A sintering, microstructural development and dielectric property study of BaTiO3–LiF ceramics was performed to assess the potential application of low-fired multilayer capacitors. Not only does LiF allow for sintering below 1000 °C, it also allows for the manipulation of dielectric properties and interfaces within BaTiO3–LiF ceramics. Using mixing laws, a model of the dielectric properties of the core-shell microstructures is presented that agrees well with the observed experimental data.

TiO2 thin films have been deposited on sapphire (0001) substrates under various conditions by metal-organic chemical vapor deposition. The structural properties of the deposited films were characterized by x-ray diffraction and transmission electron microscopy. The important growth parameters were found to be the deposition temperature and the deposition rate. The ranges studied for the two parameters were 400 to 850 °C and 10 to 120 Å/min, respectively. Depending on the growth conditions, most of the deposited films were either single-phase anatase or rutile, or a mixture of the two. These films were all epitaxial, but none of them were single-crystal films. Three distinct epitaxial relationships were observed between the films and the substrates, and, depending on the growth conditions, a deposited film can contain one, two, or all three of them. The fact that the films we obtained, although epitaxial, were never single crystal is explained based on the consideration of the difference in the rotational symmetries of the substrate surface and the film growth plane. We believe that it should be generally true that, in heteroepitaxial growth, a true single-crystal film can never be obtained as long as the point symmetry group of the substrate surface is not a subgroup of that of the film growth plane.

Powders of calcium carbonate with strontium carbonate were solidified by mechanical compression under hydrothermal conditions. The effects of hydrothermal conditions such as temperature, pressure, and ratio of Ca/Sr on the reaction process and microstructure of the solidified bodies were examined. Solidification of every powder easily proceeded with shrinkage above 200 °C to 300 °C. The compacts of strontium carbonate were more easily solidified, and compressive strength was 190 MPa and its density was 93.5%. The solidification with shrinkage of compacts consisting of mixed powders of calcium and strontium carbonates was accelerated with an increase in strontium carbonate content. It was revealed that the small amount of strontium carbonate powder acts as a bonding material among large calcium carbonate particles.

Carbon fibers were treated with siloxane spin-on-glass and reaction bonded silicon oxycarbide coatings. The spin-on-glass (SOG) coatings were prepared by pyrolyzing solutions of polymethylsilsesquioxane (PMSO), polydimethoxysilane (PDSO), and poly(ethoxysilane)ethyltitanate copolymer (ESET). Since the flexibility of the coatings was found to be dependent on the concentration of the siloxane solution, only those of PMSO and PDSO below 1.25% were determined to be suitable for fiber coatings, and an alternative approach to the formation of a pliable silicon-based ceramic coating on the fibers was developed. Carbon fiber tows were impregnated by ethanolic solutions of organosilicon chlorides and fired at temperatures up to 900 °C to form a flexible reaction bonded silicon oxycarbide (RB–SiOC) coatings. Uncoated, SOG coated, and RB–SiOC coated carbon fibers were embedded in aluminum metal at 1000 °C. While both silica-based coatings protected the carbon surface, no wetting was observed, leading to fiber pull-out. When the coated fibers were treated with a mixture of Ti and B prior to immersion into the molten aluminum, complete wetting of the fibers occurred. In the presence of molten aluminum, the Ti/B coating enabled the exothermic formation of TiB2 and titanium aluminides, which facilitate wetting. This reaction is termed ASPIRE (Aluminum Self-Propagating Interfacial Reaction) and in combination with silicon-based ceramic coatings provides a scientific approach to the formation of stable carbon fiber/aluminum metal-matrix composites. The coated fibers and composites were characterized by scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) analysis, and x-ray photoelectron spectroscopy (XPS).

In this work, we develop a model describing the diffusion of vacancies and self-interstitials and their recombination during ion implantation. The model includes the effect of the moving surface due to regrowth and the defect generation rate as a function of depth based on Monte Carlo simulations. The results are compared to experimental measurements of the damage-to-dose ratio (DDR) after low energy, 40 eV, silicon ion implantation into silicon at 300 and 685 K. We have derived an analytic approximation which agrees with the results of the computational model, implemented on a CM-2 parallel computer. We find that the calculated effective diffusivity, the main adjustable parameter in the simulations, is much lower than predicted based on extrapolation from experiments at higher temperatures. We attribute this difference to the aggregation of self-interstitials. We also find that the effect of interstitial-vacancy recombination on DDR is negligible under the experimental conditions considered; however, the crystal surface motion has a significant impact on the results.

