Showing papers by "Paul Munroe published in 2020"
TL;DR: This study suggested that N in the Bio-MUC was shown slow releasing in water but maize growth promoting in soil, relative to conventional urea, and biochar from agro-wastes could be used for blending urea as combined organo/mineral urea to replace mineral urea so to reduce N use and impacts on global Nr.
125 citations
TL;DR: It is suggested that the redox properties of the biochar cause major changes in electron status of rhizosphere soils that drive the observed agronomic benefits.
78 citations
TL;DR: In this paper, high entropy alloy (HEA) was applied to M2 steel substrates via direct current (DC) magnetron sputtering at several nitrogen flow rates (4, 8, 15, 25 sccm).
54 citations
TL;DR: Taking advantage of both the porous microstructure and carbon coating, S-KTO@C shows excellent rate capability and cycling stability as an anode material for PIBs and can pave the way for the development of high-performance potassium-based energy storage devices.
Abstract: Benefiting from the natural abundance and low standard redox potential of potassium, potassium-ion batteries (PIBs) are regarded as one of the most promising alternatives to lithium-ion batteries for low-cost energy storage. However, most PIB electrode materials suffer from sluggish thermodynamic kinetics and dramatic volume expansion during K+ (de)intercalation. Herein, it is reported on carbon-coated K2 Ti2 O5 microspheres (S-KTO@C) synthesized through a facile spray drying method. Taking advantage of both the porous microstructure and carbon coating, S-KTO@C shows excellent rate capability and cycling stability as an anode material for PIBs. Furthermore, the intimate integration of carbon coating through chemical vapor deposition technology significantly enhances the K+ intercalation pseudocapacitive behavior. As a proof of concept, a potassium-ion hybrid capacitor is constructed with the S-KTO@C (battery-type anode material) and the activated carbon (capacitor-type cathode material). The assembled device shows a high energy density, high power density, and excellent capacity retention. This work can pave the way for the development of high-performance potassium-based energy storage devices.
52 citations
TL;DR: There was an overall increase in soil carbon, fruit yield, tree diameter and height in all biochar treatments relative to the control over the seasons and a cost-benefit analysis indicated that if yield surplus of fruit trees continued for three years, then the discounted net benefit over a hectare would amount to US$8581.
48 citations
TL;DR: In this article, a TiSiN nanocomposite coating was fabricated on to a Ti-6Al-4V substrate using reactive sputterdeposition through the double cathode glow discharge plasma technique.
41 citations
TL;DR: It is suggested that an alkaline silicon supplementation is used as an amendment to BR, which could be used as a strategic approach for tackling Cd contamination in South China rice paddies.
38 citations
TL;DR: In this paper, three FeMnNiCoCr high entropy alloy (HEA) coatings were deposited onto M2 steel substrates using a direct current (DC) magnetron sputtering system under a range of substrate bias voltages (−20,V, −60,V and −120,V).
Abstract: Three FeMnNiCoCr high entropy alloy (HEA) coatings were deposited onto M2 steel substrates using a direct current (DC) magnetron sputtering system under a range of substrate bias voltages (−20 V, −60 V and −120 V). The microstructure transformed from a fine elongated structure to coarse V-shaped columnar grains with increasing substrate bias voltage. A high density of nanotwins, together with the presence of a partial fcc-to-hcp transformation, was observed in the coating deposited at −120 V. This was attributed to the introduction of stacking faults whose presence was promoted by preferential re-sputtering effects during the deposition process. A high hardness value of ~9.1 GPa, accompanied by exceptional damage-tolerance, was achieved in the coating deposited at −120 V. Here, the formation of nanotwins and the dual-phase structure was found to contribute to this remarkable combination of hardness and resistance to plastic deformation.
26 citations
TL;DR: In this article, a bio-test of wheat straw vinegar showed strong antifungal activity on F. graminearum growth and production of deoxynivalenol (DON) with an EC50 (concentration for 50% of maximal effect) value of 3.1μl−ml−1.
25 citations
TL;DR: A low mass fraction of TiC nanoparticles was successfully introduced into a Mg-4Zn-0.5Ca matrix alloy using mechanical stirring together with ultrasonic treatment as discussed by the authors.
22 citations
TL;DR: The microstructure, texture and mechanical properties of a series of Mg-Zn-Ca-Mn alloys with three Zn/Ca ratios (2.63, 1.22 and 0.53, by weight ratio) were investigated in this paper.
