Room-temperature fracture along the (111) plane of silicon is probed at the micron-scale using chevron notched cantilever beams that enable stable crack growth before unstable fracture in successful tests. The main experimental observation is that a growing crack can extend and arrest at different stress intensity factor values within the same specimen. The present data thus provide evidence of variations in the effective Si fracture toughness along the path of a growing crack. This effect could be explained by variations in the extent of limited cracktip plasticity along the crack path. The present work also shows that the microscopic chevron notch test is, from an experimental point of view, an inconvenient method to probe the fracture toughness of silicon because it is difficult with silicon to nucleate a crack at the chevron tip at loads low enough to allow for subsequent stable crack growth.

This article provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if the same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.

Nb-based silicides are promising ultrahigh-temperature materials. However, the structural stability and mechanical properties of Nb-based silicides are markedly influenced by Nb3Si phase. Therefore, the improvement of the stability and mechanical properties of Nb3Si is a great challenge. To solve these key problems, in this work, we apply the first-principles calculations to investigate the influence of transition metals (TM = Mo, Re, Ta, W, Pt, and Ir) on the structural stability, mechanical, and thermodynamic properties of Nb3Si. Two possible doped sites: Nb site and Si site are considered. We find that these alloying elements not only can stabilize the Nb3Si phase but also effectively improve the mechanical properties of Nb3Si. The calculated electronic structure shows that high elastic modulus is attributed to the formation of the TM–Si bond. Importantly, these alloying elements improve the heat capacity of Nb3Si due to the vibration of TM atoms under high temperature. Therefore, our calculated results predict that alloying elements of Re and Ir are beneficial for improving the overall performances of Nb3Si.

A new plasmonic photocatalyst Ag/Bi7Ta3O18 was fabricated by photodeposition-hydrothermal method. The phase composition, microstructure, surface areas, average pore size, UV-vis diffuse reflection spectra, and photocatalytic activities of composite photocatalysts were investigated in detail. The results of the measurements indicated that the Ag0 nanoparticle successfully loads on the surface of Bi7Ta3O18, and the 0.06 Ag/Bi7Ta3O18 photocatalysts exhibited the best photocatalytic activity for the degradation of Rhodamine B (RhB). The improved photocatalytic activity could be contributed to the localized surface plasmon resonance caused by the collective oscillation of the surface electrons of Ag nanoparticles. Additionally, the photocatalytic reaction mechanism was studied by photoluminescence photocurrent, and electron spin resonance analysis. As a result, the Ag nanoparticles onto the Bi7Ta3O18 surface enlarged the electron–hole separation, and the (˙OH) was the dominated active species of degradation RhB in the photocatalytic process.

This research was designed for the first time to investigate the photocatalytic activities of MoO3/g-C3N4 composite in converting CO2 to fuels under simulated sunlight irradiation. The composite was synthesized using a simple impregnation-heating method and MoO3 nanoparticles was in situ decorated on the g-C3N4 sheet. Characterization results indicated that the introduction of MoO3 nanoparticles into g-C3N4 fabricated a direct Z-scheme heterojunction structure. The effective interfacial charge-transfer across the heterojunction significantly promoted the separation efficiency of charge carriers. The optimal CO2 conversion rate of the composite reached 25.6 μmol/(h gcat), which was 2.7 times higher than that of g-C3N4. Additionally, the synthesized MoO3/g-C3N4 also presented excellent photoactivity in RhB degradation under visible-light irradiation.

Copper(II) oxide (CuO) nanoparticles (NPs) in two different morphologies, spiky and spherical, were synthesized on zeolite-Y by a modified impregnation method, and their CO2 adsorbing capabilities were investigated under standard conditions (1 atm and 298 K). The properties and CO2 adsorption performances of the hybrid systems were characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, atomic absorption spectroscopy, and Brunauer–Emmett–Teller analyses. The microscopy analyses showed that spiky nanostructures have a length of approximately 450 nm, and the spherical ones are approximately 18 nm in diameter. Quantitative analyses demonstrated that CuO NPs in both morphologies on the zeolite surface led to an improvement in their CO2 adsorption capacities. This enhancement is mainly due to the higher CO2 chemisorption capability of CuO NP–zeolite systems compared to that of bare zeolite. The presence of spiky and spherical CuO NPs on the zeolite surface resulted in increases of 112% and 86% in the amount of chemisorbed CO2 on the zeolite-Y surfaces, respectively.

