• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.593-599
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• 2003

The nanoparticle magnetite of which diameter was about 3 nm was synthesized in a homogeneous aqueous solution without a template. The synthesized magnetite nanoparticle was easily oxidized to maghemite in an ambient condition. The magnetic properties of the ferrite nanoparticle show superparamagnetism at room temperature and its blocking temperature is around 93 K. Modifying the sequential adsorption method of metal bisphosphonate, we have prepared a multilayer thin film of the ferrite nanoparticle on planar substrates such as glass, quartz and Si wafer. In this multilayer the ferrite nanoparticle layer and an alkylbisphosphonate layer are alternately placed on the substrates by simple immersion in the solutions of the ferrite nanoparticle and 1, 10-decanediylbis (phosphonic acid) (DBPA), alternately. This is the first example, as far as we know, of nanoparticle/alkyl-bisphosphonate multilayer which is an analogy of metal bisphosphonate multilayer. UV-visible absorption and infrared reflection-absorption studies show that the growth of each layer is very systematic and the film is considerably optically transparent to visible light of 400-700 nm. Atomic force microscopic images of the film show that the surface morphology of the film follows that of the substrate in μm-scale image and the nanoparticle-terminated surface is differentiated from the DBPA-terminated one in nm-scale image. The magnetic properties of this ferrite/DBPA thin film are almost the same as those of the ferrite nanoparticle powder only.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1162-1170
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• 1998

Applicability of crystallization kinetics on thermal analysis was investigated for PbO-TiO2-B2O3-BaO glass systems together with theoretical background of kinetics and electron microscopic observations on nu-cleation and crystallization. Kissinger equation can be used on DTA under the assumption that the nucleus density is fixed during DTA runs. Crystallization mechanism affected on the activation energy Ek obtained from powder samples which is used for domination of surface crystallization. Avrami parameter n that was obtained from Ozawa equation represented closely the crystallization mechanisms observed by an electron microscope. The modified Kissinger equation takes into account crystallization mechanism thereby pro-ducing the true activation energy of crystallization.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.605-612
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• 1990

In Pb1-xLax(Zry, Tiz)1-x/4O3 system, it selects the composition 7/65/35 (x=7, y=65, z=35) that was reported to have eminent Pyroelectric properties, and that is sintered with PbZrO3＋0.3wt.% PbO2 atmosphere powder. From the sintered ceramic and Poly Vinyl Alcohol, the thin wafers are fabricated with 0-3connectivity, and they are researched in Pyroelectric properties and the others according to volume ratio between ceramic and polymer. It was possible to fabricate the film containing ceramic up to 80vol% in PVA polymer. The increment of PLZT ceramic volume fraction improve the pyroelectric coefficient of the composite. On Pyroelectric coefficient and the figure of merit, a little inflection caused by glass point(Tg) of PVA appeared. The degree of inflection is proportioned to the amount of PVA.

• Journal of the Korean Ceramic Society
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• v.50 no.4
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• pp.280-287
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• 2013

Plate-type phosphor is a promising substitute in overcoming the issues related to the powder phosphor paste mixed with resin. In this research, $Ca-{\alpha}-SiAlON:Eu^{2+}$ plate phosphor ($Ca_xSi_{12-(m+n)}Al_{m+n}O_nN_{16-n}:Eu_y$) was investigated for the varied compositions (m,n) of the host crystal with the fixed Eu content (y). Densification was promoted for the compositions with increasing 'm' values for the m=2n relationship. Dictated by the Eu concentration inside the phosphor crystal, photoluminescence intensity was stronger in ${\alpha}2$ specimen (m = 3.0, n = 1.5) containing the second phases when compared to ${\alpha}1$ specimen (m = 1.5, n = 0.75) comprising a single-phase ${\alpha}$-SiAlON. The concentration of Eu in the non-emitting amorphous interfacial glass phase was 2~4 times of the designed Eu concentration inside the ${\alpha}$-SiAlON crystal.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.4
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• pp.165-170
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• 2018

W, Fe, and carbon powders were mechanical alloyed to produce $W_{35}Fe_{43}C_{22}$ ternary alloy powders containing nanocrystal W embedded within amorphous matrix. When the powder samples were heated to the primary crystallization temperature of $735^{\circ}C$, most parts of their amorphous region were fully crystallized to [W,Fe]-rich $M_6C$ carbides. Interestingly, a little portion of the carbides changes to stoichiometric line compounds ($M_{12}C$ and $W_6Fe_7$) and a solution phase (Fe-rich bcc), and remaining parts of the crystallites were amorphized again. The resulting microstructure was retained even by cyclic heating between room temperature of $1,200^{\circ}C$, and thus we found that the amorphous structure can be irreversibly formed at above glass transition temperature.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.634-638
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• 1998

