Mullite ceramics with controlled microstructure in terms of residual glassy phase and density were produced from diphasic silica/boehmite sols using pressure filtration, die-pressing, and extrusion techniques. The effect of the compaction process on the green and sintered densities and on the final mullite microstructure was investigated. It is shown that glassy-phase-free mullite with high green and sintered densities can be produced from engineered diphasic colloidal suspensions using pressure filtration. The results show that the green body formation technique strongly determines the final sintered density, but it has no effect on the final phase composition of diphasic sol-derived sintered mullites.

HfO2–SiO2 and La2O3–SiO2 amorphous alloys were prepared, and their crystallization behavior was studied. The results suggest that higher permittivities can be achieved in the La-containing system without devitrification. The crystallization mechanisms between systems are distinctly different, yet observations are consistent with bulk material. Hf-containing materials tend toward phase separation, while La-containing materials tend toward silicate formation. For Hf-containing films, negligible thickness or time dependence was observed. In La-containing films, rapid thermal anneals could improve crystallization resistance, and thickness effects related to interface reactions were observed. These behaviors are discussed in the context of phase diagrams and metastable immiscibility.

Lead zirconate titanate (PbZr0.52Ti0.48O3; PZT) thick film with a thickness of 70 µm was prepared by the electrophoretic deposition method from a raw oxide mixture of PbO, ZrO2, and TiO2. X-ray diffraction and scanning electron microscopy were used to characterize the sintered PZT thick film. Single phase PZT was observed in the films sintered at 900 °C and above. The film sintered at 1000 °C for 30 min exhibited a dielectric constant of 1050 with a dielectric loss of about 0.05 measured at 1 kHz, a maximum polarization of 29 µC/cm2, a remnant polarization of 19 µC/cm2, and a coercive field of 21 kV/cm. This simple process to form PZT thick films may also be applied to the preparation of other multicomponent ceramics and ceramic films.

In the equilibrium immiscible Y–Mo system, the total energies of the possible structures for YMo3 and Y3Mo metastable phases were calculated as a function of their lattice constants, by employing the Vienna ab initio simulation package, and the results suggested that the D019, L12, and L60 structures were three possible metastable states in the system. Experimentally, hcp and fcc YMo3 metastable phases were obtained in the Y–Mo multilayers driven far from equilibrium by ion irradiation. Moreover, the lattice constants determined by diffraction analysis were in agreement with the predicted values.

Single-crystal 6H–SiC wafers were irradiated at 300 K with 50 keV He+ ions to fluences ranging from 7.5 to 250 He+/nm2. Ion-channeling experiments with 2.0 MeV He+ Rutherford backscattering spectrometry were performed to determine the depth profile of Si disorder. The measured profiles are consistent with SRIM-97 simulations at and below 45 He+/nm2 but higher than the SRIM-97 prediction at both 100 and 150 He+/nm2. Cross-sectional transmission electron microscopy study indicated that the volume expansion of the material is not significant at intermediate damage levels. Results from elastic recoil detection analysis suggested that the implanted He atoms diffuse in a high-damage regime toward the surface.

The stability of single-wall carbon nanotubes under hydrothermal conditions (100 MPa pressure, from 30 min to 48 h in the temperature range from 200 to 800 °C) has been investigated. The resultant products were characterized by Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. The stability range of single-wall carbon nanotubes (SWCNTs) under hydrothermal conditions suggests that they, similar to fullerenes, can only survive mild and short-term treatment in high-temperature, high-pressure water. SWCNTs gradually transform into multiwall carbon nanotubes (MWCNTs) and polyhedral graphitic nanoparticules. After 48 h at 750 °C only the Raman spectra characteristic of graphitic carbon were observed. Transmission electron microscopy revealed that after 800 °C and 48 h of treatment SWCNTs fully transformed into MWCNTs and polyhedral carbon nanoparticles.

Magnetic structure and domains of hydrothermal NiZn ferrites were studied through magnetic force microscopy by using different magnetically characterized tips. The magnetic patterns varied according to the tip employed and were correlated to the magnetic induced field generated by these different coated tips. Low-moment tips were found to be the most adequate to study magnetic domains in these hydrothermal ferrites.

Microcrystalline Cr-O-C films, synthesized by the plasma immersion ion processing technique, were annealed in vacuum and air at 700 °C for different times so their thermal stability could be evaluated. The study showed that annealing does not greatly change the chemical composition of the Cr–O–C films but induces a transformation ofthe film structure from the mixed phases of Cr2O3, CrO2, and CrC1.13O0.12 to the dualphases of Cr3C2, and Cr2O3. In addition, the annealed Cr–O–C films exhibit excellentnonwetting qualities to liquid aluminum despite the presence of pin holes. The contactangle of resolidified molten aluminum against the Cr–O–C films was found to be ashigh as 120–150°. The aluminum contact angle was found not to vary with thermal aging of the Cr–O–C films. The Cr–O–C films showed high hardness (16–24 GPa) and good wear resistance as compared to the steel substrates (H13 and 304 stainless steels)used in this study.

