Search

Further development of solid oxide fuel cell (SOFC) oxygen electrodes can be achieved through improvements in oxygen electrode design by microstructure miniaturization alongside nanomaterial implementation. In this work, improved electrochemical performance of an La

This paper aims at analyzing the effect of heat treatment using Concentrated Solar Energy (CSE) on the martensitic microstructure evolution of Ti-6Al-4V alloy manufactured by Selective Laser Melting (SLM) technology. The application of CSE, a renewable energy sources, in post-processing of SLMed Ti-6Al-4V alloy is discussed based on heat treatments performed at Plataforma Solar de Almeria, Spain, using solar furnace SF40. In SLM process of Ti-6Al-4V powder because of local high heating followed by a rapid cooling the microstructure consists of an acicular martensite (α′ phase). Decomposition of α′ martensite of SLMed Ti-6Al-4V after heat treatment in solar furnace, using CSE, by SEM, EDX, TEM, SAED, and XRD analyses, was investigated. It has been found that for treatment below β-transus at 705 °C, because of low temperature, the α′ martensite was not fully converted into α + β and the β phase was not identified by XRD analysis. Heat treatments below (940 °C followed by 650 °C) and above (1050 °C) β-transus have revealed that α′ martensite was converted into a lamellar α + β mixture and also β phase was identified by XRD and TEM analysis. In the analyzed areas, middle areas of the samples contain an area fraction of β phase greater than the top areas. Area fraction of β phase, after heat treatment above β-transus, at 1050 °C, is greater than that obtained after treatment below β-transus.

The equiaxed Ni-based superalloy René 108 was subjected to short-term annealing at five temperatures between 900 °C and 1100 °C. The phase composition, phase lattice parameters, microstructure, stereological parameters, and chemical composition of γ′ precipitates were investigated by thermodynamic simulations, X-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Analysis of the γ and γ′ lattice parameters using the Nelson-Riley extrapolation function showed that the misfit parameter for temperatures 900 °C to 1050 °C is positive (decreasing from 0.32 to 0.11 pct). At 1100 °C, the parameter becomes negative, δ = − 0.18 pct. During the short-term annealing, γ′ precipitates dissolution occurred progressing more rapidly with increasing temperatures. The surface fraction of γ′ precipitates decreased with increasing temperature from 0.52 to 0.34. The dissolution of γ′ precipitates did not only proceed through uninterrupted thinning of each individual precipitate, but also included more complex mechanisms, including splitting. Based on transmission electron microscopy, it was shown that after γ′ precipitates dissolution, the matrix close to the γ/γ′ interface is strongly enriched in Co and Cr and depleted in Al.

Development of environmentally friendly, high performing oxygen evolution reaction (OER) catalysts is an important research challenge. In this work, iron doped strontium titanates with a general formula SrTi1-xFexO3-δ (x = 0.35, 0.50, 0.70, 0.90, and 1.00) denoted as STFx, were synthesized via a solid state reaction technique and characterized in terms of oxygen evolution reaction electrocatalysis in an alkaline electrolyte (0.1 M KOH). The produced powders were characterized by a high specific surface area (>20 m2 g−1), beneficial for OER. The evaluation of specific activity indicated the following trend of increasing performance: STF35 < STF50 < STF70 < SFO < STF90. The lowest overpotential at 10 mAcm−2 GEO of 410 mV (350 mV at 25 μA cm−2OX) was achieved by STF90 with the corresponding Tafel slope of 60 mV dec−1. The two materials with the highest Fe content (i.e. STF90 and SFO) showed, however, poor chemical stability in alkaline solution demonstrated by the dissolution of Sr. Based on the good electrochemical performance (~460 mV at 10 mA cm−2GEO, ~405 mV at 25 μA cm−2OX) and chemical stability for at least 30 days (no Sr dissolution) of STF50, it can be considered an interesting, working at room temperature OER catalyst based on non-toxic and abundant elements.

The research presented in this paper is part of a larger project concerning deformation behavior, microstructure and mechanical properties of high-manganese steels with different chemical compositions and processed under various conditions. The current investigation deals with the development of microstructure and crystallographic texture of Fe-21.2Mn-2.73Al-2.99Si steel deformed in tension until fracture at ambient temperature. The deformation process of the examined steel turned out to be complex and included not only dislocation slip and twinning but also strain induced phase transformations (γ → ε) and (γ → α′). The formation of ε-martensite with hexagonal structure was observed within the microstructure of the steel starting from the range of lower strains. With increasing deformation degree, the α′-martensite showing a cubic structure gradually began to form. Attempts have been made to explain the circumstances or conditions for the occurrence of the deformation mechanisms mentioned above and their impact on the mechanical properties. The obtained results indicate that the strength and plastic properties of the steel substantially exceed those of plain carbon steels. Since both, mechanical twinning and the strain-induced phase transformations took place during deformation, it seems that both types of deformation mechanisms contributed to an increase in the mechanical properties of the examined manganese steel.

