Zinc oxide (ZnO) nanomaterial is a superior material for photoanode. However, the different reaction concentrations, growth time and reaction vessel have influences on the structure and morphology of ZnO, and and ultimately have a bearing on the performance of solar cells. In this article, we used the hydrothermal method for the preparation of ZnO nanostructure. For avoiding direct contact of electrolyte with fluorine-doped tin oxide conducting glass, and decrease the recombination probabilities, we used titanium tetrachloride pretreatment. For obtaining flower-like ZnO nanostructure that was composed of smaller diameter ZnO nanorods, we fabricated a smaller-particle seed layer prior to growing ZnO nanostructure. For the sake of getting the best performances of solar cells, we examined the various effects of different deposition cycles on the performance of the solar cells. We discovered that when the deposition cycles increased, short-circuit current density, open-circuit voltage, fill factor and conversion efficiency all increased. But when the deposition exceeded 9 cycles, the values of all the parameters decreased. When the deposition cycle is 9, the conversion efficiency is 1.156%.

The review describes the workflow of a high-throughput screening process for the rapid identification of new and improved gas sensor materials. Multiple nanoparticulate metal oxides were synthesized via the polyol method, and material diversity was achieved by volume and/or surface doping. The resulting materials were applied as thick films on multielectrode substrates to serve as chemiresistors. This high-throughput approach including automated preparation, complex impedance measurements, and evaluation procedures enables reproducible measurements and their visual representation. Selected examples demonstrate the state of the art for applying high-throughput impedance spectroscopy in search of new sensitive and selective gas sensing materials as well as in analyzing structure–property relations.

The highly specific functions of DNA can be used for designing novel functional materials. However, aqueous solubility and biochemical instability of DNA impede its direct utilization as a functional component. Herein, preparation of a hybrid material encapsulating the DNA molecules (double-stranded salmon sperm, 50–5000 base pairs) in robust host—sol–gel-derived silica—has been described. The encapsulation was carried out in two steps: hydrolysis of an acidic tetraethylorthosilicate [Si(OC2H5)4] sol and was followed by condensation near physiological pH upon addition of alkaline DNA-containing solutions. The gelation behavior and structural properties of the DNA–silica hybrids were investigated by 29Si nuclear magnetic resonance and by nitrogen adsorption. The selective adsorption of a DNA-interactive reagent molecule (ethidium bromide) in their diluted aqueous solutions on DNA–silica hybrids confirmed that the DNA molecules remained entrapped within the silica host without any deterioration. A DNA encapsulation mechanism correlating the silica microstructure and DNA holding efficiency has been proposed.

The nanoindentation fracture behavior of gallium arsenide (GaAs) is examined from two perspectives in two parent papers. In the first paper (part I), we address the morphology of the crack field induced by different types of indenters by means of in situ nanoindentation inside a scanning electron microscope (SEM) and of cleavage cross-sectioning techniques. In the present paper (part II), we investigate the early stage of crack nucleation under wedge nanoindentation through cathodoluminescence and transmission electron microscopy. We find that the apex angle of the wedge indenter influences the dislocation microstructure and, as a consequence, the mechanism of crack nucleation under nanoindentation. The formation of microtwins depends on both the orientation of the indenter with respect to the orientation of the GaAs crystal and on the apex angle of the indenter. For dicing applications of GaAs wafers, it is desirable to have an opening angle of the indenter smaller than 70° to facilitate the formation of precursor cracks.

A novel surface enhanced Raman scattering (SERS) substrate was produced by combining Ag nanoparticles (AgNPs) and carbon nanocoils (CNCs). Three different methods were developed for loading AgNPs on CNCs, which include (i) direct deposition of AgNPs on CNCs by radio-frequency magnetron sputtering (RFMS) to form an Ag–CNC hybrid, (ii) deposition of a TiO2 film on CNCs by RFMS, followed by photoinduced growth of AgNPs to form an Ag–TiO2–CNC hybrid (called A-substrate), and (iii) deposition of a TiO2 film on CNCs by spin coating and then photoinduced growth of AgNPs to form an Ag–TiO2–CNC hybrid (called B-substrate). Experimental SERS results showed that B-substrates exhibited the highest SERS enhancement with an enhancement factor of over 107 for rhodamine 6G. The as-prepared Ag–TiO2–CNC substrates also showed much higher Raman signal enhancement than ordinary planar SERS substrates in our system. This was mainly due to the unique three-dimensional structure where the large surface area was available for loading more densely packed AgNPs which contribute to abundant Raman hot spots.

A new technology to coat open-celled foams homogeneously by using a vertical centrifuge and shear-thinning slurries is presented. The technology is exemplified by a complex multilayer-coated foam for catalytic applications (Fig. 3). Furthermore, a new calculation model for the estimation of coating thickness and for quality assessment is introduced and proved by comparing the calculated and experimental data. Based on these results, various material combinations are shown, e.g., layers made of rough particles, zeolites, activated carbon, γ-Al2O3, perovskites, mullite, and yttria–alumina–garnet on SiC–, Al2O3–, or cordierite foams. Theses “functionalized foams” can be used for a wide variety of practical applications, e.g., as adsorbents and catalysts in environmental engineering, as preforms for metal matrix composites, and for special purpose applications that require corrosion and oxidation resistance.

