• Journal of Microbiology
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• v.41 no.4
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• pp.345-348
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• 2003

The bio-mediated production of calcite crystals by calcinogenic bacteria has great applicable value for the restoration of deteriorated calcareous monuments, because of its high purity and coherency. An investigation of the conditions for calcite production by an alkalophilic Bacillus amyloliquefaciens CMB01 strain was made. Optimal calcite precipitation occurred when the bacterium was cultured at pH 8.0 and 30$^{\circ}C$, and in B4 medium that consisted of 0.4% yeast extract, 0.5% glucose, and 1.5% calcium acetate. Calcium ion of the bacterially induced calcite was analyzed by an inductively coupled plasma (ICP) spectrophotometer. Optical and scanning electron microscopy (SEM) of the calcite revealed a typical rombohedral polycrystalline structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.764-767
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• 2004

This study was to measure the minuteness structure, dielectric properties of (0.3-x)PMN - XPSS-0.7PZT+0.5wt%NiO+0.5wt%$MnO_2$(x=0.05, 0.10, 0.15, 0.20, 0.25)ceramics according to sintering temperature and PSS moi percentage after manufacturing the specimens with a general method. the results of this study were gotten such as follows. The crystal structure of ceramic has the rombohedral structure in XRD. it appeared that addition of Ni, Mn additive was helpful to the formation of stable structure. Dielectric constant at $20^{\circ}C$ showed its maximum value 890.001 in specimens sintered at $1000^{\circ}C$, x=0.15mol. and dielectric loss showed its minimum value 6.95[%] in specimens sintered at $1000^{\circ}$, x=0.05mol. The variation rate of dielectric constant according to the change of frequency was decreased by increasing frequency, The variation rate of dielectric constant according to the change of temperature was increased by increasing temperature.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.51-53
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• 2005

This study was to measure the minuteness structure, dielectric properties of 0.03PCW-0.07PNN-0.9PZT ceramics according to sintering temperature manufacture the specimens with a general method. The results of this study were gotten such as follows. The crystal structure of ceramic changed the rombohedral structure into teteragonal structure according to rising sintering temperature in XRD. Dielectric constant at $20^{\circ}C$ showed its maximum value 510.599 in specimens sintered at $1100^{\circ}C$ and dielectric loss showed its minimum value 7.43% in specimens sintered at $1100^{\circ}C$. The variation rate of dielectric constant according to the change of frequency showed its minimum value 0.029/kHz at $1100^{\circ}C$. The variation rate of dielectric constant according to the change of temperature showed its minimum value $1.40/^{\circ}C$ at $1500^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.806-808
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• 2001

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, electromechanical factor(kp) little is changed. kp was maximum value 23.37[%] at xPMB 0.03[mol%]. mechanical quality factor(Qm) was maximum value 237.04 at xPMB 0.03[mo1%].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.578-580
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• 2002

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, electromechanical factor(kp) little is changed. kp was maximum value 23.37[%] at xPMB 0.03[mol%]. mechanical quality factor(Qm) was maximum value 237,04 at xPMB 0.03[mol%].

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1524-1526
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• 2001

In this thesis, specimens was manufactured in general method annexing PMB-PZT system ceramic, and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the tetragonal structure which is close to rombohedral structure, and consequently the specimen characterized by MPB was manufactured. According to dopping with xPMB, the dielectric constant at 20[$^{\circ}C$] reduced on the whole, dielectric constant was maximum value $8.0{\times}10^2$ at xPMB 0.01[mol%]. Dielectric loss was maximum value 4.1[%] at xPMB 0.01[mol%].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.650-652
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• 2002

In this paper, specimens was manufactured in general method annexing PAN-PZT+0.8wt%Mn+1wt% Nb ceramics doped by Sr(0.0 ~ 1.2 wt%). and the following conclusion has been deduced. In XRD, the crystal structure of ceramic has the rombohedral structure and consequently the specimen characterized by MPB was manufactured. According to dopping with Sr, electromechanical factor(kp) little is changed. kp was maximum value 31.31[%] at Sr 1.2[wt%]. mechanical quality factor(Qm) was maximum value 371.879 at Sr 0.6[wt%].

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1624-1626
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• 2004

This study was to measure the minuteness structure, piezoelectric properties of (0.3-x)PMN- xPSS -0.7PZT+0.5[wt%]NiO+0.5(wt%)$MnO_2$ (x=0.05, 0.10, 0.15, 0.20, 0.25)ceramics according to sintering temp- erature and PSS(mol%) after manufacturing the specimens with a general method. the results of this study were gotten such as follows. The crystal structure of ceramic has the rombohedral structure in XRD. It appeared that addition of Ni, Mn additive was helpful to the formation of stable structure. The electrome- chanical coupling coefficient(kp) showed good properites on the whole, showed its maximum value 25.94[%] in specimens sintered at 1100[$^{\circ}C$], x=0.25mol. The mechanical quality coefficient(Qm) showed its maximum value 272.42 in specimens sintered at 1150[$^{\circ}C$], x=0.05mol. and was decreased by increasing PSS[mol%] The temperature coefficient of the resonant frequency(TCFr) showed stable properties in all sintering temperature with x=0.05mol. Especially good stability of 0.0054[%/$^{\circ}C$] showed in specimens sintered at 1100$^{\circ}C$, x=0.05mol.

• Journal of the Korean Magnetics Society
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• v.12 no.1
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• pp.14-19
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• 2002

The iron-doped perovskite La$_{0.67}$Sr$_{0.33}$Mn$_{0.99}$$^{57}$Fe$_{0.01}$O$_3$compound has been studied by x-ray diffraction, Mossbauer spectroscopy, and vibrating sample magnetometry. The single phase of the polycrystalline La$_{0.67}$Sr$_{0.33}$Mn$_{0.99}$$^{57}$Fe$_{0.01}$O$_3$powder has been prepared by a waterbased solgel method. Crystalline La$_{0.67}$Sr$_{0.33}$Mn$_{0.99}$$^{57}$Fe$_{0.01}$O$_3$was a rombohedral structure with lattice parameters a$_{0}$=5.480 $AA$, $alpha$=60.259$^{circ}$. Mossbauer spectra of La$_{0.67}$Sr$_{0.3}$/Mn$_{0.99}$$^{57}$Fe$_{0.01}$O$_3$have been taken at various temperatures ranging from 20 to 400 K. As the temperature increases toward the Curie temperature, T$_{c}$=375 K, the Mossbauer spectra show line broadening and the difference between the 1,6 and 3,4 linewidths is caused by the anisotropic hyperfine field fluctuation. The anisotropic field fluctuation of +H (P$_{+}$=0.80) is greater than -H (P$_{-}$=0.20). We calculated that the anisotropy energy was 124.01 erg/cm$^3$for T=150 K which is associated with the large line broadening.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.169-173
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• 2004

We have synthesized monodispersed $\alpha$-F $e_2$ $O_3$ nano particles to investigate the spin change during the Morin transition temperature( $T_{M}$). The particle size was founded to have a very uniform distribution of 80 nm by x-ray diffraction and size dispersion analyzer. The Mossbauer spectra between the 4.2 K and the room temperature show that $T_{M}$ was shifted and the spin states of Fe ion were changed with the particle size. The Morin transition temperature of bulk usually quoted in literature is 265 K but, it decreases with the size and no transition was found at the critical size down to 4.2K. The spin direction of 80 nm sized particles are normal to the hexagonal c-axis above the $T_{M}$ and are tilted about 28～29$^{\circ}$ below $T_{M}$, which is the [110] direction of rombohedral structure.