This paper focuses on optimizing process parameters such as tool rotating speed, preheat-treated workpiece temperature, traverse speed, and tool pin profile for dissimilar friction stir welding (FSW) of brass and AA 6063. The hardness of the friction stir-welded joint created is measured as a response variable. The Taguchi design of experiments approach was utilized to finalize the experimental strategy, and ANOVA was employed to analyze the data. The best input factors for a better weld and a harder FSW workpiece were predicted. The experimental results show that the input factors influenced the hardness and defects in the welds in the following order: tool rotation speed (28.98%), tool pin geometry (22.30%), travel speed (11%), and temperature of the preheat treated workpiece (10.95%), respectively. Optical microscopy identified three distinct zones: the nugget zone, the thermomechanically affected zone, and the heat-affected zone. The nugget zone had a maximum value of hardness (around a 27% increase) due to the formation of very fine recrystallized grains.

One of the excellent choices for compression ignition engines is emulsions. The current experimental analysis deals with transesterified Pongamia biodiesel. This work gives a substantial track to synthesize and to enhance fuel by including aluminium oxide nanoparticles. Emulsification is used to prepare fuel consisting of 88% of Pongamia biodiesel, 10% water, and 2% surfactants with series chemical emulsification techniques. This is then mixed with the ratio of 50 ppm and 100 ppm by mass with aluminium oxide nanoparticles by employing ultrasonication techniques. This work is carried out on compression ignition engines in different phases using biodiesel, nanoparticles, surfactants, and water. It was inferred from the results that there was a considerable enhancement in performance and decrease in emission when compared with diesel. It is found that the system exhibited 15% improvement in brake thermal efficiency and 45% reduction in oxides of nitrogen. The system exhibited considerable improvement in performance and reduction in emission.

Plastics materials which are used in our daily life especially for packaging applications are derived from petrochemicals. Though these plastic materials satisfy the required properties of packaging materials in terms of strength, water resistance, and durability, they are not biodegradable and stay in landfills for plenty of years. This causes serious environmental threat and pollution. Owing to this, biodegradable plastics have been emerged as an alternative to conventional plastics. However, most of the biodegrade plastics are dependent on forest reserves even some may affect food supply. Nevertheless, agar and polyvinyl alcohol (PVA) neither causes deforestation nor affect the food stock. Though agar and PVA neither causes deforestation nor affect the food supply, they have high water absorption and a moderate tensile strength. This restricts the use of these polymers for applications. Researchers have used physicochemical modification methods to improve the properties of biodegradable polymers with due attention of agar and PVA. This review presents the basics of polymers, biodegradable polymers, chemistry of biodegradation, environmental impacts of biodegradable polymers, and the physicochemical modification of biodegradable polymers with a special focus of agar and PVA.

In this work, aluminium composites have been evaluated in terms of their characteristics and behaviour. Stirring metallics and a specific quantity of ceramic-derived silicon nitride resulted in AA6061 composites (Si3N4). The mechanical, corrosion, and tribological properties of composites were investigated. Tensile, corrosion, and hardness characteristics have been improved in composites with a constant weight percent of ceramic and advanced metallic fortification. The improved hardness of the composite has decreased wear and friction. Furthermore, by using ceramic strengthening with the metal, the impact strength of the composites was condensed. In addition to the research, the design of experiments method was used to optimize the important wear test elements such as reinforcement %, applied stress, sliding distance, and speed. Analysis of variance was used to find the most significant testing features and its interface with wear performance and the friction coefficient of the composite specimen.

In this study, a new method to prepare polyvinyl alcohol (PVA) hydrogel-based woven fabric composite is presented. In this method, the woven fabric was first stitched with PVA yarn and then subjected to the borax solution for simultaneously dissolving and crosslinking PVA. The prepared PVA hydrogel-based woven fabric composite was chemically, mechanically, and thermally characterized. FTIR analysis was performed to confirm the crosslinking of PVA on the reinforced fabric surface. X-ray diffraction analysis was carried out to investigate the crystallinity of the composite. An optical microscope was used to investigate the surface morphology of the composites. Moreover, a DSC analysis was done to investigate the thermal characteristics of the composite. The mechanical and fluid absorbency characteristics of the composite were analyzed to investigate the effect of the concentration of PVA yarn on the tensile strength and water absorbency of composites. The results showed that the tensile strength and rigidity of the composite increased by increasing the PVA yarn content in the composite.

