Design assessment for manufacturability of supporting structures for IWS and ELM coil of ITER vacuum vessel

A vacuum vessel is one of the core facilities of ITER (International Thermonuclear Experimental Reactor) and basically all-welded structure. Korea is responsible for the procurement of sector 1 and 6 of the main vessel. Accordingly, the design review for the fabrication is in progress by ITER Korea and Hyundai Heavy Industries. Due to anticipated manufacturing problems such as the welding distortion, the design of some components of main vessel, IWS (In-Wall Shield) supporting rib and ELM (Edge Localized Mode) coil support, needs to be modified. To release the risk of welding distortion, the welding method called “bridge type” is suggested and the shape of weld joint is adjusted to secure the manufacturability of the issued components. The elastic and limit analyses with fatigue evaluation have been performed under the most critical loading condition to verify the structural integrity of modified design. Analysis results show that the proposed designs meet the design criteria of RCC-MR. The design deviation requests have been submitted to ITER Organization and ANB (Agreed Notified Body) for approval and their verification is currently in progress.     

The catalytic properties of the sputtered iron on carbon nanotubes for polymer electrolyte membrane fuel cells

Pure iron metal target was sputtered onto carbon nanotube grown on carbon paper to fabricate iron-based catalysts for the oxygen reduction reaction (ORR). The carbon nanotube-supported Fe-based catalysts have active sites which are believed to include iron cations coordinated by pyridinic nitrogen functionalities between the graphitic sheets. A Fe-based electrocatalyst treated at 950 °C displayed the highest mass activity. The treated sample at lower temperature could not form the Fe/N/CNT sufficiently. On the other hand, the formed Fe/N/CNTs were degraded thermally at higher temperature. Cyclic voltammetry of the Fe-based electrocatalysts showed similar trends with mass activity which is the largest value at 950 °C. Even though the catalytic activity is not comparable with that of Pt/C catalysts yet, sputtered Fe-based electrocatalysts are promising to explore the non-precious metal electrocatalysts.     

Evaluation of hot workability of particle reinforced aluminum matrix composites by using deformation efficiency

The high temperature deformation behavior of Al 6061 composites reinforced with SiC and Al₂O₃ particles has been studied in the temperature range of 300–550°C and the strain rate range of 0.1–3.0/sec by hot torsion test. The deformation efficiency , given by (2m/m + 1), where m is the strain rate sensitivity, is calculated as a function of temperature and strain rate to obtain iso-efficiency contour map. The composite reinforced with SiC particle exhibited a domain of dynamic recrystallization (DRX) with a peak efficiency of 40% at the temperature range of 450–500°C and strain rate range of 0.2–0.5/sec. On the other hand, the composite reinforced with Al₂O₃ particle showed the DRX domain at the temperature range of 450–480°C and strain rate range of 0.1–0.2/sec. The characteristics of these domain have been investigated with the help of microstructural observation and hot ductility measurements.     

A Small-Volume Apparatus for the Measurement of Phase Equilibria

An apparatus has been designed and constructed for the measurement of vapor-liquid equilibrium properties. The main components of the apparatus consist of an equilibrium cell and a vapor circulation pump. The cell and all of the system valves are housed inside a temperature controlled, insulated aluminum block. The temperature range of the apparatus is 260 K to 380 K to pressures of 6 MPa. The uncertainty of the temperature measurement is 0.03 K, and the uncertainty in the pressure measurement is 9.8 × 10⁻⁴ MPa. An automated data acquisition system is used to measure temperature and pressure at equilibrium. The apparatus has been performance tested by measuring the vapor pressures of propane, butane, and a standard mixture of propane + butane.     

Solvent effect on particle morphology in recrystallization of HMX (cyclotetramethylenetetranitramine) using supercritical carbon dioxide as antisolvent

Supercritical fluid processes have gained great attention as a new and environmentally benign method of preparing the microparticles of energetic materials like explosives and propellants. In this work, HMX (cyclotetramethylenetetranitramine) was selected as a target explosive. The microparticle formation of HMX using supercritical antisolvent (SAS) recrystallization process was performed and the effect of organic solvent on the size and morphology of prepared particles was observed. The organic solvents used in this work were dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), cyclohexanone, acetone, and N-methyl pyrrolidone (NMP).     

