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Interest has grown in recent time on the development of three-component polymer nanocomposite with enhanced properties. However, the study focuses on the effect of TiO2 nanofiller on the mechanical, tribological, dielectric, and corrosion resistance properties of boron-free glass fiber (BGF) reinforced polyimide (PI) composite produced with spark plasma sintering route. Microstructure of the samples was examined using scanning electron microscopy. Mechanical, tribological, dielectric, thermal, and corrosion behaviour of the samples were characterized by nanoindenter, ball-on-disc, LCR meter, TGA, and potentiodynamic polarization test, respectively. The SEM results show that the introduction of the nanoparticles into the BGF/PI composite aids in more uniform distribution of the BGF particles within the PI matrix, and thus good interfacial interaction of the glass fiber and the PI matrix structure. Comparing the BGF/PI composite sample with BGF/TiO2/PI nanocomposite, it was observed that the nanocomposite depicted better hardness, elastic modulus, low friction coefficient and wear rate, dielectric, and enhanced corrosion properties. With TiO2 additions, hardness and modulus of the PI composite was improved by 56.6% and 10.1%, respectively. In addition, PI composites filled with TiO2 depicted a 0.07 coefficient of friction and wear rate of about 67.7% in reduction than that of neat PI and 9.0% in reduction than that of the pristine BGF/PI composites. Improved interactions between the reinforcements and the host matrix are suggested as the possible mechanism resulting to the desirable properties of the three-component PI nanocomposite recorded. Finally, the developed nanocomposite is suggested to be favourable for automobile, aerospace, and microelectronic device applications. [ABSTRACT FROM AUTHOR]

Nile tilapia Oreochromis niloticus is one of the most important fishery resources and a valuable fish species for aquaculture programmes. It is found in almost all waters and is widely dispersed. Several natural populations of this species have been impacted by genetic pollution despite their significant economic relevance. Understanding population structure is a crucial first step in protecting this species in its native habitats as well as in choosing which wild stocks to use in hatchery initiatives. To demonstrate the genetic-population structure of this species, genetic differences among three geographically secluded populations of O. niloticus were investigated utilizing mitochondrial DNA cytochrome b gene sequences. The results were used to estimate the levels of genetic variability within and among the populations. The 56 cyt b (821 bp) sequences analysis revealed 21 haplotypes, with a nucleotide diversity of 0.0510 and a haplotype diversity of 0.881. In each of the populations, seven (7) singleton variable sites and 19 informative-parsimony sites, genetic diversity could be identified and few population haplotypes were found, indicating a minor genetic distinction between them. For the purpose of conservation and/or Nile tilapia breeding programmes, this information would assist in choosing the fish populations that maintain greater genetic variation in O. niloticus.

The use of polyimide-reinforced composite materials in the design and fabrication of components for mechanical and tribological operation systems remains a research focus. As such, the present study investigated the effect of electrical corrosion resistance (ECR) glass on the mechanical and tribological properties of hybrid-polyimide composites using spark plasma sintering (SPS) method. The hardness and elastic modulus of the thermoplastic polyimide reinforced with TiO2 and ECR particles was investigated in this study with a nanoindentation tester under applied load of 200 mN. While the friction and wear behavior of the composites was ascertained with pin-on-disc tester under 10 N at 150 rpm with a stainless steel counterpart at room temperature. The results showed that the ECR glass addition remarkably improved the hardness and elastic modulus of the hybrid composites. Incorporation of the 10 wt% ECR glass effectively reduced the friction coefficient and wear rate by 55.5% and 92.2%, respectively, corroborating the potential of these ECR-TiO2-PI composites for applications requiring a low friction coefficient and wear rate with high mechanical properties. [ABSTRACT FROM AUTHOR]

