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Suche nach „[J.] [Zhang]“ hat 7 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.

    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.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    Y. Liu, J. Zhang, T. Ma, Günther Benstetter, D. Liu

    A triangular section magnetic solenoid filter for removal of macro- and nano-particles from pulsed graphite cathodic vacuum arc plasmas

    Surface & Coatings Technology, vol. 200, no. 7, pp. 2243-2248

    2005

    DOI: 10.1016/j.surfcoat.2004.09.032

    Abstract anzeigen

    A novel magnetic filter with the triangular section has been designed to remove the macro- and nano-particles from the pulsed cathodic arc plasmas utilized to prepare the tetrahedral amorphous carbon (ta-C) films. The macro- and nano-particles at the surfaces of ta-C films were observed using an optical microscope and an atomic force microscope. The filter was found to be very effective in removing the macro- and nano-particles due to its zigzag-type inner surface structure. Particles that collided with the inner surface of the filter were reflected along the direction opposite to the plasma beam, and therefore separated from the arc plasma. The effect of arc current on the filter efficiency has also been investigated.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    Y. Liu, J. Xu, J. Zhang, Günther Benstetter, D. Liu

    Growth processes and surface properties of diamondlike carbon films

    Journal of Applied Physics, vol. 97

    2005

    DOI: 10.1063/1.1890446

    Abstract anzeigen

    In this study, we compare the deposition processes and surface properties of tetrahedral amorphous carbon (ta-C) films from filtered pulsed cathodic arc discharge (PCAD) and hydrogenated amorphous carbon (a-C:H) films from electron cyclotron resonance (ECR)-plasma source ion implantation. The ion energy distributions (IEDs) of filtered-PCAD at various filter inductances and Ar gas pressures were measured using an ion energy analyzer. The IEDs of the carbon species in the absence of background gas and at low gas pressures are well fitted by shifted Maxwellian distributions. Film hardness and surface properties show a clear dependence on the IEDs. ta-C films with surface roughness at an atomic level and thin (0.3–0.9 nm) graphitelike layers at the filmsurfaces were deposited at various filter inductances in the highly ionized plasmas with the full width at half maximum ion energy distributions of 9–16 eV. The a-C:H filmsdeposited at higher H/C ratios of reactive gases were covered with hydrogen and sp3 bonded carbon-enriched layers due to the simultaneous interaction of hydrocarbon species and atomic hydrogen. The effects of deposited species and ion energies on filmsurface properties were analyzed. Some carbon species have insufficient energies to break the delocalized π(nC)bonds at the graphitelike filmsurface, and they can govern filmformation via surface diffusion and coalescence of nuclei. Dangling bonds created by atomic hydrogen lead to uniform chemisorption of hydrocarbon species from the ECR plasmas. The deposition processes of ta-C and a-C:H films are discussed on the basis of the experimental results.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    D. Liu, Günther Benstetter, J. Zhang, W. Wang

    Effect of pressure on the deposition of hydrogen-free amorphous carbon and carbon nitride films by the pulsed cathodic arc discharge method

    Journal of Vacuum Science & Technology A, vol. 22

    2004

    DOI: 10.1116/1.1798691

    Abstract anzeigen

    Hydrogen-free amorphous carbon and carbon nitride films were deposited using the pulsed cathodic arc discharge at different argon and nitrogen pressures. The surface and mechanical properties of these films were found to strongly depend on the gas pressure. The tetrahedral amorphous carbon and hard films with smooth surfaces (rms roughness: ) were prepared at lower gas pressures. Incorporation of an increasing amount of nitrogen in films caused a decrease in filmhardness. All the films were covered with the thin graphite-like surface layers. The filmhardness was correlated to the soft surface layer thickness, and the films with thinner surface layers exhibit higher hardness. The mean energies of pulsed plasma beams were measured as the functions of argon and nitrogen pressures. The mean energies of plasma beams decrease in an exponential fashion with increasing gas pressure due to the carbon ion collisions with the neutral gas species. The effects of mean energies of deposited species on the filmdeposition were explained in terms of the thermal spike migration of surface atoms. The formation of graphite-like surface layers is associated with the low-energy deposition process. The low-energy species diffusing on filmsurface lead to the formation of graphite-like films with plenty of grains. The higher-energy species may produce the strong thermal spike at filmsurface, and contribute to the formation of bonded structure at a bonded matrix.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    Y. Liu, J. Vancea, Edgar Lodermeier, J. Zhang, Günther Benstetter, D. Liu

