The increasing demand for portable and low-power electronics for applications in self-powered devices and sensors has spurred interest in the development of efficient piezoelectric materials, via which mechanical energy from ambient vibrations can be transformed into electrical energy for autonomous devices, or which can be used in strain-sensitive applications. Semiconducting piezoelectric materials are ideal candidates in the emerging field of piezotronics and piezophototronics, where the development of a piezopotential in response to stress/strain can be used to tune the band structure of the semiconductor and hence its electronic and/or optical properties. Furthermore, research into nanowires of these materials has intensified due to the enhancement of piezoelectric properties at the nanoscale. In this regard, nanowires of ZnO and the III-nitrides have been extensively studied, but the piezoelectric properties of non-nitride III–V semiconductor nanowires remain less-explored. Indeed, direct measurements of the piezoelectric properties of single III–V nanowires are tellingly rare due to the difficulties associated with measurements of piezoelectric properties of nanoscale objects using conventional scanning probe microscopy techniques. This review addresses the challenges related to the study of piezoelectricity in III–V nanowires and the opportunities that lie therein in terms of device applications.

Drug delivery systems (DDSs) have been developed to target tumor cells by releasing active biomolecules at the specific site of infection, thus eliminating the side effects of anticancer drugs. However, DDSs are generally limited by high drug dosage, biobarriers, poor target recognition, etc. To address these deficiencies, we propose a new noninvasive method consisting of exposing the cancer cells to a combination of low-intensity pulsed ultrasound (LIPUS) and static magnetic field (SMF). This combined treatment found to negatively regulate colon cancer cell (HCT116) activities in vitro by altering their cell membrane potential and permeability thus increased the DDS efficacy by 40%. The treated cancer cell membrane became hyperpolarized leading to cancer cell death. The combination treatment (LIPUS + SMF) restricted the cancer cell proliferation to 16 and 5% in the presence of bare anticancer drug and DDS, respectively, in 72 h, which is almost 40% higher than that observed without the treatment. The acceleration of cancer cellular inhibition was confirmed by the significant increase in the apoptosis of the cell exposed to the LIPUS + SMF treatment. The observed improvement is believed to be due to changes in the cell membrane stability/permeability as a result of mechanical (20–22 kPa) and electrical (19–23 µV/cm) stimuli generated during the LIPUS + SMF treatment.

Special needs patients often require specific dental treatments and modified restorative materials that reduce clinical discomfort. Starting from glass ionomer cements (GICs), some different fillers were added to improve their mechanical and clinical performances. The effect of nanohydroxyapatite, antibiotic, and mucosal defensive agent on the mechanical and thermal properties of GICs was investigated. Compressive tests, calorimetric analysis, and morphological investigation were conducted. The middle percentages of fillers increased the elastic modulus while the highest decreases are recorded for highest percentages. Filler and environment also influence the compressive strengths and toughness. The introduction of fillers led to a reduction of the enthalpy with a maximum decrease with the middle percentage. The morphological characterization showed a good dispersion of the fillers. The filler percentages should be selected with a compromise between the elastic modulus, the compressive strength, and the curing time. Obtaining new materials with good clinical and mechanical properties can represent an innovative aspect of this work with positive implication in clinical practice, mainly in uncollaborative patients in which the use of traditional protocols is problematic.

Ti6Al4V alloy samples with large pores suitable for bone implants are fabricated by pressing and sintering. Ti6Al4V powder is mixed with different volume fractions of salt particles. The sintering behavior up to 1260 °C is studied by dilatometry and pore features are observed by scanning electron microscopy and X-ray microtomography. Sintered materials with a relative density between 0.26 and 0.97 are obtained. 3D image analysis proves that large pores form a connected network when the amount of salt is 20% and above. The Young’s modulus and the yield stress of sintered materials deduced from compression tests span over wide ranges of values, which are consistent with real bone data. A simple analytical model is proposed to estimate the relative density as a function of the fraction of salt. This model combined with classical Gibson and Ashby’s power equations for mechanical properties can predict the fraction of salt required to obtain prescribed properties.

