Nanocrystalline tin dioxide (SnO2) thin films were prepared on glass substrate by pulse laser deposition for the first time. The thin films were characterized for their composition, morphology, and crystalline structure by x-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. It was found that the thin films consisted only of the tetragonal phase SnO2 with no structural change, and they were well crystallized during deposition. In most cases, SnO2 particles were overlapped, predominantly grown on preferred (101) plane, and connected with two or three neighbors through necks. The average grain size of the as-prepared thin films was about 12 nm. These facts are of great importance for sensor characteristics, since smaller grains and preferred orientation properties provide higher gas sensitivity to the whole thin films. Our findings indicate that the n-type wide-band-gas semiconductor nanocrystalline thin films can be manipulated by using pulse laser deposition techniques, offering new opportunities to control material fabrication.

Sn/Ni interfacial reactions at 100 °C with and without the passage of electric currents were studied by using the Sn/Ni/Sn sandwich-type reaction couples. The Ni3Sn4 and metastable NiSn3 phases were formed at both the Sn/Ni and Ni/Sn interfaces in the couples reacted at 100 °C without the passing through of electric currents. Metallographical analyses revealed that the metastable NiSn3 phase nucleated and grew at the grain boundary, and the growth rate of the NiSn3 phase was much faster than that of the Ni3Sn4 phase. For the couples with the passage of electric currents of 4 × 103 A/cm2 density, the Ni3Sn4 reaction layers were found at both interfaces as well. However, the NiSn3 phase was found only at the Ni/Sn interface where the directions of electron flow and Ni diffusion were the same, and the NiSn3 phase was not found at the Sn/Ni interface. The NiSn3 phase formed at the Ni/Sn interface was found to nucleate and grow much faster than those without the passage of electric currents. It is likely that the electromigration effect enhances the movement of Ni atoms and accelerates the nucleation and growth of the NiSn3 phase while at the Sn/Ni interface, where the directions of electron flow and Ni diffusion are opposite, electromigration effects retard the movement of Ni atoms and inhibit the nucleation of the NiSn3 phase.

Subsolidus equilibria in air in the RuO2–Bi2O3–CeO2 systems were studied with the aim of obtaining information on possible interactions between a Bi2Ru2O7-based cathode and a CeO2-based solid electrolyte in solid-oxide fuel cells. Bi2O3 is soluble in CeO2, and forms a cubic fluorite solid solution Bi1-xCexO2-x/2 up to Bi1/3Ce2/3O1.83, while no solid solubility of the CeO2 in Bi2O3 was detected. No ternary compound was found in the system. The tie line is between Bi2Ru2O7 and the CeO2 solid solution.

Thermal analysis and x-ray diffraction have confirmed that single-phase, cubic-spinel-structured NiMn2O4 (2:1 Mn2O3:NiO) begins to decompose into a rocksalt and a second spinel-structured phase above 907 °C. The decomposition product in samples air-quenched from 900 and 1200 °C was therefore investigated using transmission electron microscopy. Samples quenched from 900 °C (below decomposition temperature) did not show the expected single-phase microstructure, but instead grains contained nanoregions of a lenticular fringe contrast. Samples quenched from 1050 to 1200 °C were generally composed of Mn-rich spinel grains in addition to grains containing Mn-rich spinel precipitates (30–50 nm) surrounded by a Ni-rich rocksalt matrix. As temperature increased, the spinel grains and precipitates became clearly tetragonal, exhibiting a ferroelastic domain structure arising from a cooperative Jahn–Teller distortion. A decomposition mechanism based on the degree of inversion is proposed to explain these microstructures. Slow cooling samples from 1250 °C resulted in partial recomposition, leading to a microstructure principally composed of cubic spinel and regions of much smaller spinel structured precipitates (50–120 nm) in a rocksalt structured matrix. The slow-cooled samples showed a larger increase in resistance over time than single-phase samples did when held at 400 °C. X-ray diffraction measurements carried out before and after electrical characterization showed a reduction in the amount of rocksalt structured material present in slow-cooled samples.

