Intrinsic generation of OH groups in dry silicon dioxide upon thermal treatments

We show the existence of an intrinsic generation mechanism of OH groups in synthetic dry silicaupon thermal treatments. Samples are treated for ~160 h at 390 °C in He at 2.7 or 180 bar, and thegrowth of the OH IR absorption band at 3670 cm−1 is observed. An OH concentration of~10^18 cm^−3 is estimated. Possible contributions of reactions with molecules absorbed from theatmosphere are excluded. Reactions with H2O already contained in the samples are rejected by IRmeasurements. The observed OH generation is attributed to the reaction of network sites with H2already present in the material. Possible reaction paths are examined