The effect of Co on element segregation and microstructure is investigated in the third generation Ni-based single crystal superalloys with 4, 8.5, and 11.5 wt% Co addition. The results show that the increase of Co content leads to a severe element segregation in as-cast microstructure. After heat treatment, the size of γ′ phase is slightly reduced with Co content increase. During the thermal exposure, the γ′ phase coarsens gradually but its coarsening rate decreases with increasing Co content. In addition, some acicular and blocky topologically close-packed (TCP) phases are precipitated in 4% Co and 8.5% Co alloys. However, no TCP phase can be found in 11.5% Co alloy. Finally, it may be concluded that although a higher Co content is harmful for the element segregation, it is beneficial to maintain the cuboidal morphology of γ′ phase, decrease its coarsening rate, and impede the precipitation of TCP phase.

A key issue in two-dimensional structures composed of atom-thick sheets of electronic materials is the dependence of the properties of the combined system on the features of its parts. Here, we introduce a simple framework for the study of the electronic structure of layered assemblies based on perturbation theory. Within this framework, we calculate the band structure of commensurate and twisted bilayers of graphene (Gr) and hexagonal boron nitride (h-BN), and of a Gr/h-BN heterostructure, which we compare with reference full-scale density functional theory calculations. This study presents a general methodology for computationally efficient calculations of two-dimensional materials and also demonstrates that for relatively large twist in the graphene bilayer, the perturbation of electronic states near the Fermi level is negligible.

The effect of solution treatment (ST) on the microstructure and mechanical properties of cast Al–3Li–1.5Cu–0.2Zr alloy was investigated. Results showed that the volume fraction of secondary phases (Al2Cu, Al3Li) decreased obviously after ST. It was found that the strengthening of Al–3Li–1.5Cu–0.2Zr alloy was a balance of the precipitation strengthening, residual phase strengthening and fine grain strengthening. The residual phase strengthening and fine grain strengthening decreased with increasing the solution temperature and time, while precipitation strengthening increased. After ST at 560 °C for 40 h, the elongation of Al–3Li–1.5Cu–0.2Zr alloy reaches the highest value of 22.1%. In addition, the tensile properties are up to the highest values, ultimate tensile strength of 359 MPa and elongation of 3.5% after optimal ST at 560 °C for 40 h followed by aging treatment.

The double perovskite Tb2MnCoO6 and two simple perovskites TbMnO3 and TbCoO3 were synthesized by a solid sintering reaction method. The Rietveld refinement results based on the x-ray powder diffraction data identified all samples as orthorhombic perovskite structures with space group Pbnm (62). The lattice parameters of Tb2MnCoO6 were a = 5.278 (3) Å, b = 5.579 (4) Å, and c = 7.513 (4) Å with a cell volume V = 221.2 (6) Å3, Z = 2. Meta-magnetic behavior was observed near 92 K for Tb2MnCoO6, which was considered to be related to the coexistence of and competition between the ferromagnetic order and antiferromagnetic order. Temperature-dependent resistance (R–T) was also measured. Compared with TbCoO3 and TbMnO3, Tb2MnCoO6 is more conductive, with its activation energy reduced from 0.3062 eV for TbCoO3 (0.2754 eV for TbMnO3) to 0.1949 eV. The results reported here can assist in understanding the multiferroic physics mechanism of double perovskite materials.

The synthesis technique that can be used to accelerate the discovery of materials for various energy conversion and storage applications is presented. Specifically, this technique allows a rapid and controlled synthesis of mixed metal oxide particles using plasma oxidation of liquid droplets containing mixed metal precursors. The conventional wet chemical methods for synthesis of multimetal oxide solid solutions often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control. The concept is demonstrated by synthesizing binary and ternary transition metal oxide solid solutions with control over entire composition range using metal precursor solution droplets oxidized using atmospheric oxygen plasma. The results show the selective formation of metastable spinel and the rocksalt solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMnz Fe2−z O4 (0 ≤ z ≤ 1), exhibits considerable electrocatalytic activity toward oxygen evolution reaction, achieving an overpotential of 0.39 V at a benchmarking current density of 10 mA/cm2 for a low manganese content of z = 0.20.

