Abstract: The SnO2 thin films doped with traces of silicon were deposited on the p-type (100) Si substrate by the r.f. magnetron sputtering method from Sn0.94Si0.06O2 target for the application of lithium secondary micro-battery anode. The crystal orientation of tin oxide thin films was changed from (110) to (101) or (211) with the increase of the substrate temperature. Contrarily, the
crystallization of tin oxide thin films, which were heat-treated in the RTA furnace from 450°C to 650 °C under the O2 ambient, did not show significant difference. As a result of the electrochemical analysis, we could see that the irreversible capacity was reduced during the first discharge/charge cycle. Capacity increased with the increase of substrate temperature, but decreased with the increase of RTA temperatures. In particular, the maximum value of reversible capacity was 700mAh/g under the deposition condition of the substrate temperature of 300°C and the Ar:O2 ratio of 7:3.
Abstract: Sol-gel coatings of TiO2 have been prepared from TiO2 sol and deposited by a dip-coating technique on 316L stainless steel sheets to study their electrochemical behavior in corrosive solutions. The influence of the coatings on the chemical corrosion of the substrate was evaluated by potentiodynamic polarization curves in different aqueous NaCl solution at 25°C. Comparative tests were performed on uncoated one. The thickness of the TiO2 coatings varied from 0.5~0.8 µm. The
values of the electrochemical parameters allow for an explanation of the role of the TiO2 films in the increased resistance of stainless steel against corrosion in moderately aggressive environments.
Abstract: After the 9∙11 terrorism and America-Iraq war, apprehension of mass destruction
weapons such as bio-chemical agents calls for much more sensitive sensors which can detect toxic gases. In this study, semiconductor gas sensors based on tin oxide were examined to detect chemical agent simulants: dimethyl-methyl-phosponate (DMMP), di(propylene glycol) methyl ether (DPGME), acetonitrile, and dichloromethane. DMMP((CH3O)3), DPGME(C7H16O3),
acetonitrile(CH3CN), and dichloromethane(CH2Cl2) gases are the simulants of nerve agent-sarin, vesicant agent-HN(N(CH2CH2Cl)3), blood agent-AC(HCN), and choking agent-CG(COCl2) gases, repectively. The SnO2 powder was prepared by a coprecipitation method from the mixture of tin chloride and zinc acetate dihydrate. Zinc oxide was doped into SnO2 from 1 wt% to 4 wt% to
improve its reliability and sensitivity. To fabricate a thick film, powders were made into paste with organic binder of ethyl cellulose and screen-printed on the alumina substrate. The phase development and morphology of ZnO-doped SnO2 film were investigated by XRD (X-ray diffraction analysis), BET (surface and pore size analyzer), and SEM (scanning electron microscope). The gas sensing characteristics for target gases were examined with a flow-type measurement system. The concentrations of simulants were controlled from 500 ppb to 1500 ppb, and working temperatures were regulated from 250 to 400 .
Abstract: Cr, Ti-substituted TiO2-loaded MCM-41 (TiO2/Cr-Ti-MCM-41) catalysts were prepared, and their photocatalytic activities for decomposition of 4-nitrophenol (4-NP) in visible light were studied. The effect of H2O2 on the photocatalytic decomposition of 4-NP was investigated. Tisubstituted MCM-41 exhibited an absorption in UV range, and the incorporation of both Ti and Cr in the MCM-41 framework created visible light absorption. The visible light absorption capability
of TiO2/Cr-Ti-MCM-41 increased with increasing TiO2 loading. The photocatalytic activity of Cr- Ti-MCM-41 for degradation of 4-NP in visible light increased with increasing TiO2 loading up to 33 wt%. The addition of H2O2 enhanced the photocatalytic activity of 33 wt% TiO2/Cr-Ti-MCM-41 for decomposition of 4-NP in visible light. H2O2 was found to promote the adsorption of 4-NP on the
Cr-Ti-MCM-41 surface, leading to increased reaction rate. In addition, H2O2 may act as an electron acceptor during photocatalytic reaction, thereby lowering the electron-hole recombination and increasing the efficiency of hole utilization.
Abstract: Rainwater utilization has great potentials for recovering hydrological cycles, for buffering extreme run-off situations in the watercourses, and for reducing the costs for water supply in urban area. However, little information is available on the water qualities and runoff properties of collected rainwater, which is critical for efficient design and maintenance strategies of rainwater harvesting facilities. In this study, characteristics of rainwater collected in a rainwater harvesting system were
examined in terms of pollutant concentrations. Based on these results, TiO2 photocatalysts were applied on the roof surface as a novel coating material to improve the quality of collected rainwater. The analysis of rainwater samples shows that the contamination by turbidity, conductivity, and color occurs during the catchment process, which may result in troubles for further use. The roof coating
technique developed in this study appeared to be effective in increasing the wash-off of pollutants and improving the water quality in roof runoff because of its increased hydrophililicy as well as photocatalytic reactivity. Further research is required on trace pollutants such as endocrine disruptors to estimate and minimize health risk in rainwater harvesting.
