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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]

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]

[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]

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]

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]

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]