• 한국결정성장학회지
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• 제18권2호
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• pp.68-71
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• 2008

승화법에 의하여 AlN 결정을 성장하였다. 성장된 결정의 상은 미세한 단결정상이 응집된 다결정상이었으며, 약 2${\sim}$3mm의 길이와 직경 1인치의 크기로 증착되어진 성상을 얻었다. 성장된 결정의 표면에 탄소의 흡착이 관찰되었으며, 광학현미경과 SEM을 통하여 AlN 결정의 성장 거동에 대하여 고찰하여 보았다.

• 한국정보처리학회논문지
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• 제7권3호
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• pp.872-878
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• 2000

In this paper a computer programming for the expression of nearest neighbor atoms in face-centered cubic (FCC) and body-centered cubic (BCC) crystals was suggested as one of the approaches to understand each of the crystal structure. By using this computer programming the distance values between a reference atom and the nearest neighbor atoms, and the numbers of the nearest neighbor atoms were calculated ane compared for the FCC and BCC crystals. In this algorithm, the positions of the atoms in a crystal were defined as two categories: the corner atoms and face- or body-centered atoms, and considered respectively. For the same order of nearest neighbor atoms except the second order ones the distance values form the reference atom were smaller in the FCC crystals than those in the BCC. Also, the numbers of he first and third nearest neighbor atoms n the FCC crystals were larger than those in the BCC. This difference was explained by the comparison of each atomic packing ratio of the FCC and BCC crystals. The algorithm used in this programming can also be expanded to the analysis of other crystal structures.

• Bulletin of the Korean Chemical Society
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• 제20권4호
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• pp.417-421
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• 1999

The complex, K3[La(TTHA)]5H,O, was prepared and its crystal structure was analyzed by single crystal X-ray diffraction method. In the complex, the La(Ⅲ) ion adopts a ten-coordinate geometry with four nitrogen atoms and six carboxyl oxygen atoms from the same TTHA ligand molecule. Its coordination polyhedron can be described as a distorted bicapped square antiprism. Each [La(TTHA)]3- anion is linked by K+ cations via carboxyl groups of TTHA ligand to form a three dimensional crystal structure. The thermal properties were investigated by TG and DTA techniques in argon atmosphere. The materials resulting from thermal treatment were La(OH)3 and K2O which were identified by powder X-ray diffraction technique.

• 한국결정성장학회지
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• 제12권2호
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• pp.91-95
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• 2002

Titannium tetra-isoporpoxide의 가수분해 반응을 이용하여 nanosize의 $TiO_2$powder를 합성하고, 가수분해 반응에 있어서 촉매로 사용되는 HCI과 $NH_4$OH의 첨가량에 따른 반응양상과 생성된 $TiO_2$분말의 특성의 변화를 조사하였다. 염기성 촉매인 $NH_4$OH,를 사용하였을 경우에 균질한 형상의 powder 형태의 $TiO_2$를 합성할 수 있었으며, 산성 촉매인 HCI을 사 용하여 p보가 5.04 이하일 경우에는 괴상이나 과립의 형태로 생성되었다. 사용한 촉매의 종류와 양에 따라 저온의 결정상인 anatase의 생성속도와 보다 안정한 rutile상으로의 상전이 속도가 영향을 받았다.

• 한국결정성장학회지
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• 제7권4호
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• pp.626-631
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• 1997

하동고령토($Al_2O_3-SiC-C$)를 출발원료로하여 AlSiCa내화재 원료를 합성하였다. 하동고령토와 탄소분말을 혼합하여 수소분위기하에서 반응시킨결과, $1300^{\circ}C$에서$Al_2O_3-SiC-C$ 복합체가 힙성되기 시작하여$1400^{\circ}C$에서 완전 합성되었고, $SiO_2$에 대한 최적carbon량은 mole비로 1:4이었다. 합성시 알루미나 용기에 탄소분말을 충전시키지 않을 때는 미합성부분이 없이 밝은 녹색을 띈 $\beta$-SiC(cubic form) 를 형성함을 확인하였다.