The changes in ATI® 718Plus™ (718Plus) superalloy microstructure after high-temperature long-term exposure (850 °C/4000 h/air) were characterized by two- and three-dimensional imaging techniques. The 718Plus microstructure consists of a γ-matrix strengthened by coherent γ′-phase and plate-like η-phase at grain boundaries. The η-phase analysis showed the presence of δ-phase stacking faults within it, along with fluctuations of chemical composition within these defects. Applied thermal exposure resulted in an increased amount of δ-, η-phases and formation of topologically close-packed phases. One of them was identified by electron diffraction as trigonal μ-phase. However, the difference in size and morphology revealed via tomographic reconstruction indicates that the formation of other topologically close-packed phases is possible. The μ-phase was enriched in Mo, Co, Fe and Cr, which causes their depletion in the γ-matrix and may detrimentally affect the superalloy mechanical properties.

Magnesium germanate (MgGeO3) ceramics represent a model system for geological study of the upper earth's mantle and are recently being investigated for applications in which red luminescence properties are required. The mechanical and optical properties of MgGeO3 are greatly influenced by the its polymorphic nature and by the complex series of phase transformations taking place in response to temperature variations and the application of mechanical pressure, as well-documented in the literature. In the present study, an additional phase transformation from orthoenstatite MgGeO3 to forsterite Mg2GeO4 with an olivine-type structure is identified in ceramics sintered in range 1350–1500 °C and ascertained by the refinement of the relative X-ray diffraction patterns. The phase transformation is believed to be driven by the volatilization of GeO2 during high-temperature sintering and it should be taken into consideration when targeting single phase and dense MgGeO3 ceramics.

The superalloys are usually used as structural material in jet engines due to their high-temperature stability and good endurance. Many components found in the hot-part of jet engines are of complex shape, therefore casting is utilized for to their production. One of the problems associated with the casting process of highly alloyed alloys, such as superalloys, is partitioning of alloying elements upon solidification. This segregation might lead to the formation of low melting temperature eutectics. Their presence in the material microstructure will have a negative effect on the weldability. Negative impact on weldability is one of the reasons why secondary phases should be avoided as microstructural elements in the welded materials. To eliminate such hazardous phases, the material should be subjected to a heat treatment with the aim of homogenizing the microstructure and chemical composition, which should enhance the weldability. The aim of this work was the application of analytical electron microscopy in combination with energy dispersive X-ray spectroscopy as well as tomographic techniques for qualitative and quantitative characterization of structural elements in as-cast Allvac 718Plus Ni-based superalloy subjected to later heat treatment. Alloy 718Plus is a newly developed superalloy in which the secondary Laves phase forms as a low-melting eutectic upon casting. The development of innovative materials for aeronautics and clean energy systems requires the use of modern research methods for structure characterization on the level from micro- to the nanoscale. The performed analysis, allowed identification of phases (Laves and η) occurring in interdendritic regions of as-cast Allvac 718Plus superalloy and analyzing their microstructure down to the atomic scale, which revealed their complex nature. The experiments and investigation show that advanced microscopic techniques and test methods in conjunction with tomographic techniques enable complementary information about solidified structures of the alloy to be obtained that can be useful for the understanding process of casting and welding of the Allvac 718Plus.

The change of γ′ phase morphology in quenched Ni-based superalloy strengthened by γ′ precipitates was investigated by means of scanning electron microscopy and X-ray diffraction. Lattice parameters of γ and γ′ phases and subsequently the δ parameter were calculated. Relatively high content of gamma prime formers resulted in a substantially high volume fraction of precipitates in the dendrite cores. The volume fraction of γ′ phase was significantly decreased due to dissolution of precipitates in the surrounding matrix, as a result of short-term subsolidus exposure. The lattice parameter of γ′ phase was higher than that of γ phase, which results in a positive δ parameter in fully heat treated (FHT) and also FHT+ Quench conditions. For (200) and (220) reflections the γ/γ′ misfit was lower in the FHT + Q sample.

