• Economic and Environmental Geology
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• v.29 no.3
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• pp.257-267
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• 1996

One hundred of thirty volcanic rocks col1ected from the Jeju island， Jeongog， Guryongpo and other areas were analyzed for major elements and trace elements with Au by inductively coupled argon plasma and graphite furnace atomic absorptiom spectrometry. The Au content is the highest values (0.2~43.4 ppb, average; 10.34 ppb) from the Jeju island volcanic rocks and the lowest (0.5~11.0 ppb, average; 1.23 ppb) from the Guryongpo volcanic area. The content of Au tends to be higher in the Quarternary volcanic rocks than Tertiary or Cretaceous volcanic rocks. The Au content of the calc alkali volcanic rocks tends to increase from mafic to felsic volcanic rocks, but that of the alkalic volcanic rocks tends to increase from felsic to mafic volcanic rocks. The Au content of the volcanic rocks collected from the Jeju island shows the highest values in the feldspar olivine basalts. Elements or oxides which have positive or negative correlations with Au are Ag, Mo, Rb, V, Y, $K_2O$, MgO and $SiO_2$, but other elements analyzed are not shown correlations with Au. It has a tendency to show that samples from the Jeju with 5 ppb gold and more are plotted in the non-Dupal area and those with less than 5 ppb gold in the Dupal area, while those from the Jeongog with 5 ppb gold and more are plotted in the Dupal area and those with less than 5 ppb gold in the non-Dupal area, in the Ba/Nb-La/Nb, Zr/Nb-Ba/Nb diagrams. It shows that samples from the Jeju and Guryongpo with high gold content are plotted in the within-plate, while those with low gold content are plotted in the arc-related area, and those from the Jeongog are scattered in the $TiO_2-Al_2O_3$, $Zr/A1_2O_3-TiO_2/Al_2O_3$ diagrams.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.378-385
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• 1999

To evaluate the effect of Sn on the corrosion behavior of Zr alloys for nuclear fuel claddings, the corrosion tests on the binary Zr-xSn and the ternary Zr-0.4Nb-xSn alloys were performed in water at $360^{\circ}C$. The binary alloys containing 0.5, 0.8 and 1.5wt.% Sn showed the transition corrosion rate at 15 days. On the other hand, the binary alloy containing 2.0wt.% Sn showed a good corrosion resistance without the transition of corrosion rate up to 80 days. The corrosion rate of the ternary alloy increased with increasing Sn content. The difference of corrosion behaviors between binary and ternary alloys is considered due to the different solubility of Sn, Nb content and precipitates. The corrosions of Zr-xSn and Zr-0.4Nb-xSn alloys would be controlled by the fraction of tetragonal-$ZrO_2$and the amount of hydrogen pick-up.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.97-104
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• 2005

The effect of Nb on interfacial bonding characteristics of Ni-Cr alloy for porcelain fused to metal crown (PFM) has been studied in order to investigate oxide layer. A specimens, which is 0.8mm in thickness, were fired at 1,000$^{\circ}C$ with four tests such as air, vacuum, air for 5 minutes and vacuum for 5 minutes in order to examine an oxide behavior of alloy surface generated by the adding of Nb to be controlled at a rate of 0, 1, 3 and 5. It observed oxide film form of the fired specimens with optical microscope and scanning electron microscope (SEM), and chemical formation of them with energy disperse X-ray spectroscopy (EDX). The other specimens, which is 2mm in thickness, were fired at 1,000$^{\circ}C$ with air and vacuum in order to analyze the diffusion behaviors of alloy-porcelain interface by X-ray dot mapping. The results of this study were as follows: 1. The observation of microstructure of specimens by SEM showed that the more Nb content is high, the more much intermediate compound of rich Nb is observed. 2. The surface morphology of oxide film is most dense in 3% Nb. The heat treatment in air constitutes denser oxide film than heat treatment under vacuum. 3. The diffusion behavior of oxide layer by X-ray dot mapping showed that Si, Al of porcelain diffuse toward metal.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.248-251
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• 1999

The microwave dielectric properties of The Dielectric Properties of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ (A = Sr, Ca, x = 0, 0.2 ,0.4 ,0.6, 0.8, 1.0) were investigated. In composition of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O, densities are decreased with increasing x values. Grain sizes are decreased with Sr content and Increased with Ca content. The hexagonally ordered superstructure was observed in $Ba_{1-x}$Sr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the intensity of superlattice increased with x value. In $Ba_{1-x}$Cr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the additional diffraction patterns were shown. The highest value of $\varepsilon$$_{r}$ was shown in x=0.2 of BCMN systems and the value was 41.9. The highest Q$\times$f was shown in x=0.2 of BSMN systems and the value was 68,000. $\tau$$_{f}$ were shown 0 ppm/$^{\circ}C$ near x=0.8.TEX> near x=0.8.0.8.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.154-158
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• 1999

