1. Irradiation effects in ceramics for nuclear waste storage Nan Jiang, Arizona State University, DMR 0603993 The successful development of materials suitable for safe nuclear waste storage requires novel strategies for controlling materials under radiation at the nanoscale or even the atomic level. Historically, radiation effects have been studied by relying on measurements of the end- products of the damage processes. Due to the complexity of radiation effects, such post-radiation observations cannot reveal the initial process of radiation damage, and so have caused confusion as to the fundamental mechanisms of damage in ceramics and glasses. We have developed a procedure to detect the early stages of radiation damage in nuclear waste glasses and ceramics using in situ electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM). This nanoscale spectroscopy offers an unprecedented combination of spatial, time and energy resolution for direct observation of the initial stages of the damage process. An example is given in the study of radiation damage in Zircon (ZrSiO 4 ), which has been extensively studied for the use for immobilization of plutonium. Our results overturn the previous suggestions of amorphization of zircon under high-energy electron irradiation. The damage is mainly cause by the preferential sputtering of O. The loss of O does not uniformly occur within the illuminated area, but rather within small sporadic regions. These isolated patches gradually connect each other. The damage does not result in forming amorphous zircon, but rather forming nanocrystalline Zr x Si y. In situ HREM images and SAED patterns of zircon showing the damage process induced by electron irradiation In situ EELS of zircon showing the damage process induced by electron irradiation. The letters represent the recording sequence of each spectrum. Spectra A and B were from undamaged zircon, while spectra J and K from damaged zircon.

2. International collaboration on photoluminescent materials Nan Jiang, Arizona State University, DMR 0603993 We hosted an exchange scholar supported by the NSF International Materials Institute (IMI) for New Functionality in Glass (DMR-0409588). The project was “preparation and characterization of novel glass-ceramics with ultra-broadband near- infrared luminescence”. Specifically, we were focusing on developing a cheap and efficient luminescent materials for solar cells. Although solar power is in rapid growth mode, the solar cells are predicted to only supply about 5% of the huge amount of carbon-free energy we will need by 2050. One of reasons is that the newly developed solar cells are too expensive. Our approach is to reconsider our philosophy in the past. We need to build new technologies as simple as possible; not by sacrificing the advanced properties, but by utilizing an inexpensive synthetic method. We proposed a new strategy to realize the broadband spectral modulation. By utilizing a designed hybrid structure of LiYbO 2 nanoparticles embedded wide band gap semiconductor ZnO, the high efficient energy transfer from ZnO substrate to Yb 3+ ions can be achieved. This SEM image shows an embedded LiYbO 2 nanoparticle in ZnO substrate. Excitation and emission spectra for (a): 1 mol% Yb 2 O 3 mixed ZnO, λ em =498 nm (black), λ em =980 nm (red), and λ ex =380 nm (blue); (b) 1 mol%Li 2 CO 3 -1 mol% Yb 2 O 3 mixed ZnO, λ em =542 nm (black), λ em =980 nm (red), and λ ex = 397 nm (blue); (c): pure ZnO (orange) and 1 mol% Li 2 CO 3 mixed ZnO (green), λ em =498 nm, λ ex =390 and 365 nm, respectively.