SELF-CLEANING GLASS and ELECTROCHROMIC GLASS UNIVERSITÀ DEGLI STUDI DI LECCE Corso di laurea in Ingegneria dei Materiali A.A. 2001/2002 Scienza e Tecnologia dei Materiali Ceramici Professore Dott. Antonio Licciulli Studente Daniela Lisi

SELF-CLEANING GLASS

SUMMARY HISTORY TITANIUM DIOXIDE SELF-CLEANING SURFACE PHOTOCATALYSIS HYDROPHILICITY SUPER-HYDROPHILICITY SELF-CLEANING WINDOWS

HISTORY The late 1960s: the University of Tokyo research photoelettrochemical solar cells. The solid-state photovoltaic device has become the technology of choice. 1972:Fujishima and Honda discovered the photocatalytic splitting of water on TiO 2 electrodes without using electricity. 1977:Professor Allen J. Bard and co-workers at the University of Texas first examined the possibilities of using TiO 2 to decompose cyanide in water. Many important fundamental results concerning TiO 2 photocatalytic reaction have been clarified by such intensive works. The late 1990s: Pilkington, PPG, SSG patent SELF-CLEANING windows.

TITANIUM DIOXIDE SELF- CLEANING and ANTIFOGGING functions PHOTOCATALYST HYDROPHILIC

RUTILE Density: 4,2 g/cc Refractive Index: 2,76 ANATASE Density: 4,2 g/cc Refractive Index: 2,52 TITANIUM DIOXIDE

White pigment in paints, cosmetics and foodstuffs. Semiconductor transparent in the visible region of the spectrum. Low costs material. Chemically inert, non-toxic, biocompatible. TITANIUM DIOXIDE

SELF-CLEANING SURFACE TO CLEAN SURFACE OF BUILDING MATERIALS CAUSES: Considerable trouble. High consumption of energy. Chemical detergents. High costs

TO REALIZE SELF-CLEANING MATERIAL SURFACES THERE ARE THREE PRINCIPAL WAYS : Super-hydrophobicity. Photocatalysis. Super-hydrophilicity and hydrophilicity SELF-CLEANING SURFACE

HYDROPHOBICITY Hydrophobic materials ("water hating") have little or no tendency to adsorb water and water tends to "bead" on their surfaces (i.e., discrete droplets). Hydrophobic materials possess low surface tension values and lack active groups in their surface chemistry for formation of "hydrogen-bonds" with water.

For a given droplet on a solid surface: the contact angle is a measurement of the angle formed between the surface of a solid and the line tangent to the droplet radius from the point of contact with the solid. CONTACT ANGLE HYDROPHOBICITY

HYDROPHOBICITY

SUPER-HYDROPHOBICITY The LOTUS EFFECT

PHOTOCATALYSIS The acceleration of the rate of a photoreaction by the presence of a catalyst (semiconductor particle). WHAT IS IT?

WHAT IS a SEMICONDUCTOR SOLID? PHOTOCATALYSIS

HOW DOES PHOTOCATALYTIC SEMICONDUCTOR WORK? PHOTOCATALYSIS

TiO 2 AS PHOTOCATALYST

OXIDATION-REDUCTION REACTION ON THE SURFACE OF TIO 2 TiO 2 AS PHOTOCATALYST

IT IS COMPETITIVE BECAUSE: A low-cost material is used as photocatalyst. The reaction is quite fast at mild operating conditions (room temperature, atmospheric pressure). A wide spectrum of organic contaminants can be converted to water and CO 2. No chemical reactants must be used and no side reactions are produced. TiO 2 AS PHOTOCATALYST

PRACTICAL APPLICATIONS TiO 2 AS PHOTOCATALYST

HYDROPHILICITY Also called hydrophilic, is a characteristic of materials exhibiting an affinity for water. Hydrophilic literally means "water-loving" and such materials readily adsorb water. The surface chemistry allows these materials to be wetted forming a water film or coating on their surface.

HYDROPHILICTY

HYDROPHILICTY MECHANISM OF PHOTO-INDUCED HYDROPHILICITY

HYDROPHILICTY a) Upon UV illumination b) In the dark TIME DIPENDENCE OF THE WATER CONTACT ANGLE IN AMBIENT ATMOSPHERE

SUPER-HYDROPHILICITY

STEP 1 STEP 2 STEP 3 STEP 4 SCHEMATIC DIAGRAM OF SUPER-HYDROPHILICITY MECHANISM

SELF-CLEANING WINDOWS

SunClean Glass

SELF-CLEANING WINDOWS

Pilkington Activ™

SGG AQUACLEAN SELF-CLEANING WINDOWS

ELECTROCHROMIC GLASS

SUMMARY OPTICAL SWITCHING TECHNOLOGY SMART WINDOWS THE SOLUTION SageGlass®

OPTICAL SWITCHING TECHNOLOGY It changes the view of glazing from a FIXED element to a DYNAMIC one.

Optical switching materials can be used for windows where optical and thermal modulation is required. OPTICAL SWITCHING TECHNOLOGY

to control the flow of light and heat into and out of window, according to an energy management scheme. THE PURPOSE IS: OPTICAL SWITCHING TECHNOLOGY

a large change in optical properties upon a change in either light intensity, spectral composition, heat, electrical field, or injected charge. THE BASIC PROPERTY IS: OPTICAL SWITCHING TECHNOLOGY

This optical change results in a transformation from highly transmitting state to a partly reflecting or absorbing state, either totally or partly over the solar spectrum. OPTICAL SWITCHING TECHNOLOGY

SMART WINDOWS Electrochromic windows change the light transmittance, transparency, or shading of windows in response to an environmental signal.

SMART WINDOWS HOW ECDs WORK?

A voltage applied across the transparent conducting oxide layers causes hydrogen or lithium anions (A + ) to be injected into the electrochromic layers. SMART WINDOWS HOW ECDs ARE MADE?

SMART WINDOWS ELECTROCHROMIC MATERIAL PERFORMANCE OBJECTIVES ARE: continuous range in solar and optical transmittance, reflectance, and absorbance between bleached and coloured states; contrast ratio (CR) of at least 5 a 1; colouring and bleaching times (switching speed) of a few minutes; switching with applied voltages of 1–5 V; acceptable neutral colour; large area with excellent optical clarity; sustained performance over 20–30 yr; acceptable cost ($100/m 2 );

SMART WINDOWS GLASS/ITO/NiO/Inorganic Electrolyte/WO 3 /ITO/GLASS

SMART WINDOWS GLASS/ITO/NiO/Inorganic Electrolyte/WO 3 /ITO/GLASS

SMART WINDOWS GLASS/ITO/NiO/Inorganic Electrolyte/WO 3 /ITO/GLASS

SMART WINDOWS GLASS/ITO/PANI/PB/PAMPS/WO 3 /ITO/GLASS

SMART WINDOWS GLASS/ITO/PANI/PB/PAMPS/WO 3 /ITO/GLASS

SMART WINDOWS ECDs as ENERGY SOURCE

SMART WINDOWS ECDs as ENERGY SOURCE

THE SOLUTION SageGlass®

THE SOLUTION - SageGlass®