The effect of particle volume fraction fp on the light transmittance of glass particle-dispersed epoxy matrix composites with a particle volume fraction of fp = 0.0001 to 0.4 was studied. The particle size used was much larger than the wavelength of light in a visible wavelength. The transmitted laser beam scattering pattern and light transmittance of the composites were obtained, and the transmitted laser beam pattern showed a broadening, which increased with an increase in particle volume fraction. This behavior appeared more remarkable in particles with smaller diameters. The light transmittance of the composite was affected by the particle volume fraction fp and was divided into two characteristic regions according to fp. For fp < 0.01, the light transmittance was slightly affected by the incorporation of the particles, while the light transmittance of the composite with fp > 0.01 was strongly affected by fp and size of the glass particle dp. The effects of fp and dp on the light transmittance are explained by the introduction of a normalized total surface area 〈 S〉 A guideline to obtain higher light transmittance of the composite is discussed based on the parameter 〈S 〉.

Semiconductor selenides of MSe (M = Cd, Hg) nanocrystalline powders were synthesized through the reactions between metal chlorides and sodium selenosulfate in the ammoniacal aqueous solution at room temperature for 6–10 h. The samples were characterized by x-ray powder diffraction, transmission electron microscopy, electron diffraction, x-ray photoelectron spectroscopy, and elemental analysis. The average diameters of CdSe and HgSe nanocrystallites are 4 and 8 nm, respectively. The storage and an interesting phase transition under hydrothermal conditions have been presented. The absorption spectrum of the as-prepared samples exhibits obvious blue shift due to the size confinement.

Highly porous microcrystalline hydroxyapatite (HAP) coatings have been prepared from calcium nitrate and phosphoric acid based sols by the aerosol-gel process. The coatings were studied after sintering at different temperatures with the use of Fourier transform infrared spectroscopy, x-ray diffraction, energy disperse x-ray microanalysis, scanning electron microscopy, and transmission electron microscopy. The composition, structure, and morphology of the coatings sintered at 650 °C fit fairly well highly porous HAP. These coatings were reproduced onto TiO2/Si substrates and studied by Rutherford backscattering. It is shown that even after chemical etching, an adherent calcium phosphate phase remains attached to the TiO2/Si substrate.

R2BaZnO5 (R = Sm, Eu, Gd, Dy, Ho, Er, and Tm) were synthesized, and the effects of the differences in ionic radii of R ions on the microwave dielectric properties and crystal structure have been investigated by using x-ray powder diffraction. It was shown that the R2BaZnO5compounds have an orthorhombic crystal structure with Pnma (No. 62) and the lattice parameters of the samples increase linearly with the increase in the ionic radii of the R ions. The dielectric constants (εr) of R2BaZnO5sintered at the optimum temperatures vary linearly from 16.1 to 19.3, suggesting that these variations in εr are the result of the differences in the ionic polarizabilities of R ions. Moreover, it is suggested that the variations in the valences of R ions determined by using bond valence sum may exert an influence on quality factor (Qf ), because the values of valences of R ions in R(1)O7 polyhedra and Qf exhibit similar tendencies with changes in the ionic radii of R ions. In the R2O3–BaO–ZnO system, Dy2BaZnO5showed the appropriate microwave dielectric properties: εr = 17.1, Qf = 29669 GHz, and τf = −1.5 ppm/°C.

Thermal oxide covered silicon wafers were polished with slurries containing either nano-sized ceria (CeO2) or newly prepared uniform colloidal silica particles coated with ceria. The polish rate of the latter was significantly higher than that of pure ceria. The experiments were carried out using different concentrations of the abrasives at pH 4 and 10. Little effect on the polishing rates was noted when the conditions of the slurries were varied, which was explained by the compensation of two opposite polishing mechanisms.

