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Undoped V2O5 is characterized by a small surface area and rapid electron-hole recombination, thus rendering it ineffective as a catalytic and antimicrobial agent. In this study, co-precipitation was employed to synthesize vanadium oxide (V2O5) and carbon spheres (CS) followed by doping with specific concentrations (3 and 6 wt%) of graphene oxide (GO) to produce GO/CS-doped V2O5 nanorods (NRs). The enhancement in catalytic and antibacterial activity provided by GO/CS-doped V2O5 was utilized to treat wastewater more efficiently. XRD analysis validated the orthorhombic and tetragonal structure of the synthesized samples. The polycrystalline nature of V2O5 was shown by vibrant circular rings in selected area electron diffraction (SAED) micrographs. TEM analysis endorsed formation of NRs, whereas UV–vis, luminescence (PL) and fourier transform infrared spectroscopy (FTIR), probed the absorption and emission along with stretching and bending vibrations in V-O-V bond. The chemically synthesized NRs exhibited excellent catalytic activity (93.71%) against rhodamine B (RhB) dye in the vicinity of NaBH4. In addition, NRs were used to evaluate in-vitro antimicrobial efficiency of 3.75 mmfor Escherichia coli (E. coli) using inhibition zone measurement. Docking investigations of GO/CS-V2O5 NRs for FabH and FabI of E. coli suggested suppression of above-mentioned enzymes as a possible mechanism. These findings demonstrate that (3 and 6 wt%) GO/CS-V2O5 possessed ample potency for industrial dye degradation and antimicrobial activity.

This study presents an unexplored method to produce formaldehyde-free MDF. Steam exploded Arundo donax L. (STEX-AD) and untreated wood fibers (WF) were mixed at different mixing rates (0/100, 50/50, and 100/0, respectively) and two series of boards were manufactured, with 4 wt% of pMDI, based on dry fibers, and self-bonded. The mechanical and physical performance of the boards was analyzed as a function of the adhesive content and the density. The mechanical performance and dimensional stability were determined by following European standards. The material formulation and the density of the boards had a significant effect on both mechanical and physical properties. The boards made solely of STEX-AD were comparable to those made with pMDI, while the panels made of WF without adhesive were those that performed the worst. The STEX-AD showed the ability to reduce the TS for both pMDI-bonded and self-bonded boards, although leading to a high WA and a higher short-term absorption for the latter. The results presented show the feasibility of using STEX-AD in the manufacturing of self-bonded MDF and the improvement of dimensional stability. Nonetheless, further studies are needed especially to address the enhancement of the internal bond (IB).

This article proposes using recycled aluminum, generating hydrogen in situ at low pressure, to power a 250 W electric bicycle with a fuel cell (FC), to increase the average speed and autonomy compared to a conventional electric bicycle with a battery. To generate hydrogen, the aluminum-water reaction with a 6 M NaOH solution is used as a catalyst. This article details the parts of the generation system, the electronic configuration used, the aluminum- and reagent-loading procedure and the by-products obtained, as well as the results of the operation without pedaling, with a resistance equivalent to a flat terrain and at maximum power of the accelerator for one and two loads of about 100 g of aluminum each. This allows us to observe different hybrid strategies, with a low-capacity battery in each case. The goal is to demonstrate that it is possible to store energy in a long-lasting, transportable, low-pressure, and sustainable manner, using recycled-aluminum test tubes, and to apply this to mobility.

This paper reports a straightforward and inexpensive method for the fabrication of gas sensing devices based on graphene oxide (GO) synthesized by a modified Hummer's method and decorated with strontium titanate perovskite (SrTiO3). The active layers developed were employed for the detection of hazardous gases such as NO2, CO2, and NH3. The physical and chemical properties were also analyzed using various experimental techniques including field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Raman spectroscopy. Repeated response and recovery cycles were applied in the detection of nitrogen dioxide (NO2), carbon dioxide (CO2), and ammonia (NH3). Accordingly, the gas sensing study reveals that decorated GO exhibits a high response towards NO2 at an operating temperature of 100 °C with good sensitivity (up to 4-fold higher than that of pristine GO) and highly improved selectivity. Additionally, the effect of ambient humidity was tested for NO2, demonstrating that GO/SrTiO3 sensors show a good immunity to humidity cross-sensitivity. Lastly, a gas sensing mechanism was schematically proposed and discussed. These findings prove that the functionalization of GO with SrTiO3 can overcome the limitations of GO-based sensors by enhancing their adsorption capability of gas molecules and their sensitivity towards target gases.

The aim of this paper is to investigate the flexural performance of a new steel–concrete composite beam system, which is required to carry higher loads when applied in flooring systems with less self-weight and cost compared with conventional composite beams. This new composite member is prepared by filling a single cold-formed steel C-section with concrete material that has varied lightweight-recycled aggregates. In addition, varied stiffening scenarios are suggested to improve the composite behavior of this member, since these cold-formed C-sections are of a slender cross-section and more likely to buckle and twist under high bending loads than those of hot-rolled C-sections. The influence of using four different lightweight-recycled aggregates that combine together in the infill concrete material was investigated. These recycled aggregates are recycled concrete aggregate (RCA), expanded polystyrene (EPS) beads, crumb rubber aggregates (CRA) and fine glass aggregates (FGA). For this purpose, 14 samples of cold-formed galvanized steel C-purlin were filled with concrete material (containing 0 to 100% recycled aggregates) which are experimentally tested under pure bending load, and 1 additional sample was tested without the filling material. Further numerical models were prepared and analyzed using finite element analysis software to investigate the effects of additional parameters that were not experimentally examined. Generally, the results confirm that filling the C-sections with concrete material that contains varied percentages of recycled aggregates offer significantly improved the flexural stiffness, bending capacity, and ductility performances. For example, using infill concrete materials with 0% and 100% recycled aggregate replacement increased the bending capacity of hollow C-section by about 11.4 and 8.6 times, respectively. Furthermore, stiffening of the concrete-filled C-sections with steel strips or screw connectors eventually improved the compo

