A Thermo-Chemical Surface Treatment of AlN Powder for the Aqueous Processing of AlN Ceramics

Olhero, Susana M.; Novak, Saša; Oliveira, Mónica; Krnel, Kristoffer; Kosmač, Tomaž; Ferreira, José Maria F.

doi:10.1557/jmr.2004.0097

Cited by 20 publications

(46 citation statements)

References 12 publications

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“…These results are according to other values reported in literature. 21 Figure 1(b) shows that adding 1 wt% anionic dispersant Duramax 3005 caused significant shifts in the values of pH IEP toward the acidic range, especially in the case of sintering additives. At the inherent pH of the suspensions (pH ∼8.5), the dissociated polyanionic groups will strongly adsorb at the surface of the positively charged particles of CaF 2 and YF 3 powders, reversing the surface charge signal.…”

Section: B Dispersing Ability Of the Powders And Characterization Ofmentioning

confidence: 98%

“…The powder was thermochemically treated with aluminium di-hydrogenphosphate (Bindal A, TKI, Hrastnik, Slovenia) species following a procedure reported elsewhere. 21 The aim was to deagglomerate them and reduce their particle sizes as much as possible to enhance the degree of homogeneity and obtain a good distribution of the sintering additives in aqueous suspensions of AlN. A polyacrilic acid (Duramax 3005, Rohm and Haas, Lauterbourg, France) was used as the dispersant.…”

Section: A Materials and Characterization Techniquesmentioning

confidence: 99%

“…Based on the electrophoretic measurements and on some results already reported, 21,22 aqueous suspensions with 50 vol% powder mixtures containing different weight proportions of AlN/CaF 2 /YF 3 were prepared using the optimized dispersion conditions (1 wt% Duramax 3005). Table I summarizes the different compositions tested and the respective sample codes.…”

Section: B Preparation and Characterization Of Suspensionsmentioning

confidence: 99%

“…However, organic solvents are expensive, unsafe, and volatile, requiring the control of emissions into the atmosphere. These drawbacks pose new challenges to the scientific community, and much research has been undertaken in recent years aimed at replacing the traditional organic solvents with water [21][22][23][24][25][26][27] and sintering AlN powders at temperatures lower than those typically used. [28][29][30][31][32] The achievement of these goals would have positive impacts at different levels (scientific, technologic, environment, economic, health, and other societal aspects).…”

Section: Introductionmentioning

confidence: 99%

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AlN ceramics processed by aqueous slip casting

2006

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Fully dense aluminium nitride (AlN) ceramics consolidated by aqueous slip casting were obtained after sintering at 1750°C for 2 h. The obtained samples were characterized by Vickers hardness (1000 Hv), flexural strength (200 MPa) and thermal conductivity (115 W/mK). YF 3 and CaF 2 were used as sintering additives in total amounts ranging from 5 to 7 wt% in YF 3 /CaF 2 weight ratios of 1.25, 1.5, and 2. The compatibility between the thermochemically treated AlN powder and the sintering additives in the aqueous suspensions was investigated by rheological and zeta potential measurements. Highly concentrated (50 vol%) and well-dispersed suspensions could be prepared and used to consolidate homogeneous green bodies by slip casting. The phosphate species used to protect the surface AlN particles against hydrolysis could no longer be detected at temperatures higher than 1400°C. X-ray diffraction results revealed that all the new crystalline phases formed upon sintering belong to the system Al-Y-O-Ca, but their specific compositions as well as the thermal properties of the sintered materials were shown to depend on the total amount and ratio of sintering aids.

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Section: B Dispersing Ability Of the Powders And Characterization Ofmentioning

confidence: 98%

Section: A Materials and Characterization Techniquesmentioning

confidence: 99%

Section: B Preparation and Characterization Of Suspensionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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AlN ceramics processed by aqueous slip casting

2006

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“…Formic acid was added to adjust the pH value to about 4 for AlN and Al 2 O 3 particles and pH 3 for MgO particles to reach the higher zeta-potential [25,26]. A silane coupling agent (SCA) was added to the solution for functionalization of the particles and the solution underwent further sonication to allow hydrolysis and silanol formation.…”

Section: Materials and Sample Preparationmentioning

confidence: 99%

Modelling of the thermal conductivity in polymer nanocomposites and the impact of the interface between filler and matrix

Kochetov¹,

Korobko²,

Andritsch³

et al. 2011

J. Phys. D: Appl. Phys.

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In this paper the thermal conductivity of epoxy-based composite materials is analysed. Twoand three-phase Lewis-Nielsen models are proposed for fitting the experimental values of the thermal conductivity of epoxy-based polymer composites. Various inorganic nano-and microparticles were used, namely aluminium oxide, aluminium nitride, magnesium oxide and silicon dioxide with average particle size between 20 nm and 20 µm. It is shown that the filler-matrix interface plays a dominant role in the thermal conduction process of the nanocomposites. The two-phase model was proposed as an initial step for describing systems containing 2 constituents, i.e. an epoxy matrix and an inorganic filler. The three-phase model was introduced to specifically address the properties of the interfacial zone between the host polymer and the surface modified nanoparticles.

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The Hydrolysis of AlN Powder – A Powerful Tool in Advanced Materials Engineering

Kocjan

2018

The Chemical Record

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The tendency for aluminium nitride (AlN) powder to undergo hydrolysis, which can lead to a complete degradation of the material, is unique in metal nitrides. Although this form of hydrolysis has been known for a long time, it is generally considered as a nuisance, because it prevents the aqueous powder processing of AlN-based ceramics. However, careful investigations of the course of hydrolysis, the reaction kinetics and the evolution of aluminium hydroxides have uncovered exceptional possibilities for the exploitation of this naturally driven process in the area of advanced materials engineering. It can be employed as superior synthesis path for hierarchically-assembled, mesoporous alumina powders or coatings consisting of 2D nanocrystalline lamellas. The beneficial surface characteristics of the powder serve as an ideal template for further modifications useful in catalysis, while the powder's flowability enables facile preparation of high-performance hierarchically porous structures. The coatings, on the other hand, are suitable as templates for superhydrophobic surfaces or as adhesive coatings for cementing zirconia dental ceramics. Finally, the hydrolysis-assisted solidification (HAS) process has proved to be an important asset in the processing science and technology for fabrication of porous and dense ceramics and nanocomposites.

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A Thermo-Chemical Surface Treatment of AlN Powder for the Aqueous Processing of AlN Ceramics

Cited by 20 publications

References 12 publications

AlN ceramics processed by aqueous slip casting

AlN ceramics processed by aqueous slip casting

Modelling of the thermal conductivity in polymer nanocomposites and the impact of the interface between filler and matrix

The Hydrolysis of AlN Powder – A Powerful Tool in Advanced Materials Engineering

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