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The low liquid limit silty soil in the North China plain area is generally unsuitable for direct use as roadbed and slope soil. In order to improve the performance of low liquid limit silty soil, xanthan gum was used as an improver. Through a series of tests, the improvement effect of xanthan gum on low liquid limit silty soil was studied. The test results showed that Xanthan gum as an improver could significantly improve the unconfined compressive strength of silty soil. With the increase in dosage and curing age, the unconfined compressive strength of improved silty soil continued to improve and eventually tended to stabilize. The optimal dosage and curing period were 2% and 7 days, respectively. In addition, Xanthan gum could greatly improve the permeability and disintegration of low liquid limit silty soil. The permeability coefficient of improved silty soil with a content of 0.75% Xanthan gum and a 7-day curing period was 4.73 × 10−4 m·s−1, which was only 1.10% of that of plain silty soil at the same curing period. After immersion in water for 12 h, the soil only experienced slight disintegration. The scanning electron microscope image showed that the gel generated by the hydration reaction of Xanthan gum could improve the compactness and integrity of the soil by filling the voids, thus significantly improving the mechanical and hydraulic properties of the low liquid limit silty soil. [ABSTRACT FROM AUTHOR]

A composite resin containing eggshell particles for the additive manufacturing according to the stereolithography (SLA) printing technology was studied. First, the viscosity properties of the eggshell-particle-reinforced resin were determined. Then, the effect of particle wt% on the hardness, tensile, and compressive behaviors of the composite specimens were investigated. Besides, the optical microscopy images of unreinforced and reinforced 3D printed composites were scrutinized. The cross-sections of the composite were analyzed by the energy dispersion spectrometry and optical and scanning electron microscopes (EDS/SEM) in order to examine its structure in detail. To analyze the damping properties and the elastic modulus determined in tension and free vibration tests were also carried out. [ABSTRACT FROM AUTHOR]

Ultra-high-rise buildings require high concrete bearing capacity. Ordinary concrete often fails to meet the project requirements. Admixture of admixtures in concrete is a means of solution. Currently, studies on the incorporation of basalt fiber (BF) and fly ash (FA) in concrete are relatively mature. However, research on incorporating nano-Titanium Carbide (nano-TiC) in concrete is still relatively scarce, which has a lot of room for development. To further improve the mechanical properties of concrete, BF, and FA synergized with nano-TiC were incorporated into concrete to produce TBF concrete in this study. And Response Surface Methodology (RSM) was used to optimize the mechanical properties of concrete. The collapse and compressive deformation damage characteristics of concrete were analyzed. The microstructure of the cement matrix was analyzed by the SEM (Scanning Electron Microscope). An optimization model of the TBF concrete craving function was developed. Optimized ratios with compressive, split tensile, and flexural strengths as response objectives were obtained, and the accuracy of the optimized ratios was investigated using the same experimental conditions. The results of the study showed that FA increased the collapse of concrete, while nano-TiC and BF decreased the collapse of concrete. Under uniaxial compression, nano-TiC, FA, and BF together incorporated into concrete can improve its compressive damage state. Moderate amounts of nano-TiC, BF, and FA could improve the mechanical properties of concrete. Their optimal mixing ratio admixtures were 0.88%, 0.24%, and 5.49%, respectively. And the measured values under the same conditions were compared with the predicted values. The maximum difference in compressive strength was 6.09%. The maximum difference in split tensile strength was 7.14%. The maximum difference in flexural strength was 8.45%. This indicated that the accuracy of the RSM optimization model was good. A moderate amount of nano-TiC, FA, and BF could improve the densification of concrete. [ABSTRACT FROM AUTHOR]

HTW-50 solid wire CO2 gas-shielded arc spot welding and resistance spot welding techniques were utilized to fabricate multiple sets of HRB400E hot-rolled ribbed seismic reinforcement cross-spot welded test specimens. These specimens were subjected to unidirectional tensile testing to investigate the impact of cross-spot welding on the mechanical properties of the steel bars. Chemical composition analysis and hardness testing were conducted on the brittle fracture test specimens using a metallurgical microscope, scanning electron microscope, and Rockwell hardness tester, among other related equipment. The brittle fracture mechanism of the cross-welded test specimens was subsequently examined from both macroscopic and microscopic perspectives. The results indicate that cross-spot welding of large-diameter rebars does not affect their strength. However, 80% of the test specimens exhibited brittle fractures that occurred at the weld point. Moreover, the elongation of the brittle fracture specimens was lower than the standard value, indicating a need for improved toughness. In comparison to CO2 gas-shielded arc spot welding, resistance spot welding had a lesser impact on the elongation of the steel bars and demonstrated greater stability. The test specimens exhibited fractures primarily at the welded area, where only a minimal amount of toughness was observed. Disintegration steps and river-like patterns were also observed at the weld, suggesting a mechanism of disintegration fracture. Additionally, tempered martensite was detected in the heat-affected zone, rendering the bars brittle, and making them prone to fracture at the weld. [ABSTRACT FROM AUTHOR]

Large-diameter polyvinyl alcohol (PVA) fiber has a broad application prospect in the field of reinforcing geomorphic building materials owing to its large diameter and excellent mechanical properties. In this work, PVA2499 polymer was used as the raw material, DMSO/H2O as the hybrid solvent, and the staged heating approach was adopted to obtain high solid content of spinning solutions, and then a series of large-diameter medium-strength PVA fibers with different solid contents of spinning solutions (SCS) were prepared by dry-wet spinning, and the Fourier transform infrared spectroscopy (FTIR), scan electron microscope (SEM), differential scanning calorimetry (DSC), thermal analysis (TGA), X-ray diffractometer (XRD) and electronic universal testing machine were performed to explore the effect of the SCS on the structure and performance of PVA fiber. The results displayed that with the increase of the SCS, the -OH stretching vibration absorption peak of PVA fiber moved from 3276 cm−1 to 3262 cm−1; The tensile strength, initial modulus, the crystallization and orientation of PVA fibers all increased first and then decreased. Especially, when the SCS was 23.5wt%, the diameter of the PVA fiber was 110.6 ± 6.0 μm (124.8 ± 6.2 dtex), the tensile strength was 7.0 ± 0.3 cN/dtex, the initial modulus was 106.2 ± 10.3 cN/dtex, the crystallization and the orientation were 49.6% and 96.8%, respectively. [ABSTRACT FROM AUTHOR]

The rapid setting rate restricts the application of sulfoaluminate cement (SAC), it is necessary to develop SAC mortar with a controlled setting time. Therefore, this paper tries to use sodium gluconate (SG) and mineral admixture to reduce its reaction speed and study the effects of SG and mineral admixture on the workability, mechanical properties and durability of SAC mortar. First, the optimal amount of SG doping was determined to be 0.4% under the comprehensive consideration of the working performance, mechanical performance, and durability of SAC. Again, based on the determination of SG dosing, the effects of four mineral admixtures, fly ash, silica fume, Ground Granulated Blast furnace Slag (GGBS), and limestone powder, on the mechanical properties and chloride ion penetration resistance of SAC were studied, and the optimal dosing of each mineral admixture was determined. Finally, a microscopic analysis of the specimen was conducted through a Scanning Electron Microscope (SEM) to reveal the reaction mechanism of SAC from a macroscopic perspective. [ABSTRACT FROM AUTHOR]

