Dept. Chem. & Bio. Eng.
Eng. Quad. E-122
Princeton, NJ 08544 USA
Project: Controlling solubility of marble
My name is Sonia Naidu and I’m currently a fourth-year PhD student in the Chemical Engineering department at Princeton University. I joined the Scherer group in January 2009 and my research goal is to reduce the dissolution of marble in the presence of acid rain by forming a protective coating of lower solubility.
Various mediaeval monuments and structures such as the Taj Mahal, the Parthenon and the Statue of David, are constructed from marble. Unfortunately, calcite, which is the mineral that makes up marble, is relatively soluble in acid rain. Hence, it is important to protect the stone from the damaging effects of acid and one way of achieving this is to chemically modify the surface of the stone.
Hydroxyapatite is the mineral that makes up the inorganic component of human teeth and bone. It is extremely durable and has a dissolution rate many orders of magnitude lower than that of calcite. Together with Prof. George Scherer and Jeff Campbell (in 2009), I have been working on a mild and non-toxic treatment to deposit hydroxyapatite coatings on marble. I have investigated the effects of precursor concentration, reaction time, pH, precursor choice and external cationic and anionic additions in obtaining a thick and adherent coating that does not visibly alter the appearance of the stone. I have also studied the hydroxyapatite precursor phases that form and how the various parameters (particularly time and pH) affect which calcium phosphate phases form.
At the moment, I am working on perfecting the apatite film formation, by reducing its porosity and increasing its density, in order to achieve maximum protective benefit. Current work includes quantitative characterisation of the film properties and investigation of the use of organic additives to change the growth habit of the crystals. I am also currently developing an accelerated weathering experiment in lab, to test the effectiveness of the coatings in a fast and reproducible manner.
Our research is funded by Lafarge, the Kress Foundation and NCPTT.
Besides research, I have been a teaching assistant for five undergraduate classes and have taken several technical and language classes during the semester.
Outside of engineering and material science, I enjoy sailing, dancing, travelling and reading.