•New multicomponent compounds (Sm,Ho)2Fe17Nx (x = 0; 2.4) are prepared.•The ball-milling process was conducted at room temperature.•Structure and magnetic properties were investigated at ...2–300 K.•Study showed the enhance of magnetic performance.•High magnetic fields reveal the presence of phase transition at 500 kOe.
The structural and magnetic properties of the compound Sm1.2Ho0.8Fe17 and the nitride powders Sm1.2Ho0.8Fe17N2.4 prepared by high energy ball milling under various milling regimes are reported. Magnetic properties of the samples are investigated at 2–300 K in steady magnetic field up to 70 kOe and in pulsed magnetic field up to 600 kOe. The application of high magnetic field reveals the presence of the second-order transition in Sm1.2Ho0.8Fe17N2.4 at 500 kOe. Magnetic hysteresis properties study shows that ball milling enhances magnetic performance of Sm1.2Ho0.8Fe17N2.4 making it perspective for the magnets fabrication.
In this research, aluminum tubes were integrated into metal syntactic foam (MSF) to manufacture novel tube-filled foam (TFF) structures. Counter-gravity infiltration casting was used to manufacture ...TFFs using an innovative single-step process. The density of the resulting TFFs was between 1.79 and 1.91 g cm−3 and thus similar to the density of the surrounding MSF. Microstructural analysis of the interface between tube and MSF indicates no significant chemical reaction. For comparison, MSF reference samples without tubes were produced. Quasi-static compression tests were conducted to determine the mechanical properties of the samples produced. The results indicate that embedded aluminum tubes and surrounding MSF mutually stabilize their deformation. TFF samples compressed with uniform barreling from the center of the sample whereas the deformation of MSFs was localized towards one end of the sample. As a result, TFFs showed superior mechanical performance compared to MSFs.
•Novel tube-filled metal foams (TFF) were successfully manufactured.•The integration of a metal tube did not increase the density.•Good bonding between metal tube and metal foam was observed.•The integration of a metal tube improved the mechanical properties of the structure.
Herein, the effect of electrodeposition time on the super-capacitive performance of three-dimensional (3D) MnO2/g-C3N4 heterostructured electrodes was investigated. MnO2 nanoparticles were ...electrodeposited on the g-C3N4 nanosheets drop-casted on the Ni foam substrate. The microstructural analysis, carried out by FE-SEM and TEM, confirmed the homogeneous distribution of MnO2 nanoparticles on g-C3N4 nano-sheet layers. The electrochemical capacitive performances of the MnO2/g-C3N4 electrodes were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge tests, and electrochemical impedance spectra (EIS). The obtained results suggested that the supercapacitor (SC) performance of all prepared g-C3N4/MnO2 composite electrodes is higher than pure MnO2 and pure g-C3N4 electrodes. The effect of electrochemical deposition time on the electrochemical performances of the fabricated electrodes was investigated as well. The specific capacitance of synthesized g-C3N4/MnO2 electrodes was measured as 87.6, 67, and 49.5 Fg-1 for 1, 2, and 3 min deposition time respectively at the current density of 0.5 Ag-1, indicating the electrode obtained with shorter deposition time delivers maximum specific capacity. Therefore, this deposition time has been validated as the optimum time for electrochemical energy storage application.
Fe-based amorphous/nanocrystalline composite coatings with a lean composition of Fe−2.5Cr−6.7Si−2.5B−0.7C (wt%) were synthesized by atmospheric plasma spraying (APS) onto a mild steel substrate. The ...effects of plasma power on the morphology and the phase content of the coatings were systematically investigated. Denser coatings with better inter-splat bonding were obtained at a higher plasma power, which was attributed to higher degree of powder melting. The retention of amorphous phase and formation of various nanocrystalline Fe-borides in the amorphous matrix was decided by the variation in plasma power, which in turn affected the mechanical properties of the coatings. Increasing plasma power resulted in higher hardness and elastic modulus of the coatings, which is attributed to the compact microstructure of the coatings containing amorphous matrix with nanocrystalline intermetallics (Fe23B6, Fe2B, and/or Fe3B) distributed. The nanoscratch results indicated that the increased plasma power resulted in uniform scratch profiles. Moreover, dry sliding wear test showed that both coefficient of friction and wear rate decreased with increasing plasma power. An analytical model was used to correlate mechanical and tribological properties of the coatings, which insinuated that the coating prepared at a plasma power of 35.5 kW exhibited significantly high shear strength than other coatings deposited at lower plasma power and approximately 3.6 times greater than that of the mild steel substrate.
