• Journal of the Korean Graphic Arts Communication Society
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• v.22 no.2
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• pp.37-54
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• 2004

IPNs have interpenetrating motion and phase separation behavior of independent polymers, respectively, and also these are affected by the physical interaction of polymer components. First of all, 2- and 3-component IPNs based on PU are prepared by combination with two or three components of PU, PMMA, PS and epoxy resin. And then the entire physical properties concerning morphological and mechanical behaviors of these IPNs are measured by employing FT-IR, SEM, Rheovibron, and DSC, etc. Compared with pure component, Tg's of IPN are shifted to higher temperature in all IPN kinds, and these are considered in attribution to internal movement of glass transition temperature or partial phenomenon of interpenetration. Rheovibron measurement results in a broader distribution with peaks of tan${\delta}$ or E", and this morphologically represents a medium degree of partially mixed IPNs in confirmation of SEM photographs.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1762-1767
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• 2001

The Posuk-Chung Pavilion if a defunct irregular stone water channel in Kyongju, Korea, once used for the meandering stream feast'by kings of Silla Dynasty during the first millennium. The poets were seated around this stone water channel who composed the Chinese poems, overlooking the streams. They load to take the punishment drinks unless they finished the poem before the drifting cup filled with the rice wine arrived at their seats on the meandering stream. In this paper, we have made computer simulation as well as well as model experiment on the ancient meandering stream of the Posuk-Chung Pavilion. The computational results are compared with the experiment and the channel flow characteristics are delineated here. It is discussed how the present Posuk-Chung channel is morphologically distinguished from the Chinese and Japanese meandering streams.

• Elastomers and Composites
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• v.48 no.4
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• pp.276-281
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• 2013

Polyester type polyurethane foam modified with acrylic polyol was prepared by quasi prepolymer method. Thermal and dynamic mechanical properties of polyurethane foam were analysed by thermal gravimetric analysis(TGA) and dynamic mechanical analysis(DMA). Also, glass transition temperature was measured by differential scanning calorimeter(DSC). As acrylic polyol contents were increased, thermal stability measured by TGA was slightly decreased. Storage modulus was increased and tan delta was decreased with increasing of acrylic polyol contents.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.144-144
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• 2017

제한된 조건에서 타이타늄을 양극산화 하였을 때, 자기 정렬된 나노 튜브 형태의 티타니아 구조를 얻을 수 있으며, 그 형태는 양극산화 조건에 따라 변할 수 있음은 학계에 이미 잘 알려져 있다. 그러나 자세한 메커니즘과 전기화학적 조건들은 아직 명확하게 밝혀지지 않았다. 본 연구에서는 자기 정렬된 티타니아 나노 구조의 형태학적 변화를 인가전압과 혼합 전해질의 농도를 변화시켜가며 체계적으로 연구하여, 티타니아 나노 튜브와 마이크로 콘이 생성되는 조건에 대한 지도를 그렸다. 일반적으로 인가 전압이 증가하고, 혼합 전해질에서의 불산의 농도가 낮을수록, 티타니아 나노 구조가 나노튜브에서 마이크로 콘으로 변화하는 것을 확인하였다. 티타니아의 다양한 기능적인 특성을 바탕으로, 구조변화에 대한 전기화학적 이해를 통해, 물 분해, 연료 감응형 태양전지(DSSCs), 광촉매, 가스 센서 등에 적용될 수 있을 것으로 기대한다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.433-434
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• 2006

Monosized germanium micro particles are prepared by a newly developed Pulsated Orifice Ejection Method. The obtained particles are categorized into two kinds of the microstructures as refined and coarse ones. The morphological difference is estimated to be determined by the undercooling level during nucleation. Actually, the increase in the temperature of the melt was effective in coarsening the microstructure, because the temperature of the melt intensely relates to the undercooling level. The transition temperature of coarse and refined microstructures is found to be 1300-1350K. Furthermore, a triggered nucleation could improve the crystallinity of the particles in the short separation.

• Korean Journal of Ichthyology
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• v.13 no.1
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• pp.74-84
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• 2001

The early developmental stages, growth and morphological changes of the Korean bullhead, Pseudobagrus fulvidraco, were studied from a series of reared specimens. Details of the early developmental stages are illustrated with special reference to morphological transformations. Egg and sperm of Korean bullhead were obtained from mature adults under hormonal treatment, fertilized artificially, and incubated in the aquarium. The incubation period of fertilized eggs was 55 to 66 hours at a temperature of 24.9${\pm}$0.34$^{\circ}$. Larvae were fed successively with Artemia salina and Daphnia magna for 2 to 15 days and artificial food after 20 days. Fertilized eggs were adhesive and spherical with a diameter of 2.04mm(n = 100). The mean total length of newly hatched larvae was about 4.92${\pm}$0.33 mm. Mouth opening occurred on one-day-old yolk-sac larvae, and initial feeding was observed on the third day after hatching. The morphological transitions from larvae to juvenile and juvenile to young stages occurred when the fish reached about 17 mm in total length (about 13days after hatching) and about 32 mm in total length (about 30 days after hatching), respectively. Many changes in proportion of body parts to total length were observed at about 7~8 mm and 30~32 mm, corresponding to the transformations from larvae to juvenile and from juvenile to young, respectively. In comparing relative growth of each body part against total length, those characteristics related to head parts showed positive growth in the pre-larval stages, while those concerning mobile abilities showed positive growth in the post-larval stage.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.1-7
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• 2021