U60 ([UO2(O2)(OH)]60 60− in water) is a uranyl peroxide nanocluster with a fullerene topology and O h symmetry. U60 clusters can exist in crystalline solids or in liquids; however, little is known of their behavior at high pressures. We compressed the U60-bearing material: Li68K12(OH)20[UO2(O2)(OH)]60(H2O)310 ( $Fm\bar 3$ ; a = 37.884 Å) in a diamond anvil cell to determine its response to increasing pressure. Three length scales and corresponding structural features contribute to the compression response: uranyl peroxide bonds (<0.5 nm), isolated single nanoclusters (2.5 nm), and the long-range periodicity of nanoclusters within the solid (>3.7 nm). Li68K12(OH)20[UO2(O2)(OH)]60(H2O)310 transformed to a tetragonal structure below 2 GPa and irreversibly amorphized between 9.6 and 13 GPa. The bulk modulus of the tetragonal U60-bearing material was 25 ± 2 GPa. The pressure-induced amorphous phase contained intact U60 clusters, which were preserved beyond the loss of long-range periodicity. The persistence of U60 clusters at high pressure may have been enhanced by the interaction between U60 nanoclusters and the alcohol pressure medium. Once formed, U60 nanoclusters persist regardless of their associated long-range ordering—in crystals, amorphous solids, or solutions.

A new waterborne acrylic (WAC) hybrid adhesive was evaluated for an untreated polypropylene lamination. The WAC hybrid adhesive was formulated with a new class of porous clay heterostructure (PCH), which was modified with 3-(trimethoxysilyl)propyl methacrylate (as a coupling agent) to promote chemical bonding with the acrylic matrix to form a methacrylate-functionalized PCH (MPCH). The WAC hybrid adhesive was based on copolymers (2-ethylhexyl acrylate, ethylene glycol methyl ether acrylate, 2-(hydroxyethyl) methacrylate, styrene and acrylic acid) with varying amounts of MPCH. The scanning electron microscopy micrographs revealed the presence of a well dispersed MPCH distributed throughout the matrix. The optimal adhesive performance, in terms of the 180° peel strength of bonded joints, of 140.2 N/m was achieved using 1.5 wt% of MPCH, while the thermal stability of the adhesives was improved with increasing MPCH loading levels.

Polyurethane-based bioadhesive was synthesized with polyols derived from castor oil (chemically modified and unmodified) and hexamethylene diisocyanate with chitosan addition as a bioactive filler. The objective was to evaluate the effect of type of polyols with the incorporation of low-concentrations of chitosan on the mechanical and biological properties of the polymer to obtain suitable materials in the design of biomaterials. The results showed that increasing physical crosslinking increased the mechanical and adhesive properties. An in vitro cytotoxic test of polyurethanes showed cellular viability. The biocompatibility of the polyurethanes favors the adhesion of L929 cells at 6, 24, and 48 h. The polyurethanes showed bacterial inhibition depending on the polyol and percentage of chitosan. The antibacterial effect of the polyurethanes for Escherichia coli decreased 60–90% after 24 h. The mechanical and adhesive properties together with biological response in this research suggested these polyurethanes as external application tissue bioadhesives.

Microstructure and mechanical properties of Mg–0.43Nd–xY–0.08Zn–0.11Zr (x = 0, 0.03, 0.06, and 0.12 at.%) alloys were investigated. The results indicated that Mg24Y5 phase was formed in the as-cast Y-containing alloys, the grains were refined and the amount of needle-like Mg12Nd phase in the α-Mg grain interior was increased with increasing Y addition. After solution treatment, the Mg24Y5 phase and needle-like Mg12Nd phase nearly completely dissolved into the α-Mg matrix and long-rod-like Zn2Zr3 phase occurred. The amount of Zn2Zr3 phase was increased with increasing Y content after age treatment. Mg–0.43Nd–0.12Y–0.08Zn–0.11Zr alloy exhibited the best combination of strength and elongation in all conditions, especially in the temperature range of 200–300 °C, and an Arrhenius model was established to study the plastic flow behavior. The improvement in mechanical properties was attributed to the grain refining, solution strengthening and enhanced precipitation hardening of Zn2Zr3 phase and β-type phase.

Nine possible native point defects in MgCaSi have been studied by employing density functional theory based ab initio calculations. The complex chemical potential limits are first determined using a two-dimension (∆μMg, ∆μCa) diagram, then the defect formation energies as a function of the atomic chemical potential are gained. The energetic results show that under Mg-rich conditions, the most favorable defect is MgCa rather than MgSi, while CaMg is predominant compared to CaSi under Ca-rich conditions. The bonding energy is first introduced to uncover the intrinsic feature of defect formation energy. The local geometric distortion around CaMg, MgSi, and CaSi antisite defects gradually increases due to the smaller atomic radii from Ca to Mg and Si, showing the important role of the geometrical mismatch. The density of states indicates that the higher stability of CaMg and MgCa originates from the smaller deviation of the Fermi level from the pseudo-gap.

Magnesium alloys with the lowest structural density exhibit unique applications in the automotive and aerospace fields. Rare earth addition is a promising method to enhance the mechanical properties of the Mg alloys. In the present study, the magnesium–aluminium (Mg–9Al) alloy containing varying wt% of gadolinium (Gd) is synthesized using the casting technique. The microstructure, mechanical, corrosion, and wear properties of the developed Mg–9Al–xGd alloy are evaluated and compared to the base Mg–9Al alloy. Microstructural investigation shows significant grain refinement and the presence of Al2Gd in addition to β-Mg17Al12 in the Gd-added alloys. Under tensile loads, the developed Mg–9Al–2Gd alloy exhibits enhancements in ultimate and yield strengths. The corrosion resistance of the alloys is found to increase with increasing Gd content and is optimal at 2 wt%. Considering the higher hardness and dispersity of the Al2Gd phase, Mg–9Al–2Gd has exhibited a higher wear resistance than that of the as-cast Mg–9Al alloy.