Wear resistance of arc ion-plated chromium nitride films has been studied. It has been found that texture and phases composing the films depend much on bias voltage and nitrogen gas pressure at the deposition. A phase diagram was constructed as a function of these two parameters, which indicated that three categories exist: CrN single, CrN and Cr2N dual, and CrN and Cr dual phased regions, respectively. Results of Falex No. 2 test showed that the wear resistance of CrN single phased films is superior to others, especially when (220) preferred orientation is developed. Since hardness and surface morphology do not differ much between these films, a high toughness of CrN single phased film is considered to make a difference by suppressing abrasion wear.

Polyimide Kapton and spin-cast polyamic acid (PAA) on sapphire have been implanted with 1 MeV Ar ions to a dose of 4.7 × 1015 cm−2 at ambient temperature. The properties of both pristine and implanted surfaces were characterized by a depth-sensing low-load indentation technique. Experiments were carried out to investigate the effects of substrate, indentation rate, relaxation, and indentation technique. The results showed that (1) hardness was depth-dependent and decreased with increasing indentation depth, (2) measurements of the ion beam hardened surface with the untreated material as a substrate underestimated the hardness while measurements over the sapphire substrate overestimated it, (3) the effects of loading/unloading rates were apparent in the load displacement results, and (4) hardness values measured using the force modulation technique showed very little depth dependence. The hardness value at 100 nm depth is used for comparison purposes since the hardness value at this depth was almost independent of substrate, indentation rate, and indentation method. The hardness of Kapton, which was measured using the techniques described herein, was increased by over 30 times after Ar implantation, from 0.43 to 13 GPa at 100 nm indentation depth. A similar increase in hardness was also observed for polyamic acid. This result suggests that spin-cast PAA film may have potential technological applications for protective coatings where hardness and wear resistance are required.

Fine granules of poly(tetrafluoroethylene) (PTFE) were heat-treated/annealed on NaCl near its melting temperature (Tm) and/or at a temperature (Tc) between upper and lower feet of the exothermic peak in the DSC cooling process from Tm. Morphological changes of the granules were examined in the bright- and dark-field modes by transmission electron microscopy. When the granules were heat-treated near Tm, microfibrils of 20–30 nm in width and fibrils of 70–120 nm in width came out of the granules. The microfibrils were also observed in the fibrils. The microfibrils formed by heat treatment near Tm seemed to be identified as microfibrils of 20–30 nm in width which were recognized outside the granules annealed at Tc. It is expected that such a microfibril will grow to be a band in the band structure observed on the surface of bulk PTFE. Since the 0015 dark-field images showed that the PTFE chains in such microfibrils and fibrils are set perpendicular to their fibril axis, the chains should fold back and forth repeatedly at both lateral side-surfaces of the microfibrils and fibrils.

Sintering of pure SnO2 to high densities is difficult due to its high vapor pressure, and hence, additives are typically used to enhance densification. In this study, the effects of two lithium compounds, LiF and LiNO3, on the densification behavior of SnO2 were evaluated. While LiF resulted in only a modest improvement in densification, LiNO3 additions resulted in densities of ≥ 95% theoretical at 1500 °C in air. Thermal, x-ray, and SEM/TEM microstructural analyses indicated no liquid phase formation. From these studies we attribute the enhanced sintering behavior to the ionic-compensation of Li+ as an acceptor dopant, i.e., 3[Li‴sn] = 2[Voö], which in turn increased the diffusivity of oxygen.

The unusual sigmoidal behavior between electrical resistivity and inverse temperature in polycrystalline porous SnO2 was intensively investigated by detecting the localized traps formed at the interparticle through the measurement of Isothermal Capacitance Transient Spectroscopy. A trap of 1.0 eV was evaluated at a higher temperature range of 460–500 °C, and 0.6 eV trap at a lower temperature range 200–280 °C. It seems that the trap of 1.0 eV originates from O2− and 0.6 eV from O− defect center. Time constants which were determined at the peak position of ICTS spectra, S(t), were increased with the increase of temperature at the intermediate temperature range, indicative of the competition among various kinds of traps. The active competition among various traps is one of the causes that result in prominent gas sensitivity in polycrystalline porous SnO2.

