  In the framework of swift heavy ion - matter interaction, the thermal spike
has proved its worth since nearly two decades. This paper deals with the
necessary refinement of the computation due to the kind of materials involved
i.e. nanomaterials such as multilayered systems or composite films constitued
of nanocylinders or nanospheres embedded in matrix. The three dimensional
computation of the thermal spike model is applied for the first time in layers
containing spherical nanoparticles embedded in a silica matrix. The temperature
profile calculated at each point (x,y,z) of the target for times up to
$10^{-10}$s allows a possible explanation of the particle shape change under
irradiation with swift heavy ions having an energy of several MeV/u.m.a. The
comparison made with the former 2D version of the code applied to cylindrical
gold nanoparticles confirms the validity of the present 3D version.
