Materials Science Forum Vols. 544-545

Abstract: Electrodeposition behavior and thermoelectric properties of the p-type (Bi,Sb)2Te3 films were investigated for thermoelectric energy conversion and nanowire applications. Composition and thermoelectric properties of the electrodeposited (Bi,Sb)2Te3 films were strongly dependent on the electrodeposition current density. The (Bi,Sb)2Te3 films electrodeposited in a 30mM solution of the 5mM Bi-15mM Sb-10mM Te concentration at current densities of 0.3~0.5 mA/cm2 exhibited the power factors of 2~3.4 ×10-4 W/K2-m, which were equivalent to the values reported for the sputter-deposited (Bi,Sb)2Te3 films.

Abstract: Encapsulated induction melting was attempted to prepare binary skutterudite CoSb3 and its thermoelectric properties were investigated. Single phase δ-CoSb3 was successfully obtained by the subsequent isothermal heat treatment at 773K-873K for 24 hours in vacuum. Thermoelectric properties were changed with constituent phases because β-CoSb and Sb are metallic/semimetallic phases, while γ-CoSb2 and δ-CoSb3 are semiconducting phases. Thermoelectric properties were remarkably improved by the proper heat treatment and they were closely related to phase transitions.

Abstract: Thick-film CO2 sensors were fabricated using a sodium super ionic conductor (NASICON: Na1+xZr2SixP3-xO12) with a series of Li2CO3-BaCO3 auxiliary phases. The powder of a precursor of NASICON with high purity was synthesized by a sol-gel process. Using the NASICON paste, an electrolyte was prepared on the alumina substrate through screen printing and then sintered at 1000°C for 5 hours. The resulted NASICON thick film was characterized by XRD and FESEM. Within a wide range of CO2 volume ratio concentration from 1,000 to 10,000 ppm, the output of the sensor showed a good electromotive force (EMF) response that was very close to the theoretical value. The sensor attached with a binary carbonate auxiliary phase Li2CO3-BaCO3 (1:2) showed fairly good CO2 sensing properties at 470°C.

Abstract: Machinable mica glass ceramics with more ZnO and B2O3 showed the phase separation by spinodal decomposition. the size of two phases formed by phase separation is in micron meter order. The nucleation and growth of crystal is performed through the diffusion of atoms. Another kind of materials with no ZnO and B2O3 addition behaves different mechanism of phase separation in terms of nucleation and growth. Many fine particles are obtained after the phase separation , the size of which is less than 100nm in diameter. Subsequently nucleation and growth in the crystallization is accomplished by aggregation and unification of the granular phase precipitation. The mechanism of the aggregation and unification nucleation-growth is different from one controlled by atom diffusion in nature. The different mechanisms in crystal nucleation and growth, caused by the composition changing.

Abstract: Boron carbide composites in Si-B-C System have been widely studied and applied in excellent engineering materials. These materials are usually used at high temperature. Unfortunately, amorphous Si-B-C ceramics have been few reports regarding the properties of Si-B-B4C ceramics. In this study, the preparation of crystallized Si-B-C system compounds using Si, B, and B4C powders was investigated to determine their potentially for applications as high hardness composites. The samples were prepared at 1673 K for 2 hours in Ar atmosphere. The sintered bodies were cut into 5 х 5 х 10 mm blocks and polished with diamond disk for Vickers hardness. The samples were subjected to X-ray diffraction (XRD) analysis for phase evolution using a powder X-ray diffractometer. The fracture surfaces of the specimens were observed using a scanning electron microscope (SEM) included an energy dispersive X-ray fluorescence spectrometer (EDX) system to estimate the microstructures.

Abstract: Effects of the O2/Ar flow ratio in the reactive sputtering process and the annealing temperature on the structure and surface roughness of ZrO2 films and the electric properties of Pt/ZrO2/Si MOS capacitors in which the ZrO2 film was deposited by magnetron sputtering have been investigated. The optimum process parameters of the Pt/ZrO2/Si capacitor based on reactively sputtered- ZrO2 determined in such a way as the capacitance is maximized and the leakage current, the oxide charge, and the interface trap density are minimized is the O2/Ar flow ratio of 1.5 and the annealing temperature of 800°C

Abstract: In the paper, ampicillin-loaded alginate(ALG) microspheres covered with chitosan (CS) were firstly prepared by emulsification/internal gelation method. These microspheres were mixed with n-HA/CS composite and then were fabricated into porous scaffold carrying micropheres by gas-foaming together with phase-separation. their properties were characterized by the methods of scanning electronic microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and inversed microscope. The drug releasing rate and entrapment efficiency were tested by spectrophotometry at 203 nm. The results show that the porous scaffold carrying microspheres has good property of slow drug releasing rate. The research will offer a new kind of degradable porous scaffold with good property of controlled drug release for bone or cartilage repairing.

Abstract: In this study, we investigated ionic conductivities of the electrolytes and cycle performances of Li/S cells using the electrolyte. (PEO)10LiCF3SO3 composite polymer electrolyte(CPE) containing carbon powders and Brij dispersant was prepared by ball milling for 12hr. The 5wt% carbon powders having high surface area (~ 80 m2/g) was added into the (PEO)10LiCF3SO3 electrolyte. To get a well-dispersed structure, Brij dispersant was also added into the (PEO)10LiCF3SO3-5wt%Carbon electrolyte. Li/CPEs/50wt%S cells showed initial discharge capacities of between 1,250 and 1,413 mAh/g-sulfur with current density of 100 mA/g-sulfur at 80 °C. These results led us to conclude that the dispersants added into the CPE improved the initial discharge capacities and cycle performances.

Abstract: Fluorine-doped tin oxide (FTO) films on PET (Polyethylene Terephthalate) substrate were prepared by the electron cyclotron resonance-metal organic chemical vapor deposition (ECRMOCVD) under an Ar-O2-H2 atmosphere. The used tin and fluorine precursor are TMT (tetramethyltin) and sulfur hexafluoride (SF6), respectively. The hydrogen content plays an important role to control the optical and electrical characteristics of the films. The HF etching effect was clearly observed with increase of H2/TMT mole ratio, on the other hand the hydro-carbon deposition increased with decrease of H2/TMT mole ratio. Therefore the optimum H2 content can be determined by the counter balance effect between HF etching and hydro-carbon deposition. The obtained optimum SnO2: F thin films exhibited over 90 % of optical transmittance at wavelength range from 380 to 780 nm and c.a. 6×10-3 ohm ·cm of electrical resistivity at 1.25 H2/TMT mole ratio.

Abstract: CuO/GDC composite powder with 50 wt% of CuO was prepared by surface modification of ~60 nm GDC powder with Cu precursors. Since copper oxide melts at lower temperature than GDC sintering temperature, fabrication procedure was modified by inducing infiltration of molten copper oxide via capillary force and then followed by heat treatment at ~1000
. Surface modification was carried out with a MgO sol to suppress agglomeration of GDC. Such prepared Cu/GDC cermets showed uniform microstructure and excellent electronic conductivity of ~8500 S/cm for the Cu/GDC cermet and ~10200 S/cm for the modified one at 800
.