Desafios da dispersão e adição do Nano-Nb205 em matrizes cimentícias

Abstract

To effectively utilize Nano Niobium Pentoxide (Nano-Nb2O5) in cementitious matrices, it's essential to overcome challenges such as agglomeration and interaction with the alkaline and complex environment of concrete. This study aims to identify the most suitable technique for dispersion in aqueous media, comprehend its responsiveness to pH fluctuations and ion presence in the porous solution. Ultimately, it aims to provide guidance for future Nano-Nb2O5 research in this context. The experimental investigation was bifurcated into two discrete stages. In the first stage, dispersion methods were assessed by analyzing hydrodynamic size and size distribution, adopting the dynamic light scattering (DLS) technique. Different sonication methods were employed, including bath ultrasound and tip ultrasound, for durations of 5, 10, or 15 minutes. Additionally, the efficacy of incorporating a polycarboxylate-based superplasticizer (SP) as a stabilizing agent was assessed. Particle size analysis was also performed after 4 hours of sonication. In the second stage, the stability of the aqueous dispersions containing Ca2+, Na+, and K + ions, representative of concrete pore solutions, was investigated through sedimentation image monitoring and pH measurement over time. The sedimented product underwent characterization using XRD, thermogravimetry, and FTIR techniques Results indicate that efficient dispersion of Nano-Nb2O5 in water is achievable with the employed techniques, allowing for its initial incorporation into cementitious matrices. Sonication for 5 minutes at 46kHz proved effective, although the addition of a superplasticizer may render this step unnecessary. In the second phase, it was observed that calcium ions could induce nanomaterial precipitation; nevertheless, stability prior to cement hardening was ensured with superplasticizer usage. Additionally, niobates were detected, suggesting a potential role in safeguarding against concrete corrosion.