Microstructure and Mechanical Behaviour of Proton-and Ion-irradiated Ll_2 Intermetallic Compounds

The results of mechanical testing and transmission electron microscopy on the ordered intermetallic Ll2 compounds1Zr3Al, Ni3Al, Ni3Si and Ni3Ge after irradiation with protons or heavy ions at high or low tem peratu re are presented and discussed. Using a minjaturjzed disk-bend test. it was found that proton irradiation of Zr3Al. Ni3Al and Ni3Si raises their yield strength :a single test of Ni3Ge shows no effect on the fracture stress of this brittle intermetallic The Vickers microhardness of all four alloys is raised by proton irradiation. The irradiations cause all the alloys to disorder. the extent of which is dependent on irradiation temperature Microstructural defects are produced by the irradiations Some exhibit strain-field contrast under dynamic two-beam diffracting conditions. Other distinct defect clusters are imaged only in dark-field using su perlattice reflections, These latter defects are discussed in the context of current arnorphization models. The strength increase of Zr3Al, Ni3Al and Ni3Si is attributed to a combination of disordering and strengthening from defects. The lack of an effect of irradiation on the fracture stress of Ni3Ge. in which voids were observed, requires further experiments

Hardening effect of multi-energyW2+-ion irradiation on tungsten–potassium alloy

Tungsten is one of the most promising plasma-facing materials (PFMs) to be used in the nuclear fusion reactor as divertor material in the future. In this work, W2+-ions bombardment is used to simulate the neutron irradiation damage to commercial pure tungsten (W) and rolled tungsten–potassium (W–K). The 7 MeV of 3 × 10^15 W2+-ions/cm2, 3 MeV of 4.5 × 10^14 W2+, and 2 MeV of 3 × 10^14 W2+-ions/cm2 are applied at 923 K in sequence to produce a uniform region of 100 nm–400 nm beneath the sample surface with the maximum damage value of 11.5 dpa. Nanoindentation is used to inspect the changes in hardness and elastic modulus after self-ion irradiation. Irradiation hardening occurred in both materials. The irradiation hardening of rolled W–K is affected by two factors: one is the absorption of vacancies and interstitial atoms by potassium bubbles, and the other is the interaction between potassium bubbles and dislocations. Under the condition of 11.5 dpa, the capability of defect absorption can reach a threshold. As a result, dislocations finally dominate the hardening of rolled W–K. Specific features of dislocation loops in W–K are further observed by transmission electron microscopy (TEM) to explain the hardening effect. This work might provide valuable enlightenment for W–K alloy as a promising plasma facing material candidate.

Silicon and III-V Solar Cells: From Modus Vivendi to Modus Operandi

In the present paper, some novel opportunities for the development of high-efficient Si and III-V-based solar cells are considered: energy-saving environment friendly low-temperature technology of forming p-n junctions in Si (1), elaboration of structurally perfect GaAs/Ge/Si epitaxial substrates (2) and application of protective antireflecting coatings based on cubic zirconia (3). As a result: 1) New technique of forming p-n junctions in silicon has been elaborated. The technique provided easy and comparatively cheap process of production of semiconductor devices such as solar cells. The essence of the technique under the study is comprised in formation p-n junctions in silicon by a change of conductivity in the bulk of the sample occurring as a result of redistribution of the impurities, which already exists in the sample before its processing by ions. It differs from the techniques of diffusion and ion doping where change of conductivity and formation of p-n junction in the sample occur as a result of introduction of atoms of the other dopants from the outside;2) The conditions for synthesis of GaAs/Ge/Si epitaxial substrates with a thin (200 nm) Ge buffer layer featured with (1 - 2) × 105 cm-2 density of the threading dislocation in the GaAs layer. Ge buffer was obtained by chemical vapor deposition with a hot wire and GaAs layer of 1 μm thick was grown by the metal organic chemical vapor deposition. Root mean square surface roughness of GaAs layers of the less than 1 nm and good photoluminescence properties along with their high uniformity were obtained;3) The conditions ensuring the synthesis of uniform functional (buffer, insulating and protective) fianite layers on Si and GaAs substrates by means of magnetron and electron-beam sputtering have been determined. Fianite films have been shown to be suitable for the use as an ideal anti-reflecting material with high protective and anticorrosive properties.