• 폴리머
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• 제25권4호
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• pp.460-467
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• 2001

Sorbitan ester(Span)와 2,2'-azobis(2-methyl propionamidine) dihydrochloride(AIBA)를 각각 입자안정제와 개시제로 사용하여 cyclohexane 분산매에서 acrylamide (AM)의 역상 현탁중합을 다양한 중합 조건하에서 수행하여 생성되는 poly(acrylamide)(PAM) 현탁입자의 입자경, 평균분자량, 수용화도 등을 조사하였다. 일반적으로 PAM 현탁입자경은 입자안정제의 농도, 진탕속도, 수용상 성분 중 물의 양이 증가함에 따라, 또는 개시제의 농도, 중합 온도가 감소함에 따라 감소하였다. PAM 현탁중합체의 평균분자량은 단량체의 농도, 입자안정제의 농도가 증가함에 따라, 또는 개시제의 농도, 중합 온도, 수용상 성분중 물의 농도가 감소함에 따라 증가하였다. 본 연구에서 얻어진 PAM 현탁입자는 구슬형의 약 2 ~ 50 ${\mu}$m 범위의 입자경과 약 800 ~ 1200만의 중량평균분자량을 나타내었다.

• 자원리싸이클링
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• 제14권6호
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• pp.37-43
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• 2005

페리튬이온전지로부터 회수된 코발트와 리튬 침출액으로부터 화염분부열분해법에 의하여 $LiCoO_{2}$ 나노분말을 제조하였다. 리튬 및 코발트 성분을 함유하는 전극물질은 열처리 및 기계적 처리에 의해 그 농도를 증가 시켰다. 리튬이온전지 양극물질을 질산으로 용해한 다음 침출액중 Li과 Co의 당량비가 1.0 되도록 $LiNO_{3}$로 조절하여 화염분무열분해용 전구체를 제조하었다. 화염분무열분해법에 의해 제조된 $LiCoO_{2}$ 분말의 평균입자크기는 전구체의 몰 농도가 증가하면서 증가되었으며, 화염온도 역시 입자의 크기를 증가시켰다. 변수실험 결과 $11{\~}35nm$ 크기의 결정형 $LiCoO_{2}$ 나노분말을 제조할 수 있었다 또한 나노 $LiCoO_{2}$의 전극재료로서의 가능성을 확인하기 위하여 충방전 특성 평가와 같은 전기화학적 분석을 수행하였다.

• Safety and Health at Work
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• 제14권2호
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• pp.215-221
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• 2023

Background: There is little information about the airborne hazardous agents released during the heat treatment when manufacturing a welding material. This study aimed to evaluate the airborne hazardous agents generated at welding material manufacturing sites through area sampling. Methods: concentration of airborne particles was measured using a scanning mobility particle sizer and optical particle sizer. Total suspended particles (TSP) and respirable dust samples were collected on polyvinyl chloride filters and weighed to measure the mass concentrations. Volatile organic compounds and heavy metals were analyzed using a gas chromatography mass spectrometer and inductively coupled plasma mass spectrometer, respectively. Results: The average mass concentration of TSP was 683.1±677.4 ㎍/m³, with respirable dust accounting for 38.6% of the TSP. The average concentration of the airborne particles less than 10 ㎛ in diameter was 11.2-22.8×10⁴ particles/cm³, and the average number of the particles with a diameter of 10-100 nm was approximately 78-86% of the total measured particles (<10 ㎛). In the case of volatile organic compounds, the heat treatment process concentration was significantly higher (p < 0.05) during combustion than during cooling. The airborne heavy metal concentrations differed depending on the materials used for heat treatment. The content of heavy metals in the airborne particles was approximately 32.6%. Conclusions: Nanoparticle exposure increased as the number of particles in the air around the heat treatment process increases, and the ratio of heavy metals in dust generated after the heat treatment process is high, which may adversely affect workers' health.

• 대한기계학회논문집B
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• 제26권2호
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• pp.227-237
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• 2002

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

• 대한기계학회논문집B
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• 제28권5호
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• pp.501-509
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• 2004

Unipolar diffusion charging of non-spherical particles was investigated for various particle shapes. We researched with TiO$_2$agglomerates produced by the thermal decomposition of titanium tetraisopropoxide (TTIP) vapor. TTIP was converted into TiO$_2$, in the furnace reactor and was subsequently introduced into the sintering furnace. Increasing the temperature in the sintering furnace, aggregates were restructured into higher fractal dimensions. The aggregates were classified according to their mobility using a differential mobility analyzer. The projection area and the mass fractal dimension of particles were measured with an image processing technique performed by using transmission electron microscope (TEM) photograph. The selected aggregates were charged by the indirect photoelectric-charger and the average number of charges per particle was measured by an aerosol electrometer and a condensation particle counter. For the particles of same mobility diameter, our results showed that the particle charge quantity decreases as the sintering temperature increases. This result is understandable because particles with lower fractal dimension have larger capacitance and geometric surface area.

