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showing 10 items of 2987 documents
Cobalt hexacyanoferrate–poly(methyl methacrylate) composite: Synthesis and characterization
2010
Abstract The preparation of cobalt hexacyanoferrate nanoparticles–poly(methyl methacrylate) (CoHCF–PMMA) composites are described together with their characterization and thermochromic properties. CoHCF nanoparticles – investigated by dynamic light scattering – were prepared by optimizing solvent composition and temperature to obtain nanoparticles with a reduced degree of aggregation. The nanoparticles were embedded in a PMMA matrix to obtain a transparent coloured composite which was studied by transmission electron microscopy. The nanoparticle chromic features, enhanced by their reduced sizes, were investigated by UV–vis and FT-IR spectroscopy.
Efficient, 23%, Solution-Processed Perovskite Tandem Cells
2019
In this issue of Joule, Palmstrom and coworkers present efficient solution-processed two-terminal solar cells employing two metal halide perovskite-based absorbers. The key to this achievement is 2-fold: the deposition of a thin yet robust transparent conductor in between the two sub-cells allows solution processing of the back-cell and enables efficient and local charge recombination. Furthermore, the insertion of large cations reduces halide segregation and enables a higher open-circuit voltage and stability for the high-band-gap sub-cell.
FORMATION OF FRACTAL MICRO- AND NANO-STRUCTURES IN CERAMIC TANTALUM PENTOXIDE UNDER CONCENTRATED FLUX OF LIGHT AND THEIR EFFECT ON THERMAL EXPANSION
2009
ABSTRACT Oxides of weak thermal expansion are the basis for stable ceramics and artefacts resistant to sharp cyclic variations of temperature. For technical applications is a wide interest in high-temperature materials of low or negative thermal expansion and, particularly, in studies of the micromechanisms in Ta2O5. Thermal expansion of ceramic pentoxides of tantalum is affected by conditions under which they are formed. After treatment by concentrated light flows anomalous segments of zero and even negative thermal expansion appear in ceramics of Ta2O5. The effect of treatment by concentrated light flux on formation of fractal nano-structures and thermal expansion of ceramic tantalum pent…
Super-Ionic State Studies in LNTN Solid Solutions by Raman Spectroscopy
2012
Raman studies of the thermal phase transformations and structural disordering preceding transition to the super-ionic state in the Li0.12Na0.88TaуNb1-уO3 solid solution ceramics are reported. Disordering of the structure brought up by the extremely mobile Li+ ions at heating is found to be homogeneous and to proceed gradually. Disorientation and considerable deformation of the BO6 oxygen octahedrons facilitate translational mobility of the Li+ ions. The static disordering of the Nb5+ and Ta5+ sub-lattice caused by tantalum decreases the temperature of the phase transformation and increases the probability of transition to the super-ionic state supposed to occur over a broad temperature rang…
Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network.
2015
Background The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. Material and Methods In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Le…
On the Elastic Behavior of a Cross-Ply Composite Pin-Joint with Clearance Fits
1999
The effect of pin/hole clearance fits on the elastic membranal behavior of a cross-ply fiber glass-reinforced epoxy laminate plate loaded in tension through a pin is examined by a finite element nonlinear contact analysis. No a priori assumption is made on the distribution of the contact pressure on the surface of the hole. Friction effects are not included. The numerical results correlate well with Hertzian theory of contact. It is demonstrated that clearance increases the peak compressive stress in the plate up to a factor of 3000% with respect to the perfect-fit case. Clearance also shifts the location of the peak tensile stress towards the pin/hole contact arc and decreases its magnitu…
Analysis of the effect of a stress raiser on the strength of a UD flax/epoxy composite in off-axis tension
2014
The effect of stress raisers in the form of a slit-like notch and an open circular hole on the tensile strength of a quasi-UD flax-fiber-reinforced composite is studied experimentally. A finite fracture mechanics approach is applied to determine the intralaminar fracture toughness of the composite and to predict the strength in the presence of stress concentration. Reasonably good agreement of the notch effect predicted using finite fracture mechanics with a coupled strength and toughness fracture criterion and test results is demonstrated.
Random short sisal fiber biocomposites: Optimal manufacturing process and reliable theoretical models
2018
Although several works have been published in literature on agave fibers and their biocomposites, accurate information about the choice of both the fibers and the manufacturing processes that allow the user to optimize the biocomposites properties in terms of strength and stiffness are not yet available; also, no theoretical models that can be used for an accurate evaluation of the mechanical properties of these biocomposites, are reported.To this aim, the present work intends to give a contribution by considering green epoxy biocomposites reinforced by both short and discontinuous sisal agave fibers arranged in proper MAT-type fabrics. In particular, an optimized manufacturing process that…
Physical and Chemical Principles of Obtaining Thermally Resistant Containers for Treatment of High Purity Niobium and Tantalum Compounds
2011
Mathematical modelling of the distribution of strain in layered quartz ceramics with protective coating of niobium (tantalum) pentoxide from two sides is reported. It is found that fragmentation of the basic layer (decreasing the area of the continuous boarder between layers) and smoothing of sharp edges of the base fragments should reduce the strains on the boundary between the substrate and coating and, correspondingly, enhance the thermal resistance of the samples. Treatment of the niobium pentoxide coating by concentrated light induces a network of fractal micro- and nano-size fractures that compensates the difference of thermal expansion between the layers.
Toward high performance renewable agave reinforced biocomposites: Optimization of fiber performance and fiber-matrix adhesion analysis
2017
Abstract The increasing sensitivity toward the environmental pollution and the recent laws on the environmental protection, have led to an increasing attention to the so called biocomposites, i.e. to ecofriendly or renewable composite materials, obtained from biopolymers reinforced by natural fibers. Although the contribution of various works reported in literature, focused on biocomposites reinforced by agave fibers, such materials are still exclusively used in the automotive industry for non-structural applications, and the implementation of high performance biocomposites for semi-structural and structural applications, is an expected, but not yet reached objective. Therefore, the present…