• Progress in Superconductivity
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• v.10 no.2
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• pp.79-86
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• 2009

We successfully fabricated C-doped ex-situ $MgB_2$ wires using two different methods such as mechanical alloying(MA) and combined process(CP) of in-situ and ex-situ. In the MA, the precursor powder was prepared with a mixture of $MgB_2$ and 1 at% C powders by planetary ball milling for 0-100 h. In the CP, on the other hand, C-doped $MgB_2$ powder was prepared with Mg, B, and C powders by in-situ process via compaction, sintering, and crushing. The powders prepared by two methods were loaded into Fe tube and then the assemblages were drawn by a conventional powder-in-tube technique. The MA treatment of C-added $MgB_2$ decreased the particles/grains size and resulted in C-doping into $MgB_2$ after sintering, improving the critical current density($J_c$) in high external magnetic field. For the C-doped $MgB_2$ wire by MA for 25 h, the $J_c$ was $4.1{\times}10^3A/cm^2$ at 5 K and 6.4 T, which was 5.9 times higher than that of pure and untreated $MgB_2$ wire. The CP also provided C-doping into $MgB_2$ and improved the $J_c$ in high magnetic field; the C-doped $MgB_2$ wire fabricated by CP exhibited a $J_c$ being 2.3 times higher than that of the ex-situ wire used commercial $MgB_2$ powder at 5 K and 6.0 T($2.7{\times}10^3A/cm^2\;vs.\;1.2{\times}10^3A/cm^2$).

• ETRI Journal
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• v.20 no.1
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• pp.28-36
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• 1998

A simple experimental method to design gain-flattened erbium-doped fiber amplifier is proposed and demonstrated based on the two linear relations between the output power and the pump power, and between the gain and the length of the eribium-doped fiber at the gain flattened state. The spectral gain variation of the eribium-doped fiber amplifiber constructed by this method was less than 0.4 dB over 12 nm (1,545~1,557nm) wavelength region. The gain flatness is also controlled within 0.4 dB over the input power range of -30~-15dBm/ch through the feedback control utilizing the amplified spontaneous emission power in the 1,530 nm region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.569-572
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• 2001

Selective. highly stable determination of epinephrine(adrenalin) was achieved in cyclic voltammetric measurement carried out at electrochemically treated conductive boron-doped diamond electrode. Boron-doped diamond electrodes were prepared on single crystal Si wafers by microwave plasma chemical vapor deposition and $B_{2}O_{3}$ was dissolved in acetone/methanol(9:1) mixture solution so that the B/C weight ratio ca. $10^{4}ppm$. Epinephrine is a kind of catecholamines, which secreted from adrenal marrow cells. The serious problem to detection of epinephrine is the interference phenomena of electroactive constituent. including AA. In this study. electrochemical treatment of BDD was carried out to discriminate between epinephrine and AA responses. Experimental results showed that the peak potential of AA oxidation shift to the positive direction and the oxidation peak of epinephrine was unchanged. The effect of electrochemical treatment was maintained up to 40hrs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.569-572
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• 2001

Selective, highly stable determination of epinephrine(adrenalin) was achieved in cyclic voltammetric measurement carried out at electrochemically treated conductive boron-doped diamond electrode. Boron-doped diamond electrodes were prepared on single crystal Si wafers by microwave plasma chemical vapor deposition and B$_2$O$_3$ was dissolved in acetone/methanol(1:1) mixture solution so that the B/C weight ratio ca. 10$^3$ppm.. Epinephrine is a kind of catecholamines, which secreted from adrenal marrow cells. The serious problem to detection of epinephrine is the interference phenomena of electroactive constituent, including AA. In this study, electrochemical treatment of BDD was carried out to discriminate between epinephrine and AA responses. Experimental results showed that the peak potential of AA oxidation shift to the positive direction and the oxidation peak of epinephrine was unchanged. The effect of electrochemical treatment was maintained up to 40hrs.

