Radiation ordering in quenched alloy sobserved “in situ” in the high voltage microscope

Different alloys with a face centered cubic disordered structure have been electron irradiated in the quenched or short range order state under direct observation in a high voltage electron microscope. Ordering due to 1 MeV irradiation has been observed in Au₄Mn, Ni₄Mo and Cu₃Pd. Care has been taken to avoid ordering due to the thermal effect of the electron beam. It has been demonstated that although similar states of order can be achieved by thermal and irradiation ordering, the path followed can be different however.     

Difficulty of dislocation-punching from densely distributed high pressure bubbles

Abstract

Dislocation punching mechanism to assess the internal bubble pressure due to Greenwoodel al. was criticized, and modification of the formalism by adding lateral stress field due to bubble swelling and thermodynamical osmotic pressure due to radiation induced vacancy supersaturation was given. This modification gives the necessary punching pressure of more than three times that of Greenwood's estimation during the implantation relevant to the present case.     

Short-time reactor neutron irradiation of YSZ prepared using reactive calcination method

The present work is devoted to study the short-time reactor neutron irradiation of yttria stabilised zirconia (YSZ) at 315 K. The samples were prepared by the reactive calcination method and characterised by X-ray diffraction (XRD) analysis and scanning electronic microscope. The prepared samples were irradiated by reactor neutrons at different exposure times and investigated by XRD analysis. The results obtained show good radiation resistance of YSZ to reactor neutron irradiation.     

Mechanical modifications in dense polyethylene induced by energetic electron beams

Effects of radiation damage in ultra high molecular weight polyethylene are investigated by using energetic electron beams. Special attention is devoted to the mechanical characterization of the polymer, before and after the modification induced by 5 MeV electrons, as a function of the absorbed dose. Elastic modules, ultimate tensile and compressive strengths and roughness and hardness, have been measured in pristine and electron irradiated polymers. Infrared spectroscopy, scanning electron microscopy and differential scanning calorimetry are employed in order to investigate the microscopic modifications induced by the electron energy release to the polymeric chains. Results indicate that the polymer loses hydrogen and becomes rich in carbon content. Cross-linking effects are responsible for the higher mechanical resistance, fragility and hardness of the polymer submitted to a high absorbed dose.     

Hardness and elastic modulus of zircon as a function of heavy-particle irradiation dose: I. In situ α-decay event damage

Abstract

For a natural single crystal of zircon, ZrSiO₄, from Sri Lanka, exhibiting zonation in U and Th contents, the hardness and elastic modulus have been determined as a function of α-decay dose using a mechanical properties microprobe (MPM). The zones vary in thickness from one to hundreds of micrometers, and have uranium and thorium concentrations such that the α-decay dose varies between 2 × 10¹⁵ and 1 × 10¹⁶ α-decay events/mg (0.15 to 0.65 dpa, displacement per atom). The transition from the crystalline to the aperiodic metamict state occurs over this dose range. For a traverse of 75 indent pairs across layers sampling a large portion of the crystalline-to-metamict transition (3.7 × 10¹⁵ to 9.7 × 10¹⁵ α-decay events/mg) both the hardness and elastic modulus decrease linearly with increasing α-decay dose. The radiation-induced softening follows a behavior similar to other radiation-induced changes, that is with the expansion of the unit cell parameters there is a decrease in density, birefringence, hardness and bulk modulus.     

The dependence of angular width ψ1/2 the axial dip on the depth of particle penetration into crystal

The depth dependence of angular width ψ_1/2 of the axial dip in the yield of backscattering of protons (E ₀ = 6.3 MeV) from a tungsten single crystal has been investigated experimentally. The interpretation of the results was based on a two-dimensional kinetic equation which accounts for the multiple scattering of channelled particles by electrons and thermal vibrations of the lattice.     

Target heating during ion implantation and related problems

We have undertaken a general analysis of wafer heating during implantation and first, we present general considerations of this problem with respect to amorphization doses extracted from Morehead and Crowder theory. Then, radiative properties of silicon wafers are measured: a law of variation of the emissivity with temperature is given; a comparison is made with values found in the literature. Dependence with experimental conditions (heat reflector, conductive losses) is also studied. Three methods for temperature measurement are used: temperature coefficient of a small resistor vacuum deposited on a face, thermocouple measurement and infrared detection. We compare the three kinds of results which are in good agreement and we make some comments about the temperature measurements using infrared detection.     

XRD and AFM study of radiation damage induced by swift heavy ions in Y3Al5O12 single crystals

Defects induced in Y₃Al₅O₁₂ single crystals by swift heavy ions are investigated by X-ray diffraction (XRD) and atomic force microscopy. The irradiation was performed at GANIL with 561 MeV ⁵¹Cr, 466 MeV ¹²⁸Te, and 957 MeV ²⁰⁸Pb ions. The XRD data reveal that the lattice strain increases with increasing electronic stopping power, whereas the hillock parameters (height and diameter) are not influenced by the electronic stopping power. According to our experimental data, for the same mean electronic stopping power, the hillock parameters are more pronounced for the lower range in contrast to swelling measurements. The experimental data show a strong increase in the hillock parameter at higher fluence, indicating the amorphization of Y₃Al₅O₁₂ single crystals.     

EPR investigations on γ-irradiated 4-hydroxyacetophenone single crystals: an NLO material

The single crystals of 4-hydroxyacetophenone (4HAP) were grown by the solution growth technique and characterized by X-ray diffraction, UV–VIS, FT-IR, and FT-Raman techniques. TGA–DTA analyses have also been carried out. Electron paramagnetic resonance spectra of γ-irradiated 4HAP were recorded and the spin Hamiltonian parameters were evaluated.