Isothermal and isochronal annealing was conducted to study the thermal stability of the nanocrystalline in the surface layer of Mg alloy AZ91D induced by high-energy shot peening(HESP) .Field emission scanning electro...Isothermal and isochronal annealing was conducted to study the thermal stability of the nanocrystalline in the surface layer of Mg alloy AZ91D induced by high-energy shot peening(HESP) .Field emission scanning electron microscope(FESEM) and X-ray diffractometer were used to characterize the microstructure.Results showed that nanocrystalline produced by HESP on the surface layer of the magnesium alloy AZ91D was 60-70 nm on average.The nanocrystalline could remain stable at about 100℃,and grew up slowly between 100℃ and 200℃.When the annealing temperature reached 300℃,the growth rate of the nanocrystalline increased significantly.The kinetic coefficient n of the nanocrystalline growth was calculated to be 2-3 and the grain growth activation energy Q=39.7 kJ/mol,far less than the self-diffusion activation energy of magnesium atoms in the coarse polycrystalline material.展开更多
Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical inno...Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations.Among them,lubrication plays a significant role in energy saving and in low CO2emission by increasing the fuel efficiency and by prolonging the service life of machines.With the advance of novel synthetic approaches,and nanoscience and technologies,novel lubrication oils and additives and their formulations are being developed to reduce friction and wear,and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication.These technologies create tremendous chances for machines to work more efficiently with low energy consumption.Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment(such as texturing,high-performance nanocomposite coatings,adapting coating),tribology design(solid and liquid lubrication),energy-conserving engine oil and novel lubricants and formula(such as ionic liquids,low S,P content additives)which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission.There is increased demand to replace fossil lubricants by degradable green lubricants.Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships.All these aspects will be also reviewed in the paper.展开更多
Hierarchical tin（Ⅲ） oxide, Sn3O4, nanospheres were synthesized via hydrothermal reaction under strongly acidic ambient conditions. The morphology of Sn3O4 varied with decreasing pH. The prickly SnaO4 nanospheres ch...Hierarchical tin（Ⅲ） oxide, Sn3O4, nanospheres were synthesized via hydrothermal reaction under strongly acidic ambient conditions. The morphology of Sn3O4 varied with decreasing pH. The prickly SnaO4 nanospheres changed into SnaO4 nanospheres covered with single-crystalline nanoplates having a high BET surface area of ca. 55.05 m^2·g^-1 and a band gap of ca. 2.25 eV. Small amounts （0.05 g） of the hierarchical Sn3O4 nanostructures completely decomposed a 30% methyl orange （MO） solution in 100 mL deionized water within 15 min under one sun condition （UV ＋ visible light）. The Sn3O4 photocatalyst exhibited a fast decomposition rate of 1.73 ×10^-1 min^-1, which is a 90.86% enhancement relative to that of the commercially available P25 photocatalyst. The high photocatalytic activity of the hierarchical Sn3O4 nanostructures is attributed to its ability to absorb visible light and its high surface-to-volume ratio.展开更多
Recent work regarding the Layer by Layer （LbL） engineering of poly（lactide-co-glycolide） nanoparticles （PLGA NPs） is reviewed here. The LbL engineering of PLGA NPs is applied as a means of generating advanced dr...Recent work regarding the Layer by Layer （LbL） engineering of poly（lactide-co-glycolide） nanoparticles （PLGA NPs） is reviewed here. The LbL engineering of PLGA NPs is applied as a means of generating advanced drug delivery devices with tailored recognition, protection, cargo and release properties. LbL in combination with covalent chemistry is used to attach PEG and folic acid to control cell uptake and direct it towards cancer cells. LbL coatings composed of chitosan and alginate show low protein interactions and can be used as an alternative to Pegylation. The assembly on top of LbL coatings of lipid layers composed of variable percentages of 1,2-dioleoyl-sn-glycero-3-choline （DOPC） and 1,2-dioleoyl-sn-glycero-3-phospho- L-serine （DOPS） increases NP uptake and directs the NPs towards the endoplasmic reticulum. The antibody anti-TNF-ct is encapsulated forming a complex with alginate that is assembled LbL on top of PLGA NPs. The antibody is released in cell culture following first order kinetics. The release kinetics of encapsulated molecules inside PLGA NPs are studied when the PLGA NPs are coated via LbL with different polyelectrolytes. The intracellular release of encapsulated Doxorubicin is studied in the HepG2 cell line by means of Fluorescence Lifetime Imaging.展开更多