Two kinds of porous hollow glass microsphere (HGM) were synthesized using HGM as a raw material. Then, silicone rubber (SR) based composites with porous HGM as inorganic filler were prepared. The microstructures of the composites were characterized by a scanning electron microscope (SEM), and the relationship between the interface structure and strengthening mechanism was explained. Due to the formation of interpenetrating networks through SR chains inserting into porous HGM, the interfacial adhesion was enhanced. Therefore, tensile strength and elongation at break of SR were greatly improved by porous HGM. Especially for HGM-2 with high specific surface area and through-hole, tensile strength of SR/HGM-2 composite with only 2 phr HGM-2 increased from 0.41 MPa to 0.91 MPa, and elongation at break increased from 103 to 251%. The densities of composites with filler content ranging from 2 phr to 15 phr were also examined. Particularly, the density of SR/HGM-1 composite with 15 phr HGM-1 further decreased to 0.75 g/cm3 compared with that of SR/HGM (0.82 g/cm3). In addition, the thermal stability of SR composites with porous HGM was also significantly improved. Along with through-hole structure of HGM-2, another straightforward consequence of SR/HGM-2 composite was high transparency caused by reduction of light scattering. [ABSTRACT FROM AUTHOR]

Facing the lack of limestone materials in some highway construction areas, the reasonable utilization of local raw materials become more and more concerned. To verify the feasibility of replacing limestone aggregate with sandstone in macadam, comparative analysis of appearance and composition between sandstone and limestone is conducted first. Then the mechanical properties, water stability and micro morphology of sandstone concrete are conducted via the compressive strength test, splitting strength test, water stability test and scanning electron microscope (SEM) test. The results showed that irregular polygonal grains and loose structure were in both limestone and sandstone, but limestone has large particles in local pores. All the mechanical properties of sandstone concrete could meet the specification requirements which provided support for alternative some limestone in cement stabilized macadam base. The strength growth rate with less than 4.0% cement content was not obvious. With curing age increasing, the splitting tensile strength of sandstone concrete with different cement content gradually increased, but the strength growth trend slowed down after 28 days. The porosity and water absorption of sandstone were larger than that of limestone, which affected the mechanical properties of sandstone. In addition, the application of sandstone replacing limestone project was evaluated, and the pavement test results verified the feasibility of sandstone concrete in expressway. [ABSTRACT FROM AUTHOR]

The water content is an important factor affecting the mechanical properties and crack development of rock. To further study the effect of water content on the mechanical properties and microcrack development of mudstone, acoustic emission (AE) tests under uniaxial compression were conducted on mudstone samples with water contents of 0, 1.14, 2.16, 4.50, 9.05, and 15.63%. The experimental results indicate that with increasing water content, the compressive strength and elastic modulus of mudstone decrease exponentially, and Poisson's ratio increases linearly. Besides, the failure mode of mudstone changes from tensile failure to shear failure with increasing water content. Based on the crack volumetric strain method combined with the cumulative AE hits analysis, the thresholds of crack closure, crack initiation and crack damage stress were identified, and the failure process was characterized by five stages of crack propagation. The relationship between the cracking stages and AE signals of mudstone samples with different water contents was analyzed. Crack damage starts at more than 0.85 times the uniaxial compressive strength. Crack initiation and crack closure start at 0.5–0.8 times and 0.4–0.6 times the uniaxial compressive strength, respectively. Furthermore, the results obtained by scanning electron microscope (SEM) demonstrate that the intrusion of water results in changes in the cementation and compaction of mudstone, which further causes degradation of the mechanical properties of mudstone. An equation to predict the strength and crack evolution stages of mudstone is established. The obtained results not only provide a theoretical basis for the influence of water content on the mechanical properties of mudstone but also have guiding significance for the study on microcrack evolution in mudstone. [ABSTRACT FROM AUTHOR]

Abundant research on geopolymer concrete in the last two decades has provided worldwide acceptability in conventional structural applications. The high-impact applications of geopolymers are mostly limited because they are quasi-brittle in nature and show moderate crack resistance; hence, they require suitable reinforcing materials such as fibers. This paper reports a study to assess the strength and durability properties of fly ash-based geopolymer concrete (FA-GPC) prepared with novel C-glass fibers. The binder mix was comprised of Fly Ash (FA), Lime (L), Silica Fume (SF) and was activated by sodium hydroxide (12 M) and sodium silicate solution, followed by curing under ambient conditions. Glass fibers were utilized in varying proportions (0.125, 0.25, 0.375, 0.5, 0.625, and 0.75%), by weight of the binder mix. It was found that the incorporation of 0.5% glass fiber significantly increased the compressive strength, split tensile strength, and flexural strength properties. From the durability perspective, the samples exhibited good resistance against seawater, MgSO4 solution, and H2SO4 when compared with the control mix. Further, the Scanning Electron Microscope (SEM) analysis was employed to explore the nature of the geopolymer–fiber matrix. It was revealed that excellent interfacial bonding existed between fiber and the geopolymer matrix. The results indicate that addition of C-glass fibers significantly improves the overall mechanical performance of FA-GPC. The research presented here establishes the advantages of using C-glass fibers-based geopolymer concrete, thus encouraging its broader utilization. [ABSTRACT FROM AUTHOR]

The influence laws of two different rolling processes on the microstructures and properties of 6016 aluminum alloys in rolling, T4, T4P states, and aging are studied, respectively. The microstructures under different rolling processes are also analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscatter diffraction (EBSD). The results indicate that during the cold rolling process, compared with B alloy, A alloy generated small initial grains. The small initial grains will increase the deformation resistance, and the strength and hardness of A alloy are better after rolling, but with poor plasticity. After solution treatment, A alloy generated small grains with recrystallization, the hardness, plasticity, and formability of A alloy in T4 state are better than B alloy after solution treatment and natural aging. A alloy is more sensitive to aging response, and artificial aging occurs during the pre-aging process. The proportion of large Angle grain boundaries in A alloy is large but with small dislocation density, uneven distribution, and small texture content. This makes A alloy have better strength and hardness in T4P and poor plasticity and formability than B alloy after solution treatment, pre-aging and natural aging. However, the strength and hardness of A alloy are also smaller than that of alloy B after artificial aging. [ABSTRACT FROM AUTHOR]

This study aimed to develop a new dental adhesive based on the nanocrystalline cellulose (NCC) along with silica in the resin matrix. Both filler components, including NCC and silica, were synthesized and characterized using various analytical techniques such as Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction, thermographic analysis, and cell viability. The fillers showed structural stability and cytocompatibility was achieved. After characterization, the fillers were added to the resin matrix in different concentrations (0–5 wt%) to prepare the dental adhesive. The prepared dental adhesives were evaluated by Vicker's microhardness, biaxial flexural strength, flexural modulus, and shear bond strength. By adding NCC in the dental adhesives, the mechanical properties increased substantially. Nanocrystalline cellulose alone and in combination with silica filler has been investigated first time to improve the properties of dental adhesive. [ABSTRACT FROM AUTHOR]

