• Macromolecular Research
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• v.13 no.3
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• pp.223-228
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• 2005

In the present work, a low-density polyethylene (LDPE) composite, filled with Zn-ion coated structural silica encapsulated with the diglycidyl ether of bisphenol-A (DGEBA), was synthesized using the conventional melt-blending technique in a sigma internal mixer. The catalytic activity of the Zn-ions (originating from the structural silica) towards the oxirane group (diglycidyl ether of bisphenol-A (DGEBA): encapsulating agent) was assessed by infrared spectroscopy. Two composites, each with a filler content of $2.5 wt\%$ were developed. The first one was obtained by melt blending the Zn-ion coated structural silica with LDPE in a co-rotating sigma internal mixer. The second one was obtained by melt blending the same LDPE, but with DGEBA encapsulated Zn-ion coated structural silica. Epoxy resin encapsulation of the Zn-ion coated structural silica resulted in its having good interfacial adhesion and a homogeneous dispersion in the polymer matrix. Furthermore, the encapsulation of epoxy resin over the Zn-ion coated structural silica showed improvements in both the mechanical and thermal properties, viz. a $33\%$ increase in the elastic modulus and a rise in the onset degradation temperature from 355 to $371^{\circ}C$, in comparison to the Zn-ion coated structural silica.

• Korean Membrane Journal
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• v.6 no.1
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• pp.44-54
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• 2004

Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.2
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• pp.27-32
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• 2020

Robust and hydrophobic tetraethoxysilane (TEOS) based silica aerogel was synthesized by supercritical alcohol drying with surface modification using the phenyl based silica co-precursor (PTMS). The aerogels were synthesized by hydrolysis and polycondensation reaction in which TEOS and PTMS in methanol were reacted together in presence of oxalic acid and ammonium hydroxide as the catalysts. Supercritical alcohol dried PTMS/TEOS composite silica aerogel were examined for the hydrophobicity, chemical interaction, surface morphology, and textural characteristics. The hydrophobic silica-based aerogels were characterized by Fourier transform infrared spectroscopy to investigate the presence of functional groups and chemical bonds. The prepared silica demonstrates hydrophobicity (76°-149°), a high specific surface area (398 ㎡/g to 739 ㎡/g). The present investigation provides a simple approach to synthesize hydrophobic and thermally stable silica aerogels.

• Advances in materials Research
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• v.12 no.3
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• pp.227-242
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• 2023

Polyester composites play a vital role in civil engineering applications, especially in bridge and car park structures. Therefore, the addition of waste silica-based fillers will both improve the mechanical and durability performance of composites and produce an environmentally friendly material. In this study, the mechanical performance of polyester composites was investigated experimentally and numerically by adding micro and nano-sized silica-based fillers, marble powder, silica fume and nano-silica. 24 cubes for the compression test and 18 prisms for the flexural test were produced in six different groups containing 30% marble powder, 5% silica fume and 1% nano-silica by weight. SEM/EDS testing was used to investigate the distribution of filler particles in the matrix. Experimentally collected results were used to validate tests in the Abaqus software. Additionally, the Extended Finite Element Method (XFEM) was used to estimate the fracture process for the flexural test. The results show that the added silica fume, marble powder and nano silica improves the compressive strength of polyester composites by 32-38% and the flexural tensile strength by 10-60% compared to pure polyester composite. The numerically obtained results matched well with the experimental data, demonstrating the accuracy and feasibility of the calibrated finite element model.

• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.118-123
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• 2019

In this study, the electrochemical characteristics of Graphite/Silicon/Pitch anode composites were analyzed to improve the low theoretical capacity of graphite as a lithium ion battery. The Graphite/Silica composites were synthesized by bonding silica onto polyvinylpyrrolidone coated graphite. The surface of used silica was treated with (3-Aminopropyl)triethoxysilane(APTES). Graphite/Silicon/Pitch composites were prepared by carbonization of petroleum pitch, the fabrication processes including the magnesiothermic reduction of nano silica to obtain silicon and varying the mass ratio of silica. The Graphite/Silicon/Pitch composites were analysed by XRD, SEM and XRD. Also the electrochemical performances of Graphite/Silicon/Pitch composite as the anode of lithium ion battery were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance tests in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC:DMC:EMC=1:1:1 vol%). The Graphite/Silicon/Pitch anode composite (silica 28.5 in weight) has better capacity (537 mAh/g). The cycle performance has an excellent capacity retention to 30th cycle of 95% and the retention rate capability of 98% in 0.1 C/0.2 C.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.809-815
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• 2014

