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Na induces the formation of acicular RuO2 in the glass melt, and the effect of Cs on the precipitation of RuO2 is not clear. In this study, sodium ruthenate (NaRu) and cesium ruthenate (CsRu) were prepared by quenching experiments, and RuO2-containing waste glass was prepared by calcination of glass surfaces. The results showed that both CsRu and NaRu induced the formation of RuO2 in the glass melts, with rod-like and acicular morphology, respectively. It can be inferred that alkali metals play an important role in the formation of RuO2 with different shapes. [ABSTRACT FROM AUTHOR]

To increase the electrical conductivity of nickel electrodes used in solar cells, this study investigated the effects of six different alcohol-based brighteners on nickel electrodeposition and elucidated their mechanisms during the deposition process. Nickel electrodeposition was conducted on a single-crystal silicon (c-Si) substrate in a Watts nickel plating bath with the addition of various additives at 1 g/L. Surface analysis and microstructure characterization were employed, alongside density functional theory calculations and molecular dynamics simulations, to analyze the influence of brightener molecule adsorption on metal grain growth and conductivity properties. These results indicate that alcohol-based additives can be automatically absorbed on the surface of the deposit, whereas long-chain polyhydroxy additives result in a smaller energy gap ( Δ E ) and more active adsorption sites than do short-chain additives, facilitating greater reactivity on the Ni surface. This resulted in a preferred orientation shift of the crystal structure from the (200) plane to the (111) plane, along with a refined grain size and conical morphology growth. Among the studied additives, long-chain molecules increased the Ni0 content in the plating layer and increased its conductivity. In particular, sorbitol effectively reduced the resistivity and grain growth rate of the coating, underscoring its potential as an additive for fabricating high-performance electrodes on c-Si substrates. [ABSTRACT FROM AUTHOR]

The fusion zone microstructures in K-TIG-welded and post-weld solution heat-treated new superalloy VDM Alloy 780 were examined. In addition, the kinetics of the base metal grain growth during solution heat treatments were analyzed. (S)TEM analyses show that major interdendritic microconstituents formed in the fusion zone due to elemental microsegregation are MC carbides and coarse irregularly shaped Laves phase. Additionally, minor secondary interdendritic phases are found to include γ′, γ″, and tiny plate-like Laves particles. To prevent any potential deterioration of mechanical properties caused by the irregular Laves phase, post-weld solution heat treatments (PWSHTs) at 954 °C to 1060 °C/1 hours were performed to remove the Laves phase. PWSHT at 954 °C only partially eliminates the Laves particles while forming an abundance of interdendritic δ/η phase. Laves phase is dissolved entirely without forming δ/η platelets after PWSHT at 1060 °C. It is proven that Laves eutectics in VDM Alloy 780's fusion zone can be eliminated through PWSHT without significantly coarsening the base metal's grain size in comparison to Alloy 718 as a result of substantial grain growth inhibition likely caused by solute segregation at grain boundaries. [ABSTRACT FROM AUTHOR]

Controllable crystallographic texture in copper foils exhibiting enhanced mechanical and electrical properties by pulse reverse electrodeposition. Highly textured and twinned Cu films fabricated by pulsed electrodeposition. 10.1103/PhysRev.26.390 2 Zhan X. Preparation of highly (111) textured nanotwinned copper by medium-frequency pulsed electrodeposition in an additive-free electrolyte. B replying to b C. Lu et al. I Nature Communications i https://doi.org/10.1038/s41467-022-32949-y (2022) In Lu et al.'s comment, the possibility of achieving textured crystal growth on textureless polycrystalline substrates is questioned. [Extracted from the article]

Morphology transformation and crystal growth strategies of metal oxide semiconductors are still extensively studied in material science recently, because the morphology and crystallinity significantly affect the physicochemical characteristics of metal oxide nanomaterials. However, understanding the morphology changes of α-MoO3 induced by annealing is still a challenge. Herein, the nanostructure transition of α-MoO3 induced by the annealing temperature is carefully investigated via the XRD and SEM methods. It can be found that crystallization is highly dependent on the annealing temperature. Interestingly, the MoO3 nanoflowers can change into nanosheets at 500 °C. Afterward, the nanosheets turned into microrods with the increase in annealing temperature due to the continuous growth of MoO3 crystal. On the other hand, the sensing performances of various MoO3 nanostructures are studied toward ethanol gas. Compared to the MoO3 nanoflowers and microrods, the MoO3 nanosheets-based sensor exhibits superior sensing performance to ethanol, and the maximum response value is 8.06. [ABSTRACT FROM AUTHOR]

The quality and the stability of devices prepared from polycrystalline layers of organic–inorganic perovskites highly depend on the grain sizes prevailing. Tuning of the grain size is either done during layer preparation or in a post-processing step. Our investigation refers to thermal imprint as the post-processing step to induce grain growth in perovskite layers, offering the additional benefit of providing a flat surface for multi-layer devices. The material studied is MAPbBr3; we investigate grain growth at a pressure of 100 bar and temperatures of up to 150 °C, a temperature range where the pressurized stamp is beneficial to avoid thermal degradation. Grain coarsening develops in a self-similar way, featuring a log-normal grain size distribution; categories like 'normal' or 'secondary' growth are less applicable as the layers feature a preferential orientation already before imprint-induced grain growth. The experiments are simulated with a capillary-based growth law; the respective parameters are determined experimentally, with an activation energy of Q ≈ 0.3 eV. It turns out that with imprint as well the main parameter relevant to grain growth is temperature; to induce grain growth in MAPbBr3 within a reasonable processing time a temperature of 120 °C and beyond is advised. An analysis of the mechanical situation during imprint indicates a dominance of thermal stress. The minimization of elastic energy and surface energy together favours the development of grains with (100)-orientation in MaPbBr3 layers. Furthermore, the experiments indicate that the purity of the materials used for layer preparation is a major factor to achieve large grains; however, a diligent and always similar preparation of the layer is equally important as it defines the pureness of the resulting perovskite layer, intimately connected with its capability to grow. The results are not only of interest to assess the potential of a layer with respect to grain growth when specific temperatures and times are chosen; they also help to rate the long-term stability of a layer under temperature loading, e.g. during the operation of a device. [ABSTRACT FROM AUTHOR]

