Fine spherical particle sized ceria (CeO_2) was prepared by homogeneous precipitation method with ammonium bicarbonate as precipitant. The prepared CeO_2 has the primary particle size of 10～50 nm when calcined betwee...Fine spherical particle sized ceria (CeO_2) was prepared by homogeneous precipitation method with ammonium bicarbonate as precipitant. The prepared CeO_2 has the primary particle size of 10～50 nm when calcined between 400～700 ℃ analyzed by XRD and the aggregated particle size is about 300 nm measured by LASER particle sizer. SEM, TG-DTA and Zeta-potential analyzer were employed individually to study the morphology and the formation of CeO_2 product. It was found that excess NH_4NO_3 can serve as an sphericallization agent to prepare spherical CeO_2 powder by precipitation method.展开更多
The surface properties of PAN-based carbon fibers electrochemically treated in aqueous ammonium bicarbonate before and after treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microsc...The surface properties of PAN-based carbon fibers electrochemically treated in aqueous ammonium bicarbonate before and after treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Dynamic Contact Angle Analysis (DCAA). The results of characterization indicated that the oxygen and nitrogen contents in carbon fiber surface were significantly increased by electrochemical treatment, and amide groups was introduced onto it, which was related with the electrolyte. The AFM photographs illustrated that the roughness of the fiber surface was also increased. The wettibality of the fibers was improved after treatment because the surface energy especially the polar part of it was increased.展开更多
In this work, the removal of SO2 from gas mixture with air and SO2 by ammonium bicarbonate aqueous solution as absorbent was investigated experi- mentally in a bubble column reactor. The effects of the concentration o...In this work, the removal of SO2 from gas mixture with air and SO2 by ammonium bicarbonate aqueous solution as absorbent was investigated experi- mentally in a bubble column reactor. The effects of the concentration of ammonium bicarbonate, the SO2 inlet concentration of gas phase and the gas flow rate on the removal rate of SO2 were studied. The results showed that the higher the SO2 inlet concentration and the gas flow rate, the shorter the lasting time of SO2 completely removed in gas outlet, and then the faster the decrease in the removal rate of SO2. The lasting time of SO2 completely removed in gas outlet increased with increasing ammonium bicarbonate concentration. During the process of SO2 absorption, there was a critical pH of solution. When the solution pH was less than the critical pH, it would sharply fall, resulting in a rapid decrease of the SO2 removal rate. A theoretical model for predicting the SO2 removal rate has been developed by taking the chemical enhancement and the sulfite concentration in the liquid phase into account simultaneously.展开更多
A new protocol for the synthesis of nearly monodisperse gold nanoparticles with controllable size is described. The pathway is based on the reduction of AuCl4 by ammonium bicarbonate in the presence of sodium stearate...A new protocol for the synthesis of nearly monodisperse gold nanoparticles with controllable size is described. The pathway is based on the reduction of AuCl4 by ammonium bicarbonate in the presence of sodium stearate under hydrothermal conditions. The particle sizes could be easily tuned by regulating the reaction conditions including precursor concentration, reaction temperature and growth time. A tentative explanation for the reduction and growth mechanism of uniform gold nanoparticles has been proposed. The as-prepared gold particles showed good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol by excess NaBH4, and a surface-enhanced Raman scattering （SERS） study suggested that the gold nanoparticles exhibited a high SERS effect on the probe molecule Rhodamine 6G.展开更多
The relationships of crystal type, crystallization speed, purity, grain size and shape of rare earth carbonate with precipitation and crystallization conditions are very important for the production of rare earth carb...The relationships of crystal type, crystallization speed, purity, grain size and shape of rare earth carbonate with precipitation and crystallization conditions are very important for the production of rare earth carbonate with high efficiency, high quality and low cost. It is necessary for us for further understand the crystallization process mechanism and the factors effect on the crystallization. In the present paper, the crystallization characteristic, composition and crystal phase type of yttrium carbonates or ammonium yttrium carbonates precipitated from yttrium chloride solution using ammonium bicarbonate as precipitant were determined by chemical analysis, X ray powder diffraction and the pH situ determination. It was found that the crystal phase type was dominated by the feed molar ratio of ammonium bicarbonate to yttrium chloride, and the crystallization speed and the crystal composition were also influenced by temperature, feed manner and aging period etc. When precipitating and aging under lower temperature, crystallization is easy to take place in the high feed molar ratio zone, and when increasing temperature, crystallization will take place both in lower and higher feed molar ratio zones. The results show that spherical yttrium carbonate with tengerite type crystal phase can be formed within the temperature 30～70℃ when feed molar ratio of ammonium bicarbonate to yttrium chloride is less than 4, and that a rhombus flake crystal, which possesses the composition of ammonium yttrium quasi double carbonate and a new XRD pattern, is formed when the feed molar ratio is over 4. Their compositions can be represented as (NH4)aY(CO3)b(OH)c·nH2O, a< 1, 1< b< 2, c=3+a-2b. A fine crystal of ammonium yttrium double carbonate with the formula of (NH4)Y(CO3)2·H2O can also be obtained as using an enough amount of ammonium bicarbonate and aging enough time.展开更多
基金Project supported by Rare Earth Department of National Development Committee Preparation of High Quality Polishing Powder
文摘Fine spherical particle sized ceria (CeO_2) was prepared by homogeneous precipitation method with ammonium bicarbonate as precipitant. The prepared CeO_2 has the primary particle size of 10～50 nm when calcined between 400～700 ℃ analyzed by XRD and the aggregated particle size is about 300 nm measured by LASER particle sizer. SEM, TG-DTA and Zeta-potential analyzer were employed individually to study the morphology and the formation of CeO_2 product. It was found that excess NH_4NO_3 can serve as an sphericallization agent to prepare spherical CeO_2 powder by precipitation method.
