Novel microencapsulated n-octadecane with natural silk fibroin (SF) shell attached with silver nanoparticles (AgNPs) on its surface was synthesized in oil-in-water emulsion via a self-assembly method. No additional reductant was used in the in situ preparation of AgNPs due to the inherent reduction property of tyrosine (Tyr) residues in SF. The microstructures and particle sizes of the resultant microcapsules were investigated by using a scanning electron microscope (SEM) and a laser scattering particle size distribution analyzer. The resulting microcapsules exhibited a regular spherical morphology with a 4–5 μm narrow diameter distribution range. And the AgNPs attached to the surface exhibited an even distribution. According to the analytical results of DSC, TGA, and infrared system, the SF-AgNPs microcapsule presents enhanced thermal stability and obvious thermal regulation properties. In addition, it was found that the SF-AgNP microcapsule also exhibited a good antibacterial activity against both Gram-positive bacteria (Staphylococcus aureus), and Gram-negative bacteria (Escherichia coli). The SF-AgNPs microcapsule synthesized in this study could be a potential candidate for thermal regulation and healthcare applications.

Nanostructured multiphase metallic materials present extraordinary properties, such as high strength, enhanced fatigue and radiation resistance, and thermal stability, compared to conventional bulk metallic materials. Previous research studies have shown that their deformation and fracture behavior are dominated by defect interactions at internal interfaces. In situ straining, including nanoindentation, compression, and tension, in a transmission electron microscope (TEM) has emerged as a powerful tool to investigate the physics of defect–interface interactions at the nano-scale and even atomic scale. The mechanistic insights gained from these experiments coupled with dislocation theory and atomistic modeling has helped develop a fundamental understanding of the mechanical properties. In this article, through some recent investigations on observing dislocation and interface activities, crack propagation, and nanopillar compression, we present current progress in utilizing in situ TEM straining to examine interface-dominated deformation mechanisms.

This study investigated the compressive response of ice-templated composites and provides an understanding of their mechanical behavior based on the properties of templated ceramic and epoxy. Results suggested a dependence of properties on the microstructure of the templated porous ceramic, whereas more interestingly composites exhibited catastrophic and progressive types of failure. Compressive strength was found to be markedly greater relative to the strength of templated ceramic and polymer, and irrespective of the failure type, strength was greatly enhanced under dynamic loading relative to quasistatic loading. Compressive strength was also calculated based on the rule of mixtures and mode of failure in ice-templated ceramic. The analysis suggested that the axial mode of failure was not dominant in composites, and failures resulted from the fracture of lamella walls, possibly due to elastic instability. Fragments of the composite specimens were analyzed using scanning electron microscopy to study the fracture characteristics and rationalize the catastrophic and progressive types of failure.

Irradiation resistance of metallic nanostructured multilayers is determined by the interactions between defects and phase boundaries. However, the dose-dependent interfacial morphology evolution can greatly change the nature of the defect–boundary interaction mechanisms over time. In the present study, we used atomistic models combined with a novel technique based on the accumulation of Frenkel pairs to simulate irradiation processes. We examined dose effects on defect evolutions near zirconium–niobium multilayer phase boundaries. Our simulations enabled us to categorize defect evolution mechanisms in bulk phases into progressing stages of dislocation accumulation, saturation, and coalescence. In the metallic multilayers, we observed a phase boundary absorption mechanism early on during irradiation, while at higher damage levels, the increased irradiation intermixing triggered a phase transformation in the Zr–Nb mixture. This physical phenomenon resulted in the emission of a large quantity of small immobile dislocation loops from the phase boundaries.

