Biological materials have developed hierarchical and heterogeneous material microstructures and nanostructures to provide protection against environmental threats that, in turn, provide bioinspired clues to improve human body armor. In this study, we present a multiscale experimental and computational approach to investigate the anisotropic design principles of a ganoid scale of an ancient fish, Polypterus senegalus, which possesses a unique quad-layered structure at the micrometer scale with nanostructured material constituting each layer. The anisotropy of the outermost prismatic ganoine layer was investigated using instrumented nanoindentations and finite element analysis (FEA) simulations. Nanomechanical modeling was carried out to reveal the elastic-plastic mechanical anisotropy of the ganoine composite due to its unique nanostructure. Simulation results for nanoindentation representing ganoine alternatively with isotropic, anisotropic, and discrete material properties are compared to understand the apparent direction-independence of the anisotropic ganoine during indentation. By incorporating the estimated anisotropic mechanical properties of ganoine, microindentation on a quad-layered FEA model that is analogous to penetration biting events (potential threat) was performed and compared with the quad-layered FEA model with isotropic ganoine. The elastic-plastic anisotropy of the outmost ganoine layer enhances the load-dependent penetration resistance of the multilayered armor compared with the isotropic ganoine layer by (i) retaining the effective indentation modulus and hardness properties, (ii) enhancing the transmission of stress and dissipation to the underlying dentin layer, (iii) lowering the ganoine/dentin interfacial stresses and hence reducing any propensity toward delamination, (iv) retaining the suppression of catastrophic radial surface cracking, and favoring localized circumferential cracking, and (v) providing discrete structural pathways (interprism) for circumferential cracks to propagate normal to the surface for easy arrest by the underlying dentin layer and hence containing damage locally. These results indicate the potential to use anisotropy of the individual layers as a means for design optimization of hierarchically structured material systems for dissipative armor.

We report on the preparation of a bioactive CaO–SiO2 monolithic scaffold with interconnected bimodal nanomacro porosity, which simulates the morphology of a natural trabecular bone, by a newly developed modified sol-gel process. This method inherently creates nanopores, whose average diameter can be tailored to approximately 5–20 nm by solvent exchange. To achieve interconnected macroporosity (pores ∼5–300 μm in size), a polymer [poly(ethylene oxide)] is added, which causes phase separation simultaneously with the sol-gel transition. High-resolution scanning electron microscopy and mercury intrusion porosimetry demonstrate a high degree of three-dimensional interconnectivity and sharp distributions of pore size. In vitro bioactivity tests in simulated body fluid (SBF) show bioactivity of the material after soaking for approximately 5 h, as verified by the formation of a hydroxyapatite layer deep into the scaffold structure. Analysis of the SBF after the reaction indicates the dissolution of the samples, another desired feature of temporary scaffolds for bone regeneration. MG63 osteoblast-like cells seeded on our sol-gel glass samples responded better to samples with nanopores enlarged by a solvent exchange process than to the one with normal nanopores. Thus, the benefits of the high surface area achieved by sol-gel and solvent exchange procedures are most clearly demonstrated for the first time.

By using homogeneous electron-beam (EB) irradiation, rapid adhesion between nylon-6 film and polymethyl methacrylate (PMMA) was successfully developed. Effects of homogeneous irradiation of electron beam with low potential (HIEBL) on adhesive strength of different polymers without glue were investigated. HIEBL less than 0.216MJ kg−1 (MGy) increased the adhesive strength and its strain of composites constructed with nylon-6 film and PMMA, although additional HIEBL at more than 0.432 MGy apparently decreased the adhesive strain. HIEBL less than 0.432 MGy also enhanced the elasticity (dσ/dε)o of composites. To evaluate the influence of HIEBL on the adhesive strength, electron spin resonance signals that relate to dangling bonds were observed. Because EB irradiation generated dangling bonds in polymethyl methacrylate and nylon-6, dangling bonds probably acted reactive and bonding sites to each polymer at interface. Therefore, HIEBL enhanced the adhesive strength as well as elasticity of the composites.

Uniform monodisperse nanospheres of tetra-kis(4-methoxylphenyl) porphynatemanganese (III) chloride [MnIII(TMOPP)Cl] of about 200 nm have been synthesized through a facile surfactant-assisted reprecipitation method at room temperature. Scanning electron microscopy, transmission electron microscope, infrared spectrum, ultraviolet–visible spectrum, and elemental analysis were adopted to characterize the as-prepared metalloporphyrin nanostructures. The influence factors in the reaction to the sizes and morphologies of porphyrin nanoparticles were discussed. The sizes of porphyrin nanoparticles were affected mainly by the porphyrin concentration and only monodisperse nanoshperes with high uniformity in sizes and shapes can self-assemble to form order two-dimensional superstructures.

