The ductile-to-brittle transition behavior of two austenitic Fe-18Cr-10Mn alloys with the combined addition of nitrogen and carbon was investigated in this study. The alloys exhibited a ductile-to-brittle transition behavior because of unusual brittle fracture at low temperatures unlike conventional austenitic alloys. The alloy with higher carbon content had higher yield and tensile strengths than that with lower carbon content due to the solid solution strengthening effect resulting from carbon addition. However, the increase in carbon content promoted the occurrence of intergranular fracture, and thus deteriorated the impact toughness. In order to develop successfully the austenitic Fe-18Cr-10Mn alloys with the excellent combination of strength and toughness in the future, therefore, more systematic studies are required to find the appropriate amount and ratio of nitrogen and carbon.

The fabrication of high quality graphene using chemical vapor deposition (CVD) method for application in semiconductor, display and transparent electrodes is investigated. Temperature and pressure have major impact on the growth of graphene. Graphene doping was obtained by deposition of $MoO_3$ thin films using thermal evaporator. Bilayer graphene and the metal layer graphene were obtained. According to the behavior of graphene growth P-type doping was confirmed. Graphene obtained through experiments was analyzed using optical microscopy, Raman spectroscopy, UV-visible light spectrophotometer, 4-point probe sheet resistance meter and atomic force microscopy.

Hydroxyapatite coatings were fabricated by a room temperature spray method on zirconia substrates and the influence of heat-treatment on their microstructure was also investigated. Phase composition of coated hydroxyapatite films was similar to the starting powder, but the grain size of hydroxyapatite particles was reduced to the size of nano-scale about 100 nm. Grain size, particle compactness, and adhesiveness to zirconia of hydroxyapatite coatings were increased with heat-treatment temperature, but some of cracks by heat-treatment above $1100^{\circ}C$ were initiated between hydroxyapatite coatings and zirconia substrate. Heat-treated hydroxyapatite layers show the dissolution in SBF solution for 5 days. Hydroxyapatite-coated specimen heat-treated at $1100^{\circ}C$ for 1 h has a good biocompatibility, which specimen induced the nanocrystalline hydroxyapatite precipitates on the coating surface by the immersion in SBF solution for 5 days.

In this study, a simulation was used to derive an optimal process of heat treatment with carburizing, and compared the derived result with SCr420HB helical gear in heat treatment with carburized quenching process about a change of the quenching method. The optimal carburizing process time is derived by the simulation with the theoretical time. The process has been performed by oil quenching and salt quenching method. Through the comparison of the results from the simulation(Hardness, effective case depth hardened by carburizing treatment and deformation) and the actual process, analyzed the error value of each quenching. And it verified the applicability of the simulation.