A method for assessing the volatility of oxides in high-temperature high-velocity water vapor

Environmental resistance of a Ti2AlC-type MAX phase in a high pressure burner rig

“…Both Al(OH) 3 and TiO(OH) 2 pressures and calculated loss rates are low compared to Si(OH) 4 . Furthermore, these estimated loss rates appear somewhat less than the linear fit measured at ∼0.012 mg/cm 2 .…”

“…In order to gain more insight regarding the loss rates and pertinent species, an attempt was made to predict volatility rates according to mass transport models used previously [1,4,34]. This exercise is meant to give a general perspective rather than precise modeling since uncertainties will always remain regarding the appropriate species.…”

“…Furthermore, only one experiment (preoxidized sample) directly lends itself to this discussion since the other tests exhibit only weight gains. Volatility rates of oxides can be calculated from the equilibrium vapor pressure of the hydroxide species and the gas conditions in the burner using the mass transport equation for laminar (or turbulent) flow in a moving boundary layer [32][33][34]1,4]. Using published values for the thermodynamic energy of compound formation, these pressures and fluxes were calculated (i.e., Jacobson) and listed in Table 3 [32, 37,38].…”

“…Other studies also indicate high rates for TiO(OH) 2 volatility [39,4]. Some uncertainty has been raised regarding the thermodynamic data used for TiO(OH) 2 due in part to analysis difficulties for the low yields of condensed species in the transpiration experiment [4,32].…”

“…For the case of SiC and SiC composites, this entails the formation of the volatile Si(OH) 4 species [1,2]. A number of test techniques have evolved to study the phenomenon, including standard furnace thermogravimetric (TGA) and steam-jet [3,4]. Early demonstrations also used high pressure burner rigs where jet fuel was combusted and projected at high velocity over SiC and Si 3 N 4 based samples [5][6][7][8], as well as a turbine combustor demonstration test [9].…”