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In this research, the main aim is to focus the enhancement of aluminium-based metal matrix composites for improving the attributes of light weight metals, aerospace structures and other tailor blank material properties. By this way, the friction stir processing (FSP) was the suited alternate technique to enhancing the mechanical attributes and superior microstructural amendment in the processed MMCs. Therefore, this study investigates the dispersion of ceramic-based strengthening particles of chromium oxide (Cr2O3) in the aluminium base matrix of A356 alloy. During the processing, the different tool pin sizes having the conical threaded tool pin profiles. Similarly, the tool spinning speed and tool travel speed also varied while in FSP. Before the processing, the A356 alloy was prepared by the grooved surfaces for packing the chromium oxide particles to compose the aluminium metal matrix composites. The tensile strength and hardness was employed to carry out from the friction stir processed A356 alloy with influencing of Cr2O3. The maximum occurred tensile processing parameters are 1500 rpm of spinning speed, 6 mm of tool pin sizes and 90 mm/min of tool travel speed. Similarly, the maximum obtained hardness processing parameter are 2000 rpm of spinning speed, 5 mm of tool pin sizes and 90 mm/min of tool travel speed. A scanning electron microscope was utilized to investigate the dispersed Cr2O3 in the A356 alloy for confirming the refinement grains in the nugget zones of FSPed A356 alloy. The increased grain boundary by the influence of different tool pin sizes was the major reason to produces the better mechanical properties in the processed A356/Cr2O3. [ABSTRACT FROM AUTHOR]

The Ni-based alloy powder has been melted and bonded to an AISI 316LN austenitic stainless steel (ASS) base material (substrate) using a high-energy disc laser with a maximum power of up to 12 kW. The substrate's hard-faced reservoir is highly diluted due to the significant difference in melting temperature between the substrate and the commonly used Ni-based alloy. The hardness, macrostructure, microstructure, and wear resistance effects of the defocusing distance were examined. The composition, microstructure, hardness, and wear resistance of phases have been examined with a pin-on-disk wear test, an energy dispersion spectroscopy (EDS), a scanning electron microscope (SEM), and X-ray diffraction (XRD). According to the findings, the height and diameter of the beads rose when the distance was increased from 17 mm to 37 mm. On the other hand, penetration and dilution decreased from 3.7 mm to 2.7 mm and from 9.7% to 3.1%, respectively. When the defocusing length is increased and the penetration profundity and dilution are limited, the density of energy per unit clad is accessible. The laser hard-faced surfaces contain microstructures of Ni-rich solid solution, boride, and carbide. These different factors cause higher hardness and resistance to wear. [ABSTRACT FROM AUTHOR]

The investigation was carried out by making use of the design of experiments method in order to achieve its objective, which was to study wear analysis in relation to a cryogenically treated nozzle that was utilized in plasma arc machining. Kerf width and surface roughness are two output characteristics that are key variables in deciding the quality of the cut and the efficiency of the operation. Both of these metrics are outputted by the process. While machining S235 steel, an investigation into the impact that nozzle treatment has on various quality metrics is currently under way. The examination is carried out with the arc voltage, the cutting speed, and the gas pressure, all serving as important components. A cryogenic treatment of the nozzle material using liquid nitrogen at a temperature of −194°C has been attempted in an effort to increase the life of the nozzle. Machining is performed using two different nozzle conditions, such as cryogenically treated and cryogenically untreated, with regard to the input parameter combinations that have been selected. To have a better understanding of the wear behavior of nozzles, an image from a scanning electron microscope is studied. Because of the treatment, the production of wear tracks in the direction that gas flow takes has been drastically decreased. This, in turn, has increased the cutting efficiency by decreasing the amount of arc current that was necessary. In addition, a grey relational analysis is carried out in order to find the best possible machining settings in both conditions. The parameters that were optimized for a nozzle that had been cryogenically treated were 6 bar of gas pressure, 120 amperes of arc current, and 1800 of cutting speed per minute. The use of cryogenic treatment resulted in a reduction of surface roughness by 0.4670 µm and a narrowing of the kerf width by 0.96 mm. It is clear from the SEM pictures of untreated and cryogenically treated nozzles that thermal distortion and wear in the nozzle tip area are minimized to a greater extent in the treated nozzle. This is evidenced by the fact that the treated nozzle has a more uniform appearance. [ABSTRACT FROM AUTHOR]

The mechanical and thermal properties of nylon 6.6 on polypropylene (PP) blends were investigated. Five weight percentages of nylon 6.6, 1 wt%—5 wt%, were blended with PP by an injection molding process to produce PP/nylon 6.6 blends. The impact of the mixture on the mechanical properties was investigated by performing a three-point bend test to determine the flexural strength and hardness test using nanoindentation. Both differential scanning calorimetry and thermogravimetric analysis were used to study the thermal properties of the mixture. Chemical and morphological testing was performed by Fourier-transform infrared spectroscopy and scanning electron microscope tests. Mechanical testing revealed improved strength, modulus, and hardness of the PP/nylon 6.6 blends. The 2 wt% blend showed elastic modulus, tensile, and yield stress enhancement. TGA showed variable results with improved thermal resistance for the 3 wt% and 4 wt% blends, whereas there was no effect for the 2 wt% blend and reduced thermal resistance for the 1 wt% and 5 wt% blends. DSC analysis revealed no influence on the melting temperature of the blends. SEM images showed a homogeneous mixture between PP and nylon 6.6, which substantiated the interfacial adhesion between PP and nylon 6.6 and was verified by FTIR. [ABSTRACT FROM AUTHOR]

The current work investigates the erosion-corrosion behaviour of thermally sprayed tungsten carbide-10% nickel (WC-10% Ni) coatings placed on the AA6061 aluminum alloy. The AA6061 aluminum alloy was coated with tungsten carbide –10% nickel coatings utilising a high-velocityoxy-fuel (HVOF) spray method. The microstructure and hardness of thermally sprayed coatings were examined using a scanning electron microscope (SEM) and a Vickers hardness tester. The slurry erosion-corrosion wear tests were carried out by varying the parameters of the slurry erosion process, such as testing time, slurry content, slurry speed, and impinging particle size, on the erosion testing equipment. The data demonstrated that when slurry concentration, slurry speed, and impinging particle size increased, so did the slurry erosion-corrosion wear loss. The wear processes of uncoated and thermally sprayed tungsten carbide –10% nickel have been examined using SEM and a 3-D confocal microscope. [ABSTRACT FROM AUTHOR]

Metal matrix composites (MMCs) and their hybrid combinations are widely incorporated in research due to their enhanced mechanical properties and wear resistance. In this work, an investigation is made to fabricate AA2024 matrix flyash and graphite-reinforced hybrid composite for industrial applications and determine its suitability by performing testing and characterization. Tensile properties and compressive strength, wear resistance, fracture toughness, impact energy, and the hardness of the composites are evaluated. A tensile strength maximum of 300 MPa was achieved. Furthermore, the thermal analysis of a disc brake of this hybrid composite is performed using SOLIDWORKS software to identify the temperature distribution up to 469°K. The addition of flyash reinforcement shows the changes in properties with weight reduction. Although the content of graphite particles shows a deterioration in mechanical properties, it acts as a lubricant and reduces wear by friction and friction between the components. The coefficient of friction (COF) for the specimen is in the range of 0.1 to 0.3. The distribution of graphite and flyash is analyzed using the scanning electron microscope. It was found that the properties of the prepared composite are lesser than the base alloy AA2024, but the fabricated composite's density (2.07 g/cc) is lesser than the base alloy AA2024 (2.78 g/cc). [ABSTRACT FROM AUTHOR]

