Abdelkhalek Henniche

New oligomeric containing aliphatic moiety phthalonitrile resins: their mechanical and thermal properties in presence of silane surface-modified zirconia nanoparticles

This study deals with the influences of both the length of the aliphatic spacer within the phthalonitrile monomers backbones, and the amount of the silane surface modified zirconia nanoparticles on the mechanical and thermal properties of the so-called second generation phthalonitrile resins. Investigation on the curing behavior under differential scanning calorimeter outlined an important gain in the processability as the aliphatic spacer became longer. Results from the mechanical tests revealed that changing the length of the aliphatic spacer affects the mechanical properties in different ways. For instance, as the aliphatic spacer became longer, the toughness state was enhanced. At the same time, the tensile modulus and stress as well as the microhardness values were slightly reduced. It was also noticed that the introduction of the reinforcing phase caused an increase in all the tested mechanical properties. Furthermore, results from the thermogravimetric analysis and dynamic mechanical analysis revealed that reducing the length of the aliphatic spacer and adding nanofillers caused an increase in the thermal stability, storage modulus, and glass transition temperature. Moreover, a morphological study has been conducted under scanning electron microscope and transmission electron microscope to put in light the mechanisms of enhancements. Finally, this study demonstrated that the excellent properties of the phthalonitrile resins can be tailored by two ways either by monomers design or by inorganic nanoparticles reinforcement.

High-performance polymeric nanocomposites from phthalonitrile resin and silane surface–modified Ti3AlC2 MAX phase

In this work, Ti3AlC2 M n + 1AX n (MAX) phase ceramic nanoparticles were prepared and used as new kind of reinforcement for a typical high-performance phthalonitrile (PN) resin. The synergistic combination of both phases led to nanocomposites with improved thermal and mechanical properties. For instance, the thermal conductivity and tensile properties of the neat resin were highly enhanced upon adding more nanofiller contents. Moreover, the PN resin toughness was ameliorated by 129% at the maximum nanoparticles loading of 15 vol%. The experimental investigations were also compared with predictions from series, Halpin–Tsai, and Kerner models, and a full discussion was provided. A high-resolution transmission electron microscope confirmed the ability of the MAX phase to create a conductive network, especially at high nanofiller amounts. Scanning electron microscope (SEM) analyses of the tensile fractured surfaces revealed positive changes in the morphology, such as an increase in the roughness and amount of hackling as well as the formation of multiple microcracks. The MAX phase also enhanced the thermal stability, stiffness, and glass transition temperature of the neat resin. This work confirms the superiority of the MAX phase ceramics over the traditional ones in enhancing the properties of the PN resin and opens the way for further research in the field.

In situ (α-Al2O3+ZrB2)/Al composites with network distribution fabricated by reaction hot pressing

In situ (α-Al2O3+ZrB2)/Al composites with network distribution were fabricated using low-energy ball milling and reaction hot pressing. Differential thermal analysis (DTA) was used to study the reaction mechanisms in the Al–ZrO2–B system. X-ray diffraction (XRD) and scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) were used to investigate the composite phases, morphology, and microstructure of the composites. The effect of matrix network size on the microstructure and mechanical properties was investigated. The results show that the optimum sintering parameters to complete reactions in the Al–ZrO2–B system are 850°C and 60 min. In situ-synthesized α-Al2O3 and ZrB2 particles are dispersed uniformly around Al particles, forming a network microstructure; the diameters of the α-Al2O3 and ZrB2 particles are approximately 1–3 μm. When the size of Al powder increases from 60–110 μm to 150–300 μm, the overall surface contact between Al powders and reactants decreases, thereby increasing the local volume fraction of reinforcements from 12% to 21%. This increase of the local volume leads to a significant increase in microhardness of the in situ (α-Al2O3–ZrB2)/Al composites from Hv 163 to Hv 251.