In recent years, graphene has attracted considerable research interest in all fields of science due to its unique properties. Its excellent mechanical properties lead it to be used in nano-composites ...for strength enhancement. This paper reports an Aluminum–Graphene Nanoplatelets(Al/GNPs)composite using a semi-powder method followed by hot extrusion. The effect of GNP nano-particle integration on tensile, compressive and hardness response of Al is investigated in this paper. It is demonstrated that 0.3 wt% Graphene Nanoplatelets distributed homogeneously in the matrix aluminum act as an effective reinforcing filler to prevent deformation. Compared to monolithic aluminum(in tension), Al–0.3 wt% GNPs composite exhibited higher 0.2% yield strength(+14.7%), ultimate tensile strength(+11.1%) and lower failure strain( -40.6%). Surprisingly, compared to monolithic Al(in compression), Al–0.3 wt% GNPs composite exhibited same 0.2% compressive yield strength and lower ultimate compression strength(- 7.8%),and lower failure strain(- 20.2%). The Al–0.3 wt% GNPs composite exhibited higher Vickers hardness compared to monolithic aluminum(+11.8%).Scanning electron microscopy(SEM), Energy-Dispersive X-ray Spectroscopy(EDS) and X-ray diffraction(XRD) were used to investigate the surface morphology, elemental percentage composition, and phase analysis, respectively.
Graphene nanoplatelets (few layer graphene) and carbon nanotubes were used as reinforcement fillers to enhance the mechanical properties of AZ31 magnesium alloy through high energy ball milling, ...sintering, and hot extrusion techniques. Experimental results revealed that tensile fracture strain of AZ31 magnesium alloy was enhanced by +49.6% with 0.3 wt.% graphene nanoplatelets compared to −8.3% regression for 0.3 wt.% carbon nanotubes. The tensile strength of AZ31 magnesium alloy was decreased (−11.2%) with graphene nanoplatelets addition, while increased (+7.7%) with carbon nanotubes addition. Unlike tensile test, compression tests showed different trend. The compression strength of carbon nanotubes-AZ31 composite was +51.2% greater than AZ31 magnesium alloy as compared to +0.6% increase for graphene nanoplatelets. The compressive fracture strain of carbon nanotubes-AZ31 composite was decreased (−14.1%) while no significant change in fracture strain of graphene nanoplatelets-AZ31 composite was observed. The X-ray diffraction results revealed that addition of reinforcement particles weaken the basal textures which affect the composite's yield asymmetry. Microstructure evaluation revealed the absence of intermetallic phase formation between reinforcements and matrix. The carbon reinforcements in AZ31 magnesium alloy dissolve and isolate β phases throughout the matrix. The increased fracture strain and mechanical strength of graphene nanoplatelets and carbon nanotubes-AZ31 composites are attributed to large specific surface area of graphene nanoplatelets and stiffer nature of carbon nanotubes respectively.
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•Powder metallurgy method was used to fabricate magnesium composites.•The AZ31-carbon materials composite were blended using ball milling.•The reinforcement particles weaken the basal texture which affects yield asymmetry of composites.•AZ31-graphene nanoplatelets composite exhibited impressive increase in tensile elongation.•AZ31-carbon nanotube composite revealed impressive increase in compression strength.•The structure of reinforcement particles influences the mechanical behavior of composite.
In present study,the microstructure,mechanical and electrochemical properties of aluminum-graphene nanoplatelets(GNPs) composites were investigated before and after extrusion.The contents of graphene ...nanoplatelets(GNPs) were varied from 0.25 to 1.0 wt.%in aluminum matrix.The composites were fabricated thorough powder metallurgy method,and the experimental results revealed that Al-0.25%GNPs composite showed better mechanical properties compared with pure Al,Al-0.50%GNPs and Al-0.1.0%GNPs composites.Before extrusion,the Al-0.25%GNPs composite showed ~13.5%improvement in ultimate tensile strength(UTS) and ~50%enhancement in failure strain over monolithic matrix.On the other hand,Al-0.50%GNPs and Al-0.1.0%GNPs composites showed the tensile strength lower than monolithic matrix.No significant change was observed in 0.2%yield strength(YS) of the composites.However,the extruded materials showed different trends.The0.2%YS of composites increased with increase in GNPs filler weight fractions.Surprisingly,UTS of composites with 0.25 and 0.50%GNPs was lower than monolithic matrix.The failure strain of the baseline matrix was enhanced by ~46%with 0.25%graphene nanoplatelets.The superior mechanical properties(in terms of failure strain) of the Al-0.25%GNPs composite maybe attributed to 2-D structure,high surface area and curled nature of graphene.In addition,the corrosion resistance of pure Al and its composites reinforced with 0.5 and 1.0 wt%GNPs was also investigated.It was found that the corrosion rate increased considerably by the presence of GNPs.