Admicellar polymerization, a novel technique for surface modification, was used in this work to enhance the compatibility between polymers with obviously different polarities, e.g., natural rubber (NR) and polylactic acid (PLA). The admicellar polymerization of methyl methacrylate over NR substrates (using potassium peroxodisulfate as an initiator) so-called poly(methyl methacrylate)–natural rubber (PMMA-ad-NR) was prepared and mixed with PLA at different contents (5, 10, and 15 wt%) in comparison to the simple PLA/NR blends. The monomer to initiator ratio was varied: 25:1, 50:1, and 100:1 corresponding to the admicelled PMMA molecular weight of 20,000, 30,000, and 40,000 g/mol, respectively. All PLA/PMMA-ad-NR blends showed good compatibility as evident by FE-SEM results revealing smooth boundary of PMMA-ad-NR domains in the PLA matrix. Moreover, the mechanical properties and thermal stability of PLA/PMMA-ad-NR blends were higher than those of PLA/NR blends, especially with increasing PMMA-ad-NR content up to 10 wt%. It was clear that the lowest molecular weight of the admicelled PMMA gave the highest toughness of PLA/PMMA-ad-NR blends.

Solar steam generation is an efficient and green technology for desalination and drinking water purification, however, impeded by high cost, low efficiency, and complicated process. Black titania is expected to exhibit excellent solar steam performance due to its outstanding light absorption properties, chemical stability, low cost, and innocuity. Herein, we design a high absorbing and efficient solar steam generation system based on a black titania/graphene oxide nanocomposite film affixed to airlaid paper wrapped over the surface of expandable polyethylene foam; the system possesses several important criteria required for the ideal solar steam generator: wide-spectrum absorption, adequate water supply, reduced heat loss for localized water heating, and porous structure for steam flow. Remarkably, we realized a solar thermal conversion efficiency of 69.1% under illumination of 1 kW/m2 without solar concentration, and the device delivered remarkable cycle stability.

As an important member of semiconducting transition metal oxides, MoO2 nanomaterials have many advantages in optical and electrical applications. However, MoO2 itself has no significant photocatalytic performance possibly because of its inferior conductivity and strong recombination of photogenerated electron–hole pairs. Here, we propose a facile, one-step pyrolysis method to prepare a novel C fibers@MoO2 nanoparticles core–shell composite, where the oxidative MoO2 nanoparticles in situ grew on the surface of conducting C fibers. Due to the compositing of MoO2 and C fibers, during photocatalysis tests, the recombination of photogenerated electron–hole pairs was effectively inhibited, and the lifetime of the photogenerated carries was efficiently prolonged, finally significantly improving the solar-driven photocatalytic activity on degrading various organic and inorganic pollutants in water, such as methylene blue, rhodamine B, phenol, and potassium dichromate, showing the great potential for environmental remediation by degrading toxic industrial chemicals in waste water under sunlight. Moreover, the composite presented good stability in composition and structure during the repeated use and long-term storage. In addition, this one-step growth method is an easy-to-handle, environmentally friendly, and low-cost synthesis method for large-scale production.

A method for extracting the substrate-independent stress–strain curves of thin films was developed using spherical nanoindentation to investigate the yield behavior of diamond-like carbon (DLC) thin films with Young’s moduli of ∼73 GPa and ∼76 GPa. The resulting stress–strain curves showed that these films commence yielding at ∼13 GPa and ∼14 GPa, respectively. These yield strength values agree with the critical pressure necessary to initiate the transformation of sp2-bonded carbon into significantly harder sp3-bonded carbon, indicating that the yielding of the materials is associated with the sp2-to-sp3 phase transition. The ability of a DLC film to accommodate a progressively increasing contact stress with strain beyond the yield point while dissipating part of the accumulated strain energy, as evidenced in this work, implies a unique mechanism of the brittle material for passively mitigating contact deformation and fracture in tribological applications.

The self-learning kinetic Monte Carlo method has been shown to be suitable for examining the temporal and spatial evolution of adatom islands on the (111) surface of several fcc metals, unbiased by diffusion processes chosen a priori. A pattern-recognition scheme and a diffusion path finder scheme enable collection of a large database of diffusion processes and their energetics. A variety of mechanisms involving single and multiple atoms, and concerted island motion are uncovered in long-time simulations. In this contribution, after reviewing the methodology, we present results comparing the diffusion kinetics of two sets of homo-epitaxial and hetero-epitaxial systems: small (2–8 atom) Pd and Ag islands on the respective (111) surfaces and small Cu islands on Ni(111) and Ni islands on Cu(111). We trace the dominance of concerted motion in Pd/Pd(111) and Ni/Cu(111) and competition among concerted, multiatom and single-atom processes in Ag/Ag(111) and Cu/Ni(111) to the strength of the lateral interaction among adatoms in these systems.

