Lowering the combustion temperature of organic components in organosiloxane gels by an incorporation of copper ions

Abstract

The sol-gel method enables glass fabrication at significantly lower temperatures than conventional methods such as the melt-quenching processes. However, heat treatment at high temperatures is still required to remove organic residues and densify the structure. Lowering the combustion temperatures of gels derived by the sol-gel method can provide not only industrial benefits but also environmental ones. In the present work, we investigated the catalytic effect of Cu compounds on lowering the combustion temperature of organic residues, thereby facilitating the removal of organic residues at reduced temperatures. Specifically, the role of Cu²⁺ as a catalyst for the decomposition of organic groups within siloxane structures was focused. Methylsiloxane, which contains methyl groups attached to the siloxane side chain, was used as a model compound to quantitatively evaluate the catalytic effect of Cu²⁺ in lowering the combustion temperature of methyl groups. Methylsiloxane powders were synthesized via the sol-gel method, and Cu²⁺-doped methylsiloxane powders were prepared by incorporating copper sources such as Cu(NO₃)₂ or others into the precursor solution. Thermogravimetric-differential thermal analysis (TG-DTA) and Fourier-transform infrared (FT-IR) spectroscopy revealed that the Si-CH₃ bonds in the Cu-doped powders underwent combustion and decomposition at significantly lower temperatures compared to those in undoped methylsiloxane powders. These findings demonstrate that Cu can effectively catalyze the low-temperature combustion of organic components. The present finding has the potential to enable silica glass fabrication at lower temperatures than previously achievable, thereby reducing energy consumption. Additionally, it offers promising opportunities for expanding the applicability of glass materials to new domains.

Graphical Abstract