• Title/Summary/Keyword: film formation

Search Result 1,837, Processing Time 0.025 seconds

Effect of polymer adsorption on film formation of silica/PVA suspension

  • Kim, Sun-Hyung;Sung, Jun-Hee;Ahn, Kyung-Hyun;Lee, Seung-Jong
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
    • /
    • 2009.10a
    • /
    • pp.79-84
    • /
    • 2009
  • Understanding the polymer adsorption in particle/binder/solvent system is important to achieve successful film products. While most of the reported work has dealt with the suspension microstructure, a few studies have focused on film formation. We investigated the effect of adsorption on film formation through measurement of adsorption amount in suspension and stress development in drying film with respect to mixing time ($t_m$). All of the adsorption amount (PVA), characteristic stress ($\sigma_{ch}$) exhibited similarities expressed by the form of $1-e^{t_m/{\tau}}$. The porous and non-unifonn dried film at short tm became close-packed and uniform with longer $t_m$. We found that polymer adsorption plays the key role in film fonnation as it introduces steric repulsion in suspension and suppresses the flocculation during solvent evaporation. We also found that the mixing time for the saturated polymer adsorption is the important variable to acquire the consolidated and uniform film microstructure.

  • PDF

Modeling of Spray-Wall Interactions Considering Liquid Film Formation (액막형성을 고려한 분무-벽 상호작용에 대한 모델)

  • Lee, Seong-Hyuk;Ryou, Hong-Sun
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.24 no.7
    • /
    • pp.1010-1019
    • /
    • 2000
  • The main purpose of this article is to propose and assess a new spray impingement model considering film formation, which is capable of describing the droplet distribution and film flows in direct injection diesel engines. The spray-wall interaction model includes several mathematical formulae, newly made by the energy conservation law and some experimental results. The model consists of three representative regimes, rebound, deposition and splash. In addition, the film flow is described in the present model by solving the continuity and momentum equations for film flows using the integral method. To assess the new spray impingement model, the calculated results using the new model are compared with several experimental data for the normally impinging diesel sprays. The film model is also validated through comparing film radius and thickness against experimental data. The results show that the new model is generally in better agreement with experimental data and acceptable for prediction of the film radius and thickness.

Binary Compound Formation upon Copper Dissolution: STM and SXPS Results

  • Hai, N.T.M.;Huemann, S.;Hunger, R.;Jaegermann, W.;Broekmann, P.;Wandelt, K.
    • Corrosion Science and Technology
    • /
    • v.6 no.4
    • /
    • pp.198-205
    • /
    • 2007
  • The initial stages of electrochemical oxidative CuI film formation on Cu(111), as studied by means of Cyclic Voltammetry (CV), in-situ Scanning Tunneling Microscopy (STM) and ex-situ Synchrotron X-ray Photoemission Spectroscopy (SXPS), indicate a significant acceleration of copper oxidation in the presence of iodide anions in the electrolyte. A surface confined supersaturation with mobile CuI monomers first leads to the formation of a 2D-CuI film via nucleation and growth of a Cu/I-bilayer on-top of a pre-adsorbed iodide monolayer. Structurally, this 2D-CuI film is closely related to the (111) plane of crystalline CuI (zinc blende type). Interestingly, this film causes no significant passivation of the copper surface. In an advanced stage of copper dissolution a transition from the 2D- to a 3D-CuI growth mode can be observed.

Effects of Film Formation Conditions on the Chemical Composition and the Semiconducting Properties of the Passive Film on Alloy 690

  • Jang, HeeJin;Kwon, HyukSang
    • Corrosion Science and Technology
    • /
    • v.5 no.4
    • /
    • pp.141-148
    • /
    • 2006
  • The chemical composition and the semiconducting properties of the passive films formed on Alloy 690 in various film formation conditions were investigated by XPS, photocurrent measurement, and Mott-Schottky analysis. The XPS and photocurrent spectra showed that the passive films formed on Alloy 690 in pH 8.5 buffer solution at ambient temperature, in air at $400^{\circ}C$, and in PWR condition comprise $Cr_2O_3$, $Cr(OH)_3$, ${\gamma}-Fe_2O_3$, NiO, and $Ni(OH)_2$. The thermally grown oxide in air and the passive film formed at high potential (0.3 $V_{SCE}$) in pH 8.5 buffer solution were highly Cr-enriched, whereas the films formed in PWR condition and that formed at low potential (-0.3 $V_{SCE}$) in pH 8.5 buffer solution showed relatively high Ni content and low Cr content. The Mott-Schottky plots exhibited n-type semiconductivity, inferring that the semiconducting properties of the passive films formed on Alloy 690 in various film formation conditions are dominated by Cr-substituted ${\gamma}-Fe_2O_3$. The donor density, i.e., concentration of oxygen vacancy, was measured to be $1.2{\times}10^{21}{\sim}4.6{\times}10^{21}cm^{-3}$ and lowered with increase in the Cr content in the passive film.

Effects of Silicone Contents and Flow Rates on the Formation and Mechanical Properties of Hard Anodized Film of Al-Si alloys (Al-Si 합금의 경질양극산화피막의 형성과 기계적 성질에 미치는 Si 함량과 전해액의 유속의 영향)

  • 김경택;안명규;이진형;권혁상
    • Journal of the Korean institute of surface engineering
    • /
    • v.24 no.4
    • /
    • pp.179-186
    • /
    • 1991
  • The effects of silicone contents and flow rates(agitation rates) of electrolyte on the formation and mechanical properties of hard anodized film of Al-Si alloy have been studied in 12% H2SO4 + 1% Oxalic acid with varying the silicone contents in the rance of 0 to 11.6% and the flow rates of electrolyte in the range of 0 to 90cm/sec. The film forming voltage required to maintain an equivalent current density significantly increase with the silicone content of Al-Si alloys due to a low conductivity of silicone. Hardness and wear resistance of the anodized film of Al-Si alloys decreases wit increasing the silicone content. The increase in the flow rate of electrolyte has a similar influence on the formation and mechanical properties of anodized film as does the decrease in bath temperature. Hardness of anodized film is rapidly increased with the flow rate being increased from 10cm/sec. It is observed that the increase in the flow rate from 11cm/sec. It is observed that the increase in the flow from 11cm/sec to 48cm/sec is more effective in enhancing the hardness of film than is the decrease in bath temperature from 1$0^{\circ}C$ to $0^{\circ}C$.

