The effects of stress-free and stress-assisted pretreatments at a relatively high temperature on the creep properties of [001] and [011] oriented Ni-based single-crystal superalloys are investigated in this article. The results show that the creep life of the pretreated samples is shorter than that of the original samples. The variation of the γ/γ′ morphology during the creep process is characterized by the microstructure period. Based on the interaction between the dislocations in the γ matrix channel and the γ′ phase, the difference in creep properties of the two oriented alloys after pretreatment is analyzed. Combined with the crystal plasticity theory and the number of activated slip systems observed in the experiments, it can be concluded that the two oriented alloys after pretreatment show obvious creep anisotropy and that the creep life increases with the number of activated slip system.

The unique properties of graphene have led to the use of this allotrope of carbon in a wide range of applications, including semiconductors, energy devices, diffusion barriers, heat spreaders, and protective overcoats. The synthesis of graphene by process methods that either directly or indirectly rely on physical vapor deposition, thermal annealing, laser irradiation, and ion/electron beam irradiation has drawn significant attention in recent years, mainly because they can provide high purity, low temperature, high throughput, and controllable growth of graphene on various substrates. This article provides a comprehensive assessment of these methods by grouping them into two main categories, i.e., indirect methods in which a carbon layer is first deposited on a substrate and then converted to graphene by some type of energetic post-treatment process and direct methods in which graphene is directly synthesized on a substrate surface by a process that uses a solid carbon source. The underlying growth mechanisms of these processes and the challenging issues that need to be overcome before further advances in graphene synthesis can occur are interpreted in the context of published results.

In this paper, the atomic resolution high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) was used as the main research method. Using HAADF-STEM, two types of long-period stacking ordered structure (LPSO)—14H and 18R-LPSO—were observed in Mg96Gd2Y1Ni1 alloy, and the precipitates at various stages of aging were observed. Moreover, a type of rectangular β precipitates were found, and the atomic models of β precipitates along the [0001]Mg and ${\tf="TeXGyrePagella-Bold (TrueType)"\char9001} 11\bar 20\hbox{]}_{{\rm{Mg}}}$ directions were identified. At the aging peak stage, a three-dimensional network structure composed of LPSO/γ′ precipitates and β′ precipitates and β precipitates was observed. The hardness of the unaged homogenized Mg96Gd2Y1Ni1 alloy was only 87 HV and the hardness value of aging peak was 128.4 HV. Compared with the unaged alloy, the hardness of the peak-aged alloy increased by 47.59%. The composite strengthening of the three types of precipitates induced a significant strengthening to the alloy.

In this study, zinc oxide nanoparticles (ZnO NPs) in powder and in thin film were successfully synthesized first time using an eco-friendly, simple and cost effective green synthesis method mediated by corn husk (Zea mays) extract as an effective chelating agent, and zinc nitrate hexahydrate as precursor. Diverse characterizations techniques such as High Resolution – Scanning Electron Microscopy (HR-SEM), Energy Dispersive X- rays Spectroscopy (EDS), X-Rays Diffraction (XRD), and UV – Vis – NIR spectroscopy as well as Photoluminescence (PL) were investigated to confirm ZnO NPs nature. For the ZnO NPs powder, highly crystalline ZnO nanoparticles (ZnO NPs) annealed at 500°C which are 48.635 nm in particles size were characterised by HR-SEM and XRD analysis. The structure morphology and the constituents of the resultant ZnO powder were investigated respectively by HR-SEM and EDS. UV – Visible spectroscopy analysis was investigated on the optical band gap of ZnO NPs, which was calculated to be 3.31 eV. This result indicates that ZnO NPs can be used in metal oxide semiconductor-based devices. For the ZnO NPs thin film, XRD patterns of hexagonal wurtzite structure with c/a ratio about of 1.60 and μ – parameter of 0.38 were obtained. PL measurements showed a broad emission band in the 380 – 800 nm range, centred at 481 nm. ZnO NPs thin film yielded relatively more intense photoluminescence spectra than the ZnO NPs powder. The intrinsic point defects and defect level transitions responsible for the broad emission are discussed.

LiNi0.5Mn1.5O4 cathode material, which has a higher working voltage (4.7 v) than NCM and a moderate specific capacity (148 mAh/g theoretical), has been studied to understand the source of capacity fade during the first 100 cycles in a half cell. The work mainly consisted of high resolution TEM observations and analysis of the surface microstructural properties, before and after cycling. We found that the pristine material consisted almost entirely of large FCC spinal domains but with cycling appears small simple cubic spinel domains at the surface. It is proposed that these small changes of the surface microstructure leads to impedance rise that results in the premature arrival to the upper cutoff voltage of 4.85V during charging and the subsequent loss of capacity with cycling.