This paper presents the new route of fabrication of H-AlSi24Cu3.8Mg0.8 alloy, assisted by ultrasonic vibration stirring and squeeze casting (UVSS). The primary objective of this investigation is to establish the tribological characteristics of the prepared aluminium alloy under dry, lubricated, and coated sliding conditions. Oil SAE20W40 is used as a lubricant and diamond-like carbon (DLC) is used as a coating. Under a load between 20 N and 50 N, a linear reciprocating tribometer (LRT) with a ball-on-plate geometry is used. Alloy was examined using an optical microscope, scanning electron microscope with EDS, 3D surface profilometer, Brinell hardness tester, and tensometer for pre- and postcharacterization of alloy, surface, and worn tracks. The DLC-coated condition yields the lowest wear and coefficient of friction. [ABSTRACT FROM AUTHOR]

In this study, a bottom pouring-type stir casting machine was used to create AZ31 magnesium alloy hybrid nanocomposites with varying weight percentages (0, 3, 5, and 7) of silicon carbide (SiC) and graphite (Gr) particles. Investigations have been made into the mechanical characteristics and microstructural distribution of manufactured hybrid nanocomposites. The outcomes demonstrate that the mechanical characteristics and uniform distribution of SiC and Gr particles are enhanced compared to those of the base alloy. In comparison to monolithic AZ31 alloy, microhardness, ultimate tensile strength (UTS), yield strength (YS), and compressive strength (CS) were raised by about 54%, 68%, 82%, and 107%, respectively. The presence of reinforced particles, the uniform distribution of particles, and the strong interfacial connection between the matrix and reinforcement all contribute to the improvement of mechanical properties. However, the addition of 7 wt. % SiC/Gr showed good mechanical properties compared to the base alloy. The microstructure of nanocomposites was analyzed using a scanning electron microscope (SEM), and particles were described using energy-dispersive spectroscopy (EDS). [ABSTRACT FROM AUTHOR]

Introducing SAP internal curing material and limestone powder into white fair-faced concrete in order to greatly improve the durability of white fair-faced concrete, alleviate the influence of mechanical property deterioration caused by SAP, and facilitate the popularization and application of SAP and limestone powder in white fair-faced concrete. Therefore, this paper studies the effect of the content of SAP and limestone powder on the properties of white fair-faced concrete, conducts slump, electric flux, standard cube compressive strength, and splitting tensile strength tests, and examines SAP and limestone powder from a macroscopic perspective. The effect of the dosage on the properties of white, fair-faced concrete was explained by a scanning electron microscope (SEM) from a microscopic point of view. The results show that SAP can increase the slump of white fair-faced concrete, and the slump of SAP white fair-faced concrete increases with the addition of limestone powder content. Adding SAP can greatly reduce the electric flux of white fair-faced concrete. The addition of limestone powder can further reduce the electric flux and improve the durability and adding SAP will deteriorate the mechanical properties of white fair-faced concrete. Adding limestone powder is beneficial to the improvement of the mechanical properties of SAP mixed with white fair-faced concrete. Adding 30% limestone powder can give full play to the optimal performance of SAP white fair-faced concrete. SAP can refine the internal structure of white fair-faced concrete, and the filling and nucleation effects of limestone powder can improve the situation where SAP deteriorates the mechanical properties of white fair-faced concrete, further optimizing concrete internal structure. [ABSTRACT FROM AUTHOR]

The increasing demand for eco-friendly materials and technology has made the industry focus on bio-compatible composites. This made the researchers explore the potential of eco-friendly, bio-degradable, and inexpensive banana fibre for automotive applications. This work reports the preparation and testing of banana fibre natural hybrid composite fibres randomly oriented with and without adding silica filler (5–15 wt.%) through a hand lay-up process. The mechanical properties such as tensile modulus, flexural modulus, hardness, impact strength, and water absorption capacity were measured. Composite specimens having a fibre length of 30 mm (15 wt.% of silica) exhibited better mechanical properties. The hardness, tensile, flexural, and impact strength measured were 46.74 HV, 54.71 MPa, 127.94 MPa, and 15.19 kJ/m2. The results showed significant improvement in mechanical properties in silica-reinforced hybrid composite compared to composites without silica filler. The wt.% of banana fibre increases, and the number of free hydroxyls (-OH) groups increases in cellulose, increasing moisture absorption. The pattern in which the composite absorbs the moisture at room temperature is called "Fickian behaviour." Furthermore, scanning electron microscope (SEM) characterisation studied the interaction between fibre matrix and the distribution of silica reinforcement. This research concludes that bio-composites that exhibit improved mechanical properties are eco-friendly and are found to be suitable for automotive applications that meet present-day requirements. [ABSTRACT FROM AUTHOR]

This study assesses hydration, rheology, and sorptivity of cementitious pastes using relatively low-cost Arduino-based platforms with integrated sensors. The prime objective is to develop a correlation between conventional apparatus-based and Arduino-integrated sensor-based assessment. A total of six samples of cementitious paste were prepared at a room temperature of 26°C, with a w/b ratio of 0.3, containing cement, fly ash, and silica fume. First, the conventional apparatus was employed to assess hydration, rheology, and sorptivity of cementitious mixes. Afterward, a platform arranged for data acquisition, comprising Arduino Mega 2560, a temperature sensor, a soil moisture sensor, and a voltage supply, was used to assess the same properties. The recorded temperature and moisture content data were transmitted using the Android application and the Wi-Fi modem router. A 5-minute moisture analysis test was conducted to monitor the rheological behavior of cementitious mixes. The heat of the hydration mechanism was evaluated for 32 hours using a temperature sensor, enabling continuous and real-time monitoring. Moreover, a sorptivity test on cube samples was performed using shielded self-based apparatus in an adiabatic condition, resulting in relatively long-term monitoring. The microscopic details are analyzed by using a scanning electron microscope (SEM) in conjunction with EDX analysis. Thus, the potential application of the inexpensive sensor-based method is verified. [ABSTRACT FROM AUTHOR]

Coffee husk (CH) is a sustainable and abundantly available cellulosic waste material. Its fiber consists of cellulose as the major structural part which leads to potential utilization for the manufacturing of microcrystalline cellulose (MCC) products that can be utilized for different industrial applications. In the present study, chemical composition of outer skin-isolated coffee husk was determined and sequential treatments of various untreated (UT) sample, ethanol—toluene treated sample through dewaxed (DW) treatment, sodium hydroxide (NaOH)—treated sample through alkali (AT) treatment, and sulfuric acid (H2SO4)—treated sample through bleaching (BL) treatment have been carried out. The Micro Crystalline Cellulose (MCC) has been extracted through hydrogen peroxide (H2O2) after BL treatment. The BL treatment for MCC extraction process was conducted without chlorine and additional harsh acid treatment, respectively. The characterization of chemically treated samples was carried out to investigate their morphological, physico-chemistry, and thermal behavior through a scanning electron microscope (SEM), Fourier transform infrared—ray (FTIR), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and differential temperature analyzer (DTA). From the chemical composition analysis; the cellulose, hemicellulose, lignin, and extractive content were determined and its values were (52.9%), (12.5%), (24.3%), and (9.4%), respectively. In the morphological examination, the great untreated (UT) fiber sample was greatly reduced into a micro-sized BL sample, revealing that (from FTIR analysis) the lignin and hemicellulose contents were greatly removed during chemical treatments and the presence of a micro crystalline cellulose region with 54.7% yield. Also, the sample AT and BL showed the lowest amorphous region in X-RD due to the removal of hemicellulose and lignin. The highest crystallinity index has been determined for the BL sample, i.e., 89.9%. Additionally, the thermal analysis shows that the AT and BL sample has great thermal stability than other (UT and DW) samples at high temperature. Therefore, the outer skin separated coffee husk was prepared from agricultural waste was subjected to eco-friendly chemical treatments to yield MCC. Thus, the extracted MCC is expected to be reliable for replacing other plant materials for the production of crystalline nanomaterial and reinforcing constituent for the fabrication of bio composite. [ABSTRACT FROM AUTHOR]