Abstract: Al doped ZnO (AZO) films were deposited on porous silicon (PS) substrates by a reactive rf-cosputtering process from two targets of ZnO and Al. The effect of ZnO target rf-sputtering power on the structural and photoluminescence (PL) properties of AZO/PS heterojunctions were studied. Strong monochromatic blue emission located at 2.78 eV was observed for the AZO films
deposited at 150 W. Freshly prepared PS showed an emission band in the green spectral region. We show that deposition of AZO on PS does not degrade the skeleton of the PS and enhance the PL intensity. The PL band shifted to the high energy for AZO films deposited on PS and the intensity became stable.
Abstract: This paper describes the morphology and microstructure of graphitic nanofibers(GNFs) synthesized by the catalytic decomposition of ethylene in the presence of Ni:Cu(70wt%:30wt%) as catalyst at 550°C to 700°C. The catalyst was prepared by the coprecipitation method using aqueous solution of metal nitrates. The catalysts and the graphitic nanofibers(GNFs) were characterized by
FE-SEM, HR-TEM and EDXS. The shape, composition and microstructure of the catalyst according to the synthesis temperature of graphitic nanofibers(GNFs)were changed so that it brought about the change of morphology and microstructure of graphitic nanofibers(GNFs). In particular, it should be noted that the composition change of catalysts with different synthesis temperature is one of the key factors in determining the morphology of graphitic nanofibers(GNFs)
Abstract: The polyaniline (PAn) polymer was synthesized by a chemical method using aniline (AN) as monomer, ammonium persulfate (APS) as initiator, and dodecylbenzene sulfonic acid (DBSA) as dopant at 0ı. Conducting polymer films were prepared on the alumina substrate with an interdigitated electrode by using the dip coating method. These films were soaked in methanol solvent for 1h at room temperature to remove excessive DBSA and then were heated at 70ı for 4h
in N2. The detecting materials having a liquid phase at one atmospheric were precisely controlled by the system having a mass flow controller (MFC), temperature controller and measuring chamber. The sensitivity was estimated by heating from 70ı. The sensitivity observed in PAn sensor was lower than PAn-DBSA sensor at 1000 ppm methanol vapors under N2. because the additional
thermal doping effect was resulted from increasing molecular motion in polymer chain to 70ı but DBSA used as dopant was decomposed by heating over 120ı. It caused the melting point of DBSA to be lower than 120ı. So the thermal properties of PAn and PAn-DBSA were investigated by DSC (differential scanning calorimetry). The DSC was scanned with a heating rate of 10ı/min. The PAn
sample did not show the melting peak but PAn-DBSA sample showed the melting peak at 190ı. From this result, the new crystalline-region was evaluated in PAn-DBSA and increased of crystallinity of PAn polymer. And FE-SEM studies showed that the presence of the dopant strongly influenced the morphology of the polymer.
Abstract: Recently, the titania photocatalyst has been widely used in the environmental fields.
However, because the past titania photocatalyst used only the range of ultraviolet rays, the usage has been limited. We attempted to develop a new type of titania photocatalyst that activates to respond not only in the ultraviolet rays region but also in the visible radiation region. The titania photocatalyst fine particles that zirconium oxide was uniformly added in the titania fine particles,
and introduced simultaneously nitrogen into the crystal lattice in addition were synthesized. It was showed the high photo-absorption ability of the titania photocatalyst added the zirconium compared with not done by the absorption spectrum. Furthermore, it was found that the titania fine particles that introduced nitrogen colored to yellow, had also the high photo-absorption ability in the visible
range of 600nm to 400nm in addition to the range of ultraviolet rays. It was thought that this depended on the reason based on the difference of the amount of the nitrogen introduction in the titania that originated in the zirconium. Moreover, it was compared the stability maintenance for the titania introduced nitrogen with it not done by the bleaching test of heating. As a result, the stability of the titania added the zirconium was higher than not added.
Abstract: Rutile TiO2 nanoparticles have been synthesized by direct hydrolysis method using TiCl3, TiCl4 as starting materials, yielding two different morphologies. The hydrolysis of TiCl3 resulted in needlelike rutile titania with the specific surface area of 74.5m2/g, while round particles about 200~400 nm with small acicular at edge, with specific area as high as 175m2/g, were obtained using TiCl4 as starting materials. The precipitates from TiCl4 hydrolysis could be changed into anatase phase without filtering and separation by varying pH of the system. The phenomenon was explained from the viewpoint of structure. The photocatalysed properties of rutile powders were compared with those of anatase of the same specific surface area. Rutile powders with initial crystalline size of 7 nm were found to have higher photocatalysed activity in the phenol degradation reaction than that which
anatase has. The high activity of the as prepared lab-made rutile was attributed to the abundance of hydroxy groups in powders, which was proved by TG data, making the degradation reaction have more active sites. The agglomeration form of the rutile powder makes it easy for separation and reuse.