  • PDF

A Study on Dry Film Formation of Clay Solution (점토 혼합액의 건조박막 형성에 관한 연구)

  • 박헌휘
    • Journal of Energy Engineering
    • /
    • v.7 no.2
    • /
    • pp.180-186
    • /
    • 1998
  • In this study, the effect of shear rate on the viscosity variation is examined to understand the flow characteristics of the mixture of bentonite and water. The variation of film thickness according to mixing ratio and viscosity is measured to characterize the film formation. And, the separation of dried film is studied according to film thickness. Specific surface area affecting on adsorption capability is measured using BET method. The viscosity decreases and the film thickness increases as the mixing ratio increases. The separation characteristic of dried film is suitable within a range of 40 to 150 ${\mu}{\textrm}{m}$ in film thickness and 5 to 10% in mixing ratio.

  • PDF

Relationship between Hydrophobicity and Pellicle Formation in a Film Strain of Hansenula beijerinckii FY-5 Isolated from Apple Wine (사과주(酒) 산막효묘(産膜酵母) Hansenula beijerinckii FY-5 의 소수성(疏水性)과 산막성(産膜性)과의 관련성(關聯性))

  • Song, Hyung-Ik;Chung, Ki-Taek
    • Korean Journal of Food Science and Technology
    • /
    • v.17 no.3
    • /
    • pp.203-207
    • /
    • 1985
  • Relationship between cell surface hydrophobicity and pellicle formation was studied in a film strain isolated from stored apple wine and identified as Hansenula beijerinckii FY-5. In the media containing non-ionic surface-active agents the pellicle formation of strain FY-5 was efficiently repressed, whereas growth of the yeast was possible, and also cell surface hydrophobicity was greatly decreased by the addition of these agents. These results indicate that a pellicle formation factor, which keeps yeast cells floating on the medium surface, is necessary for the pellicle formation, and surely this factor is the hydrophobicity of the cell surface. The pellicle formation in the film strains was abundant with the increase of the cell surface hydrophobicity, whereas the non-film strains had less hydrophobicity as compared with the film strains. Ethanol, as a sole carbon source, efficiently increased hydrophobicity more than glucose, and the hydrophobicity was lowered with the rise of pH. In the experiments of time course, the hydrophobicity was increased in proportion to cell growth, and was maximum during the stationary phase.

  • PDF

Effect of pre-treatment in 0.5 M oxalic acid containing various NH4F concentrations on PEO Film Formation of AZ91 Mg Alloy (NH4F가 첨가된 0.5 M 옥살산 전처리가 AZ91 마그네슘 합금의 PEO 피막 형성에 미치는 영향)

  • Kwon, Duyoung;Song, Pung-Keun;Moon, Sungmo
    • Journal of the Korean institute of surface engineering
    • /
    • v.55 no.1
    • /
    • pp.24-31
    • /
    • 2022
  • This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C2H2O4) solution containing various ammonium fluoride (NH4F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm2 of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na2SiO3 solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH4F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH4F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH4F more than 0.3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.

Study on Misfit Dislocations and Critical Thickness in a $Si_xGe_{1-x}$ Epitaxial Film on a Si Substrate (Si 모재 위의 $Si_xGe_{1-x}$ 박막에서 부정합 전위와 임계두께에 관한 연구)

  • Shin, J.H.;Kim, J.H.;Earmme, Y.Y.
    • Proceedings of the KSME Conference
    • /
    • 2001.06a
    • /
    • pp.298-303
    • /
    • 2001
  • The critical thickness of an epitaxial film on a substrate in electronic or optoelectronic devices is studied on the basis of equilibrium dislocation analysis. Two geometric models, a single dislocation and an array of dislocations in heteroepitaxial system, are considered respectively to calculate the misfit dislocation formation energy. The isotropic linearly elastic stress fields for the models are obtained by means of complex potential method combined with alternating technique, and are used for calculating the formation energies. As a result, the effect of elastic mismatch between film and substrate on critical thickness is presented and $Si_xGe_{1-x}/Si$ epitaxial structure is analyzed to predict the critical thickness with varying germanium concentration.

  • PDF

Role of Energy and Composition of Film-Forming Species in Formation of Composition and Structure of Compound Films

  • Shaginyan, L.R.
    • Journal of the Korean institute of surface engineering
    • /
    • v.34 no.5
    • /
    • pp.455-464
    • /
    • 2001
  • Effect of bombardment of the growing film by energetic particles on its properties is know over many years and is widely used for modification of the film properties. Despite of this there are no final answers on such questions as: what is the mechanism of compositional changes that take place for some compound films deposited under the ion bombardment, how the ion bombardment influences the epitaxial growth, what mechanisms govern the growth of the film on its early stages during deposition under the ion bombardment. The role of composition of film-forming species in formation of film structure is barely investigated or even not investigated at all. Experimental evidence and discussion of the influence of ion bombardment and composition of film-forming species on structure and composition of compound films are briefly considered in the review.

  • PDF