• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.110-110
• /
• 2011

The nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value for lithiated silicon nanowire and a higher value for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value than that of the Si nanowire substrate by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The Young's modulus obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively higher value than lithiated silicon nanowire due to the elastically soft amorphous structures. The frictional forces acting on the tip sliding on the surface of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process.

• 대한화학회지
• /
• 제33권5호
• /
• pp.496-503
• /
• 1989

란탄나이드 3가 (Pr(III)와 Yb(III))와 2,2,6,6-tetramethyl-3,5-heptanedione(dipivaloylmethane) 착물들의 전기화학적 거동을 DC와 DP 그리고 CV 방법으로 조사하였다. 란탄나이드 3가 착물들 중 Pr(III)의 환원은 Ag-AgCl 전극으로 Epc = -0.13 V와 -0.80 V 그리고 Yb(III)는 -0.02 Ⅴ로 1전자이동에 의한 것임을 알았고, 1차 화학평형반응이 가역과 비가역으로 진행되는 ErCr전극과정임을 DP와 CV로부터 알았다. 평형상수 lnK는 여러 용매들로부터 얻었고, 이들 상수는 용매의 유전상수가 감소함에 따라 증가됨을 알았다. 이들 반응에서 lnK는 여러 용매에 대한 ln(1/D)을 도시하면 좋은 직선관계에 있었고, 이 때 란탄나이드의 거동은 원자번호가 증가함에 따라서 lnK가 감소하였다.

• 한국재료학회지
• /
• 제30권9호
• /
• pp.458-464
• /
• 2020

Zinc-ion hybrid supercapacitors (ZICs) have recently been spotlighted as energy storage devices due to their high energy and high power densities. However, despite these merits, ZICs face many challenges related to their cathode materials, activated carbon (AC). AC as a cathode material has restrictive electrical conductivity, which leads to low capacity and lifetime at high current densities. To overcome this demerit, a novel boron (B) doped AC is suggested herein with improved electrical conductivity thanks to B-doping effect. Especially, in order to optimize B-doped AC, amounts of precursors are regulated. The optimized B-doped AC electrode shows a good charge-transfer process and superior electrochemical performance, including high specific capacity of 157.4 mAh g^-1 at current density of 0.5 A g^-1, high-rate performance with 66.6 mAh g^-1 at a current density of 10 A g^-1, and remarkable, ultrafast cycling stability (90.7 % after 10,000 cycles at a current density of 5 A g^-1). The superior energy storage performance is attributed to the B-doping effect, which leads to an excellent charge-transfer process of the AC cathode. Thus, our strategy can provide a rational design for ultrafast cycling stability of next-generation supercapacitors in the near future.

• 한국표면공학회지
• /
• 제49권6호
• /
• pp.539-548
• /
• 2016

The non-noble 1D nanofibers(NFs) prepared by electrospinning and calcination method were used as oxygen evolution reaction (OER) electrocatalyst for water electrolysis. The electrospinning process and rate of solution composition was optimized to prepare uniform and non-beaded PVP polymer electrospun NFs. The diameter and morphology of PVP NFs changed in accordance with the viscosity and ion conductivity. The clean metal precursor contained electrospun fibers were synthesized via the optimized electrospinning process and solution composition. The calcined $CuCo_2O_4$ NFs catalyst showed higher activity and long-term cycle stability for OER compared with other $Co_3O_4$, $NiCo_2O$ NF catalysts. Furthermore, the $CuCo_2O_4$ NFs maintained the OER activity during long-term cycle test compared with commercial $CuCo_2O_4$ nanoparticle catalyst due to unique physicochemical and electrochemical properties by1D nanostructure.

• Corrosion Science and Technology
• /
• 제15권6호
• /
• pp.281-289
• /
• 2016

The effect of nitrogen on the electrochemical corrosion and nanomechanical behaviors of martensitic stainless steel was examined using potentiodynamic polarization and nanoindentation test methods. The results indicate that partial replacement of carbon with nitrogen effectively improved the passivation and pitting corrosion resistance of conventional high-carbon and high- chromium martensitic steels. Post-test observation of the samples after a potentiodynamic test revealed a severe pitting attacks in conventional martensitic steel compared with nitrogen- containing martensitic stainless steel. This was shown to be due to (i) microstructural refinement results in retaining a high-chromium content in the matrix, and (ii) the presence of reversed austenite formed during the tempering process. Since nitrogen addition also resulted in the formation of a $Cr_2N$ phase as a process of secondary hardening, the hardness of the nitrogen- containing steel is slightly higher than the conventional martensitic stainless steel under tempered conditions, even though the carbon content is lowered. The added nitrogen also improved the wear resistance of the steel as the critical load (Lc2) is less, along with a lower scratch friction coefficient (SFC) when compared to conventional martensitic stainless steel such as AISI 440C.

• 한국재료학회지
• /
• 제32권1호
• /
• pp.14-22
• /
• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• 자원리싸이클링
• /
• 제31권5호
• /
• pp.59-66
• /
• 2022

니켈, 코발트 및 구리 전해채취의 반응율속단계 규명을 위해 회전원판전극(rotating disc electrode, RDE)를 사용하여 전해액 온도 및 교반속도에 대한 실험을 수행하였다. 유가금속 별 전해채취 공정에서의 활성화에너지를 구하여 반응율속단계를 규명한 결과 니켈은 혼합율속, 코발트는 화학반응율속, 구리는 물질전달율속으로 판단되었다. 니켈, 코발트 및 구리의 전해액 온도 및 교반속도 변화에 따른 전해채취 공정을 수행하여 전류효율을 비교한 결과 반응율속단계 결과와 일치하였다.