The effect of aging on the mechanical properties of silicone rubber (SR) was investigated by means of ultrasonic, dynamic mechanical analysis, and FTIR techniques. Both longitudinal and shear (Ultrasonic wave velocities) were measured at room temperature and at frequencies of 2 MHz. Density, molar volume, ultrasonic wave velocities, tensile strength, mechanical properties, and FT–IR showed the improvement of the silicone rubber network with aging time from 0 to 70 days, while loosening of the network structure was observed at 14 days and 50 days aging. These behaviours were explained in terms of the change in cross-link density and average stretching force constant of bonds with aging. Thermogravimetric analysis and differential scanning calorimetric techniques showed quite low thermal stability and temperature performance for aged SR at 14 and 50 days than virgin SR which was confirmed by the cracks and voids appeared under scanning electron microscope. [ABSTRACT FROM AUTHOR]

There has been an increasing trend of using natural fibre reinforcements as an alternative to manmade fibre reinforcements for engineered composite applications. Natural fibres are alternative composite reinforcement materials due to their biodegradability, inexpensiveness, abundance and excellent physical properties. This study aims at analysing the mechanical properties of the fabricated bio-composite from polyester resin reinforced with silk waste fabric. The specific objectives of this work are to characterise physical and mechanical properties of silk waste fabric, fabricate a bio-composite from silk waste fabric treated with zinc oxide nanoparticles and polyester resin and to analyse the static mechanical properties (tensile, flexural and impact). The silk waste fabric is characterized and the composite fabricated using hand lay-up technique and a mould with dimensions 360 × 210 × 4 mm. Central composite design is used in the design of experiments, and the fibre weight fraction was varied from 11 to 25%. Treatment with nanoparticles is done by soaking silk waste fabric in a 6% concentration of zinc oxide nanoparticles and 1% citric acid. A sonicator uses to evenly distribute the nanoparticles in the solvent, and the fabric is coated using the pad dry cure method. The fabricated composites are cured at room temperature for 24 h under consolidated pressure of 2.65 kN/m2. The mechanical properties of the composites are determined using D790, D638 and D6110 ASTM standards, whereas the morphology is investigated using a scanning electron microscope. The areal density of the silk waste fabric is 76 g/m2, and its tensile strength was 16.80 MPa. The tensile, flexural and impact strengths of uncoated composites are 27.92 MPa, 52.13 MPa and 32.17 kJ/m2, respectively. The flexural and tensile strengths of the coated bio-composites increase with increasing fibre weight fraction up to peak values of 32.23 MPa and 53.47 MPa, respectively. Bio-composites produced with silk waste fabric treated with nanoparticles had slightly better strengths (tensile 32.23 MPa and flexural 53.47 MPa) compared to bio-composites with non-treated silk waste fabric (tensile 27.92 MPa and flexural 52.13 MPa). The static mechanical properties attained in this study reveal that these bio-composites may be used for non-structural applications for instance partitioning walls and ceiling boards. The study recommended future research studies on increasing the number of plies beyond six with different fabric weave designs of twill, satin, sateen and warp rib and use of thermal evaporation as a coating technique of nanoparticles onto silk waste fabric to establish their effect on mechanical and thermal properties and morphology. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of different functional groups on graphene on the mechanical behavior of carbon fiber reinforced epoxy composites were fabricated by hand layup technique. In this study, three different variety of functionalized graphene (–NH2, –COOH, and –OH) with varying weight percent (i.e. 0.1, 0.3, and 0.5 wt%) was considered. Tensile, interlaminar, and three-point flexural tests were conducted to evaluate the effects of graphene concentration and fiber stacking sequence (i.e. 0/90° and 0/90/ ± 45°) on composites. The microstructures of the composites were characterized by a scanning electron microscope. Experimental results showed that pristine and functionalized graphene significantly improved the mechanical properties of carbon fiber epoxy composites. Compared to neat carbon fiber epoxy composites, the maximum tensile strength of 33.34% and 26.35% were noticed for 0/90°–COOH–0.5 and 0/90/ ± 45°–NH2–0.3 stacked functionalized graphene modified carbon fiber epoxy composites, respectively. Moreover, 48.44% and 59.1% flexural strength were recorded for 0/90°–COOH–0.3 and 0/90/ ± 45°–OH–0.5 stacked functionalized graphene modified carbon fiber epoxy composites, respectively. Furthermore, maximum interlaminar shear strength (ILSS) of 120.25% was observed for 0/90/ ± 45° stacked carbon fiber epoxy composites. Finally, the results obtained with graphene as reinforcement filler can cause a significant improvement in the mechanical performance of fiber composites. Henceforth, they can also be considered as a promising candidate for designing composites for structural applications. [ABSTRACT FROM AUTHOR]

The present study presents the synergistic effects of casting thickness and various amounts of SiCp (0, 1, 3, 5, and 7 wt% SiC) on the microstructure, hardness, and tensile properties of Mg–Mg3Sb2 in-situ composite. Initially, Mg–Mg3Sb2–xSiC composite melts were made via the stir casting method which were poured into a modified green sand mold (with 6, 12, 18, and 24 mm section thicknesses). Then, the structural studies were performed by means of an optical microscope, a scanning electron microscope, and an X-ray diffraction for phase identification. It was found that the composites were comprised of primary Mg, Mg3Sb2 intermetallics, and SiCp. The addition of SiC particles to the Mg–5Sb in-situ composite did not change the average length of Mg3Sb2 phases significantly. The macrostructural studies revealed that average grain size decreased with the addition of SiC particles and increased when the casting section thickness was enlarged due to a lower cooling rate. Tensile and hardness tests were performed on all composites, and fracture surfaces of the tensile test specimens were examined via electron microscopy. As the amount of SiC increased, the hardness of the composites improved consistently, but the tensile strength and elongation of the samples showed an improvement first and then reduced. In the terms of tensile properties, the best results were observed in the Mg–5Sb–3SiC composite with a thickness of 6 mm and reached almost 151 MPa. The fracture surface observations showed that fracture mode in these composites formed of cleavage and semi-cleavage planes. [ABSTRACT FROM AUTHOR]

Polymers used in food packaging should have unique properties, including anti-bacterial properties, good mechanical properties and permeability to air and water. To achieve these properties, some nanomaterials are incorporated into the polymeric matrix to be suitable for such a precise application. Thus, polymer nanocomposites emerged as one of the most important recent trends in the packaging materials industry. Here, titanium dioxide nanoparticles (TiO2-NPs) were synthesized by the sol–gel method and incorporated into pure low-density polyethylene (P-LDPE) at different concentrations (0, 2, 4, 8 wt %.). The prepared nanocomposites were characterized via a scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis. The size of TiO2-NPs is ranged from 13 to 47 nm. The crystallinity index of LDPE increased by the addition of TiO2-NPs from 0.32 to 0.55. Also, the thermal stability of LDPE improved by 67 °C. Studies of the mechanical properties, antibacterial activity and permeability measurements of nanocomposites films have demonstrated their potential for use in perishable food packaging. The results showed an increase in oxygen permeability from 55.25 cc/M2 day for P-LDPE to 72.84 cc/M2 day for LDPE-loaded with 8% TiO2. On the contrary, the impeded TiO2-NPs inside LDPE films reduced the water vapor transmission from 2.22 g/(m2 day) to 0.92 g/(m2 day). The tensile strength of P-LDPE increased from 16.7 MPa to 28.95 MPa for nanocomposite loaded with 8% TiO2. The ability of TiO2-NPs O2 to generate the potentially reactive radical species induced the antibacterial activity of LDPE to Gram-negative and Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

