We present an experimental study on the epitaxy and orientational relationships of WO2 and NbO2 films on (0001) Al2O3, (111) MgAl2O4, and (111) MgO substrates, as well as WO2 on (111) SrTiO3. The higher symmetry of the substrate planes compared to the film planes leads to the formation of epitaxial structural variants, and they are related by the surface rotational symmetry elements of the substrates. WO2 and NbO2 crystallize in distorted versions of the rutile structure, and we discuss our findings in context of the rutile unit cell. Our results are applicable to other compounds that occur in (distorted) rutile structures. For the case of NbO2 thin films, we also demonstrate that they can be grown epitaxially on (10$\bar 1$2) and (10$\bar 1$0) Al2O3, lower symmetry surfaces; in these cases, surface symmetry does not induce the formation of epitaxial rotational variants, though domains related by glide symmetry are possible.

Electronic devices made from single crystal thin films attached to inexpensive support substrates offer reduced material costs compared to wafer-based devices; however, scalable and inexpensive processes for producing these single crystal film structures have remained elusive. In this work, we describe a new approach for fabricating these structures. In our approach, an epitaxial film is grown on a single crystal template and is then separated from its growth surface via fracture along a weak heteroepitaxial interface between the single crystal film and its growth substrate. We show that epitaxial films of Si, Ge, and GaAs, with thicknesses ranging from 100 nm to 1 μm, grown on epitaxial CaF2 overlayers on Si <111> substrates, can be transferred to glass substrates by inducing fracture along the heteroepitaxial interface between the semiconductor film and CaF2, or between CaF2 and the Si wafer, assisted by the presence of water as in moisture-assisted cracking.

Multilayer thin films have been widely used for their enhanced mechanical and tribological properties relative to the monolayers of equivalent thickness. However, the mechanical properties of the each constituent layer are rarely investigated due to the difficulty in separating the effects of the constituent layers. An inverse analysis method to identify the elastic moduli of the constituent layers of multilayer films is developed by fitting the finite element calculations with indentation measurements within the framework of numerical optimization. The method is verified against typical monolayer, bilayer, and trilayer film structures both numerically and experimentally. Uniqueness and substrate-independence of the extracted moduli are ensured by the multiple loading–unloading cycles of the indentation tests. The method provides a feasible way to characterize the intrinsic mechanical properties of the constituent layers of multilayered thin films and further to explore the dominant mechanism for the enhancement of their mechanical properties.

Core–shell nickel oxide/carbon nanotube (CNT) microwires, with interconnected nickel oxide nanoflakes (∼10 nm in thickness) vertically oriented on polymer-based CNTs, were synthesized by using low-cost starting materials and a scalable growth route. As revealed by morphological characterization, sheet–sheet and wire–wire interwoven of the composite constructed a porous structure. The composite as lithium ion battery anode exhibited high reversible capacity of 752 mAh/g at a current density of 100 mA/g over 30 cycles with 82% capacity retention. Even at high rate (1000 mA/g), the composite still delivered a high charge capacity (304 mAh/g) over 25 cycles. When the rate was reset to its initial value, 87.7% of the initial charge capacity was recovered. The composite showed remarkably enhanced performance compared to pure NiO, which was presumably due to the advantages of porous structure, oriented attachment, and attractive synergetic effect.

A novel graphene-modified LiMnPO4 composite as a performance-improved cathode material for lithium-ion batteries has been prepared with LiH2PO4, Mn(CH3COO)2·4H2O, and graphite oxide (GO) suspension by spray-drying method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and galvanostatic charge–discharge tests are applied to characterize these materials. The structure analysis shows that LiMnPO4 sheets with width of 100–200 nm and thickness of 20–30 nm are attached to the graphene sheets in pieces. The graphene sheets with good electrical conductivity serve as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during the discharge/charge process. The electrochemical tests show that the composite cathode material could deliver a capacity of 105.1 mAh/g at 0.05 C in the voltage range of 2.5–4.4 V. Moreover, the cells showed fair good cycle ability over 50 cycles.

