Papers by Keyword: Hydrothermal Degradation

Abstract: Hydrothermal degradation (HTD) experiments of lawn-grass by the catalytic action of low acid were carried out in the pilot digestor. The effect of the low acid on treated lawn-grass products was investigated in different treatment severities. A severity parameter which combines time and temperature was introduced for comparing results among experiments. The results show that, with the severity increasing, the weight of the solid products, the hemicellulose and cellulose content remarkably decrease; the conversion rate of the organic matter increases; the HTD products by low acid catalysis reach stable in the low severities. At the same time, the soluble sugars and the acetic acid content increase until the treatment severity is over 4.05, however, and furfural content always increases in the liquid products.

Abstract: Effect of low-temperature degradation of 3Y-TZP ceramics (polycrystalline zirconia stabilized by 3mol% of yttria) on contact damage resistance has been studied applying scratch testing technique. Friction properties and damage mechanisms have been investigated for various degrees of hydrothermal ageing, i.e. for different grain sizes and crystallography, and for different thickness of the degraded surface layer. The onset of plastic damage, catastrophically cracking, grain pull-out, spalling and chipping due to top layer debonding have been identified. The contact damage micromechanisms corresponding to various degrees of degradation have been studied in detail by interferometry and microscopy.

Abstract: Phase transformation of 3Y-TZP with different ternary oxide additions (Al2O3, La2O3, Sc2O3 and CeO2) was evaluated by hydrothermal degradation tests in water vapor at 180°C. Monoclinic phase quantification from XRD patterns showed an improved degradation resistance of the specimens with oxide additions in comparison to the 3Y-TZP base material. Cross sectional sample analysis showed that, even though for all the compositions the exposed surface became saturated with monoclinic phase, the penetration of the transformation varied. Alumina-lanthana doped materials exhibited the thinnest degraded layer.