This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine...This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX^? XD, PRIMEX^? reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.展开更多
Ab initio and classical molecular dynamics simulations show that water can flow through graphdiyne—an experimentally fabricated graphene-like membrane with highly dense (2.4 × 10^18 pores/m^2), uniformly ordered...Ab initio and classical molecular dynamics simulations show that water can flow through graphdiyne—an experimentally fabricated graphene-like membrane with highly dense (2.4 × 10^18 pores/m^2), uniformly ordered, subnanometer pores (incircle diameter 0.57 nm and van der Waals area 0.06 nm^2). Water transports through subnanopores via a chemical-reaction-like activated process. The activated water flow can be precisely controlled through fine adjustment of working temperature and pressure. In contrast to a linear dependence on pressure for conventional membranes, here pressure directly modulates the activation energy, leading to a nonlinear water flow as a function of pressure. Consequently, high flux (1.6 L/Day/cm^2/MPa) with 100% salt rejection efficiency is achieved at reasonable temperatures and pressures, suggesting graphdiyne can serve as an excellent membrane for water desalination. We further show that to get through subnanopores water molecule must break redundant hydrogen bonds to form a two-hydrogen-bond transient structure. Our study unveils the principles and atomistic mechanism for water transport through pores in ultimate size limit, and offers new insights on water permeation through nanochannels, design of molecule sieving and nanofluidic manipulation.展开更多
The surface-enhanced Raman spectroscopy(SERS)is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale,yet the fabrication of SERS materials such as nanoparticl...The surface-enhanced Raman spectroscopy(SERS)is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale,yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution,largely limiting the application of SERS.Here,we report a complex hierarchical metallic glassy(MG)nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique.The MG nanostructure displays an excellent SERS effect and moreover,a superhydrophobicity and self-cleaning behavior.The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface,which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain(FDTD)simulation.Our works show that the MG could be a new potential SERS material with low cost and good durability,well extending the functional application of this kind of material.展开更多
文摘This paper deals with a series of novel processing techniques based on the in situ production of metal matrix composites (MMCs). In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. As a result, this provides thermodynamic compatibility at the matrix-reinforcement interface. The reinforcement surfaces are also likely to be free of contamination and, therefore, a stronger matrix-dispersion bond can be achieved. Some of these technologies including DIMOX^? XD, PRIMEX^? reactive gas infiltration, high-temperature self-propagating synthesis (SHS), and liquid-solid, or solid-gas-liquid reactions as well as plasma in situ MMCs are expressed in this paper.
文摘Ab initio and classical molecular dynamics simulations show that water can flow through graphdiyne—an experimentally fabricated graphene-like membrane with highly dense (2.4 × 10^18 pores/m^2), uniformly ordered, subnanometer pores (incircle diameter 0.57 nm and van der Waals area 0.06 nm^2). Water transports through subnanopores via a chemical-reaction-like activated process. The activated water flow can be precisely controlled through fine adjustment of working temperature and pressure. In contrast to a linear dependence on pressure for conventional membranes, here pressure directly modulates the activation energy, leading to a nonlinear water flow as a function of pressure. Consequently, high flux (1.6 L/Day/cm^2/MPa) with 100% salt rejection efficiency is achieved at reasonable temperatures and pressures, suggesting graphdiyne can serve as an excellent membrane for water desalination. We further show that to get through subnanopores water molecule must break redundant hydrogen bonds to form a two-hydrogen-bond transient structure. Our study unveils the principles and atomistic mechanism for water transport through pores in ultimate size limit, and offers new insights on water permeation through nanochannels, design of molecule sieving and nanofluidic manipulation.
基金The authors would like to thank the support of the National Natural Science Foundation of China(Nos.51822107,51671121,51761135125,and 61888102)the National Key Research and Development Program(No.2018YFA0703603)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDB07030200 and XDB30000000)We appreciate Professor Di Zhang’s deep discussions on the usage of bio-templates.The authors also thank Ruhao Pan and Xianzhong Yang for discussions on collecting Raman spectra,Mo Han Wang for the measurement of UV–vis absorption spectra and Kun Chen for the dielectric coefficient measurement.
文摘The surface-enhanced Raman spectroscopy(SERS)is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale,yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution,largely limiting the application of SERS.Here,we report a complex hierarchical metallic glassy(MG)nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique.The MG nanostructure displays an excellent SERS effect and moreover,a superhydrophobicity and self-cleaning behavior.The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface,which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain(FDTD)simulation.Our works show that the MG could be a new potential SERS material with low cost and good durability,well extending the functional application of this kind of material.