During plastic deformation, dislocation boundaries are formed and orientation differences across them arise. Two different causes lead to the formation of two kinds of deformation-induced boundaries: a statistical trapping of dislocations in incidental dislocation boundaries and a difference in the activation of slip systems on both sides of geometrically necessary boundaries. On the basis of these mechanisms, the occurrence of disorientations across both types of dislocation boundaries is modeled by dislocation dynamics. The resulting evolution of the disorientation angles with strain is in good agreement with experimental observations. The theoretically obtained distribution functions for the disorientation angles describe the experimental findings well and explain their scaling behavior. The model also predicts correlations between disorientations in neighboring boundaries, and evidence for their existence is presented.

The free volume of metallic glasses has a significant effect on atomic relaxation processes, although a detailed understanding of the nature and distribution of free volume sites is currently lacking. Positron annihilation spectroscopy was employed to study free volume in a Zr–Ti–Ni–Cu–Be bulk metallic glass following plastic straining and cathodic charging with atomic hydrogen. Multiple techniques were used to show that strained samples had more open volume, while moderate hydrogen charging resulted in a free volume decrease. It was also shown that the free volume is associated with zirconium and titanium at the expense of nickel, copper, and beryllium. Plastic straining led to a slight chemical reordering.

The effect of the irradiation of electrons with 10–70 keV on optical properties, including spectral reflectance ρ and solar absorptance as, of aluminized polyimide films was investigated. The spectral reflectance was measured in situ before and after electron exposure. Experimental results showed that the reflective properties of aluminized polyimide film were apparently degraded in the 500–1200 nm wavelength range of the solar spectrum. Under the exposure of electrons, no charging effects were found on the aluminized polyimide film serving as an ion-conductive polymer. After the exposure, an “annealing” or “bleaching” effect occurred. At a given irradiation fluence, the change in solar absorptance (Δas) of the aluminized polyimide film was increased with electron energy. There is a threshold value of electron flux φcr which affects the change in Δas of the aluminized polyimide film, approximately φcr = 6 × 1012 electrons/cm2s. When φ < φcr, the change in Δas is independent from the flux; when φ > φcr, Δas increases with the flux monotonically. The change in Δas with electron fluence Φ can be expressed in the form of a power function: Δas = αΦβ. The factors α and β are related to electron energy and show a maximum and a minimum value at 50 keV, respectively.

Critical strain arguments are often used to model the thickness dependence of the strength of thin films on substrates. In these arguments, plastic deformation occurs when the stress in a film is high enough that the strain energy relieved by the introduction of a misfit dislocation is sufficient to generate the line energy of that misfit. Such models typically assume compact dislocation cores. However, experimental evidence suggests that, under certain circumstances, dislocation cores may spread out into the interface between the film and the substrate. If this happens, the energy of the misfit dislocation, and the critical stress needed for its propagation, will be lowered. In this paper, the effect of dislocation core spreading on the critical stress has been modeled. The effects of interface strength, film thickness, and misfit dislocation spacing are considered.

Spectrophotometry in the ultraviolet-visible-infrared range was used to investigate the optical properties of polymer bilayers obtained by spin coating polycarbonate films about 1 μm thick on top of pyrromethene-doped polyvinylcarbazole (PVK) layers deposited on glass. Due to the light confinement in the PVK plane, the laser-dye photoluminescence collected along the polymer plane was linearly polarized and shifted from green to yellow according to the active film thickness. To laterally contain light, microstructures were imprinted on laser-dye-doped PVK films by soft lithography. The photoluminescence coming out of a microstructured film and the film topography were analyzed by scanning near-field optical microscopy.

The high porosity and uniform pore size of mesoporous oxide films offer unique opportunities for microelectromechanical system (MEMS) devices that require low density and low thermal conductivity. This paper provides the first report in which mesoporous films were adapted for MEMS applications. Mesoporous SiO2 and Al2O3 films were prepared by spin coating using block copolymers as the structure-directing agents. The resulting films were over 50% porous with uniform pores of 8-nm average diameter and an extremely smooth surface. The photopatterning and etching characteristics of the mesoporous films were investigated and processing protocols were established which enabled the films to serve as the sacrificial layer or the structure layer in MEMS devices. The unique mesoporous morphology leads to novel behavior including extremely high etching rates and the ability to etch underlying layers. Surface micromachining methods were used to fabricate three basic MEMS structures, microbridges, cantilevers, and membranes, from the mesoporous oxides.

