• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.443-448
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• 1997

Titanium carbonitride (Ti(CxN1-x)) ceramics were prepared by hot pressing of the mixture of TiN and graphite. Hot pressing was performed in a graphite mold at 198$0^{\circ}C$ for 40 min under 44 MPa in N2 atmosphere. The effect of graphite addition on sinterability and the mechanical properties of titanium carbonitride were investigated. In this study, the solubility limit of graphite in Ti(CxN1-x) was slightly below 10 wt% based on the results of XRD analysis. Within the solubility limit, graphite dissolved completely into titanium nitride and formed the single phase Ti(CxN1-x) solid solution. Peak relative density of 99% and hardness of 16 GPa were observed for Ti(CxN1-x) ceramics with 7 wt% graphite while maximum flexural strength of 500 MPa and fracture toughness of 4.0 MPa.m1/2 were observed for Ti(CxN1-x) ceramics with 10 wt% graphite. The electrical resistivities of the ceramics with 7 wt% and 10 wt% graphite were observed 40 {{{{ mu OMEGA }}cm and 50 {{{{ mu OMEGA }}cm respectively.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1056-1064
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• 1995

95Pb(Mg1/3Nb2/3)O3-5PbTiO3 (hereinafter designated as 95PMN-5PT) system was prepared by the columbite-precursor method with 2 mol% excess PbO to compensate the PbO loss during thermal process. The amount of CuO was 1~10 mol%, and the effects of CuO addition on the dielectric properties of this system have been investigated. From the microstructures, XRD analysis and dielectric measurements, the solubility limit of CuO in 95PMN-5PT was found to be around 3 mol%. Lattice parameter and Curie temperature were found to be decreased as the amount of CuO increased up to the solubility limit. This result confirmed that the Cu2+-ions substituted the Pb2+-ions. It was revealed that the addition of CuO on 95PMN-5PT promoted the sinterability and properties. The room temperature dielectric constant, the loss factor and the specific resistivity of the specimens processed with optimum conditions were 23000, 1%, and 8$\times$1011Ω.cm, respectively.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.450-455
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• 2011

[ $Al_2TiO_5$ ]has a high refractive index and good solubility of the chromophore in the $Al_2TiO_5$ lattice, which allows this structure to be a good candidate for the development of new ceramic pigments. However, pure $Al_2TiO_5$ is well known to decompose on firing at $900{\sim}1100^{\circ}C$. However, this process can be inhibited by the incorporation of certain metal cations into its crystalline lattice. In this study, the synthesis of gray ceramic pigment was performed by doping cobalt on the $Al_2TiO_5$ crystal structure. The $Al_2TiO_5$ was synthesized using $Al_2O_3$ and $TiO_2$, and doped with $Co_3O_4$ as a chromophore material. In order to prevent the thermal decomposition during the cooling procedure, MgO was added to samples by 0.05 mole, 0.1 mole, and 0.15 mole as a stabilizer. The samples were fired at $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigment were analyzed using XRD, Raman spectroscopy, UV, and UV-vis. $Al_2O_3$ was available for the formation of $CoAl_2O_4$, which should also be considered in order to explain the small amount of this phase detected in the sample with the higher $Co^{2+}$ content (${\geq}$ 0.03 mole). It was found that the solubility limit of $Co^{2+}$ in the $Al_2TiO_5$ crystal was 0.02 mole% through an analysis of Raman spectroscopy. Through the addition of a pigment with 0.02 mole% of $Co^{2+}$ to lime-barium glaze, stabilized gray color pigments with 66.54, -2.35, and 4.68 as CIE-$L^*a^*b^*$ were synthesized.

• Biotechnology and Bioprocess Engineering:BBE
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• v.2 no.2
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• pp.117-121
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• 1997

Glutamic acid can be crystallized inside cation exchange column when displacer NaOH concentration is high enough to concentrate displaced glutamic acid beyond its solubility limit. Resulting crystal layer of glutamic acid was moved with liquid phase through the column, and thus could be eluted from the column and recovered in fraction collector. For the purpose of enhancing crystal recovery, effects of operating parameters on the crystal formation were investigated. The increase in the degree of crosslinking of resin favored crystal recovery because of its low degree of swelling. Higher concentration of displacer NaOH was advantageous. If NaOH concentration is too high, however, crystal recovery was lowered due to the solubility-enhancing effects of high pH and ionic strength. The decrease of mobile phase flow rate enhanced crystal recovery because enough time to attain local equilibrium could be provided, but film diffusion would control the overall crystal formation with extremely low flow rate. Lower temperature reduced solubility of glutamic acid and thus favored crystal formation unless the rate of ion exchange was severely reduced. The ion exchange operated by displacement mode coupled with crystallization was advantageous in reducing the burden of further purification steps and in preventing purity-loss resulted from overlapping between adjacent bands.

