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The acetone-methanol extractive distillation using water as an entrainer was simulated on Aspen Plus software package using rigorous methods. Calculation of the vapor-liquid equilibrium for the ternary system was done by the UNIQUAC model according to the experimental results obtained in a previous work. The effects of the solvent to feed molar ratio, reflux ratio, feed stage, feed solvent stage, and solvent feed temperature were studied to obtain the best design of the extractive distillation column with minimal energy requirements. The most appropriate configuration is 52 theoretical stages. The best binary mixture and entrainer feeding stages were obtained at 48 and 22 respectively with a solvent to feed molar and reflux ratio of 2.0 and 5.0, respectively. The simulation results show the effect of the main variables on the extractive distillation process.

Due to its impressive properties such as a high absorption coefficient, long diffusion length and low exciton dissociation energy, [2] the perovskite has been exploited in several applications, among them light amplifiers and lasers, [3-,5] light emitting diodes (LEDs), [6-8] and photovoltaic devices. [9,10] The halide perovskite structure, ABX 3 [11] allows multiple atom combinations, making it very versatile. In addition, it can be synthesized at a low temperature permitting a relatively easy synthesis by a broad range of methods. The monovalent cation A (formamidinium [FA], [12] methylammonium [MA], [13] or cesium [14]) is located in the cage of BX 6 4− octahedra, where B is the metal (commonly, lead or tin) and X a halide or combination of them. The most studied hybrid-perovskite materials are MAPbI 3 and FAPbI 3. Both compounds result in a perovskite structure, despite the difference in the tolerance factor (0.95 and 1.03, respectively, and the same octahedral factor. [15,16] MAPbI 3 is intrinsically phase stable at ambient Formamidinium-based perovskite solar cells (PSCs) present the maximum theoretical efficiency of the lead perovskite family. However, formamidinium perovskite exhibits significant degradation in air. The surface chemistry of PbS has been used to improve the formamidinium black phase stability. Here, the use of PbS nanoplatelets with (100) preferential crystal orientation is reported, to potentiate the repercussion on the crystal growth of perovskite grains and to improve the stability of the material and consequently of the solar cells. As a result, a vertical growth of perovskite grains, a stable current density of 23 mA cm −2 , and a stable incident photon to current efficiency in the infrared region of the spectrum for 4 months is obtained, one of the best stability achievements for planar PSCs. Moreover, a better reproducibility than the control device, by optimizing the PbS concentration in the perovskite matrix, is achieved. These outcomes validate the synergistic use of PbS nanoplatelets to improve formamidinium long-term stability and performance reproducibility, and pave the way for using metastable perovskite active phases preserving their light harvesting capability.

Several atmospheres based on N 2 -H 2 gaseous mixtures, with occasional additions of CH 4 were used to study the sintering behaviour of Astaloy CrM at temperatures of 1100 and 1240uC. Theoretical thermodynamic calculations and sintering experiments, with and without admixed graphite additions, were carried out devoting particular attention to the oxide reduction reactions. The role of carbon in the reduction of oxides is discussed with reference to Boudouard's reaction, proposing the indirect carbothermal reduction as the controlling mechanism. The microstructural characterisation of the material included inspection of the powder particles as well as sintered specimens. It was established that the Astaloy CrM particles contain two distinct types of oxides. One associated with the particle surface and another, mainly constituted by Cr, forming a dispersion of internal oxides. These internal oxides were microstructurally characterised, both directly and by carbon extraction replicas. A selection of powder mixtures containing 0 and 0 . 4%C additions were used for obtaining tensile specimens in order to assess neck development, by the strength and elongation obtained under various atmospheres and temperature combinations.PM/1110

A composite based on polyaniline (PANI) and low density polyethylene (LDPE) with electrical conductivity was developed. Polyaniline was polymerized by chemical oxidation and doped with dodecyl-benzene-sulfonic acid (DBSA). PANI-LDPE composites were prepared via melt blending and the films were obtained by compression molding. The influence of three variables of the blending (temperature, [PANI], rotor speed) on conductivity, microstructure and mechanical properties of the composites was studied by means of statistical tools and a 2 3 experimental design. The results show that the PANI concentration is the most influential variable, which mainly affects the conductivity and the elongation at break of the composites. These changes are related to the microstructure of the composites. Statistically, the other variables don't show significant influence on conductivity and mechanical properties in the studied range. POLYM. COMPOS.

No abstract

In this work, SiO2 nanoparticles (NPs) were integrated into the mesoporous TiO2 layer of a perovskite solar cell to investigate their effect on cell performance. Different concentrations of SiO2/ethanol have been combined in TiO2/ethanol to prepare pastes for the fabrication of the mesoporous layer with which perovskite solar cells have been fabricated. Addition of SiO2 NPs of 50 and 100 nm sizes produces an enhancement of cell performance mainly because of an improvement of the photocurrent. This increment is in good agreement with the theoretical predictions based on light scattering induced by dielectric SiO2 NPs. The samples using modified scaffolds with NPs also present a significant lower current–potential hysteresis indicating that NP incorporation also affects the ion accumulation at the perovskite interface, providing an additional beneficial effect. The results stress the importance of the appropriated management of the optical properties on further optimization of perovskite solar cell technology.

This paper presents results on the chemical vapor deposition of aluminum on silicon carbide starting from triisobutylaluminum. The deposited films show important systematic trends in surface roughness and porosity. Considering literature information on the deposition of aluminum on silicon, pretreatments of the deposition surface with hydrofluoric acid and/or titanium tetrachloride have been tested. They lead to films with a smoother morphology and stronger adhesion with the substrate than in the case of an untreated surface. Different heteroelements are observed at the interface under these conditions. A short thermal activation of the nucleation process following these pretreatments does not unambiguously improve the characteristics of the aluminum films. The obtained results can be considered for the modification of surface characteristics of silicon carbide particles which are used in discontinuously reinforcement aluminum composite materials with the aim to improve their mechanical properties and corrosion resistance as well as their fabrication process.The fabrication and operating conditions of a composite material depend strongly on the physicochemical characteristics of the matrix and on the near-surface region of the reinforcement. When these two parts are joined, an interphase is often created, whose role is critical in the mechanical behavior of the material. Processing of high performance interphases is a complex task, and the ultimate verification of its accomplishment requires ͑i͒ the fabrication of the composite material leading to the identification of the phases formed, and ͑ii͒ the subsequent performing of appropriate mechanical tests to allow final validation of the selection made a priori for the prerequisite application. Optimization of a composite material often comes through a process of trial and error which may be long, expensive, and difficult to establish. It is thus important to minimize and simplify it whenever possible. This can be achieved in part by various experimental simulations of the interfacial zone, leading to the fabrication of diffusion couples, to the identification of interfacial phases, and to the characterization of their physicochemical and mechanical properties. Examples of these approaches, concerning the ͑silicon-carbon͒/titanium and the silicon/metal systems can be found in Ref. 1-4 and in Ref. 5-8, respectively. However, they are exclusively focused on the physicochemical characterization of the interphases involved.For many years we have used the chemical vapor deposition ͑CVD͒ technique for the investigation of interfaces which reproduce those existing in metal matrix composites ͑MMCs͒. We thus studied the ͑Si-C͒/Ti model system 9 and the ͑Si-C͒/͑Ti-22Al-23Nb͒ system of technological interest, 10 with particular emphasis on the composition and morphology of the microstructures obtained. In the present work we investigate, for the first time to our knowledge using CVD, the aluminum/silicon carbide ͑Al/SiC͒ couple. This system is involved in power electronics ap...