For the flow-synthesized HTs reported here, the surface area (SBET) does not change significantly when increasing the aging temperature from 65 to 80 °C, which is in agreement with results from Climent et al for the batch-synthesized samples . The biggest difference in SBET is observed for the Ni HT and the Co HT samples, showing an increase by 23 and 19 m 2 g -1 respectively for the samples aged at 80°C.