Y-α-sialons (Y0.333Si10Al2ON15) were prepared by hot pressing using 5 wt.% BaAl2Si2O8 as an additive. The results showed that barium aluminosilicate not only.served as a liquid-phase sintering aid to promote densification, but also facilitated the.development of elongated α-sialon grains. The obtained self-toughened α-sialon was.both hard and tough. The Vickers hardness, flexural strength, and fracture toughness.are 18.9 GPa, 802 MPa, and 6.0 Mpam1/2, respectively. Post heat treatment could.promote the growth of elongated α-sialon grains, hence further increasing its.toughness.

The tribological properties of a B2-type Al–Pd–Mn quasicrystal approximant were investigated and compared with those of an Al–Pd–Mn icosahedral quasicrystal. The approximant was of the _ phase, having a crystalline CsCl-type structure and nominal composition Al48Pd42Mn10. Friction coefficients measured in ultrahigh vacuum between a pair of Al48Pd42Mn10 samples having truly clean surfaces were found to be twice as high as those reported for the Al70Pd21Mn9 quasicrystal. When the surfaces were oxidized by exposure to O2 or H2O, the friction coefficients decreased by roughly a factor of two for both materials but the friction coefficient for the approximant remained roughly twice that of the quasicrystal. The rate of oxidation of the approximant was found to be one order of magnitude higher than that of the quasicrystal. This corroborates findings that suggest that quasicrystals exhibit an inherent resistance to oxidation and corrosion. Vickers hardness measurements show that the quasicrystal is roughly three times as hard as the approximant.

Nucleation can play an important role during the formation of silicides, especially when the difference in Gibbs free energy ΔG between the existing and newly formed phase is small. In this work, it is shown that the addition of elements that form a solid solution with either the existing or nucleating phase influences the entropy of mixing and thus changes ΔG. In this way, the height of the nucleation barrier may be controlled, thus controlling the nucleation temperature. The influence of mixing entropy on silicide nucleation is illustrated by experiments for two ternary systems: Co–Mn–Si and Ni–Pd–Si. It is shown that the nucleation temperature of CoSi2 is increased by the addition of Mn, the nucleation temperature of MnSi1.7 is increased by the presence of Co, the nucleation temperature of NiSi2 is increased by the addition of Pd, and the nucleation temperature of PdSi is decreased by the addition of Ni. In all four cases, the effect of the alloying element on the nucleation temperature can be explained by a model on the basis of the concept of mixing entropy.

Large-scale single-crystal cubic PbS nanorods were successfully achieved by using ultrasound irradiation in certain ethylenediamine tetraacetic acid (EDTA) solutions, particularly in the solution of Pb:EDTA = 1:1. The obtained PbS nanorods were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersed x-ray spectrometry, selected area electronic diffraction, and high-resolution transmission electron microscopy. The results reveal that the PbS nanorods with straight and uniform structure have a diameter of about 70–80 nm and length of about 1000 nm, where the growth mechanism is tentatively discussed. The successful synthesis of these cubic structure semiconductor PbS nanorods may open up new possibilities for using these materials as building blocks to create functional two-dimensional or three-dimensional nanostructured materials.

Structural properties of polycrystalline Pb(Zr0.35Ti0.65)O3 (PZT) thin films grown by metalorganic chemical vapor deposition on Ir bottom electrodes were investigated. Symmetric x-ray diffraction measurements showed that as-deposited 1500 íthick PZT films are partially tetragonal and partially rhombohedral. Cross-section scanning electron microscopy showed that these films have a polycrystalline columnar microstructure with grains extending through the thickness of the film. X-ray depth profiling using the grazing-incidence asymmetric Bragg scattering geometry suggests that each grain has a bilayer structure consisting of a near-surface region in the etragonal phase and the region at the bottom electrode interface in the rhombohedral hase. The required compatibility between the tetragonal and rhombohedral phases in he proposed layered structure of the 1500 Å PZT can explain the peak shifts observed n the symmetric x-ray diffraction results of thicker PZT films.