Matrix-mediated in situ synthesis of monodispersed magnetite and maghemite nanoparticles (2–16 nm) was carried out using the cavities present in gels of globular proteins such as egg white and bovine serum albumin. Under stringent conditions, spatial-charge-distribution-assisted molecular recognition of proteins for inorganic ions led to the site- and polymorph-specific synthesis of superparamagnetic iron oxide particles. A transformation from magnetite to maghemite as a nucleating phase could be observed by partially denaturing the egg white protein, signifying the delicate role of quaternary structure of proteins under different reaction conditions, in determining the size and shape of the polymorph.

Engineering ceramics and cermets are widely used for demanding tribological applications. In this perspective, the objective of this paper was to understand the friction and wear behavior of some of the potential tribomaterials, e.g., ZrO2–30 vol% TiB2 composite, sialon–40 vol% TiB2 composite, TiB2-based cermet with 16 vol% Ni3(Al,Ti) binder, and monolithic TiB2 in fretting contacts. Wear tests on the TiB2-containing materials under dry unlubricated conditions (23–25 °C, 50–55% relative humidity) were performed against corundum on a ball-on-flat tribometer. The obtained friction and wear data were critically analyzed to investigate how the binder phase in TiB2 matrix influences the tribological performance. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms discussed. X-ray photoelectron spectroscopy analysis of the worn surfaces in the monolithic TiB2/alumina revealed the pronounced transfer of mixed oxides containing TiO2 and B2O3 to the alumina counterbody and also indicated the transfer of alumina to TiB2 flat. Tribochemical reactions and abrasion along with the material transfer between the counterbodies were observed to play a major role in the wear of the fretting couples.

The potential use of barium zirconate for the manufacture of corrosion-resistant substrates emphasizes the need for a simple, inexpensive, and easily scalable process to produce high-quality powders with well-controlled composition and properties. However, the classical solid-state preparation of barium zirconate leads to an inhomogeneous powder unsuitable for applications in highly corrosive environment. For this paper, the possibility to use the spray-drying technique for the preparation of BaZrO3 powders with a controlled size distribution and morphology was investigated. The influence of the nature and concentration of the precursor solution and the influence of the spray-drying step are discussed on the basis of x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and dilatometric measurements.

Effects of Ni and Au from Ni/Au substrate metallizations on the interfacial reactions of solder joints in flip-chip packages during long-term thermal aging were systematically investigated. It was found that both Au and Ni influenced the solid-state interfacial reactions, underbump metallization (UBM), and intermetallic compound (IMC) evolution. Because large amounts of Ni could incorporate into IMC to form a multicomponent (Cu, Ni)6Sn5 phase during assembly reflow, while Au could only affect the reaction during thermal aging through the reconfiguration of AuSn4 phase, Ni had stronger effects on solid-solution type Ni–V UBM consumption than Au. It was found that the UBM consumption process was faster in the eutectic SnPb solder system than that in the SnAgCu solder system during aging. A porous structure was formed in the UBM layer after Ni in UBM was consumed. Electrical resistance of flip-chip packages increased significantly after the porous structure reached certain extents. The results showed that the diffusion process of Ni from UBM and Sn from solder in the presence of (Cu, Ni)6Sn5 or (Ni, Cu)3Sn4 phase at solder joint interfaces could be much faster than that in the case of binary Cu6Sn5 or Ni3Sn4 IMC.

The thermal endurance of poly(butylene terephthalate) was evaluated by both consolidated long-term conventional life tests and a short-term analytical procedure. The latter is based on oxidative stability measurements by isothermal differential calorimetry in a pure oxygen flow. The capability of the analytical technique to provide an activation energy for the thermo-oxidation process was verified. The results obtained by the two methods were compared and discussed. It is shown that the temperature index derived by the analytical procedure can be close to that obtained by the conventional tests, provided that a suitable selection of the test temperatures and failure criteria is made; however, benefits in term of test time shortening are lower than those previously obtained for polyolefin-based materials.

