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Although XLPE cables are widely used in power transmission and distribution systems, their insulating properties are susceptible to degradation due to thermal aging. In order to clarify the influence law of the thermal aging process on the structural and dielectric properties of XLPE cables, this paper investigates the thermal aging characteristics of XLPE cables by using polarization and depolarization current measurement. Results show that when the XLPE cable is aged at 140 °C, the crystallinity of the insulation layer appears to increase and then decrease. With the increase in aging time, micron-sized microvoids appear on the surface of the XLPE. At the same time, the DC conductivity and 0.1 Hz dielectric loss factor of the insulating layer increase with the aging time. The average DC conductivity increased from 2.26 × 10−16 S/m for new cables to 4.47 × 10−16 S/m after aging for 432 h, while the dielectric loss increased from 0.11% to 0.42%. The polarization characteristics of thermal-aged cables were further analyzed using the extended Debye model. Results indicate that the time constant of the third branch of the model increased significantly with increasing aging time. A correspondence between this parameter and the thermal aging time of the cable was established. Thermal aging can damage the crystalline structure of XLPE, so that the number of interfaces between the crystalline and amorphous regions of the material increases, resulting in structural damages and a decline in the dielectric properties of the cable insulation. [ABSTRACT FROM AUTHOR]

Spherulite-related space–charge electret properties of polypropylene (PP) have been widely discussed in the past decades. In the present paper, a less-common crystalline structure in PP—transcrystalline PP—is studied regarding its electret behavior in comparison with the typical spherulitic morphology. Polarized light microscopy and differential scanning calorimetry were employed to characterize the crystallite types and crystallinities of transcrystalline and spherulitic PP. Their electret functionality is investigated by means of thermally stimulated discharge experiments, where the cross-over phenomenon is observed on transcrystalline PP films, whereas surface-potential saturation and undercharging on the surface occur on the spherulitic samples. Besides, an asymmetrical behavior of positive and negative surface-charge stabilities is found on PP with spherulites, the negatively charged spherulitic surfaces show a better charge stability. It is shown that PP electrets are very sensitive to changes in the microscopic crystalline structures and their interfaces as well as in the molecular conformations controlled through adjustments of the respective processing steps. In addition, surface and bulk nanocomposites of PP or low-density polyethylene with inorganic particles are included in the comparison. In view of recent developments in the areas of PP-based electret-fiber filters and cellular-foam ferroelectrets, the observed changes in the charge-storage properties may have particular relevance, as the required film, fiber, or foam processing might significantly modify crystalline morphologies and nano-scale interfaces in PP electrets. Limitations in the charge-storage capabilities of interface structures may also be of interest in the context of high-voltage electrical-insulation materials where reduced space–charge accumulation and slightly increased charge transport can be advantageous. [ABSTRACT FROM AUTHOR]

In this work, the epitaxial semipolar (11–22) AlN was prepared on nonpolar m-sapphire substrate by combining sputtering and high-temperature annealing. According to our systematic measurements and analysis from XRD, Raman spectra, and AFM, the evolution of crystalline structure and morphology was investigated upon increasing AlN thickness and annealing duration. The annealing operation intensively resets the lattice and improves the crystalline quality. By varying the film thickness, the contribution from the AlN-sapphire interface on crystalline quality and lattice parameters during the annealing process was investigated, and its contribution was found to be not so obvious when the thickness increased from 300 nm to 1000 nm. When the annealing was performed under durations from 1 to 5 h, the crystalline quality was found unchanged; meanwhile, the evolution of morphology was pronounced, and it means the crystalline reorganization happens prior to morphology reset. Finally, the annealing treatment enabled a zig-zag morphology on the AlN template along the sapphire [0001] direction in the plane, which potentially affects the subsequent device epitaxy process. Therefore, our results act as important experience for the semipolar nitride semiconductor laser device preparation, particularly for the epitaxy of microcavity structure through providing the crystalline evolution. [ABSTRACT FROM AUTHOR]

The concave behaviour of the Porod invariant observed during the calcination of CaCO3 powder samples suggests the following picture of the evolving internal structure of the samples. The outset sample is formed by a crystalline CaCO3 phase and a void phase. During the calcination, the first phase shrinks in volume at fixed density since the temperature increase breaks down the crystalline structure at the interface, leading to the formation of an amorphous phase comprising an equal number of CO2 and CaO atomic groups. The last groups gradually condense, forming a third phase of solid CaO of constant density and increasing volume fraction, while the companion CO2 groups flow out of the sample. The amorphous phase occupies, with a variable density, all the volume left free by the other two phases. At the end of the calcination, both the volume fraction of the first phase and the density of the amorphous phase vanish so that the sample will again be made up of two phases: the voids and the solid CaO. Best‐fitting the resulting theoretical expressions of the Porod invariant and of the Porod law coefficient to the observed values, one can determine the matter densities, volume fractions and specific surface areas of the phases. [ABSTRACT FROM AUTHOR]

