• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.162-167
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• 2005

Using Pechini method, we synthesized the $La_{0.6}Ca_{0.41}CrO_3$ (LCC41) and $La_{0.8}Sr_{0.05}Ca_{0.15}CrO_3$ (LSCC) powders for slurry dip coating, and $La_{0.75}Ca_{0.27}CrO_3$ (LCC27) powder for air plasma spray coating. The sintering property of the powders and their coating properties were investigated. The average particle sizes of the LCC41, LSCC, LCC27 were 0.6, 0.9, $1.5{\mu}m$, respectively. The relative density of LCC41 bulk was to be found about 98%. The LSCC coating on anode support prevented Ca migration of the coated LCC41 on the anode some or less, which was confirmed from EDS result. The air plasma spray-coated LCC27 with the dip-coated LCC41 were more dense and showed better electrical conductivity than those of the air plasma spray-coated LCC27 and the dip-coated LSCC and LSCC41. The LCC41 and LCC27 showed good electrical conductivities, but the LSCC had a poor electrical conductivity probably due to low sinterability

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.391-398
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• 1996

In order to understand the electrostrictive behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) solid solutions the dielectric constants and the electric-field-induced strains in (1-x)PMN-xPT (x=0.0-0.4) were investigated in the temperature range -5$0^{\circ}C$-20$0^{\circ}C$. Powder of (1-x)Pb(Mg2/3Nb2/3)O3-xPbTiO3 (x=0.0, 0.1, 0.2, 0.3, 0.35, and 0.4) were prepared from the oxide forms of Pb, Mg, Nb and Ti via a columbite precursor method As the amount of PbTiO3 increases the temperature of maximum dielectric constant(T$\varepsilon$max) increases and the phase transition become less diffusive. The strain maximum occurs only when the diffuse phase transition occurs from rhombohedral to cubic or rhombohedral to tetragonal as in x=0.1-0.35 The strains monotonically decrease with temperature in the materials in which phase transition occurs from tetragonal to cubic as in x=0.4.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.292-297
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• 2005

$LiMO_{2}(M=Co,Ni)$ samples were synthesized with $Li_{2}CO_{3},\;Co_{3}O_{4}$, and NiO by the solid-state reaction method. In the case of $LiCoO_{2}$, at low temperature$(T=400^{\circ}C)$ spinel structure was synthesized and the obtained spinel phase was transformed to layered phase at high temperature$(T\ge600^{\circ}C)$. The phase transition behaviors of $LiCoO_{2}$ were investigated with various heating temperature and time. The rate of transition was directly proportional to the concentrations of reactant, and activation energy of reaction was around 6.76 kcal/mol. When CoO(rock salt structure) was used as a starting material instead of $Co_{3}O_{4}$(spinel structure), layered structure of $LiCoO_{2}$ was obtained at low temperature. In the case of $LiNiO_{2}$ the transition from layered structure to rock salt structure occurred easily by disordering/ordering reaction, but did not occur in $LiCoO_{2}$. The difference in metal ion radii in $LiCoO_{2}$ and $LiNiO_{2}$ results in different behaviors of phase transitions.

• Journal of dental hygiene science
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• v.14 no.2
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• pp.140-149
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• 2014

The purpose of this study was to investigate the influence of etching surface treatment and aging treatment of zirconia on the shear bond strength between zirconia core and veneered ceramic. Four groups of zirconia-ceramic specimens were prepared; 1) NEZ group (no etching zirconia), 2) EZ group (etching zirconia), 3) ANEZ group (aging and no etching zirconia), 4) AEZ group (aging and etching zirconia). The shear bond strength between zirconia and porcelain was measured using Instron Universal Testing Machine. Surface texture with crystalline structure of zirconia surface was examined by the field emission scanning electron microscopy (FE-SEM) with ingredient analysis. The fractured surfaces of specimens were examined to determine the failure pattern by a digital microscope. The mean${\pm}$standard deviation of shear bond strengths were $23.47{\pm}3.47$ Mpa in NEZ, $28.30{\pm}4.34$ Mpa in EZ, $21.85{\pm}4.65$ Mpa in ANEZ, $24.65{\pm}3.65$ Mpa in AEZ group, respectively, and were significantly different (p<0.05). The average shear bond strength was largest in EZ group, followed by AEZ, NEZ, and ANEZ groups. Most specimens in NEZ group showed adhesive failure and most specimens in EZ, AEZ, and ANEZ group showed mixed failure. Surface of etching treatment group (EZ and AEZ) showed complex micro-structure and irregular surface texture which may facilitate mechanical interlocking, while untreated zirconia surface presented simpler micro-structure. In conclusion, an etching treatment improved bonding strength between zirconia and porcelain by forming mechanical interlocking.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1577-1587
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• 1994

