Influence of Solution Volume on the Dissolution Rate of Silicon Dioxide in Hydrofluoric Acid

Experimental data and modeling of the dissolution of various Si/SiO₂ thermal coatings in different volumes of hydrofluoric acid (HF) are reported. The rates of SiO₂‐film dissolution, measured by means of various electrochemical techniques, and alteration in HF activity depend on the thickness of the film coating. Despite the small volumes (0.6–1.2 mL) of the HF solution, an effect of SiO₂‐coating thickness on the dissolution rate was detected. To explain alterations detected in HF activity after SiO₂ dissolution, spectroscopic analyses (NMR and FTIR) of the chemical composition of the solutions were conducted. This is associated with a modification in the chemical composition of the HF solution, which results in either the formation of an oxidized species in solution or the precipitation of dissolution products. HF₂^? accumulation in the HF solution, owing to SiO₂ dissolution was identified as the source of the chemical alteration.     

Complete Caps in with Both N and q Odd

In this work, an inductive method to construct complete caps in affine spaces is provided. Using this tool, for odd and q odd, complete caps smaller than all already known ones are obtained.