Mossbauer study of the thermal behaviour of garnets used in high-energy water jet technologies

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 Mossbauer spectra of initial powdered almandine samples are characterised by one doublet corresponding to Fe2+ in dodecahedral position 24c. Almandine garnet, industrial product Barton HP 80 as reference material in all experiments, has a second doublet corresponding to Fe3+ in octahedral position 16a. In room-temperature spectra of heated almandine garnet samples from locality Ktis and Medenec (heated under temperatures 200-1000 degreesC by 100 degrees for 1 hour in air) a new doublet originating from gamma-Fe2O3 nanoparticles appeared. Under a heating temperature of higher than 800degreesC, the broad sextets of alpha-Fe2O3 and epsilon-Fe2O3 in spectra were discovered. No additional doublets or sextets appeared in room-temperature Mossbauer spectra of reference material of almandine garnet Barton HP 80 heated under each temperature.