Vector Correlations and Product Rotational Alignments of Reactions Ca+RBr→CaBr+R(R=CH_(3),C_(2) H_(5) and n-C_(3) H_(7))

The quasiclassical trajectory method is used to study the vector correlations of the reactions Ca＋RBr （R=CH3, C2H5 and n-C3H7Br） and the rotational alignment of product CaBr. The product rotational alignment parameters at different collision energies and the vector correlations between the reagent and product are numerically calculated. The vector correlations are described by using the angle distribution functions P（θr）, P（φr）, P（θr, φr） and the polarization-dependent differential cross sections （PDDCSs）. The peak values of P（θr） of the product CaBr from Ca＋CH3Br are larger than those from Ca＋C2H5Br and Ca＋n-C3H7Br. The peak of P（θr） at φr= 3π/2 is apparently stronger than that at φr= x/2 for the three reactions Ca＋RBr. The calculation results show that the rotational angular momentum of the product CaBr is not only aligned, but also oriented along the direction which is perpendicular to the scattering plane.The product CaBr molecules are strongly scattered forward. The orientation and alignment of the product angular momentum will affect the scattering direction of the product molecules to varying degrees.

Study on the preparation and fretting behavior of bonded oriented MoS_(2)solid lubricant coating

The bonded MoS_(2)solid lubricant coating is an effective measure to mitigate the fretting wear of AISI 1045 steel.In this work,the amino functionalized MoS_(2)was protonated with acetic acid to make the MoS_(2)positively charged.The directional arrangement of protonated MoS2 in the coating was achieved by electrophoretic deposition under the electric field force.The bonded directionally aligned MoS_(2)solid lubricant coating showed high adaptability to various loads and excellent lubrication performance under all three working conditions.At a load of 10 N,the friction coefficient and wear volume of the coating with 5 wt%protonated MoS_(2)decreased by 20.0%and 37.2%compared to the pure epoxy coating,respectively,and by 0.07%and 16.8%than the randomly arranged MoS_(2)sample,respectively.The remarkable lubricating properties of MoS_(2)with directional alignment were attributed to its effective load-bearing and mechanical support,barrier effect on longitudinal extension of cracks,and the formation of a continuous and uniform transfer film.

Strong and Tough TPU Fibers with Orientedly Aligned CNTs Reinforced by Amorphous ZrO_(2)

High strength and high toughness are vital for fibers’engineering applications,but are hard to simultaneously achieve.Herein,we synthesize a carbon nanotube(CNT)-thermoplastic polyurethanes(TPU)fiber reinforced by an amorphous ZrO_(2)layer through the wet-spinning method.The amorphous ZrO_(2)layer is in-situ grown on the surface of CNT and the hybrid nanowires are orientedly aligned with TPU to form the ternary fiber.The fiber possesses an excellent combination of high strength(84.6 MPa)and toughness(126.7 MJ/m^(3)),which is outstanding when compared with previously reported CNT-TPU fibers.The pull-out of nanowires attributed to the oriented alignment structure and the enhanced interface and restriction of deformation obtained from the amorphous ZrO_(2)layer are considered as the primary strengthening and toughening mechanisms.We anticipate that our fiber synthesis strategy gives a new path to design strong and tough fibers.

Dynamical analysis of the effect of elliptically polarized laser pulses on molecular alignment and orientation

In this Letter, we study the molecular alignment and orientation driven by two elliptically polarized laser pulses.It is shown that the field-free molecular alignment can be achieved in a three-dimensional（3D） case, while the field-free molecular orientation is only along the x and y directions, and that the field-free alignment and orientation along different axes are related to the populations of the rotational states. It is demonstrated that changing the elliptic parameter is efficient for controlling both in-pulse and post-pulse molecular alignment and orientation. The delay time also has an influence on the field-free molecular alignment and orientation.

Spatiotemporal rotational dynamics of laser-driven molecules

Molecular alignment and orientation by laser fields has attracted significant attention in recent years,mostly due to new capabilities to manipulate the molecular spatial arrangement.Molecules can now be efficiently prepared for ionization,structural imaging,orbital tomography,and more,enabling,for example,shooting of dynamic molecular movies.Furthermore,molecular alignment and orientation processes give rise to fundamental quantum and classical phenomena like quantum revivals,Anderson localization,and rotational echoes,just to mention a few.We review recent progress on the visualization,coherent control,and applications of the rich dynamics of molecular rotational wave packets driven by laser pulses of various intensities,durations,and polarizations.In particular,we focus on the molecular unidirectional rotation and its visualization,the orientation of chiral molecules,and the three-dimensional orientation of asymmetric-top molecules.Rotational echoes are discussed as an example of nontrivial dynamics and detection of prepared molecular states.

Simultaneous field-free molecular orientation and planar delocalization by THz laser pulses[Invited]

This study shows the unexpected and counterintuitive possibility of simultaneously orienting a molecule while delocalizing its molecular axis in a plane in field-free conditions.The corresponding quantum states are characterized,and different control strategies using shaped terahertz(THz)laser pulses are proposed to reach such states at zero and nonzero temperatures.The robustness against temperature effects of a simple control procedure combining a laser and a THz pulse is shown.Such control strategies can be applied not only to linear molecules but also to symmetric top molecules.

Hierarchical mechanical behavior of cobalt supracrystals related to nanocrystallinity

Here, we report on hierarchical mechanical behavior of 500-nm-thick Conanocrystal 3D superlattices （supracrystals） induced by either the crystalline structure （nanocrystallinity） or the length of the coating agent of Co nanocrystals. Increasing the nanocrystal shape anisotropy of Co nanocrystals through the control of their nanocrystallinities induces a higher level of ordering with both translational and orientational alignment of nanocrystals within the supracrystals. The hierarchy in ordering at various scales, i.e., from the atomic lattice within the nanocrystals to the nanocrystal superlattices within supracrystals, is correlated with marked changes in the Young＇s modulus of supracrystals： From 0.7 ±0.4 to 1.7 ±0.5 and to 6.6 ±1.5 GPa as the crystalline structure of Co nanoparticles changes from amorphous-Co to ε-Co and to hexagonal compact packing （hcp）-Co, respectively. Moreover, for supracrystals of 7 nm amorphous Co nanoparticles, the Young＇s modulus decreases by one order of magnitude from 0.7 ±0.4 to 0.08 ±0.03 GPa upon reducing the alkyl chain length of the ligands coating the Co nanoparticles from C18 （oleic acid） to C12 （lauric acid）. The hierarchical mechanical behavior is rationalized using a dimensional model of the stress-strain relationship in supracrystals.

Aligning Crystal Orientation of Poly-Crystalline Bi-Te With a High Magnetic Field

We investigated the effect of aligning crystal orientation in the microstructures containing sub micro-sized grains on the thermoelectric properties for polycrystalline Bi-Te materials.Bi-Te powder,prepared through the conventional pulverization process,was sufficiently dispersed in an appropriate solvent,and then was formed into c-axis aligned green bodies under a designated high magnetic field.The green bodies were sintered with spark-plasma-sintering machine.The degree of crystal alignment of sintered bodies was examined with the electron-back-scatter-diffraction SEM and the X-ray diffraction patterns.It was observed that for both p and n type thermoelectric Bi-Te materials,aligning crystal orientation properly made electrical resistivity decreased with keeping Seebeck coefficient and thermal conductivity remained unchanged.As a typical result,the aligned Bi-Te material with the magnetic field of 10 tesla showed 30%enhancement of the thermoelectric performance.