David Ascienzo
Dept. Physics
CUNY Hunter College
New York, NY 10065
Project: Protection of marble from acid rain
I am currently a senior at CUNY Hunter pursuing a concentration in Physics and a certificate in Mathematics. I hope to work towards graduate study in condensed matter physics and materials science.
My present work with the Scherer research group involves the task of finding, testing, and analyzing possible ion substitutes within a hydroxyapatite film applied to calcium carbonate stones for greater protection. In the research by Sonia Naidu, it has been shown that protective layers of hydroxyapatite (HAP) can be deposited onto calcite (the mineral in marble) by exposing the stone to a solution of diammonium hydrogen phosphate (DAP). To avoid dissolution of the marble, the DAP solution also includes a small concentration of calcium and carbonate ions. This produces a dense layer of HAP, but that crystal has about a 5% lattice mismatch with calcite, so the bonding between the two crystals is strained. We plan to investigate whether the match can be improved by substituting larger ions into the HAP. Proposed candidates for substitution include strontium and barium, which are larger than calcium, but are known to fit into the crystal structure of HAP. We hope that these substitutions will favor nucleation of HAP on the calcite surface, and allow growth of thicker films.
A special thanks goes out to Professor Scherer, Sonia Naidu, and the PCCM/PRISM REU program for this exciting research opportunity.