To prevent soiling of marble exposed outdoors, the use of TiO2nano-particles has been proposed in the literature by two main routes, both raising durability issues: (i) direct application to marble surface, with the risk of particle leaching by rainfall; (ii) particle incorporation into inorganic or organic coatings, with the risk of organic coating degradation catalyzed by TiO2photoactivity. Here, we investigated the combination of nano-TiO2and hydroxyapatite (HAP), previously developed for marble protection against dissolution in rain and mechanical consolidation. HAP-TiO2combination was investigated by two routes: (i) sequential application of HAP followed by nano-TiO2("H+T"); (ii) simultaneous application by introducing nano-TiO2into the phosphate solution used to form HAP ("HT"). The self-cleaning ability was evaluated before and after prolonged exposure to simulated rain. "H+T" and "HT" coatings exhibited much better resistance to nano-TiO2leaching by rain, compared to TiO2alone. In "H+T" samples, TiO2nano-particles adhere better to HAP (having flower-like morphology and high specific surface area) than to marble. In "HT" samples, thanks to chemical bonds between nano-TiO2and HAP, the particles are firmly incorporated in the HAP coating, which protects them from leaching by rain, without diminishing their photoactivity and without being degraded by them.

Durable self-cleaning coatings for architectural surfaces by incorporation of TiO2nano-particles into hydroxyapatite films

Sassoni, Enrico
;
D'Amen, Eros;Roveri, Norberto;Scherer, George W.;Franzoni, Elisa
2018

Abstract

To prevent soiling of marble exposed outdoors, the use of TiO2nano-particles has been proposed in the literature by two main routes, both raising durability issues: (i) direct application to marble surface, with the risk of particle leaching by rainfall; (ii) particle incorporation into inorganic or organic coatings, with the risk of organic coating degradation catalyzed by TiO2photoactivity. Here, we investigated the combination of nano-TiO2and hydroxyapatite (HAP), previously developed for marble protection against dissolution in rain and mechanical consolidation. HAP-TiO2combination was investigated by two routes: (i) sequential application of HAP followed by nano-TiO2("H+T"); (ii) simultaneous application by introducing nano-TiO2into the phosphate solution used to form HAP ("HT"). The self-cleaning ability was evaluated before and after prolonged exposure to simulated rain. "H+T" and "HT" coatings exhibited much better resistance to nano-TiO2leaching by rain, compared to TiO2alone. In "H+T" samples, TiO2nano-particles adhere better to HAP (having flower-like morphology and high specific surface area) than to marble. In "HT" samples, thanks to chemical bonds between nano-TiO2and HAP, the particles are firmly incorporated in the HAP coating, which protects them from leaching by rain, without diminishing their photoactivity and without being degraded by them.
2018
Sassoni, Enrico*; D'Amen, Eros; Roveri, Norberto; Scherer, George W.; Franzoni, Elisa
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/628257
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