by the laser of atomic force microscopes

    Review of Scientific Instruments, vol. 87, no. 8

    2016

    DOI: 10.1063/1.4960597

    Abstract anzeigen

    The conductive atomic force microscope (CAFM) has become an essential tool for the nanoscale electronic characterization of many materials and devices. When studying photoactive samples, the laser used by the CAFM to detect the deflection of the cantilever can generate photocurrents that perturb the current signals collected, leading to unreliable characterization. In metal-coated semiconductor samples, this problem is further aggravated, and large currents above the nanometer range can be observed even without the application of any bias. Here we present the first characterization of the photocurrents introduced by the laser of the CAFM, and we quantify the amount of light arriving to the surface of the sample. The mechanisms for current collection when placing the CAFM tip on metal-coated photoactive samples are also analyzed in-depth. Finally, we successfully avoided the laser-induced perturbations using a two pass technique: the first scan collects the topography (laser ON) and the second collects the current (laser OFF). We also demonstrate that CAFMs without a laser (using a tuning fork for detecting the deflection of the tip) do not have this problem.

    NachhaltigAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    S. Liu, J. Sun, C. Sang, Thomas Stirner, S. Dai, D. Wang

    Molecular dynamics simulation of the formation, growth and bursting of bubbles in tungsten exposed to high fluxes of low energy deuterium

    Journal of Nuclear Materials - PLASMA-SURFACE INTERACTIONS 21 — Proceedings of the 21st International Conference on Plasma-Surface Interactions in Controlled Fusion Devices Kanazawa, Japan, May 26-30, 2014, vol. 463, no. August, pp. 363-366

    2015

    DOI: 10.1016/j.jnucmat.2014.12.060

    Abstract anzeigen

    Molecular dynamics simulations are carried out to investigate the formation, growth and bursting of bubbles in tungsten exposed to the irradiation of an extremely high deuterium flux. It is found that the bubbles form in the region near the location of the implanted ion distribution peaks, and that the effect of the substrate temperature on the bubble formation depth is negligible; it is also found that the percentage of deuterium that is found in D2 molecules increases as the bubble grows, and that the evolution of the bubble’s internal pressure is strongly associated with the properties of its surrounding structure. The simulations display the development of a dome-shaped structure at the tungsten surface during the bubble growth. The merging of two deuterium bubbles is also observed. The present simulations also show that the bubble bursts by generating a partially opened lid, which has already been observed in previous independent experiments.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    S. Liu, J. Sun, Thomas Stirner, et al.

    Dynamic Monte Carlo simulation of film-substrate interface mixing in the deposition of Co on Cu (001)

    Surface Science, vol. 605, no. 13-14, pp. 1298-1303

    2011

    Abstract anzeigen

    Dynamic Monte Carlo simulations are performed to investigate the interface mixing of Co atoms deposited on a Cu (001) substrate. A tight-binding potential was used to determine the input parameters (jump probabilities and energy barriers) for the Dynamic Monte Carlo model. The results show that more Co adatoms penetrate into the substrate as the temperature rises and/or as the deposition rate decreases, and that the intermixing between the layers becomes concomitantly more pronounced. Cu atoms migrating into the Co layer via exchange processes during the growth of consecutive Co layers are proposed to be responsible for the intermixing. Furthermore, an initial Co clustering followed by a layer-by-layer growth mode was observed in the simulations, with the surface concentration of Cu atoms depending on the fraction of migrating Cu atoms and decaying into the Co film following a power law. The fraction of Cu atoms migrating into the Co layer can be adjusted by varying the deposition rate and the substrate temperature.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    S. Liu, J. Sun, Thomas Stirner, et al.

    A general model for chemical erosion of carbon materials due to low-energy H+ impact

    Journal of Applied Physics, vol. 108

    2010

    Abstract anzeigen

    Modeling the chemical erosion of carbon materials due to low-energy H+ impact is of paramount importance for the prediction of the behavior of carbon-based plasma-facing components in nuclear fusion devices. In this paper a simple general model describing both energy and temperature dependence of carbon-based chemical erosion is presented. Enlightened by Hopf’s model {Hopf et al. , [J. Appl. Phys.94, 2373 (Year: 2003)}, the chemical erosion is separated into the contributions from three mechanisms: thermal chemical erosion, energetic chemical sputtering, and ion-enhanced chemical erosion. Using input from the Monte Carlo code TRIDYN, this model is able to reproduce experimental data well.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    H. Du, D. Liu, Günther Benstetter, S. Zhang, S.-E. Ong

    Surface and electron emission properties of hydrogen-free diamond-like carbon films investigated by atomic force microscopy

    Materials Science & Engineering A, vol. 426, no. 1-2, pp. 114-120

    2006

    Abstract anzeigen

    In this study, we have deposited hydrogen-free diamond-like carbon (DLC) films by using DC magnetron sputtering of graphite target at various r.f. bias voltages. Surface and nanoscale emission properties of these DLC films have been investigated using a combination of atomic force microscopy (AFM)-based nanowear tests and conducting-AFM, by simultaneously measuring the topography and the conductivity of the samples. Nanowear tests show that these DLC films are covered with the thin (1.5–2.0 nm) graphite-like layers at surfaces. Compared to the film bulk structure, the graphite-like surface layers are more conductive. The graphite-like surface layers significantly influence the electron emission properties of these films. Low-energy carbon species can be responsible for the formation of graphite-like surface layers. Nanoscale electron emission measurements have revealed the inhomogeneous emission nature of these films. The low-field emission from these films can be attributed to the existence of sp2-configured nanoclusters inside the films.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    Y. Liu, S. Yu, X. Xang, T. Ma, Günther Benstetter, D. Liu

    Medium- to high-pressure plasma deposition of a-C:H films by dielectric barrier discharge

    New Diamond and Frontier Carbon Technology, vol. 13, no. 4, pp. 191-206

    2003

    Maschinenbau und Mechatronik

    Beitrag (Sammelband oder Tagungsband)

    S. Rude, Karl Hain, H. Grabowski, C. Liu

    Supporting the Search for Design Solutions Based on Information Recognition and Automated Classification

    Report on the 2nd Workshop on Product Knowledge Sharing and Integration (ProKSI-97), Sophia Antipolis, Frankreich 17.-18.04.1997

    1997

    Maschinenbau und Mechatronik

    Vortrag

    S. Rude, Karl Hain, H. Grabowski, C. Liu

    Finden von Wiederhollösungen auf Basis von Informationsrekonstruktion und automatischer Klassifikation

    9. Forschungsseminar der Hochschulgruppe Arbeits- und Betriebsorganisation (HAB), St. Gallen, Schweiz

    1996