Pulsed Laser Deposition of CsPbBr3 Films: Impact of the Composition of the Target and Mass Distribution in the Plasma Plume

All-inorganic cesium lead bromine (CsPbBr3) perovskites have gained a tremendous potential in optoelectronics due to interesting photophysical properties and much better stability than the hybrid counterparts. Although pulsed laser deposition (PLD) is a promising alternative to solvent-based and/or thermal deposition approaches due to its versatility in depositing multi-elemental materials, deep understanding of the implications of both target composition and PLD mechanisms on the properties of CsPbBr3 films is still missing. In this paper, we deal with thermally assisted preparation of mechano-chemically synthesized CsPbBr3 ablation targets to grow CsPbBr3 films by PLD at the fluence 2 J/cm2. We study both Cs rich- and stoichiometric PbBr2-CsBr mixture-based ablation targets and point out compositional deviations of the associated films resulting from the mass distribution of the PLD-generated plasma plume. Contrary to the conventional meaning that PLD guarantees congruent elemental transfer from the target to the substrate, our study demonstrates cation off-stoichiometry of PLD-grown CsPbBr3 films depending on composition and thermal treatment of the ablation target. The implications of the observed enrichment in the heavier element (Pb) and deficiency in the lighter element (Br) of the PLD-grown films are discussed in terms of optical response and with the perspective of providing operative guidelines and future PLD-deposition strategies of inorganic perovskites.

Circular Steel: How Information and Actor Incentives Impact the Recyclability of Scrap

Recycling plays a vital role in preserving resources like steel and consequently in a circular economy. Scrap dealers and steel mills, the main business units in this system, often encounter opposing financial and sustainability incentives in using scrap as feedstock because regular sorting and scrap-preparation infrastructure cannot deal with the increasing complexity of steel scrap. Mismatches between the inputs and the target composition of the recycled steel result in trade-offs that favor the economics at the expense of resource efficiency. By examining literature and interviewing several actors, different scrap characteristics were identified as dimensions of scrap quality. Quality is typically associated with chemical composition, which is important, but this study aims to elaborate the concept of quality further and to connect it to the realities of scrapyard operations. Industry actors have different definitions for desired content, physical condition, shape and size, and homogeneity, based on their needs. Very few studies examine these details. Additionally, the relationship of quality and the level of information about the characteristics of the material was established. Having more definitive information on scrap increases opportunities for resource-efficient actions. This work offers an alternative perspective on how to address issues pertinent to recycling. Graphical Abstract

Effect of Sand Type and PVA Fiber Content on the Properties of Metakaolin Based Engineered Geopolymer Composites

This study investigates the mechanical and physical properties of engineered geopolymer composites (EGCs) consisting of metakaolin (MK) based geopolymer (GP) binder, microsilica sand (MS) or river sand (RS), and polyvinyl alcohol (PVA) fiber. Plain GP matrices and fiber-reinforced composites were studied. Aspects of the material composition evaluated here included binder composition, aggregate type, and fiber content. Compressive strength test results revealed that GP mortars presented greater compressive strength than pure GP binders. Moreover, the addition of PVA fibers produced an important increment in compressive strength while increases in fiber content generally enhanced compressive strength. MS composites tended to produce higher compressive strength than RS composites. While exhibiting low densities (i.e., 1.80–1.94 g/cm3), the composite materials evaluated exceeded the compressive strength of regular concrete (i.e., 30 MPa). Furthermore, the best performing composite presented a compressive strength of 57.5 MPa, thus falling in the category of high-strength concrete. The EGC-like tensile pseudo strain-hardening (PSH) behavior of MK-based GP composites was confirmed by a uniaxial tensile test with MS-composites exhibiting greater tensile strength and ductility compared with RS composites; yet, robust PSH behavior was not achieved mainly because of a lack of proper fiber dispersion. Scanning electron microscopy (SEM) revealed unreacted metakaolin particles in some areas within the geopolymer gel of both GP binders evaluated in this study, suggesting incomplete geopolymerization in the binder. Furthermore, energy dispersive X-ray spectroscopy (EDS) microchemical analysis of a geopolymer gel encountered close agreement between the target composition of the GP binders produced and the actual chemical composition encountered in the specimens evaluated.

