Graphene, a two-dimensional (2D) crystalline material exhibits unique electronic, optical, and mechanical properties which makes it a promising candidate for optomechanical and optoelectronic devices. The giant plasmonic activity of graphene sheets enables low-dimensional confinement of light and enhanced light–matter interaction leading to significant enhancement of optical forces which may give rise to large mechanical deformations on account of ultralow mass density and flexibility of graphene. The multilayer stack and heterostructures of 2D materials provide access to a spectrum of guided modes which can be used to tailor the optical forces and mechanical states of graphene sheets. Here, we study the optical forces arising from the coupling of guided modes in layered structures of graphene sheets. We obtain the mechanical deformation states corresponding to each guided mode and demonstrate that the optical forces can be adjusted by changing the interlayer spacing as well as the chemical potential of graphene layers. Our results can be used for various designs of graphene-based optomechanical devices.

Atomically thin transition metal dichalcogenides (TMDCs), such as WS2 and MoS2, have opened up new opportunities for the next generation of optoelectronics owing to their unique properties such as optical transparency, high carrier mobility, widely tunable band gap, and strong light–matter interaction. The photodetection performance relies primarily on the light absorption efficiency and separation efficiency of photoexcited electron–holes. The photodetectors with all broadband response, high photoconductive gain, high response speed, and high detectivity is arduous challenge to realize using one photo-active material. Building of photodetectors composed of two or more light absorber materials of different band gaps was an efficient route to realize high performance light detection. The application of a thin sensitizing layer atop the TMDCs has proven to be a viable route to improve the photodetection performance due to the efficient charge separation at the interface, and fast charge transfer process due to the high carrier mobility. In this article, we review the progress made toward hybrid photodetector based on TMDCs with various sensitizers from metal to large band-gap semiconductor in architectures from zero-dimensional quantum dot to two-dimensional crystal.

Methylammonium-tin-iodide (MASnxI3, 0.9 ≤ x ≤ 1.4) systems were prepared by self assembly process in aqueous solutions. The “as-prepared” MASnxI3 systems exhibit a crystalline tetragonal structure (space group I4cm) with polyhedral-shaped crystallites. The as-prepared samples were annealed at T = 150 °C, t = 8 h under nitrogen and synthetic air. Under nitrogen, the CH3NH3SnxI3 systems adopted a cubic crystalline structure (space group P4mm) with crystallites of 2–4 μm length, whereas under air, the formation of noncrystalline phases was observed. The optical absorption spectra displayed absorption edges at 1107.0 nm (x = 0.9), 1098.6 nm (x = 1.0), and 1073.2 nm (x = 1.1), respectively, whereas at higher Sn-content (x ≥ 1.2), a broad tail of the absorbance profile was observed. The photoluminescence (PL) emission spectra (RT, λexc = 500 nm) showed major PL-events over 1 µm range and the appearance of additional bands at increasing the Sn-content. The fabrication of layers with a semiconducting behavior was demonstrated.

This work reports an investigation of electron transport in monoclinic β-Ga2O3 based on a combination of density functional perturbation theory based-lattice dynamical computations, coupling calculation of lattice modes with collective plasmon oscillations, and Boltzmann theory-based transport calculations. The strong entanglement of the plasmon with the different longitudinal optical (LO) modes makes the role LO-plasmon coupling crucial for transport. The electron density dependence of the electron mobility in β-Ga2O3 is studied in the bulk material form and also in the form of a two-dimensional electron gas. Under high electron density, a bulk mobility of 182 cm2/V s is predicted, while in the 2DEG form, the corresponding mobility is about 418 cm2/V s when remote impurities are present at the interface and improves further as the remote impurity center moves away from the interface. The trend of the electron mobility shows promise for realizing high-electron mobility in dopant-isolated electron channels. The experimentally observed small anisotropy in mobility is traced through a transient Monte Carlo simulation. It is found that the anisotropy of the IR-active phonon modes is responsible for giving rise to the anisotropy in low-field electron mobility.

Gold, palladium, and platinum aerogels were prepared by a rapid, direct solution-based reduction synthesis with densities of 0.54, 0.065, and 0.055 g/cm3, respectively. Salt solutions were reduced at 1:1 (v/v) with dimethylamine borane and sodium borohydride to rapidly form gels within seconds to minutes above a threshold salt concentration and were then rinsed and freeze dried. Au, Pd, and Pt aerogels had no presence of oxide phases confirmed by X-ray diffractometry. Specific surface areas determined with gas physisorption were 3.06, 15.43, and 20.56 m2/g for Au, Pd, and Pt. Electrochemically determined specific capacitances using electrochemical impedance spectroscopy and cyclic voltammetry were 2.18, 4.13, and 4.20 F/g, and 2.67, 7.99, and 5.12 F/g for Au, Pd, and Pt, respectively. The rapid synthesis, high solvent accessible specific surface area, conductivity, and capacitance make these noble metal aerogels candidates for many of catalytic, energy, and sensor applications.

