Research on graphene has been developing at a relentless pace as it holds the promise of delivering composites with exceptional properties. In particular, the excellent mechanical properties of graphene make it a potentially good reinforcement ingredient in ceramic composites while their impressive electrical conductivity has roused interest in the area of multifunctional applications. However, the potential of graphene can only be fully exploited if they are homogenously embedded into ceramic matrices. Thus, suitable processing route is critical in obtaining ceramic composites with desired properties. This paper reviews the current understanding of graphene ceramic matrix composites (GCMC) with three particular topics: (i) principles and techniques for graphene dispersion, (ii) processing of GCMC, and (iii) effects of graphene on properties of GCMC. Besides, toughening mechanisms and percolation phenomenon that may occur in these composites are elaborated with appropriate examples. Challenges and perspectives for future progress in applications are also highlighted.

The high-energy oscillating electric current pulse (ECP) technology was introduced to relieve the residual stresses in the small AISI 1045 steel specimens treated by the pulsed-laser surface irradiation. The high-energy oscillating ECP stress relief experiments were conducted to study the effectiveness of the high-energy oscillating ECP technology. In addition, the electroplasticity framework was developed based on the thermal activation theory to reveal the mechanism of the high-energy oscillating ECP stress relief. The results show that the high-energy oscillating ECP stress relief has good effects on eliminating the residual stress. Furthermore, the residual stress relieving mechanism of the high-energy oscillating ECP stress relief can be attributed to the electric softening effect and the dynamic stress effect. The findings confirm that the significant effects of high-energy oscillating ECP on metal plasticity and provide a basis to understand the underlying mechanism of the high-energy oscillating ECP stress relief.

Pr2−x Cex CuO4+δ thin films were grown hetero-epitaxially on (001) SrTiO3 substrates using ozone-assisted molecular beam epitaxy. High-quality epilayers with a cerium concentrations of x = 0.15 were grown and characterized electrically, structurally, and by magnetization measurements. The Pr2−x Cex CuO4+δ films were found to maintain the tetragonal Nd2CuO4 (T′) crystal structure with a linear dependence of lattice constant on the Ce concentration. The superconductivity of the Pr2−x Cex CuO4+δ films was maintained up to x ≈ 0.23 with a T c up to 12.6 K. For x < 0.15, control of the oxygen concentration δ by annealing is crucial for the induction of superconductivity in Pr2−x Cex CuO4+δ and this still holds for x > 0.20. We show that the electron mean free path length $\ell$ may be significantly enhanced by optimizing those annealing conditions. Moreover, the enhancement of $\ell$ leads to a reduction of the upper critical field, suggesting that superconductivity of Pr2−x Cex CuO4+δ is to be considered in the clean limit.

Hot compression tests of a hot isostatically pressed (HIPed) Ni based powder metallurgy (P/M) superalloy were carried out under various combinations of temperatures and strain rates. To bridge the relationship between stresses and strain rates, constitutive equations were established based on a hyperbolic sine Arrhenius equation, which yielded predicted stresses under the test conditions. It was found that the predict values fit the experimental values with good accuracy. Processing maps of the alloy under the test conditions were established; and the corresponding microstructures after test were examined to elaborate the workability of the alloy. It revealed that surface cracks occurred when strain was higher than 0.25, which initiated at the prior powder boundaries (PPBs) and propagated along the boundaries. The optimum hot working parameters for the alloy were proposed to beat the strain rate of 0.014 s−1 and 1075 °C.

The effect of nitrogen gas addition in Ar-based double-layer shielding gas on the impact toughness of welded ultra-ferritic stainless steel during an autogenous gas tungsten arc welding (GTAW) process was investigated. The nitrogen behavior was proposed. The microstructure, mechanical properties, and fracture surface morphology of the weld metals have been evaluated. More equiaxed crystals, refined grain, narrow HAZ width, and increased microhardness were produced with nitrogen addition. Experimental findings indicated that nitrogen diffused into HAZ and dissolved into weld pool. The solute distribution was changed thus bringing significant constitutional supercooling and decreased temperature gradient of weld pool, which contributed to fine microstructure. Impact toughness at room temperature was enhanced from 2J to 9J (welds), 5J–13J (HAZ). Ductile fracture zone was produced about 0.3–0.5 mm thickness distance from the weld surface. A significant increased impact toughness of weld metal was due to the refinement of microstructure and element addition.

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) absorbers are considered promising alternatives to commercial thin film technologies including CdTe and Cu(In,Ga)Se2 (CIGSe) owing to the earth abundance and non-toxicity of their constituents. However, to be competitive with the existing technologies, the photovoltaic performance of CZTSSe solar cells needs to be improved beyond the current record conversion efficiency of 12.6%. In this study, nanoscale elemental mapping using Auger nanoprobe microscopy (NanoAuger) and nano secondary ion mass spectrometry (NanoSIMS) are used to provide a clear picture of the compositional variations between the grains and grain boundaries in Cu2ZnSn(S,Se)4 kesterite thin films. NanoAuger measurements revealed that the top surfaces of the grains are coated with a Zn-rich (Zn,Sn)Ox layer. While thick oxide layers were observed at the grain boundaries, their chemical compositions were found to be closer to SnOx . NanoSIMS elemental maps confirmed the presence of excess oxygen deeper within the grain boundary grooves, as a result of air annealing of the CZTSSe films.