Cement stabilized soil (CSS) yields wide application as a routine cementitious material due to cost-effectiveness. However, the mechanical strength of CSS impedes development. This research assesses the feasible combined enhancement of unconfined compressive strength (UCS) and flexural strength (FS) of construction and demolition (C&D) waste, polypropylene fiber, and sodium sulfate. Moreover, machine learning (ML) techniques including Back Propagation Neural Network (BPNN) and Random Forest (FR) were applied to estimate UCS and FS based on the comprehensive dataset. The laboratory tests were conducted at 7-, 14-, and 28-day curing age, indicating the positive effect of cement, C&D waste, and sodium sulfate. The improvement caused by polypropylene fiber on FS was also evaluated from the 81 experimental results. In addition, the beetle antennae search (BAS) approach and 10-fold cross-validation were employed to automatically tune the hyperparameters, avoiding tedious effort. The consequent correlation coefficients (R) ranged from 0.9295 to 0.9717 for BPNN, and 0.9262 to 0.9877 for RF, respectively, indicating the accuracy and reliability of the prediction. K-Nearest Neighbor (KNN), logistic regression (LR), and multiple linear regression (MLR) were conducted to validate the BPNN and RF algorithms. Furthermore, box and Taylor diagrams proved the BAS-BPNN and BAS-RF as the best-performed model for UCS and FS prediction, respectively. The optimal mixture design was proposed as 30% cement, 20% C&D waste, 4% fiber, and 0.8% sodium sulfate based on the importance score for each variable.

Conductive fillers, such as graphite particles (GP), steel slags (SS), and ground granulated blast furnace slag (GGBS) have been widely utilized in designing electrically conductive cementitious composites (ECCC) for various applications, including traffic detection, structural health monitoring (SHM), and pavement deicing. Owing to the complex working field, a comprehensive understanding of the role that the conductive fillers played in ECCC is essential for designing high-performance ECCC. In the present study, mechanical and conductivity experiments were conducted to explore the influences of these fillers on ECCC performances in strengths and electrical resistance. In addition, the reactive molecular dynamic (MD) simulation was firstly performed to quantify the interfacial properties of GP, SS, and GGBS in ECCC at the molecular level. Simulation results indicated that the chemical components of these conductive fillers dominate the atomic interfacial properties. Mineral components in SS or GGBS, especially Al2O3 and SiO2, led to a stronger interfacial bonding with cement in comparison to graphite in GP. At last, a hybrid mixing design of GP and SS was proposed in this study, balancing the mechanical and conductive performance of ECCC.

The glass fiber-reinforced polymer (GFRP) rebar reinforced cemented soil is widely employed to solve the weak foundation problem led by sludge particularly. The robustness of this structure is highly dependent on the interface bond strength between the GFRP tendon and cemented soils. However, its application is obstructed owing to the deficient studies on the influence factors. Therefore, this study investigates the effects of water content (Cw: 50%–90%), cement proportion (Cc: 6%–30%), and curing period (Tc: 28–90 days) on peak and residual interface bond strengths (Tp and Tt), as well as the unconfined compression strength (UCS). Results indicated that mechanical properties were positively responded to Tc and Cc, while negatively correlated to Cw. Besides, Random Forest (RF), one of the machine learning (ML) models, was developed with its hyperparameters tuned by the firefly algorithm (FA) based on the experimental dataset. The pullout strength was predicted by the ML model for the first time. High correlation coefficients and low root-mean-square errors verified the accuracy of established RF-FA models in this study. Subsequently, a coFA-based multi-objective optimisation firefly algorithm (MOFA) was introduced to optimise tri-objectives between UCS, Tp (or Tt), and cost. The Pareto fronts were successfully acquired for optimal mixture designs, which contributes to the application of GFRP tendon reinforced cemented soil in practice. In addition, the sensitivity of input variables was evaluated and ranked.

The effect of adding both Al2O3 and ZrO2 to limestone (CaCO3) to enhance the cyclic stability and reaction kinetics of endothermic CO2 desorption and exothermic CO2 absorption is investigated. The formation of CaZrO3 and Ca-Al-O compounds, e.g. CA5Al6O14, is evident, which enables a substantial >80% capacity retention over 50 calcination/carbonation cycles. The additives enable fast reaction kinetics where an 80% energy storage capacity is reached within 20–30 min, which is attributed to the synergetic effect of having both Ca-Zr-O and Ca-Al-O ternary additives present. The inert nature of the formed compounds prevents sintering of the particles, whilst allowing ion migration throughout the crystal structures, catalysing the carbonation reaction.

Geopolymer is a synthetic amorphous aluminosilicate material that can be used as an inorganic binder to replace ordinary Portland cement. Geopolymer is produced by mixing aluminosilicate source materials with alkali activators and curing the mixture either at ambient or low temperatures. Geopolymer research for lunar-based construction is actively underway to enable astronauts to stay on the moon for long periods. This research has been spurred on by earnest discussions of in situ resource utilization (ISRU). Recent research shows that the lunar regolith simulant-based geopolymers have high application potential to protect astronauts from the harsh moon environment. However, not all the simulants perfectly reproduce the lunar regolith, and the characteristics of the lunar regolith vary depending on the site. Issues remain regarding the applicability of geopolymer technology to contribute to ISRU through an elaborate and systematic plan of experiments. In this paper, the potential of geopolymers is assessed as a lunar-based construction material with the latest research results. Future work to develop the lunar regolith-based geopolymer technology is also proposed.