Carbon aerogels (CAs) are a unique class of high surface area materials derived by sol–gel chemistry. Their high mass-specific surface area and electrical conductivity, environmental compatibility, and chemical inertness make them very promising materials for many applications, such as energy storage, catalysis, sorbents, and desalination. Since the first CAs were made via pyrolysis of resorcinol–formaldehyde (RF)-based organic aerogels in the late 1980s, the field has really grown. Recently, in addition to RF-derived amorphous CAs, several other carbon allotropes have been realized in aerogel form: carbon nanotubes (CNTs), graphene, graphite, and diamond. Furthermore, the popularity of graphene aerogels has inspired research into aerogels made of a host of graphene analog materials (e.g., boron nitride, transition metal dichalcogenides, etc.), with potential for an even wider array of applications. Finally, the development of three-dimensional-printed aerogels provides the potential for CAs to have an even broader impact on energy-related technologies. Here, we will present recent work covering the novel synthesis of RF-derived, CNT, graphene, graphite, diamond, and graphene analog aerogels.

The behavior of extruded Mg–Gd–Al–Zn magnesium alloys at elevated temperatures was studied to elucidate the effect of intermetallic compounds on thermal stability, grain coarsening mode, and grain growth kinetics. The presence of the fine and widely distributed intermetallic (Mg,Al)3Gd phase in the extruded microstructure of the Mg–4.8Gd–1.2Al–1Zn alloy was found to be quite effective in inhibiting grain growth. This was not the case for the Mg–3Gd–3Al–1Zn alloy, where the extruded microstructure showed that the grain boundaries are not effectively pinned by the main Al2Gd intermetallic phase. The grain coarsening situation was found to be more severe for the Mg–6Al–1Zn alloy because no second phases were present to pin the grain boundaries at elevated temperatures. The simultaneous presence of Al and Gd was found to be helpful in increasing the solidus temperature, and in this way, it further contributes to increasing thermal stability of the magnesium alloys. The abnormal grain growth occurred by penetrating into grain boundaries of smaller grains and by the formation of discrete islands inside large abnormal grains, which provided evidence for the occurrence of the solid-state wetting mechanism in this magnesium alloy.

This study describes results from mechanical tests conducted on magnesium single crystals in comparison with polycrystalline magnesium. It was found by impact testing that the magnesium single crystal is highly ductile due to energy absorption by twinning and slip, while the polycrystalline samples fracture easily upon impact. Compressive testing along two orthogonal directions at low plastic strains was also performed. The microstructure studies by electron backscatter diffraction and XRD pole figure analysis revealed profuse ( $10\overline12$ ) twinning when compression is done along the growth plane (72 16 $\overline {88}$ 62). The twinning and interaction between different twin modes resulted in incipient recrystallization at strains as low as 8% at room temperature. Compression along the nearly orthogonal plane (2 2 $\bar{4}$ 15) was marked by a much lower degree of both twinning and recrystallization. The variation in microstructural response with the orientation of loading allows for a wide range for tailoring mechanical properties of pure magnesium single crystals without any need of alloying.

The effect of mold temperature on microstructure and mechanical properties of a rheo-squeeze casting (RSC) Mg–3Nd–0.2Zn–0.4Zr (NZ30K) alloy were investigated. The results indicated that the rise of mold temperature contributed to the increase of particle size and alloy density and the decrease of dislocation density. The rapid coarsening and then the normal growth of the particles during solution treatment were observed, and the long-rod-like Zn2Zr3 phase occurred. After age treatment, rod-like β′ precipitate was found in the conventional squeeze casting (CSC) alloy, while two types of precipitates including β′ phase and small plate-like β″ phase were observed in the RSC alloy. The amount of Zn2Zr3 phase was increased with rising mold temperature. Compared with the T6-treated CSC sample, the T6-treated RSC sample presented higher mechanical properties due to the larger precipitation strengthening contribution, and the yield strength, ultimate tensile strength, and elongation were up to 160 MPa, 296 MPa, and 7.7%.

