• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1828-1833
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• 2003

In a foaming process of microcellular plastics (MCPs) with a batch process, amorphous plastics and crystalline plastics have different characteristics for a foaming temperature. It is known that a foaming of amorphous plastics occurs at the temperature above a glass transition temperature, however, it is discovered that crystalline plastics do not take place above a glass transition temperature without exception, and even though the foaming occurs, it does not in all the range. In this research, to measure foaming temperature of crystalline polymer, a foaming experiment was performed using one of the typical crystalline polymer, polypropylene. To analyze whether the foaming occurs both at amorphous and crystalline fields, SEM was applied

• 연구논문집
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• s.33
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• pp.147-155
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• 2003

In order to fabricate porous materials having an anisotropic thermal conductivity by aligning plate-shaped pores structure, alumina powder (AM-21, mean particle size $4\mum$) and flake crystalline graphite was used. The aligned pore structure was realized using multi-pressing process. Degree of pore orientation increased with the number of pressing and thermal conductivity, parallel to the pressing direction, decreased with the number of pressing. Thermal conductivity decreased significantly to the addition of 30vol% crystalline graphite, however, in the case of 60vol%, thermal conductivity did not decrease significantly due to the breakage of crystalline graphite. An anisotropy of the thermal conductivity increased with the content of crystalline graphite up to 30vol%. Graded pore structure was fabricated by controlling the content and size of crystalline graphite, which provides, possibly, the enhancement in mechanical strength and thermal insulation properties of the insulating bricks.

• Bulletin of the Korean Chemical Society
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• v.20 no.5
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• pp.517-524
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• 1999

By heating the magnesiumsilicate (Mg2SiO4:forsterite) xerogel in carbon dioxide, carbonaceous component was intentionally introduced into the amorphous solid precursor. Carbon was introduced homogeneously as unidentate carbonate. Upon being heated at 800 。C in carbon dioxide, the xerogel which had homogeneously distributed carbonaceous component in it crystallized into a single phase product of a new crystalline material, which had approximate composition of Mg8Si4Ol8C. The powder X-ray diffraction pattern of the new crystalline material did not match with any known crystalline compound registered in the powder diffraction file. Crystallization from amorphous xeroget to the new crystalline phase occurred in a very narrow range of temperature, from 750 。C to 850 。C in carbon dioxide, or in dty oxygen. Upon being heated above 850 。C, carbonaceous component was expelled from the product, accompanied by irreversible transition from the new crystalline material to forsterite.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.649-653
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• 2010

In this paper, double texturization of multi crystalline silicon solar cells was studied with laser and reactive ion etching (RIE). In the case of multi crystalline silicon wafers, chemical etching has problems in producing a uniform surface texture. Thus various etching methods such as laser and dry texturization have been studied for multi crystalline silicon wafers. In this study, laser texturization with an Nd:$YVO_4$ green laser was performed first to get the proper hole spacing and $300{\mu}m$ was found to be the most proper value. Laser texturization on crystalline silicon wafers was followed by damage removal in acid solution and RIE to achieve double texturization. This study showed that double texturization on multi crystalline silicon wafers with laser firing and RIE resulted in lower reflectance, higher quantum yield and better efficiency than that process without RIE. However, RIE formed sharp structures on the silicon wafer surfaces, which resulted in 0.8% decrease of fill factor at solar cell characterization. While chemical etching makes it difficult to obtain a uniform surface texture for multi crystalline silicon solar cells, the process of double texturization with laser and RIE yields a uniform surface structure, diminished reflectance, and improved efficiency. This finding lays the foundation for the study of low-cost, high efficiency multi crystalline silicon solar cells.

• The Korean Journal of Malacology
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• v.26 no.2
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• pp.165-170
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• 2010

The location of the style sac and morphology of the crystalline style were described morphologically in three bivalve species (Tegillarca granosa, Mytilus galloprovincialis and Saxidomus purpuratus) which inhabited in different area. The style sac of them was connected to the posterior stomach. There was the crystalline style in the style sac. The crystalline style of three species was long circular cone of translucent gelatin form, which was hard and elastic. There was a red-yellow and spiral filament inside the crystalline style of Tegillarca granosa and Mytilus galloprovincialis. A white and long tube was located from basal portion to the end of crystalline style in Saxidomus purpuratus. RLC (relative length of crystalline style) of Tegillarca granosa, Mytilus galloprovincialis and Saxidomus purpuratus was 47.69, 48.97, 64.20% and RWC (relative weight of crystalline style) was 0.54, 0.54, 0.39%, respectively.

