Functional Coatings on Steel in the Built Environment-Current and Future Technologies

Dr Sanjay GhoshResearch OfficerSanjayghosh.uk@gmail.comBangor University

Functional coating is all about material that do things

Application of Functional Coating on Steel

Energy efficiency1. Photovoltaic electricity generation2. Solar heating3. Electroluminescent display

Healthcare and safety1. Intumescent coating for fire protection2. Anti-microbial coating for health

Key area :

Intumescent Coating on Exposed Structural Steelwork Festival Place, Basingstoke and City Point, London (Leigh’s Paints)1. Corrosion resistance paint

Weather Protection

Solar Cell Fabrication on Low Cost Rough Steel Surface

0.3mm

400nm200nm

2.5-3mm

400nm500nm

Organic photovoltaic (OPV) Amorphous silicon solar cell (a-Si:H)

Functional coating: SU8 compatible for OPV, Sol-gel, SiOx compatible for a-Si:H & OPV

PCE = 3%

PCE = 6%

Sol. Energy Mater. Sol. Cell 2016, 157, 305 Sol. Energy 2016, 124, 216

Characterisation of Steel + Functional coating (IL) for PV

Leakage current

For solar applications : Ra~0.03μm, Rz~0.3μm

Steel (Roughness high) Steel +IL (Roughness low)

Functional coating

Steel +

IL

Electrical insulation

Diffusion barrier

Mechanical & Thermal stability

Surface leveling

Pencil method

4

Sol-gel (SiOx) Formulation and Development

SiOx mix = Tetraethylorthosilicate (TEOS) + Methyltriethoxysilane (MTES) + Polyethylene Glycole (PEG) + HNO3 + H2O

SiOx coating is compatible with both vacuum and non vacuum deposition method

Spray coat, bar coat, PVD deposition

Temperature of curing = 100 -300 oC for PV application

SU8 (IL) Formulation and Development

Gamma Butyrolactone) 22-60%

Mixed Triarylsulfonium/ Hexafluoroantimonate Salt 1-2%

Propylene Carbonate

Epoxy Resin (Formaldehyde, polymer with 2-(chloromethyl)oxirane and 4,4'-(1-methylethylidene)bis[phenol])

35-75%

Volume

1-5%

Substrate (steel)

cleaning

coat (K-bar)

Soft bake,

125 -150 oC,

10 min

Develop, 15 min

Hard bake,

230-250 oC,

15 min

SU8 Mix

Processing steps

Surface coverage = 70 g/m2, 60 um thickness film, Bar coat

Economic Viability of Low Carbon Steel + IL as substrate for PV

Cost Steel + ILs should be below 0.175 €/Wp for PV

Annu. Rev. Mater. Res. 2011, 41, 297Sol. Energy 2016, 124, 216

Solar Heater

Ren. Sus. Energy Rev. 2016, 58, 574

Evacuated-tube Solar Collector (Riomay)

Evacuated-tube Solar Collector (Espionoza Energy)

Fe2O3/Stainless Steel at Different temperature

High Temperature Solar Absorber on Steel

Author Coat Technique Absorptanceα

Emittance ε

Remarks

Ambriosini et al. 2010

FeCo2O4

NiCo2O4

Spin coat 0.880.82

0.590.46

Thermal stability above 600 oC

Liu et al. 2012

NbTiON/SiON Magnetronsputtering

0.95 0.07 Thermal stability above 500 oC

Valleti et al. 2014

TiAlCrN/TiAlN/AlSiN Cathodic arcPVD

0.91 0.07 Degrade at high temperature

Cespedes et al.2014

Mo-Si3N4 Magnetronsputtering

0.93 0.02 Potential to be used for CSP

Liu et al.2014

Cr-Al-O Cathodic arc ion plating

0.92 0.21 Suitable for collector at higher temperature

Liu et al. 2017

TiC-WCTiC-WC/Al2O3

Magnetronsputtering

0.780.92

0.110.11

Stable up to 500 oC

Wu et al. 2017

Fe2O3 Thermal oxidation

0.91 0.18 Stable up to 900 oC

Future Trend of Functional Coatings

Example: Acronal® Pro 7600 - latest innovation for corrosion protection for industrial metal coatings presented at the European Coatings Show this month.

Conventional to sustainable technology-water based environmental friendly

With VOC regulations at 50 g/L and below,

Self healing, self cleaning properties, sensing abilities, etc.

April 2017, Germany Chem. Mater., 2010, 22 , 4406

Anti-corrosion paint (BASF)

Thank you