A single phase of glassy Co75Ti25 alloy powders was synthesized by high-energy ball milling the elemental powders at room temperature, using the mechanical alloying method. The final product of the glassy alloy, which is obtained after ball milling for 86 ks, exhibits soft magnetic properties with polarization and coercivity values of 0.67 T and 2.98 kA/m, respectively. This binary glassy alloy, in which its glass transition temperature (Tg) lies at a rather high temperature (833 K), transforms into face-centered-cubic Co3Ti (ordered phase) at 889 K through a single sharp exothermic reaction with an enthalpy change of crystallization (ΔHx) of −2.35 kJ/mol. The supercooled liquid region before crystallization ΔTx of the synthesized glassy powders shows an extraordinary high value (56 K) for a metallic binary system. The reduced glass transition temperature [ratio between Tg and liquidus temperatures, Tl (Tg/Tl)] was 0.56. We also demonstrated postannealing experiments of the mechanically deformed Co/Ti multilayered composite powders. The results show that annealing of the powders at 710 K leads to the formation of a glassy phase (thermally enhanced glass formation reaction). Its heat formation was measured directly and found to be −0.56 kJ/mol. The similarity in the crystallization and magnetization behaviors between the two classes of as-annealed and as-mechanically alloyed glassy powders implies the formation of the same glassy phase.

In an effort to understand the effects of a quartenary element introduced into a ternary quasicrystalline system, quartenary Al71Pd21Mn8−XReX quasicrystals were grown, where X had values of 0, 0.08, 0.25, 0.4, 0.8, 2, 5, and 8. X-ray data confirm that the addition of a fourth element does not alter the quasiperiodicity of the sample. Because electronic transport is governed by different mechanisms in the parent systems (Al71Pd21Mn8 and Al71Pd21Re8), electrical and thermal transport measurements in the alloyed system have been performed on these samples and are presented here.

Ti0.50Al0.50 and Ti0.75Al0.25 compounds were mechanically alloyed by ball milling of elemental Ti and Al powders. Radioactive 111In atoms incorporated into these compounds were used to investigate the different locally ordered crystalline structures by perturbed γγ-angular correlation spectroscopy (PAC). The formation of the intermetallic compounds γ–TiAl and α2–Ti3Al was observed on an atomic scale and occurred as a consequence of the heat treatment of mechanically alloyed Ti0.50Al0.50 and Ti0.75Al0.25, respectively. Due to the sensitivity of PAC to local order on an atomic scale, information about formation conditions and thermal stability of a new metastable phase with an ordered tetragonal crystal structure is presented for Ti0.50Al0.50 samples. In addition, the formation of the ordered phase Ti2AlN was observed, indicating the incorporation of N during the milling process. The PAC investigations were complemented by x-ray diffraction and differential scanning calorimetry measurements.

In his classic paper on thermal grain boundary grooving Mullins [W.W. Mullins, J. Appl. Physics 28, 333 (1957)] assumes that the dihedral angle at the groove root remains constant and predicts that the groove width and depth grow αt0.25. Here, we derive models describing groove growth while the dihedral angle changes. In our grooving experiments with tungsten at 1350 °C in which the dihedral angle decreased, the growth exponent for the groove depth reached values as high as 0.44 while the growth exponent for the width decreased slightly from Mullins' value of 0.25. Hence groove width data alone are not sufficient for verifying Mullins' growth law unless the dihedral angle is constant. The observed changes in the dihedral angle are used as an input for numerical simulations. With the simulations we are able to extract the surface diffusion constants. Atomic force microscope observations of groove widths and depths in tungsten are in excellent agreement with the simulations.

