Nanomaterials have been intensively studied over the past decades with many advantages over traditional bulk materials in many applications. Nanomaterials' properties are largely governed by their chemical compositions, sizes, shapes, dimensions, morphologies and structures, which are primarily controlled with the chemical and/or physical fabrication methods and processes. This prospective will highlight recent progress on the modifications of oxide nanomaterials' properties by hydrogenation, namely heat treatment under hydrogen or hydrogen plasma environment, for various applications.

Zeolite molecular sieves are indispensable materials for acid-based catalysis and separation processes. This article overviews zeolite-type microporous materials containing a secondary system of larger (meso-/macro-) pores. These materials, often referred to as hierarchical zeolites, show better performance in reactions where slow mass transport impedes the reaction rate. A critical analysis of different synthetic strategies for preparation of hierarchical zeolites is presented. The industrial prospects of these materials are also discussed.

Hierarchical structure is a hallmark of many biological materials that naturally originate from their growth process, which starts with the biosynthesis of molecular building blocks that self-assemble into larger units. Compartmentalization is used to locally control the synthesis and self-assembly and, thus bridge multiple length scales between the atomistic and macroscopic worlds. Multiscalar structures have the advantage that different physical properties may be adjusted at various structural levels. In particular, when these properties are conflicting, the result can lead to exceptional multifunctional materials. The fiber is a ubiquitous structural motif of biological materials, although its biochemical basis can be diverse. While fibers perform well under tension, they do not under compression. Biological materials are also adaptive and possess self-repair capabilities—properties that require the transport of matter and information. This requires networks of transport and communication that are also hierarchically organized to conciliate the conflicting goals of maximum accessibility and minimal perforation of the material volume. Several examples are discussed in this article.

This paper reviews our recent investigations of compound semiconductors and heterovalent interfaces using the technique of aberration-corrected scanning transmission electron microscopy. Bright-field imaging of compound semiconductors with a collection angle that is comparable in size to the incident-beam convergence angle is demonstrated to provide better atomic-column visibility for lighter elements in comparison with the more traditional high-angle annular-dark-field approach. Several pairs of Group II–VI/Group III–V compound semiconductors with zincblende structure have been studied in detail. These combinations are all valence-mismatched (i.e., heterovalent), and include CdTe/InSb (Δa/a ≤ 0.05%), ZnTe/InP (Δa/a = 3.8%), and ZnTe/GaAs (Δa/a = 7.4%). CdTe/InSb (001) interfaces are observed to be defect-free with a slight lattice contraction at the interface plane. For interfaces with larger lattice-parameter mismatch, the primary interfacial defects are identified as Lomer edge dislocations and perfect 60° dislocations. However, the atomic structure of the dislocation cores has not yet been unambiguously determined.

This paper presents a periodic density functional theory study on the adsorption of H, CO, and OH on Pt2Ru3 alloy surfaces containing different conformations of Pt and Ru atoms. The results show that for separate adsorption, H is preferentially adsorbed at Pt sites, whereas CO and OH are preferentially adsorbed at Ru sites. The adsorption strengths of H, CO, and OH are affected by ratio of the alloying atoms in top surface, the nature of the neighboring atom nearest to the adsorption site, and the conformation of alloying atoms in subsurface. We also investigated the coadsorption of CO with OH and the coadsorption of CO with H and found that the Pt–CO bond strength weakens. We also uncovered some information about the competitive adsorption behavior of adsorbates (CO, OH) with the aim of designing CO-tolerant Pt–Ru alloy catalysts.

We use first-principles calculations based on density functional theory to investigate the interplay between oxygen vacancies, A-site cation size/tolerance factor, epitaxial strain, ferroelectricity, and magnetism in the perovskite manganite series, AMnO3 (A = Ca2+, Sr2+, Ba2+). We find that, as expected, increasing the volume through either chemical pressure or tensile strain generally lowers the formation energy of neutral oxygen vacancies consistent with their established tendency to expand the lattice. Increased volume also favors polar distortions, both because competing rotations of the oxygen octahedra are suppressed and because Coulomb repulsion associated with cation off-centering is reduced. Interestingly, the presence of ferroelectric polarization favors ferromagnetic (FM) over antiferromagnetic (AFM) ordering due to suppressed AFM superexchange as the polar distortion bends the Mn–O–Mn bond angles away from the optimal 180°. Intriguingly, we find that polar distortions compete with the formation of oxygen vacancies, which have a higher formation energy in the polar phases; conversely the presence of oxygen vacancies suppresses the onset of polarization. In contrast, oxygen vacancy formation energies are lower for FM than AFM orderings of the same structure type. Our findings suggest a rich and complex phase diagram, in which defect chemistry, polarization, structure, and magnetism can be modified using chemical potential, stress or pressure, and electric or magnetic fields.