Reactions in Ni/Al nanolaminates exhibit high combustion temperatures and wave speeds that are customizable through changes to nanostructure. Nanolaminates fabricated via vapor deposition exhibit columnar grains with average diameters on the order of the individual layer thickness; yet, their role on nanolaminate combustion has not been previously investigated. The current work uses molecular dynamics simulations to elucidate the effect of grain size on reaction rates and combustion temperatures in Ni/Al nanolaminates. Decreasing grain size is shown to increase reaction rates as well as increase peak temperatures consistent with the excess enthalpy of smaller grain sizes. Additionally, grain boundaries provide heterogenous nucleation sites for the diffusion-restricting B2–NiAl phase. Focusing on Ni diffusion into liquid Al, an effective diffusion coefficient is computed as a function of grain size, which may be used in thermodynamic models for this stage of the reaction.

Concurrently assessing localized residual stresses and mechanical properties in cases where there are gradients in stresses and properties (such as those resulting in metallic alloys from shot peening processes) is challenging. Most indentation-based stress measurements assume uniform properties, which is not necessarily the case in this common industrial process. By using the energy envelope describing the total work of indentation by a load–displacement curve from instrumented indentation, localized residual stresses after shot peening were evaluated experimentally. A framework is developed to describe the appropriate indentation depth at which to assess properties that effectively define the volumetric resolution of the method. The residual stresses predicted via the nanoindentation experiment and energy analysis were validated with X-ray measurement of residual stresses on a shot-peened 52100 steel. The energy method can be applied directly from the indentation load–displacement curve without considering the contact area.

Increasing the number of quantum bits while preserving precise control of their quantum electronic properties is a significant challenge in materials design for the development of semiconductor quantum computing devices. Semiconductor heterostructures can host multiple quantum dots that are electrostatically defined by voltages applied to an array of metallic nanoelectrodes. The structural distortion of multiple-quantum-dot devices due to elastic stress associated with the electrodes has been difficult to predict because of the large micrometer-scale overall sizes of the devices, the complex spatial arrangement of the electrodes, and the sensitive dependence of the magnitude and spatial variation of the stress on processing conditions. Synchrotron X-ray nanobeam Bragg diffraction studies of a GaAs/AlGaAs heterostructure reveal the magnitude and nanoscale variation of these distortions. Investigations of individual linear electrodes reveal lattice tilts consistent with a 28-MPa compressive residual stress in the electrodes. The angular magnitude of the tilts varies by up to 20% over distances of less than 200 nm along the length of the electrodes, consistent with heterogeneity in the metal residual stress. A similar variation of the crystal tilt is observed in multiple-quantum-dot devices, due to a combination of the variation of the stress and the complex electrode arrangement. The heterogeneity in particular can lead to significant challenges in the scaling of multiple-quantum-dot devices due to differences between the charging energies of dots and uncertainty in the potential energy landscape. Alternatively, if incorporated in design, stress presents a new degree of freedom in device fabrication.

The cyclic oxidation experiment of yttria-stabilized zirconia coatings deposited on NiCoCrAlYHf alloys by air plasma spraying was investigated at 1050 °C in air and in air containing water vapor. The results revealed that water vapor has a great influence on the oxidation resistance of the thermal barrier coatings (TBCs). Compared with the samples oxidized in air atmosphere, TBCs oxidized in air containing water vapor had a longer lifetime. It was also found that different atmospheres could lead to different HfO2 formation positions, which could decrease the rumpling in the oxide layer. In particular, after the coatings on Hf-doped NiCoCrAlY were first pretreated in air containing water vapor for 24 h at 1050 °C, the lifetime of the pretreated coating was doubled compared to the coating in laboratory air only. The water vapor pretreatment of the coatings could be an important method for optimizing the lifetime of TBCs.

Nanodomained heterogenous structures characterized by randomly dispersed nanograins (NGs) embedded in the coarser grains (CGs) have demonstrated an exciting potential to break the strength–ductility trade-off, providing high strength without the loss of ductility. Here, using a combination of discrete crystal plasticity finite element (discrete-CPFE) model and dislocation density-based CPFE model, we study the effects of grain size, volume fraction of nanograins on the strength and deformation in nanodomained materials. Our analysis shows that the overall flow stresses of nanodomained samples are equal or higher than the strengths predicted by rule of mixtures. Smaller NGs or higher volume fraction of NGs can make the nanodomained samples stronger, as they can be more effective to promote the dislocation accumulations inside the CGs and eventually raise the critical resolved shear stress for each slip system during the plastic flow. Areas surrounding NGs stored higher dislocation densities and less plastic strain, due to the restricted dislocation motion. Furthermore, NGs grain embedded in the CGs can effectively reduce the anisotropy of strength in the nanodomained samples.

