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ABSTRACTThough the trilateral cycle (TLC) is a promising heat recovery-to-power cycle, its application has not been widely accepted or commercialised due to some thermodynamic feasibility concerns. This study examined the performance analysis and sensitivity of the system parameters on the thermodynamic performance of the TLC power generator systems for waste heat recovery-to-power generation. Thermodynamic models of the simple, recuperative, reheat and regenerative TLCs were established. Performance analysis and sensitivity of the system parameters on the cycles’ performance were conducted at the expander inlet temperature of 453 to 473 K, expander pressure of 2 to 3 MPa and expander isentropic efficiency of 50% to 100%. The expander inlet temperatures, pressures, and its isentropic efficiencies have significant effects on the thermodynamic efficiencies and net work output of the cycles. At 473 K cycle high temperature, the thermal efficiencies of the cycles increase from 20.13% to 21.97%, 23.29% to 23.91%, 20.62% to 22.07% and 20.66% to 22.9% for the simple, recuperative, reheat and regenerative TLCs, respectively. Their corresponding net power outputs varied from 131.6 to 134.1 kW, 145.9 to 152.2 kW, 113.8 to 124.1 kW and 124.9 to 130.5 kW, respectively. The cycles’ thermodynamic performance increased with an increase in expander inlet temperature, expander pressure and expander isentropic efficiencies.

High-entropy alloy (HEA) has gained considerable interest in the research community because of its essential properties over conventional alloys. Hence, this work was aimed at development of Ti20–Al20–V20–Fe20–Ni20 HEA with the objective of determining its suitability in high-strength applications. Spark plasma sintering (SPS) was the fabrication technique used. SEM–EDS and XRD were used in the characterization, while nanoindenter and tribometer were used in the Vickers hardness and wear testing, respectively. Results obtained showed that sintering temperature of 1100 ℃ was the optimal temperature. The developed HEA had Vickers hardness improvement of 130% over Ti6Al4V alloy, wear rate improvement of 130% over Inconel 718 alloy and 666% over TiAl alloy. It was concluded that the developed HEA can perform much better than the famous Ti6Al4V superalloy in high-temperature/strength applications.

Direct infusion analysis using soft ionization techniques coupled to ultra-high-resolution mass spectrometers (UHRMS) allows screening of thousands of organic species in complex samples. Despite the high analytical throughput of direct infusion, this technique is known to be prone to matrix effects caused by changes in the ionization efficiency of an analyte, ion suppression, or enhancement due to the presence of certain compounds and inorganic salts in the sample. In this study we compared two soft ionization sources, that is, heated electrospray ionization (HESI) and nano-ESI for the analysis of atmospheric aerosol samples in the negative ionization mode. In-source fragmentation tests were conducted and experiments involving sample desalting through solid-phase extraction (SPE) with a reversed phase functionalized polymeric sorbent and spiking samples with inorganic salt were performed. Both ionization sources showed specific advantages and disadvantages for the direct infusion analysis of atmospheric aerosol extracts. The mass spectra of aerosol samples analyzed using HESI contained a large number of high molecular weight homologues containing sulfur and nitrogen, suggesting that this source is prone to formation of salt adducts and noncovalent compounds in samples enriched with inorganic salts. Data from the same aerosol sample extracts analyzed using nanoelectrospray ionization (nano-ESI) show less adduct formation; however, a decrease in the number of homologues was observed, as well as loss of molecules at higher mass range, indicating that the nano-ESI source is more prone to ion suppression. Irrespective of ionization source, SPE pretreatment significantly improved ion recoveries for organic species with nonpolar and moderately polar functional groups, but lower recoveries were obtained for highly oxygenated molecules. Therefore, while SPE reduced in-source adduct formation, it also limited the range of compounds identified through a single analysis.

