Temperature dependence of near-field radiative heat transfer above room temperature

Stefan-Boltzmann's law indicates that far-field blackbody radiation scales at the fourth power of temperature. The temperature dependence radiative heat transfer in near field is expected to be very different due contribution evanescent waves. In this work, we experimentally observe such deviation on thermal conductance by bringing a hot micrometric sphere nearfield room-temperature planar substrate, down separation distance few tens nanometers. influence materials assessed using either SiO2 or graphite spheres, and SiO2, InSb substrates. Temperature differences as large 900 K are imposed. A maximum near-field about 70 nW.K-1 found for graphite-graphite configuration. experimental results demonstrate exponent weakens field, ranging from 2.2 4.1, depending gap materials. These have broad consequences, particular design high-temperature nanoscale energy devices.