@article{zhang_varga_ishimaru_edmondson_xue_liu_moll_namavar_hardiman_shannon_et al._2014, title={Competing effects of electronic and nuclear energy loss on microstructural evolution in ionic-covalent materials}, volume={327}, ISSN={0168-583X}, url={http://dx.doi.org/10.1016/j.nimb.2013.10.095}, DOI={10.1016/j.nimb.2013.10.095}, abstractNote={Ever increasing energy needs have raised the demands for advanced fuels and cladding materials that withstand the extreme radiation environments with improved accident tolerance over a long period of time. Ceria (CeO2) is a well known ionic conductor that is isostructural with urania and plutonia-based nuclear fuels. In the context of nuclear fuels, immobilization and transmutation of actinides, CeO2 is a model system for radiation effect studies. Covalent silicon carbide (SiC) is a candidate for use as structural material in fusion, cladding material for fission reactors, and an inert matrix for the transmutation of plutonium and other radioactive actinides. Understanding microstructural change of these ionic-covalent materials to irradiation is important for advanced nuclear energy systems. While displacements from nuclear energy loss may be the primary contribution to damage accumulation in a crystalline matrix and a driving force for the grain boundary evolution in nanostructured materials, local non-equilibrium disorder and excitation through electronic energy loss may, however, produce additional damage or anneal pre-existing defects. At intermediate transit energies where electronic and nuclear energy losses are both significant, synergistic, additive or competitive processes may evolve that affect the dynamic response of materials to irradiation. The response of crystalline and nanostructured CeO2 and SiC to ion irradiation are studied under different nuclear and electronic stopping powers to describe some general material response in this transit energy regime. Although fast radiation-induced grain growth in CeO2 is evident with no phase transformation, different fluence and dose dependence on the growth rate is observed under Si and Au irradiations. While grain shrinkage and amorphization are observed in the nano-engineered 3C SiC with a high-density of stacking faults embedded in nanosize columnar grains, significantly enhanced radiation resistance is attributed to stacking faults that promote efficient point defect annihilation. Moreover, competing effects of electronic and nuclear energy loss on the damage accumulation and annihilation are observed in crystalline 4H-SiC. Systematic experiments and simulation effort are needed to understand the competitive or synergistic effects.}, journal={Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms}, publisher={Elsevier BV}, author={Zhang, Y. and Varga, T. and Ishimaru, M. and Edmondson, P.D. and Xue, H. and Liu, P. and Moll, S. and Namavar, F. and Hardiman, C. and Shannon, S. and et al.}, year={2014}, month={May}, pages={33–43} }
 @article{zhang_ishimaru_varga_oda_hardiman_xue_katoh_shannon_weber_2012, title={Nanoscale engineering of radiation tolerant silicon carbide}, volume={14}, ISSN={1463-9076 1463-9084}, url={http://dx.doi.org/10.1039/C2CP42342A}, DOI={10.1039/c2cp42342a}, abstractNote={Radiation tolerance is determined by how effectively the microstructure can remove point defects produced by irradiation. Engineered nanocrystalline SiC with a high-density of stacking faults (SFs) has significantly enhanced recombination of interstitials and vacancies, leading to self-healing of irradiation-induced defects. While single crystal SiC readily undergoes an irradiation-induced crystalline to amorphous transformation at room temperature, the nano-engineered SiC with a high-density of SFs exhibits more than an order of magnitude increase in radiation resistance. Molecular dynamics simulations of collision cascades show that the nano-layered SFs lead to enhanced mobility of interstitial Si atoms. The remarkable radiation resistance in the nano-engineered SiC is attributed to the high-density of SFs within nano-sized grain structures that significantly enhance point defect annihilation.}, number={38}, journal={Physical Chemistry Chemical Physics}, publisher={Royal Society of Chemistry (RSC)}, author={Zhang, Yanwen and Ishimaru, Manabu and Varga, Tamas and Oda, Takuji and Hardiman, Chris and Xue, Haizhou and Katoh, Yutai and Shannon, Steven and Weber, William J.}, year={2012}, pages={13429} }