The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and t...The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.展开更多
The surface properties of superfine alumina trihydrate （ATH） after surface modification were studied by measuring the contact angle, active ratio, oil adsorption, total organic carbon, adsorption ratio, and Fourier ...The surface properties of superfine alumina trihydrate （ATH） after surface modification were studied by measuring the contact angle, active ratio, oil adsorption, total organic carbon, adsorption ratio, and Fourier transform infrared （FTIR） spectrum. The contact angle increased initially and then slowly decreased with an increase of the amount of stearic acid. However, the surface flee energy decreased ini- tially and then increased. Surface modification with stearic acid or sodium stearate can benefit from elevating temperature. The base surface tension component and the free energy of Lewis acid-base both declined sharply following the surface modification. Excess stearic acid was physically adsorbed in the form of multilayer adsorption, and an interaction between oxygen on the ATH surface and hydroxyl in stearic acid was subsequently determined. Our results further indicated that the contact angle and adsorption ratio can be used as control indicators for surface modification compared with active ratio, oil adsorption and total organic carbon.展开更多
Pyrochlore-type WO3 powder was synthesized via hydrothermal method using aqueous sodium tungstate solution and oxalic acid as raw materials. The as-prepared powder was made into a soliquoid, from which films were made...Pyrochlore-type WO3 powder was synthesized via hydrothermal method using aqueous sodium tungstate solution and oxalic acid as raw materials. The as-prepared powder was made into a soliquoid, from which films were made by dip coating process with indium-tin oxide （ITO）. The obtained films were characterized by thermogravimetric and differential thermal analysis （TG-DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, cyclic voltammetry （CV）, chronoamperometry （CA） and ultraviolet- visible （UV-Vis） absorption. Results show that the crystal of the pyrochlore-type WO3 powder is perfect. When the calcination temperature rises from room temperature to 500℃, the pyrochlore-type structure first becomes deformed, then it is destroyed and turns into amorphous phase, finally it will completely convert to WO3 with a monoclinic structure. Electrochemical and optical tests demonstrate that the film calcined at 300℃ exhibits the best electrochromic performance and has a coloration efficiency of up to 68.5 cm^2-C^-1 at 884 nm.展开更多
基金Project(51604309)supported by the National Natural Science Foundation of ChinaProject(201509048)supported by the Environmental Protection’s Special Scientific Research for Chinese Public Welfare IndustryProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
基金Project(2019M652799)supported by China Postdoctoral Science FoundationProject(51604309)supported by the National Natural Science Foundation of China。
基金Project(51374239)supported by the National Natural Science Foundation of ChinaProject(201509048)supported by Environmental Protection’s Special Scientific Research for Chinese Public Welfare IndustryProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
基金Project(51274243)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan in Central South University,China
基金financially supported by the National Natural Science Foundation of China (No.51274242)the Fundamental Research Funds for the Central Universities of Central South University (No.2016zzts038)
文摘The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.
基金Project(51274242) supported by the National Natural Science Foundation of ChinaProject(2015CX001) supported by the Innovation-driven Plan of Central South University,China
基金financially supported by the National Natural Science Foundation of China (No. 51274242)
文摘The surface properties of superfine alumina trihydrate （ATH） after surface modification were studied by measuring the contact angle, active ratio, oil adsorption, total organic carbon, adsorption ratio, and Fourier transform infrared （FTIR） spectrum. The contact angle increased initially and then slowly decreased with an increase of the amount of stearic acid. However, the surface flee energy decreased ini- tially and then increased. Surface modification with stearic acid or sodium stearate can benefit from elevating temperature. The base surface tension component and the free energy of Lewis acid-base both declined sharply following the surface modification. Excess stearic acid was physically adsorbed in the form of multilayer adsorption, and an interaction between oxygen on the ATH surface and hydroxyl in stearic acid was subsequently determined. Our results further indicated that the contact angle and adsorption ratio can be used as control indicators for surface modification compared with active ratio, oil adsorption and total organic carbon.
基金Project(2015BAB04B01)supported by the National Key Technology Research&Development Program of ChinaProject(CSUZC201811)supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
基金Project(51274243)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan of Central South University,China
基金financially supported by the National Natural Science Foundation of China (No. 51274243)the Project of Innovation-Driven Plan in Central South University, China (No. 2015CX001)
文摘Pyrochlore-type WO3 powder was synthesized via hydrothermal method using aqueous sodium tungstate solution and oxalic acid as raw materials. The as-prepared powder was made into a soliquoid, from which films were made by dip coating process with indium-tin oxide （ITO）. The obtained films were characterized by thermogravimetric and differential thermal analysis （TG-DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, cyclic voltammetry （CV）, chronoamperometry （CA） and ultraviolet- visible （UV-Vis） absorption. Results show that the crystal of the pyrochlore-type WO3 powder is perfect. When the calcination temperature rises from room temperature to 500℃, the pyrochlore-type structure first becomes deformed, then it is destroyed and turns into amorphous phase, finally it will completely convert to WO3 with a monoclinic structure. Electrochemical and optical tests demonstrate that the film calcined at 300℃ exhibits the best electrochromic performance and has a coloration efficiency of up to 68.5 cm^2-C^-1 at 884 nm.
