• Title/Summary/Keyword: Particle morphology

Search Result 779, Processing Time 0.027 seconds

Analysis of Filtration Performance by Brownian Dynamics (Brownian Dynamics 를 이용한 입자 포집 과정 및 여과 성능 해석)

  • Bang, Jong-Geun;Yoon, Yoong-Sup
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.33 no.10
    • /
    • pp.811-819
    • /
    • 2009
  • In the present study, deposition of discrete and small particles on a filter fiber was simulated by stochastic method. Trajectory of each particle was numerically solved by Langevin equation. And Lattice Boltzmann method (LBM) was used to solve flow field around the filter collector for considering complex shape of deposit layer. Interaction between the flow field and the deposit layer was obtained from a converged solution from an inner-loop calculation. Simulation method is properly validated with filtration theory and collection efficiency due to different filtration parameters are examined and discussed. Morphology of deposit layer and its evolution was visualized in terms of the particle size. The particle loaded effect on collection efficiency was also discussed.

The Synthesis of $Fe_3O_4$ Powder through Glycothermal Process (Glycothermal Process에 의한 $Fe_3O_4$ 분말 합성)

  • 노준석;조승범;최상흘
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.11
    • /
    • pp.1159-1164
    • /
    • 1997
  • Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $\alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $\alpha$-FeOOH to $\alpha$-Fe2O3 and finally Fe3O4 at 27$0^{\circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{\circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $\alpha$-FeOOH or $\alpha$-Fe2O3 was recrystalized.

  • PDF

Nano-Soot Particle Formation in Inverse Diffusion Flames (인버스 확산화염에서의 나노 수트 입자 생성)

  • Lee, Eui-Ju;Shin, Hyun-Joon;Oh, Kwang-Chul;Shin, Hyun-Dong
    • 한국연소학회:학술대회논문집
    • /
    • 2003.12a
    • /
    • pp.19-26
    • /
    • 2003
  • Experimental measurements of flame structure and soot characteristics were performed for ethene inverse diffusion flames (IDF). IDF has been considered as the excellent flow field to study the incipient soot because soot particle do not experience the oxidation process. In this study, LIF image clarified the reaction zone of IDF with OH signal and PAH distribution. laser light scattering technique also identified the being of soot particle. To address the degree of soot maturing, C/H ratio and morphology of soot sample were investigated. From these measurements, the effect of flow residence time and temperature on soot inception could be suggested, and more details on soot characteristic in the IDF was determined according to fuel dilution and flame condition. The fuel dilution results in a decrease of temperature and enhancement of residence time, but the critical dilution mole fraction is existed for temperature not to effect on soot growth. Also, the soot inception evolved on the specific temperature and its morphology are independent of the fuel dilution ratio of fuel.

  • PDF

Analysis of Particle Morphology Change and Discrete Element Method (DEM) with Different Grinding Media in Metal-based Composite Fabrication Process Using Stirred Ball Mill (교반볼밀을 이용한 금속기반 복합재 제조공정에서 다른 분쇄매체차이에 대한 입자형상변화와 DEM 시뮬레이션 해석)

  • Batjargal, Uyanga;Bor, Amgalan;Batchuluun, Ichinkhorloo;Lee, Jehyun;Choi, Heekyu
    • Korean Chemical Engineering Research
    • /
    • v.55 no.4
    • /
    • pp.456-466
    • /
    • 2017
  • This work investigated the particle morphology change to difference in milling media in a metal based composite fabrication process using a stirred ball mill with ball behavior of DEM simulation. A simulation of the three dimensional motion of grinding media in the stirred ball mill for the research of grinding mechanism to clarify the force, kinetic energy, and medium velocity of grinding media were calculated. In addition, the rotational speed of the stirred ball mill was changed to the experimental conditions for the composite fabrication, and change of the input energy was also calculated while changing the ball material, the flow velocity, and the friction coefficient under the same conditions. As the rotating speed of the stirred ball mill increased, the impact energy between the grinding media to media, media to wall, and media and the stirrer increased quantitatively. Also, we could clearly analyze the change of the particle morphology under the same experimental conditions, and it was found that the ball behavior greatly influences in the particle morphology changes.

