• Applied Chemistry for Engineering
• /
• v.21 no.3
• /
• pp.265-271
• /
• 2010

Desalination effects of capacitive deionization (CDI) process was studied using $TiO_2$/activated carbon electrode. In order to enhance the wettability of electrode and decrease a electrode resistance, $TiO_2$ was coated on activated carbon. By means of $TiO_2$ coating on activated carbon, electric double layer to adsorption content in CDI process was increased. It was identified from TEM, XRD, and XPS that the activated carbon based on $TiO_2$ composite was fabricated successfully by means of sol-gel method. As a results of cyclic voltammetry and impedance, it was identified that $TiO_2$/activated carbon electrode has more electric double later capacitance and less diffusion resistance than activated carbon. Also charge-discharge and ion conductivity profiles showed that the ion removal ratios of $TiO_2$/activated carbon electrode in NaCl electrolyte of $1000\;{\mu}S/cm$ more increased about 39% than that of activated carbon. In conclusion it was possible to identify that the carbon electrode coated $TiO_2$ as electrode material was more effective than raw carbon electrode.

• Applied Chemistry for Engineering
• /
• v.28 no.5
• /
• pp.534-538
• /
• 2017

In this study, the molecular weight controlled pitches derived from pyrolyzed fuel oil (PFO) were prepared using solvent extraction and were carbonized. Electrochemical characteristics of lithium battery anode materials were investigated using these petroleum pitches. Three pitch samples prepared by the thermal reaction were 3903 (at $390^{\circ}C$ for 3 h), 4001 (at $400^{\circ}C$ for 1 h) and 4002 (at $400^{\circ}C$ for 2 h). The prepared hexane insoluble pitches were analysed by XRD, TGA, SEM and Gel permeation Chromatography (GPC). The electrochemical characteristics of the PFO-derived pitch as an anode material were investigated by constant current charge/discharge, cyclic voltammetry and electrochemical impedance tests. The coin cell using pitch (4001) and the electrolyte of $LiPF_6$ in organic solvents (EC : DMC = 1 : 1 vol%, VC 3 wt%) has better initial capacity (310 mAh/g) than that of other pitch coin cells. Also, this carbon anode showd a high initial efficiency of 82%, retention rate capability at 2 C/0.1 C of 90% and cycle retention of 85%. It was found that modified pitches improved the cycling and rate capacity performance.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.142-149
• /
• 2020

In this study, the electrochemical performance of Graphite/Silicon/Pitch composites as anode material was investigated to improve the low theoretical capacity of artificial graphite. Spherical artificial graphite surface was coated with polyvinylpyrrolidone (PVP) amphiphiles material to synthesize Graphite/Silica material by silica islands growth. The Graphite/Silicon/Pitch composites were prepared by petroleum pitch coating and magnesiothermic reduction. The Graphite/Silicon/Pitch composite electrodes manufactured using poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) binders. The coin type half cell was assembled using various electrolytes and additives. The Graphite/Silicon/Pitch composites were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and a thermogravimetric analyzer (TGA). The electrochemical characteristics of Graphite/Silicon/Pitch composite were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy. The Graphite/Silicon/Pitch composites showed high cycle stability at a graphite/silica/pitch ratio (1:4:8 wt%). When the electrode is prepared using PAA binder, the high capacity and stability is obtained. The coin type half cell assembled using EC: DMC: EMC electrolyte showed high initial capacity (719 mAh/g) and excellent cycle stability. The rate performance has an capacity retention (77%) at 2 C/0.1 C and an capacity recovery (88%) at 0.1 C / 0.1 C when the vinylene carbonate (VC) was added.

