Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scann...Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.展开更多
The evolution of the surface oxide film along the depth direction of typical aluminum alloy under mediumtemperature brazing was investigated by means of X-ray photoelectron spectroscopy(XPS). For the alloy with Mg con...The evolution of the surface oxide film along the depth direction of typical aluminum alloy under mediumtemperature brazing was investigated by means of X-ray photoelectron spectroscopy(XPS). For the alloy with Mg content below 2.0wt%, whether under cold rolling condition or during medium-temperature brazing process, the enrichment of Mg element on the surface was not detected and the oxide film was pure Al2O3. However, the oxide film grew obviously during medium-temperature brazing process, and the thickness was about 80 nm. For the alloy with Mg content above 2.0wt%, under cold rolling condition, the original surface oxide film was pure Al2O3. However, the Mg element was significantly enriched on the outermost surface during medium-temperature brazing process, and MgO-based oxide film mixed with small amount of MgAl2O4 was formed with a thickness of about 130 nm. The alloying elements of Mn and Si were not enriched on the surface neither under cold rolling condition nor during mediumtemperature brazing process for all the selected aluminum alloy, and the surface oxide film was similar to that of pure aluminum, which was almost entire Al2O3.展开更多
Ammonium aluminum carbonate hydroxide（AACH）, the precursor of α-Al2O3, was fabricated with NH4Al（SO4）2 and NH4HCO3 via a precipitation method. During the heat treatment AACH undergoes such a phase transformation ...Ammonium aluminum carbonate hydroxide（AACH）, the precursor of α-Al2O3, was fabricated with NH4Al（SO4）2 and NH4HCO3 via a precipitation method. During the heat treatment AACH undergoes such a phase transformation process: amorphous（350℃）→γ（700℃）→γ+θ（1050℃）→θ+α （1100℃）→α （1200℃）. Oxides, such as TiO2 sol and MgO sol were introduced into the precursor. Then both the α transformation temperature and the particle sizes of α-Al2O3 are decreased. The microstructures and its surface electronic properties of the powders are modified, and its dispersion property is improved. Doping TiO2 sol grains, AACH completes α phase transformation nearly at 1100℃, its first-order diameter is about 120nm. Doping with MgO sol grains, α phase transformation completes after being sintered at 1100℃.展开更多
In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of...In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of mefenamic acid prior to quantification by UV detection at λmax ？ 286 nm. Extraction procedure is based on the adsorption of mefenamate anions on the Ni-Al（NO3？ ） LDH and/or their exchange with LDH interlayer NO3？ anions. The effects of several parameters such as cations and interlayer anions type in LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent and co-existing ions on the extraction were investigated and optimized. Under the optimum conditions, the calibration graph was linear within the range of 2-1000 mg/L with a correlation coefficient of 0.9995. The limit of detection and relative standard deviation were 0.6 mg/L and 0.84% （30 mg/L, n ？ 6）, respectively. The presented method was successfully applied to determine of mefenamic acid in human serum and pharmaceutical wastewater samples.展开更多
The mechanical properties of aluminum alloy treated by plasma microarc oxidation (PMAO) were researched. The tensile tests were carried out at room temperature, 100, 200 and 300℃, respectively. Then the fractograph...The mechanical properties of aluminum alloy treated by plasma microarc oxidation (PMAO) were researched. The tensile tests were carried out at room temperature, 100, 200 and 300℃, respectively. Then the fractographs of tensile specimens and surface morphology of ceramic coating were studied by using SEM, at the same time, the nano-hardness and elastic modulus of the ceramic coating were determined using Nano Indenter XP system. The results show that the surface hardness of aluminum alloy increases greatly and the fracture strength of aluminum alloy coated by ceramic coating is not reduced at high temperature.展开更多
A new nano-assembly approach has been proposed for the preparation of macropore volume mesoporous aluminum oxide supports. Secondary nano-assembly and a frame structure mechanism for large pore volume mesoporous suppo...A new nano-assembly approach has been proposed for the preparation of macropore volume mesoporous aluminum oxide supports. Secondary nano-assembly and a frame structure mechanism for large pore volume mesoporous supports have been proposed. In a primary nano-assembly supersoluble micelle,aluminum hydroxide nanoparticles were precipitated in situ in surfactants with a volume balance (VB) less than 1,followed by secondary nano-assembly in linear and cylindrical shapes. The secondary nano-assembly of cylindrical aluminum hydroxides was calcined to form nano cylindrical aluminum oxides. For the formation of macropore volume mesoporous supports,we utilized a frame structure mechanism of mesoporous support,in which the exterior surface of the carrier may not be continuous. This macropore volume support has been used for the hydrotreatment of a residual oil catalyst,which possesses the following physical characteristics:pore volume 1.8―2.7 mL·g-1,specific surface area 180―429 m2·g-1,average pore diameter 17―57 nm,average pore diameter more than 10 nm (81%―94%),porosity 87%―93%,and crush strength 7.7―25 N·mm-1.展开更多
Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbo...Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system抯 pH value played an important role in this experiment. The growth rate is 12 nm/h with the deposition at [Al2(SO4)3]=0.0837 molL-1, [NaHCO3]=0.214 molL-1, 15 ℃. Post-growth annealing not only densifies and purifies the films, but results in film crystallization as well. Excellent quality of Al2O3 films in this work is supported by electron dispersion spectroscopy, Fourier transform infrared spectrum, X-ray diffraction spectrum and scanning electron microscopy photograph.展开更多
Studying liquid phase nanoscale dynamic processes of oxide nanoparticles is of considerable interest to a wide variety of fields.Recently developed liquid phase transmission electron microscopy(LP-TEM)is a promising t...Studying liquid phase nanoscale dynamic processes of oxide nanoparticles is of considerable interest to a wide variety of fields.Recently developed liquid phase transmission electron microscopy(LP-TEM)is a promising technique,but destabilization of oxides by solid-liquid?electron interactions remains an important challenge.In this work we present a methodology to assess LP-TEM oxide stability in an aqueous phase,by subjecti ng several oxides of tech no logical importa nee to a controlled electr on dose in water.We show a correlati on based on the Gibbs free en ergy of oxide hydrati on that can be used to assess the stability of oxides and dem on strate the existenee of several remarkably stable oxides,with no observable structural changes after one hour of electron beam irradiation in LP-TEM.Rationalizing such destabilization phenomena combined with the identification of stable oxides allows for designing LP-TEM experiments free from adverse beam effects and thus in vestigati ons of numerous releva ntnano scale processes in water.展开更多
A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back laye...A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back layer,was fabricated from a replica molding process.Anodic aluminum oxide(AAO)template was used as the replica mold to be replicated to the polymethylmethacrylate layer by a thermal infiltration process under a vacuum condition.Results indicate that PMMA/PDMS soft templates with different sizes could be easily fabricated from the as-prepared AAO replica mold.The PMMA/PDMS soft templates were then employed to imprint a TiO_2 gel for achieving TiO_2 nano-pore arrays.After the imprinting process,the PDMS layer was firstly peeled off and the PMMA layer was then removed into acetonitrile,which can avoid any demolding problems like damages or distortions.The TiO_2 nano-pore arrays with the crystalline of anatase could be obtained at a heat treatment temperature of 450°C.展开更多
文摘Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and potentiodynamic polarization methods. It has been found that by increasing the acetic acid/CeCl3·7H2O molar ratio, high uniform and crack-free films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.
基金Supported by National Natural Science Foundation of China(No.51005163 and No.51275351)Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China
文摘The evolution of the surface oxide film along the depth direction of typical aluminum alloy under mediumtemperature brazing was investigated by means of X-ray photoelectron spectroscopy(XPS). For the alloy with Mg content below 2.0wt%, whether under cold rolling condition or during medium-temperature brazing process, the enrichment of Mg element on the surface was not detected and the oxide film was pure Al2O3. However, the oxide film grew obviously during medium-temperature brazing process, and the thickness was about 80 nm. For the alloy with Mg content above 2.0wt%, under cold rolling condition, the original surface oxide film was pure Al2O3. However, the Mg element was significantly enriched on the outermost surface during medium-temperature brazing process, and MgO-based oxide film mixed with small amount of MgAl2O4 was formed with a thickness of about 130 nm. The alloying elements of Mn and Si were not enriched on the surface neither under cold rolling condition nor during mediumtemperature brazing process for all the selected aluminum alloy, and the surface oxide film was similar to that of pure aluminum, which was almost entire Al2O3.
文摘Ammonium aluminum carbonate hydroxide（AACH）, the precursor of α-Al2O3, was fabricated with NH4Al（SO4）2 and NH4HCO3 via a precipitation method. During the heat treatment AACH undergoes such a phase transformation process: amorphous（350℃）→γ（700℃）→γ+θ（1050℃）→θ+α （1100℃）→α （1200℃）. Oxides, such as TiO2 sol and MgO sol were introduced into the precursor. Then both the α transformation temperature and the particle sizes of α-Al2O3 are decreased. The microstructures and its surface electronic properties of the powders are modified, and its dispersion property is improved. Doping TiO2 sol grains, AACH completes α phase transformation nearly at 1100℃, its first-order diameter is about 120nm. Doping with MgO sol grains, α phase transformation completes after being sintered at 1100℃.
