Papers by Author: Sung Hyun Kim

Abstract: The effect of ScSZ - YSZ composite on stabilization and electrical conductivity has been investigated. Composite of (8YSZ)x(10ScSZ)(1-x)(x=0~1) were mixed by wet milling process and sintered at 1400°C for 5h and characterized by XRD, SEM, dilatometry and impedance spectroscopy. the long-term stability of the electrolyte materials was examined at 900°C for up to 1000h. The cubic phase shifts from an YSZ character to a ScSZ character with increase in percentage of ScSZ. The conductivity of composite with increasing ScSZ content is slightly higher than YSZ. Especially, above 50wt% ScSZ composition exhibited higher electrical conductivity. All compositions showed conductivity degradation after annealing at 900°C for 1000h.

Abstract: This paper presents an experimental finding in the Split Hopkinson Pressure Bar (SHPB) technique to obtain a better compressive stress strain data for rubber materials. An experimental technique which modifies the conventional SHPB has been developed for measuring the compressive stress strain responses of materials with low mechanical impedance and low compressive strengths such as rubber. This paper uses an all-polymeric pressure bar to achieves a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident pulse to ensure stress equilibrium and homogeneous deformation of rubber materials. It is found that the modified technique can determine the dynamic deformation behavior of a rubber more accurately.

Abstract: This paper presents a modified Split Hopkinson Pressure Bar (SHPB) technique to obtain compressive stress-strain data for rubber materials. An experimental technique that modifies the conventional SHPB has been developed for measuring the dynamic compressive stress-strain responses of rubber materials with low mechanical impedance and low compressive strengths. This paper introduces an all-polymeric pressure bar set-up which achieves a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident wave which helps the stress equilibrium and homogeneous deformation of rubber materials. It is found that the modified technique can determine the dynamic deformation behavior of NR and NBR rubber more accurately than those from the conventional SHPB technique.

Abstract: We report the sonochemical synthesis of mercury telluride (HgTe) nanoparticles and the photocurrents of these nanoparticles and their organic hybrid system. The HgTe nanoparticles were about 5 nm in size and their lattice structure was cubic. Poly(N-vinylcarbazole)(PVK) was added to the HgTe nanoparticles for the formation of an inorganic(HgTe)-organic(PVK) hybrid system. The room-temperature photocurrents of the HgTe nanoparticles and the HgTe-PVK hybrid system were compared in this study. The photocurrent was significantly enhanced for the HgTe-PVK hybrid system.