A buffered oxide etch solution of 6:1 volume ratio of 40% NH4F to 49% HF will etch
thermally grown oxide at approximately 2 nanometres per second at 25 degrees Celsius. HF solution buffered with can be used to provide better etching of
zeolite for the creation of larger pores, to improve the characteristically poor rate of diffusion in these microporous structures. Simple HF solutions (and other acidic methods of etching) show high selectivity in removing
aluminum from zeolites, reducing the number of potential
Brønsted acid sites, and subsequently reducing certain
catalytic performance. However, the addition of a buffer results in a solution with more HF and present, which removes Al and Si in more equal proportion. == References ==