A series of characterization tests were performed to elucidate the high-cycle fatigue (HCF) behavior in SAE 1050 steel subjected to tensile elastic pre-deformation at different strain rates. In the pre-strained stage, the deformation was maintained constant at 0.16%, which was close to the low yield point at strain rates ranging from 10−5 s−1 to 10−2 s−1. Although pre-deformation occurred entirely in the elastic regime, using different pre-straining rates resulted in the occurrence of heterogeneous microscopic strain at different sites and locations during subsequent fatigue tests. It was found that the effect of pre-straining rate on crack initiation and crack propagation was not monotonous and was influenced by the homogeneity of deformation within grain boundaries, the integrity of the boundary structure, and the fracture toughness. In addition, the rough set theory model was introduced for the attribute reduction of characteristic parameters and provided a scientific basis to establish the fatigue model. The model was able to effectively predict the lifetime of the process of HCF in pre-strained steel. Hence, the pre-straining rate should be an important boundary condition in further studies.

Hot-rolled Nb-stabilized ferritic stainless steel samples were produced with and without annealing. The samples were then cold rolled and isothermally annealed at 650–1000 °C for 10–14,400 s. The recrystallized volume fraction was quantified using the Johnson–Mehl–Avrami–Kolmogorov model and by measuring the microhardness of samples annealed for various duration. The texture evolution was analyzed using electron backscatter diffraction. The calculated Avrami exponents were between 0.8 and 1.2. The intensity of the {111}〈121〉 and {111}〈011〉 components of the γ-fiber increased and the deformation texture seen in the α-fiber decreased with increasing annealing time. The intensity of the rotated-cube component decreased with increasing annealing time. The intensity distributions of the early nucleation and full recrystallization textures were noticeably different. The {554}〈225〉 texture component, which was associated with the largest grains, appeared during the late stages of recrystallization. The final annealing led to a grain refinement with a final average grain diameter of 8 µm.

When two materials interact, the processes between the phases determine the functional properties of the compound. Pivotal interface phenomena are diffusion and redistribution of atoms (molecules). This is especially of interest in Lithium ion batteries where the interfacial kinetics determines the battery performance and impact cycling stability. A new phase field model, which links the atomistic processes at the interface to the mesoscale transport by a redistribution flux controlled by the so called ‘interface permeability’ was developed. The model was validated with experimental data from diffusion couples. Calculations of the concentration profiles of the species at the electrode–electrolyte interface are reported. Active particle size, morphology and spatial arrangement were put in correlation with diffusion behavior for use in reverse engineering.

There is growing interest in using instrumented indentation to characterize mechanical properties of soft materials, including tissue properties related to damage and disease. However, sample surface detection has been a major challenge. The multi-indent approach (MIA) is a novel method to indirectly detect the surface using data from multiple indents to determine the preload-induced indentation depth. Elastic modulus and shear modulus determined by MIA were equivalent to bulk measurements for 19 and 49 kPa gels. However, the traditional Oliver–Pharr approach significantly overestimated these properties. MIA is also important to accurate characterization of poroelastic properties and allows for much smaller probes and indentation depths to be used for all measurements. This is particularly important for poroelasticity, where the relaxation time scales with the size of the indenter. The novel approach helps to resolve the long-standing challenge of surface detection and has the potential to broaden the use of instrumented indentation for soft materials.

Recently, cold metal transfer (CMT) process has been successfully applied to weld dissimilar metals. In this paper, two different aluminum alloy AA6061-T6 and pure copper T2 lapped joints were performed by CMT with AA4043 aluminum alloy wire as the filler metal. Results indicated that sound lapped joints between aluminum alloy AA6061-T6 and pure copper T2 could be performed by CMT technology. The joint was composed of Al–Al welding joint and Al–Cu brazing joint. The Al–Al welding joint was formed between the Al weld metal and the Al base metal, and the weld metal in Al–Al welding joint was composed of α-Al solid solution, α-Al, and CuAl eutectic phase. Al–Cu brazing joint was formed between the Al weld metal and the local molten Cu base metal, and composed of three copper-weld metal interfaces with a large amount of intermetallic compounds (IMCs), i.e., CuAl2, CuAl. The optimum strength of two joints could reach up to 1.23 kN and 1.56 kN, respectively, which was mainly due to the differences of the size of Cu/Al IMCs and stress condition. In addition, the distribution of microhardness and fracture surface of two joints were observed and analyzed in detail.

We calculate, compare, and discuss the charge transport properties through quasi fullerene C40 obtained in three different electrode–C40–electrode testbeds by employing density functional theory combined with nonequilibrium Green's function, to predict the electronic structure of molecular junctions formed from copper, silver, and gold electrodes. We investigate various metrics such as chemical potential of electrodes, density of states, transmission spectra, Mulliken population, and molecular projected self-consistent Hamiltonian eigen states to develop a novel insight about the varying transport phenomenon as the metallic part of the scattering region is modified. We conclude that all the junctions exhibit strong metallic character displaying ballistic conductance of order of more than G 0 accompanied by pronounced ripples in their conductance spectrum and small rectifying behavior in their current spectrum. This rectifying behavior is found to stem from the asymmetric shifting of orbital energies with changing bias voltage due to change in relative charge transfer through central molecule C40.