Mathematical analysis is performed to examine the reflection and transmission phenomena of plane waves at the corrugated interface of crystalline structure separating two distinct monoclinic thermoelastic media. Analysis of this phenomena is achieved adopting classical dynamic coupled, Lord–Shulman, and Green–Lindsay theories. Using Rayleigh's methods, the expressions of reflection and transmission coefficients of reflected and transmitted waves are deduced for the case of corrugated as well as plane interfaces. The influence of corrugation and frequency parameters on reflection and transmission coefficients for all three theories has been extensively analyzed with a comparative approach. Findings of the study are demonstrated through numerical and graphical results. Furthermore, the obtained result is validated with the preexisting result. [ABSTRACT FROM AUTHOR]

Recently, the crystallographic phases of HfO2 and ZrO2, including the polar phases, have been well characterized, and also the total and free energies have been calculated. However, less is known about the structure and energy of the crystalline coherent interface—also called the interphase. The formation of domain and phase boundaries is determined by interphase energies and properties, and their knowledge is indispensable to better understand the phase formation and phase stability. We have calculated the interphase energy for HfO2 and ZrO2 at T = 0 K for the relevant phase pairs with two methods, which are in good agreement. The method is applicable to any crystalline material with metastable phases. The values range in a few 100 mJ/m2, which is consistent with previous estimates from room temperature but too large for estimates from high-temperature processes. We propose a temperature dependence of interphase energy such that it becomes small close to the phase transition. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-entropy alloy nanolaminates are obtained. • The coherent interface in nanolaminates is designed to improve ductility. • The crystalline/amorphous hierarchical nanostructure is designed to enhance strength. Introducing nanolaminates structure is a promising strategy to obtain the controllable microstructure and mechanical properties of high entropy alloy (HEA). In this work, the Al 0.5 CoCrFeNi/CoCrCuFeNi nanolaminates with coherent interface and crystalline/amorphous hierarchical nanostructure was designed. On the one hand, the coherent interface with continuous slip direction and planes enables nanolaminates with great deformability. On the other hand, the hierarchical nanostructure in the nanolaminates contributes to high strength via the interaction between crystalline and amorphous structures. Microstructural observations indicated that abundant nanotwins and stack faults were filled in the columnar nanocrystalline cutting across the interface, leading to a high hardness due to the dislocation-interface interactions. The results of nanoindentation tests revealed that the hardness of the nanolaminates up to 8.02 GPa, which markedly exceeds many HEA films with face-centered cubic (FCC) phase. The findings provide a new avenue for improving the mechanical properties of HEA nanolaminates in a controllable manner. [ABSTRACT FROM AUTHOR]

[Display omitted] • a/c-RuCoMo y O x /NF was synthesized by coprecipitation-microwave method. • Microwave time affects the transition from crystalline to amorphous structure. • a/c-interface and electron interaction make a/c-RuCoMo y O x /NF have mighty activity. • The η 10 value of a/c-RuCoMo y O x /NF is 39 and 166 mV for HER and OER. Due to the vast difference in structure and the unique electronic state at the heterointerface, the amorphous/crystalline (a/c) heterostructure exhibits excellent potential in electrocatalysis. However, there are great challenges in constructing the material with ample a/c-heterointerfaces and controllably modulated a/c-heterointerface region through a simple one-step method. Herein, the a/c-RuCoMo y O x /NF (nickel foam) electrocatalyst is synthesized by the coprecipitation-microwave treatment method. Notably, microwave time directly affects the ratio of amorphous region (RuCoMoO x) to crystalline region (CoMoO 4 and CoO). Surprisingly, the a/c-RuCoMo y O x /NF with abundant crystallinity/amorphous heterointerfaces exhibits the ultralow η 10 values of 39 and 166 mV for HER and OER, which are 0.5-fold and 0.63-fold lower than that of Pt/C-NF and RuO 2 -NF benchmarks, respectively. Overall, this work provides a novel idea and convenient method for the construction of amorphous/crystalline heterointerfaces with modulated interface region, and guides the direction for the preparation of superior electrocatalysts by regulating the a/c-heterointerface region. [ABSTRACT FROM AUTHOR]

