Optical properties. V.M. Sglavo GlassEng - UNITN V.M. Sglavo GlassEng - UNITN Licurgo Cup (Rome IV c. AD)

Transcription

1 Optical properties Licurgo Cup (Rome IV c. AD)

2 Electromagnetic spectrum electronic transitions vibrations of bonds nm

3 Solar spectrum 3% 55% 42%

4 Transmission & re1lection I Light intensity decay (Lambert s law): I I = I 0 e β d R 0 absorption coef?icient I i d R I t Transmittance: T = I t I i = (1 R ) 2 e β s brown soda-lime glass Introduction to ceramics, W. D. Kingery, H. K. Bowen and D. R. Uhlmann, J. Wiley & Sons, 1975

5 Re1lected fraction (for orthogonal radiation): R = (n 1 n 2 )2 (n 1 + n 2 ) 2 n 1, n 2 = refractive index of the media 1 & 2 if 2 = air, n 2 = ρ (ρ = density in kg/m 3 ) è R = (n 1 1)2 (n 1 + 1) 2 n 1.5 R = 4% n 1.9 R = 10%

6 Refraction idex (Snell s law) n 12 = n 1 n 2 = c v = ε r 12 = sinϑ i sinϑ r I i i R r electrons density (atomic weight, stress state) polarizability (bonds energy) n D = n(589.3 nm) - Na - n F = n(486.1 nm) - H - n C = n(656.3 nm) - H - n d = n(587.6 nm) - He - Glass structures, J. Wurm, Birkhäuser Verlag, 2007 Glass science, 2nd edition, R.H. Doremus, J. Wiley and Sons, 1994

7 Limit angle total re1lection (n 1 > n 2 ) 0 90 Glass structures, J. Wurm, Birkhäuser Verlag, 2007

8 Glass n d V.M. Soda-lime Sglavo silicate GlassEng UNITN 2017 Pyrex 1.47 Lead for lenses Silica Vycor 1.46 Fluoride-containing 1.3 As 2 S Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

9 Light as waves invisible lenses, glasses: high refraction + low re?lection λ visibie /4

10 Glasses for optical devices (lenses) Abbe number: v d = (n d 1) (n F n C ) n F = n(486.1 nm) n C = n(656.3 nm) n d = n(587.6 nm) Dispersion power: w =1/v d Suggested reading: Glass: the eye of science, M. Bolt, Int. J. Appl. Glass Science, 2017

11 International Journal of Applied Glass Science 1 [1] (2010)

12 Transmittance coloured glasses IR Chemistry of glass, W. Vogel / N. Kreidl, The American Ceramic Society, 1985 Vetri, G. Scarinci, T. Toninato e B. Locardi, Casa Editrice Ambrosiana, 1977

13 ideal transmittance for packaging brown violet dangerous radiations for biological / biochemical products (foods, medicines) green Vetri, G. Scarinci, T. Toninato e B. Locardi, Casa Editrice Ambrosiana, 1977

14 Example: wine bottles Fe 3+ absorption (410 nm) Fe 2+ absorption (1100 nm) green blue

15 Coloured 1ilters Band-pass 1ilters International Journal of Applied Glass Science 1 [1] (2010)

16 Absorption in the visible range 1) ligand?ield theory (3d or 4f orbitals) O 2- excited M + O 2- M + orbitals cystalline structure normal λ = nm

17 Glass science, 2nd edition, R.H. Doremus, J. Wiley and Sons, 1994

18 soda-lime silicate glass at 1400 C R = [red]/[ox] = redox ratio fo 2 = O 2 fugacity in the melt po 2 (= 0.21 in air) reduced state propensity - O 2 partial pressure - interaction among different ions - possible formation of metal colloids Fundamenals of inorganic glasses, A.K. Varshneya, SGT, UK, 2006

19 O2-2) amber colour O2- Fe in tetraedric site V.M. Sglavo GlassEng 2017 Fe3+- UNITN 3+ hν S2- O2-3) colloids (Au red -, Ag yellow -, Cu2O red - CdS yellow -) Au-Ag Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

20 Photosensitive and photochromatic glass M+ M+ UV AgF AgF AgF grey-brown CuCdF green M+ M = Au, Ag, Cu (+CeO 2 ) AgF transparent M M M M M M M M M M HT (Ce 3+ Ce 4+ ) chemical etching (acid) Ag 0 (needles with Å size) AgF AgF AgF (Fe 2+ Fe 3+ ) coloured M

21 Applications multifocal lenses n NT > n ET > n FT photochromatic lenses Schott Guide to Glass, 2nd edition, Chapman & Hall, 1996

22 V.M.porous or textured glass Sglavo GlassEng - UNITN 2017 Explorations in glass, S. D. Stookey, American Ceramic Society, USA, 2000