Silica has shown numerous applications in different fields such as environmental, biomedical, agriculture, and even in chemical processing. However, due to high energy-intensive and cost-effective issues, researchers show interest to replace the conventional methods with biobased environmentally-friendly techniques for biosilica production from renewable biomass sources. Generally, silica is found to be available in amorphous and crystalline structures. For commercial purposes, silica is produced from alkyl orthosilicates ore that consists of polyethlydiorthosilicate, tetraethyl ortothosilicate, and tetramethyl orthosilicate. Another form of silica, silica gel, is produced from the selected resources of biomass, such as palm tree, wheat straw, maize leaves, teff straw, sugarcane bagasse, rice husk, rice straw, sugarcane leaf, oat husk, bamboo leaf, and corn cob. The production of biobased silica gel from agricultural residues is found to be a sustainable which receives a significant attention that can be replaced with inorganic-based silica gel for environmental concerns. Based on this context, there is a huge look for developing a process to produce biobased silica and silica gel from biomass resources with low energy utilization as promising alternatives to conventional methods. Keeping in view, current trends and methods for synthesis, the characterization of biobased silica and silica gel, as well as its wide prognostic applications were focused on a comprehensive review.

Kaolin mineral is a commercially solid powder with a comparatively low level of purity and is regularly used for a variety of applications, including filler, paints, ceramics, adsorbents, and paper. In Ethiopia, the kaolin clay mineral is significant for financial growth as the raw material used in the industry sector. However, slight consideration was given to the chemical, physical, mineralogical, and morphological properties of kaolin. In this study, the property of kaolin is investigated by using advanced instruments such as X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermogravimetric analysis (DTA). Based on the XRF test, the main component of kaolin clay contains SiO2 (58.73%), Al2O3 (24.35%), K2O (5.36%), and other impurities, including Fe2O3 (2.06%) and TiO2 (0.13%). The FTIR spectra displayed the functional groups Si-O, Al-OH, Al-O, and Si-O-Al. The XRD diffractogram identified kaolin clay as the main mineral phase in the existence of quartz, halloysite, and chlorite.

At present, the concrete-filled steel tube structure has been widely used in various practical projects. Due to the low tensile strength of the core concrete of round steel tube concrete (CFST) specimens, the axial tensile performance of CFST specimens is far from superior to its compressive performance. However, in practical projects, the concrete-filled steel tube members bearing tensile load often appear. In order to study the axial tensile properties of CFST specimens, the axial tensile tests of 5 CFST specimens and 1 pure steel tube specimen were carried out with steel tube diameter and concrete strength as variation parameters. The results show that the bearing capacity of CFST specimens is increased by 7.5%–16.3% compared with that of pure steel tube specimens with the same cross-sectional area, mainly because the core concrete limits the circumferential shrinkage of the outer steel tube. The larger the cross-sectional area of CFST specimens is, the higher the bearing capacity is. In this paper, the stress-strain relationship and the overall failure mode of CFST members under tensile force are studied, and the deformation characteristics and stress of steel pipe and core concrete are analyzed, which is expected to provide a reference for the application of CFST specimens in practical engineering.

