Surface characterization of calcium hydroxylapatite by Fourier transform infrared spectroscopy

Abstract

the bulk equilibrium value cannot be explained by the heat effects.(c) The surface charge may alter the interfacial equilibrium. In the present study the charge on the droplets ranged from lo4 to lOe elementary charges. For the droplet size range (2 pm 5 a 5 20 pm) encountered in this study the effect of surface charge density on the equilibrium composition is negligible. Moreover, the observed moisture content shows no correlation with the surface charge density. ConclusionsWe have measured the evaporation and growth of single glycerol droplets by suspending them individually inside an electrodynamic balance in a stream air of precisely controlled humidity and temperature. By changing the relative humidity of the air stream, we have obtained the growth and evaporation rates of the same droplets over a wide range of relative humidities. The growth and evaporation rates of the droplets have been obtained from two independent methods: light scattering and balancing voltage data. The data obtained by these two methods are in excellent agreement. We have also demonstrated that the resonant peaks found in an intensity spectrum can be used to obtain droplet size and refractive index simultaneously with high precision. From the experimental data, we draw the following conclusions.(i) The time required by a droplet to reach the maximum size is considerably higher than the time predicted by the diffusion theory for the reported value of the liquid-phase diffusion coefficient of a glycerol-water system. The unusually slow growth rates indicate either the existence of interfacial resistance or the presence of other rate-controlling mechanisms.(ii) During the evaporation period, the square of the droplet radius changes linearly with time. The slope of the a2 versus t plot decreases as the relative humidity increases. At a given relative humidity, the observed slopes are highly reproducible.(iii) From the ratio of the slopes in humid air to that in dry air we have obtained the thermodynamic parameter YAXAPAIWU as a function of relative humidity. The experimentally measured slope ratios are significantly higher than the theoretically predicted values based on the equilibrium composition with respect to water vapor in the bulk gas phase, indicating that the droplet interface contains glycerol in excess of the equilibrium value.(iv) For a given relative humidity, the maximum (Le., steady state) water content found in a droplet is always lower than the value predicted by the glycerol-water bulk equilibrium data. The steady-state water content increases with increasing droplet size. The steady-state water content data also raise the possibility of rate-controlling steps other than diffusion being involved in the growth and evaporation processes. Acknowledgment.Surface characterization by FTIR spectroscopy was carried out on heat-treated and water-exposed colloidal nonstoichiometric calcium hydroxylapatite (HAP), synthesized from orthophosphoric acid and calcium hydroxide in an aqueous phase. Two IR bands were newly found at 3682 a...

Designing of hydroxyapatite-gelatin based porous matrix as bone substitute: Correlation with biocompatibility aspects

“…HA was synthesized by the slow addition of 0.6 M H 3 PO 4 to an aqueous suspension of 1.0 M Ca(OH) 2 under constant heating at 150°C in N 2 atmosphere as per the method reported in literature [14]. In order to obtain uniform size crystals of HA the pH of the reaction mixture was strictly controlled i.e.…”

SYNTHESIS AND CHARACTERIZATION OF Mn-DOPED CALCIUM HYDROXYAPATITE PARTICLES

“…3-ions to compensate the cation deficiency of CaHap 40,42 . By replacement of Ca 2+ ions by Mn ones, the sharpness of 3572 cm -1 band is steeply weakened at XMn≤0.04.…”

“…At the same time, 3628 and 3655 cm -1 bands are weakened at XMn≥0.08 but 3681 cm -1 band remains. It was reported that the acidic surface P-OH groups exhibit blue shift and appears at higher wavenumber such as 3681 cm -1 42 . Therefore, the blue shift observed for surface P-OH bands in Fig.…”

Synthesis and characterization of calcium hydroxyapatite (Hap) and Ti(IV)-substituted Hap particles by forced hydrolysis of Ca(OH)₂–Na₄P₂O₇ solution

“…20) Ishikawa et al reported that surface POH groups for the pure Ca deficient highly crystallized Hap particle will be appeared at 3659, 3673 and 3682 cm ¹1 . 20) The single POH peak at 3680 cm ¹1 for AE particles could be due to the low crystallinity with aggregated crystal structure of these particles. Similar result was observed on the Hap particles produced from the Ca(OH) 2 -tpp system as reported previously.…”