ZSR-P loaded nano-TiO 2 composite photocatalysts (TiO 2 /ZSR-P) have been prepared by the sol–gel method using the by-product Zr-containing silica residue (ZSR) as precursors during the production process of zirconium oxychloride, the structure and properties of TiO 2 /ZSR-P were characterized in this paper. The results showed that the TiO 2 /ZSR-P composite photocatalysts were characterized by the uniform loading of nano-TiO 2 on the surface of amorphous SiO 2 particles in ZSR-P. TiO 2 and SiO 2 were combined by forming -Ti-O-Si- bonds at the interface and the crystalline structure of TiO 2 powders was identified a mixed phase of anatase and rutile, its loading amount was 17.14%, the particle size raged from 7 to 12 nm. The degradation rate of TiO 2 /ZSR-P to the concentration of 5 ppm and 10 ppm methyl orange solution reached 99.52% and 100% respectively after 140 min of ultraviolet irradiation, and it still maintained stable performance after repetitive-use of the catalyst for 4 times. [ABSTRACT FROM AUTHOR]

Neutron total scattering of disordered crystalline materials provides direct experimental access to the local (short-range) structure. The ways in which this local structure agrees (or disagrees) with the long-range crystal structure can provide important insight into structure-property relationships. High-pressure neutron diffraction using a Paris-Edinburgh (P-E) pressure cell allows experimenters to explore the ways in which materials are affected by pressure, can reveal new synthetic routes to novel functional materials and has important applications in many areas, including geology, engineering and planetary science. However, the combination of these two experimental techniques poses unique challenges for both data collection and analysis. In this paper it is shown that, with only minor modifications to the standard P-E press setup, high-quality total scattering data can be obtained from crystalline materials in the gigapascal pressure regime on the PEARL diffractometer at ISIS. The quality of the data is assessed through the calculation of coordination numbers and the use of reverse Monte Carlo refinements. The time required to collect data of sufficient quality for detailed analysis is assessed and is found to be of the order of 8 h for a quartz sample. Finally, data from the perovskite LaCo0.35Mn0.65O3 are presented and reveal that PEARL total scattering data offer the potential of extracting local structural information from complex materials at high pressure. [ABSTRACT FROM AUTHOR]

The catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF) is highly desirable, but the 5-HMF yield obtained using heterogeneous catalysts is still low compared to homogeneous catalysts, and the mechanism is not elucidated completely. In addition, the isolation and purification of 5-HMF still present a challenge as degradation reactions take place and side products form. The formation of 5-HMF from glucose has been reported using several solid acid catalysts; still metal–organic framework (MOF) catalysts could, so far, catalyze the cascade reaction of glucose to 5-HMF only in low yields of less than 16%. Glucose conversion using MOFs is little investigated and here sulfonated MIL-101Cr (MIL-SO3H) was found to achieve 29% conversion of glucose to 5-HMF after 24 h in a THF : H2O (v : v 39 : 1) mixture. The conversion of maltose resulted in 50% 5-HMF yield (saccharide solutions were 5 wt%). When the reaction was carried out in pure THF using MIL catalysts no product was formed, revealing the indispensability of water for the glucose-to-5-HMF conversion. Importantly, MIL-SO3H preferentially leads to 5-HMF over levulinic acid (molar ratio 1 : 0.3), while the catalysts Amberlyst-15 and sulfuric acid form mostly levulinic acid in 5-HMF to levulinic acids ratios of 1 : 3 and 1 : 10, respectively. At the same time, MIL-NO2 is the most selective, yielding only 5-HMF and showing no formation of levulinic acid. Using 5-HMF as a substrate did not result in any conversion to levulinic acid in the presence of MIL-SO3H, thereby ruling out the catalytic formation of levulinic acid from 5-HMF. Catalyst recycle experiments showed that MIL-SO3H stays porous and crystalline, but becomes deactivated through fouling by humin formation. With the use of ethanol as an alternative reaction medium, the formation of insoluble humins could be prevented, but the yield of 5-HMF and 5-ethyl-HMF decreased. [ABSTRACT FROM AUTHOR]

