• Korean Journal of Materials Research
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• v.11 no.3
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• pp.171-177
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• 2001

The thermal and mechanical properties of amorphous Z $r_{62-x}$N $i_{10}$C $u_{20}$A $l_{8}$ $Ti_{x}$ (x=3, 6, 9at%) alloys were investigated. The crystallization process was confirmed as amorphous longrightarrow amorphous + Z $r_2$A $l_3$+ Zr + (Ni,Ti) longrightarrow Z $r_2$Cu + Al + (Ni,Ti) for 3at%Ti, amorphous longrightarrow amorphous + Al longrightarrow $Al_2$Ti + NiZr + CuTi for 6at%Ti and amorphous longrightarrow amorphous + Zr + Al longrightarrow Zr + $Al_2$Zr + Al $Ti_3$+ CuTi for 9at%Ti. lickers hardness ( $H_{v}$ ) increased with increasing volume fraction( $V_{f}$ ) of pricipitates for all concerned compositions. Tensile fracture strength ($\sigma_{f}$ ) showed a maximum value 1219MPa at $V_{f}$ = 38% for 3at%Ti, 1203MPa at $V_{f}$ = 2% for 6at%Ti and 1350MPa at $V_{f}$ = 5% for 9at%Ti. The $\sigma_{f}$ was rapidly decreased after showing the maximum value. The $V_{f}$ corresponding to rapidly decreased $\sigma_{f}$ coincided with the $V_{f}$ transited from ductile to brittle fracture surface.ace.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.5
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• pp.401-406
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• 2008

Recently, portable magnetic sensors with high sensitivity are strongly required for various applications such as biosensor, nondestructive testing and directional sensor. A novel magnetic sensor system was developed by utilizing giant magnetoimpedance(MI) effect of soft magnetic ribbons. The sensor system consists of sensing head of $Co_{66}Fe_{4}Si_{15}B_{15}$ ribbon having asymmetric MI characteristics through exchange coupling produced by field-annealing in open air and circuit for signal processing. The sensor system showed almost linear characteristics in dynamic range of $-1\;Oe\;{\sim}\;1\;Oe$ and sensitivity of 10.5 V/Oe. The sensor was applicable to nondestructive testing system to detect defects in wire ropes.

• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.231-238
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• 2006

Transports of heterogeneously charged particles were investigated based on column experiments. Synthesized mono-dispersed ferrihydrite (${\sim}100nm$) and amorphous $SiO_2\;({\sim}40nm\;and\;{\sim}80nm)$ particles, of which surfaces are oppositely charged under pH < 9.0 (ferrihydrite, positive; amorphous silica, negative), were used. $177{\sim}250{\mu}m$ quartz sand was used as a stationary matrix. The results show that even favorable particles (i.e., ferrihydrite) can show a conservative transport through the oppositely charged media (i.e., quartz) when they coexist with humic acid or with much greater number of oppositely charged particles. These results imply that transports of both negatively and positively charged contaminants may be possible at the same time under a condition of heterogeneous colloidal system.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.259-270
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• 1997

Reaction kinetics for the solid-state reaction of $\alpha-Al_2O_3$ with amorphous $TiO_2$ to produce $Al_2TiO_5$ (Tialite) was studied in the temperature range of $1200~1300^{\circ}C$. Rate of kinetic reaction were determined by using $TiO_2$-coated $Al_2O_3$ compact containing 50 mol% $TiO_2$ and heating the reactant mixtures in MgO at definite temperature for various times. Amount of products and unreacted reactants were determined by X-ray diffractometry. Data from the volume fraction and ratio of peak intensities of $\beta-Al_2TiO_5$ indicated that the reaction of $\alpha-Al_2O_3$ with $TiO_2$ to form pseudobrookite starts between 1280 and $1300^{\circ}C$. The activation energy for solid-state reaction was determined by using the Arrhenius equation ; The activation energy was 622.4 kJ/mol.

• Journal of the Korean Vacuum Society
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• v.4 no.S1
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• pp.178-184
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• 1995

SiO2 위에 as-dep. 비정질 Si1-xGex 합금박막을 증착하기 위하여 Si2H6 와 GeH4 가스를 사용한 저압 화학 기상증착(LPCVD)에 관하여 연구하였다. 증착온도는 $400-500^{\circ}C$였으며, 공정압력은 0.5-1Torr 였다. 박막내의 Ge 함량은 온도 및 증착가스의 유량이 일정하면 공정압력이 증가함에 따라 증가하였고, 공정압력 및 증착가스의 유량이 일정하면 증착온도에 관계없이 일정하였다. 일정한 Si2H6가스의 표면반응은 박막내의 Ge 원자에 의해 촉진됨을 알 수 있었다. 조성이 일정한 Si1-xGex 박막의 증착속도는 증착온도 증가에 따라 Arrhenius 형태로 증가하여, Si, Si0.84Ge0.16,Si0.69Ge0.31박막증착의 활성화에너지는 각각 1.5, 1.13, 1 eV로서 박막내의 Ge함량이 증가함에 따라 활성화 에너지는 감소하였다.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.90-95
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• 2005

