Search

One of the challenges of storing hydrogen in saline aquifers is the possible geochemical reactions between host rock, formation solution, and hydrogen. This study investigated the effect of hydrogen treatment on the mechanical properties of sandstone samples from Hulett member of Sundance Formation, a potential underground hydrogen storage host in Wyoming, USA. Cylindrical specimens were treated with brine, brine+50%H 2, and brine+100%H 2 for two weeks at a pressure of 15 MPa and a temperature of 83 °C. X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), uniaxial compression, and triaxial compression tests were conducted on specimens. Results showed that specimens treated with brine+50%H 2 and brine+100%H 2 , on average, exhibited 24 and 41% lower peak strength, respectively, compared to that of specimens treated with the brine. XRD results showed a decrease in dolomite and clay content of specimens after exposure to hydrogen, causing degradation of the mechanical and elastic properties of the specimens. • The effect of hydrogen on the mechanical properties of Hulett sandstone was investigated. • Dolomite and clay dissolution was observed after the treatment with hydrogen. • Specimens treated with hydrogen on average showed 41% lower strength. • An average 43% decrease in elastic modulus was observed after hydrogen treatment. [ABSTRACT FROM AUTHOR]

The aim of the present work was to evaluate six commercially available abutment screws by characterising roughness parameters, microstructure and mechanical properties. Six abutment screws from each implant system, were used. The surface roughness parameters (S a , S q , S sk , S ku , S pk , S k and S vk) were identified by an optical interferometric profiler. Microstructural observations and crystallographic analysis were performed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) device for elemental analysis and an X-ray diffractometer (XRD), respectively. The Martens Hardness (HM), Indentation Modulus (E IT), elastic index (η IT) and Vickers hardness (HV) of all specimens were determined by instrumented indentation testing (IIT). The results were analyzed by one-way ANOVA and Tukey multiple-comparison tests (a=0.05). EDX and XRD showed the abutment screws to be mixed α- and β-phase titanium alloys. Microstructural analysis revealed a fine homogeneous microstructure without porosity, consisting of fine dispersoid rods of β-phase embedded in a continuous α-phase matrix. Statistically significant differences were found among the mechanical properies and surface roughness parameters apart from S q , S pk and S vk. The tested abutment screws showed significant differences in the probed properties, and, thus, differences in their clinical behaviour are anticipated. [ABSTRACT FROM AUTHOR]

High-entropy MAX phase (Ti 0.5 Nb 0.15 Zr 0.1 Mo 0.1 Ta 0.1 W 0.05) 2 AlC was synthesized via current-assisted sintering using Ti/Al/NbC/ZrC/MoC/TaC/WC as the raw material. The phase composition, microstructure, and elemental distribution are analyzed by X-ray diffraction, scanning electron microscope and transmission electron microscope with energy-dispersive spectrometer elemental analysis. The results obtained indicate that the as-synthesized bulk exhibits high purity with minimal elemental segregation at the grain boundary. The doped atoms caused numerous dislocations and severe lattice distortions in the crystal structure. By means of mechanical properties tests, the hardness, flexural strength, and fracture toughness of (Ti 0.5 Nb 0.15 Zr 0.1 Mo 0.1 Ta 0.1 W 0.05) 2 AlC are determined to be 9.3 ± 0.2 GPa, 433 ± 27 GPa, and 8.9 ± 0.3 MPa m1/2, respectively. These findings demonstrate notable enhancements in terms of hardening, strengthening, and toughening effects compared to the Ti 2 AlC phase. [ABSTRACT FROM AUTHOR]

In this study, the primary factors affecting the performance of PcBN (Polycrystalline cubic boron nitride) tool materials were investigated by high temperature/high pressure sintering through the variation of TiB 2 -Sialon volume ratio, the strength of TiB 2 -Sialon binder itself, as well as the matching of the average coefficient of thermal expansion (CTE) with cBN (Cubic boron nitride). The effects of TiB 2 -Sialon on the phase composition, microstructure, and mechanical properties of PcBN composites were studied by X-ray diffraction (XRD), universal testing machine, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the properties of TiB 2 -Sialon binder are analogous to those of the corresponding composites. The phase composition of PcBN composite is not affected by the change of volume ratio. It was found that prepared composite, have TiB 2 rod crystals growing along the (100) plane and Sialon rod crystals growing on the (001) plane. The influence of the volume ratio of TiB 2 -Sialon on the mechanical properties of the composites is principally concerned with the density, mechanical properties, and thermal expansion coefficient of the used binder. The extent to which the binder matches the coefficient of thermal expansion is favorable to the strength of the composite. When the volume ratio of TiB 2 to Sialon was 1:3, the hardness (25.21 GPa, 37.44 GPa) and toughness (7.09 Pa m1/2 and 7.48 Pa m1/2) of TiB 2 -Sialon binder/TiB 2 -Sialon-cBN composites reached the maximum value, and the optimal impact resistance was also achieved. The density of the binder and the composite material was maximized when the volume ratio is 1:4. The average thermal expansion coefficient of the binder hoc tempore matches comparatively with cBN, and the interface bonding is better, displaying the best flexural strength (805.30 MPa and 1059.60 MPa) and wear ratio (2005). Therefore, adjusting the volume ratio of TiB 2 -Sialon within a certain range is beneficial to further enhance the binder's strength and mechanical properties. [ABSTRACT FROM AUTHOR]

• Innovative latex nanodispersions were employed for the consolidation of porous stone. • Their effectiveness to improve mechanical properties of Prague sandstone was proved. • Consolidation can be tuned according to type of applied latex and its concentration. This investigation aims at assessing the potential of polyacrylate latex nanodispersions as consolidation agents for sandstones. Four different latex types, implementing polymer fluorination and chemical crosslinking, have been synthesized at the scope and fully characterized. The Prague sandstone employed in this study has been selected as an example of highly porous stones used as building materials for many historical monuments. Two different concentration levels of nanodispersions have been adopted. The consolidated stone samples have been tested using a combination of physical-mechanical tests and microscopic observations. Compared to the non-treated samples, significant increments of mechanical properties (e.g. up to 3.3 times higher bending strength) have been detected after the consolidation treatment with concentrated products. Moreover, when 10 times diluted latex nanodispersions have been applied, the improvement of mechanical properties has still been significant, while moisture transport properties, such as water absorption, have been found to be comparable with those of the untreated sample. Fluorinated polymers imparted better hydrophobic properties with a contact angle above 100°. Observations using a scanning electron microscope revealed the good filling and bridging capacity of the applied consolidation agents. As demonstrated, by acting on the polymer structure, that is, by tuning the degree of crosslinking, polymer fluorination and gel content, the properties of these novel polyacrylate latex nanodispersions can be tailored to the specific stone and type of decay in order to improve the effectiveness of the treatments and obtain the desired final properties. The flexibility of their chemistry offers new opportunities for preserving objects of cultural heritage that are also at risk due to the ongoing climate change. [ABSTRACT FROM AUTHOR]

The ceramic composites were designed through the regulation of the composition and temperature in the in-situ oxidized SiC/Al–Mg–Si composites process. The evolutions of the phase and microstructure were studied by X-ray Diffraction(XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope(TEM) in different alloy addition and heating temperature. The products of in-situ oxidized SiC/Al–Mg–Si composites showed similar compositions due to high oxidation resistance on SiC since the heated temperature was below 1500 °C. Alloy addition dislodges the oxide shell on SiC. It promoted the oxidation of SiC, providing the sustained-release Si source to form the cordierite, mullite, and forsterite. Moissanite/spinel, mullite/spinel, and cordierite/spinel were obtained by controlling temperature or adding alloy. The mullite rods formed in 20% alloy addition samples at 1350 °C was detected. The step-like microstructure revealed that grains abide by a layer growth mechanism. The bending strength was enhanced from 13.83 ± 3.6 MPa to 22.32 ± 4.3 MPa by eutectic melting, which increased with the alloy addition and elevated temperature. [ABSTRACT FROM AUTHOR]