Abstract: The microstructure, texture and mechanical properties of a series of Mg–Zn–Ca–Mn alloys with three Zn/Ca ratios (2.63, 1.22 and 0.53, by weight ratio) were investigated. The dominant second phase changed from MgZn to Ca2Mg6Zn3 as the Zn/Ca ratio decreased from 2.63 to 1.22. With decreasing Zn/Ca ratio, the grain size of the as-cast alloys was significantly decreased, accompanied by an increase in the volume fraction of second phase.
For as-extruded Mg–1.4Zn–2.6Ca–0.5Mn, the finest (~ 0.36 μm) recrystallized grain structures, containing both fine MgZn2 precipitates and α-Mn particles, were obtained at an extrusion speed of 0.01 mm/s. The texture of the deformed structure was more intense (~ 30.39 mud) relative to the recrystallized region (~ 8.33 mud). As the Zn/Ca ratio decreased, basal plane texture was weakened deriving from grain refinement following recrystallization. Superior mechanical properties with a yield strength of ~ 387.8 MPa and ultimate tensile strength of ~ 409.2 MPa were achieved in the Mg–1.4Zn–2.6Ca–0.5Mn alloy extruded at 270 °C at an extrusion speed of 0.01 mm/s. A number of factors were determined to contribute to strengthening including Hall–Petch effects from the fine recrystallized grains (contribution ~ 58.7%), dislocation strengthening of the deformed region (contribution ~ 29.3%) and Orowan strengthening (contribution ~ 12%).
TL;DR: The Ag+ release was found to be the dominant antimicrobial mechanism for the Ag:ZnO NP sample in the authors' experiment, and insights into the mechanisms underlying the antimicrobial effects were revealed: synergistic effect of reactive oxygen species (ROS) generation andAg+ release.
TL;DR: FeMnCoCrC high entropy alloy coatings were deposited onto high speed steel substrates using magnetron sputtering under a range of substrate bias voltages as mentioned in this paper, which exhibited a novel α-Mn crystal structure and highly refined columnar grains.
TL;DR: In this article, a NiCrMoAl alloy was coated onto a mild steel substrate by arc spraying, which was extensively characterized by a combination of X-ray diffraction, scanning electron microscopy and focused ion beam microscopy.
Abstract: Arc spraying is a flexible thermal spray coating that can be used in on-site applications. In this study, a NiCrMoAl alloy was coated onto a mild steel substrate by arc spraying. The cored wire feedstock and the deposited coating were extensively characterized by a combination of X-ray diffraction, scanning electron microscopy, focused ion beam microscopy and transmission electron microscopy. Vickers microhardness and nanoindentation were used to investigate the mechanical properties of individual phases in the coating. The results showed that the NiCrMoAl alloy cored wire feedstock primarily consisted of material in elemental form including Ni, Cr, Mo, Al, Si, and Ti, whilst the arc sprayed coating contained a solute-lean γ-Ni phase, a (Mo, Si)-rich γ-Ni phase, elemental Mo splat as well as Cr2O3, Al2O3, and SiO2 at intersplat regions, together with ≤100 nm spherical Al2O3 particles within the splats. Partitioning of Mo and Si into the γ-Ni phase was observed following the rapid solidification of the splat on deposition. The Vickers hardness analysis showed that the average overall hardness of the coating was about 3.65 ± 0.56 GPa. However, nanoindentation indicated that the highest hardness was in the γ-Ni splat regions, especially those containing a high concentration of solute. The microstructural evolution, as well as the structure and chemistry of the phases that affect mechanical properties in the coating are discussed in detail.
TL;DR: In this paper, a new Mg-2.2.5% Zn alloy with nano-sized MgZn2 precipitates and α-Mn nanoparticles was developed and subjected to extrusion under different extrusion parameters.
Abstract: A new Mg-2.2 wt% Zn alloy containing 1.8 wt% Ca and 0.5 wt% Mn has been developed and subjected to extrusion under different extrusion parameters. The finest (~ 0.48 μm) recrystallized grain structures, containing both nano-sized MgZn2 precipitates and α-Mn nanoparticles, were obtained in the alloy extruded at 270 °C/0.01 mm s−1. In this alloy, the deformed coarse-grain region possessed a much stronger texture intensity (~ 32.49 mud) relative to the recrystallized fine-grain region (~ 13.99 mud). A positive work hardening rate in the third stage of work hardening curve was also evident in the alloy extruded at 270 °C, which was related to the sharp basal texture and which provided insufficient active slip systems. The high work hardening rate in the fourth stage contributed to the high ductility extruded at 270 °C/1 mm s−1. This alloy exhibited a weak texture, and the examination of fracture surface revealed highly dimpled surfaces. The optimum tensile strength was achieved in the alloy extruded at 270 °C/0.01 mm s−1, and the yield strength, ultimate tensile strength and elongation to failure were ~ 364.1 MPa, ~ 394.5 MPa and ~ 7.2%, respectively. Fine grain strengthening from the recrystallized fine-grain region played the greatest role in the strength increment of this alloy compared with Orowan strengthening and dislocation strengthening in the deformed coarse-grain regions.