We used the Clusters model to study the densification kinetics and resulting porosity of a compact of polydispersed soda-;lime-;silica glass spheres. In addition to the physical data (viscosity, surface tension, particle size distribution) required by the Clusters model, for the first time in glass-;sintering studies, we took extra variables into account: the average number of necks per sphere, the effects of pre-;existing crystals on the particle surfaces, and sample size. The model predicted both the densification kinetics and the resulting pore-;size distribution of sintered compacts. A cross section of a porous sample displayed a porosity pattern that agreed with computer-;simulated cross sections, whose pore-;size distributions was calculated via the Clusters model using a Monte Carlo technique. Its capacity to predict both density and pore-;size distribution makes the Clusters model a valuable tool for designing sintered glasses with any desired microstructure.

Transformation kinetics of mullite formation in kaolin–Al2O3 ceramics was studied by x-ray diffraction, transmission electron microscopy, and energy dispersion spectrometry. The mullitization process of kaolin–Al2O3 ceramics is described by two stages; one is the primary mullite transformation at 1273 to 1573 K, and the other is the secondary mullite formation at 1573 to 1873 K. The activation energy of 1164.6 kJ mol-1 obtained for the secondary mullite formation is lower than 1356.9 kJ mol-1 for the primary mullite transformation by the general form of the Johnson–Mehl–Avrami equation. The lower value of growth morphology parameter strongly supports that in the secondary mullite formation the added alumina is dissolved into glassy phase and the mullite is then precipitated.

Sheets of α-sialon were prepared by tape casting and pressureless sintering. Suspensions consisting of precursor α-sialon powders, dispersant, binder, plasticizer, and 60 MEK/40E as solvent were optimized for tape casting by rheological measurements. Crack-free green tapes with good flexibility and high strength were obtained from suspensions with suitable rheological properties (moderate viscosity, shear-thinning behavior, and negligible thixotropy). The obtained green tapes showed great homogeneity by means of scanning electron microscope observation and pore-size distribution, leading to homogeneous α-sialon sheets after pressureless sintering at 1750 °C for 2 h. The results showed that it was possible to fabricate homogeneous α-sialon sheets with smooth surfaces through tape casting and pressureless sintering.

By the combination of two successive dry milling processes (i.e., by using a multiring mill and subsequently a pin-type disintegrator), downsizing of Si powders was achieved to 30 nm crystallites and their aggregated mean volume diameter about 100 nm, with the top size less than 400 nm. Combination of the two dry milling processes proved to be effective to reduce the particle size and sharpen the size distribution of the aggregates without using any additives, tedious wet processes, or subsequent classification. Increase in the impurity due to milling was <0.1% for Fe and <0.4% for Zr, being well within a tolerable limit for most of the technological purposes.

A comparison of bending and compressive/tensile loading cases of multilayered composites is given. Bending perpendicular to the layer interfaces is suggested as a sensitive and experimentally convenient method for determining the elastic modulus of compliant isotropic layers within a multilayered composite. Different approaches to analyze the strain and compliance behavior of the composite and individual layers are derived. Ranking of the relevant equations with respect to strain sensitivity is made, which favors the bending test perpendicular to the layer interfaces. The derived relationships permit a prediction of the bending behavior and the flexural rigidity of the composite. Furthermore, the properties of a layer within the structure can be determined. Limitations that exist for the bending perpendicular to the layer interfaces in the case of low stiffness of the layers can be overcome using either a compressive or a tensile loading mode. Application of the formulas to buckling and interfacial delamination is considered. Materials, such as plasma-sprayed thermal barrier coatings, that are supposed to behave elastically different in tension and compression are given special consideration. Although determination of elastic moduli is the main interest, in the case of known elastic moduli, the formulas can be used to determine the thickness of individual layers within a composite structure.

A new method for making substrate-independent hardness measurements by nanoindentation techniques that applies to soft metallic films on very hard substrates is presented. The primary issue to be addressed is substrate-induced enhancement of indentation pileup and the ways it influences the indentation contact area. On the basis of experimental observations of soft aluminum films deposited on silicon, glass, and sapphire substrates, an empirical relationship was derived that relates the amount of pileup to the contact depth. From this relationship and the associated experimental observations, a method was developed that allows the intrinsic hardness of the film to be estimated, even when the indenter penetrates through the film into the substrate. The method should prove useful for very thin films (<100 nm) in which it is not possible to make measurements at penetration depths small enough to avoid subtrate effects.

