• Journal of Ceramic Processing Research
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• 제19권5호
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• pp.413-418
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• 2018

All-solid-state lithium batteries (ASSBs) using inorganic sulfide-based solid electrolytes are considered prospective alternatives to existing liquid electrolyte-based batteries owing to benefits such as non-flammability. However, it is difficult to form a favorable solid-solid interface among electrode constituents because all the constituents are solid particles. It is important to form an effective electron conduction network in composite cathode while increasing utilization of active materials and not blocking the lithium ion path, resulting in excellent cell performance. In this study, a mixture of fibrous VGCF and spherical nano-sized Super P was used to improve rate performance by fabricating valid conduction paths in composite cathodes. Then, composite cathodes of ASSBs containing 70% and 80% active materials ($LiNi_{0.6}Co_{0.2}Mn_{0.2}O_2$) were prepared by a solution-based process to achieve uniform dispersion of the electrode components in the slurry. We investigated the influence of binary carbon additives in the cathode of all-solid-state batteries to improve rate performance by constructing an effective electron conduction network.

• 센서학회지
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• 제31권4호
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• pp.228-237
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• 2022

Two-dimensional (2D) nanomaterials have demonstrated the potential to replace silicon and compound semiconductors that are conventionally used in photodetectors. These materials are ultrathin and have superior electrical and optoelectronic properties as well as mechanical flexibility. Consequently, they are particularly advantageous for fabricating high-performance photodetectors that can be used for wearable device applications and Internet of Things technology. Although prototype photodetectors based on single microflakes of 2D materials have demonstrated excellent photoresponsivity across the entire optical spectrum, their practical applications are limited due to the difficulties in scaling up the synthesis process while maintaining the optoelectronic performance. In this review, we discuss facile methods to mass-produce 2D material-based photodetectors based on the exfoliation of van der Waals crystals into nanosheet dispersions. We first introduce the liquid-phase exfoliation process, which has been widely investigated for the scalable fabrication of photodetectors. Solution processing techniques to assemble 2D nanosheets into thin films and the optoelectronic performance of the fabricated devices are also presented. We conclude by discussing the limitations associated with liquid-phase exfoliation and the recent advances made due to the development of the electrochemical exfoliation process with molecular intercalants.

• 한국표면공학회지
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• 제43권6호
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• pp.297-303
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• 2010

The effect of solution acidity and organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was systematically investigated in the view point of electroreduction of trivalent chromium ions and solution stability. It was found that solution acidity controlled at pH 2.5 showed the widest current range for bright electrodeposits in the presence of PEG additives, which reduced the local current intensification at high current densities. Through complex interaction between PEG additives and hydrogen ion, that is, solution acidity, electrode potential was moved in the negative direction in the bulk solution, while it shifted in the positive when electric potential was scanned. In conjunction with electrochemical quartz crystal microbalance (EQCM), it was found that PEG additives had a role in promoting the electron transfer to trivalent chromium ion complexes in bulk solution and their adsorption at the electrode surface as well as interfering with hydrogen ion reduction process below pH 2.5. The PEG additives developed the nodular morphology during electroreduction of trivalent chromium ions with the increase of solution acidity and enhanced its current efficiency by maintaining the consumption of complexant, formic acid, at low speed.

• 한국결정성장학회지
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• 제32권2호
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• pp.61-67
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• 2022

폐리튬이차전지 스크랩으로부터 회수한 유가금속인 니켈, 코발트, 망간을 정제하여 제조한 리튬이차전지 전구체 금속염 용액으로 테일러반응을 통해 NCM 811 전구체를 제조하였다. 반응 시간에 따른 전구체 형태 변화를 SEM, PSA, ICP 분석 결과를 기반으로 합성 조건을 확립하였다. 이에 상업용 전구체와 재활용하여 합성한 전구체의 전기 화학적 특성인 충·방전 특성, 율특성, 수명특성 등을 평가하여 비교 연구하였으며, 상업용 전구체와 비교 시 큰 차이가 없거나 일부 특성에서는 우수한 특성을 확인할 수 있었다.

