Influence of solids concentration on the microstructure of suspension plasma sprayed Y-TZP/Al2O3/SiC composite coatings

Effect of fructose-containing feedstocks on the microstructure of multicomponent coatings deposited by suspension plasma spraying

“…The flow curves show the evolution of shear stress with shear rate for different sonication times and the enlargement of the curves is represented for a better evaluation in the high shear rate range. InFigure 2a, the flow curves are very similar to those reported in other previous research[28,32], i.e. suspensions show a practically Newtonian behaviour with a little trend of dilatant fluid at high shear rates.…”

“…The higher the amount of added fructose, the greater the reduction of TSI parameter with time. For the same reason, the increase of solids content from 20 to 30 wt.% favours the stabilisation of the suspension due to the greater electrostatic repulsion between particles, as previously reported [32]. According to equipment specification, an index value lower than 10 TSI indicates low sedimentation tendency, for this reason an even lower TSI value of 5 has been established in order to estimate an optimum stability time for the SPS process.…”

“…As set out in the introduction, multifunctionality of fructose in ceramic processing together with its high compatibility in aqueous suspensions allow to use this saccharide in large amounts in ceramic suspensions. However, the viscosity of the suspension must be kept below certain limits in order not to compromise the feeding of the suspension into the plasma torch as reported elsewhere [29,32]. For this reason, preliminary experimentation was carried out to determine the effect of fructose addition on water viscosity.…”

“…However, an increase in the crystallinity (full width at half maximum of tetragonal zirconia peaks decrease) of the main phase (tetragonal zirconia) can be observed as the fructose content grows. This crystallinity enhancement could be, in some extent, related to the effect of fructose reported in the literature [25] which favours the development of tetragonal zirconia crystalline phase while the drastic change in the coating structure could also affect.As previously reported[32], SiC was quantified by Rietveld analysis in the highest intensity peak at d = 35.65º Å in order to estimate the amount of preserved SiC in the final coatings. Rietveld method reveals that remaining percentage of silicon carbide is about 50% in all the coatings (with and without fructose) indicating that fructose content in the suspension feedstock does not appear to affect to the decomposition of the SiC.…”

Suspension and Solution Precursor Plasma and HVOF Spray: A Review

“…Similarly, using high solid content (or lower liquid medium) in feedstock could be cost-and energy-efficient as less energy is required to evaporate the suspension medium. (Ref [24][25][26]. Sometimes, the coatings developed using a feedstock with higher solid content are thicker.…”