Biocomposites are promising candidates for some engineering applications owing to the growing environmental and economic challenges to replace petrochemical-based polymers with biodegradable polymers. Herein, sisal fiber reinforced polylactic acid (PLA) composite specimens were fabricated using an injection molding machine with and without plasticizer. The weight percentage (wt%) of the sisal fiber varied between 5% and 20%. The effect of the sisal fiber wt% on water absorption resistance and mechanical properties was investigated experimentally using water ageing, mechanical, and morphological studies. The results revealed that tensile and flexural specimens after water ageing exhibited lower tensile and flexural strengths with higher water absorption behavior at 20 wt% sisal fiber than 5 wt% sisal fiber, while the impact strength increased after water ageing. In addition, the sisal fiber/PLA composites exhibited higher water absorption behavior and lower strength and modulus at 20 wt% sisal fiber after water ageing. Moreover, the water absorption decreased with the incorporation of the plasticizer.

The versatility of metal matrix composites (MMCs) makes them a promising material for various industrial applications. The current study used a ball milling to mechanically AA7178 powder and strengthened with zirconium silicate (ZrSiO4) nanoparticles. In addition, the AA7178 matrix was ball-milled to distribute the ZrSiO4 nanoparticles throughout the material. The AA7178 reinforced with ZrSiO4 nanoparticles was compacted and consolidated using two distinct powder metallurgy (PM) sequences: double pressing, double sintering, and hot pressing. In tests measuring microhardness, compression strength, and elongational break, the new nanocomposites surpassed the AA7178. The adequate interfacial bonding and even distribution of ZrSiO4 nanoparticles throughout the AA7178 matrix were essential to the strengthening mechanism. With the use of hot pressing, the mechanical characteristics of the nanocomposites were enhanced. As reinforcement concentration increased beyond 2.5% by weight, mechanical properties drastically degraded due to ZrSiO4 nanoparticles clumping and unequal distribution. Improved mechanical parts attain through the uniform distribution of ZrSiO4 nanoparticles in the AA7178 and the maintenance of their mechanical properties.

The continuous demand of today’s scenario and ecological consciousness has made the researchers think about the utilization of alternate sources of materials without compromising the mechanical behavior and characteristics while focusing on the fulfillment of the desired requirements in the wide range of industrial applications. The present work is a noble attempt and a step towards the development of silk fibre composites (SFCs) reinforced with the vinyl ester matrix material. The processing and fabrication of SFRCs have been carried out using the traditional hand layup technique using untreated silk fibres (SFs) and silk cloths (SCs) in the form of single, double, and triple layers of SFs and SCs laminates oriented in uniaxial and biaxial directions. For the prepared composite samples, the density and void contents in the sample, mechanical characteristics in terms of their tensile and flexural strength, and tribological characteristics as well as the electrical impedance have been investigated. The percentage void content was found to be within the acceptance limit. The tensile and flexural test results show a considerable increment which indicates proper stress transfer from matrix phase to fibre with triple-layer cloths showing the highest tensile and flexural properties. In the tribological test, the coefficient of friction is higher in the case of cloth loading as fibre concentration increases significantly. In the impedance test, almost for all samples, the trend of change in conductivity with applied frequency is the same. From the economic perspective, the proposed composite is suitable for a wide range of applications in industries as well as this can be utilized as an alternate source of traditionally used floor tiles currently using ceramic materials. Also, the proposed composite has a biodegradable characteristic that is completely in accordance with the demand and consciousness involved in environmental and ecological perspectives.

Numerous engineering and environmental issues can be resolved using the bacterial-induced calcite precipitation (BCP), which has the potential to be environmentally friendly, sustainable, and economical. In BCP, bacterial enzymes used substrates and divalent cations to bind negatively charged ions to the bacterial surface and produce biocementation. Various metabolic pathways involved in the calcite precipitation and ureolysis are the principal bacterial pathways that have been illustrated by most bacteria including Sporosarcina pasteurii, Bacillus subtilis, and Pseudomonas putida. Ammonia is produced by these bacteria, which is toxic and should be eliminated. Therefore, BCP via carbonic anhydrase could be a preferred option because the end-products are not toxic. The growing global requirement of ground improvement boosted the demand for biostabilization because of its numerous benefits, including environmental issues. Dust suppression, remediated soil contaminants, polychlorinated biphenyl calcium ions, and CO2 sequestration, proving that BCP is environmentally friendly and sustainable. Furthermore, for fine-grained soils having pores smaller than 0.5 μm, the enzyme-induced calcite that uses enzymes instead of bacteria is more suitable to stabilize the soil by precipitating the calcite. The use of BCP as binders for soil stability and strengthening, innovative construction materials, subsurface barriers, and impermeable crusts is an emerging field. Calcite precipitated in the pores increases strength more than 20 times, resulting in a significant reduction in compressibility. Similarly, reduced soil permeability to up to 99% broadens its applicability. This review argues that BCP can be induced by multiple approaches, including urease expressing bacteria and carbonic anhydrase expressing bacteria as well as free enzymes.

