Xradia 520 versa

The morphology of 2D-WEGs was investigated with a scanning electron microscope (SEM, FLexSEM 1000). Optical photos and videos are taken with the camera (SONY Alpha ILCE-7RM3). X-ray diffraction (XRD) patterns were recorded on a Bruker AXS D2 PHASER diffractometer with a Cu Kα irradiation source (λ = 1.54 Å). The 3D microstructure of 2D-WEG was examined by the X-ray nano-tomography system (ZEISS Xradia 520 Versa) and the structural tortuosity was calculated from X-ray nano-tomography images using the method as reported⁴⁰ . Fourier-transform infrared (FTIR) spectra were recorded by UATR Two FT-IR spectrometer. X-ray photoelectron spectroscopy (XPS) was measured by PHI Quantera II (Ulvac-Phi Incorporation) photoelectron spectrometer with Al Kα (1846.6 eV). Raman spectra measurements were carried out using a LabRAM HR Raman spectrometer (Horiba Jobin Yvon) with a 532 nm laser. Zeta potential was investigated by Zeta potential analyzer (Zetasizer Nano ZS90, Malvern, UK). Tensile and bending tests were conducted by using an Instron 5943 universal testing machine with a strain rate of 2 mm min⁻¹ for stretching. The laser (HGTECH LSU3EA) used for cutting was focused with an objective lens with a focal length of 170 mm.

A more detailed description of the scanning procedure is available in a previously published study^{34 (link)}. Here we provide a brief summary of experimental set-up. X-ray $\mu$ CT scans with X-ray microscope (Xradia 520 Versa; ZEISS, Pleasanton, CA, USA) were used in the current study of a 3D distribution of cracks and other features in the teeth samples. The general layout of the experiment consisted of the X-ray source, the specimen, and the detector. The distances between the source-sample and sample-detector were adjusted to achieve the maximum magnification with the full field-of-view of the tooth sample. For this experiment the following distances were used: source-sample =  $21\text{mm}$ and sample-detector =  $125\text{mm}$ . The sample projection images were obtained in absorption mode using geometrical magnification and a CCD detector resulting in a detector size of 2048 $\times$ 2048 pixels. To achieve the optimal signal-to-noise level (intensities of >5,000 grey value over low transmission regions), the exposure time of $5\text{s}$ was selected. The distances between the source, sample and detector resulted in a $5\times 5\times 5{\mathrm{\mu }\text{m}}^3$ voxel size which in this case defines the experimental resolution^{34 (link)}. The final result of the scanning procedure was four data-cubes of $\sim$ 10 ${}^3$ mm ${}^3$ ( $\sim$
${2000}^3$ ) voxels, containing values stored as 16-bit integers, with voxel edge of $\sim$
$5\mathrm{\mu }\text{m}$ .