Materials Science Forum Vols. 544-545

Abstract: The solid-phase photocatalytic degradation of poly (vinyl chloride) (PVC) films was investigated in ambient air. The photodegradation of the PVC and PVC-TiO2 was compared with that of plasma-treated PVC and plasma-treated PVC-TiO2
performing a weight loss monitoring and scanning electron microscopic (SEM) analysis. The SEM of the PVC-TiO2 film treated by plasma showed many cracks on the surface after photodegradation. Furthermore, the surface wettability and surface structure of PVC after nitrogen plasma treatment was characterized by contact angle, surface tension, and electron spin resonance (ESR). The experiment indicated that the surface free energy and wettability of PVC treated by plasma increased greatly. ESR revealed that the signal of radicals on the surface of the plasma-treated PVC film was enhanced after treatment. The free radicals on the surface of plasma-treated PVC possibly decreased the activating energy of photocatalytic reaction, which belongs to the free radicals reaction, because the chemical activity of the free radicals was high. According to these findings, a mechanism on the photodegradation of plasma-treated PVC-TiO2 is proposed.

Abstract: TiO2-coated SiO2 particles were prepared using industrially-wasted amorphous SiO2 powder by an alkoxide method, in which the mean particle size of SiO2 was approximately 100 nm. The SiO2 powder and titanium tetraisopropoxide were mixed in ethanol and an appropriate amount of distilled water was added to the suspension for hydrolysis of the alkoxide. The product was calcined in the temperature range from 600 to 1300°C to crystallize the deposited TiO2. The homogeneous deposition of TiO2 on the SiO2 surface was observed by SEM. It was found that the SiO2-support tended to retard the transformation from anatese to rutile. The maximum photocatalytic activity for decomposition of methyleneblue was obtained on the TiO2-coated SiO2 powder calcined at 1000°C, and was higher than that of a commercial TiO2 powder.

Abstract: A novel Zr2ON2 catalyst was successfully prepared by nitriding ZrO2, which has a potential enough for H2 formation by the reduction of water under UV irradiation. It was found that the Zr2ON2 had a stable photocatalytic activity for water oxidation and reduction in the presence of sacrificial reagents (methanol or Ag+) under visible light irradiation (λ < 500 nm).

Abstract: Nitrogen-doped TiO2 has been prepared by calcining technical grade guanidine hydrochloride and commercial anatase TiO2 powders. XRD patterns indicate that the prepared powders are composed of anatase. XPS results show that N atoms have been incorporated into the lattice of anatase. UV-Vis reflectance spectra show that the light absorption of the synthesized N-doped anatase powders has red-shifted well into visible-light region. Degradation of methylene blue (MB) aqueous solution by N-doped anatase has been investigated by UV-Vis light spectrophotometer. The 400-mL 10 mg/L aqueous solution of MB could be degraded with 4 g N-doped TiO2 within 4.5 hrs of visible light irradiation. Photocatalytic paint was prepared by adding the synthesized N-doped nanocrystalline anatase TiO2 powders into self-engineered oxidation resistance latex paint system. The effects of the amount and types of the TiO2 in the paints on the sterilization were systematically investigated. The colony counting method was used to study its sterilization performance under visible light irradiation. The sterilization experiments show that the rate of sterilizing E. coli by the N-doped TiO2 modified paint can exceed more than 99% after irradiation by the visible light for 2 to 4 hours.

Abstract: After solid-solution and aging treatment, the copper-bearing ferritic stainless steel has been investigated by TEM fitted with X-ray EDS and XPS methods. The TEM and EDS shown that the rod-like precipitation phase was є-Cu, and distributed dispersively throughout in the matrix. The most important result from XPS analysis confirmed that except the topmost of passive film, copper appeared as element state and its concentration kept constant in the inner surface of the material. It was found that the material shown an excellent antibacterial property to staphylococcus and coliform bacteria, after passive film elimination,

