BaTiO$_3$ 세라믹스의 전기저항에 미치는 첨가제와 냉각속도의 영향(I) - TiO$_2$, SiO$_2$ 및 Al2O$_3$ 단미첨가 -

염희남,하명수,이재춘,정윤중 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.9

Microstructure, room temperature resistivity and temperature coefficient of resistance of BaTiO3 ceramics were studied by varying cooling rates and additives such as TiO2, SiO2 and Al2O3. The basic composition of the BaTiO3 ceramics was formed by adding 0.25 mol% Dy2O3 and 0.07 mol% MnO2 to the BaTiO3 composition. Unlike the additives of SiO2 and Al2O3, an addition of 2 mol% TiO2 to the basic composition was effective to control the grain size of the fired specimens. The room temperature resistivity and the temperature coefficient of resistance for the specimen of this particular compostion were measured as about 102 ohm.cm and 16.5%/$^{\circ}C$, respectively. The observed grain boundary phase of the sample with Al2O3 additive was BaTi3O7, while that of the samples with SiO2 additive was confirmed as BaTiSiO5.

고밀도 탄소재 제조시의 함침효과

염희남,김경자,이종민,정윤중 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.10

The effect of coal tar ptch-impregnated carbon materials which were made from petroleum coke was investigated at various pressure time and impregnation-sintering cycle. As a result, density and bending strength of the carbon materials were remarkably increased in the condition of pressure times of 5hrs and of the cycle of 3rd times. And the value of d002 and Lc of the graphitic carbon sintered at 230$0^{\circ}C$ shwoed 3.387$\AA$ and 167$\AA$, respectively.

Aluminum 촉매에 의한 석유 Cokes의 흑연화

염희남,김경자,정윤중 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.6

The effect of catalytic graphitization of petroleum cokes by the addition of aluminum were investigated. The degree of graphitization carbon body only fired at 230$0^{\circ}C$ was 0.5. But when the aluminum additive was added, the degree of graphitization was increased to 0.93. And Ts-effect was appeared as the catalytic effect. This effect was occurred by the formation-decomposition of aluminum carbide through the reaction of aluminum and cokes.

Raw Coke의 하소온도에 따른 구조변화

염희남,장진석,이종민,정윤중 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.10

The effect of temperature on the structural changes of petroleum raw coke during calcination was studied and then the properties of carbon solids prepared from those calcined coke using binder were examined. The notable structural change of raw coke was observed in the range from 800$^{\circ}C$ to 900$^{\circ}C$ from the results of volatile matter, porosity, X-ray diffraction and scanning electron microscopy. The bending strength, density of the carbon solid carbonized at 1400$^{\circ}C$ was 400 kg/$\textrm{cm}^2$ and 1.40g/㎤, respectively.

탄소재 제조에 있어서 Raw Coke의 전처리의 영향

염희남,황인수,이종민,정윤중 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.1

The influence of ground petroleum coke, preheat-treated at temperatures ranged of 150~35$0^{\circ}C$, was studied. It has been found that the coke powder preheat-treated at the temperature of 175$^{\circ}C$ has been spherical-shaped in grinding and have showed the highest strength and density in sintering. The coke powder was also the best for the binding force and the (H/C) values showed 0.45 at the above temperature.

Raw Cokes의 흑연화 및 내산화성에 미치는 $B_4C$첨가 효과

염희남,김경자,김인기,정윤중 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.4

The specimens which were prepared from cokes with additions of 0~25 wt% B4C were sintered in Ar atmosphere at 220$0^{\circ}C$. The effects of B4C content on graphitization and oxidation resistance of cokes were investigated. B4C accelerates the graphitization of cokes and at 220$0^{\circ}C$ the degree of graphitization increased from 0.33 which is the value of pure carbon to 0.56, which increased bluk density and porosity. Especially bending strength increased as th graphitization temperature increased. Oxidation resistance property was greatly improved when B4C was added more than 10wt% at 80$0^{\circ}C$ and when B4C was added more than 20wt% at 100$0^{\circ}C$. This was because that the thin layer of B2O3 glass phase on the surface of the composite could be identified to increase the oxidation resistance.