In this study, carbide slag (CS) and coal gangue (CG) powder were utilized to enhance the properties of the subgrade soil. CS-CG stabilized soil underwent lab experiments to assess its mechanical properties and durability. Tests included unconfined compressive strength (UCS), compressive resilient modulus (CRM), and California bearing ratio (CBR) at stabilizer dosages of 5 %, 10 %, and 15 %. Additional tests, such as dry-wet cycling, salt solution immersion, permeability, leaching, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP), were conducted specifically for the 10 % dosage. The mechanical properties and durability were comprehensively analyzed, with a microscopic investigation into pore size. Furthermore, the soil-water characteristic curve (SWCC) of CS-CG stabilized soil is derived through MIP, providing insights into its impact on the material's strength. Results showcased favorable bearing capacity and durability of CS-CG stabilized soil. The optimal mixing dosage is 10 %, with the best ratio being CS: CG= 70: 30. After 6 dry-wet cycles, UCS loss rate was 18.6 %, comparable to 4 % Portland cement (PC) stabilized soil. Dry-wet cycle characteristics surpassed PC and Lime stabilized soils. Immersion in a 5 % NaCl solution for 30 days yielded a UCS of 3.8 MPa at 28-day age, while exposure to 5 % Na 2 SO 4 solution led to an 11.6 % strength decrease compared to NaCl. Permeability coefficient indicated low permeability akin to PC and Lime stabilized soils. Heavy metal content met standards, with minimal increase during cycles. Hydration products mainly comprised C-S-H gel, Ca(OH) 2 crystals, and carbonate modification. Analysis suggested capillary and transition pores predominantly, with minimal macropores presence. Dry-wet cycles induced a marginal increase in pore size, with negligible overall impact. SWCC predicted water content (θ s) ranged from 30 % to 32 %, with a slight increase in matrix suction during dry-wet cycles. CS-CG stabilized soil shows favorable mechanical properties, durability, and environmental sustainability, indicating its potential as a substitute for traditional cement and lime treatments in subgrade soil reinforcement. • The study explored the feasibility of using CS-CG to enhance soil conditions. • Extensive analysis evaluated CS-CG stabilized soil's durability comprehensively. • Findings highlighted beneficial SWCC traits in CS-CG stabilized soil. • CS-CG stands out as an environmentally sustainable soil improvement technique. [ABSTRACT FROM AUTHOR]

Phthalonitrile composites are highly anticipated in fields such as aerospace, marine, and electronics due to their exceptional heat resistance, excellent high-temperature mechanical properties, and outstanding processability. The conversion of nitrile functional groups to macrocyclic structures during post-curing is essential for performance enhancement. However, the influence of post-curing conditions on the mechanical properties of phthalonitrile composites is complicated, and the underlying mechanism remains unclear. In this study, an experimental and machine learning synergic strategy was employed to optimize the post-curing parameters of the phthalonitrile composites, including temperature, time, and pressure. Through mechanical experiments conducted at both room temperature and 400 °C, scanning electron microscope, and dynamic mechanical analysis, the underlying mechanism of the influence of post-curing parameters on the composite mechanical properties was revealed. The enhancement of the polymerization degree brought about by post-curing is the decisive factor for high-temperature performance, while the room-temperature properties are a tradeoff between the polymerization degree improvement and the defect proliferation. The genetic algorithm-optimized backpropagation (GA-BP) neural network was trained for the efficient and accurate prediction of the optimal post-curing parameters. The tendency of mechanical properties with the post-curing parameters predicted by machine learning is consistent with the mechanism revealed by experiments. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, Ti(C,N)-Fe-based green cermets with different metallic alloying elements have been consolidated by pressureless liquid-phase sintering. The addition of different metallic binders on Ti(C,N)-based cermet such as Nb and Mo on high chromium Ferrous based binder has been investigated. Detailed analysis of the phase constitution was conducted using thermodynamic calculations and experiments, as well as a systematic study of the microstructure evolution and room temperature mechanical properties including hardness and fracture toughness was conducted. The Nb and Mo addition to the binder system affects the sintering temperatures and can significantly affect the phase formation and microstructural development. Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS) technique were used to examine the microstructure, composition, and fracture surface of cermets. The addition of the Mo, and Nb reveals lower porosity and finer microstructure as compared to the reference material (Ti(C,N)-Fe-Cr). The refinement of microstructure improves mechanical properties such as hardness and fracture toughness of Ti(C,N)-Fe-Cr-Mo-Nb-based cermets. Further, the addition of these binder elements may reduce the formation of Fe-Cr-based intermetallic complex carbides, allowing cermets to perform better in terms of toughness and corrosion resistance. As a result of the experiments, it is evident that Nb and Mo dissolve in Ti(C,N) and form solid solutions during sintering. The increased number of coreless grains, spinodal decomposition, and crack deflection in cermet further enhance the fracture toughness. • Recent efforts have been made in developing and tailoring advanced "green" TiCN-high chromium Fe-based cermets. • The incorporation of alloying elements such as Nb and Mo facilitates the densification of TiCN-Fe based cermets. • Thermodynamic calculations and experimental investigation with different alloying elements affect phase formation. • Ti(C,N) solid solutions are facilitated by Nb and Mo addition, improving cermet microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

The present study examines the mechanical and morphological characteristics of a green composite reinforced with pineapple leaf fiber (PLF) under different environmental conditions. PLF underwent chemical treatment at optimal conditions, using a 1% w/v sodium carbonate solution for 6 hours, to produce an environmentally friendly pineapple leaf fiber (PLF)/polylactic acid (PLA)-based composite via injection molding. The optimal injection settings of 165℃ (melting temperature), 50 mm/sec (injection speed), and 110 bars (injection pressure) to produce the PLF/PLA composite. The PLF/PLA composite was developed with a fiber loading of 20% and a length of 3 mm. The produced PLF/PLA composites were then exposed to a variety of environmental conditions, including water, soil, refrigeration, and room temperature. The impact of these diverse conditions on the mechanical properties (tensile, flexural, compression, and shear) was scientifically observed for four-week. Additionally, the morphology of the fractured specimens was assessed using a scanning electron microscope (SEM). The contact angle measurement was conducted to assess the hydrophilic characteristics of the PLF/PLA green composite. There has been a lack of comprehensive research on the effects of different environmental conditions on the mechanical, wettability, and morphological properties of green composites derived from PLF/PLA. Thus, in this study, emphasis is given for investigating the effect of various environmental conditions on the mechanical properties of PLF/PLA injection-molded green composite. The composite material demonstrated the highest water absorption and swelling thickness at 6.45% and 5.51%, respectively, in comparison to the dry PLF/PLA samples. The green composite of PLF/PLA demonstrated excellent mechanical performance under ambient conditions compared to other environmental conditions. The PLF/PLA composite displayed a peak contact angle of 83.26° when subjected to soil burial conditions. On the contrary, the initial samples of the PLF/PLA composite displayed the minimum contact angle of 56.72°. • The mechanical behaviour was better in room temperature than refrigerating, soil burial, and water immersion conditions.. • The maximum water absorption and thickness of swelling were observed as 6.45% and 5.51% in comparison to the dry samples. • The soil buried composite samples showed maximum contact angle of 83.26°. • Morphological study showed minor damages to the samples exposed to refrigerator and room temperature conditions. [ABSTRACT FROM AUTHOR]

The study investigates the application of waste rubber in cement-stabilized base course (CBC), aiming to address internal stresses, reflective cracks, and waste disposal issues. Mixtures of gravel and sand stabilized with varying cement and rubber content were examined, including reference mixtures and those with granulated rubber or rubber threads, a total of 17 mixtures. Mechanical properties, durability, and environmental impact were evaluated through standard tests such as Proctor elements, compressive and tensile strengths, freeze thaw resistance, shrinkage, and scanning electron microscope analysis. Non-standard, non-contact methods like ultrasonic pulse velocity and 3D digital image correlation were employed. Results indicate the feasibility of using waste rubber in CBC, with the optimal mixture containing 5 % cement and 20 % rubber as a replacement for sand showing satisfactory compressive strength (3.01 MPa) for application as a base layer, reduced stiffness, improved frost resistance (9.76 %), improved tensile to compressive strength ratio (52.99 %), and increased resistance to reflective cracking comparing to reference mixture. Moreover, it exhibited minimal shrinkage compared to other mixtures. The study underscores the importance of assessing environmental acceptability in waste materials for road construction, emphasizing the need for further research. Furthermore, the possibility of employing non-contact testing methods has been demonstrated. [Display omitted] • The optimal composition of rubberized CBC has been defined. • Rubber improves freeze – thaw resistance of CBC. • Rubber decreases the shrinkage of CBC. • The use of rubber in CBC does not pose an environmental risk. [ABSTRACT FROM AUTHOR]

