Indium tin oxide particles were prepared using three different spray synthetic techniques: conventional, salt-assisted, and low pressure. Optimum conditions for the preparation of small size, nonagglomerated particles were investigated for these three methods. The use of the conventional spray pyrolysis method resulted in only larger particles (submicrometer order). Salt-assisted spray pyrolysis (SASP) and low-pressure spray pyrolysis (LPSP) produced highly crystalline, dense, homogeneous, and nearly nonagglomerated nanoparticles that were less than 25 nm in size. The size of the particles was in the range 12–24 nm for the SASP method and 8–14 nm for the LPSP method. In addition, the LPSP method led to the production of single nanometer-size multicomponent particles in a single step with less heating time without the need for any post heat treatment and additives.

Particulate composites of magnetostrictive Terfenol-D were prepared with polyamine and anhydride cured epoxy polymer matrices with the presence or the absence of a strong magnetic field. These composites were studied to investigate (i) the influence of magnetic field that is applied during specimen preparation in strain output levels, (ii) performance loss at high temperatures, and (iii) the influence of matrix material in magnetostrictive strain performance. A six-way comparison is made of materials processed under magnetic field with materials processed under no magnetic field, and magnetostrictive strain performance at glass transition finish temperature with magnetostrictive strain performance at glass transition start temperature, and magnetostrictive strain performance in low modulus matrix systems with magnetostrictive strain performance in high modulus matrix systems. A four-way comparison is also made between the micrographs for strain-cycled and non-strain-cycled samples and relative damage incurred by samples prepared using high and low modulus matrix systems.

Nanoindentation is one of the very few techniques that can measure both the elastic and plastic properties of very small volumes of materials. Recently it has been shown that the properties of thin coatings can be determined by nanoindentation, even when the normal indentation response includes a significant component due to the substrate. This paper takes the method a step further and shows how by combining acoustical test methods with nanoindentation, a validated set of values for the thickness, Young's modulus, and Poisson ratio for a coating can be obtained.

Strength properties of silicon substrates containing dense oxide and nitride surface films are investigated using nanoindentations to introduce small flaws of predetermined scale. The indentation flaws provide favored sites for failure in subsequent flexure loading, even in the subthreshold region for indentations without visible corner cracking, confirming that microflaws generated within the indentation zone act as effective crack sources in the substrate. Deposition of the oxide films increases the strength while the nitride films diminish it at any given indentation load. The strength shifts are attributed primarily to the presence of residual compressive stress in the oxide, tensile stress in the nitride. A fracture mechanics formulation based on a previous analysis for monolithic substrates is here adapted to allow for a superposed crack closing or opening stress-intensity factor term associated with the residual stresses. Allowance is also made in the mechanics for the influence of the film on effective hardness and modulus of the substrate. The formulation accounts for the basic strength shifts and enables evaluation of the magnitude of the residual stresses. The results quantify the susceptibility of basic device materials to damage from small-scale contacts and impacts.

We studied the self-organization process of F16CuPc films (20–30 ML) on stepped Al2O3 (1120) substrates. X-ray diffraction measurements revealed a highly ordered layered structure with the molecules in a nearly upright configuration. The morphology, investigated by atomic force microscopy, consisted of long (several microns) and narrow (20–100 nm) needlelike terraces unidirectionally aligned along one of the main crystallographic directions of the Al2O3 (1120) surface. High resolution atomic force microscopy images revealed in-plane molecular order with the molecular stacking direction parallel to the needlelike terraces. Such anisotropic morphology is the result of a self-organization process of F16CuPc in elongated crystallites driven to a preferential orientation by the interaction with the substrate. Spectroscopic ellipsometry showed that these films exhibit anisotropic optical properties correlated with the molecular arrangement.

Using dimensional analysis and finite element calculation, we studied spherical indentation in elastic–plastic solids with work hardening. We report two previously unknown relationships between hardness, reduced modulus, indentation depth, indenter radius, and work of indentation. These relationships, together with the relationship between initial unloading stiffness and reduced modulus, provide an energy-based method for determining contact area, reduced modulus, and hardness of materials from instrumented spherical indentation measurements. This method also provides a means for calibrating the effective radius of imperfectly shaped spherical indenters. Finally, the method is applied to the analysis of instrumented spherical indentation experiments on copper, aluminum, tungsten, and fused silica.

HfB2 and (ZrB2 + HfB2)-based ceramics containing 19.5 vol% SiC particulate were developed from commercially available powders by hot-pressing. With the assistance of 3 vol% HfN as sintering aid, after hot-pressing at 1900 °C and 50 MPa of applied pressure, full density in both the composites was successfully achieved. The materials revealed a homogeneous microstructure, characterized by faceted diboride grains(2 μm average size) and SiC particles regularly dispersed. Limited levels of secondary phases were found. The thermomechanical properties of the composites were promising: about 22 GPa microhardness and 500 GPa Young’s modulus for both. The HfB2–SiC composite showed values of strength of 650 ± 50 and 465 ± 40 MPa at 25 and 1500 °C, respectively. Likewise, the (ZrB2–HfB2)–SiC composite exhibited values of strength of 765 ± 20 and 250 ± 45 MPa at 25 and 1500 °C, respectively. The excellent response at high temperature in air was attributed to the refractoriness of the phases constituting the composites and to the resistance to oxidation enhanced by the presence of the SiC particulate.

