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산화 바나디움, 몰리브데늄, 리티움계 융제법에 의한 합성 Emerald 단결정 육성
최의석,김무경,이종민,안영필,서청교,안찬준 한국결정성장학회 1996 한국결정성장학회지 Vol.6 No.1
천연 베릴을 이용하여 $V_20_5$, $Mo0_3$, $Li_2O$계 융제 및 첨가제 조성, 베렬의 용해도 그 리고 결정성장 온도와 같은 결정성창 조건을 제어하여 에메랄드 단결정을 성장시켰다. Flux와 첨가제를 조정하여 저온($1100^{\circ}C$ 이하)에셔 용해성이 높은 과포화 용융체를 만들고 온도 구배 (${\Delta}t 100^{\circ}C$), 열진동 효과 등을 정멀 제어 조정하므로써 고품질의 대형 emerald 단결정을 성장 시킬 수 있었다. 성장된 에메랄드 단결정의 특성은 굴절률 : 1.56 - 1.57, 비중 : 2.65 - 2.67인 6각 주상($c^*m$ : 1000, 1010)의 취록색 투명 단결정이였다. Emerald (3BeO{\cdot}Al$_{2}$O_{3}{\cdot}6SiO_2 : Cr^{3+}$) single crystals were grown by flux method of $Li_2O-MoO_3 - V_2O_5$ system. The composition of starting materials were 1, 3, 5 mole ratio of $MoO_3 - V_2O_5/$Li_2O$, 20 - 15% of emerald content to flux composition and 1% of $Cr_2O_3$ colordopant to emerald composition. After mixing those were melted at $1100^{\circ}C$ in Pt crucible of electric furnace. Single crystal growth was cooled down slowly rate of $3^{\circ}C$/hr from $1100^{\circ}C$ to $650^{\circ}C$, for the cooling period it was controlled and prevented the nucleation of microcrystallite from variation of each thermal fluctuation range. Specially it has been obtained plenty of large emerald single crystal when thermal fluctuation was treated for cooling period at $1050 ~ 950^{\circ}C$, in 3 mole ratio of $V_2O_5 - MoO_3/Li_2O$ flux. Emerald single crystal growing effect and $Cr_{+3}$ ion of substitutional solid solution effect for $Al_{+3}$ ion was good than mole ratio of 5. Emerald single crystals were c (0001) hexagonal rystal face of preferencial direction and m (1010) post side. Emerald was hexagonal columnar greenish transparent and 2.65 ~ 2.66 of specific gravity.
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천연베릴을 이용한 온도구배 환류법에 의한 합성 Emerald 단결정 육성
최의석,김무경,안영필,서청교,안찬준,이종민 한국결정성장학회 1998 한국결정성장학회지 Vol.8 No.4
한국산 천연베릴을 잉요하여 온도구배융제환류법에 의해 에메랄드($3BeO{\cdot}Al_2O_3{\cdot}6SiO_2:Cr^{3+}$) 단결정이 성장되었다. 리튬-몰리브데늄-바나디움 산화물계 융제는 $(MoO_3+V_2O_5)/Li_2O$, 와 $V_2O_5-Li_2O$를 서로 다르게 용융한 2종류의 융제를 혼합하여 제조하였다. 융제의 최적 조성은 산화몰리브데늄.바나디움에 대한 산화리튬의 몰비($(MoO_3+V_2O_5)/Li_2O$)가 3몰이었고 융제첨가제는 Li2O량에 대하여 $K_2O$ 또는 $Na_2O$를 0.2mole% 이내로 치환하였다. 베릴원료의 용융 농도는 융제량에 대하여 3~10% 함량이었고, $Cr_2O_3$ 발색제는 베릴량에 대하여 1%이었다. 융액은 용융, 성장, 회수 블록으로 나뉘어진 3지대 온도구배 결정성장로에서, $1100^{\circ}C$와 $1000^{\circ}C$ 사이의 안정상태에서 연속적으로 순환되도록 하였다. 에메랄드 단결정은 성장지대에서 950~$1000^{\circ}C$ 구간에서 1일 1회 2시간동안 열진동 처리하였을 때 미소핵의 생성이 억제된 대형 단결정을 성장시킬 수 있었다. 육각주상 에메랄드 단결정의 우선성장방향은 c(0001) 바닥면이었고, m(1010) 기둥면에 수직이었다. Emerald ($3BeO{\cdot}Al_2O_3{\cdot}6SiO_2:Cr^{3+}$) single crystal was grown by temperature gradient reflux method with using Korean natural beryl. The flux of lithium-molibudenium-vanadium oxide system was made by means of mixing the 2 sort of flux which were differently melted $Mo_3-Li_2O$ and $V_2O_5-Li_2O$ each other. The optimum composition of flux was 3 mole ratio of molibudenium. vanadium oxides to lithium oxide ($(MoO_3+V_2O_5)/Li_2O$), flux additives were substituted more less then 0.2 mole% of $K_2O$ or $Na_2O$ to the $Li_2O$ amount. The melting concentration of mixing beryl material was 3~10% content to the flux, that of $Cr_2O_3$ color dopant was 1% to the beryl amount. In the crystal growing apparatus with temperature gradient in the 3 zone furnace which was separated into the block of melt, growth and return, the solution have got to circulate continuously between $1100^{\circ}C$ and $1000^{\circ}C$ in steady state. When thermal fluctuation was treated to during 2 hrs once on a day at 950~$1000^{\circ}C$ in growth zone, the supersaturation solution was maintained, controled and emerald single crystal can be grown large crystal which was prevented from the nucleation of microcrystallite. The preferencial growth direction of hexagonal columnar emerald single crystal was the c(0001) plane of botton side and vertical to the m(1010) plane of post side.
