• 연구논문집
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• s.24
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• pp.161-174
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• 1994

The Ni-Al intermetallic compound that has the greatest potential to be commercialized shows the high ductility at room temperature with the addition of boron, but has extremely low ductility at high temperature and oxidation environment. On this research work, the changes of microstructure and compressive fracture properties were studied in ($NiAl+Ni_3Al$) two-phase alloys. The precipitation behavior of $Ni_3Al$ after solution treatment at $1300^\circC$ for 14hrs and aging treatment at $800^{\circ}C$ for 14hrs was varied with Al content in ($NiAl+Ni_3Al$) two-phase alloys. These microstructure could be modified dramatically by suitable heat treatments. Martensite or martensite plus $Ni_3Al$ microstructure was obtained upon oil quenching from $1300^\circC$. Aging of Martensite at $800^\circC$ resulted in the $Ni_3Al$ plus NiAl phase. The compressive fracture strength and compressive fracture strain were improved by the $Ni_3Al$ plus NiAl phase mixtures at room temperature and $1100^\circC$. Microcracks are observed mostly in the region of NiAl and the interface of $NiAl-Ni_3Al$ phase after compressive test at room temperature. In the case of high temperature compressive test, microcracks are formed in the region of $Ni_3Al$ phase.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.125-129
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• 2021

We investigated the electronic property and atomic structure for chalcopyrite (CH) Al_xGa_1-xAs semiconductor by using first-principles FPLMTO method. The CH-Al_xGa_1-xAs exhibits a p-type semiconductor with a direct band-gap. For low Al concentration unoccupied hole-carriers are induced, but for high Al concentration it is formed a localized bonding or anti-bonding state below Fermi level. The hybridization of Al(3s)-Ga(4s, or 4p) is larger than that of Al(3s)-As(4s, or 4p). And the Al film on As-terminated surface, Al/AsGa(001), is more energetically favorable one than that on Ga-terminated (001) surface. Consequently, the band-gap of CH-Al_xGa_1-xAs system increases exponentially with increasing Al concentration. The change of lattice parameter is shown two different configurations with increasing Al concentration. The calculated lattice parameters for CH-Al_xGa_1-xAs system are compared to the experimental ones of zinc-blend GaAs and AlAs.

• Journal of the Korean Chemical Society
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• v.37 no.9
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• pp.787-792
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• 1993

Semiempirical MNDO calculations are employed to study relation properties on bridging OH group with Al-O(P-O) bond length and Al-O-P bond angle of structural characteristics using birdging $(OH)_3AlOP(OH)_3$ and $(OH)_3AlOHP(OH)_3^+$ model culster. We know that the O-H bond dissociation energy of bridging OH group is increased with increasing Al-O(P-O) bond length and decreasing Al-O-P bond angle. The bridging OH group is formed into enlarged Al-O(P-O) bond length and shortened Al-O-P bond angle in bridging oxygen atom by a hydrogen migration. The negative net charge of bridging oxygen atom is increased with longer Al-O-P bond angle, while the positive net charge is decreased with longer Al-O-P bond angle.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.3
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• pp.275-280
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• 1997

The experiment was carried out to determine Al tolerance ranges of two rice cultivars(Ilpumbyeo and Hyangmibyeo) during germination and early growth. The amount of 0, 300, 600 and 900ppm Al were treated in the germination media. Plant height and root length of rice cultivars were decreased significantly with Al concentration. The reduction of growth was more remarkable in root than in shoot. Germination rates in all Al concentrations were decreased comparing with untreated control. Two rice cultivars were not different in Al concentrations. As Al concentration was increased, chlorophyll content were decreased. Ca and Mg contents in 300ppm of Al treatment were sharply increased. Free proline contents of both rice cultivars grown at the 300, 600, and 900ppm of Al treatments were increased only in the 3 days after Al treatments.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.205-212
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• 2016

This research investigates the influence of ground granulated blast furnace slag (GGBFS) composition on the alkali-activated slag cement (AASC). Aluminum oxide ($Al_2O_3$) was added to GGBFS binder between 2% and 16% by weight. The alkaline activators KOH (potassium hydroxide) was used and the water to binder ratio of 0.50. The strength development results indicate that increasing the amount of $Al_2O_3$ enhanced hydration. The 2M KOH + 16% $Al_2O_3$ and 4M KOH + 16% $Al_2O_3$ specimens had the highest strength, with an average of 30.8 MPa and 45.2 MPa, after curing for 28days. The strength at 28days of 2M KOH + 16% $Al_2O_3$ was 46% higher than that of 2M KOH (without $Al_2O_3$). Also, the strength at 28days of 4M KOH + 16% $Al_2O_3$ was 44% higher than that of 4M KOH (without $Al_2O_3$). Increase the $Al_2O_3$ contents of the binder results in the strength development at all curing ages. The incorporation of AASC tended to increases the ultrasonic pulse velocity (UPV) due to the similar effects of strength, but increasing the amount of $Al_2O_3$ adversely decreases the water absorption and porosity. Higher addition of $Al_2O_3$ in the specimens increases the Al/Ca and Al/Si in the hydrated products. SEM and EDX analyses show that the formation of much denser microstructures with $Al_2O_3$ addition.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.285-292
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• 1996

