• Advances in materials Research
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• v.3 no.1
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• pp.259-269
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• 2014

The boron-nitrogen-containing phenol-formaldehyde resin (BNPFR)/$SiO_2$ nanocomposites (BNPFR/$SiO_2$) were synthesized in-situ, and structure of BNPFR/$SiO_2$ nanocomposites was characterized by FTIR, XRD and TEM. The loss modulus peak temperature $T_p$ of BNPFR/$SiO_2$ nanocomposites cured with different nano-$SiO_2$ content are determined by torsional braid analysis (TBA). The thermal degradation kinetics was investigated by thermogravimetric analysis (TGA). The results show that nano-$SiO_2$ particulate with about 50 nm diameter has a more uniformly distribution in the samples. The loss modulus peak temperature $T_p$ of BNPFR/$SiO_2$ nanocomposite is $214^{\circ}C$ when nano-$SiO_2$ content is 6 wt%. The start thermal degradation temperature $T_{di}$ is higher about $30^{\circ}C$ than pure BNPFR. The residual rate (%) of nanocomposites at $800^{\circ}C$ is above 40 % when nano-$SiO_2$ content is 9 %. The thermal degradation process is multistage decomposition and following first order.

• 연구논문집
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• s.26
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• pp.103-112
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• 1996

$Al_2O_3/SiC$ Hybrid-Composite has been fabricated by conventional powder process. The addition of $\alpha-Al_2O_3$ as seed particles in the transformation of $\gamma-Al_2O_3 to $\alpha-Al_2O_3$ provided a homogeneity of the microstructure, resulting in increase of mechanical properties. The grain growth of $Al_2O_3$ are significantly surpressed by the addition of nano-sized. SiC particles, increasing in fracture strength. The addition of SiC plates to $Al_2O_3$ nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC plates with nitrides such as BN and /SiC$Si_3N_4$ enhanced fracture toughness much more than uncoated SiC plates by inducing crack deflection.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.225-225
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• 2009

In this study, Nano and micro-filler mixture composites were fabricated by fixed value of $SiO_2$ nano-filler 0.4 [wt%] according to increase of $SiO_2$ micro-filler [wt%] from 1 to 10. Composites with a good dispersion of mixed $SiO_2$ Nano and micro-particles in the epoxy resins were prepared and experiments were performed to measure the dielectric breakdown strength properties with various temperature and thickness. The dielectric strength properties are compared and analyzed with respect to nano/micro-composites filled with $SiO_2$ fillers less than properties obtained for nanocomposites.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.118-119
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• 2007

Phase stability and morphological investigation on the $Si/SiO_2/HfO_2$ and $Si/SiO_2/ZrO_2$ stack are presented. Thermal stability of $HfO_2$ and $ZrO_2$ determines the quality of interface and subsequently the performance of device. The stacks have been fabricated and annealed at $1000^{\circ}C$ for various time. In evolution of crystalline phase and morphology (electrical and geometrical) of high-k materials, annealing time and process are observed to be crucial factors. The crystallization of some phase has been observed in the case of $Si/SiO_2/HfO_2$. The chemical environment around Zr and Hf in respective samples is observed to be different.

• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.43-47
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• 2008

[ $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ ] nano-glass has been prepared by sol-gel method. The mean particle size was 60.3 nm with narrow size distribution. The nano-galss has been used as a sintering aid for the densification of the NiZnCu ferrites. The ferrite was sintered with nano-glass sintering aids at $840{\sim}900^{\circ}C$, 2 h and the initial permeability, quality factor, density, and saturation magnetization were also measured. The initial permeability of 0.5 wt% nano-glass added toroidal sample for NiZnCu ferrites sintered at $900^{\circ}C$ was 193.3 at 1 MHz. The initial permeability and saturation magnetization were increased with increasing annealing temperature. As a result, $ZnO-Bi_2O_3-Al_2O_3-B_2O_3-SiO_2$ nano-glass systems were found to be useful as sintering aids for multilayer chip inductors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1233-1238
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• 2009

This study analyzed the characterization of high temperature strength of $Si_3N_4$ composite ceramics additive based on variations in the amount of nano colloidal $SiO_2$ added. Semi-elliptical cracks about 100 ${\mu}m$ length were obtained from a Vickers indenter using a load of 24.5 N. The results showed that the heat-treated smooth specimens with $SiO_2$ nano colloidal coating exhibited the highest bending strength at 0.0 wt% $SiO_2$ nano colloidal added, which is amounted to a 187 % increase over that of smooth specimen. Limiting temperature for bending strength of crack-healed zone for bending strength was about 1273 K. However, the bending strength of SSTS-3 and SSTS-4 was considerably increased while that of SSTS-1 and SSTS-2 was decreased at a temperature of 1,573K.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.82.2-82
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• 2003

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.50-53
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• 2009

Multi-walled carbon nanotubes (MWNTs) were synthesized on different substrates (bare Si and $SiO_2$/Si substrate) to investigate dye-sensitized solar cell (DSSC) applications as counter electrode materials. The synthesis of MWNTs samples used identical conditions of a Fe catalyst created by thermal chemical vapor deposition at $900^{\circ}C$. It was found that the diameter of the MWNTs on the Si substrate sample is approximately $5{\sim}10nm$ larger than that of a $SiO_2$/Si substrate sample. Moreover, MWNTs on a Si substrate sample were well-crystallized in terms of their Raman spectrum. In addition, the MWNTs on Si substrate sample show an enhanced redox reaction, as observed through a smaller interface resistance and faster reaction rates in the EIS spectrum. The results show that DSSCs with a MWNT counter electrode on a bare Si substrate sample demonstrate energy conversion efficiency in excess of 1.4 %.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.406-412
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• 1997

Al2O3/SiC hybrid-composite has been fabricated by the conventional powder process. The addition of $\alpha$-Al2O3 as seed particles in the transformation of ${\gamma}$-Al2O3 to $\alpha$-Al2O3 provided a homogeneity of the microstructure. The grain growth of Al2O3 are significantly surpressed by the addition of nano-size SiC particles. Dislocation were produced due to the difference of thermal expansion coefficient between Al2O3 and SiC and piled up on SiC particles in Al2O3 matrix, resulting in transgranular fracture. The high fracture strength of the composite was contributed to the grain refinement and the transgranular fracture mode. The addition of SiC platelets to Al2O3/SiC nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC platelets with nitrides such as BN and Si3N4 enhanced fracture toughness much more than non-coated SiC platelets by enhancing crack deflection.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.04b
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• pp.50.3-50.3
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• 2004