Portland cement (PC) is considered the most energy-intensive building material and contributes to around 10% of global warming. It exacerbates global warming and climate change, which have a harmful environmental impact. Efforts are being made to produce sustainable and green concrete as an alternative to PC concrete. As a result, developing a more sustainable strategy and eco-friendly materials to replace ordinary concrete has become critical. Many studies on geopolymer concrete, which has equal or even superior durability and strength compared to traditional concrete, have been conducted for this purpose by many researchers. Geopolymer concrete (GPC) has been developed as a possible new construction material for replacing conventional concrete, offering a clean technological choice for long-term growth. Over the last few decades, geopolymer concrete has been investigated as a feasible green construction material that can reduce CO2 emissions because it uses industrial wastes as raw materials. GPC has proven effective for structural applications due to its workability and analogical strength compared to standard cement concrete. This review article discusses the engineering properties and microstructure of GPC and shows its merits in construction applications with some guidelines and suggestions recommended for both the academic community and the industrial sector. This literature review also demonstrates that the mechanical properties of GPC are comparable and even sometimes better than those of PC concrete. Moreover, the microstructure of GPC is significantly different from that of PC concrete microstructure and can be affected by many factors.

To understand the extent of the temperature dependence on the deoxidation reactions during cooling of molten steel and the influence of solute microsegregation during solidification on the formation of oxide inclusions, changes in the morphology and composition of Mn–Si–Al deoxidation products of two actual steel samples are experimentally investigated herein. It is found that from 1823 K to just above the liquidus temperature of steel, oxide inclusion composition does not change significantly, suggesting that the temperature dependence of the deoxidation reactions on oxide inclusion formation can be ignored. Meanwhile, during solidification from the liquidus to the solidus temperature of steel, it is found that positive segregation of Mn and Si in the residual molten steel phase largely influences oxide inclusion composition such that the equilibrium oxide phase shifts from high- to low-Al2O3 region. It is confirmed that the higher Al2O3 oxide inclusions are present in the solid, while the lower Al2O3 oxide inclusions are present in the liquid steel phase. These results suggest that the microsegregation behavior of solute elements in molten steel plays an important role in the formation of inclusions, which is of great importance in the production of high-quality steels.

A previous effort to characterize respirable coal mine dust in 16 US mines turned up a curious finding: particle-based analysis using scanning electron microscopy (SEM) tended to overpredict the abundance of dust sourced from rock strata, and underpredict the abundance of coal, when compared to mass-based thermogravimetric analysis (TGA). One possible explanation is the occurrence of coal-mineral microagglomerates (MAGs). Coal particles covered with fine mineral dust could be mostly coal by mass but classified as minerals by SEM due to their surface elemental content. In the current study, a subset of the previously analyzed mine dust samples was re-examined, and SEM images and elemental mapping showed that MAGs are indeed present. Furthermore, dust samples were created and sampled passively in the laboratory, demonstrating that MAG formation can occur due to dust generation processes and the sampling environment, rather than as a mere artifact of respirable dust sampling procedures. Finally, experiments were conducted to evaluate dispersibility of MAGs in liquid suspensions, which might shed some light on their possible fate upon inhalation. Results indicated that sonication in deionized water was effective for MAG dispersion, and a solution that mimics natural lung surfactant also appeared to enhance dispersibility. An understanding of MAG occurrence might be important in terms of exposure assessment.

Since the mid-1990s, there has been a resurgence of severe lung disease among US coal miners. This has prompted efforts to better characterize and monitor respirable dust exposures—especially with respect to mineral constituents sourced from rock strata surrounding the coal, which is believed to play a central role in many cases of disease. Recently, a rapid analysis method for silica (quartz) mass has been developed using direct-on-filter Fourier transform infrared (FTIR) spectroscopy. It can concurrently provide an estimate of kaolinite, presumably a primary silicate mineral in many coal mines. Other methods, including thermogravimetric analysis (TGA) and scanning electron microscopy with energy-dispersive X-ray (SEM–EDX), can also be used to estimate respirable coal mine dust constituents. However, there have been few efforts to compare results across multiple methods. Here, FTIR, TGA, and SEM–EDX were used to analyze 93 sets of respirable dust samples collected in 16 underground coal mines across the USA.

The aims of this study were to investigate the clinical effectiveness and patient acceptability of a modified glass ionomer cement placed using the atraumatic restorative treatment (ART) technique to treat root caries, and to carry out microbiological analysis of the restored sites. Two clinically visible root surface carious lesions per participant were restored using ART. One was restored with commercial glass ionomer cement (GIC) (ChemFil® Superior, DENTSPLY, Konstonz, Germany) which acted as the control. The other carious root lesion was restored with the same GIC modified with 5% chlorhexidine digluconate (GIC-CHX; test). Patient acceptability and restoration survival rate were evaluated at baseline and after 6 months. Plaque and saliva samples around the test and control restorations were collected, and microbiological analysis for selected bacterial and fungal viability were completed at baseline, and after 1, 3, and 6 months. In total, 52 restorations were placed using GIC and GIC-CHX in 26 participants; 1 patient was lost to follow-up. After reviewing the restorations during their baseline appointments, participants indicated that they were satisfied with the appearance of the restorations (n = 25, 96%) and did not feel anxious during the procedure (n = 24, 92%). Forty-eight percent (n = 12) of the GIC-CHX restorations were continuous with the existing anatomic form as opposed to six for the GIC restorations (24%), a difference which was statistically significant (p = 0.036). There was no statistically significant reduction in the mean count of the tested microorganisms in plaque samples for either type of restorations after 1, 3, or 6 months. Restoration of carious root surfaces with GIC-CHX resulted in higher survival rates than the control GIC. ART using GIC-CHX may therefore be a viable approach for use in outreach dental services to restore root surface carious lesions where dental services are not readily available, and for older people and special ne

