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Advances in electronics and nuclear energy have led to devices producing greater heat and therefore requiring more efficient cooling systems. The proposed liquid metal based on eutectic Ga-Sn-Zn meets such expectations. First, however, the materials which are used for storage and mostly applied in electronics, such as Cu, should be examined. The investigated liquid/Cu substrate couples were cross-sectioned and subjected to scanning electron microscopy to observe interfacial microstructure changes. The created intermetallic Cu-Ga phase layer at the liquid/Cu substrate interface was identified by x-ray diffraction analysis, and the kinetics of the formation and growth of the IMC layer were determined. [ABSTRACT FROM AUTHOR]

The problems associated with the corrosion of aluminum connections, the low mechanical properties of Al/Cu connections, and the introduction of EU directives have forced the potential of new materials to be investigated. Alloys based on eutectic Zn-Al are proposed, because they have a higher melting temperature (381 °C), good corrosion resistance, and high mechanical strength. The Zn-Al-Si cast alloys were characterized using differential scanning calorimetry (DSC) measurements, which were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed at temperature ranges of −50 to 250 °C and 25 to 300 °C, respectively. The addition of Si to eutectic Zn-Al alloys not only limits the growth of phases at the interface of liquid solder and Cu substrate but also raises the mechanical properties of the solder. Spreading test on Cu substrate using eutectic Zn-Al alloys with 0.5, 1.0, 3.0, and 5.0 wt.% of Si was studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed with contact times of 1, 8, 15, 30, and 60 min, and at temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreadability of Zn-Al-Si on Cu was determined. Selected, solidified solder/substrate couples were cross-sectioned, and the interfacial microstructures were studied using scanning electron microscopy and energy dispersive x-ray spectroscopy. The growth of the intermetallic phase layer was studied at the solder/substrate interface, and the activation energy of growth of CuZn, CuZn, and CuZn phases were determined. [ABSTRACT FROM AUTHOR]

The pteropod Cuvierina constructs very lightweight, thin, flexible, and resistant shells with the most unusual microstructure: densely packed, continuous crystalline aragonite fibers that coil helically around axes perpendicular to the shell surface. The high degree of fiber intergrowth results in a particular interlocking structure. The shell is constructed by guided self-assembly, outside the animal's soft body. A prerequisite to understand its formation is to resolve the underlying crystallographic building principle. This is basic in order to use this hierarchically structured and highly functional biomaterial as inspiration for the production of new materials. It teaches us about the optimization of structures over millions of years of evolution under strict consideration of energetic costs and efficient use of available resources and materials. We have described how helical coiling proceeds by using a combination of diffraction and imaging techniques, which complement at different levels of resolution. Despite their curling, the fibers are continuously crystalline and show a preferred crystallographic growth direction. When the latter can no more be maintained due to the imposed curving, abrupt changes across twins permit to continue growth in the desired direction. This is a nice example of how crystallographically continuous fibers can grow helically. [ABSTRACT FROM AUTHOR]

Crystallization under hydrothermal conditions allowed us to prepare nanometric powders in the MgO–ZrO2 system of different magnesia concentrations. Sintering runs of these powder compacts studied using dilatometry measurements during heating and cooling revealed essential differences in their behavior. The microstructure of the resulting polycrystal is strongly related to the magnesia content in the starting powder, which strongly influences the phase composition of the resulting material and its mechanical properties. It should be emphasized that the novel processing method of such materials differs from the usual applied technology and leads to magnesia–zirconia materials of a different microstructure than that of "classical" materials of this kind. [ABSTRACT FROM AUTHOR]

The effect of using two different deposition systems on the microstructure and mechanical properties was studied in this paper. For this purpose, laser-engineered net shaping (LENS) and high-power CO2 laser deposition processes were applied to fabricate Inconel 625 samples. The microstructure of the Inconel 625 produced by both additive techniques was characterized using light microscopy (LM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The mechanical properties were characterized by tensile tests and microhardness measurements. High-power laser application resulted in a strong <100> build texture, while, at low powers, the {011} <100> Goss component increased. Both types of deposited materials showed dendritic microstructures with Ti-, Mo-, and Nb-rich zones at the cell boundaries, where numerous precipitates (Nb2C, NbC, titanium carbides, Nb3Ni, and NbNiCr) were also observed. It was also noted that both variants were characterized by the same slope with a proportional length, but the Inconel 625 fabricated via LENS showed a higher average yield strength (YS; 524 MPa vs. 472 MPa) and ultimate tensile strength (UTS; 944 MPa vs. 868 MPa) and lower elongation (35% vs. 42%) than samples obtained with the high-power CO2 laser deposition process. [ABSTRACT FROM AUTHOR]

