High Temperature Diffraction Study of In‐Situ Crystallization of TiO ₂ Photocatalysts

Effect of pressure on TiO2 crystallization kinetics using in‐situ high‐temperature synchrotron radiation diffraction

“…The TiO 2 nanopowders at atmospheric pressure crystallized partially to initially form anatase and rutile by 400°C and 600°C, respectively. This finding is consistent with literature data reporting crystallization‐onset temperatures for anatase and rutile ranging between ~ 400°C and 600°C, and 400°C and 1200°C, respectively, which values are consistent with the literature on TiO 2 transformations . Therefore, the initial anatase crystallization temperature under pressure was reduced by 200°C compared with material heated at atmospheric pressure, whereas the anatase‐to‐rutile transformation had not commenced by 800°C for the pressurized material.…”

“…Anatase‐rutile mixtures have been synthesized by thermal treatment of amorphous TiO 2 , where the initial crystalline TiO 2 phase formed from amorphous TiO 2 is anatase, which transforms to rutile at elevated temperature . The anatase‐to‐rutile transformation temperature ranges from 400°C to 1200°C depending on reaction atmosphere, doping and synthesis method, particle size, and surface area …”

Mineral and textural transformations in mixtures of Al-rich and Al–K-rich clays with firing: Refractory potential of the fired products

“…Like the clay minerals, boehmite was not present at 1000 • C due to a dehydration process that transforms boehmite (γ-AlOOH) into γ-Al 2 O 3 at 490-510 • C [25][26][27]. Furthermore, neither the small amounts of anatase detected in all the raw samples nor the goethite detected in sample BX100 were present at 1000 • C. This can be explained by the fact that goethite dehydrated into hematite at 500-600 • C [28,29] and that anatase transforms into rutile at 500-550 • C [30]. In addition, the presence of small amounts of amorphous or poor crystalline iron oxides (not detected by XRD in the raw samples) that would destabilize with temperature, along with the dehydration of goethite into hematite in sample BX100, may be the cause of the increase in the hematite content at 1000 • C in all the samples.…”