This study reports the generation of periodic parallel silicone strips by simply peeling a silicone sheet, oxidized by UV/ozone, from its bonded substrate. This spontaneous formation of strips is initiated by a mixed mode of separation along the peeling direction and subsequent channeling of initiated cracks. The periodicity of the strips is tuned by the bending strain acting on the silicone sheet during peeling, and the regularity and the locus of failure are determined by the extent of oxidization.

The synthesis of monodisperse magnetite nanoparticles (Fe3O4 NPs) has been widely investigated over the last decade. Among the various synthetic methods, thermal decomposition of iron acetylacetonate, Fe(acac)3, or the premade iron-surfactant complex, was demonstrated to be promising to obtain monodisperse Fe3O4 NPs with controllable size and morphology. However, toxic and expensive precursors or tedious experimental procedures are normally required in these approaches. In this communication, we report a facile chemical top-down method to synthesize monodisperse magnetite NPs by using rust, which is mainly composed of γ-Fe2O3, as the iron source and oleic acid as the capping agent. The particle size, and hence the magnetization, of NPs can be readily controlled by adjusting the rust/oleic acid ratio and reaction temperature. This process is a green chemical approach and is easy to be reproduced and scaled up, which could be developed as an effective way to convert waste materials into high quality nanocrystals.

The present work reports on the conditions of nanoparticle growth and splitting under energetic ion irradiation. Cohesive energy that determines the thermal stability of a given nanoparticle system was calculated by extending surface area difference (SAD) and liquid drop model (LDM). Based on the size-dependent cohesive energy calculations, the interparticle coalescence mechanism is discussed for a ZnS-based nanoparticle system with special reference to a variety of matrices. The interparticle separation is found to play key role in particle–particle coalescence leading to nanoparticle growth or partial evaporation that results in splitting.

Inks containing silver nanoparticles of 12 nm, 80 nm, and a 15%/85% mixture of the two sizes were used to evaluate the effect of particle size and size distribution on the electrical properties of sintered films. The silver layers deposited with a “drop-on-demand” inkjet printer were heated at temperatures ranging from 125 to 200 °C. The small particles formed less resistive films at 125 °C, while the larger ones provided better electrical conductivity above 150 °C. The inks containing mixed small and large particles yielded the most conductive silver films over the entire investigated temperature range. A mechanism explaining these results is proposed based on the evolution of film microstructure with temperature.

The microstructures of two pressureless sintered ceramics, ZrB2 and HfB2 with 20 vol% MoSi2 added, were analyzed by scanning and transmission electron microscopies. Carbides and oxides of the transition metals and MoB were observed to be well dispersed within the boride matrix. Mo5Si3 and Mo5SiB2, with Zr or Hf impurities, were observed at triple grain junctions and showed a partial wetting of the matrix. It was also noticed that the borides had a core-shell structure, which was especially pronounced in the ZrB2-based composite. The experimental results suggest the formation of a Mo–Si–B liquid phase at high temperature, which strongly promoted the densification. The densification mechanisms are discussed in light of the microstructure evolution on sintering, thermodynamic considerations, and the phase diagrams of the species involved.

We synthesized Ta3N5 by ammonolysis of Ta(OH)5. Ta(OH)5 was prepared by titration using TaCl5. The stirring speed and the amount of NH4OH to be added were important factors for controlling the particle size and formation of Ta(OH)5 during titration. During transformation of Ta(OH)5 to Ta3N5, the color changed from white to red. A small particle size and high level of formation of Ta(OH)5 improved nitridation, which was related to the color value. An x-ray diffractometer was used for phase identification. A scanning electron microscope was used to determine the microstructure, particle shape, and size. A colorimeter was used to obtain CIELab values. Ultraviolet–visible (UV–VIS) spectroscopy was carried out to determine the absorbance of colored powders. Thermogravimetry and a differential scanning calorimeter were used in air with a heating rate of 5 °C/min for thermal stability and behavior. An ON detector was used for detecting oxygen and nitrogen contents in Ta3N5.

