Vapor Phase Adsorption of Water on Hydroxyapatite

Abstract

Water vapor adsorption isotherms were determined gravimetrically on three hydroxyapatite sampel differing in preparation and with surface areas of 70.4, 22.5, and 3.0 M2/gm, respectively. Heats of adsorption for the first layer of water were found to be 13.3, 13.2, and 13.9 kcal/mole on these hydroxypatites. From repeated thermal desorption and adsorption cycles of water, stepwise adsorption was observed which diminished with each outgassing cycle until it disappeared after the fourth cycle. Cross-sectional area of adsorbed water molecule on hydroxyapatite surface was estimated at 11.5 A2. Standard free energies, isosteric heats, changes in enthalpy, and entropy of adsorption of water on HAP samples outgassed at 300 C were determined.

Fabrication of Bio-Nanocomposite Nanofibers Mimicking the Mineralized Hard Tissues via Electrospinning Process

“…This peak completely disappears in the DTGA curve of the dried electrospun PVA/HAp NC fibers. This result clearly indicates that the peak at 312 o C arises from the loss of lattice water which may be called "structural" water or water trapped within HAp nanorods, consisting with data of Rootare and Craig [54] for the chemisorbed water layer. Over about 600 °C, all TGA diagrams become flat and mainly the inorganic residue (i.e.…”

Patterned Thermal Destruction in a Forensic Setting

“…Although studies thus far have been unable to specifically pinpoint required exposure times or temperatures for causing these changes, some researchers have been successful in identifying temperature ranges with which they can be associated (Bonucci and Graziani, 1975;Civjan et al, 1971;Holager, 1970;Rootare and Craig, 1977;Shipman et al, 1984;Thompson, 2004).…”

Adsorption of 4-Methacryloxyethyl Trimellitate Anhydride (4-META) on Hydroxyapatite and its Role in Composite Bonding

“…The surface-active groups of a potential coupling agent (between the apatite and a prosthetic resin) must not interact too strongly with the substrate lest they sequester calcium or phosphate ions or dissolve the apatite, thus destroying any anchoring on the surface. It could be reasonably assumed that a coupling agent possessing one or more hydrogen-bonding moieties may interact with the physically adsorbed water on the apatite substrate (Dry and Beebe, 1960;Rootare and Craig, 1978;Misra, 1986b), but it must concomitantly possess hydrophobic moieties so that water or other fluids may not easily displace it from the surface.…”