Magnetic properties and microstructure of nanocrystalline $\alpha$-(Fe, Co)-based Nd-(Fe, Co)-B-Nb-Cu alloys have been investigated. $Nd_x(Fe_{0.9}Co_{0.1})_{90-x}B_6Nb_3Cu_1$(x=2, 3, 4, 5, 6) alloys prepared by rapid solidification process show amorphous phase except the one with x=2. By a proper annealing, the amorphous in the alloy is changed to a nanocrystalline phase. It is confirmed that the nanocrystalline alloys are composed of $\alpha$-(Fe, Co) and $Nd_2(Fe, Co)_{14}B_1$ phase. The optimally annealed $Nd_3(Fe_{0.9}Co_{0.1})_87B_6Nb_3Cu_1$ alloy shows the highest remanence of 1.55 T. The coercivity increases with the increase of Nd content The maximum coercivity of 4.6 kOe is obtained from an optimally annealed $Nd_6(Fe_{0.9}Co_{0.1})_84B_6Nb_3Cu_1$ alloy, resulting in the maximum energy product of 10.6 MGOe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.98-102
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• 2003

$Ba_2NaNb_5O_{15}$, hereafter BNN, thin films are attractive candidates for nonvolatile memory and electro-optic devices. In the present work, thin films that have different contents of Ba, Na and Nb have been prepared by H-MOD technique on silicon and Pt substrates. XRD and SEM were used to investigate the phase evolution behavior and the microstructure of the films. It was found that the films of about 450nm thick were crack-free and uniform in microstructure. Nb content strongly influenced the phase formation of the films, where low temperature phase was always formed at the stoichiometric BNN composition. However, the amount of low temperature phase decreased with the increase of excess Nb content, and the single phase (orthorhombic tungsten bronze structure) BNN thin film was obtained at the temperature as low as $750^{\circ}C$ for samples with excess niobium. From this study, the sub-solidus phase diagram below $850^{\circ}C$ for $BaO-Na_2O-Nb_2O_5$ ternary system is proposed.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.839-845
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• 1995

The structural and dielectric properties of Pb(Mg1/3Nb2/3)O3 ceramics substituted by Nd3+, La3+, K+ and Na+ were studied over 0~50 at.% substituent content. The 1 : 1 ordering behavior of Mg2+ and Nb5+ ions in the B site sublattice was observed in Nd3+-and La3+-modified compounds. The degree of ordering was increased with Nd3+, La3+ content in the compounds. But K+-or Na+-modified compounds did not exhibit the ordering behavior. This was explained by charge and size effect of A and B site cations and oxygen vacancies. As the mole fractions of substituent increased, the maximum values of dielectric constants were rapidly decreased and the phase transitions were broadened. Phase transition temperature was correlated with the covalency of A-O and B-O bonding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1989.06a
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• pp.70-73
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• 1989

(1-x-y)Pb($Zn_{1/3}Nb_{2/3})O_3-Ba(Zn_{1/3}Nb_{2/3})O_3-PbTiO_3(0.12{\leq}x{\leq}0.21, 0.24{\leq}y{\leq}0.33$) ternary compound ceramics were fabricated by the mixed oxide method. The sintering temperature and time were 1050 [$^{\circ}C$], 2[hr]. Morphotropic phase boundary region was chosen for the composition. 0.55 PZN-0.21 BZN-0.24 PT specimen had the highest value of relative dielectric constants, 5353. The curie temperature of specimens were increased linearly with PT content. Near the morphotropic phase boundary, electro-mechanical coupoling factor and mechanical quality factor of the specimens had the highest values.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.864-870
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• 1998

The effect of {{{{ {{Nb }_{2 }O }_{5 } }} and CoO addition on the temperature dependence of the {{{{ {BaTiO }_{3 } }}-based ceramic capa-citor has been studied. X7R with moderate temperature dependence has been developed by means of pre-cisely controlled {{{{ {{Nb }_{2 }O }_{5 } }}/CoO ratio. Dielectric constant(K) and dissipation factor(DF) were 3500 and 1.5% respectively. As the content of {{{{ {{Nb }_{2 }O }_{5 } }} was increased the curie temperature(Tc) was shifted to lower tem-perature and the dielectric constant at Tc was decreased. The proper addition of CoO with {{{{ {{Nb }_{2 }O }_{5 } }} improved the temperature dependence of dielectric properties of the {{{{ {BaTiO }_{3 } }}-based ceramic capacitor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.260-260
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• 2007

Low-temperature sintering and dielectric properties of the $1-xBiNbO_4-xZnNb_2O_6$ ceramics (x=0.3, 0.5, and 0.7) with 10 wt% zinc borosilicate (ZBS) glass was investigated as a function of the substitution of $ZnNb_2O_6$ with a view to applying this system to LTCC technology. The all composition addition of 10 wt% ZBS glass ensured a successful sintering below $900^{\circ}C$. The the amount of $ZnNb_2O_6$ on $ZnNb_2O_6$ ceramics increased the $Q{\times}f$ values, but it decreased the sinterability and dielectric constant due to the higher $Q{\times}f$ value and sintering temperature of $ZnNb_2O_6$ than that of $ZnNb_2O_6$ ceramics. The increase of $ZnNb_2O_6$ content from 0.3 to 0.7 in the $1-xBiNbO_4-xZnNb_2O_6$ ceramics with 10 wt% ZBS glass sintered at $900^{\circ}C$ demonstrated 30~20 in the dielectric constant (${\varepsilon}_r$), 3,500~4,500 GHz in the $Q{\times}f$ value.