• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.205-209
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• 2019

The exquisite structure and attractive biological properties of biominerals have great potential and increased interest for use in a wide range of medical and industrial applications. Calcium carbonate biomineralization, mainly controlled by shell matrix proteins, has been used as a representative model to understand the biomineralization mechanism. In this study, in vitro calcium carbonate crystallization was carried out under room temperature and atmospheric pressure using recombinant shell matrix protein GRP_BA and artificial shell matrix protein GG1234. Both proteins inhibited the growth of typical rhombohedral calcite crystals in the calcium carbonate crystallization using $CaCl_2$ solution and $(NH_4)_2CO_3$ vapor, and spherulitic calcite crystals with rosette-like structures were synthesized in both the presence of GRP_BA and GG1234. These results might be caused by the properties of block-like domain structure and intrinsically disordered proteins. We expect that this study can contribute to enhance understanding of the calcium carbonate biomineralization controlled by shell matrix proteins.

• Composites Research
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• v.35 no.2
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• pp.93-97
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• 2022

The application of infrared heating in the hot press forming of the thermoplastic composites is conducive to productivity with high-speed heating. However, high energy, high forming temperature, and high-speed heating derived from infrared heating can cause material degradation and deteriorate properties such as re-melting performance. Therefore, this study was conducted to optimize the process conditions of the hot press forming suitable for carbon fiber reinforced polyetherketoneketone(CF/PEKK) composites that are actively researched and developed as high-performance aviation materials. Specifically, the degradation mechanisms and properties that may occur in infrared high-speed heating were evaluated through morphological and thermal characteristics analysis and mechanical performance tests. The degradation mechanism was analyzed through morphological investigation of the crystal structure of PEKK. As a result, the size of the spherulite decreased as the degradation progressed, and finally, the spherulite disappeared. In thermal characteristics, the melting temperature, crystallization temperature and heat of crystallization tend to decrease as degradation progresses, and the crystal structure disappeared under long-term exposure at 460℃. In addition, the low bonding strength was observed on the degraded surface, and the bonding surfaces of PEKK did not melt intermittently. In conclusion, it was confirmed that the CF/PEKK composite material degraded at 420℃ in the infrared high-speed heating. Furthermore, the spherulite experienced morphological changes and the re-melting properties of thermoplastic materials were degraded.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.445-453
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• 2013

The Uiseong Tapriri Five-Storied Stone Pagoda (National Treasure No. 77) is typical stone cultural heritage in Unified Silla Dynasty, Korea. The pagoda has been occurred black, brown discoloration and microcrack, exfoliation, granularity decomposition with white discoloration because of continuous weathering. As the results of analysis for the contaminants, chemical weatherings are generated that black contaminant by manganese oxide, brown contaminant by iron oxide, white contaminants by gypsum and taranakite. And physical weatherings, such as microcrack, exfoliation, are occurred by salt(gypsum) crystallization. Therefore, these need to remove the contaminants according to the conservation treatment manual, and regular monitoring using P-XRF to preserve long-term the Five-Storied Stone Pagoda at Tapri-ri, Uiseong.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.750-758
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• 1994

The purpose of present study is to find out the formation mechanism of hemi-spherical grained(HSG) polysilicon film. Silicon film was deposited using LPCVD. Polycrystalline silicon film was deposited at $575^{\circ}C$ contained crystalline HSG in the amorphous matrix phase. The crystalline HSG can be categorized into two grains : lower grains and upper grains. Lower grains are located at interface between silicon dioxide and silicon film, and upper grains are located at surface. The growth orientations of HSG were identified as (311) or (111) directions for lower grains and perferentially (110) direction for upper grains. This difference of growth orientations seems to be caused by the difference of formation mechanisms. That is, lower grain is formed by soild phase crystallization, on the other hand, upper grain is formed by surface diffusion of silicon atoms. It was thus, proposed that the formation of practical HSG polysilicon film is mainly controlled by surface diffusion of silicon atoms.

• Korean Journal of Materials Research
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• v.6 no.3
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• pp.309-317
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• 1996

