Materials Science Forum Vol. 1106

Abstract: In this study, electrochemical measurements and observations investigated galvanic corrosion behavior between various metals with or without projection-shaped Ni–Cu alloy plating film and carbon-fiber-reinforced thermoplastic (CFRTP) of corroded areas. Stainless steel, aluminum alloy, and CFRTP plates were prepared. Ni and Ni–Cu alloy electroplating were performed on the stainless steel plate. Electroless zinc plating, Ni, and Ni–Cu alloy electroplating were performed on the aluminum alloy plate. The galvanic current between the metal and CFRTP plates was measured using an electrochemical measurement system. The test solution was 0.06 mol/L NaCl aqueous solution. For Stainless steel/CFRTP, the galvanic current flow was negligible with and without the Ni–Cu alloy plating film. For aluminum alloy/CFRTP without the Ni–Cu alloy plating film, the galvanic current ranged from-80 to-120 μA/cm² at a test temperature of 60°C. For aluminum alloy with the Ni–Cu alloy plating film, the galvanic current ranged from-60 to-80 μA/cm². The galvanic current for the aluminum alloy plate with Ni–Cu alloy plating was lower than that of the aluminum alloy plate without Ni–Cu alloy plating film. The result suggests that the formation of the Ni–Cu alloy plating on the aluminum alloy improves corrosion resistance.

Abstract: Ni-cellulose nanofiber (CNF) composite plated films were fabricated by electroless plating method. The deposition conditions and basic properties of the Ni-CNF composite film were investigated. A C1100 plate was used as the plated material, and a Ni-P electroless plating bath was prepared as the plating solution. 5 g/L of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized CNF or carboxymethyl cellulose was added to the plating solution. Sodium dodecyl sulfate (SDS) was added as a surfactant. It was confirmed that CNFs were complexed on the surface of the plated film, and the addition of SDS made CNFs disperse into the plated film. The surface of the plated film obtained by adding both TEMPO oxidized CNF and SDS had the highest Vickers hardness among all conditions investigated.

Abstract: In modern electrochemical coating technology, it is common practice to create uniform layers. However, this study focuses on the deposition of non-uniform layers achieved through a deliberate arrangement of micro structured electrodes on the anode side. The "dog bone effect” was employed as the primary approach [1]. When electroplating on an otherwise uniform surface, this effect selectively processes an area influenced by the geometric edge effect (figure 1 left). The coating within this area is intended to be (i) unevenly distributed and (ii) non-reproducible. Process data was obtained through electrochemical simulations and subsequently applied to a specially designed micro-galvanic setup. This enabled the production of suitable micro structured anodes, validation of coating parameters, and the deposition of visually imperceptible structured areas with inhomogeneous properties using "adhesive gold" on appropriate substrates such as silver and nickel. The layers and their local topography were characterized and analyzed using confocal laser microscopy, X-Ray fluorescence analysis (XRF), as well as a self-designed and constructed laser interference device. As a result, this specific galvanic process technology successfully produced metallic layers that (i) cannot be visually confirmed by the naked eye, (ii) exhibit varied microstructural anode geometries, (iii) display unique differences in layer thickness, (iv) possess non-reproducible and chaotic topographies, and (v) can be detected and identified using conventional analysis techniques or a simple interference setup.

Abstract: In this paper, we discuss our previous experimental results and recent considerations on the preparation of solidified oxide eutectic coating on non-oxide ceramics by unidirectional solidification method using light focusing apparatus. As an example, an explanation is given here with regard to the formation mechanism of Al₂O₃-HfO₂ eutectic coatings on SiC substrate. The Al₂O₃ component in oxide melt easily reacts with SiC and primary HfO₂ phase solidified on SiC substrate. However, the solidified HfO₂ phase also react with SiC substrate and HfC-HfO₂ graded functional layer is formed on SiC substrate and Al₂O₃-HfO₂ eutectic microstructure is formed on the graded functional layer

Abstract: This paper reports on the mechanisms and provides worked examples of using pulsed electric current to improve the surface properties of conductive materials during solidification. A rough surface is formed via the freezing of thermomechanical fluctuations and external disturbances during solidification. Pulsed electric current provides an extra driving force for the fluctuations to relax in a shorter duration toward the equilibrium state before the material loses the fluidity during cooling. This additional mechanism is associated with the electric current free energy, which depends on the current density distribution at various materials geometries, including the surface profile. The mechanism has been validated by experimental characterization of the surface roughness evolution with and without electropulsing treatment.

Abstract: Since there are no fusion reactors generating high-flux 14 MeV neutrons, it is necessary to evaluate materials’ performance in fusion reactors based on a correlation of fission neutron and charged particle irradiations. However, the irradiation tests involve various issues which prevent simple correlation and evaluation. In this paper, the issues related to irradiation temperature control and dose rate effects are pointed out and analyzed, and proposals regarding future irradiation tests are given.

Abstract: Space environment is rich of high energy particles that form the radiation field. Human beings as well as electronic devices are susceptible to their action, even if the exposure time is limited. For this reason, radiation shields are needed to carry out safe space missions. Traditionally, in-space shielding frames are made up of aluminum, but more recent studies have shown that a good shielding efficiency can be achieved by hydrogen (H)-rich materials, as polyethylene (PE). Moreover, it was noticed that small mass atoms as H, boron (B) and nitrogen (N) can reduce secondary emissions. In this work, radiation shields of high-density PE (HDPE) filled with boron nitride (BN) have been manufactured. Since BN particles dispersion into the polymeric matrix strongly affects the composite shielding ability, 2 filling routes have been investigated. The first manufacturing strategy is about melt-mixing: HDPE is melted at 200 °C into a batch-mixer, then BN powder is inserted, and mixing is carried out until the torque exerted by the rollers reaches a plateau. Subsequently, the shield is obtained by molding and machining. The second strategy is about the filler spray deposition; BN is spayed on HDPE plates surface after which stacking occurred and consolidation is carried out at 130 °C for 24 h. At the end, machining is performed. The shields dimensions are 25x25x10 mm³ and 50x46x35 mm³, respectively. Both of them show a good level of agglomeration and a good fillers dispersion, with a final density close to the HDPE nominal value.

Abstract: Silicon carbide (SiC) continuous fiber reinforced SiC matrix composites (SiC/SiC) are considered as promising candidates for pressurized water reactor (PWR) due to their small neutron capture cross-section, excellent high temperature strength and irradiation resistance, etc. SPICRI have been working on the R&D of SiC/SiC composites cladding tubes for the last decade. This report will show the recent research in material development, properties and irradiation response of SiC/SiC composites. Several critical issues to be solved for PWR fuel cladding applications, such as mechanical properties, hermeticity, thermal properties and irradiation resistance are discussed here.

Abstract: Low-activation characteristics and dominant radioactive isotopes limiting materials recycling were analyzed for a fusion-reactor-grade vanadium alloy, NIFS-HEAT-2. In order to reduce contact dose rate after use in fusion reactors, purification of the base metal vanadium was examined by chemical aqueous separation, electron-beam vacuum melting and zone refining, focusing on the removal of the dominant high-activation impurities, such as Co, Cu, Fe, Nb, Ni and Mo. Based on the measured impurity levels, remote recycling of vanadium alloy is possible within ten years after use in fusion reactors under operation condition with 100 dpa irradiation. Early quasi-hands-on recycling requires further purification and re-design of alloy composition especially with low Ti and high Cr content. The present paper discusses status of material R&Ds for the ten-year recycling and impact on operation of fusion reactors.