Search

With Sm 0.5 Sr 0.5 CoO 3 microparticles as the raw material, high solar absorptive and high infrared emissive coatings were successfully prepared on 6061 aluminum alloys using a new method including firstly microparticle pre-deposition by gravity and then plasma electrolytic oxidation (PEO) technique. All four coatings were characterized by XRD, SEM and EDS respectively. The solar absorbance (α s ) and infrared emittance (ε T ) were also investigated. The results showed that all four coatings were black and rough; the Na and P elements from the electrolyte were incorporated into the coatings; amorphous compounds containing Na and P also existed in the coatings. All four coatings had a complex multiphase composition mainly consisting of Sm 2 O 3 , SrAl 4 O 7 , AlPO 4 and CoAl 2 O 4 phases, which might derive from drastic reactions under high temperature and high pressure during the PEO process. The surface morphology and the relative content of main crystal phases changed with increasing current density or time. The cross-section of the coatings exhibited a layer structure. As current density or time increased, the α s decreased but ε T increased. All four coatings showed a high solar absorbance value ≥ 0.85 and high infrared emittance value ≥ 0.90, which indicated that the coatings might have promising applications in solar and infrared heating for aluminum alloys. [ABSTRACT FROM AUTHOR]

The present study discusses the development of a simulation model of transient impact between a particle and a substrate. The equations for structural behavior are coupled with those of heat transfer, wherein material properties are taken as temperature dependent. The set of equations is solved with Ansys program using a direct coupling method. At first, structural model is solved without heat transfer. Then, coupled thermo-mechanical model is solved with and without thermoelastic effects. Computational results indicate that thermal consideration has significant effects on contact problem. In addition, it is shown that, themoelasticity consideration is crucial for simulating these problems to determine the structural and thermal parameters. [ABSTRACT FROM AUTHOR]

Optical functional surfaces are key components of nearly every optical device and they have become a special focus in both academia and industry. The no contact, one step, direct, and maskless laser surface texturing technique is one of the most encouraging approaches for realizing the surface functions. We use a high power and high repetition rate ultrafast laser system to produce micro–nano structures on metal surfaces. We demonstrate that metal surface micro–nano structures and correspondingly their optical responses can be facilely tailored by simple controlling the ultrafast laser processing parameters. Nano particles of tens to hundreds nm, sub-micro particles of 0.5–1 μm, fine-micro particles of 1–10 μm, micro particles of 10–50 μm, and coarse-micro particles larger than 50 μm have been fabricated on Cu surfaces. And surface reflection of copper surfaces has been tuned from 10% to 90% in spectra level and from UV to MIR in spectrum range, with unique optical properties like visible selective reflection, linear changing reflection, band reflection, and broadband absorption being achieved. The formation processes of those particle structures as well as the underlying mechanisms for their optical responses are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Addition of 10−2 M cationic surfactants with longer carbon chain to basic solution reduced particle adhesion on InGaAs. • Addition of 10−2 M CTAB into basic solution enhanced formation of bilayer micellar structure on SiO 2 surface. • Adhesion of silica particles on InGaAs surface was reduced with the formation of bilayered CTAB micellar structures. • Interaction force between silica particles and InGaAs was studied to find the relationship of particle adhesion with energy barrier. • Addition of 10−2 M CTAB reduces attraction and enhances repulsion between InGaAs and silica particle surfaces. The surface properties of InGaAs, such as zeta potential, surface energy components, acid–base energy constant, and Hamaker constant and its interaction force with silica particles, have not yet been elucidated. In this study, the adhesion of silica particles on an InGaAs surface in a 1/1/100 ammonium hydroxide (NH 4 OH)–hydrogen peroxide (H 2 O 2)–H 2 O mixture (APM) solution was investigated. In particular, the effect of the addition of cationic surfactants and the concentration of hexadecyltrimethylammonium bromide (CTAB) on the particle adhesion/desorption was examined. To understand the adhesion behavior of silica particles on the InGaAs surface, the Lifshitz–van der Waals energy, acid–base interaction energy, and electrostatic energy between the silica particles and the InGaAs surface were estimated. It was found that the behavior of the energy barrier was strongly related to the number of silica particles that were adhered to the InGaAs. The energy barrier was reduced in the APM solution with 10−4 M CTAB, facilitating the adhesion of silica particles. However, when the CTAB concentration increased to 10−2 M, the energy barrier was elevated, and the adhesion of silica particles was reduced. The adhesion and desorption behaviors of silica particles on the InGaAs surface can be explained by the change in the energy barrier between the particles and InGaAs. [ABSTRACT FROM AUTHOR]

• ZnO powders were fabricated by sol-gel process with different heating rate. • Effect of the heating rate on structure, optical and photocatalytic properties was investigated. • Non-isothermal and thermodynamic parameters of ZnO powders were studied. • Bulk and surface oxygen vacancies increased as heating rate went up. • ZnO sample prepared at 1 °C/min heating rate exhibited the excellent photocatalytic efficiency. In this work, ZnO particles were fabricated by sol-gel method at different heating rate at 500 °C for 2 h. The ZnO powders were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and photoluminescence, respectively. The effect of heating rate on photocatalytic activities of ZnO particles was evaluated by degradation of methylene blue (MB). The non-isothermal kinetics and thermodynamic properties were also estimated. The XRD results showed that ZnO had hexagonal wurtzite structure. The different heating rate didn't influence the surface morphology of ZnO powders. It was observed that the heating rate had a profound effect on reduction of band gap and photocatalytic performances. The band gap of the ZnO particles varied from 3.10 to 3.17. The ZnO sample prepared at 1 °C/min exhibited the highest photocatalytic activity. Its relative photocatalytic degradation rate and kinetic constant were 92.7% and 1.069 × 10-2 min−1, respectively. The results might be ascribed to low bulk vacancies, high surface oxygen vacancies and narrow band gap energy. Also, ZnO photocatalysts showed good stability after four sequence tests. This study provides a new strategy to improve the photocatalytic performances of ZnO photocatalyst for the degradation of organic contaminant. [ABSTRACT FROM AUTHOR]