Nanoparticle Thin Film Coatings With Self-Cleaning Properties Dr. Abedini By NiloofarTaghizadeh
Content • FSP • Microwave • Electrostatic precipitation • Scattering • Plasma spray • LBL technology • CDC • Characterization techniques • AFM & STM • SEM & TEM • XRD • Noxer block for air purification • Self-cleaning wool & silk fabrics • Solarclean for clean building exteriors • Hydrophobic coating • Anti-fingerprint & Non-stick coating • Antibacterial & Biocide products • Future self-cleaning materials • References • Introduction • History of self-cleaning glass • TiO2 coating • type of TiO2 • Self-cleaning materials • Self-cleaning and lotus effect • Self-cleaning Titania • Titaniaapplications • Titania can be applied on • Nanotechnology • Nano is an invention of nature • Nanoparticle properties • Nanocomposite characteristics • Substrate pre-treatment • Nano powder synthesis approaches • Production of nanoscaled particles • Coating methods on substrate • Laser assisted aerosol • Cold spray • NPDS
Introduction • Self-cleaning materials is a specific type of material with a surface which keeps itself free of dirt and grime through photocatalytic decomposition under UV light for outdoor uses,(3,4) • The story of self-cleaning materials begins in nature with the sacred lotus effect (Nelumbonucifera) ,Wilhelm Barthlott ,University of Bonn,Germany, 1965.(17) • titania when exposed to UV, could split water into hydrogen and oxygen, Akira Fujishima, graduate student at the University of Tokyo, 1967. • nano TiO2, 1990. • for Visible light and indoor uses • 1)Spiked with nitrogen ions. • 2)Doped with metal oxide like WO3 ,metal like Sn4+,or used TiO2nanotubes array.
Self-cleaning TiO2 and lotus effect Lotus effect Self-cleaning TiO2 • Superhydrophobic • Waxiness • Microscopic bumps • Water drops have • minimize • contact with the Surface • Air trapped between the • water and bumps increases • the contact angle Normal surface • Superhydrophilic • Self-cleaning & Anti-fogging • Photocatalitic activity • Fagussylvatica & Magnolia
Self-cleaning Titania(21) Ultraviolet rays excite electrons and holes in the titania. (2a) electrons combine with oxygen molecules to form negatively charged superoxideradical anions (2b) holes combine with hydroxide anions from water to form neutral hydroxyl radicals (3) These highly reactive species kill microbes and break down organic materials on the surface The ultraviolet light also changes to generate OH groups, making it superhydrophilic which allows water to wash off dirt (4)
TiO2 coating • TiO2, anatasephase,n-type semiconductor , • Low costs, permanent coating, nontoxic coating, • Protect aesthetics properties, Increases the life of materials, • photo catalyst properties near UV (λ~380 nm), transparent • Especially suitable for facades, becausethe photocatalysis • need water in sufficient quantity • Doping with C, N, WO3, etc broadens the reaction light • spectrum from the UV regime toward the visible/IR regime, • Doping with Ag or Cu enhances the anti-bacterial effect, and • also prevents the recombination of e &h at the TiO2 surface, Operation of a photochemical excited TiO2 particle • Since the total catalytic surface • area plays a very important role, • increasing the surface area is • crucial for enhanced efficiency,
Self-cleaning materials • Self-cleaning surfaces • Thitania • Silver nanoparticles clothing items • Other (zinc oxide, plasma) • Nano-Tex • Nano-Dry • Nano-Care • Nanoposts • Nanosphere (the first self-cleaning clothes) SiO2nanoparticle
