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Aluminum nitride (AlN) is a covalently-bonded ceramic material which exhibits high thermal conductivity and electrical insulation, and is stable in an inert atmosphere at temperatures greater than 2000degC. The unique combination of these properties makes it an attractive candidate for applications in optoelectronics and other advanced materials.
Commercial aln powders are produced by two methods: direct nitridation of aluminum metal and carbothermal reduction-nitridation of alumina. Both of these processes produce different AlN particle sizes and shapes and entail different costs.
Synthesis of aln by plasma nitridation
A plasma-based method is a new technique for synthesizing aln powder that has advantages over traditional thermal nitridation techniques. It generates a large amount of active species at 550 degC and avoids the need to melt Al metal as a pre-synthesis step. This also enables mass production of AlN particles in a short reaction time.
SEM images of well-dispersed aln powders without agglomeration were obtained by this method at 550 degC for 2 min, Al: NH4Cl = 1:1. This was followed by thermal nitridation at 950 degC for 1 h, as shown in Figure 2.
Morphology of AlN/Al powdersproduced by the thermal nitridation technique is similar to that of the original Al ball-shape powders, but larger sized and more irregular as the temperature increased. As the reaction temperature increases, agglomeration becomes more serious in both powders.
To measure the powder dispersion stability, it is necessary to determine the change curve of the zeta potential, which is a function of the attraction and repulsion strength between powder particles. The original aln powder has a low zeta potential in the low pH phase, and the modified aln powder has a higher zeta potential in the high pH phase.