High pressure synthesis of solid material tends to increase the density, coordination number, symmetry of material and shorten bond length. The solid synthesized at a high pressure and decompressed to ambient pressure...High pressure synthesis of solid material tends to increase the density, coordination number, symmetry of material and shorten bond length. The solid synthesized at a high pressure and decompressed to ambient pressure often exhibits a meta- stable "stretched" state, within the high pressure stability field. The crystal grown at a high pressure is of great importance with the development of high pressure technology. Crystal growth is an important factor in the material synthesis. And many me- thods including gas, solid and solution methods have been used to obtain various single crystalstl]. Especially, flux method is an important method for crystal growth, where the components of the desired substance dissolved in a solvent(flux) grow in the process of deposit.展开更多
Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of ...Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of the hexagonal phase of La(OH)3, indicating that the hydration process is very rapid. The as-prepared La(OH)3 is almost entirely with a needle- or rod-like shape with a width of 2 - 3 μm and a length of 5 - 8 μm. The mechanism of the formation of La(OH)3 with rod-like morphology was preliminarily presented. It is easier to expand the simple hydration process on a large scale than the hydrothermal process.展开更多
Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_(x)(OH)_(y)),and deposite...Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_(x)(OH)_(y)),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaO_(x)(OH)_(y) catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaO_(x)(OH)_(y).Furthermore,the as-formed lanthanum carbonate(La_(2)O_(2)CO_(3)) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O_(2),severely impair the reactivity of Pt/LaO_(x)(OH)_(y).On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized P_(t)O_(x) atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity.展开更多
Using the hydrothermal method, lanthanum hydroxide nanorods were synthesized by the reaction of LaC13·7H20, ethyl- enediamine, and hydrazine. According to SEM results, ethylenediamine and hydrazine with pH manage...Using the hydrothermal method, lanthanum hydroxide nanorods were synthesized by the reaction of LaC13·7H20, ethyl- enediamine, and hydrazine. According to SEM results, ethylenediamine and hydrazine with pH management could control the parti- cle growth and played an important role in formation of lanthanum hydroxide nanorods. The morphology and microstructure of the obtained products were characterized by X-ray diffraction (XRD) spectra, energy-dispersive X-ray spectroscopy (EDX), Fourier transformed infi'ared (FTIR) spectrum, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Further- more, the effects of the molar ratio of the precursors as well as the reaction temperature and time on the morphology and particle size of the products were investigated.展开更多
基金Supported by the National Natural Science Foundation of China(No.21271082) and the Development of Science and Tech- nology Plan of Jilin Province, China(No.20110341).
文摘High pressure synthesis of solid material tends to increase the density, coordination number, symmetry of material and shorten bond length. The solid synthesized at a high pressure and decompressed to ambient pressure often exhibits a meta- stable "stretched" state, within the high pressure stability field. The crystal grown at a high pressure is of great importance with the development of high pressure technology. Crystal growth is an important factor in the material synthesis. And many me- thods including gas, solid and solution methods have been used to obtain various single crystalstl]. Especially, flux method is an important method for crystal growth, where the components of the desired substance dissolved in a solvent(flux) grow in the process of deposit.
基金Project supported bythe National Natural Science Foundation of China (20161002) ,the Natural Science Foundation of JiangxiProvince (0220004) and the Education Department of Jiangxi Province
文摘Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of the hexagonal phase of La(OH)3, indicating that the hydration process is very rapid. The as-prepared La(OH)3 is almost entirely with a needle- or rod-like shape with a width of 2 - 3 μm and a length of 5 - 8 μm. The mechanism of the formation of La(OH)3 with rod-like morphology was preliminarily presented. It is easier to expand the simple hydration process on a large scale than the hydrothermal process.
基金Project supported by the National Natural Science Foundation of China(21773288)National Key Basic Research Program of China(2017YFA0403402)。
文摘Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_(x)(OH)_(y)),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaO_(x)(OH)_(y) catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaO_(x)(OH)_(y).Furthermore,the as-formed lanthanum carbonate(La_(2)O_(2)CO_(3)) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O_(2),severely impair the reactivity of Pt/LaO_(x)(OH)_(y).On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized P_(t)O_(x) atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity.
基金the council of University of Kashan for their unending effort to provide financial support to undertake this work (159271/284)
文摘Using the hydrothermal method, lanthanum hydroxide nanorods were synthesized by the reaction of LaC13·7H20, ethyl- enediamine, and hydrazine. According to SEM results, ethylenediamine and hydrazine with pH management could control the parti- cle growth and played an important role in formation of lanthanum hydroxide nanorods. The morphology and microstructure of the obtained products were characterized by X-ray diffraction (XRD) spectra, energy-dispersive X-ray spectroscopy (EDX), Fourier transformed infi'ared (FTIR) spectrum, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Further- more, the effects of the molar ratio of the precursors as well as the reaction temperature and time on the morphology and particle size of the products were investigated.
基金This work was supported by the National Basic Research Program of China (973 Project,No.2013CB932901),and the National Natural Science Foundation of China (Nos.11274066,51172047,51102050,amd U1330118).This project was sponsored by Shanghai Pujiang Program and 'Shu Guang' project of Shanghai Municipal Education Commission and Shanghai Education Development Foundation (No.09SG01).