Randomly oriented ZnO nanowires were grown directly onto alumina substrates having platinum interdigitated screen-printed electrodes via the chemical vapor deposition method using Au as catalyst. Three different Au film thicknesses (i.e., 3, 6 or 12 nm) were used in the growth of nanowires, and their gas sensing properties were studied for ethanol and NO2 as reducing and oxidizing species, respectively. ZnO nanowires grown employing the 6 nm thick layers were the less defective and showed the most stable, repeatable gas sensing properties. Despite ZnO nanowires grown employing the thickest Au layers reached the highest responses under dry conditions, ZnO nanowires grown using the thinnest Au film were more resilient at detecting NO2 in the presence of ambient moisture. The gas sensing results are discussed in light of the defects and the presence of Au impurities in the ZnO nanowires, as revealed by the characterization techniques used, such as X-ray diffraction, field-emission scanning electron microscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. Promising results were obtained by the implementation of ZnO NWs directly grown over alumina substrates for the detection of ethanol and NO2, substantially ameliorating our previously reported results.

A series of Dy3+-doped sodium lanthanum orthosilicate oxyapatites, NaLa9?xDyx(SiO4)6O2 (NLSO:xDy, x = 0–0.3), were synthesized by the solid-state reaction method at 1100 °C, with the aim of developing yellow emitting phosphors for applications in w-LEDs. Their crystal structure, morphology and particle size distribution, electronic structure, Raman spectra, concentration- and temperature-dependent luminescent properties were investigated for the first time. The crystal structure was refined by the Rietveld method. Undoped NLSO is hexagonal (space group P63/m – C26h) with lattice constants a = b = 9.6917(3) Å and c = 7.1836(4) Å. It is shown that Dy3+ ions substitute for the La3+ ones in two types of sites with C3 and Cs point symmetries. The first-principle calculations for undoped NLSO revealed an indirect bandgap of 5.06 eV. The NLSO:0.2Dy phosphor exhibited intense yellow emission with CIE 1931 chromaticity coordinates of (0.469, 0.495) and a correlated color temperature of 3150 K owing to the hypersensitive electric-dipole transition 4F9/2?6H13/2 (571 nm) dominating in the luminescence spectrum. Excellent thermal stability was found for this apatite phosphor (the activation energy is 0.23 ± 0.02 eV). © 2021 The Authors

This work demonstrates the introduction of various α-aminophosphonate compounds to an epoxy resin system, thereby improving flame retardance properties. The α-aminophosphonate scaffold allows for covalent incorporation (via the secondary amine) of the compounds into the polymer network. This work explores the synergistic effect of phosphorus and halogens (such as fluorine) to improve flame retardancy. The compounds were all prepared and isolated in analytical purity and in good yield (95%). Epoxy samples were prepared, individually incorporating each compound. Thermogravimetric analysis showed an increased char yield, indicating an improved thermal resistance (with respect to the control sample). Limiting oxygen index for the control polymer was 28.0% ± 0.31% and it increased to 34.6% ± 0.33% for the fluorinated derivative

The inhomogeneity of the resistance of conducting polypyrrole-coated nylon–Lycra and polyester (PET) fabrics and its effects on surface temperature were investigated through a systematic experimental and numerical work including the optimization of coating conditions to determine the lowest resistivity conductive fabrics and establish a correlation between the fabrication conditions and the efficiency and uniformity of Joule heating in conductive textiles. For this purpose, the effects of plasma pre-treatment and molar concentration analysis of the dopant anthraquinone sulfonic acid (AQSA), oxidant ferric chloride, and monomer pyrrole was carried out to establish the conditions to determine the sample with the lowest electrical resistance for generating heat and model the experiments using the finite element modeling (FEM). Both PET and nylon-Lycra underwent atmospheric plasma treatment to functionalize the fabric surface to improve the binding of the polymer and obtain coatings with reduced resistance. Both fabrics were compared in terms of average electrical resistance for both plasma treated and untreated samples. The plasma treatment induced deep black coatings with lower resistance. Then, heat-generating experiments were conducted on the polypyrrole (PPy) coated fabrics with the lowest resistance using a variable power supply to study the distribution and maximum value of the temperature. The joule heating model was developed to predict the heating of the conductive fabrics via finite element analysis. The model was based on the measured electrical resistance at different zones of the coated fabrics. It was shown that, when the fabric was backed with neoprene insulation, it would heat up quicker and more evenly. The average electrical resistance of the PPy-PET sample used was 190 Ω, and a maximum temperature reading of 43 °C was recorded. The model results exhibited good agreement with thermal camera data.

This study investigates the effect of grain size and composition on the material properties and forming limits of commercially supplied stainless steel foil for bipolar plate manufacture via tensile, stretch forming and micro-stamping trials. It is shown that in commercially supplied stainless steel the grain size can vary significantly and that ‘size effects’ can be influenced by prior steel processing and composition effects. While the forming limits in micro-stamping appear to be directly linked to the plane strain forming limits of the individual stainless steel alloys, there was a clear effect of the tensile anisotropy. In contrast to previous studies, forming severity and the likelihood of material failure did not increase with a decreasing channel profile radius. This was related to inaccuracies of the forming tool profile shape.