Subsurface microstructure alteration has been a major concern to implement micromachining of titanium alloy in the high-tech industry. To quantitatively promulgate the underlying mechanisms of this alteration, a discrete dislocation dynamics-based model is proposed and used to simulate the subsurface defects and their evolution under different cutting conditions. The model considers the subsurface dislocation configuration and inner stress distribution during the orthogonal cutting of titanium alloy. The results show that subsurface defect structure consists of plenty of dislocation dipoles, twining dislocation bands, and refined grains after cutting. In the primary shear zone, two different characteristics of subsurface damage layers can be found, the near-surface damage layer and deep-surface damage layer, which have different structural natures and distribution features. Moreover, it is found that high cutting speed and small depth of the cut can suppress the formation and propagation of subsurface defects. A powerful inner stress state would promote the distortion of the lattice and result in a microcrack within the subsurface matrix. The simulation results have been compared with experimental findings on the machined surface and subsurface of similar materials, and strong similarities were revealed and discussed.

A comparison of microstructure, mechanical properties and fracture behavior of Mg–9Gd–3Y–xZn–0.5Zr (x = 0, 0.2, 0.5, 1.0, and 1.5) (wt%) alloys under different thermal treatment conditions was investigated in this study. The results showed that the as-cast alloys were comprised of Mg matrix, eutectic compounds and cuboid-shaped phases. The eutectics were Mg24(Gd, Y)5 in the alloys of Zn content ≤0.2 wt%, while (Mg, Zn)3RE in the other three alloys. Fine lamellar long period stacking ordered structure formed inside of matrix of the as-cast Zn-containing alloys and its quantity increases with raising Zn content. Mg12(Gd, Y)Zn was observed at grain boundary of Mg matrix after solution treatment in the alloys of Zn content ≥0.5 wt%. Peak-aged Mg–9Gd–3Y–0.5Zn–0.5Zr alloy exhibited a desirable combination of strength and elongation with 244 MPa in yield strength, 371 MPa in ultimate tensile strength and 3.8% in EL. Meanwhile, the fracture behavior of the studied alloys was also investigated.

In this paper, corrosion behaviors of Mg–10Gd–5Y–2Zn–0.5Zr (wt%) alloy (GWZ1052K) in different aging stages are investigated using immersion tests and electrochemical measurements in 3.5 wt% NaCl aqueous solution. The corrosion resistance is found to increase from the solution-anneal to peak-aged condition, which is attributed to microstructure evolutions of β′ precipitates and nearly unchanged long period stacking ordered (LPSO) structures. The broken network LPSO structures no more act as corrosion barriers, thus inversely worsening the galvanic corrosion. β′ precipitates uniformly surround the LPSO lamellas, those partly enhancing corrosion resistance. The potentiodynamic polarization curves also show the best corrosion resistance in the peak-aged stage, suggesting the similar tendency of corrosion behaviors. And the results of electrochemical impedance spectrum are consistent with the morphology of the corrosion surface. Further equivalent circuit is established to investigate the corrosion mechanism.

The influences of pressure and aging treatment on microstructures and mechanical properties of rheo-squeeze casting (RSC) Mg–3Nd–0.2Zn–0.4Zr alloys were studied. It was found that the nucleation rate, solid solubility of Nd and Zn in the α-Mg matrix, and dislocation density were increased with increasing applied pressure. After aging treatment, the amount of the Zn2Zr3 phase was increased with increasing pressure; β″ phase and β′ precipitates were observed in the RSC alloy and finer β′ precipitates formed in the permanent mold casting (PMC) alloy. The mechanical properties of as-cast alloys were initially increased and then decreased with increasing pressure, while the properties of T6-treated alloys were increased continuously. Due to the larger grain boundary strengthening contribution, the T6-treated RSC sample showed higher mechanical properties than the PMC sample, and the yield strength, ultimate tensile strength, and elongation could reach 165 MPa, 309 MPa, and 5.7%, respectively.