Thermal stability of the nanolayered Fe2AlB2 in nitrogen and argon atmospheres

The thermal stability and decomposition mechanisms of Fe₂AlB₂ powders, synthesized by reactive powder metallurgy, were studied under nitrogen (N₂) or argon (Ar) atmospheres. The effects of using different FeB precursors to synthesize the Fe₂AlB₂ and hydrochloric acid (HCl) purification treatments on the thermal stability were also investigated. When as-synthesized Fe₂AlB₂ powders are treated in dilute HCl to dissolve impurity phases, decomposition in N₂ atmospheres occurs readily above 1200 K. The decomposition reaction involves β-FeB precipitation and the liberated Al atoms reacting with the ambient N₂ to form AlN. Under Ar environments, HCl-treated Fe₂AlB₂ powders decompose and precipitate β-FeB, by the out-diffusion of Al from the nanolaminated structure. Interestingly, isothermal annealing under N₂ atmospheres revealed that Fe₂AlB₂ was more thermally stable when synthesized from lab-synthesized, instead of commercially available, FeB precursors and when the HCl treatment was avoided. The effects of the various factors on the decomposition temperature and decomposition mechanisms are discussed herein.     

A Parametric Study on the Inception and Evolution of Underground Coal Fires Based on a Lab-Scale Experimental Setup

Fire Technology - The tendency of self-ignition of coal is the root cause of underground coal fires (UCFs). A parametric study is carried out on a lab-scale experimental setup developed based on...     

Influence of Laser Peening With and Without Coating on the Surface Properties and Stress Corrosion Cracking Behavior of Laser-Welded 304 Stainless Steel

Metallurgical and Materials Transactions A - This study aims to investigate the effect of laser peening with (LP) and without coating (LPwC) process on subsurface microstructural evolution,...     

Application of sorption-reagent materials in the technology of liquid radioactive waste treatment

Some examples of sorption-reagent materials and variants of their application in the practice of treating liquid radioactive waste have been considered. The data on the strontium sorption on samples of a sorption-reagent material under dynamic conditions at different degrees of dilution and different concentrations of seawater have been presented. These data demonstrate that the most efficient practical applications of sorption-reagent materials consist of decontaminating of seawater concentrates of strontium radionuclides. This task is stated during treatment of liquid radioactive waste (LRW) streams at the Fukushima-1 NPP (Japan), where reverse osmosis concentrates constitute the main problem of localization of the aftermath of the disaster that occurred in 2011.     

Structure formation in binary Al-TM (TM = Mn,Co, Ni,Cu) melts

The structures of binary Al-TM (transition metal TM = Mn, Co, Ni, Cu) melts at near-liquidus temperatures are studied by X-ray diffraction and simulation using the reverse Monte Carlo method. The melts are found to have chemical local atomic ordering, and this ordering depends on the nature and content of TM. Chemical local atomic ordering leads to a medium-range order as a result of TM atom localization at distances of 0.4–0.5 nm in the composition of polytetrahedral clusters having icosahedral symmetry. A medium-range order in the melts is identified due to the presence of an additional maximum (prepeak) in the left slope of the first peak in experimental structure factor curves. The local atomic orders in the melts and the corresponding crystalline and quasicrystalline phases are found to correlate with each other.     

Conversion of brown coal in supercritical water without and with addition of oxygen at continuous supply of coal-water slurry

A study of conversion of organic matter of brown coal in supercritical water (SCW) at 30 MPa, 400−760 °C and continuous supply of coal-water slurry (CWS) into a tubular reactor is presented. It was found that 48−63% (depending on the SCW temperature) of coal organic matter (COM) is ejected from CWS coal particles as liquid and gaseous products when they move through the reactor. We termed this stage of SCW conversion as dynamic conversion (DC) of coal. It turns out that the particles which underwent the DC stage did not aggregate in the reactor during static conversion (SC) within a coal layer due to continuous pumping through this layer. The experimental data on the composition of DC and SC products, degree of coal conversion, and the data on the degree of combustion of carbon in the presence of oxygen are given.     

Local atomic order in the Al-Cu-Fe melts corresponding to crystalline and quasicrystalline phases

The local atomic order in the Al₇₀Cu₂₀Fe₁₀ and Al_61.9Cu_25.4Fe_12.7 melts that correspond to the tetragonal τ₂ and quasicrystalline phases was studied. The structures of these ternary melts were investigated by high-temperature X-ray diffraction and Reverse Monte Carlo simulation at various temperatures. The structural models of the melts are analyzed using the Voronoi polyhedra and the Delaunay simplexes. The specific features in the structure factor curves were comprehensively discussed: a shoulder in the second maximum and a prepeak on the left side of the principal maximum. The prepeak in the structure factor curves in the diffraction vector range 11–22 nm^?1 is shown to be caused by chemical local atomic ordering, and the shoulder on the right side of the second maximum is shown to result from the presence of icosahedral polytetrahedral clusters in the melts.     

Pattern of the atom ordering in a melt and surface properties of systems with intermetallic compounds

A local atomic structure of the Ni-Al, Ni-Ge, and Ni-Sn melts has been analyzed using the models reconstructed from experimental curves of the structure factor employing the reverse Monte Carlo and Voronoy-Delaunay methods. It has been found that a decisive effect on the formation of the short-range structure, type of the atomic interaction, and surface properties of melts of systems with intermetallic compounds is exerted by the retention of the component interaction intensity and the chemical bond type in melting intermetallic phases, which causes the correlation between the structures of the liquid and solid phases. A change in the pattern of the atom ordering in melts (an intensification of the interaction between like atoms, while the interaction between unlike atoms weakens in the Ni-Al → Ni-Ge → Ni-Sn order) results in the change of thermodynamic and surface properties of melts.     

Hybrid photovoltaic devices from regioregular polythiophene and ZnO nanoparticles composites

The nano size zinc oxide (ZnO) was successfully synthesized at low temperature solution method. The structural characterization, size and distribution of synthesized ZnO particles were performed using X-ray diffraction (XRD) and neutron scattering technique. The hybrid polymer-metal oxide bulk heterojunction solar cell has been fabricated by blending of ZnO and regioregular poly(3-hexylthiophene) (P3HT) through solution process and flow coating on the flexible substrate. The decrease in the photoluminescence (PL) emission intensity more than 79% for ZnO:P3HT composites film indicates high charge generation efficiency. The cell shows the V_oc and I_sc of 0.33 V and 6.5 mA/cm², respectively. The performance and stability of cell were investigated using UV illumination of white light.