S 4800 cold field emissionscanning electron microscope

Atomized spherical magnesium powder (Mg) has a particle size <45 μm and purity of 99.9%, Shanghai Shuitian Material Technology Co., Ltd., Shanghai, China. The amorphous boron powder (B) had a particle size of 1~3 μm and purity of 99.7%, Liaoning Yingkou Fine Chemical Company. MgB₂ was prepared by a combination of mechanical alloying and heat treatment.
The following instruments were used: a vibrating high-energy ball mill (Beijing Nonferrous Metals Research Institute, Beijing, China), a vacuum operation box (ZKX-2, Nanjing Nanda Instrument Factory, Nanjing, China), a tube furnace (SGL-1700-II, Shanghai Jujing Precision Instrument Manufacturing Co., Ltd., Shanghai, China), an X-ray diffractometer (D8 ADVANCE, Bruker, Karlsruhe, Germany), an S-4800 cold field emission scanning electron microscope (Hitachi, Tokyo, Japan), and a microcomputer automatic calorimeter (TRHW-7000E, Hebi City Tianrun Electronic Technology Co., Ltd., Hebi, China).

SEM was performed to examine the leaf tissues of G. pentaphyllum. Small sections of the leaves, measuring 2 mm × 2 mm, were selected from a consistent location near the middle vein. The samples (1 g) were fixed with 2.5% glutaraldehyde in a phosphoric acid buffer (pH = 7.4, 5 mL) for 12 h. After fixation, the samples were rinsed three times with 0.1 M phosphate buffer (pH 7.4) for 10 min each. Subsequently, a stepwise dehydration process was carried out using ethanol at concentrations of 30%, 50%, 70%, 90%, 95%, and 100% (10 mL/per step and 20 min per step) and a temperature of 4 °C. This gradual dehydration procedure effectively eliminated moisture from the leaf tissues. The dried leaves were then placed in an oven at 65 °C for 30 min until their complete desiccation. Finally, the prepared samples were analyzed using a Hitachi S-4800 Cold Field Emission Scanning Electron Microscope.