We have measured the densities of 1s5 and 1s3 argon metastables as a function of the abundance of molecular oxygen in an inductively coupled plasma (ICP) in mixtures of Ar and O2. Laser absorption spectroscopy was used to determine the densities of the metastables. It was found that even small abundances of oxygen lead to large increases in metastable density, mostly due to the reduction in the electron number density, since electron-induced quenching determines the metastable density. At abundances higher than 7% to 15% for powers between 50 and 150 W, quenching by oxygen molecules begins to dominate and the metastable density drops again.
It is known that bones and teeth are composed mostly of hydroxyapatite (HAp), and that iron is present in them as a trace element. Crystal growth after the incorporation of Fe, however, has not been reported extensively yet. In this work, HAp particles doped with Fe ions were synthesised using hydrothermal method. The influence of Fe addition and pH values on the crystal growth of HAp was studied. It was shown that a higher pH will increase the crystal size and thereby increase the crystallinity of HAp. Fe 2z/3z has a smaller ionic radius than Ca 2z and can be incorporated directly, resulting in poor crystallinity and a concomitant reduction in crystal size. At an Fe concentration of 0?2, the rod-like Fe-HAp transformed to a spherical morphology. It suggests that Fe ions can affect the morphologies by the adsorption on specific crystal faces that inhibit growth.
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