    Filtered pulsed carbon cathodic arc: plasma and amorphous carbon properties

    Journal of Applied Physics, vol. 95, pp. 7624-7631

    2004

    DOI: 10.1063/1.1753081

    Abstract anzeigen

    The carbonplasma ion energies produced by the filtered pulsed cathodic arc discharge method were measured as a function of filter inductance. The energy determination is based on the electro-optical time-of-flight method. The average ion energies of the pulsed ion beams were found to depend upon the rise time and duration of pulsed arc currents, which suggests that a gain of ion kinetic energy mainly arises from the electric plasma field from the ambipolar expansion of both electrons and ions, and an electron drag force because of the high expansion velocity of the electrons. The tetrahedral amorphous carbon (ta-C) films with a sp3 fraction of ∼70% were deposited on silicon substrates at the average ion energies of >6 eV in the highly ionized plasmas. The ta-C films were found to be covered with a few graphitelike atomic layers. The surfaceproperties of ultrathin carbonfilms, such as nanoscale friction coefficients, surface layer thickness, and silicon contents were strongly dependent on the ion energies. The growth of amorphous carbonfilms was explained in terms of the thermal spike migration of surfacecarbon atoms. In terms of this model, the thermal spike provides the energy required to release surface atoms from their metastable positions and leads to the formation of the sp3 bonded carbon on a sp3 bonded matrix. The experimental results indicate that the low-energy (<3 eV)carbon ions have insufficient energies to cause the rearrangement reaction within the film and they form graphitelike structures at filmsurface.

    Elektrotechnik und Medientechnik

    Zeitschriftenartikel

    Edgar Lodermeier, J. Ding, T. Ma, Y. Liu, Günther Benstetter, J. Zhang, X. Chen, D. Liu

    Surface and structural properties of ultrathin diamond-like carbon coatings

    Diamond and Related Materials, vol. 12, pp. 1594-1600

    2003

    DOI: 10.1016/S0925-9635(03)00248-6

    Abstract anzeigen

    Nanoscale wear resistance, friction, and electrical conduction tests using atomic force microscope (AFM) have been conducted on ultrathin diamond-like carbon (DLC) coatings, including tetrahedral amorphous carbon (ta-C) deposited using pulsed cathodic arc (PCA) and filtered-PCA, and hydrogenated amorphous carbon (a-C:H) deposited using electron cyclotron resonance—chemical vapor deposition (ECR-CVD). The low-resistant layers at the surfaces of these thin DLC coatings were revealed by AFM-based nanowear tests. Their thickness is mainly determined by the deposition methods and does not show an obvious variation with the coating thickness decreasing from tens of nm to a few nm. The ∼3 nm ta-C coatings from PCA and filtered-PCA deposition were found to have the stable bulk structure beneath the thin (0.3–0.95 nm) surface layers. The ∼3 nm a-C:H coating from ECR-CVD had the extremely low load-carrying capacity and exhibited the evidence of coating delamination, which can be related to the thicker (1.5±0.1 nm) soft surface layers of a-C:H coatings. The results from conducting-AFM measurements indicate that a-C:H coatings have H and sp3 C enrichment surface layers while the soft surface layers of ta-C coatings have graphite-like structure. The nanoscale friction coefficients of these thin ta-C and a-C:H coatings were compared by AFM-based lateral force microscope. The lower friction coefficient of ta-C coatings can be attributed to the existence of graphite-like surface structure.