• Korean Journal of Microbiology
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• v.41 no.1
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• pp.8-12
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• 2005

Some genes, which are involved in the biosynthesis of polysaccharides, could be found by the genome project of Sphingomonas chungbukensis DJ77. In this study, we identified the complete nucleotide sequence of a gene, encoding the glucosyl-isoprenyl phosphate-transferase, which catalyzes the first step in the biochemical pathway for the synthesis of the sphingan type polysaccharide. This gene, named spsB, is initiated by the ATG codon and terminated by the TGA, and its open reading frame consists of 1392 bp, encoding 463 amino acids. The predicted amino acid sequence of this enzyme indicates $50\%$ similarity to SpsB of Sphingomonas spp S88, also produces sphingan, and $48\%$ to GelB of Sphingomonas paucimobilis ATCC 31461.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.152-158
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• 2000

The crystallographic grain orientation of {{{{ { ZrB}_{2 } }}}}-ZrC composite sintered by pressureless a sintering(PLS) and spark plasma sintering (SPS) was analysed by the SEM-EBSP technique. In the case of PLS, (160) plane of {{{{ { ZrB}_{2 } }}}} was oriented to ND direction, (101) and (111) plane of ZrC were oriented to ND direction. In the case of SPS, (0001) plane of {{{{ { ZrB}_{2 } }}}} was strongly oriented to ND direction. Only (001) plane of ZrC was oriented to ND direction. The PLS specimen had weakly oriented grain structure and interface between {{{{ { ZrB}_{2 } }}}} and ZrC was found to be more stable than that of SPS but the SPS specimen had a preferentially oriented grain structure.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1449-1450
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• 2011

The SiC-$ZrB_2$ composites were produced by subjecting a 40:60 (vol.%) mixture of zirconium diboride($ZrB_2$) powder and ${\beta}$-silicon carbide (SiC) matrix to spark plasma sintering(SPS) under argon atmosphere at 50MPa(P50) and 60MPa(P60) pressure. The relative density, 94.13% of P60 sample was lower than that, 94.75% of P50 sample. Reactions between ${\beta}$-SiC and $ZrB_2$ were not observed via x-ray diffraction (hereafter, XRD) analysis. The trend of flexural strength of SiC-$ZrB_2$ composites were in accordance with the relative density. The properties of a SiC-$ZrB_2$ composites through SPS under argon atmosphere were positive temperature coefficient resistance in the temperature range from $25^{\circ}C$ to $500^{\circ}C$, and electrical resistivity of P50 and P60 sample were $6.75{\times}10^{-4}$ and $7.22{\times}10^{-4}{\Omega}{\cdot}cm$ at room temperature, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2083-2087
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• 2011

The SiC-$ZrB_2$ composites were produced by subjecting a 40:60 vol.% mixture of zirconium diboride($ZrB_2$) powder and ${\beta}$-silicon carbide (SiC) matrix to spark plasma sintering(SPS). Sintering was carried out for 60sec at $1400^{\circ}C$ (designation as TP145 and TP146), $1500^{\circ}C$(designation as TP155 and TP156) and uniaxial pressure 50MPa, 60MP under argon atmosphere. The physical, electrical, and mechanical properties of the SiC-$ZrB_2$ composites were examined. The relative density of TP145, TP146, TP155 and TP156 were 94.75%, 94.13%, 97.88% and 95.80%, respectively. Reactions between ${\beeta}$-SiC and $ZrB_2$ were not observed via x-ray diffraction (hereafter, XRD) analysis. The flexural strength, 306.23MPa of TP156 was higher than that, 279.42MPa of TP146 at room temperature, but lower than that, 392.30MPa of TP155. The properties of a SiC-$ZrB_2$ composites through SPS under argon atmosphere were positive temperature coefficient resistance (hereafter, PTCR) in the range from $25^{\circ}C$ to $500^{\circ}C$. The electrical resistivities of TP145, TP146, TP155 and TP156 were $6.75{\times}10^{-4}$, $7.22{\times}10^{-4}$, $6.17{\times}10^{-4}$ and $6.71{\times}10^{-4}{\Omega}{\cdot}cm$ at $25^{\circ}C$, respectively. The densification of a SiC-$ZrB_2$ composite through hot pressing depend on the sintering temperature and pressure. However, it is convinced that the densification of a SiC-$ZrB_2$ composite do not depend on sintering pressure under SPS.