Red-emitting phosphor of Ca0.8Zn0.2TiO3:0.2 mol% Pr3+ was synthesized by the hydrothermal method with urea as a mineralizer. The crystalline structure, micromorphology, and luminescent properties of the resultant phosphor were investigated. Results show that elevated calcination temperature does not change the shape of particles that are hollow spheres with a shell thickness of 210–480 nm, and smaller particles are in the middle of the larger ones. The emission intensity at 612 nm originated from 1D2 → 3H4 transition of Pr3+ ions increases with the elevated calcination temperature due to a higher crystallinity. Excitation curves consist of two strong broad bands centered at about 330 and 380 nm and a weaker broad band range from 450 to 500 nm. The sample prepared by the hydrothermal method has better luminescent properties than that of its counterpart prepared by the solid-state method, especially the improvement of near-UV region (380 nm) excitation intensity.

Fine-sized powders of BaSi3Al3O4N5:Eu2+ phosphors with high stability and improved photoluminescence properties were successfully synthesized by the traditional solid-state reaction method under a reductive atmosphere using BaF2-fluxing additives in the raw powder mixture. The produced phosphors had strong blue emission under excitation in ultraviolet (UV) and vacuum ultraviolet (VUV) light, due to the 4f 5d–4f7 transition of Eu2+ ions. X-ray diffraction, scanning electron microscopy, XANES, and the photoluminescence (PL) spectra under UV and VUV were used to characterize the as-received samples. The experimental results showed that the addition of BaF2 flux improved the crystalline regime and the PL properties of the produced phosphors. Most significantly, it allowed control of the particle size and particle size distribution in the final powders but did not jeopardize the high thermal and chemical stability of the phosphors produced. With the modification of the BaF2 flux, the blue-emitting BaSi3Al3O4N5:Eu2+ phosphors will show excellent packing and coating properties and could be a good candidate for the light-emitting diodes and plasma display panels.

All-oxide ultraviolet (UV) photosensors based on NiO/ZnO nanowire heterostructure were fabricated on corning glass substrates. The p-type NiO layers were directly deposited on the ZnO nanowire arrays grown on the AZO bottom electrode/glass for the formation of a p–n diode, followed by the growth of the ITO top electrode layer for the electrical interconnection of nanostructures. The fabricated device structure showed a transmittance value of about 60% in the visible region, resulting in semitransparent properties. The current–voltage (I–V) characteristics of the fabricated p–n heterostructure showed a typical rectifying behavior with a current rise at about 4 V and an I(forward)/I(reverse) ratio of about 11.3 at 8 V. In addition, the ITO/p-NiO/n-ZnO/AZO structure responded at a wave-length position of 370 nm in reverse bias, together with weak photoresponse in the visible region. An UV sensor based on the all-oxide ZnO nanowire absorber exhibited improved photoresponse compared to the device based on a ZnO thin film.

The influence of calcium fluoride (CaF2) on combustion characteristics of Na2WO4 + 3 Mg system and microstructure of the produced W and WO3/W crystals is investigated. The results of thermodynamic analysis and experimental investigations show that CaF2 simultaneously enhances the conversion of Na2WO4 toward tungsten and binds sodium through the formation of NaF phase. The examination of the microstructure of quenched combustion products and differential scanning calorimetry analysis indicate that at early stages of combustion, a part of Na2WO4 is reduced by Mg to tungsten, whereas another part reacts with CaF2 forming CaWO4 and NaF. Subsequent magnesium reduction of CaWO4 significantly increases the overall temperature of the combustion process. Such modification in reaction mechanism coupled with postcombustion processing (e.g., acid/basic treatment) of the product allows us to produce either pure tungsten nanocrystals or tungsten oxide—tungsten nanostructures consisting of two-dimensional WO3 nanoflakes assembled on a W core. It is found that CaF2 does not influence the sizes of tungsten nanocrystals. However, since the addition of CaF2 leads to the increase of overall reaction temperature, it facilitates the formation of W particles with equilibrium crystal shape by faceting process.