• Progress in Superconductivity
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• v.10 no.2
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• Nuclear Engineering and Technology
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• v.29 no.2
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• pp.127-137
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• 1997

Equilibrium concentrations of major elements in an underground repository with a capacity of 100,000 drums have been simulated using the geochemical computer code (EQMOD). The simulation has been carried out at the conditions of pH 12 to 13.5, and Eh 520 and -520 mV. Solubilities of magnesium and calcium decrease with the increase of pH. The solubility of iron increases with pH at Eh -520 mV of reducing environment while it almost entirely exists as the precipitate of Fe(OH)$_3$(s) at Eh 520 mV of oxidizing environment. All of cobalt and nickel are predicted to be dissolved in the liquid phase regardless of pH since the solubility limit is greater than the total concentration. In the case of cesium and strontium, all forms of both ions are present in the liquid phase because they have negligible sorption capacity on cement and large solubility under disposal atmosphere. And thus the total concentration determines the equilibrium concentration. Adsorbed amount of iodide and carbonate are dependent on adsorption capacity and adsorption equilibrium constant. Especially, the calcite turns out to be a solubility-limiting phase on the carbonate system. In order to validate the model, the equilibrium concentrations measured for a number of systems which consist of iron, cement, synthetic groundwater and radionuclides are compared with those predicted by the model. The concentrations between the model and the experiment of nonadsorptive elements cesium, strontium, cobalt nickel and iron, are well agreed. It indicates that the assumptions and the thermodynamic data in this work are valid. Using the adsorption equilibrium constant as a free parameter, the experimental data of iodide and carbonate have been fitted to the model. The model is in a good agreement with the experimental data of the iodide system.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1093-1096
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• 2001

The Solid solution of A $l_2$ $O_3$ into ZnO can be defined by the substitution reaction of Al$\^$3+/ ions into the Zn$\^$2+/ sites of ZnO crystal lattice, the tetrahedral interstices composed of four neighbor oxygen ions in the wurtzite structure. Since the reaction either creates new zinc vacancies or consumes the oxygen vacancies, it should be in equilibrium with ZnO nonstoichiometry and disorder reactions. The relationships make oxygen partial pressure P$\sub$o2/ control the concentrations of the vacancies and consequently limit the Al solubility in ZnO, [Al$\sub$zn/]$\sub$max/. This paper firstly reports with a refined model for defect quilibria in ZnO that the solubility decrease with the increase of P$\sub$o2/, [Al$\sub$zn/]$\sub$max/ P$\sub$o2/$\^$-1/4/.

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.43-49
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• 1986

By simple substitution of divalent cobalt nickel copper ion in the calcium-fluorapatite the ability to produce color was explored. To determine the solubility limit of cobalt nickel copper in the calcium-fluorapatite and the absorption spectrum with the addition of each transition elements XRD and visible range Spectroscopy were emp-loyed.

• Journal of the Korean Ceramic Society
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• v.23 no.6
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• pp.52-58
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• 1986

$Pb(Zr_{0.525} Ti_{0.475})O_3$ piezoelectric ceramics both unmodified and doped with NiO were prepared by the conventional oxide techniques using sintering temperature from 900 to to 125$0^{\circ}C$. The difference in densification process between unmodified and NiO doped PZT ceramics was studied by shrinkage vs. firing temperatures and it was caused by increasing defect concentration in calcining process of NiO doped PZT ceramics. And nickel oxide solubility limit for $Pb(Zr_{0.525} Ti_{0.475})O_3$ ceramics is shown to be at the range from 0.2wt% to 0.5wt% from this defect model micro-structures dielectric and piezolectric properties of Nio doped PZT ceramics.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.453-459
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• 2001

It is important for the fabrication of nuclear cladding to optimize the microstructure, because the properties of Zr-based nuclear claddings such as mechanical properties, oxidation-resistance and corrosion- resistance vary widely with its microstructure. The microstructure in Zr-based alloy is strongly dependent on the solubility of alloying element. However, it is very difficult to measure the solubility due to the low solution limit of alloying elements in Zr-based alloy. In this study, Thermoelectric Power(TEP) measurements are used to determine the solubility of Nb in Zr-0.8Sn alloy, which is confirmed by optical microscopy and transmission electron microscopy. The solutioning of Nb obtained by a homogenization treatment and water-quench leads to a decrease of TEP The saturation of TEP appears with the increase of homogenization temperature, which means the saturation of the Nb content in the matrix. From these results, the solubility ($C_{Nb}$) of Nb in Zr-0.8Sn with temperature could be expressed as fellow equation : $4.69097{\times}10^{16}{\times}e^{-25300\times\;I/T}$(ppm.at.%)