• 한국세라믹학회지
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• 제17권2호
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• pp.96-100
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• 1980

The castable refractory, CaO.$2Al_2O_3$ is a useful alumina cement for iron, steel and cement for iron, steel and cement industries, however it is difficult to produce CaO.$2Al_2O_3$because of its high melting point(180$0^{\circ}C$) and narrow firing range. In this study, the coprecipitation method was used to produce CaO.$2Al_2O_3$ for lower temperature firing . This method involved the titration of mixed solution of calicum and aluminate which extracted from domestic kaolin with $NH4_OH$ solution under blowing $CO_2$ gas into the solution. The coprecipitate and its clacined products were analyzed by X-ray diffraction and DTA. The calcined products fired between 400 and 90$0^{\circ}C$ were amorphous, but at 100$0^{\circ}C$ the coprecipitate was converted into one compound, CaO$2Al_2O_3$. From those experimental results, it was found that we could synthesizze CaO.$2Al_2O_3$ at about 100$0^{\circ}C$ which is lower than conventional firing temperature by around 80$0^{\circ}C$. The refractoriness of this alumina cement was SK 34 and the compressive strength ( 1 day) was about 250kg/$\textrm{cm}^2$.

• 한국세라믹학회지
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• 제31권4호
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• pp.427-435
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• 1994

Cu-metallized low firing temperature substrates were synthesized by cofiring green sheet of cordierite-based glass with Cu. By Sol-Gel method, Cu powder was coated with borosilicate gel which should act as a glass frit in Cu paste during cofiring. Theoretical weight ratios of Glass/Cu were controlled to be 2.5, 5, 10 and 15% by varying alkoxide concentrations. Average particle size of coated Cu was 0.629~0.674 ${\mu}{\textrm}{m}$ in comparison to that of as-received Cu(0.596 ${\mu}{\textrm}{m}$), which increased with alkoxide concentration but did not increase above certain concentration. The weight ratios of coated layer were 2.11~5.37%. The properties of Cu-metallized low firing temperature substrate, cofired at 90$0^{\circ}C$ for 1h under H2/N2 atmosphere, were as follows; sheet resistance was 13~43 m{{{{ OMEGA }}/$\square$, adhesion strength was 1.0~2.1 kgf/$\textrm{mm}^2$. From the observations of SEM photographs, the gel coated on Cu performed excellently as a glass frit.

• 한국세라믹학회지
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• 제22권5호
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• pp.71-75
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• 1985

This study deals with sintering and corrosive behavior of sintered zircons mixed with 5wt% of clay $Cr_2O_3$ $CrO_3-MgO$ aqueous solution and $CrO_3-Mg(OH)_2$ aqueous solution. Measurements were conducted by firing specimens at 135$0^{\circ}C$ 145$0^{\circ}C$ and 155$0^{\circ}C$ 1$650^{\circ}C$ for 3hrs in oxidized and reduced atmospheric conditions. Following results were obtained. 1. Sintered zircon with 5 wt% clay showed that highest compressive strength and the lowest apparent porosity and the other showed less positive result than above specimen in order of zircon with $CrO_3-MgO$ aqueous solution $CrO_3-Mg(OH)_2$ aqueous solution and $Cr_2O_3$. 2. The more firing temperature increased the more its strength improved and porosity decreased and specimen which was fired over 155$0^{\circ}C$ and in reduced atmospheric condition showed better results. 3. Zircon with additives which was fired over 155$0^{\circ}C$ showed the evidence of thermal dissociation but it was not rebonded completely during cooling. 4. Zircon with $CrO_3-MgO$ aqueous solution and $CrO_3-Mg(OH)_2$ aqueous solutiion showed more corrosive resistance than zircon itself and zircon-clay system.

• 대한치과기공학회지
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• 제29권2호
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• pp.119-128
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• 2007

Although there are many different ways that restorations can be made, it can be said that the biocompatibility of abutment and crown is very important in this experiment. When placed in the actual oral cavity, the differences were obvious. Compared to In-ceram Aluminium, the structure that is obtained after firing reveals a particularly homogeneous distribution of the crystal and glass phase. The In-ceram aluminium system had many problems, such as having weak tensile strength, and having low bonding strength due to the shrinking that occurs after firing. Because of the opaque finish of the metal frame, the two may look similar from the outside, but it is evident that there are differences between using a metal frame and In-ceram. VITA VM9 has been designed as a special ceramic featuring a fine structure or stabilized Zro2 substructures, and so the VITA VM9 excels in its light refraction and reflection behavior, which is similar to natural teeth. It also has outstanding chemical balance, which presents advantages such as considerably reduced accumulation of plaque on the ceramic surface.? This ultimately results in easier care and cleaning for the patient.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2233-2235
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• 1999

The ac plasma display panel(PDP) is a flat light-emitting gas discharge device. Discharge gases directly take effects to the discharge phenomena of ac PDP. Therefore it is necessary to understand the characteristics of the discharge gases. In this paper, we have studied the effects of discharge gases by voltage transfer curves which show the discharge characteristics of ac PDP and the change of the effective wall capacitance during a discharge which depends on lateral spreading of charge distribution and the strength of discharge. As gas pressure increases, memory margins increases. and the firing voltage of a mixed gas is lower than that of a single gas such as He gas. The minimum sustain voltage and the maximum sustain voltage or firing voltage increases with decrease in the frequency. The effective wall capacitance increases as the discharge strength that is, the gap voltage between discharge electrodes increases.

