NiO nanoparticles (NPs) were synthesized at different annealing temperatures via a thermal decomposition process and characterized using X-ray diffraction, scanning electron microscopy, and UV-vis spectroscopy. The NiO NPs prepared at higher annealing temperature (400 °C) were shown excellent adsorption and photocatalytic activity toward textile dyes reactive black 5 (RB-5) and methylene blue (MB). About 87.2% of RB-5 in 60 min and 70.2% of MB in 5 h was removed using NiO NPs synthesized at 400 °C. The photocatalytic degradation of MB was found to increase with an increase in the annealing temperature of the catalyst. Moreover, the kinetic study revealed that the adsorption and photocatalytic activity of NiO NPs followed the second and first-order kinetics, respectively. The enhanced performance of NiO NPs toward dye removal might be related to its optical and structural properties.

We report a rapid combustion synthesis method for producing band gap tunable gallium zinc oxynitrides, a material of interest for water splitting applications. By varying the ratio of zinc and gallium, we can tune the band gap from 2.22 to 2.8 eV. Furthermore, nitrogen can be incorporated up to nearly 50% via replacement of oxygen without the need for high temperatures or an additional ammonolysis step. X-ray photoelectron spectroscopy (XPS) and EDX analysis suggests a preferential segregation of Zn to the surface of the as-synthesized particles, though the surface Ga/Zn molar ratio in the as-synthesized particles is correlated with the Ga/Zn molar ratio of the precursor materials. Photoelectrochemical measurements show that the oxynitride powders are photoactive under both AM1.5 and visible-only (λ > 435 nm) irradiation. Hydrogen and oxygen were both evolved in half-reaction experiments under simulated AM1.5 irradiation without externally applied bias, although addition of an OER catalyst did not enhance the rate of oxygen formation, suggesting that intra- and interparticle recombination are significant.

AZ91 magnesium plates with a thickness of 6 mm were subjected to one- and two-pass friction stir processing (FSP). Microstructures and mechanical properties of the experimental materials were investigated. The results show that FSP can significantly refine the microstructures of magnesium alloys, and two-pass FSP can prepare slightly finer grains in comparison with one-pass FSP. Some coarse β-Mg17Al12 phases existed in the first pass FSP break and dissolve into the matrix under the action of the second pass FSP. Microhardness distribution of the two-pass FSP AZ91 alloy exhibits no too much difference with that of the one-pass FSP AZ91 alloy. Due to further finer microstructures, the tensile properties of the two-pass FSP alloy are slightly higher than those of the one-pass FSP alloy. Both FSP AZ91 alloys show typical ductile fracture characteristics, while the dimples on the two-pass FSP specimen are much deeper and increase in quantity.

Large strain extrusion machining (LSEM) emerges as an innovative severe plastic deformation method of fabricating ultrafine grained materials. However, substantial heat generated during LSEM would sacrifice the mechanical properties of materials. Cryogenic temperature (CT) LSEM is put forward to overcome this shortcoming. The Al 7075 was processed by cryogenic and room temperature (RT) LSEM to investigate their comparative effects on mechanical and microstructural properties. Results indicate that the chip morphology of CT LSEM is featured with better integrity. Grains are refined to less than 200 nm by CT LSEM. A more complicated microstructure with high dislocation density is observed in the CT LSEM specimens. The hardness of cryogenic and RT LSEM specimens increases with the compression ratio and reaches the highest values of 187HV and 170HV, respectively. Dislocation strengthening is the main contributor, accounting for the higher hardness of CT LSEM specimens.

Contamination by bacterial biofilms has a strong negative impact, especially on the surface of prostheses, implants, pins, and other medical-surgical devices. To prevent their formation, one of the alternatives is the modification of the metal surface incorporating silver by low-energy ion implantation, thus avoiding initial bacteria adhesion to the modified surface and further development of the biofilm. The bactericidal properties of silver atoms incorporated on commercially pure titanium surfaces by low-energy ion implantation (4 keV) were evaluated. The surface modifications were analyzed by Rutherford backscattering spectrometry, glow discharge-optical emission spectroscopy, contact angle measure, optical profilometry, and X-ray photoelectron spectroscopy. The microbiological assays were conducted by using Escherichia coli (E. coli). The results demonstrated a reduction on bacterial counting. No toxic effect of silver was detected on human MG-63 cells. The choice of parameters to obtain a bactericidal and nontoxic biomaterial for human cells should consider the ideal combination “energy + silver concentration”. Therefore, it can be considered for industrial application.

