Cu-Fe composite oxides were prepared by co-precipitation method and tested for higher alcohol synthesis from syngas. The selectivity to C2＋OH and C6＋OH in alcohol distribution was very high while the methane product...Cu-Fe composite oxides were prepared by co-precipitation method and tested for higher alcohol synthesis from syngas. The selectivity to C2＋OH and C6＋OH in alcohol distribution was very high while the methane product fraction in hydrocarbon distribution was rather low, demonstrating a promising potential in higher alcohols synthesis from syngas. The distribution of alcohols and hydrocarbons approximately obeyed Anderson-Schulz-Flory distribution with similar chain growth probability, indicating alcohols and hydrocarbons derived from the same intermediates. The effects of Cu/Fe molar ratio, reaction temperature and gas hourly space velocity （GHSV） on catalytic performance were studied in detail. The sample with a Cu/Fe molar ratio of 10/1 exhibited the best catalytic performance. Higher reaction temperature accelerated water-gas-shift reaction and led to lower total alcohols selectivity. GHSV showed great effect on catalytic performance and higher GHSV increased the total alcohol selectivity, indicating there existed visible dehydration reaction of alcohol into hydrocarbon.展开更多
The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the low-cost urea route, and the effects of preparation temperatures, molar ratios of the raw materials and oxidation treatment on the composi...The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the low-cost urea route, and the effects of preparation temperatures, molar ratios of the raw materials and oxidation treatment on the composition, structure and surface morphology of the products were investigated through FT-IR, XRD and SEM. The results show that the products ceramize and crystallize gradually with the increase of the temperature. When the molar ratio and reaction temperature are 3：2 and 850 ℃, respectively, the products have high purity, compact structure and nice shape. The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitride but effectively remove the impurities.展开更多
The effect of B2O3 dopant and SrTiO3 (ST) content on lattice parameters and ferro-paraelectric phase transition temperature (i.e. Curie point) of Ba1-xSrxTiO3 (BST, x=0～0.4) ceramics was investigated, and then BST gr...The effect of B2O3 dopant and SrTiO3 (ST) content on lattice parameters and ferro-paraelectric phase transition temperature (i.e. Curie point) of Ba1-xSrxTiO3 (BST, x=0～0.4) ceramics was investigated, and then BST graded ceramics with controllable transition temperature zone were fabricated and characterized for their dielectric properties. The results show that with the increase of ST content, c/a ratio and Curie point of both doped and undoped ceramics decreased linearly but with different rate of change, resulting from different ionic radiuses of Ba2+, Sr2+ and B3+. Moreover, both c/a ratio and Curie point of doped BST increased slightly in comparison with that of undoped ones while the Curie point changed scarcely with dopant amount rising, which perhaps means that for BST grains with different ST content, B2O3 solubility was different but limited and most of boron (B) did not incorporate into BST grains. Through controlling composition,transition temperature of graded ceramics can be designed. For doped graded ceramics sintered at 1250℃, its dielectric properties was much better than that of undoped one sintered at 1400℃, and Curie peak of both samples was broadened effectively via graded structure.展开更多
The improved properties of CdTe nanocrystals （NCs） synthesized by hydrothermal method were introduced. The experimental results indicated that the NCs properties could be dramatically influenced by means of changing...The improved properties of CdTe nanocrystals （NCs） synthesized by hydrothermal method were introduced. The experimental results indicated that the NCs properties could be dramatically influenced by means of changing Cd-to-Te molar ratio （the molar ratio of CdC12 and NaHTe in the precursor） of the MPA-capped CdTe NCs. With the increase of the ratio from 2 ： 1 to 10 ： 1, the formation time of near-infrared-emitting CdTe NCs was shortened. In particular, high Cd-to-Te molar ratio brought about MPA-capped CdTe NCs of superior radical oxidation-resis- tance and photostability. As a result, the optimum ratio was found to be 8 ： 1 or 10 ： 1 in the study in order to efficiently attain stable, water-dispersed CdTe NCs.展开更多
基金the State Key Fundamental Research Program(Ministry of Science and Technology of China,No.2011CBA00501)Shanghai Municipal Science and Technology Commission,China(Grant No:11DZ1200300)the Foundation of State Key Laboratory of Coal Conversion(Grant No:1112610)
文摘Cu-Fe composite oxides were prepared by co-precipitation method and tested for higher alcohol synthesis from syngas. The selectivity to C2＋OH and C6＋OH in alcohol distribution was very high while the methane product fraction in hydrocarbon distribution was rather low, demonstrating a promising potential in higher alcohols synthesis from syngas. The distribution of alcohols and hydrocarbons approximately obeyed Anderson-Schulz-Flory distribution with similar chain growth probability, indicating alcohols and hydrocarbons derived from the same intermediates. The effects of Cu/Fe molar ratio, reaction temperature and gas hourly space velocity （GHSV） on catalytic performance were studied in detail. The sample with a Cu/Fe molar ratio of 10/1 exhibited the best catalytic performance. Higher reaction temperature accelerated water-gas-shift reaction and led to lower total alcohols selectivity. GHSV showed great effect on catalytic performance and higher GHSV increased the total alcohol selectivity, indicating there existed visible dehydration reaction of alcohol into hydrocarbon.
基金Funded by the National Natural Science Foundation of China (Nos.50902150 & 90916019)the Graduate Innovation Foundation of the National University of Defense Technology(No.S100103)
文摘The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the low-cost urea route, and the effects of preparation temperatures, molar ratios of the raw materials and oxidation treatment on the composition, structure and surface morphology of the products were investigated through FT-IR, XRD and SEM. The results show that the products ceramize and crystallize gradually with the increase of the temperature. When the molar ratio and reaction temperature are 3：2 and 850 ℃, respectively, the products have high purity, compact structure and nice shape. The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitride but effectively remove the impurities.
文摘The effect of B2O3 dopant and SrTiO3 (ST) content on lattice parameters and ferro-paraelectric phase transition temperature (i.e. Curie point) of Ba1-xSrxTiO3 (BST, x=0～0.4) ceramics was investigated, and then BST graded ceramics with controllable transition temperature zone were fabricated and characterized for their dielectric properties. The results show that with the increase of ST content, c/a ratio and Curie point of both doped and undoped ceramics decreased linearly but with different rate of change, resulting from different ionic radiuses of Ba2+, Sr2+ and B3+. Moreover, both c/a ratio and Curie point of doped BST increased slightly in comparison with that of undoped ones while the Curie point changed scarcely with dopant amount rising, which perhaps means that for BST grains with different ST content, B2O3 solubility was different but limited and most of boron (B) did not incorporate into BST grains. Through controlling composition,transition temperature of graded ceramics can be designed. For doped graded ceramics sintered at 1250℃, its dielectric properties was much better than that of undoped one sintered at 1400℃, and Curie peak of both samples was broadened effectively via graded structure.
文摘The improved properties of CdTe nanocrystals （NCs） synthesized by hydrothermal method were introduced. The experimental results indicated that the NCs properties could be dramatically influenced by means of changing Cd-to-Te molar ratio （the molar ratio of CdC12 and NaHTe in the precursor） of the MPA-capped CdTe NCs. With the increase of the ratio from 2 ： 1 to 10 ： 1, the formation time of near-infrared-emitting CdTe NCs was shortened. In particular, high Cd-to-Te molar ratio brought about MPA-capped CdTe NCs of superior radical oxidation-resis- tance and photostability. As a result, the optimum ratio was found to be 8 ： 1 or 10 ： 1 in the study in order to efficiently attain stable, water-dispersed CdTe NCs.
