Na_(2)O-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5)玻璃的结构和析晶性能研究

Structure and Crystallization Behavior of Na_(2)O-Al_(2)O_(3)-SiO_(2)-P_(2)O_(5) Glasses

采用熔融-淬冷法制备了不同(Al_(2)O_(3)+P_(2)O_(5))含量的碱铝硅酸盐玻璃,通过拉曼光谱、X射线衍射光谱、扫描电镜研究了其结构特征和析晶性能。发现随着(Al_(2)O_(3)+P_(2)O_(5))含量减少,玻璃中Na_(2)O含量增加,玻璃化转变温度从685℃降低到622℃,当减少至摩尔分数为22%时,出现析晶峰且起始析晶温度降低。拉曼光谱表明Q_(P)^(4)对应的拉曼峰强度变低且逐渐向低波数方向移动,说明Na_(2)O作为网络修饰体使硅酸盐玻璃结构逐步解聚,玻璃的析晶能力逐渐增强。结果表明:当(Al_(2)O_(3)+P_(2)O_(5))摩尔分数为22%时热处理后的样品存在晶型转变,700℃热处理时以NaAlSiO_(4)霞石晶体为主,900℃时转变为以Na_(6.8)Al_(6.3)Si_(9.7)O_(32)霞石晶体为主。当(Al_(2)O_(3)+P_(2)O_(5))的摩尔分数为21%和20%时,热处理后的样品能稳定析出Na_(3)PO_(4)和Na_(6.8)Al_(6.3)Si_(9.7)O_(32)晶体。热处理后的样品析出了耐酸侵蚀性较差的富磷相和Na_(3)PO_(4)晶体,导致化学稳定性变差。

Alkali-aluminosilicate glasses with different(Al_(2)O_(3)+P_(2)O_(5))concentrations were prepared by the melting-quenching method,and their structural characteristics and crystallization behavior were studied by Raman spectroscopy,X-ray diffraction spectroscopy,and scanning electron microscopy.It is found that as the concentration of(Al_(2)O_(3)+P_(2)O_(5))decreases,the concentration of Na_(2)O increases,resulting in the glass transition temperature decreases from 685℃to 622℃.When the(Al_(2)O_(3)+P_(2)O_(5))concentration decreases to 22%(mole fraction),a crystallization peak appears and the onset crystallization temperature gradually decreases.The intensity of the Raman vibration band corresponding to Q_(P)^(4) becomes lower and gradually shifts towards low frequency,indicating that the Na_(2)O as a network modifier gradually depolymerizes the structure of silicate glass and enhances the crystallization ability of the glass.The results show that there is a crystalline transformation after heat treatment when the concentration of(Al_(2)O_(3)+P_(2)O_(5))is 22%(mole fraction).The main precipitation crystals are NaAlSiO_(4) nepheline at 700℃for 2 h while it transforms to Na_(6.8)Al_(6.3)Si_(9.7)O_(32) nepheline crystals at 900℃for 2 h.When the concentration of(Al_(2)O_(3)+P_(2)O_(5))is 21%and 20%(mole fraction),Na_(3)PO_(4) and Na_(6.8)Al_(6.3)Si_(9.7)O_(32) crystals are precipitated after heat treatment.After heat treatment,phosphorus-rich phase and Na_(3)PO_(4) crystals with poor acid corrosion resistance are precipitated,resulting in poor chemical stability.