• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.816-820
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• 2007

Novel new red-light emitting perylene fluoroionophore N,N'-dipropyl-1,7-bis(calix[4]azacrown-5-crown-5)- 3,4,9,10-perylene tetracarboxy diimide (3) was prepared by reacting N,N'-dipropyl-1,7-dibromo-3,4,9,10- perylene tetracarboxy diimide (1) with calix[4]azacrown-5-crown-5. Also the alternating copolymer (4) with similar repeating unit was prepared reacting by calix[4]bisazacrown-5 with 1. Metal ion binding by 3 and 4 leads to a blue-shift of absorption band and emission spectra. When ionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions, polymeric ionophores displayed large fluorescence decreasing effects with K+, Ag+ and Ba2+, which was rationalized by photo-induced charge transfer (PCT).

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.178-182
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• 1999

Simple binary $Na_2S-SiO_2$ oxysulfide glasses were prepared by a conventional melt-quench method in order to investigate the role of sulfur in glass structure and the electronic state. By X-ray photoelectron spectroscopy(XPS) measurement, S2p binding energy of the glass was observed at approximately 161eV which was close to that of ionic $S^{2-}$. The coordinating state around silicon atoms were investigated by ${29}^Si$ MAS-NMR measurement. The chemical shift observed from NMR supported that sulfur atom was joined to a silicon atom by substituting for an oxygen atom and was present as a non-bridging sulfide ion in low alkali content. On the other hand, it could be presumed that a portion of sulfur anions existed in an isolated state from the glass-network frame at high alkali content. The state of these sulfurs was also studied by Raman spectroscopy in detail.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.120-129
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• 1997

The fire protective coating can reduce certain damages in case of fire, also conserve energy by thermal insulation and prevent corrosion and errosion in normal daily life by means of blocking thermal transfer, that were generally made of organic, inorganic and metallic materials as adiabatic coating. In case of inorganic material such as soluble silicate, it produces less toxic substances which are exposed to Ore, and have a plenty of raw material. Also inorganic thermal insulator is good in heat resistance. To develope such a excellent inorganic thermal insulator, the study of fire protective coating using the alkali silicate is necessary The principle of intumescence for alkali silicate is from rapid evolution of water in the coating material, the quantity of water in it is of course influenced on the degree of intumescence. The phenomenon of intumescence in ternary silicate is increased as the radius of ion is bigger, and this is caused by evolution of so many kinds of water. The individual degree of intumescence is ordered like this ; $K^+$ > $Na^+$ > $Li^+$ . The best protection effect is similarity found to intumescence of ternary silicate. The result of X-ray diffraction analysis indicates that $KHSi_2O_5$ is an important ingredient in K-silicate.

• Korean Journal of Materials Research
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• v.16 no.5
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• pp.277-284
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• 2006

The alloys were prepared by a non-consumable vacuum arc melting and homogenized at $1050^{\circ}C$ for 24 hrs. Two kind of surface modifications were performed alkali treatment in 5.0M NaOH solution subsequent and heat treatment in vacuum furnace at $600^{\circ}C$, and were oxidizing treatment at the temperature range of 550 to $750^{\circ}C$ for 30 minutes. After surface modification, these samples were soaked in SBF which consists of nearly the same ion concentration as human blood plasma. Cytotoxicity tests were performed in MTT assay treated L929 fibroblast cell culture, using indirect methods. A porous and thin activated layer was formed on Titanium and Ti-8Ta-3Nb alloy by the alkali treatment. A bone-like hydroxyapatite was nucleated on the activated porous surfaces during the in vitro test. However, Ti-8Ta-3Nb alloys showed better bioactive properties than Titanium. According to XRD results, oxide layers composed of mostly $TiO_2$(rutile) phases. Cytotoxicity test also revealed that moderate oxidation treatment lowers cell toxicity and Ti-8Ta-3Nb alloy showed better results compared with Titanium.