The TiN, TiA1N and TiA1SiN coatings were deposited on H13 hot-worked mold steel by cathodic arc ion plating （CAIP）. The morphologies, phase compositions, and nanoindcntation parameters, such as creep hardness, elast...The TiN, TiA1N and TiA1SiN coatings were deposited on H13 hot-worked mold steel by cathodic arc ion plating （CAIP）. The morphologies, phase compositions, and nanoindcntation parameters, such as creep hardness, elastic modulus and plastic de- formation energy of the coatings were analyzed with field emission scanning electron microscopy （FESEM）, X-ray diffraction （XRD） and nanoindentation testing, respectively, and the test results were compared with equation describing the indentation model. The results show that the TiN, TiA1N and TiAISiN coating surfaces were dense and composed of TiN, TiN ＋ TiA1N, TiN ＋ Si3N4 ＋ TiAIN phases, respectively. There was no spalling or cracking on the indentation surface. The creep hardness of the TiN, TiA1N and TiAISiN coatings was 7.33, 13.5, and 15.2 GPa, respectively; the corresponding hardness measured by nanoindentation was 7.09, 15.6, and 21.7 GPa, respectively; and the corresponding elastic modulus was 201.93, 172.79, and 162.77 GPa, respectively. The contact depth and elastic modulus calculated by the indentation model were close to those of the test results, but the remaining indentation parameters showed discrepancies. The sequence of plastic deformation energy was TiN 〉 TiA1N〉TiAISiN.展开更多
Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystal...Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystals into submicron clusters, coating of these clusters with a silica layer, thermal treatment to remove organic ligands and improve the crystallinity of the clusters, and finally removing silica to expose the mesoporous catalysts. With the help of the silica coating, the clusters not only maintain their small grain size but also keep their mesoporous structure after calcination at high temperatures （with BET surface area as high as 277 m2/g）. The etching of SiO2 also results in the clusters having high dispersity in water. We have been able to identify the optimal calcination temperature to produce TiO2 nanocrystal clusters that possess both high crystallinity and large surface area, and therefore show excellent catalytic efficiency in the decomposition of organic molecules under illumination by UV light. Convenient doping with nitrogen converts these nanocrystal clusters into active photocatalysts in both visible light and natural sunlight. The strategy of forming well-defined mesoporous clusters using nanocrystals promises a versatile and useful method for designing photocatalysts with enhanced activity and stability.展开更多
A stretch-release strategy is proposed to analyze the problem of surface energy-induced stress fields in nanocrystals,which is resolved into a stretch sub-problem and a release sub-problem using the superposition prin...A stretch-release strategy is proposed to analyze the problem of surface energy-induced stress fields in nanocrystals,which is resolved into a stretch sub-problem and a release sub-problem using the superposition principle.The surface effect of silicon nanowires with hexagonal cross-sections is analyzed by the proposed method.The severe stress concentration near the triple junctions of the wire surfaces and the large shear stress on the plane{111}is quantified,which provides a solid mechanical explanation for the kink phenomena in growth transition from direction〈111〉to〈112〉observed in experiments.Different from the conventional view of negligible surface effect for bulk material,we found that there exists a size-independent part of the surface effect on the stress in the order of tens or hundreds of mega Pascal,which corresponds to the stretch-induced biaxial stress in the surface layer and the shape influence of the geometry of nanocrystals.This size-independent part could well explain the size-independent kinking phenomenon during the growth of silicon nanowires.展开更多
文摘Isothermal and isochronal annealing was conducted to study the thermal stability of the nanocrystalline in the surface layer of Mg alloy AZ91D induced by high-energy shot peening(HESP) .Field emission scanning electron microscope(FESEM) and X-ray diffractometer were used to characterize the microstructure.Results showed that nanocrystalline produced by HESP on the surface layer of the magnesium alloy AZ91D was 60-70 nm on average.The nanocrystalline could remain stable at about 100℃,and grew up slowly between 100℃ and 200℃.When the annealing temperature reached 300℃,the growth rate of the nanocrystalline increased significantly.The kinetic coefficient n of the nanocrystalline growth was calculated to be 2-3 and the grain growth activation energy Q=39.7 kJ/mol,far less than the self-diffusion activation energy of magnesium atoms in the coarse polycrystalline material.