Proton exchange membrane fuel cells (PEMFC) are widely used in transportation systems owing to their desirable characteristics such as high efficacy and low operating temperature. However, the fuel cell systems exhibit load changes as well as voltage and power losses so as to reduce dependence on the battery. The aim of the present study was to explore the composition and basic working principle of PEMFC. A PEMFC electrochemical reaction model was then established according to the electrochemical reaction principle of fuel cell to evaluate the effects of Nernst electromotive force, activation overvoltage, Ohmic overvoltage, concentration overvoltage, and electric double layer. The effects of activation loss, concentration loss, and Ohmic loss on the fuel cell were evaluated through simulation analysis. The effect of various factors on the dynamic output of a 60 kW PEMFC was explored through dynamic simulations. The findings showed that a change in current modulated a change in voltage through the Ohmic loss equivalent resistance. The activation loss equivalent resistance and the concentration loss equivalent resistance decreased the voltage loss owing to the presence of the capacitor. The output voltage of the fuel cell decreased with an increase in load current, whereas the output power increased with an increase in load current. Increase in partial pressure of oxygen caused an increase in output power and output voltage of the cell. The internal chemical reaction rate and the voltage output of the fuel cell increases with an increase in the working temperature. The findings of this study provide a basis for conducting further studies to produce efficient fuel cells for application in various systems.

This work pursues two primary aims: identifying the precursory point by the CSD analysis of AE series and using acoustic emission parameters to predict the compressive strength of concrete utilizing the artificial neural network (ANN), extreme learning machine (ELM), and support vector machine (SVM). The concrete specimens with a water-cement ratio of 0.45 and 0.55 were tested for compressive strength, and the failure process of concrete was monitored by acoustic emission. The results demonstrate that the advantage of variance was being intuitive, robust, and less affected by the window. The fluctuation and abrupt increase of the variance can be regarded as the critical point and the formation of the main failure surface, which provided warning information for preventing catastrophic failures. The precursory point determined by the variance was 80%–90% of the ultimate strength, consistent with the improved b value (Ib). Then, an approach to predict the compressive strength of concrete was proposed to predict the compressive strength of concrete utilizing the ANN, ELM, and SVM. The results of the ELM were more outstanding than those of the ANN and SVM. The results suggest that it was possible to predict the compressive strength of concrete with a small number of samples using the AE parameters.

This research aims to increase the utility of globally and abundantly available waste natural fibres of Gallus-Gallus fibres coir waste from mattress and car seat manufacturing factories. The composite samples were prepared with a rally round of polyester resin of grade GP500 bio-epoxy by synthesizing specially treated Gallus-Gallus fibres selectively used for reinforcement and characterizing them through static and dynamic mechanical analyses to identify their wide range of applicability. The Gallus-Gallus fibres are preprocessed with sodium oxidative and a half per cent of potassium manganate (VII) chemical solution. The selective use includes 5 mm, 10 mm, 15 mm, and 20 mm length of the Gallus-Gallus fibre, and the quantity of reinforcement was 10%, 20%, and 30%. Five alternate layers of matrix and fibres, with vertical and horizontal orientation, are considered; 12 different samples of Gallus-Gallus fibres reinforced polyester polymer composites and a neat polyester composites were synthesized and characterized for moisture absorbability, tensile strength, tensile modulus, flexural strength, flexural modulus, wear resistance, and outperformed composites were included in microscopic examination and dynamic Mmchanical analysis. The interesting results are the preferred resin, supported for good surface finish, interface bonding, and totally in the enhancement of Composite properties. The composites are strong in tension (760.89 MPa) and sufficiently flexible (flexural modulus 5441.32 MPa), absorbed less moisture (5.8 g), high wear-resistant (least weight loss upon abrasion with a value of 0.1989 g), secured good results in dynamic analysis, and ensured homogeneous distribution of fibres in the matrix through a scanning electron microscopy image. The composites CPPC10, CPPC11, and CPPC12 performed well but composite CPPC12 outperformed.

