Nominal Composition Research Articles

Enhanced Electrochemical Performance of Disordered Rocksalt Cathodes Enabled by a Graphite Conductive Additive.

Cobalt-free cation-disordered rocksalt (DRX) cathodes are a promising class of materials for next-generation Li-ion batteries. Although they have high theoretical specific capacities (>300 mA h/g) and moderate operating voltages (∼3.5 V vs Li/Li+), DRX cathodes typically require a high carbon content (up to 30 wt %) to fully utilize the active material which has a detrimental impact on cell-level energy density. To assess pathways to reduce the electrode's carbon content, the present study investigates how the carbon's microstructure and loading (10-20 wt %) influence the performance of DRX cathodes with the nominal composition Li1.2Mn0.5Ti0.3O1.9F0.1. While electrodes prepared with conventional disordered carbon additives (C65 and ketjenblack) exhibit rapid capacity fade due to an unstable cathode/electrolyte interface, DRX cathodes containing 10 wt % graphite show superior cycling performance (e.g., reversible capacities ∼260 mA h/g with 85% capacity retention after 50 cycles) and rate capability (∼135 mA h/g at 1000 mA/g). A suite of characterization tools was employed to evaluate the performance differences among these composite electrodes. Overall, these results indicate that the superior performance of the graphite-based cathodes is largely attributed to the: (i) formation of a uniform graphitic coating on DRX particles which protects the surface from parasitic reactions at high states of charge and (ii) homogeneous dispersion of the active material and carbon throughout the composite cathode which provides a robust electronically conductive network that can withstand repeated charge-discharge cycles. Overall, this study provides key scientific insights on how the carbon microstructure and electrode processing influence the performance of DRX cathodes. Based on these results, exploration of alternative routes to apply graphitic coatings is recommended to further optimize the material performance.

Accelerating the precipitation kinetics of nano-sized T1 and S’ phases in Al-Cu-Li alloys by hot-deformation and creep-aging

ABSTRACT It is well known that a Cu/Li ratio over 4.0 leads to significant precipitation hardening in the third generation of Al–Li alloys, which have been widely used in aerospace and aeronautic industries. However, increasing Cu levels not only cancels some gains in weight reduction but also results in reductions in ductility when the traditional age-hardening process is adopted. In this study, we show that higher strength and ductility can be achieved simultaneously by replacing traditional artificial aging with new creep aging and tailoring the entire process from casting to age hardening without changing any nominal chemical compositions. Surprisingly, the precipitation kinetics of AA2060 alloy is significantly enhanced through the combination of hot extrusion, creep aging, and pre-strain compared to traditional artificial aging. For example, at 160°C, it follows the transformation path of supersaturated solid solution (SSSS)→GP zones + δ′+T1 precursors which will further transform into T1 +S’; at 200°C, SSS→ GP zones, and they transform into T1 + S’ immediately. The precipitation of θ′ and δ′ phases is significantly inhibited at elevated temperatures due to the competing relationship with T1 and S’ phases at a peak-aged state. Contrary to traditional knowledge in Al–Li alloys, we have found that the greater extrusion ratio at 33.0 and higher aging temperature at 200°C can give a much higher peak aging strength with average ultimate tensile strength 659 MPa.

Comparative Study of the Synthesis of a Red Ceramic Pigment Using Microwave Heat Treatment