The Permian volcanic reservoir in Sichuan Basin is mainly composed of three types of volcanic rocks (basalt, tuff and breccia), showing an intertwined distribution of their characteristics. The mechanical properties of these rocks, affected by the invasion of water-based drilling fluid, are significantly different, resulting in frequent and complex wellbore instability problems during drilling operations. Thus, using compression tests and scanning electron microscope tests, the mechanical properties and microscopic failure mechanisms of these rocks are studied considering the effect of water absorption, and their implications for wellbore stability are discussed. The results demonstrate the following points. (1) The strength, elastic modulus, cohesion and internal friction angle of basalt are significantly greater than those of tuff and breccia, and these values of tuff are the smallest, but the axial strain of tuff at peak stress is the largest. (2) With the effect of hydration, the elastic deformations of the three kinds of volcanic rocks would weaken, and the plastic deformations are enhanced. These trends for tuff and breccia are more obvious than those of basalt. With the increase in water absorption time, the strength, strains at peak stress, elastic modulus, cohesion and internal friction angle all decrease significantly, but Poisson's ratios change irregularly. (3) The hydration of clay minerals will lead to the surface expansion of mineral particles in these rocks, especially the mineral particles of tuff and breccia will be fragmented and disintegrated to form some loose particle structures in local areas. (4) The collapse mud weight for the tuff well section is the highest, followed by that of the breccia well section and that of the basalt well section, but it decreases most significantly for the breccia well section after water absorption. The collapse mud weights determined by the result of tuff well sections agree with the practical situation. [ABSTRACT FROM AUTHOR]

Heavy structures built on untreated collapsible soil remain susceptible to failure due to abrupt changes in the soil structure upon wetting. Industrial wastes like cement kiln dust (CKD) can be used to solve this problem. For this study, undisturbed and disturbed collapsible soil samples were collected from Thal Haro arid area, Punjab, Pakistan. CKD was mixed up to 20% to stabilize the collapsible soil with a maximum of 28 days of curing time. To perform strength tests and collapsible potential tests, samples were remolded at optimal water content and maximum dry unit weight. The CKD content exponentially improves the unconfined compression strength, deformation modulus, and soaked California bearing ratio; however, it marginalizes the ductility of treated soil. With the addition of CKD, the strain at failure and deformability index is significantly decreased. Moreover, for microstructural characteristics comparison, X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDAX) analyses were performed on untreated and treated samples. Due to the addition of CKD, XRD and EDAX results show the new peaks of calcium and calcium silicate, respectively, in treated samples. The formation of the new element and compound indicates the generation of bonds among soil partials owing to the hydration and pozzolanic reactions which is also verified by the SEM results. The SEM analyses manifest the conversion of the dispersed and silt-dominated structure of the native collapsible soil to a reticulated structure without micropores due to the addition of CKD. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure characterization and mechanical properties of Al alloy fabricated by additive friction stir deposition (AFSD). Microstructure characterizations of the Al alloy 5B70 base material (BM) and build were compared using optical microscope (OM) and electron back scattered diffraction (EBSD). The hardness distribution in the direction perpendicular to the cross-section of the deposited area was systematically evaluated. Tensile tests were performed on the BM and the build using digital image correlation (DIC), and the real-time stress distribution states of the specimens were analyzed. After the tensile tests, the fracture micromorphology was characterized using scanning electron microscope (SEM). The results indicated that a high degree of recrystallization occurred in the deposition zone, where fine, equiaxed, and differently oriented grains are formed. It was found that the strength of the deposition layer was lower compared to that of the BM, but its toughness was significantly improved. Also, obvious anisotropy of mechanical properties was identified in the deposition layer. [ABSTRACT FROM AUTHOR]

Locusts (Locusta migratoria) have outstanding flying abilities, and most of their lift is provided by their hind wings. Insect aerodynamic performance is strongly affected by wing deformation during stroke, which is closely related to its functional morphology (particularly its mechanical properties). The cross-vein is one of the main morphologies in the hind wing of locusts. However, few studies on the mechanical properties of cross-veins have been conducted. This study evaluated the cross-veins of the locust hind wing using uniaxial tensile tester, scanning electron microscope, and finite element methods. Four cross-vein types were identified at different locations on the hind wing, including periodical semi- and full-ellipsoidal humps and periodical semi- and full-conical humps. The four cross-veins showed similar tensile stiffness but differed in bending compliance. We suggest that the mechanical properties of the four cross-veins can be attributed to their physiological functions. This study elucidates cross-veins of locust hind wing and contributes our understanding of the flapping flight mechanism in locusts. [ABSTRACT FROM AUTHOR]

This study is made to obtain controllable and improved microstructural properties of a material obtained by stacking copper wires and then combining them with hot diffusion welding. The mechanical performance of the new approach to obtain a copper billet was assessed and accordingly the diffusion welding parameters were optimized. Samples with a dimension of 60×40×5 mm were produced by stacking. Copper wires with different diameters were stacked in the same direction and welded with hot diffusion welding under 69.5-139-208.5 MPa pressures, for 20-60-90 minutes, at 600 °C. Strength of the bonding was tested by bending and microhardness tests. In addition, the diffusion interface was examined by optical microscope and SEM. The interfacial bond strength after welding increased with temperature, pressure and time. Especially, the increase in diffusion time actuated the formation of common grains in the fusion area by decreasing or completely eliminating the interfaces of the wires. [ABSTRACT FROM AUTHOR]

The present work is focused on the influences of reinforced particles on mechanical, microstructural, and tribological performances of AA7075 hybrid metal–matrix composites (HMMCs). Al2O3 and coconut shell ash (CSA) were reinforced using two-stage stir casting by varying the wt% (0–5) of reinforcement. Microstructural analysis and various phase identifications were examined with the help of scanning electron microscope (SEM) equipped with EDX and optical microscope. Various mechanical testing such as tensile, hardness, 3-point bend test, and tribological behaviors were carried out to know the HMMCs properties. Microstructural images revealed a homogeneous distribution of reinforced particles in the metal–matrix and EDX confirmed the presence of dispersed reinforcements (Al2O3 and CSA) in the HMMCs. It was seen that mechanical properties and tribological behavior have been increased after addition of Al2O3 and CSA reinforced particles whereas slightly decreased in impact strength. Transgranular cleavage facets, micro-void coalescence, dimples, and crack were shown in SEM images of fractured specimens during impact and tensile testing. [ABSTRACT FROM AUTHOR]

