• 한국분말재료학회지
• /
• 제30권5호
• /
• pp.387-393
• /
• 2023

Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni₃Co₆S₈-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni₃Co₆S₈@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni₃Co₆S₈@C-YS exhibited an impressive reversible capacity of 525.2 mA h g^-1 at a current density of 0.5 A g^-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni₃Co₆S₈ yolk shell nanopowder (Ni₃Co₆S₈-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni₃Co₆S₈@C-YS were attributed to the pitch-derived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

• 한국재료학회지
• /
• 제20권1호
• /
• pp.25-30
• /
• 2010

Si nanowire/multiwalled carbon nanotube nanocomposite arrays were synthesized. Vertically aligned Si nanowire arrays were fabricated by Ag nanodendrite-assisted wet chemical etching of n-type wafers using $HF/AgNO_3$ solution. The composite structure was synthesized by formation of a sheath of carbon multilayers on a Si nanowire template surface through a thermal CVD process under various conditions. The results of Raman spectroscopy, scanning electron microscopy, and high resolution transmission electron microcopy demonstrate that the obtained nanocomposite has a Si nanowire core/carbon nanotube shell structure. The remarkable feature of the proposed method is that the vertically aligned Si nanowire was encapsulated with a multiwalled carbon nanotube without metal catalysts, which is important for nanodevice fabrication. It can be expected that the introduction of Si nanowires into multiwalled carbon nanotubes may significantly alter their electronic and mechanical properties, and may even result in some unexpected material properties. The proposed method possesses great potential for fabricating other semiconductor/CNT nanocomposites.

• 자원리싸이클링
• /
• 제9권6호
• /
• pp.9-14
• /
• 2000

CSAC와 WPAC의 흡착특성을 보면 H공장 2차 처리수와 D공장 배출수에 함유된 ABS흡착에서 얻어진 Freundlich흡착등온식은 WPAC인 경우 q=23.12 $C^{ 0.42}$, q=18.32 $C^{0.38}$ 이고 CSAC인 경우 각각 $q=36.76C^{1.37}$ , q=26.67 $C^{0.42}$ 이었다. H공장 방류수의 파과점은 CSAC인 경우 680분이었고 WPAC는 610분이었다. 한편 D공장 배출수의 파과점은 CSAC인 경우 720분이었고 WPAC은 640분이었다. 이상의 결과로부터 CSAC 대체물로서 WPAC이 가능성이 있을 것으로 생각된다.

• 한국압력기기공학회 논문집
• /
• 제11권1호
• /
• pp.1-11
• /
• 2015

Feedwater Heaters are important components in a nuclear power plant. As the age of heater increases, the maintenance cost required for continuous operation also increases. Most heaters have the carbon steel shells, tube support plates and flow baffles. The carbon steel is susceptible to flow-accelerated corrosion. This is especially true if the flow has a two-phase mixture of steam and condensate. The wall thinning around the wet steam entrance area of the shell is inevitable during some long term operation. The structural integrity of the feedwater heater shell affects the safe operation of the nuclear power plant. Therefore, it is needed for the thinned shell to be repaired. The maintenance method for preventing failure of the shell should be determined by investigating various factors including the stress distribution of thinned area. The stress analysis of the shell including the steam entrance region is studied in this paper. The results of thinned shell is compared with that of intact shell.

• 전기화학회지
• /
• 제15권2호
• /
• pp.90-94
• /
• 2012

We report nanostructure electrodes with $TiO_2$ as a core and carbon as a shell ($TiO_2$@C) for oxygen reduction in alkaline solution. The structure of core-shell electrodes is characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction method, and X-ray photoelectron microscopy. The electrochemical properties of the $TiO_2$@C electrodes are characterized using a potentiostat and compared with those of carbon supported Pt catalyst. In particular, the core-shell electrode with dominant pyridinic-N component exhibits an imporved electrocatalytic activity for oxygen reduction reaction in alkaline solution.

