Photonic dualism of icosahedral quasicrystals

Here we report on fabrication of 3D submicron-size dielectric icosahedral quasicrystals and show a photonic dualism of these structures. Relying on far-field measurements, we found pronounced patterns of unconventional Bragg diffraction, which indicates the existence of multiple photonic pseudogaps.

A Quick and Accurate Method to Determine Submicron Size Coating Thickness Using Micro-Indentation along with a Mathematical Model

Hard and adherent wear-resistant thin surface coatings are synthesized on an aerospace alloy AA2219-T6 alloy using plasma-assisted physical vapor deposition. Submicron size TiN coatings with Ti interlayers are deposited and evaluated as a function of different deposition temperatures varying from 100 °C to 200 °C. Features of deposited surface layers are evaluated using different techniques; these include field emission scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction. Mathematical models developed by Yu. A. Bykov and S. Hogmark are considered to estimate the coating thickness using the Composite Hardness measurements. The values predicted by Bykov’s model grossly underestimated the thickness values and thus a correction factor is proposed. The actual coating thickness is measured by sandwiching the thin coating between the substrate and electrolytically deposited nickel layer; the observations are made using field emission scanning electron microscope. The present study successfully used corrected Bykov’s Model along with micro-indentation proved to be an easy, quick and accurate method to estimate the coating thicknesses of thin hard coatings on the soft substrate over a wide range coating thicknesses.

Size-Segregated Particulate Matter from Gasification of Bulgarian Agro-Forest Biomass Residue

The main purpose of the present work was to evaluate the efficiency of the gasification process of three different types of agro-forest biomass residue (rapeseed, softwood, and sunflower husks) along with the characterization of size-segregated particulates’ emissions. The experiments were carried out in a drop tube furnace (DTF), using two different gasifying agents (O2/N2 and O2/N2/CO2) at atmospheric pressure and a constant temperature of 1000 °C. In focus was the effect of biomass and the gasifying agent on syngas composition (CO, H2, CH4, and CO2), cold gas and carbon conversion efficiency, and on the emissions of by-products, such as particulate matter (PM), known for having negative environmental and health impacts. The collected particulates were characterized by SEM/EDS and XPS analysis. The results reveal that: (i) the introduction of CO2 increased the production of CO and CH4 and syngas’ lower heating value (LHV), thus leading to higher cold gas and carbon conversion efficiency; (ii) CO2 decreased the production of H2, leading to lower H2/CO ratio (between 0.25 and 0.9). Therefore, the generated syngas is suitable for the synthesis of higher hydrocarbons, (iii) CO2 lowered the emissions of char (cyclone) particles but increased the overall PM10–0.3. Submicron size PM was the dominant fraction (PM1–0.3) in O2/N2 and (PM1.6–0.3) in O2/N2/CO2. Unimodal PM size distribution was observed, except for sunflower husks gasification in O2/N2/CO2; (iv) the SEM/EDS and XPS analysis confirmed that submicron-sized PM1–0.3 contain above 80% of carbon associated to soot, due to incomplete oxidation, whereas in cyclone (char) particles, carbon decreased to about 50%. The SEM/EDS results showed that K and Cl are typical constituents of the submicron size PM, whereas the alkaline earth metals were detected mainly in fine and coarse particulates. Detailed analysis of the XPS (C1s) spectra showed that the most common oxygen-containing groups on the PM1 surface were carbonyl and carboxyl.

Growth of β-NaYF4:Eu3+ Crystals by the Solvothermal Method with the Aid of Oleic Acid and Their Photoluminescence Properties

Lanthanide-doped hexagonal β-NaYF4 crystals have received much attention in recent years due to their excellent photoluminescence properties. However, lanthanide-doped β-NaYF4 crystals with micron and submicron scales as well as uniform morphology have received less attention. In this study, Eu3+-doped β-NaYF4 (β-NaYF4:Eu3+) crystals of micron and submicron size scales were synthesized using the solvothermal method with ethylene glycol as the solvent. The β-NaYF4:Eu3+ crystals were highly crystallized. A comparison of the characteristics of the β-NaYF4:Eu3+ crystals synthesized with and without the use of oleic acid as a surfactant was conducted. It was found that the utilization of oleic acid as a surfactant during their synthesis greatly decreased their particle size from micron to submicron scale, while adding a small amount of ethanol further reduced their particle size. In addition, they exhibited much smoother surfaces and more uniform morphologies, which were hexagonal prism bipyramids. The microstructural characteristics and photoluminescence properties of the β-NaYF4:Eu3+ crystals were studied in detail. Results showed that β-NaYF4:Eu3+ crystals prepared with the aid of oleic acid as a surfactant during their synthesis exhibited stronger photoluminescence.

The first data about the structure and mineral composition of the ores of the Tarakon potential gold ore field (the Far East of Russia)

The obtained original materials, in conjunction with the literature data (hydrochemical contrasting halos), make it possible to predict a new (Tarakonsky) gold ore field within the eastern part of the Argun superterrane. Industrial concentrations of gold are noted in quartz metasomatites from granites and limestones. The amount of ore minerals usually does not exceed 5-10%. They are present in the rocks in micron and submicron size, represented mainly by pyrite, less often galena, sphalerite, chalcopyrite, ilmenite, hematite, magnetite, faded ores, and native high-grade gold. It is assumed that the formation of the Tarakonsky gold ore field, as well as most of the ore objects in the region, is associated with the manifestation of Late Mesozoic magmatism.