Dynamic softening behavior of Al−18Si alloy produced by spray forming

The high-temperature deformation behavior and dynamic softening transition from dynamic recrystallization (DRX) to dynamic recovery (DRV) of Al-18 wt.%Si alloy was studied by torsion tests in a temperature range of 573∼773 K and a strain rate range of 0.001∼1/sec. The alloy was produced by spray-forming followed by hot extrusion. The dependence of flow stress (σ) on strain rate and temperature (T) could be described by the power Arrhenius relationship,. The activation energy and stress exponent values were higher at the low temperature region than those at the high temperature region. The alloy showed a flow curve of DRX in the temperature range of 573∼673 K, while at 673∼773 K, the alloy exhibited a flow curve of DRV. These results were analyzed by observing the shapes of the flow curves throughout the deformation condition. Also, the transition behavior from DRX to DRV has been investigated through observation of deformed microstructure and flow curves during hot deformation.     

Supplementation of alkaline phytase (Ds11) in whole-wheat bread reduces phytate content and improves mineral solubility

Abstract: In this study, alkaline phytase was added to whole‐wheat bread and the phytate content and mineral profiles were compared to commercially available acidic phytase. At neutral pH, some phytate (approximately 20%) was degraded by endogenous phytase in wheat flour, while 40% of phytate was hydrolyzed by alkaline phytase DS11 and a 35% reduction was observed with acidic phytase. Most of the enzymatic activity occurred during the proofing stage, and the rate of reaction depended on pH. DS11 phytase effectively degraded the phytate level within a 30 min treatment at pH 7; however, at least 60 min was needed with acidic phytase to achieve the same hydrolysis level. Mineral profiles were also dramatically affected by the phytate reduction. The biggest increase was observed in Fe²⁺ by the phytase treatment. The Fe²⁺ content increased 10‐fold at pH 7 and 8‐fold at pH 5 with alkaline phytase DS11. Alkaline phytase DS11 was shown to be effective at phytate reduction in whole‐wheat bread preparation. Additionally, phytate degradation enhanced the mineral availability of bread.     

Effects of ball-milled graphite in the synthesis of SnO2/graphite as an active material in lithium ion batteries

Nano-sized SnO₂ particles supported on ball-milled graphite were manufactured by the in situ NaBH₄ reduction method and were used as an anode active material in lithium-ion batteries. Their physical and electrochemical characteristics were investigated using various characterization techniques: Raman spectroscopy, x-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). From coin half-cell tests, the SnO₂ particles supported on graphite that was ball-milled for 24 hr showed a reversible capacity better than that of commercial graphite and other SnO₂/graphite materials for which the graphite was ball-milled for longer lengths of time.     

Downregulation of Runx2 by 1,25-Dihydroxyvitamin D3 Induces the Transdifferentiation of Osteoblasts to Adipocytes

1,25-Dihydroxyvitamin D₃ (1,25(OH)₂D₃) indirectly stimulates bone formation, but little is known about its direct effect on bone formation. In this study, we observed that 1,25(OH)₂D₃ enhances adipocyte differentiation, but inhibits osteoblast differentiation during osteogenesis. The positive role of 1,25(OH)₂D₃ in adipocyte differentiation was confirmed when murine osteoblasts were cultured in adipogenic medium. Additionally, 1,25(OH)₂D₃ enhanced the expression of adipocyte marker genes, but inhibited the expression of osteoblast marker genes in osteoblasts. The inhibition of osteoblast differentiation and promotion of adipocyte differentiation mediated by 1,25(OH)₂D₃ were compensated by Runx2 overexpression. Our results suggest that 1,25(OH)₂D₃ induces the transdifferentiation of osteoblasts to adipocytes via Runx2 downregulation in osteoblasts.     

Effect of powder alloy composition on the microstructure and properties of kinetic sprayed Cu-Ga based coating materials

This study attempted to manufacture Cu-Ga coating materials via the kinetic spray process and examined the effect of powder alloy composition on the microstructure and properties of the kinetic sprayed Cu-Ga based coating materials. Cu-15 at%Ga, Cu-20 at%Ga, and Cu-30 at%Ga powders were prepared and used. Annealing heat treatments were conducted at 200 °C~800 °C. The results showed that the coating layers could be manufactured with Cu-15 at%Ga and Cu-20 at%Ga powders via the kinetic spray process, except for Cu- 30 at%Ga. A single phase of pure Cu was observed in the Cu-15 at%Ga coating layer and Cu and Cu₃Ga phases in the Cu-20 at%Ga coating layer. A small amount of Ga₂O₃ was also detected between deposited particles in both coating layers. It was difficult to obtain the coating layer due to the shattering of powders during the kinetic spraying with Cu-30 at%Ga powder, which is made up of a variety of inter-metallic compounds. Porosity and hardness decreased as the annealing temperature increased, and porosity decreased into 0.48% (Cu-15 at%Ga), 0.74%(Cu-20 at%Ga) at 800 °C. Annealing heat treatment appeared to be effective in enhancing the density of the coating layers without generating a new phase. This study also considered to suggest the optimal alloy composition of kinetic sprayed Cu-Ga based coating material for sputtering target.