Microwave-Assisted and Metal-Induced Crystallization: A Rapid and Low Temperature Combination

Abstract

Here we present a new crystallization process, which by combining microwaves and metal-induced devitrification, reduces both the time and the temperature of crystallization compared to other 2 known methods. Titania crystallization initiates at a temperature as low as 125 °C within a few minutes of microwave radiation. Several cations induce this low-temperature crystallization: Mn 2+ , Co 2+ , Ni 2+ , Al 3+ , Cu 2+ and Zn 2+ . The crystallization mechanism is probed with electron microscopy, elemental mapping, single particle inductively plasma mass spectrometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning Auger mapping. These techniques show that the metal ion migration through the vitreous titania under microwave radiation occurs prior to crystallization. The crystalline particles are suspended in solution at the end of the treatment, avoiding particle aggregation and sintering. The crystalline suspensions are thus ready for processing into a material or employment in any other application. This combination of microwaves and metal-induced crystallization is applied here to TiO2, but we are investigating its application to other materials as an ecofriendly crystallization method.

Metal-Induced Crystallization in Metal Oxides

“…2020, 59 (9), 6232−6241. 1 The structure is preserved in titania spheres, crystallized at 150 °C in suspension. This article opens the door toward hybrid materials with postsynthetically crystallized TiO 2 .…”

Analytical applications of single particle inductively coupled plasma mass spectrometry: a comprehensive and critical review

“…The analysis of pristine nanoparticles is regarded as the least complex scenario, since there is no matrix in which they are contained. Engineered nanomaterials commonly produced at laboratories for research or industrial purposes, 61,[63][64][65][66][67][68][69][70][71][72]75,76 but also commercial suspensions, 60,62,73,74 have been considered in this section. Table 2 summarizes the applications of SP-ICP-MS to the analysis of such pristine nanoparticles.…”

“…In that way, the yttrium contained in nanotubes allowed their detection, 73,74 although the concentration was underestimated due to the difficulties of detecting nanotubes with low loads of yttrium. The characterisation of pristine nanoparticle by SP-ICP-MS has been complemented by electron microscopy techniques for size and shape characterisation 57,61,64,65,[68][69][70]73,74 and XRD 68,69,72,75 for confirmation of their nature through their crystalline structure.…”

Recent advances in ultra-low temperature (sub-zero to 100 °C) synthesis, mechanism and applications of titania (TiO2) nanoparticles

“…TiO 2 nanoparticles with suitable sizes, morphologies have been synthesized via MW methods for various energy conversion and storage devices. [143][144][145][146] The anatase titania nanostructures of size ∼7 nm and ∼100-400 nm were synthesized successfully from the thiobenzoate complex of titanium in benzyl alcohol and ethanol. The transparent and scattering nanoparticles of anatase TiO 2 obtained were successfully used as photoanode in solar cells application.…”