The wire-arc process is a low-cost thermal spray method simply utilizes electrical energy to melt the feedstock wire. It is more userful for field applications, especially to coat large surface area. In this paper, a special Fe-based alloy coatings by using the wire-arc process were developed. Nanoscale composite coatings were achieved either during spraying or through a post heat treatment. As-sprayed Fe-based alloy coatings had been an amorphous matrix structure, after heating to $700^{\circ}C$ for 10 minutes a solid state transformation occurred in the some fraction of amorphous matrix which resulted in the formation of nanostructured recrystallized phase. Scanning electron microscopy (SEM) and field emotional scanning electron microscope(FE-SEM) were applied to analyze the microstructure of the coatings. Additionally hardness and bend resistance of the Fe-based alloy coatings were examined, and these results were compared with those of partially stabilized zirconia(PSZ) coatings by using the plasma spray process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.76-78
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• 2002

The influence of laser annealing on gaint magnetoimpedance effect of glass-covered Co-based amorphous microwires is investigated by illuminating pulse Nd:YAG laser on the etched microwires. The maxium GMI ratio reaches maximum of around 85 % at the frequency of 5 MHz for the sample iluminated by the pulse with laser energy fo 132 mJ/pulse.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.164-165
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• 2007

Si(중간층)/DLC(diamond-like carbon)막은 스퍼터와 이온소스(ion source)법에 의한 복합방식(hybrid method)을 이용하여 3mTorr의 반응가스 벤젠($C_6H_6$)분위기에서 Si wafer에 기판온도 $130^{\circ}C$로 180분간 증착하였다. 평가는 표면과 단면에 대해 주사전자현미경(scanning electron microscopy, SEM)과 투자전자현미경(trasmission electron microsope, TEM)으로 관찰하였다. 경도와 마찰계수는 나노인텐터(nanoindetor)와 마모시험기를 이용하였으며, 박막의 구조는 라만스펙트럼으로 분석하였다. 그 결과 박막의 두께는 약 $0.9{\mu}m$, 표면조도는 약 $0.34{\sim}1.64nm$로 평탄한 표면을 가지며 경도는 약 $35{\sim}37GPa$, 마찰계수는 약 $0.02{\sim}0.07$로 관찰되었다. 라만분광법과 전자회절패턴에 의해 IG/ID의 함량비는 $0.54{\sim}0.59$로 $sp^2$와 $sp^3$가 혼재된 전형적인 비정질 구조임을 확인하였다.

• Journal of the Korean Magnetics Society
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• v.19 no.4
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• pp.121-125
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• 2009

Amorphous $Ge_1$_$_xMn_x$ semiconductor thin films grown by low temperature vapor deposition were annealed at various temperatures from 400 to $700^{\circ}C$ for 3 minutes in high vaccum chamber. The electrical and magnetotransport properties of as-grown and annealed samples have been studied. X-ray diffraction patterns analysis revealed that the samples still maintain amorphous state after annealling at $500^{\circ}C$ for 3 minutes and they were crystallized when annealing temperature increase to $600^{\circ}C$. Temperature dependence of resistivity measurement implied that as-grown and annealed $Ge_1$_$_xMn_x$ films have semiconductor characteristics, the increase of resistivity with annealling temperature was obseved. The $700^{\circ}C$-annealed sample exhibited negative magnetoresistance (MR) at low temperatures and the MR ratio was ${\sim}$8.5% at 10 K. The asymmetry was present in all MR curves. The anomalous Hall Effect was also observed at 250 K.

• Journal of the Korean Magnetics Society
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• v.7 no.3
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• pp.140-145
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• 1997

The amorphous state of $NdFe_{10.7}TiB_{0.3}$ and its nanocrystallization have been studied by X-ray diffraction, 모스바우어 spectroscopy, and a vibrating sample magnetometer (VSM), $NdFe_{10.7}TiB_{0.3}$ amorphous ribbons were fabricated by a sigle-roll melt-spinning method. The average hyperfine field $H_{hf}$(T) of the amorphous state shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.46(T/T_c)^{3/2}-0.34(T/T_c)^{5/2}$ for $T/T_c<0.7$ indicative of spin wave excitation. The quadrupole splitting just above the Curie temperature $T_c$ is 0.46 mm/s, whereas the average quadrupole shift below $T_c$ is zero. The Curie and crystallization temperatures are determined to be $T_c$=380K and $T_x=490K$, respectively, for a heating rate of 5 K/min. The occupied area of nanocrystalline phase at around 770K is about 65%. Above the Curie temperature, VSM data show magnetic moments increases again. The formation of $\alpha$-Fe is the main reason for the increasing moment as conformed with the 모스바우어 measurements.