A novel tree-like nanostructured Ag crystal, with stems, branches, and leaves, has been synthesized by pre-forming Au seeds, soaking, and annealing, based on monolithic mesoporous silica. The obtained Ag nanotrees are of single-crystal nature and statistically symmetrical in geometry. Further experiments revealed that the interconnected channels of the porous silica, heating at low temperature, and the pre-formed Au seeds are crucial to form such structure. Its formation can be attributed to the low nucleation rate and preferentially unidirectional diffusion of Ag atoms to the Au seeds along interconnected channels. This nanostructured material is of great potential to be building blocks for assembling some mini-functional devices of the next generation. The current study is also of importance in studying the diffusion mechanism of single-crystal formation, and especially in improving our understanding of the underlying physical structure of both natural and synthetic porous materials.

The use of three-dimensional x-ray structural microscopy for nondestructive investigations of the deformation microstructure under microindents was demonstrated. Point to point, micrometer-resolution x-ray microbeam measurements of local lattice rotations were made for selected positions under 100-mN Berkovich and conical indents in single-crystal copper. Local lattice orientation measurements were used to extract micrometer by micrometer lattice misorientations and rotation axes along x-ray microbeams. Measurements of the deformation microstructure in symmetry and off-symmetry geometries are reported and discussed in terms of their potential for fundamental deformation investigations.

Nanosized powders of Ni–Fe–O were synthesized by a pulsed wire discharge method and sintered at 600 °C for 1 h in air. Abrupt electrical resistivity changes were observed in the temperature dependence of resistivity for the sintered Ni–Fe–O powders above 203 °C. Similar resistivity curves, which had been observed in V–O samples and had been used for the critical temperature resistors, had never been reported in Ni–Fe–O samples. Possible mechanisms to explain the resistivity change in NiFe2O4, including order-disorder transition, semiconductor-metal transition, and surface spin pinning, are discussed.

The cathodic electrodeposition of molybdenum oxide thin films prepared from aqueous solutions containing iso-polymolybdates and peroxo-polymolybdates is described. Chronocoulometry, x-ray photoelectron spectroscopy, spectroelectrochemistry, and electrochemical quartz crystal microgravimetry were used to establish corresponding reaction mechanisms for films grown at different deposition potentials. Electrodeposition from acidified iso-polymolybdate solutions proceeds by the reduction of molybdic acid, whereas deposition from aqueous peroxo-based solutions involves the graded reduction of several solution components, primarily comprising molybdic acid and peroxo-polymolybdates. Careful regulation of the deposition potential allows for controlled growth of distinct molybdenum oxide compositions producing films with varied water content and valency.

A basic sulfate precursor [Sc(OH)SO4·2H2O] for well-sinterable Sc2O3 powders was precipitated from mixed solutions of scandium nitrate [Sc(NO3)3] and ammonium sulfate [(NH4)2SO4] at room temperature and which was subsequently converted to Sc2O3 via dehydroxylization and desulfurization at temperatures ≥900 °C. With the reactive powders synthesized in this work, polycrystalline Sc2O3 ceramics showing high inline transmittances of approximately 70% in the visible wavelength region (corresponding to ∼90% of the theoretical value of single crystals) have been fabricated via vacuum sintering at a relatively low temperature of 1700 °C.

In this paper, the results of a temperature dependent x-ray diffraction (XRD) study on BaTi0.95Sn0.05O3 (BTS-5) ceramics are compared with dielectric measurements. The orthorhombic-tetragonal phase transition at T2 = 306 K is found to proceed in a considerably wider temperature range than expected from the dielectric anomaly. Although the macroscopic properties of BTS-5 indicate a rather sharp ferroelectric phase transition at Tc = 358K, we observe anomalous XRD-patterns in a 25 K wide temperature range. This is interpreted in terms of mechanically clamped tetragonal and cubic phase, coexisting in the vicinity of Tc in grains with inhomogeneous Sn-distribution.

Finite element simulation of the Berkovich, Vickers, Knoop, and cone indenters was carried out for the indentation of elastic–plastic material. To fix the semiapex angle of the cone, several rules of equivalence were used and examined. Despite the asymmetry and differences in the stress and strain fields, it was established that for the Berkovich and Vickers indenters, the load–displacement relation can closely be simulated by a single cone indenter having a semiapex angle equal to 70.3° in accordance with the rule of the volume equivalence. On the other hand, none of the rules is applicable to the Knoop indenter owing to its great asymmetry. The finite element method developed here is also applicable to layered or gradient materials with slight modifications.

Chemically prepared zinc oxide powders are fabricated for the production of high aspect ratio varistor components. Colloidal processing was performed to reduce agglomerates to primary particles, form a high solids loading slurry, and prevent dopant migration. The milled and dispersed powder exhibited a viscoelastic to elastic behavioral transition at a volume loading of 43–46%. The origin of this transition was studied using acoustic spectroscopy, zeta potential measurements, and oscillatory rheology. The phenomenon occurs due to a volume fraction solids dependent reduction in the zeta potential of the solid phase. It is postulated to result from divalent ion binding within the polyelectrolyte dispersant chain and was mitigated using a polyethylene glycol plasticizing additive. This allowed for increased solids loading in the slurry and a green body fabrication study to be presented in our companion paper.

