Search results for "crystallinity"
showing 10 items of 248 documents
Properties-morphology relationships in electrospun mats based on polylactic acid and graphene nanoplatelets
2018
Abstract Aligned and randomly oriented polylactic acid (PLA) biocomposite nanofiber mats filled with Graphene nanoplatelets (GnP) were prepared by electrospinning. The morphological analysis revealed the successful alignment of the fibers achieved by collecting the mats on a high-speed rotary drum. Furthermore, GnP addition on the polymeric solution leads to an increase of the viscosity with a consequent increment of the fiber diameter. Tensile tests demonstrated that the reinforcing effect of GnP when added to the PLA matrix was more than three times higher in the aligned systems if compared with the respective randomly oriented mats. DSC analysis showed that GnPs were able to slightly inc…
Dual-source vacuum deposition of pure and mixed halide 2D perovskites: thin film characterization and processing guidelines
2020
The dual-source vacuum deposition of 2D perovskite films of the type PEA2PbX4, (PEA = phenethylammonium and X = I−, Br−, or a combination of both) is presented. Low-temperature deposited 2D perovskite films showed high crystallinity with the expected trend of bandgap as a function of halide type and concentration. Importantly, we observed an unavoidable halide cross-contamination among different deposition runs, as well as a strong dependence of the material quality on the type of halide precursors used. These findings should be taken into account in the development of vacuum processing for low-dimensional mixed halide perovskites.
Characterization and osteogenic activity of a silicatein/biosilica-coated chitosan-graft-polycaprolactone.
2014
Several attempts have been made in the past to fabricate hybrid materials that display the complementary properties of the polyester polycaprolactone (PCL) and the polysaccharide chitosan (CHS) for application in the field of bone regeneration and tissue engineering. However, such composites generally have no osteogenic activity per se. Here we report the synthesis of a chitosan-graft-polycaprolactone (CHS-g-PCL) and its subsequent characterization, including crystallinity, chemical structure and thermal stability. Upon surface-functionalization of CHS-g-PCL with osteogenic biosilica via the surface-immobilized enzyme silicatein, protein adsorption, surface morphology and wettability were a…
Boosting the Performance of One-Step Solution-Processed Perovskite Solar Cells Using a Natural Monoterpene Alcohol as a Green Solvent Additive
2021
The perovskite film is the core of a perovskite solar cell (PSC), and its quality is crucial for the performance of such devices. The morphology, crystallinity, and surface coverage of the perovskite layer greatly affect the power conversion efficiency (PCE), hysteresis, and long-term stability of PSCs. The incorporation of appropriate solvent additives in the perovskite precursor solution is an effective strategy to control the film morphology and reduce the defects and grain boundaries. However, the commonly used solvent additives are environmentally harmful and highly toxic. In this work, α-terpineol (a nontoxic, eco-friendly, and low-cost monoterpene alcohol) is employed for the first t…
Design of a reactor operating in supercritical water conditions using CFD simulations. Examples of synthesized nanomaterials
2011
International audience; Direct information about fluids under supercritical water conditions is unfeasible due to the engineering restrictions at high pressure and high temperature. Numerical investigations based on computational fluid dynamics (CFD) calculations are widely used in order to get extensive information on the fluid behavior, particularly to help the design of a new reactor. This paper presents the numerical investigations performed on an original supercritical water device, especially in the level of the reactor. CFD calculations allow to design and optimize the present reactor described in this study. Currently, this process produces some nanometric oxide powders in continuou…
Influence of mechanical activation on the physical stability of salbutamol sulphate.
2003
Abstract In order to obtain the optimal particle size distribution for pharmaceutical powders in dry powder inhalers the particles have to be micronised. In most cases the process of micronisation is connected with a high input of energy which induces disorder and defects on the surface of the drug particles and as a result changes in the crystallinity. Consequently, changes in the physical stability of the powders may occur. To investigate changes on the physical stability of the powder, different analytical methods are used in the present investigation: laser diffraction, Differential Scanning Calorimetry (DSC), isothermal microcalorimetry and DVS-method. Air-jet-milling is one of the mos…
Influence of calcination on the structural properties of earth abundant Cu2ZnSnS4
2021
Abstract In the present work, we report on the synthesis of nano-crystalline kesterite copper zinc tin sulfide (CZTS) in powder form and the post-annealing process at high temperatures (calcination), and study their physical properties. We have successfully synthesized CZTS by direct fusion, and the resulting material was crushed to obtain a fine powder. Then, the resulting powder was calcined at high temperatures: 800–1000 ∘C. The calcined samples have been characterized with a number of different structural: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and optical techniques: photoluminescence (PL), Raman and diffuse reflectance spectr…
Absolute crystallinity and photocatalytic activity of brookite TiO2 samples
2017
Abstract This study reports a method to determine the absolute crystallinity of partly crystalline brookite TiO2 photocatalysts. A natural, a commercial and various home-prepared brookite powders were characterized by X-ray diffraction analysis, Raman spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy and nitrogen adsorption measurements. The absolute crystallinity was calculated from the ratio between the full width at half maximum intensity of the (121) X-ray diffraction peaks of the brookite samples and the (111) peak of CaF2 as internal standard. The photocatalytic activity of the powders was tested employing the photodegradation of 4-nitrophenol as well…
Oxidation of nanocrystalline aluminum by variable charge molecular dynamics
2010
International audience; We investigate the oxidation of nanocrystalline aluminum surfaces using molecular dynamics (MD) simulations with the variable charge model that allows charge dynamically transfer among atoms. The interaction potential between atoms is described by the electrostatic plus (Es+) potential model, which is composed of an embedded atom method potential and an electrostatic term. The simulations were performed from 300 to 750K on polycrystalline samples with a mean grain size of 5 nanometers. We mainly focused on the effect of the temperature parameter on the oxidation kinetic. The results show that, beyond a first linear regime, the kinetics follow a direct logarithmic law…
Heterogeneous photocatalytic materials for sustainable formation of high-value chemicals in green solvents
2021
Abstract The most investigated materials used as heterogeneous photocatalysts for the formation of high-value chemicals under mild experimental conditions are presented in this survey. Only papers reporting reactions carried out in harmless solvents such as water, the green solvent par excellence, are reported. Metal oxides have been used often, but carbon-based materials such as carbon nitride and graphene, metal nanoparticles, sulphides and selenides also have received a great attention mainly due to their good performances both in partial oxidations and reductions. The results presented indicate that an appropriate choice of the photocatalytic material is the main problem to be faced to …