The mechanical property of deep complex jointed rock mass is a hot topic in rock mechanics. In order to grasp the deformation and damage rules of through-going variable dip joint rock masses, the triaxial compression test and joint surface morphology scan test were conducted on cylindrical specimens in dry and wet conditions under 0, 5, 10, and 20 MPa water pressure. Through these tests, the deterioration law of rock samples under different pore water pressure in dry and wet conditions was studied. The effect of pore water pressure on the strength of saturated jointed rock sample is nonlinear. The imposed pore water pressure can significantly increase the axial deformation of rock samples, and higher pore water pressure can facilitate the deformation deterioration of samples. When the pore pressure is high, the rock samples show the characteristics of sliding shear failure. Under different pore pressure, the compressive strength of dry jointed rock is significantly higher than that of saturated jointed rock, and the saturated rock is more susceptible to sliding in the joint plane than dry rock. Dry jointed rock samples have stronger deformation ability than saturated jointed rock samples. The change rate of the morphologic parameters and the distribution of the failure cracks indicate that the stress concentration is evident in the middle of the joint plane.

Polycrystalline diamonds were sintered with the binder of Ti3Si0.8Al0.2C2 to solve the shortcomings of conventional metal binders and ceramic binders. Ti3Si0.8Al0.2C2 bonded polycrystalline diamond composites have been synthesized from a mixture of Ti3Si0.8Al0.2C2 powder (40 wt%) and diamond powder under 4.5–5.5 GPa at 1050–1300°C by high press and high-temperature technology. The characteristic peaks of TiC were observed at 4.5 GPa and above 1100°C. From the microstructure analysis, the diamond particles are equally dispersed throughout the Ti3Si0.8Al0.2C2 matrix and firmly bound to the matrix. The effects of the sintering conditions, test parameters, and counterparts on the friction properties of diamond composites were systematically analyzed. The friction coefficient between diamond composite and glass counterpart is between 0.18 and 0.33 and increases significantly at the speed of 400 rpm/min. SEM and EDS analysis show Ti3Si0.8Al0.2C2 has a strong holding force on the diamond particles. The wear mechanism is mainly abrasive, and there are obvious grooves on the surface of the glass ball. The friction coefficient of diamond composite sintered at 1050°C with POM decreases monotonically with increasing load and reaches the minimum value of 0.42 at 12 N. The higher sintering temperature (1150°C) resulted in lower friction coefficient for diamond/POM pairs. The friction coefficient of diamond/PP pairs decreases first and then increases with increasing load, reaching a minimum value of 0.431 at 10 N. The wear mechanism of PP and POM is a combination of abrasive wear and adhesive wear, while the abrasive chips of POM are small salt-like particles and the abrasive chips of PP are long flocs. The wear track of PP balls has a smoother surface than that of POM balls. For an Al pair, the friction coefficient of diamond composite sintered at 1150°C is higher than that of the composite sintered at 1050°C except for the 10 N load. The friction coefficient of the diamond composites with Cu pairs varies slightly with increasing load, with values ranging from 0.443 to 0.518 and decreases with increasing speed, reaching a minimum value of 0.396 at 600 rpm/min. The wear mechanism of Cu and Al is mainly based on adhesive wear. The presence of the diamond second phase improves the stability of Ti3Si0.8Al0.2C2 compared to the high-pressure treatment of single phase Ti3SiC2. The analysis of friction properties indicates that Ti3Si0.8Al0.2C2 bonded diamond composites are promising candidates for superhard tool materials.