In the research study, incorporation of Cu with hard SiC and Ni micron-sized particles was applied in the fabrication of a multifunctional copper-based metal matrix composite using spark plasma sintering. The developed spark plasma-sintered Cu–xNi and Cu–xNi–xSiC composite charateristics were studied by conducting morphological analysis, electrochemical, microhardness, and densification tests. Analytical equipments used include scanning electron microscopy, equipped elemental dispersive spectroscopy, X-ray diffractometry, and Vickers hardness tester. Electrochemical characterizations using potentiodynamic polarization for the electrochemical stability of the sintered composite in 0.5 M H2SO4 was also carried out. 96% densification and 90.20% corrosion resistance were obtained. The Cu–Ni composite showed an increase in corrosion resistance as a result of Ni addition in H2SO4 environment, while Cu–xNi–xSiC composite showed a slight decrease in corrosion resistance with excess SiC. It can be inferred that Cu–xNi and Cu–NixSiC composites improves the hardness values and corrosion resistance for electrical application when applied.

Background: In Nigeria, the specialty of family medicine (FM) has endured its own share of identity crises. This study was aimed at generating hypotheses about what describes a practising family physician (FP) and the specialty, according to young Nigerian FPs.Methods: Using the online platform for young African FPs alongside text messages and emails from volunteer research assistants over an eight-week period (March 3 to April 30, 2015), a purposive sample of young Nigerian FPs were asked to describe their favourite aspect of FM in a single word/phrase. Responses were provided in English/individual’s mother tongue. Translation of the words was performed by respondents and additional collaborators fluent in these languages. Thematic analysis using the grounded theory approach was performed.Results: Twenty-four responses were received consisting of four themes: Scope, Family, Skills/Feelings/Values, and Professional Fulfilment. The resulting data portrayed the FP as one who possesses a unique skill-set, enjoys fulfilment in the profession, deals with undifferentiated diseases and is able to provide holistic care for patients (irrespective of age and gender) from a family-centred perspective. When compared with accepted domains of FM for Africa and Europe, roles of the FP in community-oriented care and primary care management were absent.Conclusion: While this showcases the young Nigerian FPs’ acceptance of their role in providing comprehensive primary care, it suggests a lesser acceptance of their role in community-oriented primary care as well as primary care management. This study provides a basis for future, quantitative research describing attitudes and competence in these areas.

The occurrence of earthquakes in oceanic trenches can pose a tsunami threat to lives and properties in active seismic zones. Therefore, the knowledge of focal depth, magnitude, and time distribution of earthquakes along the trenches is needed to investigate the future occurrence of earthquakes in the zones. The oceanic trenches studied, were located from the seismicity map on: latitude +51° to +53° and longitude −160° to 176° (Aleutian Trench), latitude +40° to +53° and longitude +148° to +165° (Japan Trench), and latitude −75° to −64° and longitude –15° to +30° (Peru–Chile Trench). The following features of seismic events were considered: magnitude distribution, focal depth distribution, and time distribution of earthquake. The results obtained in each trench revealed that the earthquakes increased with time in all the regions. This implies that the lithospheric layer is becoming more unstable. Thus, tectonic stress accumulation is increasing with time. The rate of increase in earthquakes at the Peru–Chile Trench is higher than that of the Japan Trench and the Aleutian Trench. This implies that the convergence of lithospheric plates is higher in the Peru–Chile Trench. Deep earthquakes were observed across all the trenches. The shallow earthquakes were more prominent than intermediate and deep earthquakes in all the trenches. The seismic events in the trenches are mostly of magnitude range 3.0–4.9. This magnitude range may indicate the genesis of mild to moderate tsunamis in the trench zone in near future once sufficient slip would occur with displacement of water column.

As the reports in the literature regarding corrosion performance of Al/TiB2 MMC are rather contradictory, the optimization of laser surface alloying parameters for these composite coatings seems to be necessary. The characterization of the MMC was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and x-ray diffraction (XRD). Partial melting of the alloying powder occurred and the chemical reactions with the a-Al in the matrix led to the formation of AlTi and AlB2 phases. Eutectics of TiB2/Al and TiB2/Ti were observed. The results of the tests indicate that TiB2 reinforcement does not give significant increase in microhardness of aluminium. The corrosion resistance of a single laser trackline MMC in a 3.65 % NaCl solution was improved, especially for the sample produced at high scan speed, with the lowest volume fraction of TiB2 particles.

