Al–AlN composite powders containing 9–55 vol%AlN were fabricated in situ by nitriding a powder mixture of AA6061–2% Mg–1% Sn at 560 °C. Transmission electron microscopy (TEM) revealed that the in situ formed AlN reinforcements are present as nanoscale AlN whiskers on each powder particle. The composite powder was consolidated by hot extrusion at 450 °C with an extrusion ratio of 11:1. This produced an AlN-free and an AlN-containing lamellar structure along the extrusion direction. The nanoscale AlN is dispersed in the AlN-containing lamella and shows excellent bonding with the Al matrix, free of decohesion and voids. The lamellar composite containing 9 vol%AlN has an ultimate tensile strength of 332 MPa and tensile elongation of 3%. Composites containing ≥17.5 vol%AlN achieve much higher tensile strengths (538 MPa) but zero tensile elongation. However, they show a low coefficient of thermal expansion up to 450 °C and may therefore have potential for selected elevated temperature applications.

A family of ultrahigh strength Co-based bulk metallic glasses (BMGs) with critical diameters up to 2 mm is synthesized in Co65–xTaxB35 (at.%, x = 5–10) alloys by copper mold casting. The improved glass-forming ability associated with near eutectic compositions is attributed to the appropriate addition of Ta. The glassy alloys exhibit high glass transition temperature of 930–975 K, ultrahigh compressive strength of 5.6–6.0 GPa, high specific strength of 639–654 N·m/g, Vickers hardness of 15–16 GPa, and distinct plastic strain of 0.5–1.5%. The strength and the specific strength are the highest values reported for bulk metallic materials known so far. Several universal criteria correlated with the thermal properties, elastic constants, and mechanical properties were validated in the Co-based BMG system. These Co–Ta–B BMGs combining with superior mechanical properties, high thermal stability, and simple elemental composition are significant for scientific research as modeling materials and industrial application as advanced structural materials.

A rich research history exists for crystalline growth by vapor–liquid–solid (VLS) methods, but not for amorphous growth. Yet VLS growth in the absence of crystallographic influences provides an ideal laboratory for exploring surface energy effects, including the role of line tension. We discuss the growth of amorphous silica nanowires from indium droplets by a modified VLS method. Multiple strands issue from each droplet, each strand having <1% (i.e., < 5 nm) of the radius of the droplet. We analyze the surface forces for this system, including line tension, and combine data in a novel way to estimate the surface energy of silica, the interfacial energy of liquid indium on silica, and the line tension at the three-phase boundary. The results suggest that the growth of these silica strands would be impossible without the presence of a negative line tension that also serves to stabilize the strand radii against perturbation.

One way to further optimize the thermoelectric properties toward a higher ZT is a temperature stable nanoengineering of materials, where the thermal conductivity is reduced by increasing the phonon scattering at the grain boundaries. To study this, Nb-substituted CaMnO3 perovskite-type material was synthesized by ultrasonic spray combustion (USC). The grain growth has been characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Finally, the thermoelectric properties of compacted and sintered bulk samples from powder prepared by a continuous scalable USC process were measured up to 1050 K. The thermoelectric legs were prepared by an adapted sintering process. Here, a compromise between enhanced porosity to reduce the thermal conductivity and securing of mechanical stability and low resistivity should be obtained. Based on the grain growth mechanisms, an advanced sintering process for additional interconnection of the particles without particle growth is needed to further increase the thermoelectric performance.

Vanadium oxide nanowires have gained increasing interest as the electrode materials for Li-ion batteries. This article presents the recent developments of vanadium oxide nanowire materials and devices in Li-ion batteries. First, we will describe synthesis and construction of vanadium oxide nanowires. Then, we mainly focus on the electrochemical performances of vanadium oxide nanowires, such as VO2, V2O5, hydrated vanadium oxides, LiV3O8, silver vanadium oxides, etc. Moreover, design and in situ characterization of the single nanowire electrochemical device are also discussed. The challenges and opportunities of vanadium oxide nanowire electrode materials will be discussed as a conclusion to push the fundamental and practical limitations of this kind of nanowire materials for Li-ion batteries.

