• 한국입자에어로졸학회지
• /
• 제9권1호
• /
• pp.7-21
• /
• 2013

Twelve-hour size-resolved atmospheric aerosols were measured to determine size distributions of water-soluble organic carbon(WSOC) during daytime and nighttime, and to investigate sources and formation pathways of WSOC in individual particle size classes. Mass, WSOC, ${NO_3}^-$, $K^+$, and $Cl^-$ at day and night showed mostly bimodal size distributions, peaking at the size range of $0.32-0.55{\mu}m$(condensation mode) and $3.1-6.2{\mu}m$(coarse mode), respectively, with a predominant condensation mode and a minor coarse mode. While ${NH_4}^+$ and ${SO_4}^{2-}$ showed unimodal size distributions which peaked between 0.32 and $0.55{\mu}m$. WSOC was enriched into nuclei mode particles(< $0.1{\mu}m$) based on the WSOC-to-mass and WSOC-to-water soluble species ratios. The sources and formation mechanisms of WSOC were inferred in reference to the size distribution characteristics of inorganic species(${SO_4}^{2-}$, ${NO_3}^-$, $K^+$, $Ca^{2+}$, $Na^+$, and $Cl^-$) and carbon monoxide. Nuclei mode WSOC was likely associated with primary combustion sources during daytime and nighttime. Among significant sources contributing to the condensation mode WSOC were homogeneous gas-phase oxidation of VOCs, primary combustion emissions, and fresh(or slightly aged) biomass burning aerosols. The droplet mode WSOC could be attributed to aqueous oxidation of VOCs in clouds, cloud-processed biomass burning aerosols, and small contributions from primary combustion sources. From the correlations between WSOC and soil-related particles, and between WSOC and sea-salt particles, it is suggested that the coarse mode WSOC during daytime is likely to condense on the soil-related particles($K^+$ and $Ca^{2+}$), while the WSOC in the coarse fraction during nighttime is likely associated with the sea-salt particles($Na^+$).

• 한국세라믹학회지
• /
• 제29권11호
• /
• pp.893-899
• /
• 1992

Composite specimens, which are composed MDF cement of HAC-PVA system were prepared by adding carbon fiber, hydrated silica and SiC powder, and we studied effect of additives on the flexural strength of the composites. All of additives is effective in the improvement of flexural strength of the composite specimens. The size of average pore diameter in the specimens which have high flexural strength property was small. Specimen mixed with hydrated silica was effective in the particle compact property. Flexural strength of carbon fiber reinforced MDF cement composites were improved because of crack deflection of carbon fiber in cementitious matrix.

• 한국입자에어로졸학회지
• /
• 제6권4호
• /
• pp.185-192
• /
• 2010

This paper reports that the installation of a carbon fiber ionizer in front of an activated carbon fiber(ACF) filter enhanced the antibacterial efficiency. In addition, the effect of the ionizer on the filtration of bioaerosols is reported. Negative air ions from the ionizer were used as antibacterial agent. The test bacteria(Escherichia coli) were aerosolized using an atomizer and were deposited on the ACF filter media for 10 minutes. E. coli deposited on the filter were exposed to negative air ions for 0, 1, 5 and 10 minutes. Then they were separated from the ACF filter by shaking incubation with nutrient broth for 4 hours. The separated E. coli were spread on nutrient agar plates and incubated at $37^{\circ}C$ for 1~3 days. The antibacterial efficiency of E. coli was measured using a colony counting method. The antibacterial efficiencies of E. coli exposed to negative air ions for 1, 5 and 10 minutes were 14%, 48% and 71%, respectively. The filtration efficiency was evaluated by measuring the number concentration of bioaerosols at the upstream and downstream of the filter media. The increase of filtration efficiency by air ions was 14%, that is similar to the 17% filtration efficiency by none air ions. The ozone concentration was below the detection limit (under 0.01ppm) when the carbon fiber ionizers were on.

• Composites Research
• /
• 제19권2호
• /
• pp.7-12
• /
• 2006

본 연구에서는 탄소섬유의 첨가가 흑연 보강 전도성 고분자 복합재료의 전기적, 기계적 특성에 미치는 영향을 고찰하였다. 압축성형법을 이용하여 흑연입자/탄소섬유 혼합 보강 전도성 고분자 복합재료를 제조하였으며 흑연입자의 고비율 충진은 복합재료 내에서 입자 사이의 직접 접촉을 통해 높은 전기 전도도(>100S/cm)를 얻는 것을 가능하게 하였다. 하지만 흑연입자의 비율이 높아짐에 따라 소재의 강도가 점차 떨어지게 되므로 이를 보완하기 위해 탄소섬유를 첨가하여 그에 따른 소재의 전기적, 기계적 특성 변화를 연구하였다. 탄소섬유의 충진 비율이 증가함에 따라 소재의 굽힘 강도는 증가하였으나 탄소섬유의 클러스터 형성으로 인해 탄소섬유 사이에 비전도성 영역이 발생하여 복합재료의 전기 전도도는 감소함을 확인하였다. 탄소섬유의 충진 비율이 전체 시스템의 20wt.%인 경우에는 굽힘 강도는 12% 증가한 반면 전기 전도도가 27% 감소하였다.

