Synthesis of Organic–Inorganic Hybrid Sols Using Trifunctional Organoalkoxysilanes for Dispersion Agents

Park, Hoyyul,Kang, Dongjun,Ahn, Myeongsang,Lee, Hyeonhwa American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.2

Characteristics of coating films synthesized by a sol-gel reaction using nanosized boehmite

Hoyyul Park,Moonkyong Na,Myeongsang Ahn,Dongjun Kang,Dongsik Bae 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.5

We investigated the properties of organic-inorganic hybrid coating films prepared by a sol-gel reaction using a nanosized boehmite sols. The sol was synthesized as a protective coating, functional coating, binder, etc. The sol was prepared from spherically shaped boehmite, and a mixture of spherical and fibrous shaped boehmite. Sol solutions were used to deposit onto substrates by way of a dip-coating process. In order to investigate the surface hydrophobicity, roughness and transmittance of coating films, a contact angle meter, a surface profiler and a UV-Vis spectrophotometer were used. In addition, surface modification of boehmite was investigated by a FT-IR spectrometer. Contact angle and surface roughness of coating films gradually increased with increasing reaction time due to the gelation of the sol by successive condensation reactions. The transmission rate of coating films within the visible-wavelength region was greater than 90% when the reaction time was less than 48 h. FT-IR measurement showed the spectra of condensation of MTMS and boehmite. We investigated the properties of organic-inorganic hybrid coating films prepared by a sol-gel reaction using a nanosized boehmite sols. The sol was synthesized as a protective coating, functional coating, binder, etc. The sol was prepared from spherically shaped boehmite, and a mixture of spherical and fibrous shaped boehmite. Sol solutions were used to deposit onto substrates by way of a dip-coating process. In order to investigate the surface hydrophobicity, roughness and transmittance of coating films, a contact angle meter, a surface profiler and a UV-Vis spectrophotometer were used. In addition, surface modification of boehmite was investigated by a FT-IR spectrometer. Contact angle and surface roughness of coating films gradually increased with increasing reaction time due to the gelation of the sol by successive condensation reactions. The transmission rate of coating films within the visible-wavelength region was greater than 90% when the reaction time was less than 48 h. FT-IR measurement showed the spectra of condensation of MTMS and boehmite.

Characteristics of Inorganic-Organic Hybrid Coating Films Synthesized from Nano Boehmite and Methyltrimethoxysilane

Park, Hoyyul,Na, Moonkyong,Ahn, Myeongsang,Kang, Dongjun,Lee, Hyeonhwa,Chung, Ildoo TaylorFrancis 2009 Molecular Crystals and Liquid Crystals Vol.510 No.1

<P> We studied the properties of inorganic-organic hybrid coating films prepared by boehmite sol. Sols were synthesized by sol-gel process using nano boehmite and methyltrimethoxysilane in variation with the amount of methyltrimethoxysilane at different reaction time. In order to understand physical and chemical properties of sols prepared from boehmite and methyltrimethoxysilane, coating films were fabricated on glass substrates by dip-coating process. The crystalline pattern and morphology of sol powder of boehmite were observed. Contact angle, surface roughness, transmittance, chemical bond and thermal stability of coating films were investigated.</P>

Dielectric Properties of Polymer Thin Films for the Organic Gate Dielectric Layer

Na, Moonkyong,Park, Hoyyul,Ahn, Myeongsang TaylorFrancis 2009 MOLECULAR CRYSTALS AND LIQUID CRYSTALS - Vol.510 No.1

<P> Polymethylmethacrylate (PMMA)'s thermal and mechanical stability, high resistivity, and suitable dielectric constant make it an ideal candidate for the polymer thin film for the dielectric layer. PMMA thin films were fabricated on a glass substrate, using the spin coating process, at room temperature. The thermal-degradation temperature of PMMA was about 280°C, and the glass transition temperature (Tg) was about 110°C. To determine the effect of annealing, the coating films were annealed at 70-200°C for 60 m under argon atmosphere. The surfaces of the coating films were compact and uniform at all the annealing temperatures. The surface energies of the coating films were obtained by measuring the contact angles with deionized water and di-iodomethane. The coating films were found to have low surface energies. Up to below Tg, the dielectric constants of the coating films slightly increased owing to an increase of the total polarization arising from dipoles and trapped charge carriers. Above Tg, the coating films began to degrade; as such, their dielectric constants decreased. To ensure the reliability of the thermal endurance of the dielectric properties of the coating films, annealing was repeated three times, at 100°C. The coating films then showed no degraded dielectric properties.</P>

Properties of nano-hybrid sol-gel coating films synthesized with colloidal silica and organoalkoxy silanes

Moonkyong Na,Hoyyul Park,Myeongsang Ahn 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.5

