Moessbauer Study of the Thermal Behaviour of Garnets Used in High-Energy Water Jet Technologies

摘要

A high-energy water jet combined with silicate garnets as abrasives has been proven to be a powerful tool for disintegration of hard materials. Thermal heating of the garnets is one way for structure improvement of the abrasive material. Room-temperature Moessbauer spectra of initial powdered almandine samples are characterised by one doublet corresponding to Fe~(2+) in dodecahedral position 24c. Almandine garnet, industrial product Barton HP 80 as reference material in all experiments, has a second doublet corresponding to Fe~(3+) in octahedral position 16a. In room-temperature spectra of heated almandine garnet samples from locality Ktis and Medenec (heated under temperatures 200―1000℃ by 100 degrees for 1 hour in air) a new doublet originating from γ-Fe_2O_3 nanoparticles appeared. Under a heating temperature of higher than 800℃, the broad sextets of α-Fe_2O_3 and ε-Fe_2O_3 in spectra were discovered. No additional doublets or sextets appeared in room-temperature Moessbauer spectra of reference material of almandine garnet Barton HP 80 heated under each temperature.