Porous, strong, and stiff ceramic materials are required for a range of technical applications, involving for instance, liquid or gas flow. Natural materials such as wood can provide useful structural guidelines for the optimal microstructural design, although only few processing routes are able to turn these guidelines into actual materials. We illustrate here, how ice templating of anisotropic particle suspensions can be modified to obtain a honeycomb structure with pores of 30 µm diameter. The growth of ice crystals in the slurry induces self-assembly of the anisotropic particles, leading to relatively thin walls (10 µm). Because large anisotropic particles are difficult to sinter, a glassy phase was introduced to facilitate this densification step and then to further reduce the walls' porosity. Young's modulus and compressive strength were both improved by the addition of a glassy phase by an order of magnitude due to the denser walls. These macroporous materials are more robust and stiff than materials with an equivalent morphology, while offering a simple alternative to the current wood replica processing routes.

Achieving control of crystalline quality is a key barrier to developing thermoelectric (TE) nanowires. We show that the structural properties of free-standing Bi2(Te.97Se.03)3 nanowire arrays on substrates can be improved by postdeposition annealing. Nanowires were electrochemically deposited into anodized aluminum oxide nanopore templates formed directly on metallized Si(100). The templates were chemically removed prior to annealing in a 3% H2/Ar environment to prevent microcrack formation that results from thermal stresses. Grain sizes grew exponentially with annealing temperature until reaching the full 75-nm diameter of the nanowires at 300 °C; growth was linear above this temperature since grains could grow further only in the axial directions. Crystalline quality, along with the development of the preferred (110) orientation for optimal TE properties, improved with increasing annealing temperature between 200 and 400 °C. However, continued loss of Te composition with annealing led to a mixed phase of Bi2Te3 and Bi4Te3 at 500 °C.

Ordered 30-nm Co1−xSnx (0 ≤ x ≤ 0.78) nanowire arrays have been prepared by co-electrodeposition of Co and Sn into pores of homemade anodized aluminum oxide (AAO). The magnetic properties of the Co1−xSnx nanowires are presented as a function of Sn content (x), annealing, electrolyte pH, electrodeposition frequency, and wave form. The result of energy-dispersive x-ray spectroscopy (EDX) showed anomalous co-deposition for Co and Sn. The nanowires have uniaxial magnetic anisotropy with easy magnetization direction along the nanowire axis due to the large shape anisotropy. As-deposited and annealed alloy nanowires, determined by x-ray diffraction (XRD), have amorphous phase. The nanowires electrodeposited at different pH and the electrodeposition frequencies have significantly different magnetic properties. Magnetization measurement showed that variation in magnetic properties of the nanowire arrays rooted in surface formation of Co(OH)2 and Sn(OH)2 in upper pH. The XRD patterns of Co and Co0.97Sn0.03 of nanowires obtained at pH = 2 and 4 obviously illustrated that pH affects the crystal structure of Co nanowires but has no effect on alloy nanowires. Moreover, the precipitation process was affected by raising the electrodepositing frequency via changing the rate of reduction of solute ions. The electrodeposition wave form has no significant effect on nanowire magnetic properties. The considerable enhanced coercivity has been measured in annealed nanowires. Experimental data demonstrate that the optimized composition for annealed Co1−xSnx nanowire is around Co0.93Sn0.07 in which the coercivity (Hc) has a maximum value of 2030 Oe.

A strategy for identifying the preferred sites and overall propensity of a Sn film to form whiskers has been developed based on film textures, local grain orientations, and elastic strain energy densities (ESEDs), with preferred sites predicted to be grains with local high ESEDs. Using β-Sn films with various textures, ESED distributions were simulated for elastic and thermoelastic stresses depending on isothermal aging or thermal cycling conditions. Local high ESEDs are preferentially induced in (110) or (100) oriented grains with c-axes nearly parallel to the film plane; films with overall low ESEDs have strong (100) textures for elastic stresses and strong (001) textures for thermoelastic stresses, suggesting low propensities to form whiskers. This work establishes a model for understanding the effect of the β-Sn anisotropy on whisker formation and provides guidelines for testing whether engineering specific film textures will reduce a film's propensity to form whiskers.

