Calcium phlogopite

Phospha.tes. Many phosphates cl aim unique material advantages over siUcates that make them worth the higher material costs for certain apphcations. Glass-ceramics containing the calcium orthophosphate apatite, for example, have demonstrated good biocompatibiUty and, in some cases even bioactivity (the abiUty to bond with bone) (25). Recent combinations of fluorapatite with phlogopite mica provide bioactivity as well as machinability and show promise as surgical implants (26). 

In axenic cultures, some EMF can get access to non-exchangeable potassium and calcium reserves in micas such as phlogopite and vermicu-lite (Paris et al., 1995a, b, 1996). Application of limiting amounts of potassium and magnesium in the nutrient media increased the release of potassium from phlogopite, and seemed to be accompanied by increased exudation of oxalic acid by the EMF (Paris et al., 1995a, 1996). Exposure... 

Trioctahedral micas, such as phlogopite or biotite, are characterized by four distinct cation lattice sites tetrahedral (Z) sites occupied by silicon and aluminum octahedral (Y) sites, denoted Ml and M2, occupied by Al, Cr, Fe +, Ti, Fe +, Mg, and Mn and a large 12-fold coordinated interlayer X-site occupied by potassium, sodium, calcium, and other large cations. The low partition coefficients for lanthanides, uranium and thorium in phlogopite (<2X 10 ) indicate, however, that large highly charged cations cannot... 

A comparison of the properties of surface-treated phlogopite mica with talc, calcium carbonate, glass, and the unfilled resin is given in a technical bulletin produced by Marietta Resources International, Ltd. (10). Table 14.7 shows that 40 wt% mica-filled polypropylene (Profax 6523) had a higher flexural modulus than 30 wt% glass fiber-filled polypropylene (1.04 X 10 psi versus 0.93 X 10 psi). The compound filled with 40 wt% surface-modified mica also had higher Izod impact than the 40 wt% talc-filled compound (0.65 versus 0.45 ft-lb/in). 

KAl2(AlSi3)Oio(OH,F)2, muscovite, and KMg3(AlSi3)Oio(OH,F)2, phlogopite. Both are somewhat harder than talc (Mohs hardness of 2-3) but, since they are platy in nature, are softer and less abrasive than calcium carbonate. Mica fillers have a specific gravity of about 2.8 and are slightly alkaline (pH about 8). 

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