Nnormal exhalation, the diaphragm and intercostal muscles relax to contract the chest, which creates a positive pressure. this is what type of process?

This is the passive type of process.

As the diaphragm relaxes, the pleural cavity contracts, which exerts pressure on the lungs. As a consequence, the volume of the lungs reduces and the air is passively pushed out of the lungs. Exhalation is passive, thanks to the elastic properties of the lungs.