Abstract: As the reports in the literature regarding corrosion performance of Al/TiB2 MMC are rather contradictory, the optimization of laser surface alloying parameters for these composite coatings seems to be necessary. The characterization of the MMC was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and x-ray diffraction (XRD). Partial melting of the alloying powder occurred and the chemical reactions with the a-Al in the matrix led to the formation of AlTi and AlB2 phases. Eutectics of TiB2/Al and TiB2/Ti were observed. The results of the tests indicate that TiB2 reinforcement does not give significant increase in microhardness of aluminium. The corrosion resistance of a single laser trackline MMC in a 3.65 % NaCl solution was improved, especially for the sample produced at high scan speed, with the lowest volume fraction of TiB2 particles.

Surface characteristics of laser surface engineered iron oxide coatings on a cast aluminium alloy developed for improved wear performance have been studied by atomic force microscopy (AFM) in association with microhardness measurements. An attempt is made to relate the grain size and surface roughness of FeO and Fe3O4based coatings to wear performance determined by block-on-disk dry sliding wear testing. Fe3O4based coating exhibits finer grain and smoother surface in comparison to FeO coating. However, FeO displays superior wear performance even though the Knoop microhardness of both coatings was comparable.

AbstractPolyaniline–polypyrrole composite coatings were deposited onto Al 2024 using an electrochemical process. The effect of incorporating inorganic fillers such as clay and yttria stabilised zirconia on the corrosion performance of the composite coating was studied. The coatings were analysed using infrared spectroscopy and scanning electron microscopy. The electrodeposition parameters such as feed monomer ratio, applied current density, and reaction time were systematically varied. Results showed that the composite coatings improved the corrosion resistance of the substrate.

Polyaniline–polypyrrole composite coatings were deposited onto Al 2024 using an electrochemical process. The effect of incorporating inorganic fillers such as clay and yttria stabilised zirconia on the corrosion performance of the composite coating was studied. The coatings were analysed using infrared spectroscopy and scanning electron microscopy. The electrodeposition parameters such as feed monomer ratio, applied current density, and reaction time were systematically varied. Results showed that the composite coatings improved the corrosion resistance of the substrate.

Abstract: This article presents the results of a combined experimental and analytical study of the fatigue and fracture behavior of a polymer/metal composite which was developed recently for self-lubricating applications in automotive engines that utilize liquefied natural gas as fuel. For comparison, the microstructure and the fatigue and fracture behavior of a nonpolymer-containing “matrix” material are also presented. Since the crack profiles observed in both systems under monotonic or cyclic loading reveal significant components of ligament bridging, micromechanics models are presented for the modeling of crack bridging. The resulting predictions of resistance-curve behavior are compared with measured resistance curves. The shielding effects of ligament bridging are also quantified under cyclic loading. The implications of the work are also discussed for the modeling of fatigue damage and fracture in polymer/metal coatings.

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Abstract: The cold gas-dynamic spray method produces coatings or deposits by introducing solid feedstock particles into a supersonic gas stream developed through the use of a converging-diverging (de Laval) nozzle. The particles thus accelerated impact on a substrate surface and develop into a dense deposit through a process believed to be similar to cold compaction. The work reported here explores the internal nature and physical characteristics of copper deposits produced by the cold gas-dynamic spray method using two vastly different starting powders: in one case, a “spongy” copper obtained by a direct-reduction process, and in the second, a denser, more spheroidal particulate produced by gas atomization. Optical and electron microscopies (scanning electron microscopy [SEM] and transmission electron microscopy [TEM]) were used to observe details of microstructure in the feedstock particles and deposits. Young’s modulus and residual stress measurements for the deposits were obtained through mechanical means, and measurements of hardness and electrical conductivity are reported. The internal structure of the cold-spray deposit was influenced by the surface purity of the feedstock material.