This study utilized 1D carbon nanotubes (CNTs) and 2D graphene nanosheets (GNs) in preparation of 3D microstructured polypropylene (PP) nanocomposites with improved anti-wear and nanomechanical responses. The nanocomposites fabricated through melt compounding using Haake Rheomixer showed well dispersed nanoparticles in the matrix due to the aid of PP grafted maleic anhydride (PP-g-MA) coupling agent. The developed PP-CNTs-GNs hybrid nanocomposite showed lower coefficient of friction compared to the pure PP and its nanocomposites containing individual CNTs and GNs. PP-1CNTs-1GNs hybrid nanocomposite had lower wear rate of about 1.01 × 10−5 mm3/mN compared to 8.9 × 10−5 mm3/mN, 4.2 × 10−5 mm3/mN, and 4.8 × 10−5 mm3/mN measured for the pure PP, PP-3CNTs and PP-3GNs nanocomposites, respectively. The PP-1CNTs-1GNs nanocomposite respectively showed reduction in mass loss of about 78.7%, 62.2%, and 69.1% when related to the pure PP, PP-3CNTs and PP-3GNs nanocomposites. Maximum hardness and elastic modulus of about 153 MPa and 2.7 GPa were measured for PP-3CNTs-1GNs hybrid nanocomposite, while about 86.4 MPa and 1.5 GPa were recorded for the pure PP, respectively. The enhanced properties of the hybrid nanocomposites are due to the good synergetic effect of CNTs-GNs and the formation of 3D microstructures in the PP matrix with relaxed molecular chains and network hardening of the PP matrix. [ABSTRACT FROM AUTHOR]

Graphene–polymer nanocomposites have shown promising potential as high dielectric constant and electrostatic energy storage materials. However, such nanocomposites often faced challenges of high energy dissipation and low voltage endurance due to direct contact of graphene nanosheets and localized electric field concentration. Various efforts have been made to address these shortcomings such as the insulative coating of graphene nanosheets in a polymer matrix. In this study, we simulated (using COMSOL Multiphysics) the effects of such insulative coatings on localized voltage concentration around graphene nanosheet in a polymer matrix. The simulation was done by consideration of various insulative materials with different dielectric constant and coating thickness on graphene nanosheets. It was noted that insulative coating can reduce localized voltage concentration around a graphene nanosheet in a polymer matrix, thereby improve the breakdown strength. Further increase in the coating thickness with low dielectric constant coating materials can further enhance breakdown strength. However, high coating thickness resulted in lowering the microcapacitance of the microcapacitor in the polymer matrix. Therefore, for the optimal energy density of such nanocomposites, a compromise dielectric constant of a coating material and coating thickness on graphene nanosheet must be reached. This study showcased the influence of insulative coatings on graphene nanosheets. It will be a guide for further studies on the selection of coating materials for graphene nanosheets for high breakdown strength nanocomposites. [ABSTRACT FROM AUTHOR]

In most engineering applications where fluid lubrication is practically impossible such as high temperature environment, solid lubrication becomes an alternative option. Polymers such as polytetrafluoroethylene are often used for solid lubrication due to their ability to provide low friction on interfacial sliding conditions. However, polymeric materials often show low wear resistance, which limits their applications. Therefore, there is need for high wear resistance polymers or polymer composites for such application. In this study, wear resistance of poly (vinylidene fluoride) (PVDF) was improved by incorporating hydroxylated titanium dioxide (TD-OH) and functionalized graphene nanoplatelets (fGNPs). The composites were fabricated by solution blending and further processed by melt compounding. Raman and X-ray diffractometer were used to characterize the particles, while morphological study and wear scars on the composite samples were examined using scanning electron microscope. From the results obtained, wear volume (WV) reduced from about 0.6255 mm3 for pure PVDF to 0.2439 mm3 for 3.34 wt% fGNPs composite and further reduced to 0.1473 mm3 with the addition of 10 wt% TD-OH to 3.34 wt% fGNPs composite. These are about 61% and 76% reduction respectively, compared to pure PVDF. It was noted that increase in TD-OH content up to 20 wt% in fGNPs binary composites increased the WV of the ternary composites. This indicates that ceramic nano-fillers at appropriate proportions in polymer/graphene composites can enhance the wear resistance of such composites. On the other hand, the ternary composites showed lower thermal stability compared to the binary composites, which was attributed to low thermal stability product(s) of chemical reaction between fGNPs and TD-OH in the PVDF matrix. [ABSTRACT FROM AUTHOR]