The thermochemical energy storage properties of calcium hydride (CaH2) destabilised with either silicon (Si) or CaxSiy compounds at various molar ratios, were thoroughly studied by a combination of experimental and computer assisted thermodynamic calculations. Particularly, the destabilisation effect of Si on CaH2 at five different molar ratios (1:1, 1:2, 2:1, 3:4, 5:3 CaH2 to Si) was extensively investigated. Theoretical calculations predicted a multi-step thermal decomposition reaction between CaH2 and Si forming CaxSiy at varying temperatures, which was confirmed by in-situ synchrotron X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and mass-spectroscopic measurements. The most suitable destabilisation reactions between CaH2 and Si or CaxSiy that meet the criteria of a thermal energy storage system for the next-generation of concentrated solar power (CSP) plants were identified. The CaH2 and CaSi system (in a 2:3 molar ratio of CaH2 to CaSi) showed desirable operating conditions with a decomposition temperature of 747 ± 33 °C at a hydrogen pressure of 1 bar. Pressure composition isothermal measurements were conducted on this system to determine its practical enthalpy of decomposition to form Ca5Si3. The calculated value (107.3 kJ mol−1 H2) was lower compared to the experimentally determined value (154 ± 4 kJ mol−1 H2). This mismatch was mainly due to the formation of CaO and a CaSi solid solution in addition to the desired Ca5Si3 phase.

The effects of mono (single type) and hybrid (mixed types) fibres on the workability, compressive strength, flexural strength, and toughness parameters of fly ash geopolymer mortar were studied. The ratio of sand to geopolymer paste of the mortar was 2.75. It was found that workability of mortar decreased more with the use of PP fibres due to its higher dispersion into individual filaments in geopolymer mortar compared to the bundled ARG and PVA fibres. Compressive strength increased by 14% for using 1% steel with 0.5% PP fibres compared to that of the control mixture, which was 48 MPa. However, 25 to 30% decrease of compressive strength was observed in the mortars using the low-modulus fibres. Generally, flexural strength followed the trend of compressive strength. Deflection hardening behaviours in terms of the ASTM C1609 toughness indices, namely I5, I10 and I20 were exhibited by the mortars using 1% steel mono fibres, 0.5% ARG with 0.5% steel and 1% PVA with 0.5% steel hybrid fibres. The toughness indices and residual strength factors of the mortars using the other mono or hybrid fibres at 1 or 1.5% dosage were relatively low. Therefore, multiple cracking and deflection hardening behaviours could be achieved in fly ash geopolymer mortars of high sand to binder ratio by using steel fibres in mono or hybrid forms with ARG and PVA fibres.

This study investigated the effect of abrasive water jet kinematic parameters, such as jet traverse speed and water pressure, on the surface of magnesium-based metal matrix nanocomposites (Mg-MMNCs) reinforced with 50 nm (average particle size) Al2O3 particles at concentrations of 0.66 and 1.11 wt.%. The extent of grooving caused by abrasive particles and irregularities in the abrasive waterjet machined surface with respect to traverse speed (20, 40, 250 and 500 mm/min), abrasive flow rate (200 and 300 g/min) and water pressure (100 and 400 MPa) was investigated using surface topography measurements. The results helped to identify the mode of material disintegration during the process. The nanoindentation results show that material softening was decreased in nanocomposites with higher reinforcement content due to the presence of a sufficient amount of nanoparticles (1.11 wt.%), which protected the surface from damage. The values of selected surface roughness profile parameters—average roughness (Ra), maximum height of peak (Rp) and maximum depth of valleys (Rv)—reveal a comparatively smooth surface finish in composites reinforced with 1.11 wt.% at a traverse speed of 500 mm/min. Moreover, abrasive waterjet machining at high water pressure (400 MPa) produced better surface quality due to sufficient material removal and effective cleaning of debris from the machining zone as compared to a low water pressure (100 MPa), low traverse speed (5 mm/min) and low abrasive mass flow rate (200 g/min).

A great deal of effort has been dedicated to improve the fundamental understanding of the mechanism of desilication product crystallization under Bayer process refinery conditions. Differences in the mineralogy of the reactive silica found in bauxite could change the kinetics and possibly the formation pathways of the desilication product. In this work, halloysite was investigated and compared to kaolinite, which is commonly found in bauxite. Different ratios of kaolinite and halloysite were used to form desilication product and the solids formed were characterized thoroughly to determine the impact the presence of the clay had. In addition, differences in dissolution rate due to the presence of halloysite was determined. The results show that the presence of halloysite led to a faster dissolution rate of the clay overall, which can be attributed to the total specific surface area of the reactive silica source. Thus, the crystallinity of the clay was found to have limited impact. The presence of halloysite also increased the measured maximum solution [SiO2] in solution, which in turn increases the driving force for the formation of desilication product. The increase in halloysite content thus results in desilication product being observed at an earlier stage and, overall, leads to an enhanced rate of desilication product formation.

This article proposes a new model of power supply for mobile low power machines applications, between 10 W and 30 W, such as radio-controlled (RC) electric cars. This power supply is based on general hydrogen from residual aluminum and water with NaOH, so it is proposed energy valorization of aluminum waste. In the present research, a theoretical model allows us to predict the requested aluminum surface and the required flow of hydrogen has been developed, also considering, in addition to the geometry and purity of the material, two key variables as the temperature and the molarity of the alkaline solution used in the hydrogen production process. Focusing on hydrogen production, isopropyl alcohol plays a key role in the reactor's fuel cell vehicle as it filters out NaOH particles and maintains a constant flow of hydrogen for the operation of the machine, keeping the reactor temperature controlled. Finally, a comparison of the theoretical and experimental data has been used to validate the developed model using aluminum sheets from ring cans to generate hydrogen, which will be used as a source of hydrogen in a power fuel cell of an RC car. Finally, the manuscript shows the parts of the vehicle's powertrain, its behavior, and mode of operation.

