This paper focuses on the electrical properties and stability against DC accelerated aging stress of ZnO-V2O5-MnO2- Nb2O5-Bi2O3-Co3O4-Dy2O3 (ZVMNBCD) varistor ceramics sintered at 850 - 925 ℃. With the increase of sintering temperature, the average grain size increases from 4.4 to 11.8 mm, and the density of the sintered pellets decreases from 5.53 to 5.40 g/ cm3 due to the volatility of V2O5, which has a low melting point. The breakdown field abruptly decreases from 8016 to 1,715 V/cm with the increase of the sintering temperature. The maximum non-ohmic coefficient (59) is obtained when the sample is sintered at 875 ℃. The samples sintered at below 900 oC exhibit a relatively low leakage current, less than 60 mA/cm2. The apparent dielectric constant increases due to the increase of the average grain size with the increase of the sintering temperature. The change tendency of dissipation factor at 1 kHz according to the sintering temperature coincides with the tendency of the leakage current. In terms of stability, the samples sintered at 900 ℃ exhibit both high non-ohmic coefficient (45) and excellent stability, 0.8% in ΔEB/EB and -0.7% in Δα/α after application of DC accelerated aging stress (0.85 EB/85 oC/24 h).

In this study, effects of carbon and nickel on microstructure and low temperature Charpy impact properties of HSLA (high strength low alloy) steels are investigated. To understand the complex phase transformation behavior of HSLA steels with high strength and toughness before and after welding processes, three kinds of HSLA steels are fabricated by varying the carbon and nickel content. Microstructure analysis, low temperature Charpy impact test, and Vickers hardness test are performed for the base metals and CGHAZ (coarse-grain heat affected zone) specimens. The specimens with the lowest carbon and nickel content have the highest volume fraction of AF, the lowest volume fraction of GB, and the smallest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the highest. The specimens with increased carbon and nickel content have the lowest volume fraction of AF, the highest volume fraction of GB, and the largest GB packet size. So, the low temperature Charpy absorbed energy of the CGHAZ specimen is the lowest.

본 연구에서는 저온 소성 굴 패각의 재활용을 위한 기초적 연구로서 메조코즘 실험을 통해 저온 소성 굴 패각의 피복에 따른 연안 오염 퇴적물의 성상 변화를 조사하였다. 이를 위해 350 °C에서 소성시킨 굴 패각을 연안 오염 퇴적물에 피복하여 직상수와 간극수의 성상변화를 분석하는 메조코즘 실험을 수행하였다. 실험 결과, 굴 패각의 피복에 의해 수층과 퇴적층이 분리되었기 때문에 직상수의 산화 환원전위(ORP) 증가 및 DIN 중의 NH3-N의 비율의 감소가 실험구에서 관측되었다. 실험구의 DIP의 농도는 대조구와 비교하여 유의한 차이를 확인하기 어려웠다. 굴 패각의 피복에 의한 퇴적물의 총유기탄소(TOC)는 감소하였으며, 산휘발성황화물(AVS)은 저온 소성 굴 패각의 황화물 흡착 능력으로 인해 최대 50%까지 감소한 것으로 확인되었다. 본 연구의 결과로부터 저온 소성 굴 패각은 연안 오염 퇴적물의 정화를 위해 이용될 수 있는 재료인 것으로 결론 지을 수 있다.

This present study deals with the effect of micro-alloying elements and transformation temperature on the correlation of microstructure and tensile properties of low-carbon steels with ferrite-pearlite microstructure. Six kinds of lowcarbon steel specimens were fabricated by adding micro-alloying elements of Nb, Ti and V, and by varying isothermal transformation temperature. Ferrite grain size of the specimens containing mirco-alloying elements was smaller than that of the Base specimens because of pinning effect by the precipitates of carbonitrides at austenite grain boundaries. The pearlite interlamellar spacing and cementite thickness decreased with decreasing transformation temperature, while the pearlite volume fraction was hardly affected by micro-alloying elements and transformation temperature. The room-temperature tensile test results showed that the yield strength increased mostly with decreasing ferrite grain size and elongation was slightly improved as the ferrite grain size and pearlite interlamellar spacing decreased. All the specimens exhibited a discontinuous yielding behavior and the yield point elongation of the Nb4 and TiNbV specimens containing micro-alloying elements was larger than that of the Base specimens, presumably due to repetitive pinning and release of dislocation by the fine precipitates of carbonitrides.