Reduced titanium oxide structures are regarded as promising materials for various catalytic and optoelectronic applications. There is thus an urgent need for developing methods of controllable formation of crystalline nanostructures with tunable oxygen nonstoichiometry. We introduce the Extremely Low Oxygen Partial Pressure (ELOP) method, employing an oxygen getter in close vicinity to an oxide during thermal reduction under vacuum, as an effective bottom-up method for the production of nanowires arranged in a nanoscale metallic network on a SrTiO3 perovskite surface. We demonstrate that the TiO nanowires crystallize in a highly ordered cubic phase, where single nanowires are aligned along the main crystallographic directions of the SrTiO3 substrate. The dimensions of the nanostructures are easily tunable from single nanometers up to the mesoscopic range by varying the temperature of reduction. The interface between TiO and SrTiO3 (metal and insulator) was found to be atomically sharp providing the unique possibility of the investigation of electronic states, especially since the high conductivity of the TiO nanostructures is maintained after room temperature oxidation. According to the growth model we propose, TiO nanowire formation is possible due to the incongruent sublimation of strontium and crystallographic shearing, triggered by the extremely low oxygen partial pressure (ELOP). The controlled formation of conductive nanowires on a perovskite surface holds technological potential for implementation in memristive devices, organic electronics, or for catalytic applications, and provides insight into the mechanism of nanoscale phase transformations in metal oxides. We believe that the ELOP mechanism of suboxide formation is suitable for the formation of reduced suboxides on other perovskite oxides and for the broader class of transition metal oxides.

Materials characterization 178, 111290 (2021). doi:10.1016/j.matchar.2021.111290, This paper investigate the thermophysical properties of the liquid as well as the rapid solidification ofAl5.0Mg0.2Sc alloys with 3.0 and 6.0 Li wt% by the discharge crucible, and Impulse Atomization techniquesrespectively. The discharge crucible method, allowed a simultaneous determination of density, surface tensionand viscosity as a function of the temperature. While the density and surface tension are found to decrease withLi content, the viscosity increases due to short-range ordering occurring in intermetallic phases. In order todetermine their characteristic temperatures, the alloys powder generated by Impulse Atomization were investigatedusing a Differential Scanning Calorimeter, while microstructural observations and chemical analyseswere conducted using scanning and transmission electron microscopy with energy dispersive X-ray spectroscopy.To study the influence of Li on the microstructural phase formation in these alloys, diffraction patterns analysesin transmission electron microscopy, as well X-ray diffraction using synchrotron measurements were carried out.The conducted measurements and microstructure observations revealed the precipitations of Al3Sc and Al2MgLiphases in both alloy compositions. In addition, AlLi precipitates were observed in Al5.0Mg0.2Sc6.0Li alloy,which is in agreement with the phase diagram., Published by Science Direct, New York, NY

Understanding the mechanisms of charge generation and their recombination in rutile TiO2 is of key importance in the design of optoelectronic and photocatalytic devices. In this study, we investigate the impact of both extrinsic and intrinsic defects on photoluminescence (PL) decay dynamics. The exploitation of two-photon fluorescence lifetime imaging microscopy (FLIM) enabled differentiation to be made between photoluminescence originating from dislocations and bulk in Nb-doped rutile TiO2. It was found that dislocations pinned at grain boundaries feature lower photoluminescence intensity and faster decay times (by 100 ps) than those in the bulk. This can be reversed upon reduction, whereby trap states are preferentially formed near to dislocation sites. We also evaluated the dependence of the extrinsic doping level on the charge carrier dynamics of rutile, and show that PL lifetimes are governed by predominant Auger processes that are insensitive to reduction, unlike dislocations. We believe that the oxygen deficiency suppression of charge carrier recombination at grain boundaries is the key factor in improving the photocatalytic activity of real TiO2-based materials.

The ATI 718Plus® is a creep-resistant nickel-based superalloy exhibiting high strength and excellent oxidation resistance in high temperatures. The present study is focused on multiscale 2D and 3D characterization (morphological and chemical) of the scale and the layer beneath formed on the ATI 718Plus superalloy during oxidation at 850 °C up to 4000 h in dry and wet air. The oxidized samples were characterized using various microscopic methods (SEM, TEM and STEM), energy-dispersive X-ray spectroscopy and electron diffraction. The 3D visualization of the microstructural features was achieved by means of FIB-SEM tomography. When oxidized in dry air, the ATI 718Plus develops a protective, dense Cr2O3 scale with a dual-layered structure. The outer Cr2O3 layer is composed of coarser grains with a columnar shape, while the inner one features fine, equiaxed grains. The Cr2O3 scale formed in wet air is single-layered and features very fine grains. The article discusses the difference between the structure, chemistry and three-dimensional phase distribution of the oxide scales and near-surface areas developed in the two environments. Electron microscopy/spectroscopy findings combined with the three-dimensional reconstruction of the microstructure provide original insight into the role of the oxidation environment on the structure of the ATI 718Plus at the nanoscale.

