The current review outlines the size-dependent plastic behavior of high-entropy alloys (HEAs) and the underlying deformation mechanisms. Particular focus is laid upon the influence of microstructural design on the small-scale deformation characteristics. The role of defect types as carriers of plasticity is appraised and correlated with the frequently observed mechanical behavior peculiar to the breed of HEAs. Deformation response is classified on the basis of mechanical testing techniques probing intrinsic (nanoindentation techniques) as well as extrinsic size (micro/nanopillar compression) effects. The mechanisms of incipient plasticity and serrated flow behavior in HEAs are discussed. Furthermore, the role of interfaces between crystallographically dissimilar lattices on small-scale deformation behavior in these alloys is assessed. The article provides a clear overview of the existing HEA research in this avenue as well as the critical knowledge gaps that need to be addressed.

Magnesium alloy (AZ31) reinforced with carbon nanotubes (CNTs) and grapheme nanoplatelets (GNPs) were fabricated with the method of hot-pressing sintering and hot extrusion processes. GNPs and CNTs were predispersed with Al and Zn powders by ball milling used as precursor for sintering, which effectively guaranteed the integrity and dispersion of them. The microstructure and mechanical properties of the composites (denoted as Mg–3 wt% Al–1 wt% Zn–1 wt% (xCNTs + yGNPs)(x:y = 1:1, 1:2, 1:3) were investigated. The results show that the CNTs and GNPs are uniformly distributed in the matrix and closely combined with the matrix in nanoscale. Among the tested composites, Mg–3 wt% Al–1 wt% Zn–1 wt% (xCNTs + yGNPs)(x:y = 1:2) exhibits the most favorable mechanical properties, and the yield strength, tensile and compressed strength, and elongation of composites are substantially improved by the addition of 0.33 wt% CNTs and 0.67 wt% GNPs. Novel strengthening mechanisms such as three-dimensional reinforced structure formed by CNTs and GNPs are found for the remarkable improvement in mechanical properties.

The effects of misorientation on the quasi-static and dynamic mechanical behaviors of a second generation Ni-based single crystal superalloy DD5 were investigated. A Split-Hopkinson pressure bar system was used to perform dynamic compression. The crystallographic misorientation between the stress axis and the [001] direction was characterized through rotating orientation X-ray diffraction. The results demonstrated that the flow stress was closely related to the misorientation. It decreased first and consequently increased as the misorientation increased from 0° to 45°. The dynamic flow stress was significantly higher than the quasi-static stress. Moreover, the flow stress under dynamics was more sensitive to the misorientation. A constitutive model was used to illustrate the misorientation effect on the mechanical behavior. Finally, the effect of strain rate on the crystal orientation was also investigated. It was discovered that the orientation deviation change following quasi-static compression could be neglected. By contrast, the orientation changed by 3–9° subsequently to dynamic compression.

The micro-nano rough structure promotes the formation of superhydrophobic surfaces, while the formation of superoleophobic surfaces requires the support of re-entrant structures. Electrochemical etching and boiling water treatment methods were used to process the superoleophobic surface in the Al–Mg alloy substrate. The differences between the potential of the aluminum and the magnesium promoted the formation of the surface microstructure under the current stimulation, and the surface was formed into dense nanoscale needle-like coating after boiling water treatment. Scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurement were performed to characterize the morphological features, chemical composition, and surface wettability, respectively. The so-prepared superoleophobic surfaces showed high contact angles and small sliding angles for water, ethylene glycol, and hexadecane. In addition, surface topography, reaction mechanism, and experimental parameters were also studied.

Palladium (Pd) and gold (Au) nanoparticles (NPs) hybridized on two types of carbon supports, graphene and granular activated carbon (GAC), were shown to be promising catalysts for the sustainable hydrodehalogenation of aqueous trichloroethylene (TCE). These catalysts are capable of degrading TCE more rapidly than commercial Pd-on-GAC catalysts. The catalysts were synthesized at room temperature without the use of any environmentally unfriendly chemicals. Pd was chosen for its catalytic potency to break down TCE, while Au acts as a strong promoter of the catalytic activity of Pd. The results indicate that both graphene and GAC are favorable supports for the NPs due to high surface-to-volume ratios, unique surface properties, and the prevention of NP aggregation. The properties of NP catalysts were characterized using electron microscopy and spectroscopy techniques. The TCE degradation results indicate that the GAC-supported catalysts have a higher rate of TCE removal than the commercial Pd-on-GAC catalyst, and the degradation rate is greatly increased when using graphene-supported samples.