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•Fe-based amorphous/nanocrystalline coatings were deposited by plasma spraying.•Coatings consist of nano-sized α-Fe and Fe-borides distributed in amorphous matrix.•Higher plasma power resulted in more devitrification and better intersplat bonding.•High hardness resulted due to denser coating and presence of hard Fe-borides.•Wear resistance of the coatings increased with increasing plasma power.
In this study, we performed scanning transmission X-ray microscopy with a spatial resolution of approximately 50 nm to investigate the two-dimensional mapping of the chemical states of carbon in Fe–C ...alloy. The lamellar texture (pearlite) consisting of ferrite (α-Fe) and θ-Fe3C with an interval of approximately 100 nm was identified by absorption from the carbon 1s→2p excitation in the X-ray absorption image. It was clearly observed that there exist more than two types of chemical states of carbon in θ-Fe3C depending on the microtextures. The differences in chemical states were found between grained θ-Fe3C and lamellar θ-Fe3C in pearlite, which might have originated from the texture and morphology of the θ-Fe3C. To consider the origins of the differences, we performed first-principles calculations by assuming the distortion and crystal anisotropy of the unit cell of the θ-Fe3C structure. The results suggest that the anisotropy of the crystal structure of θ-Fe3C and the lattice strain within lamellar θ-Fe3C fail to explain the differences, and therefore, other factors should be considered.
Sample preparation is of utmost importance for any microscopy and microstructural analysis. Correct preparation will allow accurate interpretation of microstructural features. A well‐polished section ...is essential when scanning electron microscopy (SEM) is used in backscattering electron (BSE) mode and characteristic X‐rays are to be quantified using an energy‐dispersive spectroscopy (EDS) detector. However, obtaining a well‐polished section, especially for cementitious materials containing aggregates, is considered to be challenging and requires experience. A sample preparation procedure consists of cutting, grinding and polishing. Undercutting of soft and brittle paste between harder aggregates can be overcome by vacuum epoxy impregnation offering mechanical support in the matrix. Furthermore, most of the attention during the sample preparation is given to the polishing of the sample. There is a wide range of suggestions on polishing steps, ranging from grain sizes, time and applied force; however, the final assessment of a polish surface is often subjective and qualitative. Therefore, a quantitative, reproducible guidance on the grinding steps, effect of experimental parameters and the influence of different grinding steps on the surface quality are required. In this paper, the influence of grinding was quantitatively evaluated by a digital microscope equipped with optical profilometry tools, through a step‐wise procedure, including sample orientation, grinding time and the difference between cement paste and concrete. Throughout the grinding procedure, the surface profiles were determined after each grinding step. This showed the step‐wise change in surface roughness and quality during the grinding procedure. Finally, the surface qualities were evaluated using optical and electron microscopy, which show the importance of the grinding/prepolishing steps during sample preparation.
In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas ...atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.
