We have grown single-crystal thin films of Ti2GeC and Ti3GeC2 and a new phase Ti4GeC3, as well as two new intergrown MAX-structures, Ti5Ge2C3 and Ti7Ge2C5. Epitaxial films were grown on Al2O3(0001) substrates at 1000 °C using direct current magnetron sputtering. X-ray diffraction shows that Ti–Ge–C MAX-phases require higher deposition temperatures in a narrower window than their Ti–Si–C correspondences do, while there are similarities in phase distribution. Nanoindentation reveals a Young’s modulus of 300 GPa, lower than that of Ti3SiC2. Four-point probe measurements yield resistivity values of 50–200 μΩcm. The lowest value is obtained for phase-pure Ti3GeC2(0001) films.

Occurrence of brittle interfacial fracture at an electroless Ni(P)/immersion gold–solder joint has long been a serious problem not yet fully understood. In our previous report on the electroless Ni(P) [J. Mater. Res.19, 2428 (2004)], it was shown that crystallization of the Ni(P) film and growth of the Ni3SnP layer were accelerated after the intermetallic compound (IMC) spalling, and accurate failure locus of the brittle fracture due to so-called “IMC spalling induced microstructure degradation of the Ni(P) film” is presented for the first time in this communication. For Sn–3.0Ag–0.5Cu solder joints, (Ni,Cu)3Sn4 and/or (Cu,Ni)6Sn5 ternary IMCs formed at the interface, and neither spalling nor interfacial fracture was observed. For Sn–3.5Ag joints, Ni3Sn4 compound formed, and the brittle fracture occurred through the Ni3SnP layer in the solder pads where Ni3Sn4 had spalled. Since the Ni3SnP layer is getting thicker during or after Ni3Sn4 spalling, control of IMC spalling is crucial to ensure the reliability of Ni(P)/solder system.

The novel rare-earth scandium-based bulk metallic glasses (BMGs) are obtained by the copper mold casting method. Compared with other rare-earth BMGs reported so far, the Sc-based BMGs exhibit the highest elastic moduli (e.g., Young’s modulus, E = 85 GPa; bulk modulus, B = 77.5 GPa), glass transition temperature (Tg = 662 K), and crystallization temperature (Tx = 760 K) combined with a large region of supercooled liquid (ΔT = 98 K). A good correlation between glass transition temperature and elastic moduli is found in a variety of rare-earth-based BMGs.

We report that lightly abrading the surface of a commercial leaded brass results in the room temperature spontaneous growth of Pb whiskers and hillocks. The aspect ratios and submicron diameters of the whiskers that form render them easily dispersible in the atmosphere, with potentially serious health effects, especially for people that deal with leaded brass on a daily basis.

Exceptionally high tensile ductility of commercial Mg alloy ZK60 is reported. It was achieved by equal channel angular pressing without any extra processing steps. The tensile ductility at 220 °C was 2040% and 1400% for the strain rates of 3 × 10−4 s−1 and 3 × 10−3 s−1, respectively. The strain rate sensitivity of the flow stress exhibited a value slightly above 0.5, which is characteristic of superplastic deformation. The grain structure associated with this behavior was shown to be bi-modal with further separation in two fractions with different grain sizes within the small grain size population.

Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 °C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At 100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.

Glassy [(Fe0.8Co0.1Ni0.1)0.75B0.2Si0.05]96Nb4 alloy rods with glass transition temperature of 835 K, followed by a large supercooled liquid region of 55 K were produced in the diameter range up to 2 mm by copper mold casting. The glassy alloy rods exhibit super-high true fracture strength of 4225 MPa combined with elastic strain of 0.02 and true plastic strain of 0.005. The super-high strength alloy simultaneously exhibits high magnetization of 1.1 T, low coercivity of 3 A/m, and high permeability of 1.8 × 104 at 1 kHz. The success of synthesizing a super-high strength Fe-based bulk glassy alloy with some compressive plastic strain and good soft magnetic properties is encouraging for future development of Fe-based bulk glassy alloys as new engineering and functional materials.

We report on the growth of nanowires and unusual hollow microducts of tungsten oxide by thermal treatment of tungsten films in a radio frequency H2/Ar plasma at temperatures between 550 and 620 °C. Nanowires with diameters of 10–30 nm and lengths between 50 and 300 nm were formed directly from the tungsten film, while under certain specific operating conditions hollow microducts having edge lengths∼0.5 μm and lengths between 10 and 200 μm were observed. Presence of a reducing gas such as H2 was crucial in growing these nanostructures as were trace quantities of oxygen, which was necessary to form a volatile tungsten species. Preferential restructuring of the film surface into nanowires or microducts appeared to be influenced significantly by the rate of mass transfer of gas-phase species to the surface. Nanowires were also observed to grow on tungsten wires under similar conditions. A surface containing nanowires, annealed at 500 °C in air, exhibited the capability of sensing trace quantities of nitrous oxides (NOx).

Single-walled carbon nanotubes (SWCNTs) were successfully solidified without any additives by hot-pressing and spark plasma sintering (SPS). The elastic modulus and fracture strength of the SWCNT solid prepared by the SPS method were about three and two times higher than that of the hot-pressed SWCNT solid prepared under the same processing condition. The enhancement of the mechanical properties of the SPS specimen may be due to the formation of comparatively stronger bond between SWCNTs, which is possibly brought about by the spark plasma generated in the SPS process.

