The dust formation process in the winds of Asymptotic Giant Branch stars is discussed , based on full evolutionary models of stars with mass in the range 1 M _ { \odot } \leq M \leq 8 M _ { \odot } , and metallicities 0.001 < Z < 0.008 .
Dust grains are assumed to form in an isotropically expanding wind , by growth of pre–existing seed nuclei .

Convection , for what concerns the treatment of convective borders and the efficiency of the schematization adopted , turns out to be the physical ingredient used to calculate the evolutionary sequences with the highest impact on the results obtained .

Low–mass stars with M \leq 3 M _ { \odot } produce carbon type dust with also traces of silicon carbide .
The mass of solid carbon formed , fairly independently of metallicity , ranges from a few 10 ^ { -4 } M _ { \odot } , for stars of initial mass 1 - 1.5 M _ { \odot } , to \sim 10 ^ { -2 } M _ { \odot } for M \sim 2 - 2.5 M _ { \odot } ; the size of dust particles is in the range 0.1 \mu m \leq a _ { C } \leq 0.2 \mu m. On the contrary , the production of silicon carbide ( SiC ) depends on metallicity .
For 10 ^ { -3 } \leq Z \leq 8 \times 10 ^ { -3 } the size of SiC grains varies in the range 0.05 \mu { m } < { a _ { SiC } } < 0.1 \mu m , while the mass of SiC formed is 10 ^ { -5 } { M } _ { \odot } < { M _ { SiC } } < 10 ^ { -3 } { M } _ { \odot } .

Models of higher mass experience Hot Bottom Burning , which prevents the formation of carbon stars , and favours the formation of silicates and corundum .
In this case the results scale with metallicity , owing to the larger silicon and aluminium contained in higher–Z models .
At Z= 8 \times 10 ^ { -3 } we find that the most massive stars produce dust masses m _ { d } \sim 0.01 M _ { \odot } , whereas models of smaller mass produce a dust mass ten times smaller .
The main component of dust are silicates , although corundum is also formed , in not negligible quantities ( \sim 10 - 20 \% ) .