APC electrolyte exhibited strong potential to suppress the freezing of electrolyte solutions and revealed the reversible capacity of 78.56 mAh g−1 at −20 °C.
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•Electrochemistry of LTO ...is elaborated for Mg/Li hybrid ion battery at different temperatures.•Capacity of 228 mAhg−1 at 20 mAg−1 and specific energy of 178 Whkg−1 was achieved at RT.•APC-THF solution suppresses the freezing of electrolyte.•Battery exhibited capacity of 78.56 mAhg−1 at −20 °C.•Ex-situ characterizations were carried out to understand the reaction kinetics.
Magnesium–lithium hybrid ion batteries have emerged as a new class of energy storage systems owing to dendrite free cycling of magnesium anode and possibility of practice of numerous conventional lithium cathodes. In present work, we used hybrid ion strategy to analyze the performance of lithium titanate based lithium cathode, magnesium metal anode, and all-phenyl complex (APC) electrolytes at different temperatures (25 °C, 10 °C, 0 °C, −10 °C, and −20 °C). The hybrid ion battery exhibited excellent rate performance (228 mAh g−1/20 mA g−1 and 163 mAh g−1/1000 mA g−1) with stable voltage plateaus at 0.90 and 0.75 V, which corresponds to specific energy of 178 Wh kg−1 at room temperature (25 °C). Experimental results revealed that APC-THF solutions have strong potential to suppress the freezing of electrolyte solutions owing to low boiling point of THF. The low temperature electrochemical testing revealed the reversible capacities of 213.4, 165.5, 143.8, 133.2 and 78.56 mAh g−1 at 25, 10, 0, −10, and −20 °C, respectively. Furthermore, ex-situ XRD, SEM, and EIS tests were carried out to understand the reaction kinetics of both Mg2+ and Li+ ions inside the lithium titanate cathode. We hope this work will shed light on low temperature prospective of electrochemical devices for use in cold environments.
This work aims to investigate the performance of a free piston Stirling engine that implements a new concept of using expansion bellow instead of conventional piston cylinder configuration. The ...proposed configuration combines both advantages of eliminating complicated seals and maximizing engine swept volume. A simplified dynamic and thermal model was developed to conduct this study. An experimental prototype was designed, fabricated and tested for model validation and experimental investigation. Obtained experimental data showed that at partial loading conditions the engine started at 190 °C and achieved a maximum allowed stroke of 54 mm at 390 °C, while at full load conditions it started at 310 °C and achieved the maximum measured power at 460 °C with a stroke of 3.1 mm and frequency of 7.16 Hz. The experimental and theoretical results were compared. A theoretical investigation for the engine under variable loading was carried out. The P-V diagram, output power, engine frequency, and efficiency were illustrated and analyzed. The model results showed that by gradually increasing the load coefficient from 0 to 12 N.s/m over a 40 s period, the engine average power dropped by 61%, the equivalent mass and displacer stroke decreased by 42.5% and 35.1% respectively.
Coating of graphene and graphene/polymer composites on metals improves the corrosion resistance of metal substrates. On other hand, graphene embedded inside metal (especially Mg) matrices increases ...or decreases corrosion, is a crucial factor and must be explored. In present study, electrochemical behaviors of magnesium alloys (AZ31 and AZ61) and their composites reinforced with graphene nanoplatelets (GNPs) were carried out in 3.5% NaCl solution by polarization method. The surface morphology of composites before and after corrosion tests were analyzed using scanning electron microscopy. Experimental results revealed that presence of graphene nanoplatelets in different matrices decrease corrosion resistance of composites. This may be attributed to presence of graphene nanoplatelets which activates the corrosion of magnesium/alloys due to the occurrence of galvanic corrosion and this effect increases with increasing graphene nanoplatelets content. Further, an appropriate model describing the corrosion mechanism was proposed.
•The Mg–Al–graphene nanoplatelets (GNPs) composite is synthesized using semi powder metallurgical method followed by hot extrusion.•The Mg–1.0Al–0.18GNPs composite revealed maximum yield strength ...(0.2%YS), ultimate tensile strength (UTS), failure strain (%) and Vickers hardness (up to 190,254MPa, 15.5 and 58, respectively).•Achieved strength is better than earlier reported Mg–Al–CNTs and Mg–ceramic composites. Better performance of GNPs over CNTs is due to its high specific surface area, superior nanofiller matrix adhesion and the two dimensional geometry.
The Mg–Al–graphene nanoplatelets (GNPs) nano-composites were synthesized using the powder metallurgy method. The effect of Al–GNPs hybrids addition in to pure Mg was examined through tensile and Vicker hardness tests. The GNPs content was kept constant (0.18wt.%) and Al content was varied from 0.5wt.% to 1.5wt.%. The increase in Al content led to increase in 0.2%YS, UTS and failure strain (%). However for Al content exceeding over 1wt.%, the failure strain(%) started to decrease. The best improvement was achieved with 1wt.% Al (Mg–1.0Al–0.18GNPs). Mechanical strength of synthesized composites proved to be better than Mg–Al–CNTs and Mg–ceramic composites.
