approach to enhance the stability of the material under device working condition, i.e., light and thermal stress. [6,7] ABX 3 halide perovskites most commonly used in solar cells contain cesium, methylammonium (MA) and formamidinium (FA) in the A site, Pb in the B, and Br and I in the X site of the crystalline lattice. [1,8-10] Compositions based on organic cations, such as MA and FA, can be prepared with a bandgap of around 1.5 eV, which is suited for an efficient single junction solar cell. [11] However, the presence of organic cations, and in particular the volatile MA, is linked to the relatively poor thermal stability and the high sensitivity to humid air, which affect most of the perovskite compositions employed in highly efficient PSCs. [12-16] Swapping entirely or in part the organic with inorganic cations, such as cesium (Cs), can help to enhance the stability of halide perovskites at the cost of a bandgap higher than 1.5, [17,18] which is suboptimal for a single junction solar cells. For example, the fully inorganic CsPbI 3 perovskite has a bandgap of 1.7 eV, which is not optimal for single junction but is instead nearly ideally suited for perovskite-silicon tandem solar cell. [19-21] Unfortunately, CsPbI 3 is only stable in the photovoltaic active perovskite structure-black phase-at temperatures above 300 °C, [22-25] which is not useful for applications. Partially (or completely) replacing iodide (I) with bromide (Br), i.e., exploring CsPbI x Br (3−x) compositions, can stabilize the active photovoltaic phase at room temperature with progressively increasing bandgap as the bromine content increases. This mixed halide approach is extensively used to prepared stable inorganic halide perovskite both for photo voltaic and light emitting devices. [26-32] As restricted to photovoltaics, it is a challenge controlling the interplay between phase stability, which can be obtained by enhancing the Br content, while maintaining the smallest possible bandgap. Indeed, the larger ionic radius of I as compared to Br upsets the stability perovskite, which tends to relax in a photovoltaic inactive delta phase. [33-37] The I/Br ratio must be therefore adjusted to achieve the lowest possible bandgap without sacrificing the perovskite phase stability. In the search for the best I/Br ratio, CsPbI 2 Br (I 67%, Br 33%) has been so far indicated as the optimum to achieve the highest efficiency PSC with a stable inorganic perovskite. [34-38] Liu et al. reported
Time-temperature evolutions of different parts inside a pot were recorded during three experimental surface (bonfire) firings. The experimental vessels were shaped from a calcareous clay, tempered with 30% vol. of oolithic limestone. The temperature-time recording showed: (1) T max. was reached after 12-22 min and differed between the firings as well as inside individual vessels; (2) the range of the thermal variation within one single firing was found to be as high as 390°C, and up to 220°C on a specific cross-section; (3) the lowest temperature was not systematically recorded in the core of the object, as is generally expected. Under the polarizing microscope, no textural and mineralogical changes were observed in the ceramic bodies. This is sustained by powder X-ray diffraction analyses evidencing no dolomite or calcite breakdown. The presence or absence of specific illite and chlorite peaks can be generally related to T max. and soaking time, but equivalent firing temperature estimations do not match the measured temperatures.
-We demonstrate that laser ablation of a gold target immersed in superfluid and normal fluid helium leads to the formation of elongated gold nano-fragments. In the superfluid phase these nano-fragments aggregate into filaments with extremely large aspect ratios displaying metallic electric conductivity. We attribute this unusual structure to the coalescence of gold particles trapped on quantized vortices. Our observations suggest new ways to visualize the structure of quantized vortex bundles and a new approach for producing centimeter-long metal nanowires. Superfluid4 He (HeII) exhibits the outstanding macroscopic quantum property of superfluidity when cooled below 2.172 K. Associated with this property is the appearance of one-dimensional structures around which the fluid motion has a circulation that is quantized in units of h/m He . Such vortex lines have been studied in detail for more than 50 years as reported in the comprehensive review by Donnelly [1]. More recently the flow of superfluid and normal fluid helium has received renewed attention in the context of quantum turbulence [2,3].Because of the strong pressure gradient in the vicinity of their core, quantized vortices can bind foreign particles. This fact has been used for the visualization of vortex bundles by the electrostatic extraction and projection of vortex-attached electrons onto a phosphor screen [4]. The pressure gradients are strong enough to attract also heavier particles, such as 3 He or other guest atoms and clusters. Because of the one-dimensional structure of the vortex line one expects [5] the formation of monoatomic chains or high-aspect-ratio filaments following the coalescence of particles on the vortex core. The formation of macroscopic filament-like structures by impurity particles suspended in superfluid helium was indeed reported by several authors [6][7][8][9] as well as the lining-up of micronsized solid hydrogen clusters injected into normal fluid He, (a) E-mail: peter.moroshkin@unifr.ch followed by a transition to the superfluid phase [10,11]. No such unidimensional structures appear in normal fluid helium. All previous studies were limited to visual observations in the He bath only, since the filament materials were either hydrogen or alkali metals which oxidize in contact with air. The experimental results presented below suggest a new approach to this problem. By doping liquid helium with a chemically inert material that keeps its shape and properties after the helium evaporation, we were able to form solid filaments and analyze them by means of optical and electron microscopy. In doped HeII we observe the production of centimeter-long gold filaments, whose analysis reveals a very rich substructure at the nanometer scale and the formation of metallic binding. On the other hand, when the doping is done in normal fluid helium we obtain only chaotically oriented gold nanonetworks which (because of their small size) escaped observation in previous studies. Our observations open new ways for visualizing the pattern...
The marine environment in the Gulf of Gabes (southern Tunisia) is severely impacted by phosphate industries. Nowadays, three localities, Sfax, Skhira and Gabes produce phosphoric acid along the coasts of this Gulf and generate a large amount of phosphogypsum as a waste product. The Gabes phosphate industry is the major cause of pollution in the Gulf because most of the waste is directly discharged into the sea without preliminary treatment. This study investigates the marine environment in the proximity of the phosphate industries of Gabes and the coastal marine environment on the eastern coast of Djerba, without phosphate industry. This site can be considered as "pristine" and enables a direct comparison between polluted and “clean” adjacent areas.Phosphorous, by sequential extractions (SEDEX), Rock-Eval, C, H, N elemental analysis, and stable carbon isotope composition of sedimentary organic matter, X-ray diffraction (qualitative and quantitative analysis) were measured on sediments. Temperature, pH and dissolved oxygen were measured on the water close to the sea floor of each station to estimate environmental conditions. These analyses are coupled with video surveys of the sea floor. This study reveals clear differentiations in pollution and eutrophication in the investigated areas.
Three types of antimony‐based, opaque ceramic colours were used in the faience workshop of Le Bois d’Épense during the first decades of the 19th century; that is, yellow, tawny and green. Yellow is generated by lead antimonate crystals (Naples Yellow), which are incorporated into an uncoloured glass matrix. According to SEM–EDS measurements, these pigments contain iron. The tawny colour is the optical result of the combined presence of similar yellow, iron‐bearing lead antimonate particles in a Fe‐rich, brownish glass matrix. The green opaque colour is produced by the combination of a blue cobalt glass and yellow Pb–Sn–Fe‐antimonate crystals. Cores of zoned pigments lighten the recipes, according to which the pigments were produced. First, they were synthesized by calcination, ground and then mixed with a colourless, brown or blue glass powder. The resulting powder mixture was added to a liquid agent and used as high‐temperature ceramic colour.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.