Millimetre UO2 single crystals were cut and oriented at JRC Karlsruhe. The orientation of each face of the parallelepiped single crystals was determined with Laue diffraction and the corresponding surface area by geometric measurements. Then, the (111), (100), (110) faces of each single crystal were polished to optical grade and characterized by XRD in order to confirm the surface orientation. The dissolution of the three single crystals was achieved in nitric acid media under dynamic conditions, at room temperature. Two dissolution regimes were observed for all samples. The normalized dissolution rate measured in the first step was not influenced by the crystallographic orientation of the faces. However, during the second step, (110) oriented faces were found to dissolve 4 times faster than the (100) faces. One explanation could involve the atomic composition of each oriented surface in the fluorite-type structure

Perovskite chalcogenides are gaining substantial interest as an emerging class of semiconductors for optoelectronic applications. High-quality samples are of vital importance to examine their inherent physical properties. We report the successful crystal growth of the model system, BaZrS3 and its Ruddlesden–Popper phase Ba3Zr2S7 by a flux method. X-ray diffraction analyses showed the space group of Pnma with lattice constants of a = 7.056(3) Å, b = 9.962(4) Å, and c = 6.996(3) Å for BaZrS3 and P42/mnm with a = 7.071(2) Å, b = 7.071(2) Å, and c = 25.418(5) Å for Ba3Zr2S7. Rocking curves with full width at half maximum of 0.011° for BaZrS3 and 0.027° for Ba3Zr2S7 were observed. Pole figure analysis, scanning transmission electron microscopy images, and electron diffraction patterns also establish the high quality of the grown crystals. The octahedral tilting in the corner-sharing octahedral network is analyzed by extracting the torsion angles.

We deposit films of tin–calcium sulfide by atomic layer deposition (ALD) and demonstrate the metastability of this material. Rough and spiky films are obtained by using Sn and Ca precursors with different ligands, whereas compact and smooth films are obtained when the two metal sources share the same ligands. Compositional and quartz crystal microbalance results indicate that part of the underlaying SnS film is replaced and/or removed during the CaS ALD cycle during the ternary film deposition, possibly via a temperature-dependent cation exchange mechanism. The crystal structure transforms from orthorhombic to cubic as the calcium content increases. Furthermore, resistivity increases with calcium content in the alloy films, whereas optical band gap only depends weakly on Ca content. After annealing at 400 °C in an H2S environment, the cubic alloy film undergoes a phase transition into the orthorhombic phase and its resistivity also decreases. Both phenomena could be explained by phase separation of the metastable alloy.

Nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 suffers from severe structural instability and irreversible capacity loss during cycling due to cation disorder of Li+ and Ni2+. To solve this problem, the precursor Ni0.8Co0.1Mn0.1(OH)2 and well-ordered LiNi0.8Co0.1Mn0.1O2 cathode materials were successfully synthesized via controlled crystallization and high-temperature solid-state methods. The structure, morphology, and electrochemical performance of the precursor and LiNi0.8Co0.1Mn0.1O2 powders were investigated. The results show that the precursor Ni0.8Co0.1Mn0.1(OH)2 is made of sphere-like particles composed of needle-like primary crystal and LiNi0.8Co0.1Mn0.1O2 possesses a perfect layered structure with low Li/Ni disorder. Electrochemical data demonstrate that the material rate capabilities are 203.3, 187.7, 170.4, and 163 mA h/g from 0.1C to 10C, respectively. The capacity retention is 87.9% after 100 cycles at 1C, even the cut-off voltage was increased to 4.5 V. The high discharge capacity and outstanding cycling life can be attributed to the merits of a perfect crystal lattice with low Li/Ni disorder, fast lithium ion transport, and relatively low charge transfer resistance.

Atomically resolved imaging of materials enabled by the advent of aberration-corrected scanning transmission electron microscopy (STEM) has become a mainstay of modern materials science. However, much of the wealth of quantitative information contained in the fine details of atomic structure or spectra remains largely unexplored. In this article, we discuss new opportunities enabled by physics-informed big data and machine learning technologies to extract physical information from static and dynamic STEM images, ranging from statistical thermodynamics of alloys to kinetics of solid-state reactions at a single defect level. The synergy of deep-learning image analytics and real-time feedback further allows harnessing beam-induced atomic and bond dynamics to enable direct atom-by-atom fabrication. Examples of direct atomic motion over mesoscopic distances, engineered doping at selected lattice sites, and assembly of multiatomic structures are reviewed. These advances position the scanning transmission electron microscope to transition from a mere imaging tool toward a complete nanoscale laboratory for exploring electronic, phonon, and quantum phenomena in atomically engineered structures.