A novel hybridized neodymium iron based-composite consolidated with 5%AIN-5%NI-5%Nb has been fabricated via powder metallurgy (PM). Thus, Taguchi statistical procedure was applied to examine the influence of sintering parametric process namely, sintering temperature, dwell time, pressure, and heating rate, relative densification, and microhardness of the fabricated novel composite. The fabricated composite was successful and subjected to various analyses and characterization. Scanning electron microscope (SEM) was used to investigate the of the microstructural modification of the fabricated composite developed. The SEM morphology shows a bonding neck formation which indicates a uniform dispersion between the matrix and reinforcement phase. The result of the optimized procedure reveals that all the factors significantly contributed to hardness and densification of the composite. However, temperature shows the major that significantly influenced the procedure above 90%. The maximum microhardness value of 680.52 HV was revealed by the material sintered at 700 °C, 30 MPa of pressure, 5 min of dwell time, and heating rate of 300 °C/minute. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the improvement made on the mechanical properties of the composites by the addition of micro- and nanoparticles to aluminium matrix. The micro- and nano-composites having different weight percentages of particles were fabricated using stir-casting and ultrasonic cavitation probe-assisted casting processes, and they were characterized using metallurgical microscope and scanning electron microscope. The mechanical properties of the composites, such as tensile strength, impact strength, and hardness, were analysed as per the ASTM standards. The analysis indicated that the nanoparticles' reinforcement in aluminium matrix composite significantly improved the mechanical properties compared to the micro-particles owing to their high surface energy. [ABSTRACT FROM AUTHOR]

HIPS-g-MAH compatibilizer and the other three compatibilizers were prepared and added to the polyamide 66/polyphenylene oxide (PA66/PPO) alloy. The FT-IR spectra showed that the maleic anhydride (MAH) had successfully undergone grafting on the high impact polystyrene (HIPS). The effect of the MAH ratio in the HIPS-g-MAH compatibilizer, the HIPS-g-MAH compatibilizer weight ratio, and the PA66/PPO ratio on the mechanical properties of PA66/PPO alloy was systematically studied. The results showed that the PA66/PPO alloy possessed the optimal mechanical properties when the HIPS-g-MAH compatibilizer weight ratio was 7% and the MAH ratio in HIPS-g-MAH compatibilizer ranged 4% ~ 8%. The fracture morphologies of PA66/PPO alloy with different HIPS-g-MAH compatibilizer weight ratios were characterized by scanning electron microscope (SEM). The PA66/PPO alloy without HIPS-g-MAH compatibilizer showed a typical brittle fracture. The mechanical properties of PA66/PPO alloys with the HIPS-g-MAH compatibilizer were improved. In addition, the crystallization temperature of PA66/PPO alloy decreased with the increase in the HIPS-g-MAH compatibilizer weight ratio. The PA66/PPO ratio also played an essential role in the PA66/PPO alloy properties. The coefficient of friction and wear rate both increased with the increase in the PPO ratio. [ABSTRACT FROM AUTHOR]

The present study aims at to study the effect of chemical composition, intercritical annealing parameters (temperature and holding time) on microstructure and mechanical properties of dual phase steels. Three normalized steels (A, B and C) with different compositions were subjected to inter-critical annealing at 760°C and 810°C for different holding times (3, 6 and 9 min). The microstructural characterization was carried out using a scanning electron microscope (SEM) and mechanical properties were evaluated using micro-hardness measurements and tensile tests. The strength has been found to increase from 500 MPa (steel A) to >1200 MPa (steel C) at the cost of a decrease in elongation from 25% (steel A) to 7.5% (steel C). Results have been analysed and discussed. [ABSTRACT FROM AUTHOR]

Titanium alloy extruded profiles with complex cross-section are usually used to manufacture special-shaped structural parts in the aviation industry. In this paper, a Ti-6Al-4 V profile with asymmetric Y shape was manufactured by a direct extrusion process. A comparative study was conducted at the different lubrication conditions, in which the different process deformation mechanisms, resulting microstructures, and mechanical properties of profiles have been investigated by finite element simulation and a series of experiments, i.e., scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). It was revealed that the metal flow is blocked at the narrow die orifice due to the deterioration of lubrication, resulting in the continuous shrinkage defect. The metal deformation coordination mechanism becomes gradually significant due to poor friction contact, which promotes the internal stress in the cross-sectional center to transfer outward to balance the friction at the edge of the orifice, resulting in the reduction of the effective strain in the center. The heat generated by friction weakens the heat exchange behavior between the metal and the die, which helps the profile retain a more uniform temperature field. In the sectional center of the profiles made from the two different lubrications, extrusion with good lubrication results in greater grain/colony refinement due to greater effective strains, and a slightly greater dislocation density was found due to the uniform deformation. The tensile tests revealed that compared with poor lubrication, due to the improvement of Hall–Petch strengthening and dislocation strengthening in the cross-sectional center with good lubrication, the variation range of yield strength and tensile strength is reduced to 11 MPa and 7 MPa, respectively, and the variation range of microhardness is reduced to 44 HV and 32 HV, respectively. The improvement of lubrication not only helps to reduce forming defects but also can obtain uniform mechanical properties. [ABSTRACT FROM AUTHOR]

Laser beam welding (LBW) has found wide applications in several fields, including electronics, aerospace, and automobile industries, owing to its inherent capabilities over existing welding techniques. Dissimilar laser welding is one of the challenging fabrication processes. However, joining of different materials poses challenging issues because material properties of each material interacts to give rise to hybrid system performance. In present study weld of Al-Cu and Cu-Al has been performed using Ytterbium pulsed fibre laser with a maximum laser power of 300 W. The scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDS) has been employed to investigate the microstructural and chemical composition of the welded joints. The EDS analysis showed the presence of possible intermetallic compounds (IMCs) like AlCu and Cu2Al in the fusion zone. The Al-Cu and Cu-Al welded joints had maximum shear strength of 295 N and 84 N, respectively. The results showed the efficacy of Al-Cu joints over Cu-Al joints. The study further demonstrated that the Al-Cu weld had a better microstructure with fewer pores and cracks than the Cu-Al welds by varying the laser powers. [ABSTRACT FROM AUTHOR]

The variations in the austenite–ferrite dual-phase structure of hyper-duplex stainless steels subjected to tensile deformation were analysed in the present work. The blocks of ASTM A890 7A hyper-duplex steel were cast and heat treated to obtain a clean dual-phase structure. Unilateral tensile stress was applied on specimens prepared from the blocks. Heat-treated specimens were deformed under a displacement control mode for various percentage elongations. Scanning electron microscope and metallurgical microscope images revealed that the austenite phase was more deformed compared to that of the ferrite phase. X-ray diffraction analysis was carried out to find the crystallographic planes where maximum deformation has occurred and to explain how different phases participated in the deformation process. The austenite phase was found to be far more deformed than the ferrite phase, with the greatest deformations in the (111) and (200) planes. The distribution of constituent alloying elements was evaluated using energy-dispersive X-ray analysis (EDAX) and area-scan techniques and it was found that there were no substantial changes in the concentration of alloying elements as a result of deformation. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis and properties of WC-Co-Ti(C0.5, N0.5)-Mo cemented carbides with various compositions by employing powder metallurgy processing technology. The effect of adding Mo to cemented carbides on their microstructure and mechanical properties is investigated. The volume shrinkage, porosity, microstructure characteristics, hardness, and indentation toughness are examined by analytical balance, indentation method, scanning electron microscope, and X-ray diffractometer, respectively. By adding 0.5 weight percent Mo to cemented carbides, the density and hardness can be increased to 14.12 g/cm3 and 1804.56 kgf/mm2, respectively, while the indentation fracture toughness remains at a tolerable level of approximately 7.6 MPa·m1/2. Furthermore, the addition of Mo to the WC-Co-Ti(C0.5, N0.5) cemented carbides can effectively inhibit Co loss, reduce microdefects in the systems, and improve the microstructure. [ABSTRACT FROM AUTHOR]

