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This study proposed a new metal-based material design with a modulus of elasticity and thermal conductivity comparable to that of wood by architecturing of metal sheets. The proposed new material is designed in a form in which metal sheets of the same shape with beads are repeatedly stacked. In order to find a design with the target modulus of elasticity and thermal conductivity values, designs were derived using the Design of Experiment (DOE) and the material properties were predicted accordingly. For the prediction of material properties designed in the shape of a metal sheet architecture, finite element analysis combined with the homogenization method was used in consideration of the repeatability of the material microstructure. The reliability of the prediction of material properties based on the finite element analysis using a unit cell was verified by comparison with the results obtained from the compression test and the temperature wave method for the specimen. By analysing the modulus of elasticity and thermal conductivity data corresponding to the designs derived by DOE, we evaluated the effect of the design variables of the metal sheet architecture on the material properties. In addition, we investigated whether the material properties comparable to wood or leather were included within the derived design domain, and presented detailed design data of a metal sheet architecture that provides targeted material properties. It can be inferred from this study that the use of architecturing of metal sheets enables the development of new metal-based materials that can simulate the properties of other materials while utilizing the advantages of fire resistance and recyclability inherent in metals.

Medium and large battery technology for energy storage devices or electric vehicles requires long life times and low cost as well as excellent safety. As a next generation high energy density type secondary battery, a lithium ion battery has been developed. However, when lithium metal cathodes is used, a redox reaction occurs at the interface between the electrode surface and the electrolyte, and lithium ions are eluted and lithium electrodeposits are concentrated. This phenomenon causes a problem that dendrite grows and causes an internal short circuit of the battery. In this study, metal oxide nanoparticles were coated to form a porous layer on the surface of lithium metal for suppressing dendrite growth and interfacial transport of lithium ions during charging/discharging. The porous metal oxide coated Li metal unit cell showed an improvement of life times with maintaining the initial potential difference during charging/discharging.

What causes the transformation of a solar cell is the behavior difference of thermal expansion occurred between the substrate and the layer of semiconductor used in the solar cell. Therefore, the substrate has to possess a behavior of thermal expansion that is similar with that of semiconductor layer. This study employed electroforming to manufacture Fe-Ni alloy materials of different compositions. To verify the result from a finite element analysis, a two-dimensional Mo substrate was calculated and its verification experiment was conducted. The absolute values from the finite element analysis of Mo/substrate structure and its verification experiment showed a difference. However, the size of residual stress of individual substrate compositions had a similar tendency. Two-dimensional CIGS/Mo/SiO2/substrate was modeled. Looking into the residual stress of CIGS layer occurred while the temperature declined from 550 o C to room temperature, the smallest residual stress was found with the use of Fe-52 wt%Ni substrate material.

Fe-Ni has been of great interest because it is known as one of low thermal expansion alloys as various application areas. This alloy was fabricated by electroforming process, and effect of heat treatment on thermal expansion and hardness was investigated. Nano-crystalline structure of 13.3 - 63.5 nm in size was observed in the as-deposited alloy. To investigate the effect of heat treatment on grain growth and mechanical/thermal properties, we conducted hardness and coefficient of thermal expansion (CTE). From this, we confirmed these properties were varied by heat treatment. In this nano-crystalline alloy, we could observe abnormal behavior in thermal expansion between 350 - 400oC. Additionally, an abrupt change in hardness has also been observed. However, once the grains grow up to micro-sized the mechanical and thermal properties mentioned above were stabilized similar to those of bulk alloys due to heat treatment.

For the usage and shaping of engineering parts of nanocrystalline (NC) materials, deformation behavior at both the service temperature and the forming temperature is necessary. For characterization of the mechanical properties of metallic NC materials, NC nickel has been synthesized using electrodeposition processing. In this study, experimental uniaxial tensile testing was performed to elucidate the deformation behavior of NC nickel of 12 nm grain size under various strain rate conditions. In addition to the experimental approach, we provide an account of the mechanical properties of NC nickel materials from our current viewpoint. This is based on recent modeling that appears to provide a conclusive description of the phenomenology and the mechanisms underlying the mechanical properties of NC materials. The experimental results indicate that the deformation in an elastic range is large (∼2%) and strain rate insensitive whereas in a plastic deforming range the deformation is small and strain rate sensitive. The fracture strain and stress increases with increasing strain rate. Overall, limited fracture strain results from the absence of strain hardening soon after the elastic limit. Phase mixture modeling could simulate the absence of strain hardening associated with the grain boundary mediated plastic deformation mechanism.

The effect of bath condition on Ni–Fe alloy coating was investigated. The composition of Ni–Fe alloys was highly dependent on the concentration of iron ions rather than nickel ions. Duty cycle and pH did not show an impact on the composition of Ni–Fe alloys, however the composition of alloys was highly dependent on the current density. When the temperature of the bath was over 45 °C, the composition of nickel was increased, since the limiting current density of nickel was increased. The optimum concentration of bath and operating concentration for the invar Ni–Fe alloy was obtained.

Thermal expansion behavior of Al, Ti, Mo, stainless steel and Fe–Ni alloy foils, which could be used for the substrate of flexible solar cells, were studied experimentally using thermomechanical analyzer (TMA). Electroformed Fe–Ni alloy foils and commercially available 50 μm thick Al, Ti, Mo and stainless steel were used for experiment. The thermal stresses and the displacement of solar cell systems consisted of metal foil substrate and virtual CIS top cell were numerically analyzed. Then measured coefficient of thermal expansion of metal foils and reference thermal expansion coefficient of CIS were used to compute the thermal stresses and the displacement of the thin film layers and the substrates of solar cell systems.

Differences in the thermal expansion of the semi-conductor layer and the substrate of thin film solar cells can lead to thermal deformation of the cell during thermal processing. To control this deformation, the substrate needs to have a thermal expansion behavior similar to that of the semi-conductive layer of the cell. In order to develop such a metal substrate for thin film silicon solar cells, a Fe-42 wt. %Ni alloy with low thermal expansion characteristics was fabricated by electroforming. The thermal expansion behaviors of as-deposited and heat-treated Fe-42 wt. %Ni alloys were measured using a Thermal Mechanical Analyzer. A rapid change in thermal expansion was observed between 350 and 400 °C in the as-deposited Fe-42 wt. %Ni alloy. However, when the alloys were heat treated at temperatures higher than 500 °C, their thermal expansion behaviors were stable and their thermal expansion coefficients were 4–5 × 10−6/ °C. Based on such data, Finite Element Analysis was applied to calculate the thermal deformation of the cell that occurs during cooling from a virtual coating process temperature to room temperature, using the Algor program. The analyses showed that the cell on the heat-treated Fe-42 wt. %Ni alloy substrate had less residual stress and a lower amount of deformation compared to that on a commercial stainless steel substrate.

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