• Sensing capability of PLA-nanofiber reinforced PCL composite-based smart porous scaffolds for online health monitoring. • Fused filament fabrication parameters for maximizing yield stress. • Simulated return loss , specific absorption ratio, and resonance frequency for PCL and PCL composites. In the past, studies were reported on polycaprolactone (PCL) and polylactic acid (PLA) nanofibers (NF)-based scaffolds for tissue engineering applications. But hitherto, little has been reported on the sensing capability of PLA-NF reinforced PCL composite (PPNC)-based smart porous scaffolds for online health monitoring (OHM) of joint strains/ tendon tears/ contusions/ rhabdomyolysis, etc. In this study, smart porous scaffolds (SPS) were fabricated by fused filament fabrication (FFF) using PPNC for OHM (of joint strains/ tendon tears/ contusions/ rhabdomyolysis, etc.) with tuneable sensing and mechanical properties. The results suggest that FFF parameters, zigzag fill pattern, 0.20 mm layer thickness, and 80 % infill percentage are the best-predicted settings for maximum yield stress (σ ymax) of SPS. Further, a vector network analyzer was used to ascertain the sensing capability of SPS. The resonance frequency (R f) for PCL (virgin) and PPNC with minimum yield stress (σ ymin) and σ ymax were observed as 2.3021, 2.6008, and 2.4315 GHz respectively. The simulated return loss (S 11) , specific absorption ratio (SAR), and R f for PCL (−10.7593 dB, 0.977 W/kg, and 2.6450 GHz), PPNC with σ ymin (−10.5737 dB, 1.437 W/kg and 2.3400 GHz) and PPNC with σ ymax (−10.9429 dB, 1.155 W/kg and 2.5050 GHz) indicate that experimental data is in good co-relation with the observed values. The results are supported by a scanning electron microscope and differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

• The proposed method improved the precision and accuracy of measurement and reduced the time in measuring the displacement. • A novel material deformation measurement method is suggested to evaluate the mechanical properties of thin films. • The method requires images during an in-situ SEM (Scanning Electron Microscope) tensile test and analyze them. • Some images of low resolution (768 x 614) during in-situ SEM tensile test of the thin film are acquired and restored to high resolution (3840 x 3072) images using the deep learning model. In this study, a novel material deformation measurement method is suggested to evaluate the mechanical properties of thin films. It is important to identify the mechanical properties of thin films in order to do a reliable design of these products. One of the methods to get the mechanical properties of thin films is to acquire images during an in-situ SEM (Scanning Electron Microscope) tensile test and analyze them. However, SEM image acquisition is mostly affected by the time varying motion of pixel positions in the consecutive images, a phenomenon called drift and distortion. In this study, some images of low resolution during in-situ SEM tensile test of the thin film are acquired in short time and restored to high resolution images using the deep learning model called Super Resolution Residual Network (SRResNet) to calculate the deformation of thin films. The proposed method increased the precision of measurement by 5 times, improved the accuracy of measurement by 20%, and reduced the measurement time by 19 times. [ABSTRACT FROM AUTHOR]

This paper provides a current overarching review of several commonly used carbon nanomaterials applied within cementitious composites. It reviews the typical weight percentages used within mixes from several researchers in the field and assesses the application of these nanomaterials on the mechanical properties. Mechanical properties covered include compressive strength, flexural strength and tensile strength as well as elastic modulus. It was clear from this extensive but initial review that the dispersion methods and techniques used during mixing not only influenced the mechanical properties but also influenced the percentages of nanomaterials used in the mixes. This leads to a further review of dispersion methods and dispersion measurement techniques in order to gain insight into the best approach to take. The effect of dispersion methods on the quantities of nanomaterials used in mixes raised an interesting, last review on pricing comparisons (2020) and the development of a cost-to -weight ratio to better evaluate and compare between options from a cost perspective. Recommendations from this extensive review include; low percentage of graphene oxide provides better improvement compared with other carbon nanomaterials; Use of superplasticiser in mixes such as ADVA 210 to better aid dispersion; use of ultra-sonication for a short cycle to improve dispersion; and finally, a mixed mode approach to the measurement of dispersion in mixes which includes scanning electron microscope (SEM) + ultraviolet–visible spectroscopy (UV–Vis) testing at solution phase + Mechanical properties after 28 days. [ABSTRACT FROM AUTHOR]

• 1. With increasing re-fused scanning more than once, successive energy input exacerbates the roughness both on the top and side surface and changes the shape and sizes of the molten pool. • 2. With increasing the re-fused times, a preferential crystallite growth orientation along (2 0 0) α -Al crystal plane is enhanced. • 3. There is little difference in yield strength, tensile strength and elongation with combinations of zs + nc, frs + fcs, and srs + scs methods. Laser powder bed fusion (LPBF) stands out as the foremost method for achieving intricate structure with superior design flexibility among additive manufacturing technologies. Within the LPBF process, surface roughness serves as a critical metric governing both fabrication precision and build quality. This study delves into the evolution of the top and side surface roughness as re-fused scanning times increase in LPBF-fabricated AlMgScZr alloy. Concurrently, the investigation evaluates alterations in microstructural characteristics and mechanical properties. Various characterization techniques, including confocal laser scanning microscope, scanning electron microscope, X-ray diffraction, electron backscatter diffraction, as well as tensile and microhardness tests, are employed. The findings concerning the top surface reveal that the initial application of re-fused scanning contributes to enhanced surface roughness. This improvement stems from refined grain structures and induced lattice distortions, facilitated by rapid heat dissipation and thermal recycling within the solidified layer. Consequently, microhardness increases. However, introducing the subsequent re-fused scanning exacerbates surface roughness and instigates Marongoni flow instability, magnesium depletion, and alterations in lattice structures. Moreover, with increasing the re-fused times, there is a noticeable enhancement in preferential crystallite growth orientation along the (2 0 0) α -Al crystal plane. Regarding the side surface, escalating re-fused times correlate with deteriorating roughness and alterations in molten pool shape and size, attributable to successive energy input. Despite these surface variations, minimal differences are observed in yield strength, tensile strength, and elongation. In essence, this research offers valuable insights into selecting optimal scanning methodologies during the LPBF process, thus guiding improvements in fabrication precision and component quality. [ABSTRACT FROM AUTHOR]

Nanobubble water with the ability to capture carbon dioxide (CO 2) was used as the mixing water for the development of Carbon Consuming Concrete (CCC). The mechanical properties, volume stability, and pore structures were initially evaluated. Scanning electron microscope (SEM) image was analyzed to confirm formation and calcium component on the surface. Differential thermogravimetry (DTG) analysis and nuclear magnetic resonance (NMR) spectroscopy were used to evaluate the reactivity of cement according to mixing water type. The ability was confirmed in priority that convert calcium hydroxide (CH) into calcium carbonate (CaCO 3) by utilizing abundantly captured CO 2. The nanobubble increased the calcium content and ratio of micropores, while the total porosity decreased when CO 2 gas was injected. Depending on the mixing water type, each specimen showed strength in the production of different major components (C-S-H, CH, and CaCO 3), affecting the compressive strength development, and the injection of CO 2 gas also affected shrinkage behavior. • Concrete with CO 2 -capturing nanobubbles achieves excellent compressive strength. • Nanobubbles in concrete suppress the carbonation shrinkage. • The utilization of nanobubbles improves C-S-H production. • Abundant CO 2 condition increases the chance of calcium ions to react. • A synergistic effect of nanobubbles and CO 2 leads to higher CaCO 3 production. [ABSTRACT FROM AUTHOR]

This research investigates the combined effect of steel and natural fibre on the mechanical properties and spalling resistance of ultra-high performance concrete (UHPC) before and after exposure to elevated temperatures. The effects of two parameters, namely temperature (ambient temperature, 200 °C, 400 °C and 600 °C) and fibre type (solely macro end hooked steel fibre (MHS) and hybrid of micro straight steel fibre (MSS), macro end hooked steel (MHS) fibre and micro jute (MJ) fibre) on the mechanical properties, spalling resistance and mass loss of UHPC were studied. Micrographs from scanning electron microscope (SEM) test were utilized to appraise the steel fibre and jute fibre before and after exposure to elevated temperatures. The test results exhibited that the residual tensile strength and flexural strength were significantly declined after exposure to high temperatures for UHPC specimens reinforced with macro steel fibre only. Moreover, explosive thermal spalling occurred for this group of specimens under 600 °C. Whereas the combined use of jute fibre and micro-macro steel fibre was an effective approach to prevent the explosive thermal spalling under 600 °C and improve the residual tensile strength, flexural strength and toughness of UHPC. Furthermore, preliminary empirical expressions have been developed in this study to predict the residual mechanical properties of UHPC as a function of natural fibre content, steel fibre content and temperature. [ABSTRACT FROM AUTHOR]

