Vachagan V. Harutyunyan

Radiation-modified natural zeolites for cleaning liquid nuclear waste (irradiation against radioactivity)

There have been comparatively few investigations reported of radiation effects in zeolites, although it is known that these materials may be modified substantially by exposure to ionizing radiation. Thus, by exposure to γ-rays or high-energy particles, the charge states of atoms may be changed so to create, and accumulate, lattice point defects, and to form structurally disordered regions. Such a technique may permit the creation, in a controlled fashion, of additionally useful properties of the material while preserving its essential stoichiometry and structure. Accordingly, we present an application, in which the cation-exchange capacity of a natural zeolite (clinoptilolite) is substantially enhanced, for the treatment/decontamination of water contaminated with radionuclides e.g. 134Cs, 137Cs and 90Sr, by its exposure to high-energy (8 MeV) electrons, and to different total doses.

Quasi-Chemical Reactions in Irradiated Silicon Crystals with Regard to Ultrafast Irradiation

This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.

The Use of Different Pulsed Electron Irradiation for the Formation of Radiation Defects in Silicon Crystals

This paper reports the formation of structural defects in the lattice of silicon (n-Si) single crystals, as a result of irradiation by different intensities and pulses of electrons. The samples were studied by means of Hall effect measurements of electro-physical parameters (specifically the concentration of the main charge carriers) as a function of temperature and radiation dose. The role of the radiation current density (pulse height) is discussed, which gives rise to a peculiar behavior in the electrical-physical properties of n-Si. In particular, thermal processes are found not to develop, due to the ultrafast (pulse duration in the range 10−12–10−13s) nature of the incident radiation, which causes an almost “pure” energy interaction to occur between the radiation and the atoms within the crystal, and the formation of cluster defects. A scheme for the time-scale of the formation of these radiation defects is presented. From the dose and temperature dependences of the concentration of main charge carriers, the radiation defects introduction rates were determined.

The influence of hydrochloric acid treatment and temperature on the electro-physical properties of super-thin basalt fibers

Electro-physical parameters of super-thin basalt fiber (STBF) from Armenian basalt rocks are measured before and after hydrochloric acid treatment. It is shown that specific resistance and dielectric parameters of super-thin basalt fiber change essentially after hydrochloric acid treatment. The temperature dependence of these parameters was studied too. The probable cause of the change is an increase in the total amount of pores and modification of the share of pores of various sizes in STBF, followed by an increase of absorption of water molecules from the ambient medium. The results (in both alternating and direct electric fields) are interpreted within the framework of the dipole-relaxation mechanism of the polarization of water molecules in STBF pores.