In this study, a new red ceramic pigment has been developed within a perovskite structure, and microwave heat treatments have been applied. Those red ceramic pigments within the YAlO3 system doped with chromium with the nominal composition Y0.98Al0.98Cr0.04O3 were synthesized by traditional routes and alternative methods like coprecipitation. Also, heat treatment has been studied comparing a traditional electric and microwave kiln. Different flux agents have been incorporated to improve the synthesis reaction. Prepared pigments have been characterized by X-ray diffraction (XRD) as having a predominant phase of perovskite structure, which is responsible for the red shade, and a minority garnet phase that causes more brown colorations. Studies by Ultraviolet-Visible spectroscopy gave rise to a series of absorption bands that indicate the presence of Cr(III) in the octahedral position corresponding to perovskite and Cr(IV) corresponding to garnet in both the octahedral and tetrahedral positions. The perovskite phase is favored with the use of flux mix, corroborating the UV-visible results and being more pronounced in traditional high temperature thermal treatments. The coprecipitation route has been studied to increase the reactivity of the particles given their nanometric size; however, this reactivity favors a greater appearance of undesirable garnet phases with both types of flux. Scanning Electron Microscopy (SEM) micrographs offer information obtained from the secondary electrons of predominantly cubic crystalline phases with sizes between 1 µm and 2 µm in pigments synthesized via the traditional method and sizes less than 1µm together with the glassy phase in pigments synthesized via coprecipitation. Microwave thermal treatments have been studied, obtaining pigments with a majority structure of perovskite and garnet at lower temperatures and relatively short synthesis times. The feasibility of use in porous single-fired ceramic glazes has been studied, whose chromatic coordinates have been collected using an Ultraviolet-Visible Spectrophotometer based on the CIEL*a*b* system.

Magneto-structural transitions driven giant magnetocaloric effect in Ni42Mn43Cr4Sn11 Shape Memory Heusler Alloy near room temperature

In the current work, a Ni–Mn-X (X = Sn, In) type off-stoichiometric, polycrystalline magnetic shape memory alloy (MSMA) having nominal composition Ni42Mn43Cr4Sn11 (at. %) has been thoroughly investigated in terms of its crystal structure, microstructure, magnetic properties, and magnetocaloric effect (MCE). X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), differential scanning calorimetry (DSC), and magnetic and magneto-transport measurements are used to characterize it. By offering a significant value of parameters related to MCE at the first-order martensite transition (FOMT) and the second-order magnetic transition (SOMT), the “Cr” doping at the “Ni” site enables considerable magnetic refrigeration to occur close to room temperature (RT). The alloy crystallises into coexisting cubic L21 austenite and tetragonal L10 martensite phases, among which the first one prevails as the leading phase at room temperature (RT) without exhibiting any geometric frustration. Lattice strain is enumerated using the Williamson-Hall method. A huge working temperature spans of 29.65 K and 26.16 K; the maximum magnetic entropy changes of +8.70 J kg−1.K−1 and −5.04 J kg−1.K−1 and the maximum refrigerant capacities (RC) of 284.24 J. Kg−1 and 234.10 J. Kg−1 across FOMT and SOMT, respectively at an applied magnetic field of 6 T are found to be most suitable for real technological applications. This MSMA offers a comparatively low cost of the constituent elements (Ni, Mn, Cr, and Sn), as well as exhibits giant MCE and RC across both FOMT and SOMT, making it an excellent candidate for magnetic refrigeration near RT. It also opens up new avenues for future research on novel Heusler alloys of this type.

A comparative study of solute trapping in Fe-(33–45 at%) Cu alloys manufactured by laser directed energy deposition

The high cooling rates in laser directed energy deposition (DED-LB) of alloys lead to substantial amounts of solute trapping as solute atoms cannot diffuse away from the solid/liquid interface before it advances. In some concentrated alloys, this results in supersaturated solid phases that form nanoscale hierarchical microstructures when the solute atoms precipitate out during reheating from subsequent laser passes. We choose the Iron-Copper (Fe-Cu) binary alloy as model system as it is chemically homogeneous in the liquid phase and has negligible solid solubility at room temperature. Two alloys with nominal compositions in atomic (at.) %, Fe67Cu33 and Fe55Cu45, were manufactured using DED-LB. Scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS) and wavelength dispersive spectroscopy (WDS) were used to characterize the nanostructures and heterogeneous chemical compositions. A non-equilibrium solute partitioning model was used to compute the supersaturated chemistries of the constituent phases and validated with experimentally measured compositions. The measured phase compositions of the two alloys were very similar, at roughly 12 at% Cu and 4 at% Fe in the α(bcc)-Fe and ε(fcc)-Cu phases respectively, despite having different processing parameters and mechanical behavior. This indicates that the total thermal history, that depends on both the processing parameters and laser scan pattern, plays a stronger role on the final microstructure evolution than just the initial quantity of trapped solute. Additionally, we find that current non-equilibrium solute partitioning models applied on the continuum scale fall short of predicting accurate quantitative phase compositions in concentrated alloys, although the qualitative trends are captured correctly.