Conventional experimental studies in concrete primarily focus on strength properties and microstructural analysis and ignore the environmental impacts of chosen waste in concrete. The present study ...addresses this critical research gap and uses industrial-based polyvinyl chloride (PVC) waste to demonstrate and meet the requirements of field practitioners and researchers. In the present study, various proportions of industrial-based PVC waste powder (PWP) (0–30%) by weight of cement were considered to partially replace cement in an M60 grade of self-compacting concrete (SCC). The first part of the study covers the fresh and strength properties of SCC, which was prepared using cement, sand, gravel, water, superplasticizer, SCM-like silica fume, ground granulated blast furnace slag, and PWP. In the second part of the study, the microstructure of various SCC mixes was investigated to understand the effects of PWP on the microstructure of the prepared SCC mixes. The optimum design mix for SCC was chosen based on extensive experimental and microstructural investigations. Further, a life cycle assessment was used to determine the influence of PWP on SCC usage from an environmental impact point of view for the optimized mixes. Considering all criteria, the results show that an SCC containing 5–10% PWP as a replacement for cement can be used. The present study establishes that using PWP in SCC is beneficial for the environment and can help lower the cost of SCC without compromising its strength and durability.
•The fresh and strength properties of SCC made with PVC waste powder were assessed.•The evaluation of the microstructure of SCC made from PVC waste powder was observed.•An optimized amount of PVC waste powder was chosen for this SCC.•The life cycle analysis of this optimized SCC was demonstrated.
Reducing solid waste emission is the development direction of cleaner production in the future. This paper proposes to use the agricultural solid waste rice husk ash (RHA) as an alternative ...cementitious material for the underground filling of mines. The pore structure and mechanical properties of cemented paste backfill with different RHA dosages (RCPB) are analyzed. The results reveal that: (1) The pore structure of RCPB is divided into three types: micropores (<0.1 μm), secondary pores (0.1–100 μm), and main pores (>100 μm). The total number of micropores accounts for the largest proportion, followed by secondary pores and main pores. The total volume of secondary pores accounts for the largest proportion, followed by micropores and main pores. (2) The porosity decreases and the UCS increases with the increase of RHA dosage and curing time. The UCS decreases linearly with the increase of RHA dosage. The UCS has a linear negative correlation with porosity. (3) The cracks of RCPB initiated at the yield point, gradually expanded at the peak point, and finally penetrated at the post-peak point. The failure mode of RCPB is mainly a tensile failure, accompanied by a small number of secondary tensile cracks. (4) The hydration products of RCPB are mainly C–S–H and AFt gels. The greater the RHA dosage and CT, the more hydration products, the fewer pores, the greater the strength, and the greater the average gray value. The outcome of this work will afford a new ideas and methods for using solid waste (Rice husk) as backfilling.
•Minor La addition significantly increases the dynamic recrystallization.•No new intermetallics except Mg17La12 were introduced after La addition.•La addition achieves high yield strength of 480 MPa ...and high ductility of ~6%.•Grain refinement by recrystallization is the key to good strength-ductility.
Effects of 0.5 wt% La addition on microstructures and mechanical properties of a traditional hot-extruded Mg–9Gd–3Y–0.5Zr alloy were thoroughly investigated in this work. The results indicate that minor La addition obviously improves the alloy’s mechanical performance at room temperature, accomplished an ultra-high tensile yield strength of 480 MPa with the elongation of ~6%, although leading to much lower high-temperature strength. Microstructural analysis reveals that after extrusion, minor La addition leads to a significantly higher level of recrystallization (the volume fraction is improved from 21% to 68%), much finer dynamically recrystallized (DRXed) grains (the average sizes are refined from 4.12 µm to 3.26 µm), and also finer non-recrystallization stripes. La addition promoting recrystallization is mainly attributed to the finer grains and much more intermetallics not only at grain boundaries but also in α-Mg grains of the ingots before extrusion. During peak-aging, minor La addition does not change intermetallics/precipitates in both DRXed grains and non-recrystallized regions except some extra coarse Mg17La2 particles mainly in extrusion stringers. Therefore, minor La addition improving both strength and ductility of the hot-extruded Mg–9Gd–3Y–0.5Zr alloy at room temperature is mainly by grain-refinement strengthening which is also the underlying cause for the lower work hardening coefficient, high-temperature strength but higher ductility.
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