The electronic structures of KMPO4 (M = Sr, Ba) were calculated by the density functional theory with the local-density approximation. The calculated result shows that KSrPO4 and KBaPO4 are direct-band gap materials with direct energy gaps of 4.52 and 4.35 eV, respectively. Meanwhile, by analyzing the valence band structures of KMPO4 (M = Sr, Ba), the strength of binding of valence band electrons of KBaPO4 is stronger than that of KSrPO4. In addition, the photoluminescence (PL) properties of the intense red-emitting phosphors KM1–xPO4:Eu3+x (M = Sr, Ba) were investigated. The PL emission spectra excited at 393 nm are dominated by the peak at 611 nm due to the forced electric dipole 5D0–7F2 transition of Eu3+ ions, which is attributed to low local symmetry sites occupied by Eu3+ ions in these hosts. And the optimum integrated intensities for KSr1–xPO4:Eu3+x and KBa1–xPO4:Eu3+x are 1.3 times and 1.1 times of that for commercial Y2O3:Eu3+, respectively.

Eu3+ ion-doped BaY2ZnO5 phosphors were synthesized using a vibrating milled solid-state reaction. The phosphors exhibit a series of Eu3+ ion intra-4f excited state 5DJ (J = 3, 2, 1, 0) transitions under an excitation of 395 nm. The maximum photoluminescence intensity for 5D0 → 7F2 transition (625 nm) was obtained at a Eu3+ ion concentration of 40 mol%; quenching occurred at higher concentrations. The critical distance (Rc) for the 5DJ (J = 3, 2, 1) → 7F1 transition was 18.1 Å, which is longer than that of 6.67 Å for the 5D0 → 7F2 transition, indicating that 5DJ (J = 3, 2, 1) is easier for concentration quench because of the cross-relaxation mechanism. The red emission of the BaY1.6Eu0.4ZnO5 phosphor has CIE chromaticity coordinates of (0.66, 0.34), which are close to the NTSC system standard red chromaticity (0.67, 0.33). BaY1.6Eu0.4ZnO5 may thus be potentially applicable as a red phosphor for ultraviolet light-emitting diodes converted in solid-state lighting technology.

Halloysite nanotubes (HNT) reinforced polylactic acid (PLA) nanocomposite fibers were produced using an electrospinning approach for biomedical applications. The PLA/HNT nanocomposite fibers were characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The various factors such as type of solvent, solution concentration, HNT loading and feed rate, affecting the electrospinning process, and the morphology of the nanofibers were investigated, and the optimum values for these parameters are suggested. The results indicated that the addition of dimethylformamide (DMF) to chloroform facilitated the electrospinning process because of the improvement in electrical conductivity and viscosity of the solution. Nanometer-sized fibers were obtained by the addition of HNT to PLA. HNT loadings had a significant effect on the morphology of the nanofibers. Bead-free fibers were produced at feed rates between 1 and 4 mL/h.

This study examined the performance of poly(3-hexylthiophene-2,5-diyl)(P3HT)- and [6,6]-phenyl C61 butyric acid methyl ester (PCBM)-based organic solar cells (OSCs) with a pyromellitic dianhydride (PMDA) cathode interfacial layer between the active layer and cathode. The effect of inserting the cathode interfacial layer with different thicknesses was investigated. For the OSC samples with a 0.5 nm thick PMDA layer, the power conversion efficiency (PCE) was approximately 2.77% under 100 mW/cm2 (AM1.5) simulated illumination. It was suggested that the PMDA cathode interfacial layer acts as an exciton blocking layer, leading to an enhancement of the OSC performance.