Polymer/graphene nanocomposites (PGNs) have shown great potential as dielectric and energy storage materials. However, insolubility of graphene in most solvents, hydrophobic behaviour and poor dispersion in polymer matrix restrict wider fabrications and applications of PGNs. In this study, we present co-fabricated PGNs engineered by solution blending and melt compounding methods with improved dielectric performance. Further processing of PGNs by melt mixing after solution blending not only improved dispersion of graphene in the matrix but also ensured good interfacial interaction of the composites' constituents and reduction of oxygen content in PGNs. Graphene nanoplatelets used in this study was slightly functionalized (fGNPs) to enhance dispersion in the polymer matrix. It was later characterized using Fourier transform infrared (FTIR) and Raman spectrometer. Scanning electron microscope (SEM) was used in morphological study of the fabricated composites. Dielectric properties, electrical conductivity, breakdown strength and energy storage capacity of the fabricated composites were investigated. The results obtained showed well-dispersed fGNPs in poly (vinylidene fluoride) (PVDF) matrix and improved dielectric performance. For instance, with 3.34 wt% and 6.67 wt% fGNPs co-fabricated composites, dielectric constant increased from about 9 for neat PVDF to 9930 and 38,418 at 100 Hz, respectively. While 7588 and 12,046 were respectively measured for solution blended-only composites at similar fGNPs content. These resulted to about 176.9% and 376.4% increase in energy storage density with 3.34 wt% and 6.67 wt% fGNPs co-fabricated composites when compared to their counterparts. These results were also credited to strong bonding, reduction of oxygen and recovered graphene structure by melt-mixing approach. [ABSTRACT FROM AUTHOR]

The population structure and genetic variability of North African catfish Clarias gariepinus (Burchell 1822) were investigated using partial mitochondrial DNA cytochrome b region sequences. Fifty-four (54) samples were investigated from three geographically isolated rivers in Nigeria. The analysis of 53 haplotypes revealed greater haplotype diversity (0.99930) and nucleotide diversity (p) (0.07270). According to an analysis of molecular variance (AMOVA), the genetic diversity of North African catfish within populations is significantly higher than the genetic diversity across populations. The FST scores (0.75000, 0.94792 and 0.95699) indicated that North African catfish populations in three Nigerian freshwater bodies had a strong genetic structure. The phylogenetic reconstruction of unique haplotypes revealed the placement of a haplotype (Ogbese) linked by others from all three groups with a point mutation ranging from 1 to 24 nucleotides. North African catfish populations in the Asejire and Ureje are genetically diverse, as evidenced by a high level of haplotype diversity of 1.0000, low nucleotide diversity spanning from 0.05101 to 0.07889, and high FST values (within-population genetic variation). The common haplotypes between some populations and mixes of haplotypes from different populations within the same genetic cluster demonstrate that the population genetic structure is not distinct.