• Korean Journal of Materials Research
• /
• v.11 no.5
• /
• pp.339-344
• /
• 2001

An all solid-state thin film supercapacitor (TFSC) with Co$_3$O$_4$/LiPON/Co$_3$O$_4$ structure was fabricated on Pt/Ti/Si substrate using Co$_3$O$_4$ thin film electrode. Each Co$_3$O$_4$ film was grown by reactive dc reactive magnetron sputtering with increasing $O_2$/[Ar+O$_2$] ratio. Amorphous LiPON electrolyte film was deposited on Co$_3$O$_4$/Pt/Ti/Si in pure nitrogen ambient by using reactive rf magnetron sputtering. The electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ multi-layer structures exhibits a behavior of a bulk-type supercapacitor, even though much lower capacity (from 5 to 25 mF/$\textrm{cm}^2$-$\mu\textrm{m}$) than that of the bulk one. It was found that the TFSC showed a fairly constant discharge capacity with a constant current of 50 $\mu\textrm{A}/\textrm{cm}^2$ at the cut-off voltage 0-2V during 400 cycles. It is shown that the electrochemical behavior of the Co$_3$O$_4$/LiPON/Co$_3$O$_4$ TFSC is dependent upon the sputtering gas ratio. The capacity dependency of electrode films on different gas ratios was explained by different structural, electrical, and surfacical properties.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.4
• /
• pp.219-223
• /
• 2000

All-solid state lithium rechargeable thin film batteries were fabricated with the configuration of$Cu_{0.5}V_2O_5/Lipon/Li$ using sequential thin film techniques. Copper vanadium oxide thin films and Lipon thin films were prepared by DC reactive dual source magnetron sputtering and RF magnetron sputtering, respectively. According to XRD analysis, we found out that copper vanadium oxide thin films were amorphous. The electrochemical behaviour of them was examined in half cell system using EC : DMC(1:1 in IM $LiPF_5$) liquid electrolyte. The ionic conductivity of Lipon thin film was $1.02\times10^{-6}S/cm$ at $25^{\circ}C$ and $Cu_{0.5}V_2O_5/Lipon/Li$ cell showed that the discharge capacity was about $50{\mu}Ah/cm^2{\mu}m$ beyond 500cyc1es.

• Journal of the Korean Electrochemical Society
• /
• v.8 no.2
• /
• pp.82-87
• /
• 2005

The cathode material, $LiNi_{0.5}Mn_{1.5}O_4$, for high voltage applications of Li-ion batteries exhibits impurity phases due to oxygen deficiency during the high temperature heat treatment. The impurity phase reduces the electrochemical properties of the electrode since the deficiency spinel structure disturbs the lithium ion intercalation and deintercalation. In this study, Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4(0{\leq}x{\leq}0.05)$ powders are synthesized by a sol-gel method in order to reduce the amount of the impurity phases in the $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4$. Thermal analysis of the cathode material shows that the $LiNi_{0.5}Mn_{1.5}O_4$ without Cr substitution looses $2\%$ of its weight due to oxygen deficiency but the amount of weight loss is diminished when Cr is substituted. XRD analysis also supports the reduction of the impurity phases in the cathode after chromium substitution, suggesting that the improvement of the electrochemical properties such as the capacity retention and electrochemical stability are attributed to the low content of impurity phases in the Cr-substituted $LiNi_{0.5-x}Mn_{1.5}Cr_xO_4.$

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05a
• /
• pp.139-141
• /
• 2005

이번 실험에서는 변방전형 교류 PDP에서의 3차원적인 전자온도와 이온밀도의 측정을 마이크로 랑뮈르 탐침법을 통해 실험적으로 연구하였다. 스테핑 모터에 연결된 마이크로 랑뮈르 탐침은 20um씩 움직이며 탐침에 인가하는 플러스와 마이너스의 직류전압을 통해 I-V곡선을 구할 수 있고 이를 통해서 전자온도와 플라스마 밀도를 구할 수 있다. Ne+Xe(4%) 200Torr의 혼합가스에서 전극의 테두리를 따라(X축) 전자온도 및 플라스마 밀도를 측정한 결과 중앙지점에서와 전극의 경계지역에서 이온밀도는 $7.69{\sim}11.1{\times}10^{11}cm^{-3}$ 까지 측정되었다. 또한 전자온도는 플라스마 밀도와 균형적인 관계에 있다는 것은 주목할 만하다. 전자온도는 전극 사이의 중심에서 가장 적게 1.3 ~ 3.15eV까지 측정되었다. Y축으로 측정했을 경우 이온 밀도와 전자온도는 전극 갭 중앙에서부터 약 80um 떨어진 지점에서 서로 교차하며 증가 및 감소였으며 이온밀도는 $8.3{\sim}11.1{\times}10^{11}cm^{-3}$로 측정되었고 전자온도는 이와 균형적인 관계를 가지고 1.2~1.6eV로 측정되었다. 또한 이러한 특성은 AC PDP 에서 나타나는 줄무늬 현상과 관련이 있는 것으로 보인다. Z축으로 측정했을 경우 약 125um높이에서 가장 높게 측정되었으며 $1.1{\times}10^{12}cm^{-3}$정도로 측정되었다.

