Ertugrul Arpac

Photocatalytic antibacterial performance of Sn4+-doped TiO2 thin films on glass substrate.

Pure anatase, nanosized and Sn(4+) ion doped titanium dioxide (TiO(2)) particulates (TiO(2)-Sn(4+)) were synthesized by hydrothermal process. TiO(2)-Sn(4+) was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn(4+) doping to TiO(2) against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO(2)-Sn(4+) in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO(2)-Sn(4+) is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO(2)-Sn(4+) from 10 to 50% in the coating solution increased antibacterial effect.

Modelling of ORMOCER coatings by processing

Hydrolysis, condensation and polymerization of γ-glycidyloxipropyltrimethoxysilane was studied under different reaction conditions and yields a hard coating material for polyethyleneterephthalate substrates. The progress of hydrolysis was followed by 29Si-NMR spectroscopy and Karl Fischer filtration. Hydrolysis proceeds very slowly at pH 5.5, but can be enhanced at pH 9. Independent from submitted water and pH the solutions only one half of hydrolyzable methoxy groups can be removed. Condensation and polymerization were investigated on coated substrates and start during thermal curing. The formation of the polysiloxane network takes place by elimination of methanol. Polymerization of the epoxy groups to polethyleneoxide units is achieved above 100°C using a special catalyst. The properties of the cured coatings depend on the free water and glycol content in the solution. Minimizing the amount of both components leads to an ORMOCER coating on polyethyleneterephthalate which features a good abrasion resistance in combination with a high flexibility.

On the Hydrolytic Stability of Organic Ligands in Al-, Ti- and Zr-Alkoxide Complexes

The complexation degrees of Al-, Ti- and Zr-butoxide (M) with unsaturated and saturated β-diketones (3-allylpentane-2.4-dione-APD, acetylacetone-ACAC) and β-ketoesters (methacryloxyethyl-acetoacetate-MEAA, allylacetoacetate-AAA, ethylacetoacetate-EAA) as organic ligands (L) were examined by IR and 13 C NMR spectroscopy and were found to be L:M ≥ 1.5. The hydrolytic stability of the ligands of the metal alkoxide complexes (L:M = 1) during hydrolysis/condensation reactions at the molar ratio h (H2O : OR) = 0.5–2.0 decreases with increasing H2O:complex ratio. Furthermore, the ligand stability depends on the type of metal in the complexes and decreases in the order Al- > Zr- > Ti-butoxide complexes at h=1. The ACAC ligand likewise shows in the Al-, Ti- and Zr-butoxide complexes a high hydrolytic stability (95–100%) at h=1 within 7 days. The Ti- and Zr-butoxide complexes with β-ketoesters as ligand show at h=1> a release to a different extent e.g., up to 60% in the case of the MEAA-ligand in the Ti-butoxide complex after 2 days. In general, the hydrolytic stability of the ligands in the Ti-butoxide complexes (L:M = 1, h=1) decreases in the order ACAC > APD > AAA > EAA ≥ MEAA. The hydrolysis/condensation reaction of complexes having a weak ligand stability leads to larger particle sizes in the sols than those with stable ACAC ligands. The results contribute to a more controlled synthesis of sols and of new inorganic-organic hybrid polymers via the sol-gel process.

Semiconductor clusters in the sol-gel process : synthesis and properties of CdS nanocomposites

CdS nanocomposites (CdS cluster sizes < 5 nm) were prepared via multifunctional inorganic-organic sol-gel processing. In CdS sols as precursors, the CdS clusters are carrying inorganic components as stabilizing centers, along with bifunctional ligands acting as inorganic and organic network formers. Hydrolysis and condensation produces an inorganic skeleton yielding viscous liquids useful to prepare films or monoliths. The final organic cross-linking at T < 100°C results in optically transparent materials. The nature of stabilizing centers and the starting synthesis conditions influence strongly the resulting electronic properties. Cd2+ complexed by mercapto compounds gives smaller cluster sizes with a narrower distribution than Cd2+ complexed with amine or carboxylate groups. Mercaptosilane-stabilized CdS clusters synthesized via cleavage of bis triethoxy silyl propyl tetrasulfides show an enhanced room temperature photoluminescence compared with similarly stabilized clusters prepared through H2S exposure.

Sol-gel thin films with anti-reflective and self-cleaning properties

Self-cleaning photocatalytic TiO2 films are beneficial since they reduce the maintenance cost and enhance the efficiency of various optical systems, especially thermal and photovoltaic solar systems. However, the presence of a TiO2 layer on glass reduces the transmission of incident light, which leads to a decrease in efficiency. This drawback can be overcome by applying a layer of anti-reflective coating beneath the TiO2 layer. Generally, the anti-reflective layer is porous silica. The presence of the anti-reflective layer compensates for the loss of light transmittance caused by the photocatalytic TiO2 top layer. This paper reviews some of the previous and the latest fundamental studies in the literature on anti-reflective, self-cleaning and multi-functional films.