Synthesis, structural and microstructural properties of Bismuth Vanadate BiVO4

Metal vanadates MVO4 demonstrate exceptional visible-light photo-activity due to their desirable properties, including high responsiveness to visible light, a narrow bandgap, affordability, non-toxicity, chemical stability, resistance to corrosion, low environmental impact, and the ability to control their morphology. In this study, BiVO4 phase was synthesized without the use of surfactants through a coprecipitation process followed by calcination at 500 °C. The synthesized oxides were initially analyzed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The structural and morphological characterization indicated that BiVO4 exhibited a monoclinic crystalline phase. The crystal cell of BiVO4 was found to be monoclinic, with parameters a, b, c, and β, and belonging to the I2/b space group. SEM images revealed the presence of spherical-like crystallites with a consistent local nominal composition of BiV.

Structure and Properties of Water in a New Model of the 10-Å Phase: Classical and Ab Initio Atomistic Computational Modeling

The 10-Å phase is an important member of the family of dense hydrous magnesium silicates (DHMSs) that play a major role in the water budget in the Earth’s upper mantle. Its nominal composition is usually written as Mg3Si4O10(OH)2·xH2O, and its structure is often described as layers of talc with some amount of water present in the interlayer space. However, its actual structure and composition and the detailed mechanisms of retaining H2O molecules within the mineral are not yet sufficiently known. In particular, more recent spectroscopic and diffraction data indicate the presence of Si vacancies in the tetrahedral silicate sheets of the 10-Å phase leading to the formation of Q2-type Si sites terminated by silanol groups. These silanols are, in turn, hydrogen bonded to interlayer H2O molecules. Here, we use classical and ab initio molecular dynamics (MD) simulations to compare the structures and properties of ideal and defect models of the 10-Å phase under ambient conditions. For classical MD simulations, the most recent modification of the ClayFF force field is used, which can accurately account for the bending of Mg–O–H and Si–O–H angles in the mineral layers, including the structural defects. The crystal lattice parameters, elastic constants, structure, and dynamics of the interlayer hydrogen bonding network for the model 10-Å phase are calculated and compared with available experimental data. The results demonstrate that the inclusion of Si vacancies leads to better agreement with crystallographic data, elastic constants, and bulk and shear moduli compared to a simpler model based on the idealized talc structure. The results also clearly illustrate the importance of the explicit inclusion of Mg–O–H and Si–O–H angular bending terms for accurate modeling of the 10-Å phase. In particular, the properly constrained orientation of the silanol groups promotes the formation of strong hydrogen bonds with the interlayer H2O molecules.

Single-crystal structure, cation distribution, and optical/magnetic properties of Ce3+-doped Gd3Al2Ga3O12 crystal

Ce-doped Gd3Al2Ga3O12 (Ce3+:GAGG) scintillator finds practical application in industrial computed tomography and medical imaging, however a precise understanding of its single-crystal structure has been lacking. In this study, we grew a 1-inch-sized single crystal with the nominal composition 0.5%Ce3+:GAGG using the Czochralski method. To determine the crystal structure, we employed single-crystal XRD along with element analyses using ICP and XRF-WDS techniques. Our analysis revealed the precise formula of the crystal as 0.1% Ce3+:Gd3(Ga0.543Al0.457)2(Ga0.721Al0.279)3O12. Notably, Ga3+ cations exhibit a stronger preference at the tetrahedral sites compared to Al3+ cations. The optical absorption and luminescence resulting from Ce3+ 4f–5d transitions are cross-validated in the transmission and photoluminescence spectra. From 1.8 to 300 K, Ce:GAGG exhibits paramagnetic behavior and obeys the Curie-Weiss law. The 8S7/2 ground state of Gd3+ ion contributes to the overall effective magnetic moment on the one hand and plays a significant role in energy transfer from Gd3+ and Ce3+ upon excitation on the other hand. The magneto-optical Faraday rotation measurement of Ce:GAGG was performed to determine Verdet constants at 532 nm and 633 nm. These results may help a better understanding and the practical exploitation of Ce3+:GAGG as a multifunctional material in optic and magnetic fields.