• The Ni–W layer protect Ni substrate before dissolution by Ga-Sn-Zn up to 250 °C. • For the aging treatment at 100, 250 °C there are no IMC from Ni-Ga system at interface. • In the aging treatment at 500 °C the Ni substrate dissolution was observed. Requirements connected with increasing energy demands lead to the development of new thermal management systems. Liquid metals are an effective coolant, but are highly corrosive to most metals. This problem needs to be overcome to successfully employ gallium-based cooling systems. In this work, we present a potential corrosion protection Ni–W layer for nickel and nickel alloys. We investigated the interface between the Ga-Sn-Zn eutectic liquid metal and nickel substrates covered with an Ni–W protective layer at different temperatures. Cross sections of the couples were prepared and analysed using scanning electron microscopy to reveal microstructural changes, and EDS analysis was carried out. We concluded that Ni–W provides sufficient protection for Ni in a corrosive liquid metal environment up to 250 °C. [ABSTRACT FROM AUTHOR]

In this research, we investigate the connection between an observed enhancement in solid oxide fuel cell stack performance and the evolution of the microstructure of its electrodes. A three dimensional, numerical model is applied to predict the porous ceramic-metal electrode performance on the basis of microstructure morphology. The model features a non-continuous computational domain based on the digital reconstruction obtained using focused ion beam scanning electron microscopy (FIB-SEM) electron nanotomography. The Butler–Volmer equation is used to compute the charge transfer at reaction sites, which are modeled as distinct locally distributed features of the microstructure. Specific material properties are accounted for using interpolated experimental data from the open literature. Mass transport is modeled using the extended Stefan–Maxwell model, which accounts for both the binary, and the Knudsen diffusion phenomena. The simulations are in good agreement with the experimental data, correctly predicting a decrease in total losses for the observed microstructure evolution. The research supports the hypothesis that the performance enhancement was caused by a systematic change in microstructure morphology. [ABSTRACT FROM AUTHOR]

The effect of calcination temperature on the structural properties and phase formation of synthesized CaO-Al2O3 nanopowder was investigated and discussed. The calcination products were identified by differential thermal analysis (DTA) and the crystalline phase formation was analyzed by X-ray diffraction (XRD). The obtained results showed that the crystallization started at 460 °C. Finally, the microstructures of the nanoparticles were observed by scanning (SEM) and transmission electron (TEM) microscopes. The investigation showed that an increase in the calcination temperature led to the appreciable increase in the crystallite size and the crystallinity of the final product. The obtained data confirmed that the prepared materials were mayenite with different surface area in the range of 71.18 m2/g to 10.34 m2/g after annealing in the temperature range of 470 °C to 960 °C. [ABSTRACT FROM AUTHOR]

In this research, a fully three-dimensional, multiphase, microstructure-scale heterogeneous (non-continuous) electrode, Solid Oxide Fuel Cell (SOFC) stack model is implemented in order to assess the impact of homogeneity disturbance in an SOFC anode. The Butler–Volmer model is combined with recent empirical relations for conductivity and aspects of the Maxwell–Boltzmann kinetic theory describing the transport of mass within the porous medium. Methods for the localized quantification of electrode morphology parameters (such as triple phase boundary length) are implemented. The exchange current distribution in the electrode, the partial pressures and the electric potential fields for each phase are computed numerically. In order to simulate heterogeneity, transfer barriers of varying placement and size are added to an otherwise homogeneous, virtual microstructure based on data from FIB-SEM tomography. The results are compared to a model based on the continuous electrode theory, and the points of discrepancy are highlighted. [ABSTRACT FROM AUTHOR]

Crossed-lamellar microstructures are the most common shell-forming biomaterials in mollusks. Because of their complex hierarchical 3D arrangement and small crystallite size, previous crystallographic studies are scarce and have centered on particular species with no comprehensive analysis available. To evaluate the crystallographic diversity of the crossed-lamellar microstructures, we have studied a large set of bivalve and gastropod species with crossed-lamellar layers using X-ray diffraction and electron backscatter diffraction. From the number, distribution, and relationships of maxima, we have classified pole figures into nine different recurring crystallographic patterns. According to their crystallographic equivalences, these patterns can be grouped into five groups. A first division is established according to whether there is one or two main orientations for the c-axis of aragonite. In the latter case, each orientation corresponds to one of the two sets of alternating first-order lamellae. The two main orientations of the c-axis diverge by rotation within the plane of the first-order lamellae around either a common a- or b-axis. We also show how some patterns may derive from others. Patterns with two c-axis orientations represent crystal relationships until now completely unknown in biogenic and abiogenic aragonite and are most likely produced by particular proteomic pools. [ABSTRACT FROM AUTHOR]