In this study, six kinds of low-carbon steel specimens with different ferrite-pearlite microstructures were fabricated by varying the Nb content and the transformation temperature. The microstructural factors of ferrite grain size, pearlite fraction, interlamellar spacing, and cementite thickness were quantitatively measured based on optical and scanning electron micrographs; then, Charpy impact tests were conducted in order to investigate the correlation of the microstructural factors with the impact toughness and the ductile-brittle transition temperature (DBTT). The microstructural analysis results showed that the Nb4 specimens had ferrite grain size smaller than that of the Nb0 specimens due to the pinning effect resulting from the formation of carbonitrides. The pearlite interlamellar spacing and the cementite thickness also decreased as the transformation temperature decreased. The Charpy impact test results indicated that the impact-absorbed energy increased and the ductile-brittle transition temperature decreased with addition of Nb content and decreasing transformation temperature, although all specimens showed ductile-brittle transition behaviour.

저온진공건조 조건에 따른 곶감의 건조특성 및 품질적 변화를 분석하였다. 곶감의 건조 특성 은 전형적인 항율건조기간과 감율건조기간이 존재함을 확인 할 수 있었다. 진공압력이 높을수록 가열온 도가 높을수록 곶감의 당도, 당 함량, 경도 값은 높게 나타났으며 이에 비해 명도 값은 낮게 나타남을 알 수 있었다. 기존 천일 및 열풍건조를 대처할 수 있는 진공건조의 최적 조건은 진공압력이 40~50kPa abs., 가열온도 30℃, 건조시간은 3~4일 이었다.

The thermoelectric power and dc conductivity of La2/3+xTiO3-δ (x = 0, 0.13) were investigated. The thermoelectric power was negative between 80K and 300K. The measured thermoelectric power of x = 0.13 increased linearly with increased temperatures and was represented by S0+BT. The x = 0 sample exhibited insulating behavior, while the x = 0.13 sample showed metallic behavior. The electric resistivity of x = 0.13 had a linear temperature dependence at high temperatures and a T3/2 dependence below about 100K. On the other hand, the electric resistivity of x = 0 has a linear relation between lnρ/T and 1/T in the range of 200 to 300K, and the activation energy for small polaron hopping was 0.23 eV. The temperature dependence of thermoelectric power and the resistivity of x = 0 suggests that the charge carriers responsible for conduction are strongly localized. This temperature dependence indicates that the charge carrier (x = 0) is an adiabatic small polaron. These experimental results are interpreted in terms of spin (x = 0.13) and small polaron (x = 0) hopping of almost localized Ti 3d electrons.

Solution-based Sb-doped SnO2 (ATO) transparent conductive oxides using a low-temperature process werefabricated by an electrospray technique followed by spin coating. We demonstrated their structural, chemical, morphological,electrical, and optical properties by means of X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanningelectron microscopy, atomic force microscopy, Hall effect measurement system, and UV-Vis spectrophotometry. In order toinvestigate optimum electrical and optical properties at low-temperature annealing, we systemically coated two layer, four layer,and six layers of ATO sol-solution using spin-coating on the electrosprayed ATO thin films. The resistivity and opticaltransmittance of the ATO thin films decreased as the thickness of ATO sol-layer increased. Then, the ATO thin films with twosol-layers exhibited superb figure of merit compared to the other samples. The performance improvement in a low temperatureprocess (300oC) can be explained by the effect of enhanced carrier concentration due to the improved densification of the ATOthin films causing the optimum sol-layer coating. Therefore, the solution-based ATO thin films prepared at 300oC exhibitedthe superb electrical (~7.25×10−3Ω·cm) and optical transmittance (~83.1%) performances.

