dip coating

excellent presentation about dip coating

1. Dip Coating Presented By Engr. Mukhtiar Ahmed Supervised By Dr. Saeed Gul Chemical Engineering Department University of Engineering & Technology Peshawar

2. Dip Coating Introduction Background Applications Methods

3. Dip Coating Introduction “Dip Coating refers to the immersing of a substrate into a tank containing  precursor solution, removing the piece from the tank, and allowing it to drain .” It is widely used for the preparation of porous ceramic membranes. [1]

4. Dip Coating Background Oldest commercially applied coating process First patent based on this process was issued to Jenar Glaswork Schott and Gen in 1939 Before dip coating porous substrate has to be polished with a layer of smaller particles

5. Dip Coating Steps to form defect-free membranes [2] : A homogenous support Substrate cleaning and filtration Sufficient de-aeration of sol/suspension Not too thick coating which results in drying shrinkage and tensile stress Avoid dust and other foreign particulates in air or coating fluids

6. Dip Coating Process The process may be separated into three important technical stages [3] : Immersion & dwell time: The substrate is immersed into the precursor solution at a constant speed followed by a certain dwell time in order to leave sufficient interaction time of the substrate with the coating solution for complete wetting. Deposition & Drainage: By pulling the substrate upward at a constant speed a thin layer of precursor solution is entrained, i.e. film deposition. Excess liquid will drain from the surface.

7. Dip Coating Evaporation : The solvent evaporates from the fluid, forming the as-deposited thin film, which can be promoted by heated drying. Subsequently the coating may be subjected to further heat treatment in order to burn out residual organics and induce crystallization of the functional oxides.

8. Dip Coating Substrate is usually withdrawn vertically from solution reservoir at constant speed Withdrawal speed ranges from 1-10mm/s Competition among various forces decide the thickness of coating Dip-coating is dependent on angle of withdrawal

9. Dip Coating

10. Dip Coating References: [1] Geffcken W, Berger E (1939) Verfahren zur Anderung des Reflexionsvermogen Gla¨ser . Deutsches Reichspatent , assigned to Jenaer Glaswerk Schott & Gen ., Jena 736 41 [2] Scriven LE (1988) Physics and application of dip-coating and spin-coating In: Brinker CJ Clark DE, Ulrich DR ( eds ) Better ceramics through chemistry III, vol 121, Materials Research [3] Grosso D (2011) How to exploit the full potential of the dip-coating process to better control film formation. J Mater Chem 21:17033–17038