• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.989-994
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• 1995

Rigid porous carbon fiber composites with the uniform pore size distribution were prepared by vacuum forming from water slurries containing carbonized PAN fibers, a phenolic resin and ceramic binders. The composites were designed to use for highly efficient carbon fiber filters for particulate filtration and gas adsorption. As the as-received carbon fibers of 1mm in length were milled to an approximate average length of 300${\mu}{\textrm}{m}$, modulus of rupture (MOR) of the composite filter was increased from 1MPa to the value larger than 5 MPa. Modulus of rupture (MOR) for the composite filter fabricated using the milled carbon fiber was increased from 5 MPa to 10 MPa as the carbonization temperature of the PAN fiber was raised from 90$0^{\circ}C$ to 140$0^{\circ}C$. The air permeability and an average pore size of the composite filter were increased from 40 to 270cc/min.$\textrm{cm}^2$ and from 35 to 80${\mu}{\textrm}{m}$, respectively, as the apparent porosity increased from 80 to 95%. It was shown that the MOR of the carbon fiber composite filter was dependent primarily on the average length of carbon fiber, carbonization temperature and the type of bonding materials.

• Journal of Auto-vehicle Safety Association
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• v.11 no.1
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• pp.23-29
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• 2019

Recently, use of composite materials has been increasing for body structures and chassis parts in the car industry because of weight reduction effect and excellent mechanical thermal characteristics. However, application of composite materials in brake system is very difficult because it is hard to obtain enough brake performance due to low heat storage capacity of the composite materials. In this paper, we will present new carbon ceramic composite disc with high flow characteristic. To obtain this characteristic, new vent structures were designed by using ARIZ method and substance-field model analysis. The flow effect of these vent structures on the brake performance was verified by pugh matrix and cooling test. The test results show improvement of cooling performance up to $30^{\circ}C$. Finally, These results will improve brake the reliability of the brake performance for the high performance vehicles and electric vehicles.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1181-1186
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• 2008

Insulators which are used in the domestic electrical industries are mostly depended on importation from some advance countries. Even though insulators which are made of ceramic material have been mostly used domestically, the ratio of usage on composite insulators is recently being increased because of difficulties in manufacturing and high cost regarding ceramic stuffs. In this research, we are trying to develop the composite insulators which are very efficient in insulation regardless of the matter of weight. Even though the technique of manufacturing composite insulator are quite generalized worldwide at the moment, one of the most important issue is to keep security on the know-how that an ingredient of insulated material named 'SF6 gas' is included. Therefore, The aim of this paper is to improve the bonding force and air tight property between two components of composite insulator, Flange and FRP Tube.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.419-423
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• 2018

A newly conceived geopolymer composite was fabricated by a combination of the geopolymer and polyurethane sponge. The density and porosity of hardened geopolymer composite, corresponded to different pore sizes of polyurethane sponge, exhibited no significant differences from each other. However, the mechanical behavior, the compressive strength and flexural strength, showed slight differences accordingly. Fracture of the geopolymer composite exposed to high compressive load was not observed from all specimens containing polyurethane sponge. The toughness enhancement of the geopolymer composite, due to spontaneous elasticity of polyurethane sponge, crack spread, and crack diffraction, was identified through the stress-strain curve and microstructure of fracture surface. The newly designed geopolymer composite having a 3-dimensional sponge skeleton showed relatively higher flexural strength of 8.0 MPa than other conventional geopolymer composites.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.287-294
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• 2012

Ceramic Matrix Composites (CMCs) represent a class of non-brittle refractory materials for harsh and extreme environments in aerospace and other applications. The quasi-ductility of these structural materials depends on the quality of the interface between the matrix and the fiber surface. In this study, a manufacture route is described where in contrast to most other processes no additional fiber coating is used to adjust the fiber/matrix interfaces in order to obtain damage tolerance and fracture toughness. Adapted microstructures of uncoated carbon fiber preforms were developed to permit the rapid infiltration of molten alloys and the subsequent reaction with the carbon matrix. Furthermore, any direct reaction between the melt and fibers was minimized. Using pure silicon as the reactive melt, C/SiC composites were manufactured with an aim of employing the resulting composite for friction applications. This paper describes the formation of the microstructure inside the C/C preform and resulting C/C-SiC composite, in addition to the MAX phases.