Abstract: Effects of 0.5 wt% Sn-addition to the dental casting Au-12Pt-0.6Cu alloy on the interfacial microstructures and bonding strength between porcelain and the alloy were investigated. Porcelain powders (SiO2-based oxides) are bonded through a thermal schedule consisting of preoxidation, 1st firing, and 2nd firing. Interfacial microstructures were examined after pre-oxidation and 2nd firing, respectively, by scanning and transmission electron microscopy. The bonding strength of the Au-12Pt-0.6Cu and Au-12Pt-0.6Cu-0.5Sn alloys with porcelain was about 24.6 MPa and 46.2 MPa, respectively. The higher bonding strength of the Sn-added alloy compared with that of the alloy without Sn is attributed to the SnO2 formed at the interface between porcelain and the alloy during pre-oxidation. SnO2 layer is thought to enhance chemical bonding with various oxides in the porcelain and, accordingly, improve bonding strength.

Abstract: The present study was experimentally investigated the effect of ultrasonic vibrations on boiling heat transfer augmentation during the heating process. The experiments were carried out under the constant wall temperature condition and were divided into two cases applying with and without ultrasonic vibrations, respectively. Also, the temperature distributions in a vessel filled with water were measured using thermocouples during the heating process, heat transfer coefficient and augmentation ratio of heat transfer on states of convection, subcooled boiling and saturated boiling were calculated from obtained temperature profiles. In addition, the profiles of pressure variations measured using a hydrophone were compared with the augmentation ratio of heat transfer in acoustic fields. The results of experimental study were revealed that general profiles of heat transfer coefficient and augmentation ratio of heat transfer is more increased the convection state than the others states. Moreover, the profiles of acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer. In the end, as well as known “acoustic streaming” induced by ultrasonic vibrations is one of the prime effects acoustically augmented boiling heat transfer or phase change heat transfer.

Abstract: The surface oxidation behavior was investigated over a range of solid state bonding condition of the Ti-6Al-4V ELI alloy. Since the oxides at the bonding interface may prevent the materials from complete bonding, it is important to understand the oxidation behavior at solid state bonding condition. The activation energy of oxidation of Ti-6Al-4V ELI is estimated to be 318 KJ/mol in an environment of solid state bonding process. For Ti-6Al-4V ELI alloy, strucutral integrity of bonding interface without oxides have been obtained at 850°C applying pressure of 3MPa for 1 hour. Solid state diffusion bonding of Ti-15V-3Cr-3Sn-3Al alloy was also obtained under a pressure of 6MPa for 3 hours at 925°C.

Abstract: To develop the extraction media for Cd and Ni from aqueous solutions, magnetic beads containing IDA group with strong attraction to heavy metals were produced using the activating agents Epichlorhydrin (Ep) and 1,4-Butanedioldiglycidylether (Bu), respectively. Then the beads were agitated at a pH of 6 after being added to Cd and Ni aqueous solutions of various concentrations. It was confirmed that the heavy metals combined with the magnetic beads within a short time through the process. After the process, the magnetic beads were collected with a magnet, and then dissolved in acid for the analysis of heavy metal concentration. The analysis of heavy metals in the acid solution could be analyzed with an AAS (atomic absorption spectrometer). The results showed that the heavy metal extraction efficiency of Bu was relatively higher than that of the Ep. It supported the hypothesis that the relatively longer length of Bu’s spacer made more free positioning possible when the IDA group combined with the heavy metal.

Abstract: Copper (Cu) and silver (Ag) known as antimicrobial materials were deposited on activated carbon fibers (ACF) by an electroless plating method. The metal deposited ACF filters were characterized by using SEM, EDX and XRD analyses. To verify the effects of metal deposition on the adsorptive characteristics of ACF filters, the specific surface area and pore structure were determined by BET equation and BJH method, respectively. The antimicrobial activities of metal deposited ACF filters against E. coli, P. fluorescens, B. subtilis and M. luteus were characterized by modified Kirby-Bauer method. By SEM-EDX and XRD analyses, it was confirmed that the electroless plating method was adequate for deposition of Cu and Ag on the surface of ACF filters. BET and BJH analyses showed that the micropore volume of metal plated ACF filters decreased compared to the pristine ACF filter. The inhibition zones, which represent the antimicrobial effects, were formed around the Cu and Ag deposited ACF filters whereas not in the case of pristine ACF.