The mechanisms involved in the formation of titanium (Ti) nanoclusters produced by sputtering and inert gas condensation were investigated experimentally and numerically. Ti nanoclusters were generated inside an ultrahigh vacuum compatible system under different source parameters, i.e., inert gas flow rate (fAr), length of the aggregation region (L), and sputtering discharge power (P). Nanocluster size and yield were measured using a quadrupole mass filter (QMF). The variation of the above source parameters enabled fine-tuning of the nanocluster size and yield. Herein, Ti nanoclusters were produced within the size range 3.0–10.0 nm. The combination between the nanocluster size and yield as a function of source parameters enabled understanding Ti nanocluster formation mechanisms, i.e., three-body and two-body collisions. The results show that two-body collisions dominate nanocluster production at low fAr while the three-body collisions dominate at high fAr. In addition, nanocluster size increases as L increases due to the increase in nanocluster nucleation and growth times. The maximum nanocluster yield was obtained at fAr that maximize the probability of three-body and two-body collisions. Nanoclusters could be produced within an optimum range of the sputtering discharge power wherein the nanocluster size and yield increase with increasing the discharge power as a result of increasing the amount of sputtered material. The experimental results were compared with a theoretical model of nanocluster formation via three-body collision. Detailed understanding of the evolution of size and yield of Ti (and Ti-oxide) nanoclusters is essential for producing nanoclusters that can be utilized for environmental applications such as conversion of carbon dioxide and water vapor into hydrocarbons.

Copper nanoparticles (Cu-NPs) were prepared in virgin coconut oil (VCO) using a laser ablation technique. A copper plate immersed in VCO was irradiated by an Nd:YAG laser at wave lengths of 532 nm for 5, 10, 20, and 30 min. By increasing the ablation time from 5 to 30 min, the particle size inside the nanofluid decreased from 11 to 4 nm and the concentration, refractive index, and the volume fraction of copper nanofluid increased. The Cu-NPs were capped with oxygen from hydroxyl groups of the VCO, as verified by Fourier transform infrared spectroscopy. The refractive indices, obtained by analysis of the surface plasmon resonance signals increased from 1.44371 + 0.0034i to 1.44387 + 0.0142i, and special self-phase modulation due to nonlinearity effect was investigated.

A straightforward approach allowing three-dimensional (3D) visualization of subsurface deformation beneath nanoindents using reconstructed cross-sectional transmission electron microscopy (TEM) data is demonstrated. This approach relies on generating an array of nanoindents, extracting a thin (<200 nm) cross section using a focused ion beam (FIB) and imaging with a transmission electron microscope. By rotating the orientation of the FIB cross section with respect to the array of nanoindents at the optimal angle, it is guaranteed that a different section of each nanoindent's subsurface plastic zone is contained within the final cross section. Subsequently, TEM images corresponding to different sections are reconstructed into a 3D image of a representative nanoindentation plastic zone. This approach can be extended to any array of nominally identical features that can be patterned with regular spacing and included in a single FIB cross section. It was also found to significantly enhance the throughput of preparing routine site-specific TEM samples, even when 3D visualization is not necessary. In this article, the approach is applied to visualize the plastic zones beneath nanoindents in GaAs (001), for loads of 50–1000 µN.

The Ag@SiO2 core–shell structure nanoparticles prepared by chemical method were dispersed into epoxy matrix. By comparing with the epoxy-based composites filled with the mixed Ag and SiO2 nanoparticles (Ag + SiO2), it is found that the Ag@SiO2 core–shell structure fillers had important effects on the improved dielectric properties of the Ag@SiO2/epoxy composites. The core–shell structure fillers introduce a duplex interfacial polarization and a small number of free charge carriers, which enhance the dielectric permittivity of the composites. At the same time, the insulating SiO2 shell layer changes the interfacial interaction between the Ag filler and the epoxy matrix, not only avoiding Ag particles to connect directly and aggregate together but also providing a rough surface to contact with the epoxy host, which enhances the compatibility between the Ag@SiO2 fillers and the epoxy matrix. As the Ag@SiO2 packing ratio increases, the permittivity of the composites straightly increases and the loss tangent decreases, reaching the maximum and minimum respectively with the filler loading up to 60%.

Rubberlike insect cuticle is a light fibrous composite, which exhibits great deformability and long-range elasticity due to the presence of a large amount of the elastomeric protein resilin. The presence of resilin in specific locations in the insect body leads to the assumption that its main function is loss-free storage of energy. Rubberlike cuticle was identified, for the first time, in the femur base of the sand field cricket, Gryllus firmus, using fluorescence microscopy and various staining methods. Dynamic nanoindentation testing was then used to investigate the differences in the mechanical properties of rubberlike cuticle between males and females and wing morphs of this species. Significant changes in storage, loss moduli, and resilience were captured between female wing morphs. The results provide insight into the structure–function relations associated with the properties of insect joints from different morphs and genders.