During the mechanical alloying of a prealloyed Fe–Mo and Mn powder, a large amount of energy is involved because of continuous collisions between the grinding media and the powder. The energy is transformed into massive plastic deformation and solid solution formation. Both phenomena increase in the hardness of the milled particles. To quantify the contribution of both effects to the hardening, nanoindentation experiments were performed on the as-milled powder and after an annealing treatment, based on the assumption that the thermal process would eliminate the lattice distortions due to plastic deformation. When the indentation profile was measured, a significant pileup around the perimeter of the indentation track was observed; therefore, it was necessary to measure the actual amount of contact area by atomic force microscopy. Thus, parameters of mechanical powders can be determined, giving to the conclusion that 40% of the hardening induced can be attributed to the plastic strain.

Selective CdSe tip growth on CdTe tetrapod-shaped colloidal seeds has been achieved for a Cd:surfactant molar ratio of 1:2, where surfactant is oleic acid. The average length of tetrapod arms increased from 12 to 21 nm while arm width remained constant of 3 nm. Formation of CdSe tips shifts the excitonic absorption maximum to the near-infrared region and the appearance of low-intensity absorption feature corresponding to a charge-transfer band. At the same time, luminescence band splits into a narrow (about 100 meV width) CdTe excitonic subband and a 230-meV-wide charge-transfer subband, with splitting energy increasing up to 260 meV depending on CdSe tip length. The intensity ratio of charge transfer to excitonic luminescence increases exponentially with splitting energy rise. Considerable modification of the photoluminescence spectrum has been observed with temperature variation in the range of 10–60 °C.

Development of phase composition in one-component, three-phase systems containing a liquid phase (melt) and two polymorphic solids has been discussed. Two types of polymorphic systems have been analyzed: enantiotropic systems composed of three thermodynamically stable phases and monotropic systems with two stable and one metastable phase. Detailed relations between transition rates, molecular characteristics, and external conditions have been derived. Simulation of isothermal crystallization of a model system has been performed and discussed.

A simple and controllable fabrication of TiO2 nanowires by electrospinning and their applications to the electron transporting layer for hybrid organic–inorganic photovoltaic cells are reported. TiO2 nanowires were directly electrospun onto an indium tin oxide on glass substrate from a solution in methanol of polyvinylpyrrolidone, titanium(IV) butoxide, and acetylacetone. The nanowire electrode obtained was consequently subjected to calcination at 450 °C. Solution of blended [6,6]-phenyl-C61-butyric acid methyl ester and poly(3-hexylthiophene) was spin coated on the TiO2 nanowire electrode, followed by thermal annealing and deposition of Au electrode. Hybrid organic–inorganic photovoltaic cells made of TiO2 nanowires exhibited remarkable improvement of the cell efficiencies in terms of photocurrent density and open-circuit voltage as compared with those of references, TiO2 flat films. Maximum energy conversion efficiency of hybrid organic–inorganic photovoltaic cells made of TiO2 nanowires of 1.27% was achieved.

In this study, we show that the volatile monoxide species generated during the active oxidation of Ge and Si substrates can be utilized in the presence of Au catalytic nanoparticles to nucleate and grow GeOx and SiOx nanowires. A simple thermodynamic model is developed to ascertain the critical O2 partial pressure as a function of temperature required for the active oxidation of Ge and Si substrates and is experimentally verified. The ideal conditions for uniform nanowire growth across the substrate are shown to be primarily dependent on the O2 partial pressure, the annealing temperature and thicknesses of the surface oxide, and deposited Au. The role of a metastable surface oxide separating the active oxidation and NW nucleation processes is also discussed.

We report fabrication of compacted Bi0.5Sb1.5Te3 nanoplatelets using hydrothermal methods followed by cold pressing and sintering in an evacuated ampoule at various temperature of 300–380 °C. The compacted Bi0.5Sb1.5Te3 sintered at 340 °C has the highest power factor of 11.6 μW/cm·K2 and its thermal conductivity is 0.37 W/m·K at 295 K, which is very low as compared to the typical value of 1 W/m·K. The resulting dimensionless figure of merit ZT is 0.93 at 295 K.