I'm trying to sinter inorganic oxide powder and achieve density close to theoretical. I first agglomerate powder and then sinter it via SSS process. Because I can't compact the powder properly I can't achieve more than 80% of theoretical density. I’m thinking about trying LPS with sintering aids but my concern is that agglomerated particles will start sintering to each other.
Does anybody has successful experience sintering free flowing powder via LPS?
The only way to sinter an agglomerated powder to 100% density without the agglomerates joining together is to heat it in a hot gas stream (plasma). You need two things at the same time: temperature close to or even higher than melting point and separate agglomerates. These two conditions only exist in plasma gas, where the particles are introduced with a gas stream. This process already exists on an industrial scale and is called plasma spheroidization.
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I'm fully aware about plasma spheroidization as we have it but I can't use as my compound melts incongruently.
It is not easy to control such process since it going to have two phases; solid agglomerate oxide powder in powder melt matrix. therefore, this case should considered as similar to the sintering in composite. If so, the driving force for liquid phase sintering become the reduction of physiochemical potential by dissolving of original agglomerates. This forced caused by the different in the growth behavior of agglomerates from that in the matrix and this could raise the tendency for abnormal grain growth during sintering leading to unwanted defects. For that I say it is not easy process to control but it is possible.
Best regards
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