Versatile acrylate-epoxy hybrid formulations are becoming widespread in photo/thermal dual-processing scenarios, especially in 3D printing applications. Usually, parts are printed in a stereolithography or digital light processing (DLP) 3D printer, after which a thermal treatment would bestow the final material with superior mechanical properties. We report the successful formulation of such a hybrid system, consisting of a commercial 3D printing acrylate resin modified by an epoxy-anhydride mixture. In the final polymeric network, we observed segregation of an epoxy-rich phase as nano-domains, similar to what was observed in a previous work. However, in the current work, we show the effectiveness of a coupling agent added to the formulation to mitigate this segregation for when such phase separation is undesired. The hybrid materials showed significant improvement of Young's modulus over the neat acrylate. Once the flexible, partially-cured material was printed with a minimal number of layers, it could be molded into a complex form and thermally cured. Temporary shapes were readily programmable on this final material, with easy shape recovery under mild temperatures. Inspired by repairable 3D printed materials described recently, we manufactured a large object by printing its two halves, and then joined them covalently at the thermal cure stage with an apparently seamless union.

In this article, it is proposed to use aluminum breakage scraps to obtain green hydrogen through the aluminum-water reaction with caustic soda as a catalyst with experimental research. From this exothermic reaction, both hydrogen and the heat generated can be used. Due to the low price of aluminum chips, this allows us to produce green hydrogen below the current price that is obtained using renewable energy sources and electrolyzers. We have also developed a process that is sustainable since it is obtained as alumina and caustic soda waste that can be reused. This alumina obtained, once filtered, has high purity which allows us to produce high-quality primary aluminum without the need to use bauxite and the production of red sludge is also reduced. A comparative study-analysis was carried out between two of the forms in which the most common aluminum is presented in industry to analyze which one performs better by studying key factors such as the hydrogen produced, and the waste generated during the process. Finally, the mathematical model has been defined to be able to control the flow based on different key parameters such as temperature, molarity, and geometry. Undoubtedly, the study that we present represents a milestone for the recovery of metallic aluminum waste and may be of great interest to industries that use aluminum in their processes, such as recuperators, as well as the vehicle and aerospace industries.

Our investigation was focused on the preparation and characterization of novel plasters based on Carboxymethyl Chitosan derivative (CMC), to be used for the treatment of radiation dermatitis with Biologic Active Compounds (BACs) in a moist wound-healing environment. After performing the extraction and characterization of BACs from Cistus L., we optimized the BACs/CMC solution for subsequent plaster preparation. Then, plasters were prepared by dip-coating with a different number of layers, and we characterized them by Environmental Scanning Electron Microscopy (ESEM), Contact Angle (CA) and release tests in water for 24 h. Taking into account the flexibility of the plasters and the amount of released BACs after 24 h, the sample obtained after two dip-coating steps (2La) appeared promising in regard to comfortable mechanical properties and active principles administration. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test performed on keratinocytes cultured in standard medium shows that cells treated with released extract from 2La start to proliferate, extend cellular viability and form colonies typical for epidermal cells.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Dual-curing thermosetting systems are recently being developed as an alternative to conventional curing systems due to their processing flexibility and the possibility of enhancing the properties of cured parts in single-or multi-stage processing scenarios. Most dual-curing systems currently employed in three-dimensional (3D) printing technologies are aimed at improving the quality and properties of the printed parts. However, further benefit can be obtained from control in the curing sequence, making it possible to obtain partially reacted 3D-printed parts with tailored structure and properties, and to complete the reaction by activation of a second polymerization reaction in a subsequent processing stage. This paves the way for a range of novel applications based on the controlled reactivity and functionality of this intermediate material and the final consolidation of the 3D-printed part after this second processing stage. In this review, different strategies and the latest developments based on the concept of dual-curing are analyzed, with a focus on the enhanced functionality and emerging applications of the processed materials.

Natural dye’s poor affinity for cotton and poor fastness properties still hinder its applications in the textile industry. In this study, a doubled-layered chitosan coating was cured on cotton fabric to serve as bio-mordant and form a protective layer on it. Under the optimal treatment conditions, the maximum qe (adsorption amount) of the natural dye sodium copper chlorophyllin (SCC) calculated from the Langmuir isothermal model was raised from 4.5 g/kg to 19.8 g/kg. The dye uptake of the treated fabric was improved from 22.7% to 96.4% at 1% o.w.f. dye concentration. By a second chitosan layer cured on the dyed fabric via the cross-linking method, the wash fastness of the cotton fabric dyed with SCC can be improved from 3 to 5 (ISO 105 C-06). The natural source of the biopolymer material, chitosan, and its ability to biodegrade at end of life met with the initial objective of green manufacturing in applying natural dyes and natural materials to the textile industry.

Two groups of martensitic alloys were examined for changes induced by deep cryogenic treatment (DCT). The first group was a range of binary and ternary compositions with 0.6 wt % carbon, and the second group was a commercial AISI D2 tool steel. X-ray diffraction showed that DCT made two changes to the microstructure: retained austenite was transformed to martensite, and the dislocation density of the martensite was increased. This increase in dislocation density was consistent for all alloys, including those that did not undergo phase transformation during DCT. It is suggested that the increase in dislocation density may be caused by local differences in thermal expansion within the heterogeneous martensitic structure. Then, samples were tempered, and the cementite size distribution was examined using small angle neutron scattering (SANS) and atom probe tomography. First principles calculations confirmed that all magnetic scattering originated in cementite and not carbon clusters. Quantitative SANS analysis showed a measurable change in cementite size distribution for all alloys as a result of prior DCT. It is proposed that the increase in dislocation density that results from DCT modifies the cementite precipitation through enhanced diffusion rates and increased cementite nucleation sites.