The novel visible-light-responsive direct solid-state Z-scheme g-C3N4/BiOI heterojunction has been synthesized successfully by means of a solid phase calcination method and used for the degradation of microcystin-LR (MC-LR). The layered g-C3N4 disperses on the surface of BiOI microspheres. The samples are characterized by FESEM, HRTEM, XRD, FT-IR, UV-vis spectroscopy, XPS, BET, PL, and Mott–Sckottky. The photocatalytic activity and photodegradation mechanism of the as-prepared g-C3N4/BiOI microsphere photocatalysts are conducted under visible light irradiation using MC-LR as the target pollutant. The g-C3N4/BiOI material exhibits superior photocatalytic performance when compared with pure BiOI, the possible reason is the efficient separation of photogenerated carriers at the interface between g-C3N4 and BiOI. The heterostructure is responsible for the improved separation efficiency of photogenerated electron–hole pairs and thus the higher photocatalytic activity. The possible photocatalytic mechanism is proposed based on relative band positions of these two semiconductors.

Axisymmetric reverse extrusion experiments were conducted on annealed Cu rod specimens to form cup-shaped structures with sidewall thicknesses ranging from ∼400 µm down to ∼25 µm. Changes in Cu grain morphology, size, and texture were examined through scanning electron microscopy and electron backscatter diffraction (EBSD). Pole figure and orientation distribution function analysis of EBSD data showed the same texture components in the present small-scale metal forming experiments as those observed in macroscale sheet metal rolling. The plastic deformation became inhomogeneous as the characteristic dimension for extrusion decreased to ∼25 µm, such that the deformation process involved a small number of Cu grains. Extrusion force–punch displacement curves were measured as a function of extruded cup sidewall thickness and compared to outputs of a continuum plasticity finite element analysis in corresponding geometries. The present work illustrates materials characteristics in small-scale metal forming and suggests directions of future work for bringing improved correspondence between experimentation and modeling.

Titania nanoparticles (anatase or anatase + rutile) with enhanced photocatalytic activity were successfully produced by treating titanyl sulfate with various peroxo compounds (hydrogen peroxide, ammonium persulfate, and urea hydrogen peroxide) with further annealing. Transformation of titanyl sulfate to titanium dioxide was investigated by X-ray diffraction, electron microscopy, X-ray microanalysis, IR, Raman, X-ray photoelectron, and UV/vis spectroscopy. The peroxo compound and annealing temperature play an important role in phase composition and properties of the samples. Correlations between phase composition, oxygen content, band gaps, and constant rates for methyl orange (MO) discoloration were found. The [TiOx(O2)2−x(H2O)m] phase, which forms on the first stage of the reaction, contains nanoparticles with small crystallites (1–2 nm) and promotes formation of titanium dioxide with the anatase structure. Thermal decomposition of the peroxo-containing phase results in formation of titanium dioxide. Oxygen excess prevents transformation of anatase to rutile, decreases band gap, and increases activity of titanium dioxide (anatase or anatase + rutile) in the model reaction of MO destruction.

Manufacturing of advanced functional materials should also rely on the green chemistry principles like utilization of natural renewable resources. Marine environment offers plenty of renewable raw materials like chitin and its derivative chitosan. The paper presents how urea treatment has influenced several textural, chemical, and electrocatalytic properties of N-doped activated carbons (N_ACs) obtained from chitosan and chitin. The materials were subjected to an activation procedure (with different activators) as well as nitrogenation by premixing the precursors with water solutions of urea. Raw and premixed precursors were carbonized in the temperature range of 700–800 °C. The urea treatment resulted in a spectacular increase in the nitrogen content by weight (up to 68%) and an improvement of the surface area (up to 42%) along with total/micro-/mezo-pore volume (up to 49%). Some urea-modified N_ACs were capable of reducing oxygen in an alkaline solution as effectively as a Pt-loaded carbon material. The highest number of electrons transferred to O2 molecule was found to be equal to 3.76 for a chitosan derived sample. This ability of chitosan and chitin derived N-rich activated carbons was studied by means of the method named rotating ring disc electrode.