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.

Morphological and crystallographic effects of a high magnetic field on the primary Al6Mn phase formed during the solidification of hypereutectic Al–3.25wt%Mn were investigated. Without the field, the primary Al6Mn crystals are mainly concentrated in the lower part and reveal a dispersed needle-like shape. In three dimension, the needles are in the form of a quadrangular prism (laterally bound by {110} and preferentially growing along <001>). When the magnetic field is applied, they tend to be distributed homogenously and show some extra agglomerate- or chain-like forms (preferentially extending along <100>). Furthermore, they also tend to preferentially orient with <100> parallel to the field direction. The homogenous distribution is caused by the magnetic viscosity resistance force. The “agglomerates” or “chains” are the result of a “bifurcation effect” due to the breakdown at the sharp edges of the quadrangular prisms. The preferential orientation should be attributed to the magnetocrystalline anisotropy of Al6Mn.

Ordered arrays of titania nanotubes (NTs) are considered as good candidates for photocatalytic applications including water splitting. Considering that the functionality of these nanostructures is influenced by their morphology, electronic and the crystallographic structure, fundamental understanding of these properties and their possible correlations can clarify the approaches toward enhanced photocatalytic efficiency. In this work, ordered arrays of titania NTs are synthesized electrochemically and are subjected to isochronal annealing treatments in various atmospheres (oxygen-rich, oxygen-deficient and reducing) to modify their morphology, crystal and electronic structure. Upon characterization of these NTs, direct correlations are found between the annealing atmosphere and the corresponding unit cell volume and the crystallite size. Furthermore, correlations between the NTs’ structure and magnetic response are observed, revealing changes in the electronic structure such as the density of states, that are in turn relevant to the functional catalytic properties of titania.

Grain boundary engineering (GBE) has been carried out in nickel-based Alloy 690 with different initial grain sizes. The microstructure evolution during GBE-processing is characterized using electron backscatter diffraction to study the initial grain size effects on the grain boundary network (GBN). The microstructures of the partially recrystallized samples revealed that the GBE-processing is a strain-recrystallization process, during which each grain-cluster is formed by “multiple twinning” starting from a single recrystallization nucleus. Taking into consideration the coincidence site lattices (CSLs) and ∑, which is defined as the reciprocal density of coincidence sites, a high proportion of low-∑ CSL grain boundaries (GBs) and large grain-clusters are found to be the features of GBE-processed GBN. The initial grain size has a combined effect on the low-∑ CSL GBs proportion. A large initial grain size reduces the number of recrystallization nuclei that form, increasing the cluster size, but decreasing twin boundary density. On the other hand, smaller initial grain sizes increase the density of twin boundary after recrystallization, while decreasing grain-cluster size. Neither the grain-cluster size nor the twin boundary density is the sole factor influencing the proportion of low-∑ CSL GBs. The ratio of the grain cluster size over the grain size governs the proportion of low-∑ CSL GBs.

Semicoherent interfaces containing discrete dislocations are more energetically favorable than those containing continuous distributions because of lower chemical energy. The classical Frank-Bilby theory provided a way to determine the interface Burgers vectors content but could not effectively predict the characteristics of discrete dislocations. Atomistic simulations provide insights into analyzing the characteristics of discrete dislocations but the analysis is often disturbed by the reaction of interface dislocations. By combining the classical Frank-Bilby theory and atomistic simulations, an atomically informed Frank-Bilby theory proposed in this work can overcome shortcomings in both the classic Frank-Bilby theory and atomistic simulations, and enable quantitative analysis of interface dislocations. The proposed method has been demonstrated via studying two typical dissimilar metallic interfaces. The results showed that Burgers vectors of interface dislocations can be well defined in a Commensurate/Coherent Dichromatic Pattern (CDP) and the Rotation CDP (RCDP) lattices. Most importantly, the CDP and RCDP lattices are not simply a geometric average of the two natural lattices, that is the lattice misfit and the relative twist take the nonequal partition of the misfit strain and the twist angle.

Compositional patterning in two-phase immiscible alloys during severe plastic deformation at elevated temperatures has been investigated. Kinetic Monte Carlo computer simulations were used to test the proposed idea that patterning derives from a dynamic competition between homogenization by forced chemical mixing and phase separation by thermally activated diffusion [P. Bellon and R.S. Averback, Phys. Rev. Lett.74, 1819 (1995) and F. Wu et al., Acta Mater.54, 2605 (2006)]. We utilize the concept of pair diffusion coefficients to compare thermal diffusion with forced chemical mixing and discuss the fundamentally different behavior with respect to pair separation distance in both mechanisms. While the general ideas of this model are verified and are in good quantitative agreement with our simulations, it is found that the dynamic processes of alloys under high-temperature shear are very complex, even in highly idealized systems, making experimental verification of this model very difficult. We illustrate our findings for a model AB alloy with properties similar to Cu–Ag by showing how alloy morphology and solubility depend on shear rate, temperature, and composition.