Monodisperse, spherical $PMSQ/TiO_2$ composite fine powders were prepared by modified sol-gel process where 300 nm $TiO_2$ fine powders were used as seed particles for hetero-condensation with hydrolyzed MTMS (Methyltrimethoxysilane). The reaction was carried out under $N_2$ atmosphere at ambient temperature using $NH_3$ as a catalyst. Methanol was used as a solvent. Powder was obtained by the filtration of the solution with a glass filter and washing with acetone. The stirring rate, reaction temperature, $[H_2O]/[MTMS]$ and $[MTMS]/[TiO_2]$ ratio were varied to investigate shapes and sizes of particles. Monodisperse particles of $1-2{\mu}m$ diameter were obtained with [MTMS]=0.2 M, $[NH_3]=0.6M$, $[H_2O]/[MTMS]=100$, $[MTMS]/[TiO_2]=10-50$ at ambient temperature with mild stirring condition. These composite particles had a contact angle of almost 180 degree contact angle with water, which proves their excellent hydrophobicity. The study of UV absorption spectra showed that they have UV protecting effect.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.322-328
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• 2010

This study was initiated to investigate the physical and chemical properties of the clay mineral illite and its effect on the growth of cherry tomato (Hongjak) as affected by the forms and concentrations of illite using the bed soil in the glass house. The composition of illite was analyzed by SEM(scanning electron microscope). The cherry tomato was cultivated in the bed soil in the glass house at Chungbuk National University for 10 weeks of total duration. The application rates of illite used as particulate and powder forms were standard 1:20 (w/w), two times 1:10 (w/w), four times 1:5 (w/w) of standard application, respectively. The surface of illite used in the study appeared to be hexagonal sheet and it included K and the variety of other elements. The growth lengths of cherry tomato were 11-23% greater in the pots treated than in the untreated pots. Based on the analyses of the major cations, K, Ca, and Mg from the cherry tomato the amounts of K taken in the leaf and stem of the cherry tomato were 8-45% and 3-30% greater than untreated pots, respectively. The amount of Ca in the leaf and stem taken up by the cherry tomato were 6-39% and 11-40% greater than untreated pots, respectively. The amounts of Mg in the leaf and stem taken up by the cherry tomato were 17-62% and 19-54% greater than untreated pots, respectively. Based on the analysis for the amount of cations, such as K, Ca, and Mg taken up by cherry tomato in treated and untreated bed soil, it appears that the illite treatment enhanced the early growth of cherry tomato.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.1
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• pp.57-65
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• 2005

This study suggested a new method for the solidification of molten salt waste generated from the electro-metallurgical process in the spent fuel treatment. Using binary material system, sodium silicate and phosphoric acid, metal chlorides were converted into metal phosphate in the micro-reaction module formed by SiO$_{2} particles. The volatile element in the reaction module would little vaporized below 1100$^{circ}$C After the gel product was mixed with borosilicate glass powder and thermally treated at 1000$^{circ}$C, li exists as Li$_{3}$PO$_4$ separated from glass phase and, Cs and Sr would be incorporated into an amorphous phase from XRD analysis. In case of the addition of ZrCl$_{4}$ to the binary system, the gel products were transformed into NZP structure considered as an prospective ceramic waste form after heat-treatment above 700 $^{circ}$C. From these results, the gel-route pretreatment can be considered as an effective approach to the solidincation of molten salt waste by the confirmed process or waste form and this also would be an alternative method on the ANL method using zeolites in USA by the confirmation of its chemical durability as an future work.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.401-418
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• 2000