Colloidal silica (CS)-silane sols were synthesized as a dispersion medium of dispersoid, ceramic powders. Functionalizing silanes for nano-hybrid sols were methyltrimethoxysilane (MTMS) and γ-glycidoxypropyltrimethoxysilane (GTMS). GTMS was added to sols in different amounts. The stability of the sol was evaluated as a function of reaction time up to 10 days through the variation of the viscosity and the transmittance. The viscosity of the sols increased only slightly with reaction time before 10 days. When the sols were reacted for 10 days, the viscosity increased and the transmittance decreased markedly, as well. The coating films were formed on a glass substrate using a spin coating procedure. The coating films were flat and transparent without cracks. Also, the properties of the coating films such as contact angle, roughness, and thermal property were characterized. The CS/MTMS coating films showed a large contact angle. When a large amount of GTMS was added, the contact angle decreased due to the epoxy group. The roughness of the coating films was found to be very low, less than 20 nm. However the roughness of the coating films reacted for 10 days increased due to degradation of the stability of the sol. No thermal degradation of the CS/MTMS coating film occurred up to 600 oC. The CS/MTMS/GTMS coating films degraded at 400 oC due to decomposition of the epoxy group which has a long organic chain easily degraded by the thermal shock. Colloidal silica (CS)-silane sols were synthesized as a dispersion medium of dispersoid, ceramic powders. Functionalizing silanes for nano-hybrid sols were methyltrimethoxysilane (MTMS) and γ-glycidoxypropyltrimethoxysilane (GTMS). GTMS was added to sols in different amounts. The stability of the sol was evaluated as a function of reaction time up to 10 days through the variation of the viscosity and the transmittance. The viscosity of the sols increased only slightly with reaction time before 10 days. When the sols were reacted for 10 days, the viscosity increased and the transmittance decreased markedly, as well. The coating films were formed on a glass substrate using a spin coating procedure. The coating films were flat and transparent without cracks. Also, the properties of the coating films such as contact angle, roughness, and thermal property were characterized. The CS/MTMS coating films showed a large contact angle. When a large amount of GTMS was added, the contact angle decreased due to the epoxy group. The roughness of the coating films was found to be very low, less than 20 nm. However the roughness of the coating films reacted for 10 days increased due to degradation of the stability of the sol. No thermal degradation of the CS/MTMS coating film occurred up to 600 oC. The CS/MTMS/GTMS coating films degraded at 400 oC due to decomposition of the epoxy group which has a long organic chain easily degraded by the thermal shock.

Synthesis of organic-inorganic hybrid sols with nano silica particles and organoalkoxysilanes for transparent and high-thermal-resistance coating films using sol-gel reaction.

Na, Moonkyong,Park, Hoyyul,Ahn, Myeongsang,Lee, Hyeonhwa,Chung, Ildoo American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.10

<P>Organic-inorganic hybrid sols were synthesized from nano silica particles dispersed in water and from organoalkoxysilanes, using the sol-gel reaction. This work focuses on the effects of the three multifunctional organoalkoxysilanes dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), and tetramethoxysilane (TMOS) to form a transparent and high-thermal-resistance coating film. The stability of the hybrid sol was evaluated as a function of the reaction time for 10 d through the variation of the viscosity. The viscosity of the silica/DMDMS and silica/MTMS sol was slightly increased for 10 d. The multifunctional organoalkoxysilanes formed dense silica networks through hydrolysis and condensation reaction, which enhanced the thermal resistance of the coating films. No thermal degradation of the silica/DMDMS sample occurred up to 600 degrees C, and none of the silica/MTMS and silica/TMOS samples occurred either up to 700 degrees C. The organic-inorganic hybrid sols were coated on the glass substrate using a spin-coating procedure. The organic-inorganic hybrid sols formed flat coating films without cracks. The transmittance of the hybrid sol coating films using MTMS and DMDMS was shown to be over 90%. The transmittance of the silica/TMOS sol coating film reacted for 10 d abruptly decreased due to faster gelation. The silica/DMDMS and silica/MTMS hybrid sols formed smooth coating films while the surface roughness of the silica/TMOS coating film markedly increased when the hybrid sol reacted for 10 d. The increase of the surface roughness of the silica/TMOS coating film can be attributed to the degradation of the stability of the hybrid sol and to the loss of transmittance of the coating film. It was confirmed in this study that the use of organic-inorganic hybrid sol can yield transparent and high-thermal-resistance coating films.</P>

Photopatternable and refractive-index-tunable solegel-derived silicaetitania nanohybrid materials

Dong Jun Kang,Go Un Park,Hyeon Hwa Lee,Hoyyul Park,박장웅 한국물리학회 2013 Current Applied Physics Vol.13 No.8

