• 한국세라믹학회지
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• 제33권1호
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• pp.101-109
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• 1996

The mechanical propertieso f sintered AlN with the addition of alumina were investigated The flexural strength of the AlN dispersed ALON specimens was higher than that of ALON and fracture toughness showed similar tendency. The high-temperature flexural strength of specimens which 50 and 64.3 mol% alumina was added to AlN was constant up to 100$0^{\circ}C$ with about 290 and 420 MPa respectively but abruptly decreased at 120$0^{\circ}C$ In the specimens which contained 5 and 30mol% alumina the flexural strength increased to about 14% at 100$0^{\circ}C$ and did not decrease at 120$0^{\circ}C$ compared to at room temperature.

• 한국표면공학회지
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• 제24권4호
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• pp.222-229
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• 1991

The oxidation behavior of Ni-6wt.% Cr alloys with various concentration of alumina dispersions(5vol.% 10vol.%) was determined at 1000 and 110$0^{\circ}C$ in oxygen of 1 atm. pressure. Some general observations were ascertained. These include: (a) the addition of alumina dispersoids significantly increased the oxidation resistance of Ni-6wt.% Cr alloy; (b) the rate of oxidation was distinctly decreased as a function of the volume percent of oxide dispersion; and (c) the presence of alumina dispersions promoted the formation of continous, protective Cr2O3 layer at 6 wt.% Cr.

• 한국표면공학회지
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• 제29권2호
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• pp.109-119
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• 1996

In order to improve adhesion of electroless copper deposits on alumina substrates, some stabilizers such as 2-Mercapto Benzothiazole, thiourea and NaCN were added over a wide range of concentrations. The adhesion tests of the deposits were performed by using the cellophane tape and the push-pull scale. With the minor addition of the stabilizers, 2-MBT having a large molecular size gives poor adhesion, together with a finer grain structure, whereas Thiourea and NaCN show a high mechanical strength of the deposits. The high mechanical strength is supposed to be due to the easy desorption of hydrogen gas generated from the electroless reactions. A large amount of the three stabilizers decreases the adhesion for all the cases, resulting from strong adsorption of the stabilizers to the substrates.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.831-835
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• 2015

본 연구에서는 바이오매스 유래 생리활성물질인 (+)-dihydromyricetin을 정제하기 위한 분별침전공정에서 분별침전용액의 제타전위가 분별침전 양상(순도, 수율, 침전물 형태와 크기)에 미치는 영향을 조사하였다. 제타전위 조절을 위한 실리카-알루미나의 첨가량(반응액 부피당 표면적) $100mm^{-1}$에서 가장 높은 수율을 얻을 수 있었다. 실리카-알루미나의 제타전위가 양(+)의 값으로 증가할수록 (+)-dihydromyricetin 수율과 침전물의 크기는 증가하였다. 가장 큰 제타전위 값(+4.99 mV)을 가진 실리카를 이용한 분별침전의 경우에는 가장 작은 제타전위 값(-19.00 mV)을 가진 알루미나를 이용한 분별침전의 경우보다 2배 이상 높은 수율을 얻을 수 있었다. 또한 분별침전 과정에서 제타전위 절대값이 증가할수록 (+)-dihydromyricetin 수율과 침전물의 크기는 감소하여 제타전위 절대값에 반비례함을 알 수 있었다. 반면 표면적증가물질 실리카-알루미나의 제타전위 변화에도 (+)-dihydromyricetin 순도는 거의 변화가 없었다.

• 한국세라믹학회지
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• 제41권7호
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• pp.508-512
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• 2004

치과 임프란트의 상부구조물로 응용하기 위해 Zr $O_2$, $Y_2$ $O_3$, Nb$_2$ $O_{5}$를 각각 90.24, 5.31, 4.45mo1%씩 혼합한 정방정 지르코니아 고용체에 알루미나를 부피비로 10-90%를 10vo1%간격으로 첨가하여 (Y, Nb)-TZP/알루미나 복합체를 제조하였다. 최적의 기계적 물성은 알루미나를 10vo1% 첨가했을 때 이축 곡강도는 900MPa이었으며 파괴인성은 8.9MPam$^{1}$2/이었고 20$0^{\circ}C$ 오토크레이브하에서 10시간 열처리했을 때 저온열화가 관찰되지 않았다. 복합체를 임프란트 상부구조물로 제작하여 40명의 환자에게 총 65개를 시술한 후 2년 동안 관찰한 결과 부작용이나 나사의 풀림 또는 파절이 전혀 일어나지 않아 우수한 임상결과를 보였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1288-1291
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• 2004

