Thin Film Coating

Thin Film CoatingUsing

Ultrasonic Spray Nozzles

Manoj D. Bhataria([email protected])

Inventys Research Company Pvt. Ltd.Particle Science

503-504, Keshava, Bandra-Kurla Complex, Bandra (East), Mumbai 400051

AOFC 2015CGCRI, Kolkata

Manoj D. Bhataria (Inventys) Thin Film Coating 12/Mar/2015 1 / 21

Outline of this Presentation

1 What is a Thin Film?Some definitions of Thin FilmsDeposition Techniques

2 Ultrasonic AtomisationUltrasonic and LiquidsOperation of an Ultrasonic NozzleConstruction of an Ultrasonic Nozzle

3 ApplicationsPEM Fuel CellCoating MethodsFC Coating Comparison

4 ConclusionAdvantages of Ultrasonic SprayReferences

What is a Thin Film?

PC Magazine Encyclopedia

A thin film is a microscopically thin layer of material that is deposited ontoa metal, ceramic, semiconductor or plastic base.

Wikipedia

A thin film is a layer of material ranging from fractions of a nanometer(mono-layer) to several micrometers in thickness.

Smith

Thin film technology involves deposition of individual molecules or atoms,whereas thick film technology involves deposition of particles.

Wikipedia

Smith

Wikipedia

Smith

What is Thin?

Foll

A film is thin if its thickness is in some order of magnitude smaller thansome intrinsic length scale of the system we are considering.

Example

For a flat surface of the dimension dx dy and a layer of dz on it.The layer would be classified as thin, if

dz dx , dy .

What is Thin?

Foll

Example

dz dx , dy .

What is Thin?

Foll

Example

dz dx , dy .

What is a Film?

Foll

A film should be solid

Adherance to the substrate

Uniformity over the substrate (thickness)

Homogenity of the coating (composition)

What is a Film?

Foll

What is a Film?

Foll

What is a Film?

Foll

Deposition Techniques

Chemical

PlatingI Dip Coating, Electroplating, etc

Chemical Solution DepositionI Sol-Gels, etc

Chemical Vapour DepositionI MOCVD, PECVD, ALD, etc

Physical

Spray DepositionI Ultrasonic nozzle, Electrospray, etc

Physical Vapour DepositionI Evaporative

MBE, etcI Sputtering

PLD, Arc-PVD, etc

Deposition Techniques

Chemical

PlatingI Dip Coating, Electroplating, etc

Chemical Solution DepositionI Sol-Gels, etc

Chemical Vapour DepositionI MOCVD, PECVD, ALD, etc

Physical

Spray DepositionI Ultrasonic nozzle, Electrospray, etc

Physical Vapour DepositionI Evaporative

MBE, etcI Sputtering

PLD, Arc-PVD, etc

Progress of this Presentation

What is Ultrasonic Atomisation?

Figure: A Typical Ultrasonic Bath1

1Sono-tek Corp., USA

Making the Wave

1 When liquid is added to a resonating nozzle,waves are formed on the atomizing surface

2 Increasing the power causes the wave peaks toget so high that droplets fall off the tips of thewave.

3 These droplets have a mathematically definablesize.

4 Notice also that less of the atomizing surface isused (for a given flow rate).

Making the Wave

Figure: Close-ups of a Crest2

Some Maths

Wavelength of Capillary Waves

C =(8sf 2

)1/3where, C = wavelength of the capillary wave,s = surface tension of the liquid, = density of the liquid andf = frequency of the vibration.

Number Mean Drop Diameter

dN,0.5 = 0.34 (8sf 2

)1/3where, dN,0.5 = that diameter, in a sample of Ndrops, for which half of the drops are smaller than,and the other half larger than dN,0.5

An Ultrasonic Nozzle

Figure: Construction of an Ultrasonic Nozzle 3

Components of a PEM Fuel Cell

Figure: Components of a PEM fuel cell 4

Coated Components of a PEM Fuel Cell

Membrane

Gas Diffusion Layer

Bipolar Plate4E. G. & G. Technical Services, Inc., Fuel Cell Handbook, Department of Energy, USA, 2004.

Coating Methods

Figure: Area Fill Figure: Inward Spiral

Ultrasonic Coating Methods

Coating Methods

Figure: Area Fill Figure: Inward Spiral

Ultrasonic Coating Methods

Comparison of Coatings

Figure: SEM images of Hand Painted and Screen Painted GDEsManoj D. Bhataria (Inventys) Thin Film Coating 12/Mar/2015 16 / 21

Figure: SEM images of Ultrasonic Nozzle Coated GDEsManoj D. Bhataria (Inventys) Thin Film Coating 12/Mar/2015 17 / 21

Peak PowerPt. Loading Hand Painted Ultrasonic Spray0.40 mg/cm2 1.7 W /mg 1.7 W /mg

0.15 mg/cm2 3.5 W /mg 4.5 W /mg

0.05 mg/cm2 9.8 W /mg 10.9 W /mg

Peak Power Comparison5

(Hand Painted and Ultrasonic Spray Coated GDEs)

5Millington, B., et al, A novel method for preparing proton exchange membrane fuel cell electrodes by the

ultrasonic-spray technique, Journal of Power Sources, 196, 8500-8508, 2011.

Advantages of Ultrasonic Spray Nozzles

Ultrasonic nozzles are proven with all common coating materials

Waste reduction from 20% 75%

Controllable droplet size

Excellent repeatability

Ultrasonic nozzle are non-clogging

Scalability from R&D to high volume production lines

Deagglomeration of catalysts increases active surface area, resultingin reduction of expensive platinum use

Excellent stiction (high durability of coatings)

References

1 Sono-tek Inc, http://www.sono-tek.com

2 Berger, H., Ultrasonic Liquid Atomisation : Theory and applications,PHP, Hyde Park, NY, 1998.

3 E. G. & G. Technical Services, Inc., Fuel Cell Handbook, Departmentof Energy, USA, 2004.

4 Senthil Kumar, A., Development of a Novel Light Weight BipolarPlate System for Polymer Electrolyte Fuel Cells, M.Tech. Thesis,Dept. of Energy Science & Engineering, IIT Bombay, Mumbai, 2009.

5 Hoffman, C. J. and Walczyk, D. F., Development of a PEM Fuel CellElectrode Coating Testbed, Proceedings of the ASME 2010 EighthInternational Fuel Cell Science, Engineering and TechnologyConference, FuelCell2010, Brooklyn, New York, 2010.

6 Millington, B., et al, A novel method for preparing proton exchangemembrane fuel cell electrodes by the ultrasonic-spray technique,Journal of Power Sources, 196, 8500-8508, 2011.

What is a Thin Film?Some definitions of Thin FilmsDeposition Techniques

Ultrasonic AtomisationUltrasonic and LiquidsOperation of an Ultrasonic NozzleConstruction of an Ultrasonic Nozzle

ApplicationsPEM Fuel CellCoating MethodsFC Coating Comparison

ConclusionAdvantages of Ultrasonic SprayReferences