The microstructural evolution of ultrathin (<3 nm) oxide films grown on bare Al-based AlMg alloy substrates, by thermal oxidation in the temperature range of 300 to 610 K and at partial oxygen pressures in the range 10−4–10−2 Pa, was investigated by high-resolution transmission electron microscopy. Angle-resolved x-ray photoelectron spectroscopy was applied to establish the chemical constitution of the analyzed oxide films (i.e., the overall Al/Mg cationic ratio, as well as the relative depth distributions of Al and Mg in the grown oxide films). The ˜0.8-nm-thick (Al,Mg)-oxide film grown at 300 K is fully amorphous. A gradual development of long-range order in the oxide film sets in for thickening (Al,Mg)-oxide films of relatively high Mg content at T ≥ 475 K. The amorphous-to-crystalline transition proceeds by a phase separation: still predominantly amorphous oxide regions exist next to crystallized oxide regions, which are constituted of an MgO-type of oxide phase with a face-centered-cubic oxygen sublattice and an average lattice parameter of 4.146 ± 0.1 Å.

Ion implantation has been widely used to improve the mechanical and tribological properties of single crystalline silicon, an essential material for the semiconductor industry. In this study, the effects of four different ion implantations, Ar, C, N, and Ne ions, on the mechanical and tribological properties of single crystal Si were investigated at both the nanoscale and the microscale. Nanoindentation and microindentation were used to measure the mechanical properties and fracture toughness of ion-implanted Si. Nano and micro scratch and wear tests were performed to study the tribological behaviors of different ion-implanted Si. The relationship between the mechanical properties and tribological behavior and the damage mechanism of scratch and wear were also discussed.

The preparation of high-quality ferroelectric PbTiO3-based ultrathin films by chemical solution deposition, using a diol-based sol-gel method, has proved to be successful. However, there is a critical thickness below which the films break up into isolated structures. According to previous studies, above a certain grain size to thickness ratio a microstructural instability occurs and the coatings are no longer continuous. We explore the use of the solvent chemistry to control this phenomenon, as an alternative to the more conventional variation of the crystallization parameters. The use of diols with short C chain lengths leads to films with smaller grain sizes, whose critical thicknesses are lower. A reduction from 40 to 15 nm is achieved by reducing the number of C of the diol used from 5 to 2. A critical value of G/t < 5.0 is necessary to obtain continuous ultrathin films with the processing conditions used.

As-deposited ZnO/diamondlike carbon (DLC) was prepared using the laser ablation technique on ZnO/C targets, and in situ oxidized ZnO/DLC was prepared by using the same technique, but with the presence of oxygen on Zn/C targets. Transmission electron microscopy showed that ZnO/DLC films were obtainable by using both methods, but only in situ oxidized ZnO/DLC films showed the ultraviolet absorption at ˜370 nm. In situ oxidized films are highly sp3-bonded and rougher than as-deposited films, but as-deposited films are mechanically harder, stiffer, and have higher adhesion strength than in situ oxidized films. X-ray photoelectron spectroscopy revealed that a lower fraction of SiC, but a higher fraction of sp3 bonding was formed in the in situ oxidized ZnO/DLC. This hinted that the presence of oxygen might have scattered the plume’s expansion and reduced the energy possessed by the ions, thus reducing the graphitization and the formation of SiC in DLC matrix. Hence, by altering the deposition mechanism during laser ablation, ZnO/DLC films with modified material properties can be tailored.

The effect of the presence of diamondlike carbon coatings deposited on (100) Si substrates on the deformation mechanisms operating in the silicon substrate during contact loading have been investigated by both cross-sectional transmission electron microscopy and modeling of the stresses generated beneath the indenter tip. The observed subsurface microstructures were correlated to the Tresca shear stress and the hydrostatic stress generated in the silicon substrate beneath the indenter tip. The presence of the coating altered the stresses generated in the substrate, and changed the deformation mechanism from one of principally phase transformation in uncoated Si to predominantly dislocation motion in the silicon substrate for the diamondlike C–Si system. The magnitude and distribution of the shear and hydrostatic stresses in the substrate were found to depend on both the indentation load and the thickness of the coating. Furthermore, the observed width of deformation, parallel to the interface, which was found to increase with coating thickness, was correlated to the wider distribution of the Tresca shear stress in the substrate brought about by the presence of the coating.