In this study, physical characteristics of alumina slurry on variation of pH value and the effect of non-ionic surfactants on alumina slurry for copper chemical mechanical planarization (CMP) slurry have been investigated. After pH value of the slurry with alumina abrasive was changed by adding various amount of $HNO^3$ or KOH, the differences of settling rate, particle size, and zeta-potential were estimated. Better settling rates were shown in slurries with alumina abrasive at near pH 1. Higher zeta-potential was shown at around pH 2 in alumina slurry and the point of zero charge (PZC) was measured at about pH $9\sim10$. Non-ionic surfactant was added in the slurry with 5wt% alumina abrasive to get its effect on slurry practically. Abrasive size was smaller increased when amount of surfactant increased in slurry with P-4 as abrasive; on the other side, it was smaller when amount of surfactant decreased with AES-12. Variation of zeta-potential has no tendency with adding surfactant; however, values of zeta-potential were between $35\sim50mV$. The proper amount of surfactant was $0.1\sim1.0wt%$ in slurry with P-4 and $0.5\sim1.0wt%$ in slurry with AES-12 respectively. Excellent dispersion stabilization was obtained by addition of non-ionic surfactant

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1637-1639
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• 2004

In order to analyze the physical and chemical characteristics of the home production porcelain insulators by change of the alumina addition amount, 36000lbs ball socket type suspension insulators which were manufactured in 1989, 1995 and 2001 removed in transmission line and an experiment was performed. By the result, 8 [wt.%] alumina that influences the mechanical properties and arc resistance properties in case of insulators that were manufactured in 1989 was contained, and the relative density and the fracture toughness of insulators appeared by 94.2% and 1.4 [MPa $M^{1/2}$], respectively. However, 12 [wt.%] alumina was contained in case of insulators that were manufactured in 1995, and the relative density and the fracture toughness of insulators appeared preferably lower by 92% and 1.3 [MPa $M^{1/2}$], respectively. Amount of alumina was contained most by 17 [wt.%] in case of insulators that were manufactured in 2001. It was confirmed that the electrical and mechanical characteristics such as the relative density and the fracture toughness appeared excellently by 96% and 1.7 [MPa $m^{1/2}$], respectively.

• 한국재료학회지
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• 제19권2호
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• pp.115-118
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• 2009

The use of dolomite refractories has increased during the past several years in the manufacturing of clean steel during the stainless steelmaking process. However, at the same time, the use of dolomite refractories has led to what is known as the skull formation. In the present work, to understand the skull formation, the wetting characteristics of dolomite substrates by liquid Fe-19wt%Cr-10wt%Ni alloys in various oxygen partial pressures were initially investigated at 1753K using the sessile drop technique. For comparison, the wetting characteristics of alumina substrates were investigated with the same technique. It was found that the wetting index, (1+$cos{\theta}$), of dolomite is approximately 40% higher compared to those of alumina. In addition, the oxygen partial pressure to generate the surface oxide, which may capture the liquid metal on the refractory surface, for dolomite is much lower than that for alumina. From this study, it was concluded that the use of dolomite is much more closely associated with the skull formation compared to the use of alumina due to the stronger wettability and the surface oxide formation at a lower oxygen partial pressure of dolomite.

• Corrosion Science and Technology
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• 제6권1호
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• pp.24-28
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• 2007

Alumina coated SiC whiskers were prepared by homogeneous precipitation of aluminum sulfate. The Si3N4 composites reinforced with coated SiC whiskers were fabricated by hot-pressing at $1800^{\circ}C$ for 2 h under an $N_{2}$ atmosphere of 0.1 MPa to examine the effects of coated whiskers on the mechanical properties of SiC whisker reinforced $Si_{3}N_{4}$ composite. By the addition of alumina coated SiC whiskers instead of as received ones, the fracture toughness of composite was about 6.7 $MPam^{1/2}$ which was slightly lower than as received SiC whisker reinforced composite. This result seems to be caused by the fact that the crack deflection and whisker pull-out were decreased. Thus, alumina coated SiC whiskers were considered to form relatively strong interface bond with $Si_{3}N_{4}$ matrix.

• 한국세라믹학회지
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• 제30권5호
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• pp.347-356
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• 1993

In joining alumina ceramics to metal by using Mo-Mn metallizing process the effects of metallizing thickness, temperature, and the composition of paste on the bond strength and the microstructure of joining interface were investigated. The bond strength variation in the range of metallizing temperature, 1350~155$0^{\circ}C$ was more than 150MPa above 145$0^{\circ}C$ and the optimum metallizing thickness was 30${\mu}{\textrm}{m}$. The optimum contents of Mn in Mo-Mn paste was 5% due to the bond strength decrease with the increase of addition. The effect of SiO2 addition in paste on bond strength was saturated around 200MPa. It was also observed that as the particle size of Mo decreased, the joinning with higher bond strength was shown in spite of low metallizing temperature.