$BaTiO_3$ 세라믹스의 전기저항에 미치는 첨가제와 냉각속도의 영향: (II) $TiO_2$, $SiO_2$ 및 $Al_2O_3$ 복합첨가

염희남,하명수,이재춘,정윤중 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.10

Microstructure, room temperature resistivity and temperature coefficient of resistance of BaTiO3 ceramics were characterized and measured in this study. The basic composition of the BaTiO3 cremics was formed by adding 0.25 mol% Dy2O3 and 0.07 mol% MnO2 to the BaTiO3 composition. Samples of the BaTiO3 ceramics were prepared by adding various amounts of the TiO2, SiO2 and Al2O3 to the basic composition. An addition of 1 mol% TiO2, 2 mol% SiO2 and 0.5 mol% Al2O3 to the basic composition resulted both the values of the room temperature resistivity and the temperatured coefficient being maxium. Meanwhile, an addition of 1 mol% TiO2 and 1 mol% Al2O3 to the basic composition resulted the value of the room temperature resistivity maxium and the temperature coefficient minimum. The temperature coefficient showed a maximum value as well as a minimum value when the three kinds of the additives were added together to the basic composition of the BaTiO3 ceramics. Maxed phases of BaTi3O7, BaTiSiO5 and BaAl2Si2O8 were present at the grain boundary.

콘크리트 발수제용 Silane의 유화

황인동,염희남,정윤중 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.8

Recently, the protection of construction is demanded with environmental pollution. These protect modes are use of concrete admixture, coat of protective polymer and impregnate of surface with chemicals etc. The most widely used impregnation is economical and effective. The define of Impregnation for construction protect is reacted in and consolidated substrate after absorbed. The impregnation agents are Polyesters, Acrylic monomers, Epoxy and Silicone derivatives. Commonly, because the Silane has good water repellency and environmental advantages that it widely used to water proofing agents, dampproofing agents and absorption reducer for concrete of bridges. When application of Silane, it occurs pollution and harmfulness as included organic solvent. The manufactures have tired to emulsification of Silane for the reducing of the defects. The Silane emulsion is vary unstable and does not stored long periods, and it is diminished in good properties with internal reaction. In this study we tried to emulsification of Silane for effectiveness improvement and reduce pollution and hazard and discussed properties variation of emulsion. The Silane emulsions are achieved emulsifying with W/O and O/W type surfactants. It used 0.24% PVA as protective colloid and stable phase is creamy. The creamy Silane emulsion performance as the penetration depth and water absorption rate are above 4 mm and below 0.1. It stable about 6 month at room temperature.

Physical properties of Poly(latic acid) and starch blends

최종규,염희남,최미애,안종일,이영관,김용주 한국고분자학회 2004 한국고분자학회 학술대회 연구논문 초록집 Vol.29 No.2

팽창재를 포함한 시멘트 모르터의 팽창 요인

황인동,염희남,정윤중 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.6

Two type of expanding cement generally referred to as CSA with Hauyne(3CaO 3Al2O3 CaSO4) and Quick lime(CaO). Hauyne is formed to ettringite when there are presented with CaO and CaSO4, and CaO reacts wtih water to form Ca(OH)2. REcently, the mechanism of compensation and expand mortar or concrete tend to same and it has been used improving on its shrink property. The volume of cement paste varies with its water content shrink with drying and re-wetting. Concrete and mortar works are required shrinking compensation and expansion properties to reduce of potential crack. The use of expansion cement may improve on its shrinking volume changes. CSA dosages for shrinking compensation limited by cement weight, but obtained difference expansion rate with varied W/C or inorganic admixture. This paper studies expansion rate according to expansion cement dosages, water and inorganic admixtures as Silica fume. Therefor, the expansion factor has to considered before the application.