SYNTHESIS AND CHARACTERIZATION OF CALCIUM HYDROXYZINCATE USING X-RAY-DIFFRACTION, FT-IR SPECTROSCOPY, AND SCANNING FORCE MICROSCOPY

Since calcium hydroxyzincate (CHZ) has been found to be central to the mechanism of Zn retardation of cement setting, pure samples of calciu m hydroxyzincate (CHZ) have been prepared to provide pristine samples for characterization and to provide insight into the mechanism of its crystal growth. X-ray diffraction (XRD), Fourier transform infrared sp ectroscopy (FT-IR), and scanning force microscopy (SFM) have been used to provide structural, molecular, and morphological characteristics, respectively. The XRD results of the compound are in agreement with li terature data which corresponds to the molecular formula CaZn2(OH)(6) . 2H(2)O. The FT-PR results delineate the O-H stretching vibrations du e to discrete noninteracting OH groups on the surface of CHZ. An ideal ized model structure is proposed to identify the positions and chemica l environments of the discrete noninteracting OH groups in the hydroxy lated zincate compound. The SFM images of CHZ crystals are presented, and these images provide information on growth mechanisms of this comp ound in a liquid. It is proposed that the growth of CHZ is initiated w ith the formation of surface nuclei, which quickly grow and coalesce t o form layers across the surface. Some features characteristics of spi ral dislocation was also observed on certain crystal surface. The mech anism of the formation of CaZn2(OK)(6) . 2H(2)O is discussed.