Uniform nanosized NiO particles were prepared by a chedrical coprecipitation usingNiCl2.6H2O as the starting material. The relationship between various annealing telnperaturesand grain size of NiO crystallite was inve...Uniform nanosized NiO particles were prepared by a chedrical coprecipitation usingNiCl2.6H2O as the starting material. The relationship between various annealing telnperaturesand grain size of NiO crystallite was investigated. Optical reflectivity spectra of Nanometer-sizedNiO powders at roonl temperature were studied. The results show that seven optical absorptionbands (P1. P2. P3. P4. P5. P6 and P7) with the peak energies of 3.30, 2.99, 2.78, 2.25,1.92, 1.72 and 1.07eV, respectively, are located on a continuous refiectivity background. P1.P2. P3 and P4 exhibit "blue shift", but P5. P6 and P7 present "red shift"in comparison withthat of single crystal NiO. The continuous reflectivity background increases rapidly with increasingthe annealing temperature from 500℃ to 600℃ to 700℃. The origins of P1 to P7 and thereasons of "blue shift", "red shift" and the increase of the reflectivity background with increasingthe annealing temperature have been analyzed in detail.展开更多
As catalytic materials, nanometer rare earth perovskites LaMnO3 were prepared by NaOH-Na2CO3 coprecipitation, followed by supercritical drying, vacuum drying and air drying respectively. The effect of drying processes...As catalytic materials, nanometer rare earth perovskites LaMnO3 were prepared by NaOH-Na2CO3 coprecipitation, followed by supercritical drying, vacuum drying and air drying respectively. The effect of drying processes was studied on the catalyst performance through XRD, TEM, SEM and BET analysis. The results demonstrated that about 30 nm LaMnO3 particles could be prepared by three drying processes respectively. The catalyst materials LaMnO3 dried in vacuum presented the largest specific surface area as 28.71 m2·g－ 1. Compared to the catalyst prepared by dipping cordierite directly in the salt solutions, nanometer LaMnO3 showed better catalytic activity. The light-off temperatures for CO and HC oxidation were both lowered by 100℃ , and its NOx conversion could be up to 100％ at 570℃ .展开更多
文摘Uniform nanosized NiO particles were prepared by a chedrical coprecipitation usingNiCl2.6H2O as the starting material. The relationship between various annealing telnperaturesand grain size of NiO crystallite was investigated. Optical reflectivity spectra of Nanometer-sizedNiO powders at roonl temperature were studied. The results show that seven optical absorptionbands (P1. P2. P3. P4. P5. P6 and P7) with the peak energies of 3.30, 2.99, 2.78, 2.25,1.92, 1.72 and 1.07eV, respectively, are located on a continuous refiectivity background. P1.P2. P3 and P4 exhibit "blue shift", but P5. P6 and P7 present "red shift"in comparison withthat of single crystal NiO. The continuous reflectivity background increases rapidly with increasingthe annealing temperature from 500℃ to 600℃ to 700℃. The origins of P1 to P7 and thereasons of "blue shift", "red shift" and the increase of the reflectivity background with increasingthe annealing temperature have been analyzed in detail.
文摘As catalytic materials, nanometer rare earth perovskites LaMnO3 were prepared by NaOH-Na2CO3 coprecipitation, followed by supercritical drying, vacuum drying and air drying respectively. The effect of drying processes was studied on the catalyst performance through XRD, TEM, SEM and BET analysis. The results demonstrated that about 30 nm LaMnO3 particles could be prepared by three drying processes respectively. The catalyst materials LaMnO3 dried in vacuum presented the largest specific surface area as 28.71 m2·g－ 1. Compared to the catalyst prepared by dipping cordierite directly in the salt solutions, nanometer LaMnO3 showed better catalytic activity. The light-off temperatures for CO and HC oxidation were both lowered by 100℃ , and its NOx conversion could be up to 100％ at 570℃ .