For the present investigation, Tungsten heavy alloys (WHAs), (90-x)W-6Ni-4Cu-xLa 2 O 3 are synthesized using the powder metallurgy route by liquid phase sintering at 1400 °C for 1 h in hydrogen atmosphere. The effect of variation of La 2 O 3 (Lanthanum oxide) dispersion in W-Ni-Cu alloy (0, 0.1, 0.5, 1.0, 1.5, and 2.0 wt%) on microstructural evolution was investigated using a scanning electron microscope (SEM) and transmission electron microscopy (TEM). The distribution of the tungsten, matrix, and La 2 O 3 were analyzed using X-ray energy dispersive spectroscopy (EDS). The influence of La 2 O 3 content on the densification behavior was also determined. The stereological quantifications were done on particle size and contiguity. The lowest W particle size was observed in sample of 2.0 wt% La 2 O 3 added WHA. However, this sample was found to have more porosity. The W particle size was reduced by about 30% with 2.0 wt% addition of La 2 O 3. The maximum value of bulk hardness of about 320 HV 5 was observed in 1.0 wt% La 2 O 3 content WHA. The three-point bend test was performed to determine the bending behavior of these alloys. The alloy with 1.0 wt% La 2 O 3 showed the maximum compressive strength of 1481 MPa and bending strength of 1021 MPa. Fractography revealed W-W interface de-cohesion fracture mechanism to operate pre-dominantly. W particle cleavage fracture mode was observed to increase with the addition of La 2 O 3 up to 1.0 wt% in the WHAs. • W-Ni-Cu alloys with La 2 O 3 processed via powder metallurgy LPS at 1400 °C. • With 2.0 wt% La 2 O 3 in W-Ni-Cu alloy reduces W particle size by 30 %. • The addition of 1.0 wt% La 2 O 3 turns out to give the best mechanical property. • Quantification of operational fracture modes attempted. [ABSTRACT FROM AUTHOR]

During the extraction of geothermal heat, the changes in temperature and pressure environments can alter the mechanical and hydraulic behavior of fractured rock masses, affecting the overall transmissivity and heat extraction efficiency accordingly. This study carried out a series of experiments, including X-ray diffraction (XRD), scanning electron microscope (SEM), uniaxial compression tests, and surface morphological scanning, to explore the influence of reservoir temperature on the mechanical behavior of granite and fracture surface topography. The results indicate that as the temperature increases, the uniaxial compressive strength, elastic modulus, and Poisson's ratio of granite show similar variation patterns that increase as the temperature approaches 200 °C and then decrease. In addition, with the increase in temperature, the overall surface elevation and roughness parameters generally decrease due to surface asperity degradation, with the maximum mean mechanical aperture found at 200 °C. Flow simulations were conducted to further explore the influence of temperature and pressure environments on fracture transmissivity and flow fields. It is found that the normalized equivalent hydraulic aperture B N of the tested fractures decreases progressively as the stress increases, and more scattered distributions of B N are observed under higher compressive stresses. Moreover, with the continuous increase in temperature, the average B N slowly increases to its peak of ~0.78 at 200 °C, then it decreases to ~0.76 at 300 °C and remains nearly constant. These findings can be important for assessing heat production performances during the geothermal extraction process with spatially and temporally varying reservoir temperatures and pressures. • Temperature and pressure effect on granite properties are analyzed. • Surface roughness decreases due to heat-induced asperity degradation. • UCS and transmissivity reach their maximum at 200 °C with increasing temperature. [ABSTRACT FROM AUTHOR]

In light of environmental concerns such as global warming, there has been a dramatic rise in natural fiber concrete (NFC) research and development. The advantages of these materials over others, such as low environmental impact and minimal cost, warrant interest and support their potential across various applications. This study investigates mechanical properties and micro-structural analysis for M70 grade of high-strength concrete (HSC) under the effect of natural fiber with alccofine. Cement was partially replaced in this investigation by 15 % alccofine content. In this experiment, natural banana fiber (BF) and coir fiber (CF) were selected and added in concrete at 0.5 %, 1 %, 1.5 %, and 2 % by volume. Nine concrete mix compounds were developed and investigated the mechanical characteristics, including uniaxial compressive strength, splitting tensile strength, flexural strength, impact strength, and bond strength of concrete, and microstructural analysis, including scanning electron microscope (SEM), energy dispersive Xray spectroscopy (EDS), Fourier transform infrared (FTIR), and X-ray diffraction (XRD), were examined. The outcome of the results revealed that the inclusion of BF and CF with alccofine improves the mechanical characteristics of concrete compared to the control mix. Compared with reference HSC, 1 % banana fiber increased the mechanical performance after 28 days of curing. BF significantly enhanced the mechanical properties of high-strength concrete compared to CF. Furthermore, banana fiber provides early warning of failure due to its elasticity. [ABSTRACT FROM AUTHOR]

Magnesium oxychloride cement (MOC) as a green cement has superior mechanical properties such as high strength and quick gain of early strength, however the inherent brittleness has limited its applications where ductility is crucial. To enhance the strength and ductility, a novel hybrid fibre-reinforced MOC-based composite (FRMOC) is developed for the first time using polyethylene (PE) fibres and basalt fibres (BF) to reinforce the MOC. A systematic investigation of the effect of fibre dosage on the flowability, rheological properties, compressive strength, and tensile properties of the developed FRMOC is conducted in this study. The results revealed that the addition of fibre reduces flowability while increasing the yield stress and plastic viscosity. The 1-day compressive strength of the FRMOC reached 68.2–85.4% of the corresponding value at 28 days, demonstrating its high early strength characteristic. The mix with 1.25% PE and 0.75% BF exhibited the maximum compressive strength at all curing ages. All the mixes consistently demonstrated excellent tensile strength and tensile strain capability (ductility), with the tensile strength and tensile strain capacity of 10.95 MPa and 4.41% achieved for the mix of 2% PE fibre, and 8.49 MPa and 2.43% for the mix of 1.25% PE and 0.75% BF respectively. Moreover, a decline in strength characteristics and strain capacity was observed as BF percentages increased. Scanning electron microscope (SEM) analysis was further employed to investigate the morphological changes in the FRMOC matrix at the microscale to discover the fibre reinforcing mechanism. • Hybrid fibre reinforced MOC (FRMOC) with enhanced strength and ductility is developed. • FRMOC demonstrates high-early-strength characteristic. • Rheological, physical, and mechanical properties were evaluated. • 1.25% PE and 0.75% BF-reinforced FRMOC exhibited maximum tensile strength and strain capacity. • Microstructural analysis is performed to analyse the morphological alterations. [ABSTRACT FROM AUTHOR]

For facilitating carbon utilization and minimizing carbon emission, steel fiber was coated with polyethyleneimine and subjected to a moist condition to capture carbon dioxide, and the CO 2 captured steel fiber (CPSF) was formed, which was used to prepare ultra-high performance concrete (UHPC). After heat curing, compressive strength and splitting tensile strength of UHPC were determined. The results reveal that, compared to the UHPC with polyethyleneimine-coated steel fiber (PSF), the compressive strength and splitting tensile strength of UHPC with CPSF increased by 16.3% and 3.4%, respectively. The microstructural tests including environmental scanning electron microscope, X-ray diffraction and thermogravimetric analysis prove that, under a combined curing of 90 °C hot water and subsequent 200 °C dry-air heating, carbon dioxide chemically combined in the coating of CPSF can be released during the combined curing and react with calcium hydroxide or cement clinkers in the matrix surrounding CPSF to generate calcium carbonate and calcium-silicate-hydrate (C–S–H) gels, which is responsible for both the refinement of microstructure and enhancement of mechanical properties of UHPC. [ABSTRACT FROM AUTHOR]

Polylactide (PLA) represents one of the promising biodegradable polymers with great potential to replace petroleum-derived plastic. In the last decade, massive efforts have been devoted to overcoming the brittleness of PLA, expecting comparable mechanical properties to traditional polyolefin and polyester. Introducing oriented texture into PLA has recently been reported to be an effective approach to improve ductility without sacrificing their high strength. However, the understanding of the mechanism is absent. Herein, we study the fracture behaviors of anisotropic PLA with oriented lamellar crystal by employing operando synchrotron X-ray scattering and diffraction. It has been found that the cavities generated parallel with stress direction can restrain the fast failure of PLA. Nevertheless, the load-carrying ability of oriented PLA lamella is still limited. On this basis, we further introduce the flexible nanofibers into an oriented PLA matrix that enables crystals to effectively participate in the stress dissipation, resulting in significant enhancement of the ductility of PLA while maintaining their high strength. Combined with morphological study by scanning electron microscope, we propose a qualitative model to describe the detailed fracture behavior of PLA with oriented texture, which may provide a reliable theoretical guideline towards further optimization of the mechanical properties of PLA. [Display omitted] • Synchrotron X-ray techniques was used to study the fracture behaviors of PLA. • Cavity along orientation direction plays important role in fracture process. • A new way for enhancing the ductility of PLA while maintaining high strength. [ABSTRACT FROM AUTHOR]

