Solid State Phenomena Vols. 124-126

Abstract: In this work, PtRu/CNTs catalysts were prepared by pulse potential plating methods. The particle size and loading level of catalysts were measured by changing the plating time and pulse interval of pulse potential plating method. Electrochemical activities of PtRu/CNTs catalysts were measured by cyclic voltammetry (CV). PtRu/CNTs catalysts showed an increased the electrochemical activity of methanol oxidation up to 24min and a slightly decreased activity over 24min. The electrochemical activity was increased with increasing of the pulse interval. Consequently, it was found that optimal plating time was 24min and optimal pulse interval was 0.5s for electrochemical activity of PtRu/CNTs catalysts.

Abstract: To investigate the effect of oxygen pressure on the synthesis of LiNiO2 cathode material for Li secondary battery, powder was prepared by emulsion method and calcined at 750°C for 24 h under various oxygen gas pressures. LiNiO2 single phase could be synthesized under oxygen pressure of 101.3~103.3 kPa but not under air atmosphere. Cation mixing in Li site of LiNiO2 lowered as oxygen pressure increased and was saturated around 103.3 kPa. The lowest cation mixing, 7.0% of Ni3+ in the Li site was obtained at 750°C for 24 h under 103.3 kPa of oxygen pressure.

Abstract: Lithium manganese oxide (LiMn2O4) had been a promising material for lithium-ion and thin film batteries. However, the LiMn2O4 had some problems such as the manganese dissolution into liquid electrolyte. In order to improve cycleability, we introduced SnOx layer as protective layer. This layer was deposited on spinel LiMn2O4 by using radio frequency magnetron sputtering. The deposited SnOx layer fully covered the LiMn2O4 , and didn’t make a change the crystallinity of the spinel films. The SnOx layer prevented direct contact of liquid electrolyte and improved the cycle retention.

Abstract: The graphite particles with average size of 15 μm were used as the anode base materials for lithium ion battery. Tin oxide was incorporated into graphite particles by a precipitation method. As SnO2 content increased from 0 to 80 wt%, the initial discharge capacities of SnO2/graphite composite electrodes raised from 357 to 688 mAh/g, approaching to their theoretical capacities. The composite electrodes exhibited plateau characteristics of SnO2 at 0.85
1 V range in the charge voltage-capacity curves of the first cycle. Increased reversible capacity of the composites suggested that lithium ion could be stored in the both lattices of tin and graphite. It was demonstrated by XRD that the tin metal decomposed from tin oxide in the first cycle of charge played a leading role of charge/discharge thereafter.

Abstract: We prepared nano-sized La1-xSrxMnO3 (x=0.2~0.5) cathode catalyst for the zinc air secondary batteries by citrate method and measured cathode’s electrochemical characteristics according to content of strontium compose the cathode catalyst. We heat treated the prepared precursor at various calcination temperature (500~900
), and examined the optimum calcinations temperature by XRD analysis and electrochemical evaluation. We examined the ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) performance of the prepared La1-xSrxMnO3 catalyst powder. La0.7Sr0.3MnO3 and La0.8Sr0.2MnO3 catalyst has shown the best performance in the ORR. But in the OER, La0.7Sr0.3MnO3 catalyst has shown better performance. When we consider ORR and OER performance simultaneously, La0.7Sr0.3MnO3 catalyst has shown the best performance because of its lowest voltage difference between charge and discharge.

Abstract: Nanosized TiO2-Ag-SiO2 sols were prepared with modified sol-gel method using reduction agent. The physical properties of the prepared particles were investigated by TEM, XRD and FT-IR. The titanium tetraisopropoxide (TTIP, 98% Aldrich), teraethylorthosilicate (TEOS, 98% Aldrich) and silver nitrate were used as precursors of titania, silica and silver, respectively. Sodium citrate tribasic dihydrate (C6H5Na3.2H2O, Aldrich) was used as a reduction agent. This paper presents the effect of nanosized TiO2-Ag-SiO2 sols on the formation of methane hydrate in a semi-batch vessel. The micrographs of TEM showed that the TiO2-Ag-SiO2 particles possessed a spherical morphology with a narrow size distribution. The crystallite size of particles decreased with an increasing the SiO2 content. In addition, the water solution with 1.0 wt% of TiO2-Ag-SiO2 particles acted as promoter for methane hydrate formation.

Abstract: Effects of substrate temperature and phosphor doping on electrochemical characteristics of the silicon film anode were investigated. The silicon thin films were synthesized directly on copper foil by radio-frequency capacitively coupled plasma-enhanced chemical-vapor deposition (r.f.-CVD). The cyclability of the silicon anode greatly depends on the surface morphology and surface resistivity. The silicon film anodes which have granular structure and high conductivity showed higher cyclabilty than those of planer and low conductivity, respectively.

Abstract: The destruction of the Carbon fibers reinforcement occurs during an infiltration with metallic matrix, under well-defined technological circumstances. The Al carbide resulted plays an important role in transferring the efforts trough the interface as long as it doesn’t significantly reduce the diameter of the carbon fibers. The interface reaction can be controlled by adding K2ZnF6 and Zn, thus improving the wetting of the reinforcement and reducing the Al reactivity against carbon. This article deals with a simulation using specific technological parameters in order to achieve an evolution of the Al carbide thickness of the layer, when Zn percentages of the Al matrix change.

Abstract: In the polymer impregnation and pyrolysis (PIP) process for the fabrication of SiCf/SiC composite, the curing process should be included to increase the conversion yields. During the curing process, unintended oxygen is introduced. Control of this oxygen is very important to obtain composites with a good high temperature stability. Using the electron beam curing process with full doses of 2~10 MGy and the pyrolysis process at 1300~1500oC, composites with an oxygen contents of less than 1 wt% could be obtained.

Abstract: We report sintering additive systems to decrease the densification temperature of the corrosion resistant AlN-SiC-TiB2 system. Since oxide additives degrade the high temperature properties of the system, and other kinds of metallic additives may affect the formation of protective mullite during oxidation, only the constituent elements were applied as additives. Dense samples ( > 98 % relative density) could be fabricated at 1850 oC and 1900 oC by spark plasma sintering (SPS) and hot pressing method, respectively.