Phase Stability of Iron Nitride Fe4N at High Pressure—Pressure-Dependent Evolution of Phase Equilibria in the Fe–N System

Although the general instability of the iron nitride γ′-Fe4N with respect to other phases at high pressure is well established, the actual type of phase transitions and equilibrium conditions of their occurrence are, as of yet, poorly investigated. In the present study, samples of γ′-Fe4N and mixtures of α Fe and γ′-Fe4N powders have been heat-treated at temperatures between 250 and 1000 °C and pressures between 2 and 8 GPa in a multi-anvil press, in order to investigate phase equilibria involving the γ′ phase. Samples heat-treated at high-pressure conditions, were quenched, subsequently decompressed, and then analysed ex situ. Microstructure analysis is used to derive implications on the phase transformations during the heat treatments. Further, it is confirmed that the Fe–N phases in the target composition range are quenchable. Thus, phase proportions and chemical composition of the phases, determined from ex situ X-ray diffraction data, allowed conclusions about the phase equilibria at high-pressure conditions. Further, evidence for the low-temperature eutectoid decomposition γ′→α+ε′ is presented for the first time. From the observed equilibria, a P–T projection of the univariant equilibria in the Fe-rich portion of the Fe–N system is derived, which features a quadruple point at 5 GPa and 375 °C, above which γ′-Fe4N is thermodynamically unstable. The experimental work is supplemented by ab initio calculations in order to discuss the relative phase stability and energy landscape in the Fe–N system, from the ground state to conditions accessible in the multi-anvil experiments. It is concluded that γ′-Fe4N, which is unstable with respect to other phases at 0 K (at any pressure), has to be entropically stabilised in order to occur as stable phase system. In view of the frequently reported metastable retention of the γ′ phase during room temperature compression experiments, energetic and kinetic aspects of the polymorphic transition γ′⇌ε′ are discussed.

The Effect of Fluoride and Iron Content on the Clinkering of Alite-Ye’elimite-Ferrite (AYF) Cement Systems

Alite–ye’elimite–ferrite (AYF) cement is a more sustainable alternative to Portland cement (PC) that may offer improved mechanical, rheological, and chemical performance. Using traditional raw materials and conventional clinker processing conditions, alite (C3S) and ye’elimite (C4A3$), the major phases in PC and calcium sulfoaluminate (CSA) cements, respectively, cannot be coproduced. The typical formation temperature in the kiln for alite is >1350°C, but ye’elimite normally breaks down above 1300°C. However, with careful composition control and in the presence of fluoride, alite can be mineralized and formed at lower temperatures, thus enabling the production of AYF clinkers in a single stage. In this study, the production of AYF cement clinkers with different chemical compositions is attempted at 1250°C. The sensitivity of the fluoride content is initially assessed with a fixed target clinker composition to determine the optimal requirements. The effect of altering the target ferrite (C4AF) and alite (C3S) contents is also assessed followed by the effect of altering the target C4AF and C4A3$ contents. It is shown that AYF clinkers can be produced in a single stage through the careful control of the fluoride content in the mix; however, the formation/persistence of belite and mayenite could not be avoided under the conditions tested. It is also shown that ∼10 wt% ferrite in the target composition provides sufficient AYF clinker burnability and the amount of fluoride needs to be controlled to avoid stabilization of mayenite.

Properties of Metallic and Oxide Thin Films Based on Ti and Co Prepared by Magnetron Sputtering from Sintered Targets with Different Co-Content

In this work, selected properties of metallic and oxide thin films based on titanium and cobalt were described. Thin-film coatings were prepared using the magnetron sputtering method. The deposition was carried out from sintered targets with different Co-content (2 at.%, 12 at.% and 50 at.%). The relation between the Ti–Co target composition and the Co-content in the metallic and oxide films was examined. There was 15–20% more cobalt in the films than in the target. Moreover, the deposition rate under neutral conditions (in Ar plasma) was even 10-times higher compared to oxidizing Ar:O2 (70:30) plasma. A comprehensive analysis of the structural properties (performed with GIXRD and SEM) revealed the amorphous nature of (Ti,Co)Ox coatings, regardless of the cobalt content in the coating. The fine-grained, homogenous microstructure was observed, where cracks and voids were identified only for films with high Co-content. Optical studies have shown that these films were well transparent (60% ÷ 80%), and the amount of cobalt in the target from which they were sputtered had a significant impact on the decrease in the transparency level, the slight shift of the absorption edge position (from 279 nm to 289 nm) as well as the decrease in their optical band gap energy (from 3.13 eV to 1.71 eV). Electrical studies have shown that in (Ti,Co)Ox thin films, a unipolar memristive-like effect can be observed. The occurrence of such effects has not been reported so far in the case of TiO2 coatings with the addition of Co.

