Phase and morphology of calcium carbonate precipitated by rapid mixing in the absence of additives.

Calcium carbonate is one of the most common minerals, and its polymorphic formation and transformation pathways from the amorphous to crystalline phases are well documented. However, the effects of locally created pH changes on the preferential formation of amorphous calcium carbonate (ACC) or its crystalline phase remain poorly understood. In this study, the influence of the initial solution pH on the precipitated polymorphs of calcium carbonate was investigated by the rapid mixing of each solution containing calcium or carbonate ions in the absence of additives.

Effects of temperature on the carbonation of flue gas desulphurization gypsum using a CO2/N2 gas mixture.

The carbonation of flue gas desulphurization (FGD) gypsum using a CO2/N2 gas mixture was investigated to study the feasibility of using the flue gas directly in the gypsum carbonation. The effect of the reaction temperature on the carbonation reaction and the carbonation conversion efficiency of the samples were considered. In this study, the carbonation conversion efficiency was calculated using a new method for decreasing the error range from a sample containing unreacted gypsum.

Mechanical characteristics and morphological effect of complex crossed structure in biomaterials: fracture mechanics and microstructure of chalky layer in oyster shell.

The complex crossed structures with a polymorph of calcite, termed a chalky layer, which make up much of the shell of an oyster, are composed of flames and leaflets. Two layers, folia and the chalky layer in the giant Pacific oyster (Crassostrea gigas) were examined using SEM (scanning electron microscope), micro-area-XRD (X-ray diffraction) and FT-IR (Fourier transform infrared spectrometer) to determine their morphologies and component characteristics. The chalky layer was also tested using microindentation to assess its mechanical properties, and a microcrack was generated to study the fracture mechanism of the chalky layer.