The effect of AlN on the thermal conductivity of aluminum oxide pressurelessly sintered at nitrogen atmos-phere was investigated. Increasing aluminium nitride content up to 1~10 mol% the thermal conductivity of $Al_{2}O_{3}$-AlN system was singnificantly decreased and was constant with adding 20 and 25 mol% aluminium nitride. The thermal conuctivity of $Al_{2}O_{3}$ containing 1~10 mol% the thermal conductivity of $Al_{2}O_{3}$-AlN system was singificantly decreased and was constant with adding 20 and 25mol% aluminum nitride. The thermal conctivity of $Al_{2}O_{3}$ containing 1~10 mol% AlN showed a maximum at $1700^{\circ}C$ and decrea-sed with increasing sintering tempertures. This phenomenon was attributed to $\alpha$-$Al_{2}O_{3}$ and ALON formed by reacting $Al_{2}O_{3}$ with AlN up to $1700^{\circ}C$ and the secondary phases such as ${\gamma}$-ALON ($9Al_{2}O_{3}$.AlN)and $\Phi$($5Al_{2}O_{3}$.AlN) phase above $1750^{\circ}C$ The thermal conductivity of $Al_{2}O_{3}$ containing 20 and 25 mol% AlN showed maximum value at $1800^{\circ}C$ Both $\alpha$-$Al_{2}O_{3}$ and ALON existed up to $1600^{\circ}C$ value at $1800^{\circ}C$ Both $\alpha$-$Al_{2}O_{3}$ and ALON existed up to $1600^{\circ}C$ while only AlON phase existed above $1650^{\circ}C$.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.349-355
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• 2018

$BaMnAl_{11}O_{19}$ was prepared by urea-induced homogeneous precipitation and characterized by X-ray diffraction and scanning electron microscopy. At increased precipitant concentrations, AlOOH replaced $Al(OH)_3$ as an Al precursor. $BaMnAl_{11}O_{19}$ exhibited enhanced catalytic combustion performance and inhibited CO generation. Catalytic performance was also enhanced by the presence of $BaAl_2O_4$ and $BaMnAl_{11}O_{19}$. Compared to $BaAl_2O_4$, $BaMnAl_{11}O_{19}$ exhibited superior catalytic combustion activity.

• Journal of the Korean Chemical Society
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• v.38 no.1
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• pp.1-7
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• 1994

Semiempirical MNDO calculations are employed to study ionicity of OH groups and stability in $T_1-OH-T_2bridges(T_1$ = Al, B and $T_2$ = P, Si) such as found in aluminophosphate family($AlPO_4-5$, BAPO-5, and SAPO-5) molecular sieves. Dimeric model clusters of Al-OH-P, B-OH-P and Al-OH-Si bridges were considered. It is shown that the elongation of the T-O bond, upon replacement of Al by B, occurs preferentially by a local deformation of the Al-O-P bridge. But the elongation of the T-O bond occurs preferentially by a rotation of Al-O-Si bridge upon substitution P for Si. Also, the ionicity of OH groups and stability increase in order to B-OH-P < Al-OH-P < Al-OH-Si bridge.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1545-1555
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• 2020

In the present study, we investigated the antioxidant activity of Aucklandia lappa Decne (AL). Cell viability was measured in an MTT assay. Antioxidant effects were evaluated based on total polyphenol/flavonoid contents, ABTS radical scavenging activity, DPPH radical scavenging activity, SOD activity, and ROS content. AL was found not to be toxic at concentrations of 1 ㎍/mL, 10 ㎍/mL, and 100 ㎍/mL, respectively. The phenolic content was higher in AL-D than in AL-E, while the flavonoid content was higher in AL-E than in AL-D. AL-E exhibited higher ABTS radical scavenging activity than AL-D, and the EC50 values for BHA were 217.1 ㎍/mL in AL-D and 180.5 ㎍/mL in AL-E. AL-E also showed the highest DPPH radical scavenging activity. EC50 values for BHA were 114.2 ㎍/mL in AL-D and 95.8 ㎍/mL in AL-E. The SOD-like activity of AL-E was higher than that of AL-D. The EC50 values for ascorbic acid were 48.5 ㎍/mL in AL-D and 72.9 ㎍/mL in AL-E, indicating that both AL extracts have a SOD activity higher than that of ascorbic acid. AL-E reduced relatively more ROS than AL-D. With 100 ㎍/mL AL-E, the reduction level was almost similar to that of dexamethasone. Our results demonstrate that AL have antioxidant effects, and we believe that they could be very valuable as raw materials for anti-aging products, based on their antioxidant activity.

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.269-278
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• 1991

Fine AlN powder was synthesized by carbothermal reduction and nitridation of alumimun hydroxide prepared from Al-isopropoxide. AlN ceramics with Y2O3 and CaO were prepared by hot-pressing under the pressure of 30 MPa at 180$0^{\circ}C$ for 1 h in N2 atmosphere. Grain boundary behavior and purification mechanism of AlN lattice were examined by heat treatment of AlN ceramics at 185$0^{\circ}C$ for 1-6 h in N2 atmosphere. AlN ceramics without sintering additives showed poor sinterability. However, Y2O3-doped and CaO-doped AlN ceramics were fully densified nearly to theoretical density. As the heat treatment time increased, c-axis lattice parameter increased. This is attributed to the removal of Al2O3 in AlN lattice. This purification effect of AlN attice depended upon the quantity of secondary oxide phase in the inintial stage of heat treatment and the heat treatment time.