Silicaetitania nanohybrid materials were synthesized using functionalized organosilanes and organically chelated titanium alkoxide in a simple solegel process. The synthesized silicaetitania nanohybrid materials exhibited good solution processability and homogeneous dispersion without any phase separation regardless of the ratio of the mixture of the two components. The silicaetitania nanohybrid materials exhibited good photoinitiator solubility and effective photocurability with a high degree of degree under ultraviolet (UV) exposure. Because of their high photocurability and solution processability, the silica etitania nanohybrid materials were readily converted into silicaetitania nanohybrid films and were used for direct photopatterning without requiring the developing process used in the photomask method. In particular, the refractive indices of the silicaetitania nanohybrid materials could be decreased by decreasing the content of chelated titanium alkoxide in the materials. Moreover, the silicaetitania nanohybrid films exhibited high transmittance in the visible wavelength range, and their surface roughnesses were very smooth, exhibiting values <1 nm. On the basis of these observations, the fabricated silicaetitania nanohybrid materials can be used in solution-processable materials for producing optical and electro-optical elements.

Effects of Substitution of K2O for Na2O on the Bioactivity of CaO-Na2O-SiO2-P2O5 Glasses

Taehee Kim,Chawon Hwang,Donggun Gwoo,Hoyyul Park,류봉기 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.5

The compositional dependences of bioactivity, thermal properties, atomic structure, and surface morphology have been investigated in the CaO-Na2O-SiO2-P2O5 system; this system is known as a bioglass. 45S5 Bioglass®is known to be a general and highly bioactive material. However, the bioactivity of this glassy material is expected to be improved by modifying the alkali-metal composition. Thermal properties, density, and molar volume were measured to investigate the structural packing. FT-IR spectra and X-ray diffraction were used to confirm the structures of these glasses. The morphology was examined using field emission electron microscopy,and the formation of a Ca-P layer was studied using an energy-dispersive system. This study shows that the tendency to form a calcium phosphate layer is increased with the substitution of K2O for Na2O.

Fabrication and characterization of silver-doped silica composite membranes by a reverse micelle and Sol-Gel process

Hyeon Cheol Kim,Hyun Ju Kim,Hoyyul Park,Dong Sik Bae 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3

Ag-doped SiO2 composites nano-powders were synthesized by a reverse micelle and sol-gel process. The average particle size of the mixed sol was below 25 nm and was well dispersed in the solution. TEM results show the microstructure of Ag- doped SiO2 nanoparticles was homogeneous and Ag was below 5 nm and Ag was well dispersed in the ceramic nano-particles. Agdoped SiO2 composite membranes were fabricated by a sol-gel process. Ag-doped SiO2 composite membranes showed a crackfree microstructure and a narrow particle size distribution even after heat treatment up to 500℃. The average particle size of the membrane was 30-40 nm, and the pore size of Ag-doped SiO2 nano composite membranes was below 10 nm. The particle size of Ag after heat treatment at 500℃was below 5 nm. Ag-doped SiO2 composites nano-powders were synthesized by a reverse micelle and sol-gel process. The average particle size of the mixed sol was below 25 nm and was well dispersed in the solution. TEM results show the microstructure of Ag- doped SiO2 nanoparticles was homogeneous and Ag was below 5 nm and Ag was well dispersed in the ceramic nano-particles. Agdoped SiO2 composite membranes were fabricated by a sol-gel process. Ag-doped SiO2 composite membranes showed a crackfree microstructure and a narrow particle size distribution even after heat treatment up to 500℃. The average particle size of the membrane was 30-40 nm, and the pore size of Ag-doped SiO2 nano composite membranes was below 10 nm. The particle size of Ag after heat treatment at 500℃was below 5 nm.

Role of silica nanoparticle in multi‐component epoxy composites for electrical insulation with high thermal conductivity

Lee, Dae Ho,Lee, Nakyung,Park, Hoyyul Wiley-Blackwell 2018 Journal of the American Ceramic Society Vol.101 No.6

<P>Multicomponent epoxy micro/nano-composites containing micro-alumina, micro-quartz, and nano-silica were fabricated to develop electrical insulation materials with high thermal conductivity. Simply changing the ratio between the alumina and quartz microparticles caused a trade-off relationship between the thermal conductivity and electrical insulation. Increasing the alumina content in the epoxy-alumina/quartz micro-composites enhanced the thermal conductivity but deteriorated the dielectric strength. An increase in the thermal conductivity without incurring a loss in the dielectric strength was achieved by incorporating silica nanoparticles in the epoxy micro-composites. Adding silica nanoparticles to the epoxy micro-composites was found to be more efficient in improving the thermal conductivity compared to increasing the alumina ratio, especially at low alumina/quartz ratios. This behavior corresponded to theoretical models. Therefore, we provide a useful insight, both practical and theoretical, into the more advanced optimization of designing multicomponent epoxy composites for electrical insulation with high thermal conductivity.</P>