• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.85-92
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• 1993

Oxynitride glasses in Na-Ca-Si-O-N system were prepared by melting at 135$0^{\circ}C$ for 2 hours in N2 gas. The effects of Si/Na mole ratio and the various Si3N4 contents were investigated. Stable oxynitride glasses can be obtained up to 9wt.% Si3N4 content in case the Si/Na mole ratio was 2.12 and 1.62, but $\beta$-Si3N4 was precipitated at 9wt.% Si3N4 content in case the Si/Na mole rtio was 1.12. Density (p), chemical durability, hardness (Hv), and fracture toughness (KIC) increased with increasing Si3N4 content. In cae the Si/Na mole ratio was 1.12, the increment of properties was remarkable but hardness and fracture toughness did not increase no longer owing to precipitation of $\beta$-Si3N4.

• 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.

• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.3-12
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• 1979

The effects of sintering temperature and sintering atmosphere on magnetic properties and microstructuresof Mn-Zn ferrites have been studied. Mixture of 52.8mole% $Fe_2O_3$, 26.4mole% MnO, 15.1mole0% ZnO and 5.7mole% NiO was prepared, and 0.1mole% CaO, 0.02mole% $SiO_2$ were added as minor additives. After calcining and ball milling the powder was granulated for compacting. The specimens were sintered at $1, 250^{\circ}$, $1, 300^{\circ}$and 1, 35$0^{\circ}C$ in the various atmosphere of $N_2$, $N^_2\DIV0.6% O_2$, $N_2＋2.7% O_2$, $N_2＋4.1% O_2$, $N^2＋8.2% O_2$ and air for 3 hours and cooled in $N_2$ atmosphere. The grian growth rate and densities increase as sintering temperature and oxygen content of atmosphere increase. At the sintering temperature of $1, 250^{\circ}C$ the initial permeabilities increase as oxygen content of atmosphere increase. At the sintering temperature of$ 1, 300^{\circ}$and $1, 350^{\circ}$ the initial permeabilities show maximum values at $N_2＋4.1% O_2$ atmosphere. The secondary peaks of initial permeabilities are observed between 100$^{\circ}$and 20$0^{\circ}C$, and the positions of secondary peaks move to higher temperature as oxygen content of atmosphere increases. Q-factors decrease as sintering temperature increases and oxygen content of atmosphere decreases.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.410-421
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• 1993

Phase equilibria and reaction paths of the superconducting phases and other compatible phases at $850^{\circ}C$ in the Bi-Sr-Ca-Cu-O system were studied. $Bi_2O_3$ was added to $Sr_2CaCu_2O_x$ by 5% up to 40 mole% Bi in the pseudo-binary $Bi_2O_3-(Sr_2CaCu_2O_x)$ system and the heat treated samples were analysed using XRD. SEM, EDS. and DT A. When Bi contents were greater than 35 mole% Bi, liquid phase was formed which was compatible with $Bi_2Sr_2CaCu_2O_8$ phase. The m.p. of $Bi_2Sr_2CaCu_2O_8$ phase decreased as the content of (Sr+Ca)decreased. $Bi_{2+x}Sr_2CaCu_2O_8$ phase first segregated out of liquid phase around $Bi_2Sr_2CaCu_2O_8$ phase during cooling of liquid phase.

• Journal of the Korean Chemical Society
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• v.16 no.3
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• pp.157-165
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• 1972

Thermal decomposition of ammonium metavanadate has been investigated by using the quartz spring balance and differential thermal analysis. It showed that the decomposition of ammonium metavanadate is proceeded at two stages which correspond to $180^{\circ}C-220^{\circ}C$ and $310^{\circ}C-330^{\circ}C$ decomposition temperatures, respectively. Evolved ammonia gas in thermal decomposition has been analyzed quantitatively by titration. And the constituents of gases evolved have been evaluated by gas chromatography and omegatron spectrometer. From these results, it was concluded that the gases evolved in the first step decomposition were $NH_3$ and $H_2O$ with 2:1 ratio and the second step decomposition corresponded to the formation of $NH_3$, $H_2O$ and $N_2O$ which was produced in oxidation of $NH_3$ by $V_2O_5$. The decomposition products were identified by means of X-ray diffraction method. The decomposition product in air was V_2O_5 and the product in vacuum $V_3O_7.$ The kinetics of the thermal decomposition was studied, giving the values of the activation energy of 41.4 kcal/mole and 64.4 (kcal/mole) respectively.

