微晶玻璃的中子衍射研究

Neutron Diffraction Study on Glass-Ceramics

应用中子衍射方法和Rietveld法全谱图拟合,研究了微晶玻璃在缓冷和急冷两种热处理条件下微结构和内应力的变化。与缓冷处理相比,急冷处理使析出的β硅灰石晶体的晶胞沿着3个晶轴方向进一步拉伸,晶体受到残余非晶相的拉应力作用更大,但原子位置无序相对要小,过高的局部应力导致了应力集中区内微裂纹的出现。急冷处理样品在高角度处的非晶峰强度远高于缓冷处理样品,表明急冷处理样品中残余玻璃相的比例更高。中子衍射获得的应变值与X射线衍射结果有显著差别,显示材料体内应力和表面应力有很大不同。中子衍射是测定大块微晶玻璃试样的平均残余应变和研究其复杂的两相共存结构的一种可行方法。

Neutron diffraction and Rietveld investigate the evolution of microstructure full-pattern-fitting methods were applied to and internal stress of glass-ceramics under slow cooling and rapid cooling. Comparing to slow cooling, rapid cooling results in further elongation of the three axes for the unit cell of precipitated β-wollastonite crystal, and larger tensile stress from the residual glass phase, but smaller atomic displacive disorder. Excessive local stress results in the ermergence of micro crack in the area where stress centralizes. The intensity of amorphous peaks at high diffraction angles for the rapid cooling sample is much higher than that of the slow cooling sample, showing that the percentage of the residual glass phase in the rapid cooling sample is higher than that in the slow cooling sample. The strain value measured by neutron diffraction is very dif- ferent from that of X-ray difffraction, showing that the internal stress differs signifi- cantly from the stress existing at the surface. Neutron diffraction is a practical method for determination of average residual strain in bulk glass-ceramics and for investigation of its complex microstructure where crystalline phase and glass phase coexist.