Damage Accumulation in Nuclear Ceramics

Abstract

Ceramics are key engineering materials in many industrial domains. The evaluation of radiation damage in ceramics placed in a radiative environment is a challenging problem for electronic, space and nuclear industries. Ion beams delivered by various types of accelerators are very efficient tools to simulate the interactions involved during the slowing-down of energetic particles. This article presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on new results concerning the damage build-up. Ions with energies in the keV-GeV range are considered for this study in order to explore both regimes of nuclear collisions (at low energy) and electronic excitations (at high energy). The recovery, by electronic excitation, of the damage created by ballistic collisions (swift heavy ion beam induced epitaxial recrystallization process) is also reported. 61.80.Jh, 61.82.Ms, 61.85.+p, 68.37.Lp PACS Introductory remarksCeramics are refractory solids which possess very interesting physico-chemical properties, such as high strength, low thermal expansion, chemical stability, strong resistance against oxidation, good behavior under irradiation, etc. These materials are therefore often employed in hostile media where efficient use of energy is a prime need, e.g. extreme temperatures, corrosive surroundings, radiative environment, etc. Examples of the interest of ceramics for applications are provided by electronic, space and nuclear industries. For instance, such materials are nowadays widely used for surface coating and electronic packaging, and they are envisioned in a near future for the safe and long-term disposal of radioactive waste, and the development of inert fuel matrices for actinide transmutation. They may also be employed as cladding materials for gas-cooled fission reactors and structural components in fusion reactors. For all these applications, there is an urgent need of data concerning the behavior of nuclear ceramics upon irradiation.The topic that is concerned here is so broad that it requires a whole book to cover the main issues; the state of knowledge was regularly upgraded in thorough reviews [1][2][3][4][5][6][7][8][9][10]. To deal it in a short article, we focus on the presentation of a few remarkable examples concerning the ion-beam modifications of nuclear ceramics (zirconia, pyrochlores, silicon carbide, etc.) with an emphasis on the mechanisms leading to damage cre- * corresponding author; e-mail: thome@csnsm.in2p3.fr ation and phase transformations. We report typical results obtained using advanced characterization techniques (the Rutherford backscatteringspectrometry associated to channeling (RBS/C), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman) for ceramics irradiated with ions in a broad energy range (from keV to GeV) in order to explore both nuclear collision and electronic excitation regimes.The first section is devoted to the presentation of general considerations about the damage build-up in ion--irradiated crystals and of a new mo...

Monitoring of the microstructure of ion‐irradiated nuclear ceramics by in situ Raman spectroscopy

“…Results are compared to the f d determined by the RBS‐C technique in ex situ conditions . Both damage build‐ups are in very good agreement and may be reproduced using the multi‐step damage accumulation (MSDA) model represented by the equation: where f D,i sat is the level of damage at saturation, n is the number of steps required for the achievement of the total disordering process, Φ i is the threshold ion fluence of the i th step and σ i the disordering cross section at the i th step. G corresponds to the Heaviside function H multiplied by its argument.…”

“…Total disorder deduced from in situ Raman (filled squares) and RBS/C (filled circles) for irradiated 6H‐SiC samples as a function of ion fluence. The curves are least‐squares fits of Raman and RBS/C data with the MSDA ( n = 2).…”

Structure and Physicomechanical Properties of Nanostructured (TiHfZrNbVTa)N Coatings after Implantation of High Fluences of N+(1018cm-2)

“…This process is used to change the physical-mechanical, tribological, chemical, or electrical properties of the solid [3][4][5][6][7][8][9][10]. The ions alter the elemental composition of the target, stopping in the target and staying there, causing many chemical and physical changes in the target by transferring their energy and momentum to the electrons and atomic nuclei of the target material.…”

“…In its turn, it causes a structural change, in that the crystal structure of the target can be damaged or even destroyed by the energetic collision cascades. As the masses of the implanted ions are comparable to those of the target atoms, the implanted ions knock the target atoms out of place even more than electron beams do [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The main advantage of ion implantation is preservation of sample sizes, locality (small projected range), high reproducibility, no problems with adhesion, etc., which allows using it in various technological processes.…”

Monitoring by Raman spectroscopy of the damage induced in the wake of energetic ions

“…From previous studies, one of the key questions relies on the possibility to determine the amount of damage created in a crystalline material all along the trajectories of incident ions. The channeling technique, generally associated with Rutherford backscattering spectrometry (RBS), is certainly, up to now, the most frequently used methodology to achieve this task . Very recently, high‐resolution transmission electron microscopy (HRTEM) was also implemented to determine the structure of ion tracks from the surface of samples up to several micrometers .…”