We are revealing the mechanism of non-Fourier heat conductions in materials at nanoscale using the thermon gas model,which is based on the thermomass concept by assigning effective mass to the thermal energy according to the Einsteins energy-mass equivalence.We introduce the gas dynamic equations to describe the macroscopic conduction behavior of thermal energy in materials based on similarity of microscopic statistical theories of gas molecules and thermons/phonons.By considering the "rarefied gas" effects,we are therefore able to study and reveal the mechanism of non-Fourier conduction in nanoscale materials from the point of view of thermon gas model.This model has been validated for both the transient and the steady-state heat conduction in nanomaterials.For transient conduction,the unphysical temperature distribution under zero predicted by the other models does not appear in the predictions by the present model.The steady-state non-Fourier heat conduction equation derived by the present model has been applied to predict the effective thermal conductivities of nanomaterials.The temperature and size dependences of effective thermal conductivities of nanofilms,nanotubes and nanowires from the present predictions agree well with the available data from experiments or MD simulations in the literature,which again proves the validity of the new heat conduction equations.Our studies suggest that(1)the non-Fourier heat conduction in nanomaterials is only an external manifestation of nonlinear heat transfer at nanoscale,but not the change of intrinsic thermal conductivity of materials;(2) the inertial effect of high-rate heat and the interactions between heat/thermons and surface in confined nanostructures dominate the non-Fourier heat conduction in nanoscale materials.This new model is also compatible with the existing thermodynamic laws.