Multilayer Si/Ge heterostructures with the thickness of Ge layers varying from 2 to 12 monolayers (MLs) were formed by molecular beam epitaxy on the (001) Si substrates at 300 °C (Ge) and 450 °C (Si). Using conventional and aberration corrected scanning transmission electron microscopy, x-ray reflectometry and x-ray standing waves, a thorough study of the Si/Ge heterostructures was performed. Optical properties of the heterostructures were probed by photoluminescence spectroscopy. It is shown that the growth of Ge layers up to a thickness of 5 ML occurs through the Frank–van der Merwe mechanism. For thicker Ge layers the growth mechanism of the Si–Ge heterostructure changes to Stranski–Krastanov with Si–Ge islands having the shape of inverted pyramids. We discuss the intermixing of Si and Ge due to stress induced interdiffusion. An explanation of the influence of the observed structural peculiarities on the PL spectra of the heterostructures is given.

Benzoxazine resins are a new class of thermosetting phenolic resins that have emerged in recent decades, overcoming the traditional properties of epoxy and phenolic resins applied in the aerospace industry. The incorporation of low mass concentration of carbon nanotube (CNT) in polymer matrices can produce structural materials with superior properties. Thus, this work aims to prepare nanostructured composite benzoxazine resin/CNT and to evaluate the cure kinetic study by differential scanning calorimetry of neat benzoxazine resin and their nanostructured composites produced. Calculations of the activation energy, the reaction order, and kinetic constants are performed by a nonisothermal procedure. In general, it was observed that CNTs act as catalysts for curing the benzoxazine matrix without affecting the initial and final cure temperatures.

By taking the machine stiffness into the classic Hertzian solution rather than assuming a constant machine stiffness, we developed an approach to simultaneously derive the spherical indenter tip radius and machine stiffness in arbitrary ranges of loads and indenter radii. In contrast, the direct Hertzian fitting method tends to underestimate the radius, especially for larger indenter tips. The success is based on indention tests on two materials with known material stiffness, and the displacement difference under the same load is not affected by the machine stiffness. A total of eight spherical indenter tips with the radii ranging from a few microns to hundreds of microns have been indented on fused silica and single crystal sapphire. Our method gives correct indenter radii for all indenters. The machine stiffness is found to indeed vary with the indentation load and indenter radius. This method has many potential applications in the area of nano-indentation with spherical indenters, such as indentation size effect, modulus and hardness measurement, and micropillar testing.

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.

ZnS/CdS semiconductor composites were synthesized successfully by combining a hydrothermal route with a homogeneous precipitation process. The as-prepared products were characterized by x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectrometer. The results showed that the as-prepared products were composed of ZnS microspheres with a face-centered cubic phase and CdS nanoparticles with hexagonal phase, CdS nanoparticles were found to be assembled on the surfaces of the cubic ZnS microspheres. In addition, the ultraviolet-visible absorption spectroscopy and the room temperature photoluminescence (PL) spectroscopy of the ZnS microspheres and ZnS/CdS composites were also investigated. The PL testing indicated that the emission peak of as-prepared ZnS/CdS composites not only exhibited an obvious blue shift but also its intensity had a large enhancement compared to the pure ZnS microspheres. Furthermore, the photocatalytic degradation test showed that the as-prepared ZnS/CdS composites showed excellent photocatalytic degradation activity for methyl orange under UV irradiation. This enhanced activity may be related to the modification of CdS nanoparticles on the surfaces of ZnS microspheres.

Carbon-bonded alumina filters for steel melt filtration are increasingly used by industries. Their potential regarding the material characteristics and the filtration efficiency appears, however, not used in full measure up to now. In the course of the present work, a new approach, due to the application of active oxide coatings, whose chemical phase equates to that of the nonmetallic oxidic inclusions in the steel melt, was created. The main emphasis consists of the generation of cold-applied, active alumina, spinel, and mullite coatings. Coatings have been developed due to the variation of sintering temperatures and a thermal pretreatment, which lead to increasing cold crushing strength. A basic understanding regarding the adhesion and the interface between the oxide coating and the carbon-bonded filter substrate has been created. Therefore, the essential factor is traceable back to thermal-related mechanisms.

Storage is the main problem to use hydrogen as a fuel in the car industry. Porous carbons are promising storage materials. We have performed computer simulations to investigate carbide-derived porous carbons, showing that these materials exhibit a structure of connected pores with graphitic walls. We then apply a thermodynamic model to evaluate the hydrogen storage. The model accounts for the quantum effects of the motion of the molecules in the pores. The pore widths optimizing the storage depend on pore shape, temperature, and pressure. At 300 K and 10 MPa, the optimal widths lie in the range 6–10 Å. The predictions are consistent with experiment. The calculated storage capacities fall below the targets proposed by the U.S. Department of Energy. This is a consequence of the weak interaction between hydrogen and the pore walls. Metallic doping enhances the binding energy of hydrogen to the walls, which has promising consequences for hydrogen storage.