• Fibers and Polymers
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• v.6 no.3
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• pp.206-218
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• 2005

Structural studies of series of 'as spun' and drawn PEEK fibers have been carried out using X-ray diffraction and optical microscopy techniques. The analysis of results suggest that fibers produced at a constant draw ratio with increasing draw temperatures show enhanced orientation and crystalline behaviour. The resolved equatorial and meridional traces provide additional structural parameters in terms of crystallinity, crystallite size, and crystallite thickness. It is concluded that drawing at a temperature below $T_g(i.e.,\;144^{\circ}C)$ results in poorly oriented non-crystalline materials, whereas drawing above $T_g$ results in highly oriented semi crystalline materials. Additional drawing proved to increase the overall orientation with slight improvements in lateral order of the chain molecules. Quantitative analysis revealed that the crystallite size increases with increasing drawing temperature. The results also revealed the increased crystallite size upon additional drawing. Crystalline orientation parameter, $_c$, suggests almost perfect orientation. In all cases, the amorphous orientation is found to be lower than the overall orientation parameter obtained from the optical birefringence. As a result of additional drawing, crystalline orientation was found to increase slightly but the increase in the orientation of non-crystalline material was found to be substantial. An average crystalline density was determined from the orthorhombic unit cell dimensions. It was found to vary as a result of processing conditions. It was also found that the value of the maximum birefringence shows heavy dependence on the chain conformation.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.178-182
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• 2008

Planar type micro catalytic combustible gas sensor was developed by using nano crystalline $SnO_2$ Pt thin film as micro heater was deposited by thermal evaporation method on the alumina substrate. The thickness of the Pt heater was around 160 nm. The sensor showed high reliability with prominent selectivity against various gases(Co, $C_3H_8,\;CH_4$) at low operating temperature($156^{\circ}C$). The sensor with nano crystalline $SnO_2$ showed higher sensitivity than that without nano crystalline $SnO_2$. This can be explained by more active adsorption and oxidation of hydrogen by nano crystalline $SnO_2$ particles. The present planar-type catalytic combustible hydrogen sensor with nano crystalline $SnO_2$ is a good candidate for detection of hydrogen leaks.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1100-1101
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• 2008

After lamination process, Isc is increased by sheet reflection. This paper presents the electrical output characteristics by back sheet reflection. The experiments was conducted by using single crystalline and multi crystalline PV module. The reflection area of single crystalline PV module is larger than multi one due to the difference of solar cell manufacturing. The experiments show that the increased performance ratio of single crystalline PV module output power is 1.55% rather than that of multi crystalline PV module output power is 1.13%. In addition, it is expected that the output power of single one rather than multi-one is increased by the lower temperature when the PV module is installed outside. The results can be reconsidered by the test material and test process. Back sheet used for humidity prevention makes PV module output power increasing.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.24 no.3
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• pp.111-115
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• 1998

We investigated the stability of all-trans-retinol on the liquid crystalline O/W emulsion composed of mainly alkyl polyglycerine, alkyl polyglucose and glycerine, and compared the activity of all-trans-retinol in the various forms of liquid crystal. Under certain conditions, novel liquid crystalline gel was formed around oil droplets, and layers of this liquid crystalline gel were very wide and rigid. (SWLC; Super Wide Liquid Crystal) SWLC was very helpful to stabilize retinol in O/W emulsion. After storage at 45 C for 4 weeks, all-trans-retinol in O/W emulsion composed of SWLC retained above 85% of the activity upon HPLC analysis, whereas those within no liquid crystalline emulsion gave 47% and normal liquid crystalline emulsion composed of fatty alcohols gave 40 60%. Retinol in oil phase is nealy insoluble in pure water, but in cosmetic emulsion systems can be slightly solubilized into water because emulsifiers and polyols in emulsion systems function as solubilizers. In this case, water in outer phase acts as a media for oxygen transporation$.$and thus destabilizes retinol. As a result, retinol in O/W emulsion has a tendency to become unstable. SWLC surrounding oil droplet which contains retinol is wide and rigid, therefore reduces contact between inner phase and outer phase To make SWLC, properties of emulsifiers are very important phase transition temperature should be high, and the structure of surfactants should be bulky, and their ratio should be suitable to make rigid and wide liquid crystalline gel layer in order to reduce contact between retinol in inner phase and water in outer phase.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.392-398
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• 1998