Fluorination effect of activated carbons on performance of asymmetric capacitive deionization

Jo, Hanjoo,Kim, Kyung Hoon,Jung, Min-Jung,Park, Jae Hyun,Lee, Young-Seak Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.409 No.-

<P><B>Abstract</B></P> <P>Activated carbons (ACs) were fluorinated and fabricated into electrodes to investigate the effect of fluorination on asymmetric capacitive deionization (CDI). Fluorine functional groups were introduced on the AC surfaces via fluorination. The specific capacitance of the fluorinated AC (FAC) electrode increased drastically from 261 to 337F/g compared with the untreated AC (RAC) electrode at a scan rate of 5mV/s, despite a decrease in the specific surface area and total pore volume after fluorination. The desalination behavior of asymmetric CDI cells assembled with an RAC electrode as the counter electrode and an FAC electrode as the cathode (R || F-) or anode (R || F+) was studied. For R || F-, the salt adsorption capacity and charge efficiency increased from 10.6mg/g and 0.58–12.4mg/g and 0.75, respectively, compared with the CDI cell assembled with identical RAC electrodes at 1V. This CDI cell exhibited consistently better salt adsorption capacity and charge efficiency at different applied voltages because FAC electrodes have a cation attractive effect originating from the partially negatively charged fluorine functional groups on the AC surface. Therefore, co-ion expulsion in the FAC electrode as the cathode is effectively diminished, leading to enhanced CDI performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Partially negatively charged fluorine functional groups were introduced on AC surface via fluorination. </LI> <LI> The FAC electrode was applied for asymmetric CDI. </LI> <LI> Salt adsorption capacity and charge efficiency were improved in R || F-. </LI> <LI> FAC exhibited cation attractive effect. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

전자선 조사로 표면 구조가 제어된 활성탄소섬유의 전기화학적 특성 향상

조한주(Hanjoo Jo),정민정(Min-Jung Jung),이영석(Young-Seak Lee) 한국고분자학회 2017 폴리머 Vol.41 No.3

본 연구에서는 활성탄소섬유를 제조한 뒤 전자선 조사를 실시하였으며, 다양한 흡수선량에 따른 활성탄소섬유 표면의 물리화학적 특성 변화가 전기화학적 특성에 미치는 영향을 알아보았다. 전자선 조사에 의하여 활성탄소섬유 표면의 구조적 결함은 감소하고 C-C (sp²) 결합은 증가하였다. 또한 전자선 조사된 활성탄소섬유가 미처리된 활성탄소섬유보다 비표면적 및 기공부피가 훨씬 더 컸다. 이러한 표면 구조 변화는 전자선 조사에 따른 활성탄소섬유 표면에서의 결함 형성 및 탄소원자의 재 혼성화에 의한 것으로 여겨진다. 200 kGy로 조사된 활성탄소섬유의 비정전용량은 미처리된 활성탄소섬유보다 39% 향상되었다. 전자선 조사 활성탄소섬유의 이러한 전기화학적 특성의 향상은 활성탄소섬유 표면의 비표면적 및 기공 부피 증가에 기인되었다. In this study, activated carbon fibers (ACFs) were prepared and then irradiated by electron beam (e-beam) to investigate effects of physicochemical properties of ACF surface on the electrochemical properties of ACFs according to various irradiation doses. Defects of the ACF surface were decreased and C-C (sp²) bonds onto that were increased via the e-beam irradiation. The specific surface area and pore volume of the e-beam irradiated ACFs were also much higher than those of the untreated ACFs. These changes of the surface structure on ACFs were caused by formation of defects and rehybridization of carbon atoms by e-beam irradiation. The specific capacitance of the ACFs irradiated with 200 kGy increased by 39% compared with the untreated ACFs. These enhancements of the electrochemical properties in e-beam irradiated ACFs were attributed to the increase in the specific surface area and pore volume.