Titania fibers were synthesized by a liquid mix process, starting by complexing titanium isopropoxide with a chelating agent solution to form a precursor resin for further fiber drawing. The as-drawn continuous precursor fibers underwent a weight change of 80% and a volume change of 75% after heat treatment at 800 °C in nitrogen followed by an additional treatment at 600 °C in air. The fibers consisted mainly of rutile with 5–10% anatase. Further treatment at 700 °C transformed the anatase completely into rutile. Fibers with finished diameter less than about 15 μm were solid with smooth surfaces. Fibers with finished diameter greater than about 15 μm were hollow and spirally cracked in a uniform manner. Fibers treated at 600 °C showed no visible grains. Additional annealing at 800 °C grew grains to an average size of 0.3–0.4 μm. The fibers appeared solid and dense.

A high-resolution laser-assisted loading dilatometer was applied for the precise measurement of radial and axial strain rates under different uniaxial loads, using alumina as a model material. As a continuous application of an external load can lead to an anisotropic microstructure, a discontinuous hot forging technique was utilized to determine the viscous Poisson's coefficient. In these studies, samples were presintered to different densities and only then were hot-forging tests performed. The result provides an isotropic viscous Poisson's coefficient, which increases smoothly between 0.21 and 0.42 within the accessible density range. Combined with the uniaxial viscosity measured before using the same technique, the hydrostatic sintering stress, bulk viscosity, and shear viscosity as a function of density are now available for solid-state sintering. A comparison of the experimentally obtained results with several theoretical models is included.

A 650 °C annealed thin film was found to be a single phase of SrBi2Ta2O9 (SBT) and showed the c-axis orientation without ultraviolet irradiation. The crystallinity and crystal orientation of the thin films were improved by ultraviolet irradiation using an ultrahigh-pressure mercury lamp (UHPML) or a low-pressure mercury lamp (LPML) under three conditions. In particular, the crystal orientation of the 650 °C annealed thin films dramatically changed by ultraviolet irradiation using a LPML at room temperature or using an UHPML at 150 °C. The 650 °C annealed SBT thin film prepared by ultraviolet irradiation using an UHPML at 150 °C showed a remanent polarization (Pr) of 4.3 μC/cm2 and a coercive electric field (Ec) of 101 kV/cm at 10 V.

We describe the synthesis and characterization of aligned carbon nanotubes deposited on quartz substrates by pyrolysis of a xylene–ferrocene mixture at 700 °C at atmospheric pressure. For microscopic characterization of the pyrolyzed products, scanning and transmission electron microscopies and scanning tunneling microcopy were used, and properties of bulk samples were characterized by Raman spectroscopy and x-ray powder diffraction methods. The nanotubes have topological defects and many contain metal particles. Scanning tunneling spectroscopy proved that the nanotubes had a metallic electrical conductivity with resonant states near the Fermi energy. The states are ascribed to the dangling bonds originating from the defects.

Rutile titania powders were synthesized via a sol-gel/hydrothermal process using nitric acid as the catalyst. A molar acid to alkoxide ratio of 10 and a water to alkoxide molar ratio of 250 produced 100% rutile powders when precipitated below 45 °C. Higher temperatures yielded initially either anatase or mixtures of anatase and rutile. Spherulitic growth produced cauliflower-shaped agglomerates with a mean size of 760 nm. The agglomerates could be broken apart into approximately 100-nm large broomlike agglomerates via a dissolution and reprecipitation process when reacted with approximately 2.4 molar nitric acid. Transmission electron microscopy observations showed that the broomlike agglomerate consisted of linear clusters of rodlike agglomerates composed of crystallographically aligned, primary particles approximately 4 nm in size.

The heat-treatment retention time effect of carbonized polyvinylidenechloride (PVDC) was investigated. Homogeneous PVDC with a crystallite size of 267 Å was used as a precursor material for an electric double-layer capacitor electrode. The P-120m material, which was heat treated for 120 min at 700 °C, shows a larger specific capacitance than any other material in this study. It shows the largest values reported up to now, reaching values as high as 100.2 F/g for a two-electrode system, which is equivalent to 400.8 F/g in a conventional three-compartment electrode system. It is difficult to distinguish the difference in the pore-size distribution by way of gas adsorption as the retention time is varied. However, the difference can be clarified using a novel method based on the analysis of transmission electron microscopy images. As the retention time for heat treatment increases, the pore size grows through the coalescence of small pores. Furthermore, a new concept for the electric double-layer capacitance is suggested on the basis of analysis of the transmission electron microscopy observations.