Spherical scratch tests were conducted in individual grains of a randomly oriented polycrystalline body-centered-cubic (bcc) Ti–Nb alloy. For each grain, scratch tests were conducted at four different levels of normal load, which resulted in varying amounts of plastic strain during indentation. The results show a dependence of the horizontal load component on the crystallographic orientation and on the amount of plastic strain. The component of the horizontal force that resulted from plastic deformation was found to correlate with the active slip systems for the particular grain orientation.

Precise calibration of the indenter shape is an important procedure in nanoindentation analysis since the indenter geometry enters directly into the most common methods of data analysis in this type of testing. Not only is the geometry required to be known with some precision, but also the sharpness of the tip, especially in the case of pyramidal indenters, is important for the use of indenters for testing hardness in thin film specimens—the most common application of nanoindentation. In this paper, a method of determining the area function and tip radius for a Berkovich indenter is described. It is shown that the tip radius estimated from the area function data is in reasonable agreement with a direct measurement using a calibrated atomic force microscope. It is shown that subjective decisions about tip radius may lead to unjustified rejection of a tip for hardness measurement. A new criterion for tip quality is presented in terms of tip radius and specimen material properties.

The Young’s modulus of single crystalline rutile TiO2 nanoribbons was investigated using nanoindentation. During the experiments, the nanoribbons were laid on three different substrates, including 1 μm thick SiO2 layer on silicon (SiO2/Si), Si(100), and sapphire(0001). Experimental results show the substrates have significant effects on load-indenter displacement curves. To further understand the experimental findings, three-dimensional finite element modeling was carried out to simulate the indentation of nanoribbon-on-substrate systems using ABAQUS. The results show that the receding contact mechanics is a good approximation when describing the contact between the nanoribbon and the substrate. The results also demonstrate that the substrate effect must be carefully considered when performing nanoindentation on one-dimensional nanostructures. Otherwise, the Young’s modulus of the nanostructures could either be overestimated or underestimated. The Young’s modulus is about 360 GPa, comparable to that of bulk TiO2.

High strength (Ti0.705Fe0.295)100-xSnx (0 ≤ x ≤ 6) composites have been prepared through arc melting and cold crucible casting. The microstructure consists of two phase ultrafine eutectic comprised of FeTi and β-Ti phases. The effect of Sn addition to the Ti70.5Fe29.5 eutectic is assessed in terms of microstructure variations such as eutectic spacing, morphology, cell size, lattice parameter of the phases, and the resulting mechanical properties in terms of strength and plasticity under compression. The mechanical properties (maximum strength 1939 MPa, fracture strain 13.5%) of the ternary Ti-Fe-Sn (2 ≤ x ≤ 6) are considerably improved compared to the Ti70.5Fe29.5 binary alloy (1733 MPa, 3.4%). The change in the morphology of the eutectic, the microstructure refinement, structural fluctuations, and supersaturation in the β-Ti phase, and the elastic properties of nanophases are crucial factors for improving the plastic deformability of the ultrafine eutectic alloys without presence of any additional micrometer-size toughening phase.

In this study, we produced an Al matrix composite material reinforced by Al-Cu-Fe particles of the icosahedral phase. The composite material was prepared using a hot isostatic pressure technique at T = 673 K and P = 180 MPa. The mechanical properties were investigated by compression tests performed at constant strain rate over the temperature range 290–823 K. The results show a vigorous strengthening effect resulting from the reinforcement particles. Strengthening is attributed to two main contributions arising from load transfer between the Al matrix and the reinforcement particles and from plastic deformation of the Al grains. The present results are compared with those obtained in a previous work on an Al-based composite reinforced by Al-Cu-Fe particles of the ω-tetragonal phase.