Room temperature facile synthesis of olivine-Co₂SiO₄ nanoparticles utilizing a mechanochemical method

Abstract

Impact pressure induces synthesis of nanocrystalline olivine Co2SiO4.

Binary CoOx–SiO2 Porous Nanostructures for Catalytic CO Oxidation

“…Considering the pale blue color of the MUB-100(1) monolith (Figure b), we first intuited that the phase present was amorphous Co 2 SiO 4 , but this phase is normally appearing only above 1100 °C when addressing acidic based syntheses, while the thermal treatment applied here is reaching a maximum temperature of 700 °C. To get the spinel Co 2 SiO 4 at relatively low temperature, the synthetic path should be addressed under alkaline conditions (above the silica isoelectric point) where the Co 2+ species will have molecular affinity with the negatively charged silicate precursors . In the present cases, the Co 2 SiO 4 phase appears only above 3 wt % of Co (Table and Figure ), certainly for the Co 2+ species to be concentrated highly enough to both circumvent phase separation between positively charge siliceous precursors and the Co 2+ and optimize the Co thermal diffusion when the thermal treatment is applied.…”

“…To get the spinel Co 2 SiO 4 at relatively low temperature, the synthetic path should be addressed under alkaline conditions (above the silica isoelectric point) where the Co 2+ species will have molecular affinity with the negatively charged silicate precursors. 39 In the present cases, the Co 2 SiO 4 phase appears only above 3 wt % of Co (Table 1 and Figure 6), certainly for the Co 2+ species to be concentrated highly enough to both circumvent phase separation between positively charge siliceous precursors and the Co 2+ and optimize the Co thermal diffusion when the thermal treatment is applied. In contrast, at low cobalt wt %, the phase separation between siliceous precursor and silica is effective during the sol−gel synthetic step, while providing the β-Co(OH) 2 embedded within the siliceous host when the thermal treatment is applied.…”

Mechanochemical Synthesis of Nanocrystalline Olivine-Type Mg2SiO4 and MgCoSiO4

“…The one-pot synthesis of olivine-type Fe 2 SiO 4 highlights the early work of Šepelák et al, starting from Fe 2 O 3 , Fe, and SiO 2 and milled under Ar inert atmosphere [25]. Mechanochemically synthesized nanocrystalline Co 2 SiO 4 has also been reported recently by our lab using a 2:1 molar ratio mixture of CoO and SiO 2 [26]. In an effort to standardize the Mg-Co silicate solution series preparation, we report here the results of our investigation into the mechanochemical synthesis of olivine-type Mg 2 SiO 4 and ternary olivine MgCoSiO 4, starting with stoichiometric amounts of MgO, SiO 2 and CoO, MgO, SiO 2 , respectively.…”

“…To set up a baseline methodological approach, forsterite Mg 2 SiO 4 was prepared by the high-energy milling of a 2:1 molar ratio mixture of MgO and SiO 2 for 180 min. Our synthesis follows the general procedure of Nguyen et al for the synthesis of olivine Co 2 SiO 4 [26]. Figure 1 illustrates the results of the Rietveld refinement of 180 min milled Mg 2 SiO 4 , which converge to a final figure of merit R wp = 6.524.…”

“…Preparation of Mg 2 SiO 4 /MgCoSiO 4 . The synthetic procedure was based on the methodology developed previously by our group for the synthesis of the nanocrystalline Co 2 SiO 4 [26]. A mixture of a 2:1 molar ratio of magnesium oxide (0.62 g) and silicon oxide (0.47 g) and a second mixture of a 1:1:1 molar ratio of magnesium oxide (0.25 g), cobalt oxide (0.47 g), and silicon oxide (0.37 g) were loaded into 2 separate 25 mL tungsten carbide (WC) jars and mechanically milled under dry conditions with two 15 mm diameter WC balls (40:1 ball to powder ratio) oscillating at a frequency of 30 Hz for various durations of time, ranging from 0 to 360 min.…”