(HfMoTiWZr)C high entropy carbides (HEC) were prepared from the commercial carbide powders of IVB (Hf, Ti, Zr) and VIB (Mo, W) group metals of the periodic table via high energy ball milling (HEBM) and spark plasma sintering (SPS). Metal carbide powders (HfC, TiC, ZrC, Mo 2 C and WC) were HEBM'd for 3 h in a vibratory ball mill, and then SPS'd at different temperatures (1800, 1900, 2000 and 2100 °C). The HEBM'd powders and SPS'd ceramics were characterized in composition, density and microstructure using an X-ray diffractometer (XRD), a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), a particle size analyzer and a pycnometer. Also, microhardness and sliding wear tests were conducted on the SPS'd ceramics. Based on the performed characterization, a single-phase FCC structure was observed at all sintering temperatures indicating a high entropy carbide ceramic, and they all have high hardness and wear resistance values. [ABSTRACT FROM AUTHOR]

Graphene-based nanomaterials possess broad applications because of their excellent multi-functional properties. In this work, a facile self-assembling method was presented for preparing one kind of graphene oxide-based paper/hollow microspheres hybrid. It was found that most of the hollow microspheres can strongly anchored on the surface of graphene oxide paper (GOP) by an in-situ scanning electron microscope peeling testing combining with molecular dynamics (MD) simulation. In addition, the uniform distribution of hollow microspheres on the surface of GOP cannot only provide a better surface wettability, but also can effectively improve the interfacial stress-transfer capability between such hybrid and polymer matrix. Our work provides a guidance for the structural designs of graphene-based nanomaterials and broaden their applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The primary purpose of this work is to study the fabrication of a flexible natural cellulosic fiber composite. In this respect, natural cellulosic fiber was obtained by modified poplar wood fiber through sodium hydroxide (NaOH) and γ-Aminopropyl Triethoxysilan. Then, the composites were fabricated by hot-pressing the modified wood fibers and polyurethane following characterization. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM) observation results confirmed that some of the hemicellulose and lignin were removed from wood fibers after NaOH modification and successfully grafted with alkoxy structures after KH550 modification. NaOH&KH550 modification improved the interfacial compatibility between poplar wood fibers and polyurethane. The flexibility of the composites was improved (the slenderness value was reduced by 113 %), allowing flexible deformations such as bending, twisting, and knotting. In addition, thermal stability, tensile strength (increased by 105 %), elongation at the break (increased by 125 %), and water resistance were increased. This flexible natural cellulosic fiber composite is expected to be applied in the veneering of curved materials and special-shaped structure furniture, providing a theoretical basis for improving the added value of wood-based composites. [ABSTRACT FROM AUTHOR]

As an environmentally friendly material, alkali-activated fly ash-slag (AAFS) is considered as a promising alternative cement because of its excellent mechanical properties and thermal stability. Nevertheless, high temperature induced damage in AAFS can potentially bring serious risks for its practical applications. This paper presents a systematic experimental study on behaviour of AAFS paste subjected to elevated temperatures up to 800 °C in terms of microstructure as well as thermal and mechanical properties. Microstructural evolution was characterised by means of Rietveld-based quantitative X-ray diffraction (QXRD), backscattered scanning electron microscope (BSEM) and X-ray microcomputed tomography (XCT), while thermal and mechanical properties were evaluated from thermogravimetric analysis (TGA), thermal deformation and compressive and flexural strengths. Results indicate that the compressive strength of AAFS paste rises by 77.5 % at 200 °C, followed by a mitigation from 200 to 600 °C and a regain at 800 °C. Different phases in AAFS paste including unreacted particles, reaction products and pores took up 30 %, 67.7 % and 2.31 % at ambient temperature, and 4.95 %, 84.8 % and 10.3 % after exposure to 800 °C, respectively, suggesting the recrystallisation with the formation of nepheline and gehlenite. In addition, the relationships between microstructural characteristics including three-dimensional (3D) pore structure features and thermal and mechanical properties of AAFS paste at elevated temperatures were explored and discussed in depth to gain insights into the underlying degradation mechanisms including pore pressure build-up, thermal gradient and phase transformation. [ABSTRACT FROM AUTHOR]

Melia dubia is a rapidly expanding tree species in southern India, but its main drawback has been limited use in wood-based panel products until recently. To address this research gap, this study aimed to develop three reinforcement materials for producing Reinforced Laminated Veneer Lumber (RLVL) using Melia dubia. Three types of reinforcement materials, chopped glass fiber mat (CGM), glass fiber mesh (GM), and bamboo mat (BM) were employed in two layers to manufacture RLVL. The investigated parameters included physical, mechanical, and bonding performance. Furthermore, morphological images were analyzed using optical and scanning electron microscopes. The research findings revealed that the highest performance was demonstrated by BM, followed by GM and CGM. These results suggest that all three reinforcements enhanced the mechanical properties and overall performance of RLVL. Arranging the reinforcement layers closer to the surface veneer layer in the assembly resulted in outstanding mechanical properties for RLVL. The performance is superior to solid wood made from the same wood species. The findings indicate that RLVL demonstrated superior mechanical properties to laminated veneer lumber (LVL) and solid wood. The modulus of rupture for LVL reinforced with CGM, GM and BM was 7.27%, 30.91%, and 32.73% greater respectively, than that of unreinforced LVL. The composite LVL reinforced with bamboo and glass matting exhibits potential for successful utilization in outdoor structural applications, including beams, rafters, and purlins. • LVL reinforced with CGM, GM, and BM exhibited excellent modulus of rupture. • RLVL demonstrated superior mechanical properties to LVL and solid wood. • LVL reinforced with GM and BM can successfully utilized in outdoor structural applications. [ABSTRACT FROM AUTHOR]

The current investigation aims to choose an alternate potential replacement for the nonbiodegradable synthetic fibers used in polymer composites. This goal motivated the thorough characterization of Rosa hybrida bark (RHB) fibers. The research explored fiber characterization such as morphological, mechanical, thermal, and physical properties. The suggested fiber features a percentage of cellulose, hemicellulose molecules, and lignin of 52.99 wt%, 18.49 wt%, and 17.34 wt%, respectively according to chemical composition studies, which improves its mechanical properties. It is suitable for lightweight applications due to its decreased density (1.194 gcm−3). The purpose of the Fourier transform infrared spectroscope was to observe and record how various chemical groups were distributed throughout the surface of the fiber. The presence of 1.41 nm-sized crystalline cellulose and further XRD analysis showed a crystallinity index of 75.48 %. Scanning electron microscope studies revealed that RHB fibers have a rough surface. According to a single fiber tensile test, for gauge length (GL) 40 mm, Young's modulus and tensile strength of RHB fibers were 6.57 GPa and 352.01 MPa, respectively, and for GL 50 mm, 9.02 GPa and 311 MPa, respectively. Furthermore, thermo-gravimetric examination revealed that the isolated fibers were thermally stable up to 290 °C and the kinetic activation energy was found to be 75.32 kJ/mol. The fibers taken from the Rosa hybrida flower plants' bark exhibit qualities similar to those of currently used natural fibers, making them a highly promising replacement for synthetic fibers in polymer matrix composites. [ABSTRACT FROM AUTHOR]

