Summary Samples of enamel and dentin from human molar teeth were heated in air from room temperature (25°C) up to 1200°C and the phase transition from hydroxyapatite (HAP) to tricalcium phosphate (β‐TCP) was recorded. The changes produced in morphology and chemical composition in the tooth during heating were analysed by light microscopy, scanning electron microscopy (SEM), characteristic x‐ray energy dispersion spectroscopy (EDS), x‐ray diffraction (XRD), electron diffraction, transmission electron microscopy (TEM) and high‐resolution electron microscopy (HRTEM). The results indicated a high correlation relationship among Ca content, P content, O content and Na content, and the existence of the Kirkendall effect during the HAP‐ β‐TCP phase transition. Lay Description This work is related with tooth materials. Samples of enamel and dentine from human molar teeth were heated in air from 25°C up to 1200°C and the phase transition from hydroxyapatite (HAP) to tricalcium phosphate (β‐TCP) was recorded. The β‐TCP phase is also known as whitlockite. The changes produced in morphology and chemical composition in the tooth during heating were analysed by electron microscopy and X‐ray diffraction. The results indicated a high correlation relationship among Ca, P, O and Na contents, and the existence of the Kirkendall effect, the atomic diffusion producing voids, during the HAP‐ β‐TCP phase transition.

The present work reports the photodegradation results of the Reactive Black 5 (RB5) izo dye by using titanium oxide films as photocatalysts. The films were obtained by ultrasonic spray pyrolysis deposit technique from a 0.0076 M of Ti(IV)-acetyl-acetonate and N,Ndimethylformamide solution over corning glasses as substrates. The film obtained by deposition at 450 °C for 6.0 min shows the best photocatalysis behavior, which may degrade 50% of 100 ppm RB5 in a period of 120 min, as monitored with a spectra-photometer UV-Vis between 190 to 900 nm. After 180 minutes of degradation, a 70% conversion could be obtained. These results are better than that obtained with TiO 2 powders as photocatalyst.