The utilization of construction and demolition waste is useful for sustainable infrastructure development and protecting the environment. In this research, the properties of self-compacting concrete produced by replacing the natural coarse aggregates (NCA) with inferior recycled coarse aggregates (RCA) were investigated. The properties of self-compacting concrete (SCC) and self-compacting mortar (SCM) with varying replacements of RCA (0, 25, 50, and 100%) in NCA were determined. The flow, strength, early shrinkage tests, and microstructure using X-ray diffraction (XRD) and a scanning electron microscope (SEM) were investigated. The fresh property results indicated that the viscosity of freshly mixed SCC increased with higher replacement levels of RCA, thus reducing flow. The compressive strength of RCA SCC was reduced up to 30% for a 100% replacement level, while the flexural strength was reduced by about 15%. The compressive strength and flexural strength of SCMs, however, increased up to 12% and 28% for 100% replacement with RCA. The mechanical strength of SCM increases with RCA because of high fine content which reduces the porosity and makes the system denser. The early age linear shrinkage increases with RCA due to its greater water absorption. The results indicate that recycled coarse aggregate can be effectively used as the replacement of NCA in SCC to produce sustainable and eco-friendly structural concrete. [ABSTRACT FROM AUTHOR]

The organic soil is widely distributed around Dianchi Lake in Kunming, which is rich in the humic group (HG). In order to explore the effect of HG on the strength development of organic soil, this paper adopts the method of adding humic acid (HA) reagent into the undisturbed cohesive soil (blending method) and soaking it in fulvic acid (FA) solution (steeping method) to simulate the organic soil. Then, the effect of HG on soil is analyzed by the unconfined compressive strength (UCS) and the scanning electron microscope (SEM) tests. The UCS test shows that HA can significantly reduce the UCS of the samples, and it continues to decrease with the increase of the HA reagent content. FA can substantially enhance the UCS of the samples, which continues to increase with the concentration of FA solution (decreasing the pH value). Under each HG condition, the steeping of FA can significantly increase the UCS of the sample when the content of the HA reagent is less than 10%, and the growth rate of the UCS decreases when it is greater than 10%. With the increase of steeping age, the UCS of the 5% HA samples continued to increase and gradually became stable, and when the content of the HA reagent is more than 5%, the UCS curve first increases and then decreases. The SEM test shows that adding HA reagent can significantly increase the pore size, improve the connectivity between the pores, and weaken the connection of the soil structure. The steeping of FA can reduce the pore size, weaken the connectivity between the pores, and strengthen the connection of the sample structure. [ABSTRACT FROM AUTHOR]

Quasi-brittle behaviors of cement-based material can be reinforced through diverse methods due to its unique multiscale features. Among them, reinforcing agents are the most direct and effective means, such as slag, metakaolin, and fly ash. These materials can improve the performance of cement stone to a certain extent, but their chemical composition is still mainly silica, which does not in essence change the defects of cement. Therefore, in this experiment, magnesium borate whisker (Mg2B2O5) was used as reinforcer of 90°C class G oil well cement and magnesium borate whisker reinforced cement-based material (MBWRC) was prepared. On the one hand, the performance of mechanical strength was controlled, and the resistance to compression, traction, and bending was included. Furthermore, static stress-strain behaviors analysis and toughness behaviors analysis (dynamic multicycle loading test) were further conducted. Second, mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were used to test the characteristics of pores and interfaces of cement-based materials. Through multiscale microstructure analysis, MBWRC was found to have excellent 90°C mechanical performances when compared to control sample's, for which tensile strength increased to 235% of controlled sample's, and flexural strength increased to 130%, plus a healthy developed compressive performance, and MBWRC showed much denser pore structure, in which harmless micropore increased from 13.3% to 14.40%, porosity decreased from 17.01% to 16.20%, and permeability decreased from 0.2533% to 0.0205%. Furthermore, MBWRC showed resistance capability to mechanical loading, which can be attributed to the formation of denser pore structure and more excellent mechanical performance. [ABSTRACT FROM AUTHOR]

The main objective of this investigation is to analyze the microstructure, tensile properties, and impact toughness of Ti6Al4V alloy joints developed using optimized parameters of linear friction welding (LFW) for gas turbine blisk assembly applications. The 6 mm thick plates of Ti6Al4V alloy were joined using a friction time of 40 sec, a friction pressure of 20 MPa, a forging pressure of 10 MPa, a forging time of 3 sec, and an oscillating frequency of 14 Hz. The different regions of joints were analyzed using a stereo zoom microscope. Optical and scanning electron microscope (SEM) was used for analysing the microstructural features of joints. The room temperature tensile properties, hardness, and impact toughness of LFW-Ti6Al4V alloy joints were evaluated and correlated to the microstructural features of weld region. The fractured sections of tensile and impact toughness specimens of joints were analyzed using SEM and the failure of joints was correlated with the hardness survey. Results showed that the LFW-Ti6Al4V alloy joints developed using the optimized parameters exhibited a tensile strength (TS) of 1015 MPa, a yield strength (YS) of 940 MPa, and an elongation (EL) of 8%. The joints revealed 98.54%, 95.91%, and 66.67% of tensile strength, yield strength, and ductility of the parent metal. The LFW joints disclosed impact toughness (IT) of 17.2 J which is 89.77% impact toughness of the parent metal. The superior tensile properties and impact toughness of LFW-Ti6Al4V alloy joints are mainly attributed to a greater degree of refinement of α + β grains in the weld interface, which offers greater resistance to tensile deformation and crack propagation. [ABSTRACT FROM AUTHOR]

In order to determine the effect of graphene oxide (GO) on the physical property and microstructure of the asphalt binder, GO material was selected to prepare GO-modified asphalt for analysis. Firstly, the surface/interface characterization and chemical analysis were performed on GO and GO-modified asphalt. The physical properties of GO-modified asphalt were investigated through softening point, ductility, and penetration tests. The impact of GO material on the rheological behavior of asphalt was characterized by Brookfield viscosity and dynamic shear rheological tests (DSR). Furthermore, the typical microstructure of GO inside asphalt material was also identified and analyzed through a scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the modifying effect of GO materials could promote the fusion between asphalt and GO. A modified GO could improve the high temperature of asphalt, but it would degrade the low temperature property of the asphalt binder. A modified GO could be integrated with asphalt and achieve a modifying effect on the asphalt material. This study would provide references for the application of graphene oxide in asphalt pavement materials. [ABSTRACT FROM AUTHOR]

