Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps a...Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps as the raw materials. According to this method, AACH samples prepared were used to fabricate nano alumina powders by thermal decomposition. The microstructural properties of as-formed alumina were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), special surface analysis and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Experimental observations revealed that highly pure (99.99%) α-alumina with mean diameter of 49 nm could be obtained.展开更多
The enol form of ethyl acetoacetate(EAA)displays interesting spectroscopic characteristics;this form of ethyl acetylacetate is very important in condensation reaction.In this investigation,we have studied the interact...The enol form of ethyl acetoacetate(EAA)displays interesting spectroscopic characteristics;this form of ethyl acetylacetate is very important in condensation reaction.In this investigation,we have studied the interactions and the complex formation constants(K_(f))with nano alumina(10–20 nm)particle and alumina(mesh 135)compounds as Lewis acids in the acetonitrile solvent using absorption spectroscopy and related calculations.Furthermore,in this study we calculated the thermodynamic parameters of this reaction.The trend of reactivity of the ethyl acetoacetate(EAA)complexes toward the above Lewis acids,based on the solvent as follows:nano alumina compound>alumina compound.展开更多
A general procedure for surface modification of nano-alumina using N, N＇-dicyclohexyl- carbodiimide （DCC） mediated amidation is reported. Aliphatic and aromatic carboxylic acids reacted smoothly with nano-alumina p...A general procedure for surface modification of nano-alumina using N, N＇-dicyclohexyl- carbodiimide （DCC） mediated amidation is reported. Aliphatic and aromatic carboxylic acids reacted smoothly with nano-alumina pretreated with 3-aminopropyltriethoxysilane in the presence of DCC, giving modified aluminas having organic surfaces. The grafted aluminas have been characterized qualitatively by FT-IR or ^13C CPMAS NMR spectroscopy, and quantitatively by thermogravimetric analysis and elemental analysis. The procedure was applied to polyether dendrons bearing carboxyl groups at the focal points, giving successful grafting of dendrimers onto nano-alumina.展开更多
Cobalt supported on carbon nanotubes （CNTs）-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis （FTS）. Problems associated with shaping of Co/CNTs into ...Cobalt supported on carbon nanotubes （CNTs）-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis （FTS）. Problems associated with shaping of Co/CNTs into extrudates or pellets as well as catalyst attrition rendered these materials unfavorable for industrial applications. In this investigation regular γ- and nano-structured （N-S） alumina as well as CNTs-covered regular γ- and N-S-alumina supports were impregnated by cobalt nitrate solution to make new cobalt-based catalysts which were also promoted by Ru. The catalysts were characterized and tested in a micro reactor to evaluate their applicability in FTS. γ-Al2O3 was prepared by calcination of bohemite and N-S-Al2O3 was prepared by sol-gel method using aluminum chloride as starting material. Catalyst evaluations indicated that N-S-Al2O3 was superior to regular γ-Al2O3 and that CNTs-covered alumina supports were favored over non-covered ones in terms of activity and heavy hydrocarbon selectivity. These were justified by porosimetric characteristics of the catalysts and existence of CNTs points of view. CNTs-covered catalysts also showed higher wax selectivity and better resistance to deactivation. Furthermore, TPR analysis indicated that the cobalt aluminate phase, which is responsible for the permanent deactivation of alumina supported Co-based catalysts, did not form on alumina supported Co-based catalysts covered with CNTs due to weaker interactions between cobalt and alumina.展开更多
The role of nano-SiO 2 and ultra-fine boron carbide on the properties of alumina-graphite materials was investigated. The study showed that the ultra-fine boron carbide added modified the microstructure of residual c...The role of nano-SiO 2 and ultra-fine boron carbide on the properties of alumina-graphite materials was investigated. The study showed that the ultra-fine boron carbide added modified the microstructure of residual carbon and promoted the chemical bond between residual carbon from phenolic resin and flake graphite. The carbon white could strengthen the residual carbon from phenolic resin. These two additives improved the mechanical properties of AG refractories at both room temperature and high temperature, and thermal shock resistance was improved noticeably. When the two additives were doped together, carbon white could retard the evaporation of B 2O 3. Thermal shock resistance was guaranteed with a smaller amount of ultra-fine boron carbide.展开更多
