Monika Wójcik-Bania

This study explores the structural and thermal behavior of different smectites intercalated with the cationic surfactant ethyl lauroyl arginate (LAE®) at loadings up to 1.0 of the smectites' cation exchange capacity (CEC). X-ray diffraction (XRD) confirmed systematic expansion of the basal spacing ( d ₀₀₁ ), reaching up to 2.29 nm, with changes governed by surfactant content, exchangeable cation type, and layer charge. LAE® was incorporated exclusively via ion exchange, as evidenced by exchangeable cation release, although steric hindrance limited full CEC saturation at higher loadings. Fourier transform infrared spectroscopy (FTIR) showed that the smectite framework remained intact, while band shifts in the N–H, C=O, and CH ₂ regions indicated strong surfactant–clay mineral interactions and LAE® conformational changes. Thermogravimetric analysis revealed a reduction in decomposition steps from six (pure LAE®) to four upon intercalation, alongside a shift in the main decomposition peak from 285.7°C to 305.1°C for sample based on the Arizona smectite having high layer charge. Evolved gas analysis (TG-FTIR) confirmed altered degradation pathways for the organosmectites, with the suppression of nitrogen-containing volatiles such as NH ₃ and NO ₂ . High-temperature FTIR (HT-FTIR) further demonstrated reduced molecular mobility and enhanced thermal stability, particularly in samples with the highest LAE® content. Quantitative spectral analysis showed persistent C–H, C=O, and C–N–H bands at elevated temperatures, confirming the stabilizing effect of interlayer confinement. These findings underscore the potential of LAE®-modified smectites as thermally robust, non-toxic hybrid materials with promising applications as feed additives. Graphical abstract

Polysiloxanes with silver nanoparticles (Ag NPs) have garnered attention for their distinctive physicochemical properties, which make them promising candidates for advanced material applications. This study presents a systematic investigation into the thermal properties and degradation mechanisms of polysiloxane/Ag nanocomposites, emphasising the innovative incorporation of Ag NPs directly into polysiloxane networks via in situ reduction of Ag⁺ ions by Si-H groups. Six polysiloxane matrices were synthesised by hydrosilylation of poly(methylhydrosiloxane) (PMHS) or poly(vinylsiloxane) (polymer V₃) with three cross-linking agents of varying molecular structures and functionality. Thermogravimetric analysis combined with mass spectrometry revealed that the introduction of Ag NPs alters the thermal properties of polysiloxane networks, primarily affecting the redistribution of Si bonds that occurs during the pyrolysis of these systems. Monitoring the pyrolysis process using FTIR spectroscopy allowed us to investigate the effect of the presence of Ag NPs on the degradation mechanism of the studied nanocomposites. The presence of the free-carbon phase and metallic silver phase in the Ag-containing silicon oxycarbide materials obtained was confirmed by Raman spectroscopy and XRD analyses, respectively. These findings demonstrate the possibility of fabricating Ag/SiOC materials with ceramic residues in the range of 43 to 84%. This work provides new insights into the thermal behaviour of polysiloxane/Ag nanocomposites and underscores their potential for high-performance applications in thermally demanding environments.

The oxidation behavior of four γ/γ′ Ni-based alloys: without additions, and containing: Hf (1.0 wt%), a combination of Hf and Y (0.3 wt% and 0.03 wt%, respectively), and a combination of Hf and Si (1.0 wt% and 1.0 wt%, respectively) was studied in air under isothermal (50 h) and thermal cycling (up to 2225 1-h cycles) conditions. Samples were characterized using SEM, EDX and XRD techniques. The results indicated that all the additions improved the oxidation resistance of the alloy but only in the case of materials containing the (Hf + Y) combination of additions was a long-term effect achieved. Substantial weight losses were observed on the other unmodified and (Hf + Si)-containing materials during thermal cycling after short exposure periods, while on material containing only additions of Hf, they occurred significantly later. Kinetic studies showed the highest oxidation rate in the case of the (Hf + Si)-containing alloys and the fastest initial oxidation, prior to the parabolic law-obeying stage, of alloy with Hf-additions, only. The results indicate the superior effect of simultaneous application of Hf and Y additions at levels not exceeding their solubility limits and that lowering its effectiveness Hf overdoping (1 wt%) cannot be effectively counteracted by the addition of 1% Si.

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH₃)₂R’NR]⁺, where R = C₁₂, C₁₄, C₁₆, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.