Titania applications • Self-cleaning • Anti-fogging (TiO2-SiO2) • Self-assembly • Sterilizing • Deodorizing • Anti-fouling • Anti-corrosion (SnO2-TiO2) (Bis-silane-TiO2) • Anti-reflection • Hydrolysis catalyst • Cathodic protection • Photocatalytic activity (Anti-bacterial & Anti-Algae) (TiO2-CuO) • Air & water purification • Energy storage (TiO2-MoO3) • Dye-sensitized solar cell
Noxer block & air purificator(30) • Pre-Filter: The air first enters the pre-filter, largest particles are trapped. • High-Efficiency HEPA Filter: The most effective type of air filter. Dust, allergens, and bacteria are trapped. • Activated Carbon Filter: The best type of air filter for trapping chemicals, gases, odors, and cigarette smoke. • Photocatalytic Oxidation Filter: This is coated with TiO2 which produces highly reactive ions that attach to chemical molecules, bacteria, and odor-causing coupounds. • Germicidal UV Lamp: The most effective way to destroy micro-organisms, such as germs, viruses, fungi (such as mold) and bacteria. This also destroys micro-organisms, including those that are trapped by the HEPA air filter, preventing them from reproducing and through the room. • Safe and Effective Ionizer: Circulates trillions of negative ions to neutralize floating pollutants throughout the room. (20)Noxer blocks are blocks of cement mortar with a 5-7mm thick surface layer of Titanium(IV)oxide (titanium dioxide), which is a heterogeneous catalyst, on it. form stable compounds. Mechanism H2O → H+ + OH (radical) + e- O2 + e- → O2- (a superoxide ion) H2O + O2 → H+ + O2- + OH NO2 + OH → H+ + NO3- NO + O2- → NO3-
Titania can be applied on • Ceramic Tile & Cement • Glass • Brick & Masonry • Concrete • Metal siding & cladding • Stucco • Painted surfaces • Acrylic & • Polycarbonatematerial • Industrial Fabric & • Awning, Marquee & sail • Dental industrial • Reactor substrates • Sidewalks • Holding tanks • Boats & Planes Misericordia Church, Roma 2003 Highway wall painted with TiO2 elimination of gases (NOx) Osaka, 1999
Nanotechnology • Nanotechnology is a term that refer to an applied science inwhich • the goal is to manipulate matter on an atomic molecular level of 100 • nanometers or less,itis equal to one billionth of a meter, • A nanoparticle compared to a soccer ball, is the same as the soccer • ball compared to the earth, • encompassing nano-scale science, engineering and technology; • Nanotechnology involves imaging, measuring, modeling, and • manipulating matter at this length scale. Egyptian ink based on carbon particles Nanoscaled gold in coloured glass windows Opalescent soap bubble created by interference of nanometer thin films
Nano is an invention of nature Gecko Efficient grip Butterfly Colour brilliance without colour Nautilus Nacre is light, hard and Resistant to corrosion Lotus Non-wetting surface Shark Laminar Streaming by placoid flakes
(2)Nanoparticle properties • Optical clarity • Size and refractive index of • particles are important, • Nanoparticles are smaller than • the wavelength of visible light; • reduces chance of light scattering, • Surface area dependent on size. • A particle of 10nm diameter • has 20% surface atoms, • A particle of 2nm diameter has • 80% surface atoms, • A particle of 1nm diameter has • 100% surface atoms, • Single wall Carbon nanotube
Substrate pre-treatment • Type of substrate • Metal • Glass • Polymer • Fabrics • Stone • Wood • Ceramic Pre-treatment (22) • Etching of the substrate • As-received • Grinded • Pre-calcined 1. Wet etching where the material is dissolved when immersed in a chemical solution 2. Dry etching where the material is sputtered or dissolved using reactive ions or a vapor phase etchant Typical parallel-plate reactive ion etching system.