The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5%...The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5% ZnO as sunscreen to cut the cost of SiO2 nanoporous insulation board. The hot volume stability and thermal conductivity （flat plate method ） of the specimens were tested and multi-Jimetion simulation equipment was used to study the thermal insulation performante. The results show that： （1） with high alumina fiber addition increasing, the linear shrinkage rate decreases, but thermal eonductivity changes a little; （2） adding ZnO can decrease thermal conductivity obviously; （3）for the specimen with ZnO and 15% of high alumina fiber, its cold face temperature hardly rises during the simulation experiment at 1 000 ℃ for 2 h, and the cold face temperature of the specimen with the smallest thickness of 2 cm doesn＇t exceed 180 ℃.展开更多
Nanosheet(S) and nanoplate(P) γ-Al_2O_3 were synthesized by simple hydrothermal methods and employed as supports for Ni catalysts in CO_2 methanation.Both of the nanostructured Ni/Al_2O_3 catalysts displayed good act...Nanosheet(S) and nanoplate(P) γ-Al_2O_3 were synthesized by simple hydrothermal methods and employed as supports for Ni catalysts in CO_2 methanation.Both of the nanostructured Ni/Al_2O_3 catalysts displayed good activity.In comparison,the Ni/Al_2O_3-S catalyst showed higher CO_2 conversion than the Ni/Al_2O_3-P counterpart at the reaction temperature ranging from 250 to 400 °C.The physical and chemical properties of the catalysts were systematically characterized by N2 sorption,X-ray diffraction(XRD),high resolution-transmission electron microscopy(HR-TEM),hydrogen temperature-programmed reduction(H2-TPR) and CO_2 temperature-programmed desorption(CO_2-TPD) techniques.Higher specific surface area and stronger metal-support interactions were confirmed on the Ni/Al_2O_3-S catalyst,which may lead to smaller particle size of Ni nanoparticles.Moreover,the Ni/Al_2O_3-S catalyst possessed more abundant weak and medium basic sites,which would benefit the activation of CO_2.The smaller Ni size and more suitable basic sites may rationalize the superior activity of the Ni/Al_2O_3-S catalyst.Besides,the Ni/Al_2O_3-S catalyst exhibited excellent stability at 325 °C for 40 h.展开更多
Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubst...Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubstit,ting for Al203 micropowder. After m＆ing and ;haping, the bricks were fired at 1 550 ℃, 1 600 91℃, t 650 ℃ and 1 750℃, respectively. The microstruc-ure , sintering property, mechanical properties, thermal ;kock resistance and shtg resistance of the specimens with he addition of nano-Al2O3 were investigated. The results indicate that the performance of brick with 4 mass% of nano-Al2O3 is greatly improred afier firing at 1 650 ℃.展开更多
In order to reduce the sintering temperature and improve the properties of sintered corundum,corundum specimens were prepared by granulation and sintering with nano-η-A l203 as the raw material and polyvinyl alcohol ...In order to reduce the sintering temperature and improve the properties of sintered corundum,corundum specimens were prepared by granulation and sintering with nano-η-A l203 as the raw material and polyvinyl alcohol as the binder.The effects of different sintering temperatures(1550,1600,1650 and 1700℃)and holding time(2,4 and 6 h)on the properties and microstructures of the specimens were studied,and the transformation mechanism ofη-Al203 was analyzed.The results show that dense sintered corundum with bulk density of 3.74 g/cm^3 and apparent porosity of 1.77%is obtained by calcinating at 1650℃for 6 h;the phase transition fromη-Al203 toα-Al203 occurs first on the surface of alumina particles and then diffuses rapidly to the interior;at lower sintering temperatures there is no abnormal growth of crystals,the bonding between the grains is tight,transgranular fracture is the main fracture mode,there are fewer intergranular pores,and the grain size is in the range of 3.5-7.5μm.展开更多
基金the National Natural Science Foundation of China (NSFC 20503015)
文摘Ammonium aluminum carbonate hydroxide (AACH) was synthesized by the reaction of ammonium aluminum sulphate (AA) with ammonium hydrogen carbonate (AHC). AA was obtained by the reaction of NH4HSO4 with aluminum scraps as the raw materials. According to this method, AACH samples prepared were used to fabricate nano alumina powders by thermal decomposition. The microstructural properties of as-formed alumina were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), special surface analysis and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Experimental observations revealed that highly pure (99.99%) α-alumina with mean diameter of 49 nm could be obtained.
