Fe ultra plus 55

Imaging
of ceramic fracture surfaces was performed with a scanning electron
microscope (Zeiss Fe-Ultra Plus 55) equipped with a field-emission
gun, Gemini lenses, and an Oxford Instruments EDX-Silicon drift detector
(50 mm², energy resolution < 127 eV @ Mn Kα).
Secondary electron (SE) images providing topological information and
backscattered electron (BSE) images showing z-contrast (see the Supporting Information) were acquired at short
working distances of around 3 mm and an accelerating voltage between
5 and 20 kV, with an InLens (ILs) SE and AsB (Angular selective Backscatter)
detector, respectively. To limit charging, the scanning electron microscopy
(SEM) samples were coated with a few nanometer-thick layer of carbon
with a Cressington Carbon Coater 108 carbon/A (2 × 15 s, 4.0
V, background pressure 0.06 mbar) and additionally adhered to the
sample holder with copper tape. Image as well as grain size analysis
was performed with ImageJ (V1.52a) and the SmartTiff (V3.0) software
package from Zeiss.

Electron microscopy images were acquired using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM instrument (Zeiss FE-Ultra Plus 55) is equipped with a field-emission gun and Gemini lenses and was used at short working distances of around 3 mm and an accelerating voltage between 5 and 10 kV, with InLens and SE detectors. The diameters of the electrospun fibers were evaluated from the SEM images by measuring the diameter with the software program ImageJ (V1.52a). The TEM (JEOL JEM-F200 TEM) was operated at 200 ​kV and is equipped with a cold field-emission electron source and a TVIPS F216 2 k by 2 k CMOS TEM camera. Particle size distribution plots before and after sintering and fiber diameters after thermal treatment were obtained from TEM images using the EM Measure software program from TVIPS.