基金support from the Research Council of Azarbaijan Shahid Madani University (ASMU,Iran)
文摘In this work, the nickel-aluminum layered double hydroxide （Ni-Al LDH） with nitrate interlayer anion was synthesized and used as a solid phase extraction sorbent for the selective separation and pre-concentration of mefenamic acid prior to quantification by UV detection at λmax ？ 286 nm. Extraction procedure is based on the adsorption of mefenamate anions on the Ni-Al（NO3？ ） LDH and/or their exchange with LDH interlayer NO3？ anions. The effects of several parameters such as cations and interlayer anions type in LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent and co-existing ions on the extraction were investigated and optimized. Under the optimum conditions, the calibration graph was linear within the range of 2-1000 mg/L with a correlation coefficient of 0.9995. The limit of detection and relative standard deviation were 0.6 mg/L and 0.84% （30 mg/L, n ？ 6）, respectively. The presented method was successfully applied to determine of mefenamic acid in human serum and pharmaceutical wastewater samples.
文摘The mechanical properties of aluminum alloy treated by plasma microarc oxidation (PMAO) were researched. The tensile tests were carried out at room temperature, 100, 200 and 300℃, respectively. Then the fractographs of tensile specimens and surface morphology of ceramic coating were studied by using SEM, at the same time, the nano-hardness and elastic modulus of the ceramic coating were determined using Nano Indenter XP system. The results show that the surface hardness of aluminum alloy increases greatly and the fracture strength of aluminum alloy coated by ceramic coating is not reduced at high temperature.
文摘A new nano-assembly approach has been proposed for the preparation of macropore volume mesoporous aluminum oxide supports. Secondary nano-assembly and a frame structure mechanism for large pore volume mesoporous supports have been proposed. In a primary nano-assembly supersoluble micelle,aluminum hydroxide nanoparticles were precipitated in situ in surfactants with a volume balance (VB) less than 1,followed by secondary nano-assembly in linear and cylindrical shapes. The secondary nano-assembly of cylindrical aluminum hydroxides was calcined to form nano cylindrical aluminum oxides. For the formation of macropore volume mesoporous supports,we utilized a frame structure mechanism of mesoporous support,in which the exterior surface of the carrier may not be continuous. This macropore volume support has been used for the hydrotreatment of a residual oil catalyst,which possesses the following physical characteristics:pore volume 1.8―2.7 mL·g-1,specific surface area 180―429 m2·g-1,average pore diameter 17―57 nm,average pore diameter more than 10 nm (81%―94%),porosity 87%―93%,and crush strength 7.7―25 N·mm-1.
文摘Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system抯 pH value played an important role in this experiment. The growth rate is 12 nm/h with the deposition at [Al2(SO4)3]=0.0837 molL-1, [NaHCO3]=0.214 molL-1, 15 ℃. Post-growth annealing not only densifies and purifies the films, but results in film crystallization as well. Excellent quality of Al2O3 films in this work is supported by electron dispersion spectroscopy, Fourier transform infrared spectrum, X-ray diffraction spectrum and scanning electron microscopy photograph.
文摘Studying liquid phase nanoscale dynamic processes of oxide nanoparticles is of considerable interest to a wide variety of fields.Recently developed liquid phase transmission electron microscopy(LP-TEM)is a promising technique,but destabilization of oxides by solid-liquid?electron interactions remains an important challenge.In this work we present a methodology to assess LP-TEM oxide stability in an aqueous phase,by subjecti ng several oxides of tech no logical importa nee to a controlled electr on dose in water.We show a correlati on based on the Gibbs free en ergy of oxide hydrati on that can be used to assess the stability of oxides and dem on strate the existenee of several remarkably stable oxides,with no observable structural changes after one hour of electron beam irradiation in LP-TEM.Rationalizing such destabilization phenomena combined with the identification of stable oxides allows for designing LP-TEM experiments free from adverse beam effects and thus in vestigati ons of numerous releva ntnano scale processes in water.
基金supported by the Ministry of Science and Technology of China through 863-project under grant 2009AA03Z218the Major Program of the National Natural Science Foundation of China under Grant No.90923012the Research Fund for the Doctoral Program of Higher Education of China under grant 200806980023
文摘A novel soft polymer template containing a double-layer structure,which includes a thin layer of polymethylmethacrylate(PMMA)used as a pattern layer and a thicker layer of polydimethylsiloxane(PDMS)used as a back layer,was fabricated from a replica molding process.Anodic aluminum oxide(AAO)template was used as the replica mold to be replicated to the polymethylmethacrylate layer by a thermal infiltration process under a vacuum condition.Results indicate that PMMA/PDMS soft templates with different sizes could be easily fabricated from the as-prepared AAO replica mold.The PMMA/PDMS soft templates were then employed to imprint a TiO_2 gel for achieving TiO_2 nano-pore arrays.After the imprinting process,the PDMS layer was firstly peeled off and the PMMA layer was then removed into acetonitrile,which can avoid any demolding problems like damages or distortions.The TiO_2 nano-pore arrays with the crystalline of anatase could be obtained at a heat treatment temperature of 450°C.