Two types of ion beam surface modifications have been performed. 1.(i) Superficial amorphization has been induced in an industrial NiTi shape memory alloy by direct ion implantation. A remarkable increase in the wear resistance and exceptional reduction in the friction coefficient has been observed for an implantation of 3 × 1017N+cm-2.2.(ii) An FeAl coating 1 μm thick on steel has been obtained by iron and aluminium evaporation simultaneously with argon ion irradiation. This coating significantly improves the tribological behaviour of this steel and presents an exceptional adherence to the substrate, which is not so if the coating is performed without ion assistance.

Recent innovations in equipment, processes, and diagnostics make thermal spray coatings both practical and desirable for use in large scale automotive manufacturing.The advent of rotating devices and surface preparation methodologies such as high pressure water jet, electrodischarge machining, and chemical fluxes permit thermal spray coating applications on cylinder bore and valve seat areas of engines. Low carbon steel alloy composite and aluminium bronze coatings have been successfully tested on cylinder bores. The Fe–Fe3O4/Ni–NiO–CrO composite coating obtained by spraying carbon steel and nickel base alloy wires using a two wire arc gun works well as a valve seat material.

Water is essential for livelihood, development, and industrial growth. Its exploration in sufficient quantity is required where it does not freely occur on the surface. This research was aimed to delineate aquifer regions and provide information on the subsurface lithology of Moloko-Asipa Southwestern Nigeria. A combination of eight traverses investigated with very low frequency electromagnetic (VLF-EM) method at 5 m constant sampling interval and ten vertical electrical sounding (VES) were carried out in the survey. Measurements from the VLF-EM survey were processed with Karous and Hjelt filtering to give the resistivity contrast across the selected profiles. The VES data processing involved an automatic approximation of the initial resistivity and thickness of the geoelectric layers with IPI2Win and further filtering by WinResist iteration. Estimation of Dar-Zarrouk parameters was also employed to investigate the aquifer protective capacity of the area. The processed VLF-EM results showed the geology of the area to an average depth of 25 m. The geoelectric section of the VES data revealed minimum of 3 layers from sandy top soil to weathered layer and fresh basement with an average resistivity values of 1,816, 926 and 17,503 Ωm, respectively. The integration of VLF-EM and VES in the investigation revealed that the potential for groundwater exploration in the study area is poor due to the thin nature of the weathered layer and its shallow depth to basement. The aquifer protective capacity of the area was likewise inferred to be poor.

The influence of varied process parameters involving three levels of temperature, pressure, heating rate and dwell time on the microstructure, densification and microhardness of spark plasma sintered Ti-6Al-4V/h-BN binary composite was studied. Taguchi design method was adopted to randomize the SPS process parameter levels. The microstructure was analyzed by optical microscopy, densification was determined based on the principle of Archimedes and Vickers microhardness tester was used to evaluate the microhardness of the sintered composite. The consolidation of Ti-6Al-4V powder and nanoparticles of 3 wt.% of h-BN via SPS produced nearly full theoretical densification of 99.77% and the sintered composite gave a microhardness value of 710.37 HV which is more than 200% that of the monolithic alloy. The best combination of relative densification and microhardness were obtained at the sintering parameters of 1000 degC of temperature, 40 MPa of pressure, 100 degC/min heating rate and 15 min of dwell time. Generally, it was found that improved microstructure, densification and microhardness were influenced by the high temperature of sintering and low rate of heating that gave room for adequate diffusional mass transport resulting in solid bonding between the particles of the matrix and the ceramic reinforcement.

Aluminium 1000 alloy has high purity and good electrical conductivity required for high power transmission conductors but lacks adequate thermal conductivity which induces sagging in service. To augment this deficiency, Nb nanopowder was incorporated into it as a reinforcement and consolidated with spark plasma sintering (SPS). The SPS was conducted with pre-optimized processing parameters of 630 degC, 30 MPa, 10 mine and 200 degC/min. The sintering was conducted in a vacuum with graphite die of 20 mm in diameter. Thereafter, the sintered samples were metallographically prepared and subjected to thermal conductivity testing. A laser flash analyzer was used to generate the thermal diffusivity of the samples. Then their thermal conductivities were computed. Results obtained showed that Al-4Nb had the highest thermal conductivity of 115. 95 +- 6.9 W/mK which represented 42% improvement. So, it follows that Al-Nb composite is a better replacement for monolithic Aluminium 1000 alloy in power transmission conductors with a potential property of low sag.