Microstructure Evolution in a Fast and Ultrafast Sintered Non-Equiatomic Al/Cu HEA

One of the attractive characteristics of high entropy alloys (HEAs) is the ability to tailor their composition to obtain specific microstructures and properties by adjusting the stoichiometry to obtain a body-centered cubic (BCC) or face-centered cubic (FCC) structure. Thus, in this work, the target composition of an alloy of the FeCrCoNi family has been modified by adjusting the Al/Cu ratio in order to obtain a BCC crystalline structure. However, processing conditions always play a key role in the final microstructure and, therefore, in this work, the microstructure evolution of FeCrCoNiAl1.8Cu0.5 HEA sintered by different powder metallurgy (PM) techniques has been investigated. The techniques used range from the conventional PM sintering route, that uses high heating rates and sintering times, going through a fast sintering technique such as spark plasma sintering (SPS) to the novel and promising ultrafast sintering technique electrical resistance sintering (ERS). Results show that the increase in the processing time favours the separation of phases and the segregation of elements, which is reflected in a substantial change in the hardness of the alloy. In conclusion, the ERS technique is presented as a very promising consolidation technique for HEA.

Hot laser fusion or low temperature nuclear reactions? Analysis and current prospects of the first experiments on laser fusion

The paper considers the features and quantitative characteristics of the first successful laser experiments on the formation of a thermonuclear plasma and registration of neutrons in nuclear fusion reactions under pulsed irradiation of a LiD crystal. Quantitative analysis shows that the production of neutrons recorded in these experiments is not associated with thermonuclear reactions in hot laser plasma. The most probable mechanism of neutron generation is associated with nuclear reactions at low energies and is due to the formation of coherent correlated states (CCS) of deuterons. In this experiment, such states can be formed in two different processes: due to the effect of a shock wave in the undisturbed part of the target lattice on the vibrational state of deuterium nuclei or when deuterium nuclei with energy of about 500 eV move in the lattice. This part of the deuterium nuclei corresponds to the high-energy "tail" of the Maxwellian distribution of the total flux of particles entering from the laser plasma into the interplanar channel. In this second case, the process of the formation of the CCS is associated with the longitudinal periodicity of the interplanar crystal channel, which is equivalent to a nonstationary oscillator in the own coordinate system of moving particle. The expediency of repeating these experiments is shown, in which, in addition to neutrons, one should expect a more efficient generation of other nuclear fusion products due to low-energy reactions involving lithium isotopes from the target composition.

“No weight for height” case detection strategies for therapeutic feeding programs: sensitivity to acute malnutrition and target composition based on representative surveys in humanitarian settings

Background One newly proposed approach to determining eligibility of children aged 6–59 months for therapeutic feeding programs (TFPs) is to use mid-upper arm circumference (MUAC) < 115 mm, bilateral oedema or Weight-for-Age Z-score (WAZ) < − 3 as admission criteria (MUAC+SWAZ). We explored potential consequences of this approach on the eligibility for treatment, as compared with the existing WHO normative guidance. We also compared sensitivity and specificity parameters of this approach for detecting wasted children to the previously described “Expanded MUAC” approach. Methods We analyzed data from 558 population representative cross-sectional cluster surveys conducted since 2007. We retrieved all children classified as severe acute malnutrition (SAM), moderate acute malnutrition (MAM), and those who are both wasted and stunted (WA + ST), and calculated proportions of previously eligible children who would now be excluded from treatment, as well as proportions of non-malnourished children among those who would become eligible. We also analyzed the expected changes in the number and demographics (sex, age) of the selected populations of children according to the different admission approaches. Results Both MUAC+SWAZ and Expanded MUAC case detection approaches substantially increase the sensitivity in detecting SAM, as compared to an approach which restricts detection of SAM cases to MUAC< 115 mm and oedema. Improved sensitivity however is attained at the expense of specificity and would require a very large increase of the size of TFPs, while still missing a non-negligible proportion (20–25%) of the SAM caseload. While our results confirm the sensitivity of the MUAC+SWAZ case detection approach in detecting WA + ST (over 80%), they show, on the other hand, that about half of the additional target detected by using SWAZ criterion will be neither SAM nor WA + ST. Conclusions These results suggest that recently promoted approaches to case detection inflate TFPs’ targets through the allocation of treatment to large numbers of children who have not been shown to require this type of support, including a significant proportion of non-acutely malnourished children in the MUAC+SWAZ approach. Considering the scarcity of resources for the implementation of TFPs, the rationale of abandoning the use of WHZ and of these alternative case detection strategies need to be critically reviewed.