Grain boundary (GB) migration and grain growth in nanocrystalline metals are major obstructions to exploit these materials to their fullest potential, thus limiting their utility as advanced structural materials. Here, we investigate the effect of Zr segregation to a Ni GB on migration and subsequent strengthening during shear deformation and high-temperature bending creep. Specifically, using molecular dynamics simulation, we simulate deformation of a Ni bicrystal specimen having a symmetric ∑5 grain boundary with and without segregated Zr. It is found that GB segregation up to 0.4 at.% pins the CSL boundary resulting in increased shear strength. Similar behavior is also observed in the case of bending creep deformation where the creep resistance increases only up to 0.4 at.%. This study indicates that larger amounts of GB segregation cause destabilization of the local atomic structure and consequently affect the GB stiffness. Moreover, we investigate the effect of Zr segregation on the interaction between the GB and a dislocation. We find that the preexisting dislocation is absorbed in the GB region for both clean and segregated specimens; however, the absorption path of the dislocation is different due to the change in GB stiffness caused by the Zr segregation. [ABSTRACT FROM AUTHOR]

The growth of crystals of metals, alloys, chalcogenides, and pnictides in melts of alkali metal halides under conditions of stationary temperature gradient has been studied. The formation of crystals with participation of elements that were not considered in previous studies (mercury, zirconium, hafnium, germanium, sodium, potassium, rhenium, and osmium) is described. Mechanisms of element transport in salt melts are proposed. It is shown that most of crystals are obtained from ions in which necessary elements exist in most conventional oxidation states. [ABSTRACT FROM AUTHOR]

Bi2O3- and MgO-doped BaTiO3–(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 (BT–NBMT) ceramics were synthesized from a solid-state approach, and then the impacts of Bi2O3 and MgO dosages on the structures and dielectric characteristics were studied. Obvious dual peaks were observed with Bi2O3 dosage to 0.04 and MgO dosage to 0.02. The low-temperature dielectric stability and grain size of the Bi2O3 dopant were improved, while those of the MgO dopant hardly changed with MgO dosage to 0.02, indicating the core/shell microstructure of BT–NBMT was formed following the dissolving-precipitating mechanism of BT systems doped with low-melting-point substances. The low-temperature dielectric stability of the Bi2O3- or MgO-doped BT–NBMT ceramics first improved and then deteriorated with the increase of doping concentrations. High-temperature stability and diffuse-state transition were found in the optimal ceramics. The second phases of Bi2O3 and MgO, magnesium titanium compounds were observed in Bi2O3 and MgO dopants, respectively. Bi2O3-doped and MgO-doped ceramics exhibited a fine-grained microstructure and significant grain growth, respectively, and the core/shell microstructure was responsible for the dielectric temperature stability for Bi2O3 dopants and collapsed to a homogeneous one with remarkable grain growth and the second phases for MgO dopants. [ABSTRACT FROM AUTHOR]

A long right tail is a common feature of experimental quasi-stationary size distributions of particles and grains that is not explained by the classical theories based on the mean field hypothesis. In this work, it is shown that the "pairwise interaction" approach, here presented in a comprehensive exposition involving both Ostwald ripening and grain growth, is a valid alternative to classical mean field theories since it produces more realistic predictions of the distribution shapes. The new analytical models are based on the mean field concept but rely on a detailed physical description of the elementary interactions responsible for the exchange of matter. They are jointly reviewed and compared with the corresponding classical Lifshitz–Slyozov–Wagner and Hillert models. The interactions are treated as a sum of elementary and specific contributions rather than as a generalized exchange with the mean field. The framework is complemented by the introduction of the "interaction volume" in Ostwald ripening and of the "local grain boundary curvature" in grain growth which are both size-dependent and permit to represent more precisely the local physics of the exchanges. The excellent results obtained in reproducing the experiments without any ad hoc parameters suggest that the mean field hypothesis adopted in the classical theories to describe the environment of a growing particle or grain represents a too drastic approximation. Therefore, it is proposed to replace the classical mean field by a "local mean field," i.e., the ensemble of actual mean environments interacting with any single element of a given size. This alternative assumption induces a higher growth rate for large particles or grains compared with their respective mean field theories, thus producing right-skewed asymptotic distributions. For particles at small volume fraction the stationary distribution resembles a lognormal function, whereas for grains in normal grain growth regime the Rayleigh distribution is found as solution. [ABSTRACT FROM AUTHOR]

The effects of sintering temperature and Ti substitution on the microstructure and microwave magnetic properties of Li-Zn ferrites prepared by a ceramic process were investigated. The pure spinel phase of the specimens was observed from X-ray diffraction patterns. The densification and grain growth were enhanced due to the increase of sintering temperature. The grain growth had negative effects on the squareness ratio of high-porosity specimens. Moreover, the magnetic anisotropy constant (K1) was estimated and discussed. The ferromagnetic resonance linewidth (ΔH) values measured at the Ku-band decreased by 18% owing to improved microstructure. The contributions of other linewidths to ∆H were estimated. [ABSTRACT FROM AUTHOR]

