Unraveling the Crystallization Kinetics of 2D Perovskites with Sandwich-Type Structure for High-Performance Photovoltaics

2D perovskite solar cells with high stability and high efficiency have attracted significant attention. A systematical static and dynamic structure investigation is carried out to show the details of 2D morphology evolution. A dual additive approach is used, where the synergy between an alkali metal cation and a polar solvent leads to high-quality 2D perovskite films with sandwich-type structures and vertical phase segregation. Such novel structure can induce high-quality 2D slab growth and reduce internal and surface defects, resulting in a high device efficiency of 16.48% with enhanced continuous illumination stability and improved moisture (55–60%) and thermal (85 °C) tolerances. Transient absorption spectra reveal the carrier migration from low n to high n species with different kinetics. An [PbI₆]⁴⁻ octagon coalescence transformation mechanism coupled with metal and organic cations wrapped is proposed. By solvent vapor annealing, a recrystallization and reorientation of the 2D perovskite slabs occurs to form an ideal structure with improved device performance and stability.     

Catalytic pyrolysis and kinetic study of real-world waste plastics: multi-layered and mixed resin types of plastics

Clean Technologies and Environmental Policy - Multi-layered and mixed resin types of plastics are a great challenge for the waste recycling industry. The majority consist of two or more types of...     

Crystallization behavior of calcium phosphate glass powder

The crystallization behavior of calcium phosphate glass powder with the molar ratio [CaO]/[P₂O₅] = 0.88, to which 6.38 mol% TiO₂ and 10 mol% Al₂O₃ were added as nucleation agents, was investigated. The results indicate complex crystallization behavior which depends on the powder particle size and the crystallization temperature. In the crystallization temperature range T _c < 900°C the surface mechanism of crystallization dominates in the case of all particle sizes ranging from 0–1 mm and the -Ca₂P₂O₇ phase is formed. At very long annealing times volume crystallization occurs and the TiP₂O₇ and AlPO₄ phases are formed. In the temperature interval T _c > 900°C the dominant crystallization mechanism depends on the particle size. In the size range 0.15–0.5 mm the surface mechanism of crystallization is replaced by the volume one. In the range >0.5 mm the volume mechanism of crystallization is dominant. The phases -Ca₂P₂O₇, TiP₂O₇ and AlPO₄ are formed in that temperature interval for all particle sizes. The additives TiO₂ and Al₂O₃ influence the nucleation and formation of TiP₂O₇ and AlPO₄ but do not influence the formation of -Ca₂P₂O₇.     

The indentation size effect of sintered Fe/3.3 wt-%Cu + CnHm measured by Vickers scale

ABSTRACT

The aim of the submitted work is to study the influence of applied loads (test forces) between 0.09807 and 2.9421?N on the measured value of micro-hardness of sintered Fe/3.3?wt-%Cu?+?C_nH_m. The Indentation Size Effect (ISE), i.e. the influence of the load on the micro-hardness is expected. The results were evaluated by Meyer’s index n, t-test, and non-parametric tests. The applied load has a statistically significant influence on the type and size of the ISE. Tested sintered material shows ‘normal’ ISE with Meyer’s index n?=?1.7588.     

The stress stability of olanzapine: studies of interactions with excipients in solid state pharmaceutical formulations

Stress stability testing represents an important part of the drug development process. It is used as an important tool for the identification of degradation products and degradation pathways, as well as for the assessment of changes in physical form of drug molecules. The impact of excipients on the stability of olanzapine confirms that levels of impurities and degradants are limiting parameters and are therefore used for stability evaluation. The major degradation product of olanzapine was identified as 2-methyl-5,10-dihydro-4H-thieno[2,3-b][1,5]benzodiazepine-4-one (III). The structure of III was determined by using LC-MS, IR and NMR. Compatibility and stress stability results demonstrated that tablet formulations of olanzapine are sensitive to temperature and moisture. In samples protected from moisture, the increase in concentration of III was shown to be highly temperature dependent and the degradation followed zero-order kinetics. In addition, studies of olanzapine with excipients and in formulated tablets revealed polymorphic phase changes in some samples, influenced by a combination of stress temperature and humidity conditions. Polymorphic transitions were monitored using x-ray powder diffraction (XRPD) analysis and exhibited no correlation between the phase change (appearance of a new polymorph) and the degradation process.     

