Calcium carbonate with three-dimensional chrysanthemun flower-like structure was successfully prepared from calcium chloride and sodium carbonate ethanol/water mixed solution by a simple precipitation method,using trisodium citrate as crystal modifier.The experimental results show that the three-dimensional structure of chrysanthemun flower-like calcium carbonate is built up with several symmetrical micrometer multi-layer petals arranged around the multi-layer pancake-liked center,and the micrometer center and petals are assemblied by a large number of nanometer spherical particles with size 10-20 nm.It is found that the amount of trisodium citrate,the ethanol volume content has an important influence on the formation of this morphology.A possible mechanism is proposed to explain the formation of three-dimensional chrysanthemun flower-like calcium carbonate according the results.Scanning electron microscopy(SEM),X-ray powder diffraction(XRD),flourier transform infrared spectroscopy(FT-IR),thermogravimety analysis(TG),transmission electron microscopy(TEM) equipped with energy-dispersive X-ray(EDX),and selected area electron diffraction(SAED) were used to characterize the crystals.
The decomposition reaction of phosphate rock under the action of microwave plasma was investigated.Phosphate rock and its decomposition products were characterized by x-ray diffraction(XRD),energy disperse spectroscopy(EDS),and chemical analysis.The measurements of electron temperature(T_(e)) and electron density(N_(e)) of plasma plume under atmospheric pressure were carried out using optical emission spectroscopy(OES).The electron temperature(T_(e)) was determined based on the calculation of the relative intensity of the O Ⅱ(301.91 nm) and O Ⅱ(347.49 nm) spectral lines.Correspondingly,electron densities were obtained using the Saha ionization equation which was based on the C Ⅰ(247.86 nm) line and the C Ⅱ(296.62 nm) line under the assumption of local thermodynamic equilibrium(LTE).The relationship between the relative intensity of the active components and the gas output was studied by the spectrometer.Finally the reaction mechanism of the decomposition of the phosphate rock under the action of the atmospheric pressure microwave plasma was proposed.The results showed that with the increase of CO flow and microwave power,the electron temperature and electron density in the plasma show a decreasing and increasing trend.The CO is dissociated into gaseous carbon ions under the action of microwave plasma,and the presence of gaseous carbon ions promotes the decomposition of the phosphate rock.
