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With the growing general concern about the pollution by fly ash (FA), there has been global interest in its utilization. Purified FA or FA micro-beads are suitable as polymer filling materials because of their density, good dispersity and fluidity of globular particles. However, FA as a filler has not been widely used up to now on account of low whiteness values and low friction of untreated FA surface. In order to improve the FA quality, a surface modification method by using isothermal heating is proposed in this paper. Preparation of composite fly ash (CFA) in the Ca(OH) 2 –H 2 O–CO 2 system is described. Good coating results on FA surfaces can be achieved under suitable operating parameters. The characteristics of CFA are discussed and analyzed based on data from X-ray diffraction, scanning electron microscopy (SEM), infrared spectra, and BET multiple-point nitrogen adsorption method. Feedstocks with less than 45 μm grain size, 2.86 m 2 g −1 specific surface area, and 36.68 whiteness value revealed an increase in specific surface area ranging from 8.69 to 10.01 m 2 g −1 and an increase in whiteness values ranging from 63.67 to 73.13 after coating. A SEM study allowed a detailed determination of the morphology of the surface roughness. Filling tests also show that a rough surface of the CFA enhances contact opportunities and improves the interface between polymer and CFA blended with polypropylene (PP).

Magnetic bioactive glass-ceramics (M GC) were prepared by doping apatite-wollastonite glass-ceramic (A-W GC) with Mn-Zn ferrite. The effect of different contents of Mn-Zn ferrite on the phase structure, magnetic property and bioactivity of A-W GC was investigated. X-ray powder diffraction results showed that A-W GC exhibited apatite, fluorapatite and wollastonite as the main phases. The doping of Mn-Zn ferrite caused the formation of a new phase Zn(0.75)Mn(0.75)Fe(1.5)O(4) in M GC. The amount of this new phase increased with increasing content of Mn-Zn ferrite. Under a magnetic field of 7.96 x 10(5) A m(-1), the saturation magnetization of M GC increased from 4.63 to 9.7 A m(2) kg(-1), but the coercive forces of M GC decreased from 2.39 x 10(4) to 7.56 x 10(3) A m(-1) as the Mn-Zn ferrite content increased from 5% to 20% in the material. The bioactivity of samples was evaluated by soaking in simulated body fluid (SBF). The results showed that the doping of Mn-Zn ferrite decreased the bioactivity of A-W GC dramatically. It took 7 days for an apatite layer to form on the surface of A-W GC, while at least 30 days was needed for an apatite layer forming on the surface of M GC.