Polycrystalline silicalite-1 layers: texture and kinetics of growth

HF etching of as-synthesized polycrystalline silicalite-1 layers caused formation of deep sharp slits along grain boundaries and thus it visualized individual crystal blocks. Contrary to this result etching of calcined layers led to a kind of a negative image represented by preserved thin shells at crystal boundaries which were found to be impregnated by carbon residues formed during template removal. Results of etching experiments together with results of recent XPS strongly indicate a presence of a thin layer at the interfaces of neighbouring crystals which is composed of only partially consolidated fine particles of silica material.