Rare-earth (RE) containing alkali aluminoborosilicate glasses find increasingly broad technological applications, with their further development only impeded by yet-poor understanding of coordination environment and structural role of RE ions in glasses. In this work we combine free induction decay (FID)-detected electron paramagnetic resonance (EPR), electron spin echo envelope modulation (ESEEM), and MAS NMR spectroscopies, to examine the coordination environment and the clustering tendencies of RE3+ in a series of peralkaline aluminoborosilicate glasses co-doped with Nd2O3 (0.001-0.1 mol%) and 5 mol% La2O3. Quantitative EPR spectral analysis reveals three different Nd3+ forms coexisting in the glasses: isolated Nd3+ centers, dipole-coupled Nd clusters (Nd-O-X-O-Nd, where X = Si/B/Al), and spin-exchange-coupled Nd clusters, (Nd-O-Nd) and (Nd-O-La-O-Nd). Extensive RE clustering is observed at high RE2O3 concentrations, with more than 90% REs converting to dipole- and exchange-coupled Nd clusters already at [RE2O3] = 0.01 mol%. ESEEM analysis of the EPR-detectable Nd centers indicates a Na/Si-rich environment (four Na+ per Nd3+) for the isolated Nd3+ centers and the Na/Si/B-rich environment (2-3 Na+ and 1-2 boron per each Nd3+) for the dipole-coupled Nd clusters, while the EPR-undetectable exchanged-coupled RE clusters are predicted to exist in a Na/B-rich environment. The RE clustering induces nano-scale glass phase separation, while the Na/B-rich environment of the RE clusters implies a depletion of the same elements from the remaining host glass. Based on our results, we develop a mechanistic model that explains the high tendency of RE3+ to form clusters in alkali aluminoborosilicate glasses.
Effect of the nature of alkali and alkaline-earth oxides on the structure and crystallization of an aluminoborosilicate glass developed to immobilize highly concentrated nuclear waste solutions
Effect of changing the rare earth cation type on the structure and crystallization behavior of an aluminoborosilicate glass
一种铝硼硅酸盐玻璃，含有高量的稀土（RE），其组成为50.68 SiO 2 - 4.25 Al 2 O 3 - 8.50 B 2 O 3 - 12.19 Na 2 O- 4.84 CaO - 3.19 ZrO 2 - 16.35 RE 2 O 3（重量%），目前正在研究用于固定化核废料溶液。在这项工作中，我们要调查的影响，改变稀土阳离子类型的玻璃结构和其结晶行为。为此，一系列的玻璃阐述了RE的性质是不同的镧，镥。在该玻璃系列中，仅观察到对玻璃结构的影响很小。相反，通过不同的热处理对结晶行为的强烈影响是显而易见的。以1 μ/℃/min的速度缓慢冷却熔体，发现含有离子半径接近钙的稀土的样品中磷灰石Ca_2RE_8（SiO_4）_6O_2明显结晶。另一种热处理，包括连续的成核和生长阶段，进行强制结晶的散装和减少任何表面结晶效果，提出证据的存在下，一个强烈的非均匀的第二稀土丰富的硅酸盐相的样品含有低离子半径（从Y到Lu）。
When supporting electrolyte matters - tuning capacitive response of graphene oxide via electrochemical reduction in alkali and alkaline earth metal chlorides
调节氧化石墨烯（GO）的电荷存储性质的能力对于能量转换应用是极其重要的。在这里，我们表明，GO的电化学还原对溶液中存在的阳离子高度敏感。GO在碱金属氯化物溶液中比在碱土金属氯化物中在更低的电势下被还原。在还原过程中，GO的电容从10倍增加到70倍。还原GO的最大电容在65和130 F g-1之间，这取决于电解质和导电添加剂的存在。我们建议，在还原过程中的阳离子与GO的氧官能团的不同的相互作用是负责所观察到的效果。
