The microstructures of rapidly solidified (RS) Al-Fe-Ce-Ti and Al-Fe-V-Si alloys obtained by means of rotating blade quenching were studied with optical microscopy,transmission electron microscopy (TEM).The featureles...The microstructures of rapidly solidified (RS) Al-Fe-Ce-Ti and Al-Fe-V-Si alloys obtained by means of rotating blade quenching were studied with optical microscopy,transmission electron microscopy (TEM).The featureless zone observed in the two alloys reveals that the new technique offers a higher solidification rate than the inert-gas-atomized method.Under TEM observation the featureless zone presents virtually a micropartition or partitionless feature,and the solute contents in it are almost the same as the chemical composition of alloys.展开更多
In the present study, laser alloying of electroless Nie P coating on aluminum substrate was conducted using Nd：YAG pulsed laser under the condition of 5.36 109W/m2 in power density and 3.0 mm/s in scanning speed. The...In the present study, laser alloying of electroless Nie P coating on aluminum substrate was conducted using Nd：YAG pulsed laser under the condition of 5.36 109W/m2 in power density and 3.0 mm/s in scanning speed. The rapidly solidified microstructure in the alloyed layer was studied. The results showed that the alloying element distributed in the alloyed layer is inhomogeneous. The dendrite containing relatively high Ni was identified as Al3Ni phase and the areas between the dendrites are rich in Al content. Featureless with cell structure in Al-rich areas was firstly displayed by z-contrast image. Amorphous structure was revealed to exist in Al-rich areas.展开更多
Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media...Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.展开更多
文摘The microstructures of rapidly solidified (RS) Al-Fe-Ce-Ti and Al-Fe-V-Si alloys obtained by means of rotating blade quenching were studied with optical microscopy,transmission electron microscopy (TEM).The featureless zone observed in the two alloys reveals that the new technique offers a higher solidification rate than the inert-gas-atomized method.Under TEM observation the featureless zone presents virtually a micropartition or partitionless feature,and the solute contents in it are almost the same as the chemical composition of alloys.
文摘In the present study, laser alloying of electroless Nie P coating on aluminum substrate was conducted using Nd：YAG pulsed laser under the condition of 5.36 109W/m2 in power density and 3.0 mm/s in scanning speed. The rapidly solidified microstructure in the alloyed layer was studied. The results showed that the alloying element distributed in the alloyed layer is inhomogeneous. The dendrite containing relatively high Ni was identified as Al3Ni phase and the areas between the dendrites are rich in Al content. Featureless with cell structure in Al-rich areas was firstly displayed by z-contrast image. Amorphous structure was revealed to exist in Al-rich areas.
文摘Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.
