Advanced Materials Research Vols. 93-94

Abstract: Titanium dioxide (TiO2) films were prepared on glass substrates without external heating by DC magnetron reactive sputtering. Argon and oxygen were used as sputtering and reactive gases, respectively. Initially TiO2 films were produced under a constant discharge power of 300W, total operated pressure of 1.10 Pa, the Ar:O2 flow rate of 50:45 sccm and film thickness of 300 nm. After deposition, the films were annealed in air and in vacuum (8×10-1 Pa) at a temperature of 350 °C and an annealed time of 2 hours. Films structure, optical properties, photocatalytic activity (methylene blue degradation) and photo-induced hydrophilicity properties were mainly investigated to produce self-cleaning surface. Because of higher crystallinity of vacuum-annealed films lead to the highest MB degradation under UV irradiation. While, air-annealed films showed lower MB degradation than as-deposited films that could be affected of contamination on surface and defect from annealing. Vacuum-annealed films showed changes of water contact angle on the films surface higher than as-deposited films and air annealed- films.

Abstract: Bi4-xLaxTi3O12 (where x = 0, 0.25, 0.50, 0.75 and 1) powders and ceramics were prepared using conventional solid state reaction and sintering procedures. The calcination was carried out at 750 °C for 4 h and sintering was done at 1150 °C for 4 h. The density of all ceramics was found to be comparable regardless of La concentration. X-ray diffraction analysis showed that preferred orientation of ceramic grains was reduced with addition of La ions. This reduced preferred orientation was accompanied by a decrease in grain size. The temperature dependence of dielectric constant showed a decrease in Tc with increasing La concentration.

Abstract: In this research a new structurally-modified monomer, 2,2'-bis[(p-phenoxy phenyl)]-4,4'-diaminodiphenyl ether (PPAPE) was synthesized by a three-step manner starting from 4,4'-dinitrodiphenyl ether. Novel classes of wholly aromatic polyamides and polyimides were prepared from PPAPE through the conventional polycondensation reactions including triphenyl phosphate-activated phosphorylation method for the preparation of the polyamides and cyclodehydration of in situ-formed polyamic acid precursors for the preparation of the polyimides. n and w values were determined by GPC measurements. Crystallinity, organosolubility, and qualitative film characteristics of the resulting aromatic polyamides and polyimides were investigated. A low crystallinity extent was only observed using their wide-angle X-ray diffractograms. All polymers had excellent organosolubility in common polar solvents such as DMAc, DMF, DMSO, and NMP. The resulting well-designed polymers could also be cast into transparent and flexible films.

Abstract: The modified cellulose film was synthesized from corn husk and waste cotton fabrics in LiCl/DMAc solvent system by esterification reaction under microwave energy using lauroyl chloride and DMAP as an esterifying agent and a catalyst, respectively. By varying microwave power and reaction time used in the esterification reaction, modified cellulose powder with various degree of substitution (DS) was obtained. The structure of modified cellulose was proved by FT-IR and 1H-NMR analysis. The DS value of modified cellulose was measured by 1H-NMR. The modified cellulose films with different DS values were prepared by casting method. The influences of DS values on the properties of the prepared modified cellulose films were tested for their wettability, water absorption, gloss, and tensile properties. The results showed significant effect of the cellulose source and the DS values on the properties of modified cellulose film. The modified cellulose from corn husk resulted in the film with greater tensile strength and elongation at break than the film from waste cotton fabrics. The esteried-cellulose from both sources with high DS values yielded the film with higher tensile properties and lower water absorption.

Abstract: Photoelectrochemical (PEC) devices based on Fe-doped and Pt-loaded nanostructured- TiO2 films acting as working electrodes were fabricated for solar hydrogen production. Anatase nanocrystalline titania (nano-TiO2) thin films were deposited on glass slides and Ti metal sheet substrates by a sol-gel dip-coating method. The sol-gel of nano-TiO2 was prepared in nitrogen atmosphere using a home-made nitrogen dry box and titanium tetraisopropoxide Ti[OCH(CH3)2]4 was used as a precursor. The effects of annealing temperatures on the crystallite size and the phase transformation also were investigated. The diameters of the particles in the rage of 12 nm were obtained in different methods of making the sol-gels and different annealing temperatures. Photoelectrochemical (PEC) devices consist of the Fe-doped and Pt-loaded TiO2 films as working electrodes, Pt as counter electrodes, 1.0 M KOH as electrolyte, and Nafion Perfluorinated membrane as a proton exchange membrane. The maximum photocurrent density occurred of 0.80 mA/cm2 without an external applied bias potential under irradiation of 100 mW/cm2 corresponding with photoconversion efficiency of 0.98 %. Impurity and undesired phases may be the cause of electron-hole recombination that results in lowering photocatalytic activity.