Boron nitride nanotube (BNNT) reinforced titanium (Ti) matrix composites were prepared using the cold press-and-sinter method. In the composite sintered at 800 °C for 1 h, BNNTs were homogeneously distributed in the Ti matrix and restricted the growth of Ti grains. The compressive strength of the as-sintered Ti–4 vol% BNNT composite achieved 985 MPa at room temperature versus 678 MPa without the BNNT reinforcements. The highest compressive strength of 277 MPa at 500 °C was obtained from the Ti–5 vol% BNNT composite. When sintered at 1000 °C, chemical reactions occurred between Ti and BNNTs leading to the formation of the interfacial TiB phase, which serves as a strong binding between BNNTs and the Ti matrix. The reinforcements were attributed by a mixture of BNNTs and TiB after sintering at 1000 °C for 3 h. However, no BNNT was observed in the microstructure after sintering at 1100 °C for 3 h due to complete transformation into TiB whiskers.

MgO/Cu composites containing a 1.0% volume fraction of MgO particles were prepared by internal oxidation and powder metallurgy, respectively. The interfacial bonding state between the MgO particles and Cu matrix was characterized by scanning electron microscopy and transmission electron microscopy. The effect of the MgOp/Cu interfacial bonding state on the arc erosion resistance of the MgO/Cu composites was investigated, and the arc erosion resistance was examined using a JF04C electrical composite testing system. The results indicate that the 1.0 vol% MgO/Cu composite with a semicoherent MgOp/Cu interface experiences a lower arc erosion rate and smaller fluctuations of arcing energy than those of the 1.0 vol% MgO/Cu composite with an incoherent MgOp/Cu interface. Erosion morphology observations further indicate that a solid to liquid phase transformation occurs under arcing and MgO particles dispersed in the molten copper both prevent the copper matrix from splashing and enhance the arc erosion resistance of the MgO/Cu composites. While the shallow electric erosion pits are distributed uniformly on the arc surface of the MgO/Cu composites with a semicoherent interface, the MgO/Cu composite with an incoherent interface has deep and uneven pits on its arc surface, characterized by large electric erosion molten droplets.

Laminate sheets attract increasing attention from researchers and engineers. In this paper, Al/Ti/Al laminate sheets were fabricated by using cryogenic roll bonding for first time. The edge defects, mechanical properties, and interface bonding of laminate sheets by cryogenic roll bonding technique were compared with these by room-temperature roll bonding technique. Results show that there are some edge cracks in laminate sheets by room-temperature roll bonding while they do not appear when subjected to cryogenic roll bonding. The ultimate tensile stress of laminate sheets by cryogenic roll bonding increases up to 36.7% compared to that by room-temperature roll bonding. When laminate sheets are rolled to 0.125 mm from 2.025 mm, the interfaces between Al and Ti layers are bonded well for both cryogenic roll bonding and room-temperature roll bonding. Finally, we discussed the improvement in edge quality and mechanical properties and the mechanism of interface bonding of Al/Ti/Al laminate sheets during cryogenic roll bonding.

Oxygen is known to have a significant impact on the strength of Ti alloys, whereas it can also reduce the ductility substantially. Thus, the usage of oxygen to strengthen Ti is restricted in the industry. In this study, we rekindled the research of oxygen behavior in Ti with the purpose of developing Ti alloys with high strength and suitable ductility by using no expensive and poisonous element. To this end, experiments of producing high performance commercially pure Ti using only oxygen solid solution were carried out. The oxygen element was introduced into the Ti by two different powder metallurgy methods. The microstructural examination and mechanical test were performed for the samples, which indicated a strong hardening effect of oxygen in spite of the processing routes. Most importantly, the results suggested that a high elongation to failure of over 20% can still be obtained in the samples having yield stress over 800 MPa, up to an oxygen content of 0.8 wt%, which is far beyond the previously recognized limit.

The hot deformation behavior of Nb–V–Ti microalloyed ultra-high strength steel was investigated by isothermal compression at 900–1200 °C with strain rates from 0.01 to 10 s−1. The microstructure evolution and precipitation behavior were studied using an optical microscope and a transmission electron microscope Results indicate that the peak stress of experimental steel increases with increasing the strain rate and decreasing the deformation temperature. The constitutive equation of hot deformation was developed with the activation energy Q being about 407.29 kJ/mol. The processing maps were also obtained to identify the instable regions of the flow behavior and to evaluate the efficiency of hot deformation. The size of dynamically recrystallized grains increases gradually with a decrease in the strain rate. Three types of carbides were identified, namely M3C, rich-Ti MC, and rich-Nb MC. With the increase of the deformation rate, the amounts of carbides increase, and the average sizes of the carbides decrease gradually.