The effects of Cu content on the microstructure, mechanical property, and hot tearing susceptibility of die casting Al–22Si–0.4Mg alloy have been investigated. Different Cu contents (1.5, 2.5, 3.5, 4.5 wt%) were added in Al–22Si–0.4Mg alloy. In the as-cast microstructure, the amount, volume fraction, and average size of Al2Cu phase increase with more Cu addition. The morphology of grain boundary white Al2Cu phase turns from particle to lump. The UTS (ultimate tensile strength) of Al–22Si–xCu–0.4Mg alloy improves with Cu added, which is mainly caused by the strengthening effect of intergranular Al2Cu. The hot tearing susceptibility apparently rises with Cu content increased, which is due to longer quaternary eutectic reaction time, larger amount of residual intergranular Cu-rich liquid film spreading out over α-Al grain boundary, and higher quaternary eutectic reaction temperature. Considering both the mechanical property and hot tearing susceptibility, optimal Cu content for die casting Al–22Si–0.4Mg alloy found in this paper is 2.5 wt%.

The electric field-assisted extrusion process is applied in Zr–45Ti–5Al–3V alloy. A transition from phase α to phase β is observed at various zones during the extrusion, and a complete transition is achieved by the considerable shear deformation. When subjected to the electric field-assisted extrusion, the continuous dynamic recrystallization is significant at the edges and the major shear deformation zones, and the equiaxed phase β grain structure is refined to a size of 250–300 µm. In addition, the phase β grains contain a minor amount of large residual lath-shaped phase α structures. The edges and the major shear deformation zones form a cubic texture along the {100}〈001〉 direction with a slightly weak polarity, while the polarity of the texture at the center is strong. The extrusion is found to decrease the edge strength from 1580 MPa to 1185 MPa and to increase the elongation up to 7.2%.

A novel, simple, quick, and economic method has been developed to etch samples for characterizing the structural aspects of carbonized pitch alone and in baked anodes. Hot air is used to etch the polished carbonized pitch surface for creating its topography; followed by the characterization of the structure using scanning electron microscope. Hot air preferentially etches the carbonized pitch, which make the differentiation of carbonized pitch from the calcined coke particles possible in baked anode. After etching, lamellar parallel cracks are created and fine granular mosaics are observed on the surfaces of carbonized pitch. The structural composition in baked anode differs visibly from the pure carbonized pitch baked under the same conditions. This may be due to the effect of fine coke particles in anode on the formation of structure during baking. The etching technique permits the determination of the internal structure of carbonized pitch and its interface with coke in anode.

Motivated by low cost, low toxicity, mechanical flexibility, and conformability over complex shapes, organic semiconductors are currently being actively investigated as thermoelectric (TE) materials to replace the costly, brittle, and non-eco-friendly inorganic TEs for near-ambient-temperature applications. Metal–organic frameworks (MOFs) share many of the attractive features of organic polymers, including solution processability and low thermal conductivity. A potential advantage of MOFs and MOFs with guest molecules (Guest@MOFs) is their synthetic and structural versatility, which allows both the electronic and geometric structure to be tuned through the choice of metal, ligand, and guest molecules. This could solve the long-standing challenge of finding stable, high-TE-performance n-type organic semiconductors, as well as promote high charge mobility via the long-range crystalline order inherent in these materials. In this article, we review recent advances in the synthesis of MOF and Guest@MOF TEs and discuss how the Seebeck coefficient, electrical conductivity, and thermal conductivity could be tuned to further optimize TE performance.

Future electronics will be conformal, bendable, and wearable. Taking inspiration from the characteristics of human skin, we are developing a new generation of electronic materials to enable devices that are flexible, stretchable, biodegradable, and self-healable. We have developed various sensors and circuits, all of which are based on organic materials, polymers, and carbon nanomaterials. These materials will provide us with a long-term path toward adding various skin-inspired functions.

Metal–organic frameworks (MOFs) are porous ordered arrays of inorganic clusters connected by organic linkers. The compositional diversity of the metal and ligand, combined with varied connectivity, has yielded more than 20,000 unique structures. Electronic structure theory can provide deep insights into the fundamental chemistry and physics of these hybrid compounds and identify avenues for the design of new multifunctional materials. In this article, a number of recent advances in materials modeling of MOFs are reviewed. We present the methodology for predicting the absolute band energies (ionization potentials) of porous solids as compared to those of standard semiconductors and electrical contacts. We discuss means of controlling the optical bandgaps by chemical modification of the organic and inorganic building blocks. Finally, we outline the principles for achieving electroactive MOFs and the key challenges to be addressed.

The development of new hierarchical materials capable of efficient energy transfer along a predesigned pathway will boost various applications, ranging from organic photovoltaics to catalytic systems. Due to their exceptional tunability and structural diversity, metal–organic frameworks (MOFs) offer a unique platform to study and model directional energy-transfer processes and, thereby, an efficient path for energy utilization. This article summarizes the latest advances in MOF applications in the fields of optoelectronics, photoswitching, sensing, and photocatalysis, for which development is highly dependent on fundamental studies of MOF photophysics.

The well-known synthetic versatility of metal–organic frameworks (MOFs) is rooted in the ability to predict the metal-ion coordination geometry and the vast possibilities to use organic chemistry to modify the linker groups. However, the use of molecules occupying the pores as a component of framework design has been largely ignored. Recent reports show that the presence of these so-called “guests” can have dramatic effects, even when they are a seemingly innocuous species such as water or polar solvents. We term these guests “non-innocent” when their presence alters the MOF in such a way as to create a new material with properties different from the MOF without the guests. Advantages of using guest molecules to impart new properties to MOFs include the relative ease of introducing new functionalities, the ability to modify the material properties at will by removing the guest or inserting different ones, and avoidance of the difficulties associated with synthesizing new frameworks, which can be challenging even when the basic topology remains constant. In this article, we describe the “Guest@MOF” concept and provide examples illustrating its potential as a new MOF design element.