Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the n...Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.展开更多
In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing...In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing time , and so on . The best conditions in this research are : the concentration of Na2SiO3 and organic matters are 4. 50% and 26.4% respectively, pH = 3.3 , T = 65℃ , ageing time is 30min , dried at 150 ℃ , the size of SiC precursors is about 2.0μm .展开更多
In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests a...In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests also lie in the feasibility for controlling the average grain size of the final structure in the submicron range on an ab initio basis.Purposely,Fourier transform infrared spectroscopy（FT-IR）,Raman（Stokes and Anti-Stokes）,X-ray diffraction（XRD） and scanning electron microscopy（SEM） are used to examine the microstructural characteristics based on previously reported differential thermal analysis/thermal gravimetric analysis（DTA/TGA） data.The results show a crystallization temperature of 800℃ to attain pure perovskite phase with excellent morphological quality,average grain size 〈DG〉〈 300 nm and with average crystallite size 〈DC〉〈15 nm.展开更多
Complex ZrO2-Y2O3 sol were prepared from precursors of inorganic salts and metal alkoxides. The processes for complex ZrO2-Y2O3 sol preparation and purification, the sol-gel transformation and the characterization of ...Complex ZrO2-Y2O3 sol were prepared from precursors of inorganic salts and metal alkoxides. The processes for complex ZrO2-Y2O3 sol preparation and purification, the sol-gel transformation and the characterization of the sol from the two kinds of precursors were discussed and compared. It was found that the colloidal particles were amorphous in nature, and extremely fine (<10nm) in the both cases. ZrO2-Y2O3 coatings on GH220 superalloy samples MCrAlX (M=Fe, Co, Ni, X=Y, Ta,Hf…) pre-coated) were prepared using sols from the two different processes and tested at 1000 ℃ for 100 h in laboratory air. Results showed that only the coatings from the metal alkoxides derived sol offered excellent oxidation resistance.展开更多
Nd∶GGG ultrafine polycrystalline powders for transparent ceramics precursor powder were synthesized by sol-gel method, and sol-gel transformation mechanics was discussed. Nd∶GGG polycrystalline material was analyzed...Nd∶GGG ultrafine polycrystalline powders for transparent ceramics precursor powder were synthesized by sol-gel method, and sol-gel transformation mechanics was discussed. Nd∶GGG polycrystalline material was analyzed by XRD, SEM and fluorescence spectrum. XRD analysis shows that Nd∶GGG polycrystalline phase is formed at 1000 ℃, and the grain size increases with rising sintering temperature by SEM, and the particle size is about 100 nm. They are used as transparent ceramics precursor powder. Fluorescence spectrum test shows that the strongest fluorescence emission peak is 1061.45 nm for the Nd∶GGG polycrystalline precursor powder, which is the fluorescence-emission of Nd 3+ 4F_ 3/2—4I_ 11/2.展开更多
基金supported by the Open Foundation of Key Laboratory of the Ministry of Educationof Nonferrous Metal Alloys and Processes(No.EKL09002)The Ph.D.Fund Project of Lanzhou University of Science and Technology(No.BS01200904)
文摘Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.
文摘In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing time , and so on . The best conditions in this research are : the concentration of Na2SiO3 and organic matters are 4. 50% and 26.4% respectively, pH = 3.3 , T = 65℃ , ageing time is 30min , dried at 150 ℃ , the size of SiC precursors is about 2.0μm .
基金support provided by the CCADET-UNAM Schol-arship Programme
文摘In this work,we intend to perform a detailed study on the crystallization process of PZT 53/47 nanostructured powders by starting out with an amorphous precursor synthesized by a sol-gel based solution.Our interests also lie in the feasibility for controlling the average grain size of the final structure in the submicron range on an ab initio basis.Purposely,Fourier transform infrared spectroscopy（FT-IR）,Raman（Stokes and Anti-Stokes）,X-ray diffraction（XRD） and scanning electron microscopy（SEM） are used to examine the microstructural characteristics based on previously reported differential thermal analysis/thermal gravimetric analysis（DTA/TGA） data.The results show a crystallization temperature of 800℃ to attain pure perovskite phase with excellent morphological quality,average grain size 〈DG〉〈 300 nm and with average crystallite size 〈DC〉〈15 nm.
文摘Complex ZrO2-Y2O3 sol were prepared from precursors of inorganic salts and metal alkoxides. The processes for complex ZrO2-Y2O3 sol preparation and purification, the sol-gel transformation and the characterization of the sol from the two kinds of precursors were discussed and compared. It was found that the colloidal particles were amorphous in nature, and extremely fine (<10nm) in the both cases. ZrO2-Y2O3 coatings on GH220 superalloy samples MCrAlX (M=Fe, Co, Ni, X=Y, Ta,Hf…) pre-coated) were prepared using sols from the two different processes and tested at 1000 ℃ for 100 h in laboratory air. Results showed that only the coatings from the metal alkoxides derived sol offered excellent oxidation resistance.
文摘Nd∶GGG ultrafine polycrystalline powders for transparent ceramics precursor powder were synthesized by sol-gel method, and sol-gel transformation mechanics was discussed. Nd∶GGG polycrystalline material was analyzed by XRD, SEM and fluorescence spectrum. XRD analysis shows that Nd∶GGG polycrystalline phase is formed at 1000 ℃, and the grain size increases with rising sintering temperature by SEM, and the particle size is about 100 nm. They are used as transparent ceramics precursor powder. Fluorescence spectrum test shows that the strongest fluorescence emission peak is 1061.45 nm for the Nd∶GGG polycrystalline precursor powder, which is the fluorescence-emission of Nd 3+ 4F_ 3/2—4I_ 11/2.