基金supported by the National Natural Science Foundation of China(Grant Nos.21125316,50935008,51305428) the"Hundred Talents Program"of CAS
文摘Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations.Among them,lubrication plays a significant role in energy saving and in low CO2emission by increasing the fuel efficiency and by prolonging the service life of machines.With the advance of novel synthetic approaches,and nanoscience and technologies,novel lubrication oils and additives and their formulations are being developed to reduce friction and wear,and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication.These technologies create tremendous chances for machines to work more efficiently with low energy consumption.Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment(such as texturing,high-performance nanocomposite coatings,adapting coating),tribology design(solid and liquid lubrication),energy-conserving engine oil and novel lubricants and formula(such as ionic liquids,low S,P content additives)which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission.There is increased demand to replace fossil lubricants by degradable green lubricants.Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships.All these aspects will be also reviewed in the paper.
文摘Hierarchical tin（Ⅲ） oxide, Sn3O4, nanospheres were synthesized via hydrothermal reaction under strongly acidic ambient conditions. The morphology of Sn3O4 varied with decreasing pH. The prickly SnaO4 nanospheres changed into SnaO4 nanospheres covered with single-crystalline nanoplates having a high BET surface area of ca. 55.05 m^2·g^-1 and a band gap of ca. 2.25 eV. Small amounts （0.05 g） of the hierarchical Sn3O4 nanostructures completely decomposed a 30% methyl orange （MO） solution in 100 mL deionized water within 15 min under one sun condition （UV ＋ visible light）. The Sn3O4 photocatalyst exhibited a fast decomposition rate of 1.73 ×10^-1 min^-1, which is a 90.86% enhancement relative to that of the commercially available P25 photocatalyst. The high photocatalytic activity of the hierarchical Sn3O4 nanostructures is attributed to its ability to absorb visible light and its high surface-to-volume ratio.
基金funded by the Spanish Ministry of Science and Innovation(MAT2010-18995)the Marie Curie project "Transport Studies on Polymer Based Nanodevices and Assemblies for Delivery and Sensing"(TRASNADE) (- FP7 People International Research Staff Exchange Scheme Grant reference:247656)the Marie Curie Project "Design of Novel Polyelectrolyte Multilayer Based Delivery Systems for Therapeutic Antibodies and siRNA" (DeSIRNA) (FP7-People IAPP Grant reference 251646)
文摘Recent work regarding the Layer by Layer （LbL） engineering of poly（lactide-co-glycolide） nanoparticles （PLGA NPs） is reviewed here. The LbL engineering of PLGA NPs is applied as a means of generating advanced drug delivery devices with tailored recognition, protection, cargo and release properties. LbL in combination with covalent chemistry is used to attach PEG and folic acid to control cell uptake and direct it towards cancer cells. LbL coatings composed of chitosan and alginate show low protein interactions and can be used as an alternative to Pegylation. The assembly on top of LbL coatings of lipid layers composed of variable percentages of 1,2-dioleoyl-sn-glycero-3-choline （DOPC） and 1,2-dioleoyl-sn-glycero-3-phospho- L-serine （DOPS） increases NP uptake and directs the NPs towards the endoplasmic reticulum. The antibody anti-TNF-ct is encapsulated forming a complex with alginate that is assembled LbL on top of PLGA NPs. The antibody is released in cell culture following first order kinetics. The release kinetics of encapsulated molecules inside PLGA NPs are studied when the PLGA NPs are coated via LbL with different polyelectrolytes. The intracellular release of encapsulated Doxorubicin is studied in the HepG2 cell line by means of Fluorescence Lifetime Imaging.