The effect of pore size and uniformity on the humidity response of nanoporous alumina, formed on aluminum thick films through an anodization process, is reported. Pore sizes examined range from approximately 13 to 45 nm, with a pore size standard deviations ranging from 2.6 to 7.8 nm. The response of the material to humidity is a strong function of pore size and operating frequency. At 5 kHz an alumina sensor with an average pore size of 13.6 nm (standard deviation 2.6 nm) exhibits a well-behaved change in impedance magnitude of 103 over 20% to 90% relative humidity. Increasing pore size decreases the humidity range over which the sensors have high sensitivity and shifts the operating range to higher humidity values. Cole–Cole plots of 5 to 13 MHz measured impedance spectra, modeled using equivalent circuits, are used to resolve the effects of water adsorption and ion migration within the adsorbed water layer. The presence of impurity ions within the highly ordered nano-dimensional pores, accumulated during the anodization process, appear highly beneficial for obtaining a substantial variation in measured impedance over a wide range of humidity values.

Superplastic deformation was studied in fine-grained (0.7–1.1 μm) YBa2Cu3O7–x/Ag composites containing 2.5–25 vol% Ag. The compression tests were conducted in the temperature range of 750–875 °C and at strain rates of 10−5 to 10−3/s. For the YBa2Cu3O7−x/25%Ag composites with grain size of 0.7–1.1 μm, deformed at 800–850 °C and 10−5 to 10−3/s, the stress exponent, grain size exponent, and the activation energy of deformation were 2.0 ± 0.1, 2.5 ± 0.7, and 760 ± 100 kJ/mol, respectively. These values were the same as those of the pure YBa2Cu3O7−x, indicating that the deformation of the composite was controlled by that of the rigid YBa2Cu3O7−x phase. However, the strain rate was increased by the addition of silver as explained by the soft inclusion model of Chen. The dependence of the flow stress on the silver content was in close agreement with the prediction of the model.

The permittivity of two primary phases within the Bi2O3–ZnO–Ta2O5 system was measured from 100 Hz to approximately 8.7 GHz. A cubic pyrochlore (Bi3/2Zn1/2)(Zn1/2Ta3/2)O7 phase (a phase) exhibited a dielectric constant of 71 at low frequency which decreased to 64 at approximately 10 GHz. A lower symmetry zirconolite Bi2(Zn1/3Ta2/3)2O7 phase (β phase) was also measured and had a frequency independent dielectric constant of 60. The temperature dependence of the capacitance (τC), measured from −55 to 120 °C, was 78 ppm/°C for the β phase and nonlinear for the α phase having no unique slope. The primary difference in dielectric properties between these two phases was a low-temperature relaxation of the α phase, which is modeled as a basic Debye-type relaxation.

Nanocrystalline carbon (n-C) thin films were deposited on Mo substrates using methane (CH4) and hydrogen (H2) by the hot-filament chemical vapor deposition (HFCVD) technique. Process parameters relevant to the secondary nucleation rate were systematically varied (0.3–2.0% methane concentrations, 700–900 °C deposition temperatures, and continuous forward and reverse bias during growth) to study the corresponding variations in film microstructure. Standard nondestructive complementary characterization tools such as scanning electron microscopy, x-ray diffraction, atomic force microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy were utilized to obtain a coherent and comprehensive picture of the microstructure of these films. Through these studies we obtained an integral picture of the material grown and learned how to control key material properties such as surface morphology (faceted versus evenly smooth), grain size (microcrystalline versus nanocrystalline), surface roughness (from rough 150 rms to smooth 70 rms), and bonding configuration (sp3 C versus sp2 C), which result in physical properties relevant for several technological applications. These findings also indicate that there exist fundamental differences between HFCVD and microwave CVD (MWCVD) for methane concentrations above 1%, whereas some similarities are drawn among films grown by ion-beam assisted deposition, HFCVD assisted by low-energy particle bombardment, and MWCVD using noble gas in replacement of traditionally used hydrogen.

A simple and novel method was developed for efficient synthesis of aligned multiwalled carbon nanotubes (CNTs) in methanol and ethanol under normal pressure. The CNTs' alignment and structures were investigated using Raman scattering and x-ray diffraction spectroscopy. A unique kind of coupled CNT was synthesized in which one rotated to the left and one rotated to the right. Chains periodically bridged the coupled CNTs. The growth mechanism of the CNTs within organic liquid is proposed to be a catalytic process at the Fe film surface in a dynamic and thermal nonequilibrium condition in organic liquids.