含铬R_2O—CaO—Al_2O_3—SiO_2系统结晶质玻璃球状析晶机理的研究

Mechanism of Spheroidal Crystallization in R_2O-CaO-A1_2O_3-SiO_2 System Glasses Containing Chromium

采用顺磁共振(ESR)、扫描电镜(SEM)、能谱分析(EDAX)、X射线衍射(XRD)等实验方法,研究了Cr_2O_3对R_2O-CaO-Al_2O_3-SiO_2系统玻璃析晶行为的影响,并对其球状析晶机理进行了分析。球晶是由放射状的针形晶体所构成,尺寸约为几个毫米,且呈均匀分布,主晶相为β-CaSiO_3。析晶机理是玻璃中的铬在热处理过程中首先以铬钙尖晶石固熔体[CaCr_2O_4]的形式析出,然后β-CasiO_3以铬钙尖晶石为成核位析出放射状的针形晶体,各针形晶体之间为玻璃相。

The effects of Cr2O3 on the nucleation and crystallization of R2O-CaO-Al2O3-SiO2 system glasses have been investigated by means of ESR,STEM,EDAX,XRD,DTA and so on . The results show that the hase glass eontaining more than 1. 5 wt% Cr2O3 can be nucleated internally and converted to spheroidal erystals inlaid glass matrix. The spheroidal crystal consists of fibrous wollastonite crystals radiating from a centre . The residual glass phase filled the interstices between the fibres and the spherulltes. The spheruHte diameter ranges from 3.0 to 4.0 mm,depending upon the heat treatment schedules. EDAX analysis proved that the spheruHte centre composition enrich with Cr3+and Ca2+ions. During heat treatment process,the valence states of chromium changed from Cr6+ to Cr3+and precipitated Cr-spinel [CaCr2O4]simultaneously, the Cr-spinel could act as a nucleating center on which the principal crystalline phase of wollastonite grew epitaxially. The colse similarity of lattice parameters in some dimension of Cr-spinel and wollastonite made it possible to nucieate heterogeneously. From this study,a new kind of building material named Crystallized Glass can be obtained.