에멀젼을 이용한 $Al_2O_3$-$ZrO_2$복합분체의 제조 : III. 에멀젼-공침법

현상훈,김의수 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.4

$Al_2O_3$-20w/o $ZrO_2$ composite powders were prepared by the emulsion-coprecipitation method and the effects of preparative conditions on powder characteristics were investigated. In the preparation of $Al_2O_3$-$ZrO_2$ composite powders, toluene was used instead of kerosene as the oil phase in emulsions. After coprecipitation, the emulsion was easily broken into a single liquid phase by adding methanol, and then precipitates could be effectively collected by filteration. The fact that all $ZrO_2$ phases present at room temperature in composite powders calcined at $1100^{\circ}C$ after washed by methanol had a tetragonal structure confirmed that methanol-washing enhanced the dispersibility of fine $ZrO_2$ particles in $Al_2O_3$ matrix. $Al_2O_3$-$ZrO_2$ composite powders were spherical particles of 0.2${\mu}{\textrm}{m}$ diameter. Pellets sintered at $1650^{\circ}C$ for 2hrs showed the relative theoretical density of 97.3% and the fracture toughness of 5.01MN/$m^{3/2}$.

극미세 입자 Aluminosilicate 계 졸의 합성 및 응용 : (Ⅰ) SiO₂및 γ-AIOOH졸의 제조 및 케릭터라이제이션

현상훈,송재권,강범석 연세대학교 산업기술연구소 1993 논문집 Vol.25 No.1

Nanoparticulate silica sols could be synthesized by an interfacial hydrolysis reaction between TEOS and high alkaline water. The silica sols were extremely stable at pH of 8 and their average particle sizes were less than 3 nm, while very unstable between 4 and 5 of pH. The sol particles grew up to about 10 nm within 1 day in the region of pH less than 7. It was found that the silica sol with pH less than 2 was stabilized without further growing after 1 day-aging. The particle size of γ-AlOOH sols synthesized via the modified Yoldas-method could be controlled according to the mole ratio of nitric acid/aluminium tri-sec-butoxide(0.07∼1.0). The stable γ-AlOOH sol with the average particle size of 45 nm, which was prepared using the mole ratio of 0.07, was estimated to be suitable for coating reproducible γ-AlOOH membrane layers with the high specific surface area.

황화물의 화학수송반응에 관한 연구

현상훈,이강호 연세대학교 산업기술연구소 1984 논문집 Vol.16 No.2

The flow method of a chemical transport reaction was examined to investigate the migration property of sulfides in the temperature gradient. The effect of reaction parameters on the transport amount of sulfides was analyzed using a model developed in this study. When I₂was used as a transport agent, SnS was more transportable than any other sulfides(i.e., CdS, ZnS, and PbS), while MnS, NiS and FeS gave no measurable transport. The experimental result showed that the mixture of α-ZnS and β-ZnS was effectively transported in the form of cubic β-ZnS single crystal (purity of about 100%), under the reaction conditions of the temperature gradient of 1273 →1023 K, initial iodine pressure of about 159 ㎜ Hg, and flow rate of 0.1 cc/sec.

$Al_2O_3-ZrO_2-Spinel$계 복합체의 미세구조 및 물성제어: II. 용액침투법에 의한 $Al_2O_3-ZrO_2-Spinel$ 복합소결체

현상훈,송원선 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.10

Al2O3/ZrO2-Spinel composites were prepared by infiltrating magnesium sulfate solution into the porous preform made from Al2O3-20wt% ZrO2 composite powders derived through an emulsion route. The microstructure and composition of the modified composites could be controlled by manipulating the presingtering temperature of the preform, infiltration time, and so on. It was found that spinel phases were concentrated near the surface than in the interior of the Al2O3/ZrO2-Spinel composites infiltrated for 6hrs, while spinel phases were uniformly distributed in the comosites infiltrated for 2 days. The relative density and fracture toughness of the composite infiltrated for 6 hrs were 98.6% and 7.2MN/m3/2, respectively.

모의 폐기물유리의 화학적 내구성

현상훈,송원선 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.4

The dependence of the chemical durability of simulated waste glasses containing the simplified waste similar to the SRP waste on compositions of host glasses, amounts of waste loading, and kinds of leachants has been investigated as a basic study on the waste immobilization through vitrification. The maximum limit of the amount of waste loading for glassforming with the host sodium borosilicate glasses selected in this study was 50wt%. The chemical durability of waste glasses whose host glass belonged to the immiscible composition region was much higher than that of waste glasses whose host glass belonged to the miscible composition region. The former waste glass showed lower chemical durability in deionized and silicate waters than in brine, while the latter glass showed the lowest chemical durability in deionized and silicate waters than in brine, while the latter glass showed the lowest chemical durability in silicate water. It was also observed that the total leaching rates in brine were noticeably small in comparison with those in other solutions. The composition of the host borosilicate glass which was suitable for the treatment of the waste through vitrification was found to be 25 Na2O-5B2O3-70SiO2(wt.%).

