Comparison of freeze drying and spray drying to obtain porous nanostructured granules from nanosized suspensions

Applied Surface Science

Rayón

et al. 2014

Versión / Versió:Preprint were used as starting materials. The coatings microstructure and phase composition were fully characterised using FEG-SEM and XRD techniques. Nanoindentation technique was used to determine the coatings hardness and elastic modulus properties.Results have shown that the addition of titania to alumina SPS coatings causes different crystalline phases and a higher powder melting rate is reached. The higher melted material achieved, when titania is added leads to higher hardness and elastic modulus when the same spraying parameters are used.

Section: Methodsmentioning

confidence: 99%

“…The main nanosuspensions properties are summarised in table 1 as given by the manufacturer. Both suspensions have been fully characterised in previous works [26][27].…”

Section: Methodsmentioning

confidence: 99%

Effect of TiO 2 addition on the microstructure and nanomechanical properties of Al 2 O 3 Suspension Plasma Sprayed coatings

Bannier

Applied Surface Science

Rayón

et al. 2014

“…Both suspensions were then reconstituted into sprayable granules in 2 steps: a) Spray-drying. Spray-dried agglomerates were obtained in a spray dryer (Mobile Minor, Gea Niro, Denmark) [8,10,11]. b) Thermal treatments.…”

Section: Feedstock Preparationmentioning

confidence: 99%

“…Still, the nanoparticles need to be previously agglomerated into a sprayable powder, as they can not be directly fed into the plasma torch [6][7][8]. This agglomeration process is usually done by using spray-drying [6][7][8][9][10][11] or freezedrying [11] from a nanoparticle suspension, frequently followed by a thermal treatment in order to decrease the granule porosity [6,8]. The quality of the feedstock depends on the characteristics of the initial nanosuspension, which should present high solid content, low viscosity and high stability.…”

Section: Introductionmentioning

confidence: 99%

Influence of the feedstock characteristics on the microstructure and properties of Al2O3–TiO2 plasma-sprayed coatings

Surface and Coatings Technology

Bannier

Benavente

et al. 2013

Atmospheric plasma spraying (APS) is an interesting technique to obtain nanostructured coatings due to its versatility, simplicity and relatively low cost. However, nanometric powders can not be fed into the plume using conventional feeding systems, due to their low mass and poor flowability, and must be adequately reconstituted into sprayable micrometric agglomerates.In this work, Al 2 O 3 -13wt%TiO 2 nanostructured and submicron-nanostructured powders were deposited using APS. The feedstocks were obtained by spray drying from two starting suspensions, prepared by mixing two commercial nanosuspensions of Al 2 O 3 and TiO 2 , or by adding nanosized TiO 2 and submicron-sized Al 2 O 3 powders to water. The spray-dried granules were heat-treated to reduce their porosity and the resultant powders were fully characterised.Optimisation of the deposition conditions enabled the reconstituted powders to be successfully deposited, yielding coatings that were well bonded to the substrate. The coating microstructure, characterised by SEM, was formed by semi-molten feedstock agglomerates surrounded by fully molten particles that act as a binder.Moreover, microhardness, adhesion, and tribological behaviour were determined, and the impact of the granule characteristics on these properties was studied. It was found that changing the feedstock characteristics allows to control the coating quality and properties.2

“…Handling of nanoparticulate systems is difficult and hazardous due to their volatility and the subsequent inhalation risks. One of the most extended routes to allow handling of nanoparticulate systems is the production of free-flowing agglomerates from colloidal suspensions subjected to a controlled drying process, such as spray and freeze drying [18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Dispersion of mixtures of submicrometer and nanometre sized titanias to obtain porous bodies

Sánchez

Molina

et al. 2013

Ceramics International

The stability and rheological behaviour of bimodal titania suspensions was studied.Bimodal mixtures were prepared by mixing nanosized TiO 2 powders with an average primary size of ~20-40 nm and surface area of ~50 m 2 /g and/or a colloidal titania suspension of the same nanopowders dispersed in water with a submicrometer sized titania. The dispersing conditions were studied as a function of pH, type and content of dispersant, and sonication time for a constant solids content of 30 vol.% (62 wt%). The mixtures were slip cast and presintered at low temperatures (800−1000 ºC) in order to obtain porous materials with anatase as the major phase. The pore size distribution, microstructure and phase composition were characterised using MIP, SEM and XRD techniques, respectively.