The poor interface bonding between graphene and copper matrix significantly impair the strengthening effect of graphene, but it can be improved by graphene modification. In this work, the Ni-rGO compound powders were synthesized via hydrothermal method, and the Cu matrix bulk composites reinforced by Ni-rGO and rGO were prepared by the molecular-level mixing method along with spark plasma sintering, respectively. The sintered bulk materials were examined by transmission electron microscope, scanning electron microscope, Raman spectroscope and X-ray diffractometer, and the mechanical and electrical properties were tested as well. The results indicated that the incorporation of Ni-rGO exhibits a more obvious strengthening effect. As compared to the 0.1wt.%rGO/Cu composite material, the yield strength, tensile strength and elongation of the 0.1wt.%Ni-rGO/Cu composite material are increased by 10.9, 13.5 and 23.9%, respectively. This can be ascribed to the modified structure of graphene along with the improved interface bonding by the incorporation of Ni nanoparticles in rGO. [ABSTRACT FROM AUTHOR]

Al–5.7Si–2Cu–0.3Mg alloy was subjected to a thixoforming process. The impact behaviour of the thixoforming process on microstructure characterisation and mechanical properties was investigated. A cooling slope (CS) technique was applied here to get thixoforming feedstock material at three different pouring temperatures of 640 °C, 650 °C and 660 °C, plate lengths 300 mm, 400 mm and 500 mm and constant CS angle 60°. Some samples of thixoformed were treated using T6 heat treatment. These samples were characterised via optical microscopy, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction investigations, tensile and hardness tests. Consequently, the optimum conditions of CS casting process were 650 °C pouring temperature and 400mm plate length. The thixoformed alloys observed fine globular α-Al phase microstructure surrounded by uniformly distributed Si particle, minimum of porosity and refined fragmented intermetallic phase. The hardness of the thixoformed-T6 sample was roughly twice as much as-cast sample. The tensile and yield strength of thixoformed-T6 samples were enhanced by 45% and 39%, respectively, compared to as-cast samples. The thixoformed-T6 samples observed the highest value of tensile elongation to fracture of 4.8 ± 0.4%. The tensile fractures surface of thixoformed-T6 samples exhibited decline in each of tensile strength and ductility, due to occurrence of Fe-rich intermetallic on the samples. [ABSTRACT FROM AUTHOR]

In this study, composite was made by the addition of 10 wt% SiC particles in the LM25 matrix through gravity casting and thixocasting processes. Thixocasting temperature was varied to investigate its effect on the microstructure, mechanical and thermal properties. Properties of thixocast samples were also compared with gravity cast ones. XRD analysis was done to analyse the phases present in the samples. Optical microscope and scanning electron microscope were used to record the microstructures of gravity cast as well as thixocast samples. Tensile, compressive and flexural tests were performed on universal testing machine with the prepared composite samples according to the ASTM standards. Thermal diffusivity tests of gravity cast and thixocast samples were done on laser flash diffusivity instrument. Results reveal that thixocast samples are sounder than the gravity cast samples. The microstructure of α-Al phase transformed from dendritic to globular shape due to the thixocasting. Also, volume fraction of eutectic phase in the sample increased with the increment of thixocast temperature. Tensile strength, compressive strength and flexural strength were found higher in the case of thixocast samples as compared to gravity cast. Thermal diffusivity considerably increased due to thixocasting, while its value slightly reduced with increment of thixocast temperature. [ABSTRACT FROM AUTHOR]

Fluorine rubber (FKM) is often used in bearing seals, bearing seal will be affected by high temperature in the process of use and performance decline. Therefore, in this paper, the effect of CeO2 on the high temperature composite properties of FKM was studied by filling CeO2 nanoparticles into FKM. 5% CeO2/FKM composites were prepared by mechanical blending and hot-pressing process after nano CeO2 was treated with silane coupling agent KH-570. After mechanical and high temperature friction tests of CeO2/FKM composites, the morphology of CeO2/FKM composites was characterized by three-dimensional topography instrument and scanning electron microscope. The mechanical strengthening mechanism and anti-wear and anti-friction mechanism of CeO2 on FKM were expounded. The results showed that the microstructure of Fluor elastomer with CeO2 particles was reinforced, and the defects of fluorine rubber itself were filled. Specifically, compared with the original FKM, the strength of CeO2/FKM composite was improved, in which the tensile strength reached 20.75 MPa, increased by 18.5%, and the tear strength reached 43.44 N/mm, increased by 3.5%. CeO2/FKM composites show outstanding anti-wear and low friction coefficient properties at high temperature (200 °C). The main mechanism is that nano-CeO2 keeps high hardness of FKM, and CeO2/FKM composites have high crosslinking density. [ABSTRACT FROM AUTHOR]

Present work explores the utilization of forest waste (pine cone) and plastic waste (recycled HDPE) to fabricate wood plastic composites (WPCs) using microwave-assisted compression molding. The developed WPCs were experimentally subjected to physical, thermal, and mechanical characterization. Physical properties deteriorated when the filler loading level was maximized over the weight percentages due to poor wettability. The thermal study revealed that the melting point of the composites was influenced by filler weight percentage. The composites reinforced with 20 Wt.% filler exhibited the highest tensile, flexural, and impact strength of 20.01 MPa, 20.98 MPa, and 15.79 kJ/m2, respectively. Scanning electron microscope (SEM) micrographs revealed voids, microcracks, and poor filler dispersion were dominantly responsible for composites failure with increased filler weight fraction. [ABSTRACT FROM AUTHOR]

The paper studies the structure and mechanical properties of the copper alloy based on a Cu–Al–Si–Mn system, produced by wire-feed electron-beam additive manufacturing (EBAM). Energy dispersive X-ray spectroscopy on the scanning electron microscope is carried out to investigate the microstructure and composition of the obtained copper alloy specimens. The tensile strength and microhardness of the alloy specimens are studied to determine its mechanical properties. It is shown that the structure of the manufactured material consists of the κ-phase dendrite grains and the γ-phase layers. According to static tension tests, the copper alloy possesses isotropic hardness and anisotropic ductility. Its hardness values also indicate the anisotropy of mechanical properties due to, mainly, a two-phase structure and nonuniform distribution of microhardness in the bulk of the Cu–Al–Si–Mn system-based copper alloy deposited using wire-fed EBAM. [ABSTRACT FROM AUTHOR]

The aim of this study is to simultaneously improve ultimate tensile strength, elongation, weld length and hardness of Al–Cu welded sheets by optimizing the electromagnetic welding parameters such as voltage, standoff distance and distance between spacers. Finite element analysis was conducted for the electromagnetic welding of Al–Cu sheets, and the results were used to predict the formation of weld. The experimental tests were then executed by response surface methodology in order to extract the regression models for predicting the optimal values of the parameters. The assessment of the weld quality was performed by observation of the microstructure of weld interface using the optical and scanning electron microscopes. The mechanical properties of Al–Cu weld were improved simultaneously using the desirable values of parameters as validated by confirmation experiments. It was also observed from the weld microstructure that the most important potential sources for reducing the weld length and weld strength are the high thickness intermetallic layers with micro-cracks and the entrapped oxides in the weld interface. [ABSTRACT FROM AUTHOR]