Thermal control effect on the incidence of some post-harvest rot pathogens of Solanum tuberosum (potato) was investigated in this study. Three cultivars of potato tuber whose local names are, Patiska, Mai Bawondoya and Nicola were used for the study. Five pathogenic fungi viz: Botryodiplodia theobromae, Fusarium redolens, Fusarium oxysporum, Penicillium sp. and Rhizopus oryzae associated with post harvest storage rot of root-tubers, were isolated from diseased potatoes. Among the three species of potatoes used in the study, Patiska was found most resistant followed by Mai Bawondoya, while Nicola was the least resistant. Increase in substrate (i.e. soluble starch or CMC) concentration enhanced a proportional increase in mycelial growth and in the amount of extracellular enzymes produced. Some of these test pathogens were found to produce cell wall degrading enzymes (i.e. amylase and cellulase). Preferential utilization of carbohydrate sources was established in this study based on the growth of test pathogens. Growth on potato broth medium was highest followed by growth on Cocoyam and Sweet potato broth media and least on Cassava broth medium. Growth of the test pathogens on carbohydrate sources was found at variant. The use of hot water treatment at different temperatures was found to significantly reduce post-harvest fungal populations on the surface of root-tubers. The efficacy of blanching in hot water at 60˚C was significantly higher than that of blanching in hot water at other temperatures. The control method adopted in this study showed that the problems of potatoes’ rot disease in storage (especially by the peasant farmers) can be eradicated by thermal treatments without reducing the quality of the Irish tuber.

The current study aimed at assessing the immunostimulatory properties of silver nanoparticles (AgNPs) on Labeo rohita , and understanding how it affects the growth, cellular ultrastructure, the expression level of immune genes, and infection risk from Aeromonas hydrophila . Fish (avg wt: 30.1±3.26 g) were fed diets with four separate AgNP inclusion levels (0 µgKg -1 [basic diet, T1], 10 µgKg -1 [T2], 15 µgKg -1 [T3], and 20 µgKg -1 [T4]) for 56 days. After the feeding trial, growth, histological, immunological parameters, and protective immune response against A. hydrophila were assessed. The fish in the treatment groups including T1(control), the T3 growth indices, such as specific growth rate (7.56±0.26) and percent weight gain (231.05±3.21), was statistically higher (P < 0.05). In the immunological and oxidative parameters, levels of SOD and catalase decreased in correlation with a rise in the inclusion doses of AgNP in the liver, and a reduction in catalase values was recorded in the gill. With the addition of AgNP, the NBT value was decreased in the gill, and T3 had a considerably larger (P<0.05) value in the liver (0.493±0.02). The kidney of the L. rohita fed AgNP (0 and20 µgKg -1 AgNP) showed expansion through Bowman's gaps, severing of glomeruli with haemorrhage, as well as atrophic spots between its gaps. The liver showed fibrosis, karyolysis, and the removal of the hepatocytes wall. The gill, liver, kidney, and muscle of fish-fed diets supplemented with AgNP, showed that interleukin-8 (IL-8), and cyclooxygenase-2 (COX-2), were up-regulated. Expression was considerably higher in T3 compared with the control. However, the control group that wasn't given AgNP supplemented diet had increased levels of TGF-beta. Additionally, fish on the T3 diet showed much greater post-challenge survival rates (90%). These findings strongly suggest that dietary inclusion of AgNP (at 10 and 15 µgKg -1 feed) enhances growth, health, and protective immune response against A. hydrophila ., Competing Interests: No competing interests are disclosed by the authors., (© 2022 The Author(s).)

The high strength-to-weight ratio property of titanium aluminide (TiAl) based intermetallic alloys makes researchers regard this type of material as a potential replacement for the heavier superalloys of nickel. These alloys have been applied as turbocharger wheels of automobile and turbine blades of aircraft engines. A much recent alloy type of TiAl called the TNM alloy has emerged and primarily amenable to mechanical working; while providing the best combinations of mechanical properties that could be achieved through manufacturing processes with subsequent heat treatments. This is attained by solidifying entirely through the disordered β-phase (A2 structure). Effects of major alloying elements such as strength improvement, microstructural stability and phase formation demand the understanding of these alloying elements addition in TiAl-based intermetallic alloys. This review paper aims at encapsulating several works regarding the effects of major alloying elements on β-solidifying TiAl-based alloys and summarizing the characteristic effects of Si for these types of alloys. An impetus for future works on these types of intermetallic TiAl-based alloys is also presented., (© 2020 The Authors.)