The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and c...The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and crystallinity of synthesized C4AF,and impact of urea to metal nitrates（UR/MN）molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis,X-ray diffraction and Fourier transform inferred spectrometry.It is found that pure C4AF can be prepared by the SPCR method in 2 h at 500℃.The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel,purity,crystallinity and crystallite size of synthesized C4AF.Ignition temperature should be not lower than 500℃but higher temperatures were unnecessary.No trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition phase.Further calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity,purity and crystallite size.Reaction activation energy of the further calcination process is 119.6 kJ/mol.It is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.展开更多
基金Funded partly by the National "973" Program of China(No.2015CB655101)National Natural Science Foundation of China(No.51379163)
文摘The self-propagating combustion reaction（SPCR）method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel.Thermal decomposition behavior of dried gels,phase identification and crystallinity of synthesized C4AF,and impact of urea to metal nitrates（UR/MN）molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis,X-ray diffraction and Fourier transform inferred spectrometry.It is found that pure C4AF can be prepared by the SPCR method in 2 h at 500℃.The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel,purity,crystallinity and crystallite size of synthesized C4AF.Ignition temperature should be not lower than 500℃but higher temperatures were unnecessary.No trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition phase.Further calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity,purity and crystallite size.Reaction activation energy of the further calcination process is 119.6 kJ/mol.It is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.