Europium-doped yttrium oxide (Y2O3:Eu3+) luminescent coatings were produced in a single step directly from a solution precursor using a radio frequency induction plasma spray technique. Crystalline and luminescent coatings were grown on Si(100) and steel substrates by this process. X-ray diffraction analyses on these coatings confirmed that polycrystalline cubic Y2O3 phase formed in situ with no impurity phases. The observed photoluminescence from these coatings is in all probability due to the highly crystalline nature of the coating combined with submicron spherical morphology of the grains.

Surface chemical properties of nanoguasicrystalline powders of Al–Cu–Fe synthesized by the ball-milling technique have been investigated using x-ray photoelectron spectroscopy (XPS). The samples were exposed to ambient conditions at room temperature as well as higher temperatures. Our XPS results reveal that the surfaces of nanopowders of Al70Cu20Fe10 are coated with an Al2O3 layer within which the quasicrystalline phase resides. It also appears that the thickness of this layer does not increase significantly on either heating below 873 K or prolonged exposure to ambient conditions.

To estimate the effect of the spherical interface of the T-type joint structure on bonding strength, thermal residual stress on the outer surface and in the interface were investigated by thermal elastoplastic finite element analysis, in terms of principal stress and principal axis direction. These numerical results were compared with experimental fracture patterns and the tensile strength. The relationship between the maximum principal stress around the interface edge and the joint angle was studied. As a result,an optimal joint angle was shown by the experimental data and also by the principal stress calculated.

Pulsed laser deposition of TiO2 and BaF2 layers at room temperature and subsequent annealing in flowing oxygen were used to form homogeneous epitaxial BaTiO3 films on LaAlO3. This oxide film synthesis method, known as the precursor technique, is frequently used for making combinatorial libraries. In this paper, we investigated the microstructures of the films at different stages of annealing using cross-sectional transmission electron microscopy, high-resolution imaging, and electron energy loss spectroscopy. It was shown that epitaxial BaTiO3 thin films with large grains could be formed on a LaAlO3 substrate. Their formation process consists of the following stages: At 200 °C, the BaF2 layer is partially oxidized. At 400 °C, the amorphous TiO2 layer crystallizes, further transformation of BaF2 into BaO takes place, and interdiffusion begins. At 700 °C, the formation of a polycrystalline structure with different Ba–Ti oxides occurs, epitaxial BaTiO3 grains nucleate on the film/substrate interface, and significant interdiffusion takes place. Finally, at 900 °C, the interdiffusion is completed, and the epitaxial BaTiO3 grains coalesce and grow. The presence of nonepitaxial polycrystalline regions in fully annealed films can be explained as the following: (i) stoichiometric transient regions not yet consumed by recrystallization of BaTiO3; (ii) nonstoichiometric regions resulting from inhomogeneous deposition of BaF2.

This paper investigates the possibility of reducing the deposition temperature of polycrystalline silicon germanium to a level compatible with complementary metal-oxide semiconductor (CMOS) post processing. To achieve this goal, the exact wafer temperature during deposition was experimentally determined and it was found to be 30 °C lower than the reactor setting temperature. The deposition temperature was reduced from 625 to 500 °C. The impact of varying the deposition pressure from 10 to 760 torr and the germanium content from 15% to 100% was investigated. X-ray diffraction spectroscopy and transmission electron microscopy showed that the SixGe1−x films deposited at an actual wafer temperature of 520 °C are polycrystalline for germanium contents as low as 15%. Also, it was shown that the deposition conditions can be adjusted to yield a low tensile stress at an actual wafer temperature of 520 °C, which is suitable for integrating surface micromachined micro-electromechanical systems on top of standard CMOS wafers with Al interconnects.

The relaxation time scales in a commercial-grade Zr41.25Ti13.75Ni10Cu12.5Be22.5 (at.%) bulk metallic glass were examined using transient and dynamic mechanical experiments. The viscoelastic and sub-Tg relaxations were well described by the Kohlrausch–Williams–Watts relaxation function. A large activation energy (4.0 eV) and small nonexponentiality parameter (approximately 0.5) were observed for viscoelastic relaxation above Tg consistent with the cooperative nature of atomic movements leading ultimately to viscous flow. Conversely, a small activation energy (0.1 eV) and large nonexponentiality parameter (approximately 0.9) were observed for the sub-Tg relaxation suggesting localized atomic adjustments which may involve different structural units or mechanisms. The glass transition was manifested as a decoupling of the sub-Tg and viscoelastic relaxation. The resulting transition temperature determined at a selected time scale was in agreement with the value obtained from calorimetric studies.