Anatase TiO2-doped activated carbon fibers prepared by ultrasonication and their capacitive deionization characteristics

Da Hee Kang,Hanjoo Jo,Min-Jung Jung,Kyoung Hoon Kim,Young-Seak Lee 한국탄소학회 2018 Carbon Letters Vol.27 No.-

TiO2-doped activated carbon fibers(ACFs) were successfully prepared as capacitive deionization(CDI) electrode materials by facile ultrasonication-assisted process. ACFs were treated with titanium isopropoxide(TTIP) and isopropyl alcohol solutions of different concentrations and then calcinated by ultrasonication without heat-treatment. The results show that a certain amount of anatase TiO2 was present on the ACF surface. The specific capacitance of the TiO2-doped ACF electrode was remarkably improved(by 93.8% at scan rate of 50 mV s-1) over that of the untreated ACF electrode, despite decreases in the specific surface area and total pore volume upon TiO2 doping. From the CDI experiments, the salt adsorption capacity and charge efficiency of the sample with TTIP percent concentration of 15% were found to considerably increase by 71.9 and 57.1%, respectively. These increases are attributed to the improved wettability of the electrode, which increases the number of surface active sites and facilitates salt ion diffusion in the ACF pores. Additionally, the Ti-OH groups of TiO2 act as electrosorption sites, which increases the electrosorption capacity.

The electrical and heating properties of copper-incorporated graphite fibers fabricated using different ultrasonication techniques

Kyeong Min Lee,Min-Ji Kim,Hanjoo Jo,Sang Young Yeo,Young-Seak Lee 한국탄소학회 2017 Carbon Letters Vol.24 No.-

Effect of CuO introduced on activated carbon fibers formed by electroless plating on the NO gas sensing

Kim, Min-Ji,Lee, Sangmin,Lee, Kyeong Min,Jo, Hanjoo,Choi, Suk Soon,Lee, Young-Seak Elsevier 2018 Journal of industrial and engineering chemistry Vol.60 No.-

<P><B>Abstract</B></P> <P>High-performance gas sensors were fabricated from activated carbon fibers (ACFs) introduced with CuO. The electroless CuO plating of ACFs was carried out to investigate the nitric oxide (NO) gas sensing ability with respect the plating time. The gas sensors were fabricated by dropping a solution (CuO-introduced ACFs+DMF) onto SiO<SUB>2</SUB>/Si wafers patterned with Pt electrodes. The NO gas sensing behavior of the ACF-based gas sensors was determined by resistance measurements. As the plating time increased, the CuO content on the ACF surface increased, and the specific surface area of the ACFs decreased. The gas sensor fabricated from untreated ACFs showed a 4% resistance change upon exposure to NO gas, whereas the sensor with CuO-introduced ACFs showed an approximately 12.5% resistance change. This phenomenon is attributed to the increased number of hole carriers in the ACFs due to CuO, which promotes electron transfer, and benefits the effective detection of NO gas. This method provides as a unique surface treatment strategy to improve the NO gas sensing efficiency.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CuO particles were introduced on ACFs surface via electroless copper plating. </LI> <LI> The CuO-ACF electrodes were used as NO gas sensors. </LI> <LI> When the plating time is 15min, NO gas sensing and recovery were improved than untreated ACFs. </LI> <LI> The introduced CuO acts as a catalyst on ACFs surface to transfer electrons. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>To improve the sensitivity of NO gas, ACFs were treated according plating time conditions and used as a NO gas sensor material.</P> <P>[DISPLAY OMISSION]</P>

국방 공급망 품질경영 수준 측정을 위한 모형 개발 연구

김형근 ( Hyeunggeun Kim ),성시일 ( Si-il Sung ),유한주 ( Hanjoo You ),정욱 ( Uk Jung ),박종우 ( Jongwoo Park ),조동혁 ( Donghyuk Jo ) 한국품질경영학회 2016 품질경영학회지 Vol.44 No.2

Purpose: This paper treats a defense-supply chain quality management model for analyzing the Korea defense industry. Methods: Various literature, the quality collaboration index for supply chain management model proposed by Korean Standards Association and shared growth index presented by Korea Commission for Corporate Partnership are reviewed to develop the defense supply chain quality management index and model based on the method presented by Hafeez et al.(2006). In addition, based on the proposed model, we survey the supply chain quality management efficiency including focused group interviews in the defense industry. Results: We propose a defense-supply chain quality management index and model for analyzing the quality level between the parent companies and its partners. In addition, the results of applying the model are proposed to improve the quality of military items. Conclusion: A model is developed for improving the quality of military items. This proposed model will be adopted to enhance the quality of military items.