To improve the low-temperature toughness of epoxy resins, in this study, an epoxy-terminated hyperbranched polysiloxane (EPTS-12) was synthesized and introduced into the epoxy resin as a toughener. The structure of EPTS-12 was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR), and the fractured surfaces of the modified resins were observed by a scanning electron microscope (SEM). With the content of EPTS-12 at 5 wt%, under room temperature (RT) and − 72 °C, the maximum values of elongation at break were 14.19% and 16.06%, increasing by 35.66% and 74.19% respectively. The test results of dynamic mechanical analysis (DMA) also showed that the toughness of the modified epoxy resins was improved. The SEM images of the fractured surfaces of the modified resins were used to investigate the toughening mechanism of the toughener (EPTS-12). With the virtue of a simple synthesis process, low cost, and good reproducibility, this toughener can further expand the application of epoxy resins. [Display omitted] • With 5phr EPTS-12, under RT and − 72 °C, the elongation values were increased by 35.66% and 74.19% respectively. • The dynamic thermomechanical behaviors of the composites were investigated via dynamic mechanical analysis (DMA). • The working mechanism of the toughener was studied by SEM images of the fractured surfaces. • These research results can provide a reference for the design and development of epoxy tougheners. [ABSTRACT FROM AUTHOR]

To obtain a robust diffusion-bonded joint at a relatively low temperature, Nb foil was applied as an interlayer to the diffusion bonding of Zr-4 alloy, and a wide process parameter involving the bonding temperature of 720–820 °C and holding time of 30–120 min was investigated to reveal the evolution of interfacial structure and mechanical properties of the joints. The β-(Zr, Nb) and Widmanstädter microstructure formed at the interface induced by the eutectoid transformation of the diffused Zr and Nb at the bonding temperatures over 740 °C. The phase structure and the thickness of β-(Zr, Nb) layer were not considerably influenced by the increase in diffusion parameters while the Widmanstädter zone thickened significantly. Moreover, the tensile strength and elongation of the resultant joints could be stabilized above 433 MPa and 7.8%, respectively, when the bonding temperature exceeded 760 °C with a holding time of 30 min. By extending the holding time to 60 min at 760 °C, the tensile strength and elongation could reach 454 MPa and 12.6%, respectively, comparable to those obtained at an elevated temperature of 820 °C for 30 min. Additionally, the samples fractured at the diffusion layer were characterized by the in-situ tensile test under the scanning electron microscope, and it was discovered that the crack initiation and propagation process occurred mainly between the β-(Zr, Nb) and Widmanstädter diffusion zone. • The well-bonded Zr-4 joints were achieved by the application of Nb interlayer. • The diffusion layer consisted of β-(Zr, Nb) and Widmanstädter microstructure. • The Nb addition lowered bonding temperature without weakening tensile properties. • The fracture occurred between the β-(Zr, Nb) and Widmanstädter diffusion zone. [ABSTRACT FROM AUTHOR]

The surface topography and interface characteristics play a significant role in determining the mechanical properties of carbon fiber reinforced polymer (CFRP) composites. These features are primarily influenced by the surface chemical structures and their interactions with the matrix resin. Here, we developed a rigid-flexible coating consisting of polyetheramine (PEA) and polydopamine (PDA) on the fiber surface to control the interface and improve the mechanical properties of CFRPs. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrum (FT-IR) results validated the successful introduction of polymeric chains and fiber surface characteristics including rough surfaces, slim polymer layers and uniform dots were examined by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Contact angle tests indicate that the functionalized coating noticeably enhances the interaction force between carbon fibers, promoting improved wettability by the matrix resin. The bending and interlaminar shear strength of CFRP prepared by functional carbon fiber are increased by 45.76 % and 47.63 %, respectively. The drop weight impact (DWI) test confirms the positive effect of improved interfacial properties on the out-of-plane impact resistance of CFRPs. [Display omitted] [ABSTRACT FROM AUTHOR]

This study aims to evaluate the effect of using single and combined marble dust (MD), granite dust (GD) and nano alumina (NA) on the performance of Portland cement concrete. MD and GD were separately replaced by different percentages of cement (2, 4, 6, 8 and 10 wt%). Furthermore, NA was used as addition by different percentages (0.25, 0.5, 0.75, 1.0 and 1.25 wt%) in the individual mixtures. The optimal ratios for MD, GD and NA were used to design two concrete mixtures with combined 6%MD+ 1%NA and 6%GD+ 1%NA. The physical properties (consistency, initial and final setting times), the workability (slump cone test), the mechanical properties (compressive, splitting tensile and flexural strengths) and microstructure analysis (X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray (EDX)) were carried on the single and combined mixtures in addition to control mix. Results revealed a rise in the water quantity needed to achieve standard consistency, along with a reduction in both initial and final setting times, as the content of GD and NA increased. However, in comparison to the control mix, minor effects in the consistency or the setting times was observed when various MD contents were used. Regarding workability, its consistently decreased in all cases in correlation with the surface area of the materials utilized. The highest reduction was observed when employing NA, characterized by the largest surface area, followed by GD, and then MD, which had a marginal effect on workability. For hardened concrete, there was an improvement in strengths of samples with replacing individually MD and GD content up to 6% at all curing ages, followed by a decrease in strengths when the content reached 10% of cement replacement compared to control sample. Concrete mixtures with addition of NA showed significant improvement in strengths at all percentages of addition until reached the maximum increase in strength at 1% then slightly decreased. Concrete with combined (6%MD+1%NA) and (6%GD+1%NA) show significantly improved mechanical properties and compact microstructure enriched with C-S-H in comparison to concrete samples using 6%MD, 6%GD and 1%NA separately. • The water of consistency increased while the initial and final setting times were shortened. • The workability of concrete was significantly diminished by NA particles. • An improvement in strength was recorded for the combined use of 6% MD and 1% NA. • An enhancement of flexural and tensile strength was attributed to the individual use of MD, GD, and NA additives. • The results of EDX analysis confirmed that lower Ca/Si ratio led to higher mechanical properties. [ABSTRACT FROM AUTHOR]

To realize the application of xylan based film in food and drug packaging, the poor mechanical property and film-forming property of xylan based film must be overcome. Herein, a good oxygen barrier composite film with desired mechanical properties was prepared based on carboxymethly xylan (CMX), chitosan (CS), and graphene oxide (GO). The results of scanning electron microscope revealed the composite film had a dense and continuous structure, which will endow the composite film with excellent mechanical property. As expected, the composite film with the 0.5% mass fraction of GO exhibited best mechanical property, among which the tensile stress, tensile strain, and Young's modulus of the composite film reached 50.81 MPa, 47.61%, and 1.39 GPa, respectively. The oxygen barrier properties of the composite films significantly increased with the addition of graphene oxide due to the dense, stacked multilayer structure. In addition, these composite films exhibited good antibacterial properties. Therefore, these films show great promise in the field of food packaging and wound dressing due to their excellent mechanical, oxygen barrier and antibacterial properties. • Flexible composite films based on CMX, CS, and GO prepared by casting method. • Desired mechanical properties of the composite films were obtained by adding GO. • The composite films exhibit good oxygen barrier and antibacterial properties. [ABSTRACT FROM AUTHOR]

During the selection of materials for anti-lithium ion corrosion, magnesium aluminate spinel has been found to have good corrosion resistance and low cost. During the preparation of light-weight spinel ceramics, it is considered to be kiln body material. In this work, spinel bubbles were prepared using electrofusion injection process. Bulk density, volume density and pressure resistance of spinel bubbles in different particle sizes were counted. Light-weight spinel bubble ceramics with different densities were prepared by using electrofused spinel bubbles as light aggregates and using ρ-Al 2 O 3 and caustic burnt magnesia powder as matrix powders. The microstructure of spinel bubbles with different particle sizes and light spinel ceramics was analyzed using scanning electron microscope. Results show that the spinel bubble has complete structure, good sphericity, perfect grain crystallization, and clear edges and corners. Although there are some fine cracks and cavities, grains are tightly bound. Compressive strength and bending strength of light-weight spinel ceramics, whose density were found to lie within the range of 0.99–1.63 g cm−3, were found to be 5.19–36.33 MPa and 3.48–12.84 MPa, respectively. [ABSTRACT FROM AUTHOR]

In this work, the properties of yttria-stabilized zirconia-based ceramics, Y-TZP containing Fe 2 O 3 as coloring agent were evaluated. Nanoparticled powder of 3Y-TZP (ZrO 2 - 3 mol.% Y 2 O 3) doped with different amounts of Fe 2 O 3 (0.002–0.136 wt%) were compacted into monolithical or multilayered samples and sintered at 1475 °C - 2 h. The samples were characterized by X-ray diffraction analysis (XRD), relative density, scanning electron microscope (SEM). Hardness and fracture toughness in the color interface were investigated using the Vickers indentation method and the biaxial flexural strength was determined by the piston on 3 balls method (P–3B). Furthermore, optical parameters were measured using spectrophotometry in regard to sample thickness and Fe 2 O 3 content. The results indicated a good adhesion between layers, proven by indentation cracks randomly growing between different regions, because the powders used produced very similar morphological characteristics. The different amounts of Fe 2 O 3 studied in this work did not interfere in densification, phase composition, or microstructure of the sintered ceramics. The fracture toughness and flexural strength did not significantly change due to the addition of Fe 2 O 3 , presenting values close to 7 MPa m1/2 and 1120–1150 MPa, respectively, in all studied compositions. On the other hand, increasing Fe 2 O 3 contents lead to an increase in the hardness of the material (1280–1330 H V), and higher contrast ratios (CR) with a consequent loss of translucency. Color variation (ΔE) depended also on the thickness of the material. [ABSTRACT FROM AUTHOR]

