Confinement effects in dip coating

2017 ◽  
Vol 827 ◽  
pp. 1-30 ◽  
Author(s):  
Onyu Kim ◽  
Jaewook Nam
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
Dip Coating ◽  
Liquid Pool ◽  
Viscous Drag ◽  
Moving Plate ◽  
Simple Process ◽  
Meniscus Shape ◽  
Withdrawal Speed ◽  
Stationary Wall

When a flat plate is withdrawn from a liquid pool, a liquid film is deposited on the plate. This simple process is called dip coating. In the case of vertically upward withdrawal, gravity competes with the surface tension and viscous drag, and the balance between those determine the meniscus shape and hence the film thickness. Most of the previous studies on dip coating assumed that the pool is sufficiently large so that the stationary container wall does not affect the film thickness. However, the cases where the stationary wall affects the entrained film have not been examined thoroughly so far. In this confined dip coating, the film thickness deviates from that of unconfined dip coating under the same conditions such as the withdrawal speed and the physical properties of the liquid. The meniscus in a confined pool is more curved than that in an unconfined pool owing to wetting on the stationary wall, which is parallel to the plate. Besides, a channel between the moving plate and the stationary wall appears; therefore, the flow inside the channel should be included in an analysis of confined dip coating. In the present study, we analyse the mechanism that determines the film thickness, both theoretically and numerically.

The elastocapillary Landau–Levich problem

2013 ◽  
Vol 735 ◽  
pp. 1-28 ◽  
Author(s):  
Harish N. Dixit ◽  
G. M. Homsy
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
Functional Dependence ◽  
Dip Coating ◽  
Relative Strength ◽  
Capillary Length ◽  
Viscous Forces ◽  
Flow Speeds ◽  
Numerical Coefficient ◽  
Image Position

AbstractWe study the classical Landau–Levich dip-coating problem for the case in which the interface possesses both elasticity and surface tension. The aim of the study is to develop a complete asymptotic theory of the elastocapillary Landau–Levich problem in the limit of small flow speeds. As such, the paper also extends our previous study on purely elastic Landau–Levich flow (Dixit & Homsy J. Fluid Mech., vol. 732, 2013, pp. 5–28) to include the effect of surface tension. The elasticity of the interface is described by the Helfrich model and surface tension is modelled in the usual way. We define an elastocapillary number, $\epsilon $, which represents the relative strength of elasticity to surface tension. Based on the size of $\epsilon $, we can define three different regimes of interest. In each of these regimes, we carry out asymptotic expansions in the small capillary (or elasticity) numbers, which represents the balance of viscous forces to surface tension (or elasticity).In the weak elasticity regime, the film thickness is a small correction to the classical Landau–Levich law and can be written as $$\begin{eqnarray*}{\tilde {h} }_{\infty , c} = (0. 9458- 0. 0839~\mathscr{E}){l}_{c} C{a}^{2/ 3} , \quad \epsilon \ll 1,\end{eqnarray*}$$ where ${l}_{c} $ is the capillary length, $Ca$ is the capillary number and $\mathscr{E}= \epsilon / C{a}^{2/ 3} $. In the elastocapillary regime, the film thickness is a function of $\epsilon $ through the power-law relationship $$\begin{eqnarray*}{\tilde {h} }_{\infty , ec} = {\bar {h} }_{\infty , e} L\hspace{0.167em} f(\epsilon )C{a}^{4/ 7} , \quad \epsilon \sim O(1),\end{eqnarray*}$$ where ${\bar {h} }_{\infty , e} $ is a numerical coefficient obtained in our previous study, $L$ is the elastocapillary length, and $f(\epsilon )$ represents the functional dependence of film thickness on the elastocapillary parameter.

scholarly journals The Effect of Film Thickness and Content on Film Formation from PS/ Nanocomposites Prepared by Dip-Coating Method

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
M. Selin Sunay ◽  
Onder Pekcan ◽  
Saziye Ugur
Keyword(s):  
Film Thickness ◽  
Elevated Temperatures ◽  
Film Formation ◽  
Fluorescence Emission ◽  
Dip Coating ◽  
Atomic Force ◽  
Annealing Step ◽  
Coating Method ◽  
Fluorescence Emission Intensity ◽  
Dip Coating Method

Steady-state fluorescence (SSF) technique in conjunction with UV-visible (UVV) technique and atomic force microscope (AFM) was used for studying film formation from TiO2covered nanosized polystyrene (PS) latex particles (320 nm). The effects of film thickness and TiO2content on the film formation and structure properties of PS/TiO2composites were studied. For this purpose, two different sets of PS films with thicknesses of 5 and 20 μm were prepared from pyrene-(P-) labeled PS particles and covered with various layers of TiO2using dip-coating method. These films were then annealed at elevated temperatures above glass transition temperature () of PS in the range of 100–280°C. Fluorescence emission intensity, from P and transmitted light intensity, were measured after each annealing step to monitor the stages of film formation. The results showed that film formation from PS latexes occurs on the top surface of PS/TiO2composites and thus developed independent of TiO2content for both film sets. But the surface morphology of the films was found to vary with both TiO2content and film thickness. After removal of PS, thin films provide a quite ordered porous structure while thick films showed nonporous structure.