Ferroelectric K0.5Na0.5NbO3 (KNN) thin films were prepared by a chemical solution deposition approach with polyvinylpyrrolidone (PVP) of different molecular weights introduced in the precursor solutions. The volatilization of the alkali ions and the effects of the molecular weight of PVP were examined with x-ray diffraction (XRD), thermal analysis, mass spectrometry, and x-ray photoelectron spectroscopy (XPS). The results clearly showed that the volatilization of the alkali ions mainly happened at moderate temperatures before the crystallization of the KNN perovskite phase. Loss of Na was more significant than K ions during the heating process of KNN. The introduction of PVP with the appropriate molecular weight could effectively promote the crystallization of the KNN perovskite phase at reduced temperature and substantially suppress the loss of the alkali ions before crystallization. Therefore, a high dielectric constant, piezoelectric coefficient, and well saturated ferroelectric hysteresis loops were obtained in the KNN films in which PVP of the right molecular weight were introduced.

Bonding character, elastic mechanical parameters, ideal strengths, and atomistic shear deformation mechanisms of M3AlN (M = Zr and Hf) were studied by first-principles method. M3AlN exhibits layered chemical bonding character due to the alternately stacking of relatively soft Al–M and strong N–M covalent bonds. The second-order elastic constants and mechanical parameters of M3AlN were reported for the first time. The stress–strain relationships for different deformation modes were studied and the ideal shear and tensile strength were obtained. M3AlN ceramics are predicted to be “quasi-ductile” layered nitrides based on the low shear-modulus-to-bulk-modulus ratios, positive Cauchy pressure (c12–c44), and lower ideal shear strength compared to ideal tensile strength. Investigation of the atomistic shear deformation mechanism of Hf3AlN shows that stretching of soft Al–Hf bonds and relatively weak bridge N–Hf1 bonds dominate the shear deformation; while the rigid N–Hf2 bonds resist against the applied shear strain. Chemical bonding characteristics and shear deformation mechanism of M3AlN are similar with those of other “quasi-ductile” ceramics, such as MAX phases, LaPO4 monazite, and γ-Y2Si2O7. The results further suggest that M3AlN nitrides should be quasi-ductile and damage tolerant.

The Rockwell indentation test was used to generate interface delamination in an EB-PVD thermal barrier coating (TBC) system that was thermally cycled between 300 °C and 1050 °C. Luminescence spectroscopy was applied to measure the thermally grown oxide (TGO) stresses in indentation-affected and perfectly bonded regions. Comparison between experimental stress mapping in bonded and delaminated regions by luminescence spectroscopy and finite element analysis was shown and the effect of delamination paths was presented. Zigzag delamination paths alternating between the top TBC-TGO interface and TGO-bond coat interface were shown to induce TGO stress releases and fluctuations in the delaminated region. Luminescence spectroscopy measurements successfully detect such behavior, making it possible to identify nondestructively the size of the delaminated region, the delamination crack front position, and the delamination paths in part.

Three-dimensional spherical assemblies of Ni-doped ZnO nanocrystals have been prepared by the solution phase synthesis process. It has been observed that transition metal ions (Zn, Ni) are uniformly distributed in the sample and exist in the +2 oxidation state. Detailed investigation of structural defects formed during the formation of spherical assemblies by oriented attachment of nanocrystals was carried out by high-resolution transmission electron microscope (HRTEM), Raman and photoluminescence (PL) spectroscopy. HRTEM analysis revealed the existence of various crystal defects, such as stacking faults, dislocations, etc. The incorporation of Ni2+ into ZnO structure strongly influences the vibrational and optical properties of the sample due to the increment of defect densities. Compared to the optical phonons of ZnO, additional mode observed at 538 cm−1 in Raman spectra of Ni-doped ZnO could be associated with the incorporation of Ni2+ in Zn2+ site. The increase in PL intensity of green emission with Ni2+ doping indicates the formation of a higher concentration of oxygen vacancy in doped nanostructures.

Ca0.5Th0.5VO4 was prepared by a solid-state reaction of component oxides and characterized by powder x-ray diffraction (XRD) at ambient and higher temperatures and impedance spectroscopy. Crystal structure was refined by Rietveld refinements from powder XRD data. At room temperature, Ca0.5Th0.5VO4 has a zircon-type tetragonal (I41/amd) lattice with unit cell parameters: a = 7.2650(1) and c = 6.4460(1) Å. Despite the large charge difference, Ca2+ and Th4+ are statistically distributed over a single site. The crystal structure of Ca0.5Th0.5VO4 is built from the (Ca/Th)O8 (bisdisphenoid) and VO4 tetrahedra. The in situ high-temperature XRD studies on Ca0.5Th0.5VO4 revealed anisotropic thermal expansion behavior with coefficients of thermal expansion αc = 10.96 × 10−6/°C and αa = 5.32 × 10−6/°C. The impedance measurements carried out in the temperature range from ambient to 800 °C indicate semiconducting behavior with appreciable ionic conductivity above 400 °C. The activation energy obtained from the temperature-dependent AC conductivity data is ∼1.37 eV. In wider range of frequencies and temperatures, the relative permittivity of approximately 50 to 60 is observed for Ca0.5Th0.5VO4.