Materials properties of γ (austenite), α (ferrite), and γ-α duplex stainless steels were experimentally examined using samples with different grain sizes (8 to 1000 µm) and different ratios of the γ to α phase (γ proportion: 35 to 78 pct). The mechanical properties (hardness and tensile strength) of the duplex stainless steel were about 1.5 times higher than those of the austenitic and ferritic stainless steels. Two main reasons for the high strength of duplex stainless steel were identified as follows: (i) severe interruption of slip deformation in the γ phase on the α phase; (ii) a high misorientation angle around phase boundaries between the γ and α phases, caused by bonding of the different lattice structures: γ-fcc and α-bcc. The ultimate tensile strength of duplex stainless steel increased with increasing proportion of the γ phase to 50 pct, but decreased with a further increase in the amount of γ phase. The mechanical properties improved with decreasing grain size of the stainless steels, which follows the Hall-Petch relationship; however, the reverse relationship was obtained for ferritic stainless steel, especially with large grain sizes (100 to 1000 µm), in which the size of hard Cr23C6 precipitates increased with increasing grain size. [ABSTRACT FROM AUTHOR]

The present overview gives a new approach toward developments and recent achievements in severe plastic deformation. The review focuses on several subjects. First, an outline of SPD research status in the world is presented by literature analysis based on the total number of publications, citations, and the contribution of the top-ranked countries. Second, the mechanisms of grain refinement and grain growth during SPD processing are discussed by means of the latest concepts. Third, all SPD methods invented so far are classified based on a new approach. Up to now, the growing tendency of researchers to introduce new SPD techniques results in a large number of SPD methods which can be considered as new or modified techniques or a combination of previous ones. Such a reference can help to prevent the future duplication to introduce the SPD processes, which are technically similar. At the end, the practical applications of ultrafine/nanostructured materials and industrial commercialization of SPD methods are summarized. [ABSTRACT FROM AUTHOR]

Advanced thermo-mechanical processing of mild steels in the ferrite phase field has recently achieved breakthrough in grain refinement into the submicron regime. However, these steels often suffer from grain boundary failure and low rates of work hardening. A potential approach to overcome these challenges is to process modern high-strength low-alloy steels with multi-scale hierarchical microstructures. Thus, the applicability of advanced thermo-mechanical processing for achieving such microstructures in a high-strength low-alloy steel was studied. The microstructural evolution during warm deformation of a martensitic/bainitic starting microstructure using a Gleeble 3500 thermo-mechanical simulator at 600 °C followed by a direct aging step was investigated. The strain rate of 10 s−1 led to strain localization and, therefore, the formation of a macroscopic shear band. High-resolution characterization techniques such as electron channeling contrast imaging, electron backscatter diffraction, and transmission electron microscopy were used to reveal the ultrafine grain sizes (~ 0.5 μm) in this shear band. The mechanism behind this refinement is continuous dynamic recrystallization, as the initial grains subdivided into smaller crystallites that are confined by a mix of subgrain and high-angle grain boundaries. Two populations of precipitates were formed. Larger precipitates (mean diameter ~ 150 nm) decorate grain boundaries, whereas smaller precipitates (~ 15 nm) nucleate on dislocations and subgrain boundaries. [ABSTRACT FROM AUTHOR]

Metastable β titanium alloys usually exhibit nonuniform β grain growth behavior under β solution treatment, resulting in “black spots” with dimension of millimeter or centimeter. In this paper, the nonuniform recrystallization and growth behavior of β grains were studied in the Ti-5Al-5Mo-5V-1Cr-1Fe metastable β titanium alloy. Electron backscatter diffraction technique was used to characterize the crystallographic orientation after β solution in both the normal and abnormal (black spot) macroscopic regions, containing grains with high misorientation angles (> 10 deg) and subgrains with low misorientation angles (< 10 deg), respectively. The nonuniform growth behavior of β grains in the abnormal regions was clarified based on the following two aspects: (1) β grain recrystallization and growth inside the abnormal region were delayed due to the low-accumulated plastic strain and low-angle subgrain boundaries; and the growth of some subgrains with favorable neighboring region was accelerated with the transition from low-angle subgrain boundary to high-angle grain boundary; (2) with enough holding time at the β phase region, the abnormal region was consumed via the normal grains growing inside. The migration of grain boundaries with various orientations depends on the interfacial energy, which is relevant to the misorientation angle and the interfacial plane between the neighboring grains. [ABSTRACT FROM AUTHOR]

The effect of different initial structures on the simulation of microstructure evolution during normal grain growth was comparatively studied by using a two-dimensional phase-field model. Three methods, standard Voronoi construction, weighted Voronoi construction, and hand drawing, were used to generate the initial structures. For the hand-drawn initial structure, different boundary conditions, including periodic and gradient boundary conditions, were also applied. The phase-field simulation of normal grain growth in the succinonitrile-coumarin152 system was chosen as the benchmark, and compared with the experimental microstructure evolution. The phase-field simulated results generally conformed to Hillert’s theory, Von Neumann-Mullins law, and the experimental results. Different initial structures with similar initial grain size distribution showed similar grain size evolution. The simulation results for the “experimental” initial structure constructed by hand drawing showed best agreement with the experimental results during the early stage of grain growth process. With the increased time, the accuracy of simulation appeared strongly dependent on the grain numbers, and thus the gradient boundary condition is more suitable for long-time grain growth simulation than the periodic boundary condition. Overall, the combination of phase-field simulation and “experimental” initial microstructures allows the study of the grain growth in arbitrary polycrystalline materials, as demonstrated here for comprehensive study of austenite grain growth in two commercial high-strength steels. [ABSTRACT FROM AUTHOR]

Based on the data on the atomic density of a film and degree of its homogeneity during the formation of the interface between 3d transition metals (Cr, Co, Fe, or Cu) and silicon, a new concept of forming a contact between a reactive metal and a semiconductor has been justified. According to this concept, the low-temperature vapor-phase deposition of a metal onto a semiconductor is accompanied by the formation of a two-dimensional nanophase wetting layer of a metal or its mixture with silicon with a thickness of several monolayers, which significantly affects the interface formation and structure. This concept changes a perspective of forming a contact between a metal and a semiconductor substrate: it is necessary to take into account not only the formation of surface phases and clusters and/or the mixing process, but also the effect of elastic wetting of a substrate by the forming phases. [ABSTRACT FROM AUTHOR]