• Polymer(Korea)
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• v.24 no.1
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• pp.133-139
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• 2000

Poly(ethylene glycol) with number-average molecular weight (M$_{n}$) of 200 (PEG 200) or 400 (PEG 400) was reacted with various linking agents (CH$_2$Cl$_2$, CH$_2$Br$_2$, CH$_2$I$_2$, Br(CH$_2$)$_3$Br) in the presence of alkali to form of oxyalkylene linked chains. Molecular weights of copolymers were controlled using feed mole ratio of alkali/CH$_2$C1$_2$/PEG. The M$_{n}$ of the polymers measured by end group analysis and that measured by GPC agreed well. Molecuglar weights of polyether copolymers obtained from PEG 200 and PEG 400 were about 500~8500 and 1000~2000, respectively. Polyether copolymers prepared from PEG 400 showed melting points of around 1$0^{\circ}C$. Glass transition temperatures of the copolymers were around -75$^{\circ}C$ and the crystallinity was about 0~25%. The polyether copolymers prepared from PEG 200 had no crystallinity below the M$_{n}$ of 2500. 2500.

• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.37-44
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• 2010

This study examined the practical application of ground granulated blast-furnace slag (GGBS) based alkali-activated (AA) binders for the development of cementless environmental-friendly secondary products of concrete, such as brick, shore protection blocks and interlocking blocks. The addition amount and type of alkaline ion to activate GGBS varied according to the diverse qualities of the secondary products of concrete required in Korean industrial standards (KS) and other specifications. Test results showed that the secondary products of concrete using GGBS-based AA binders surpassed the demanded capacities of KS and other specifications. In addition, shore protection block had a pH value close to neutral, enabling an advantageous environment for marine life. Therefore, the GGBS-based AA binders can be effectively applied to develop eco-friendly secondary products of concrete with reduced $CO_2$.

• Journal of the Korean Chemical Society
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• v.55 no.1
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• pp.92-97
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• 2011

The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/$SiO_2$ catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle's diameter.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.1-6
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• 2011

The possibility of ASR(alkali-silica reaction) for coarse aggregates had known to be low up to recently in Korea. But the distress of ASR was identified and reported by ASTM C 1260 test. The purpose of this paper was to identify the effect of environmental conditions on length expansion of mortar-bar by alkali-silica reaction with KS F 2546 and ASTM C 1260 test. The results of this study were as following; The result of KS F 2546 test for five kinds of aggregates shows that all of them are non-reactive. But that of ASTM C 1260 test shows that all of aggregates except Andesite-2 are over possible reactive because of environmental condition such as external alkali ion by 1N NaOH, high temperature and humidity. The result of variety of NaOH concentration on ASTM C 1260 using Siltstone indicates that length expansion rate increases highly as NaOH concentration increases. And, comparison results of KS F 2546 for Siltstone with that of 0.00N NaOH experiment indicates that length expansion rate increases as temperature and humidity increases.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.67-72
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• 2022

Concrete prevents corrosion of reinforcing bars due to its strong alkalinity. However, in the sea, strong alkali components with a pH of 12 to 13 are eluted, which adversely affects the ecological environment and growth of marine organisms. In this study, the mechanical properties and durability of the low alkali mortar were evaluated for the development of a low alkali mortar for the 3D printed artificial reefs. As a result of evaluation of strength characteristics, the α-35 mixture, which were produced with fly ash, silica fume and α-hemihydrate gypsum, satisfied the strength requirement 27 MPa in terms of compressive strength. As a result of pH measurement, it was found that mixing with alpha-type hemihydrate gypsum resulted in minimizing pH due to the the formation of calcium sulfate instead of calcium hydroxide production. As a result of the chloride ion penetration resistance test, the α-35 mixture exhibited the best performance, 3844C. As a result of measuring the length change over time, the α-35 mixture showed the shrinkage 33.5% less compared to the Plain mix.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.160-168
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• 2014

In the present study, water vapor adsorption was evaluated at 298.15K for 9 different zeolites having LTA, FAU, CHA, and RHO frameworks, and then effect of framework type, Si/Al molar ratio, and alkali ion type on water up-take was investigated. Zeolites showed water up-takes which were increased in an order of $RHO<CHA{\approx}LTA<FAU$ frameworks. NaY zeolite having FAU framework showed a water up-take of 406 mg/g at p/po=0.5. The up-take was a little larger than that of 13X zeolite with the same framework. Among LTA zeolites, Ca-type 5A zeolite showed the highest water adsorption (282 mg/g at p/po=0.5) which could be explained by the large pore volume. Both CHA zeolite with a Si/Al molar ratio of 2.35 and RHO zeolite with a Si/Al molar ratio of 3.56 showed considerable water up-takes, even though the Si/Al molar ratio was much larger than that of LTA zeolite. In the present study, it is announced that in addition to FAU and LTA zeolites, CHA and RHO zeolites can be a promising dehumidification adsorbent.