Melt-electrospinning is an eco-friendly method for producing ultra-fine fibers without using any solvent. We prepared webs of poly(ethylene terephthalate) (PET) through melt-electrospinning using CO2 laser irradiation for heating. The PET webs comprised ultra-fine fibers of uniform diameter (average fiber diameter = 1.66 μm, coefficient of variation = 19%). The co-existence of fibers with high and low molecular orientation was confirmed through birefringence measurements. Although the level of high orientation corresponded to that of commercial highly oriented yarn, crystalline diffraction was not observed in the wide-angle X-ray diffraction (WAXD) analysis of the webs. The crystallinity of the webs was estimated using differential scanning calorimetry (DSC). The fibers with higher birefringence did not exhibit any cold crystallization peak. After annealing the web at 116 °C for 5 min, a further increase in the birefringence of the fibers with higher orientation was observed. The WAXD results revealed that the annealed webs showed crystalline diffraction peaks with the orientation of the c-axis along the fiber axis. In summary, the formation of fibers with a unique non-crystalline structure with extremely high orientation was confirmed.

Multiwalled carbon nanotubes have outstanding mechanical properties that, when combined with Portland cement, can provide cementitious composites that could lead to the innovative construction of stronger, lighter, and thinner built infrastructure. This paper addresses a knowledge gap that relates to the durability of CNT–cement composites. The durability to corrosive chloride, uptake of water by sorption, and flow of the permeability of water acting under high water pressure are addressed. Flow simulations were undertaken through segmented 3D pore networks, based on X-ray computed microtomography measurements, the creation of a virtual microstructure, and fluid simulations that were compared with larger-scale samples. The investigation showed decreased water sorptivity of CNT–cement mixtures, indicating improved durability for the cover zone of concrete that is prone to the uptake of water and water-borne corrosives. Chloride diffusion of CNT–cement composites provided up to 63% improvement compared with control samples. The favourable durability bodes well for the construction of long-life CNT-reinforced concrete infrastructure.

Two low-C steels microalloyed with niobium (Nb) were fabricated by simulated strip casting, one with molybdenum (Mo) and the other without Mo. Both steels were heat treated to simulate coiling at 900 °C to investigate the effect of Mo on the precipitation behaviour in austenite in low-C strip-cast Nb steels. The mechanical properties results show that during the isothermal holding at 900 °C the hardness of both steels increases and reaches a peak after 3000 s and then decreased after 10,000 s. Additionally, the hardness of the Mo-containing steel is higher than that of the Mo-free steel in all heat-treated conditions. Thermo-Calc predictions suggest that MC-type carbides exist in equilibrium at 900 °C, which are confirmed by transmission electron microscopy (TEM). TEM examination shows that precipitates are formed after 1000 s of isothermal holding in both steels and the size of the particles is refined by the addition of Mo. Energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) reveal that the carbides are enriched in Nb and N. The presence of Mo is also observed in the particles in the Nb-Mo steel during isothermal holding at 900 °C. The concentration of Mo in the precipitates decreases with increasing particle size and isothermal holding time. The precipitates in the Nb-Mo steel provide significant strengthening increments of up to 140 MPa, higher than that in the Nb steel, ~96 MPa. A thermodynamic rationale is given, which explains that the enrichment of Mo in the precipitates reduces the interfacial energy between precipitates and matrix. This is likely to lower the energy barrier for their nucleation and also reduce the coarsening rate, thus leading to finer precipitates during isothermal holding at 900 °C.

© 2019 Elsevier B.V. Chalcopyrite (CuFeS2) is the primary ore mineral for copper, but leaching of this mineral under atmospheric conditions is slow due to the formation of surface passivating phases such as elemental sulphur and jarosite. Here, we studied chalcopyrite leaching in a sulphuric acid solution at 75 °C and 750 mV (relative to the standard hydrogen electrode), and found that after adding 20 vol% of tetrachloroethylene (TCE) into the leaching solution, elemental sulphur was dissolved from chalcopyrite and surface passivation was removed at the early stage of leaching. The removal of surface sulphur significantly enhanced the leaching rate by approximately 600% compared with TCE-free leaching. However, adding dimethyl sulfoxide (DMSO) did not improve the leaching rate. At the later stage of leaching, the increasing concentrations of Fe3+ from the dissolution of chalcopyrite and K+ possibly from the dissolution of minor amount of gangue minerals resulted in the precipitation of a potassium jarosite layer on the surface of chalcopyrite. The jarosite shell did not passivate TCE-free leaching due to its porous structure. However, in the case of leaching with TCE, elemental sulphur filled the pores, and the jarosite shell became nearly impermeable, resulting in passivation after 80% copper extraction. This study demonstrates a way for effective removal of sulphur passivation at the early stage of chalcopyrite leaching by adding sulphur dissolving solvent such as TCE, but to prevent jarosite formation at the later stage of leaching, it is necessary to keep the concentrations of Fe3+ and K+ at low levels.

© 2020 Elsevier B.V. The synergistic leaching system using glycine as the main lixiviant with low levels of cyanide as a catalyst has been shown to be an effective approach to leach gold‑copper ores and concentrates, allowing the consumption of cyanide to be remarkably reduced. The recovery of gold from the synthetic cyanide-starved glycine leachate in the presence of copper has been investigated using. It was found that the adsorbed copper was mostly cuprous cyanide. The effects of [CN−]:[CuT] and [Gly]: [CuT] molar ratios were not significant on the adsorption of gold and copper using IXOS-AuC resin. The gold recovery increased, while the copper recovery decreased with the increasing initial gold concentration. The equilibrium and kinetics studies were undertaken, and the experimental adsorption equilibrium and rate data showed an excellent fit using the Freundlich isotherm and pseudo-second-order models respectively. Elution tests showed that the loaded copper can be selectively pre-eluted over gold by 0.4 M NaCN at pH 11.5. Gold can be effectively eluted by either acidic thiourea or alkaline thiocyanate. The multi-cycle adsorption/elution tests showed that the resin can be effectively regenerated by both acidic thiourea and alkaline thiocyanate, with an insignificant decrease in adsorption and elution efficiency over 3 adsorption/elution cycles. From SEM analysis, the change of surface morphology of the resin was not significant after adsorption and the adsorption/elution cycles.