The thermo-optic coefficient (dn/dT) of inorganic–organic hybrid material films prepared by the sol-gel process of organoalkylsilanes is measured using a prism coupler equipped with a hot stage. The effect of the organic modifier on the variation of dn/dT in inorganic–organic hybrid material films has been investigated. The value of dn/dT becomes more negative with increasing molecular weight of the organic modifier or with an increase in the proportion of modifier in the sample. On the other hand, dn/dT increases with an increase in the degree of organic photopolymerization. From these results, it can be seen that the value of dn/dT in these films can be varied between −0.83 × 10−4/°C to −2.43 × 10−4/°C by changing the organic modifier concentration and type.

The effects of various surface pretreatments on the adhesion of electroless and sputter-deposited copper metallizations to a hybrid polymer material were investigated. Without pretreatment, the adhesion between copper and the polymer was virtually zero. The adhesion of electroless copper to the polymer was poor regardless of the pretreatment used. However, the wet-chemical pretreatment of the polymer surface markedly increased the adhesion of sputtered copper to the polymer. It preferentially removed the inorganic part of the polymer and formed micropores on the surface. The plasma and reactive ion etching pretreatments, in turn, selectively etched away the organic part of the polymer and noticeably increased the hydrophilicity. Although this resulted in even higher increase in the surface free energy than was achieved with the chemical treatment, the granular surfaces became mechanically brittle. With the help of x-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and contact-angle measurements and with the recently developed pull test, the physicochemical changes of the wet-chemically pretreated polymer surfaces were demonstrated to have significant effects on the adhesion.

Oxide melt solution calorimetric measurements were made to determine the enthalpy of formation of cubic-yttria-stabilized zirconia (c-YSZ) with respect to the oxides m-ZrO2 and C-type YO1.5. The enthalpy of formation can be fit either by a quadratic equation or by two straight line segments about the minimum near x = 0.40. The quadratic fit gives a strongly negative interaction parameter, Ω=-93.7 ± 12.0 kJ/mol, but does not imply regular solution behavior because of extensive short-range order. In this fit, the enthalpy of transition of m-ZrO2 to c-ZrO2, 9.7 ± 1.1 kJ/mol, is in reasonable agreement with earlier estimates and that of C-type to cubic fluorite YO1.5, 24.3 ±14.4 kJ/mol, is consistent with an essentially random distribution of oxide ions and anion vacancies in the high-temperature fluorite phase. The two straight-line segments give 6.1 ± 0.6 kJ/mol and 5.5 ± 2.5 kJ/mol for these transitions, respectively. The latter value would imply strong short-range order in cubic fluorite YO1.5. Clearly more complex solution thermodynamic descriptions need to be developed. The enthalpy of transition from the disordered c-YSZ phase to the ordered δ-phase at 25 °C was also measured and was 0.4 ± 1.6 kJ/mol. No energetic difference between the disordered c-YSZ phase and the ordered δ-phase underscores the importance of short-range order in c-YSZ. Enthalpy data were combined with Gibbs free energy data to calculate entropies of mixing. Using the quadratic fit, negative excess entropy of mixing in the cubic solid solution, relative to a system with maximum randomness on cation and anion sublattices, was found and was another indication of extensive short-range order in c-YSZ.

The piezoelectric poly(vinylidene fluoride) (PVDF) surface possessing low surface energy was modified by the ion-assisted-reaction (IAR) method for the application of thin film speaker. The IAR-treated hydrophilic PVDF surface was investigated using atomic force microscopy and x-ray photoelectron spectroscopy. The adhesion strength between various types of electrodes and the film was dramatically improved due to the hydrophilic functional groups, such as –C–O–, –(C=O)–, –(C=O)–O–, and so forth. A durable loudspeaker film was fabricated by enhancing the adhesion between the screen-printed poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) and the modified PVDF films. The PVDF speaker film with the PEDOT/PSS electrode showed higher durability, flatter sound pressure level characteristics, and easier processability compared to metals or indium tin oxide electrodes.