Using first principle density functional calculations, we study the formation of 2D transition metal dichalcogenides (TMDs) on TiC1−xAx, (A = S, Se, and Te) surfaces. We examine the structural misfits between chalcogen-containing TiC and different TMDs and demonstrate that the conditions for formation of TMDs are fulfilled in TiC1−xAx. We also demonstrate the influence of chalcogens on the cohesive properties and electronic structure of the carbides. We find that they react with W and form W-dichalcogenides. In the experimentally reported Ti–C–S nanocomposite coatings, the carbide grains are embedded in an amorphous carbon matrix. We discuss here the role of this matrix in the reaction. We propose that TiC1−xTex and TiC1−xSex are the favorable sources for dichalcogenide formation and suggest an alternative way to produce 2D materials in general. Furthermore, we argue that using Ti–C–Te or Ti–C–Se in nanocomposite coatings may be more advantageous for tribological applications than that of Ti–C–S.

One of the barriers for wide usage of hydrogen energy system is efficient storage. To store more hydrogen efficiently, physisorption is a choice among the others with high storage performance, reversibility, and lifecycles. Metal organic framework (MOF) structured organometallic orotate-Co(II) complexes could serve as sorbents which store hydrogen by physisorption. In this work, mono- and bidentate MOF structured orotate-Co(II) complexes are synthesized, characterized, and then investigated for hydrogen storage experimentally and theoretically. It is found that these compounds could store hydrogen. Especially, the monodentate complex could uptake hydrogen better than the other. Storage performances for mono- and bidentate complexes were 0.80 and 1.15 wt% at 77 K and approximately 80 bars experimentally, 1.03 and 1.16 wt% theoretically for the same conditions.

Gold–silver (Au–Ag) bimetal dispersed SiO2 composite films were fabricated via a chemical solution approach combining sol–gel with a spin-coating process, and they were investigated by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and ultraviolet-visible absorption spectra. TEM image indicated that Ag and/or Au nanoparticles (NPs) had a spherical structure with large size distributions. The XPS results demonstrated that the presence of both Ag and Au NPs in the composite film is in each metal state. The optical absorption spectra of the composite film further confirmed the formation of nanosized Au and Ag particles, given by the two surface plasmon resonance (SPR) peaks. Unlike other Au–Ag composite films, these two SPR peaks had almost the same intensity, which is rarely obtained by a chemical approach. Compared to optical absorption spectra calculated by the modified Mie theory, the location and intensity of SPR peaks had a little difference, which could be attributed to large size distributions of Ag and Au bimetal NPs in the composite film along with the experimental process. In addition, the intensity of both SPR peaks was content-related.

Nb, F-codoped TiO2 (NFT) nanoparticles are prepared via hydrothermal processes using Nb2O5 and hydrofluoric acid as doping source. Nb and F distribute homogeneously in the NFT nanoparticles as shown in scanning transmission electron microscopy elemental mappings. The codoping of Nb and F improves the crystallinity of TiO2 significantly and increases the Ti3+ concentration, which results in the enhancement of electron injection and in the increase of the charge-transfer ability in dye-sensitized solar cells. The relative energy conversion efficiency can be 66.1% higher than that of the cell, based on pure TiO2, when the Nb:F:Ti molar ratio is about 0.03:0.15:0.97.

Electron-withdrawing halogen atoms are often bonded to the surface of carbon nanotubes to assist in the conversion from metallic to semiconducting properties. Single-walled carbon nanotubes (SWCNTs) were surface modified using UV photolysis with: (i) a broad band of wave lengths from approximately 250 to 400 nm having a maximum intensity at approximately 300 nm for photolysis of Cl2, (ii) low-pressure Hg lamps emitting 253.7 nm photons for photo-decomposition of HBr, and (iii) low-pressure Hg lamps emitting both 253.7 and 184.9 nm for photo-dissociation of HCl and HBr, respectively, and analyzed by x-ray photoelectron spectroscopy. Chlorine atoms adhered more readily than bromine atoms with the π-conjugation of the SWCNTs. The dominant increase with treatment was observed in the singly bonded chlorine moiety. Chlorine atoms, generated by UV photolysis of Cl2, produced a higher Cl saturation level of approximately 36 at.% than previously observed for multi-walled carbon nanotubes (13 at.%).The degree of chlorination depended on the amount of oxygen on the surface of the SWCNTs. Photo-dissociation of gaseous HCl and HBr showed lower amounts of halogenation on SWCNTs (approximately 5.8 at.% Cl and 2.5 at.% Br, respectively) than photolysis of Cl2.