The thermodynamic properties of ZnxMn3−xO4 and Mg1−zCuzCr2O4 spinel solid solutions have been studied using high-temperature oxide melt solution calorimetry. Except for MgCr2O4 spinel, which possesses cubic structure, the other three end-members are tetragonal. The enthalpies of mixing are small endothermic and fit subregular solution behavior. The main contribution to the energetics of mixing of both spinel systems comes from the difference in the crystal structure between the end-members: a change in the tetragonal distortion for ZnxMn3−xO4 solid solutions and a transition from cubic to tetragonal for the Mg1−zCuzCr2O4 system. If all Mg1−zCuzCr2O4 spinels possessed the same structure, the mixing enthalpies would be close to zero. Because both series have normal cation distributions, the entropies of mixing are equal to the configurational entropies of mixing of Zn2+ and Mn2+ and of Mg2+ and Cu2+ on tetrahedral sites, and the activities would follow Raoult’s law. The calculated Gibbs energy of mixing confirms the absence of solvus at any temperature for both systems.

In this work, a new phenylethylene derivative, named 2-((3,5-di(9H-carbazol-9-yl)phenyl)(p-tolyl)methylene)malononitrile (DCPTMM), is synthesized and characterized by 1H NMR, 13C NMR spectroscopies, mass spectrum, and X-ray crystallography. Its photophysical properties are systematically studied and the result illustrates that DCPTMM shows aggregation-induced emission (AIE). The X-ray single crystal diffraction shows that the individual structure of crystals is monoclinic system with space group symbol P21/c and presents a twisted propeller-type structure as well as the packing structure of crystals has multiple types of hydrogen bonds (C–H⋯π and C–H⋯N) formed between adjacent molecules, and there is no π–π interaction between the aromatic rings, which is the main reason for the formation of AIE. Nondoped OLED fabricated with DCPTMM as light emitting layer emits greenish yellow light with a maximum emission peak of 554 nm and has relatively good performance with a maximum current efficiency of 5.53 cd/A and a maximum brightness of 6936 cd/m2.

The discovery, design, and development of new alloys have long been critical elements of advanced engineering systems. Challenged by their chemical and structural complexity, this design process is, however, often too slow. This article highlights progress in theory, computation, data, and advanced experimental techniques that are advancing our capabilities for rapid discovery and design of new multicomponent alloys. Applied across the length scales, these new capabilities support exploration across broad composition spaces; examples of new materials and associated advances in the understanding of underlying thermochemical and thermomechanical phenomena are presented. We highlight current challenges, gaps, and specific areas that, if further developed, could have future high payoff.

Three different high entropy-alloys consisting of six elements (Ti, Zr, V, Cr, Ni, and Fe) with varying Fe content were synthesized by using the RF induction melting technique. All the as-cast, slow-cooled, and rapidly quenched alloys exhibit C14 Laves phase, and it is found to be stable at high temperature. A lattice contraction has been observed with the addition of Fe. To the best of our knowledge, this is the first report on the synthesis of a single-phase high-entropy complex intermetallic compound in the hexanary alloy system. It has been shown that the thermodynamic calculations following Miedema’s approach and the parametric approach utilizing several descriptors comprising configurational entropy, mixing enthalpy, atomic size mismatch, electronegativity, and valence electron concentration favor the stability of the high-entropy multicomponent Laves phase.

The growth mechanism of C14 Laves phase in the bcc αFe matrix was determined as the ledge mechanism on the (110)α//(0001)C14 habit plane in Fe-20Cr-0.5Nb-1Mo (at%) alloys annealed at 1073 K for 24 hours, using conventional and scanning transmission electron microscopy. Terrace planes are the basal plane of hcp-based C14 structure. Precipitation particles tend to grow in plate shape depending on the anisotropic difference of lattice mismatch. The addition of Si with Mo remarkably enhances C14 Laves phase precipitation. The area fraction of Laves phase increases from 5.9% to 12.1% by the 2Si addition on Fe-20Cr-0.5Nb-2Mo alloys. Contrary to this, the addition of Si is not effective to increase Laves phase precipitation. It is indicated that Si improves the phase stability of C14 Laves phase while the partitioning of Mo into C14 Laves phase would be promoted due to the attractive interaction between Mo and Si.

