Search results for "Metallurgy"
showing 10 items of 1419 documents
Rheological Response of Polyethylene/Clay Nanocomposites to Annealing Treatment
2007
The rheological response of a polyethylene/clay nanocomposite to annealing treatment under air and nitrogen atmospheres was studied. The treatment influences the rheology of the nanocomposite significantly. In particular, the viscosity and the non-Newtonian behavior dramatically increase with annealing time, and a liquid-like/solid-like transition is observed. The annealed samples were characterized by ATR-FT-IR spectrometry and it was shown that a silicate-rich layer is formed on the surface of the nanocomposite. This result was confirmed by TEM images of bulk and surface of annealed samples. It was demonstrated that the formation of this coating is the main cause of the change of rheologi…
Twin coarsening in CdTe(111) films grown on GaAs(100)
2006
Abstract We present a scanning force microscopy study of twin coarsening in CdTe(1 1 1) films grown on GaAs(1 0 0). Two types of CdTe(1 1 1) twins grow epitaxially and with equal probability on the long-range wavy surface structure developed by previous in situ annealing of the GaAs(1 0 0) substrate. Due to this initial substrate wavy structure, the grain coarsening during film growth leads to a quasi-one-dimensional rippled pattern. We propose a coarsening mechanism between twins driven by the formation of stacking faults.
Mechanical and metallurgical effects of in process cooling during friction stir welding of AA7075-T6 butt joints
2010
This paper presents the results of a combined experimental and numerical investigation focused on the effects of an in process water cooling treatment aimed at improving the final quality of friction stir welded butt joints in terms of mechanical resistance and metallurgy of the processed material. Micro and macro observations, together with the evolution of an already developed finite element tool, have been used to analyze specimens obtained under different process conditions. Water cooling was found to enhance joint strength, reducing the material softening usually observed in the thermo-mechanically affected zone area, with no detrimental effect on nugget integrity.
Polycaprolactone-based scaffold for oil-selective sorption and improvement of bacteria activity for bioremediation of polluted water
2017
Abstract A novel floatable and biodegradable sponge for the selective absorption of oil from water and potentially useful as cell carrier for bioremediation treatments was prepared in polycaprolactone (PCL). The eco-friendly process for fabricating the PCL sponge does not involve either synthetic routes or organic solvents, thus minimizing environmental hazard. In particular, the 3D porous materials have been prepared by mixing in the melt the polymer matrix with two water-soluble porogen agents (NaCl and PEG) and thereafter leaching the obtained PCL/NaCl/PEG composites in water. The PCL sponges here proposed are capable to remove different types of oily pollutants (up to 500 wt%), and were…
Sintering of Fe2NiO4 with an internal binder: a way to obtain a very dense material
2003
Abstract The coupled synthesis and sintering of Fe2NiO4 can be carried out from the calcination under air at high temperatures (>1200 °C) of precompacted (under 12 MPa) pellets of different mixtures: NiO/α-Fe2O3; NiO/α-Fe2O3/Fe; NiO/α-Fe2O3/Ni. The densest material is obtained at 1200 °C only from the following mixture: NiO (40 mol%), α-Fe2O3 (50 mol%) and Ni (10 mol%). Because the metallic nickel is very ductile, it is used as an internal binder in order to enhance the precompacting of the samples. Moreover, the role of nickel is to enhance the sintering reaction. This route leads to a final material of relative density close to 98±2%.
SAXS/WAXS study of the annealing process in quenched samples of isotactic poly(propylene)
1999
The structural rearrangement in samples of quenched isotactic poly(propylene) (iPP) submitted to different annealing treatments has been studied using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) at the synchrotron radiation source of DESY, Hamburg. From a quantitative analysis of the WAXS profiles the values of the α-monoclinic, mesomorphic, and amorphous mass fractions coexisting in the material were determined. It is demonstrated that the SAXS patterns were characterized by two different long-period values that are attributed to α- and mesomorphic periodicity, respectively. The related α- and mesomorphic volume phase fractions, calculated from the analysis of the SAXS …
On the formation of lamellae during annealing of extended chain crystals of radiation-polymerized trioxane
1969
Abstract The structure changes of radiation-polymerized trioxane taking place during annealing have been studied by means of electron microscopy, X-ray small- and wide-angle scattering, and differential thermal analysis. The original fibrillar crystals, supposedly consisting of extended chains, change into lamellar crystals due to annealing at temperatures between 150° and 190°C. Lamella formation can be connected with the appearance of a long period of about 200A which is not observed in the unannealed sample. During annealing within the same temperature range the X-ray reflections due to the twin structure of the original polytrioxane disappear, whereas the orientation of the fraction wit…
Self-Healing Properties of Bioinspired Amorphous CaCO3/Polyphosphate-Supplemented Cement
2020
There is a strong interest in cement additives that are able to prevent or mitigate the adverse effects of cracks in concrete that cause corrosion of the reinforcement. Inorganic polyphosphate (polyP), a natural polymer that is synthesized by bacteria, even those on cement/concrete, can increase the resistance of concrete to progressive damage from micro-cracking. Here we use a novel bioinspired strategy based on polyP-stabilized amorphous calcium carbonate (ACC) to give this material self-healing properties. Portland cement was supplemented with ACC nanoparticles which were stabilized with 10% (w/w) Na&ndash
Low-temperature positron-lifetime studies of proton-irradiated silicon
1990
The positron-lifetime technique has been used to identify defects created in high-purity single-crystal silicon by irradiation with 12-MeV protons at 15 K, and the evolution of the defects has been studied by subsequent annealings between 20 and 650 K. Two clear annealing steps were seen in the samples, the first starting at 100 K and the other at 400 K. The first is suggested to be a result of the migration of free, negatively charged monovacancies, and the second is connected to the annealing of some vacancy-impurity complexes, probably negatively charged vacancy-oxygen pairs. The specific trapping rate of positrons to both of these negatively charged monovacancy-type defects has been fou…
Photoelectrochemical and XPS characterisation of oxide layers on 316L stainless steel grown in high-temperature water
2015
Passive films on AISI 316L stainless steel were grown by exposure in high temperature (300 °C and 150 bar) water. X-ray photoelectron spectroscopy was employed to study their composition as a function of immersion time. A photoelectrochemical investigation, supported by electrochemical and impedance measurements, allowed to get information on the solid-state properties of the investigated layers. The experimental results suggest the formation of a stratified layer with an outer iron-rich layer and an inner Cr-rich oxide layer, whose relative thickness and composition are dependent on the immersion time.