Search results for "Ceramic"
showing 10 items of 2129 documents
Helical supramolecular polymerization of C3-symmetric amides and retroamides: on the origin of cooperativity and handedness.
2016
The cooperative supramolecular polymerization of 1 and 2 yields P- or M-type helical aggregates depending on the absolute configuration (S or R) of the stereogenic centres attached to the side chains. The connectivity of the amide group does not affect the handedness of the helical aggregates, but determines a larger cooperativity for retroamides 1.
The production of traditional building materials in Oristano (Sardinia, Italy)
2016
The study of ceramic-making communities which employ traditional practices can provide insights into the raw materials and techniques used over the centuries in a particular territory. The archaeometric study of ceramic products and of the raw materials used in their production is an effective complement to the existing ethnographic information. This paper focuses on the brick and tile making tradition of Oristano, a town in Central-Western Sardinia (Italy). Applying a combination of techniques, it includes an extensive analysis of traditional handmade and early industrial bricks and tiles, and a study of the local clays that may have been used as raw materials. Although we were unable to s…
Ceramic raw materials: how to recognize them and locate the supply basins—mineralogy, petrography
2020
This tutorial paper is focused on the mineralogical-petrographic characterization of clayey raw materials with the purpose of sourcing supply basins and answering questions about the provenance of the corresponding archaeological ceramic artefacts. The first part gives general indications of how to profitably study archaeological ceramic thin sections through the polarizing microscope. Brief notes are provided on the theoretical basis of optical microscopy. A scheme is then provided for the petrographic description of ceramic samples, concerning the textural and compositional characteristics of aplastic inclusions and groundmass. Suggestions are also given for identifying any minero-petrogr…
Interaction of Oily Water with Floating Porous Ceramic and Immobilized Microorganisms
2018
Oily water was treated with porous ceramic granules and immobilized microorganisms. Floating granules with bulk density of 0.63-0.66 g cm-3were used. The sorption of motor oil was investigated for dry and wetted granules. Respiration experiments showed that microorganisms immobilized on floating ceramic carrier and treated with oily water were influenced by agitation of liquid. The treatment of oily water with low salinity (1-9 g L-1) showed that oil removal efficiency decreased after increasing water salinity. Likewise, oil removal efficiency decreased from 12 to 9% per gram of ceramic carrier after increasing the spill of oil from 9 to 35 g per square meter. Porous granules with immobiliz…
Failure maps to assess bearing performances of glass composite laminates
2018
Aim of this article is the assessment of the bearing mechanical performances of pin-loaded glass laminates as function of their geometrical configuration. To this concern, 32 specimens having different hole diameter (D), laminate width (W), and hole center to laminate free edge distance (E) have been tested under bearing conditions. The maximum bearing stress and the stress-displacement curves were analyzed as function both of hole to laminate free edge distance E and hole diameter D. Moreover, an experimental 2D failure map was created by placing the experimental results (i.e., the kind of failure mechanism occurred for each geometrical configuration) in the plane E/D versus W/D ratios. In…
Weld quality prediction in linear friction welding of AA6082-T6 through an integrated numerical tool
2016
Abstract A numerical and an experimental campaign were carried out with varying oscillation frequency and interface pressure. The local values of the main field variables at the contact interface between the specimens were predicted by a Lagrangian, implicit, thermo-mechanical FEM model and used as input of a dedicated Neural Network (NN). The NN, integrated in the FEM environment, was designed in order to calculate both a Boolean output, indicating the occurrence of welding, and a continuous output, indicating the quality of the obtained solid state weld. The analysis of the obtained results allowed three different levels of bonding quality, i.e., no weld, sound weld and excess of heat, to…
Influence of friction stir processing conditions on the manufacturing of Al-Mg-Zn-Cu alloy/boron carbide surface composite
2018
Abstract Surface metal matrix composites were synthesized via friction stir processing (FSP) on the surface of aluminium alloy 7075 (AA 7075) sheets by incorporating B4C particles (B4CP). The influence of tool rotational speeds, powder particle sizes, and change in tool travel direction between FSP passes on particle distribution and resulting properties were studied in detail. Change in tool travel direction, decreased tool rotation speed and fine B4C particles enhanced B4CP distribution and wear properties thereof. Wear resistance of composites were doubled on account of the B4CP distribution and resultant several strengthening mechanisms.
The application of the random balance method in laser machining of metals
2008
International audience; Features peculiar to laser technology offer some advantages over more traditional processes, but, like all processes, it has its limitations. This article studies the limitations of laser machining of metals, and quantifies, through an experimental design method, the influence of operating parameters on productivity and on the quality of the machined surface. Three study materials were used: an aluminium alloy, stainless steel and a titanium alloy. An initial reading of the results indicates that productivity depends mainly on the frequency of the laser pulse and that the aluminium alloy behaves differently from the other two. The quality of the machined surface, jud…
A numerical model for Wire integrity prediction in Friction Stir Extrusion of magnesium alloys
2017
Abstract A numerical model for the prediction of the wire quality produced by the novel direct machining chip recycling technique known as Friction Stir Extrusion (FSE) is presented. Wire microstructure and wire integrity have been predicted by embedding in the code the equations enabling the calculation of the Zener-Hollomon parameter as well as the W parameter of the Pivnik-Plata solid bonding criterion. The proposed model, developed for the AZ31 magnesium alloy using the commercial simulation package DEFORM, is 3D Lagrangian, thermo-mechanically coupled with visco-plastic material behavior. The model was first validated against experimental temperature measurements and then used to predi…
Contactless generation of cavitation in high temperature liquid metals and its impact on particle dispersion in solidified iron and steel samples
2021
Abstract A recently developed method for the contactless magnetic generation of cavitation is demonstrated for high-melting-point metals. The approach is based on the floating-zone technique, which is truly contactless and crucible-free as it uses electromagnetic forces. Using this method, ultra-high-temperature ceramic particles, such as TiN, TiB2 and TiC, are admixed in liquid iron and 316L steel. The dispersion and particle refinement caused by cavitation treatment during melting and solidification are investigated. Magnetic fields up to 8 T that correspond to pressure oscillation amplitude of 0.83 MPa are used. The signal emitted by the collapsing bubbles is captured and visualized for …