Ni-Fe-Cr-Al alloy has been subjected to a short aging treatment, which increased the mechanical properties and resulted in discontinuous precipitation at the grain boundaries. In this study, analytical electron microscopy was applied to explore the relationship between the occurring grain boundary phenomena and mechanical behavior. Within the discontinuous precipitation zone, three different phases were recognized, namely γ solid solution with lamellar Cr23 C6 carbides and elongated γ’ precipitates at the reaction front. Coherency of the discontinuous precipitates was identified as they have shown a cube-on-cube orientation relationship. Furthermore, the development of multiple discontinuous reactions was discussed.

AIII-BV semiconductors have been considered to be a promising material for decades in overcoming the limitations of silicon semiconductor devices. One of the important aspects within the AIII-BV semiconductor technology is gold-semiconductor interactions on the nanoscale. We report on the investigations into the basic chemical interactions of Au atoms with AIII-BV semiconductor crystals by the investigation of the nanostructure formation in the process of thermally-induced Au self-assembly on various AIII-BV surfaces by means of atomically resolved High Angle Annular Dark Field (HAADF) Scanning Transmission Electron Microscopy (STEM) measurements. We have found that the formation of nanostructures is a consequence of the surface diffusion and nucleation of adatoms produced by Au induced chemical reactions on AIII-BV semiconductor surfaces. Only for InSb crystals we have found that there is efficient diffusion of Au atoms into the bulk, which we experimentally studied by Machine Learning HAADF STEM image quantification and theoretically by Density Functional Theory (DFT) calculations with the inclusion of finite temperature effects. Furthermore, the effective number of Au atoms needed to release one AIII metal atom has been estimated. The experimental finding reveals a difference in the Au interactions with the In- and Ga-based groups of AIII-BV semiconductors. Our comprehensive and systematic studies uncover the details of the Au interactions with the AIII-BV surface at the atomic level with chemical sensitivity and shed new light on the fundamental Au/AIII-BV interactions at the atomic scale.

The metal–semiconductor (M-S) junction based devices are commonly used in all sorts of electronic devices. Their electrical properties are defined by the metallic phase properties with a respect to the semiconductor used. Here we make an in-depth survey on the origin of the M-S junction at the atomic scale by studying the properties of the AuIn2 nanoelectrodes formed on the InP(0 0 1) surface by the in situ electrical measurements in combination with a detailed investigation of atomically resolved structure supported by the first-principle calculations of its local electrical properties. We have found that a different crystallographic orientation of the same metallic phase with a respect to the semiconductor structure influences strongly the M-S junction rectifying properties by subtle change of the metal Fermi level and influencing the band edge moving at the interface. This ultimately changes conductivity regime between Ohmic and Schottky type. The effect of crystallographic orientation has to be taken into account in the engineering of the M-S junction-based electronic devices.

Chrome plating is used to improve the properties of metal surfaces like hardness, corrosion resistance and wear resistance in machine building. To further improve these properties, an electrodeposited chromium coating on steel, modified with nanodiamond particles is proposed. The nanodiamond particles (average size 4 nm measured by TEM) are produced by detonation synthesis (NDDS). The composite coating (Cr+NDDS) has an increased thickness, about two times greater microhardness and finer micro-structure compared to that of unmodified chromium coating obtained under the same galvanization conditions. In the microstructure of specimen obtained from chrome electrolyte with concentration of NDDS 25 g/l or more, “minisections” with chromium shell were found. They were identified by metallographic microscope and X-ray analyser on etched section of chromium plated sample. The object of further research is the dependence of the presence of NDDS in the composite coating from the nanodiamond particles concentration in the chroming electrolyte.

Micro-arc oxidation is a simple, single-step surface modification method used to produce coatings on titanium alloys for biomedical applications. The formation and properties of coatings can be widely controlled by adjusting process parameters such as applied voltage, frequency, processing time and electrolyte composition. In the present study, three different electrolytes were used to obtain well adherent, rough, porous, hydroxyapatite containing, oxide coating on Ti6Al7Nb alloy. Coatings were investigated in terms of their microstructure, chemical composition, roughness, hardness, adhesion strength and biocompatibility. Among the coatings produced in different electrolytes, one of them exhibited both good mechanical properties and bioactivity, while containing crystalline hydroxyapatite on the surface, whereas the other two coatings were mostly amorphous. Thereby, we have proposed an efficient electrolyte containing calcium and phosphorous species in order to modify titanium based alloys to improve their biocompatibility and osseointegration. Such properties are achieved by formation of a rough outer layer with open pores, providing high surface area for cells to adhere, proliferate and migrate into the coating, promoting firm anchorage of the coated implant in the bone.