The nano/micro-bimodal powder injection molding (PIM) process takes advantage of nano-PIM. Most studies of the process were performed with bimodal powder feedstocks containing only small amounts of nanoparticles because they focused on properties of the samples with the optimal contents of nanoparticles. This study presents how nanoparticles in bimodal powder affect the PIM process. Five different feedstocks were prepared with the powders containing nanoparticles from 0 to 100 pct. The result demonstrated that a decrease in solids loading was offset by nanoparticle addition due to the bimodal packing effect. The nanoparticles also increased the difficulty of the debinding process. Sintering was conducted at 1173 K (900 °C), at which the highest sintered density could be obtained, with various isothermal holding times. Unlike the density, the hardness did not reveal any dependence on the holding time due to grain growth. From this study, 25 pct was regarded as the optimal content of the nanoparticles in the bimodal powder for the maximum density and hardness. [ABSTRACT FROM AUTHOR]

In situ synchrotron X-ray radiography observations of the Zr-poisoning phenomenon of an Al-20 wt pct Zn alloy inoculated by Al-5Ti-1B were carried out. The effects of Zr addition on heterogeneous nucleation, grain growth, and final grain size were quantitatively studied and further analyzed using the interdependence model. The experimental results show that the undercooling needed for nucleation increases and the nucleation rate decreases at the early stage of solidification with Zr addition, resulting in fast grain growth, a high solidification rate and increased severity of solute segregation in the solid-liquid coexistence regions. At the same time, the poisoning is a progressive process that is enhanced with the increasing Zr content, holding temperature, and holding time. The nucleation-free zone of the Zr-containing sample, either measured from the radiographs or calculated by the interdependency theory, is larger than that of the Zr-free sample. Our analysis shows that both the increase in the nucleation-free zone and the average interparticle spacing of the most potent available nucleation particles contribute to the increase of the grain size caused by Zr poisoning. [ABSTRACT FROM AUTHOR]

Thermodynamic modeling is performed for phase formation of nitrogen-containing steel 04Kh20N6G11M2AFB during crystallization, solidification, and cooling that shows crystallization proceeds through δ-ferrite. In this case depending on alloying element content within the limits of the grade composition δ-ferrite may exist both at temperatures corresponding to the cuidus — solidus interval, and also be retained below the solidus temperature. Ingot metal is examined comprehensively in different ingot zones in order to study structure formation throughout the ingot volume, alloying element liquation, and nonmetallic inclusion and secondary phase composition and distribution. [ABSTRACT FROM AUTHOR]

Results are provided for a study of the structure and mechanical properties of alloy AK12 modified with tabletted ultra-finely dispersed modifier based on silicon carbide, introduced "beneath a metal stream" without additional mixing, and in a rotary device. It is established that the optimum method for introducing modifier is that of "beneath a metal stream." In this case the ultimate breaking strength increases from 110 to 150 MPa, nominal yield strength from 85 to 94 MPa, and relative elongation from 2.3 to 6.2% (metal pouring temperature into a mold 750 °C). Metallographic examination is used to determine the reduction in macro-grain size in test pigs (ingots) by a factor of four compared with control alloys, absence of porosity, and an increase in ingot density from 2.59 to 2.66 g/cm3. Introduction of ultra-finely dispersed modifier based on silicon carbide increases the number of crystallization centers in a 1 kg ingot to 2·1011 units. [ABSTRACT FROM AUTHOR]

The microstructure and superplasticity indices are compared for specimens of alloy AA5083 prepared by two technologies: using intermediate heterogenization annealing and without it. As a result of heterogenization β -phase is separated that during recrystallization stimulates new grain growth, and therefore the grain size within specimens is smaller by almost a factor of two than for specimens not subjected to annealing. Use of heterogenization annealing provides a relative elongation up to 650% at 550°C and a constant strain rate of 1·10−3 sec−1, and lower residual porosity. Sheet prepared by this technology makes it possible to increase forming rate by several factors. [ABSTRACT FROM AUTHOR]

The evolution of the microstructure of P92 steel during heat processing has a significant effect on the final performance of steel products and is thus an area of critical interest. Accordingly, the grain growth behavior of austenite and δ-ferrite changes in P92 steel is comprehensively investigated in this study through thermodynamic calculations and physical simulation. The results show that the AC1, AC3 and γ-δ transformation temperatures of P92 steel are 841 °C, 878 °C and 1095 °C, respectively, which are comparable to the measured values of 850 °C, 879 °C and 1175 °C, respectively. When the temperature exceeds the AC1 temperature, the austenite grain size increases with increasing temperature and longer holding times, and the growth rate of austenite grains increases with higher temperatures but decreases with holding time at a certain temperature. A model that shows the austenite grain growth kinetics is established: Dn − D0n =  2.03 × 1016exp(− 498,770/RT)t, in which the time exponent n decreases from 4.52 to 2.11 with an increase in temperature from 1000 °C to 1200 °C due to the reduced pinning effect resultant of the dissolution of precipitates, M23C6, VX and NbX at 887 °C, 1073 °C and 1200 °C, respectively. The formation of δ-ferrite at 1200 °C when held for 600 s and 1300 °C when held for 60 ~ 600 s causes a smaller austenite grain size. The relationship between the evolution of the microstructure of P92 steel and the mechanical properties is also studied. The results show that the prior austenite grain size has an inverse relationship with impact energy and ultimate tensile strength at 620 °C, while the presence of soft δ-ferrite leads to a reduction in the microhardness, impact energy and ultimate tensile strength at 620 °C. [ABSTRACT FROM AUTHOR]

The formation of thin layers of luminescent defects on the faces of planar lithium fluoride crystals located in the positive column and Faraday dark space of a glow gas discharge was studied by time-resolved confocal scanning luminescent microscopy and time-correlated single photon counting. The formation of aggregated color centers in the surface layers of crystals was established using the spectral and kinetic characteristics of luminescence appearing after irradiation. The role of gas discharge electrons, ions, and photons in the defect formation mechanism was considered. The defects were shown to be formed under the influence of vacuum ultraviolet (VUV) photons. The VUV radiation intensity distribution in the discharge gap was measured by the method of thermostimulated luminescence. The main source of this radiation was the anodic and cathodic voltage drop regions in a glow discharge. [ABSTRACT FROM AUTHOR]