A new kind of nontoxic, water-soluble copolymer consisting of isobutylene and maleic anhydride was used to gelcast alumina ceramics at room temperature in air. The polymer acts as both a dispersant and a gelling agent. The influence of the polymer on zeta potential, rheological and gelling behavior of the alumina slurry was studied. Copolymers with a lower molecular weight had greater dispersing ability. Copolymers with a larger molecular weight had greater gelling ability. Alumina slurries with solids loading up to 58 vol% were prepared by adding copolymer (0.3 wt%, relative to the powder) with both short and long molecular chains. Increasing solids loading from 50 to 58 vol% decreased the linear shrinkage from 4.63% to 1.50% after drying, and from 14.51% to 13.18% after sintering, respectively. A solids loading of 56 vol% was associated with the highest flexural strength, as high as 534 MPa.

A reduction of iron (III) oxides deposited on expanded graphite (EG) matrixes of three types in hydrogen flow was studied in dynamic and static regimes. In the dynamic regime, the EG matrix was shown not to influence the temperature range of the iron (III) oxide reduction. However, the C/O atomic ratios, varying depending on the type of EG matrixes, affect the completeness of reduction of these oxides to metallic iron. The reduction kinetics of iron (III) oxides deposited on EG and of bulk oxides were found to be similar and could be described by the combination of expanded Prout–Tompkins autocatalysis and n-dimensional growth of nuclei models. The prolonged hydrogen treatment at 600 °C of the samples in the static regime results in quantitative reduction of iron (III) oxide to α-Fe independent of the type of EG matrix used. The obtained samples demonstrate the relatively high values of saturation magnetization of 35 emu/g together with a high sorption capacity for crude oil of 93 g/g.

Aluminum matrix fly ash (AMFA) cenosphere composites were fabricated using the stir casting technique. The used type of fly ash cenosphere, which accounted for over 60% in all fly ash particles, was in narrow and small size (2–30 μm). During synthesis, effects of several key technological parameters on microstructure and properties were investigated using orthogonal experimental design. The optimal technological parameter was achieved as: melt temperature of 700 °C + stirring rate of 1200 r/min + stirring time of 6 min + fly ash cenosphere content of 13 wt%. With this optimal technological parameter, as-cast and forged composites were manufactured. Their tensile strengths were measured and improved maximally by 50% when the cenosphere content is 13 wt%. Such size and content of fly ash cenosphere and technological parameter could largely improve the properties of composites, which should be introduced into the production process of AMFA composites.

The bulge test was used to investigate the fatigue properties of gold thin films with a thickness between 100 and 300 nm. The membranes were pressurized at a rate of 0.2 Hz up to 105 times, during which their stress and strain states were continuously recorded. Gold films on a silicon nitride substrate were cyclically loaded into tension and compression. Due to the presence of the substrate, no membrane failure was observed, but the residual stress shifted from an initially tensile state to an increasingly compressive one. Typical fatigue damage mechanisms consisting of extrusions were found in some large grains. Freestanding films were cyclically loaded in pure tension until failure occurred. The data acquired during the fatigue tests show a strong ratcheting of the films, which is indicative of cyclic plastic creep. Microstructural investigations clearly show grain boundary sliding in very thin films with columnar grains extending through the thickness.

A theoretical model of nanovoid nucleation at triple junctions in nanocrystalline materials is developed in this article. The sliding of grain boundaries (GBs) meeting at triple junctions, which can be attributed to the gliding of GB dislocations (GBDs), provides the driving force for nanovoid nucleation. The GB sliding is accommodated by the emission of partial dislocations from GBs as well as GB diffusion. The corresponding energy characteristics of the pile-ups of GBDs, the emission of partial dislocations from the GBs, and GB diffusion are calculated, respectively. Furthermore, an energy balance method to calculate the nucleation of nanovoid at triple junctions is studied. The analysis demonstrates that the nucleation of the triple junction nanovoid depends mainly on the applied stress, the GB length (length of the pile-up), the GB structures, and the GB sliding accommodations.

Barium strontium titanate (BST) glass-ceramics were fabricated via controlled crystallization with different crystallization routes. Effects of the microwave crystallization and microwave treatment on the microstructure and energy storage properties of the glass-ceramics were systematically investigated. Results showed that microwave crystallization can increase the dielectric constant. In addition, it was found that the microwave process had little impact on the crystallinity (about 90 wt%), but preferred the crystallization of SrAl4O7. Most importantly, the dielectric breakdown strength (BDS) of the glass ceramics was significantly improved from 561.3 to 791.4 kV/cm by the microwave crystallization. And it can be further enhanced to 900.0 kV/cm by conventional crystallization combined with microwave treatment. The corresponding energy densities of samples derived from the microwave processes were increased to 1.05 and 1.13 J/cm3, respectively, compared with the sample fabricated by the conventional crystallization route (0.47 J/cm3).