Inhibition of the Dissolution of Calcium Carbonate Filler

RESULTS

Surface Analysis

XPS

The XPS survey spectra of GGG and GCC treated with H3PO4 are shown in Figure 3. The atomic composition (in atomic %) calculated from the spectra using the software provided with the instrument is tabulated below. The presence of Al and Si oserved in both spectra were due to impurities such as clay present in the sample. XPS analysis clearly confirmed that the presence of phosphorus only on the surface of the treated GCC.

 

 

 

 

 

 

 

TEM

Figure 4 shows the TEM scan of GCC treated with H3PO4. Thin, sheet-like solid fragments were found to attach to both GCC and clay particles (impurities) but did not seem to fully cover the particles surfaces. Only a few isolated fragments were found whihch indicated that the Ca-P precipitates were mostly formed on the GCC particles. Figure 5 shows the fragments at a higher magnification.

 

EDX

Figure 6 compares the EDX spectra of the fragments (obtained from the area highlighted by a dotted line circle on Figure 5) with that of untreated GCC. Clearly, it can be confirmed that the fragments composed of Ca, P and O.

 

 

 

XRD

X-ray powder diffraction traces for GCC and treated GCC are given in Figure 7. The upper plot shows a characteristic pattern of GCC with intensities at d-spacings corresponding to 0.303, 0.190 and 0.187 nm. The trace for treated GCC did not show any differences from the pure chalk with now new peaks detected. Hence if new solids were precipitated because of the treatment, they were not crystalline as XRD did not detect them. However, it is possible that this precipitated coating was too thin in thickness ( in very small amount) to give a different diffraction pattern.

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