• Carbon letters
• /
• 제14권4호
• /
• pp.228-233
• /
• 2013

In this work, we report in-situ observations of changes in catalyst morphology, and of growth termination of individual carbon nanotubes (CNTs), by complete loss of the catalyst particle attached to it. The observations strongly support the growth-termination mechanism of CNT forests or carpets by dynamic morphological evolution of catalyst particles induced by Ostwald ripening, and sub-surface diffusion. We show that in the tip-growth mode, as well as in the base-growth mode, the growth termination of CNT by dissolution of catalyst particles is plausible. This may allow the growth termination mechanism by evolution of catalyst morphology to be applicable to not only CNT forest growth, but also to other growth methods (for example, floating-catalyst chemical vapor deposition), which do not use any supporting layer or substrate beneath a catalyst layer.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 추계학술대회 논문집
• /
• pp.305-305
• /
• 2009

The carbon nano-structured materials could be applied to the fields of advanced fillers, templates, electrode materials, sensor, storage, and absorption materials. The polyacrylonitrile (PAN) based carbon nano-particles provide the remarkable properties of high specific surface area, large pore volume, chemical inertness, and good mechanical stability. In this study, well-defined carbon nano-particles were obtained through pyrolysis of polyacrylonitrile based particles. The precursor nano-particles were prepared by modified aqueous dispersion polymerization using hydrophilic poly(vinyl alcohol) in a water/ N,N-dimethylformamide mixture media. Synthesized precursor nanoparticles have relatively monodisperse particles ranging 80 ~ 250nm. Stable spherical particles are obtained without coagulum or secondary particles in our system. The characteristic of the carbon nanoparticles were investigated in terms of surface area, morphology, and size distribution.

• Nuclear Engineering and Technology
• /
• 제48권1호
• /
• pp.175-181
• /
• 2016

This study investigates the dispersibility of carbon in carbon contained ammonium diuranate (C-ADU) gel particles and the characteristics of C-ADU gel liquid droplets produced by the vibrating nozzle and integrated aging-washing-drying equipment. It was noted that the excellent stability of carbon dispersion was only observed in the C-ADU gel particle that contained carbon black named CB 10. ADU gel liquid droplets containing carbon particles with the excellent sphericity of approximately 1,950 mm were then obtained using an 80-100-Hz vibrating nozzle system. Dried C-ADU gel particles obtained by the aging-washing-drying equipment were thermal decomposed until $500^{\circ}C$ at a rate of $1^{\circ}C/min$ in an air or in 4% $H_2$ gas atmosphere. The thermally decomposed C-ADU gel particles showed 24% weight loss and a more complicated profile than that of ADU gel particles.

• 대한기계학회논문집B
• /
• 제24권7호
• /
• pp.984-993
• /
• 2000

Characteristics of carbon soot particles generated in diffusion flames were studied. Non-sooting and sooting normal diffusion flames using propane or ethylene as fuel were selected. In the flames, soot volume fraction was measured by a thermocouple, and primary particle diameter and cluster size were analyzed by TEM photographs. The characteristics of soot particles depended on flame(non-sooting or sooting) and fuel(propane or ethylene) type. Unlike the sooting diffusion flames, particle growth and oxidation processes were clearly observed in the non-sooting diffusion flames. In the sooting diffusion flames, soot particle size was slightly changed at the flame tip.

• Structural Engineering and Mechanics
• /
• 제8권3호
• /
• pp.273-283
• /
• 1999

Two physical experiments are performed to verify the effectiveness of beam-particle model for simulating the progressive failure of particulate composites such as sandstone and concrete. In the numerical model, the material is schematized at the meso-level as an assembly of discrete, interacting particles which are linked through a network of brittle breaking beams. The uniaxial compressive tests of cubic and parallelepipedal specimens made of carbon steel rod assembly which are glued together by a mixture are represented. The crack patterns and load-displacement response observed in the experiments are in good agreement with the numerical results. In the application respect of beam-particle model to the particulate composites, the influence of defects, particle arrangement and boundary conditions on crack propagation is approached, and the correlation existing between the cracking evolution and the level of loads imposed on the specimen is characterized by fractal dimensions.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권4호
• /
• pp.2461-2476
• /
• 2013

To assess environmental contamination with carcinogens, carbonaceous compounds, water-soluble ionic species and trace gaseous species were identified and quantified every three hours for three days st three different atmospheric layer at the heart of chiang-Mai, bangkok and hat-Yai from December 2006 to February 2007. A DRI model 2001 Themal/Optical Carbon Analyzer with the IMPROVE thermal/optical reflectance (TOR) protocol was used to quantify the organic carbon(OC) and elemental carbon content in $PM_{10}$. Diurnal and vertical variability was also carefully investigated. In general, OC and EC contenttration shoeed the highest values at the monitoring period o 21.00-00.00 as consequences of human activities at night bazaar coupled with reduction of mixing layer, decreased wind speed and termination of photolysis nighttime. Morning peaks of carboaceous compounds were observed during the sampling period of 06:00 -09:00, emphasizing the main contribution of traffic emission in the three cities. The estimation of incremental lifetime partculate matter exposure (ILPE) raises concern of high risk of carbonaceous accumulation over workers and residents living close to the observatory sites. The average values of incremental lifrtime particulate matter exposure (ILPE) of total carbon at Baiyoke Suit Hotel and Baiyoke Sky Hotel are approsimately ten time shigher then those air sample collected at prince of songkla University Hat-Yai campus corpse incinerator and fish-can maufacturing factory but only slightly higher than those of rice straw burnig in Songkla province. This indicates a high risk of developing lung cancer and other respiratory diseases across workers and residents living in high buildings located in Pratunam area. Using knowledge of carbonaceous fractions in $PM_{10}$, one can estimate the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs). Dachs-Eisenreich model highlights the crucial role of adsorption in gas-particle partitioning of low molecular weight PAHs, whereas both absorption and adsorption tend to account for gas-particle partitioning of high molecular weight PAHs in urban residential zones of Thailand. Interestingly, the absorption mode alone plays a minor role in gas-partcle partitiining of PAHs in Chiang-Mai, Bangkok and hat-Yai.