The biosynthesized magnesium oxide nanoparticles were pigeon-holed with X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectrophotometer, scanning electron microscope (SEM), and photoluminescence spectrometer (PLs) and antibacterial activity. Datura stramonium leaves extract has been used in the present work,; which has medicinal value, and we have synthesized magnesium oxide nanoparticles from both chemical and biosynthesis techniques. The XRD result indicates the realization of crystalline magnesium oxide nanoparticles, and again it is also inveterated with an ultraviolet-visible (UV-Vis) spectrophotometer. The superficial morphology expresses that magnesium oxide nanoparticles have a bulbous morphological shape for both biosynthesis and chemosynthesis. The antibacterial activity of magnesium oxide nanoparticles obtained from Datura stramonium leaves against E. coli and S. aureus was studied. The antibacterial activity also shows a good zone of inhibition. Both techniques are promising for the preparations of MgO nanoparticles in antibacterial activity and show the same result. This outcome demonstrates that the biosynthesized nanoparticles originate from having some medicinal uses and are biodegradable. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the synthesis optimization of activated carbon-driven scrap tires for adsorbent yield and methylene blue removal under response surface methodology. The scrap tire sample was activated by KOH using ethanol as a solvent. The optimized activated carbon was characterized using proximate analysis, scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer Emmett Teller (BET) method. The activated carbon was demineralized using 5 M NaOH + 98% H2SO4 (1 : 1) as a solvent to enhance the surface area. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were used to check the adsorption isotherm. The adsorption kinetics was checked using pseudo-first-order and pseudo-second-order models. Weber-Morris intraparticle diffusion model was used to study the diffusion mechanism. The optimum impregnation ratio, impregnation time, and carbonization temperature for synthesizing the activated carbon were 2 g/g, 12 hr, and 700°C, respectively. The moisture content, volatile matter, ash content, fixed carbon, and bulk density of the activated carbon were 6.13%, 9.42%, 5.34%, 79.11%, and 0.89 mg/L, respectively. The surface area of optimized activated carbon was enhanced by demineralization process and increased from 53 m2/g to 260.26 m2/g. Temkin adsorption isotherm with R2 values of 0.982 and pseudo-second-order adsorption kinetics with R2 values of 0.999 best fits the experimental data respectively. Intraparticle diffusion was not the only rate-controlling step for both optimized and demineralized (NaOH + H2SO4) activated carbon. It can be concluded that the optimized and demineralized activated carbon derived from scrap tires has a promising potential to be used as a low-cost adsorbent in developing countries including Ethiopia. However, further investigation needs to be conducted before scaling up at industrial level. [ABSTRACT FROM AUTHOR]

Laser cladding is a repair and surface-strengthening technology for the protection of metal parts. It is an effective method for improving the properties of various metal substrates. The process involves melting and solidifying alloy powder on the surface of the substrate. The aim of the present study was to explore the effect of iron-based alloy laser cladding coating on Q235 substrate. Three types of specimens were obtained from Q235 base material using a 5 kW cross-flow CO2 laser beam. Sample 1 and sample 2 were obtained by the addition of rosin to the iron-based alloy powder. Sample 3 was obtained through the addition of rosin and vanadium to the iron-based alloy powder. A gas curtain was used to wrap the molten pool of samples 2 and 3. The surface hardness of the specimens was determined using a Rockwell hardness tester, and the tensile strength was evaluated using the universal mechanical testing machine. The microstructure of the cladding coating was explored using an Olympus optical microscope and SEM. The results showed that the average hardness of sample 2 and sample 3 was 6.42% and 19.84% higher than that of sample 1. The average tensile strength of samples 2 and 3 was 7.42% and 10.37% higher than that of sample 1. The grain of sample 3 was finer than that of sample 2, and that of sample 2 was finer than that of sample 1 under the same magnification. Rosin minimized oxidation of the substrate, whereas the gas curtain prevented the entry of air into the molten pool, hence the improved properties of samples 2 and 3 compared with that of sample 1. Rosin and the gas curtain protected the powder from oxidation loss and improved the quality of the cladding coating. The results of the present study show that rosin reduced the oxidation of iron-based powder, whereas vanadium improved the hardness and strength of the substrate as well as refined the grain size. [ABSTRACT FROM AUTHOR]

As a modified material, nano-SiO2 can be compounded with many high molecular polymer resins to improve the performance of the polymer and be used as a concrete filler. PVA is a kind of synthetic fiber made of high-quality polyvinyl alcohol with a high degree of polymerization and processed by specific advanced technology. This research mainly discusses the optimization of the antifreeze, antipermeability, and anticorrosion performance of the concrete reinforced by nano-SiO2 and PVA fiber synergistically. In this paper, nanosilica PVA fiber-modified concrete was synthesized. Through compressive strength test, split tensile strength test, rapid freeze-thaw test, and microstructure test (X-ray diffraction and scanning electron microscope), this paper also analyzed the modification effect of PVA fiber concrete in different blends and the corresponding mechanism of nanoparticles. The instrument model of the scanning electron microscope used is S-4700; the manufacturer is Hitachi, a Japanese company; and the test voltage is 20 kV. Before the test, the hydrogel was placed in a freeze-drying oven at −40°C for 48 hours to remove water. Then, we put the sample in liquid nitrogen and break. The morphology of the cross-section was observed by SEM, and the microscopic morphology changes brought by different amounts of MTMS to the hydrogel were analyzed. After the test piece is immersed in water to reach a saturated state, we check the appearance size of the test piece, wipe the surface of the test piece clean with a rag, weigh the unfreeze-thaw test piece, then measure the ultrasonic wave speed of the test piece with a nondestructive testing instrument, and do good record. After every 25 freeze-thaw cycles, we measure the mass and relative dynamic elastic modulus of each group of specimens, make corresponding records, then put them into the freeze-thaw box, and add clean water as the freeze-thaw medium to continue the test. The average initial crack load of the three specimens of W W3 is increased by 52% compared with that of the specimens of W W1, and the load of W W4 is increased by 77%. This research helps promote the application of concrete on roads. [ABSTRACT FROM AUTHOR]

This article focuses on the microstructure and mechanism analysis of the novel coating MgO– B2O3–SiO2–Zn prepared by plasma spraying and flame spraying on the SUS304 alloy substrate. Firstly, the crystal compositions of the powders were analyzed by XRD (X-ray diffraction). Secondly, the surface and cross section microstructures of the coating were observed by SEM (Scanning Electron Microscope) and EPMA (electron probe microanalysis) in order to study the mechanism of the thermal insulation performance. It is concluded that, the microstructure, different thickness and compositions have various effect on heat insulation. [ABSTRACT FROM AUTHOR]

Fe:TiO2 nano particles were deposited through sol-gel techniques, and the influence of pH values on structural, morphological, optical, and photoluminescence spectral behaviors was studied. Iron doped titanium dioxide nanopowders were analyzed using XRD, SEM, UV–ViS, and PL. Nano crystallized samples of titanium dioxide (72 nm, 77 nm, 78 nm, and 83 nm) were gained from X-Ray diffraction data and showed that there was the creation of unalloyed anatase and ructile segment with tetragonal configuration. The average crystal size was 77.5 nm. pH values provide the alteration of segments from anatase to ructile. The crystal size of prepared iron doped titanium dioxide nanoparticles was greater than before as pH value rises from 2 to 6 while FWHM and scrap sizes declined. Homogeneously disseminated cylindrical forms of iron doped titanium dioxide nanoparticles were perceived from scanning electron microscope graphics and rises in size with growing pH values from 2 to 6 in an acidic medium. Extremely translucent nanopowders are witnessed in the observable region by visible and redshifts near advanced wavelengths with rising pH values because of an increase in the size of particles from XRD data and SEM micrographs. The band gap of energy produced by nano concentrates was reduced with growing pH values that resemble the redshift of optical absorption superiority. The structural behaviors of deposited nanoparticles were also analyzed by Raman spectra and disclosed the existence of tetragonal anatase and ructile segments. EDS results confirmed that the dopant of pH values of the solutions might affect the size distributions of the Fe: TiO2 nanoparticles. The general decrement intensity was witnessed from photoluminescence outcomes. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize and evaluate the effects of UV radiation on the rheological and physicochemical properties of ASA polymer-modified asphalt. The conventional properties (penetration, softening point, ductility, and Brookfield viscosity) of ASA polymer-modified asphalt were tested. Based on rheology, the effect of different UV irradiation times on the high-temperature performance of ASA polymer-modified asphalt was systematically characterized, the thermogravimetric analyzer (TGA) was used to analyze thermogravimetric properties of ASA polymer-modified asphalt, and the micromorphological characteristics of ASA-modified asphalt under different UV irradiation times were characterized by scanning electron microscope (FIB-SEM). The results show that the ASA polymer has a significant effect on the basic properties of asphalt. Compared with the base asphalt, the high-temperature stability of the modified asphalt was decreased, and the low-temperature ductility performance was improved. ASA polymer can effectively reduce the aging effect of ultraviolet radiation on the base asphalt and inhibit the generation of microcracks. ASA polymers improve the thermal stability of asphalt binders. During the aging process, the formation of carbonyl and sulfoxide groups was inhibited, indicating that ASA polymer can effectively delay the UV aging of asphalt. [ABSTRACT FROM AUTHOR]