A new phase in the Dy–Si–O system, Dy4.67(SiO4)3O, was prepared in powderform using the mixed oxide method. Dy4.67(SiO4)3O was first observed at 1300 °C, and phase purity was achieved after 96 h at 1600 °C. The crystal structure was determined using single crystal diffraction using synchrotron radiation, and powder x-ray diffraction data was refined using the Rietveld method. The structure was found to be apatite-type, hexagonal, with space group P63/m and a = b = 0.93883(2) nm,c = 0.67820(1) nm, Z = 2. High-temperature x-ray powder diffraction was used to characterize the anisotropic thermal expansion over the temperature range of 24–1450 °C, providing the axial and cell volume expansion.

Secondary mullite has been formed in 60 wt% kaolin–40 wt% Al2O3 ceramics by solution-precipitation in the glassy phase in contact with Al2O3 particle, showing a plate-like morphology, at temperatures above 1673 K. The lattice constant modification of secondary mullite has been determined: the lattice parameters of orthorhombic structure of a, b, and c axes decrease from 8.653, 8.770, and 3.167 Å to 7.958, 8.064, and 2.926 Å, respectively. The Al2O3 content in the secondary mullite crystals increases from 59.69 to 70.41 wt% when the grain width increases from 15 to 40 nm. Both the formation of secondary mullite and its grain growth are intimately related to the presence of the glassy phase originated from impurity (K2O) in the kaolin. Their locations as well as their chemical composition of mullite grains, Al2O3 grains, and glassy phase are provided by the meticulous experiments using high-resolution transmission electron microscopy, selected-area electron diffraction, and energy dispersive spectroscopy techniques.

A procedure for extracting simple constitutive parameters from microindentationtests is described. The analysis used to interpret the indentation tests is based onthe analysis of the spherical indentation test developed by Hill et al. for power law materials. Indentation tests are supplemented by scanning interference microscopyof the residual indented surface profiles and a method is suggested for using the residual surface profiles to estimate the actual contact surface. This, in turn, allowsfor the construction of the entire stress versus strain curve.

The sintering of nanosize powders of fully stabilized zirconia was investigated using the spark plasma sintering (SPS) method. The influence of sintering temperature, heating rate, direct current pulse pattern, sintering time, and sintering pressure on the final density and grain size of the product was investigated. The dependence of densification on temperature showed a maximum at 1200 °C, resulting with nearly fully dense zirconia with a crystallite size of about 100 nm. Heating rate (50∼300 °C min−1) and sintering time (5–16 min) had no significant influence on the final density and the crystallite size. Pulsing patterns ranging from 2:2 to 48:2 (on:off) had no influence on the density or the crystallite size. However, the applied pressure had a significant influence on the final density but no apparent effect on crystallite size for a sintering temperature of 1200 °C and a hold time of 5 min.

A series of experiments were conducted to investigate chemical interactions between silicon carbide (SiC) and synthetic ash compositions expected to be deposited on the surfaces and within the pore structure of a diesel particulate filter. The chosen ash compositions simulated those arising from lubricants and three fuel types: standard diesel, diesel containing ferrocene as a catalytic additive, and diesel containing a cerium-based catalyst. Results demonstrated that SiC suffered little chemical or oxidative degradation in the presence of the ashes at 900 °C. For the ash not containing Fe or Ce, ash sintering effects were a possible mechanism causing filter blockage at temperatures above 970 °C. For ashes containing Fe or Ce, appreciable sintering effects were not observed below 1100 °C. Based upon the work conducted the suitability of SiC as a construction material for diesel particulate filters is not compromised by chemical degradation in the presence of lubricant/additive derived ash at temperatures less than 1100 °C.

A commercial aluminum foil was used to braze alumina plates in air. Although the outer surface of the aluminum oxidizes in air, the majority of the aluminum underneath remains unoxidized during brazing, allowing the ceramic pieces to be joined together with adequate strength. Joint strength testing and subsequent examination of the fracture surfaces of the joints indicate that the joints are inherently ductile, even after long-term, high-temperature air exposure.

Cubic boron nitride (cBN) film was deposited on Co-containing WC substrates by dc jet plasma chemical vapor deposition from an Ar–N2–BF3–H2 gas system. The formation of cobalt nitrides was observed at interface, and the hindrance of Co on cBN growth was demonstrated. Growth temperature and etching treatment of the substrate before deposition influenced the cBN growth greatly. At 1050 °C, cBN films were obtained on etched substrates but not on unetched substrates. At 1090 °C, cBN films were not obtained even on etched substrates. At 960 °C, cBN films deposited even on unetched substrate but the films always peeled off after exposing to air. The film quality of cBN deposited at 960 °C is better than that deposited at 1050 °C.