Configuration of a Simple Method for Different Polyamides 6.9 Recognition by ATR-FTIR Analysis Coupled with Chemometrics.

This study proposes a simple approach for the recognition of polyamide 6.9 samples differing in impurity amounts and viscosities (modulated during the synthesis), which are parameters plausibly variable in polymers' manufacturing processes. Infrared spectroscopy (ATR-FTIR) was combined with chemometrics, applying statistical methods to experimental data. Both non-supervised and supervised methods have been used (PCA and PLS-DA), and a predictive model that could assess the polyamide type of unknown samples was created. Chemometric tools led to a satisfying degree of discrimination among samples, and the predictive model resulted in a great classification of unknown samples with an accuracy of 88.89%. Traditional physical-chemical characterizations (such as thermal and mechanical tests) showed their limits in the univocal identification of sample types, and additionally, they resulted in time-consuming procedures and specimen destruction. The spectral modifications have been investigated to understand the main signals that are more likely to affect the discrimination process. The proposed hybrid methodology represents a potential support for quality control activities within the production sector, especially when the spectra of compounds with the same nominal composition show almost identical signals.

On the constitution and cobalt alloy formation in WC-1.4 wt% Ru-9.5 wt% Co cemented carbides

Our work confirms that the addition of Ru to Co-based cemented carbides significantly broadens the carbon processing window. Using a WC-10.9 wt% (Co-12.8Ru) alloy, the width of the two-phase window is extended from about 0.16 wt% C (Ru-free) to about 0.21 wt% C on addition of Ru.According to semi-quantitative EDS analysis, the amount of W dissolved in the Co binder is significantly higher in Ru-containing materials at all carbon contents. This higher degree of solubility is also reflected in the lattice parameter. When decreasing the carbon content (from precipitation of graphite to the formation of eta carbides), the lattice parameter increases steadily from 3.585 Å to 3.609 Å respectively. In contrast, Ru-free materials present 3.548 Å in equilibrium with graphite, and 3.576 Å in equilibrium with eta carbides.The relative magnetic saturation value of the alloys with Ru was significantly lower when compared to Ru-free alloys (from 80.2% at graphite precipitations to 41.4% with dendritic eta phase), which is also in agreement with the higher W solubility observed in these alloys.DTA measurements of WC-4.4 wt% Ru-30 wt% Co samples (same Ru to Co ratio in the nominal composition) demonstrated a similar melting and solidification regime as compared to Ru-free WC-30 wt% Co materials.

Microstructure, chemical composition, and dielectric response of CaCu3Ti4O12 ceramics doped with F, Al, and Mg ions

Ceramics with nominal chemical composition CaCu3Ti4O12 (CCTO), CaCu3Ti3.96Al0.04O11.96F0.04 (CCTOAF), and Ca0.98Mg0.08Cu2.94Ti3.96Al0.04O11.96F0.04 (CCTOMAF) were prepared by the solid-state reactions technique. Using SEM, EDX, XPS, EPR, NMR, and complex impedance spectroscopy, the microstructure, elements distribution, chemical composition of grains and grain boundaries, and the dielectric response of ceramics were investigated. In the ССТО, CCTOAF, and CCTOMAF series, the average grain size increases, the degree of copper segregation at the grain boundaries is inversely related to grain size, and the dielectric loss decreases from 0.071 to 0.047 and 0.030, respectively, while dielectric permittivity ε′ at 1 kHz is 5.6 × 104, 7.1 × 104, and 4.3 × 104, respectively. Additives of Al, Mg, F and milled particles (ZrO2, Al2O3, and SiO2) can either partially introduce into the perovskite structure or form low-melting eutectics at the grain boundaries, causing abnormal grain growth. The presence of copper ions in various oxidation states, as well as evidence of exchange spin interactions between them, was confirmed in all samples.