In order to better discuss the influence of pore structure characteristics of primary coal on coalbed methane adsorption, suburban coal and Zhaozhuang coal in Henan Province were systematically sampled. The analysis method of pore structure characteristics of primary coal is divided into shooting research and experimental analysis. Scanning electron microscope (SEM) was used to analyze the formation reason of coal micropores, pore shape, pore connectivity, pore size, and filling effect on coalbed methane adsorption. Experimental analysis is mainly based on CO2 adsorption experiments to obtain specific surface, pore volume, and distribution of coal samples. The pore-specific surface area, pore volume, and adsorption-desorption curve of coal samples were obtained by ultralow-temperature N2 adsorption experiment. Finally, the influence of pore structure characteristics of primary tectonic coal on coalbed methane adsorption was discussed by fusion of phase study and experimental analysis. [ABSTRACT FROM AUTHOR]

In this work, we investigate the fiber tensile strength of the Agave cantala roxb leaves based on the treatment of immersion in liquid smoke which was obtained from mature coconut shells. Four different time variations of treatments, namely, one hour, two hours, three hours, and four hours, have been carried out. After the immersion, we investigated the chemical contents of the Agave cantala using scanning electron microscope (SEM) which is equipped by energy dispersive spectroscopy (EDS). Furthermore, the tension strength is tested using tensile strength plus 50 N. The test is applied for a single Agave cantala fiber. The results of the tensile test of single fiber showed an increase in tensile strength when compared with fiber tensile strength without immersion. The tensile strength of a single fiber of Agave cantala leaves increased with increasing duration of immersion time. After reaching a certain strength, however, the strength of the fiber decreases. The tensile strength of a single fiber without immersion is 192.85 MPa and the highest is 670.82 MPa for Agave cantala after immersion for three hours, with an elongation of 0.68 mm. By increasing the tensile strength of Agave cantala through liquid smoke immersion treatment, it can potentially improve its performance as a material composite reinforcement. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of nano polymer materials on the UV aged performance of asphalt binder, a nano PA modifying agent was selected to prepare modified asphalt. Under the effect of UV radiation, the modifying effect of nano PA on the rheological properties of asphalt was studied. With the extension of UV ageing time, the microstructure variation of PA modified asphalt was characterized by using a focused ion beam scanning electron microscope (FIB-SEM). The thermophysical properties of PA modified asphalt were investigated by thermogravimetric analysis (TG). Furthermore, the functional group compositions of PA modified asphalt were investigated by dynamic FTIR. The results showed that with the extension of UV ageing time, the PA modifier could mitigate the ageing effect of UV radiation on the asphalt binder. PA modifier could achieve an increasing effect on the viscoelasticity of asphalt during the UV ageing process. PA modifier suppressed the generation of microcracks in the surface microzone of UV aged asphalt samples. PA modifier could promote the thermal stability improvement of asphalt binder when subjected to UV radiation. The generation of carbonyl and sulfoxide groups in asphalt was inhibited during the UV ageing period, which indicated that the UV induced reaction of asphalt could be postponed by the PA modifying agent. [ABSTRACT FROM AUTHOR]

The reduction of surface roughness on additively manufactured components has become a critical factor in engineering applications. This paper reports the electropolishing of additively manufactured Ti-6Al-4V by powder bed selective laser melting (SLM) using a nontoxic electrolyte solution. The results have shown that the salt-based electrolyte can be used to electropolish titanium alloys. The surface waviness of the as-built Ti-6Al-4V alloy was reduced by five times the average roughness of the as-built specimen. The minimum surface roughness obtained was 9.52 μm. The specimens were characterized by scanning electron microscope, Gwyddion software, and electrochemical impedance spectroscopy (EIS) to evaluate the surface morphology, surface profile, and charge transfer resistance. The X-ray photon spectroscopy (XPS) and X-ray diffraction (XRD) spectroscopy were used to characterize the surface chemistry of the specimen. The XPS and XRD showed TiO2 as the significant component on the surface of Ti-6Al-4V, and the atomic percentage on the surface increased after electropolishing. In addition, the EIS data indicated the high charge transfer resistance of the electropolished specimen, which shows the growth formation of the oxide layer. [ABSTRACT FROM AUTHOR]

As unpredictable fracture of the front axle will lead to serious safety accidents, its failure behavior study is essential. This paper analyzes typical cracks on I-shaped and leaf springs of the front axle made by Steel A and Steel B. Steel B has a lower content of S, N, Cu, and Sn than Steel A. In order to identify the failure mechanism difference, the low magnification etch test, and metallographic and scanning electron microscope analyses were conducted. The results show that the microstructures are tempered sorbite, and the cracks are with intergranular fracture characteristics. The aggregated distribution of sulfide inclusions in the matrix of Steel A is higher than that of Steel B. Copper-rich particles are detected in the cracks of Steel A. The result indicates that the purity distinction of raw steel can have a big difference on the cracking rate of the front axle even under the same manufacturing process. Relevant suggestions to reduce the cracking are put forward from the aspects of raw materials and process conditions. [ABSTRACT FROM AUTHOR]

Solid-state friction stir welding (FSW) is a sophisticated technique that can join materials that are similar and different without significantly affecting the properties of the base materials. The purpose of this study is to enhance the tensile strength, micro-hardness, and fatigue strength of the copper (C1100) butt-joints reinforced with B4C nanoparticles. The effects of B4C nanoparticle inclusion on the mechanical properties of the fabricated joints are studied in correlation with the microstructural features of the welded joints using optical microscopy. The joints are fabricated on a specialized friction stir welding machine (VMC-TC-1200) with a square pin-profiled tool. Defect-free joints of 3 mm copper plates are produced at the constant tool rotational speed of 1100 rpm, welding speed of 30 mm/min, plunge depth of 0.25 mm, and constant axial stress of 5 kN. B4C particles of 1, 2, 3, and 4wt% are added to the joints and their properties are compared with the joints produced without the inclusion of B4C particles to study the effects of the addition of nanoparticles. The joints attained a maximum micro-hardness of 123 HV, fatigue strength of 159 MPa, and tensile strength of 203 MPa with the addition of 3% B4C. Microstructural investigations performed through an optical microscope and scanning electron microscope (SEM) indicated the presence of homogeneously distributed B4C particles engulfed by finely refined grains. The thermal conductivity of the B4C particles facilitated the smooth flow of copper around the particles by forming a thin lubricating layer, thus improving the properties of the joints. Furthermore, this study has established that the addition of B4C particles is an effective and eco-friendly method of producing strong joints which could be used for industrial and defense applications. [ABSTRACT FROM AUTHOR]

The introduction of soluble calcium additives contributes to forming calcium-containing geopolymer (N,C)-A-S-H and/or calcium (alumino)silicate hydration C-(A)-S-H in alkali-activated fly ash-based composites (AAFCs). However, the quantitative determination of the final gel product has yet been unclear due to the different chemical components, which influences the prediction of mechanical strength and microstructure. This study aims to propose a method to clarify the gel products in AAFCs by the critical elemental compositions in gel products. Furthermore, the AAFCs were prepared (by casting method) using soda residue (SR) as the calcium additive, fly ash as the aluminosilicate precursor, and sodium silicate solution as the alkaline activator. The compressive strengths of the AAFCs with different SR contents were recorded. The microstructures and gel products of AAFCs were detected through scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and 29Si nuclear magnetic resonance spectrometer (29Si NMR). Finally, the proposed determination method was verified with the experimental results. The new proposed quantitative method refers to a limit value of 2Ca/Al = 1.00 about the critical chemical elements in gel products, which helps to determine the calcium-containing geopolymer (N,C)-A-S-H or/and calcium (alumino)silicate hydration C-(A)-S-H in stable AAFCs. Results show that the gel products are determined as single (N,C)-A-S-H gels when 2Ca/Al is lower than 1.00; meanwhile, (N,C)-A-S-H and C-(A)-S-H gels coexist when 2Ca/Al is higher than 1.00 by the above proposed quantitative determination method. Furthermore, it works that the industrial solid waste SRs regarded as calcium additive are applied in the AAFCs to verify the gel products by 2Ca/Al = 1.00 as the limit value. The results provide the theoretical and experimental basis for the performance prediction and microstructural determination. [ABSTRACT FROM AUTHOR]

