Wpływ mikrostruktury na zmiany termiczne w bentonicie

Ewa Stępkowska, Stephan Arthur Jefferis



Indications were obtained by SEM and other methods that in a bentonite slurry (sodium smectite) either flocs or clusters or parallel structure may form, depending on the stirring energy and storing time of the slurry, thus depending on particle interactions.
Thermal behaviour and water sorption depend as well on preparation of the slurry, thus they are related to microstructural features (Stępkowska and Jefferis, 1983).
On the external surface of samples of bentonite slurries dried at 45°C there was formed a crust of parallel structure. Its quantity was dependent on preparation of the slurry (concentration, stirring storing time energy). This structure indicated increased sorption properties. When heated at 800°C (1 hr or 18 hrs) this external crust did not change colour and indicated an increased Na2O content (7.64% as compared to 5.62% in powder sample). By SEM of heated samples either parallel particle arrangement was shown or their fusion into a solid block. The internat core of the dried sample ( 4.45% Na2O) assumed brown colour at 800°C and SEM indicated a much more open structure. This structure was formed either of partly fused clusters or of molten flocs which resulted in cheese - like structure with big circular holes.
SEM study of samples stirred at various stirring energy indicated that various types of microstructure result in formation of various minerals in heating: feldspar may form from cluster or parallel structure, zeolites may form from flocs and paragonite develops from parallel structure.

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