Spectroscopic studies of transition-metal oxides, silicates, and pnictides: developing materials capable of sequestering nunclear waste

随着各国政府出于对环境的担忧考虑逐步淘汰以化石燃料为基础的发电机，核能再次成为一种重要的替代能源。虽然核反应堆产生的电力是“清洁的”，但也会产生有害的放射性废物。加拿大供应全球铀(U)供应量的25%(产值25亿美元)，其中很大一部分将用于核电设施。为了提高加拿大在铀市场的地位，开发用于储存核废料的材料是很重要的。这些废物可以被隔离在密集包装的化合物中，并延缓放射性元素的向外扩散。这一研究计划的长期目标是开发能够将铀隔离在结构中并抵抗辐射引起的结构损伤的有序化合物。为了开始这项研究，将考察代表主体材料的模型化合物，以便清楚地了解晶体结构组成、成键、电子结构和表面反应性与诸如U之类的辐系元素的固定之间的关系。在本计划中，烧绿石陶瓷(A2B2X6X‘；A=Ca，Mn，Fe，稀土(RE)；B=Ti，Nb，Ta；X/X’=O，F，OH)，采用锆石(AsiO4；A=Zr，Hf)和锆石(A2B2O7；A/B=Ca，V，Zr，Ti，Hf)结构，无定形硅酸盐([AO2]x[A‘O2]y[SiO_2]1-x-y；A/A’=Ti，Zr，Hf)和Skutterudite(REM4Pn12；RE=La，Ce，Eu，Gd；M=Fe，Co；Pn(PNictide)=P，As，Sb，Bi)。这些材料的电子结构和氧化能力将通过X射线衍射、X射线光电子能谱和X射线吸收光谱来研究，利用同步辐射。研究晶态和无定形硅酸盐将允许研究辐射引起的结构损伤如何影响材料隔离铀的能力(上述许多材料也在半导体设备、发电和制冷方面有应用)。本研究计划致力于应用X射线能谱研究上述体系的氧化行为和电子结构随元素取代的变化，以开发能够隔离核废料的材料。

With governments considering phasing out fossil fuel based power generators because of environmental concerns, nuclear energy is once again a serious alternative. Although the power generated by nuclear reactors is "clean", hazardous radioactive waste is produced. Canada supplies >25% of the worlds' uranium (U) supply (production value >$2.5 billion), with much of it destined for nuclear power facilities. To increase Canada's position in the U market, it is important to develop materials for use in the storage of nuclear waste. This waste can be sequestered in compounds that are densely packed and retard outward diffusion of the radioactive elements. The long-term goal of this research program is the development of ordered compounds that can sequester U in the structure and resist radiation induced structure damage. To initiate this research, model compounds representing host materials will be examined in order to gain a clear understanding of the relationship between crystal structure composition, bonding, electronic structure, and surface reactivity to the sequestration of actinides like U. In this program, pyrochlore ceramics (A2B2X6X'; A=Ca, Mn, Fe, rare-earths (RE); B=Ti,Nb,Ta; X/X'=O, F, OH), materials adopting the zircon (ASiO4; A=Zr, Hf) and zirconolite (A2B2O7; A/B=Ca, V, Zr, Ti, Hf) structures, amorphous silicates ([AO2]x[A'O2]y[SiO2]1-x-y; A/A'=Ti, Zr, Hf), and skutterudites (REM4Pn12; RE=La, Ce, Eu, Gd; M = Fe, Co; Pn (pnictide)=P, As, Sb, Bi) will be synthesized. The electronic structure and ability of these materials to be oxidized will be investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, utilizing synchrotron radiation. Studying crystalline and amorphous silicates will allow for an examination of how radiation induced structure damage affects a materials ability to sequester U. (Many of the above materials also have applications in semiconductor devices, power generation, and refrigeration.) This research program is dedicated to applying X-ray spectroscopy to the study of the oxidation behaviour and changes in electronic structure with elemental substitution of the systems described above, so as to develop materials capable of sequestering nuclear waste.