Organometallic perovskite is one of the potential materials in the various optoelectronic research fields. This study demonstrates the synthesis of CH3NH3PbI3 : ZnS microrods via one-step spin coating for optoelectronic applications. Incorporation of ZnS in the perovskite material caused bandgap variation in the visible wavelength range. Structural and chemical properties have been observed using X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy. The optical and electrical properties were studied via UV-Vis spectroscopy and impedance analyzer. The addition of ZnS caused to increase the optical absorption coefficient from ∼104 cm−1 to ∼105 cm−1. The bandgaps of the thin films were calculated using the Tauc relation and electrical method, obtained in the range 1.51 eV–1.64 eV, suitable for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

The aluminium metal matrix composites (AMMCs) are preferred in automotive and aerospace industries for higher strength, weight ratio, good corrosion resistance, and also better tribological properties. This study proposed that the AA7075 alloy methodology was enhanced by stir casting with titanium diboride (TiB2) particles at different percentages (5, 10, and 15 wt. %). The preheated titanium diboride powder is spread to the molten state AA7075 at 870°C to provide good weight resistance and delivery. The prepared composites are evaluated by wear analysis, tensile properties, hardness range, and microstructural behavior studies. Pin-on-disk and Rockwell hardness tester were used to analyze the wear behaviour and hardness level. The tensile strength and hardness have defined the strength of the proposed composite while the addition of TiB2 particles improves the hardness and tensile stress. The findings showed that adding TiB2 particles in the Al7075 matrix strengthened all properties compared to the Al7075 matrix. The scanning electron microscope and EDS were used to analyze the eroded surface and chemical composition of composites. [ABSTRACT FROM AUTHOR]

The shale fracture permeability is critical in determining gas production and deep CO2 sequestration performance. Moreover, how shale fracture permeability evolves after interactions with supercritical carbon dioxide (Sc-CO2) should be understood to constrain the shale reservoir permeability and evaluate the long-term sealing ability of shale formations. In this research, we conducted soaking experiments with shale fractures and Sc-CO2 at various times and then measured the shale fracture permeability and hydraulic aperture evolution under different stress states. Additionally, we quantify the chemical compositions, pore characteristics, fracture surface roughness alternation through X-ray diffraction, nuclear magnetic resonance, scanning electron microscope, and optical profilometry techniques. Our results indicate that soaking with Sc-CO2 will dramatically increase the shale fracture permeability and aperture due to the calcite and dolomite dissolution. This free-face dissolution process will remove the mineral particles in the fracture surface, resulting in larger pores, peaks, and valleys in the fracture surfaces. This process may last for seven days, and after that, chemical reactions may terminate, and the rock-Sc-CO2 system turns stable. Our results explain how Sc-CO2 alters the shale fracture permeability through the chemical dissolution of specific minerals from a microscale analysis. [ABSTRACT FROM AUTHOR]

Most mechanical systems (in particular, gear transmission system) undergo relative motion which results in increased friction phenomenon (friction coefficient, stresses, and wear rate) and thereby results in loss of efficiency. Mechanical parts undergo relative motion in different geometry configurations and orientations that induce a different state of stress as a result of friction. Till date, attempts are being made to minimize the friction with full sphere pin geometry configuration. The present work focused to reduce the frictional and wear rate, and experiments are conducted with tribo-pairs. i.e., nickel-coated pin surface slide against Al6061 alloy disc. The friction studies are carried out at different loads and geometries of pin surfaces (sphere and hemisphere configured at different orientations such as full sphere and hemisphere configured at 0°, 45°, and 90°) to induce different stress states with reference to sliding directions. Change in the geometry of EN8 pin material and their orientation with reference to sliding direction resulted in a different state of stress. The resulting stress levels were examined under the scanning electron microscope, which revealed the mechanisms of adhesion, abrasion, and extrusion. At a lower magnitude of orientation and load, the extent of asperity breaking lessens and material removal from pin surface decreases. Abrasion wear mechanism was observed corresponding to full sphere configuration on Al 6061 disc, whereas adhesive wear mechanisms are seen with hemisphere pins. The amount of aluminum transfer on pin surface with a hemisphere pin is comparatively more than that of full sphere configuration. At a lower magnitude of state of stress, the mechanism of sliding was dominated by the adhesion effect. At a higher level of state of stress, the mechanism of sliding was dominated by abrasion and extrusion. [ABSTRACT FROM AUTHOR]

In this present research work, TiZrN and TaZrN multilayer coating was deposited on 4140 steel by RF/DC magnetron sputtering for comparative work also prepared in single layer. The flow rate ratio of Ar/N2 was set to 15 : 3 sccm and the thin film was prepared by the PVD (physical vapor deposition) method by RF/DC magnetron using a Ti-Zr and Ta-Zr target with a purity of 99.99%. The crystal structure, surface morphology microstructure, and component arrangements were explored by X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM). It has been found that the crystal structure, surface morphology, microstructure, and elemental composition of the membrane are strongly dependent on deposition parameters. It is mechanically characterized by corrosion and Vickers hardness. In AFM measurements, coarse cluster particles with increasing Ti and Ta values not only increase the average roughness (Ra) by 2.341 nm (200°C) and 2.951 nm (400°C) but also have a continuous average thickness which was shown to increase by 1.504 nm and 781.75 nm. With the increase of hardness, the roughness decreases correspondingly. The TiZrN multilayer microhardness augmented to 314 GPa at 200°C and 371 GPa for TaZrN (400°C). [ABSTRACT FROM AUTHOR]

This paper focuses on the disposal of iron tailings sand (ITS) and reclaimed inorganic binder stabilized aggregate (RAI), and a new "ITS plus RAI" solid waste treatment method is innovatively proposed, which uses ITS and RAI as a new base course material to replace of new aggregates by 100%. It is found that the new ITS and RAI mixture has excellent compressive performance by designing the material composition of the mixture, which can meet the design strength of different levels of pavement under various load conditions. A series of laboratory tests are used to study the effect of the content of special cementitious material and iron tailings on the uniaxial compressive strength, flexural-tensile strength, compressive resilience modulus, and flexural-tensile resilience modulus of recycled mixture. And, the scanning electron microscope test (SEM) and X-ray diffraction test (XRD) are used to compare the surface morphology characteristics and hydration products of the recycled mixture under different ratios and to discuss the formation mechanism of the strength of the mixture. The test results show that the macroscopic change pattern in laboratory tests is basically consistent with the results in microanalysis. The relationship between compressive strength and compressive resilience modulus and flexural resilience modulus is also established by linear regression. This solid waste treatment method is applied to the pavement renovation project of national and provincial roads in Shanxi Province (within Linfen), to replace the existing base material by using recycled mixture, and the results show that it can save not only the carbon emission from stone mining and processing but also the construction cost, while producing good social and economic benefits and promoting the process of carbon neutralization in the world. [ABSTRACT FROM AUTHOR]

