대기오염 입자의 인테 호흡기내 비대칭 국부침전 특성에 관한 연구

구재학,김종숭 한국대기환경학회 2003 한국대기환경학회지 Vol.19 No.5

Particle deposition in human lungs was investigated theoretically by using asymmetric five-lobe lung model. The volumes of each of the five lobes were different, thereby forming and asymmetric lung structure. The tidal volume and flow rate of each lobe were scaled according to lobar volume. The total and regional deposition with various breathing patterns were calculated by means of tracking volume segments and accounting for particle loss during inhalation and exhalation. The deposition fractions were obtained for each airway generation and lung lobe, and dominant deposition mechanisms were investigated for different size particles. Results show that the tidal volume and flow rate have a characteristic influence on particle deposition. The total deposition fraction increases with an increase in tidal volume for all particle sizes. However, flow rate has dichotomous effects: a higher flow rate results in a sharp increase in deposition for large size particles, but decreased deposition for small size particles. Deposition distribution within the lung shifts proximally with higher flow rate whereas deposition peak shifts to the deeper lung region with larger tidal volume. Deposition fraction in each lobe was proportional to its volume. Among the three main deposition mechanisms, diffusion was dominant for particles<0.5㎛ whereas sedimentation and impaction were most influential for larger size particles. Impaction was particularly dominant for particles>8㎛. The results may prove to be useful for estimating deposition dose of inhaled pollutant particles at various breathing conditions.

Effect of particle size on various substrates for deposition of NiO film via nanoparticle deposition system

Kim, H.,Yang, S.,Ahn, S.H.,Lee, C.S. Elsevier Sequoia 2016 THIN SOLID FILMS - Vol.600 No.-

We report the deposition mechanism of NiO particles using a nanoparticle deposition system. To understand the effects of particle size and substrates on the deposition, nano-, 100-nm-, sub-micro-, and micro-sized NiO particles were deposited on Si wafers, Ni-coated Si wafers, and fluorine-doped tin oxide (FTO)-coated glass. It was found that 100-nm- and nano-sized NiO particles were deposited, forming loosely compacted coating layers, by the breaking up of agglomerates, regardless of the type of substrate. In contrast, sub-micro- and micro-sized NiO particles formed dense and compact coating layers by deformation and fracturing on the Si and Ni-coated Si wafers. Moreover, sub-micro- and micro-sized NiO particles were not deposited on FTO glass; this was likely attributable to the NiO being harder than FTO glass and the micro-sized NiO particles would likely have rebounded on impact, resulting in no deposition. Thus, the deposition mechanism of NiO particles may be greatly related to the relative hardness difference between the NiO particles and the substrate. Moreover, it was found that different particle sizes resulted in different friction and mobility, based on response angle measurements, influencing the deposition mechanism(s), especially at the interface. When the particle size was greater than 100nm, the deposition was due primarily to deformation and fracturing during the collision with the substrate. In particular, the 100-nm-sized NiO particles showed both mechanisms, a two-step process, with deformation or fracturing at the interface between the substrate and particles, followed by a loosely compacted coating layer forming, preserving the original particle shape. Thus, it was confirmed that the 100-nm-sized NiO particles were at or near a boundary for deposition mechanisms. The effects of particle size and substrate for dry deposition were explained successfully by assessing the deposition behavior using analytical tools.

Correlation between particle deposition and the size ratio of particles to patterns in nano- and micro-patterned membrane filtration systems

Jang, Jun Hee,Lee, Jaewoo,Jung, Seon-Yeop,Choi, Dong-Chan,Won, Young-June,Ahn, Kyung Hyun,Park, Pyung-Kyu,Lee, Chung-Hak Elsevier 2015 Separation and purification technology Vol.156 No.2

<P><B>Abstract</B></P> <P>Recently, membrane surface patterning has attracted much attention as an innovative alternative to control membrane fouling that occurs with membrane filtration used in water and wastewater treatment. However, limited attention has been focused on patterned membranes with nano-scale features due to their difficult fabrication. As a result, there is a lack of research on membrane fouling by particle deposition occurring with a wide range of pattern sizes. In this study, we prepared patterned membranes with nano-scale hexagonally packed arrays using nanoimprint lithography as well as micro-scale patterned membranes. Filtration tests were conducted using the membranes in cross-flow ultrafiltration to demonstrate the effect of the size ratio of particles to membrane patterns on fouling by particle deposition on the membrane surface. We found that particle deposition was most efficiently mitigated by the patterned membranes when the size ratio was approximately 3. On the other hand, when the size ratio was much smaller than 3, particle deposition was significant and was nearly as much as that of non-patterned membranes. In addition, when the size ratio was larger than 3, particle deposition increased with the increase in the size ratio. We explained the correlation between particle deposition and the size ratio of particles to membrane patterns in terms of shear stress near the surface of the membrane patterns using a computational fluid dynamics simulation technique. We anticipate that this study will provide a deeper understanding of the particle deposition phenomena in nano- and micro-patterned membrane filtration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We prepared nano- and micro-patterned membranes using a nanoimprint lithography method. </LI> <LI> We conducted membrane filtration tests using polystyrene latex particles. </LI> <LI> We demonstrated the effect of the size ratio of particles to patterns on particle deposition. </LI> <LI> We calculated shear stress near the membrane surface based on computational fluid dynamics. </LI> <LI> We explained the correlation between particle deposition and the size ratio in terms of shear stress. </LI> </UL> </P>

