Search results for "Annealing"
showing 10 items of 434 documents
Helium bubbles in alpha-irradiated aluminium: positron lifetime studies
1985
The formation of He-stabilised voids in aluminium single crystals injected with helium is monitored by positron lifetime measurements. The bubbles are observed to grow during annealing from 300 to 930K. The bubbles are extremely stable and survive annealing up to the melting point. Positron lifetime data are used to discuss the He density inside the bubbles and their growth mechanism.
A nondestructive analysis of the B diffusion in Ta–CoFeB–MgO–CoFeB–Ta magnetic tunnel junctions by hard x-ray photoemission
2010
This work reports on hard x-ray photoelectron spectroscopy (HAXPES) of CoFeB based tunnel junctions. Aim is to explain the role of the boron diffusion for the observed improvement of the tunneling magnetoresistance ratio with increasing annealing temperature. The high bulk sensitivity of HAXPES was used as a nondestructive technique to analyze CoFeB–MgO–CoFeB magnetic tunnel junctions. The investigated samples were processed at different annealing temperatures from 523 to 923 K. Hard x-ray core level spectroscopy reveals an enforced diffusion of boron from the CoFeB into the adjacent Ta layer with increasing annealing temperature. The dependence of the tunneling magnetoresistance on the ann…
The combined influence of grain size distribution and dislocation density on hardness of interstitial free steel
2020
Abstract Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties. The relationship between mean grain size and yield strength is established by the well-known Hall-Petch equation. But due to the complexity of the grain configuration within materials, considering only the mean value is unlikely to give a complete representation of the mechanical behavior. The classical Taylor equation is often used to account for the effect of dislocation density, but not thoroughly tested in combination with grain size influence. In the present study, systematic heat treatment routes and…
Optimization of spinning, drawing, and annealing conditions in the production of highly oriented fibers from the polycaprolactam/3.7% LiCl system
1982
A polycaprolactam/3.7% w/w LiCl system, obtained by anionic polymerization of caprolactam directly in the presence of salt, has been employed for the production of highly oriented fibers. More particularly, an optimization of spinning, drawing, and annealing conditions has been performed, finally obtaining fibers which shows very satisfactory mechanical results. Namely, average moduli values up to 12 GPa and strength values up to 1 GPa when fracture is far from clamps, have been observed.
Shear-aligned block copolymer monolayers as seeds to control the orientational order in cylinder-forming block copolymer thin films
2016
We study the dynamics of coarsening of a cylinder-forming block copolymer thin film deposited on a prepatterned substrate made of a well-ordered block copolymer monolayer. During thermal annealing the shear-aligned bottom layer drives extinction of the disclinations and promotes a strong orientational correlation, disturbed only by dislocations and undulations along the cylinders of the minority phase. The thin film bilayer system remains stable during annealing, in agreement with self-consistent field theory results that indicate that although the thickness of a stack of two monolayers is not at the optimum thickness condition, it is very close to equilibrium. Phase field simulations indic…
Highly Ordered Nanoporous Thin Films from Photocleavable Block Copolymers
2011
Poly(styrene-block-ethylene oxide) with an o-nitrobenzyl ester photocleavable junction (PS-hν-PEO) was synthesized by a combined RAFT polymerization and “click chemistry“ approach and represents the first report utilizing this method for the synthesis of photocleavable block copolymers. After solvent annealing, highly ordered thin films were prepared from PS-hν-PEO. Following a very mild UV exposure and successive washing with water, PS-hν-PEO thin films were transformed into highly ordered nanoporous thin PS films with pore diameters of 15–20 nm and long range ordering (over 2 μm × 2 μm). Afterwards the pores were filled with PDMS by spin-coating in combination with capillary forces. After…
Orientation and order in thin films of a combined liquid crystalline polymer
1994
The order in thin films of a combined liquid crystalline polymer is studied by X-ray reflection. Films of thicknesses of less than 200 nm on float glass are investigated as a function of temperature. The polymer with mesogenic groups in the main and side-chains exhibits smectic and cholesteric mesophases. Measurements in the smectic phases show a Bragg peak and smectic layers are oriented parallel to the substrate. The sample is thus macroscopically ordered by the influence of substrate and free surface. The film surface is very smooth after spincoating; surface roughness is typically 0.8 nm. First annealing of samples leads to a significant roughening of the free surface; roughness increas…
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.
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 …