Search results for "visual_art"
showing 10 items of 2987 documents
Data on phase and chemical compositions of black sands from “El Ostional” beach situated in Mompiche, Ecuador
2020
Abstract Data revealing the phase and chemical compositions of natural black sands from “El Ostional” beach, located in the northern Ecuadorian Pacific coast have been presented. The samples were collected from six points over the shore area of approximately 500 × 40 m2. The data on crystalline phases (iron titanium oxide, orthoclase feldspar and zircon) were determined by X-ray powder diffraction (XRPD), while semi-quantitative chemical analyses of major (Fe and Ti) and trace elements were obtained by X-ray fluorescence spectroscopy (XRF). The phase composition was verified by scanning electron microscopy (SEM), using backscattered electron (BSE) mode and energy dispersive spectroscopy (ED…
Electrochemical behaviour and electrical percolation in graphite-epoxy electrodes
1994
The electrochemical properties of mouldable graphite-epoxy composite electrodes have been studied as a function of graphite content. The shape of ferri-ferrocyanide voltammograms relates to the ratio of graphite and an adsorption process. The dielectric constant from spectroelectrochemical impedance measurement of this composite electrode is maximum when the proportion of graphite is ca. 60 wt%. An electrochemical equivalent circuit is proposed. The graphite-epoxy composite acts as a multi-microelectrode near this proportion.
Composition-related structural, thermal and mechanical properties of Ba1−xSrxTiO3ceramics (0 ≤x≤ 0.4)
2015
The Ba1−xSrxTiO3 (BST) ceramics were prepared by conventional ceramic method. The crystalline structure and morphology were studied by X-ray diffraction and scanning electron microscopy, respectively. Experimental results show that increase of sintering temperature leads to an uncontrolled precipitating of the phase with a lower content of Ti. The dielectric constant and specific heat as a function of composition and temperature were investigated. The increasing concentration of Sr ions leads to a shift of the Curie point below room temperature. To determine the elastic constants (the Young's modulus E, the shear modulus G and the Poisson's ratio v) of BST, a method of measurement of the lo…
Determining efficacy of monitoring devices on ceramic bond to resin composite
2012
Objectives: This paper aims to assess the effectiveness of 3D nanoroughness and 2D microroughness evaluations, by their correlation with contact angle measurements and shear bond strength test, in order to evaluate the effect of two different acids conditioning on the bonding efficacy of a leucite-based glass-ceramic to a composite resin. Study Design: Ceramic (IPS Empress) blocks were treated as follows: 1) no treatment, 2) 37% phosphoric acid (H3PO4), 15 s, 3) 9% hydrofluoric acid (HF), 5 min. Micro- and nano-roughness were assessed with a profilometer and by means of an atomic force microscopy (AFM). Water contact angle (CA) measurements were determined to assess wettability of the ceram…
Thermosetting composites based on bronze particles for archaeological and artistic metal heritage cloning
2018
peer-reviewed Artificial Metals are polymeric semi-metallic composites obtained by combining thermosetting resins with atomized metal powders in order to achieve composite materials capable of reproducing metals, even in a rusty or corroded condition. These composites provide a solution for the reproduction of archaeological artefacts, sculptures, and ornaments for the purpose of conservation. This work explores mechanical properties of three different resins bronze composites loaded with two different proportions of metal filler. The degree of conversion of the samples was measured by differential scanning calorimetry (DSC) and flexural tests were carried out to determine their mechanical …
Metal nanodumbbells for nanomanipulations and tribological experiments
2015
Nanomanipulation experiments were carried out on nanodumbbells (NDs) to study their kinetic behavior and tribological properties. Ag, Au and Cu NDs were produced by laser-induced melting of corresponding nanowires (NWs). NDs were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Manipulation experiments were performed first with atomic force microscope (AFM) at ambient conditions, and then inside SEM at high vacuum conditions. Different regimes of motion were observed. In-plane and out-of-substrate-plane rotation were identified as the most preferred motion types of NDs.
Influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic systems
2017
BACKGROUND To evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces. MATERIAL AND METHODS All-ceramic systems tested were lithium disilicate and zirconia veneered by layering technique. Sixty specimens (n=20) were subjected to shear bond strength. Ten of them were thermal and mechanical cycled. Fracture analysis was performed with stereomicroscopy and scanning electron microscopy. Energy dispersive X-ray spectroscopy analysis was performed across core/veneer interfaces. RESULTS Thermal and mechanical cycling did not influence on bond strength. However, there was significant difference among syste…
Enamel evaluation by scanning electron microscopy after debonding brackets and removal of adhesive remnants
2017
Made available in DSpace on 2022-04-29T08:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Background: The bonding of accessories in the dental crown during the orthodontic treatment creates microporosities, thus promoting micromechanical retention of the adhesive to the enamel structure. After debonding brackets, at the end of the active orthodontic treatment, a certain amount of adhesive remnants must be mechanically removed from the enamel. The objective of this study was to compare, by means of scanning electron microscopy, three different methods to remove the adhesive remnants after orthodontic bracket removal. Material and Methods: An experimental analytical study w…
Metal doping effects in NIR Raman spectra of YBCO epitaxial films
1996
Metal doping (Co, Zn) of YBCO epitaxial thin films leads to large changes of the scattering efficiencies of various lattice modes in near-infrared (NIR) -Raman spectra (1064 nm) if it is accompanied by a variation of the charge carrier concentration. The results resemble earlier observations in oxygen depleted YBCO thin films. In contrast, no effect is found when metal doping does not change the carrier concentration even if it leads to a massive Tc suppression.
Nanomechanical Properties of Epoxy Composites with Carbon Fillers
2013
The key point of this study is investigation of nanomechanical properties of epoxy-based nanocomposites filled with different kinds of carbon nanofillers like exfoliated graphite, high surface-area carbon black, single-walled carbon nanotubes and multi-walled carbon nanotubes