The aim of the work was to characterise the new coating material based on zinc with the addition of molybdenum, electrodeposited on steel substrate from nontoxic, citrate based electrolytes. The surface composition of deposits was ascertained by chemical analysis (WDXRF). The morphology of coatings was studied by SEM. The surface morphology and roughness of Zn–Mo coatings on steel was investigated by AFM. The microhardness and Young modulus were determined by indentation technique, whereas the coating adhesion to the substrate was examined by means of scratch test. The optimal ranges of electrodeposition parameters, enabling the preparation of good quality coatings (i.e. uniform, compact, with good adhesion to the substrate), was specified. The morphology of deposits depends significantly on the content of molybdenum and on the thickness of electrodeposited layer. The microhardness of Zn–Mo coating increases with the increase of molybdenum content up to 3 wt.% and then reaches about 3.5 GPa, which is almost five times that of the value of the microhardness of the Zn coating studied. [ABSTRACT FROM AUTHOR]

• (Ce,Gd,Nd,Sm,Pr,Mo x)O 2- δ and (Ce,Gd,Nd,Sm,Pr,Mo x)O 2- δ , x = (0−0.5) are synthesized. • Addition of Mo x ≥ 0.3 allows stabilizing single-phase fluorite structure. • Mo acts as a substitutional dopant, with Mo6+ valence state. • The stabilization mechanism resembles the one in δ-Bi 2 O 3 -based materials. • Electrical measurements indicate mixed ionic-electronic behavior. (Ce,Gd,Nd,Sm,Pr)O 2- δ and (Ce,Gd,La,Nd,Pr)O 2- δ rare-earth high-entropy oxides (HEOx) with the oxygen vacancy-ordered Ia- 3 structure are doped with a small amount of molybdenum, to prepare two series of materials, (Ce,Gd,Nd,Sm,Pr,Mo x)O 2- δ and (Ce,Gd,Nd,Sm,Pr,Mo x)O 2- δ with x = (0, 0.1, 0.2, 0.3 and 0.5). The first-ever stabilization of the fluorite-type Fm- 3 m structure (i.e. with disordered vacancies) in the ceria-based HEOx is achieved. Structural, microstructural and transport properties of the compounds are systematically studied. The substitution level of x ≥ 0.3 allows to fully stabilize Fm- 3 m symmetry, with samples exhibiting good homogeneity. Influence of Mo on the oxygen vacancy concentration and charge state of the elements is studied with the use of Raman spectroscopy and XPS methods, showing decrease of the vacancy content and dominating presence of Mo6+, Ce4+ and mixed Pr3+/4+ states. Measured for the first time in this group of materials, the electrical conductivity of the Mo-doped oxides indicates the mixed ionic-electronic behavior. [ABSTRACT FROM AUTHOR]

Possibility of formation of quinary and senary equimolar high entropy oxides from the Co-Cr-Fe-Mg-Mn-Ni-O system is presented. Different proposed compositions are synthesized using the solid-state reaction route at high temperatures (900−1100 °C) and quenched to room temperature. Phase composition of the samples is studied, showing tendency toward formation of two main phases: rock salt-structured Fm-3 m and spinel-structured Fd-3 m. It is documented that the annealing temperature has a profound effect on stability of both structures, and at 1100 °C usually the highest content of Fm-3 m phase is usually observed. Three different oxides, namely, (Co,Cr,Fe,Mn,Ni) 3 O 4 , (Co,Cr,Fe,Mg,Mn) 3 O 4 and (Cr,Fe,Mg,Mn,Ni) 3 O 4 are obtained as single-phase materials, which structure can be described as the high entropy Fd-3 m spinel one. The latter two compounds have not been previously reported in the literature. Activated character of the electrical conductivity dependence on temperature is observed, with relatively high total conductivity at high temperatures and corresponding high absolute values of Seebeck coefficient. [ABSTRACT FROM AUTHOR]