Polycrystalline (Pb0.75La0.25)TiO3 (PLT25) thin films have been fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The room-temperature structures and dielectric properties are studied by x-ray diffraction, scanning electron microscopy, and HP4294A impedance/phase analyzer. The temperature-dependent ferroelectric properties are systematically investigated by using a RT66A ferroelectric tester combined with a temperature-controllable vacuum chamber. For well-saturated hysteresis loops, with the temperature decrease from 295 to 97 K, the coercive field (Ec) and remanent polarization (Pr) increase and the saturated polarization (Ps) is almost temperature-independent. However, this is not the case for the unsaturated hysteresis loops. Temperature-dependent fatigue-resistance of the PLT25 films is also experimentally established: after 2.22 × 109 switching cycles, the nonvolatile polarizationdecreases 38% when measured at room-temperature and it decreases 15% at 97 K. The nature and population of point defects and their effects on the subtle variations of the Ec, Ps, Pr, and fatigue-resistance against temperature are discussed in detail.

Thin films Ni−Ti (<100 nm) having surface Ni content below 5 at.% were prepared by ion-implanting Ni into Ti surfaces. The Ni-containing phase exposed or buried within the Ti matrix was amorphous. Following an anodic oxidation in NaOH, the material was shown to be redox active and to promote the electrocatalytic oxidation of glucose depending on the surface Ni–Ti composition. Compared to the Ni–Ti bulk alloy (55.9:44.08), the Ni-implanted Ti displayed a more efficient catalytic activity and improved corrosion resistance.

Three electromagnetically well-characterized bulk samples with nominal resistivities at 40 K [ρ(40 K)], varying from 1 to 18 μΩcm, were investigated by conventional and high-resolution transmission electron microscopy. Clean, coherent, or semi-coherent grain boundaries and dirty-grain boundaries wetted by amorphous phases were found in all three samples, even though the starting sample A had the very low resistivity of 1 μΩcm at 40 K, characteristic of clean-limit samples. Taking into account its porosity and wetted-grain boundary area, the true resistivity value is about 0.5 μΩcm. Additional samples B and C, prepared by exposing sample A to Mg vapor, showed enhanced ρ(40 K) values of 14 and 18 μΩcm, without noticeable change in either inter- or intra-granular microstructure. Intragranular nanoprecipitates with characteristics of a spinodal of MgB7, with a size of 1–5 nm, were observed in a few areas of samples A and B at high local density; however at too low an overall density to explain the increased resistivities and upper critical fields.

A nanocrystalline titania–silica (1:1 molar ratio) binary oxide material was synthesized by microwave-induced combustion process in a modified domestic microwave oven (operated at 2.45 GHz frequency and 700 W power) in approximately 60 min from in situ synthesized titanyl nitrate and siliconyl nitrate using urea as fuel. For the sake of comparison, two different types of TiO2–SiO2 powders were also synthesized by the sol-gel and the co-precipitation methods. All the synthesized powders were characterized with the help of thermogravimetriy/differential thermal analysis, x-ray diffraction, transmission electron microscopy (TEM), and Brunauer–Emmett–Teller surface area measurements and the results compared. The as-synthesized TiO2–SiO2 powder obtained by the combustion process showed an average crystallite size of 10 nm and the specific surface area of 115 m2g-1. Among the three differently synthesized TiO2-SiO2 powders, only the microwave-induced combustion synthesis yielded crystalline material. TEM in particular confirmed the presence of nano-sized particles in the microwave-induced combustion-synthesized powder. Among the three analogies, microwave synthesis was found to be superior in terms of ease of processing leading to time and power savings.

We investigated the use of a pulsed excimer laser having a wavelength of 248 nm, a pulse duration of 38 ns, and an average fluence between 120 and 780 mJ/cm2 to locally tailor the physical properties of Si1−xGex (18% < x < 90%) films deposited by low-pressure chemical vapor deposition at temperatures between 400 and 450 °C. Amorphous as-deposited films showed, after laser annealing, strong {111} texture, a columnar grain microstructure, and an average resistivity of 0.7 mΩ cm. Atomic force microscopy indicated that the first few laser pulses resulted in a noticeable reduction in surface roughness, proportional to the pulse energy. However, a large number of successive pulses dramatically increased the surface roughness. The maximum thermal penetration depth of the laser pulse is demonstrated to depend on the fluence and the film structure being either polycrystalline or amorphous. Finally, a comparison between excimer laser annealing and metal-induced crystallization and rapid thermal annealing is presented.