• The optical and mechanical properties of pure zirconia are affected by low temperature degradation. • First and second generation 3Y-TZP subjected to autoclave aging undergoes significant t-m phase transformation. • t-m Phase transformation in ZTA composites is limited after hydrothermal aging. • ZTA's optical and mechanical properties remain stable after aging. To synthesize a zirconia toughened alumina (ZTA) composite with 70% alumina reinforced by 30% zirconia for dental applications and to characterize its microstructure and optical properties for comparison with the isolated counterpart materials and a first-generation 3Y-TZP. Disc-shaped specimens were divided in four groups (n = 70/material): (1) 3YSB-E (first generation 3Y-TZP), (2) Zpex (second generation 3Y-TZP), (3) alumina, and (4) ZTA-Zpex 70/30. After synthesis, ceramic powders were pressed, and green-body samples sintered following a predetermined protocol. Specimens were polished to obtain a mirror surface finish. Apparent density was measured by Archimedes principle. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the crystalline content and microstructure. Reflectance tests were performed to determine the contrast-ratio (CR) and translucency-parameter (TP). Mechanical properties were assessed by biaxial flexural strength (BFS) test. All analyses were conducted before and after artificial aging (20 h, 134 °C, 2.2 bar). Optical parameters were evaluated through repeated-measures analysis of variance and Tukey tests (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). High density values (95–99%) were found for all ceramic materials and SEM images exhibited a dense microstructure. While XRD patterns revealed the preservation of crystalline content in the ZTA composite, an increase in the monoclinic peak was observed for pure zirconias after aging. Significantly higher CR and lower TP values were observed for the ZTA composite, followed by alumina, 3YSB-E, and Zpex. The highest characteristic stress was recorded for 3YSB-E, followed by intermediate values between ZTA and Zpex, and the lowest for alumina. Aging affected the optical and mechanical properties of both zirconias, while remained stable for ZTA composite and alumina. The synthesis of experimental 70−30% ZTA composite was successful and its relevance for dental applications relies on its higher masking ability, aging resistance, and strength similar to zirconia. [ABSTRACT FROM AUTHOR]

To control food contamination and meet the growing demand for high quality food, a novel and excellent starch composite film as packing material with optimized physical, mechanical properties and antimicrobial activity was produced in this paper. Starch-based composite films incorporated with salicylic acid (SA) and waxy maize starch nanoparticles/κ-carrageenan (WMSNs/KC) were used to achieve antimicrobial activity and improve the mechanical properties. WMSNs were fabricated through enzymolysis and recrystallisation method, followed by individually adding KC to form WMSNs/KC by self-assembly, and used as a nanofiller and stabilizer to be incorporated into hydroxypropyl tapioca starch-based films at a concentration of 0–9%. Characterization of macromorphology and scanning electron microscope indicated the starch composite films with WMSNs/KC were smooth, uniform, and transparent. X-ray diffraction pattern and Thermogravimetric analysis also showed strong interactions such as hydrogen bond formation among films, WMSNs/KC and SA. Compared with the pure starch-based films, the composite films reinforced by the addition of WMSNs/KC significantly increased the tensile strength, water vapor barrier and thermal stability, while the transparency and elongation at break decreased slightly. Moreover, the starch composite films showed excellent antimicrobial activity for three typical undesired microorganisms in foods, Escherichia coli , Staphylococcus aureus , and Bacillus subtilis. • Novel antibacterial and biodegradable starch composite films were proposed. • Mechanical properties, water vapor barrier of our films were reinforced by WMSNs/KC. • For the first time, starch-based films with SA achieved antimicrobial activity. • Substantial bacteriostatic effect was obtained in yogurt in contact with our films. • This product was nontoxic, edible and could extend the shelf life of food. [ABSTRACT FROM AUTHOR]

In this study, briquettes of Ti–TiB–TiB 2 composite were produced by mixing Ti and B powders, performing self-propagating high-temperature synthesis process and by applying hydrostatic pressure on the reaction products with a high-capacity press. Ti–TiB–TiB 2 was then coated to Ti 6 Al 4 V substrate by Electro-Spark Deposition (ESD) technique under two atmospheres of air and argon, single and double-layer coatings and in two energy levels of 40 W and 110 W as input powers. Coatings microstructure were examined by Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS) analyzer. Comparison of the coatings microstructure with the electrode microstructure shows that the coatings have a much finer microstructure than that of the electrode due mainly to the high solidification rate in the ESD process. Microstructural observations also revealed that the main phases in the coatings are needle-shaped TiB and particle-shaped TiB 2 in the Ti matrix. The coating microstructure was much finer due to an increase in solidification rate by reducing the input power from 110 to 40 W. In such a situation, two phases of TiB 2 and TiB with nanometer sizes were scattered in the Ti matrix. Also, due to the trapping of the gases in low input power of 40 W, a limited number of very small gas pores was created in the microstructure. Interface examination of the coating and the substrate by the Line Scan and X-ray Image show a good coherence of the coating with the substrate. Adhesion results showed that the bond strength between the coating and the substrate was higher than 50 MPa in all coatings. No crack was observed in the coatings after bending tests which were performed, in accordance with the intended standard, on the samples around a mandrel. The hardness of all coatings was increased with decreasing the input energy from 110 to 40 W. [ABSTRACT FROM AUTHOR]

The impact of the microstructural properties of alumina on its mechanical properties is examined in this study. Furthermore, a comparison of the mechanical behaviours of alumina samples obtained by two-step and existing sintering techniques is presented. The results are rationalised by evaluating the changes in the densities and grain sizes of alumina samples. Different two-step treatments were used on commercial alumina (99.7 mass%-Al 2 O 3 content, 0.73 μm average particle size) and compared with the existing sintering technique. Alumina powder was formed by uniaxial pressing, and the samples were treated using heat. Microstructural analyses of the samples were performed with a scanning electron microscope. The mean grain size was determined via the intercept method. Porosity was determined by the relationship between the apparent and theoretical densities of the sintered alumina. The bending strength test was performed based on ASTM 1161–13. Fracture toughness was measured based on the notch method. The microhardness test was performed using the Knoop technique. The results showed that mechanical properties of the samples prepared using two-step sintering were improved—the bending strength, fracture toughness, and Knoop microhardness increased from 286 to 303 MPa, 4.09–4.35 MPa m0.5, and 17.5–17.6 GPa, respectively—compared with those fabricated using the existing sintering technique, even with a higher porosity of 2.36% in samples obtained by two-step sintering and 1.80% in the existing sintering technique. Factorial analysis demonstrated that the temperature and holding time of the second step individually affect the relative density; however, the impact of temperature is more significant. Despite this, the interaction between temperature and holding time of the second step has the most significant impact on the average grain size. [ABSTRACT FROM AUTHOR]

• Acid treatment changed the pore structure of coal and increased the porosity. • Acid treatment reduces the residual energy in coal, and weakens the impact tendency. • Compared with raw coal, acidized coal is easier to form fracture network under axial load. • Acidified coal shows a special stress-strain curve. To explore the influence of acid solution with different components on the pore structure and mechanical properties of coal, nuclear magnetic resonance (NMR), scanning electron microscope (SEM), energy dispersion spectrum (EDS) and uniaxial compression experiments were used to analyze the acid-treated coal samples. The results show that acid treatment can obviously improve the connectivity of coal, increase the porosity of coal, and is conducive to the circulation and diffusion of gas, but the promotion effect of acid solutions of different components on pores with different pore sizes is different. After acid treatment, the number of mineral particles on the surface of the coal samples are obviously reduced, and the space filled with mineral particles is gradually exposed, thus increasing the density of pores and fractures of the coal samples. The energy spectrum analysis shows that acid solution added HF has a good removal effect on kaolinite minerals, iron minerals and calcite minerals. For the mechanical properties of the coal samples, acid treatment can reduce the strength and elastic modulus of coal samples, but increase its toughness. In addition, the fracture evolution of the acid-treated coal samples mainly goes through four stages: initial stage, transition stage, expansion stage and destruction stage. Because most of the energy accumulated in the acid-treated coal samples is used to damage the coal body, the acid-treated coal samples are easy to form fracture network, and is mostly broken in blocks when unstable. [ABSTRACT FROM AUTHOR]