High-viscosity modified asphalt (HVA) is widely used as the binder for permeable asphalt pavement, and hydrated lime (HL) attracts a strong technical interest as an effective moisture additive in asphalt for a long time. However, the application of HL in HVA has been rarely studied. The present study evaluates the influence of HL on the high-temperature rheological properties of HVA and selects the optimum HL content and fineness. The asphalt mortars of HVA and HL of different contents and fineness were prepared. Temperature scanning (DSR-TS), multiple stress creep recovery (MSCR) by using a dynamic shear rheometer, and scanning electron microscope (SEM) tests were carried out to evaluate the high-temperature rheological properties and microstructure morphology characteristics of the asphalt mortars. Based on the DSR-TS and MSCR tests, the results showed that high-temperature performance together with the ability to deformation resistance of HVA was improved apparently with the increase of the HL content. When the HL content is above 1.2, the stress sensitivity of HVA is lower. The SEM results clearly showed that the uniformity of asphalt mortars could be effectively guaranteed when the HL content was 1.2 and the fineness was 800 mesh. The HL fineness has little effect on the high-temperature performance of HVA. In summary, taking into account the high-temperature performance and microstructure of HVA with HL, the optimum HL content and fineness could be finally determined. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles (NPs) were extracted from a commercial paste in both colloidal and precipitate forms. The Zetasizer analysis performed on the colloid showed ZnO NPs ranging from ∼30 nm to ∼100 nm. Thin films of ZnO were deposited on glass substrates by spin-coating technique from a mixture of the extracted colloid and precipitate. The scanning electron microscope (SEM) images showed uniformly arranged, mesoporous, and nanostructured ZnO particles of different shapes, with an estimated film thickness of 0.67 μm. Analysis by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction analysis (XRD) confirmed the presence of ZnO in the films, with no impurities or remnants of other materials. The XRD analysis showed a polycrystalline nature of the films and identified a pure phase formation of the hexagonal wurtzite structure. The average crystallite size calculated from the diffraction peaks is ∼43.25 nm. The calculated crystal tensile strain is 1.954 × 10−3, which increases the crystal volume by 0.728% compared with the crystal volume of standard ZnO. The calculated crystal parameters are a = b = 3.258 Å and c = 5.217 Å. The calculated dislocation density (d) and bond length Zn–O (L) are 5.35 × 10−4 nm−2 and 2.695 Å, respectively. Ultraviolet-visible absorption spectra showed an optical band gap of ∼3.80 eV. [ABSTRACT FROM AUTHOR]

In this research, microstructural events and mechanical behaviors in dissimilar friction stir welding (FSW) of aluminium (Al) alloy AA6082-AA7075 joints have been evaluated to apply aerospace, defense, and military sectors. FSW parametric effects have a more significant impact on the mechanical performances and microstructure of produced joints. FSW tool rotational speed, welding speed, and tool plunge speed were chosen to make the weld joints. The rotational tool speeds of 1600 rpm and 2300 rpm, welding speeds of 40 mm/min and 60 mm/min, and tool plunge speeds of 20 mm/min and 30 mm/min were set as the upper and lower limits. A constant axial force of 5 kN was maintained throughout the joint fabrication process. A taper pin-profiled tool was utilized to produce the butt welded joints. Mechanical properties of microhardness, tensile strength, yield strength, elongation, and bending strength of the joints were analyzed. The response of the stir zone microstructure to processing parameters was evaluated using optical microscopy (OM) and fractographic analysis of a tensile specimen shown by scanning electron microscope (SEM). The weld joints produced at 2300 rpm, tool traveling rate of 40 mm/min, and tool plunge speed of 30 mm/min showed the greatest tensile strength of the 191 MPa hardness of 145 Hv at the weld center and also the maximum bending strength of 114.23 N/mm2 was achieved. The lowest bending strength of 25.38 N/mm2 was obtained at 1600 rpm with 60 mm/min due to inappropriate mixing of the base metals and poor joint quality. Furthermore, this study revealed that a higher tool plunge speed facilitates the formation of equiaxed grains in the thermomechanically affected zone (TMAZ) on the advancing side (AS). Additionally, the increment in tool rotational speed significantly improved the tensile strength, weld joint quality, and joint efficiency. [ABSTRACT FROM AUTHOR]

This paper investigated the effects of silane impregnation on the protective properties of alkali-activated slag (AAS) mortars. The surface silane impregnation on water absorption, contact angle, and penetration depth were examined. The related protective mechanism regarding silane impregnation was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier infrared spectroscopy (FT-IR). The results showed that the surface of the AAS mortar after silane impregnation was transformed from hydrophilic to hydrophobic with an increased contact angle of 80° from 36° to 116°. And the water absorption was significantly decreased by 74.42% to 97.79%. The penetration depth of the two-layer coating was dramatically higher than that of the one-layer coating. The optimal coating method and dosage of silane were two-layer coating and 200 g/m2. In addition, silane impregnation formed a stable Si-O bond with AAS mortars through a hydrolytic condensation reaction and the −CH2CH3 group of the silane acted on the surface of the AAS mortars. [ABSTRACT FROM AUTHOR]

In the Loess Plateau, seasonal freeze and thaw cause great damage to the mechanical behavior and microstructure of soil, which leads to frequent geological disasters during winter and spring. To investigate the influence of freeze-thaw (FT) cycling (FTC) on the shear strength and microstructure of intact loess, triaxial shear, nuclear magnetic resonance, and scanning electron microscope tests were carried out on soil samples after target FT cycles. The results indicate that the FTC has limited changes to the soil stress-strain curve, but has a significant attenuation effect on the peak deviatoric stress. The peak deviatoric stress was attenuated by FTC but changed insignificantly after ten cycles. The cohesive force decays exponentially with the number of FT cycles, while the internal friction angle increases slightly. Moreover, under FTC, the T2 hydrogen spectra of soil samples showed a multimodal distribution, with the main peak appearing to have two obvious upward shifts that occurred at 6 and 10 FT cycles. Indeed, a depolarization phenomenon related to the directional frequency of soil particles was observed, and the mass fractal dimension of the pore network increased slightly. In an FT environment, the shear strength declines due to accumulated internal microstructural damage. These findings contribute to a better understanding of the response of loess to FTC and provide novel ideas for the prevention of frost damage in loess areas. [ABSTRACT FROM AUTHOR]

Gravity thickening is an important aspect to solve numerous environmental and safety problems that were created by tailings discharging at low solid concentrations. Furthermore, in order to efficiently facilitate the separation of released water and solid sediments, a continuous thickening system with ultrasonic equipment has been used to investigate the thickening performance of copper-mine tailings under different ultrasonic frequencies (16 kHz, 20 kHz, 22 kHz, 25 kHz, and 28 kHz). After freeze-drying treatment, the underflow samples are imaged using the scanning electron microscope (SEM); then, the structure of floc or aggregates in the SEM images is quantifiably analyzed using the software of Image J. Results show that the underflow concentration increases as the ultrasonic frequency increases and decreases afterwards. A linear logarithmic function can explain the relationship between underflow concentration and run time at a certain ultrasonic. The underflow concentration is maximized at 64.47 wt. % when the ultrasonic frequency is 22 kHz. Based on the analysis on the microstructure of underflow samples, the minimum pore average size and pore average fraction are obtained when the ultrasonic frequency is 22 kHz, implying that 22 kHz is the optimum ultrasonic frequency combining the results of the underflow concentration. [ABSTRACT FROM AUTHOR]