• 한국연초학회지
• /
• 제16권2호
• /
• pp.181-190
• /
• 1994

Various active carbons were made from plant sources of coconut shell, pine tree, oak tree and lignite coal. Pore characteristics of these adsorbents were investigated. 1, With increasing activation time, specific surface area and pore volume increased, but the development of micropores was limited at a certain level. The average pore diameter, by BET, of coconut active carbon was 15.5-21.8$\AA$ and that of lignite carbon was 15.6-31.3$\AA$. The pore diameters of silica-gel, sepiolite and zeolite was 30.9$\AA$, 58.6$\AA$ and 55.7$\AA$, respectively. 2. The Horvath - Kawazoe micropore diameter of coconut shell active carbon was under 10.5$\AA$ and that of the other active carbon was under 20.9$\AA$ but silica-gel 33$\AA$, sepiolite 103 $\AA$ and zeolite was unexpectedly large to be 175$\AA$. From the difference between BET micropore diameter and Howath - Kawazoe diameter, it could be said that silica - gel has comparatively uniform pore diameter but sepiolite and zeolite have very uneven diameter. 3. Total pore volume of coconut shell active carbon was 0.27-1.04 cm3/g but that of the other active carbon, 0.23-0.62 cm3/g, was much lower than that of coconut shell active carbon. Hydrophilic adsorbent silica - gel and sepiolite showed big difference in specific surface area, but pore volumes of these were 0.47 and 0.56 cm3/g showing similar value and micropore volumes of these were, respectively, 0.06 cm3/g and 0.04 cm3/g. Total pore volume of zeolite was 0.1 cm3/g and that of micropore was only 0.02 cm3/g.

• Composites Research
• /
• 제37권3호
• /
• pp.186-189
• /
• 2024

본 연구는 나노필러가 혼합된 열가소성 탄소섬유강화 복합재료(Carbon fiber reinforced thermoplastic polymer, CFRTP)의 물성을 비교 평가하였다. Polyamide 6 (PA6) 수지에 Multi-wall carbon nano tube (MWCNT), Silicon oxide, Core shell rubber, Aramid nano fiber 등의 다양한 나노필러를 혼합한 후, 이를 기지재(Matrix)로 탄소섬유강화복합 재료(CFRP)를 제조하여 그 물성을 측정하였다. 나노필러의 종류와 혼합비율에 따라, 인장강도, 층간계면결합력 (Inter-laminar shear strength), Izod 충격 강도 등이 측정되었다. 인장 강도와 충격 강도의 경우 Core shell rubber를 혼합한 경우 가장 높은 물성을 가졌으나, 계면결합력은 silicon oxide를 1 wt.% 이하 혼합하였을 때 최적값을 가졌다.

• 대한화학회지
• /
• 제51권2호
• /
• pp.154-159
• /
• 2007

유리 및 고정화된 Bacillus brevis에 의한 큐놀린의 분해를 조사하였다. 코코넛 껍질 탄소에 고정화된 Bacillus brevis에 의한 큐놀린 분해 속도는 폼조각에 고정화되었거나 유리된 미생물에 의한 속도보다 빠르다. 시료에 존재하는 큐놀린 100 ppm을 완전히 제거하기 위해서는 코코넛 껍질 탄소에 고정화된 Bacillus brevis로 만든 생촉매를 물속에서 20시간 유지시키면 되었다. 이 생촉매는 꽤 긴 보존기간과 적절한 재생력을 가지고 있었다.

• Advances in nano research
• /
• 제9권2호
• /
• pp.69-82
• /
• 2020

In this paper, a new explicit analytical formula is derived for the critical buckling load of Double Walled Carbon Nanotubes (DWCNTs) embedded in Winkler elastic medium without taking into account the effects of the nonlocal parameter, which indicates the effects of the surrounding elastic matrix combined with the intertube Van der Waals (VdW) forces. Furthermore, we present a model which predicts that the critical axial buckling load embedded in Winkler, Pasternak or Kerr elastic medium under axial compression using the nonlocal Donnell shell theory, this model takes into account the effects of internal small length scale and the VdW interactions between the inner and outer nanotubes. The present model predicts that the critical axial buckling load of embedded DWCNTs is greater than that without medium under identical conditions and parameters. We can conclude that the embedded DWCNTs are less susceptible to axial buckling than those without medium.

• 대한화학회지
• /
• 제62권2호
• /
• pp.79-86
• /
• 2018

This study reported the adsorption of Cu(II) ions onto activated carbon prepared from Myristica Fragrans shell (MFS AC) over independent variables of contact time, activating chemical (NaOH) concentration, initial adsorbate concentration, initial pH of adsorbate solution and adsorption temperature. The MFS AC structure, morphology and total surface area were characterized by FTIR, SEM and BET techniques, respectively. The Cu(II) ions adsorption on the MFS AC (activated using 0.5 M NaOH) fitted best to Freundlich adsorption isotherm (FAI), and the FAI constant obtained was 0.845 L/g at $30^{\circ}C$ and pH 4.5. It followed the pseudo first order of adsorption kinetic (PFOAK) model, and the PFOAK based adsorption capacity was 107.65 mg/g. Thermodynamic study confirmed the Cu(II) ions adsorption should be exothermic and non-spontaneous process, physical adsorption should be taken place. The total surface area and pore volume based on BET analysis was $99.85m^2/g$ and 0.086 cc/g, respectively.