基金Sponsored by the Scientific Research Foundation of Harbin Institute of Technology(Grant No. HIT. 2003.57)
文摘The surface properties of PAN-based carbon fibers electrochemically treated in aqueous ammonium bicarbonate before and after treatment were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Dynamic Contact Angle Analysis (DCAA). The results of characterization indicated that the oxygen and nitrogen contents in carbon fiber surface were significantly increased by electrochemical treatment, and amide groups was introduced onto it, which was related with the electrolyte. The AFM photographs illustrated that the roughness of the fiber surface was also increased. The wettibality of the fibers was improved after treatment because the surface energy especially the polar part of it was increased.
文摘In this work, the removal of SO2 from gas mixture with air and SO2 by ammonium bicarbonate aqueous solution as absorbent was investigated experi- mentally in a bubble column reactor. The effects of the concentration of ammonium bicarbonate, the SO2 inlet concentration of gas phase and the gas flow rate on the removal rate of SO2 were studied. The results showed that the higher the SO2 inlet concentration and the gas flow rate, the shorter the lasting time of SO2 completely removed in gas outlet, and then the faster the decrease in the removal rate of SO2. The lasting time of SO2 completely removed in gas outlet increased with increasing ammonium bicarbonate concentration. During the process of SO2 absorption, there was a critical pH of solution. When the solution pH was less than the critical pH, it would sharply fall, resulting in a rapid decrease of the SO2 removal rate. A theoretical model for predicting the SO2 removal rate has been developed by taking the chemical enhancement and the sulfite concentration in the liquid phase into account simultaneously.
基金We gratefully acknowledge the financial support from the National Natural Science Foundation of China （No. 21071136）, the National Basic Research Program of China （No. 2010CB934700）, the Program for New Century Excellent Talents in Universities from the Chinese Ministry of Education （No. NCET2006-0552）, and the Foundation of Anhui Provincial Education Department （No. KJ2008A071）.
文摘A new protocol for the synthesis of nearly monodisperse gold nanoparticles with controllable size is described. The pathway is based on the reduction of AuCl4 by ammonium bicarbonate in the presence of sodium stearate under hydrothermal conditions. The particle sizes could be easily tuned by regulating the reaction conditions including precursor concentration, reaction temperature and growth time. A tentative explanation for the reduction and growth mechanism of uniform gold nanoparticles has been proposed. The as-prepared gold particles showed good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol by excess NaBH4, and a surface-enhanced Raman scattering （SERS） study suggested that the gold nanoparticles exhibited a high SERS effect on the probe molecule Rhodamine 6G.
文摘The relationships of crystal type, crystallization speed, purity, grain size and shape of rare earth carbonate with precipitation and crystallization conditions are very important for the production of rare earth carbonate with high efficiency, high quality and low cost. It is necessary for us for further understand the crystallization process mechanism and the factors effect on the crystallization. In the present paper, the crystallization characteristic, composition and crystal phase type of yttrium carbonates or ammonium yttrium carbonates precipitated from yttrium chloride solution using ammonium bicarbonate as precipitant were determined by chemical analysis, X ray powder diffraction and the pH situ determination. It was found that the crystal phase type was dominated by the feed molar ratio of ammonium bicarbonate to yttrium chloride, and the crystallization speed and the crystal composition were also influenced by temperature, feed manner and aging period etc. When precipitating and aging under lower temperature, crystallization is easy to take place in the high feed molar ratio zone, and when increasing temperature, crystallization will take place both in lower and higher feed molar ratio zones. The results show that spherical yttrium carbonate with tengerite type crystal phase can be formed within the temperature 30～70℃ when feed molar ratio of ammonium bicarbonate to yttrium chloride is less than 4, and that a rhombus flake crystal, which possesses the composition of ammonium yttrium quasi double carbonate and a new XRD pattern, is formed when the feed molar ratio is over 4. Their compositions can be represented as (NH4)aY(CO3)b(OH)c·nH2O, a< 1, 1< b< 2, c=3+a-2b. A fine crystal of ammonium yttrium double carbonate with the formula of (NH4)Y(CO3)2·H2O can also be obtained as using an enough amount of ammonium bicarbonate and aging enough time.