The co-bonded dissimilar composite under a wide range of temperature change shows thermal distortion due to the differences in thermal expansion characteristics of the composite materials. Analysis of the thermal expansion characteristics of each composite is required for the design of co-bonded dissimilar composite structure with considering the shape distortion during the manufacturing process. In this work, digital image correlation (DIC) technique is introduced for measuring the thermal distortion characteristics of co-bonded dissimilar composite specimen, carbon/epoxy and silica/phenolic. The thermal distortion of co-bonded dissimilar composite specimen is numerically estimated and compared with the experiments. The estimated results is successfully validated using the measured results.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.482-487
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• 1993

Organic nonlinear optical materials such as MNA(2-Methyl-4-nitro-aniline), Carbazole 1(5-Nitro-9-hydroxyethyl Carbazole), Carbazole 2(5-Nitro-9-ethyl Carbazole) and DR 1(Disperse Red 1) were incorporated into silica matrix to form a composite thin films. The thermal stability and degree of degradation were compared to these organic-inorganic composite film. Among those films, Carbazole 1 and DR 1 which have terminal -OH group showed enhanced stability for thermal degradation. The effect of polarization and degree of relaxation for the composite thin films incorporated with Carbazole 1 were measured by the absorbance change of UV spectra with time. With polarization treatment of Carbazole 1 incorporated composite film, the intensity of UV absorbance was remarkably reduced. And slow relaxation of Carbazole 1 molecule was suggested from the slightly recovered intensity of UV absorbance after removing the electric field at rooma temperature.

• Membrane Journal
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• v.25 no.5
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• pp.456-463
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• 2015

In this study, we synthesize novel silane based inorganics for preparation of the polymer electrolyte membrane with high proton conductivity under high temperature condition and developed membranes are characterized. SPAES, hydrocarbon based polymer are synthesized and used as main polymeric material. We used sol-gel method to prepare inorganic material with high performance using silica, phosphate and zirconium. Three types of inorganics were prepared by control of the mole ration of each component. As a result of EDX analysis, the inorganic materials are well dispersed in the polymer membrane. The water uptake of the composite membrane is increased by introduction of the hydrophilic inorganic material in the membrane. When the content of the zirconium in the membrane is increased, the proton conductivity of the composite membrane shows the higher value than pure SPAES membrane at the high temperature. And the silica based inorganics effect to increase the proton conductivity under low temperature condition.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.144-149
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• 2017

A proton-conducting bisphenylpropaned sulfonated fluorinated blockcopolymer (BPSFBC) was synthesized. Five kinds of polymer electrolyted composite membranes were preparated by incorporating silica ($SiO_2$) with various weight ratio. And their characteristics were investigated by FT-IR (fourier transform infrared), $^1H-NMR$ ($^1H$ nuclear magnetic resonance), TGA (thermogravimetric analysis), water uptake, FE-SEM (field emission scanning electron microscopes), and ion conductivity properties. The water uptake and ion conductivity were increased until 9 wt% $SiO_2$, and then decreased. The maximum proton conductivity equal to $52mScm^{-1}$ was measured for the BPSFBC/$SiO_2$-9 composite membrane at $90^{\circ}C$ and 100% relative humidity. From the measured results, it is distinct that the manufactured composite membrane BPSFBC/$SiO_2$-9 can be considered as a polymer membrane suitable for a fuel cell electrolyte.

• Journal of the Korean Applied Science and Technology
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• v.22 no.3
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• pp.281-288
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• 2005

The silica nanoparticles were used as support of catalyst, filling material, electronic assembler, thin film material, and sensor material. And, the titania nanoparticles were used as pigment, dielectric substance, sensor and photocatalyst. In this paper, the spherical composite particles of $TiO_2/SiO_2$with narrow size distribution and phase pure were synthesized by ultrasonic spray pyrolysis method from $TiOSO_4$ and colloidal silica solution. Using ultrasonic apparatus, this starting solution was vaporized to droplets, and these droplets were induced into tube furnace by carrier gas. The resulting composite powder was characterized by scanning electron microscopy, X-ray diffraction analysis, TG-DTA, in vitro sun protection factor(SPF) and BET surface area analysis.