The current investigation is a part of project concerning microstructure and texture in a series of ferrite-austenite stainless steels after deformation and annealing. The present paper focuses on deformation behavior of constituent phases in a metastable duplex type steel subjected to cold-rolling in the range of high reductions. Optical microscopy was used to examine changes in the morphology and the formation of ferrite-austenite band-like structure. Transmission electron microscopy was applied to analyze the microstructure and deformation mechanisms within the bands of austenite and ferrite. Additional research included the examination of texture changes in both constituent phases. Special attention was paid to deformation mechanisms operating within ferrite-austenite banded structure at high rolling reductions, including the formation of micro-shear bands, the occurrence of micro-twinning as well as deformation induced martensitic transformation. Transmission electron microscopy analysis indicates that the phase transformation occurred most likely through direct (γ→α') mechanism and obeyed predominantly Kurdjumov-Sachs orientation relationship. Within strongly fragmented two-phase microstructure at high strains the formation of α'-martensite proceeded in most cases at internal interfaces in micro-bands from the operating deformation systems.

Elastic and durable, magnetic and non-magnetic polysiloxane microspheres containing a large number of SiOH groups were obtained by a simple and cheap emulsion process. N-chelating ligands were grafted on these microspheres by the condensation of their silanol groups with N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. A platinum catalyst was immobilized on these microspheres. At every stage of the microspheres modification they were characterized by spectroscopy methods as well as by SEM microscopy. The catalyst appears only in the form of Pt(II) complex. The Pt(0) form was obtained by reducing this complex using sodium borohydride. The catalytic activity of the obtained catalysts was compared using model reactions, which were the hydrosilylation of phenylacetylene and hydrogenation of cinnamaldehyde. In both of these reactions the new platinum catalysts were recycled several times with the retention of their high catalytic activity. The hydrogenation of cinnamaldehyde leads to two products hydrocinnamaldehyde (HCA) and 3-phenyl-1-propanol (PP). The comparison of the rate of formation of the products with the rate of HCA and cinnamyl alcohol (CA) hydrogenation indicates that neither HCA nor CA are intermediate in the main pathway of the formation of PP.

Multi-layer coatings (composed of outer hydroxyapatite and inner titania layers) have been synthesized on Ti6Al4V alloy for biomedical applications by employing micro-arc oxidation at positive and negative voltages of 400 and 80, respectively. Addition of silver nitrate (at concentrations of 0.1 g/L and 0.4 g/L) into the calcium acetate hydrate and disodium hydrogen phosphate anhydrous containing base electrolyte provided an enhancement in bio- and antibacterial activities of the synthesized coating, while imposing precipitation of silver nanoparticles on the hydroxyapatite layer. It is finally concluded that addition of 0.1 g/L AgNO 3 into the base electrolyte is promising for MAO process of titanium-based implants, when the structural characteristics and risk of cytotoxicity are of concern for the synthesized multi-layer coatings.

In the present work, the influence of alumina (Al2O3) and zirconia (ZrO2) incorporation on the structural properties and wear resistance of titania (TiO2) based micro-arc oxidation (MAO) coatings fabricated on Ti6Al4V alloy was studied. For this purpose MAO was employed in a silicate-based electrolyte with and without additions of Al2O3 and ZrO2 particles. The structural properties were determined via X-ray diffraction (XRD) and X-ray photoelectron (XPS) spectroscopy analysis and an energy dispersive spectrometer (EDS) equipped scanning electron microscope (SEM). Furthermore, thermochemical simulations were made by using FactSage 7.3. Mechanical properties of the MAO coatings were determined by hardness measurements and dry sliding reciprocating wear tests. Structural examinations revealed that the MAO coatings fabricated in Al2O3 and ZrO2 added electrolytes comprised of these oxides and their complex forms (Al2TiO5 and ZrTiO4, respectively) along with TiO2 and amorphous silica (SiO2). Although incorporations of Al2O3 and ZrO2 did not remarkably improve the hardness of the MAO coatings, the highest wear resistance was obtained from the one formed in the ZrO2 added electrolyte. On the other hand, the MAO coating fabricated in the Al2O3 added electrolyte exhibited lower wear resistance than that of fabricated in the particle-free silicate-based electrolyte.

We have investigated the temperature-dependent morphology and composition changes occurring during a controlled self-assembling of thin Au film on the Gallium arsenide (001) surface utilizing electron microscopy at nano and atomic levels. It has been found that the deposition of 2 ML of Au at a substrate temperature lower than 798 K leads to the formation of pure Au nanoislands. For the deposition at a substrate temperature of about 798 K the nanostructures of the stoichiometric AuGa phase were/had been grown. Gold deposition at higher substrate temperatures results in the formation of octagonal nanostructures composed of an AuGa 2 alloy. We have proved that the temperature-controlled efficiency of Au-induced etching-like of the GaAs substrate follows in a layer-by-layer manner leading to the enrichment of the substrate surface in gallium. The excess Ga together with Au forms liquid droplets which, while cooling the sample to room temperature, crystallize therein developing crystalline nanostructures of atomically-sharp interfaces with the substrate. The minimal stable cluster of 3 atoms and the activation energy for the surface diffusion E d = 0.816 ± 0.038 eV was determined. We show that by changing the temperature of the self-assembling process one can control the phase, interface and the size of the nanostructures formed.