• Clean Technology
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• v.27 no.2
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• pp.146-151
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• 2021

Pure and Sm ion doped BiVO₄ catalysts were synthesized using a conventional hydrothermal method and characterized by XRD, DRS, SEM, and PL. We also examined the activity of these materials on the photocatalytic decomposition of rhodamine B under visible light irradiation. The doping of Sm ion into BiVO₄ catalyst changed the ms-BiVO₄ crystal structure into the tz-BiVO₄ crystal structure in the low synthesis temperature. Light absorption analysis using DRS showed that all the catalysts displayed strong absorption in the visible range of the electromagnetic spectrum regardless of Sm ion doping. In addition, an amorphous morphology was shown in the pure BiVO₄ catalyst, but the morphology of the BiVO₄ catalyst doped with Sm ion was changed into an ellipse shape and also the particle size decreased. In the photocatalytic decomposition of rhodamine B, Sm ion doped BiVO₄ catalyst showed higher photocatalytic activity than the pure BiVO₄ catalyst. In addition, the Sm3-BVO catalyst doped with 3% Sm ion showed the highest photocatalytic activity, as well as the highest formation rate of OH radicals (•OH) and the highest PL peak. This result suggests that the formation rate of OH radicals produced in the interface between the photocatalyst and water is well correlated with the photocatalytic activity.

• Proceedings of the Materials Research Society of Korea Conference
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• 1999.05a
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• pp.31-31
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• 1999

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.499-504
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• 1994

Ti-doped BSG (borosilicate glass) soot films on the silicone substrate have been deposited in the mixture of $SiCl_{4}$, TMB, $TiCL_{4}$ by flame hydrolysis deposition technique. The soot films are melted to form integrated fine glass films. We can fabricate thick films of serveral $10{\mu}m$ with deposition rate,more than $0.5{\mu}m$/min. Refractive index difference of BSG films are increased to more than 0.3% as function of the amount of Ti dopant. As a result of the process an optical waveguide which is simmilar with dimmension and refractive difference of optical fiber is produced. $BCl_{3}$ is widely used for B dopant, but we abtained the good results by the use of TMB in place of $BCl_{3}$. The melting point of silica soot glass is reduced to $1200^{\circ}C$ increasing B dopant. From FTIR analysis $B_2O_3$ content up to about lOmol% in BSG films. films.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1249-1255
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• 2008

1530nm band has been studied as pump wavelength for long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530nm band, 1545nm pump demonstrates 0.45dB/mW gain coefficient, which is twice better than that of conventional 1480nm pumped EDFA. The noise figure of 1530nm pump is at worst 6.36dB, which is 0.75dB higher than that of 1480nm pumped EDFA. Such high gain coefficient indicates that the L-band EDFA consumes low power.

• Journal of Magnetics
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• v.16 no.1
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• pp.15-18
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• 2011

We have studied the $TiO_2$ doping effects on the flux pinning behavior of an $MgB_2$ superconductor synthesized by the in-situ solid-state reaction. From the field-cooled and zero-field-cooled temperature dependences of magnetization, the reversible-irreversible transition of $TiO_2$-doped $MgB_2$ was determined in the H-T diagram (the temperature dependence of upper critical magnetic field and irreversibility line). For comparison, the similar measurements are also obtained from SiC-doped $MgB_2$. The critical current density was estimated from the width of hysteresis loops in the framework of Bean's model at different temperatures. The obtained results manifest that nano-scale $TiO_2$ inclusions served as effective pinning centers and lead to the enhanced upper critical field and critical current density. It was concluded that the grain boundary pinning mechanism was realized in a $TiO_2$-doped $MgB_2$ superconductor.

• Carbon letters
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• v.11 no.2
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• pp.127-130
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• 2010

Boron doped fullerene $C_{60}$ ($B:C_{60}$) films were prepared by the thermal evaporation of $C_{60}$ powder using argon plasma treatment. The morphology and structural characteristics of the thin films were investigated by scanning electron microscope (SEM), Fourier transform infra-red spectroscopy (FTIR) and x-ray photo electron spectroscopy (XPS). The electrochemical application of the boron doped fullerene film as a coating layer for silicon anodes in lithium ion batteries was also investigated. Cyclic voltammetry (CV) measurements were applied to the $B:C_{60}$ coated silicon electrodes at a scan rate of $0.05\;mVs^{-1}$. The CV results show that the $B:C_{60}$ coating layer act as a passivation layer with respect to the insertion and extraction of lithium ions into the silicon film electrode.