In this research, reduced graphene oxide/polypyrrole (rGO/PPy) particles were synthesized and used to measure the amount of dopamine (DA) electrochemically. The obtained rGO/PPy particle was characterized by Fourier Transform Infrared Spectrophotometer (FTIR), UV–Visible Spectrophotometer (UV–Vis), and X-Ray Diffraction Diffractometry (XRD). To investigate the DA sensor performance, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to acquire electrochemical measurements of the sensor. Current values of 1.65 and 5.9 mA were observed in the CV at 0.2 mM and 1.2 mM concentrations of target molecule, respectively. Under optimized conditions, the linear calibration plots were found to exhibit significant sensitivity in the linear range of 0.2 and 1.2 mM, with a corresponding detection limit of 0.061 μM for DA. The results obtained were similar to the sensor results of DA made using precious metals. This work was a demonstration of the feasibility of high-sensitivity electrochemical analysis with conductive carbon materials without the use of precious metals. It was also observed that the cost-effective rGO/PPy exhibited a very high potential for DA detection.

In this study, numerical modeling on the gas flow and off-gases in the low temperature carbonization furnace for carbon fiber was analyzed. The furnace was designed for testing carbonization process of carbon fibers made from various precursors. Nitrogen gas was used as a working gas and it was treated as an incompressible ideal gas. Three-dimensional computational fluid dynamics for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The off-gas mass fraction and cumulative emission gas of species were incorporated into the CFD analyses by using the user defined function(UDF). As a results, during the carbonization process, the emission of CO2 was the dominant among the off-gases, and tow moving made the flow in the furnace be uniform.

본 연구는 농식품 소비자패널을 대상으로 설문조사를 실시하여 소비자의 소비성향에 따른 저탄소인증농산물의 소비행태를 살펴본다. 소비자의 소비성향을 윤리적 소비성향과 합리적 소비성향으로 구분하여 집단을 구성하였고, 집단 간 소비행태 차이를 분석하였다. 윤리적 소비성향 집단과 합리적 소비성향 집단 간에 저탄소 농산물 인증제의 인지도, 탄소발생 감소를 위한 노력, 탄소중립 개념 인지도 및 저탄소인증농산물에 대한 구매의도 는 유의미한 차이가 있는 것으로 나타났다. 따라서 저탄소인증농산물의 소비활성화를 위해서 합리적 소비성향을 가진 소비자들의 저탄소인증농산물 구매를 유도할 수 있는 방안을 마련할 필요가 있다.

The surface of carbon films deposited with inverted plasma fireballs is analysed in this paper. Measurements were conducted with Raman spectroscopy, atomic force microscopy and nanoindentation. The latter was used to obtain Young’s modulus as well as Martens and Vickers hardness. The roughness of the film was measured by atomic force microscopy and its thickness was measured. It was shown with Raman spectroscopy that the films are homogeneous in terms of atomic composition and layer thickness over an area of about 125 × 125 mm. Furthermore, it was demonstrated that inverted plasma fireballs are a viable tool for obtaining homogeneous, large area carbon films with rapid growth and very little energy consumption. The obtained films show very low roughness.

Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes – thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

정부가 2050년까지 탄소중립 목표를 선언함에 따라 농업 분야도 많은 양의 온실가스를 감축해야 한다. 이 연구의 목적은 저탄소농업 지원정책 추진현황을 살펴보고, 저탄소농업 지원정책 참여요인을 분석하는 데 있다. 연구 목적 달성을 위해 농가를 대상으로 설문조사를 실시하였으며, 프로빗모형을 이용하여 저탄소농업 지원정책 참여요인을 분석하였다. 2019년 기준 농업분야의 국가 온실가스 감축목표 달성률을 평가한 결과 매우 낮은 수준으로 나타났다. 프로빗 모형분석 결과, 경지 규모가 클수록, 농업 교육 프로그램 참여도가 높을수록, 저탄소농업 지원정책에 참여할 확률이 높은 것으로 분석되었다. 또한 농업분야 온실가스 감축 필요성과 2030 감축로드맵에 대한 인지도가 높을수록, 영농경력이 많을수록, 지원정책 참여 확률이 높았다. 따라서 저탄소농업을 활성화시키기 위해서는 저탄소농업 지원정책에 대한 인지도를 높여야 하며, 이를 위해 차별화 전략과 타켓팅 전략이 필요하다.

In this study, gas flow pattern and temperature distribution in a laboratory scale low temperature furnace for carbonization were numerically analyzed. The furnace was designed for testing carbonization process of carbon fibers made from polyimide(PI) precursor. Nitrogen gas was used as a working gas and it was treated as an ideal gas. Three-dimensional computational fluid dynamics analysis for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The results showed that more uniform velocity profile and axisymmetric temperature distribution could be obtained by varying mass flow rate at the inlets.