Particle deposition behaviors of monolithic De-NOx catalysts for selective catalytic reduction (SCR)

Hongke Feng,Chunhua Wang,Ying Huang 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.11

A major issue when using selective catalytic reduction (SCR) De-NOx catalysts is the risk of physical deactivation due to particle deposition and plugging of the monolithic catalysts. In the present study, numerical computations were carried out to investigate the particle deposition behaviors in monolithic SCR catalysts. Based on the calculation results, the effects of particle diameter, particle density, gas velocity, turbulent intensity, chemical reaction and channel size on particle deposition were analyzed in detail. Increasing gas velocity and equivalent diameter of channel can mitigate particle deposition. The increases of turbulent intensity and channel length both lead to the rise of particle deposition ratio. For particles with high Stokes number, particle deposition mainly takes place in the inlet section of catalysts. For particles with low Stokes number, sediment can be observed in the middle and outlet sections of catalysts. De-NOx chemical reaction can mitigate particle deposition, but the effect of chemical reaction on particle deposition is inactive.

Deposition mechanism of dry sprayed ceramic particles at room temperature using a nano-particle deposition system

Chun, D.M.,Ahn, S.H. Elsevier Science 2011 ACTA MATERIALIA Vol.59 No.7

The nano-particle deposition system (NPDS) is a new dry spray process used to deposit metal and ceramic particles at room temperature. Low temperature deposition techniques for metals and ceramics that involve particle spraying include the NPDS, cold spray, and aerosol deposition methods. These are widely used to minimize thermal damage to the substrate when fabricating metal or ceramic layers. To optimize the process conditions for the intended applications and improve the deposition quality one must understand the mechanism of particle deposition at room temperature. The bonding mechanism in metal particle deposition by the cold spray method has already been researched. Adiabatic shear instability near the particle/substrate interface due to plastic deformation was reported to be the bonding mechanism for metal particles below the melting temperature. However, the bonding mechanism of ceramic particles has not been fully determined. This study assessed the bonding of ceramic particles by NPDS using numerical analysis and experimental results. A bonding mechanism is suggested after considering the experimental results for shock compaction, which is a process similar to that of the NPDS. The suggested deposition mechanism for ceramics involves the fragmentation of submicron ceramic particles into nanoparticles and the successive impact of submicron particles, which provides sufficient bonding energy, with heat and high pressure, to nanoparticles fragmented by the shock wave.

Behavior Evaluation of Ash Deposition and Consequent Fine Particle Emissions produced from Combustion of Low-rank Coal Impregnated with Molasses in Drop Tube Furnace

Zi-Xiang Xu,Joo-Chang Park,Hueon Namkung,Li-Hua Xu,Hyung-Taek Kim 한국열환경공학회 2019 한국열환경공학회 학술대회지 Vol.2019 No.춘계

The co-combustion of low-rank coal with biomass is regarded as a prospective technology for reducing CO2 emissions to mitigate the issues related to the excess global warming. However, the ash deposition and fine particle formations problems were severe with the addition of biomass. Therefore, it is vital to investigate ash deposition and fine particle formation to ensure the normal operation of equipment in thermal power plant and improve thermal conversion efficiency as well as protect air environment. In this study, two types of raw coals (Berau coal, Bayan coal) and three types of hybrid coals (Berau coal impregnated with 10 wt%, 20 wt% molasses; and Bayan coal impregnated with 3 wt% molasses) are used as the samples to conduct DTF experiment. The propensity associated with ash deposition and fine particle formation are studied at excess air under combustion temperature of 1300℃. The ash deposits generated at the probe top surface maintained at 800℃, and the fine particles carried by the flue gas were collected by the filter paper. A range of analytical techniques including SEM-EDX and XRD were used to analyze the morphology and elemental distribution of ash deposits and fine particles for clarifying the ash deposits behavior. It is found that the deposition tendency of 3% HCK is lower than other fuels. As far as the fine particle formation is concerned, the contents of Si and Al in coarse particles were apparently higher than those in fine particle. S and K is higher in fine particles.