TL;DR: In this paper, a nickel powder was sprayed on a polished aluminum substrate using the high-velocity oxy-fuel spraying process, and detailed microstructural characterization was conducted to analyse the mechanims of splat formation, with particular attention to the changes occurring at the splat-substrate interface and the subsequent bonding behavior due to the impact of high thermal and kinetic energy particles with a soft, low melting point substrate.
Abstract: In this study, nickel powder was sprayed on a polished aluminum substrate using the high-velocity oxy-fuel spraying process. Detailed microstructural characterization was conducted to analyse the mechanims of splat formation, with particular attention to the changes occurring at the splat-substrate interface and the subsequent bonding behaviour due to the impact of high thermal and kinetic energy particles with a soft, low melting point substrate. Characterization was performed using scanning electron microscopy, focused ion beam microscopy, transmission electron microscopy, together with the scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that a large number of particles had rebounded upon impact, which was correlated with the degree of substrate melting and the associated time for re-solidification. The remnant splats that adhered to the substrate surface were found to exhibit both mechanical and metallurgical bonding with the substrate. The experimental results were supported by transient finite element based thermal simulation.
TL;DR: In this article, multidirectional forging (MDF) and extrusion (EX) was applied to the TiC nanoparticle-reinforced Mg−4Zn−0.5Ca matrix nanocomposites.
TL;DR: In this article, oxide layers on Ni and Ni20Cr particles were formed through isothermal pre-oxidation prior to spraying and their influence on droplet spreading and splat-substrate interfacial interactions was investigated.
Abstract: During plasma spraying in air, molten metallic droplets can develop a surface oxide shell which is postulated to play a significant role on the subsequent impact and spreading on the substrate surface resulting in splat formation. In this work, oxide layers on Ni and Ni20Cr particles were formed through isothermal pre-oxidation prior to spraying and their influence on droplet spreading and splat-substrate interfacial interactions was investigated. The results showed that the presence of this oxide shell readily induced finger splashing, irrespective of the oxide shell thickness. In addition, small oxide nodules were frequently detected inside the splats. An oxygen-enriched interfacial interlayer was observed for the pre-oxidized-Ni splats. A mechanism is proposed to account for the inclusion of oxide fragments from the particle surface oxide shell, in the deposition of single plasma-sprayed Ni and Ni20Cr splats.
TL;DR: In this paper, microstructural analysis was carried out to investigate the effect of substrate surface chemistry on splat formation, which revealed that a mixture of mechanical and metallurgical bonds exists between the splats and both substrates.
Abstract: In the present study, microstructural analysis was carried out to investigate the effect of substrate surface chemistry on splat formation. Ni powder was sprayed onto stainless steel substrates exhibiting two different surface conditions (polished and oxidized) by high-velocity oxy-fuel (HVOF) thermal spray. X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical state of the surfaces which indicated the presence of the adsorbates on the oxidized substrate. Single splats of different morphologies from both samples were examined using a range of characterization techniques including scanning electron microscopy (SEM), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM) and energy-dispersive x-ray spectroscopy (EDS) interfaced to both SEM and TEM. This provided information on the particle solidification behavior and splat formation mechanism following impact on substrates with distinct surface conditions. The results showed the effect of oxidized surface adsorbates on splat morphology, pore formation and splat–substrate interactions. These microstructural findings, aided by theoretical models, revealed that a mixture of mechanical and metallurgical bonds exists between the splats and both substrates.
07 Oct 2020-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a novel TiC nanoparticle reinforced Mg-2.9Zn-1.1Ca-0.5Mn nanocomposite, with a mixed grain microstructure exhibiting high strength and targeted for biocompatible/structural applications was successfully prepared by ultrasonic assisted semi-solid stirring and extrusion at ultra-slow speeds of 1, 0.1 and 0.01 mm/s.