Numerous fabrication protocols are known to yield transition metal oxides with structures related to layered double hydroxides, but the effect of fabrication protocol on the uniformity of mixed-metal compositions remain largely unexplored. We have analysed the apparent solubility limits and the structural implications of iron ions in nickel hydroxide lattices for materials prepared by four different fabrication protocols. Opposing shifts in the (100) and (001) reflection in powder X-ray diffraction results revealed a contraction of the nickel lattice upon successful incorporation of iron, with Ni-M distances exhibiting an apparently linear decrease with respect to iron content. This feature revealed the amount of iron incorporated into nickel-based materials to be dependent on fabrication protocol, varying from apparently negligible concentrations to over fifty atomic percent. The dependency of structure on fabrication protocols provides a handle to improve fundamental understanding of catalytically relevant coordination environments.

CdSe nanoparticles were grown using a colloidal method, in which the pH was the main parameter that was varied (from 8 to 12) with the objective of knowing the morphological and structural effects after the synthesis process. The samples were characterized with X-ray diffraction and High-Resolution Transmission Electron Microscope to know their crystalline structure. We identified the formation of two crystalline phases in a single sample, as well as the different crystal direction of the material, the crystallites size was calculated from the X-ray diffraction pattern using the Debye- Scherrer equation. The distance between planes was also calculated using the Fast Fourier Transformation (FFT). The results and analysis of the experimental work are reported.

Aqueous rechargeable batteries are attractive owing to their higher operational safety, high ionic conductivity, scalable and easy manufacturing. These aqueous batteries form an economic option for large-scale (grid) power storage. In the aqueous battery sector, Mn-based compounds are highly attractive with their non-toxic nature, low-cost, rich mineral chemistry and robust operational safety. Several Mn-based systems like LiMn2O4 spinel and LiNi1/3Mn1/3Co1/3O2 have seen successful commercialization. Pursuing Mn-based materials, we have shown layer structured Na2Mn3O7 as a versatile cathode material for non-aqueous systems like Li-, Na- and K-ion batteries. In the current work, we have exploited Na2Mn3O7 as a cathode material for aqueous Zn-ion battery for the first time. This Na-Mn-O ternary system was prepared using two-step emulsion-based synthesis. The phase-pure Na2Mn3O7 was formed in a triclinic structure with a space group of P-1. It exhibited versatile electrochemical insertion of different ions like Li-, Na- and K-ions involving phase transition. Na2Mn3O7 exhibited reversible Zn-ion intercalation delivering capacity of 245 mA h g-1 with a nominal voltage of 1.5 V. Upon discharge, it triggered phase transformation to an unknown phase. Layered Na2Mn3O7 oxide was found to act as an efficient cathode for Zn-ion batteries with good cycling stability.

One of the founding concepts of the high-entropy alloy (HEA) field was that the lattice structures of multicomponent solid solution phases are highly distorted. The displacement of the constituent atoms, away from their ideal locations (local lattice strain), has been widely cited as the reason for a number of the observed physical and mechanical properties. However, very little data directly characterizing these lattice distortions exist and, thus, the validity of this hypothesis remains an open question. Here, the concept is reviewed by considering the underlying principles of the lattice distortions, the suitability of different assessment methods, and the direct experimental data currently available. It is found that, at present, there is no clear evidence that the lattice distortions in HEAs are significantly greater than those of conventional alloys. However, so few alloys have been appropriately characterized that this conclusion cannot be considered overarching and further research is required.

ZnAl–Zr(X) hydrotalcite-like materials were synthesized by co-precipitation using a Zn/Al molar ratio of 2 and Zr/Al(X) molar ratios of 0.0, 0.10, and 0.25. The effect of the activation temperature on the catalytic performance of these materials was analyzed, revealing that at relatively low temperature (200 °C), the collapse of the material structure is diminished, leading to FAME yields varying from 68 to 82%. This remarkable catalytic activity is related to the formation of hydrotalcite, zincite, and hydrozincite which in turn lead to the generation of Brönsted basic sites and Lewis acid–basic pairs. Incorporation of Zr+4 into the brucite-like structure of hydrotalcites enhances the basicity of ZnAl–Zr(X) catalysts, which correlates well with the increase in catalytic activity observed for these catalysts. The stability of the ZnAl–Zr(0.25) catalyst was further studied, showing insignificant deactivation after five subsequent reaction cycles. A simplified reaction scheme was proposed for the transesterification reaction over these materials.