Highlights • DIR-SOFC time-dependent numerical model was developed. • Numerical solver verified analytically, with relative error below 5 × 10−3%. • Anode microstructural parameters determine the heat balance in DIR-SOFC cell. • Fuel starvation the most likely to occur in upstream of the DIR-SOFC cell. • Fuel starvation unable to prevent in DIR-SOFC, if methane and steam only are supplied. Abstract In this paper, a transient microstructure-oriented numerical simulation of a planar Direct Internal Reforming Solid Oxide Fuel Cell (DIR-SOFC) is delivered. The performance criteria in a direct steam reforming for a fuel starvation scenario are analyzed in order to optimize the underlying process. The proposed two-dimensional multiscale model takes into account mass and heat transport, electrochemistry, as well as the intrinsic steam-reforming kinetics. In the paper, the methane/steam reforming process over the Ni/YSZ catalyst is experimentally investigated to verify the used chemical reaction model. A three-dimensional digital microstructure representation of the commercial anode is analyzed using a Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) and the nickel-pore contact surface is calculated to relate the reforming reaction rate to the catalyst's active area. Based on the complete DIR-SOFC model, a parametric study is carried out, to simulate the dynamic response of a fuel cell for different design and operating conditions. The results prove the dominant impact of inlet fluid temperature and methane content on the calculated distribution of hydrogen across the channel, while the collected current density was found to be a less important factor. The simulations indicate, that in the case of the direct reforming, fuel starvation is likely to occur in the upstream of the anode channel, where the reforming reaction does not keep up with producing hydrogen. The obtained results provide a significant insight into safe and efficient control strategies for Solid Oxide Fuel Cells. [ABSTRACT FROM AUTHOR]

Abstract This work describes results concerning the corrosion behaviour of Li, Na and Si doped eutectic Zn-Al alloys. Corrosion properties were investigated with the use of several complementary electrochemical techniques: time resolved OCP analysis, potentiodynamic studies, rotating disc electrode (RDE) and electrochemical impedance spectroscopy (EIS). The corrosion potential (E corr) and corrosion current (i corr) were obtained using potentiodynamic tests. The corrosion studies revealed that the alloying addition to eutectic Zn-Al resulted in slightly lower corrosion resistance than observed for Zn-Al. The results indicate that the addition of Si reduced corrosion resistance the least, compared to Li and Na. Graphical abstract Image 1 Highlights • Corrosion behaviour of high temperature soldering materials ZnAl was investigated. • The additions of Li, Na and Si to ZnAl alloys reduced corrosion resistance. • The microstructure of alloys after testing was analysed towards corrosion products. • Al reduced zinc dissolution by stabilisation of protective corrosion products. [ABSTRACT FROM AUTHOR]

Electrodeposition process is a very promising method for producing metal matrix composites reinforced with ceramic particles. In this method insoluble particles suspended in an electrolytic bath are embedded in a growing metal layer. This paper is focused on the investigations of the nickel matrix nanocomposite coatings with hard α-Al 2 O 3 nano-particles, electrochemically deposited from modified Watts-type baths on steel substrates. The influence of various current densities on the microstructure, residual stresses, texture, hardness and corrosion resistance of the deposited nickel/alumina coatings was investigated. The surface morphology, cross sections of the coatings and distribution of the ceramic particles in the metal matrix were examined by scanning electron microscopy. The phase composition, residual stresses and preferred grain orientation of the coatings were characterized using X-ray diffraction techniques. The coating morphology revealed that α-Al 2 O 3 particles show a distinct tendency to form agglomerates, approximately uniformly distributed into the nickel matrix. [ABSTRACT FROM AUTHOR]

Axially symmetric magnets with good mechanical properties in the surface layer and good magnetic properties in the volume of material are essential in the production of increasing number of modern electrical devices. In order to obtain this type of gradient structure, two phase (α + γ) hard magnetic FeCr22Co15 alloy was subjected to tension and torsion in temperature range 725–850 °C. The microstructure observations of deformed samples showed the formation of gradient microstructure with minimum grain size (about 1 μm) in the surface layer of material. On the basis of TEM observations, it was found that the deformation resulted in the martensitic transformation of γ into α γ phase. The microstructure observations also showed the presence of intermetallic σ phase (Fe–Cr) with the maximum precipitates amount in the surface layer of material. The measurements of magnetic properties showed decreasing coercive force of FeCr22Co15 alloy after deformation due to preservation of α γ phase (about of 35%) in the microstructure after magnetic treatment. On the other hand, α γ phase might have appeared as a plastic constituent among brittle grains of α phase, which had a positive influence on mechanical properties of the material. [ABSTRACT FROM AUTHOR]