NachhaltigF: Elektrotechnik und MedientechnikI: IQMA
L. Liu, S. Li, D. Liu, Günther Benstetter, O. Man, J. Michalicka, Y. Zhang, Y. Hong, H. Fan, W. Ni, Q. Yang, Y. Wu, Z. Bi
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
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.
NachhaltigF: Elektrotechnik und MedientechnikI: IQMA
L. Liu, S. Li, D. Liu, Günther Benstetter, Y. Zhang, Y. Hong, H. Fan, W. Ni, Q. Yang, Y. Wu, Z. Bi
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
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.
I: Zentrum für Akademische Weiterbildung
A. Al Lily, J. Foland, D. Stoloff, A. Gogus, I. Erguvan, M. Awshar, J. Tondeur, M. Hammond, I. Venter, P. Jerry, A. Oni, Y. Liu, R. Badosek, López de la Madrid, M.C., E. Mazzoni, D. Vlachopoulos, H. Lee, K. Kinley, M. Kalz, U. Sambuu, T. Bushnaq, N. Pinkwart, N. Adedokun-Shittu, P.-O. Zander, K. Oliver, L. Teixeira Pombo, J. Balaban Sali, S. Gregory, S. Tobgay, M. Joy, J. Elen, Odeh Helal Jwaifell, M., M.N.H.M. Said, Y. Al-Saggaf, A. Naaji, J. White, K. Jordan, J. Gerstein, İ. Umit Yapici, C. Sanga, P. Nleya, B. Sbihi, M. Rocha Lucas, V. Mbarika, S. Schön, L. Sujo-Montes, M. Santally, P. Häkkinen, A. Al Saif, Andreas Gegenfurtner, S. Schatz, V. Padilla Vigil, C. Tannahill, S. Padilla Partida, Z. Zhang, K. Charalambous, A. Moreira, M. Coto, et al.
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
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.
F: Elektrotechnik und MedientechnikI: IQMA
D. Liu, S. Zhang, S.-E. Ong, Günther Benstetter, H. Du
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
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.