The role of Ag2O incorporation in nuclear radiation shielding behaviors of the Li2O–Pb3O4–SiO2 glass system: A multi-step characterization study

Abstract We report the gamma-ray shielding properties of five different lithium silicate glasses based on the (40 − x) Li2O–10Pb3O4–50SiO2 nominal composition. Transmission factor values and some basic shielding parameters such as linear (µ) and mass attenuation coefficients (µ/ρ), half-value layer, tenth value layer, and mean free path (MFP) values of the investigated glass samples are determined in a large photon energy range. Using the G–P fitting method at various MFP values, the exposure buildup factor and energy absorption buildup factor values of the examined glasses are also calculated. Based on the findings, it can be concluded that the S5 glass specimen, which exhibits the greatest Ag2O additive and density among the various glass samples, represents a favorable choice for the purpose of shielding against gamma radiation.

Secondary Phase CeO2 Precipitates in Ce,Er-Doped Na0.5La0.5MoO4 Single Crystals Grown by Czochralski Method

Analytical scanning and transmission electron microscopy were used to study the microstructure of Ce,Er-doped Na0.5La0.5MoO4 laser crystals. Crystals were grown by the Czochralski method from the melts with a nominal composition of Na0.5La0.5−xCexEr0.005MoO4, where x = 0.125 and 0.15, then annealed at 700 and 1000 °C in the oxidizing atmosphere. We found the secondary phase precipitation of Ce2O3 oxide in as-grown crystals, while after high-temperature annealing the CeO2 precipitated crystals are always observed. Impurity ions Ce3+ occupy the La sites, and approximately 20% of the nominal Ce content is involved in the formation of Ce oxide secondary phase precipitates. The length of CeO2 precipitated crystals ranged between 100 nm and 550 nm (average length was 200 nm) and their width was 30–70 nm. The mechanism of CeO2 formation is discussed. The orientation relationships of Na0.5La0.5−xCexEr0.005MoO4/CeO2, the degree of coherence of the interface, and the preferential directions of their growth in the matrix were established. CeO2 crystals precipitated in the matrix cause light scattering with a wavelength comparable to the size of the precipitates and lead to deterioration of optical transparency of the material.

Designing a Lead-free and high-density glass for radiation facilities: Synthesis, physical, optical, structural, and experimental gamma-ray transmission properties of newly designed barium-borosilicate glass sample

We report the design, synthesis, optical, structural, and gamma-ray attenuation properties of a newly developed Lead-free and high-density borosilicate glass sample for its potential applications in medical and industrial radiation facilities. A barium-borosilicate glass sample (BSBaZn) was designed and synthesized using nominal composition of 7B2O3-50SiO2-38ZnO-5BaO. The FTIR spectrum of the BSBaZn is revealed four fundamental regions. These regions are 400–620 cm−1, 620–770 cm−1, 800–1210 cm−1, and 1210–1500 cm−1. Transmittance rate in the wavelength range of 350–1100 nm is reported as 80 %. A high-purity Germanium (HPGe) detector along with an energetic 133Ba radioisotope is also utilized for experimental gamma-ray transmission studies. Various fundamental gamma-ray shielding parameters of BSBaZn are determined and accordingly compared with many other glass shields. MCNPX (version 2.7.0) general purpose Monte Carlo code is utilized for gamma-ray transmission factor (TF) values. The results showed that the synthesized BSBaZn sample has promising structural, optical, and physical properties in addition to promising gamma-ray attenuation properties. The high transparency of BSBaZn along with its high-density may be considered as an important selection criterion for its implementation in protection purposes in medical and industrial radiation facilities, where the source and patients monitoring play a significant role.

