Search results for "visual_art"
showing 10 items of 2987 documents
Li2OSiO2Al2O3MeIIO Glass-Ceramic Systems for Tile Glaze Applications
1991
In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li2O─Al2O3─SiO2 glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, devel…
Microstructural Evolution in Fast-Heated Cordierite-Based Glass-Ceramic Glazes for Ceramic Tile
2004
The crystallization mechanism of α-cordierite from a B 2 O 3 -and TiO 2 -containing glass submitted to fast heating in the cordierite primary phase field of the CaO-MgO-Al 2 O 3 -SiO 2 quaternary system was investigated. Addition of B 2 O 3 to a SiO 2 -rich glass suppressed the formation of μ-cordierite. This suppression facilitated densification by viscous flow before crystallization. Powder X-ray diffractometry, field-emission electron scanning microscopy, and energy-dispersive X-ray analysis revealed that α-cordierite nucleated directly from glass on the boundaries of original particles and was probably favored by TiO 2 , which acted as a nucleant. The growth kinetics of α-cordierite cry…
Thermoelectric properties of p-type Bi2Sr2Co2O9 glass-ceramics
2014
In the oxide system of Bi–Sr–Co glass melts have been prepared by adding a small amount of glass formers. A crystallization leads to crystalline phases of Bi8Sr8Co4O25, BiSrCo2Ox and Bi2Sr2Co2O9 (BC-222) densely embedded into a residual glass phase. This work shows the possibility of obtaining microstructured bulk material with low thermal conductivity and relatively high electrical conductivity via such a glass ceramic approach. Furthermore the stability of these materials under thermal cycling for temperatures up to 700 °C is shown. A characterization of the thermoelectric properties leads to a figure of merit (ZT) between 0.008 and 0.018.
Precipitation synthesis of magnetite Fe3O4 nanoflakes
2014
Precipitation can be applied to synthesize magnetite Fe3O4 nanoflakes in an ambient air atmosphere without using any surfactant, templates or special equipment. Magnetite nanoflakes were precipitated from only Fe2+ chloride solution without adding Fe3+. The formation of Fe3O4 nanoflakes is suggested to occur due to formation of an intermediate goethite phase, thus providing anisotropic crystal growth. Compared to other methods, the method presented here is fast and suitable for large scale synthesis.
A reliable procedure for the preparation of graphene-boron nitride superlattices as large area (cm x cm) films on arbitrary substrates or powders (gr…
2019
[EN] Herein, a reliable procedure for the preparation of graphene-boron nitride superlattices, either as films or powders, consisting of the pyrolysis at 900 degrees C of polystyrene embedded pre-formed boron nitride single sheets is reported. The procedure can serve to prepare large area films (cm x cm) of this superlattice on quartz, copper foil and ceramics. Selected area electron diffraction patterns at every location on the films show the occurrence of the graphene-boron nitride superlattice all over the film. The procedure can also be applied to the preparation of powdered samples on a gram scale. Comparison with other materials indicates that the superlattice appears spontaneously as…
Experimental analysis and micromechanical models of high performance renewable agave reinforced biocomposites
2017
Abstract The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the m…
Evaluation of surface roughness of enamel after various bonding and clean-up procedures on enamel bonded with three different bonding agents : an in-…
2016
Background The purpose of this study was to analyze and compare the enamel surface roughness before bonding and after debonding, to find correlation between the adhesive remnant index and its effect on enamel surface roughness and to evaluate which clean-up method is most efficient to provide a smoother enamel surface. Material and methods 135 premolars were divided into 3 groups containing 45 premolars in each group. Group I was bonded by using moisture insensitive primer, Group II by using conventional orthodontic adhesive and Group III by using self-etching primer. Each group was divided into 3 sub-groups on the basis of type of clean-up method applied i,e scaling followed by polishing, …
Solid–Solid Interfaces in Protonic Ceramic Devices: A Critical Review
2020
The literature concerning protonic ceramic devices is critically reviewed focusing the reader's attention on the structure, composition, and phenomena taking place at solid-solid interfaces. These interfaces play a crucial role in the overall device performance, and the relevance of understanding the phenomena taking place at the interfaces for the further improvement of electrochemical protonic ceramic devices is therefore stressed. The grain boundaries and heterostructures in electrolytic membranes, the electrode-electrolyte contacts, and the interfaces within composite anode and cathode materials are all considered, with specific concern to advanced techniques of characterization and to …
A critical approach to the toxic metal ion removal by hazelnut and almond shells
2018
The adsorption capacity of ground hazelnut (HS) and almond (AS) shells towards Pb(II) and Cd(II) has been studied at pH = 5, in NaNO3 and NaCl ionic media, in the ionic strength range 0.05-0.5 mol L-1. Kinetic and equilibrium experiments were carried out by using the Differential Pulse Anodic Stripping Voltammetry technique to check the amount of the metal ion removed by HS and AS materials. Different kinetic and equilibrium equations were used to fit experimental data and a statistical study was done to establish the suitable model for the data fitting. A speciation study of the metal ions in solution was also done in order to evaluate the influence of the ionic medium on the adsorption pr…
The Intrinsic Defects, Disordering, and Structural Stability of BaxSr1–xCoyFe1–yO3−δ Perovskite Solid Solutions
2012
First principles density functional theory modeling of point defects and structural disordering in BaxSr1–xCoyFe1–yO3−δ (BSCF) perovskites reveals that the material tends to decompose at low temperatures into a mixture of cubic and hexagonal perovskite and/or oxide phases. Special attention is paid to elucidating the effects of oxygen nonstoichiometry on cubic and hexagonal phase stability, decomposition energies, and oxygen vacancy formation energies. The observed lattice instability is likely to negate the advantages of the fast oxygen transport chemistry and impede the applicability of BSCF in solid oxide fuel cells and oxygen separation ceramic membranes. The general methodology present…