• Journal of Powder Materials
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• v.30 no.4
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• pp.356-362
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• 2023

Inorganic-organic composites find extensive application in various fields, including electronic devices and light-emitting diodes. Notably, encapsulation technologies are employed to shield electronic devices (such as printed circuit boards and batteries) from stress and moisture exposure while maintaining electrical insulation. Polymer composites can be used as encapsulation materials because of their controllable mechanical and electrical properties. In this study, we propose a polymer composite that provides good electrical insulation and enhanced mechanical properties. This is achieved by using aluminum borate nanowhiskers (ABOw), which are fabricated using a facile synthesis method. The ABOw fillers are created via a hydrothermal method using aluminum chloride and boric acid. We confirm that the synthesis occurs in various morphologies based on the molar ratio. Specifically, nanowhiskers are synthesized at a molar ratio of 1:3 and used as fillers in the composite. The fabricated ABOw/epoxy composites exhibit a 48.5% enhancement in mechanical properties, similar to those of pure epoxy, while maintaining good electrical insulation.

• Korean Journal of Materials Research
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• v.22 no.12
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• pp.643-649
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• 2012

Coatings composited with alumina and Perfluoro alkoxyalkane (PFA) resin were deposited on stainless steel plate (SUS304) to further improve corrosion resistance. Plate (ca. $10{\mu}m$) and/or nanosize (27~43 nm) alumina used as inorganic additives were mixed in PFA resin to make alumina-fluoro composite coatings. These coatings were deposited on SUS304 plate with wet spray coating and then the film was cured thermally. According to the amount and ratio of the two kinds of alumina having plate morphology and nano size, corrosion resistance of the film was evaluated under strong acids (HF, HCl) and a strong base (NaOH). The film prepared with the addition of 5~10 wt% alumina powders in PFA resin showed corrosion resistance superior to that of pure PFA resin film. However, for the film prepared with alumina content above 10 wt%, the corrosion resistance did not improve with the physical properties, such as surface hardness and adhesion. The film prepared with plate/nanosize (weight ratio = 1/2) alumina especially enhanced the surface hardness and corrosion resistance. This can be explained as showing that the plate and the nanosize alumina dispersed in PFA resin effectively suppressed the penetration of cations and anions due to the long penetration length and fewer defects that accompany the improved surface hardness under a serious environment of 10% HF solution for over 120 hrs.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.301-307
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• 2017

The purpose of this study is to investigate the electrical properties of thick-film resistor (TFR) prepared from $CaO-ZnO-B_2O_3-Al_2O_3-SiO_2$ (CZBAS) glass containing $RuO_2$ particles. $RuO_2$-glass composite powder was made by mixing and melting oxide powders of constituents. For comparison, $RuO_2$ powder was simply mixed with glass powder. $RuO_2$-40wt% glass composite and mixture were dispersed in an organic binder to obtain printable resistor paste and then thick-film was formed by screen printing, followed by sintering at the range between $750^{\circ}C$ and $900^{\circ}C$ for 10 min with a heating rate of $50^{\circ}C/min$ in an ambient atmosphere. $RuO_2$-glass composite sample showed much higher resistance compared to the simple mixed sample. This could be attributed to the difference in conducting mechanism. After sintering at $850^{\circ}C$, temperature coefficient of resistance of composite sample was lower than that of simple-mixed sample. TFR with dense and homogeneous microstructure could be obtained by using $RuO_2$-glass composite powder.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.283-288
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• 2014

PdO-doped $BaZr_{0.85}Y_{0.15}O_{3-\delta}$ (BZPY) proton conductors have been proposed as applicable for intermediate temperature electrolytes for protonic ceramic fuel cells (PCFCs) because the PdO doping is effective for improving the proton conductivity of $BaZr_{0.85}Y_{0.15}O_{3-\delta}$ (BZY) with high affinity for hydrogen. In order to further improve the conductivity of BZPY, two-phase composite electrolytes consisting of a BZPY and molten carbonate were designed. Dense BZPY-based composite electrolytes were fabricated after sintering at $670^{\circ}C$ for 4 h, since molten carbonates fill the grain boundary of the porous BZPY matrix. Furthermore, BZPY/$(Li-0.5Na)_2CO_3$ composites show a significantly enhanced protonic conductivity at intermediate temperatures. This may be because easy proton transport is possible through the interface of the carbonate and oxide phase.

• Transactions on Electrical and Electronic Materials
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• v.7 no.4
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• pp.167-172
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• 2006

Submicron colloidal silica coated with ceria were prepared by mixing of silica and nano ceria particles and modified by hydrothermal reaction. The polishing efficiency of the ceria coated silica slurry was tested over oxide film on silicon wafer. By changing the polishing pressure in the range of $140{\sim}420g/cm^2$ with the ceria coated silica slurries in $100{\sim}300nm$, rates, WIWNU and friction force were measured. The removal rate was in the order of 200, 100, and 300 nm size silica coated with ceria. It was known that the smaller particle size gives the higher removal rate with higher contact area in Cu slurry. In the case of oxide film, the indentation volume as well as contact area gives effect on the removal rate depending on the size of abrasives. The indentation volume increase with the size of abrasive particles, which results to higher removal rate. The highest removal rate in 200 nm silica core coated with ceria is discussed as proper combination of indentation and contact area effect.