TiO2 thin films with the substitution of oxygen with nitrogen were deposited on silicon substrate by metalorganic chemical vapor deposition (MOCVD) using Ti(OCH(CH3)2)4 (titanium tetraisopropoxide, TTIP) and N2O as source materials. X-ray diffraction (XRD) results indicated that the crystal structure of the deposited thin films was anatase TiO2 with only (101) plane observed at the deposition temperatures of 36$0^{\circ}C$ and 38$0^{\circ}C$, and with (101) and (200) plane at above 40$0^{\circ}C$. Raman spectroscopic results indicated that the crystal structure was anatase TiO2 in accordance with the XRD results without any rutile, fcc TiN, or hcp TiN structure. No fundamental difference was observed with temperature increase, but the peak intensity at 194.5 cm-1 increased with strong intensity at 143.0 cm-1 for all samples. The crystalline size of the films varied from 49.2 nm to 63.9 nm with increasing temperature as determined by slow-scan XRD experiments. The refractive index of the films increased from 2.40 to 2.55 as temperature increased. X-ray photoelectron spectroscopy (XPS) study showed only Ti 2s, Ti 2p, C 1s, O 1s and O 2s peaks at the surface of the film. The composition of the surface was estimated to be TiO1.98 from the quatitative analysis. In the bulk of the film Ti 2s, Ti 2p, O 1s, O 2s, N 1s and N 2s were detected, and Ti-N bonding was observed due to the substitution of oxygen with nitrogen. A satellite structure was observed in the Ti 2p due to the Ti-N bonding, and the composition of titanium nitride was determined to be about TiN1.0 from the position of the binding energy of Ti-N 2p3/2 and the quatitative analysis. The spectrum of Ti 2p energy level could be the sum of a 4, 5, or 6 Gaussian curve reconstruction, and the case of the sum of the 6 Gaussian curve reconstruction was physically most meaningful. From the results of Auger electron spectroscopy (AES), it was known that the composition was not varied significantly throughout the whole thickness of the film, and silicon oxide was not observed at the interface between the film and the substrate. The composition of the film was possible (TiO2)1-x.(TiN)x or TiO2-2xNx and in this experimental condition x was found to be about 0.21-0.16.

• Journal of Technologic Dentistry
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• v.29 no.1
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• pp.121-131
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• 2007

A preparation process's conditions of aqueous sol which contains anatase-type nano titania particles with photocatalyic properties was established by using Yoldas process, so called, DCS(Destabilization of Colloidal Solution) process in this study. And crystal size change and phase transformation of titania particles in aqueous titania sol depending on reaction conditions was investigated by a light scattering method and XRD analysis of frozen dried powders, respectively. This sol with photo catalytic nano titania particles was used to the following hydrophilic hybrid coating film's fabrication and its properties was evaluated. Subsequently, for coating film using the above mentioned aqueous titania sol, non-aqueous titania sol was prepared without any chemical additives and its time stability according to aging time was investigate. By using the above mentioned aqueous titania sol and non-aqueous sol, a complex oxide coating sol for metal and ceramic substrate and a organic-inorganic hybrid coating sol for polymer substrate was prepared and it's hydrophilicity depending on UV irradiation conditions was evaluated. As a conclusions, the following results were obtained. (1)Aqueous titania sol The average particle size of titania in formed aqueous titania sol was distributed between 20$\sim$90nm range depending on reaction conditions. And the crystal phase of titania powders obtained by frozen drying method was changed from amorphous state to anatase and subsequently transformed to rutile crystal phase and it is attributed to concentration gradient in aqueous sol. (2)Non-aqueous titania sol Non-aqueous titania sol was prepared using methanol as a solvent and a little distilled water for hydrolysis and nitric acid as a catalyst were used. The obtained non-aqueous titania sol was stable at room temperature for 20 days. Additionally, non-aqueous titania sol with addition of chealating reagent such as acethylaceton and ethylene glycol prolonged the stability of sol by six months. (3)Complex sol and hybrid sol with super hydrophilicity The above mentioned aqueous titania sol as a main photocataylic component and non-aqueous titania sol as a binder for coating process was used to prepare a complex sol used for metal, ceramic and wood material substrate and also to prepare the organic-inorganic hybrid sol for polymer substrate such as polycarbonate and polyethylene, in which process APMS(3-Aminopropyltrimethoxysilane), GPTS(3-Glycidoxypropyl-trimethoxysilane) as a hydrophilic silane compound and HEMA(2-Hydroxyethyl methacrylate) as a forming network in hybrid coating film were used. The hybrid coating film such as prepared through this process showed a superhydrophilicity below 1$10^{\circ}$ depending on processing conditions and a pencil's hardness over 6 H.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.460-466
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• 2002