Corrosion in steel leads to the deterioration of reinforced concrete structures due to chemical reactions between steel and its surrounding atmosphere. In this paper, a novel anticorrosive powder was derived from the waste Printed Circuit Board (PCB) and manually coated on the steel rebar of the reinforced concrete specimen. The corrosion-resistant efficiency of the developed nano PCB-coating on the steel bars was studied by polarization, electrochemical impedance spectroscopy, and accelerated corrosion technique. Also, the applicability of the nano PCB-coated rebar as reinforcement in the concrete environment was investigated. From the results, it was observed that the nano PCB-coated specimens exhibited 3.5 times reduced rate of corrosion and lost only 46.15% strength and 52.5% diameter under the accelerated rate of 6 V after 48 hours. The presence of nano PCB powder improved the corrosion-resistant behaviour of the steel rebar by 1.65 times of the noncoated specimen. Also, the nano PCB-coating reduced the loss in residual yield strength of the corroded steel rebar by 32% lesser than the noncoated specimens and exhibited similar corrosion-resistant properties as that of the existing zinc coating. In addition to the corrosion resistance, the nano PCB-coated steel rebar exhibited almost similar adhesion with concrete as that of the commercial zinc coating which is 7% lower than uncoated steel rebars. It was inferred from this research work that the proposed anticorrosive coating prepared from the waste nano PCB powder showed better corrosion-resistant behaviour and reduced the overall cost of coating by 42%, which ensures economy and serviceability.

This study investigates the effect of nano-ZnO on modified asphalt’s adhesion characteristics by preparing various mixtures with 0%, 1%, 2%, and 3% nano-ZnO contents. Within the study context, the adhesion characteristics of asphalt mixtures with different nano-ZnO to limestone, basalt, and granite contents are studied using a boiling test. The surface-free energy (SFE) parameters of four asphalt and three aggregate types are evaluated using a theoretical approach and then verified by performing pull-off tests, and the adhesion work between different asphalt and aggregates is calculated. In addition, the effect of nano-ZnO on moisture-sensitive properties of the asphalt mixture is assessed using a freeze-thaw split test and semicircle bending (SCB) test. The study results have shown that nano-ZnO can enhance adhesion characteristics of the asphalt. The surface energy of modified asphalt with high ZnO content is relatively larger, and the adhesion between asphalt and limestone is better than the basalt and granite. The aggregates’ chemical composition and the SFE’s parameters significantly affect the adhesion between asphalt and aggregates. Furthermore, the correlation between the surface-free energy theory and the pull-off test results is better than the boiling test ones. Nano-ZnO enhances the asphalt mixture’s moisture sensitivity before and after freeze-thaw cycles and impacts the initial state’s tensile strength and cracks resistance, especially after freeze-thaw cycles where the improvement is obvious.

Solar energy is the most accessible, eco-friendly, and renewable energy source available to meet the world’s expanding energy needs. Solar collectors are commonly utilized to convert solar energy directly into heat for purposes ranging from house heating to timber seasoning and crop drying. The purpose of this research is to design a modified solar air heater (SAH) with a baffle plate and to examine the performance due to the provision of zinc-ferrite nanocoated baffles. The entire system is mounted over a transformer for effective cooling and also produces hot air for industrial requirements. A flat plate collector and a centrifugal blower were used in the experiment. Maximum output air temperatures of 55°C, 62°C, and 72°C were measured for collectors without baffles, baffled collectors, and inverted baffled collectors, respectively. It was also found that the thermal efficiency of flat plate collectors without baffles was 36%, with baffles, it was 44%, and with inverted baffles it was 54%. This study shows that inverted SAH with zinc-ferrite nanocoated baffle plates works better than SAH without baffle plates or with baffle plates in the normal position.