Search results for "Metallurgy"

Annealing of Radiation Defects in X-Irradiated LiBaF3

2002

AbstractResults of application of the glow rate technique GRT for analysis of the activation energy of thermostimulated annealing of X-ray created F-type color centers in LiBaF3 crystals, pure and containing hetero-valence oxygen centers are presented. It is shown that depending on impurity composition in crystal two alternative mechanisms are involved in annealing of color centers. It is proposed that either the anion vacancy governed migration of F- centers resulting in recombination with complementary defects, or the thermal delocalization of radiation created fluorine (Fi) interstitials captured by anti-structure defects followed by recombination with all kinds of complementary F- type …

<title>Formation of dislocations and hardening of LiF crystals irradiated with energetic Au, Bi, Pb, and S ions</title>

2003

The irradiation of LiF crystals with Au, Pb, Bi, and S ions in the range of 400 - 2200 MeV leads to a remarkable increase of the hardness. The effect appears for Bi and Pb ions at fluences above 109 ions/cm2 and for S ions above 1010 ions/cm2. The increase of hardness follows the energy loss and is related to the formation of defects along the ion path. Defect complexes, clusters and aggregates with nanoscale dimensions serve as strong obstacles for dislocations and cause dispersion strengthening. Structural investigations reveal the generation of long-range stress in the adjacent non-irradiated part of the crystal. Close to the implantation zone, the stress exceeds the yield strength, caus…

Kinetics of correlated annealing of radiation defects in alkali halide crystals

1992

Abstract Kinetics of the correlated annealing of pairs of neutral (F-H) Frenkel defects in the KBr crystal is treated theoretically, taking into account defect diffusion, and annihilation at short distances stimulated by an elastic interaction. It is shown that an elastic interaction affects the annealing kinetics and the survival probability of close geminate detects considerably. The widespread description of the correlated annealing in terms of a first-order reaction fails for close defects yielding effective energies which in fact differ essentially from an activation energy of diffusion. Ea, even if it is corrected by an interaction energy. The effect of the initial distribution of def…

Hardening and formation of dislocation structures in LiF crystals irradiated with MeV–GeV ions

2002

Abstract Material modifications of LiF crystals irradiated with Au, Pb and Bi ions of MeV to GeV energy are studied by means of microindentation measurements and dislocation etching. Above a critical irradiation fluence of 10 9 ions/cm 2 , the microhardness can improve by a factor of 2 in the bulk and by more than 3 on the surface. Radiation-induced hardening follows the evolution of the energy loss along the ion path. Annealing experiments indicate that complex defect aggregates created in the tracks play a major role for the hardness change. Evidence for severe structural modifications is found when etching indentation impressions in highly irradiated crystals leading to similar pattern a…

High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties

2000

AbstractHigh-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350°C and 550°C to a fluence of 1015 cm−2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation.In the samples implanted at 350°C Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600° showed that the solid phase epitaxial regrowth of the damaged layers strongly de…

Thermal stability and crystallization kinetics of Al4Mn quasicrystals as studied by exoelectron emission and DTA methods

1995

Grazing-Incidence X-ray Diffraction Study of Octadecanoic Acid Monolayers

1998

We report the observation of X-ray scattering profiles from monolayers of octadecanoic acid in the vicinity of room temperature and evidence for the existence near room temperature of all four hexatic rotator phases L2d, Ov, L‘1, and LS, which differ in the details of their molecular tilt. While the incontrovertible triple-reflection signature of the chiral L‘1 phase was not observed, we propose that the previously reported rapid annealing behavior in this phase can lead to the disappearance of one, and in some cases two, of the three peaks.

Modification of LiF structure by irradiation with swift heavy ions under oblique incidence

2013

The structural modifications of LiF irradiated with swift heavy ions under oblique angles have been investigated using AFM, SEM, chemical etching, nanoindentation and optical absorption spectroscopy. LiF crystals were irradiated under incidence angles of 30 and 70 degrees with 2.2 GeV Au (fluence 57?l011 ions-cm2) and 150 MeV Kr ions (fluence 1012?1014 ions?cm?2). Structural study on sample cross-sections shows that two damage regions ? (1) nanostructured zone and (2) dislocation ? rich zone, which are typical for irradiations at normal incidence, appear also in samples irradiated under oblique angles. However in the latter case a more complex structure is formed that leads to stronger ion-…

Magnetic alignment of aliphatic lamellae

1993

Abstract Magnetic alignment of mesophases is normally only considered possible when the molecule contains an aromatic ring system. In this paper we report on the mesomorphous behaviour of a polyalkylacrylate resin with average sidechain length 22 and the alignment of its lamellae in cast films by annealing in a strong magnetic field.

Hardening in LiF induced by fast Ni ions and recovery of properties under annealing

2005

The recovery of hardness and optical absorbance of LiF crystals irradiated with 640 MeV nickel ions under annealing at 450–810 K is investigated. Recovery of the hardness of irradiated crystals is initiated at temperatures above 530 K, at which a transition from a complex absorption spectrum to a spectrum with only one broad peak at 275 nm is observed. Activation energy of 0.13 eV ± 0.02 eV, which is close to that necessary for migration of H centers, is obtained from the annealing data. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)