Unreinforced Al alloy lacks adequate tribological property required in service. To improve on this property, it must be reinforced with materials having good wear properties. Hence, Al was reinforced with CNTs and Nb and consolidated with spark plasma sintering (SPS). The wear experiment was conducted on a ball-on-disc Tribometer where loads of 10 N, 20 N and 30 N were systematically applied. The coefficients of friction (COF) of the sintered samples were subsequently obtained. The samples were weighed before and after each run to determine their weight losses which were used to compute their wear volumes. The experiment was designed and analyzed with Taguchi and ANOVA. Results showed that Al-8CNTs-8Nb composite had the best wear characteristics. Its COF got improved by 79% which shows that it is suitable for industrial applications.

Improvement of wear behaviour and mechanical properties of polymers as bulk and surface coating materials for advanced engineering applications have been research interest. Improved wear resistance and mechanical properties were achieved in this study by incorporation of surface modified graphene and titanium dioxide nano-powder in poly (vinylidene fluoride) matrix via solution blending and melt compounding. The morphology of the nanocomposites was studied using scanning electron microscope (SEM). The nanocomposites showed significant reduction in wear volume and enhanced mechanical properties due to the presence of surface modified nanofillers. About 76.5% reduction in wear volume, 52% and 186.5% increase in tensile strength and Young modulus respectively were achieved in this study. The surface modification of the nanofillers was essential in dispersion of the nanofillers in the polymer matrix and the improved properties recorded. Such nanocomposites can find applications as protective surface coating materials for high frictional condition and bulk materials for automobile and aerospace components.

Direct Metal Laser Deposition (DMLD) processes such as LENS are gaining ground in commercial manufacturing processes of functional end-products. This is attributed to this process being popularized as a sustainable technology with the potential to substitute the energy intensive, wasteful and environmentally unfriendly traditional techniques. However, during processing a significant fraction of the injected powders do not end up as part of the final component. The properties of these powders change due to heating resulting in coalescence and possible chemical reactions with the surrounding environment. A potential way to overcome this is by adopting an effective powder recycling procedure by which material use efficiency can be improved. Even so, these changes may have detrimental impact on the mechanical properties of the end-product. The objective of this paper is to investigate the effect of powder recycling on mechanical properties as a consequence of a change in powder characteristics. The potential for improving the LENS process by powder recycling process has been evaluated by comparatively studying the feedstock characteristics, i.e. morphology, particle size distribution and microstructure of powders in as received state and after laser exposure during repeated deposition cycles. Microstructures, micro-hardness and Density of the built samples were measured after the first deposition-normalization-reuse cycle. The results revealed a correlation between the powder characteristics and the properties of the corresponding built sample used for that specific deposition.

The indispensable properties of Ti-6Al-4V alloy coupled with poor tribological properties and delayed bioactivity make it a subject of interest to explore in biomedical application. A quite number of numerous coatings have been employed on titanium alloys, with aim to overcome the poor properties exhibited by this alloy. In this work, the possibility of laser cladding different ad-mixed powders (Ti - 5 wt.% Al2O3 and Ti - 8wt.% Al2O3) on Ti-6Al-4V at various laser scan speed (0.6 and 0.8 m/min) were investigated. The microstructure, phase constituents and corrosion of the resultant coatings were characterized by scanning electron microscope (SEM), Optical microscope, X-Ray diffractometer (XRD) and potentiostat respectively. The electrochemical behaviour of the produced coatings was studied in a simulated body fluid (Hanks solution). The microstructural results show that a defect free coating is achieved at low scan speed and ad-mixed of Ti-5 wt. % Al2O3. Cladding of Ti - Al2O3 improved the corrosion resistance of Ti-6Al-4V alloy regardless of varying neither scan speed nor ad-mixed percentage. However, Ti-5 wt.% Al2O3 coating produced at low scan speed revealed the highest corrosion resistance among the coatings due to better quality coating layer. Henceforth, this coating may be suitable for biomedical applications.