基金supported by the Jiangsu Province Science and Technology Support Program(Industry)(Grant No.BE2014818)
文摘The TiN, TiA1N and TiA1SiN coatings were deposited on H13 hot-worked mold steel by cathodic arc ion plating （CAIP）. The morphologies, phase compositions, and nanoindcntation parameters, such as creep hardness, elastic modulus and plastic de- formation energy of the coatings were analyzed with field emission scanning electron microscopy （FESEM）, X-ray diffraction （XRD） and nanoindentation testing, respectively, and the test results were compared with equation describing the indentation model. The results show that the TiN, TiA1N and TiAISiN coating surfaces were dense and composed of TiN, TiN ＋ TiA1N, TiN ＋ Si3N4 ＋ TiAIN phases, respectively. There was no spalling or cracking on the indentation surface. The creep hardness of the TiN, TiA1N and TiAISiN coatings was 7.33, 13.5, and 15.2 GPa, respectively; the corresponding hardness measured by nanoindentation was 7.09, 15.6, and 21.7 GPa, respectively; and the corresponding elastic modulus was 201.93, 172.79, and 162.77 GPa, respectively. The contact depth and elastic modulus calculated by the indentation model were close to those of the test results, but the remaining indentation parameters showed discrepancies. The sequence of plastic deformation energy was TiN 〉 TiA1N〉TiAISiN.
文摘Mesoporous nanocrystal clusters of anatase TiO2 with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO2 nanocrystals into submicron clusters, coating of these clusters with a silica layer, thermal treatment to remove organic ligands and improve the crystallinity of the clusters, and finally removing silica to expose the mesoporous catalysts. With the help of the silica coating, the clusters not only maintain their small grain size but also keep their mesoporous structure after calcination at high temperatures （with BET surface area as high as 277 m2/g）. The etching of SiO2 also results in the clusters having high dispersity in water. We have been able to identify the optimal calcination temperature to produce TiO2 nanocrystal clusters that possess both high crystallinity and large surface area, and therefore show excellent catalytic efficiency in the decomposition of organic molecules under illumination by UV light. Convenient doping with nitrogen converts these nanocrystal clusters into active photocatalysts in both visible light and natural sunlight. The strategy of forming well-defined mesoporous clusters using nanocrystals promises a versatile and useful method for designing photocatalysts with enhanced activity and stability.
基金the National Natural Science Foundation of China(Grant No.11872237)the Natural Science Foundation of Shanghai(Grant No.18ZR1414600)the Challenging Project from China Academy of Engineering Physics.
文摘A stretch-release strategy is proposed to analyze the problem of surface energy-induced stress fields in nanocrystals,which is resolved into a stretch sub-problem and a release sub-problem using the superposition principle.The surface effect of silicon nanowires with hexagonal cross-sections is analyzed by the proposed method.The severe stress concentration near the triple junctions of the wire surfaces and the large shear stress on the plane{111}is quantified,which provides a solid mechanical explanation for the kink phenomena in growth transition from direction〈111〉to〈112〉observed in experiments.Different from the conventional view of negligible surface effect for bulk material,we found that there exists a size-independent part of the surface effect on the stress in the order of tens or hundreds of mega Pascal,which corresponds to the stretch-induced biaxial stress in the surface layer and the shape influence of the geometry of nanocrystals.This size-independent part could well explain the size-independent kinking phenomenon during the growth of silicon nanowires.