Coating of nanowires is being investigated to broaden potential uses for future applications. Coatings of Ni and Pt nanoparticles have been synthesized on silicon carbide nanowires by plasma enhanced chemical vapor deposition. Coatings with high particle densities with average particle diameters of 2.76 and 3.28 nm for Pt and Ni, respectively, were formed with narrow size distributions. Plasma enhanced chemical vapor deposition appears to be an efficient method for production of metal coatings on nanowires.

Based on a comparison of relationships between the energy dissipated during indentation and the ratio of hardness to elastic modulus, a procedure is outlined to determine hardness and elastic modulus from the ratio of the elastic to total energy dissipated during an indentation cycle for non-ideal indenters.

Using a unique combination of template-based synthesis methods involving anodization, electroplating, and selective oxidation, we have synthesized engineered metal–oxide–metal (MOM) heterojunction nanowires in the Au–SnO2–Au and Au–NiO–Au systems for possible use in nanoelectronics. The template-based synthesis method used here is generic, and it has the potential to provide control over the structure and characteristics of the resulting MOM nanowires. By virtue of their heterojunction structure, MOM nanowires have the potential to overcome some of the drawbacks associated with all-oxide nanowire building blocks, and they present a rare opportunity to measure directly fundamental functional properties of nanoscale oxides.

Sulfide stress cracking (SSC) resistance was investigated by comparing acicular ferrite (AF) and ferrite-pearlite (FP) in a microalloyed steel and in a non-microalloyedsteel. In microalloyed steel, AF exhibited better SSC resistance than FP, while in non-microalloyed steel, AF presented far worse SSC resistance than FP. In microalloyed steel, nano-sized carbonitrides and high-density pinned dislocations in AF were analyzed to behave as innocuous hydrogen traps, offering numerous sites for hydrogen redistribution and modifying critical cracking conditions. Dislocations in AF of microalloyed steel in the final analysis are attributed to pinning by the nano-sized carbonitrides.

The development of Mg–Ca–Zn metallic glasses with improved bulk glass forming ability, high strength, and significant ductility is reported. A typical size of at least 3–4 mm amorphous samples can be prepared using conventional casting techniques. By varying the composition, the mass density of these light metal based bulk amorphous alloys ranges from 2.0 to 3.0 g/cm3. The typical measured microhardness is 2.16 GPa, corresponding to a fracture strength of about 700 MPa and specific strength of around 250–300 MPa cm3/g. Unlike other Mg- or Ca-based metallic glasses, the present Mg–Ca–Zn amorphous alloys show significant ductility.

A brief overview of transmission electron microscopy as it applies specifically to obtaining surface crystallographic information is presented. This review will encompass many of the practical aspects of obtaining surface crystal information from a transmission electron microscope, including equipment requirements, experimental techniques, sample preparation methods, data extraction and image processing, and complimentary techniques.

Microscale zirconia structures with intricate three-dimensional (3D) shapes and nanoscale features were synthesized using diatom (single-celled algae) microshells as transient scaffolds. After exposure to a zirconium alkoxide-bearing solution and firing at 550–850 °C, silica-based diatom microshells were coated with a thin, continuous nanocrystalline zirconia layer. Predominantly tetragonal or monoclinic zirconia could be produced with appropriate heat treatments. Selective silica dissolution then yielded freestanding zirconia micro-assemblies that retained the microshell shape and fine features. Such hybrid (biological/synthetic chemical) processing may be used to mass-produce nanostructured micro-assemblies with a variety of 3D, biologically replicable shapes and tailored compositions for use in numerous applications.

We describe a two-step dealloying/compaction process to produce nanocrystalline Au. First, nanocrystalline/nanoporous Au foam was synthesized by electrochemically driven dealloying. The resulting Au foams exhibited porosities of ∼60% with pore sizes of 40 and 100 nm and a typical grain size of <50 nm. Second, the nanoporous foams were fully compacted to produce nanocrystalline monolithic Au. The compacted Au was characterized by transmission electron microscopy and x-ray diffraction and tested by depth-sensing nanoindentation. The compacted nanocrystalline Au exhibited an average grain size of <50 nm and hardness values ranging from 1.4 to 2.0 GPa, which were up to 4.5 times higher than the hardness values obtained from polycrystalline Au.

Organic photovoltaic devices are poised to fill the low-cost, low power niche in the solar cell market. Recently measured efficiencies of solid-state organic cells are nudging 5% while Grätzel’s more established dye-sensitized solar cell technology is more than double this. A fundamental understanding of the excitonic nature of organic materials is an essential backbone for device engineering. Bound electron-hole pairs, “excitons,” are formed in organic semiconductors on photo-absorption. In the organic solar cell, the exciton must diffuse to the donor–accepter interface for simultaneous charge generation and separation. This interface is critical as the concentration of charge carriers is high and recombination here is higher than in the bulk. Nanostructured engineering of the interface has been utilized to maximize organic materials properties, namely to compensate the poor exciton diffusion lengths and lower mobilities. Excitonic solar cells have different limitations on their open-circuit photo-voltages due to these high interfacial charge carrier concentrations, and their behavior cannot be interpreted as if they were conventional solar cells. This article briefly reviews some of the differences between excitonic organic solar cells and conventional inorganic solar cells and highlights some of the technical strategies used in this rapidly progressing field, whose ultimate aim is for organic solar cells to be a commercial reality.