Binary transition metal oxides, such as NiCo2O4 (NCO) electrode have been demonstrated to be promising candidates for high-performance supercapacitors. However, their low electrical conductivity and poor stability made the electrochemical performance of most current NCO electrodes yet below the expectation. Herein, a novel electrode (NCC) consisting of binary transition metal (Ni–Co) nanoparticles embedded N-doped porous carbon matrix on graphite papers (GPs) has been developed with a high specific capacitance of 933.5 F/g at 1 mA/cm2 which is substantially 10 times than that of the NCO electrode (99.3 F/g) and much higher than those of most reported NCO based electrode. Moreover, this NCC electrode has an ultrahigh rate capability of 725.5 F/g at 10 mA/cm2 with excellent electrochemical durability (no capacitance decreases after 10,000 cycles). These results indicate a promising potential application of Ni–Co metal composite embedded carbon matrix for using as an effective electrode material in supercapacitors.

Highly porous alumina-based oxides, γ-Al2O3, SiO2–Al2O3, and TiO2–Al2O3 were synthesized by a modified sol–gel method. Polivinylpyrrolidone was used as the pore expanding agent, whereas cetyltrimethylammonium bromide was used as the template in the presence of alkoxide inorganic precursors. Both as-synthesized and calcined solids were used as catalysts for esterification of glycerol with acetic acid (EG). The XRD and SEM-EDS measurements demonstrated that the Si-containing solids are amorphous while those containing Ti are semicrystalline with the latter composed of TiO2 rutile, TiO2 anatase, and γ-Al2O3 phases. All solids possessed ordered porous structures comprising of micro- and mesoporosity, with interconnectivity between these pores of different length scales. The high acidity of γ-Al2O3 and TiO2–Al2O3 materials resulted in good catalytic performances in the EG. Porosity of the solids plays a secondary role in determining the catalytic activity. Under the same conditions, the as-synthesized solids exhibited slightly lower catalytic performances compared to that of the calcined ones.

The influence of heat treatment (homogenization) on the microstructure, mechanical behavior, and soft magnetic properties of a face-centered cubic (fcc)-based high-entropy alloy (HEA), Fe29Co28Ni29Cu7Ti7, fabricated by casting, was investigated in detail. The as-cast Fe29Co28Ni29Cu7Ti7 HEA was composed of a primary fcc phase containing coherent dispersed L12 nanoprecipitates and trace amounts of a needle-like phase. The tensile yield strength (σ0.2), ultimate strength, and total elongation of the as-cast alloy are 917 MPa, 1060 MPa, and 1.8%, respectively. Following homogenization, the alloy having a single fcc phase shows a decrease of ∼ 55% in yield strength and a decrease of ∼ 36% in ultimate strength; however, the total elongation is increased from 1.8 to 52%. Saturation magnetization (Msat) is decreased from 111.54 to 110.34 Am2/kg, by contrast, coercivity (Hc) is increased from 266.65 to 966.89 A/m. The dissolution of precipitates and grain growth are mainly responsible for the changes in magnetic properties and mechanical behavior.

The polysaccharide alginate has received most extensive attention as bioink in bioprinting applications due to its ability to undergo gelation under cell-friendly conditions. However, absence of cell-binding motifs and the erratic degradation of alginate hydrogels have remained their persistent limitations. Honey is a conveniently available natural material, known for its role in wound healing and skin tissue regeneration. However, honey blending to improve biological response of alginate-based bioprinted scaffolds has not been yet reported. In the present work, honey-alginate bioinks were evaluated for their printability property (shape fidelity). It was found that honey blending reduced alginate viscosity, which gradually affected bioprinting fidelity. Therefore, the concentration that provides for acceptable bioprinting along with improvement in cell proliferations is determined. It is concluded that honey blending improves cell response of alginate bioinks and can be a facile approach to obtain bioinks especially for in situ skin tissue engineering applications.