The effect of the withdrawal speed on properties of nickel oxide thin films

2019 ◽  
Vol 234 (10) ◽  
pp. 647-655
Author(s):  
Zohra Nazir Kayani ◽  
Atiqa Aslam ◽  
Rabia Ishaque ◽  
Syeda Nosheen Zahra ◽  
Hifza Hanif ◽  
...  
Keyword(s):  
Thin Films ◽  
Nickel Oxide ◽  
Band Gap ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Dip Coating ◽  
Oxide Thin Films ◽  
Withdrawal Speed ◽  
Sem Micrograph ◽  
Nickel Oxide Thin Films

Abstract Nickel oxide thin films have been prepared by sol-gel dip-coating technique on glass substrate. It is shown that nickel oxide thin films have poly crystalline nature. Nickel oxide thin films exhibit high transmission (39–85%) in the wavelength range of 400–900 nm, strong absorption between 300 and 400 nm wavelengths and decrease of band gap values are in the range 3.69–3.27 eV with increase of withdrawal speed. High band gap at low withdrawal speed is because of the small average crystallite size, which decreases with increase in withdrawal speed. The SEM micrograph shows cubic crystallites and surface of thin films become dense, smooth and homogeneous with an increase in withdrawal speed. Assessment of nickel oxide deposition conditions provides gateway for effective and cheap solar cells.

Resistive Switching Behaviour of Dip Coated ZnO Films with the Changing with Drawal Speed

2020 ◽  
Vol 978 ◽  
pp. 384-389
Author(s):  
Sritama Roy ◽  
Saswati Soumya Dash ◽  
Prasanna Kumar Sahu ◽  
Smita Mishra ◽  
Jyoti Prakash Kar
Keyword(s):  
Thin Films ◽  
Resistive Switching ◽  
Sol Gel ◽  
Dip Coating ◽  
Zno Films ◽  
X Ray Diffraction ◽  
Thin Film Thickness ◽  
Withdrawal Speed ◽  
Current Voltage ◽  
P Type

Zinc Oxide (ZnO) thin films were produced by the sol gel dip coating process on the p-type silicon substrate with various withdrawal speeds changing from 1 to 4 cm/min, respectively. The films were annealed at a temperature of 500 °C for an hour in air ambient. The thin film thickness was found to be raised with the rise in withdrawal speed. The uniform distribution of the grains was appeared for all the films. The evolution of c-axis oriented (002) peak was revealed from X-ray diffraction (XRD) studies. The microstructural and optical properties of ZnO films were investigated by Raman, FTIR and photoluminescence spectroscopy (PL). The resistive switching properties of ZnO based memristors were studied by performing the current-voltage (I-V) measurements, where the thin films coated with lower withdrawal speed, have shown better switching property with rapid rise and fall of current during SET and RESET process, respectively.

Bubble Entrapment in Sprayed Films

2014 ◽  
Author(s):  
A. Dalili ◽  
S. Chandra ◽  
J. Mostaghimi ◽  
H. T. Charles Fan ◽  
J. C. Simmer
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
The Other ◽  
Bubble Motion ◽  
Sauter Mean Diameter ◽  
Glass Substrates ◽  
Buoyancy Forces ◽  
Mean Diameter ◽  
Imagej Software ◽  
Bubble Movement

A compressed air sprayer was used to spray model paint onto two glass substrates at the same time. Afterwards, one glass substrate was placed on a LED light source and still photographs were taken from the top using a DSLR camera with a timer system. The other substrate was put on a balance to record weight. Pictures and weight measurements were taken at 5 second intervals for 15 minutes. The sprayed film thickness was varied. The pictures were analyzed using ImageJ software. Bubble Count vs. Time, Sauter Mean Diameter (SMD) of Bubbles vs. Time as well as Weight vs. Time was plotted. It was seen that the pace of weight loss was faster for thinner films. The rate of bubble escape also depended on film thickness. It took a longer time for thicker films to lose the bubbles entrapped in them. In the first 30 seconds, large bubbles escaped due to buoyancy forces and afterwards surface-tension driven flows became dominant. There was also a lot of bubble movement in thicker films. The effect of gravity was studied as well. Gravity did not affect the bubble escape rate since a downward facing film had the same bubble count as an upward facing film confirming that bubble motion was not due to buoyancy forces alone. However, the SMD of bubbles in a downward facing film was larger than an upward facing film. Buoyancy is not a factor in bubble escape from the downward facing film and only surface-tension driven flows play a role.

Deformation characteristics of ultra-thin liquid film considering temperature and film thickness dependence of surface tension

2011 ◽  
Vol 17 (5-7) ◽  
pp. 983-990 ◽  
Author(s):  
Hiroshige Matsuoka ◽  
Koji Oka ◽  
Yusuke Yamashita ◽  
Fumihiro Saeki ◽  
Shigehisa Fukui
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Thickness Dependence ◽  
Deformation Characteristics

Influence of Dip-Coating Temperature Upon Film Thickness in Chemical Solution Deposition

2018 ◽  
Vol 28 (4) ◽  
pp. 1-5 ◽  
Author(s):  
Zhirong Yang ◽  
Peng Song ◽  
Feng Feng ◽  
Linli Wang ◽  
Hui Mu ◽  
...  
Keyword(s):  
Film Thickness ◽  
Chemical Solution Deposition ◽  
Dip Coating ◽  
Chemical Solution ◽  
Solution Deposition ◽  
Coating Temperature
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