Abstract: In this work, a novel TiC nanoparticle (0.5 wt %) reinforced Mg-2.9Zn-1.1Ca-0.5Mn nanocomposite, with a mixed grain microstructure exhibiting high strength and targeted for biocompatible/structural applications was successfully prepared by ultrasonic assisted semi-solid stirring and extrusion at ultra-slow speeds of 1, 0.1 and 0.01 mm/s. The experimental results revealed that the morphology of the eutectic Ca2Mg6Zn3 phase in the as-cast nanocomposite changed from plate-like to lamellar as a low mass fraction of TiCp was added. Both dynamically recrystallized grains and precipitates were gradually refined with decreasing extrusion speed. The finest recrystallized grains (∼0.46 μm), with a high volume fraction (∼4.3%) of fine precipitates, appeared after extrusion at 0.01 mm/s. The refined grain structure was not only due to dynamic recrystallization, but also the synergistic pinning effects from nano-TiCp as well as precipitated MgZn2 and α-Mn particles. The superior ultimate tensile strength (∼410.3 MPa), yield strength (∼384.5 MPa) and elongation to failure (∼4%) were obtained in the nanocomposite extruded at the slowest speed (0.01 mm/s) and had the potential to serve as a candidate material in orthopaedic applications. The improved strength was mainly related to grain refinement, thermal expansion effects and Orowan strengthening. Grain refinement, in particular, contributed to the largest strengthening increment. High tensile toughness of ∼66.6 KJ mm−3 was achieved for the nanocomposite extruded at a speed of 1 mm/s. Further, it exhibited a high strain hardening rate, θ, at stage IV. The fracture surface exhibited abundant dimples and consistent with high ductility. Remnant coarse Ca2Mg6Zn3 particles acted as crack initiators under high applied stress in tension, leading to structural failure.
TL;DR: In this paper, the α-(Nb1-xAgx)5Si3 compounds, with three different Ag contents, were deposited on Ti-6Al-4V by double cathode glow discharge method.
TL;DR: CeO2-x coatings were deposited under variable oxygen flow ratios (%fO2) onto Si substrates by reactive magnetron sputtering as discussed by the authors, which increased the hardness, elastic modulus, H/E and H3/E2 ratio with increasing oxygen flow ratio, which in turn increased the adhesion and tribological performance of the coatings.
TL;DR: In this paper, Ni powder was sprayed onto both mild and stainless-steel substrates using high-velocity oxy-fuel (HVOF) deposition to comparatively analyse the effect of substrate material properties and surface condition on splat formation.
Abstract: In the present study, Ni powder was sprayed onto both mild and stainless-steel substrates using high-velocity oxy-fuel (HVOF) deposition to comparatively analyse the effect of substrate material properties and surface condition on splat formation. A range of microscopy techniques including scanning electron microscopy (SEM), focused ion beam (FIB) microscopy, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX) were employed to characterize both the splat morphologies, including their cross-sectional structure, as well as the nature of the splat-substrate interface. It was shown that the majority of the particles reached the substrate surface in a partially melted form owing to the high velocity typical in the HVOF process. Despite some splat splashing observed on the stainless-steel sample, the diffusion profiles, determined by STEM-EDX line scans, revealed evidence of elemental interdiffusion at the splat-substrate interface, suggesting metallurgical bonding in this sample. It was observed that splat morphologies, their frequency of occurrence and splat-substrate bond quality are all greatly affected by the surface condition of the substrate. These microstructural observations were correlated with the thermo-mechanical characteristics of the substrates to explain the mechanisms driving splat formation. Differences in the degree of plastic deformation of the substrates due to particle impact are also discussed.
TL;DR: The thin film RF sputtering from the metallic cathode exhibited better pH response than those RF sputtered from the oxide cathode due to the higher percentage of the RuO3 phase present in this film.
Abstract: RuO2 thin films were prepared using magnetron sputtering under different deposition conditions, including direct current (DC) and radio frequency (RF) discharges, metallic/oxide cathodes, different substrate temperatures, pressures, and deposition times. The surface morphology, residual stress, composition, crystal structure, mechanical properties, and pH performances of these RuO2 thin films were investigated. The RuO2 thin films RF sputtered from a metallic cathode at 250 °C exhibited good pH sensitivity of 56.35 mV/pH. However, these films were rougher, less dense, and relatively softer. However, the DC sputtered RuO2 thin film prepared from an oxide cathode at 250 °C exhibited a pH sensitivity of 57.37 mV/pH with a smoother surface, denser microstructure and higher hardness. The thin film RF sputtered from the metallic cathode exhibited better pH response than those RF sputtered from the oxide cathode due to the higher percentage of the RuO3 phase present in this film.