• Korean Journal of Crystallography
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• v.17 no.1
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• pp.24-32
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• 2006

The microwave dielectric properties of $Zn_3Nb_2O_8\;with\;V_2O_5$ addition were investigated. The addition of $V_2O_5$ enhanced the sinterability of $Zn_3Nb_2O_8$, which resulted in high density of $Zn_3Nb_2O_8$ ceramic greater than 95% of the theoretical value when sintered at $900^{\circ}C$ for 4 hours. X-ray diffraction analysis of sintered $Zn_3Nb_2O_8$ ceramic showed no second phase with $V_2O_5$ addition. Dielectric permittivity(${\varepsilon}_r$) and quality factor($Q{\times}f$) varied with both density at different sintering temperature and $V_2O_5$ addition. Dielectric permittivity, quality factor and temperature coefficient($T_{cf}$) of the two mole of $V_2O_5\;added\;Zn_3Nb_2O_8$ that was sintered at $900^{\circ}C$ were 21.4, 40,000, $-54ppm/^{\circ}C$, respectively.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.84-89
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• 1993

Spatial homogenity of Mg (4 mole %):LiNb$O_3$ is investigated by studying the characteristic of Second Harmonic Generation in Mg:LiNb$O_3$ as a function of temperature and DC Electric Field. It is found that the temperaturs at which the intensity of the second harmonic is reduced to the first zero from its maximum for the phase matching condition is shifted linearly to the strength of DC Electric field applied to optic axis of Mg:LiNb$O_3$. From these results, the electro-optic coefficient of Mg:LiNb$O_3$ is estimated to be higher than that of Congruent LiNb$O_3$ by a factor of 1.5.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.148-149
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• 1999

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.161-163
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• 2008

$TiO_2-V_2O_5$ sol was fabricated using sol-gel method and $TiO_2-V_2O_5$, thin films were fabricated using dip-coating method. $V_2O_5$ sol was added 0.01mole, 0.03mole, 0.05mole into $TiO_2$ sol. Capacitance of thin films decreased with increasing $V_2O_5$ additive and it increased largest at 0.01mole. Because adsorption time and desorption time of thin films was about 2 minutes 40 seconds and about 3 minutes 40 seconds respectively, adsorption time was faster about 1 minutes than desorption time.

• Analytical Science and Technology
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• v.26 no.6
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• pp.401-406
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• 2013

Oxygen($O_2$) consumption and carbon dioxide($CO_2$) excretion of a fertile chicken egg during incubation were measured by a gas mass spectrometer. A closed sample chamber was developed to collect gas samples during the 20 days of artificial incubation of both a fertile and an infertile egg. After leaving an egg in the sample chamber for an hour, using a gas-tight syringe, samples of 2 mL of gas were collected from the closed sample chamber and analyzed using a gas mass spectrometer in 2~4 day intervals. The $O_2$ consumption and $CO_2$ excretion of chicken embryos increased rapidly after 10 days from the starting point of incubation. After 20 days, 23 mL of $O_2$ was consumed and 16 mL of $CO_2$ was excreted per hour. Throughout the whole period of incubation, concentration of $O_2$ decreased 4.3 mol% and $CO_2$ increased only 3.1 mole%, i.e., the mole of consumed $O_2$ and the mole of excreted $CO_2$ were not the same. On the other hand, during the same period, concentration of $N_2$ increased about 1.3 mol% and the increased mole fraction of $N_2$ was comparable with the difference (1.2 mol%) between the mole fraction of consumed $O_2$ and excreted $CO_2$. Therefore, we can attribute the increase of $N_2$ mole% to the difference of mole fraction between consumed $O_2$ and excreted $CO_2$. In this study, through the analysis of gas, we could explain the respiration of a fertile chicken egg during incubation.