Nano powder synthesis approaches • Catalytic Chemical Vapor Deposition: carbon nanotubes (CNTs) such as tangled CNTs, short dispersible CNTs, aligned CNTs, functionalized CNTs. A wide variety of Inner & outer diameters, lengths, functionalizations and purities are possible. • • Laser Induced Chemical Vapor Deposition: Si, SiC and oxides, with average particle sizes around 10 nm, 50 nm and 100 nm, free from aggregation. • • Plasma Enhanced Chemical Vapor Deposition: metals (average particle size of 25 nm, 60 nm, 80 nm and 120 nm) and silicon, carbides, borides and nitrides (average particle • size of 5 nm, 10 nm, 30 nm, 60 nm, 200 nm, 300 nm and 500 nm), purity of 99% or 99.9%. • Gas condensation processing(GPS) • • Chemical Vapor Condensation: Possible materials include numerous ceramics of one or more cations and certain metals. • Plasma Physical Vapor Deposition: vapor temperature less than 3,000 K, resulting in an average particle size of 90-150nm. Purities of 3N, 4N, 5N or higher. Nanoparticles can be solid elements, metal oxides, carbides, nitrides and more, with a special focus on nanoparticles with superior electronic properties. • • Wet Chemistry: metallic nanopowders (W, Mo, Ta, etc.), oxides and carbides. • High-pressure wet chemistry also possible for specific phases. • • Microemulsions: oxides and compounds with precise control of small (5-10nm).B-42 • • Sol-Gel: narrow particle size range and aggregated nanopowders. • Flame spray pyrolysis:
Production of nanoscaled particles 4. Surface modification 3. Cleaning step 2. Crystallization 1. Synthesis of precursors 5. Suspension
Coating methods on substrate • Sol-gel • Laser assisted aerosol • Cold spray • NPDS • Flame spray pyrolysis (FSP) • Spray pyrolysis (SnO2 & In2O3 & • TiO2-WO3) • Microwave • Electrostatic precipitation • Scattering • Plasma spray • LBL technology • CDC method • Dip-coating • Thermal evaporation • Hydrothermal • Magnetron spattering • Photovoltaic • Galvanic cell • Spin-coating • CVD • Foil titanium anodize • Electrodeposition • Electrophoresis
Sol-gel dip-coating process, immersion & start-up, deposition & ,evaporation ,drainage, curing • Wet chemical method for the synthesis of inorganic materials (typically metal oxides) • • Typically, the process starts from a chemical solution • • Precursors are usually metal alkoxidessuch as alkoxysilanes, TEOS (tetraethoxysilane): • These precursors are usually hydrolysed at room temperature in presence of water and a catalyst (acid or base), effect on nanostructure and morphology • Sol-gel For nanoparticle and nano structure coatings • The technique involves deposition of a liquid • precursor film onto the substrate (e.g. by dip or • spin-coating, etc.), followed by post-treatment • steps (e.g. thermal) • Dip-Coating is used for lab scale Sol-Gel coatings: • Extremely thin coatings: From a few nm to <200 nm • • Very smooth (low roughness) • • Poor mechanical stability
(29)Dip coatings may be divided in five stages: 1) immersion, substrate is slowly dipped into and withdrawn from a tank containing the sol, uniform velocity, obtain a uniform coating 2) start-up, 3) deposition, 4) evaporation 5) drainage. The dip-coating technique The waveguide preparation by dip-coating technique may be divided in four stages: · Preparation or choice of substrate; · Thin layers deposition; · Film formation; · Densification throughout thermal treatment.
(8) laser-assisted aerosol CO2 laser-assisted aerosol deposition technique Substrate is prepared by diffusion bonding of both SUS (lower electrode) and plates. (b) PZT thick film is directly deposited onto the SUS membrane by AD technique. (c) PZT film is annealed at 850◦C by CO2 laser irradiation (d) Au upper electrode is deposited onto annealed PZT film by sputtering for measurement of ferroelectrical
Cold spray (7) • Cold-spray was developed in Russia in the early 1980. • Deposition by cold-spray does not involve melting of • materials. Instead, the powders sprayed by a • supersonic gas jet were deposited on a substrate by • plastic deformation. • Its low process temperature can minimize thermal • stress and can also reduce the substrate deformation • The compressed gas flows into a gas control module. • The gas control module divides the gas into powder • carrier and pre-heater. • The carrier gas is mixed with powder and moves to • the nozzle after preheating. • The gas passes through the nozzle throat becomes a • supersonic jet of Mach 2-4 velocity and 1-3MPa • pressure
NPDS (5),(6) (NPDS) is the newly developed ceramic and metal coating process. Nano and micro sized powders are sprayed through the supersonic nozzle at room temperature and low vacuum condition and deposited on various substrates.
FSP (12), (14) FSP for producing ceramic nanoparticles and directly depositing them on a cooled substrate positioned above the Flame. b) In situ mechanically stabilized by an impinging, particle-free xylene flame. a) highly porous (98%) flame-made nanoparticle layers are deposited on silicon wafer through a shadow mask, and then
Microwave (11) • the solution temperature was below 50 °C for • all experiments in order to prevent the nucleation of TiO2 in the precursor solutionIf the external cooling • growth experiments were conducted by interrupting the MW power cyclically so as to give time for the solution to cool during the MW-off period. • This occurred in experiments with higher MW power and/or relatively longer heating times. • A recirculating flow of 2-3 mL/s was used. • The amount of circulating precursor solution was 35 mL; therefore, in the time intervals used there were • around 10-100 recirculating cycles of the precursor solution. • A Maxidigest MX 350 (Prolabo) microwave furnace operating at 2.45 GHz and 300 W maximum power was used.