A new tailor-welded process, which combines stages of welding, plastic forming, and heat treatment strengthening, was developed to produce a friction stir-welded (FSW) Al-alloy joint. The Al-Cu sheets were FSW under different welding parameters and then were plastic-deformed. The microstructural evolution and mechanical properties of the FSW joint were investigated by scanning electron microscopy and tensile tests. It was found that high heat input during FSW and low solution temperature suppress the abnormal grain growth (AGG) of the joint due to the differential in grain size and grain boundary energy. The microstructure heterogeneity of the FSW joint is effectively improved, as no AGG occurs. The retention of fine equiaxed grains and the increase in the density of precipitates result in excellent mechanical properties. The increase in the strength and micro-hardness of the joint mainly depends on the plastic deformation prior to aging treatment. [ABSTRACT FROM AUTHOR]

The current study examines the evolution of nanocrystallites of ZrO2 with time and temperature in a Fe-ZrO2 composite. The crystallite sizes were determined through X-ray peak broadening analysis by the Williamson-Hall method together with dark field transmission electron microscopy. The ZrO2 crystallites were found to be stable and retained their sizes at 973 K and 1073 K for hold durations up to 600 minutes. On the other hand, the crystallites were seen to grow at 1173 K and reached up to ~ 200 nm for a hold time of 600 minutes. The Ostwald ripening model was adopted to understand crystallite growth while a dislocation-driven pipe diffusion was adopted for understanding the kinetics of grain growth. The activation energy of grain growth was calculated as ~ 379 kJ mol−1. The modeled and experimentally calculated size evolutions with time and temperature were shown to be in good agreement with each other. A detailed discussion on the kinetics and activation energy of grain growth of ZrO2 crystallites in a Fe matrix is presented in this manuscript. [ABSTRACT FROM AUTHOR]

We have synthesized samples based on the layered compound TlGaSe2 and containing thulium: (1-x)TlGaSe2 · xTm with x = 0.001, 0.005, 0.01, and 0.02. The polycrystalline samples have been used as charges for growing crystals with the corresponding compositions by the Bridgman method. The phase composition of the (1-x)TlGaSe2 · xTm samples has been determined by X-ray diffraction analysis. Their dielectric properties have been studied in ac electric fields at frequencies in the range f = 5 × 104 to 3.5 × 107 Hz. We have identified the relaxation character of the dielectric permittivity, the nature of the dielectric loss, and the hopping mechanism of charge transport in the (1-x)TlGaSe2 · xTm crystals. Our results demonstrate that increasing the thulium concentration in the crystals reduces the mean hop distance and time of charge carriers and increases the ac conductivity and the density of localized states near the Fermi level in the crystals. [ABSTRACT FROM AUTHOR]

A single crystal of Te4+-doped KTiOPO4(Te:KTP) has been grown by the flux method. The electronic structure and density of states of KTiOPO4 (KTP) and Te:KTP were calculated from first principles. As the results reveal, there is no change in the space group or lattice structure of Te:KTP, but that some increase in lattice parameters occurred. The chemical composition of Te:KTP was analyzed using x-ray photoelectron spectroscopy (XPS). The possible existence of Ti3+ has been evaluated by measuring the electron paramagnetic resonance spectrum, and the results reveal that the ion is absent from this crystal. It was observed that Te4+ doping reduces the conductivity of the crystal from measurements of its conductivity at different temperatures and frequencies, indicating that Te:KTP has excellent electro-optical properties. The effect of Te4+ doping on the second harmonic generation in KTP was also studied. The thermal expansion, thermal diffusivity, thermal conductivity and specific heat capacity of KTP and Te:KTP were determined. [ABSTRACT FROM AUTHOR]

Germanium-lead films have been investigated as a new direct-bandgap group IV alloy. GePb films were deposited on Si via thermal evaporation of Ge and Pb solid sources using the layer inversion metal-induced crystallization method for comparison with the current laser-induced recrystallization method. Material characterization of the films using x-ray diffraction analysis revealed highly oriented crystallinity and Pb incorporation as high as 13.5% before and 5.2% after annealing. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive x-ray mapping of the samples revealed uniform incorporation of elements and complete layer inversion. Optical characterization of the GePb films by Raman spectroscopy and photoluminescence techniques showed that annealing the samples resulted in higher crystalline quality as well as bandgap reduction. The bandgap reduction from 0.67 eV to 0.547 eV observed for the highest-quality material confirms the achievement of a direct-bandgap material. [ABSTRACT FROM AUTHOR]

Room-temperature synthesis of multifunctional core-shell nanostructures with iron oxide (Fe3O4) core and zinc oxide (ZnO) shell is described. High-resolution transmission electron microscopy revealed the occurrence of heteroepitaxial growth of a ZnO shell over the iron oxide nanoparticle core. The formation of the core-shell nanostructure was also evidenced by x-ray diffraction and x-ray photoelectron spectroscopy analyses. The core Fe3O4 nanoparticles exhibited superparamagnetic behavior at room temperature in an externally applied magnetic field. However, magnetic measurements of the core-shell nanoparticles revealed ferromagnetic behavior, originating from defect-induced ferromagnetism in the ZnO shell. The prepared core-shell nanoparticles also exhibited strong photoresponse while retaining ferromagnetic behavior at room temperature. [ABSTRACT FROM AUTHOR]