Nanoparticles plays a key role in the development of novel antibacterial substances against various pathogenic microorganisms. These nanoparticles due to their smaller size could be very effective as ...they can improve the antibacterial activity through lysis of bacterial cell wall. In the present research work, ZnO, MgO, NiO, AlO nanoparticles, and MgNiO, and AlZnO composite oxides were synthesized by green method from Ocimum basilicum leaves extract. The nanoparticles formed were evaluated using FTIR, XRD, EDX, and SEM to confirm the formation of NPs and to determine the morphology, elemental composition, shape and size, composition, and nature of bonds present in the NPs. Further, the NPs were tested for their antibacterial activity. In particular, ZnO NPs showed a good inhibitory effect against Pseudomonas aeruginosa with 20 mm zone of inhibition. Hence, the process reported herein could be optimized for large‐scale preparation of NPs.
Research Highlights
Green synthesis of ZnO, MgO, NiO, AlO nanoparticles, and MgNiO, and AlZnO composite oxides using Ocimum basilicum leaves extract
NPs were characterized by various established characterization techniques like FTIR, XRD, EDX, and SEM.
NPs showed antibacterial activity which was investigated by agar well diffusion method against Bacillus cereus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus.
The method proved to be very simple, cost‐efficient, and convenient.
Characterization and antibacterial activity of green synthesized metal nanoparticles and composite oxides.
Lipoic acid (LA) and melatonin (MT) are pleiotropic molecules participating in plant stress resistance by modulating cellular biochemical changes, ion homeostasis, and antioxidant enzyme activities. ...However, the combined role of these two molecules in counteracting the detrimental impacts of salinity stress is still unknown. In the present study, we determined the effects of exogenous LA (0.5 µM), MT (1 µM) and their combination (LA + MT) on growth performance and biomass accumulation, photosynthetic pigments, enzymatic and non-enzymatic antioxidant activities, and ions homeostatic in canola (Brassica napus L.) seedlings under salinity stress (0, 100 mM) for 40 days. The results indicate that exogenous application of LA + MT improved the phenotypic growth (by 25 to 45%), root thickness (by 68%), number of later lateral roots (by 52%), root viability (by 44%), and root length (by 50%) under salinity stress. Moreover, total soluble protein, chlorophyll pigments, the concentration of superoxide dismutase (SOD), catalase peroxidase (CAT), and ascorbic peroxidase (ASA) increased with the presence of salt concentration into the growth media and then decreased with the addition of LA + MT to saline solution. Leaf protein contents and the degradation of photosynthetic pigments were lower when LA + MT treatments were added into NaCl media. The proline and phenol contents decreased in the exogenous application of LA + MT treatments more than individual LA or MT treatments under the salinity stress. The incorporation of LA or MT or a combination of LA + MT to saline solution decreased salinity-induced malondialdehyde and electrolyte leakage. In conclusion, the alteration of metabolic pathways, redox modulation, and ions homeostasis in plant tissues by the combined LA and MT application are helpful towards the adaptation of Brassica napus L. seedlings in a saline environment. The results of this study provide, for the first time, conclusive evidence about the protective role of exogenous LA + MT in canola seedlings under salinity stress.
The rapid increase in urbanization has an important effect on cropping pattern and land use/land cover (LULC) through replacing areas of vegetation with commercial and residential coverage, thereby ...increasing the land surface temperature (LST). The LST information is significant to understand the environmental changes, urban climatology, anthropogenic activities, and ecological interactions, etc. Using remote sensing (RS) data, the present research provides a comprehensive study of LULC and LST changes in water scarce and climate prone Southern Punjab (Multan region), Pakistan, for 30 years (from 1990 to 2020). For this research, Landsat images were processed through supervised classification with maps of the Multan region. The LULC changes showed that sugarcane and rice (decreased by 2.9 and 1.6%, respectively) had less volatility of variation in comparison with both wheat and cotton (decreased by 5.3 and 6.6%, respectively). The analysis of normalized difference vegetation index (NDVI) showed that the vegetation decreased in the region both in minimum value (−0.05 1990 to −0.15 2020) and maximum value (0.6 1990 to 0.54 2020). The results showed that the built-up area was increased 3.5% during 1990–2020, and these were some of the major changes which increased the LST (from 27.6 to 28.5°C) in the study area. The significant regression in our study clearly shows that NDVI and LST are negatively correlated with each other. The results suggested that increasing temperature in growing period had a greatest effect on all types of vegetation. Crop-based classification aids water policy managers and analysts to make a better policy with enhanced information based on the extent of the natural resources. So, the study of dynamics in major crops and surface temperature through satellite RS can play an important role in the rural development and planning for food security in the study area.
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