Hybrid bulk heterojunction composites are promising material for low-cost organic solar cells. Fundamental measurements with CdTe nanocrystal/MEH-PPV poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] composites and the first realization of a solar cell based on this material are presented. Optical and electrochemical properties are discussed as well as the current voltage characteristic of the resulting cell. It was found, that CdTe nanocrystal/MEH-PPV composites are well suited for an organic solar cell, even though the technological realization needs to be improved.

Nanocrystalline CeO2 powder was synthesized by a citrate-nitrate autoignition process and characterized by thermal analysis, x-ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (20–40 nm) ceria powder with fluorite structure had formed in situ during the citrate-nitrate autoignition process. The powder prepared could be sintered to density more than 98% of theoretical density at 1450 °C. The nanocrystalline CeO2 exhibited an increase in conductivity in Ar and H2 than air above 600 °C, suggesting a possible electronic contribution to the conductivity at low oxygen partial pressures. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing phase pure ceria compositions.

We investigated the effect of lead zinc niobate (PZN) on the sintering behavior and piezoelectric properties of lead zirconate titanate (PZT) ceramics. The addition of PZN improved the sinterability of PZT ceramic so remarkably, that at additions of more than 10%, the specimens were fully dense at a temperature as low as 900 °C. The phase of the PZT-PZN ceramics was affected by PZN content and the Zr/Ti ratio in the PZT. With increasing PZN content, a lower Zr/Ti ratio was required for the morphotropic phase boundary (MPB). Specimens with the MPB composition showed the highest piezoelectric properties; d33 = 500 pC/N, kp = 0.68, and S33 = 0.38% at 2 kV/mm.

Mechanical characterizations using nanoindentation technique were performed for the martensitic steel used as practical dies steel containing carbide-former elements of Cr, Mo, W, and V, which are responsible for secondary hardening by tempering. The nanohardness Hn corresponding to the matrix strength shows obvious secondary hardening, and the hardening-peak temperature coincides with that of the macroscale hardness Hv. By comparing the temper-softening behavior of the high-purity Fe–C binary martensite, the ratio of the nanohardness Hn of the dies steel to that of the Fe–C binary steel is approximately a factor of two, whereas the same ratio of the macroscopic hardness Hv is three at the secondary-hardening peak. These results suggest that the secondary hardening of the dies steel during tempering is attributed not only to the nanoscale strengthening factors such as precipitation hardening by the alloy carbides, but also to some other factors in larger scale. One of the strengthening factors in larger scale is a decomposition of 9% retained austenite to much harder phases, such as martensite and/or ferrite–cementite constituent.

Using a Ti–Cu–Ni–Sn–Ta alloy as an example, we demonstrate a strategy for the in situ formation of nanocomposite microstructures that can lead to simultaneous high strength and ductility. Our approach employs copper mold casting for the production of bulk alloys from the melt, and the solidification microstructure is designed to be composed of micrometer-sized ductile dendrites uniformly distributed inside a matrix of nanoscale eutectic reaction products. The nanostructured matrix is achieved at a relatively deep eutectic, which facilitates the formation of an ultrafine eutectic microstructure over a range of cooling rates. The multi-component recipe stabilizes a ductile solid solution as the toughening phase and helps to reduce the eutectic spacing down to nanoscale. The multi-phase microstructure (including phase distributions, morphologies, and interfaces) has been examined in detail using transmission electron microscopy (TEM) and high-resolution TEM. The metastable eutectic reaction and the nanoscale spacing achieved are explained using thermodynamic and solidification modeling. The benefits expected from the microstructure design are illustrated using the high strength and large plasticity observed in mechanical property tests. Our nanocomposite design strategy is expected to be applicable to many alloy systems and constitutes another example of tailoring the microstructure on nanoscale for extraordinary properties.

Chemically prepared zinc oxide powders were processed for the production of high aspect ratio varistor components (length/diameter >5). Near-net-shape casting methods including slip casting and agarose gelcasting were evaluated for effectiveness in achieving a uniform green microstructure that densifies to near theoretical values during sintering. The structure of the green parts was examined by mercury porisimetry. Agarose gelcasting produced green parts having low solids loading values and did not achieve high fired density. Isopressing the agarose cast parts after drying raised the fired density to greater than 95%, but the parts exhibited catastrophic shorting during electrical testing. Slip casting produced high green density parts, which exhibit high fired density values. The electrical characteristics of slip-cast parts are comparable with dry-pressed powder compacts.

A metal–organic thermal atomic layer deposition (ALD) approach was developed for the growth of ultrathin tantalum nitride (TaNx) films by alternate pulses of tert-butylimido trisdiethylamido tantalum (TBTDET) and ammonia (NH3). An optimized ALD process window was established by investigating saturation of film-growth rate versus TBTDET and NH3 exposures, as controlled by the length of reactant pulses and the duration of the inert gas purge cycles separating the reactant pulses. The resulting low-temperature (250 °C) ALD process yielded uniform, continuous, and conformal TaNx films with a Ta:N ratio of 1:1. Carbon and oxygen impurity levels were in the 5–8 at.% range. Associated film conformality in 100-nm trench structures with 11:1 aspect ratio was nearly 100%.