The development of energy storage device utilizing carbon nanomaterials possesses remarkably significant electrochemical performance. As compared to others, carbon nanomaterials including carbon black, graphene, activated carbon, and carbon nanotube have advantages in ion accessibility and specific surface area in which, more charged ions can access and transfer to the surfaces of material and thus have enhanced electrical charge storage performance. This manuscript briefly reviews the deposition of carbon nanomaterials from electrophoretic deposition technique which is good because of its simple, economical, versatility, and possibility of the thin film deposition on large substrate. The current state-of-the-art and performance of devices employing carbon as electrode material is also extensively discussed.

Thermal conductivity of single-crystal boron-doped diamond (BDD) was studied in comparison with high-quality pure IIa-type diamond in the temperature range from 20 to 400 K. Boron content in BDD was about 1019 cm−3 that is a typical value of p+ substrates used for power device applications. The thermal conductivity of BDD is about 10 times less than that of IIa diamond near 100 K, but above room temperature the difference is <30%. The observed deviation mostly takes place due to acoustic phonon scattering on extended structural defects occurring in synthetic diamond at high boron content.

This paper, for the first time, reports the results of microwave sintering of two emerging biomaterials, magnesium phosphate and amorphous magnesium calcium phosphate. Beneficial aspects of successful microwave sintering of calcium phosphate are well documented in the literature. The motivation for this work derives from the absence of any publication of similar nature on magnesium phosphates, which are becoming important with the rapid rise in interest in biodegradable Mg-alloys. Starting off with amorphous calcium magnesium phosphate and magnesium phosphate, the resulting microwave sintered product is a biphasic mixture of whitlockite substituted with magnesium and magnesium phosphate. The influence of the extent of Mg substitution on the mechanical properties, microstructure, and sintering behavior of tricalcium phosphate was evaluated. The results showed that the addition of Mg (up to the 50% wt/wt in relation to Ca mass) in the precursor compound of magnesium calcium phosphate improved the kinetics of the densification process and enhanced hardness values.

Graphene-covered copper surfaces have been exposed to borazine, (BH)3(NH)3, with the resulting surfaces characterized by low-energy electron microscopy. Although the intent of the experiment was to form hexagonal boron nitride (h-BN) on top of the graphene, such layers were not obtained. Rather, in isolated surface areas, h-BN is found to form μm-size islands that substitute for the graphene. Additionally, over nearly the entire surface, the properties of the layer that was originally graphene is observed to change in a manner that is consistent with the formation of a mixed h-BN/graphene alloy, i.e., h-BNC alloy. Furthermore, following the deposition of the borazine, a small fraction of the surface is found to consist of bare copper, indicating etching of the overlying graphene. The inability to form h-BN layers on top of graphene is discussed in terms of the catalytic behavior of the underlying copper surface and the decomposition of the borazine on top of the graphene.

We apply n- and p-type polycrystalline silicon (poly-Si) films on tunneling SiOx to form passivated contacts to n-type Si wafers. The resulting induced emitter and n+/n back surface field junctions of high carrier selectivity and low contact resistivity enable high efficiency Si solar cells. This work addresses the materials science of their performance governed by the properties of the individual layers (poly-Si, tunneling oxide) and more importantly, by the process history of the cell as a whole. Tunneling SiOx layers (<2 nm) are grown thermally or chemically, followed by a plasma enhanced chemical vapor deposition growth of p+ or n+ doped a-Si:H. The latter is thermally crystallized into poly-Si, resulting in grain nucleation and growth as well as dopant diffusion within the poly-Si and penetration through the tunneling oxide into the Si base wafer. The cell process is designed to improve the passivation of both oxide interfaces and tunneling transport through the oxide. A novel passivation technique involves coating of the passivated contact and whole cell with atomic layer deposited Al2O3 and activating them at 400 °C. The resulting excellent passivation persists after subsequent chemical removal of the Al2O3. The preceding cell process steps must be carefully tailored to avoid structural and morphological defects, as well as to maintain or improve passivation, and carrier selective transport. Furthermore, passivated contact metallization presents significant challenges, often resulting in passivation loss. Suggested remedies include improved Si cell wafer surface morphology (without micropyramids) and postdeposited a-Si:H capping layers over the poly-Si.