Fabrication of Niobium Powder for Solid-electrolyte Capacitors (고체 전해커패시터용 니오븀 분말제조)

  • Yoon, Jae-Sik;Hwang, Sun-Ho;Kim, Byung-Il
    • Journal of the Korean institute of surface engineering
    • /
    • v.42 no.5
    • /
    • pp.227-231
    • /
    • 2009
  • The niobium capacitor showed somewhat more unstable characteristics than the commercial tantalum capacitors, but is nonetheless considered applicable as a future substitute for tantalum capacitors. In this study, niobium powder was fabricated by metallothermic reduction process using $K_2NbF_7$ as the raw materials, KCl and KF as the diluents and Na as the reducing agent. The niobium particle size greatly decreased from 0.7um to 0.2 um as the amount of diluent increased. However if a higher surface area of powder is required, more diluents need to be used in the said method in order to produce niobium powder. The niobium powder morphology and particle size are very sensitive to a amount of sodium excess. The particle size of niobium powder increased with a increasing amount of sodium excess. When more diluent and sodium are used, the niobium powder will be contaminated with more impurities such as Fe, Cr, Ni so on.

Mechanical Properties of Beta-Sialon Ceramics Prepared from TEOS and Kaolin (TEOS와 카올린으로부터 제조한 $\beta$-Sialon의 기계적 성질)

  • 임헌진;이홍림
    • Journal of the Korean Ceramic Society
    • /
    • v.26 no.5
    • /
    • pp.637-644
    • /
    • 1989
  • Beta-sialon powder(Z=1) was synthesized by the simultaeous reduction and nitridation of the mixed powders of Hadong kaolin and silica. Silicon hydroxide was prepared from Si-alkoxide by a hydrolysis method and amorphous silica was obtained from the calcination of the prepared silicon hydroxide. Hadong kaolin was mixed with both the silicon hydroxide and amorphous silica, respectively. The average particle size was 4${\mu}{\textrm}{m}$ and the morphology of particle was rod-like and equiaxed in the case of beta-sialon powder prepared form Hadong kaolin and silicon hydroxide(COMPOSITION A), whereas the average particle size was 3${\mu}{\textrm}{m}$ and the morphology of particle was equiaxed in the case of beta-sialon powder prepared from Hadong kaolin and amorphous silica(COMPOSITION B). The synthesized beta-sialon powders were hot-pressed at 175$0^{\circ}C$ for 2 hours under 30 MPa in a nitrogen atmosphere after YAG composition(8wt%) was added to these powders as a sintering agent. The hot-pressed specimens were annealed a 140$0^{\circ}C$ for 4 hours in a nitrogen atmosphere. The mechanical properties of sintered bodies were investigated in terms of M.O.R., fracture toughness and hardness. The measured values are as follows. COMPOSITION A : M.O.R. 508MPa, KIC 3.5MN/m3/2, hardness 13.6GPa. COMPOSITION B : M.O.R. 653MPa, KIC 5.4MN/m3/2, hardness 13.5GPa.

  • PDF

Simulation of the Growth of Non-Spherical Particles in a Counterflow Diffusion Flame (대향류 확산 화염 중에서 비구형 입자 성장에 관한 해석)

  • Jeong, Jae In;Hwang, Jun Young;Lee, Bang Weon;Choi, Mansoo;Chung, Suk Ho
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.8
    • /
    • pp.997-1009
    • /
    • 1999
  • Silica particle formation and growth process including chemical reaction, coagulation and sintering was studied in a counterflow diffusion flame burner. The counterflow geometry provides a one dimensional flow field, along the stagnation point streamline, which greatly simplifies interpretation of the particle growth characteristics. $SiCl_4$ has been used as the source of silicon in hydrogen/oxygen/argon flames. The temperature profiles obtained by calculation showed a good agreement with experiment data. Using one and two dimensional sectional method, aerosol dynamics equation in a flame was solved, and these two results were compared. The two dimensional section method can consider sintering effect and growth of primary particle during synthesis, thus it showed evolution of morphology of non-spherical particles (aggregates) using surface fractal dimension. The effects of flame temperature and chemical loading on particle dynamics were studied. Geometric mean diameter based on surface area and total number concentration followed the trend of experiment results, especially, the change of diameters showed the sintering effect in high temperature environment.

