The thermodynamic state and kinetic process of low-temperature deoxygenation reaction of graphene oxide(GO) have been investigated for better understanding on the reduction mechanism by using Differential Scanning Calorimetry(DSC), Thermogravimetry-Mass Spectrometry(TG-MS), and X-ray Photoelectron Spectroscopy(XPS). It is found that the thermal reduction reaction of GO is exothermic with degassing of CO_2, CO and H_2O. Graphene is thermodynamically more stable than GO. The deoxygenation reaction of GO is kinetically controlled and the activation energy for GO is calculated to be 167 k J/mol(1.73 e V/atom).
Kuibo YinHaitao LiYidong XiaHengchang BiJun SunZhiguo LiuLitao Sun
The local thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics is measured and imaged by using a scanning thermal microscope (SThM) and complementary scanning electron microscope (SEM) based techniques at room temperature.The quantitative thermal conductivity for the AlN sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3ω method.A thermal conductivity of 308 W/m·K within grains corresponding to that of high-purity single crystal AlN is obtained.The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations,as demonstrated in the electron backscattered diffraction.A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites,as indicated by energy dispersive X-ray spectroscopy.