Pt films with thickness h = 20-100 nm deposited on oxidized с-Si(100) substrate have been subjected to vacuum annealing at 500°C for 1 h, which resulted in recrystallization and growth of grains. Simultaneously with the normal growth of grains, abnormal grain growth has been observed, as a result of which the grains have separated in normal and secondary grains. For h = 20-40 nm, the secondary grains become much larger than the normal ones and the grain lateral size distribution therefore becomes bimodal. It has been shown that the abnormal grain growth rate increases with decreasing h, whereas the normal grain growth rate is independent of h. From the Pt(111) and Pt(222) X-ray diffraction peaks analysis it follows that the mean size D of coherently diffracting domains increases as a result of annealing. In the annealed films, D sublinearly grows with h, whereas in the as-prepared films, D grows linearly. [ABSTRACT FROM AUTHOR]

In this work, deformation mechanism related to recrystallization behavior in single-crystal disks of Galfenol (Fe-Ga alloy) was investigated to gain insights into the influence of crystal orientations on structural changes and selective grain growth that take place during secondary recrystallization. We started with the three kinds of single-crystal samples with (011)[100], (001)[100], and (001)[110] orientations, which were rolled and annealed to promote the formation of different grain structures and texture evolutions. The initial Goss-oriented (011)[100] crystal mostly rotated into {111}〈112〉 orientations with twofold symmetry and shear band structures by twinning resulted in the exposure of rolled surface along {001}〈110〉 orientation during rolling. In contrast, the Cube-oriented (001)[100] single crystal had no change in texture during rolling with the thickness reduction up to 50 pct. The {123}〈111〉 slip systems were preferentially activated in these single crystals during deformation as well as {112}〈111〉 slip systems that are known to play a role in primary slip of body-centered cubic (BCC) materials such as α-iron and Fe-Si alloys. After annealing, the deformed Cube-oriented single crystal had a small fraction (<10 pct) of recrystallized Goss-oriented grains. The weak Goss component remained in the shear bands of the 50 pct rolled Goss-oriented single crystal, and it appeared to be associated with coalescence of subgrains inside shear band structures during primary recrystallization. Rolling of the (001)[110] single crystal led to the formation of a tilted (001)[100] component close to the 〈120〉 orientation, associated with {123}〈111〉 slip systems as well. This was expected to provide potential sites of nucleation for secondary recrystallization; however, no Goss- and Cube-oriented components actually developed in this sample during secondary recrystallization. Those results illustrated how the recrystallization behavior can be influenced by deformed structure and the slip systems. [ABSTRACT FROM AUTHOR]

The influence of lanthanum content on thermally stimulated luminescence properties of La2xLu2(1-x)SiO5:Ce (x = 0, 0.08, 0.18 and 1.50 at.%) crystals was investigated. Trapping parameters such as electron trap depth Et and electron traps content n0 were fitted with general order kinetic function. According to the results of the VUV transmittance spectra and band gap calculation which based on the density functional theory with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE), band structure of the crystals and recombination mechanisms of released electrons were further studied. Results showed that there were mainly two kinds of electron traps, namely shallow (Et ≈ 0.2 eV) and deep (Et ≈ 1.0 eV) traps. With the increasing of La content, the concentration of deep traps was obviously depressed, and the depth of deep traps decreased at the same time, which was explained by suggesting the downward shift of the bottom of conduction band. [ABSTRACT FROM AUTHOR]

Grain growth behavior of a powder metallurgy (P/M) Ti-22Al-25Nb alloy was investigated by applying a series of isothermal treatment tests over a wide range of temperatures and holding times. An isothermal treatment scheme was conducted in the B2 phase region (1070-1110 °C) and α2 + B2 phase region (1010-1050 °C) at holding times of 10, 30 min, 1, 2, and 3 h, respectively. The effects of temperature and holding time on the microstructure evolution and microhardness of the P/M Ti-22Al-25Nb alloy at elevated temperatures were evaluated using optical microscope, scanning electron microscope, x-ray diffraction, and Vickers hardness test techniques. The results revealed that the alloy’s treated microstructure was closely linked to temperature and holding time, respectively. The change law of B2 grain growth with holding time and temperature can be well interpreted by the Beck equation and Hillert equation, respectively. The B2 grain growth exponent n and activation energy Q were acquired based on experimental data in the α2 + B2 and B2 phase regions. In addition, the grain growth contour map for the P/M Ti-22Al-25Nb alloy was constructed to depict variations in B2 grain size based on holding time and temperature. [ABSTRACT FROM AUTHOR]

This paper explores the effects of aging on the mechanical behavior, microstructure evolution and IMC formation on different surface finishes of two high temperature solders, Sn-5 wt.% Ag and Sn-5 wt.% Sb. High temperature aging showed significant degradation of Sn-5 wt.% Ag solder hardness (34%) while aging has little effect on Sn-5 wt.% Sb solder. Sn-5 wt.% Ag experienced rapid grain growth as well as the coarsening of particles during aging. Sn-5 wt.% Sb showed a stable microstructure due to solid solution strengthening and the stable nature of SnSb precipitates. The increase of intermetallic compound (IMC) thickness during aging follows a parabolic relationship with time. Regression analysis (time exponent, n) indicated that IMC growth kinetics is controlled by a diffusion mechanism. The results have important implications in the selection of high temperature solders used in high temperature applications. [ABSTRACT FROM AUTHOR]

Aluminum laminates of high and technical purity layers were produced by accumulative roll bonding (ARB) at room temperature. To study the thermal stability, the laminates after 2 to 9 ARB cycles were annealed between 100 and 400 °C for one hour. Changes of the microstructure were analyzed by electron backscatter diffraction. For low ARB cycle numbers (4 or below) and 300 °C annealing temperature, the deformed technical pure layers start to recrystallize while the high-purity coarse recrystallized layers experience intralayer grain growth. For higher ARB cycle numbers (6 and 8) and an annealing temperature of 300 °C or above, the ultra-fine grained layers of technical purity are consumed by the layer overlapping growth of high-purity grains producing a banded grain structure. For 9 ARB cycles and at an annealing temperature of 400 °C, a globular grain structure develops with grain sizes larger than twice the layer thickness. The effect of impurities on recrystallization and grain growth of ARB laminates is discussed with regard to tailoring its microstructure by heat treatment. For further analyses, the results are compared with Potts model simulations finding a rather good qualitative agreement with the experimental data albeit some simplified model assumptions. [ABSTRACT FROM AUTHOR]