ε-Ga2O3, a metastable phase of Ga2O3, has excellent compatibility with substrates having a hexagonal structure or a quasi-hexagonal structure, so that a film having a relatively lower surface roughness and defect density than β-Ga2O3 can be obtained easily. Accordingly, we attempted to fabricate a high-quality β-Ga2O3 film with a low surface roughness and defect density using the property of phase transition to β-Ga2O3 when ε-Ga2O3 is annealed at a high temperature. For this, the growth of high-quality ε-Ga2O3 films must be preceded. In this study, the optimal flow rate was investigated by analyzing the structural and morphological characteristics of the ε-Ga2O3 film according to the supplied precursor ratio. In addition, the annealing condition and the effect of β-Ga2O3 mixed in the ε-Ga2O3 film on the crystallinity of β-Ga2O3 after phase transition were also investigated.

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1051-1054
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• 2004

The structural transformation behavior of $Na_2Ti_3O_7$ by hydrolysis was investigated in mild and strong acidic aqueous medium. Compared with $K_2Ti_4O_9,\;Na_2Ti_3O_7$ exhibits quite different structural and morphological transformation behavior despite their similar layered structural characteristics. $TiO_2(B)$ obtained by heat treatment of $H_2Ti_3O_7\;at\;350^{\circ}C$ transforms to rutile $H_2Ti_3O_7\;at\;900^{\circ}C$. This temperature is much lower than $1200{\circ}C$, the temperature for anatase to rutile transition when $K_2Ti_4O_9$ is used as a starting titanate. A rectangular rod shape and size of $TiO_2(B)$ particles obtained from $Na_2Ti_3O_7$ is also different from a fibrous structure of $TiO_2(B)$ prepared using $K_2Ti_4O_9$. Rutile crystals of 100 nm diameter with a corn-like morphology and large surface area are directly obtained when the hydrolysis of $Na_2Ti_3O_7$ is carried out at $100^{\circ}C$ in a strong acid solution. The structure of starting titanates and the hydrolysis conditions are an important factor to decide the particle size and morphology of $TiO_2(B)\;and\;TiO_2$.

• Macromolecular Research
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• v.15 no.6
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• pp.520-526
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• 2007

The effects of poly($({\varepsilon}$-caprolactone) (PCL) on poly(acrylonitrile-butadiene-styrene) (ABS) and polycarbonate (PC) blends were studied. Blends of ABS/PC (70/30, wt%) with PCL as a compatibilizer were prepared by a twin screw extruder. From the glass transition temperature $(T_g)$ results of the ABS/PC blends with PCL, the $T_g$(PC) of the ABS/PC (70/30) blends decreased with increasing PCL content. From the results of the morphology of the ABS/PC (70/30) blends with PCL, the phase separation between the ABS and PC phases became less significant after adding PCL in the ABS/PC blends. In addition, the morphological studies of the ABS/PC blends etched by NaOH indicated that the shape of the droplet was changed from regular round to irregular round by adding PCL in the ABS/PC blends. These results for the mechanical properties of the ABS/PC blends with PCL indicated that the tensile, flexural and impact strengths of the ABS/PC (70/30) blends peaked at a PCL content of 0.5 phr. From the results for the rheological properties of the ABS/PC (70/30) blends with PCL content, the storage modulus, loss modulus and complex viscosity increased at PCL content up to 5 phr. From the above results of the $T_g$, mechanical properties, morphology and complex viscosity of the ABS/PC blends with PCL, it was concluded that the compatibility was increased with PCL addition in the ABS/PC (70/30, wt%) blends and that the optimum concentration of PCL as a compatibilizer is 0.5 phr.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.125-131
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• 2007

Biodegradable polymeric blends are expected to be widely used by industry due to their environmental friendliness and comparable mechanical and thermal properties. Poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) are such biodegradable polymers which aim to replace commodity polymers in future applications. Since cost and brittleness of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. In this study, blends of PLA and PBS with various compositions were prepared by using a laboratory-scale twin-screw extruder at $180^{\circ}C$. Morphological, thermal, rheological and mechanical properties were investigated on the samples obtained by compression molding to explore suitability of these compositions for packaging applications. Morphology of the blends was investigated by scanning electron microscopy (SEM). Morphology showed a clear phase difference trend depending on blend composition. Modulated differential scanning calorimetry (MDSC) thermograms of the blends indicated that the glass transition temperature ($T_g$) of PLA did not change much with the addition of PBS, but analysis showed that for PLA/PBS blend of up to 80/20 composition there is partial miscibility between the two polymers. The tensile strength and modulus were measured by the Instron Universal Testing Machine. Tensile strength, modulus and percentage (%) elongation at break of the blends decreased with PBS content. However, tensile strength and modulus values of PLA/PBS blend for up to 80/20 composition nearly follow the mixing rule. Rheological results also show miscibility between the two polymers for PBS composition less than 20% by weight. PBS reduced the brittleness of PLA, thus making it a contender to replace plastics for packaging applications. This work found a partial miscibility between PBS and PLA by investigating thermal, mechanical and morphological properties.