Alumina plasma-sintered

SEM image of the fracture surface of 5.7 vol% SWCNT-Fe-Al203 composite densified by spark plasma sintering (SPS) of a mixture of nanometric alumina and ropes of SWCNTs. Reprint from Nature Materials, No. 2, 2002, pp. 38-42, Zhan G.-D., Kuntz J.D., Wan J. and Mukherjee A.K., Single-wall carbon nanotubes as attractive toughening agents in alumina-based nanocomposites, with the permission of Nature Materials and of the authors (http // www.nature.com/nmat/index.html). 

Fig. 2.1 Photographs of representative alumina (AI2O3) ceramics that were spark plasma sintered at a 1250 °C, b 1300 °C, and c-d 1350 °C, using the pretreated (a-c) and the untreated AI2O3 powder (d). Reproduced with permission from [53]. Copyright 2010, John Wiley Sons...

Kim BN, Hiraga K, Morita K, Yoshida H (2007) Spark plasma sintering of transparent alumina. Scripta Mater 57 607-610... 

Suarez M, Fernandez A, Menendez JL, Tonecillas R (2009) Grain growth control and transparency in spark plasma sintered self-doped alumina materials. Scripta Mater 61 931-934... 

Alvarez-Clemares I, Mata-Osoro G, Fernandez A, Lopez-Esteban S, Pecharroman C, Palomares J et al (2010) Transparent alumina/ceria nanocomposites by spark plasma sintering. Adv Eng Mater 12 1154-1160... 

Roussel N, Lallemant L, Durand B, Guillemet S, Ching JYC, Fantozzi G et al (2011) Effects of the nature of the doping salt and of the thermal pre-treatment and sintering temperature on spark plasma sintering of transparent alumina. Ceram Int 37 3565-3573... 

Grasso S, Hu CF, Maizza G, Kim BN, Sakka Y (2011) Effects of pressure application method on transparency of spark plasma sintered alumina. J Am Ceram Soc 94 1405-1409... 

Stuer M, Zhao Z, Aschauer U, Bowen P (2010) Transparent polycrystalline alumina using spark plasma sintering effect of Mg, Y and La doping. J Eur Ceram Soc 30 1335-1343... 

Jin XH, Gao L, Sun J (2010) Highly transparent alumina spark plasma sintered from common-grade commercial powder the effect of powder treatment. J Am Ceram Soc 93 1232-1236... 

Aman Y, Gamier V, Djurado E (2009) Influence of green state processes on the sintering behaviour and the subsequent optical properties of spark plasma sintered alumina. J Eur... 

In Fig. 4.61, the Young s modulus and hardness are shown for textured alumina obtained by spark plasma sintering [henceforth SPS] of undoped commercial... 

In this context, the aims of this study are to clarify the effect of different fast sintering techniques such as microwaves field at 2.45 GHz and external pulsed electrical field (Spark Plasma Sintering-SPS) on densification behavior of zirconia dispersed alumina nanopowders, on the microstructure and mechanic properties and to enhance the mechanical properties of the sintered composites. 

Z. Shen, M. Johnsson, Z. Zhao, M. Hygren Spark Plasma Sintering of Alumina. J. Am. Ceram. Soc. 85, p.l921-1927, (2002)... 

Experimental work is reported on the rate of sintering of alumina compacts sintered in a microwave-induced plasma. It is shown that the sintering rate is very much greater for plasma-sintered specimens than for specimens sintered by conventional means. Evidence indicates the generation of plasma inside the pores of the compact, and the increased rate of densification is related to an increased rate of diffusion. 

Fig. 3. Fracture surfaces of fine-grained plasma-sintered and coarse-grained conventionally-sintered alumina bars. 200 A of aluminum vacuum-deposited to increase reflectivity. Magnification x20.

Further studies are in progress on the kinetics of the plasma sintering process as observed in Linde A and other aluminas. Preliminary work on other oxides such as beryllia, titania, magnesia, zirconia, hafnia, and thoria shows positive effects in some cases but not in others. The reasons for this behavior are still conjectural, but may be connected with particle size and distribution, with the presence of strongly chemisorbed species, or with the type of crystal structure of the oxide concerned. Of special interest is the mechanism which prevents or at least minimizes the rate of grain growth in plasma-sintered material. 

X. Zhou, D. M. Hulbert, J. D. Kuntz, R. K. Sadangi, V Shukla, B. H. Kear, and A. K. Mukheijee, Superplasticity of Zirconia-Alumina-Spinel Nanoceramic Composite by Spark Plasma Sintering of Plasma Sprayed Powders, Mater. Sci. Eng., A394,353-359 (2005). 

Other potential applications are ceramic powders coated with their sintering aids, zirconia coated withyttria stabilizer, tungsten carbide coated with cobalt, or nickel, alumina abrasive powders coated with a relatively brittle second phase such as MgAl204 and plasma spray powders without the segregation of alloying elements. 

Khor K A, Yu L G, Li Y. Spark plasma reaction sintering of Zr02 mullite composites from plasma sphe-roidized zircon/ alumina powers. Mater Sci Eng A, 2003, 339 (12) 286-296,... 

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