Ni-Fe-Cr-Al alloy has been subjected to 2 hours aging treatment between 600-900°C, which influenced the mechanical properties and resulted in discontinuous precipitation at the grain boundaries. In this study, SEM, TEM and STEM-EDXS were applied to explore the relationship between the occurring grain boundary precipitation phenomena and mechanical behavior. Within the discontinuous precipitation zone, three different phases were recognized, namely γ solid solution with lamellar M23C6 carbides and elongated γ’ precipitates at the reaction front. Coherency of the discontinuous precipitates was identified as they have shown a cube-on-cube orientation relationship. Furthermore, the development of multiple discontinuous reactions was discussed.

Multiple attempts have been made to lower the cost of the adsorbents for the wastewater treatment. This work investigated the possibility of obtaining Mg/Al and Mg/Fe LDH without excessive use of chemical reagents, by replacing them with cheaper substrates. Magnesite and dolomite were used as Mg-sources in a facile co-precipitation synthesis at room temperature. Several variants of LDHs were studied regarding their chemical composition, MII/MIII molar ratio and the synthesis time. Their comprehensive characterization was provided and compared to the reference materials obtained from chemical reagents. Depending on the molar ratio the reference samples exhibited a clear shift of the XRD basal reflections, and different species of interlayer carbonates were identified by spectroscopic methods. The LDHs derived from minerals had similar structural features as compared to the reference samples. However, the synthesis of mineral-based LDHs resulted in the formation of additional phases. The formation of LDH from minerals with a molar ratio higher than 2:1 was impossible in the applied conditions. The 2 h ageing time was enough to enable the LDH formation. The transformation procedure of magnesite and dolomite to LDH via simplified synthesis procedure may significantly reduce the final cost of the adsorbents by excluding expensive chemical reagents.

The spreading of Zn-Al eutectic-based alloys with 0.05 wt.%, 0.1 wt.%, and 0.2 wt.% Li on Cu substrate has been studied using the sessile drop method in presence of QJ201 flux. Wetting tests were performed after 1 min, 3 min, 8 min, 15 min, 30 min, and 60 min of contact at temperatures of 475°C, 500°C, 525°C, and 550°C. Samples after spreading at 500°C for 1 min were subjected to aging for 1 day, 10 days, and 30 days at temperature of 120°C, 170°C, and 250°C. The spreadability of eutectic Zn-5.3Al alloy with different Li contents on Cu substrate was determined in accordance with ISO 9455-10:2013-03. Selected solidified solder–substrate couples were, after spreading and aging tests, cross-sectioned and subjected to scanning electron microscopy, energy-dispersive spectroscopy (EDS), and x-ray diffraction (XRD) analysis of the interfacial microstructure. An experiment was designed to demonstrate the effect of Li addition on the kinetics of the formation and growth of CuZn, Cu5Zn8, and CuZn4 intermetallic compound (IMC) phases, during spreading and aging. The IMC layers formed at the interface were identified using XRD and EDS analyses. Increasing addition of Li to Zn-Al alloy caused a reduction in the thickness of the IMC layer at the interface during spreading, and an increase during aging. The activation energy was calculated, being found to increase for the Cu5Zn8 phase but decrease for the CuZn and CuZn4 phases with increasing Li content in the Zn-Al-Li alloys. The highest value of 142 kJ mol−1 was obtained for Zn-Al with 1.0 Li during spreading and 69.2 kJ mol−1 for Zn-Al with 0.05 Li during aging. Aging at 250°C caused an increase in only the Cu5Zn8 layer, which has the lowest Gibbs energy in the Cu–Zn system. This result is connected to the high diffusion of Cu from the substrate to the solder.

The addition of Li to eutectic ZnAl alloy caused improved mechanical and thermal properties, with potential application in new design materials used in the automotive and aerospace industries. The alloys with 0.05, 0.1, 0.2, 0.5 and 1.0 Li (wt.%) content were studied using calorimetry, to determine the melting temperatures. Thermal linear expansion and electrical resistivity measurements were performed at temperatures of −50 °C to 300 °C and 30 °C to 300 °C. The microstructure of the specimens was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Chemical microanalysis was performed using energy-dispersive X-ray spectroscopy (EDS) on SEM and TEM. The possibility of the occurrence of Al–Li, Li–Zn and Al–Li–Zn precipitates was studied by X-ray diffraction (XRDs) and selected area electron diffraction (SAED). The addition of Li to eutectic ZnAl alloy increased the electrical resistivity and the coefficient of thermal expansion; however, the melting point did not change. The mechanical properties, strain and microhardness increased with Li content in alloys. Keywords: Zn–Al–Li alloys, Soldering materials, Scanning electron microscopy, Transmission electron microscopy, Microstructure, Thermal expansion, Electrical resistivity, Mechanical properties