Laboratory tests were conducted to study the physical and mechanical properties of granite after heating and water-cooling treatment for 1 and 30 cycles from room temperature to 500 °C. The change mechanisms for the water-cooling treatment were analysed via scanning electron microscope observation. At 500 °C, the volume of granite increases by 1.73% and 2.55%, the mass decreases by 0.16% and 0.31%, and the density decreases by 1.86% and 2.78% after 1 and 30 thermal cycles, respectively. The average values of UCS and E after 1 and 30 cycles both decrease as the temperature rises, while the peak strain exhibits the reverse trend. A yield platform is observed in the yield stage of the stress–strain curve above 300 °C, and the ductility of granite gradually increases with temperature. The normalized P-wave is linear with respect to the normalized UCS and E at 1 thermal cycle, whereas it shows exponential relationships with the normalized UCS and E at 30 thermal cycles. The degradation of the physical and mechanical properties of granite after 1 and 30 cycles is mainly caused by the generation and development of microcracks inside the rock. Compared to 1 thermal cycle, more microcracks are observed at 30 thermal cycles. Therefore, the thermal cyclic treatment can further deteriorate and weaken the physical and mechanical properties of granite. [ABSTRACT FROM AUTHOR]

Geothermal energy is recommended as a clean and renewable energy resource. During the exploitation process, hot rocks in a geothermal reservoir will be subjected to cyclic water cooling. Laboratory tests were conducted to investigate the physical and mechanical behaviors of water-cooled granite specimens subjected to various thermal cycles with temperatures ranging from 20 °C to 500 °C. Meanwhile, scanning electron microscope (SEM) images were used to capture the development of the microcracks within the specimens. It was found that volume increases with thermal cycle and mass, that density and P wave velocity decrease with thermal cycle, especially after the first thermal cycling, and their change rates diminish with increasing thermal cycle. Both uniaxial compressive strength (UCS) and elastic modulus (E) of granite decrease with thermal cycle. The decreasing extents gradually tend to constant with thermal cycle, and they remain almost unchanged once the thermal cycle reaches 20 iterations. The deterioration mechanisms of the physical and mechanical behaviors of granite are mainly caused by the generation and propagation of microcracks. Microcrack density increases slowly with the thermal cycle rising from 10 to 30, corresponding to the decrease of the physical and mechanical properties. The results are expected to provide an important contribution to the stability of well boreholes during the exploitation of deep geothermal energy. [ABSTRACT FROM AUTHOR]

Dissimilar weldments of AISI 316 and Monel 400 are extensively used in boiler feed water heaters where the weld roots are exposed to high pressure and hot corrosive environments. In this research, metallurgical and mechanical properties of dissimilar weldments of AISI 316 and Monel 400 obtained by pulsed current gas tungsten arc welding (PCGTAW) and constant current gas tungsten arc welding (CCGTAW) processes were compared. The heat input rate and filler wire were same in both welding techniques. Metallurgical properties are studied by employing optical microscope (OM) and scanning electron microscope (SEM). Mechanical properties of dissimilar weldments are determined by tension test and Vickers hardness. The metallurgical study has revealed fine grain structures with clear grain boundaries at the heat-affected zone in PCGTAW weldment. The ultimate tensile strength in PCGTAW and CCGTAW weldments was observed as 554 and 542 MPa, respectively. The ratio of yield strength to ultimate tensile strength is higher in PCGTAW weldment than CCGTAW weldment. The weldment developed by using PCGTAW technique has shown a higher microhardness value at HAZ of both the base metals than the weldment developed in CCGTAW technique. [ABSTRACT FROM AUTHOR]

Semisolid cast AA2024 matrix composites reinforced with 2.0 wt% titanium boride (TiB2) and varying amounts of yttria (Y2O3) (0.5 wt%, 1.0 wt%, 1.5 wt%) were developed using stir rheocasting. The metallurgical characterisation was done by X-ray diffraction, optical microscopy, and scanning electron microscope, and mechanical characterisation by Vickers's hardness testing machine and universal testing machine. The microstructure evolution and mechanical properties such as hardness, tensile strength, and fracture toughness (KQ) of the developed composites were correlated. Pure AA2024 and AA2024 reinforced with TiB2 samples were also fabricated as a benchmark to compare the effect of yttria. The highest hardness, ultimate tensile strength, and yield strength achieved were 122 HV, 310 MPa, and 230 MPa, respectively, for the AA2024/2 wt% TiB2 + 1.5 wt% Y2O3 composite. They are 25%, 45%, and 57% higher compared to the unreinforced sample. The maximum conditional fracture toughness (KQ) achieved was 25.56 MPa m1/2 for the unreinforced specimen and 19.77 MPa m1/2 for AA2024/2 wt% TiB2 + 1.5 wt% Y2O3 composite. With the addition of Y2O3 particles in the matrix, the porosity in the samples increased, resulting in lower elongation. The processing route enhanced the mechanical properties of the composite in comparison with the liquid cast matrix due to a uniform distribution of particles and grain refinement. [ABSTRACT FROM AUTHOR]

In this study, a novel severe plastic deformation method, named as thin-walled open channel angular pressing (TWO-CAP), was developed and applied to AZ31 magnesium alloy beams in U-type cross-sectional shape. First of all, the principles of the method with all parameters were determined, and the analytical model of the system was generated, and then the study was supported with the numerical analysis. Then, a proper experimental setup was established by considering theoretic outputs. After that, AZ31 magnesium alloy specimens were machined from bulk material in U-type shape as to fit the die channel, and then these specimens were annealed and pressed along the TWO-CAP die. Following the experimental studies, the specimens were tested in order to define the changes in mechanical and microstructural properties. In this stage, the tension test and hardness test were applied to determine the mechanical properties, while optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and transmission electron microscope analyses were applied to see the changes in microstructure. As a result, an improvement on strength, hardness, and toughness was observed depending on the changes on the microstructure and grain refinement due to the large plastic deformation. [ABSTRACT FROM AUTHOR]

In the present study, effect of ZrC vol.% on mechanical properties of AA6061 metal matrix composites (MMCs) produced via stir casting technique was investigated. The vol.% of ZrC particles was varied as 5,10 and 15. The composites were characterized for its microstructure and mechanical properties and their relationships were obtained. The scanning electron microscope (SEM) images revealed uniform distribution and good bonding between the AA6061 alloy and the ZrC particles. The mechanical properties of the AA6061 alloy was found to significantly improve with the addition of ZrC particles from 5 to 15 vol.%, the hardness increased from 32 to 68 HV, yield strength increased from 50 to 86 MPa and the ultimate tensile strength increased from 118 to 165 MPa. However, the % of elongation of the composite samples decreased with 15 vol.% addition of ZrC particles. Sliding wear behaviour of the composites was investigated using a pin-on-disc wear tester at a load of 9.8 N and addition of ZrC particles was significantly found to reduce the wear rate of AA6061 alloy. [ABSTRACT FROM AUTHOR]

