• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.90-91
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• 2003

Amorphous magnetic materials with competing magnetic interactions are the subject of current interest. Critical behaviour studies have been performed in order to understand the nature of the phase transition at the Curie point (T$\sub$c/) and type of magnetic ordering below the T$\sub$c/. In some cases there exists a temperature interval in which the magnetic system consists of ferromagnetic grains separated by the paramagnetic interlayers. Magnetic properties of nanoparticles embedded in amorphous matrix also are the subject of recent interest. While these materials exhibit excellent soft magnetic properties at room temperature, some of them have been found to be superparamagnetic in the temperature range above the T$\sub$c/ of the matrix. Thus the role of different magnetic phases in the intergrain magnetic coupling can possibly be taken apart in a sufficiently broad temperature range and investigated separately. In particular materials with competing magnetic exchange interactions show characteristics of enhanced magnetoresistance and softer magnetic properties when magnetic nanocrystals are dispersed in amorphous matrix. We expect careful magnetic measurements in the vicinity of T$\sub$c/ would throw some light on magnetic behaviour of above materials. We present here the FMR analysis of Fe$\sub$82/Mn$\sub$8-x/B$\sub$x/Zr$\sub$10/ alloy near the Curie point.

• Journal of the Korean Society of Tobacco Science
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• v.25 no.2
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• pp.103-110
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• 2003

This study was conducted to investigate the pyrolysis products of ι-menthol by Curie-Point pyrolysis. The pyrolysis of ι-menthol was performed at 16$0^{\circ}C$, 42$0^{\circ}C$, $650^{\circ}C$, and 92$0^{\circ}C$ by Curie-Point Pyrolyzer and their pyrolysis products were analyzed by GC/MSD. In addition, tobacco leaves added ι-menthol were pyrolyzed at the same condition in case of ι-menthol. The beginning temperature for pyrolysis formation was in the vicinity of 42$0^{\circ}C$ and the major components of the pyrolysis products identified were iso-menthol, 2-menthene, menthomenthene, and menthone. The amount of these components was increased by increasing temperature and the hydrocarbons such as hexadecene and pentadecene formed by ring cleavage were generated at 92$0^{\circ}C$. The yield of ι-menthol in pyrolysis of tobacco leaves was decreased as the temperature of pyrolysis was raised and the pyrolysis products of ι-menthol weren't identified in the pyrolysis of tobacco leaves. Also, to analyze the weight decrease, ι-menthol was analysed by thermal analyzer(TA), and then the weight decrease of ι-menthol was occurred in the vicinity of 18$0^{\circ}C$.

• Journal of the Korean Society of Tobacco Science
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• v.24 no.2
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• pp.101-106
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• 2002

This study was conducted to investigate the pyrolysis products of patchouli oil by Curie-Point pyrolysis. The pyrolysis of patchouli oil was performed at the temperature of 16$0^{\circ}C$, 42$0^{\circ}C$, $650^{\circ}C$, 76$0^{\circ}C$, and 92$0^{\circ}C$ by Curie-Point Pyrolyzer. The pyrolysis products were analyzed by gas chromatography(GC) and mass selective detector(MSD). Total 21 components were identified in the pyrolyzates of patchouli oil. The temperature for maximum formation of most of these compounds was in the range of 76$0^{\circ}C$~92$0^{\circ}C$. The major components were $\beta$-patchoulene, $\alpha$-guaiene, $\beta$-caryophyllene, $\alpha$-patchoulene, seychellene, $\delta$-guaiene, and patchouli alcohol. The numbers of the pyrolyzed products of patchouli oil were increased by increasing temperature, however, the yields of major components such as patchoulene, guaiene, seychellene and patchouli alcohol decreased as the temperature of pyrolysis was raised to 92$0^{\circ}C$, the highest temperature in this experiment. The optimum temperature for formation of the pyrolysis products such as styrene, indane and naphthalene was at 92$0^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1631-1633
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• 2000

A study was carried out on the effect of VDF mol%, on the phase transition presented by P(VDF/TrFE) copolymer cast from dimethylformamide(DMF) solution with molar ratios 70/30 and 80/20. The results from dielectric spectrum and differential scanning calorimetry(DSC) showed that the phase transitions from ferroelectric to paraelectric phase(Curie transition) were observed The Curie point slightly has shifted to high temperature with increasing in VDF mol%, however, the melting point has shifted to low temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.58-60
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• 1988

The dielectric properties of glass ceramics with BaTiO$_3$ crystallites are described. In this study measurements were made over the frequency range 1kHz-10MHz and temperature range $25^{\circ}C$-15$0^{\circ}C$. There are several minor constituents in the glass which needed to obtain the desired properties. The fluorine ion substitutes for oxygen in glass-crystallized BaTiO$_3$. And additions of Mg ion is used to shift the Curie temperature. We show the addition of Mg ion lowers the Curie point to about 323。K.

