Tuning the interfacial friction force and thermal conductance by altering phonon properties at contact interface.

Controlling friction force and thermal conductance at solid/solid interface is of great importance but remains a significant challenge. In this work, we propose a method to control the matching degree of phonon spectra at the interface through modifying the atomic mass of contact materials, thereby regulating the interfacial friction force and thermal conductance. Results of Debye theory and molecular dynamics simulations show that the cutoff frequency of phonon spectrum decreases with increasing atomic mass. Thus, two contact surfaces with equal atomic mass have same vibrational characteristics, so that more phonons could pass through the interface. In these regards, the coupling strength of phonon modes on contact surfaces makes it possible to gain insight into the nonmonotonic variation of interfacial friction force and thermal conductance. Our investigations suggest that the overlap of phonon modes increases energy scattering channels and therefore phonon transmission at the interface, and finally, an enhanced energy dissipation in friction and heat transfer ability at interface.

Preparation of mono-dispersed, high energy release, core/shell structure Al nanopowders and their application in HTPB propellant as combustion enhancers.

Mono-dispersed, spherical and core/shell structure aluminum nanopowders (ANPs) were produced massively by high energy ion beam evaporation (HEIBE). And the number weighted average particle size of the ANPs is 98.9 nm, with an alumina shell (3-5 nm). Benefiting from the passivation treatment, the friction, impact and electrostatic spark sensitivity of the ANPs are almost equivalent to those of aluminum micro powders. The result of TG-DSC indicates the active aluminum content of ANPs is 87.14%, the enthalpy release value is 20.37 kJ/g, the specific heat release S 1/Δm 1* (392-611 °C) which determined the ability of energy release is 19.95 kJ/g. And the value of S 1/Δm 1* is the highest compared with ANPs produced by other physical methods. Besides, the ANPs perfectly compatible with hydroxyl-terminated polybutadiene (HTPB), 3 wt. % of ANPs were used in HTPB propellant replaced micron aluminum powders, and improved the burning rate in the 3-12 MPa pressure range and reduced the pressure exponential by more than 31% in the 3-16 MPa pressure range. The production technology of ANPs with excellent properties will greatly promote the application of ANPs in the field of energetic materials such as propellant, explosive and pyrotechnics.

One-step modification of fabrics with bioinspired polydopamine@octadecylamine nanocapsules for robust and healable self-cleaning performance.

An in-situ polymerization to coat fabrics with polydopamine-encapsulated octadecylamine endows the fabrics with self-cleaning and self-healing abilities. The treated fabric exhibits self-healing after losing its hydrophobicity. It is durable against washing and mechanical abrasion without changing the hydrophobicity. Thanks to the versatile adhesive property of polydopamine, the approach is compatibile with a variety of substrates, such as fabrics, glass, sponge, paper, and polymeric materials.

Self-assembled-monolayers (SAMs) modified template synthesis and characterization of SrTiO3 nanotube arrays.

A self-assembled-monolayers (SAMs) modified anodic aluminum oxide (AAO) membranes were used to generate crystalline strontium titanate (SrTiO3) nanotube arrays, which have been characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), coupled with electron diffraction analysis. The possible formation mechanism can be explained by the induced nucleation effect of the functional headgroups in the SAMs.

Hydrothermal synthesis of SrTiO3 nanoplates through epitaxial self-assembly of nanocubes.

SrTiO3 nanoplates are obtained by the precipitation of an aqueous gel suspension. The gel suspension is prepared by hydrolysis of a Titanium isopropoxide [Ti(OCH(CH3)2)4] solution with NaOH and the addition of Sr(NO3)2. The amount of additive oleic acid plays a significant role in the formation of pure SrTiO3 phase with specific morphologies. The results of transmission electron microscopy (TEM) and electron diffraction (ED) investigations provide evidences that the oriented aggregation of small nanocubes is the dominant growth mechanism for the formation of the observed SrTiO3 nanoplates. The primary nanocrystals are self-assembled in a highly oriented fashion, producing defective single-crystal particles. The above results show that the directional aggregation process can be controlled by changing the temperature of the suspension as well as by adding organic molecules, by which the SrTiO3 particles can be obtained with a controlled size and shape.