Abstract: The blend membranes from PAA and NR-graft-PVA were prepared. By introducing potassium persulfate (KPS) initiator, PVA can be chemically attached to the NR latex particles which was confirmed by FT-IR spectroscopy. Most of added-PVA was grafted on the NR latex particles as indicated by the almost-linear increasing of grafting percentage. The swelling of the PAA/NR-g-PVA blend membranes was performed in different concentrations of water-ethanol solutions. For the water concentration lesser than 30 vol.%, all membranes showed almost no-swelling but beyond 30 vol.% water, the degree of swelling revealed the substantial swelling with the degree of swelling increased as PAA content in the membrane increased.

Abstract: Na--alumina with MgO stabilized was produced through solid state reaction. High purity starting material, -Al2O3, -Al2O3, Na2CO3 and MgO were used. The desired amount of starting materials corresponding to the nominal formula Na(1+x)MgxAl(11-x)O17 were mixed and calcined at temperature 1200 for 10 h under atmospheric pressure. The effect of Al2O3 source on phase formation and averaged crystallite size of Na--alumina were investigated via X-ray diffraction (XRD), SEM and TGA/DTA. The XRD result show that formation of Na--alumina with high purity is obtained when -Al2O3 was used. The larger crystallite size is found for sample prepared form -Al2O3. For SEM study the Na--alumina microstructure is seen as randomly packing of several sheets. Calculated crystallite size of sample prepared from -Al2O3 show the larger value compared to that one prepared from -Al2O3.

Abstract: Sintered TiAl alloy with composition of 50 at.% Al and 50at.% Ti are used as target in the PVD cathodic arc system to produce (Ti,Al)N film. The coating conditions are operated using substrate bias voltage and arc current bias of 100V and 70 A, respectively. In addition, the coating time was set at 1.30 h with thru different values of nitrogen gas pressures: 1, 1.5and 2 Pa. After coating the film was characterized for thickness, surface roughness, adhesion, morphology, and phase structure. It was found that phase structures, film thicknesses and adhesion of the films deposited from different nitrogen pressures are not significantly different. However, the micrographs showed that the film prepared by using 1.5 Pa of reactive N2 gas is smoother with less droplets than those film prepared at the other two pressures.

Abstract: Nitrogen (N) and Chromium (Cr) doped TiO2 was prepared by sol-gel process. A clear shift in the onset light absorption from UV region (<380) to visible region (>500 nm) was observed for the N-doped samples. The XRD results revealed the decrease in particle size with increasing N content in the lattice of anatase TiO2. Nitrogen doping does not alter the phase of anatase TiO2. The SEM and TEM images of N-TiO2 showed that the particle size is in the range of 20-25nm. The chemical nature of N in the N-TiO2 was evolved through X-ray photoelectron spectroscopy. The presence of different types of N species have been observed corresponding to different oxidation states and the presence of Ti–N and O–Ti–N have been confirmed from the observed binding energy values. Photocatalytic decomposition of methyl parathion was carried out in the visible region and found that N-doped TiO2 showed better catalytic activity than Cr and Cr/N doped TiO2.

Abstract: Due to their versatile functionalization, acetophenone and benzophenone derivatives as plastic additives were synthesized and blended into PE and PP to study rate of degradation under ultraviolet irradiation by monitoring carbonyl index, tensile strength and weight loss. The photolytic reactions of these ketones in benzene solution showed that acetophenone derivatives, especially 3-nitroacetopheone, underwent rapid degradation under the short-wave ultraviolet (254 nm) rather than in the black light (366 nm) while benzophenone derivatives showed small carbonyl index reduction. However, both groups of ketones, in hexane solution or in PE and PP films, primarily lowered the carbonyl index and rised up again except for the bromo derivatives. At 96 hrs of UV irradiation, the tensile strength of the acetophenone-blended PE film reduced only 20% while the tensile strength of the acetophenone-blended PP film decreased dramatically upto 90% and 95% for the benzophenone-blended PP.