Piezoresponse force microscopy (PFM) is one of the most established techniques for the observation and local modification of ferroelectric domain structures on the submicron level. Both electrostatic and electromechanical interactions contribute at the tip-surface junction in a complex manner, which has resulted in multiple controversies in the interpretation of PFM. Here we analyze the influence of experimental conditions such as tip radius of curvature, indentation force, and cantilever stiffness on PFM image contrast. These results are used to construct contrast mechanism maps, which correlate the imaging conditions with the dominant contrast mechanisms. Conditions under which materials properties can be determined quantitatively are elucidated.

The dielectric response of KNbO3 epitaxial ferroelectric thin films was measured as a function of bias, frequency, and temperature. Thin films with a thickness of 80 to 350 nm were deposited on spinel substrates by low-pressure metalorganic chemical vapor deposition. Bias dependence measurements showed hysteresis in the dielectric response. The dielectric constant decreased with bias, and the tunability was calculated to be between 35% and 42% for an applied field of 7 MV/cm. The frequency dependence of the dielectric constant followed a power law. A pronounced thickness effect was observed in the dielectric response, especially at the Curie temperature. With decreasing thickness, the dielectric constant and the loss tangent decreased. A diffuse ferroelectric phase transition was observed for films with a thickness less than 350 nm.

Nanocrystalline nickel particles were embedded in amorphous alumina and crystalline TiN matrices using a pulsed laser deposition process to investigate the effect of texturing on magnetic properties of nickel nanocrystallites. The crystalline quality of both the matrix and magnetic particles was investigated by cross-sectional high-resolution transmission electron microscopy. The embedded Ni nanocrystals were found to be epitaxial in the case of the TiN matrix and polycrystalline in Al2O3 amorphous matrix. The Ni nanocrystals on TiN/Si grow epitaxially because the TiN acting as a template grows epitaxially on Si substrate via domain epitaxy. On the other hand, Ni nanocrystals in the Al2O3 matrix are polycrystalline because of the amorphous nature of the alumina matrix. Magnetization versus temperature measurements have shown that the blocking temperature, above which the samples lose magnetization–field (M–H) hysteretic behavior, of the Ni–TiN sample (approximately 190 K) is significantly higher than that of Ni–Al2O3 sample (approximately 30 K) with a similar size distribution of embedded magnetic particles. A comparison of the values of coercivity (Hc) of the two samples, measured from M–H data, indicates that epitaxial Ni nanocrystals also exhibit significantly higher coercivity than polycrystalline Ni particles in amorphous alumina matrix. The high values of TB and Hc of Ni–TiN samples with respect to TB of N–A12O3 samples are believed to be associated with preferred alignment of nanocrystallites.

Well-dispersed anatase and rutile nano-particles were prepared via hydrothermal treatment of tetrabutylammonium hydroxide-peptized and HNO3-peptized sols at 240 °C. A broad particle size distribution of anatase crystals was observed in the nonpeptized TiO2 species hydrothermally treated at 240 °C. X-ray diffraction and transmission electron microscopy, as well as zeta potential measurement, were used to characterize the particles. The formation of the well-dispersed anatase and rutile particles from the peptized samples could be attributed to (i) homogeneous distribution of the component in the peptized sols, and (ii) the high long-range electrostatic forces between particles in the presence of both peptizers, which were not present in the nonpeptized samples. This work provided a new way to prepare nano-crystals of titania.

Nanocrystalline pure copper was obtained by cold rolling a commercial bulk Cu to very large extensions at subambient temperatures. The eventual formation of nanocrystalline grain structures is attributed to dynamic grain refinement (recrystallization) mechanisms activated by the low-temperature continuous plastic deformation that leads to ultrahigh densities of dislocations.

Strontium- and magnesium-doped lanthanum gallate (LSGM) was deliberately prepared to give A-site deficient nonstoichiometry with compositions (La0.9Sr0.1)z(Ga0.8Mg0.2)O3-δ (z = 1.0, 0.98, and 0.95). Creep tests in four-point bending for 950 °C < T < 1350 °C and 15 MPa < σ < 75 MPa in air demonstrated that all three compositions shared a common stress dependence, n= 1.49 ± 0.10, and a common apparent activation energy, Q = 426 ± 9 kJ/mol. Despite this agreement, the creep rates of the different compositions depended on grain size in different ways: p = 3.1 ± 0.2 for z = 0.98, and p = 1.9 ± 0.1 for z = 0.95. The measured apparent activation energy, Q, for creep is similar, though statistically significantly smaller, than that measured in another LSGM. Both are nearly twice as large as reported activation energies for cation impurity diffusion. The absolute magnitude of the creep rates, after correction for grain size, were 30 to 100 times slower than in another LSGM of similar composition.