Characteristics of Powder with Change of Temperature in Production of Tantalum Powder by MR-EMR Combination Process (MR-EMR 복합공정에 의한 탄탈륨분말의 제조시 온도변화에 따른 분말의 특성)

  • 배인성;윤재식;박형호;윤동주;이민호;설경원;김병일
    • Journal of Powder Materials
    • /
    • v.10 no.6
    • /
    • pp.395-405
    • /
    • 2003
  • In the conventional metallothermic reduction (MR) process for obtaining tantalum powder in batch-type operation. it is difficult to control morphology and location of deposits. On the other hand, a electronically mediated reaction (EMR) process is capable to overcome these difficulties and has a merit of continuous process, but it has the defect that the reduction yield is poor. MR-EMR combination process is a method that is able to overcome demerits of MR and EMR process. In this study, a MR-EMR combination process has been applied to the production of tantalum powder by sodium reduction of $K_2$TaF$_{7}$. The total charge passed through external circuit and average particle size (FSSS) were increased with increasing reduction temperature. The proportion of fine particle (-325 mesh) was decreased with increasing reduction temperature. The yield was improved from 65% to 74% with increasing reduction temperature. Considering the charge, impurities, morphology, particle size and yield, an reduction temperature of 1,123 K was found to be optimum temperature for MR-EMR combination process.

The Effect of Reduction Temperature on the Characteristic Variation of Niobium Powder During Metallothermic Reduction Process (금속열환원 공정에서 반응온도가 니오븀 분말 특성에 미치는 영향)

  • Yoon, Jae-Sik;Lee, Young-Mi;Hwang, Sun-Ho;Kim, Byung-Il
    • Journal of Powder Materials
    • /
    • v.16 no.2
    • /
    • pp.104-109
    • /
    • 2009
  • Niobium powder was made from potassium heptafluoroniobite ($K_2NbF_7$) as the raw material using sodium (Na) as a reducing agent based on the hunter process. The apparatus for the experiment was designed and built specifically for the present study. The niobium particle size greatly increased as the reduction temperature increased from $710^{\circ}C$ to $800^{\circ}C$. The particle size was fairly uniform, varying from $0.09{\mu}m$ to $0.4{\mu}m$ depending on the reduction temperatures. The niobium powder morphology and particle size are very sensitive to a reaction temperature in the metallothermic reduction process. The yield of niobium powder increased from 55% to 80% with a increasing a reaction temperature.

Preparation of Spherical Alumina Particle from Aluminum Iso-Propoxide (Aluminum Iso-Propoxide에 의한 구형 알루미나 분체의 제조)

  • Lee, Jin-Hwa;Nam, Ki-Dae;Lee, Dong-Kyu
    • Journal of the Korean Applied Science and Technology
    • /
    • v.16 no.2
    • /
    • pp.163-170
    • /
    • 1999
  • Spherical alumina powders were prepared by the controlled hydrolysis of aluminum iso-propoxide in a solution consisting of n-octyl alcohol and acetonitrile. As aluminum alkoxide's concentration increased, the particle size was increased and size distribution was more broad. As-prepared particle morphology was not spherical when acetonitrile volume fraction was increased over than 60%. As-prepared amorphous powders crystallized to ${\gamma}$-alumina at $1000^{\circ}C$ and converted to ${\alpha}$-alumina at $1150^{\circ}C$. The particle morphology was retain after crystallization ${\alpha}$-alumina. When aluminum iso-propoxide was used as aluminum source, the optimum preparation condition of spherical alumina was 0.1M AIP, 0.2M H2O, $0.1g/{\ell}$ HPC with a volume fraction (1/1) of the n-octyl alcohol/acetonitrile, 10min of reaction time and 30min of aging time.