Gyu-In Shim

A Study on the Transmittance, Heat-Resistance, and Mechanical Properties of SiO 2 , TiO 2 Anti-Reflective Single Layers Deposited on Sapphire Substrate by MOCVD

ABSTRACT To improve sensing capability of infrared, heat-resistance and mechanical properties, the SiO 2 and TiO 2 anti- reflective layers were coated on sapphire substrate by MOCVD. The standard wavelength was 4,600nm, and the thickness of anti-reflective layers were 379 and 758nm in case of λ/4 and λ/2 of incident angle(65˚), respectively. The SiO 2 and TiO 2 anti-reflective layers were coated 12.6 and 9.7nm/min of deposition rates by increasing oxygen pressure to set the ideal refractive index of 1.283. In case of SiO 2 (λ/2) coating, the transmittance increased from 55.0 to 62.7%. The transmittance of TiO 2 (λ/2) anti-reflective layer also increased from 55.0 to 64.8%. The flexural strength of SiO 2 (λ/2) and TiO 2 (λ/2) layer coated sapphire increased from 337.8 to 362.9 and 371.8MPa, respectively. The flexural strength at 500 ℃ of these materials also increased respectively to 304.5, 358.2MPa from 265.9MPa. From these results, we confirmed these materials can be used as transmission window of infrared light.Key Words : Anti-Reflective Coating(저반사 코팅), Sapphire(사파이어), Transmittance(투과율)

Synthesis and Antibacterial Properties of Silver and Copper Ions Against Escherichia Coli, Salmonella Typhimurium, Staphylococcus Aureus and Pseudomonas Aeruginosa

The antibacterial effects of silver and copper ions contained film against Escherichia coli, Salmonella typhimiiriimi, Staphylococcus aureus and Pseudomonas aeruginosa were investigated. The 0.2~1.0mol% concentrations of sol were prepared with different amounts of precursor. The films of silver and copper were deposited by sol gel spin and spray coating technique on glass, stainless steel, polycarbonate, ceramic tile substrates. Hard, antibacterial, and transparent organic-inorganic hybrid coatings were prepared by sol gel technique to improve the weak scratch resistance of polycarbonate substrate and get the antibacterial effect. The morphological changes in the cell wall exposed to silver and copper ions were observed by scanning electron microscope. The surfaces coated 0.2mol% of silver and copper ions were shown the 99.9% of antibacterial effect. According to these results, the film contained silver and copper ions can be used across a wide variety of applications such as transparent display glasses, housewares and medical devices.

Strengthening of Borosilicate Glass by Ion Exchange for Lightweight Transparent Bulletproof Windows Materials

Transparent bulletproof windows play an important role in the munitions industry. The thickness of bulletproof windows including soda-lime silicate(SLS) glass, polyvinyl butyral, poly urethane, main defense(200MD), and safety film was reduced from 40mm to 29mm by adjustment of SLS glass laminated array. Borosilicate glasses generally have lower surface density and more excellent mechanical properties than SLS glass. Borosilicate glass was strengthened by ion exchange in the powder. The maximum mechanical properties were observed at for 10min. The Vickers hardness, fracture toughness and 3-point bending strength of ion exchanged samples were about , and 764MPa each, which are about 27%, 149% and 249% higher than parent borosilicate glass, respectively. The penetration depth of K+ ion at for 10min was . As a result, the transparent bulletproof windows were predicted to be more lightweight by ion exchange of borosilicate glass. If the SLS glass for bulletproof windows is replaced by ion exchanged borosilicate glass, the bulletproof windows can be expected to be lightweight and thinner.

Crystallization of Borosilicate Glasses for High-Strength Bulletproof Materials

Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of 80.4SiO24.2Na2O-2.4Al2O3-13.0B2O3. The 2-step crystallization was performed around 584°C of glass transition temperature (Tg), and 774°C of crystallization temperature(Tc). The maximum nucleation rate was 8.8×10/mm·hr at 600°C and the maximum crystal growth rate was 3.5nm/min at 750°C. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, 752kg/mm, 1.082MPa·mm. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.