Non-invasive fast imaging of grain microstructure of polycrystalline ceria with sub-micrometric spatial resolution is performed via time-domain Brillouin scattering. The propagation of a nanoacoustic pulse is monitored down to 8 μm deep in a 30 × 30 μm² area. Grains boundaries are reconstructed in three-dimensions via a two-step processing method, relying on the wavelet synchro-squeezed transform and the alphashape algorithm. Imaging contrast is improved by taking advantage of stronger sensitivity to anisotropy of transverse acoustic waves, compared with longitudinal waves. Utilization of transverse waves in the image processing reveals additional boundaries, confirmed by an electron backscattering diffraction pattern but not discerned using longitudinal waves. A buried inclined interface between differently oriented grains is identified by monitoring changes in amplitude (phase) of the portion of the signal associated with transverse (longitudinal) waves. Estimates of the inclination angle of this interface prove the sensitivity of our laser ultrasonic method to image inclined boundaries.

通过时域布里渊散射对具有亚微米空间分辨率的多晶氧化铈晶粒微观结构进行非侵入性快速成像。在 30 × 30 μm ^{2 中}监测深达 8 μm 的纳米声脉冲的传播区域。依靠小波同步压缩变换和alphashape算法，通过两步处理方法在三维重建晶粒边界。与纵向波相比，通过利用对横向声波的各向异性更强的敏感性来提高成像对比度。在图像处理中利用横波揭示了额外的边界，由电子背散射衍射图案证实，但使用纵波无法识别。通过监测与横向（纵向）波相关的信号部分的幅度（相位）变化来识别不同取向晶粒之间的掩埋倾斜界面。该界面倾角的估计证明了我们的激光超声方法对倾斜边界成像的敏感性。