材料期刊网

在英国和法国的很多高放核废料中都含有大量的钼。钼在核废料玻璃中的溶解度很低，过量的钼会导致玻璃产生钼酸盐分相从而影响核废料玻璃化的效率和安全。主要研究了钼酸盐在硼酸盐玻璃中的溶解度与玻璃中碱土金属元素的关系以及钼酸盐的溶解对玻璃的结构和性质的影响。在其它玻璃组分不变的情况下，对玻璃中的碱土金属（由镁至钡）进行等摩尔量替换。结果发现，当碱土金属为钙时钼酸盐的溶解度最高，为2.84 mol%。XRD结果显示除了明显分相的玻璃外其它均一玻璃均为无定形态。SEM结果显示玻璃基体内的分相大多为球状/水滴状并呈随机分布；其尺寸与钼酸盐的过量程度有关，但直径都小于1mm。对钙硼硅酸盐玻璃中析出相的 EDX 分析表明其中富含钼和钙，而 TEM 结果证明这些析出相为晶体相且符合钼酸钙的电子衍射特征。含钼玻璃有两个强烈的拉曼峰（分别位于320和910 cm–1附近）：其强度随玻璃中钼含量的增加而增加，其位置随玻璃中碱土金属元素的变化而偏移。此外，钼的加入也会导致玻璃的玻璃转变温度降低以及玻璃密度增加。

MoO3 is one of the challenging oxides in nuclear waste vitrification in the UK. It has a poor solubility in the conventionally used nuclear waste glasses and its excess presence may cause the formation of “yellow phase” which is highly detrimental to vitrification process. This work investigates the compositional dependence of MoO3 solubility in borosilicate glasses with varying alkaline earth species as well as the effects of MoO3 addition on glass structure and properties. Among all alkaline earths Ca is the best in terms of MoO3 solubility, with 2.84 mol% in calcium borosilicate glass (CBS) without causing any visible phase separation. Magnesium borosilicate glass (MBS) has the lowest MoO3 solubility (≤1 mol%). XRD results indicate that, while the visibly homogeneous glasses all remain amorphous nature, the visibly heterogeneous glasses contain tiny molybdate crystals. According to SEM results, the separated particles forming within glass matrices are mostly spherical, submicron in diameter and randomly dispersed; the size of these particles are dependent on the extent to which MoO3addition is excessive. Compositional analysis for separated phases in CBS glass with excess MoO3 suggests that the phases are rich in Mo and Ca, while TEM results prove the crystallinity of separated particles whose electron diffraction patterns are in accordance with those of CaMoO4. Two Raman bands are observed due to addition of MoO3 in glass; the bands are assigned tobending and stretching vibrations of MoO42– and their intensities increase with MoO3 addition. The positions of these bands shift with alkaline earth species in glass, indicating that the local environment of MoO42– is closely associated with alkaline earth cations in glass network. MoO3 addition to glass also results in decreased glass transition temperatureTg, which suggests a depolymerized network due to MoO42– incorporation. Glass density is increased with the increase amount of MoO3 in glass as long as the glass remains homogeneous.