The electrochemical behavior of TiNi(1−x)Nbx (x = 0, 0.05, 0.1, 0.2) ternary intermetallic compounds synthesized by mechanical alloying was investigated and compared to that of binary TiNi. The structure of 20-h milled product with initial stoichiometric composition of TiNi0.95Nb0.05 was found to be amorphous/nanostructured. Upon cycling, this ternary milled product exhibited the highest discharge capacity (166.1 mA h/g) after 10 cycles and best cycle stability (∼91%) while those of the binary TiNi were 147 mA h/g and ∼83%, respectively; i.e., slight amount of Nb substitution (0.05 mol) for Ni in the TiNi not only increased discharge capacity and cycle stability but also enhanced the kinetics of hydrogen absorption/desorption through increasing the exchange current density and hydrogen diffusion coefficient. However, additional Nb content was found to have negative effect on electrochemical properties; this was related to the existence of Nb element in addition to the ternary amorphous/nanocrystalline structures.

First principles was carried out studying the properties of (Ti, Nb)C compounds based on density functional theory. The integration of mechanical behavior, electronic structures, and thermodynamic properties can be optimized by mediating the concentration of the titanium alloying element. The results revealed that these transition metal compounds were stable with the negative formation energy. Nb0.5Ti0.5C (29.15 GPa) demonstrated the largest hardness characterized by moduli (B, G) because of the stable shell configuration. NbC exhibited the strongest anisotropy from the universal anisotropic index (AU) and three-dimensional surface contours. TixNb1−xC compounds displayed relatively strong stress responses along the [001], [110], and [111] directions. Due to the weakening p–d bonding, the ideal tensile strength gradually decreased with the increasing titanium concentration. The electronic structures revealed that the bonding characteristics of the (Ti, Nb)C compounds were a mixture of metallic and covalent bonds. On the other hand, NbC and TiC exhibited a minimum (740.55 K) and maximum (919.29 K) Debye temperature, indicating the stronger metalic bonds of NbC and covalent bonds of TiC.

Introducing architected cuts is an attractive and simple approach to tune mechanical behaviors of planar materials like thin films for desirable or enhanced mechanical performance. However, little has been studied on the effects of architected cuts on functional materials like piezoelectric materials. We investigated how architected cut patterns affect mechanical and piezoelectric properties of polyvinylidene fluoride thin films by numerical, experimental, and analytical studies. Our results show that thin films with architected cuts can provide desired mechanical features like enhanced compliance, stretchability, and controllable Poisson’s ratio and resonance frequency, while maintaining piezoelectric performance under static loadings. Moreover, we could observe maximum ∼30% improvement in piezoelectric conversion efficiency under dynamic loadings and harvest energy from low frequency (<100 Hz) mechanical signals or low velocity (<5 m/s) winds, which are commonly existing in ambient environment. Using architected cuts doesn't require changing the material or overall dimensions, making it attractive for applications in self-powered devices with design constraints.

Advanced alloys with both high strength and ductility are highly desirable for a wide range of engineering applications. Conventional alloy design strategies based on the single-principle element are approaching their limits in further optimization of their performances. Precipitation-hardened high-entropy alloys (HEAs), especially those strengthened by coherent L12-nanoparticles, have received considerable interest in recent years, enabling a new space for the development of advanced structural materials with superior mechanical properties. In this review, we highlight recent important advances of the newly developed L12-strengthened HEAs, including the aspects of computation-aided alloy design, unique properties, atomic-level characterization, phase evolution, and stability. In particular, we focus our attention on elucidating fundamental scientific issues involving the alloying effects, precipitation behaviors, mechanical performances, and the corresponding deformation mechanisms, all of which provide a comprehensive metallurgical understanding and guidance for the design of this new class of HEAs. Finally, future research directions and prospects are also critically assessed.

In this paper, we will discuss stability and reliability requirements of organic electronic devices and evaluate different encapsulation approaches enabling stable organic ultra-thin and stretchable devices. We highlight the differences in requirements and encapsulation approaches for applications, including organic light emitting diode (OLED) displays, OLED lighting, photovoltaics, and sensors. Stability and reliability requirements addressed in this paper cover light management, mechanical characteristics, chemical compatibility, form factors, and durability. While flexible organic electronic devices have already been demonstrated and commercialized, so far only prototypes of ultra-thin and stretchable devices have been demonstrated. The technological progress is promising and by identifying the gaps between prototyping and product realization, we intend to stimulate further research and development in this area.