Amorphous silica shells, used for functionalization of inorganic nanoparticles in bioapplications, were coated on chemically synthesized NaYF4:Yb,Er upconversion fluorescent nanoparticles via a reverse microemulsion method by using dual surfactants of polyoxyethylene (5) nonylphenylether and 1-hexanol, and tetraethyl orthosilicate as precursor. NaYF4:Yb,Er nanoparticles were equiaxed with a particle size of 11.1 ± 1.3 nm. The thickness of silica shell was ∼8 nm. NaYF4:Yb,Er/silica core/shell nanoparticles were well dispersed in solvents such as ethanol and deionized water. The emission intensities of NaYF4:Yb,Er/silica core/shell nanoparticles remained the same as that of uncoated nanoparticles after surface functionalization with an amine group using (3-aminopropyl)-trimethoxysilan. Silica, although providing a good barrier to the nonradiative relaxation between the upconversion nanoparticles and the environments, did not enhance the emission intensity of upconversion nanoparticles. To increase the emission intensity of NaYF4:Yb,Er/silica core/shell nanoparticles, an undoped NaYF4 shell (∼3-nm thick) was deposited on the upconversion nanoparticles before the silica coating. The total emission intensity of NaYF4:Yb,Er/NaYF4/silica core/shell/shell nanoparticles increased by 15 times compared to that without the intermediate NaYF4 shell. The critical shell thickness of NaYF4 was ∼3 nm, beyond which no further emission intensity enhancement was observed.

Metalorganic chemical vapor deposition was used to grow N-rich side GaNSb alloys under different growth conditions, and, for the first time, a considerable amount of Sb was incorporated into the GaNSb. The amount of Sb increased as the growth temperature decreased, but the maximal Sb content seemed to be limited by the solid solubility of Sb in GaN. Absorption spectroscopy of the GaNSb revealed a strong absorption band below the band gap of GaN. The below-band gap absorption extended to 0.8 eV, which makes GaNSb a promising material to serve as an infrared absorption layer on GaN.

Electronic devices capable of performing in extreme mechanical conditions such as stretching, bending, or twisting will improve biomedical and wearable systems. The required capabilities cannot be achieved with conventional building geometries, because of structural rigidity and lack of mechanical stretchability. In this article, a zigzag-patterned structure representing a stretchable interconnect is presented as a promising type of building block. In situ experimental observations on the deformed interconnect are correlated with numerical analysis, providing an understanding of the deformation and failure mechanisms. The experimental results demonstrate that the zigzag-patterned interconnect enables stretchability up to 60% without rupture. This stretchability is accommodated by in-plane rotation of arms and out-of-plane deformation of crests. Numerical analysis shows that the dominating failure cause is interfacial in-plane shear stress. The plastic strain concentration at the arms close to the crests, obtained by numerical simulation, agrees well with the failure location observed in the experiment.

Sn whisker formation was studied in a “bimetal ledge specimen” that consisted of a uniform layer of Sn that was covered by Cu on only half the sample. Whiskers are observed to grow in the Cu-free region of the sample, which is attributed to stress generated by the diffusion of Sn atoms along the network of columnar grain boundaries. The Sn diffusion is driven by the intermetallic growth, but the whisker density extends out much further than any measurable Cu concentration. Whiskers were also observed to grow in the Cu-coated region by punching through the overlayer, leaving a Cu-grain on the tip of the Sn whisker.

The effect of repeated melting of master alloy ingots on the bending properties of Zr55Al10Ni5Cu30 bulk metallic glass (BMG) was investigated. The bending plasticity of Zr55Al10Ni5Cu30 BMG was found to be improved with the increased remelting times. When remelted 10 times, the BMG sample cast from the master alloy ingot undergoes bending, but it does not fracture even though the bending angle increases to 100°; the maximum bending stress and elastic strain remain almost constant. The bending plasticity improvement may be attributed to the fact that the increased remelting times result in more free volume and more disorder and homogeneous microstructure in the BMG, which favors the initial nucleation of profuse shear bands and reduces the probability of catastrophic fracture.

