The rapid sol–gel synthesis of macroscopic quantities of nanodiamond aerogel (NDAG) is reported at standard temperature and pressure using acid-catalyzed covalent crosslinking of air-oxidized detonation nanodiamond (DND) nanocrystals. Acetonitrile acts as a polar, aprotic solvent both to form a colloidal dispersion of DND particles and to conduct acid-catalyzed polycondensation reactions between resorcinol and formaldehyde (RF) small molecule precursors. Several characterization techniques show that nanodiamond grains are connected via covalent bonding with RF molecules to form a porous, three-dimensional network. Solvent exchange into liquid carbon dioxide and subsequent supercritical drying of NDAGs are used to recover low-density (151 mg/cm3), three-dimensional monolithic aerogels that exhibit surface areas in excess of 589 m2/g. The large accessible pore volume from the rapidly synthesized, macroscopic NDAG materials suggests a range of potential applications in catalysis, sensing, energy storage, as well as inert excipients for small-molecule pharmaceuticals.

This study presents the optical properties of layered ZnO/Al/ZnO composite thin films that are being explored for potential applications in solar cells and light emitting devices. The composite thin films are explored as alternatives to ZnO thin films. They are produced via radio frequency magnetron sputtering. The study clarifies the role of the aluminum mid-layer in a ZnO (25 nm)/Al/ZnO (25 nm) film structure. Multilayers with low resistivity ∼362 µΩ cm and average transmittances between ∼85 and 90% (in the visible region of the solar spectrum) are produced. The highest Haacke figure of merit of 4.72 × 10−3 Ω−1 was obtained in a multilayer with mid-layer Al thickness of 8 nm. The combined optical band gap energy of the multilayered films increased by ∼0.60 eV for mid-layer Al thicknesses between ∼1 and 10 nm. The observed shifts in the optical absorption edges to shorter wave lengths of the spectrum are shown to be in agreement with the Moss–Burstein effect.

Magnesium aluminate (MgAl2O4) spinel nanoparticles with an average crystalline size of 35 nm were synthesized by polymer-gel and isolation-medium-assisted calcination. In the process, a large excess of MgO, 40 times the stoichiometric amount of spinel, is added to the precursor mixture to separate the spinel particles as they are nucleated to prevent their agglomeration and coarsening during calcination. Well-dispersed MgAl2O4 nanoparticles with a single-crystal structure were obtained after acid washing of calcined product. The microstructures of the as-prepared samples were characterized by differential thermal and thermogravimetric analysis, x-ray diffractometry, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption isotherms, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. The results indicate that MgO acting as the isolation medium is effective in preventing the agglomeration of MgAl2O4 nanoparticles, and it also prevents their contamination by introducing an isolation medium during the preparation process. The nanopowder was sintered up to 95% of the theoretical density but with parallel grain growth.

BaTiO3–SnO solid solutions have been investigated from the viewpoints of synthesis and Sn ion valence. First-principles calculations show that the solution energy of Sn2+ into the Ba sites in BaTiO3 is less than that into the Ti sites under high pressure. The BaTiO3–SnO solid solutions have been synthesized under high pressure (∼20 GPa) and temperatures using a laser-heated diamond anvil cell. The synthesized materials have been characterized using x-ray diffractometry, scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. It is found from these various methods that we have successfully synthesized uniform solid solutions of BaTiO3–SnO. Furthermore, it is also clarified by the Sn L3-edge electron energy loss spectra measurements that the valences of the Sn ions in the BaTiO3–SnO solid solution are 2+. These results indicate that the Sn2+ ions are substituted into the Ba sites, according to the ion size. Consequently, the Sn ions can be substituted into the Ba sites of the shrinking BaTiO3 lattice under high pressure, which is similar to the Ca and Sn co-substitution into Ba sites under ambient pressure as reported previously.

Zn3(VO4)2 nanorods with visible light-driven photocatalytic activity were prepared by hydrothermal reaction and characterized by x-ray diffraction, Fourier transform infrared, scanning electron microscopy, x-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, and Brunauer–Emmett–Teller surface area and pore size analyzer. The Zn3(VO4)2 nanorods consisted of rods with a thickness of approximately 30 nm, length in the range 400–600 nm, and width in the range 150–250 nm. The photocatalytic degradation activities for methylene blue (MB) and 4-nitrophenol (4-NP) over the Zn3(VO4)2 nanorods were studied in detail. The photocatalytic activity of the as-prepared photocatalyst for MB and 4-NP in visible light under the same conditions was about 3.5 times and 2.5 times higher than that of N–TiO2, respectively. The main active species in the photodegradation come from •OH, and the photogenerated electrons also partly involved in the photocatalytic degradation process, in which the •OH radicals formed were in proportional to the light illumination time obeying zero-order reaction rate kinetics.

