Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficien...Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficient nonprecious metal catalysts.Herein,we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst.The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100%conversion efficiency and selectivity under mild reaction conditions,surpassing the reported high performance nonprecious HDO catalysts.Impressively,our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100%conversion efficiency and over 90%selectivity.Importantly,our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O,and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs.The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.展开更多
Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocompo...Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocomposites were subjected to density, hardness, electrical conductivity, and friction and wear tests. The results reveal that the density of nanocomposite decreases with the increase of the mass fraction of CNTs. A significant improvement in the hardness is noticed in the nanocomposite with the addition of CNTs. The developed nanocomposites show low coefficient of friction and improved wear resistance when compared with unreinforced alloy. At an applied load of 5 N, the coefficient of friction and wear loss of 2%CNTs reinforced Cu-Sn alloy nanocomposite decrease by 72% and 68%, respectively, compared with those of Cu-Sn alloy. The wear mechanisms of worn surfaces of the composites are reported. In addition, the electrical conductivity reduces with the increase of the content of CNTs.展开更多
Tribological behaviors of monolithic A356 aluminum alloy castings and A356.CNT nanocomposite castings, fabricated by fully liquid and semisolid routes were examined. Samples were prepared by melt agitation, rheocastin...Tribological behaviors of monolithic A356 aluminum alloy castings and A356.CNT nanocomposite castings, fabricated by fully liquid and semisolid routes were examined. Samples were prepared by melt agitation, rheocasting, stir casting, and compocasting techniques. Effects of addition of carbon nanotubes (CNTs), casting process and the applied load on wear properties and mechanisms were investigated. It was found that wear loss, wear rate and friction coefficient of nanocomposite samples remarkably declined by the addition of CNTs. Moreover, changing the casting process from fully liquid to semisolid routes, plus increasing fractions of the primary phase were the two factors that improved the wear properties of the investigated samples, especially nanocomposite ones. In addition, it was revealed that adhesion and delamination were the dominant wear mechanism of the monolithic samples produced by fully liquid and semisolid routes, respectively. However, regardless of fabrication techniques, the abrasion was the main wear mechanism of nanocomposite samples.展开更多
The adsorption of poly （ethylene oxide）-b-poly（4-vinylpyridine）（PEO-b-P4VP） micelles onto the surface of yttrium hydroxide nanotubes （YNTs） resulted in the hybrid nanotubes with a dense P4VP inner layer and a ...The adsorption of poly （ethylene oxide）-b-poly（4-vinylpyridine）（PEO-b-P4VP） micelles onto the surface of yttrium hydroxide nanotubes （YNTs） resulted in the hybrid nanotubes with a dense P4VP inner layer and a stretched PEO outer layer surrounding YNTs. The dense P4VP layer was further stabilized by the crosslinking using 1,4-dibromobutane as the crosslinker. Then, the crosslinked hybrid nanotubes （CHNTs） were used as a novel nano supporter for loading the catalyst gold nanoparticles （GNPs） within the crosslinked P4VP layer. The resultant GNPs/CHNTs （GNTs loaded on CHNTs） were applied to catalyze the reduction reaction of p-nitrophenol. The results indicate that this novel nano supporter has advantages such as good dispersity in the suspension, high capacity in loading GNPs （0.87 mmol/g）, high catalytic activity of the loaded GNPs （12.9 μmol-lmin-i）, and good reusability of GNTs/CHNTs.展开更多
Electric potentials were generated from carbon nanotubes immersed in flowing vapors. The nanomaterials used in this study were multiwall carbon nanotubes（MWCNTs） and silver nanopowders. These nanomaterials were disp...Electric potentials were generated from carbon nanotubes immersed in flowing vapors. The nanomaterials used in this study were multiwall carbon nanotubes（MWCNTs） and silver nanopowders. These nanomaterials were dispersed and densely packed on a substrate and immersed in flowing vapors generated from solution such as water, ethanol and KCI. The potentials generated from these samples were measured by a voltmeter. Experimental results showed that the electric potentials were produced at the surface of the MWCNT samlpes, and strongly dependent on the pretreatment of MWCNT and properties of the flowing vapors. The mechanism of vapor-flow induced potentials may be ascribed to ions in the flowing vapors. This property of MWCNTs can advantage their application to nanoscale sensors, detectors and power cells.展开更多
The chemical and biological mechanisms of life processes mostly consist of multistep and programmed processes at nanoscale levels. Interestingly enough, cell, the basic functional unit and platform that maintains life...The chemical and biological mechanisms of life processes mostly consist of multistep and programmed processes at nanoscale levels. Interestingly enough, cell, the basic functional unit and platform that maintains life processes, is composed of various organelles fulfilling sophisticated functions through the precise control on the biomolecules （e.g., proteins, phospholipid, nucleic acid and ions） in a spatial dimension of nanoscale sizes. Thus, understanding of the activities of manufactured nanoscale materials including their interaction with biological sys- tems is of great significance in chemistry, materials sci- ence, life science, medicine, environmental science and toxicology. In this brief review, we summarized the recent advances in nanotoxicological chemistry through the dis- section of pivotal factors （primarily focusing on dose and nanosurface chemistry） in determining nanomaterial- induced biological/toxic responses with particular empha- sis on the nanomaterial bioaccumulation （and interaction organs or target organs） at intact animal level. Due to the volume of manufacture and material application, we deliberately discussed carbon nanotubes, metal/metal oxide nanomaterials and quantum dots, severing as representativematerial types to illustrate the impact of dose and nanosurface chemistry in these toxicological scenarios. Finally, we have also delineated the grand challenges in this field in a conceptual framework of nanotoxicological chemistry. It is noted that this review is a part of our persistent endeavor of building the systematic knowledge framework for toxicological properties of engineered nanomaterials.展开更多
文摘Catalytic hydrodeoxygenation(HDO)is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels,but highly challenging due to the lack of highly efficient nonprecious metal catalysts.Herein,we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst.The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100%conversion efficiency and selectivity under mild reaction conditions,surpassing the reported high performance nonprecious HDO catalysts.Impressively,our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100%conversion efficiency and over 90%selectivity.Importantly,our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O,and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs.The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.