Mechanics of deformation in miniaturized indirect extrusion (IE) and their resulting process outcomes are shown to be dependent on the dimensional scale of the plastic deformation zone. Using optically transparent dies as prototypes, the effect of process length-scales on the strain, strain-rate, and rotation fields is elucidated using digital image correlation. In this regard, in situ experiments were performed on commercially pure Lead (Pb) and Aluminum (Al 1100) as prototypical nonwork/work hardening materials. By overlaying these measurements with microstructural characterization via electron backscattered diffraction, the effect of deformation volume on process–structure mappings is identified. Herein, visco-plastic self-consistent framework-based modeling of the evolution of crystallographic textures was investigated to achieve insights into the trajectories of microstructure evolution and process outcomes during IE. These findings provide a beneficial background about characteristics of plastic deformation zone and its distribution to optimize and control the properties of miniaturized components.

Diamond like carbon (DLC) films deposited using CH4 and Ar and amorphous fluorocarbon (a:C-F) films deposited using CF4 and Si2H6 as precursors were optimized for ultra-low dielectric constant applications by tuning pressure, substrate temperature, and flow rate ratio. Sixty three films belonging to three stack configurations possessed good morphology and adhesion post DLC deposition. Structural and mechanical properties with respect to film integrity, adhesion, roughness, and shrinkage rate were studied. Internal and interface stress distribution results in the increased stability of as deposited DLC–a:C-F–DLC sandwich layers in comparison to a:C-F–DLC stacks. Annealed a:C-F with DLC top coat and As deposited a:C-F are similar in bonding structure. Failure mode is buckling delamination failure with increasing severity in films with higher oxygen incorporation and can be preserved by annealing the fluorocarbon component or providing a DLC base coat. Effect of process parameters on properties relevant to integration has been determined.

Potassium dihydrogen phosphate (KDP) is an important nonlinear optical crystal material for light frequency converters and Pockels photoelectric switches in laser systems. However, KDP is apt to fracture, is deliquescent, and can suffer from microstructural changes under a temperature variation. As such, KDP has been one of the most difficult-to-handle materials, but its properties have not been well understood. This paper aims to explore the mechanical properties of KDP crystals in detail with the aid of the nanoindentation technique using a Berkovich diamond indenter. It was found that the mechanical properties of KDP can be easily altered by machining-induced subsurface damage. It was also discovered that a KDP crystal is a visco-elasto-plastic material during micro/nanoscale deformation, although it is very brittle macroscopically.

Hot compression tests on pure Ni and Ni–30Cu at 950–1150 °C and strain rates of 0.001–1 s−1 were performed to identify the physical interpretation of the apparent activation energy (Q d). For pure Ni, Q d was constant and identical to that of the self-diffusion. However, for Ni–30Cu, it decreased steadily with strain. The value of Q d was separated into thermal and mechanical parts. The thermal part was necessary to propel diffusion. For pure Ni, the mechanical part was zero at low and medium strain rates of 0.001–0.1 s−1 and the self-diffusion was the controlling mechanism. However, at 1 s−1, both the thermal and mechanical parts were needed to provide Q d. For Ni–30Cu, Q d was greater than that for the interdiffusion of Ni and Cu. The value of mechanical part decreased with increasing temperature and strain rate. Although the thermal parts for pure Ni and Ni–30Cu were nearly identical, the mechanical part for the latter was considerably higher. The difference was attributed to the strengthening effect of Cu atoms and the sluggish dynamic softening with respect to pure Ni.

The dislocation movements under the action of electric pulses (athermal effect) at cryogenic conditions were studied by ex situ transmission electron microscopy (TEM) observations and slip trace analysis innovatively. By applying electric pulses directly through aluminum TEM samples in a liquid nitrogen bath, plenty of non-octahedral-like dislocation glides generally forming at high temperatures (e.g., >453 K for aluminum) were observed at cryogenic temperatures (<130 K). Occurrence of the non-octahedral-like dislocation glides indicates a substantial increase in the degrees of freedom for dislocation glides, offering a new/complementary explanation for the acceleration effect of electric pulses on dislocation movements, especially in the sole athermal effect. In comparison, previous theories relied on extra driving force and/or increased dislocation mobility on the octahedral planes in a face-centered cubic metal. The athermal effects of electric pulse were discussed and the selective heating at the dislocation cores was proposed to account for non-octahedral-like dislocation glides.