The effect of extrusion ratio and addition of glass and fly ash on microstructural, mechanical properties, and fracture behavior of Al composites is examined. Both the composites and hybrid composites are prepared by the liquid metallurgical technique. Microstructure, extrusion effect on hardness, tensile properties, and fracture are studied using an optical micrograph, hardness tester, Universal Testing Machine, and scanning electron microscope, respectively. Experimental results show that increasing the extrusion ratio leads to a significant enhancement in mechanical properties such as tensile, compression, and yield strength and Young's modulus, but results in a small reduction of ductility. It has been revealed that the presence of glass and fly ash improve the mechanical properties significantly with a slight reduction in ductility compared to the Al alloy. Fracture behaviour of the base alloy and composites show intergranular ductile and brittle cleavage mode failure as observed by SEM. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effects of a shrinkage reducing agent (SRA) and Portland expanded cement (PEC) on the fluidity, mechanical properties, and shrinkage performance of ultrahigh-performance concrete (UHPC). The results indicated that the fluidity of the fresh UHPC mortar initially decreased and then increases along as a function of SRA dosage. When the dosage of SRA was 1%, the UHPC mortar fluidity was at its minimum. For dosages exceeding 1%, the additional water-binder ratio of the mortar increased, which in turn increased the UHPC fluidity. That is, the SRA delayed the cement hydration and increased the setting time, which is not conducive for early strength development of UHPC. As the SRA dosage was increased (i.e., 0%–2%), the autogenous shrinkage of UHPC decreased significantly such that even a small dosage of about 0.5% SRA was able to effectively reduce drying shrinkage. From the study results, it was also observed that PEC accelerated the loss of fluidity in the fresh UHPC and concurrently promoted the early strength development of UHPC. At 75% PEC content, the strength enhancement effects tended to be stable. This means that although the addition of PEC will potentially increase the autogenous shrinkage of UHPC, it has the positive effect of inhibiting drying shrinkage provided that the PEC dosage is controlled within the 25%–50% range. Furthermore, morphological analyses using a scanning electron microscope (SEM) indicated that an increase in the SRA dosage loosens the UHPC microstructure, with the formation of the hydration products remaining incomplete, thus ultimately causing the UHPC strength to decrease. Overall, the study findings indicated that 2% SRA and 25%–50% PEC can effectively reduce the shrinkage of UHPC and are, therefore, recommended as the optimum dosages. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis, phase formation, and basic characterization of polycrystalline Bi2Fe4O9, Bi1.98Ba0.02Fe4O9, and Bi1.98Ce0.02Fe4O9 samples prepared by the sol-gel technique. The crystal structure of the prepared samples has been characterized by means of X-ray diffraction and Raman scattering spectroscopy. All the obtained XRD peaks can be indexed to the orthorhombic Pbam structure and reveal the formation of Bi2Fe4O9. The Raman spectrum identifies Ag, B2g, and B3g active optical phonon modes. The crystallite size and morphology of the nanoparticles have been analyzed using scanning electron microscope (SEM). Dielectric constant (ε′) decreases as the frequency increases, and it is constant at the higher frequency region which can be explained based on the ionic conduction phenomenon in the low frequency region. The ε′ values of Bi2Fe4O9(650–850), Bi2Fe4O9(800–850), Bi1.98Ba0.02Fe4O9, and Bi1.98Ce0.02Fe4O9 samples at 10 Hz frequency are about 37, 75, 90, and 393, respectively. The observed properties signify that these materials are very useful in advanced technological and practical applications. [ABSTRACT FROM AUTHOR]

Ce0.5Sr0.5 (Co0.8Fe0.2)1−x ZrxO3−δ (CSCFZ) powders were synthesized by the sol-gel method and characterized to study structural and electrochemical properties. X-ray diffractometer (XRD) patterns of all samples give nanosized particles of a high-degree crystalline cathode having a cubic-type perovskite structure of space group Pm-3m with the existence of oxygen vacancies in the lattices. The results have the perovskite phase with average crystallite sizes of 26.57 nm, 18.14 nm, 18.13 nm, and 18.12 nm with porosities of 9.93%, 9.87%, 9.50%, and 9.08% for x = 0, 0.1, 0.15, and 0.2, respectively. Scanning electron microscope (SEM) micrographs showed the presence of pores on the microstructure. Average grain sizes of prepared samples found from SEM images were in the range of 105.30–183.02 nm. The partial substitution of zirconium at the B-site shows more stable materials than the host without decreasing the porosity that much. The results of electronic conductivity analyzed by the four-probe dc technique show that the conductivity of synthesized materials increases with the increment of both dopant concentration and temperature by the decrement of area specific resistances. The electrical conductivity of CSCFZ steadily increased with the increment of temperature which reached 42.76 Scm−1 at around 450°C. [ABSTRACT FROM AUTHOR]

The thermal effect of rocks not only depends on the temperature level but also may be influenced by the factors including heating environment, heating rate, and cooling method. In this study, approximate vacuum (V) and air circulation (A) heating condition are, respectively, applied on the limestone specimens in the whole heating process. Then, physical, mechanical, and nuclear magnetic resonance (NMR) tests were carried out to investigate the effect of heating conditions on the rock properties. The results show that heating conditions have significant effects on mechanical properties of limestone specimens (including peak strength, elasticity modulus, secant modulus, and crack initiation stress), which are due to the interference effect on the oxidation and thermal decomposition. It is worth noting that the significant temperature range of the heating condition is 450 ∼ 750°C, during which the mechanical performances of heat-treated specimens under V condition obviously outperform those under A condition. Combining the NMR results and the microstructure images from scanning electron microscope (SEM) technology, the evolution of pore distribution was revealed. As temperature increases from room temperature to 900°C, porosity increases gradually. However, pore distribution changes from small and medium pores dominating to large pore dominating and then to medium pore dominating. For limestone specimens after high-temperature treatment above 450°C, mineral crystals may melt and reconsolidate, filling in some of the previously large pores generated by thermal decomposition. [ABSTRACT FROM AUTHOR]

To study the mechanical properties of red clay under repeated dry and wet cycle test conditions, in this paper, the disturbed red clay in an engineering area in Liuzhou, Guangxi Province, was taken as the research object. By artificially controlling different dry and wet cycles in the laboratory, a direct shear test and triaxial consolidation drainage test were carried out on the red clay samples after different dry and wet cycles. The stress-strain curve and change rule of corresponding c and φ values were obtained. The results showed that, in both the direct shear test and the triaxial test, the shear strength parameters of red clay decreased with an increase in the number of dry and wet cycles and the attenuation was most obvious during the first cycle. With an increase in the number of dry and wet cycles, the attenuation gradually decreased. The constitutive model of the deviatoric stress and strain curve of red clay under dry and wet cycles was a plastic-hardening type. By analyzing the variation in parameters in the P-H model, the relationship between c, φ, and the number of dry and wet cycles n was obtained. The results showed that the parameters had different degrees of attenuation with the action of dry and wet cycles. To explain the above rules, some samples under different drying-wetting cycles were selected for environmental electron microscope scanning, and appropriate assumptions were made based on the microstructure. [ABSTRACT FROM AUTHOR]

To study the mechanical properties of red clay under repeated dry and wet cycle test conditions, in this paper, the disturbed red clay in an engineering area in Liuzhou, Guangxi Province, was taken as the research object. By artificially controlling different dry and wet cycles in the laboratory, a direct shear test and triaxial consolidation drainage test were carried out on the red clay samples after different dry and wet cycles. The stress-strain curve and change rule of corresponding c and φ values were obtained. The results showed that, in both the direct shear test and the triaxial test, the shear strength parameters of red clay decreased with an increase in the number of dry and wet cycles and the attenuation was most obvious during the first cycle. With an increase in the number of dry and wet cycles, the attenuation gradually decreased. The constitutive model of the deviatoric stress and strain curve of red clay under dry and wet cycles was a plastic-hardening type. By analyzing the variation in parameters in the P-H model, the relationship between c, φ, and the number of dry and wet cycles n was obtained. The results showed that the parameters had different degrees of attenuation with the action of dry and wet cycles. To explain the above rules, some samples under different drying-wetting cycles were selected for environmental electron microscope scanning, and appropriate assumptions were made based on the microstructure. [ABSTRACT FROM AUTHOR]