Synthesis and properties of transparent ZrO2 containing SiO2 polymethacrylate polymers

The synthesis of zirconia modified polymerized methacryloxypropylsilane as a new material with a potential for optical application has been investigated. The material is synthesized by copolymerizing 3-methacryloxypropyl trimethoxysilane and zirconium propylate chelated by methacrylic acid. The methacrylic acid serves as a complexing agent and participates in the polymerization process in order to incorporate the zirconia homogeneously into the polymer. Transparent bulk materials have been prepared by this process.

Aqueous wet coatings for transparent plastic glazing

Abstract Electrostatically stabilized particulate sols, e.g. aqueous silica or alumina sols, have been surface-modified to reduce the particle/particle interaction and to obtain electrosterically stabilized sols. Epoxy functionalized alkoxysilanes were used as surface modifiers for alumina, silica or zirconia particles to achieve water dispersible nanoparticulate coating materials. After evaporating the organic solvent (produced by hydrolysis and condensation) aqueous sol-gel coatings have been prepared with organic solvent contents below 5%. The storage stability of these materials has been investigated by 29 Si-NMR. An amino functionalized alkoxysilane was used as condensation catalyst and the nanocomposite material was thermally cured at 130°C after flow or spray coating on pretreated polycarbonate substrates. The coatings show excellent adhesion which was shown by cross cut and tape test. After 1000 cycles Taber abrasion test (CS-10F, 500 g, DIN 52347) losses of transmittance due to scattering of 2–6% were achieved with a coating thickness of about 5 μm.

New metal alkoxides: Synthesis and hydrolysis-condensation reactions; some adsorption features of the hydrolysis-condensation products

In this work, (a) hydrolyses of Ti(OEt)4 and Zr(OPrn)4 with different amounts of water, (b) complexation of the same alkoxides with varying amounts of methacrylic acid, (c) hydrolysis of the complexation products with varying amounts of water, and subsequent polymerization, (d) adsorption capacities of the hydrolysis products (a and c) for aqueous aniline and phenol, were investigated. It was found that condensation reactions which follows the hydrolysis reactions, were alcohol condensations. The products were characterized in detail. Adsorption of aniline and phenol were compared for thermally conditioned powder of the products and some powders coated with 3-glycidyloxypropyltrimethoxysilane. It was observed that the extent of adsorption was influenced significantly by the temperature at which the adsorbents were calcinated by the coating of their surfaces.

The Modification of Aluminium Tri-sec-butoxide with Different Alcohols and Chelating Ligands: Hydrolysis and Condensation of the Products

Abstract In this work, alcoholysis reactions of aluminium-sec-butoxide, Al(OBu-s)3, with 2-ethoxyethanol (EtOCH2CH2OH) and 2-butoxyethanol (BuOCH2CH2OH), complexation reactions of Al(OBu-s)3 and of alcohol-modified Al(OBu-s)3 with methacrylic acid (MAC) and ethyl acetoacetate (EAAH), and the hydrolysis reactions of Al(OBu-s)3 and modified Al(OBu-s)3 are studied in some detail. Alcoholysis reactions of Al(OBu-s)3 were performed with different mole ratios of 2-ethoxyethanol and 2-butoxyethanol at room temperature and combining ratios were found to be 1:3 [Al(OBu-s)3: alcohol] by 1H NMR analyses. Al(OBu-s)3 and alcohol-modified Al(OBu-s)3 were reacted at room temperature with equimolar amounts of methacrylic acid and ethyl acetoacetate and the products were characterized by 1H NMR, GC, FT-IR and elemental analyses. Hydrolysis-condensation reactions of the various compounds thus formed were studied in detail and the products were characterized by gas chromatography, Karl Fisher coulometric titrations, thermal...

Hybrid sol–gel coating on Al

New coating materials providing mechanical and chemical resistance to corrosion were developed for protection of metal surfaces. An aluminum plate surface was coated with polyurethane and epoxy based resins which were previously modified with ceramic powders, such as Al2O3, SiO2, or SiC. Effects of the type and particle size of ceramic powder, organic matrix, co-reactants, the dispersant type and mixing rate on the coating material were investigated. Coated metal surface was subjected to taber-abrasion, adhesion and corrosion tests. Surface properties and thermal resistance of the coating materials were characterized by scanning electron microscopy (SEM) and thermogravimetric and differential thermal analysis (TG/DTA). Results revealed that polyurethane based coatings, whether contain ceramic powder or not, seems to be more advantageous than epoxy based one, besides surface modified ceramic powders provide excellent properties to the coatings.