Modification and Characterization of Radiation Behaviour of Zircon (ZrSiO4)
EMSL Project ID
32891
Abstract
Zircon (ZrSiO4) is of great interest in the field of materials science, mineralogy and geochemistry, and it is also widely used in ceramic, foundry, welding rod coatings, refractory industries and U/Th/Pb age dating. Its crystal structure consists of a chain of alternating, edge-sharing SiO4 tetrahedra and ZrO8 triangular dodecahedra extending parallel to the c-axis. Zircon has high chemical stability and durability, and the ability to accommodate a variety of chemical impurities (e.g., U, Th, Hf, Pu, etc.). It has been proposed as a phase for the immobilization and disposition of actinides, such as the Pu from dismantled nuclear weapons. Zircon is, probably due to its well-understood crystal structure and the availability of a wide range of degree of damage in natural crystals, one important example among a limited number of materials whose structural responses to radiation damage and recrystallization, as well as the structures of the defective and amorphized phases, have been systematically studied for more than half a century. In this proposal, we would like to carry out investigations of the damage accumulation and amorphization processes in synthetic and natural zircon irradiated with high-energy ions (e.g., He+ and Au+). Specifically, we are proposing to utilize EMSL ion implantation, various ion beam techniques and surface analysis techniques to achieve the following three objectives. First, we wish to gain a better understanding of irradiation-induced structural changes in zircon by investigating Au-irradiated zircon and the interactions between high-energy particles and solids. In fact, there is a limited comprehension of the structure and vibrational modes of the aperiodic or amorphous domains produced by irradiation of zircon. Second, we compare the metamict state of natural zircon with the irradiation-induced aperiodic state in zircon by analyzing the spectral features of ion-irradiated and naturally damaged, metamict zircon and exploring the structural similarities or differences between them. We also wish to address some important, but unanswered questions. For example: can the heavy ion irradiation, as a powerful approach to simulating the ballistic effects of the alpha-recoil nucleus, ever produce the same or similar types of aperiodic domains that are observed in metamict zircon that are caused by natural alpha-decay event processes? What is the effect of the presence of radiation-induced defects in still-crystalline zircon on the formation of the amorphous domains? Third, we wish to further investigate whether and to what extent the amorphous state produced by high-energy heavy ion irradiations can be referred as the â??glassyâ?? state that commonly occurs in the melts or quenched melts, although previous data from metamict zircon have shown significant spectral differences. . The results from the different approaches reveal the radiation damage process over different length and temporal scales. Using state-of-the-art resources at the EMSL, the careful control and subsequent understanding of material radiation response and properties will help fill-in these gaps in our understanding in order to develop a full and systematic understanding of radiation damage in zircon.
Project Details
Project type
Exploratory Research
Start Date
2009-02-02
End Date
2010-02-07
Status
Closed
Released Data Link
Team
Principal Investigator