MgO-Al2O3-SiO2계 요업원료의 제조 및 소결특성 -에멀젼법에 의한 Mullite분체의 저온합성-

현상훈,이희수,송승룡 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.3

Mullite powders were synthesized from the common solution of aluminum sulfate and sodium silicate solutions by the emulsion-hot kerosene technique. The reaction temperature and mechanism for mullitization and the characteristics of synthesized mullite powders were investigated. The effect of Na components introduced from sodium silicate solution on the physical property and microstructure of sintered mullite was also examined. It was proved that mullites were formed at 75$0^{\circ}C$ through the reaction mechanism of Na2O.2.2SiO2+3.3Al2(SO4)3longrightarrow1.1(3Al2O3.2SiO2)+Na2SO4+8.9SO3. Synthetic mullite powders consisted of the compositiion of 3Al2O3.2SiO2 and showed highly agglomeration of hollow spherical particles of 1${\mu}{\textrm}{m}$ diameter. The density and fracture toughness of sintered mullites were somewhat reduced because of the effect of a very small amount of residual Na components.

극미세 입자 Aluminosilicate 계 졸의 합성 응용(III) 단일상 Aluminosilicate 졸

현상훈,이성철 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.1

에멀젼을 이용한 Al2O3-ZrO2 복합분체의 제조 : II. 에멀젼-가열석유 증발법

현상훈,백종규 한국세라믹학회 1988 한국세라믹학회지 Vol.25 No.3

Alumina-zirconia composite powders for the purpose of improving fracture toughness and thermal shock resistance of alumina were prepared by the emulsion-kerosene drying method. The average particle size of composite powders was less then 1 $\mu\textrm{m}$ and their shapes were spherical. It was shown that the average particle size of composite powders decreased with the concentration of metal-salt in solution and the amount of span 80 added when preparing emulsions. The structure of all zirconia in composite powders heat-treated at 1200$^{\circ}C$ was a tetragonal form at room temperature. This result implied that fine zirconia particles were homogeneously dispersed in the alumina matrix.

제올라이트 복합 분리막의 합성 및 특성화(I): ZSM-5계 제올라이트의 합성

현상훈,김준학,송재권 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.9

The synthetic conditions and characteristics of ZSM-5 type zeolites (ZSM-5/silicalite) for the preparation of the zeolite composite membranes for gas separation were investigated. ZSM-5 zeolites could be synthesized by the hydrothermal treatment of the mixture of colloidal silica sol aluminum nitrate sodium hydroxide and TPABr at a temperature range of 150-17$0^{\circ}C$ in the autoclave. Silicalties were done from the solution of water glass water and TPABr. Their crystalline structures transformed from orthorhombic to monoclinic from and their pore structures of three-dimensional channels were opened as TPABr filling channels was burned off at the calcination temperature of 50$0^{\circ}C$. The specific surface area of the calcined zeolite was about 360 m3/g and its surface property was hydrophobic. Crystal sizes of ZSM-5 and silicalite were 0.5-1.0${\mu}{\textrm}{m}$ and 8-10${\mu}{\textrm}{m}$ respectively having no change due to the calcination. In particular the shape and the size of the ZSM-5 type zeolite were sensitively varied with silica sources and concentrations of reaction solutions/sols.

$TiO_2$ 복합 분리막의 제조를 위한 졸-겔 코팅공정 분석

현상훈,최영민 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.5

The titania membrane thickness coated on the porous alumina support by the sol-gel method was analyzed using the slipcasting model. The thickness of calcined membrane layers increased linearly from 1.3 to 3.8 ${\mu}{\textrm}{m}$ with the square root of the dipping time (4~40 min). Growth rates of the thickness of wet gels and calcined layers were well described quantitatively by the slipcasting model. Through the regression of experimental data using model equations, the permeability and the pressure drop across wet gels, and the thickness and their growth rate constants of wet gels and calcined layers could be determined. It was also known that the gellation concentration of the TiO2 sol used in this work and the porosity of wet gel layes were 25 mol/ι and 0.53, respectively.