This article presents an extruded Mg–Gd–Zn–Zr alloy produced by conventional ingot metallurgy, exhibiting high-strength and excellent ductility at room and elevated temperatures. The superplastic behavior was observed in the Mg–Gd–Zn (–Zr) alloy at elevated temperatures above 573 K. In the alloy, both the X phase in grain boundaries and the lamellae within matrix have the 14H-type long-period, stacking-ordered structure. It indicates that the X phase and the lamellae within matrix play important roles in the excellent mechanical properties.

Based on a ternary Mg75Ni15Gd10 metallic glass former, a new Mg80Ni12Gd4Nd4 bulk metallic glass composite (BMGC) was developed by tailoring the compositions of Mg and rare earth (RE) elements. This BMGC displayed compressive ultimate strength over 900 MPa with a total strain to failure of 4.3% and specific strength of 3.12 × 105 Nm/kg. The improved mechanical properties were attributed to a “dual phases” structure consisting of Mg solid solution flakes and glassy matrix in the Mg80Ni12Gd4Nd4 BMGC. The homogeneously dispersed Mg phases reinforcement in the BMGC were characterized as a long period ordered structure (LPOS) with periodic arrays of six close-packed planes distorted from the ideal hexagonal lattice of 6H-type. The LPOS-Mg in the composite can act as a soft media to trap or interact with the unstable shear bands and contribute to plastic strain. The present study may provide a guideline for designing the Mg–TM–RE-based (TM: transition metals) BMGCs with “dual phases” structures.

A major drawback in using bulk metallic glasses (BMGs) as structural materials is their extremely poor fatigue performance. One way to alleviate this problem is through the composite route, in which second phases are introduced into the glass to arrest crack growth. In this paper, the fatigue crack growth behavior of in situ reinforced BMGs with crystalline dendrites, which are tailored to impart significant ductility and toughness to the BMG, was investigated. Three composites, all with equal volume fraction of dendrite phases, were examined to assess the influence of chemical composition on the near-threshold fatigue crack growth characteristics. While the ductility is enhanced at the cost of yield strength vis-à-vis that of the fully amorphous BMG, the threshold stress intensity factor range for fatigue crack initiation in composites was found to be enhanced by more than 100%. Crack blunting and trapping by the dendritic phases and constraining of the shear bands within the interdendritic regions are the micromechanisms responsible for this enhanced fatigue crack growth resistance.

The morphology of the fracture surfaces of a bulk metallic glass (BMG) tested under compression was systematically studied. Experimental results showed that the fracture surface always comprises two kinds of zones, starting with a relatively smooth zone followed by the second zone with vein patterns. It implies strongly that the plastic deformation of BMGs always starts with a cooperative shear. The following catastrophic fracture characterized by the vein patterns may or may not occur, depending on the magnitude of this shear, which is controlled by the sample size and machine stiffness. This phenomenon was interpreted based on the temperature rise resulting from the work done during the cooperative shear. It revealed that for small samples, the shear is so small that the temperature increase is insignificant, accounting for the extensive serrated flow, while the temperature increase in samples beyond a critical size is sufficiently high so that the temperatures are higher than the glass transition temperature or even the melting temperature, leading to catastrophic fracture.

In a carbon-free economy, nuclear power will surely play a fundamental role as a clean and cost-competitive energy source. However, new-generation nuclear concepts involve temperature and irradiation conditions for which no experimental facility exists, making it exceedingly difficult to predict structural materials performance and lifetime. Although the gap with real materials is still large, advances in computing power over the last decade have enabled the development of accurate and efficient numerical algorithms for materials simulations capable of probing the challenging conditions expected in future nuclear environments. One of the most important issues in metallic structural materials is the degradation of their mechanical properties under irradiation. Mechanical properties are intimately related to the glide resistance of dislocations, which can be increased severalfold due to irradiation-produced defects. Here, we present a combined multiscale study of dislocation-irradiation obstacle interactions in a model system (Cu) using atomistic and dislocation dynamics simulations. Scaling laws generalizing material behavior are extracted from our results, which are then compared with experimental measurements of irradiation hardening in Cu, showing good agreement.

X-ray diffraction (XRD) and transmission electron microscope (TEM) investigations have been carried out to decode the influence of stacking-fault energy (SFE) on the accommodation of large shear deformation in Cu-Al alloys subjected to one-pass equal-channel angular pressing. XRD results exhibit that the microstrain and density of dislocations initially increased with the reduction in the SFE, whereas they sharply decreased with a further decrease in SFE. By systematic TEM observations, we noticed that the accommodation mechanism of intense shear strain was gradually transformed from dislocation slip to deformation twin when SFE was lowered. Meanwhile, twin intersections and internal twins were also observed in the Cu-Al alloy with extremely low SFE. Due to the large external plastic deformation, microscale shear bands, as an inherent deformation mechanism, are increasingly significant to help carry the high local plasticity because low SFE facilitates the formation of shear bands.