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Title: Characterization of VPS-W coating layers on molybdenum after heat exposure

Abstract

Graphical abstract: - Highlights: • W powders were successfully coated on molybdenum using VPS coating technique. • W powders were completely changed into recrystallized grains after heat exposure. • VPS-W coating layer shows good adhesion to the Mo substrate after heat exposure due to the interdiffusion between W and Mo. • W-coated Mo material will extend the service life of hot-zone parts for high-temperature furnace applications. - Abstract: Tungsten (W) coating layers were successfully deposited using a vacuum plasma spraying (VPS) technique on a molybdenum (Mo) substrate. Tungsten powder with a median size of 10 μm was applied to prepare coatings via a plasma spray system. For the VPS process, argon and hydrogen were used as plasma-forming gases, and the coatings were deposited in 35 mbar vacuum pressure. A coating with a thickness of 300 μm was obtained, and some unmelted W powders were observed in the coating layer. This heat exposure experiment was performed in a sapphire crystal growing furnace at 2100 °C up to 110 h. After heat exposure, the VPS-W coating layers were soundly bonded with the Mo substrate due to the interdiffusion between W and Mo.

Authors:
; ;
Publication Date:
OSTI Identifier:
22290357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 48; Journal Issue: 12; Conference: ISFM 2012: 5. international symposium on functional materials, Perth, WA (Australia), 17-20 Dec 2012; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AFTER-HEAT; ARGON; COATINGS; CRYSTALS; LAYERS; MICROSTRUCTURE; MOLYBDENUM; PLASMA; POWDERS; SAPPHIRE; SUBSTRATES; TUNGSTEN

