Glass - Back to the Future!

Presenting Author:
Carlos G Pantano

article posted 14 April 2016

Carlos Pantano received his M.E. and Ph.D. in Materials Science and Engineering from the University of Florida in 1976. He joined Penn State, and in 1991, he created the Materials Characterization Lab and served as the Director for 10 years. In 1998, he was appointed the Director of the Materials Research Institute, a new University-level unit created to promote interdisciplinary materials research, science and engineering, which he led thru 2014. His research accomplishments address the effects of glass composition and processing on the surface composition and reactivity of glass substrates and fiber glasses. He has over 300 journal publications, 6 book chapters and has edited several monographs. He holds patents for a microporous sol/gel coating for capillary gas chromatography, glass substrates for DNA/Protein arrays and silica-doped calcium phosphate nanopartices. He is a Fellow of both the American Ceramic Society (ACerS) and the AVS. He was a Chair of the Glass and Optical Materials Division of the ACerS, was a US Council Representative for the International Commission on Glass and is an elected member of the World Academy of Ceramics. He was received the 2005 George W Morey award, and was named the 2012 Kreidl Memorial Lecturer, the 2014 Scholes Lecturer in Glass Science, and a Distinguished Alumnus of the University of Florida in 2014.

The Heterogeneity of Glass Surfaces Revealed by Temperature Programmed Desorption

Carlo G. Pantano*, Lymaris Ortiz Rivera, and Victor A. Bakaev
Department of Materials Science and Engineering, Materials Research Institute, The Pennsylvania State University, University Park, PA, USA

The surface atomic structure of multicomponent silicate glass is irregular due to its disorder and the multicomponent nature of most glass systems. This irregularity is reflected in the adsorption heterogeneity of glass surfaces. This means that active sites for physical and chemical adsorption (chemisorption) are distributed in their binding energies, and in this way, the heterogeneous distribution of surface sites determines the interaction of the glass surface with the environment. In this study, the surfaces of glass are characterized by temperature programmed desorption (TPD) with a mass sensitive detector. Pyridine and butanol were selected as model adsorbates on glass fibers with different compositions, as well as on powders of silica and the crushed fibers. The pyridine is usually employed as a probe of the Lewis acid sites on oxide surfaces; in these glasses, the boron and aluminum are candidates for producing such sites. The butanol is used as a model for water, although we recently developed a method for measuring water adsorption on the glass surfaces directly. In the case of butanol, there are two types of desorbing molecules: at lower temperatures butanol desorbs, but in the range 450-600 °C, 1-butene desorption is also observed. It is shown that 1-butene desorption is due to thermal decomposition of butanol chemisorbed to OH groups on both the glass and silica surfaces. The energy distributions for butanol and pyridine are similar on all glass compositions, but they are much more heterogeneous compared to silica; this difference is most evident for pyridine, and is attributed to the presence Al and B in some of the glasses (see below). Glass fibers are important materials for insulation, filtration, and reinforcement of polymers since in almost all these applications, chemical durability of the fibers and their eventual adhesion to organic coatings and polymers is required. Thus, the energy distribution of adsorption sites on the surfaces of glass fibers has practical relevance. More scientifically, it can be expected that the drawn fiber surface may differ in reactivity relative to the powdered glass.This can be due to differences in composition between the surface and bulk due to processing, as well as differences in atomic structure of the melt-formed fiber surface versus fracture-formed powder surfaces.