In this study, the influence of nanosilica (SiO2 NPs) on the mechanical, thermal and barrier properties of poly(butylene adipate-co-terephthalate) (PBAT) nanocomposites was investigated. The PBAT/SiO2 composites were prepared by solution blending technique. PBAT/SiO2 composites were prepared with different percentages of nano-SiO2 loading (1, 3, 5, 7 and 10 wt%). The relations of SiO2 NPs with PBAT matrix were analyzed by Fourier transform infrared spectroscopy. The mechanical properties such as tensile strength, % of elongation at break, tensile modulus and thickness were determined. The thermal properties such as thermo-gravimetric analysis were analyzed for the nanocomposites. The PBAT/SiO2 composites exhibit high mechanical and thermal performance than the pure PBAT. The nanocomposites were also investigated through scanning electron microscope (SEM) and transmission electron microscope micrographs to examine the morphology between PBAT and SiO2 NPs. In addition, the results of SEM acquired are in SiO2 agreement with the data resulting from FTIR and tensile strength of the nanocomposites. The nanocomposite shows improvement in mechanical and thermal stability than that of pure PBAT. [ABSTRACT FROM AUTHOR]

Two series of multicomponent silicone hydrogels based on poly (ethylene glycol)- polydimethylsiloxane-poly (ethylene glycol) (PEG-PDMS-PEG) triblock oligomers were prepared by copolymerization of silicon-containing monomers methacrylate-terminated PEG-PDMS-PEG (MTSM), tris (trimethylsiloxy)-3-methacryloxpropylsilane (TRIS), and hydrophilic monomers such as N,N-dimethylacrylamide (DMA), N-vinylpyrrolidone (NVP), and hydroxypropyl-methacrylate (HPMA). The influences of PEG chain length on hydrophilicity, oxygen permeability, and mechanical properties of silicone hydrogels were explored. The hydrophilic properties of silicone hydrogels were characterized by water contact angle, equilibrium water content, and swelling-dehydration process. The results showed that the water contact angles of dry samples decreased while the swollen ones increased with the increase of PEG chain length. The equilibrium water content decreased first and then increased as the length of the PEG chain increased. The results of swelling and dehydration process showed that PEG chains improved the water-retaining capacity of silicone hydrogels. Moreover, the protein adsorption of samples with PEG chains decreased. The surface morphologies of silicone hydrogels were characterized by scanning electron microscope (SEM), and a reconstruction model was proposed. In addition, the oxygen permeability and mechanical properties of silicone hydrogels also varied with the length of the PEG chain. These results could provide a theoretical reference for the design and modification of new hydrogels. [ABSTRACT FROM AUTHOR]

In this study, the effect of particle size and particle content of silicon carbide fillers in epoxy matrix on the mechanical properties and microstructure of the developed composites was investigated. Silicon carbide fillers sized to < 45 μm and 90–45 μm were incorporated to epoxy composites to obtain volume fractions of 2, 4, 6 and 8 wt% of SiC. Mechanical properties including flexural strength, compressive strength and hardness tests of the composite samples were performed according to ASTM D790-03 (2003), ASTM D695-15 (2015) and EN 1534 standards. Surface morphology, crack propagation and particulate dispersion were observed using scanning electron microscopes (SEM). The results of the mechanical properties obtained were examined statistically and the results that a strong negative correlation between hardness and flexural strength but the individual correlation between hardness and flexural modulus, compressive stress and compressive modulus were positive. Results also showed that the inclusion of small particulate silicon carbide (< 45 μm) displayed superior mechanical properties in term of flexural, compressive and hardness characterizations at a given volume fraction. Flexural properties of the composite samples decrease with increase in filler concentrations while the compressive strength and hardness increase as particulate loading increase. In terms of microstructure, uniform dispersion of silicon carbide particulates was observed within epoxy matrix with linear crack propagation. [ABSTRACT FROM AUTHOR]

This work is focused on the study of mechanical and physicochemical properties of an innovative and environmentally friendly composite material based on different sugar palm fiber (SPF) loadings (10–30 wt %) with thermoplastic polyurethane (TPU). A two-step technique was used (extrusion of TPU with SPF fibers at 190°C; rotational velocity of 40 rpm, followed by hot press 190°C for 10 min) to obtain the composites. The size of SPF was fixed at 250 µm, and different weight percentages (10, 20, and 30 wt %) of SPF were added in TPU to find the optimum composition. The mechanical (impact, tensile, and flexural) properties of the new (TPU/SPF) composite were studied as per ASTM standards. The Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and the X-ray Diffraction (XRD) were employed for structure and morphology study of TPU/SPF composites. The results proved that best tensile strength (14 MPa) and strain performance is shown with 10 wt %, while at 20 wt % exhibited maximum impact property. An increasing trend was recorded in flexural properties and tensile modulus with the increasing fiber loading. On the other hand, strain deteriorated with increment of fiber content. [ABSTRACT FROM AUTHOR]

Rutile phase TiO 2 with the diameter of 50 nm and 500 nm were used to fabricate TiO 2 modified cementitious composites (RTMCC) in this paper. The mechanical property and microstructures of RTMCC were compared. Research results showed both types of TiO 2 can improve the flexural and compressive strengths of cementitious composites. The addition of 2.32 vol.% 50 nm and 500 nm TiO 2 increased the 28 days flexural strength/compressive strength by 27.7%/10.78% and 53.71%/18.58%, respectively. In addition, the fracture toughness of cementitious composites can be enhanced by the inclusion of TiO 2. The microstructure analysis demonstrated that the strengthening effect of TiO 2 to cementitious composites results from the nucleation effect, filling effect, pinning effect and self-curing effect. However, the reinforcing effect of 500 nm TiO 2 is superior to that of 50 nm TiO 2. Nuclear magnetic resonance and energy dispersive spectrum analyses suggested that 50 nm TiO 2 can make the decalcification of the C–S–H (i.e., calcium is removed from the interlayer) and cause defect sites in the silicate chains, which lead to the less-density C–S–H. In addition, zeta potential and scanning electron microscope analyses manifested that 50 nm TiO 2 is easier to reunite, therefore generating more defects in cementitious composites. [ABSTRACT FROM AUTHOR]

Glycidyl methacrylate (GMA) functionalized polyolefin elastomers (POE) (POE-g-GMA), which was a reactive processing agent, was melt-blended with poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) by twin-screw extrusion. The mechanical property results showed that with the addition of POE-g-GMA, the elongation at break and impact toughness of PLA/PPC blends increased while the tensile strength decreased. Dynamic thermomechanical analysis (DMA) and scanning electron microscope (SEM) results indicated that PLA/POE-g-GMA/PPC blends were partly miscible and the addition of POE-g-GMA improved the compatibility of blends. The higher Tcs and lower Tms of PLA/POE-g-GMA/PPC blends showed a depressed crystalline ability of PLA caused by the decreased chain mobility according to the differential scanning calorimetry results and the thermal stability of PLA/POE-g-GMA/PPC blends was enhanced. Rheological results revealed that the addition of POE-g-GMA made the storage modulus (G′), loss modulus (G″) and complex viscosity of the blends increase, the melt strength also improved. These findings contributed to the biodegradable materials application for designing and manufacturing PLA film. [ABSTRACT FROM AUTHOR]