文摘Multiwalled carbon nanotubes （MWCNTs） reinforced Cu-Sn alloy based nanocomposite was developed by powder metallurgy route. The mass fraction of CNTs was varied from 0 to 2% in a step of 0.5%. The developed nanocomposites were subjected to density, hardness, electrical conductivity, and friction and wear tests. The results reveal that the density of nanocomposite decreases with the increase of the mass fraction of CNTs. A significant improvement in the hardness is noticed in the nanocomposite with the addition of CNTs. The developed nanocomposites show low coefficient of friction and improved wear resistance when compared with unreinforced alloy. At an applied load of 5 N, the coefficient of friction and wear loss of 2%CNTs reinforced Cu-Sn alloy nanocomposite decrease by 72% and 68%, respectively, compared with those of Cu-Sn alloy. The wear mechanisms of worn surfaces of the composites are reported. In addition, the electrical conductivity reduces with the increase of the content of CNTs.
基金financial support of the Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of NUST “MISi S” (No. К2-2019-007)
文摘Tribological behaviors of monolithic A356 aluminum alloy castings and A356.CNT nanocomposite castings, fabricated by fully liquid and semisolid routes were examined. Samples were prepared by melt agitation, rheocasting, stir casting, and compocasting techniques. Effects of addition of carbon nanotubes (CNTs), casting process and the applied load on wear properties and mechanisms were investigated. It was found that wear loss, wear rate and friction coefficient of nanocomposite samples remarkably declined by the addition of CNTs. Moreover, changing the casting process from fully liquid to semisolid routes, plus increasing fractions of the primary phase were the two factors that improved the wear properties of the investigated samples, especially nanocomposite ones. In addition, it was revealed that adhesion and delamination were the dominant wear mechanism of the monolithic samples produced by fully liquid and semisolid routes, respectively. However, regardless of fabrication techniques, the abrasion was the main wear mechanism of nanocomposite samples.
文摘The adsorption of poly （ethylene oxide）-b-poly（4-vinylpyridine）（PEO-b-P4VP） micelles onto the surface of yttrium hydroxide nanotubes （YNTs） resulted in the hybrid nanotubes with a dense P4VP inner layer and a stretched PEO outer layer surrounding YNTs. The dense P4VP layer was further stabilized by the crosslinking using 1,4-dibromobutane as the crosslinker. Then, the crosslinked hybrid nanotubes （CHNTs） were used as a novel nano supporter for loading the catalyst gold nanoparticles （GNPs） within the crosslinked P4VP layer. The resultant GNPs/CHNTs （GNTs loaded on CHNTs） were applied to catalyze the reduction reaction of p-nitrophenol. The results indicate that this novel nano supporter has advantages such as good dispersity in the suspension, high capacity in loading GNPs （0.87 mmol/g）, high catalytic activity of the loaded GNPs （12.9 μmol-lmin-i）, and good reusability of GNTs/CHNTs.
基金Funded by the Science Foundation from the Scientific Committee of Chongqing ( No.CSTC2005BB4200).
文摘Electric potentials were generated from carbon nanotubes immersed in flowing vapors. The nanomaterials used in this study were multiwall carbon nanotubes（MWCNTs） and silver nanopowders. These nanomaterials were dispersed and densely packed on a substrate and immersed in flowing vapors generated from solution such as water, ethanol and KCI. The potentials generated from these samples were measured by a voltmeter. Experimental results showed that the electric potentials were produced at the surface of the MWCNT samlpes, and strongly dependent on the pretreatment of MWCNT and properties of the flowing vapors. The mechanism of vapor-flow induced potentials may be ascribed to ions in the flowing vapors. This property of MWCNTs can advantage their application to nanoscale sensors, detectors and power cells.
基金supported by the National Natural Science Foundation of China(11305182,21277037,21320102003)the National Basic Research Program of China(2011CB933403)
文摘The chemical and biological mechanisms of life processes mostly consist of multistep and programmed processes at nanoscale levels. Interestingly enough, cell, the basic functional unit and platform that maintains life processes, is composed of various organelles fulfilling sophisticated functions through the precise control on the biomolecules （e.g., proteins, phospholipid, nucleic acid and ions） in a spatial dimension of nanoscale sizes. Thus, understanding of the activities of manufactured nanoscale materials including their interaction with biological sys- tems is of great significance in chemistry, materials sci- ence, life science, medicine, environmental science and toxicology. In this brief review, we summarized the recent advances in nanotoxicological chemistry through the dis- section of pivotal factors （primarily focusing on dose and nanosurface chemistry） in determining nanomaterial- induced biological/toxic responses with particular empha- sis on the nanomaterial bioaccumulation （and interaction organs or target organs） at intact animal level. Due to the volume of manufacture and material application, we deliberately discussed carbon nanotubes, metal/metal oxide nanomaterials and quantum dots, severing as representativematerial types to illustrate the impact of dose and nanosurface chemistry in these toxicological scenarios. Finally, we have also delineated the grand challenges in this field in a conceptual framework of nanotoxicological chemistry. It is noted that this review is a part of our persistent endeavor of building the systematic knowledge framework for toxicological properties of engineered nanomaterials.