Allvac 718Plus (718Plus) is a high strength, corrosion resistant nickel- based superalloy used for application in power generation, aeronautics and aerospace industry. The 718Plus microstructure consists of a γ matrix with γ’-Ni3(Al,Ti) and some δ- Ni3Nb phases as well as lamellar particles (η-Ni3Ti, η*-Ni6AlNb or Ni6(Al,Ti)Nb) precipitated at the grain boundaries. The primary strengthening mechanism for this alloy is a precipitation hardening, therefore size and distribution of precipitates are critical for the performance of the alloy. The aim of this study was to characterize precipitates in the 718Plus superalloy using Scanning Transmission Electron Microscope combined with Energy Dispersive X-ray Spectroscopy (STEM-EDX) and Focused Ion Beam Scanning Electron Microscope (FIB-SEM). The STEM-EDX and FIB-SEM tomography techniques were used for 3D imaging and metrology of the precipitates. Transmission electron microscopy and EDX spectroscopy were used to reveal details of the 718Plus microstructure and allow determine chemical composition of the phases. The study showed that electron tomography techniques permit to obtain complementary information about microstructural features (precipitates size, shape and their 3D distribution) in the reconstructed volume with comparison to conventional particle analysis methods, e.g. quantitative TEM and SEM metallography

Surface modifications of titanium based biomaterials are of great importance in medical field. In case of permanent implant coatings with bioactive properties are claimed to improve bone-implant connection stability. In the present study the micro-arc oxidation (MAO) is proposed as a method to modify the Ti6Al7Nb alloy surface by depositing porous and rough titanium dioxides layers with incorporated calcium phosphates. The effect of the reaction time on the microstructure of the formed coatings was investigated by means of scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM and SEM-EDS, respectively). The change in coatings thickness was observed, from initial 4-6 μm after 30 seconds of MAO treatment to final 38-44 μm after 10 minutes surface processing. By application of the electrolyte containing calcium and phosphorous ions it was possible to prepare coatings with the outer layer consisted mainly from calcium phosphates. Such phase composition together with rough and porous structure provides the perspective surface for cells attachment and ingrowth to create strong connection between implant and bone tissue.

This study was aimed at evaluating the microstructural change and thermal, electrical and mechanical properties with the addition of Na to eutectic ZnAl alloys. Solders based on eutectic ZnAl containing 0.2 to 3.0 (wt.%) of Na were developed for high temperature solder. Differential scanning calorimetry (DSC) measurements were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed over − 50 °C to 300 °C and 30 °C to 300 °C temperature ranges, respectively. The microstructure of the specimens was analyzed using scanning (SEM) and transmission electron microscopy (TEM) techniques. Chemical microanalysis was performed by energy-dispersive X-ray spectroscopy (EDS) on SEM and TEM. The precipitates of NaZn 13 were confirmed by X-ray diffraction (XRD) measurements and selected area electron diffraction (SAED) techniques. The addition of Na to eutectic ZnAl alloy increased the electrical resistivity and reduced the coefficient of thermal expansion; however, the melting point did not change. The mechanical properties, strain and microhardness increased with Na content in alloys.

In this work, the influence of the synthesis conditions on the structure, morphology, and electrocatalytic performance for the oxygen evolution reaction (OER) of Mn-Co-based films is studied. For this purpose, Mn-Co nanofilm is electrochemically synthesised in a one-step process on nickel foam in the presence of metal nitrates without any additives. The possible mechanism of the synthesis is proposed. The morphology and structure of the catalysts are studied by various techniques including scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The analyses show that the as-deposited catalysts consist mainly of oxides/hydroxides and/or (oxy)hydroxides based on Mn2+, Co2+, and Co3+. The alkaline post-treatment of the film results in the formation of Mn-Co (oxy)hydroxides and crystalline Co(OH)2 with a &beta, phase hexagonal platelet-like shape structure, indicating a layered double hydroxide structure, desirable for the OER. Electrochemical studies show that the catalytic performance of Mn-Co was dependent on the concentration of Mn versus Co in the synthesis solution and on the deposition charge. The optimised Mn-Co/Ni foam is characterised by a specific surface area of 10.5 m2&middot, g&minus, 1, a pore volume of 0.0042 cm3&middot, 1, and high electrochemical stability with an overpotential deviation around 330&ndash, 340 mV at 10 mA&middot, cm&minus, 2geo for 70 h.