• 청정기술
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• 제26권1호
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• pp.1-6
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• 2020

초임계 용액 급속팽창법(rapid expansion of supercritical solution, RESS)으로 몰시도민(molsidomine, MOL) 약물이 로딩 된 퍼아세틸-β-사이클로덱스트린(PAc-β-CD) 나노 입자를 제조하였다. 입자는 초임계 용액을 공기 중으로 급속하게 팽창시켜 제조하였다. MOL과 PAc-β-CD (0.5, 1 wt%)의 농도, 추출 온도(45 ~ 60 ℃), 모세관 노즐의 길이(5 ~ 20 mm) 및 내경(Inner diameter, ID) (50 ~ 150 μm), 그리고 분사 거리의 변화에 따라 형성된 입자의 크기와 모폴로지를 조사하였다. MOL과 PAc-β-CD의 상호작용을 ¹H-NMR 분광법으로 확인하였고, 입자 크기는 주사 전자 현미경으로 측정하였다. 온도를 45 ℃에서 60 ℃로 올리거나 노즐 내경을 150 μm에서 50 μm로 줄이면 입자 평균 크기가 증가하였으며, 반면에 일정한 압력(34.5 MPa)과 온도(45 ℃)에서 분사 거리를 늘리면 입자 평균 크기가 감소하는 효과를 나타내었다. 0.5 wt%의 PAc-β-CD 농도로서 초임계 공정을 진행한 결과, 모세관의 길이가 짧고(5 mm) 내경이 작은(50 μm) 조건에서 크기가 가장 작은(165 nm) 입자가 얻어졌다. 제조한 나노 입자는 오일 내에서 분산성과 용해도가 증가하였으며, 포접체 입자에서 MOL이 방출되는 시간이 지연되는 것을 확인하였다.

• 폴리머
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• 제27권4호
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• pp.358-363
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• 2003

하이드록시프로필 셀룰로오스와 암모니움 퍼설페이트를 각각 입자 안정제와 개시제로 사용하여 에틸 알코올/물 혼합 분산매에서 아크릴아미드의 분산 중합을 다양한 중합 조건하에서 수행하여 생성되는 poly(acrylamide) (PAM) 라텍스의 평균 입자경, 라텍스 고분자의 점도 평균 분자량, 수용화 정도 등을 관찰하였다. 일반적으로 PAM 라텍스의 평균 입자경은 개시제의 농도, 분산매 중의 물의 농도, 중합 온도가 증가함에 따라 증가하였으나 단량체의 농도, 입자 안정제의 농도는 감소함에 따라 증가하였다. 라텍스 상태로 얻어진 PAM 고분자의 점도 평균 분자량은 단량체의 농도, 입자 안정제의 농도, 분산매 중 물의 농도가 증가함에 따라, 또는 개시제의 농도, 중합 온도가 감소함에 따라 증가하였다. 본 연구에서 얻어진 PAM 라텍스는 0.5~2.4 $\mu\textrm{m}$의 평균 입자경과 20000~335000g/㏖의 점도 평균 분자량을 나타내었으며 이들은 물중에 분산하였을 때 순간적으로 수용화되었다.

• 한국염색가공학회:학술대회논문집
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• 한국염색가공학회 2008년도 제38차 학술발표대회
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• pp.111-113
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• 2008

In this study, for natural leather use, the phytoncide oil of antibacterial materials was encapsulated in several micro-diameter shell which slowly releases from the leather treated with antibacterial microcapsules. The microcapsule was synthesized by in-situ polymerization of urea and formaldehyde. The effects of surfactants on the average particle size and distributions, morphologies and antibiosis were investigated to design microcapsule.

• 한국세라믹학회지
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• 제25권5호
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• pp.509-517
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• 1988

The controlled Ti(CO2H5)4 hydrolysis reactions for the synthesis of Spherical Monodispersed Titania powders are described. Increasing the concentration of TEOT and the molar ratio of water to TEOT in alcohol solution decrease the reaction time and the particle size. The reaction time is delalyed by increasing the chain length and the number of carbon branches of alcohol as a solvent. The prepared powders with an average diameter of 0.8$\mu$ and the spherical monodispersed transfer to Rutile phase at 55$0^{\circ}C$.

• 한국세라믹학회지
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• 제29권11호
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• pp.893-899
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• 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.