n-Lin Chu

Comparison of oxidation behaviours among three Fe–Cr based alloys for solid oxide fuel cell interconnect

Abstract Two metallic alloys, containing comparable amounts of Cr, underwent oxidation in hot air simulating (the solid oxide fuel cell cathode atmosphere) for various periods. The results demonstrated that the oxidation kinetics of Crofer22 APU and equivalent ZMG232 followed the parabolic rate law and oxidation rates increased with temperature. Typical oxidation rates of Crofer22 APU and ZMG232 upon annealing treatment are approximately 0·21 orders of magnitude lower than that of ZMG232. An oxide scale electron probe microanalyser, a scanning electron microscope and X-ray diffractometer were adopted to verify the applicability of Fe–Cr based alloys in the solid oxide fuel cell interconnect component. Two alloys contain comparable amount of Cr, Mn and Fe, and their surface oxides as analysed are indicated to be Cr2O3 and (Mn,Fe)Cr2O4 spinel compound. In summary, Crofer22 APU had the best oxidation resistance of any of the alloys of interest.

Oxidation Behavior of Various Metallic Alloys for Solid Oxide Fuel Cell Interconnect

Ten iron-based alloys and nickel-based alloys were subjected to oxidation treatment in a hot air environment for various periods. In this investigation, all alloys contained a certain amount of Cr, and Cr 2 O 3 and (Mn, Fe, Cr) 3 O 4 spinel compounds are generated on the surface oxides. Other spinels that contain Cr, Mn, Fe, and Ni are also formed on it; the compositions depend on the composition of the steels and any other materials that are in contact with the interconnects. Accordingly, the role of spinels in the oxidation of interconnects must be understood.

Joint strength of Ag–9Pd–9Ga brazed interconnect and anode-supported electrolyte for solid-oxide fuel cell applications

A newly developed Ag–9Pd–9Ga active filler was vacuum brazed, and the mechanical properties between the metallic interconnects (SS430, Crofer22 APU, Crofer22 H) and a Ni–yttria-stabilized zirconia cermet anode were systematically investigated. The results indicate that the bonding between metal and cermet is well established and that the interface is smooth. The joint strength evaluated at both 25 ℃ and 800 ℃ under shear and tensile loading conditions confirmed that the brazed Ag–9Pd–9Ga sealant compared favorably with its commercially available glass-ceramic GC-9 counterpart.

Effects of Etching Variations on Ge/Si Channel Formation and Device Performance

During the formation of Ge fin structures on a silicon-on-insulator (SOI) substrate, we found that the dry etching process must be carefully controlled. Otherwise, it may lead to Ge over-etching or the formation of an undesirable Ge fin profile. If the etching process is not well controlled, the top Ge/SOI structure is etched away, and only the Si fin layer remains. In this case, the device exhibits abnormal characteristics. The etching process is emerging as a critical step in device scaling and packaging and affects attempts to increase the packing density and improve device performance. Therefore, it is suggested that optimization of operating the plasma reactor be performed through simulations, in order to not only adjust the process parameters used but also to modify the hardware employed. We are going to develop Ge junction-less devices by employing updated fabrication parameters. Besides, we want to eliminate misfit dislocations at the interface or to reduce threading dislocations by applying cyclic thermal annealing process to meet the goal of obtaining suspended structure of epitaxial Ge layers with high quality.

The combination of rolling-and-T6-treatments with Al2O3-reinforcing-particles effect on A6061 metal-matrix composites

Al–Si alloys, with excellent properties such as low weight, low thermal expansion coefficient, and high wear-resistance, are ideal materials for the automobile and aerospace industries. However, their applications have been hampered by the coarsening of the primary-Si particles in Al–Si alloys. In this study, the rolling-and-T6-treatments effect on A6061/Al2O3 metal-matrix composites is investigated. The A6061/Al2O3 metal-matrix composites with different amounts of reinforcing Al2O3 particles are examined in the aspects of wear resistance and hardness. Upon the T6 treatment, the hardness is enhanced in all cases and is summarized. The results suggest that the increase of Al2O3 particles reduce the wear rate. The possible reinforce mechanisms and the environmental temperature effects are discussed. This improvement in wear resistance is due to the particle size refinement of silicon at a high percentage-roll-reduction.

Flow stress behaviour of ABS (acrylonitrile–butadiene–styrene) at elevated temperature and application to the thermal vacuum forming process

Abstract A conventional plastic processing method, vacuum thermal forming, is adopted for manufacturing the large-size rear back of the TV set. The candidate material is the widely used engineering plastic, acrylonitrile–butadiene–styrene (ABS). The basic principle of thermal forming process is to place a heated plastic sheet on a die and clamp with a cover plate whose function is to seal around circumference to establish a vacuum or pressurised compartment. Thus, the softened sheet as being preheated will progress towards and fill up the die underneath when vacuum or pressure is applied. The major problem with thermal forming could be the uneven thickness distribution. To tackle this issue, computer simulation can be an advantageous tool to minimise the number of try-and-error experiments. To run computer simulation for thermal forming, flow behaviour of the ABS is needed as the computer input. Thus, stress–strain relation obtained by tensile tests at various elevated temperatures and strain rate is essential for performing computer simulation work. The constitutive equation based on the widely power law was established. The application was applied to simulate the vacuum thermoforming process of a large-size back cover of television set and the major problem of uneven thickness distribution was successfully simulated with suggested prevention design.

Hydrogen Storage in Iron/Carbon Nanopowder Composite Materials: Effect of Varying Spiked Iron Content on Hydrogen Adsorption

This study investigates the effects of varying the spiked iron content of iron/carbon nanopowder (Fe/CNP) composite materials on hydrogen storage capacity. Among four such samples, a maximum hydrogen uptake of approximately 0.48 wt% was obtained with 14 wt% of spiked iron under 37 atm and 300 K. This higher hydrogen uptake capacity was believed to be closely related to the physisorption mechanism rather than chemisorption. In this case, the formation of maghemite catalyzed the attraction of hydrogen molecules and the CNP skeleton was the principal absorbent material for hydrogen storage. However, as the iron content exceeded 14 wt%, the formation of larger and poorly dispersed maghemite grains reduced the available surface areas of CNP for the storage of hydrogen molecules, leading to decreased uptake. Our study shows that hydrogen uptake capacities can be improved by appropriately adjusting the surface polarities of the CNP with well dispersed iron oxides crystals.

Oxidation Behavior of Some Metallic Alloys for SOFC Interconnect and Electrical Resistance of the Oxide Scale Formed in Hot Air

Five oxidized metallic alloys, namely, Crofer22, equivalent ZMG232, stainless steel SS430, SS304 and Inconel718 were subjected to oxidation treatment in hot air environment for various period of time. Then the resulted oxide scale was studied; with microstructure analyzed by scanning electron microscopy and X-ray diffraction, and electrical resistance was measured. All the five alloys contain comparable amount of Cr, and their surface oxides as analyzed by SEM/EDS indicate to be some kind of Cr-O compound. Except SS304, all other four alloys exhibit not much different morphologies.