To promote the densification and therefore the mechanical properties of boride-based ceramics, MgO was added as sintering aid into Os 0.9 Re 0.1 B 2 powders for densification by using spark plasma sintering (SPS). The Os 0.9 Re 0.1 B 2 powders were synthesized by mechanochemical method from powder mixture of Os, Re and amorphous B. The role of MgO on densification, phase composition, microstructure and mechanical properties (hardness, fracture toughness and wear behavior) were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS), micro indentation and ball-on-disk tribometer. The results show that, with the introduction of MgO as sintering aid, the relative density of the Os 0.9 Re 0.1 B 2 ceramic samples increased. When the MgO content reached 9 wt%, the as-sintered sample is almost fully dense. No obvious regularity was found from the samples with the addition of different content of MgO. Vickers hardness values of the samples with 0, 3 wt% and 9 wt% MgO are found to be very close with each other within the experimental error (~30 GPa), while the sample with the addition of 6 wt% MgO exhibits the highest hardness of ~35 GPa. The fracture toughness of the samples is decreased slightly with the addition of MgO. The friction coefficient and wear rate of the sample with the addition of 6 wt% MgO was also found to be the lowest among all samples, which indicate best wear resistance. As a whole, with the addition content of 6 wt% MgO, the Os 0.9 Re 0.1 B 2 ceramic sample performs relatively excellent mechanical properties among four groups of samples. [ABSTRACT FROM AUTHOR]

To enhance the fracture toughness and thermal shock resistance of the thermal barrier coatings (TBCs), detonation spraying has been used to prepare modified neodymium (Ⅲ) oxide (Nd 2 O 3)-doped yttria-stabilized zirconia (YSZ) TBCs containing 20 vol% (D1 coating) and 30 vol% (D2 coating) of boron nitride whiskers (BNws). Analyses were performed using a scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and a microhardness tester to examine the manner in which the doping content of different rare earth oxides affected the coating morphology, composition, and mechanical properties. The results denoted that the porosity of the D2 coating was 47.9% higher than that of the D1 coating; the whisker content was 30 vol% in the former and 20 vol% in the latter. The increased porosity reduced the microhardness and bond strength of the coating. However, the fracture toughness (KIC) of the D2 coating was increased to 2.67 MPa·m1/2 because the whisker content was 8.5% higher than that in the D1 coating. The thermal cycling life of the D2 coating was 245 cycles, and its thermal shock resistance was 9.9% higher when compared with that of the D1 coating. A TBC with better overall performance was obtained when BNw reached 30 vol%. [ABSTRACT FROM AUTHOR]

This study compared the physical properties of conventional and monolithic yttria-zirconia (Yz) materials after low-temperature degradation (LTD). Bar-shaped specimens (2.0 mm thick × 4.0 mm wide × 16.0 mm in length) were produced. Autoclave aging was executed at 134°C under 2 bar pressure for 5 h. The surface characteristics were assessed using a confocal laser microscope, microstructural phase alterations via an X-ray diffractometer (XRD), 3-point flexural strength using a universal testing machine, Vickers microhardness via a digital microhardness tester, and toughness using a durometer. Fractured specimens and indented surfaces was observed via a scanning electron microscope for fractography characterization. All of the data underwent specific statistical tests considering their distribution and homogeneity. Regarding topography, different Yz materials were very similar after LTD. Conventional Yz materials were smoother. The XRD data support that both materials were mainly composed of tetragonal crystals, whereas slight monoclinic peaks were detected. Monolithic Yz showed higher flexural strength than conventional Yz. All of the fractures started on surface defects at the side where tensile stress was concentrated (opposite to load application) and propagated to the opposite side. Vickers microhardness and toughness analysis found that conventional Yz had higher performance than monolithic Yz. This study has found that there are slight differences in strength, hardness, and toughness between conventional and monolithic yttria-stabilized zirconia ceramics, although both materials demonstrate adequate performance for clinical use. [ABSTRACT FROM AUTHOR]

In this study, the preparation and consolidation of nanocrystalline LaB 6 powders originating from powder blends of La 2 O 3 , B 2 O 3 and Mg were reported. A consecutive route of mechanochemical synthesis (MCS) and purification was utilized for the achievement of nano-sized LaB 6 powders. As-synthesized powders were leached out from intermediate reaction products or impurities. Then, a sequential step of cold pressing (uniaxial pressure at 800 MPa) and pressureless sintering (at 1700 °C for 5 h under Ar gas flow) were utilized for the consolidation of the purified LaB 6 powders. The type of mill (vibratory and planetary high-energy ball mills) was employed as a MCS parameter to reveal its effect on the physical, microstructural and mechanical properties of the LaB 6 powders, and their bulk structures. Compositional, physical and microstructural properties of the products after powder processing were determined via X-ray diffractometer (XRD), particle size analyzer (PSA), differential scanning calorimeter (DSC), stereomicroscope (SM), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS) coupled with both SEM and TEM, and vibrating sample magnetometer (VSM). The bulk properties of the LaB 6 consolidated from nanocrystalline powders with a minimum 99.99% purity, and ∼62 nm (for vibratory ball mill) or ∼74 nm (for planetary ball mill) average particle size were compared according to various properties. LaB 6 powders were synthesized in planetary mill at an approximately six times longer duration than that of in vibratory mill. According to the results, density, surface area and mean particle size values of the vibratory ball-milled samples (containing paramagnetic powders) are better than those of planetary ball-milled (containing diamagnetic powders) ones. However, mechanical properties such as hardness, surface roughness, wear rate, friction coefficient, and also electrical conductivity were improved in the planetary ball-milled LaB 6 bulks. [ABSTRACT FROM AUTHOR]

Glow discharge plasma (GDP) was used to modify chitosan films to obtain desirable properties. The chitosan films were treated with GDP of 0–800 W for 1 min, respectively. The molecular structure of chitosan films changed under GDP treatment. Chitosan films showed an enhancement of crystallinity with the increasing power of GDP, and the GDP treatment provided them with higher thermal stability, manifested as the exothermic peaks shifted from 291.5 °C (0 W) to 294.1 °C (800 W). Scanning electron microscope (SEM) indicated that the surface of chitosan films got rougher with 0–600 W GDP treatment, accompanied by the increase of tensile strength (TS), and the TS did not increase with the 800 W GDP treatment. However, the water vapor permanent (WVP) became higher with GDP treatment. GDP treatment also exhibited influence on chromatic aberration of chitosan films. GDP is proved to be a promising green, pollution-free, rapid technology to modify chitosan films. [ABSTRACT FROM AUTHOR]

• Tetraethylorthosilicate sol-gel and silane combination treatment is used. • The reinforcing effect of fibers in composites is improved. • Combination treatment shows the highest interfacial shear strength. • Thermal properties of the modified fiber composites are improved. In order to prepare high performance sisal fiber reinforced polypropylene composites, this paper pays special attention to the changes of intrinsic mechanical properties of the sisal fiber so as to achieve the maximum reinforcing effect of the fiber. For achieving this aim, the sisal fibers were modified by tetraethylorthosilicate (TEOS) sol-gel method to form SiO 2 -based organic-inorganic hybrid materials. For a better result, a novel combined modification method by TEOS precursor solution and γ-aminopropyltriethoxysilane solution for the fibers was put forward and performed. Then the relevant mechanism was also analyzed in detail. The corresponding composites were prepared by melt blending with polypropylene matrix and polypropylene-graft-maleic anhydride (MAPP) compatibilizer, and the interfacial and mechanical properties of composites were studied by single fiber fragmentation test and mechanical test, respectively. The results show that the mechanical and thermal properties of the modified fiber composites are improved compared with the untreated fiber composite. The combined modification composite presents the highest interfacial shear strength, which increases by 259.49% compared with the untreated fiber composite. A good interfacial bonding is obviously observed in the combined modification composite by the analysis of scanning electron microscope (SEM). The tensile strength and modulus of the composite with the combined treatment (20 wt% fiber loading) increase by 21.72% and 28.18%; the flexural strength and modulus increase by 3.61% and 16.02%; and the impact strength increases by 21.28%. [ABSTRACT FROM AUTHOR]