文摘The enol form of ethyl acetoacetate(EAA)displays interesting spectroscopic characteristics;this form of ethyl acetylacetate is very important in condensation reaction.In this investigation,we have studied the interactions and the complex formation constants(K_(f))with nano alumina(10–20 nm)particle and alumina(mesh 135)compounds as Lewis acids in the acetonitrile solvent using absorption spectroscopy and related calculations.Furthermore,in this study we calculated the thermodynamic parameters of this reaction.The trend of reactivity of the ethyl acetoacetate(EAA)complexes toward the above Lewis acids,based on the solvent as follows:nano alumina compound>alumina compound.
文摘A general procedure for surface modification of nano-alumina using N, N＇-dicyclohexyl- carbodiimide （DCC） mediated amidation is reported. Aliphatic and aromatic carboxylic acids reacted smoothly with nano-alumina pretreated with 3-aminopropyltriethoxysilane in the presence of DCC, giving modified aluminas having organic surfaces. The grafted aluminas have been characterized qualitatively by FT-IR or ^13C CPMAS NMR spectroscopy, and quantitatively by thermogravimetric analysis and elemental analysis. The procedure was applied to polyether dendrons bearing carboxyl groups at the focal points, giving successful grafting of dendrimers onto nano-alumina.
基金supported by the Research and Technology Directorate of National Iranian Oil Company
文摘Cobalt supported on carbon nanotubes （CNTs）-covered alumina has been recently developed and successfully utilized as a catalyst in Fischer-Tropsch synthesis （FTS）. Problems associated with shaping of Co/CNTs into extrudates or pellets as well as catalyst attrition rendered these materials unfavorable for industrial applications. In this investigation regular γ- and nano-structured （N-S） alumina as well as CNTs-covered regular γ- and N-S-alumina supports were impregnated by cobalt nitrate solution to make new cobalt-based catalysts which were also promoted by Ru. The catalysts were characterized and tested in a micro reactor to evaluate their applicability in FTS. γ-Al2O3 was prepared by calcination of bohemite and N-S-Al2O3 was prepared by sol-gel method using aluminum chloride as starting material. Catalyst evaluations indicated that N-S-Al2O3 was superior to regular γ-Al2O3 and that CNTs-covered alumina supports were favored over non-covered ones in terms of activity and heavy hydrocarbon selectivity. These were justified by porosimetric characteristics of the catalysts and existence of CNTs points of view. CNTs-covered catalysts also showed higher wax selectivity and better resistance to deactivation. Furthermore, TPR analysis indicated that the cobalt aluminate phase, which is responsible for the permanent deactivation of alumina supported Co-based catalysts, did not form on alumina supported Co-based catalysts covered with CNTs due to weaker interactions between cobalt and alumina.
文摘The role of nano-SiO 2 and ultra-fine boron carbide on the properties of alumina-graphite materials was investigated. The study showed that the ultra-fine boron carbide added modified the microstructure of residual carbon and promoted the chemical bond between residual carbon from phenolic resin and flake graphite. The carbon white could strengthen the residual carbon from phenolic resin. These two additives improved the mechanical properties of AG refractories at both room temperature and high temperature, and thermal shock resistance was improved noticeably. When the two additives were doped together, carbon white could retard the evaporation of B 2O 3. Thermal shock resistance was guaranteed with a smaller amount of ultra-fine boron carbide.