Electrostatic precipitation (13) • The method is based on particle formation by homogeneous nucleation induced by cooling down of a SnO vapor and subsequent aggregation by Brownian motion, followed by a • size-fractionation step and a sintering /crystallization step. • a nanocrystal source in the form of a sublimation furnace, a radioactive b source which acts as a bipolar aerosol charger, a differential mobility analyzer ~DMA! • used as a size classifier, a second tube furnace for sintering and crystallization of the SnO aggregates, a deposition chamber,and a particle size measurement system consisting of a DMA and a condensation nucleus counter ~model 3025, TSI, Minneapolis, MN!.
Scattering (9) the SAXS-beamline of the third generation synchrotron ELETTRA (Italy), delivering the high flux of 8 keV necessary for such an experiment. Fresh (FX) or pretreated (PTX) films were disposed in the center of a specially designed furnace capable of heating at the rates of X ) 10 or 20 °C min-1, and equipped with apertures designed to allow the incident, the diffused, and the diffracted radiations in and out of the heating device without hindrance. The incident angle was fixed at 5(1° with the film surface to eliminate the specular reflection and the Yoneda signal from detectors in-situ time-resolved simultaneous SAXS and WAXS investigations performed on TiO2 films in various thermal treatment conditions.
Plasma spray (10) At the processing, the liquid feedstock containing fine particles is fed into plasma jet using a peristaltic pump or similar device .The suspension is fed to an atomizer and gets injected into plasma jet. The atomized droplets vaporize and remaining small solid grains are accelerated towards the substrate, being heated, molten and, finally, get splashed onto substrate.
(16)LBL technology Multilayers were prepared after dipping of the substrates alternately in positively charged PDDA and the prepared negatively charged PSS-TiO2 and SiO2 solutions for 10 min. After each adsorption step, the unadsorbed polyelectrolyte was removed by repeated washing. adsorption conditions were PDDA (0.01 M based on repeat unit) in 0.025 M NaCl, pH 4.0 or 9.0. The assembly conditions of the pH, concentration and number of PDDA/PSS-TiO2/PDDA/SiO2 are indicated in the following exampleA group of PDDA/TiO2/PDDA/SiO2 layers makes up of one cycle. Finally, the prepared coatings were calcined at 400 °C for 3 h to remove the polyelectrolyte. Preparation of TiO2/SiO2Multilayers with the LbL Deposition Method
CDC (15) (a) Corona discharge coating (CDC) apparatus. Two different kinds of corona discharge generated in the apparatus: (b) glow and (c) spark. A positive corona is initiated by an exogenous ionization event in a region of high potential gradient. The electrons resulting from the ionization are attracted toward the needle, and the positive ions are repelled from it. A directional flow of positively charged particles was formed over the substrate as shown in (b). (c) The flow of particles above the droplet induces the deformation of solution. (d) After the deformation of solution, the droplets spread onto the substrate and solvent evaporation accelerates the film formation.
Characterization techniques For Bulk/Surface morphology, microstructure and dispersion • AFM • SEM • TEM • STM • XPS • XRD • UV-VIS • FT-IR
AFM & STM (24),(25), (28) • In 1981, Gerd Binnig and Heinrich Rohrer at the • IBM Zurich Research Laboratory in Switzerland • The STM has a metal needle that scans a sample by • moving back and forth over it, gathering • information about the curvature of the surface. • The STM takes advantage of what’s called the • tunnel effect: If a voltage is applied to the tiny • distance between the needle and the sample, • electrons are able to tunnel, or jump, between the • needle and the sample, creating an electric current The deflection of a microfabricated cantilever with a sharp tip is measured be reflecting a laser beam off the backside of the cantilever while it is scanning over the surface of the sample.
SEM & TEM (26) The electron range increases with beam energy. The internal structure of the EEBD deposits can be examined at high electron beam energies in SEM. At 5 kV with shallow penetration depth, the surfac of the tips is clearly visible. At 100 keV and above, TEM images can achieve atomic resolution where .the lattice planes To achieve optimal imaging conditions for the thin TEM samples, the working distance has been made short. In most TEMs, the space for the sample holder is only about (5 mm)³ between the two objective lenses for the incoming and transmitted .When the specimen thickness is about the mean free path, λmfp, TEM can be used to achieve high resolution images such as the image above where the atomic lattice of a gold nanocrystal is visible. In a scanning electron microscope a beam is scanned over the sample surface in a raster pattern while a signal is recorded from electron Another SEM detector is the in-lens detector, where SE passing through the column aperture are accelerated towards a solid state detector.
