Etchants alkaline based

In particular, the hillocks formed on the (100) surface are crystallographic structures bounded by four (111) planes resulting from the anisotropic etching and their formation directly contributes to the roughness of the surfaces. Hillocks may, under certain conditions, form in HF-based solutions, " but most commonly in alkaline etchants. ° Because the (111) surface etches very slowly, the formation of hillocks leads to a decreased etch rate. ... 

Several pretreatments are recommended by the British Standards Institute [66]. In essence, these methods cover solvent and/or alkaline degreasing followed by surface abrasion or by the use of a chemical etchant. Grit blasting, using chiU-cast iron shot, glass or alumina, is the ideal abrasion technique. Etchants based on sulphuric, hydrochloric or phosphoric acid are recommended etching conditions are 5-30 min at temperatures from ambient to 65°C. 

Etchants and catalysts (or solvents) of cBN also react with cBN (see Secs. II.D.2.b. and IV.A.2). They are alkaline or alkaline earth metals, their nitrides and boron nitrides, H2O, alkaline salt etchants (NaOH, LiOH, KOH, Na2C03, NaNOs), and acid etchants (HNO3 + H2O). The reaction occurs promptly at high temperatures (usually above 1300-1400°C at high pressures). As described in Sec. II.D.2.b, some base etchants appear to react more rapidly with (111) nitrogen surfaces of cBN crystals and acid etchants with (111) boron surfaces. 

---