1. Production of the artificial zeolite from coal ash Coal fly ash is mainly composed of several oxides including $SiO_2$ and $Al_2O_3$ derived from inorganic compounds remained after burning. As minor components, $Fe_2O_3$ and oxides of Mg, Ca, P, Ti (trace) are also contained in the ash. These components are presented as glass form resulting from fusion in the process of the combustion of coal. In other word, coal ash may refer to a kind of aluminosilicate glass that is known to easily change to zeolite-like materials by hydrothermal reaction. Lots of hot seawater is disposing near thermal power plants after cooling turbine generator periodically. Using seawater in the hydrothermal reaction caused to produce low price artificial zeolite by reduction of sodium hydroxide consumption, heating energy and water cost. As coal ash were reacted hydrothermally, peaks of quartz and mullite in the ash were weakened and disappeared, and new Na-Pl peaks were appeared strengthily. Si-O-Si bonding of the bituminous coal ash was changed to Si-O-Al (and $Fe^{3+}$) bonding by the reaction. Therefore the produced Na-Pl type zeolite had high CEC of 276.7 $cmol^+{\cdot}kg^{-1}$ and well developed molecular sieve structure with low concentration of heavy metals. 2. Utilization of the artificial zeolite in agro-environment The artificial zeolite(1g) could remove 123.5 mg of zinc, 164.7 mg copper, 184.4 mg cadmium and 350.6 mg lead in the synthetic wastewater. The removability is higher 2.8 times in zinc, 3.3 times in copper, 4.7 times in cadmium and 4.8 times in lead than natural zeolite and charcoal powder. When the heavy metals were treated at the ratio of 150 $kg{\cdot}ha^{-1}$ to the rice plant, various growth inhibition were observed; brownish discoloration and death of leaf sheath, growth inhibition in culm length, number of panicles and grains, grain ripening and rice yield. But these growth inhibition was greatly alleviated by the application of artificial zeolite, therefore, rice yield increased $1.1{\sim}3.2$ times according to the metal kind. In addition, the concentration of heavy metals in the brown rice also lowered by $27{\sim}75%$. Artificial Granular Zeolites (AGZ) was developed for the purification of wastewater. Canon exchange capacity was 126.8 $cmol^+{\cdot}kg^{-1}$. AGZ had Na-Pl peaks mainly with some minor $C_3S$ peaks in X-ray diffractogram. In addition, AGZs had various pore structure that may be adhere the suspended solid and offer microbiological niche to decompose organic pollutants. AGZ could remove ammonium, orthophosphate and heavy metals simultaneously. Mixing ratio of artificial zeolite in AGZs was related positively with removal efficiency of $NH_4\;^+$ and negatively with that of $PO_4\;^{3-}$. Root growth of rice seedling was inhibited severely in the mine wastewater because of strong acidity and high concentration of heavy metals. As AGZ(1 kg) stayed in the wastewater(100L) for 4days, water quality turned into safely for agricultural usage and rice seedlings grew normally.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.129-146
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• 2000

An increasing demand for esthetic restorations has led to the development of new ceramic systems. In-Ceram, a glass-infiltrated alumina ceramic has three to few times greater flexural strength than other ceramic glass material. Because of its high strength, In-Ceram has been suggested as inlay, crown, laminate veneer and core material for resin bonded fixed partial dentures. This clinical application requires a stable resin bond to In-Ceram core. The purpose of this study was to evaluate the shear bond strength between In-Ceram core and resin cements according to various surface treatments and storage conditions. The surface of each In-Ceram core sample was subjected to one of the following treatments and then bonded to Panavia 21 or Variolink II resin cement. ; (1) sandblasting with $110{\mu}m$ aluminum oxide powder, (2) sandblasting and silanization, (3) sandblasting and Siloc treatment, (4) sandblasting and Targis link application. Each of eight bonding groups was tested in shear bond strengths after the following storage times and thermocycling. ; A) 24 hours storage in distilled water at $37^{\circ}C$, B) 5 weeks storage in distilled water at $37^{\circ}C$ C) 5 weeks storage in distilled water at $37^{\circ}C$ and thermocycled 2,000 thormocycling for every 10 days(totally 10,000 thermocycting) in $5^{\circ}C-55^{\circ}C$ bath. The bond failure modes were observed with scanning electron microscope(SEM). The results were as fellows : 1 The shear bond strengths of sandblasting group were significantly lesser than the other groups after 24 hours water storage. No significant difference of bonding strengths was found between storage time conditions(24 hours and 5 weeks). The shear bond strengths showed a tendency to decrease in Variolink II bonding groups and to increase in Panavia 21 bonding groups. 3. After thermocycling, the shear bond strengths of all groups were significantly decreased(p<0.01) and Targis link group exhibited significantly greater strengths than the other groups(p<0.05). 4. Panavia 21 bonding groups exhibited significantly greater bonding strengths in sandblasting group(p<0.01) and silane group(p<0.05) than Variolink II bonding groups. 5. In observation of bond failure modes, Targis link group showed cohesive failure in resin part and silane group and Siloc group showed complex failure and sandblasting group showed adhesive failure between In-Ceram and resin.