• Membrane Journal
• /
• v.25 no.5
• /
• pp.406-414
• /
• 2015

In this study, partially fluorinated cation exchange membranes were prepared by direct sulfonation of Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP) followed by a casting method for application in the Membrane capacitive deionization (MCDI). The structure of sulfonated PVDF-co-HFP (SPVDF) was confirmed by Fourier-transform infrared (FT-IR) and $^1H$ Nuclear magnetic resonance ($^1H$ NMR) analysis. For quantitative analysis of the chemical composition, the X-ray Photoelectron Spectroscopy (XPS) was used. The membrane properties such as water uptake, ion exchange capacity and electrical resistance were measured. It was suggested that the optimum direct sulfonation condition of PVDF-co-HFP ion exchange membranes was $60^{\circ}C$ and 7 hours for temperature and duration of sulfonation, respectively. The water uptake of the SPVDF ion exchange membrane was 21.5%. The ion exchange capacity and electrical resistance were 0.89 meq/g and $3.70{\Omega}{\cdot}cm^2$, respectively. It was investigated that if it is feasible to apply these membranes in MCDI at various cell potentials (0.9~1.5 V) and initial flow rates (10~40 mL/min). In the MCDI process, the maximum salt removal rate was 62.5% in repeated absorption-desorption cycles.

• Korean Journal of Food Science and Technology
• /
• v.48 no.5
• /
• pp.486-491
• /
• 2016

Efficacy of dielectric barrier discharge-cold plasma treatment (DBD-CPT) for microbial decontamination of onion powder was evaluated. Onion powder, inoculated with Escherichia coli O157:H7, Salmonella Enteritidis, or Listeria monocytogenes, was treated with helium DBD-CPT. DBD-CPT (9 kV, 20 min) inhibited E. coli O157:H7, S. Enteritidis, and L. monocytogenes by $1.4{\pm}0.5$, $2.3{\pm}0.3$, and $1.2{\pm}0.0log\;CFU/cm^2$, respectively. The inactivation levels of E. coli O157:H7, S. Enteritidis and L. monocytogenes increased by $2.2{\pm}0.1$, $2.5{\pm}0.1$ and $1.9{\pm}0.3log\;CFU/cm^2$, respectively, as water activity increased from 0.4 to 0.8, and increased by $2.3{\pm}0.4$, $2.1{\pm}0.1$ and $1.6{\pm}0.1log\;CFU/cm^2$, respectively, as the particle size increased from 0.3 to $1.0cm^2$. Neither the ascorbic acid and quercetin concentrations nor the color of onion powder was changed by DBD-CPT (p>0.05). These results demonstrate the potential for application of DBD-CPT in improving microbiological safety of onion powder while preserving the physicochemical properties.

• Korean Journal of Food Science and Technology
• /
• v.48 no.5
• /
• pp.525-529
• /
• 2016

Twenty-nine pepper products commercially available in the market were collected and investigate for contamination levels. Pepper products purchased from traditional markets had a degree of contamination of $10^6-10^7CFU/g$ aerobic bacteria, $10^4-10^5CFU/g$ Bacillus sp., and less than $10^2CFU/g$ yeast and molds. Organic pepper showed a degree of contamination of $10^4$ aerobic bacteria, $10^2-10^3$ Bacillus sp., and less than $10^1$ yeast and molds. Intense pulsed light (IPL) treatment of 10 min (1,000 V, 5 pps and 4 cm sample-to-lamp distance) showed a bacterial death rate of 1.45-1.55 log for whole peppers, and of 0.8-0.85 log for black and white pepper powder. The sterilization rate using IPL was higher than that using other non-thermal sterilization methods, such as ozone treatment or low-pressure discharge plasma sterilization, indicating that the IPL sterilization method may find potential application in the industry. However, further studies may need to be conducted to enhance the effect of sterilization.