The electrical and optical properties of fluorine-doped tin oxide films grown on polyethylene terephthalate film witha hardness of 3 using electron cyclotron resonance plasma with linear microwave of 2.45GHz of high ionization energy wereinvestigated. Fluorine-doped tin oxide films with a magnetic field of 875 Gauss and the highest resistance uniformity wereobtained. In particular, the magnetic field could be controlled by varying the distribution in electron cyclotron depositionpositions. The films were deposited at various gas flow rates of hydrogen and carrier gas of an organometallic source. Thesurface morphology, electrical resistivity, transmittance, and color in the visible range of the deposited film were examined usingSEM, a four-point probe instrument, and a spectrophotometer. The electromagnetic field for electron cyclotron resonancecondition was uniformly formed in at a position 16cm from the center along the Z-axis. The plasma spatial distribution ofmagnetic current on the roll substrate surface in the film was considerably affected by the electron cyclotron systems. Therelative resistance uniformity of electrical properties was obtained in film prepared with a magnetic field in the current rangeof 180~200A. SEM images showing the surface morphologies of a film deposited on PET with a width of 50cm revealedthat the grains were uniformly distributed with sizes in the range of 2~7nm. In our experimental range, the electrical resistivityof film was able to observe from 1.0×10−2 to 1.0×10−1Ωcm where optical transmittance at 550nm was 87~89%. Theseproperties were depended on the flow rate of the gas, hydrogen and carrier gas of the organometallic source, respectively.

We designed new compositions for lead free and low temperature sealing glass frit of ZnO-V2O5-P2O5 system, which can be used for PDP (Plasma Display Panel) or other electronic devices. The ZnO-V2O5-P2O5 system can be used as a sealing material at temperatures even lower than 430˚C. This system, however, showed lower bonding strength with glass substrate compared to commercialized Pb based sealing materials. So, we added TiO2 as a promoter for bonding strength. We examined the effect of TiO2 addition on sealing behaviors of ZnO-V2O5-P2O5 glasses with the data for flow button, wetting angle, temporary & permanent residual stress of glass substrate, EPMA analysis of interface between sealing materials and glass substrate, and bonding strength. As a result, sealing characteristics of ZnO-V2O5-P2O5 system glasses were improved with TiO2 addition, but showed a maximum value at 5 mol% TiO2 addition. The reason for improved bonding characteristics was considered to be the chemical interaction between glass substrate and sealing glass, and structural densification of sealing glass itself.

Polymer Light Emitting Diodes (PLEDs) with an ITO/PEDOT:PSS/PVK/PFO-poss/LiF/Al structure were prepared on plasma-treated ITO/glass substrates using spin-coating and thermal evaporation methods. The annealing effects of the PFO-poss film when it acts as the emission layer were investigated by using electrical and optical property measurements. The annealing conditions of the PFO-poss emission film were 100 and 200˚C for 1, 2 and 3 hours, respectively. The luminance increased and the turn-on voltage decreased when the annealing temperature and treatment time increased. After examining the Luminance-Voltage (L-V) properties of the PLED, the maximum luminance was found to be 1497 cd/m2 at 11 V for the device when it was annealed at 200˚C for 3 hours. The peak intensity of the PLED emission spectra at approximately 525 nm in wavelength increased when the annealing temperature and time of the PFO-poss film increased. These results suggest that the light emission color shifted from blue to green.

The effect of tempering temperature and microstructure on dry sliding wear behavior of quenched and tempered PM with 0.3% graphite and 1-2% Ni steels was investigated. The sintered specimens were quenched from 890℃ and then tempered at 200℃ and 600℃ for 1 hr. Wear tests were carried out on the quenched＋tempered specimens under dry sliding wear conditions using a pin-on-disk type machine at constant load and speed. The experimental results showed that the wear coefficient effectively increased with increasing tempering temperature and decreased with increasing Ni content.