Influence of thermomechanical treatment on the hardening mechanisms and structural changes of a cast Cu–6.6 wt.%Ag alloy

Investigations were carried out on the cast samples of Cu–6.6 wt.%Ag alloy, as well as pure copper samples, for the sake of comparison. Cast samples of copper and alloy were subjected to the same thermomechanical treatment. The thermomechanical treatment included the homogenized annealing, prefinal cold rolling, solution annealing, final cold rolling with a final reduction of 20%, 40% and 60% as well as the isochronal and isothermal annealing up to the recrystallization temperature. Influence of thermomechanical treatment on the hardening mechanisms and structural changes of cast Cu–6.6 wt.%Ag alloy has been investigated for the hardness and electrical conductivity measurements as well as optical microscopy. The study has shown that the anneal hardening effect appeared on the cast Cu–6.6 wt.%Ag alloy in the temperature range of 160–400 °C and was followed by an increase in the hardness and electrical conductivity.     

Experimental investigation and thermodynamic prediction of the Bi–Sb–Zn phase diagram

Phase diagram of the ternary Bi–Sb–Zn system was investigated experimentally by DTA and SEM-EDS methods and analytically by CALPHAD method. The liquidus projection, invariant equilibria, several vertical sections and isothermal section at 300 °C were predicted using COST 531 thermodynamic database. Phase transition temperatures of alloys along three predicted vertical sections of the Bi–Sb–Zn ternary system with molar ratio Bi:Sb = 1, Bi:Zn = 1 and Sb:Zn = 1, were measured by differential thermal analysis (DTA). Predicted isothermal section at 300 °C was compared with the results of the scanning electron microscope (SEM) with energy dispersive spectrometry (EDS) analysis from this work.     

Determination of corrosion rate of orthodontic wires based on nickel‐titanium alloy in artificial saliva

The goal of this study was to determine corrosion behavior of three orthodontic wires based on nickel‐titanium alloy (NiTi) in artificial saliva at temperature of 37 °C as function of immersion time. Following orthodontic wires were used: uncoated (NiTi), rhodium coated (Rh NiTi) and nitrified (N NiTi) orthodontic wires. Corrosion of investigated orthodontic wires were monitored by measuring of Ni²⁺ and Ti⁴⁺ ions released in artificial saliva by inductively coupled plasma‐optical emission spectroscopy (ICP‐OES) after 3, 7, 14, 21 and 28 days of immersion. Obtained results indicate that corrosion reaction of the NiTi wires in artificial saliva follows the parabolic rate law. According to the obtained values of parabolic corrosion rate constants, corrosion susceptibility of orthodontic wires decreases in the following order: Rh NiTi wire (K_p = 2.48 μg²/cm⁴ h) > NiTi wire (K_p = 1.6 × 10^–3 μg²/cm⁴ h) > N NiTi wire (K_p = 6.0 × 10^–4 μg²/cm⁴ h). These results indicate that in comparison with uncoated NiTi wire, rhodium coating significantly increases corrosion susceptibility, while nitrification effectively suppresses the release of Ni²⁺ and Ti⁴⁺ ions.     

Model for thermodynamic point identification in laser cutting

In recent years, laser cutting has been introduced and developed to such an extent that it is now thought to be one of the leading and indispensable manufacturing tools. At the present time, dross‐free and accurately‐cut parts are basically regarded as the major targets to aim for, because the costs and efforts associated with dross removal by postprocessing cut parts are considerable. Therefore, control of dross formation during laser cutting is an important factor in maintaining edge quality. The initial aim of this paper is to describe the importance of physico‐mechanical material properties that need to be taken into account in modeling of laser material processing in order to control melting of the material.     

An improved EAS brick element for finite deformation

A new enhanced assumed strain brick element for finite deformations in finite elasticity and plasticity is presented. The element is based on an expansion of shape function derivatives using Taylor series and an extended set of orthogonality conditions that have to be satisfied for an hourglassing free EAS formulation. Such approach has not been applied so far in the context of large deformation three-dimensional problems. It leads to a surprisingly well-behaved locking and hourglassing free element formulation. Major advantage of the new element is its shear locking free performance in the limit of very thin elements, thus it is applicable to shell type problems. Crucial for the derivation of the residual and consistent tangent matrix of the element is the automation of the implementation by automatic code generation.