Influence Of Matrix Nature Research Articles

Influence of Matrix Nature on the Structural Characteristics of In2O3–CeO2 and SnO2–CeO2 Composites Fabricated by the Impregnation Method

The structural characteristics, valence states, and distribution of cerium ions between the components in In2O3–CeO2 and SnO2–CeO2 nanocomposites fabricated using the impregnation method were studied. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) were used to show that, during impregnation, cerium ions are not included into In2O3 crystals and are disposed only on their surface in the form of nano-sized crystallites or amorphous clusters. On the other side, under the contact of CeO2 clusters with a surface of SnO2 matrix crystals, cerium ions penetrate into the surface layer of these crystals. In contrast to an In2O3–CeO2 system, where the addition of CeO2 does not affect the conduction activation energy, where cerium oxide is added to SnO2, the observed increase in the resistance of a SnO2–CeO2 composite is accompanied by a sufficient increase in activation energy. These data and the XPS spectra confirm the modification of the surface layers of conductive SnO2 crystals as, a result of the penetration of cerium ions into these layers.

Fatigue accumulated damage in notched quasi-isotropic composites under high-temperature conditions: A discussion on the influence of matrix nature on the stress energy release rate

In order to investigate the contribution of matrix nature to the fatigue behaviour, the purpose of the present work is to establish the correlation between material toughness and macroscopic damage accumulation during tensile cyclic loading in the brittle (C/epoxy) and ductile (C/Polyphenylene sulfide) matrix systems. More specifically, this article presents a fracture mechanics-based approach to compute the strain energy release rate during fracture along with the macroscopic transverse crack growth in fatigue. The knowledge of energy-absorbing processes is important as they are responsible for the toughness of the composite. Woven-ply laminates are characterised by matrix-rich regions which may stop or slow down the growth of fatigue cracks by absorbing the mechanical energy through local plastic deformations at the cracks tip depending on matrix nature. With respect to C/epoxy laminates, the local plastic deformations at the cracks tip are prominent in highly ductile composite systems (e.g. C/Polyphenylene sulfide), and ultimately results in fatigue behaviour virtually independent of the applied stress level under high temperatures T > Tg. To evaluate the influence of matrix ductility and toughness on fatigue damage, a damage variable d based on the measurement of longitudinal stiffness at each cycle was used. A model derived from a Paris law and a fracture mechanics criterion were combined to: (i) evaluate the fatigue crack growth – (ii) compare the changes in the strain energy release rate G and the macroscopic damage d during cyclic loading. Macroscopic damage appears to be well correlated with the strain energy released during fracture.

Influence of matrix nature on the functional efficacy of biomedical cell product for the regeneration of damaged liver (experimental model of acute liver failure)

Aim. A comparative analysis of the functional efficacy of biomedical cell products (BMCP) for the regeneration of damaged liver based on biopolymer scaffolded porous and hydrogel matrices was performed on the experimental model of acute liver failure. Materials and methods. Matrices allowed for clinical use were employed for BMCP in the form of a sponge made from biopolymer nanostructured composite material (BNCM) based on a highly purified bacterial copolymers of poly (β-hydroxybutyrate-co-β-oxyvalerate) and polyethylene glycol and a hydrogel matrix from biopolymer microheterogeneous collagen-containing hydrogel (BMCH). Cellular component of BMCP was represented by liver cells and multipotent mesenchymal bone marrow stem cells. The functional efficacy of BMCP for the regeneration of damaged liver was evaluated on the experimental model of acute liver failure in Wistar rats (n = 40) via biochemical, morphological, and immunohistochemical methods. Results. When BMCP was implanted to regenerate the damaged liver on the basis of the scaffolded BNCM or hydrogel BMCH matrices, the lethality in rats with acute liver failure was absent; while in control it was 66.6%. Restoration of the activity of cytolytic enzyme levels and protein-synthetic liver function began on day 9 after modeling acute liver failure, in contrast to the control group, where recovery occurred only by days 18–21. Both matrices maintained the viability and functional activity of liver cells up to 90 days with the formation of blood vessels in BMCP. The obtained data confirm that scaffolded BNCM matrix and hydrogel BMCH matrix retain for a long time (up to 90 days) the vital activity of the adherent cells in the BMCP composition, which allows using them to correct acute liver failure. At the same time, hydrogel matrix due to the presence of bioactive components contributes to the creation of the best conditions for adhesion and cell activity which accelerate the regeneration processes in the damaged liver compared to BMCP on scaffolded matrix. Conclusion. A statistically significant difference was found between the functional efficacy of the BMCP studied based on BNCM and BMCH matrices. BMCP based on hydrogel BMCH matrix was more effective for the regeneration of damaged liver.