• 한국레이저가공학회지
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• 제2권1호
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• pp.16-21
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• 1999

The surface of Alloy 600 was alloyed using a continuous wave $CO_2$ laser beam in order to improve its corrosion resistance. Laser surface alloying (LSA) was done by melting the surface electroplated with Cr of the alloy. The Cr concentration of the alloyed surface was 28-30 at.%, which is similar to that of Alloy 690. Alloying elements in the alloyed layer was observed to be distributed very homogeneously all over the alloyed region. According to the electrochemical and modified Huey tests, the corrosion resistance, in particular the grain boundary corrosion resistance, of the LSA specimens was significantly improved, compared with that of the as-received(AR) specimen. This improved corrosion resistance of the alloyed specimen might be attributed to the high Cr content which could make possible formation of more stable and dense passive film onto its surface.

• 한국표면공학회지
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• 제51권3호
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• pp.179-184
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• 2018

In this study, Ni and tungsten carbide (WC) nanoparticles are simultaneously synthesized with the mesoporous carbon nanoparticles (CNP) using a solution plasma processing (SPP) in the benzene. The Ni and WC nanoparticles were formed through the sputtering effect of electrodes during discharge, and mean time CNP were formed through reduction reaction. TEM observation showed that loaded Ni and WC nanoparticles were evenly dispersed on the CNP. The results of electrochemical analysis demonstrated that an introduction of Ni nanoparticles promoted to improve catalytic activity for oxygen reduction reaction (ORR). Moreover, Ni-WC/CNP lead to fast electron transfer process compared to that of WC/CNP. Therefore, the inexpensive Ni-WC/CNP might be a promising as catalytic material for cathodes in fuel cell applications.

• 수산해양기술연구
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• 제32권3호
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• pp.302-309
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• 1996

Cavitation erosion-corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. If the liquids corrosive to the material, a condition typically encountered in industry, the component materials may suffer serious damage by a combination of mechanical and electrochemical attack. To suppress cavitation erosion as well as cavitation erosion-corrosion to hydraulic equipments, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. This study was tested by using the piezoelectric vibrator with 20kHz, 24${\mu}$m for cavitation generation. And also, the vibratory cavitation erosion-corrosion tests on commercial mild steel SS41were carried out. We carefully observed the erosion pattern and surface photography. The geometrical mechanism of pit growth, which is to be likely these processing; shallow typelongrightarrowundercut typelongrightarrowwide shallow type.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2003년도 연료전지심포지움 2003논문집
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• pp.89-95
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• 2003

Fuel processing is an enabling technology for faster commercialization under lack of hydrogen infrastructures. It has been reported that the development of novel catalysts that are active and selective for hydrocarbon reforming reactions. It has been realized, however, that with pellet or conventional honeycomb catalysts, the reforming process is mass transport limited. This paper reports the development of catalyst structures with microchannels that are able to reduce the diffusion resistance and thereby achieve the same production rate within a smaller reactor bed. These microchannel reforming catalysts were prepared and tested with natural gas and gasoline-type fuels in a microreactor (1-cm dia.) at space velocities of up to 250,000 per hour. These catalysts have also been used in engineering-scale reactors (10 kWe, 7-cm dia.) with similar product qualities. Compared to pellet catalysts. the microchannel catalysts enable a nearly 5-fold reduction in catalyst weight and volume.

• 한국주조공학회지
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• 제25권3호
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• pp.134-141
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• 2005

To overcome the undesirable deformation, peeling off and geometrical restrictions which were mainly caused by differences in thermal expansion coefficients during the cladding of aluminum strip and stainless strip, new processing method based on vacuum die casting is designed and implemented in fabricating Al/Fe-17wt%Cr steel(stainless steel). To increase cast-bonding ability, the surface of Fe-17wt%Cr steel is electrochemically etched to have optimum pit size and density. The optimum conditions to generate best pit are as follows: Solution: 1 M $Fecl_{3}$+1 M Nacl, Addition: $CuCl_{2}+HCl$, Current density: 80 $mA/cm^{2}$, Total current: 400 $coulomb/cm^{2}$, AC frequency :60 Hz.

• 한국정보통신학회논문지
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• 제25권8호
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• pp.1130-1133
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• 2021

In this paper, a miniaturized sensor interface circuit for the respiration detection system is proposed. Respiratory diagnosis is one of the main ways to predict various diseases. The proposed system consists of respiration detection sensor, temperature sensor, and interface circuits. Electrochemical type gas sensor using solid electrolytes is adopted for respiration detection. Proposed system performs sensing, amplification, analog-to-digital conversion, digital signal processing, and i2c communication. And also proposed system has a small form factor and low-cost characteristics through optimization and miniaturization of the circuit structure. Moreover, technique for sensor degradation compensation is introduced to obtain high accuracy. The size of proposed system is about 1.36 cm².