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The properties of a volcanic ash glass obtained from the Eyjafjallajökull eruption of 2010 were studied. Crystallization experiments were carried out on bulk and powdered glass samples at temperatures between 900 and 1300 °C. Iron oxides, Fe3O4 and Fe2O3, and a silicate plagioclase, (Na,Ca)(Si,Al)4O8, were observed. Bulk samples remained mostly amorphous after up to 40 h at temperature. Powdered glass samples showed increased crystallinity after heat treatment compared to bulk samples. The average coefficient of thermal expansion of the glass was 7.00 × 10−6 K−1 over 25–720 °C. The Vickers hardness of the glass was 6–7 GPa and the indentation fracture toughness, 1–2 MPa √m Values for density, elastic modulus, and Poisson’s ratio were 2.52 g/cm3, 75 GPa, and 0.24, respectively. The viscosity of the glass was determined experimentally and compared to three common models from the literature. The implications for the deposition of volcanic ash on hot section components of aircraft turbine engines are discussed.

Abstract

Titania (TiO2) was introduced into a model calcium‐magnesium aluminosilicate (CMAS) glass in additions of 5‐20 wt%. The crystallization behavior of the mixtures was characterized over a series of temperature profiles and compared to that of CMAS alone. X‐ray diffraction, differential scanning calorimetry, light and scanning electron microscopy, and energy dispersive spectroscopy were used to characterize glass and crystalline products. Titania additions in the amount of approximately 12.5‐20 wt% aided in the formation of CaTiO3 from melts equilibrated at either 1300 or 1500°C and cooled at 10°C/min. Holding CMAS + TiO2 (TiO2 ≥ 10 wt%) at 900°C after cooling from 1300/1500°C resulted in the formation of additional crystalline phases including melilite, paqueite, and diopside. Implications for CMAS interactions with thermal and environmental barrier coatings are discussed.