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안영필,최의석,김복희 한국세라믹학회 1982 한국세라믹학회지 Vol.19 No.2
As raw materials wollastonite, kaolin and pyrophyllite were used to synthesize mullite, anorthite and pseudowoll-astonite which were known as low thermal expansion substance. Increasing the amount of wollastonite in the composition resulted in a linear thermal expansion behavior. However, the increases of pyrophyllite indicated the relatively unstable themmal expansion behavior, because the phase transition occured in quartz of the pyrophyllite compositon. To lowering sintering temperature feldspar (Kebook and Anyang) were added in the composition that showed the linear thermal expantion behavior, and over 50'C were lowered.
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박종옥,최의석,이철효,이종민 한국세라믹학회 1986 한국세라믹학회지 Vol.23 No.2
Pure submicron $SrTiO_3$ powders had been synthesized with chemical wet process that $5N-NH_4OH$ solution was sprayed into the mixed solution of $SrTiO_3$, $TiCl_4$ and $H_2O_2$ with $N_2$ carrier gas. The characteristic properties of powders obtained from this experiment were as follows. The optimum synthesis condition in reaction bath was above PH 8.5 and under $25^{\circ}C$ The particle size of precipitated SrTiO(OH) powders dried at 6$0^{\circ}C$ was under 0.01${\mu}{\textrm}{m}$ and uniform. Amorphous precipitated complex powders emitted adsorbed water at 15$0^{\circ}C$ less that and crystalline $SrTiO_3$powders was produced from calcining the complex at 30$0^{\circ}C$. Sintered body of SrTiO3 fired at 133$0^{\circ}C$ showed that relative dielectric constant was 228 at 1MHZ and bulk density was 4.73g/$cm^3$.
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RF 마그네트론 스퍼터링을 이용한 태양전지용 질화 실리콘 반사방지막
최균,최의석,황진하,이수홍,Choi, Kyoon,Choi, Eui-Seok,Hwang, Jin-Ha,Lee, Soo-Hong 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.10
Silicon nitride films for an anti-reflection coating were deposited on silicon via RF magnetron sputtering using a $Si_3N4$ target. The best result was obtained at the sputtering condition of 340 W RF power, 5 mtorr Ar atmosphere, $100^{\circ}C$ substrate temperature. The films showed 7.9% reflectance minimum with 2.35 refractive index. 0.21 absorption coefficient at 66.6 nm thickness. The surface morphology showed a smooth and dense film with good adhesion to silicon surface.
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Cemented Carbides에서의 입성장 기구와 입성장 억제를 위한 제안
최균,최의석,황농문,김도연 한국분말야금학회 2001 한국분말야금학회 학술대회논문집 Vol.2001 No.1
WC-Co 계의 입성장 억제는 현재 초경합금 분야에서 공학적으로 가장 중요한 이슈들 중의 하나이다 VC를 비롯한 입방정 탄화물이나 등의 여러 가지 탄화 물이 혼합되어 입성장 억제에 이용되는데 입성장 억제의 효과는 대략적으로 용해되는 탄화물의 양에 의존하고 있는 것으로 추정된다. 보다 효율적으로 입성장 억제를 실현하려면 입성장 기구를 명확히 할 필요가 있다. 최 등[1]은 VC가 WC 입자 표면 에서의 edge energy를 증가시켜서 2차원 핵생성의
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김복희,최의석,최석홍,이태석 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.1
Monodispersed PZT fine particles were obtained from the condition which 0.2Pb (OC3H7)2/EtOH, 0.108Zr(OC4H9)4/EtOH and 0.092 Ti (OC2H5)4/EtOH were refluxed for 5 hrs at 76$^{\circ}C$ and hydrolyzed with 0.1-0.4 H2O/EtOH. The monodispersed particle was amorphous and crystallized to the tetragonal PZT phase when heated at $600^{\circ}C$. Particle size was about 0.55${\mu}{\textrm}{m}$ in 0.3 H2O/EtOH and 0.3${\mu}{\textrm}{m}$ in other cases. Relative density of sintered body at 90$0^{\circ}C$ and 100$0^{\circ}C$ was 93.5% and 98%, respectively.
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