The FeMnCoCr high-entropy alloy/TiC/CaF2 self-lubricating coatings were successfully prepared on a Cu–Zr–Cr alloy for continuous casting mold by laser cladding for wear-resistance. The intriguing finding was that the laser-cladded FeMnCoCr is mainly composed of face-centered cubic and hexagonal close-packed solid solution phases. During the cladding process, the FeMnCoCr/TiC or the FeMnCoCr/TiC/CaF2 mixed sufficiently with Cu matrix, while FeMnCoCr exhibited a spherical shape owing to being insoluble in Cu. The average hardness of the FeMnCoCr/TiC/CaF2 self-lubricating high-entropy alloy (HEA) coatings was twice that of the pure FeMnCoCr HEA coating. By addition of TiC, the friction coefficient and wear rate were decreased from 0.35 and 3.68 × 10−15 mm3/m to 0.27 and 3.06 × 10−15 mm3/m, respectively. When CaF2 was added, the friction coefficients and wear rate were decreased to 0.16 and 2.16 × 10−15 mm3/m, respectively, which was 54% lower than the pure FeMnCoCr HEA coating. The main wear mechanism of the FeMnCoCr coating is abrasive wear while that of the FeMnCoCr/TiC coating is abrasive and adhesion wear. But adhesion wear is dominant for the FeMnCoCr/TiC/CaF2 coating.

Metal matrix composites (MMCs) have great potential to replace monolithic metals in many engineering applications due to their enhanced properties, such as higher strength and stiffness, higher operating temperature, and better wear resistance. Despite their attractive mechanical properties, the application of MMCs has been limited primarily due to their high cost and relative low fracture toughness and reliability. Microstructure determines material fracture toughness through activation of different failure mechanisms. In this paper, a 3D multiscale modeling technique is introduced to resolve different failure mechanisms in MMCs. This approach includes 3D microstructure generation, meshing, and cohesive finite element method based failure analysis. Calculations carried out here concern Al/SiC MMCs and focus on primary fracture mechanisms which are correlated with microstructure characteristics, constituent properties, and deformation behaviors. Simulation results indicate that interface debonding not only creates tortuous crack paths via crack deflection and coalescence of microcracks but also leads to more pronounced plastic deformation, which largely contributes to the toughening of composite materials. Promotion of interface debonding through microstructure design can effectively improve the fracture toughness of MMCs.

CrFeNiTix (x = 0.2, 0.3, 0.4, 0.5, and 0.6 molar ratio) compositionally complex alloys were fabricated by vacuum arc melting to investigate the microstructure, hardness, and compressive properties. The results revealed that CrFeNiTix alloys consisted of the principal face-centered cubic (FCC) phase and body-centered cubic (BCC) solid solution, with an amount of (Ni, Ti)-rich hexagonal close-packed phase. CrFeNiTix alloys exhibited the typical dendrite. Ti0.2 and Ti0.3 alloys were composed of FCC and BCC solid solutions in the dendrite, as well as ε (Ni3Ti) and R (Ni2.67Ti1.33) phases in the inter-dendrite, simultaneously. For Ti0.4, Ti0.5, and Ti0.6 alloys, (Fe, Cr)-rich solid solution separated out and ε phase transformed into R phase gradually. Meanwhile, TEM analysis indicated that Ti0.4 alloy matrix consisted of the principal FCC phase containing (Ni, Ti)-rich intragranular nanoprecipitates. The hardness values of CrFeNiTix alloys were increased with the addition of Ti content and the high compressive strength of CrFeNiTix alloys was maintained, which was attributed to the solid solution strengthening and precipitation hardening.