We report the fabrication of a Si(111) crystalline thin film on graphene by the aluminum-induced crystallization (AIC) process. The AIC process of Si(111) on graphene is shown to be enhanced compared to that on an amorphous SiO2 substrate, resulting in a more homogeneous Si(111) thin film structure as revealed by X-ray diffraction and atomic force microscopy measurements. Raman measurements confirm that the graphene is intact throughout the process, retaining its characteristic phonon spectrum without any appearance of the D peak. A red-shift of Raman peaks, which is more pronounced for the 2D peak, is observed in graphene after the crystallization process. It is found to correlate with the red-shift of the Si Raman peak, suggesting an epitaxial relationship between graphene and the adsorbed AIC Si(111) film with both the graphene and Si under tensile strain. [ABSTRACT FROM AUTHOR]

We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc2O3/Y2O3/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit<0.1%) makes the ScN/Sc2O3/Y2O3 buffer system a very promising template for the growth of high quality GaN layers on silicon. [ABSTRACT FROM AUTHOR]

Nanocrystalline TiO 2 catalysts with different anatase/rutile ratios have been successfully prepared using a single-step solution combustion synthesis (SCS). The synthesized powders were characterized using XRD, Raman, XPS, FT-IR, SEM, TEM, BET and UV–vis DRS. The effects of urea-to-nitrate molar ratio on the phase structure, morphology and photocatalytic activity of the TiO 2 powders were investigated. Results show that the urea contents play an important role in controlling the crystal structure of the samples. Specifically, well-dispersed anatase/rutile TiO 2 nanocomposites (anatase 66.2%, rutile 33.8%) with excellent photocatalytic activity can be obtained when the molar ratio of urea-to-nitrate is 0.50. The synergistic effect between the anatase and rutile is responsible for the enhanced performance of this material. Moreover, a thermodynamic calculation was performed to interpret the phase transformation mechanism during the combustion process. [ABSTRACT FROM AUTHOR]

An overview is given on the ways databases can be employed to aid in the prediction of chemical compounds, in particular inorganic crystalline compounds. Methods currently employed and possible future approaches are discussed. [ABSTRACT FROM AUTHOR]

Computer simulation has been employed to study the structure of water condensate filling planar pores 1.25 and 0.62 nm wide located parallel to the basal face in a silver iodide crystal at 260 K. All stages of adsorption of single molecules up to complete pore filling have been described. At an initial stage, strong clustering of molecules is observed on the walls; then, the walls are covered with a monomolecular film; and, at the final stage, molecules are adhered to the surface of the film, thus filling the internal space of the pore. First, adsorption occurs at the wall containing positive ions on the surface and, then, on the opposite wall with negative ions. On both walls, adsorbed molecules are adhered to the surface via the interaction with ions of the second crystallographic layer; given this, two types, α and β, of molecule plane orientation are realized on opposite walls. The adhesion of an adsorbed molecular film to molecules filling the interior of the pore requires the partial transition of film molecules from the α- to the β-type orientation on one wall and the inverse transition on the other wall. The deficiency of α-oriented molecules on one wall and β-oriented ones on the other is the main reason for poor wettability of the surface of the monomolecular films adsorbed on the walls. In an extremely narrow pore, molecules are simultaneously captured in the field of both walls. The forces acting from the sides of both walls result in the separation of a film into spots having structures matched to the crystalline structure of each wall, with the film being on the verge of breakage. [ABSTRACT FROM AUTHOR]

An ab initio version of the model with deformable atoms has been constructed to investigate the elastic properties of compressed crystalline neon. Approximations for the calculating parameters of quadrupole deformation of atomic electron shells have been discussed. It has been shown that the pressure dependence of the deviation from the Cauchy relation δ is the result of two competitive interactions, namely, the many-body and electron-phonon interactions, which manifests itself in the deformation of atomic electron shells during the shift of nuclei. In the case of Ne, contributions of these interactions are compensated to a large degree, which provides a weakly pressure-dependent positive value for δ. The agreement of calculated elastic moduli and deviations from the Cauchy relation for Ne with the experiment is good. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of the new ternary compound TmCu4−x Sb2 (x =1.065) was determined by direct methods from X-ray powder data (diffractometer DRON-3M, Cu Kα-radiation). It crystallizes with the orthorhombic structure type ErFe4Ge2 (low-temperature modification) and is the first representative of this structure type among known antimonides: space group Pnnm, Pearson code oP14-2.13, a =7.00565(6)Å, b =7.83582(6)Å, c =4.25051(3)Å, Z =2. Investigated structure is an orthorhombically deformed derivative of the ZrFe4Si2 structure type. [Copyright &y& Elsevier]