© 2020 Informa UK Limited, trading as Taylor & Francis Group. Despite a large body of literature, mechanisms contributing to low temperature jerky flow remain controversial. Here, we report a cross-over from a smooth at room and liquid nitrogen temperatures to serrated plastic flow at 4.2 K in high-entropy CrMnFeCoNi alloy. Several complimentary investigations have been carried out to get a coherent physical picture of low temperature jerky flow in these alloys. Microstructural characterisations at 77 K and 4.2 K show that the number of Lomer-Cottrell (L-C) locks at 4.2 K is much higher than that at 77 K, inducing stronger barriers for dislocation glide at 4.2 K. A stability analysis shows that the jerky flow results from an interaction between dislocation inertial motion with L-C locks. The instability results from a competition between inertial and viscous time scales characterised by a Deborah number. A detailed nonlinear time series analysis of experimental serrated stress signals shows that jerky flow is chaotic characterised by the existence of a finite correlation dimension and a positive Lyapunov exponent. Further, the minimum degree of freedom required for the chaotic dynamics turns out to be four, consistent with four collective modes degrees of freedom used in our model equations. These results highlight the crucial ingredients for jerky flow at liquid helium temperatures.

© 2020 The Authors Globally, the accelerating use of renewable energy sources, enabled by increased efficiencies and reduced costs, and driven by the need to mitigate the effects of climate change, has significantly increased research in the areas of renewable energy production, storage, distribution and end-use. Central to this discussion is the use of hydrogen, as a clean, efficient energy vector for energy storage. This review, by experts of Task 32, “Hydrogen-based Energy Storage” of the International Energy Agency, Hydrogen TCP, reports on the development over the last 6 years of hydrogen storage materials, methods and techniques, including electrochemical and thermal storage systems. An overview is given on the background to the various methods, the current state of development and the future prospects. The following areas are covered; porous materials, liquid hydrogen carriers, complex hydrides, intermetallic hydrides, electrochemical storage of energy, thermal energy storage, hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage.

© 2019 CaH2 is a metal hydride with a high energy density that decomposes around 1100 °C at 1 bar of H2 pressure. Due to this high decomposition temperature, it is difficult to utilise this material as a thermal battery for the next generation of concentrated solar power plants, where the currently targeted operational temperature is between 600 and 800 °C. In this study, CaH2 has been mixed with calcium halide salts (CaCl2, CaBr2 and CaI2) and annealed at 450 °C under 100 bar of H2 pressure to form CaHCl, CaHBr and CaHI. These hydride-halide salts incur a thermodynamic destabilisation of their hydrogen release, compared to CaH2, so that they can operate between 600 and 800 °C within practical operating pressures (1–10 bar H2) for thermochemical energy storage. The as-synthesised metal hydrides were studied by in-situ synchrotron X-ray diffraction, temperature programmed desorption and pseudo pressure composition isothermal analysis. Each of the calcium hydride-halide salts decomposed to form calcium metal and a calcium halide salt after hydrogen release. In comparison to pure CaH2, their decomposition reactions were faster when heated up to 850 °C, and the experimental values of the desorbed hydrogen gas were very close to the theoretical ones. All samples after their decomposition showed signs of sintering, which hindered their rehydrogenation reaction.

© 2019 Elsevier B.V. Tungsten trioxide nanowires were grown employing aerosol assisted chemical vapor deposition (AACVD) and subsequently decorated with different loading levels of iridium oxide nanoparticles. AACVD has been already demonstrated to be a useful tool to load different ranges of nanoparticles on top of an already grown layer. This procedure enables growing the gas sensitive nanomaterials directly onto application substrates for the development of chemo-resistive gas sensors. The morphology and composition of the different materials were characterized via different techniques. It was found that iridium oxide loading resulted in remarkable changes in the morphology and defects of tungsten oxide nanowires. The gas sensing properties of such layers were studied towards ethanol or ammonia vapors, hydrogen, hydrogen sulfide, and nitrogen dioxide. The optimization of the operating temperature and the level of iridium oxide loading results in an improvement in the responsiveness and selectivity towards the species tested. In particular, a dramatically high increase in the response towards nitrogen dioxide is achieved. The mechanisms of gas sensing are discussed in detail.

© 2020 by the authors. Drug modification with nanomaterials is a new trend in pharmaceutical studies and shows promising results, especially considering carbon-based solutions. Graphene and its derivatives have attracted much research interest for their potential applications in biomedical areas as drug modifiers. The following work is a comprehensive study regarding the toxicity of ciprofloxacin (CIP) modified by graphene oxide (GO). The influence on the morphology, viability, cell death pathway and proliferation of T24 and 786-0 cells was studied. The results show that ciprofloxacin modified with graphene oxide (CGO) shows the highest increase in cytotoxic potential, especially in the case of T24 cells. We discovered a clear connection between CIP modification with GO and the increase in its apoptotic potential. Our results show that drug modification with carbon-based nanomaterials might be a promising strategy to improve the qualities of existing drugs. Nevertheless, it is important to remember that cytotoxicity effects are highly dependent on dose and nanomaterial size. It is necessary to conduct further research to determine the optimal dose of GO for drug modification.