MAS ‐ NMR Studies of Glasses and Glass ‐ Ceramics based on Clinopyroxene–Fluorapatite System
MAS ‐ NMR Studies of Glasses and Glass ‐ Ceramics based on Clinopyroxene–Fluorapatite System
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MAS - 基于斜辉石-氟磷灰石体系的玻璃和玻璃陶瓷的核磁共振研究
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发表时间：
2009
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通讯作者：
R. V. Law
中科院分区：
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作者：
H. Mosallam;R. Hill;N. Karpukhina;R. V. Law
采用魔角旋转（MAS）NMR、X射线粉末衍射（XRD）和热分析等方法对CaMgSi 2 O 6-NaAlSi 2 O 6-Ca 5（PO 4）3F（透辉石（Di）-硬玉（Jd）-氟磷灰石（FAp））三元系玻璃和微晶玻璃进行了研究。在该硅酸盐体系中，CaO和MgO逐渐被Na 2 O和Al 2 O3取代：（CaMgSi 2 O 6）1-x-（NaAlSi 2 O 6）x-（Ca 5（PO 4）3F）y，其中0 ≤ x ≤ 30mol%，y = 7mol%。玻璃的29 Si MAS-NMR显示对应于混合的Q 2 /Q 3硅酸盐物质的峰，其化学位移随着Na 2 O和Al 2 O 3取代的增加而略微降低。在玻璃的热处理之后，通过XRD已经确定了两个主要的结晶相：硅酸盐固溶体（单斜辉石）和FAp，其中硅酸盐相首先结晶出来。玻璃相与这些结晶相共存，并随着Na 2 O和Al 2 O 3含量的增加而变得更加明显。正如预期的那样，从XRD或MAS-NMR中没有发现结晶Jd。27玻璃的Al MAS-NMR光谱显示，添加Al 2 O3后仅存在Al（IV）。在热处理后，观察到归属于固溶体的在-4 ppm处的新的尖锐Al（VI）峰，其对应于六配位状态的Al 3+，用Na +替代额外的Mg 2+或Ca 2+来沿着结晶硅酸盐链结构替代Mg 2+以维持电荷平衡。热处理时生成的Al（VI）量随Al 2 O3的加入而线性增加，但不超过约100 μ g/L。系统中存在的总铝浓度的20%。来自热处理材料中的Al（IV）的信号属于残余铝硅酸盐玻璃相。31 P MAS-NMR显示存在混合的钙/镁/钠无定形正磷酸盐
Glasses and glass ‐ ceramics based on the ternary system CaMgSi 2 O 6 ‐ NaAlSi 2 O 6 ‐ Ca 5 (PO 4 ) 3 F (diopside(Di) ‐ jadeite(Jd) ‐ fluorapatite(FAp)) have been studied with magic angle spinning (MAS) NMR, powder x ‐ ray diffraction (XRD) and thermal calorimetry. In this silicate system Na 2 O and Al 2 O 3 has been progressively substituted for CaO and MgO: (CaMgSi 2 O 6 ) 1 ‐ x ‐ (NaAlSi 2 O 6 ) x ‐ (Ca 5 (PO 4 ) 3 F) y where 0 ≤ x ≤ 30mol% and y = 7 mol%. 29 Si MAS ‐ NMR of the glasses showed a peak corresponding to a mixed Q 2 /Q 3 silicate species which slightly decreased in chemical shift on increasing Na 2 O and Al 2 O 3 substitution. After heat treatment of the glasses two major crystalline phases: a silicate solid solution (clinopyroxene) and FAp have been identified by XRD, with the silicate phase crystallising out first. A glassy phase coexisted with these crystalline phases and became more evident with increasing Na 2 O and Al 2 O 3 content. As expected, no crystalline Jd has been found from XRD or MAS ‐ NMR. 27 Al MAS ‐ NMR spectra of the glasses shows only Al(IV) to be present on addition of Al 2 O 3 . Upon heat treatment, a new, sharp Al(VI) peak at ‐ 4 ppm assigned to the solid solution was observed, which corresponds to Al 3+ in a six coordinate state, replacing Mg 2+ along the crystalline silicate chain structure with the replacement of either an additional Mg 2+ or Ca 2+ by Na + to maintain the charge balance. The amount of Al(VI) formed on heat treatment grows linearly with addition of Al 2 O 3 , but does not exceed ca. 20% from the total aluminium concentration present in the system. The signal from the Al(IV) in the heat treated material belongs to the residual aluminosilicate glassy phase. 31 P MAS ‐ NMR shows the presence of mixed calcium/magnesium/sodium amorphous orthophosphate