The synthesis of Au and Ag metal nanoparticles stabilized by G4, G5, and G6 hyperbranched poly(amine–ester) (HPAE) is reported. The reduction of hydrogen tetrachloroaurate and silver nitrate in the presence of HPAE resulted in the formation of stable, uniform, water-soluble nanoparticles. The average particle sizes are (2.4 ±0.5)–(4.1 ±0.4) nm for Au and (2.5 ±4.9)–(10.3 ±1.7) nm for Ag, depending on the generation of HPAE and metal ion-to-end tertiary amine of HPAE (M:N) used. All of the obtained colloidal solutions are stable for a long period of time. The results from ultraviolet–visible absorption spectra and Fourier transform infrared absorption spectroscopic investigations confirm the interactions between metal and HPAE.

A simple pulse sonoelectrochemical technique was used to synthesize highly dispersed spherical palladium particles and a dendritic Pd superstructure in the presence of cethyltrimethylammonium bromide (CTAB) at room temperature. The shape and size of spherical nanocrystalline Pd can be controlled by varying current density, the interval between two continuous ultrasonic pulses, ultrasonic intensity, and the concentration of CTAB. The possible growth mechanism of dendritic-structured Pd is discussed.

Sol-gel spin coating of lead-titanate films differs from most processing routes, such as metalorganic chemical vapor deposition and pulsed laser deposition, in that crystallization cannot occur without a postdeposition annealing step. This work focuses on the annealing of sol-gel-derived PbZrTiO3 films on LaAlO3 substrates in attempts to identify the precise conditions necessary to grow films of quality similar to that obtained through other techniques. In particular, the effects of Pb excess (in precursor solutions), annealing times, and temperature were investigated through transmission electron microscopy and four-circle x-ray diffraction. The significance of this work is in the direct observation of the correlation between Pb excess and film crystallization. It is shown that the effects of Pb excess on the completeness of film crystallization become more dramatic at lower annealing temperatures, even while epitaxial quality is maintained.

The fracture toughness of small volumes of brittle materials may be investigated by using pyramidal indenters to initiate radial cracks. The length of these cracks, together with indenting load and the hardness to modulus ratio of the material, were combined to calculate the critical stress intensity factor Kc pertinent to fracture toughness. Modulus and hardness may be obtained from the literature or may be measured using nanoindentation techniques. If the material volume is very small, such as single grains in a conglomerate, a reduction of scale may be obtained by reducing the internal face angles of the indenter. This encourages crack initiation at lower loads, but cracks produced at very low loads are short and difficult to measure. Experiments on fused silica and glassy carbon suggested that radial cracks are initiated during loading and that when indenters with sufficiently small angles are used these cracks immediately pop-in, to become fully developed median/radial crack systems. Following pop-in, the rate of penetration of the indenter increases and at higher loads there is an extra increment of penetration over that which would otherwise have occurred. In this study a method is described whereby this extra penetration may be determined. Then for two dissimilar brittle materials, crack length is shown to be correlated with extra penetration leading to a relationship that may possibly avoid the necessity for crack-length measurement.

Wetting properties of lead-free solders, Sn–0.7 wt.% Cu and Sn–3.5 wt.% Ag, pure Sn, and conventional Sn–40 w.t% Pb on Ni, Cu, and Ag substrates at 250 and 240 °C were determined by using a wetting balance technique. Wetting times and wetting forces were determined directly from the wetting curves, and surface tensions of molten solders were calculated from the wetting force measurements. A statistic tool, analysis of variance (ANOVA), was used to analyze the experimental results. By using the wetting time as an indication, it was found that Sn–Pb exhibited the best wetting followed by Sn–Ag, Sn–Cu, and Sn, in that order. A very significant but frequently ignored issue is that most solders react with substrates, and the molten solders are not in contact with the original substrates but rather with intermetallic compounds. On the basis of theoretical analysis and experimental observations, it was concluded that the withdrawing forces and the surface tensions of the molten solders determined by the present technique are not significantly affected by the interfacial reactions if the interfacial reactions are not too excessive. However, wetting times are strong functions of both solders and substrates and the interfacial reactions between them.