신축성 전극을 다양한 소재와과 방식을 통해 제조되고 있으며 많은 기계적 특성 분석이 연구되고 있다. 은, 구리, 금, 나노와이어 등 다양한 금속이나 CNT, graphene, 플러렌 등을 기반으로 연구되고 있으며 대부분 높은 전도성과 신축특성을 요구하는 어플리케이션에 사용되지만 고가라는 단점이 있다. 본 연구에서는 저비용 소재와 공정으로 높은 신축특성과 반복 특성을 보유한 신축성 전극을 개발하였다. 값싼 전도성 탄소 와 흑연을 혼합하여 페이스트를 개발하였고 개발된 페이스트를 메탈마스크 인쇄 공정을 통해 TPU기판 위에 인쇄하였고 120℃에서 2시간 경화를 진행하였다. 이렇게 개발된 전극을 인장 시험과 인장 반복 시험을 통해 특성을 증명하였고 향후 어플리케이션 적용 가능여부를 확인하기 위해 무릎에 임시로 고정 후 간이 시험을 진행한 결과 20회 반복하는 동안 일정한 저항 변화를 보여줬다.

Low thermal conductivity carbon fibers from polyacrylonitrile (PAN) are currently being explored as an alternative for traditional rayon-based carbon fibers with a thermal conductivity of 4 W/m K. Compared to multiple component electrospinning, this research demonstrated another feasible way to make low thermal conductivity carbon fibrous material by electrospinning PAN followed by carbonization and alkali activation. The effects of activation condition on microstructure, pore formation, and thermal conductivity of the resultant carbon nanofibrous material were investigated. The processing-structure-thermal conductivity relationship was revealed and mechanism of thermal conductivity reduction was discussed. The overall thermal conductivity of the prepared carbon nanofibrous material is a result of combined effects from factors of carbon structure and number of pores rather than volume of pores or specific surface area. The activated carbon nanofibrous materials showed thermal conductivity as low as 0.12 W/m K, which is a reduction of ~ 99% when compared to that of solid carbon film and a reduction of ~ 95% when compared to that of carbon nanofibrous material before activation.

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.

This study demonstrates that low processing rate for producing polyacrylonitrile (PAN)-based carbon fiber is a critical to obtain a homogeneous radial microstructure with high resistance to oxidation, thereby resulting in their improved mechanical strength. The dry-jet wet spun PAN organic fibers were processed (e.g., stabilized and then carbonized) utilizing two different rates; one is 1.6 times longer than the other. The effect of processing rate on the microstructural evolutions of carbon fibers was analyzed by scanning electron microscopy after slow etching in air, as well as Raman mapping after graphitization. The rapidly processed fiber exhibited the multilayered radial structure, which is caused by the radial direction stretching of the extrusion in the spinning. In case of the slowly processed fiber, the layered radial structure formed in the spinning process was changed into a more homogeneous radial microstructure. The slowly processed fibers showed higher oxidation resistance, higher mechanical properties, and higher crystallinity than the rapidly processed one. Raman mapping confirmed that the microstructure developed during spinning was sustained even though fiber was thermally treated up to 2800 °C.

막증발 기술은 최근 해수담수화 분야에서 많은 주목을 받고 있으며, 기존 증발법과 역삼투를 대체하는 대안기술로서 개발이 활발하게 추진되고 있다. 그러나 막증발 기술의 실용화를 위해서는 극복하여야 할 몇 가지 문제점이 있다. 본 연구에서는 막증발 기술을 효율적으로 적용하기 위하여 해결해야 하는 1) 스케일업 2) 막오염 억제 3) 막젖음 예측 및 방지기술 개발하고자 하였으며, 이를 통하여 저탄소 담수화를 실현시키기 위한 방안을 제시하고자 하였다.

In the present study the microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes was characterized and identified based on various microstructure analysis methods including optical and scanning electron microscopy, and electron backscatter diffraction(EBSD). Although low-carbon steels are usually composed of α-ferrite and cementite(Fe3C) phases, they can have complex microstructures consisting of ferrites with different size, morphology, and dislocation density, and secondary phases dependent on rolling and accelerated cooling conditions. The microstructure of lowcarbon steels investigated in this study was basically classified into polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite based on the inverse pole figure, image quality, grain boundary, kernel average misorientation(KAM), and grain orientation spread(GOS) maps, obtained from EBSD analysis. From these results, it can be said that the EBSD analysis provides a valuable tool to identify and quantify the complex microstructure of low-carbon steels fabricated by controlled rolling and accelerated cooling processes.

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.

Carbon nanofiber (CNF) composites coated with spindle-shaped Fe2O3 nanoparticles (NPs) are fabricated by a combination of an electrospinning method and a hydrothermal method, and their morphological, structural, and chemical properties are measured by field-emission scanning electron microscopy, transmission electron microscopy, Xray diffraction, and X-ray photoelectron spectroscopy. For comparison, CNFs and spindle-shaped Fe2O3 NPs are prepared by either an electrospinning method or a hydrothermal method, respectively. Dye-sensitized solar cells (DSSCs) fabricated with the composites exhibit enhanced open circuit voltage (0.70 V), short-circuit current density (12.82 mA/cm2), fill factor (61.30%), and power conversion efficiency (5.52%) compared to those of the CNFs (0.66 V, 11.61 mA/cm2, 51.96%, and 3.97%) and spindle-shaped Fe2O3 NPs (0.67 V, 11.45 mA/cm2, 50.17%, and 3.86%). This performance improvement can be attributed to a synergistic effect of a superb catalytic reaction of spindle-shaped Fe2O3 NPs and efficient charge transfer relative to the one-dimensional nanostructure of the CNFs. Therefore, spindle-shaped Fe2O3-NPcoated CNF composites may be proposed as a potential alternative material for low-cost counter electrodes in DSSCs.