This work designed a facile preparation for an SiO2/C composite as the anode material for lithium ion battery. Both SiO2 and carbon are amorphous. SiO2 and carbon are mixed uniformly. The SiO2/C composite shows high specific capacity, cycle stability, and rate capability in lithium ion battery charge–discharge test. A stable reversible capacity of 1024 mA h/g at the current density of 100 mA/g is reached. The capacity retains 83% after 100 cycles. The uniform mixture of SiO2 and carbon leads to reduced volume change during the lithiation and delithiation of SiO2, together with the amorphous nature of SiO2 explains the high cycling stability. The carbon coating is a key factor for the high capacity and stability due to the increased electrical conductivity and reduced volume change. The resistance of the solid electrolyte interface film and charge transfer resistance of the SiO2/C composite are much smaller than those of pure carbon, which is a direct proof of the improved conductivity of the material by the carbon coating.

Nanocomposites based on the poly(N-vinylcaprolactam) (PVCL) fabricated from PVCL solutions at different drying temperatures (PVCL25 at 25 °C, PVCL40 at 40 °C) and titanium oxides(IV) nanoparticles (TNPs) were produced for the first time by dry mixing and grinding and mechanical milling in a planetary ball mill using different PVCL:TNP ratios. New effects in initial PVCL (hydration) and TNP [decomposition of η-phase; appearance of hydrated titanium dioxide (HTD)] samples, as well as in PVCL [(de)hydration, disordering of the heterocycles] and TNP (amorphization, dehydration of η-phase, partial crystallization of Hombifine N with anatase), involved as components in PVCL/TNP nanocomposites, were found. The different role of each type of treatments and its conditions in the specific of the effects observed was shown. Only high-frequency mechanical milling leads to the appearance of HTD and the complete disappearance of the second peak of PVCL (disordering of the heterocycles) in PVCL/TNP nanocomposites.

Polyurethane/cellulose composites were synthesized from castor-oil-derived polyols and isophorone diisocyanate using dibutyltin dilaurate (DBTDL) as the catalyst. Materials were obtained by adding 2% cellulose in the form of either microcrystals (20 μm) or nanocrystals obtained by acid hydrolysis. The aim was to assess the effects of filler particle size and the use of a catalyst on the physicochemical properties and biological response of these composites. The addition of the catalyst was found to be essential to prevent filler aggregations and to enhance the tensile strength and elongation at break. The cellulose particle size influenced the composite properties, as its nanocrystals heighten hydrogen bond interactions between the filler surface and polyurethane domains, improving resistance to hydrolytic degradation. All hybrids retained cell viability, and the addition of DBTDL did not impair their biocompatibility. The samples were prone to calcification, which suggests that they could find application in the development of bioactive materials.

Single-phase concentrated solid solution alloys (SP-CSAs) are newly emerging advanced structural materials, which are defined as multiprincipal element solid solutions. SP-CSAs with more than four components in equimolar or near-equimolar ratios are also referred to as high-entropy alloys due to their high configurational entropy. SP-CSAs are potential structural materials in advanced nuclear energy systems due to their attractive mechanical properties. Therefore many investigations have been carried out to study the irradiation-induced structural damage and defect behavior in SP-CSAs. This paper reviews recent experimental results on the irradiation responses of various SP-CSAs, focusing on the accumulation of irradiation-induced structural damage, void swelling resistance, and solute segregation behavior. In addition, the characteristic defect behavior in SP-CSAs derived from ab initio and molecular dynamics simulations, as well as the challenges in the applications of SP-CSAs for the nuclear energy systems are briefly discussed.

Surface modification by the bioactive material is a potential way to overcome the poor osseoconductivity of titanium (Ti)-based implants. A continuous wave laser source was used to deposit strontium titanate (SrTiO3)-reinforced Ti coating on the Ti substrate using the laser engineered net shaping (LENS™) process. The maximum of 10 wt% SrTiO3 could be incorporated into Ti using laser without cracking of the deposit. This study investigated the constituent phases, microstructure, compositional analysis, wettability, and electrochemical behavior of the composite coatings. XRD and EDX analyses confirmed the presence of the SrTiO3 phase in the coatings. The composite coatings also exhibited superior mechanical properties, corrosion resistance, and bioactivity compared to that of commercially pure Ti. In vitro ion release study confirmed the sustain release of Sr2+ from the composite coatings. In summary, the excellent mechanical bonding with the substrate and high in vitro bioactivity make these SrTiO3-incorporated composite coatings as a potential material to enhance osseoconductivity of Ti-based orthopedic implants.

The effect of aging time on the corrosion behavior of 6005 Al alloys has been investigated in aerated 3.5% NaCl aqueous solution. The corrosion resistance of the alloy with different aging times is analyzed by measuring potentiodynamic polarization, electrochemical impedance spectroscopy. The surface morphology is examined by scanning electron microscopy. The results demonstrated that the corrosion resistance of the alloy in the peak-aged condition is worse than the other conditions. Accordingly, corrosion rate and the corrosion current density of the alloy reach its maximum value. An Fe-rich phase is identified as the β-Al4.5FeSi phase by atomic-resolution high angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy mapping analyses. The β-Al4.5FeSi is wrapped slowly by the precipitates of Mg2Si from the process of the peak-aged condition to the over-aged condition. It is hypothesized that the change of corrosion behavior of the alloy may be attributed to the β-Al4.5FeSi wrapped slowly by the precipitates of Mg2Si.