基金support of the National Natural Science Foundation of China(No.51402265,51202225,and 51272240)
文摘The specimens were prepared with high alumina fiber accounting for 0. 5% , 10% or 15% by mass of the total amount of amorphous silica and high alumina fiber, using phenolic resin as binder, and extra-adding 0 or 0. 5% ZnO as sunscreen to cut the cost of SiO2 nanoporous insulation board. The hot volume stability and thermal conductivity （flat plate method ） of the specimens were tested and multi-Jimetion simulation equipment was used to study the thermal insulation performante. The results show that： （1） with high alumina fiber addition increasing, the linear shrinkage rate decreases, but thermal eonductivity changes a little; （2） adding ZnO can decrease thermal conductivity obviously; （3）for the specimen with ZnO and 15% of high alumina fiber, its cold face temperature hardly rises during the simulation experiment at 1 000 ℃ for 2 h, and the cold face temperature of the specimen with the smallest thickness of 2 cm doesn＇t exceed 180 ℃.
基金financially supported by the National Natural Science Foundation of China (Nos.21776007,21403012,21473185,U1532117)the Fundamental Research Funds for the Central Universities (No.buctrc201311)
文摘Nanosheet(S) and nanoplate(P) γ-Al_2O_3 were synthesized by simple hydrothermal methods and employed as supports for Ni catalysts in CO_2 methanation.Both of the nanostructured Ni/Al_2O_3 catalysts displayed good activity.In comparison,the Ni/Al_2O_3-S catalyst showed higher CO_2 conversion than the Ni/Al_2O_3-P counterpart at the reaction temperature ranging from 250 to 400 °C.The physical and chemical properties of the catalysts were systematically characterized by N2 sorption,X-ray diffraction(XRD),high resolution-transmission electron microscopy(HR-TEM),hydrogen temperature-programmed reduction(H2-TPR) and CO_2 temperature-programmed desorption(CO_2-TPD) techniques.Higher specific surface area and stronger metal-support interactions were confirmed on the Ni/Al_2O_3-S catalyst,which may lead to smaller particle size of Ni nanoparticles.Moreover,the Ni/Al_2O_3-S catalyst possessed more abundant weak and medium basic sites,which would benefit the activation of CO_2.The smaller Ni size and more suitable basic sites may rationalize the superior activity of the Ni/Al_2O_3-S catalyst.Besides,the Ni/Al_2O_3-S catalyst exhibited excellent stability at 325 °C for 40 h.
文摘Magnesia chrome bricks were prepared with fiLsed MgO- Cr2 O3 synthesized material, fused magnesite and ：hrome ore as main starting materials. Nano-Al2O3 was tdded into refractories （ 2% , 4% and 6% in mass ） ;ubstit,ting for Al203 micropowder. After m＆ing and ;haping, the bricks were fired at 1 550 ℃, 1 600 91℃, t 650 ℃ and 1 750℃, respectively. The microstruc-ure , sintering property, mechanical properties, thermal ;kock resistance and shtg resistance of the specimens with he addition of nano-Al2O3 were investigated. The results indicate that the performance of brick with 4 mass% of nano-Al2O3 is greatly improred afier firing at 1 650 ℃.
文摘In order to reduce the sintering temperature and improve the properties of sintered corundum,corundum specimens were prepared by granulation and sintering with nano-η-A l203 as the raw material and polyvinyl alcohol as the binder.The effects of different sintering temperatures(1550,1600,1650 and 1700℃)and holding time(2,4 and 6 h)on the properties and microstructures of the specimens were studied,and the transformation mechanism ofη-Al203 was analyzed.The results show that dense sintered corundum with bulk density of 3.74 g/cm^3 and apparent porosity of 1.77%is obtained by calcinating at 1650℃for 6 h;the phase transition fromη-Al203 toα-Al203 occurs first on the surface of alumina particles and then diffuses rapidly to the interior;at lower sintering temperatures there is no abnormal growth of crystals,the bonding between the grains is tight,transgranular fracture is the main fracture mode,there are fewer intergranular pores,and the grain size is in the range of 3.5-7.5μm.