The investigations the influence of methane and acetylene additions in the hybrid PVD-PECVD W-C:H coatings driven by DCMS and HiPIMS on plasma polymerization processes, carbon matrix content, its hybridization, hydrogenation and hardness revealed numerous differences related to hydrocarbon gas type and sputtering method. Close correlations between the hydrogen to carbon concentration ratio in the hydrocarbon precursor and contents of carbon phase, its hydrogenation and hybridization were established. The increase of each of these parameters had detrimental effects on hardness due to the consumption of σ bonds for C H at the expense of cross-linking among C C chains. HiPIMS and acetylene were found to provide the highest hardness (~20 GPa) in W-C:H coatings within the hybrid PVD-PECVD regime, most probably due to the best combination of hybridization, hydrogenation and cross-linking of the carbon phase. A qualitative model of growth mechanism of W-C:H coatings during hybrid PVD-PECVD with different hydrocarbon precursors and sputtering methods was proposed.

This work evaluates electrodeposited and differently treated Mn-Co catalysts for their oxygen evolution reaction activity. Catalysts are evaluated in the as-deposited and heat treated state: after 350 °C and 600 °C. Results show that the highest electrochemical activity is obtained for the as-deposited Mn-Co oxyhydroxide, which possibly possess a layered double hydroxide structure. After the heat treatment process, especially after 600 °C, the electrochemical performance decreases considerably.

Reduced titanium oxide structures are regarded as promising materials for various catalytic and optoelectronic applications. There is thus an urgent need for developing methods of controllable formation of crystalline nanostructures with tunable oxygen nonstoichiometry. We introduce the Extremely Low Oxygen Partial Pressure (ELOP) method, employing an oxygen getter in close vicinity to an oxide during thermal reduction under vacuum, as an effective bottom-up method for the production of nanowires arranged in a nanoscale metallic network on a SrTiO3 perovskite surface. We demonstrate that the TiO nanowires crystallize in a highly ordered cubic phase, where single nanowires are aligned along the main crystallographic directions of the SrTiO3 substrate. The dimensions of the nanostructures are easily tunable from single nanometers up to the mesoscopic range by varying the temperature of reduction. The interface between TiO and SrTiO3 (metal and insulator) was found to be atomically sharp providing the unique possibility of the investigation of electronic states, especially since the high conductivity of the TiO nanostructures is maintained after room temperature oxidation. According to the growth model we propose, TiO nanowire formation is possible due to the incongruent sublimation of strontium and crystallographic shearing, triggered by the extremely low oxygen partial pressure (ELOP). The controlled formation of conductive nanowires on a perovskite surface holds technological potential for implementation in memristive devices, organic electronics, or for catalytic applications, and provides insight into the mechanism of nanoscale phase transformations in metal oxides. We believe that the ELOP mechanism of suboxide formation is suitable for the formation of reduced suboxides on other perovskite oxides and for the broader class of transition metal oxides.

Co-deposition of CuO and Mn1.5Co1.5O4 by single step electrophoretic deposition is used to produce ∼15 µm coatings on Crofer22APU steel, which finds use as interconnect for high temperature solid oxide cells. Sintering of the green coatings in reducing and then oxidizing conditions led to formation of a mixed (Cu,Mn,Co)3O4 spinel. By the incorporation of Cu, the density of the coatings improved. Scanning and transmission electron microscopy observations, supplemented with energy dispersive spectroscopy, confirmed dissolution of Cu in the spinel phase. For the un-doped Mn1.5Co1.5O4 both the tetragonal and cubic phases are detected at room temperature by X-ray diffractometry, whereas the addition of Cu seems to stabilize the cubic phase. Initial (∼1000 h) high temperature corrosion evaluation at 800 °C in air showed promising properties of the mixed spinel coating.

This study has been carried out to optimise the silver (Ag) content of the coating synthesised on commercially pure titanium (Cp-Ti, Grade 4) for biomedical applications by micro-arc oxidation (MAO) process. The MAO process has been conducted in electrolytes containing silver acetate (AgC2H3O2) at different concentrations between 0 and 0.002 mol L-1. When compared to the base electrolyte, coatings synthesised in >= 0.001 mol L-1 AgC2H3O2 added electrolytes exhibited an antibacterial efficiency of 99.8% against Staphylococcus aureus (S. aureus). Detailed examination revealed that the presence of 0.01 mol L-1 AgC2H3O2 in the electrolyte resulted in incorporation of 1.4 wt-% Ag into fabricated coating consisting mainly of outer hydroxyapatite (HA) and inner titanium oxide (TiO2) layers. In comparison to the Ag-free coating, 1.4 wt-% Ag in the coating lowered the proliferation of SAOS-2 cells, which still tended to grow at a relatively low rate with increasing culturing time.