세가지 다른 방법을 이용하여 형성시킨 비정질 실리콘(SiH4 a-Si, Si2H6 a-Si, Si+ implanted SiH4 a-Si)들에 대한 저온 결정화 기구의 차이를 고전적 이론인 Avrami 식(X=1-exptn, X=결정화 분율, t=열처리 시간, n=지수)을 이용하여 검토하였다. Silane으로 형성된 비정질 실리콘의 결정화 과정에서는 Avrami 식에서의 n의 값이 2.0을 나타내고 있어, 결정성장이 이차원적으로 이루어지면서 핵생성률이 시간에 따라 감소하고 있음을 알 수가 있었다. Si+ 이온 주입에 의하여 형성된 비정질 실리콘의 결정화에서는 3.0의 지수 값이 얻어지고 있어, 정상상태의 핵생성과 함께 2차원적인 결정 성장이 이루어지고 있었다. Disilane으로 형성된 비정질 실리콘에 대한 결정화에서는 2.8의 지수값이 얻어져, 정상상태의 핵 생성이 우세하게 일어나는 2차원적인 결정성장이 일어나고 있음을 알 수 있었다. 또한 TEM을 이용하여 시간에 따라 변하는 핵생성률을 조사하여, Avrami 식의 적용이 타당성 있음을 증명하였다. 마지막으로, 최종 입자의 크기가 열처리 온도에 크게 영향을 받고 있지 않음을 확인하였다.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.236-240
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• 2012

The reticulated carbon foam have been used for their excellent properties in terms of thermal management which is getting important in industrial field currently. In this study, we measure the mechanical properties of the reticulated carbon foam which is heat-treated at various temperature from the prepared low-density phenol foam. Simultaneously, we observe microstructures with high resolution transmission microscope and measure the residual oxygen content of carbon foams to figure out the relationship between the apparent change of properties such as weight loss and linear shrinkage during heat treatment. In conclusion, the carbon foam heat-treated at $1400^{\circ}C$ shows the highest strength, and the mechanical behavior is believed to be strongly related to the creation of nano-size graphite crystals from the amorphous carbon during heat treatment. On the other hand, it is turned out that the weight loss occurred at the temperature under $1400^{\circ}C$ comes from the elimination of oxygen in the form of $CO_2$ or CO, but no evidence is found on weight loss mechanism at the temperature above $1400^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2056-2062
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• 2013

The dihydroxy naphthalene/$TiO_2$ complexes with different substitution patterns were prepared by surface modification. X-ray diffraction, UV-Vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared composite materials. The results indicated that the surface modification did not influence the crystallization of $TiO_2$. The visible-light absorbances of prepared dihydroxy naphthalene/$TiO_2$ complexes could be assigned to the ligand-to-metal charge transfer. The obtained catalyst exhibited outstanding photocatalytic activity and stability under visible light. A linear relationship existed between the percentages of hydroxynaphthalenes coordinated on $TiO_2$ surface and $H_2$ production ability. The substitution pattern of dihydroxy naphthalene and $CH_3OH$ content could also influence the photocatalytic performance remarkably. The photocatalytic $H_2$ production ability was further improved after loading with ultra low concentration of Pt, 0.02 wt %. The possible mechanism was proposed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.205-210
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• 1998

$Li^+$ and $Mo^{6+}$ containing huntite borates $YbAl_3(BO_3)_4$were grown by spontaneous crystallization. All crystal show only the huntite-borate phase detected by X-ray powder diffraction analysis. On the basis of the data of the composition analysis, the occupation mechanism of each cation in the huntite structure has been discussed. $Li^+$ and $Mo^{6+}$ containing $YbAl_3(BO_3)_4$shows a six times higher intensity of the green light SHG detected by the powder technique than YAl_3(BO_3)_4$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.47-50
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• 1999

The orientation mechanism of an amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ phase were studied by using the dilatometry. The amorphous $Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ samples brought about a volume shrinkage at the onset of the crystallization of a $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{6}$phase around $400^{\circ}C$. The random crystal growth of $Bi_{2}$$Sr_{2}$$CaCu_{2}$$O_{8}$ phase around $800^{\circ}C$. yielded a rapid volume expansion and after then samples shrinmed, accompanied with the crystal orientation. The$Bi_{2}$$Sr_{2}$$Ca_{2 x}$$Cd_{x}$$Cu_{3}$$O_{y}$ (x=0.4) sample exhibited the best-oriented structure because the liquid phase formed seemed to have the lowest viscosity which would contributed to the easy collapse of the card-house structure.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.69-77
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• 2016

We propose nano-scale Cu direct bonding technology using ultra-high density Cu nano-pillar (CNP) with for high stacking yield exascale 2.5D/3D integration. We clarified the joining mechanism of nano-scale Cu direct bonding using CNP. Nano-scale Cu pillar easily bond with Cu electrode by re-crystallization of CNP due to the solid phase diffusion and by morphology change of CNP to minimize interfacial energy at relatively lower temperature and pressure compared to conventional micro-scale Cu direct bonding. We confirmed for the first time that 4.3 million electrodes per die are successfully connected in series with the joining yield of 100%. The joining resistance of CNP bundle with $80{\mu}m$ height is around 30 m for each pair of $10{\mu}m$ dia. electrode. Capacitance value of CNP bundle with $3{\mu}m$ length and $80{\mu}m$ height is around 0.6fF. Eye-diagram pattern shows no degradation even at 10Gbps data rate after the lamination of anisotropic conductive film.