Experimental study on the microstructure and mechanical properties of the Mg-Y-Zn alloys with LPSO phases tailored by CALPHAD method

Long-Period Stacking Ordered (LPSO) phases in the Mg-Y-Zn alloys can significantly improve comprehensive mechanical properties of the Mg-based alloys. The nominal compositions of the Mg95Y3Zn2 and Mg86Y8Zn6 (at%) alloys with different contents of LPSO phases were tailored by CALPHAD method, and the tested compositions of these two alloys were Mg95.2Y2.6Zn2.2 and Mg86.2Y7.7Zn6.1, respectively. The microstructure evolutions of the studied alloys in the states of as-cast and isothermal treatments at different times were observed, and the mechanical properties of the as-extruded alloys after homogenization (short term, 12 h) and the isothermal treatment (long term, 240 h) at 500 ℃ were measured. After the isothermal treatment at 500 °C for 240 h, the phase constituent of the Mg95.2Y2.6Zn2.2 alloy changed from the as-cast three phases (18 R + α-Mg + W-Mg3Y2Zn3) into the equilibrium three phases (18 R + α-Mg + 14 H), while that of the Mg86.2Y7.7Zn6.1 alloy completely changed from the as-cast four phases (18 R + α-Mg + W-Mg3Y2Zn3 + 14 H) into the equilibrium two LPSO phases (18 R + 14 H), where the 14 H-type LPSO phase is formed by the four-phase invariant reaction of “18 R + α-Mg + W-Mg3Y2Zn3 → 14 H” at 546 ℃ and the three-phase univariant reaction of “18 R + α-Mg → 14 H” below 546 ℃. The results of mechanical properties show that the yield strength of the Mg86.2Y7.7Zn6.1 alloy composed entirely of LPSO phases is better than that of the Mg95.2Y2.6Zn2.2 alloy composed of both LPSO phases and some α-Mg matrix, while the plasticity of the Mg86.2Y7.7Zn6.1 alloy is not as good as that of the Mg95.2Y2.6Zn2.2 alloy. Therefore, the amount of LPSO phases can be increased for pursuing high strength of Mg alloys, but a certain amount of α-Mg phase needs to be kept for retaining good plasticity. For this purpose, the alloy composition with a specific amount of the LPSO phases and α-Mg matrix in the Mg-Y-Zn system can be tailored by CALPHAD method.

Impact of Mn-substitution on crystallographic, optical, and magnetic properties of nanocrystalline Li-Ni-Zn ferrites fabricated by the sol-gel autocombustion technique

The wet-chemical sol-gel autocombustion, which is a faster and inexpensive synthesis technique has been implemented to synthesize Mn-substituted Li–Ni–Zn ferrite nanoparticles with nominal compositions of Li0.15Ni0.30-xMnxZn0.40Fe2.15O4 ranging from x = 0.00 to 0.15 in the step of 0.03. Well-shaped specimens have been sintered at temperatures ranging from 1373 to 1523 K. The patterns of the XRD reveal the internal shape which ensured the growth of the spinel layout for all samples. The Debye-Scherrer formula has been carried out to estimate the as-developed powder's crystallite size which is in the range of 46–52 nm. Both the lattice constant and average grain diameter of the samples have been increased with Mn2+ ions. The topmost value of the real portion of initial permeability and relative quality factor have been observed for Li0.15Ni0.18Mn0.12Zn0.40Fe2.15O4 ferrite sintered at the temperature of 1523 K, which are 7% and 16% larger, respectively, compared to the pristine composition.

Optimization of structural, dielectric, and magnetic properties of nanocrystalline copper doped spinel ferrites

Copper-substituted spinel ferrites with nominal composition Ca0.5Ba0.5-xCuxFe2O4 (x = 0.00, 0.125, 0.250, 0.350, 0.500) were successfully prepared by the sol–gel auto combustion route. The fabricated Nano-ferrites underwent a five-hour annealing process at 800 °C in a furnace. By the X-ray diffraction (XRD) analysis and dielectric measurements, the structural and electrical behavior of Ca0.5Ba0.5-xCuxFe2O4 nanoparticles were examined. Formations of a single-phase cubic structure of all prepared samples were estimated by the X-ray diffraction analysis. Crystallite size ranges from 37.43 to 50.07 nm. With the addition of Cu2+ cation, the lattice parameter, dielectric characteristics, and magnetic parameters were enhanced. It was observed that dielectric properties were improved significantly with the doping of copper. The dielectric constant and dielectric loss were found to decrease at high frequencies. On the other hand, an increase in AC conductivity was observed with increasing frequency by Maxwell Wagner and Koop's models. The VSM study confirms the improved magnetic properties of the sample. Remanent magnetization, saturation magnetization, and coercivity were improved significantly with the doping of copper cation. Based on these improved dielectric and magnetic characteristics, the prepared materials are strongly recommended for different electronic components and energy storage devices.

