The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane （TEOS） in alkalescent condition. By analyzing the hy...The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane （TEOS） in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm^-1 were found by FI-IR, which were the characteristic bands of Si-OH and Si-O-Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 20 = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.展开更多
Baotou RE concentrate was decomposed with concentrated sulfuric acid by controlling the roasting temperature below 500℃.Thermogravimetry-differential thermal analysis（TG-DTA） and chemical analytical methods were us...Baotou RE concentrate was decomposed with concentrated sulfuric acid by controlling the roasting temperature below 500℃.Thermogravimetry-differential thermal analysis（TG-DTA） and chemical analytical methods were used to study the thermal decomposition process and the thermal decomposition effect.The Freeman-Carroll method was applied to analyze the TG-DTA curves.The activation energy, reaction order, and reaction frequency factor at different stages were calculated.The Satava method was used to deduce the reaction mechanism and the relative reaction rate during the thermal decomposition process.展开更多
基金the National Natural Science Foundation of China (Nos. 50372006, 20273007, and 20407003).
文摘The surface of an up-conversion luminescence material was modified by overcoating with SiOa, which was synthesized from a hydrolysis progress of telraethoxysilane （TEOS） in alkalescent condition. By analyzing the hydrolyzed mechanism of TEOS, it was found that there was not only physical adsorption but also chemical bonding between the up-conversion material and SiO2. At the same time, some adsorption bands at 1100, 475, 950, and 3500 cm^-1 were found by FI-IR, which were the characteristic bands of Si-OH and Si-O-Si. By analyzing the surface elements of the coated material by XPS, it was found that its surface only included Si, O, and C elements, and not F and Y. In the picture of XRD, there was no additional peak after surface modification, suggesting that the silica shell was amorphous. The small peak at 20 = 23° in the X-ray diffraction pattern of the coated material was caused by the amorphous SiO2 shell, and the TEM image also proved that the surface of the material was successfully modified by overcoating with SiO2. The amount of hydroxyls was then increased on the surface of the material, which made it easy to connect with other active groups.
基金supported by the National Natural Science Foundation of China (No. 20877008)the Program for New Century Excellent Telents in University of the Ministry of Education of China (No. 20407003)
文摘Baotou RE concentrate was decomposed with concentrated sulfuric acid by controlling the roasting temperature below 500℃.Thermogravimetry-differential thermal analysis（TG-DTA） and chemical analytical methods were used to study the thermal decomposition process and the thermal decomposition effect.The Freeman-Carroll method was applied to analyze the TG-DTA curves.The activation energy, reaction order, and reaction frequency factor at different stages were calculated.The Satava method was used to deduce the reaction mechanism and the relative reaction rate during the thermal decomposition process.