Titanium oxide film was deposited on the commercially pure titanium (cp-Ti) by thermal oxidation method for its medical application. The cp-Ti disks were cleaned and then heat-treated at the temperatures of 500, 550, 600, 650, and 700${\circ}C$, respectively, for 10 min in air or Ar. To test the ability of calcium phosphate formation, the specimens were immersed in the Eagle's minimum essential medium solution at 36.5${\circ}C$ for 15 days. The morphology and chemical composition of the surfaces before and after soaking were analyzed by using FE-SEM and EDS. The in-vitro formation of carbonated calcium phosphate on the thin films containing nano-sized $TiO_2$ crystals was identified.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.178-183
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• 2002

Zinc fluosilicate ($ZnSiF_6$, 15% aqueous solution) was prepared using zinc oxide (ZnO) and fluosilicic acid ($H_2SiF_6$) by soluiton synthetic method. The fluidity and hydration properties of cement which was added $ZnSiF_6$ (aq.) as an additive for cement were studied. At water to cement ratio (W/C) equals to 0.45, the initial fluidity and slump loss of cement paste which the addition of $ZnSiF_6$ (aq.) was increased from 1.0% to 4.0% based on cement weight were investigated. Initial fluidity of cement paste was measured by mini-slump test and slump loss was examined by measuring the fluidity variation of cement paste with time elapsed from 0 min to 120 min at intervals 30 min. Also, the effect of $ZnSiF_6$ addition on the setting and hydration of cement paste when $ZnSiF_6$ increased in the addition range 1.0% to 3.0% were investigated. The fluidity of cement paste which was added 2.1% $ZnSiF_6$ (aq.) presented the highest value among all addition ranges. The setting time of cement paste was retarded gradually and the heat evolution of hydrated cement was reduced with the increasing of $ZnSiF_6$ addition.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.758-764
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• 2003

The cylindrical ${\gamma}$-alumina pellets were prepared by forming, hydration, drying and calcination after mixing amorphous alumina and pore generating agent with water. Concentration of Fe(NO$_3$)$_3$ㆍ9$H_2O$ that was catalyst precursor was fixed and made mixing solution that changed concentration of $CH_3$COOH in range of 2.5~20%, and here ${\gamma}$-alumina pellets were immerged and were hydrothermaly treated for 3 h at $200^{\circ}C$. And then we investigated creation and change of crystal, pore characteristics, $N_2$ adsorption and desorption isotherms, changes of acid site and mechanical strengths etc. According to the concentration of $CH_3$COOH, the crystals grew to acicular shape of 0.5~2${\mu}m$ length, and crystal structure showed the pseudo-boehmite structure. When hydrothermaly treated in 10% $CH_3$COOH solution, pore volume between 100~1000 $\AA$ was highest by 0.86 cc/g, and width of hysteresis curved line due to $N_2$ adsorption/desorption appeared as was smallest. When concentration of $CH_3$COOH was in range of 5~15%, new C-H functional groups were formed. Mechanical strength of pellets was highest by 1.35 MPa when $CH_3$COOH concentration was 2.5%.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.136-142
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• 2004

A homogeneous and stable ZnO sol was prepared by dissolving the zinc acetate dihydrate(Zn(CH$_3$COO)$_2$$.$2H$_2$O) in solution of isopropanol((CH$_3$)$_2$$.$CHOH) and monoethanolamine(MEA:H$_2$NCH$_2$CH$_2$OH). ZnO thin films were prepared by sol-gel spin-coating method and investigated for c-axis preferred orientation and physical properties with preheating temperature. The c-axis growth had a difference as increaing preheating temperature. ZnO thin film preheated at 275$^{\circ}C$ and post-heated at 650$^{\circ}C$ was highly oriented along the (002) plane. After preheating at 200∼300$^{\circ}C$ and post-heating at 650$^{\circ}C$, the transmittance of ZnO thin films by UV-vis. measurement was over 85% in visible range and exhibited absorption edges at about 370 nm. The optical band gap energy was obtained about 3.22 eV, The photoluminescence emission characteristics of ZnO thin film preheated at 275$^{\circ}C$ and post-heated at 650$^{\circ}C$ was found to orange emission(620 nm, 2.0 eV) by PL measurement, which revealed the possibility for application of inorganic photoluminescence device.