Effect of spark plasma sintering and high-pressure torsion on the microstructural and mechanical properties of a Cu–SiC composite

This investigation examines the problem of homogenization in metal matrix composites (MMCs) and the methods of increasing their strength using severe plastic deformation (SPD). In this research MMCs of pure copper and silicon carbide were synthesized by spark plasma sintering (SPS) and then further processed via highpressure torsion (HPT). The microstructures in the sintered and in the deformed materials were investigated using Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). The mechanical properties were evaluated in microhardness tests and in tensile testing. The thermal conductivity of the composites was measured with the use of a laser pulse technique. Microstructural analysis revealed that HPT processing leads to an improved densification of the SPS-produced composites with significant grain refinement in the copper matrix and with fragmentation of the SiC particles and their homogeneous distribution in the copper matrix. The HPT processing of Cu and the Cu-SiC samples enhanced their mechanical properties at the expense of limiting their plasticity. Processing by HPT also had a major influence on the thermal conductivity of materials. It is demonstrated that the deformed samples exhibit higher thermal conductivity than the initial coarse-grained samples

Mechanical properties and friction coefficient of hybrid polypropylene Entada mannii composites

The current study evaluates the mechanical properties and friction coefficient of polypropylene based composites reinforced with particulate derivatives from Entada mannii fiber. The composites were fabricated by mixing different ratios of fiber ash (FA) and fiber particulates (FP) with polypropylene matrix and compounded using compression moulding method. Tensile and flexural properties, impact strength, hardness and friction coefficient were assessed, while scanning electron microscopy (SEM) was used for structural and morphological studies of the composites. The results show that the tensile, flexural, impact and hardness properties of all the composites were enhanced in comparison with the unreinforced polypropylene. The hybrid reinforced composite composition containing FA and FP in ratio 3:1, had the best tensile, flexural, and hardness properties of all composites produced, ascribed to the achievement of a more uniform dispersion of FA/FP and stronger interface bonding with the polymer matrix. Specifically, enhancement of tensile and flexural strengths of 58.7% and 62.9%, respectively in comparison with the unreinforced propylene was obtained for this composition. The friction coefficient of the single reinforced composite compositions of FA and FP were higher compared to the hybrid reinforced composites and unreinforced polypropylene. The representative morphological assessments of the composites fracture surface showed that the single reinforced composite was characterized with the agglomeration of fiber ash/fiber particulates while the hybrid reinforced composites had relatively uniform distribution of reinforcement in the matrix

The effects of solvent extracts of Citrulluslanatus seeds and Chrysophyllum albidum cotyledons on rat hepatocyte regeneration, cytochrome c oxidase activities and bacteriocin- producing gram-negative bacteria

Medicinal plants have been shown to exert a plethora of biological and pharmacological which has been associated with the presence of several bioactive components. In this study, the effects of crude extracts of Citrullus lanatus seeds (CACL) and Chrysophyllum albidum cotyledons (CACA) on rat hepatocyte regeneration, liver cytochrome c oxidase activities, and their antimicrobial properties on a few bacteriocin-producing Gram-negative bacteria were determined. CACL and CACA were screened for the presence of amino acids using TLC sprayed with ninhydrin, pyridine and modified Commassie brilliant blue (G250). The amino acids were elucidated by Gas Chromatography-Mass Spectrometry (GC/MS) and Fourier-transform infrared spectroscopy (FTIR). CACA enhanced tissue regeneration in rat hepatocytes, in situ and increased the collagen content. CACA also enhanced the activity cytochrome c oxidase in the liver mitochondrial portion, but inhibited same in the homogenate. CACA and CACL did not inhibit the bacteriocin-producing bacteria at the different concentrations tested. It is evident that CACA and CACL contain amino acids that can improve liver antioxidant functions and its mitochondrial electron transport. Both amino acid-rich fractions, combined with bacteriocin may accelerate aseptic wound healing.Fil: Molehin, O. R.. Ekiti State University; NigeriaFil: Ajayi, Ebenezer Idowu O. Department Of Biochemistry, Osun State University; Nigeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Attah, A. F.. University of Ibadan; NigeriaFil: Awope, O. R.. Osun State University; NigeriaFil: Ige, E. T.. Ekiti State University; NigeriaFil: Omotoyinbo, O. E.. Ekiti State University; NigeriaFil: Aladetuyi, B. J.. Ekiti State University; Nigeri