Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to...Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to CDs are atomically imprecise and their molecular weight distribution is broad.In this paper,a series of Pluronic-modified CDs were prepared and the structure of the CDs was briefly analyzed.Subsequently,a molecular weight measurement method based on colligative properties was developed,and the correction coefficient in the algorithm was briefly analyzed.The calculated molecular weight was applied to the determination of surface adsorption capacity.This work provided a method for averaging the molecular weight of atomically imprecise particulate materials,which is expected to provide new opportunities in related fields.展开更多
The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and inte...The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and interaction forces of cationic surfactants at solid-solution interfaces were measured in tapping mode and Pico Force mode, respectively. The images demonstrated that the adsorbed structure was varied by a variety of surfactant concentrations. The adsorbed layer on mica was monolayer at first, and then became bilayer. A striped adsorbed structure was observed in a higher concentration of CTAC,which could not be found in any other concentrations of DTAC. For force measurements, the repulsive force was exponentially decreasing with the concentration increasing till a net attractive force appeared. A largest attractive force could be observed at a certain concentration, which was close to the point of charge neutralization. The results also showed a significant impact of hydrocarbon chain length on adsorption. An adsorption simulation was established to give a clear understanding of the interaction between cationic surfactants and mica.展开更多
The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the stru...The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al-O and Si-O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition.展开更多
The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure...The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure and chemical composition of FeAI nanoparticles were investigated by transmission electron microscopy （TEM）, high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure （B2） as the bulk FeA1. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAI nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization （Ms） of FeA1 is 1.66 A/m2, and the coercivity is about 1.214×10^3 A/re.展开更多
A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials....A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials. The physiochemical properties of the synthesized samples were investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), X-ray diffractometry(XRD), and scanning electronic microscopy(SEM). The results show that the hydrothermally synthesized precursor is an essential amorphous. The precursor can be easily transferred to spinel powders with a homogeneous structure and a regularly-shaped morphology by heat treatment. Li1.05Mn1.95O4 powder obtained by heat treating the precursor at 430 °C for 12 h and then calcining at 800 °C for 12 h shows an excellent cycling performance with an initial charge capacity of 118.2 mA·h·g-1 obtained at 0.5C rate and 93.8% of its original value retained after 100 cycles.展开更多
文摘Since the discovery of carbon dots(CDs)in 2004,the unique photoluminescence phenomenon of CDs has attracted widespread attention.However,the molecular weight of CDs has not been adequately quantified at present,due to CDs are atomically imprecise and their molecular weight distribution is broad.In this paper,a series of Pluronic-modified CDs were prepared and the structure of the CDs was briefly analyzed.Subsequently,a molecular weight measurement method based on colligative properties was developed,and the correction coefficient in the algorithm was briefly analyzed.The calculated molecular weight was applied to the determination of surface adsorption capacity.This work provided a method for averaging the molecular weight of atomically imprecise particulate materials,which is expected to provide new opportunities in related fields.
基金Project(50974134)supported by the National Natural Science Foundation of China
文摘The adsorption of dedecyltrimethylammoium chloride(DTAC) and hexadecyltrimethylammoium chloride(CTAC) on muscovite mica substrates was examined using atomic force microscopy(AFM). Adsorption morphology images and interaction forces of cationic surfactants at solid-solution interfaces were measured in tapping mode and Pico Force mode, respectively. The images demonstrated that the adsorbed structure was varied by a variety of surfactant concentrations. The adsorbed layer on mica was monolayer at first, and then became bilayer. A striped adsorbed structure was observed in a higher concentration of CTAC,which could not be found in any other concentrations of DTAC. For force measurements, the repulsive force was exponentially decreasing with the concentration increasing till a net attractive force appeared. A largest attractive force could be observed at a certain concentration, which was close to the point of charge neutralization. The results also showed a significant impact of hydrocarbon chain length on adsorption. An adsorption simulation was established to give a clear understanding of the interaction between cationic surfactants and mica.
基金Project(2005CB623701) supported by the Major State Basic Research and Development Program of ChinaProject(50874118) supported by the National Nature Science Foundation of ChinaProject(2007B52) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China
文摘The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al-O and Si-O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition.
基金Project(10804101) supported by the National Natural Science Foundation of China
文摘The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure and chemical composition of FeAI nanoparticles were investigated by transmission electron microscopy （TEM）, high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure （B2） as the bulk FeA1. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAI nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization （Ms） of FeA1 is 1.66 A/m2, and the coercivity is about 1.214×10^3 A/re.
基金Project(50174058)supported by the National Natural Science Foundation of ChinaProject(2011A025)supported by the Glorious Laurel Scholar Program of Guangxi Zhuang Autonomous Region,China
文摘A simple hydrothermal process followed by heat treatment was applied to the preparation of spinel Li1.05Mn1.95O4. In this process, electrolytic manganese dioxide(EMD) and LiOH·H2O were used as starting materials. The physiochemical properties of the synthesized samples were investigated by thermogravimetry-differential scanning calorimetry(TG-DSC), X-ray diffractometry(XRD), and scanning electronic microscopy(SEM). The results show that the hydrothermally synthesized precursor is an essential amorphous. The precursor can be easily transferred to spinel powders with a homogeneous structure and a regularly-shaped morphology by heat treatment. Li1.05Mn1.95O4 powder obtained by heat treating the precursor at 430 °C for 12 h and then calcining at 800 °C for 12 h shows an excellent cycling performance with an initial charge capacity of 118.2 mA·h·g-1 obtained at 0.5C rate and 93.8% of its original value retained after 100 cycles.
