Effect of α-Al2O3 Particle Size in a Slurry on the Physical Properties of Chemically Strengthened Thin Glass Prepared by the Spray Method.

Chemical strengthening is considered as the most suitable method for strengthening thin glass sheets used in mobile phones. The spray method of chemical strengthening requires a slurry to be sprayed on the glass sample to be strengthened. This slurry is prepared by mixing various compounds. In this study, the influence of α-Al2O3 particle size in the slurry on the physical properties of the chemically strengthened glass prepared by the spray method was investigated. The compressive stress (CS) was dramatically enhanced as the particle size of Al2O3 in the slurry decreased. The glass sample with 13 nm α-Al2O3 including the KNO3-Al2O3 slurry exhibited the highest CS of 905 MPa, and the depth-of-layer (DOL) of this sample was 37 µm. The same slurry composition also achieved the highest bending strength of 640 MPa under different heat treatment conditions. The optimization of the heat treatment conditions, such as temperature and time duration, resulted in the highest value of CS (916 MPa) obtained for the sample heated at 400 °C for 1.5 h, and the maximum DOL (65 µm) was obtained for the sample at 480 °C for 4 h.

Water Resistances of Ag2O-, BaO-, and CuO-Doped V2O5-P2O5-TeO2 Glass Sealants.

V2O5-P2O5-TeO2, a low-temperature vanadate-based glass sealant, was doped with metal oxides (MO = Ag2O, BaO, or CuO), which generate Ag, Ba, and Cu ions, respectively, to strengthen the glass structure and improve its water resistance. These ions reduce the number of nonbridging oxygen atoms in the glass structure by forming V-O-M or P-O-M crosslinks in the V2O5-P2O5 glass system. Structural analysis using Fourier-transform infrared spectroscopy indicated that the numbers of P-O-P, V═O, and V-O-V bonds decreased with increasing metal oxide content. Thermal property analyses revealed that the glass transition temperatures increased by approximately 2-30 °C and that the coefficients of thermal expansion only varied within approximately ±10×10-7 K-1 among all the glass samples. The contact angles were measured to quantify the wetting properties of the doped glasses. The contact angle increased from 11 to 36° with increasing metal oxide content at 410 °C. As an indication of the water resistances of the doped glasses, the dissolution rates of the 9 mol% Ag2O-doped and pure glasses were 0.078 and 0.523 g cm-2, respectively.

Production of Cu@SiO2 Core-Shell Nanoparticles with Antibacterial Properties.

Antimicrobial agents based on organic materials have limited use owing to their low heat resistance and short lifetimes. Therefore, various studies on antibacterial agents that are based on inorganic material systems are increasingly being performed to supplement them. In this study, Cu@SiO2 core-shells are fabricated using Cu cores and SiO2 shells, and are known to have antimicrobial effects. The core-shell was coated with SiO2 using the sol-gel method. Experiments were conducted using X-ray diffraction and the shaking flask method (KS J 4206) to evaluate the characteristics of the core-shell. In the case of X-ray diffraction, both the Cu core and the core-shell fabricated using the sol-gel process were characterized. Escherichia coli and Staphylococcus aureus were evaluated using the KS J 4206 method for their antibacterial properties. Through this study, it is confirmed that a Cu@SiO2 core-shell can be fabricated via the sol-gel method, and that Cu with a core-shell structure has antibacterial effects.

Effects of Melting Conditions on Cerium Oxidation State and Catalytic Properties of CeO2-P2O5 Glass Systems.

As with any solvent, stabilizing a multivalent element at a given oxidation state in glass depends on the thermodynamic conditions. The effects of temperature on the oxidation-reduction equilibrium have been previously noted with higher temperatures being more conducive to reduced states. Herein, 30CeO2-70P2O5 binary system glasses were prepared. The melting temperature and time dependency on Ce4+ and Ce3+ ion concentrations were studied using X-ray photoelectron spectroscopy. Different melting conditions were investigated at temperatures ranging from 1300 °C to 1500 °C for 60 min, and at 1400 °C for durations ranging from 30 min to 90 min. The changes in the catalytic properties of the glasses as a function of Ce4+ and Ce3+ ion concentrations were confirmed based on the changes in the decomposition starting temperatures using thermogravimetric analysis. The main changes in the oxidation states according to melting conditions were discussed in terms of the catalytic properties of CeO2-P2O5 glass systems.

Effect of the Addition of CeO2 to Iron Phosphate Glass for Catalytic Applications.

We investigated the effect of CeO2 content on the catalytic behavior and chemical properties of the (100 - x)(80P2O5-20Fe2O3)-xCeO2 (x = 0, 4, 8, 12, 16, 20 and 24 wt%) glass system. Using thermogravimetric analysis, we confirmed that the catalytic activity increased until a CeO2 content of 16 wt%, beyond which, it decreased. The reasons for the change in the catalytic properties of the glass samples were determined using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density analyses. It was confirmed using the FT-IR and XPS-01s spectra that CeO2 acts as a network modifier in iron phosphate glass. When the CeO2 content is above 16 wt%, the number of non-bridging oxygen atoms decreases with increasing CeO2 content. For these reasons, the catalytic properties decrease when the CeO2 content is more than 16 wt%. From the dissolution rate measurements, it can be observed that cerium-iron phosphate has a high water resistance. Also, as we expected, it can be confirmed that the chemical durability is improved with increasing CeO2 content.

Optical, Structural, and Thermal Properties of Cerium-Doped Zinc Borophosphate Glasses.

In this study, we verify the relationship between the optical properties and structure of cerium-doped zinc borophosphate glasses that have concurrence of non-bridging oxygen (NBO) and bridging oxygen (BO), Ce3+ and Ce4+, and BO3 structure and BO4 structure. We prepared cerium-doped zinc borophosphate glass with various compositions, given by xCeO2-(100-x)[50ZnO-10B2O3 -40P2O5] (x = 1 mol% to 6 mol%), and analyzed their optical band energy, glass transition temperature, crystallization temperature, density, and molar volume. Some of the techniques used for analysis were Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). In the investigated glasses, the optical band gap energy decreased from 3.28 eV to 1.73 eV. From these results, we can deduce the changes when transitions occur from BO to NBO, from Ce3+ to Ce4+, and from the BO3 structure to the BO4 structure with increasing CeO2 content using FT-IR and XPS analysis. We also verified the changes in structural and physical properties from quantitative properties such as glass transition temperature, crystallization temperature, density, and molar volume.

Preparation of silica thin films by novel wet process and study of their optical properties.

Silicon dioxide (SiO2) thin films have gained considerable attention because of their various industrial applications. For example, SiO2 thin films are used in superhydrophilic self-cleaning surface glass, UV protection films, anti-reflection coatings, and insulating materials. Recently, many processes such as vacuum evaporation, sputtering, chemical vapor deposition, and spin coating have been widely applied to prepare thin films of functionally graded materials. However, these processes suffer from several engineering problems. For example, a special apparatus is required for the deposition of films, and conventional wet processes are not suitable for coating the surfaces of substrates with a large surface area and complex morphology. In this study, we investigated the film morphology and optical properties of SiO2 films prepared by a novel technique, namely, liquid phase deposition (LPD). Images of the SiO2 films were obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to study the surface morphology of these films: these images indicate that films deposited with different reaction times were uniform and dense and were composed of pure silica. Optical properties such as refractive index and transmittance were estimated by UV-vis spectroscopy and ellipsometry. SiO2 films with porous structures at the nanometer scale (100-250 nm) were successfully produced by LPD. The deposited film had excellent transmittance in the visible wavelength region.