Influence of the dual charge compensator on solid solution of the air-sintered Ca1-xCexZrTi2-2xFexCrxO7 zirconolite

In this study, a dual charge-compensator formulation was developed for zirconolite with the nominal composition Ca1-xCexZrTi2-2xFexCrxO7 (x = 0–0.30). The design strategy here was such that trivalent Fe and Cr were both targeted to substitute across the Ti site(s) to charge balance an inventory of CeO2 included as a structural analogue for Pu. The targeted solid solution was prepared by sintering constituent oxides at 1400 °C for 10 h under an air atmosphere. By means of powder XRD refinement and selected area electron diffraction analysis, the dominant zirconolite polytype was confirmed to be 2M across the solid solution. The obtained product density was significantly increased when compared to the previously discussed Ca1-xCexZrTi2-2xCr2xO7 system, suggesting that the partial inclusion of Fe in a 1:1 molar ratio with Cr may improve sintering behaviour. The limit of solid solution was reached at approximately x = 0.30, for which the segregation of CeO2 and Cr2O3 phases was clearly evidenced. An evaluation of obtained chemical compositions and bulk oxidation states was performed to inform the solid solution mechanism of Ce, Cr and Fe within zirconolite.

Vacuum melting of compressed powders and hot rolling of the as-cast Ti-48Al-2Nb-0.7Cr-0.3Si intermetallic alloy: Mechanical properties and microstructural analysis

The amalgamated effect of hot-rolling, rapid cooling and heat treatment on the grain refinement and the resultant mechanical properties of an intermetallic sheet of nominal composition Ti-48Al-2Nb-0.7Cr-0.3Si was investigated. The sheet of 4 mm thickness was fabricated by hot-pack rolling from the vacuum arc remelted (VAR) ingot using a conventional two-high rolling mill. After the final rolling pass, the canned specimen was rapidly cooled in the air to room temperature followed by heat treatment in the α + γ region. The scanning electron microscopy (SEM) micrographs of the as-rolled sheet revealed slightly elongated grains of a typical “duplex (DP)” microstructure with a mean grain size of about 3 μm which grew to about 4 μm and became more equiaxed and homogeneous after heat treatment. Moreover, the EBSD micro-texture indicated a weak cube texture in the rolled + heat-treated sheet. Furthermore, the results from the profilometry-based indentation plastometry of the rolled + heat treated specimen illustrated the balanced and improved mechanical properties compared to the as-cast and as-rolled samples, and also those of similar alloy systems found in the literature.

Short-range positional order in phase separated indium gallium oxide islands deposited in a reducing atmosphere

We report a spontaneous phase separation in indium gallium oxide thin films with a nominal composition of (In0.006Ga0.994)2O3 grown on sapphire (0001) substrates using a powder sputtering method in a reducing atmosphere. The In-rich (In0.24Ga0.76)2O3-x domains are non-stoichiometric and located underneath the surface islands, whereas the In-poor domains are nearly stoichiometric Ga2O3, forming a continuous flat surface, though both domains have a monoclinic crystal structure. Furthermore, the In-rich domains exhibit a short-range positional order with a correlation length of approximately 1 μm because the phase separation occurs along the binodal decomposition accompanying periodic concentration profiling of In atoms. The analysis of X-ray photoelectron spectroscopy confirmed that the non-stoichiometry of the thin films originated from the formation of Ga sub-oxide (Ga2O) and metallic Ga, whereas the chemical state of the In atoms was close to In2O3 rather than metallic In. Our results indicate that the spontaneous phase separation occurs in (InxGa1-x)2O3 thin films even at an In content of 0.6 at%. Also, the non-stoichiometry associated with oxygen vacancies is an important parameter for causing spontaneous phase separation via the segregation of In atoms.