Measurements of stress evolution during low-energy argon ion bombardment of Si have been made using a real-time wafer curvature technique. During irradiation, the stress reaches a steady-state compressive value that depends on the flux and energy. Once irradiation is terminated, the measured stress relaxes slightly in a short period of time to a final value. To understand the ion-induced stress evolution and relaxation mechanisms, we account for the measured behavior with a model for viscous relaxation that includes the ion-induced generation and annihilation of flow defects in an amorphous Si surface layer. The analysis indicates that bimolecular annihilation (i.e., defect recombination) is the dominant mechanism controlling the defect concentration both during irradiation and after the cessation of irradiation. From the analysis, we determine a value for the fluidity per flow defect.

The demands for highly transparent thin films for many integrated optical systems increase rapidly. The aim of the present work is to address these important needs. We show a novel approach for the nanocolloidal processing of barium titanate with enhanced optical transparency. The results showed that the stability of the prepared solution and optical transparency of the resulted thin film improved significantly. The study of the structure and properties of the prepared solutions indicated that the enhanced and homogenous transparency is due to the size-effect of the particles embedded in the solution, which are nanostructured. It seems to us that the proposed method has the capability of being a general strategy for obtaining highly transparent solutions and thin films. Moreover, the enhanced transparency of the prepared thin films can improve the energy efficiency of the solar power systems significantly.

Modified MMT clay-doped PMMA composites have been prepared by solvent casting method for different weight percentages. The prepared composite films were characterized by FTIR and SEM. Also, the DC conductivity was carried out for PMMA and PMMA composite films. Among all composites, it was found that 30 wt% shows highest conductivity of 1.59 × 10−3 S/cm. The negative thermal coefficient behavior of these polymer composite films confirms that the increase in conductivity is due to the elongation of polymer chain which helps in charge transport mechanism. Dielectric study also shows that 30 wt% has the lowest dielectric constant and dielectric loss of 2.5 and 3.3, respectively, resulting in an increase in conductivity of 5 × 10−3 S/cm. The isotropic nature of 30 wt% composite film shows a high quality factor of 0.005 because of overdamping of electron at 104 Hz. Cole–cole plots show that the semi arc originated from a single point and its area decreases with filler concentration up to 30 wt% due to drop in the electrical resistance. Tensile modulus increases because of high MMT aspect ratio and distribution ratio. The 30 wt% of the composite shows high tensile strength at 55 MPa which induces 8% of strain in the PMMA–MMT clay composite films. Therefore, these composite films can be used in many sensor and solar technologies as encapsulation materials.

Stretchable transparent conductors are required for flexible and wearable electronics. This study demonstrates biaxially stretchable transparent conductors that use silver nanowire networks. The use of buckled nanowire networks has previously been reported to lend stretchability to the transparent conductor in a single axis. However, a nanowire network that is prestrained and then buckled out-of-plane biaxially shows a deterioration of the electrical conductivity after a single cycle of stretching and releasing the strain uniaxially. This has been attributed to the loss of good electrical contact between the nanowires. By hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with good wire-to-wire junctions, a biaxially stretchable transparent conductor that maintains good electrical conductivity with stretching up to 10% is demonstrated. The methods of prestraining the nanowire network to achieve out-of-plane buckled nanowires and hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with fused junctions are expected to be practical for other classes of percolative networks based on one-dimensional (1D) materials used in flexible and stretchable applications.

The yield behavior of solid polymers may be influenced by the hydrostatic pressure, strain rate, and temperature. In the present work, we focus on evaluating the effect of hydrostatic pressure on the yield strength by instrumented indentation. Using dimensional analysis and finite element analysis, two analytical expressions were derived to relate the indentation data to the plastic properties, and a method for extracting the coefficient of internal friction which reflects the effect of hydrostatic pressure on the yield strength was established. Applications were illustrated on polypropylene (PP), polycarbonate (PC), and unplasticized polyvinyl chloride (UPVC). The coefficient of internal friction determined by this indentation method is 0.20 ± 0.02 for PP, 0.07 ± 0.01 for PC, and 0.10 ± 0.01 for UPVC, which are in good agreement with the values reported in the literature. This demonstrates the proposed indentation method which is useful to evaluate the effect of hydrostatic pressure on the yield strength of solid polymers.

