2.2.2. Preparation of C@ZrO2 microspheres
Carbon microspheres were prepared according to the literature . 250 mL 0.29 M sucrose aqueous solution was heated at 170 °C for 4 h in PF-06463922 Teflon-lined autoclave to yield carbon microspheres after centrifuge, water and ethanol washes. 0.18 g (0.015 mol) as-synthesized carbon microsopheres were dispersed in 300 mL ethanol/MeCN (v/v=4/1) solution. 18 mL de-ionized water was added into above suspension. 2.09 g ZNP (0.005 mol) was dissolved in 200 mL ethanol/MeCN (v/v=4/1) solution. Then the half-life above ZNB solution was added into the carbon microsphere suspension dropwisely. Upon completing addition of ZNB, the whole mixture continued to react at 75 °C for 1 h. Powder was acquired after centrifuge, 3 times ethanol washes and vacuum drying at 80 °C.
2.2.3. Carbothermal reduction
The as-synthesized core–shell particles were heated at 1400 or 1500 °C for 2 h in graphite crucibles under Argon atmosphere. Major reaction can be described as:ZrO2+3C=ZrC+2CO(g).