Iron-nickel-based powders and thin films were synthesized by an electroless polyol method. The growth process as a function of deposition time was studied. The Fe concentration of deposited films and precipitated powders were similar and independent of deposition time. The metalorganic intermediates were present in powders and their amount decreased with time. The morphological investigations suggested that 60 min was the optimum deposition time to deposit dense films with particles of narrow size distribution. In addition, the films deposited at 60 min also possessed the highest saturation magnetization due to a more ordered atomic environment of nickel. The as-deposited Fe was apparently oxidized in the films.

Thin separation by implanted oxygen substrates are attractive candidates for low-power, low-voltage electronic devices and can be obtained by low-dose, low-energy oxygen–ion implantation. We report in this study a variation of the process parameters that have never been investigated before, particularly for implantation with a high current density implanter. Characterization of the sample sets by transmission electron microscopy, secondary ion mass spectroscopy (SIMS), and Rutherford backscattering spectrometry (RBS) shows an optimum dose of 3.0 to 3.5 × 1017 O+/cm2 at 100 keV for forming a continuous buried oxide (BOX) layer compared to 2.5 × 1017 O+/cm2 at 65 keV. At this optimum condition for 100 keV, the thickness of Si top layers and BOX layers is in the range of 175–185 nm and 70–80 nm, respectively. Analysis of the breakdown voltage of small area capacitors shows a breakdown field in the range of 6.0–7.0 MV/cm, which is adequate for low-power, low-voltage devices. SIMS analysis shows that the maximum oxygen concentration of as-implanted samples is located at depths of 160 and 240 nm for the implantation energy of 65 and 100 keV, respectively. A significant redistribution of oxygen occurs at temperatures above 1300 °C during the ramping process. RBS analysis showed that a high-quality crystalline Si layer was produced after annealing at 1350 °C for 4 h. The defect density determined by the chemical etching method was found to be very low (<300 defects per cm2) for all samples with a dose range of 3.0 × 1017 O+/cm2 to 6.0 × 1017 O+/cm2 implanted at 100 keV. However, a 65 keV sample with a dose of 4.5 × 1017 O+/cm2 contains about 109 defects per cm2. The larger defect density in the 65-keV sample may be due to the shift of oxygen depth distribution toward the surface, resulting in easier defect extension during the annealing process. The oxide precipitates in the Si overlayer play a key role in defect reduction by blocking the extension of dislocations to the surface.

Self-propagating high-temperature synthesis was used to prepare boride-based functionally graded materials (FGMs) as thermal barriers for space re-entry vehicles. FGMs are characterized by inhomogeneous spatial composition, resulting in different spatial characteristics. In this work, the FGMs were composed of a ceramic [i.e., MB2 (M = Ti, Zr, Hf)] and a metallic (i.e., NiAl) side, joined together by composite layers of graded stoichiometries of the two components. Thus, in the same material, the boride end gives thermal insulation, while the intermetallic end offers an easy junction to the structure of the space aircraft. The prepared FGMs showed good adhesion between the layers and global compactness after preparation and thermal tests. The microhardness along the samples was measured, and their insulating capabilities were evaluated.

A nanocrystalline KNbO3 particle/polymer hybrid was synthesized through controlled hydrolysis and polymerization of metalorganics below 100 °C. A KNbO3 precursor was synthesized from potassium ethoxide, niobium ethoxide, and acetoacetoxyethyl methacrylate. The K–Nb alkoxide precursor was hydrolyzed and polymerized yielding KNbO3 particle/polymer hybrid. The organic matrix included nanometer-sized crystalline particles depending upon the hydrolysis conditions. The nanocrystalline particles were identified to be potassium niobate by electron diffraction and energy dispersive x-ray analysis. The suspension of the hybrid in silicone oil revealed a yield stress dependent upon various conditions, such as concentration and applied field. The hybridization was found to have a pronounced effect on the electrorheological properties of the fluid, including the KNbO3 particle/polymer hybrid.

More than 2500 indentations were made on a silicon wafer surface using a range of different unloading rates and maximum applied loads. The unloading curves were examined for characteristic events (pop-out, kink pop-out, elbow followed by pop-out, and elbow) that were assigned to different phase transitions within the affected material based on Raman microspectroscopy analysis of residual imprints. The effect of unloading rate and maximum applied load on the average contact pressure at the beginning of the event was found. A permissible range for each event to occur was established.