• 한국염색가공학회지
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• 제17권4호
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• pp.41-47
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• 2005

Costume heritages of an excavated silk fabrics should be preserved without damage. In order to artificially restore the excavated silk fabrics, alkaline aqueous solution, as a simulated corpse, and two kinds of silk fabrics were used. Two kinds of silk fabrics were treated by aqueous alkaline solution according to strength retention value(100, 80, 60, 40, 20$\%$). The fine structure and physical properties of alkaline treated silk fabrics were investigated with various techniques such as wide-angle X-ray diffraction, tensile test, weight loss, shrinkage, SEM. and yellowness. As the alkaline treatment time increased tensile strength of silk fabrics decreased. However, weight loss and shrinkage slightly increased. The diffraction intensity of $\beta-form$ crystal declined and $\alpha-form$ crystal diffraction intensity disappeared with the treatment.

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.214-219
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• 1991

To study the effect of solvents and counterions in Z-DNA crystal of d(5BrC-G-5BrC-G-5BrC-G), we performed the local energy analysis and then molecular dynamics simulations. Since counterions raise serious caging problems in crystal simulations, it is very important to search for the possible positions before simulations. For this purpose, the local energy analysis was done for the whole crystal volume. It is shown from our simulation that counterions along with water molecules play a bridging role to bind adjacent oligomers so as to form the crystal. In this crystal, each water molecule bound to Gua-N2H, either directly or indirectly, hydrates the adjacent anionic phosphate oxygen, and thus assists Gua to be in a syn position. From the simulation, the average root-mean-square deviation of allthe DNA heavy atom coordinates from the X-ray data is $0.99{\AA}$ . The bases are less deviated from the X-ray positions than the phosphates. The temperature factors from the simulation are consistent with those from the X-ray refinement, showing that the phosphates are more mobile than the bases.

• 한국결정성장학회지
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• 제32권1호
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• pp.16-24
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• 2022

A computational study of combined thermal and solutal convection (double diffusive convection) in a sealed crystal growth reactor is presented, based on a two-dimensional numerical analysis of the nonlinear and strongly coupled partial differential equations and their associated boundary conditions. The average Nusselt numbers for the source regions are greater than those at the crystal regions for 9.73 × 10³ ≤ Gr_t ≤ 6.22 × 10⁵. The average Nusselt numbers for the source regions varies linearly and increases directly with the thermal Grashof number form 9.73 × 10³ ≤ Gr_t ≤ 6.22 × 10⁵ for aspect ratio, Ar (transport length-to-width) = 1 and 2. Additionally, the average Nusselt numbers for the crystal regions at Ar = 1 are much greater than those at Ar = 2. Also, the occurrence of one unicellular flow structure is caused by both the thermal and solutal convection, which is inherent during the physical vapor transport of Hg₂Br₂. When the aspect ratio of the enclosure increases, the fluid movement is hindered and results in the decrease of thermal buoyancy force.

• 한국의류학회지
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• 제11권3호
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• pp.33-40
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• 1987

PET FDY was heat set at various temperatures and times and the microstructural changes was investigated through crystallinity, birefringence and melting behavior analyses. Crystallinity of heat set PET increased as the treatment temperature and time increased. Birefringence also increased as temperature and time increased. The melting behavior of heat set PET was as follows: In most cases, PET showed double melting peaks. As temperature and time increased, form II crystal became sharp and increased in size, and form I crystal decreased in size. The slower the heating rate, the higher the programmed heating effect during DSC analysis.

• 약학회지
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• 제41권3호
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• pp.321-327
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• 1997

Investigation of polymorphism has become a requirement in the pharmaceutical industry because the physical properties and bioavailabilities of crystalline drugs depend on their polymorphic form. Five polymorphic modifications and one pseudopolymorphic modification of ecphalothin sodium were prepared by recrystallization, and characterized by UV spectrophotometer, DSC, TGA and X-ray crystallography. The solubilities of all modifications were examined by the disslution test. Form 2 and 1 showed higher solubilities than any other crystal forms. The modifications were also investigated for their stability after storage of 2 months at 100%, 76%, 52% and 0% humidity.