An improved understanding of grain growth kinetics in nanocrystalline materials, and in metals and alloys in general, is of continuing interest to the scientific community. In this study, Mg-Al thin films containing ~10 wt pct Al and with 14.5 nm average grain size were produced by magnetron sputtering and subjected to heat treatments. The grain growth evolution in the early stages of heat treatment at 423 K, 473 K, and 573 K (150 °C, 200 °C, and 300 °C) was observed with transmission electron microscopy and analyzed based upon the classical equation developed by Burke and Turnbull. The grain growth exponent was found to be 7 ± 2 and the activation energy for grain growth was 31.1 ± 13.4 kJ/mol, the latter being significantly lower than in bulk Mg-Al alloys. The observed grain growth kinetics are explained by the Al supersaturation in the matrix and the pinning effects of the rapidly forming beta precipitates and possibly shallow grain boundary grooves. The low activation energy is attributed to the rapid surface diffusion which is dominant in thin film systems. [ABSTRACT FROM AUTHOR]

A high-performance extruded MgGdZnNi alloy containing 14H LPSO phases and two different dynamic recrystallization (DRX) grains was successfully fabricated, which exhibited superior ultimate tensile strength (400 MPa) and outstanding elongation (20%). Meanwhile, the results show that the substitution of 0.5 at.% Zn with Ni element can refine the grain size of as-cast MgGdZn alloy significantly. While limited 14H LPSO lamellae are formed near the block 14H LPSO phases due to Ni addition during solution treatment, copious 14H LPSO lamellae induced by external force are precipitated in α-Mg matrix after subsequent hot extrusion in the MgGdZnNi alloy. Furthermore, two different DRX phenomena are successively stimulated with increasing deformation strain. Discontinuous DRX emerges first at the interface of block 14H LPSO phases, and then continuous DRX occurs in the kink bands of 14H LPSO lamellae. The precipitation behaviors of 14H LPSO lamellae and two types of DRX grains contribute to the excellent mechanical properties. [ABSTRACT FROM AUTHOR]

We have studied the effect of high-temperature diffusion doping with chromium (Cr) ions on the microstructure of polycrystalline zinc selenide (ZnSe). We have determined energy and kinetic characteristics of solid-state recrystallization in ZnSe and assessed the effect of chromium concentration on the rate of grain growth during the doping process. [ABSTRACT FROM AUTHOR]

Tungsten disulfide (WS) has excellent solid lubrication properties due to its 2D layered structure. This study focuses on depositing Al-2 wt.% WS composite coating by cold spray technique. The effect of WS addition on the microstructure, mechanical and tribological properties of the composite coatings is examined in the as-deposited and heat-treated conditions. After heat treatment, the coating density increased to 99% with improved intersplat bonding. The microhardness of the heat-treated Al-2 wt.% WS coating increased by 56% as compared to the as-sprayed coating. The wear resistance of heat-treated Al-2 wt.% WS coating improved by 75% with a synergistic reduction in the coefficient of friction (COF) by 51%. Transmission electron microscopy investigation reveals the presence of layered WS within aluminum splats with a strong interface. This study shows that cold spraying can be effectively used to integrate 2D layered WS as a solid lubricant in the metallic coatings. [ABSTRACT FROM AUTHOR]

The dynamic recrystallization (DRX) behavior of Pb-30Mg-9Al-1B alloy was investigated during hot compression at temperatures ranging from 513 K to 693 K (240 °C to 420 °C) and stain rates ranging from 0.01 to 10 s. Based on the experimental results, the stress-strain curve shows the typical nature of DRX-that a peak flow stress is reached at low strains followed by a steady state at high strain. The correlation between flow stress, temperature, and strain rate can be well expressed by a modified sine hyperbolic type constitutive equation. The value of the Avrami exponent M (nearly equal to 1) in the Avrami equation suggests that the grain boundaries are prior to nucleation sites for DRX, and DRX is controlled by grain growth for Pb-30Mg-9Al-1B alloy. The variation of instability and cracking regions in the constructed processing maps at different strains exhibits the high sensitivity of processing maps to strains. According to the processing maps of Pb-30Mg-9Al-1B alloy, the optimized parameters for hot working were determined to be in the temperature range of 603 K to 693 K (330 °C to 420 °C) and strain rate of 0.01 to 0.1 s. [ABSTRACT FROM AUTHOR]

Hot-rolled steel products with high strength and good formability are in demand for automobile body parts, particularly steels which can reduce weight without sacrificing vehicle safety. Recent studies have suggested that interphase precipitation (IP) hardening is a promising approach for obtaining excellent high strength and superior formability from low-alloy steels. However, the effects of hot rolling conditions and alloying elements on IP hardening have not been clearly determined. In this study, we sought to clarify the above effects by analyzing the recrystallization behavior during hot rolling. As a result of sample testing and analysis, it was determined that the recrystallization which occurs during hot rolling plays a critical role in enhancing the IP hardening of low-alloy steels. [ABSTRACT FROM AUTHOR]

Grain boundary segregation can reduce the driving force for grain growth in nanocrystalline materials and help retain fine grain sizes. However, grain boundary segregation is enthalpically driven, and so a stabilized nanocrystalline state should undergo a disordering process as temperature is increased. Here we develop a Monte Carlo-based simulation that determines the minimum free energy state of an alloy with a strong tendency for grain boundary segregation that considers both different grain sizes and a large solute configuration space. We find that a stable nanocrystalline alloy undergoes a disordering process where grain boundary segregated atoms dissolve into the adjacent grains and increase the grain size as a function of temperature. At a critical temperature, the single crystal state becomes the most preferred. Using this method, we are able to determine how the grain size changes as a function of temperature and produce equilibrium phase diagrams for nanocrystalline alloys. [ABSTRACT FROM PUBLISHER]