Critical Velocities for High Speed Particle Deposition in Kinetic Spraying

Wu, Jingwei,Fang, Hongyuan,Yoon, Sanghoon,Lee, Changhee,Kim, HyungJun The Japan Institute of Metals 2006 Materials transactions Vol.47 No.7

<P>During kinetic spraying (or cold gas dynamic spraying), small solid particle can be deposited onto the substrate by a supersonic velocity impaction. A critical velocity of flying particle was found for the minimum deposition speed. Generally, it was thought that higher impact velocity caused higher deposition efficiency. However, some different phenomena were observed during spraying processing in laboratory.In this study, individual particle impact tests have been carried out to probe the effect of impact velocity. Instead of deposition efficiency (DE) of coatings, ratio of bonds, which was defined as the number fraction of attached particles to total impact particles (Craters + Bonds) in unit area of impact surface, was measured in our test. A maximum velocity for particle deposition was observed, because of which a high fraction of rebounded particles occurred at a high impact velocity. A model considering the adhesion and rebound energy was built up to estimate the particle/substrate interaction. The particle deposition behavior was a result of the competition between adhesion and rebound energies during the impact process. Only when the adhesion energy was higher than the rebound energy, the impacting particles could be attached onto the substrate.</P>

낮은 레이놀즈 수에서 두 개의 원형 실린더 주위 유동 및 입자 거동 해석

Aisa Diaelhag Khalifa Hamid,정석민,김동주 한국입자에어로졸학회 2021 Particle and Aerosol Research Vol.17 No.4

Understanding particle-laden flow around cylindrical bodies is essential for the better design of various applications such as filters. In this study, laminar flows around two tandem cylinders and the motions of particles in the flow are numerically investigated at low Reynolds numbers. We aim to reveal the effects of the spacing between cylinders, Reynolds number and particle Stokes number on the characteristics of particle trajectories. When the cylinders are placed close, the unsteady flow inside the inter-cylinder gap at Re = 100 shows a considerable modification. However, the steady recirculation flow in the wake at Re = 10 and 40 shows an insignificant change. The change in the flow structure leads to the variation of particle dispersion pattern, particularly of small Stokes number particles. However, the dispersion of particles with a large Stokes number is hardly affected by the flow structure. As a result, few particles are observed in the cylinder gap regardless of the cylinder spacing and the Reynolds number. The deposition efficiency of the upstream cylinder shows no difference from that of a single cylinder, increasing as the Stokes number increases. However, the deposition on the downstream cylinder is found only at Re = 100 with large spacing. At this time, the deposition efficiency is generally small compared to that of an upstream cylinder, and the deposition location is also changed with no deposited particles near the stagnation point.

Nanoscale Patterning and Welding by Solvent-free Dry Particle Spray and Focused Ion Beam

Jung-Oh Choi,Chung-Soo Kim 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.1 No.3

Nano particle deposition system (NPDS) is one of dry particle spray methods such as cold spray and aerosol deposition. It can be used to build structures from metals, ceramics, and nanomaterials without any solvents at room temperature and under low vacuum conditions, reducing energy consumption. Recent advances in dry particle spray techniques, including NPDS, have demonstrated their use with advanced nanomaterials such as carbon nanotube. However, to date, this process has not been successfully scaled down to 100-nm scales. Here, we demonstrate the use of NPDS as dry particle spray method in the nanoscale regime with the help of a focused ion beam for nanoscale manufacturing. Nanoscale patterning and welding were achieved using a nano particle deposition system with miniaturized feature sizes that were smaller than 100 nm in scale.

에어로졸 증착 공정을 통해 제작한 Al2O3 코팅층의 Al2O3 입자 크기에 따른 성막 메커니즘 연구

김익수,조명연,구상모,이동원,오종민 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.3

Al2O3 powders with particle sizes of 0.35 μm, 0.5 μm, 1.5 μm, and 2.5 μm are deposited onto glass and Cu substrates using the aerosol deposition (AD) process. The deposition characteristics of Al2O3 films using those four types of Al2O3 powders are investigated to determine the influence of the particle size on the films. To observe detailed micro-structures of the films, the cross-section and surface morphology are observed. Then, the crystalline size and internal strain are calculated from X-ray diffraction peaks in order to confirm the hammering effect as well as the micro-strain during the AD deposition. From the above results, deposition mechanisms related to the particle size are studied. The results of this study indicate the optimal particle size and formation mechanisms for dense Al2O3 film with a smooth surface roughness as well as for a porous Al2O3 film with a rough surface roughness. 0.35 μm, 0.5 μm, 1.5 μm 및 2.5 μm의 입자 크기가 다른 Al2O3 분말이 에어로졸 증착 공정을 통해 유리 기판과 구리 기판에 증착되었다. 입자 크기가 코팅층 성막에 미치는 영향을 알아보기 위해 네 종류의 Al2O3 분말을 사용하여 코팅된 Al2O3 필름의 성막 특성을 조사하였다. Al2O3 필름의 미세구조를 자세히 분석하기 위해, 단면과 표면 형상을 관찰하였다. 또한, 증착이 일어나는 동안 미세 변형과 망치 효과를 확인하기 위해 X-ray 회절 피크로부터 결정 크기 및 내부 변형을 계산하였다. 상기의 분석 결과로부터, 입자 형상과 관련지어 증착 메커니즘을 연구하였다. 본 연구에서는 거친 표면 거칠기를 갖는 다공성 Al2O3 필름뿐만 아니라 부드러운 표면 거칠기를 갖는 치밀한 Al2O3 필름 제작을 위한 최적의 입자 크기를 각각 제안하고자 한다.