XRD (27) X-ray diffraction (XRD) is a powerful method for the study of nanomaterials. Nanomaterials have a characteristic microstructure length comparable scales of physical phenomena, giving them unique mechanical, optical X-rays are produced generally by either x-ray tubes or synchrotron radiation. In a x-ray tube, which is the primary x-ray source used in laboratory x-ray instruments, x-rays are generated when a focused electron beam accelerated across a high voltage field bombards a stationary or rotating solid target. XRD Pattern of NaCl Powder
Self-cleaning wool & silk fabrics • Nano textiles properties • Water-based or solvent-containing • impregnation for textiles and leather • Moisture penetration and re-soiling is • extremely reduced • washing-resistant impregnation for • cotton and blended fabrics FESEM Pristine wool fiber, (b) Modified wool fiber, (c) T60-coated wool fiber, (d) T60-coated modified wool. • Plain wool (top row), PO, • Wool coated with stain-fighting • chemical (middle row),TO, • Wool treated with a new nanoparticle • coating (bottom row), TS, • After 0, 8, and 20 h of light • irradiation by a solar light simulator.
Solarclean for clean building exteriors Stains created by dirty water draining off the bars of the balcony Soot, dirt and oils caused this unsightly discoloring on the window Streaking on the concrete wall caused by dirty rainwater runoff Treated walls do not get dirty or discolor, because of the photocatalytic self-cleaning cycle.1999 Ideal solution prevent building exterior from becoming dirty in the first place by applying a photocatalytic coating
Hydrophobic coatings • For glass, ceramic, metal and plastic surfaces • Hydrophobic and oleophobic coatings, waterdrops run off like pearls • Easy-to-clean-Effect • For textiles, leatherwood, stone and lacquer • 2-Component-Systems • Adherences of dirt, insects, bivalves, barnacles, algae and contaminants are reduced • Breathable, water- and dirt-repelling • Multifunctional for open-pored, sucking undergrounds (Indoor glasses & ceramic) (Stone & Timber) (diverse plastics) (Car finish) (Boat finish) (car glass) (Outdoor glass applications) (alloy wheel rims) (chrome-stainless steal)
Anti-fingerprint, non-stick & car-care coating Products for Stainless Steel • Car-care (23) • This product polishes, cleans, • cares and protects your car paint • Provides a permanent and • invisible thin surface effect • quick and easy to apply leaving a • water-repellent coating. • Water- and dirt-repellent • Long-lasting effect • Also suitable for bike and Motor • In storage avoid exposure to • direct sunlight and high • temperatures. Anti-fingerprint effect • Transparent colourless • lacquer • Fingerprints can be • removed very easy • Hydrophobic coating, • easier cleaning Non-Stick coating • Non-Stick-coating for baking • dishes e.g. with continuous • heat resistance at 250°C. • Excellent release of sugary • bakery product • Excellent resistance to dish • detergents • Suitable for applications with • food contact
Antibacterial & Biocide products • Product for shoe interior • Shoe deodorant for neutralisation of • unpleasant smell • avoids smell-generating bacteriae and fungi • Containing silver particles that avoid a new • culture of bacteriae • Comfortable fresh smell by special fragrances • The Product for texeffective period can be • elongate by repeating the application • Textiles and leather • Water-based impregnation for textiles and • leather with antimicrobial effect • Silver particles generate the antimicrobial effect • Product for Stone and Timber • Water-based impregnation with fungicidal and antibacterial effect for timber • Suitable for nearly all kind of timber • Nanoscaled silver generates the antibacterial • and fungicidal effect (Timber & Stone)
Museum of the Earth, New York. Britomart Transport Centre, Auckland. The Vistas, Wychwood Park. Countryside Properties. Entropal B.V., Geldermalsen. Bourgogne, France.
Future self-cleaning materials Replaceable hydrophilic & hydrophobic surface Anti-fogging & anti-reflecting 7 nm TiO2/22 nm SiO2
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