We have investigated the potential for nonuniform grain boundary mobility to act as a persistence mechanism for abnormal grain growth (AGG) using Monte Carlo Potts model simulations. The model system consists of a single initially large candidate grain embedded in a matrix of equiaxed grains, corresponding to the abnormal growth regime before impingement occurs. We assign a mobility advantage to grain boundaries between the candidate grain and a randomly selected subset of the matrix grains. We observe AGG in systems with physically reasonable fractions of fast boundaries; the probability of abnormal growth increases as the density of fast boundaries increases. This abnormal growth occurs by a series of fast, localized growth events that counteract the tendency of abnormally large grains to grow more slowly than the surrounding matrix grains. Resulting abnormal grains are morphologically similar to experimentally observed abnormal grains. [ABSTRACT FROM AUTHOR]

A thermo-mechanical re-meshing model of friction stir welding (FSW) process of AA6082-T6 is used with a point tracking method for the determination of the final locations of the particles. The relations between the field variables and the material flows in the FSW process are discussed. Then the grain sizes after recrystallization are calculated. The comparison with the numerical and the experimental results in published literatures shows the validity of the proposed model. Based on the Zener-Hollomon parameter, the effects of strain rate and temperature on recrystallization are further discussed. [ABSTRACT FROM AUTHOR]

The high-temperature X-ray diffraction technique is used to study AgCuSe(S,Te) crystals. It is shown that, at room temperature, the AgCuSeS crystal is composed of CuS and AgCuSe phases. At a temperature of 695 K, these phases transform into a single face-centered cubic (fcc) phase. The transformation is reversible. The AgCuSeTe composition consists of three phases, specifically, CuTe, AgCuSe, and a cubic phase. At 444 K, both orthorhombic phases simultaneously transform into a diamond-like cubic phase. In this transformation, the cubic phase plays the role of a seed. From the temperature dependence of the lattice parameters, the thermal-expansion coefficients of the phases involved in both compositions are calculated for the main crystallographic directions. [ABSTRACT FROM AUTHOR]

Perovskite type chromites are studied recently for their fascinating structure and inter-related functional properties. YCrO (YCO) is one among the chromites which possess structural heterogeneity. The structural studies on YCrO (YCO) and YBiCrO (YBiCO-10) reveal that the powder diffraction patterns exhibits a single phase with orthorhombic Pnma space group. Compositional studies on YCO and YBiCO-10 indicates the cation ratios of (Y, Bi):Cr (1:1) is preserved. Microstructural studies reveal that there is an increment in grain growth in YBiCO-10 ceramics. The microstructural studies also evidently show that YBiCO-10 has more of faceted orthorhombic type of grains, whereas, YCO has a spherical grain type of features. Impedance spectroscopy studies were performed on both YCO and YBiCO ceramics and the studies reveal a significant change in grain resistance. The decrease of resistance could be due to increase of grain size which offers the conductive path of hopping of charge carriers or inherent electrical transitions of Cr in YBiCO-10 sample. These chromites can be used as potential candidates for the thermistor applications whose thermistor parameter (β) and sensitivity (α) values are 2873 K, −5 × 10 K (YCO) and 3102 K,−5.44 × 10K (YBiCO-10) at 755 K. [ABSTRACT FROM AUTHOR]

Using x-ray phase, chemical, and thermal (20-1200°C) analysis methods, phase composition and thermal properties are evaluated for three specimens of quartz-containing materials used as fluxes in copper smelting production. It is established that quartz in specimens on heating to 1000-1200°C undergoes enantiothropic polymorphic transformation by a scheme: α-quartz → β-quartz → β-cristobalite. In order to evaluate the efficiency of using materials as fluxes for copper smelting production, equations are proposed for calculating fluxing capacity depending on their chemical and phase composition. A dependence is given for the amount of slag formed as a result of slagging flux impurity oxides on material phase and chemical compositions on whose basis losses of nonferrous and precious metals are evaluated. It is suggested that flux materials are heated to a temperature for the start of polymorphic transformations accompanying quartz recrystallization (~560°C) before charging into a metallurgical unit. [ABSTRACT FROM AUTHOR]

Friction stir welding of AA6082-T6 with different welding parameters is simulated by computational fluid dynamics model. Monte Carlo method is further used to simulate the grain growth with consideration of the precipitation effects. The comparison with experimental observations can validate the proposed grain growth model with the precipitate effects. Results indicate that the final grain size can be increased by 39.7% in the nugget zone when the volume fraction of precipitation is decreased from 0.8 to 0.2% after welding. Both the grain growth speed and the final grain size on the top surface are higher than the bottom surface. The increase in the welding temperature caused by the increase in the rotation speeds or the axial forces can lead to lower volume fractions of precipitations and then lead to larger grain sizes . [ABSTRACT FROM AUTHOR]

The development of annealing twins was studied in chromium-nickel austenitic stainless steels subjected to cold or warm working. The annealing behavior can be characterized by an austenite reversal, recrystallization, and grain growth, depending on the deformation microstructures. The grain coarsening during recrystallization followed by a grain growth was accompanied by the development of twin-related Σ3 CSL boundaries. The fraction of Σ3 CSL boundaries and their density are defined by a unique parameter that is a relative change in the grain size, i.e., a ratio of the annealed grain size to that one evolved by preceding plastic working ( D/ D ). The fraction of Σ3 CSL boundaries rapidly increased at early stage of recrystallization and grain growth while the ratio of D/ D attained 5. Then, the rate of increase in the fraction of Σ3 CSL boundaries slowed down significantly during further grain coarsening. On the other hand, the density of Σ3 CSL boundaries increased to its maximum at a ratio of D/ D about 2.5 followed by a gradual decrease during subsequent grain growth. [ABSTRACT FROM AUTHOR]