• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.6
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• pp.21-27
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• 2022

C_f/SiC composites have low density, high mechanical strength, and good thermal stability, making them promising materials for high-temperature applications such as rocket propulsion and military fields. However, the remaining Si deteriorates physical and thermal properties. In this paper, the de-siliconization was introduced as a method to remove the Si of the C_f/SiC composite fabricated through Liquid Silicon Infiltration(LSI) process. The stability of composite has been tested under an oxyacetylene torch flame for up to 5 minutes. The oxidized surface and cross section of specimens were characterized by 3D scanning, X-ray diffraction(XRD), Optical microscope(OM) and Scanning electron microscope(SEM).

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.65-73
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• 2002

Because of low flame ion density in hydrogen-air mixture, many residual electric energy could be existed in the ignition system of hydrogen engine, If these residual energy discharged abnormally during intake stroke, it may be the cause of backfire occurrence which is serious problem in development of hydrogen fueled engine but unsolved in spite of many concerned research on it. In this study, the possibility of backfire occurrence by abnormal electric discharge and countermeasure of that were investigated by using the experimental single cylinder hydrogen fueled engine with two types of ignition system. The results show that abnormal electric discharge appeared in low load with low ion density and then results in back fire occurrence, It is also seen that countermeasure method installing larger earth resistance in high tension code is effective to control abnormal electric discharge.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.73-80
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• 2007

Nanocomposites are used as a new class of polymer system and many researchers have been interested in the clay nanocomposite because of its good mechanical properties, heat resistance, flame retardancy, and barrier property. Modified layered silicates as fillers are dispersed at a nanometer-level within a polymer matrix and then new extraordinary properties are observed. In this study, polypropylene/clay nanocomposites were prepared in a twin screw extruder by the melt compounding method. In order to increase the compatibility of PP with the clay, the MAPP was used as a compatibilizer. And organic modified clays were used as a nanometric filler during the melt extrusion. Through the analysis of SAXS, WAXS, the dispersion of clay was investigated. These nanocomposites compared with a neat polypropylene/talc composite have high modulus, low toughness, and reduced shrinkage at the stable dispersion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.912-919
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• 1994

The engine combustion is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake stroke breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of this relationship is not well known. This paper describes the tumble flow measurements inside the cylinder of a 4-valve S.I. engine using laser Doppler velocimetry(LDV) under motoring(non-firing) conditions. This is conducted on an optically assesed single cylinder research engine under motored conditions at an engine speed of 1000rpm. Three different cylinder head intake port configurations are studied to develop a better understanding the tumble flow generation, development, and breakdown mechanisms.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.595-599
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• 2011

ALC(Autoclaved Lightweight Concrete) is produced using quartz sand, lime and cement and water. And aluminum powder is used for blowing agent. ALC is manufactured by autoclave chamber under high-temperature and high-pressure. Generally, ALC is 1/4 levels lighter than concrete and mortar, because it has a lot of pores. So density of ALC is about 0.45~0.65 g/$cm^3$. But, ALC has a weakness, typically low strength, with its porous structure. So, it is necessary to excellent strength properties for extensive apply of ALC materials in high porosity. In this study, melamine resin was used to improve the strength characteristics of ALC materials. We performed compressive and bending strength measurements. Compressive strength of ALC with 2% melamine resin increased 26.88% than 'melamine-free' ALC. Also we performed functionality evaluation such as thermal conductivity, sound absorption, and flame-resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.251-254
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• 2001

In this paper, we analyzed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC 600[V] wire. Messurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflaming pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds genalated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of $2.5{\pm}0.04[w/cm^{2}]$ for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 25.2 to 37.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomplete combustion of FR-PVC which has high content of carbon in compound.

• Textile Coloration and Finishing
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• v.25 no.4
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• pp.292-302
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• 2013

Cotton fabrics treated with hybrid materials were developed and prepared. A halogen-free flame retardant and an aromatic amide were blended and applied to cotton fabrics. Thermal and physical properties of the treated cotton fabrics were investigated. The surface of the pure and coated cotton fabrics was characterized by Fourier transform infrared spectroscopy. The elemental composition of the coated surface of the cotton fabric was measured using X-ray photoelectron spectroscopy and compared with that of pure cotton fabric. After being solved in N,N-dimethylacetamide, m-aramid and triphenylphosphine oxide (TPP) were applied to cotton fabrics through a dip-pad-coagulation process. The treated cotton fabrics with recycled m-aramid/TPP resulted in increased limited oxygen index values and thermal resistance.

• Composites Research
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• v.18 no.3
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• pp.47-52
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• 2005

Pultrusion process of phenolic foam composite is investigated. Phenolic foam composites provide heat and flame resistance with less weight. When made into foam, a variety of properties can be obtained with different bubble size and number density. In this study, effect of process variables on the foaming characteristics of phenolic resin composites during pultrusion process has been studied experimentally. The process variables considered are the heating temperature and the pulling speed as well as the mass fraction of blowing agent. Experiments were performed using a laboratory scale pultrusion apparatus. Optimal process condition was found by observing the micro-morphology.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.251-254
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• 2001

In this paper, we analysed the properties change of electric wire when the thermal stress was applied to NFR-8 and FR-PVC [600] wire. Measurement is made of the attenuation of a light beam by smoke accumulating with in a closed chamber due to nonflamining pyrolytic decomposition and flaming combustion. Results are expressed in terms of specific optical density which is derived from a geometrical factor and the measured optical density a measurement characteristic of the concentration of smoke. Referenced documents were ASTM E662 standard test method for specific Ds generated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of 2.5${\pm}$0.04[w/$\textrm{cm}^2$] for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 7.2 to 77.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. The amount of carbon monoxide generated was found to be much higher in FR-PVC decomposition than in NFR-8 due to incomp1ete combustion of FR-PVC which has high content of carbon in compound.

• Journal of Powder Materials
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• v.12 no.2 s.49
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• pp.106-111
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• 2005

The effect of post-heat treatment on the coating characteristics and the fatigue strength of the gas flame thermally sprayed Stellite alloy coatings on $0.35\%$ carbon steel were investigated. The fatigue fracture surfaces of the heat treated samples were observed using SEM (Scanning Electron Microscopy). For as-sprayed samples, there was considerable scattering in the fatigue life due to the presence of the pores in the coating. After the post-heat treatment to improve the microstructural characteristics of the coating layer, the fatigue strength of the specimens was greatly improved, increasing with increasing the coating thickness. For the specimens with the 0.3mm and 0.5mm thick coating, the fatigue cracks originated in the substrate region just below the interface. On the contrary, for the specimens with the 1.0mm thick coating, they nucleated at the pore within the coating, and the fatigue strength was 2.6 times higher than that of the substrate due to the high fatigue resistance of the coating.