The effects of grain refinement and phase composition on superplasticity and damping capacity of eutectic Zn–5Al and eutectoid Zn–22Al alloys were investigated. For grain refinement, equal-channel angular pressing (ECAP) was applied to these alloys. ECAP completely eliminated the as-cast lamellar microstructures of both alloys and resulted in ultrafine-grained structures along with room temperature superplasticity. Furthermore, these microstructural changes with ECAP increased the damping capacity of both alloys in the dynamic hysteresis region, where damping arises from viscous sliding of phase/grain boundaries. Dynamic recrystallization at the surface and thermally activated viscous motion of grain/phase boundaries at the subsurface of the samples of both alloys were proposed as the damping mechanisms in the region where the alloys showed combined aspects of static/dynamic hysteresis damping behavior. Although the grain size is larger in Zn–5Al compared to Zn–22Al, it showed higher damping capacity due to the different sliding characteristics of its phase boundaries.

Atom probe tomography (APT) is rising in influence across many parts of materials science and engineering thanks to its unique combination of highly sensitive composition measurement and three-dimensional microstructural characterization. In this invited article, we have selected a few recent applications that showcase the unique capacity of APT to measure the local composition at structural defects. Whether we consider dislocations, stacking faults, or grain boundary, the detailed compositional measurements tend to indicate specific partitioning behaviors for the different solutes in both complex engineering and model alloys we investigated.

Boron carbide (B4C) is an attractive material for numerous applications including vehicle armor, cutting tools, blasting nozzles, and abrasive powder, owing to its extreme hardness, high melting point, high Young’s modulus, and excellent thermoelectric properties. However, the application of B4C is limited by the high-temperature synthesis process. The present work aims to explore a low-temperature manufacturing process for synthesizing B4C with a small amount of free carbon. Poly(resorcinol borate) with an aromatic structure and high char yield was chosen as the aromatic polymeric precursor. A combination of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy was performed to investigate the influences of the reaction temperature and holding time on the changes in the precursor microstructure. The results indicate that the rod-like structure of crystalline B4C is successfully synthesized at 600 °C, and the free carbon can be reduced to about 0.8 wt% in the final product. This is because the pyrolysis temperature controlled the carbon content of the B4C, which led to an enlarged contact domain between B2O3 and carbon, and a relatively low-temperature synthesis of B4C.

The hydrogen embrittlement of 12Cr2Mo1R(H) steel at different strain rates were investigated after hydrogen precharging for 4 h in a 0.5 M H2SO4 solution with 2 g/L ammonium thiocyanate. Results showed that the embrittlement index increased and gradually reached a relative stable value of about 20% at the strain rate of 5 × 10−5 s−1 with the decrease of strain rates. SEM images depicted small and deep flakes at high strain rates, while flakes grew larger at slow strain rates. Most hydrogen-induced cracks (HICs) were transgranular fracture through lath grain of bainitic ferrite. High strain field surrounds the crack tips, which makes the crack tips of two close and parallel cracks deflect toward each another and even form crack coalescence. The electron backscatter diffraction technique was used to investigate the effects of grain boundaries, recrystallization fraction, kernel average misorientation map, texture component, and coincidence site lattice boundaries on the HIC propagation. High densities of dislocations and strain concentrations were found around the cracks, where grains are highly sensitive to HIC.

A series of Ba-modified MnCeOx/TiO2 catalysts were prepared by a wet impregnation method and tested for selective catalytic reduction (SCR) of NO with NH3 at low temperature. The results showed that Ba additives obviously improved the catalytic performance of the MnCeOx/TiO2 catalyst for NH3-SCR, and the BaMnCeOx/TiO2 catalyst with 3 wt% BaO exhibited the optimal catalytic performance. Moreover, the introduction of Ba also improved the resistances toward water vapor and SO2 of catalysts. The N2 adsorption, H2-TPR, and X-ray photoelectron spectroscopy results showed that the addition of Ba increased the specific surface area, redox properties, and concentrations of surface Mn4+ and chemisorbed oxygen of catalysts. Furthermore, NH3-TPD and NO-TPD were used to investigate the absorption of NH3 and NO on the catalyst. The results revealed that although the introduction of Ba significantly promoted the adsorption of NO, it also inhibited the adsorption of NH3. Consequently, the catalytic performance of MnCeOx/TiO2 was greatly improved with the Ba additives.