A method comprising a two-step alkali/acid treatment of poly (vinylidene fluoride) (PVDF) polymer is developed for the fabrication of flat-sheet PVDF membranes functionalized with labile hydroxyl groups. This method involves the application of a short-duration modification in alkali medium (5% KOH). Extensive characterizations were performed on the prepared membranes. Modification of the polymer altered the crystallinity of the PVDF from a mixture of both α and β phases to a predominant β phase. Lower work of adhesion of the modified membrane indicated the formation of a more hydrophobic and wetting-resistant membrane surface. Centrifugation of the polymer dope after the modification had a pronounced impact on the properties of the resultant membranes. This protocol could be utilized in fine-tuning the properties of PVDF membranes for various target-specific applications such as membrane distillation. This method can also be used in functionalizing PVDF membranes further by exploiting the labile –OH group present on the membrane surface.

To improve the antimicrobial properties of ZnO, ZnO-supported 13X zeolite (X-ZnO) was prepared via the facile chemical method. Antimicrobial activities of X-ZnO and ZnO were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. X-ZnO showed noticeable antimicrobial activities against E. coli and S. aureus under visible light conditions, especially against E. coli. The minimum inhibitory concentration (MIC) of X-ZnO against E. coli was 0.12–0.24 mg/mL. However, there were still much bacteria alive in the nano-ZnO suspensions at the same concentration. To elucidate the antimicrobial activities of X-ZnO, the average concentration of the total reactive oxygen species (ROS) and Zn2+ ions released from X-ZnO and nano-ZnO were quantitatively analyzed. The obtained results indicated that the average concentration of ROS produced by supported ZnO was much higher than that of nano-ZnO. And the released Zn2+ ions from X-ZnO and nano-ZnO suspensions were much lower than the MIC of Zn2+. Thus, it is believed that the production of ROS in X-ZnO and nano-ZnO suspensions resulted in the difference of antibacterial activities.

Two-dimensional dislocation dynamics (DD) simulations are performed to simulate the increase in strength of ferritic superalloys strengthened by ordered β′(B2)–NiAl precipitates. Parametric studies for three precipitate volume fractions (10, 13, and 20%) and various radii (from 1 to 75 nm) predict strengthening via a mixture of precipitate bypassing and shearing by single- and super-dislocations of edge or screw character. DD strength contributions for various precipitate radii (for a 13% volume fraction) are compared to analytical models for ordered precipitate strengthening: good agreement exists in the overaged state, but not in the peak-aged and underaged states for either dislocation configurations. DD strength contributions, converted to hardness values, are compared to experimental hardness values from previously reported literature on a ferritic superalloy [Fe–10Cr–10Ni–6.5Al–3.4Mo–0.25Zr–0.005B (wt%)] aged at various temperatures and times. DD hardness values from the single-edge dislocation simulations accurately predict the experimental peak hardness, but not the under- and over-aged hardness values or trends. By incorporating the effect of secondary NiAl nanoprecipitates formed on cooling and solid solution strengthening of Fe in the primary precipitates, reasonable agreement is achieved in the overaged condition.

Extrusion is an efficient hot working process to aluminum production and AISI H13 (4Cr5MoSiV1) as the main material of extrusion tool suffers from fatigue and creep damage due to its extreme working condition. A new mean plastic strain life prediction has been proposed based on the energy method. In addition, statistical analysis is also taken into consideration to complement this physic-based model due to other unmeasured and unknown exogenous influences. To validate the model, a series of AISI H13 fatigue and fatigue–creep tests were conducted at 500 °C close to the practical aluminum extrusion process. The strain-controlled tests were used for obtaining the parameters, while the stress-controlled tests were utilized for validating the proposed model. It shows that the model predictions were in good agreement with the experimental results.

The aging behavior of precipitation hardenable 17-4 PH stainless steel is studied by analyzing the changes in microstrain, crystallite size, and dislocation density derived from the modified Williamson–Hall (mWH) method and the Fourier analysis of XRD profiles. Aging treatment of this steel at 380, 430, and 480 °C for 0.5, 1, and 3 h durations leads to changes in the microstrain due to precipitation and substructural changes caused by dislocation annihilation. The microstrain estimated from the mWH method is dominated by the precipitate-induced effects. The influence of precipitates and dislocations on the mean squared strain 〈ε2(L)〉 are separated by fitting the variation of 〈ε2(L)〉 with an expression P0 + P1/L + P2/L2, where the parameter (P0)0.5 and P1 are shown to be related to the precipitate-induced and dislocation density-induced microstrain, respectively. The study shows that the XRD profile analysis can be used to separate the combined effects of precipitation and dislocation annihilation.