• 한국세라믹학회지
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• 제29권12호
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• pp.935-941
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• 1992

The LAS system with good thermal properties has a narrow range of firing and sintering temperature near the melting point. So it is difficult to sinter LAS to dense sintered body. In this study, the petalite (Li2O.Al2O3.8SiO2) with good thermal properties, was taken as a base composition, and zironia was added in this composition to broaden the firing range, increase the mechanical strength, and control the thermal expansion. The thermal and mechanical properties were investigated. The results are as follows; 1. Zirconia phase was formed in LAS matrix and apparent porosity was decreased from 0.9% to 0.5%, and the mechanical strength was kincreased from 112 MPa to 190 MPa, by the densification of body. 2. The composition Li2O.Al2O3.8SiO2 has a negative thermal expansion, but the thermal expansion was changed from negative to positive with the densification and the increase of amount of synthesized zircon phase which had positive thermal expansion. The coefficient of thermal expansion, with the increase of the amount of additives, was low as -0.74~9.06$\times$10-7/$^{\circ}C$ in 20~$600^{\circ}C$, and 7.95~20.13$\times$10-7/$^{\circ}C$ in 20~80$0^{\circ}C$. 3. The mechanical strength of LZ15 (added with ZrO2.SiO2 15 wt%) composition thermal-shocked was stable in the temperature range of 0~$600^{\circ}C$, but rapidly decreased due to the increase of thermal expansion above $600^{\circ}C$.

• 보존과학회지
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• 제32권4호
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• pp.511-520
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• 2016

본 연구는 고온 XRD 분석법을 적용하여 우즈베키스탄 카라테파 불교사원에서 수습한 점토 재질로 된 벽돌의 소성온도를 추정하는데 목적이 있다. 사원에서 수습한 점토벽돌의 구성광물은 석영, 사장석, 알칼리장석, 운모, 녹니석, 석회석, 각섬석 등이 동정되고, 일부 시료에서 석고가 확인되며, 석고는 벽돌의 점착력을 향상시킬 목적으로 사용된 것으로 판단된다. 소성온도 추정결과, 구운 벽돌인 UZ-1시료에서 석영, 사장석, 휘석계열의 광물이 동정되어 지질온도계를 이용한 소성온도는 $900{\sim}1200^{\circ}C$로 추정된다. 반면 점토벽돌인 UZ-5에 고온 XRD 분석법을 적용해 보면, $1000^{\circ}C$에서 석회석이 소멸하고, $1050^{\circ}C$에서 녹니석의 회절 피크가 약해지는 것으로 보아 소성온도는 $1000{\sim}1050^{\circ}C$인 것으로 추정된다. 또한 휘석계열의 광물은 재현실험에서 $1050^{\circ}C$에서 생성되는 것을 확인하였다. 결과적으로 고온 XRD 분석 결과에 의한 소성온도 추정은 일반적인 광물 동정법에 비해 보다 정확한 추정이 가능하며, 실험 하에서 광물의 소멸 및 생성 온도 영역을 살펴볼 수 있는 분석법임을 확인하였다.

• 한국세라믹학회지
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• 제19권2호
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• pp.95-100
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• 1982

Instead of barium carbonate, domestic barite was used as the flux in manufacturing theinsulating porcelain. To avoid the problems arising from the decomposition of barite in the body during firing, BaO.$Al_2O_3$ was synthesized at $1300^{\circ}C$ for 5 hours. synthetic BaO.$Al_2O_3$ was mixed with other materials such as kaoline, alumina, clay, dolomite. The RO content (CaO. MgO. BaO) of the batches was varied from range of 4 to 14wt. % at 2wt. % - intervals, and firing temperature was varied from 1280 to 140$0^{\circ}C$-at 4$0^{\circ}C$ intervals The properties such as water absorption, bulk density. mechnical strength, specific resistance, and linear shrinkage were measured. The body containing 12 wt.% of RO content showed the satisfactory for the application in the Fixed Carbon Film Resistor.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.375-376
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• 2009

본 연구는 현재 시행중인 교토의정서 발효로 인하여 시멘트 제조시 발생되는 CO$_2$의 발생량을 감소시키기 위해 대체재로 전통건축재료인 비소성 황토를 치환한 콘크리트의 기초자료를 제시하는데 목적을 두었다.

• 한국세라믹학회지
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• 제19권3호
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• pp.215-222
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• 1982

This study is to investigate the effect of a domestic pottery stone as a batch inclusion on the synthesis of porcelain bodies and their physical properties. The basic composition of porcelain bodies studied was consisted of 50wt% kaolin, 25wt% feldspar and 25wt% quartz. The inclusion of pottery stone was performed by partial substitution for either quartz or feldspar up to 25% of the total weight of batches. Sixteen porcelain bodied different in batch composition were prepared by firing them in the temperature range from 110$0^{\circ}C$ to 135$0^{\circ}C$ and their physical properties and microstructures were carefully examined. It was found that the inclusion of pottery stone could reudce the firing temperature for vitrification up to 5$0^{\circ}C$ but appreciably decreased the mechanical strength of sintered bodies. The most faborable result could obtain with partial substitution for both quartz and feldspar at same time up to 25% of the total batch weight.