Ultrafast Molecular Movies:Probing Chemical Dynamics with Femtosecond Electron and X-Ray Diffraction

Understanding the process of chemical reactions has always been a relentless pursuit for chemists.The development of femtosecond pump-probe techniques since the 1980s has revolutionized the field of chemical dynamics,enabling the capture of timeresolved snapshots of reactions on the femtosecond timescale.Starting from the 2010s,breakthroughs in femtosecond electron and X-ray sources has enabled ultrafast electron and X-ray diffraction techniques,which is able to directly reveal the temporal evolution of atomic geometries of molecules,allowing for the creation of molecular movies.Gas-phase molecular movies reveal intrinsic intramolecular processes,while liquid-phase molecular movies provide insights for complicated solvent-solute interplay.This minireview focuses on the advances in studying gasphase and liquid-phase molecular dynamics(MD)using ultrafast electron and X-ray diffraction techniques on femtosecond and picosecond timescales.The fast-developing experimental capability of the direct observation of molecular structural evolution during chemical reactions,on its natural femtosecond timescale and subangstrom length scale,offers tremendous potential for the field of chemical kinetics and MD.

Synthesis of methanol and ethanol over CuZnAl slurry catalyst prepared by complete liquid-phase technology

A new method,named the complete liquid-phase technology,has been applied to prepare catalysts for methanol synthesis.Its main innovative thought lies in preparing slurry catalysts directly from raw solution.Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor,while CO conversion reaches 35.9%and ethanol selectivity is more than 20%,with a total alcohol selectivity of more than 87%.No deactivation was found during the 192 h reaction.

Microstructural evolution and mechanical properties of h-BN composite ceramics with Y2O3-AlN addition by liquid-phase sintering

Hexagonal boron nitride(h-BN)composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN.The effects of different Y2O3–AlN contents on microstructural evolution,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics were investigated.The results indicate that Y2O3–AlN forms a liquid phase during the sintering process achieving a good wettability with h-BN grains.In pure h-BN ceramic and h-BN composite ceramic with 40 wt%Y2O3–AlN,the h-BN grains grow well when controlled through solid-phase and liquid-phase diffusion,respectively.With the increase in Y2O3–AlN content,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics first decrease and then increase,and the properties of h-BN composite ceramic with 10 wt%Y2O3–AlN are the inflection points.Such properties are highly related to the phase compositions,porosity and microstructure.