Search results for "COMPOSITE"
showing 10 items of 4584 documents
Sonication-Induced Modification of Carbon Nanotubes: Effect on the Rheological and Thermo-Oxidative Behaviour of Polymer-Based Nanocomposites.
2018
The aim of this work is the investigation of the effect of ultrasound treatment on the structural characteristics of carbon nanotubes (CNTs) and the consequent influence that the shortening induced by sonication exerts on the morphology, rheological behaviour and thermo-oxidative resistance of ultra-high molecular weight polyethylene (UHMWPE)-based nanocomposites. First, CNTs have been subjected to sonication for different time intervals and the performed spectroscopic and morphological analyses reveal that a dramatic decrease of the CNT's original length occurs with increased sonication time. The reduction of the initial length of CNTs strongly affects the nanocomposite rheological behavio…
Comparison of local electrochemical impedance measurements derived frombi-electrode and microcapillary techniques
2009
Abstract In the present paper, local electrochemical impedance spectra were obtained on a 316L stainless steel from two configurations: a dual microelectrode (bi-electrode) and microcapillaries. With the bi-electrode, the local impedance measurements were made from the ratio of the applied voltage to the local current density calculated from the application of the ohm's law. With the use of microelectrochemical cells, the specimen surface area in contact with the electrolyte is limited by the use of glass microcapillaries and the local impedance was defined from the ratio of the local potential to the local current restricted to the analysed surface area. Differences and similarities observ…
Structure and dielectric breakdown strength of nano calcium carbonate/polypropylene composites
2013
Nanodielectrics, a 21st-century phenomena, is envisioned to be the answer for material challenges in progressive high-voltage technology. It is well known that the proper dispersion of nanoparticles plays a key role in improving the dielectric properties of a material, but to understand where changes in the properties of a material originate, it is also essential to reveal the multiscale structure of the material. In this study, the dielectric permittivity, breakdown strength, and structure of nano calcium carbonate (nano-CaCO3)/polypropylene composites with 1.8-8.1 wt % doping were characterized systematically. The combined results from transmission electron microscopy, Raman microscopy, a…
BODIPY atropisomer interconversion, face discrimination, and superstructure appending
2016
International audience; A strategy was developed to append sterically hindered apical pickets on both faces of the BODIPY platform to prevent stacking and aggregation. Ortho-substitution of both the meso-phenyl ring and the boron-bound catechol affords the right directionality to append pickets, achieve face discrimination, featuring two inter-convertible atropisomers, and is reminiscent of the picket-fence strategy in porphyrins.
Spectroscopic characterization of alkaline earth uranyl carbonates
2005
A series of alkaline uranyl carbonates, M[UO{sub 2}(CO{sub 3}){sub 3}].nH{sub 2}O (M=Mg{sub 2}, Ca{sub 2}, Sr{sub 2}, Ba{sub 2}, Na{sub 2}Ca, and CaMg) was synthesized and characterized by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after nitric acid digestion, X-ray powder diffraction (XRD), and thermal analysis (TGA/DTA). The molecular structure of these compounds was characterized by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). Crystalline Ba{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].6H{sub 2}O was obtained for the first time. The EXAFS analysis showed that this compound consists of …
Photocatalytic activity in gas–solid regime of ZnO-ZnAl2O4 composites
2011
Multi-functional Stabilizers-functionalized Carbon Nanotubes for advanced Ultra-High Molecular Weight Polyethylene-based Nanocomposites
2015
Stabilizing molecules, such as hindered phenols (both synthetic and naturally occurring), polyphenols and hindered amine light stabilizers, were covalently linked or physically absorbed onto outer surface of multi-walled carbon nanotubes (CNTs) and the obtained multi-functional fillers (Stab-f-CNTs) were dispersed in Ultra High Molecular Weight Polyethylene (UHMWPE) aiming at obtaining advanced nanocomposites with enhanced thermo- and/or photo-oxidative stability, electrical and mechanical properties. The chemical grafting or physical absorption of stabilizing molecules is confirmed by spectroscopic, spectrometric and thermo-gravimetric analyses, and the influence of the multi-functional na…
“Indagine sperimentale per la caratterizzazione meccanica di elementi strutturali misti in legno-acciaio e legno-acciaio-calcestruzzo"
2009
The paper reports the results of the research activity aimed to define the physical-mechanics characteristics of structural elements made of wood-steel, and/or wood-steel-concrete, jointed by steel con¬nectors. The elements used for the tests are: glulam beams with two dif¬ferent dimensions (110x240x4000 mms and 110x140x4000 mms); steel flats 100x6x4000 mms with holes 20 mms arranged like "quinconce"; steel connectors like: flat with 6 mms thickness; 18; angular; polymeric synthetic binder with epoxy base bicomponent (Xepox 40.3/5). Shear tests have been made to define the capacity for deformation and the re¬sistance of the different steel connectors. Moreover, bending tests have been m…
Toxicity of Dental Amalgams vs Composite Resins
2016
Ideal qualities of dental materials should include, in terms of biocompatibility, passivity towards oral tissues, so the material should not contain any leachable toxic and diffusible substances, neither release any harmful substance that can cause in time side effects, locally or generally. Even if amalgams are a group of dental materials with a long recorded history, many practitioners blame them, in contradiction with composite resins, especially for releasing free mercury into the body. On the other side, composite resins have reached great biocompatibility specifications, but also have many qualities that need more research, especially long term type.
The effect of defect location on coating fragmentation patterns under biaxial tension
2005
Fragmentation of a coating possessing orthogonal preferential crack propagation directions is modeled for equibiaxial tensile loading. Two plausible cracking scenarios are compared, caused by flaws randomly distributed over the area of the coating or along the coating fragment edges. The two fragmentation scenarios considered are shown to yield qualitatively different fragment patterns.