The effect of continuous heating and isothermal heat treatments on ductile Cu60Zr20Ti20 amorphous ribbons was monitored by differential scanning calorimetry, x-ray diffraction, synchrotron radiation transmission, and high-resolution transmission electron microscopy. Upon continuous heating, the alloy exhibited a glass transition, followed by a supercooled liquid region and two exothermic crystallization stages. Decomposition of the amorphous phase was also observed. The first crystallization stage resulted in the formation of a nanocomposite structure with hexagonal Cu51Zr14 particles embedded in the amorphous matrix, while in the second crystallization stage hexagonal Cu2TiZr-like phase was precipitated. The released enthalpies were 19 J/g and 30 J/g for each crystallization stage. Crystallization kinetics was studied by the classical nucleation theory. Deviations from the Johnson–Mehl–Avrami–Kolmogorov theory may be explained by the contribution of the decomposition of the amorphous matrix.

Cerium oxide (CeO2) nanoparticles were obtained by heating a polyethylene glycol (PEG) solution of cerium nitrate hydrate [Ce(NO3)3 6H2O] at 383 K for 3 h. When the PEG, whose molecular weight was 20,000, was used for the preparation, the monodispersed CeO2, whose particle size was about 102 nm, was obtained. When the mixture of PEG20,000 and ethylene glycol (EG) was used to prepare the PEG solution of cerium nitrate hydrate, the average particle size increased from 102 nm to 660 nm with an increase in the EG content of the solution. The pore structure in the obtained CeO2 particles also depended on the weight ratio between EG and PEG20,000.

During the operation of proton exchange membrane (PEM) fuel cells, a high-resistance oxide is often formed on the cathode surface of base metal bipolar plates. Over time, this corrosion mechanism leads to a drop in fuel cell efficiency and potentially to complete failure. To address this problem, we have developed alloys capable of forming oxides that are both conductive and chemically stable under PEM fuel cell operating conditions. Five alloys of titanium with tantalum or niobium were investigated. The oxides were formed on the alloys by cyclic voltammetry in solutions mimicking the cathode- and anode-side environment of a PEM fuel cell. The oxides of all tested alloys had lower surface resistance than the oxide of pure titanium. We also investigated the chemical durability of Ti–Nb and Ti–Ta alloys in more concentrated solutions beyond those typically found in PEM fuel cells. The oxide films formed on Ti–Nb and Ti–Ta alloys remained conductive and chemically stable in these concentrated solutions. The stability of the oxide films was evaluated; Ti alloys having 3% Ta and Nb were identified as potential candidates for bipolar plate materials.

This paper describes the nanoindentation technique for measuring sputter-deposited Au and Cu thin films’ mechanical properties at elevated temperatures up to 130 °C. A thin, 5-nm Pt layer was deposited onto the Cu film to prevent its oxidation during testing. Nanoindentation was then used to measure elastic modulus and hardness as a function of temperature. These tests showed that elastic modulus and hardness decreased as the test temperature increased from 20 to 130 °C. Cu films exhibited higher hardness values compared to Au, a finding that is explained by the nanocrystalline structure of the film. Hardness was converted to the yield stress using both the Tabor relationship and the inverse method (based on the Johnson cavity model). The thermal component of the yield-stress dependence followed a second-order polynomial in the temperature range tested for Au and Pt/Cu films. The decrease in yield stress at elevated temperatures accounts for the increased interfacial toughness of Cu thin films.

The synthesis and characteristics of strontium borate phosphate phosphors doped with cerium ions were investigated in this study. The synthesis of Sr0.95Ce0.05BPO5 in oxidizing atmosphere results in partial conversion of Ce4+ ions into Ce3+ ions. The luminescent characteristics reveal that Ce3+ ions occupy two principal sites in the host. The dominant emission at 317 nm on 275-nm excitation is attributed to Ce3+ ions located at Sr2+ sites without local charge compensation. The weak emission at 330 nm due to 295-nm excitation is ascribed to Ce3+ ions located at Sr2+ sites in association with charge compensatory vacancy. The reduction of Ce4+ ions to Ce3+ ions occurs in Sr0.95Ce0.05BPO5 heated in the reducing atmosphere. For Sr0.9Ce0.05Na0.05BPO5 and Sr0.9Ce0.05Li0.05BPO5 phosphors, enhancement in luminescence is observed due to the codoping of monovalent ions. The increased luminescence of these phosphors is attributed to the decrease in non-radiative energy transfer.

Nano-sized (Y,Gd)2O3:Eu powders were synthesized by a novel co-precipitation processing in which a mixture of ammonium hydroxide and ammonium hydrogen carbonate was adopted as a complex precipitant. Evolution behaviors of precursors during calcinations were studied by means of thermogravimetry-differential scanning calorimetry-mass spectrum, Fourier transform infrared, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy in detail. Nano-sized (Y,Gd)2O3:Eu powder as prepared possessed a primary grain size of about 30 nm and specific surface area of 38 m2/g after being calcined at 850 °C for 2 h, showing much finer grains and less agglomeration. The as prepared nanopowder shows intense luminescence at 611nm under x-ray or ultraviolet excitation. Transparent (Y,Gd)2O3:Eu ceramics can also be fabricated using this high sinterable nanopowder.