• 한국환경보건학회지
• /
• 제48권3호
• /
• pp.167-175
• /
• 2022

Background: Disinfection is essential to provide drinking water from a water source. The disinfection process mainly consists of the use of chlorine and ozone, but when chlorine is used as a disinfectant, the problem of disinfection by-products arises. In order to resolve the issue of disinfection by-products, electro-chlorination technology that produces chlorine-based disinfectants from salt water through electrochemical principles should be applied. Objectives: This study surveys the possibility of optimally producing active chlorine from synthetic NaCl solutions using an electro-chlorination system through RSM. Methods: Response surface methodology (RSM) has been used for modeling and optimizing a variety of water and wastewater treatment processes. This study surveys the possibility of optimally producing active chlorine from synthetic saline solutions using electrolysis through RSM. Various operating parameters, such as distance of electrodes, sodium chloride concentration, electrical potential, and electrolysis time were evaluated. Results: Various operating parameters, such as distance of electrodes, sodium chloride concentration, electrical potential, and electrolysis time were evaluated. A central composite design (CCD) was applied to determine the optimal experimental factors for chlorine production. Conclusions: The concentration of the synthetic NaCl solution and the distance between electrodes had the greatest influence on the generation of hypochlorite disinfectant. The closer the distance between the electrodes and the higher the concentration of the synthetic NaCl solution, the more hypochlorous acid disinfectant was produced.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.399-399
• /
• 2008

Synthesis and characterization of ZnO structure such as nanowires, nanorods, nanotube, nanowall, etc. have been studied to multifunctional application such as optical, nanoscale electronic and chemical devices because it has a room-temperature wide band gap of 3.37eV, large exiton binding energy(60meV) and various properties. Various synthesis methods including chemical vapor deposition (CVD), physical vapor deposition, electrochemical deposition, micro-emulsion, and hydrothermal approach have been reported to fabricate various kinds of ZnO nanostructures. But some of these synthesis methods are expensive and difficult of mass production. Wet chemical method has several advantage such as simple process, mass production, low temperature process, and low cost. In the present work, ZnO nanorods are deposited on ITO/glass substrate by simple wet chemical method. The process is perfomed by two steps. One-step is deposition of ZnO seeds and two-step is growth of ZnO nanorods on substrates. In order to form ZnO seeds on substrates, mixture solution of Zn acetate and Methanol was prepared.(one-step) Seed layers were deposited for control of morpholgy of ZnO seed layers by spin coating process because ZnO seeds is deposited uniformly by centrifugal force of spin coating. The seed-deposited samples were pre-annealed for 30min at $180^{\circ}C$ to enhance adhesion and crystallinnity of ZnO seed layer on substrate. Vertically well-aligned ZnO nanorods were grown by the "dipping-and-holding" process of the substrates into the mixture solution consisting of the mixture solution of DI water, Zinc nitrate and hexamethylenetetramine for 4 hours at $90^{\circ}C$.(two-step) It was found that density and morphology of ZnO nanorods were controlled by manipulation of ZnO seeds through rpm of spin coating. The morphology, crystallinity, optical properties of the grown ZnO nanostructures were carried out by field-emission scanning electron microscopy, high-resolution electron microscopy, photoluminescence, respectively. We are convinced that this method is complementing problems of main techniques of existing reports.

• 대한화학회지
• /
• 제31권6호
• /
• pp.542-554
• /
• 1987

네자리 schiff base cobalt(II) 착물로서 Co(SED), Co(SND) and Co(SOPD)들을 합성하여 이들 착물들의 DMSO 용액에서 산소를 가하여 산소첨가 생성착물로 $[Co(SED)(DMSO)]_2O_2,\;[Co(SND)(DMSO)]_2O_2$ 및 $[Co(SOPD)(DMSO)]_2O_2$들을 합성하였다. 이들의 원소분석과 Cobalt정량, IR-Spectra, T.G.A. 및 자화율을 측정하여 산소:cobalt(II) 착물의 결합비가 1:2이고 네자리 schiff base cobalt(II)와 DMSO 및 산소가 6배위 결합으로 주어짐을 알았으며 Co(SED), Co(SND) 및 Co(SOPD) 착물들의 0.1M TEAP-DMSO용액에서 순환전압-전류법에 의한 산화 환원 과정이 Co(SED) 및 Co(SOPD)는 Co(II) / Co(III)와 Co(II) / Co(I) 과정이 가역적으로 일어나고 Co(SND)는 Co(II) / Co(III)과정은 가역적이지만 Co(II) / Co(I) 과정은 비가역적이다. 또한 산소 첨가 생성물의 착물들은 0.1M TEAP-DMSO 용액에서 산소결합의 환원과정이 $E_{pc}$ = -0.80~-0.89V에서 일어나고 이에 Couple인 산화과정은 $E_{pa}$ = -0.70~-0.76V에서 준가역적으로 일어남을 알았다.