• Applied Science and Convergence Technology
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• v.24 no.1
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• pp.22-26
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• 2015

The optical properties of InP/GaP short-period superlattice (SPS) structures grown at various temperatures from $400^{\circ}C$ to $490^{\circ}C$ have been investigated by using temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL measurements. The PL peak energy for SPS samples decreases as the growth temperature increases. The decreased PL energy of ~10 meV for the sample grown at $425^{\circ}C$ compared to that for $400^{\circ}C$-grown sample is due to the CuPt-B type ordering, while the SPS samples grown at $460^{\circ}C$ and $490^{\circ}C$ exhibit the significant reduction of the PL peak energies due to the combined effects of the formation of lateral composition modulation (LCM) and CuPt-B type ordering. The SPS samples with LCM structure show the enhanced carrier lifetime due to the spatial separation of carriers. This study represents that the bandgap energy of InP/GaP SPS structures can be controlled by varying growth temperature, leading to LCM formation and CuPt-B type ordering.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.2
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• pp.75-78
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• 2005

Silicon boride ($SiB_6$) is very promising for use as thermoelectric materials at high temperature because of its high melting point and relatively large Seebeck coefficient. In the present work, spark plasma sintering (SPS) was applied for preparing dense $SiB_6$ ceramics, and their thermoelectric properties were investigated, together with their microstructural evaluation. The SPS process was found to be effective in densifying a $SiB_6$ ceramic, typically 99 % of the theoretical density at low temperature of $1500^{\circ}C$. In comparison with $SiB_6$ specimen prepared by hot-pressing, the SPS-processed specimen exhibited the significantly improved Seebeck coefficient, resulting in the higher power factor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.988-991
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• 2012

The computer simulation was performed to confirm distribution of current and power density according to inner diameter of graphite mold of SPS(Spark Plasma Sintering). When the inner diameters of a graphite mold are varied $10mm{\Phi}$, $20mm{\Phi}$, $30mm{\Phi}$ and $40mm{\Phi}$, the more the inner diameter of graphite mold is decreased, the more the current density of punch section is increased. Because the electrical resistivity of the SiC-$ZrB_2$ specimen section($7.77{\times}10^{-4}{\Omega}{\cdot}cm$) was lower than the electrical resistivity($6.00{\times}10^{-3}{\Omega}{\cdot}cm$) of graphite section, the current density and power density of specimen section was higher than those of graphite section. It is considered that a SiC-$ZrB_2$ composite is sintered by more Joule heat of specimen section than that of mold and punch section. The current and power density distribution of a SiC-$ZrB_2$ composite can be predicted through computer simulation when SPS is conducted, and an electrical resistivity of the SiC-$ZrB_2$ composite is main element of SPS.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.84-84
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• 2003

The effects of Ti addition on microstructure and mechanical properties of (Al+Xat.%Ti)2at%B (X=0.5, 1, 2) fabricated by mechanical alloying and spark plasma sintering (SPS) were investigated. These alloys were prepared by high energy ball milling (attritor) and then fracture toughness was investigated by using a charpy impact tester. The SPS method was used to consolidate (Al+Xat.%Ti)fat.%B with the pressure of 50MPa. The powders were successfully consolidated to alloy which the theoretical density is 99%. It was confirmed that the fracture toughness of Al-Bat.% matrix composites was increased by the addition of Ti.

• Journal of Powder Materials
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• v.10 no.3
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• pp.168-171
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• 2003

Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.914-920
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• 2001

The grain orientation distribution and grain boundary characterization of $ZrB_2$-ZrC composites sintered by a SPS(Spark Plasma Sintering) method, a new sintering technique were analyzed by the EBSP technique and then their crystallographic results have been compared with those of a sintered specimen using a PLS(Pressureless Sintering) method. In the $ZrB_2$-ZrC composite manufactured by SPS, (0001) planes of $ZrB_2$ were oriented in the direction normal to the specimen surface. In the case of PLS, those of $ZrB_2$ were oriented normal to the electron beam. In both cases of PLS and SPS, ZrC grains had the randomly oriented grain structure. The grain boundary characterization showed that low angle grain boundaries in the PLS and SPS processed materials constituted about 10% and 8% of the total number of boundaries, respectively, represented the only slight difference between the proportion of low angle grain boundary. However, in the distribution of CSL(Coincident Site Lattice) boundaries, it was shown the higher proportion of CSL boundaries with $\Sigma$ 3,5,7,9, 11 in the SPS processed material.