• Polymer(Korea)
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• v.26 no.6
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• pp.812-820
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• 2002

The positive temperature coefficient (PTC) characteristics of polymer composites were investigated with the nano-sized carbon black particles using solution tasting and melt compounding methods. The polymeric PTC composites should the electrical threshold at 35 wt% for the melt compounding method and 40 wt% for the solution casting method. The ethylene vinylacetate copolymer (EVA) composite showed a gradual increase of resistance as a function of temperature and showed a maximum at the polymer molting point. The resistance of the high-density polythylene (HDPE) composite remains unchanged with temperature but started to Increase sharply near the melting point of HDPE and showed a maximum resistance at the melting point of HDPE. The dispersion of nano-sized carbon black particles was investigated by scanning electron microscopy (SEM) and low resistance after electrical threshold, and both methods exhibited a well dispersed morphology. When the electric current was applied to the PTC composites, the resistance started increasing at the curie temperature and further increased until the trip temperature was roached. Then the resistance remained stable over the trip temperature. The secondary increase started at T$\sub$m/ of matrix polymer and kept increasing up to the trip temperature.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.35-41
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• 2016

The electrical transport properties of $La_{0.5}Sr_{0.5}CrO_3$ below room temperatures were investigated by dielectric, dc resistivity, magnetic properties and thermoelectric power. Below $T_c$, $La_{0.5}Sr_{0.5}CrO_3$ contains a dielectric relaxation process in the tangent loss and electric modulus. The $La_{0.5}Sr_{0.5}CrO_3$ involves the transition from high temperature thermal activated conduction process to low temperature one. The transition temperature corresponds well to the Curie point. The relaxation mechanism has been discussed in the frame of electric modulus spectra. The scaling behavior of the modulus suggests that the relaxation mechanism describes the same mechanism at various temperatures. The low temperature conduction and relaxation takes place in the ferromagnetic phase. The ferromagnetic state in $La_{0.5}Sr_{0.5}CrO_3$ indicates that the electron - magnon interaction occurs, and drives the carriers towards localization in tandem with the electron - lattice interaction even at temperature above the Curie temperature.

• Journal of the Korean Society of Tobacco Science
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• v.22 no.2
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• pp.176-183
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• 2000

This study was conducted to compare the volatile components of lamina(cutter group) and midrib of flue-cured tobacco leaves by two analytical methods, Curie-Point pyrolysis and Purge & Trap headspace technique. The pyrolysis of lamina and midrib part of tobacco leaves was performed at the temperature of $330^{\circ}C$, $650^{\circ}C$, and $920^{\circ}C$ by Curie-Point Pyrolyzer, and 33 compounds were identified in the pyrolyzates by GC/MSD. The composition of the components identified showed a quite difference between lamina and midrib. However, the amount of the pyrolyzed products from the both of lamina and midrib was increased with temperature increase except that of acetic acid, furfural, and nicotine. The content of phenolic compounds including phenol, 4-methyl phenol, and 3-methyl phenol was higher in midrib than in lamina, while that of furan compounds such as 2,3-dihydrobenzofuran, 5-hydroxymethyl furfural, was high in lamina. Interestingly, acetamide, 2-propenamide and 3-acetoxy pyridine were not defected in the pyrolyzates of lamina. By Purge & Trap headspace technique, 28 volatile components were identified in both lamina and midrib. The composition of the identified compounds and their chromatograpic patterns also showed the complete difference between the two. The content of solanone, $\beta$-damascone, $\beta$-damascenone, and megastigmatrienones, key components of tobacco aroma, was much higher in lamina than in midrib. The results indicate that lamina contains much more carbonyl compounds known to enhance the smoke taste of cigarette, whereas midrib takes nitrogenous and phenolic compounds, which are known to cause a deteriorate effect of smoke such as irritation.

• Analytical Science and Technology
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• v.13 no.1
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• pp.101-107
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• 2000

The automotive paints could be generally differentiated by color, layer sequence and chemistry of the paint layers comprising each of the topcoat and the primer system. The successful identification of hit-andrun a and traffic accidental vehicles from evidential paint fiagments is greatly facilitated with a comprehensive laboratory collection of reference paint samples and the technique for direct analysis without sample preparation. The Pyrolysis-Gas Chromatography(PGC) is a precise and reliable method for performing both quantitative and qualitative analysis of polymeric materials and forensic samples. Our Forensic Laboratory is conducting the examination and identification of 73 reference paint samples; 4 colors of each domestic automotive make that is popular in Korea, by Curie Point Pyrolyzer(JHP-3) and GC with capillary column(ultra alloy-5). This method can be used not only to compare paint traces with their suspected sources, but also to identify the type, make and model of the automotive car.

• Electrical & Electronic Materials
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• v.10 no.2
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• pp.134-140
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• 1997

PbTiO$_{3}$-PbZrO$_{3}$-Pb(Ni$_{1}$3/Nb $_{2}$3/O$_{3}$)(PZT-PNN) thin films were prepared from corresponding metal organics partially stabilized with diethanolamine by the sol-gel spin coating method. Each mol rates of PT:PZ:PNN solutions were #1(50:40:10), #2(50:30:20), #3(45:35:20) and #4(40:40:20), respectively. The spin-coated PZT-PNN films were sintered at the temperature from 500.deg. C to 600.deg. C for crystallization. The P-E hysteresis curve was drawn by Sawyer-Tower circuit with PZT-PNN film. The coercive field and the remanent polarization of #4(40:40:20 mol%) PZT-PNN film were 28.8 kV/cm and 18.3 .mu.C/cm$^{2}$, respectively. Their dielectric constants were shown between 128 and 1120, and became maximum value in MPB(40:40:20 mol%). The leakage currents of PZT-PNN films were about 9.4x 10$^{-8}$ A/cm$^{2}$, and the breakdown voltages were about 0.14 and 1.1 MV/cm. The Curie point of #3(45:35:20 mol%, sintered at 600.deg. C) film was 330.deg. C.