To evaluate the influence of strain rate on mechanical behavior of nanocrystalline (NC) materials, a phase mixture constitutive model composed of ordered grain interior phase and plastically softer grain boundary dislocation pile up zone phase was built. Because of dissimilar properties and mismatch between the two phases, dislocation density evolution controlling mechanism based on statistically stored dislocations and geometrically necessary dislocations was analyzed and extended to NC regime to consider their disparate effects. Based on the composite model, a new stress–strain constitutive relation for strain rate-dependent behaviors was firstly established based on dislocation density evolution and strain gradient theory. The calculated data were then compared with corresponding experimental curves and strong strain rate-dependent behaviors were exhibited, which indicated that the predictions kept in good agreement with experiments. Further discussions were presented for calculations of strain rate sensitivity and activation volume for NC Ni through the proposed model.

The influence of predeformation and stress on the isothermal bainite transformation has been investigated in G55SiMoV steel via microstructure observation and kinetic analysis. It was found that the bainite transformation became faster and at the end of isothermal holding the bainite fraction increased under the applied stress condition. When the stress increased to 150 MPa, the bainite distribution became to be nonrandom in G55SiMoV steel. Different deformation conditions, in which both promotion and inhibition occurred in the same steel, were created. The promoting and inhibiting factors affected bainite transformation comprehensively. 20% deformation could promote the bainite transformation when it deformed at 900 °C, but prevent bainite transformation when it deformed at 750 °C. Increase of ferrite nucleation rate caused by distortion and dislocation, would suppress the growth of bainite carbides and make most carbides without full growth be finer and shorter.

The effects of the different shot peening parameters on the 6061 alloy specimens' surface have been investigated. It is found that the compressive residual stresses and the surface roughness of the surface layer for all shot-peened specimens are improved greatly. The maximum stress value and the maximum roughness are obtained by the shot flow rate of 5.5 lbs/min and air pressure of 20 psi. The microstructure observation results indicate that a nanostructured layer with an average grain size below 100 nm has been created on the top surface layer of each specimen. In the top surface nanostructured layer, the microhardness is enhanced. It is resulted from the grain refinement and the strain hardening. The results of electrochemical measurements, surface corrosion morphology observation, and EDS analysis indicate that the corrosion susceptibility of the 6061 alloy could be significantly enhanced by means of the shot-peening-induced surface nanocrystallization.

The present investigation addressed the weldability of Super Ni 718 alloy and AISI 316L using gas tungsten arc (GTA) welding process using three different filler wires, such as ER2594, ERNiCrMo-4 and ERNiCrCoMo-1. Interface microstructures showed the formation of secondary phases at the heat-affected zone (HAZ) of Super Ni 718 alloy and delta ferrite colonies at the HAZ of AISI 316L. It was witnessed from the weld microstructures that the deleterious phases were suppressed or controlled while using these filler wires for joining the bimetals. Tensile results corroborated that the failure occurred at the parent metal of AISI 316L in all the cases. The presence of microvoids and dimples characterized for the ductile mode of fracture in these weldments. Charpy V-notch test results showed that the weldments using ERNiCrMo-4 filler exhibited higher impact energy. A detailed study has been made to investigate the structure–property relationships of these weldments using optical and scanning electron microscopic techniques.

Hot-rolled Mg–Zn–Ca alloy, followed by annealing, shows high formability at room temperature because of the reduced intensity of the basal texture. [Y. Chino et al., Mater. Trans. 51, 818 (2010).] In the present work, microstructures of the as-rolled Mg–Zn–Ca alloy were investigated using electron backscattered secondary diffraction and transmission electron microscopy. In addition, first-principles calculations were performed to investigate the twinnability of the Mg–Zn–Ca alloy. The microstructural investigations revealed that fine $\left\{ {10\bar 12} \right\}$ twins and local fine-grained microstructures were formed. It is therefore suggested that the fine twins induce this local fine-grained microstructure, which become the nuclei for recrystallization during annealing. As a result, the intensity of the basal texture is reduced. Calculations revealed that the $\left\{ {10\bar 12} \right\}$ twinnability is enhanced by the addition of Ca because of the increased unstable stacking fault energy (γus) and decreased unstable twin fault energy (γut).