Chemical vapor deposition is the predominant method to prepare MgAl_(2)O_(4)fibers.However,it faces several challenges,including exorbitantly high reaction temperatures,substantial production costs,and relatively low ...Chemical vapor deposition is the predominant method to prepare MgAl_(2)O_(4)fibers.However,it faces several challenges,including exorbitantly high reaction temperatures,substantial production costs,and relatively low yields.In this study,porous MgAl_(2)O_(4)fibers were fabricated through a solid-state reaction method,utilizing MgSO_(4)·5Mg(OH)_(2)·3H_(2)O whiskers as templates,mixed with either aluminum sol orα-Al_(2)O_(3)micropowder.The impact of various parameters on the synthesis of porous MgAl_(2)O_(4)fibres was systematically investigated,including the heat treatment temperature(1000,1100 and 1300℃),the holding time(3 and 10 h)and the aluminum source(aluminum sol orα-Al_(2)O_(3)micropowder).The results reveal that:(1)in comparison with fibers synthesized usingα-Al_(2)O_(3)as the aluminum source,those prepared with aluminum sol exhibit a significantly higher generation amount of MgAl_(2)O_(4);(2)as the heat treatment temperature increases,Al_(2)O_(3)gradually reacts with MgO,continuously increasing the formation amount of porous MgAl_(2)O_(4)with small and uniformly distributed nanopores,and the synthesized porous MgAl_(2)O_(4)fibres have small and uniform nanopores;(3)the optimal synthesis process involves using aluminum sol as the aluminum source and firing at 1300℃ for 3 h.展开更多
Fluorine-doped TiO2 sol（F-TiO2） was prepared by the modified precipitation-sol-hydrothermal crystallization method with TiCl4 as precursor.The influences of F doping, temperature and time of hydrothermal crystalliza...Fluorine-doped TiO2 sol（F-TiO2） was prepared by the modified precipitation-sol-hydrothermal crystallization method with TiCl4 as precursor.The influences of F doping, temperature and time of hydrothermal crystallization, medium pH value on the morphology and crystallization were studied.The particle size and structure of the prepared F-TiO2 sol as well as the interaction of F with TiO2 were characterized with XRD, UV-Vis-DRS, TEM, TG-DTA, FTIR and XPS.The results showed that F-TiO2 particles in sol were spherical, and partly crystallized to anatase.They were dispersed in the aqueous medium uniformly and showed narrow particle size distribution.The average particle size was 6.5 nm as calculated from XRD and TEM results.It was also shown that fluorine atoms were adsorbed by TiO2 sol particles in two forms.One was physically adsorbed on the surface of TiO2, and the other was embedded into TiO2 crystal lattice.It was found that the addition of fluorine could improve the crystallization of particle significantly, decrease the temperature and shorten the time of hydrothermal crystallization.The adsorption capacity, surface acidity and the photocatalytic activity for decomposition of Rhodamine B were enhanced remarkably with the doping of fluorine.The mechanism of improvement of the photocatalytic activity and structure of TiO2 by fluorine was discussed.展开更多
文摘Chemical vapor deposition is the predominant method to prepare MgAl_(2)O_(4)fibers.However,it faces several challenges,including exorbitantly high reaction temperatures,substantial production costs,and relatively low yields.In this study,porous MgAl_(2)O_(4)fibers were fabricated through a solid-state reaction method,utilizing MgSO_(4)·5Mg(OH)_(2)·3H_(2)O whiskers as templates,mixed with either aluminum sol orα-Al_(2)O_(3)micropowder.The impact of various parameters on the synthesis of porous MgAl_(2)O_(4)fibres was systematically investigated,including the heat treatment temperature(1000,1100 and 1300℃),the holding time(3 and 10 h)and the aluminum source(aluminum sol orα-Al_(2)O_(3)micropowder).The results reveal that:(1)in comparison with fibers synthesized usingα-Al_(2)O_(3)as the aluminum source,those prepared with aluminum sol exhibit a significantly higher generation amount of MgAl_(2)O_(4);(2)as the heat treatment temperature increases,Al_(2)O_(3)gradually reacts with MgO,continuously increasing the formation amount of porous MgAl_(2)O_(4)with small and uniformly distributed nanopores,and the synthesized porous MgAl_(2)O_(4)fibres have small and uniform nanopores;(3)the optimal synthesis process involves using aluminum sol as the aluminum source and firing at 1300℃ for 3 h.
文摘Fluorine-doped TiO2 sol（F-TiO2） was prepared by the modified precipitation-sol-hydrothermal crystallization method with TiCl4 as precursor.The influences of F doping, temperature and time of hydrothermal crystallization, medium pH value on the morphology and crystallization were studied.The particle size and structure of the prepared F-TiO2 sol as well as the interaction of F with TiO2 were characterized with XRD, UV-Vis-DRS, TEM, TG-DTA, FTIR and XPS.The results showed that F-TiO2 particles in sol were spherical, and partly crystallized to anatase.They were dispersed in the aqueous medium uniformly and showed narrow particle size distribution.The average particle size was 6.5 nm as calculated from XRD and TEM results.It was also shown that fluorine atoms were adsorbed by TiO2 sol particles in two forms.One was physically adsorbed on the surface of TiO2, and the other was embedded into TiO2 crystal lattice.It was found that the addition of fluorine could improve the crystallization of particle significantly, decrease the temperature and shorten the time of hydrothermal crystallization.The adsorption capacity, surface acidity and the photocatalytic activity for decomposition of Rhodamine B were enhanced remarkably with the doping of fluorine.The mechanism of improvement of the photocatalytic activity and structure of TiO2 by fluorine was discussed.