Citation Formats

Cho, Gue Serb, E-mail: gscho@kitech.re.kr, Choe, Kyeong Hwan, and Choi, Soon Yeol. Characterization of VPS-W coating layers on molybdenum after heat exposure. United States: N. p., 2013. Web. doi:10.1016/J.MATERRESBULL.2013.04.064.
Cho, Gue Serb, E-mail: gscho@kitech.re.kr, Choe, Kyeong Hwan, & Choi, Soon Yeol. Characterization of VPS-W coating layers on molybdenum after heat exposure. United States. doi:10.1016/J.MATERRESBULL.2013.04.064.
Cho, Gue Serb, E-mail: gscho@kitech.re.kr, Choe, Kyeong Hwan, and Choi, Soon Yeol. Sun . "Characterization of VPS-W coating layers on molybdenum after heat exposure". United States. doi:10.1016/J.MATERRESBULL.2013.04.064.
@article{osti_22290357,
title = {Characterization of VPS-W coating layers on molybdenum after heat exposure},
author = {Cho, Gue Serb, E-mail: gscho@kitech.re.kr and Choe, Kyeong Hwan and Choi, Soon Yeol},
abstractNote = {Graphical abstract: - Highlights: • W powders were successfully coated on molybdenum using VPS coating technique. • W powders were completely changed into recrystallized grains after heat exposure. • VPS-W coating layer shows good adhesion to the Mo substrate after heat exposure due to the interdiffusion between W and Mo. • W-coated Mo material will extend the service life of hot-zone parts for high-temperature furnace applications. - Abstract: Tungsten (W) coating layers were successfully deposited using a vacuum plasma spraying (VPS) technique on a molybdenum (Mo) substrate. Tungsten powder with a median size of 10 μm was applied to prepare coatings via a plasma spray system. For the VPS process, argon and hydrogen were used as plasma-forming gases, and the coatings were deposited in 35 mbar vacuum pressure. A coating with a thickness of 300 μm was obtained, and some unmelted W powders were observed in the coating layer. This heat exposure experiment was performed in a sapphire crystal growing furnace at 2100 °C up to 110 h. After heat exposure, the VPS-W coating layers were soundly bonded with the Mo substrate due to the interdiffusion between W and Mo.},
doi = {10.1016/J.MATERRESBULL.2013.04.064},
journal = {Materials Research Bulletin},
number = 12,
volume = 48,
place = {United States},
year = {Sun Dec 15 00:00:00 EST 2013},
month = {Sun Dec 15 00:00:00 EST 2013}
}
  • The deuterium (D) retention for Vacuum Plasma Spray (VPS)–tungsten (W)/F82H was studied using two different implantation methods, namely D plasma exposure and View the MathML source implantation. The D retention for polished VPS–W/F82H after plasma exposure was found to be reduced compared to that for polycrystalline tungsten. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicated that porous structures around grain boundaries and the interface between VPS–W layers would be potential D diffusion paths, leading to low D retention. In the case of View the MathML source implantation, the shape of D2 TDS spectrum was almost the samemore » as that for D plasma-exposed VPS–W/F82H; however, the D retention was quite high for unpolished VPS–W/F82H, indicating that most of D was trapped by the oxide layer, which was produced by the VPS process. The reduction of surface area due to the polishing process also reduces D retention for VPS–W/F82H. These results indicate that controlling the surface chemical states is important for the reduction of tritium retention for future fusion reactors.« less
  • The W coating by Vacuum Plasma Spraying (VPS) technology is thought to be reasonable for most plasma facing components in future fusion reactors. In this paper the deuterium retention behavior for the Vacuum Plasma Spraying (VPS) tungsten (W) coating has been studied to demonstrate the tritium retention as a function of heating temperature. It has been found that two major deuterium desorption stages were observed at the temperature regions of 400 - 700 K (Stage 1) and 900 - 1100 K (Stage 2), considering that Stage 1 has been linked to the desorption of deuterium trapped by near surface andmore » intrinsic defects, and Stage 2 has been related to the desorption of deuterium bound to impurities as C-D bonds. By heating the sample above 673 K, the major peak of C-1s shifted from C-O bond to C-C bond, where the retention of deuterium as Stage 2 has increased. Therefore it indicates that the hydrogen isotope retention was controlled by the amount of C-C bond in VPS, most of which was contaminated during the VPS coating process. The comparison of several samples (VPS-W with shading, VPS-W without shading and Polycrystalline W (PCW)) shows that the carbon impurity has a large affinity with deuterium and makes stable trapping states compared to that with intrinsic defects and grain boundaries. However, most of them was reduced by heating at 1173 K. Therefore, heating treatment is quite important to get rid of carbon impurities and refrain higher tritium retention in VPS. (authors)« less
  • To determine the physical mechanism of the action of a Pd coating, an x- ray-diffraction investigation of grids treated in experimental tubes was conducted. Unfiltered lambda CrK/sub alpha / radiation was used; the photographa were taken on a URS-60 apparatus, RKU-114M camera, D = 114.7 mm. On the x-ray diffraction picture, the lines of the intermetallic compound Pd/sub 2/ Ba are sufficiently clearly revealed. The opinion exists that the formation of such a compound under the conditions of operation of a tube with grid temperature 500 to 800 deg C is relatively improbable and is possible at 900 deg C.more » It is concluded that the anti-emission properties of Pd, like those of Au, are determined by its ability to bond Ba atoms into a stable intermetallic compound with a sufficiently high electron work function. (auth)« less
  • The tri(alkoxy)siloxy complexes MO[OSi(OtBu)3]4 (1, M = Mo and 2, M = W) were prepared from MOCl4 and LiOSi(OtBu)3. Similarly, reactions of MO2Cl2(DME) with LiOSi(OtBu)3 afforded the new siloxide complexes MO2[OSi(OtBu)3]2 (3, M = Mo and 4, M = W), which are thermally unstable at ambient temperature. More stable compounds were obtained by the crystallizations of 3 and 4 in a coordinating solvent, to form the ether adducts MoO2[OSi(OtBu)3]2(THF) (3a) and WO2[OSi(OtBu)3]2(DME) (4a). These compounds serve as soluble models for isolated molybdenum or tungsten atoms on a silica surface and were characterized by 1H, 13C, 29Si, 95Mo, and 183W NMR,more » FT-Raman, FT-IR, and UV-vis spectroscopies. Compounds 1, 2, 3a, and 4a were used to prepare metal-oxide silica composites via the thermolytic molecular precursor method. The xerogels obtained from the thermolyses of 1, 2, 3a, and 4a in toluene contained mesoporosity with surface areas of 10, 230, 106, and 270 m2 g-1, respectively. Despite the high surface areas for most samples, these xerogels contain MO3 domains. Complexes 1 and 2 were also used to introduce molybdenum and tungsten sites, respectively, onto mesoporous SBA-15 silica via displacement of the -OSi(OtBu)3 ligand for a siloxyl group from the silica surface. All molybdenum- and tungsten-containing systems were tested as catalysts for the epoxidation of cyclohexene using tert-butyl hydroperoxide (TBHP) or aqueous H2O2 as the oxidant.« less