Heteroepitaxial single crystal thin films of ZrO2 (3–40 mol % Y2O3) have been deposited on single crystal, (100) oriented ZrO2 (9.5 mol % Y2O3) substrates, using aqueous precursor solutions of zirconium acetate and yttrium nitrate. Film compositions crystallizing with the cubic structure had a lattice mismatch up to 1.59% [film composition: ZrO2 (40 mol% Y2O3)]. Precursor films were deposited by spin coating, pyrolyzed to form the oxide, and heated at high temperatures to promote epitaxial growth. Cross-sectional TEM observations of thin films annealed at 600 °C (∼0.3 Tm) show the film to be composed of two distinct regions: an epitaxial layer, 0–6 nm thick, immediately adjacent to the substrate surface, and a porous nanocrystalline region (5–10 nm grain size) comprising the bulk of the film. At higher temperatures, the epitaxial layer grows by consuming the nanocrystalline material. Porosity accumulates at the growing interface, producing a dense epitaxial layer. Lattice mismatch is accommodated by a combination of misfit dislocations and epitaxial film strain. Calculations indicate that the energy required to accommodate the lattice mismatch can be a significant fraction of the total driving energy of grain boundary elimination, suggesting that growth may be completely arrested if the misfit between film and substrate exceeds a critical value.

The mechanical properties of hot isostatically pressed monolithic Si3N4 and Si3N4−20 vol. % SiC composites have been studied by microindentation at temperatures up to 1400 °C. Indentation crack patterns and microstructures have been examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. It is shown that dense Si3N4 base materials can be synthesized by HIPing without densification aids. Both the monolithic Si3N4 and the Si3N4/SiC composites exhibit high hardness values which gradually decrease with increasing temperature. Both types of material show low fracture toughness values apparently because of strong interfacial bonding. On the other hand, the fracture toughness of the composite is about 40% higher than that of the monolithic material, due to the presence of the 20 vol. % SiC whiskers. A crack deflection/debonding mechanism is likely to be responsible for the higher toughness observed in the composite. High resolution electron microscopy shows that the grain boundaries in both samples contain a thin SiO2 layer.

The present work has examined the mechanical properties and microstructure of the new continuous oxynitride fiber and also examined the potentials of the fiber for reinforcing aluminum alloys. The composites were fabricated by squeeze casting, and the reactivity of the fiber with aluminum melt and the microstructure of the fiber/matrix interface were investigated. The fiber had good strength, reaching 4 GPa, and good Young's modulus, about 170 GPa, at room temperature. Scatter in strength was quite small. The fiber was almost amorphous but had the nanocrystalline structure locally. The microstructure of the fiber/matrix interface in the composites showed little trace of reaction. An amorphous-like layer thinner than 3 nm existed at the interface. DTA analysis revealed the exothermic reaction between the oxynitride fiber and pure aluminum occurred at about 830 °C. In the case of the fiber/6061 alloy, this critical temperature was slightly lower. The strength of the composite with the oxynitride fiber was better than that with the continuous alumina fiber but slightly lower than those with the silicon carbide fibers. The new oxynitride fiber has a great potential for use in aluminum matrix composites in general industrial fields.

Dy2O3 layers have been grown on SrTiO3 by molecular beam epitaxy. X-ray and electron diffraction patterns clearly show that Dy2O3 grows epitaxially on SrTiO3 with {100} planes parallel to the substrate surface. Transmission electron microscopy reveals that the Dy2O3 film breaks up into small domains (10–40 nm). This leads to the formation of terraces which limits the structural perfection of thin overgrown DyBa2Cu3O7 by introducing steps and small misorientations (within 3°). The resulting surface corrugation does not preclude the growth of epitaxial c-axis DyBa2Cu3O7 films with a Tc0 of 86 K. Crystallographic analysis and image calculations show that the domain growth of Dy2O3 is associated with the formation of 90° rotation twins.

Fe and Co metals were incorporated into a Ti and C mixture with a molar ratio of 1.0 over the range of 0 to 40 wt. % to study their effect on TiC combustion synthesis. The addition brought about the grain size decrease, change of grain shape (angular to spherical), and different distribution (agglomerated to isolated) of TiC grains. Both Fe and Co additives were distributed around TiC grains and served as a binder. It was observed that reaction between Ti and C was kinetically more favorable than any other reactions in the Ti–C–Fe or Ti–C–Co system. Based on the activation energy from an Arrhenius plot of In[(1−w)1/2u/Tc] vs 1/Tc, which was obtained by combustion temperature and wave velocity measurements, the reaction mechanism in combustion synthesis of TiC with the addition of 20 wt. % Fe and Co was suggested.

The SiO2–Al2O3 powders with compositions of 46.5 to 76.6 wt. % Al2O3, synthesized by the hydrolysis of metal alkoxides, were sintered at 1700 °C for 3 h in a reduced pressure of 40 Pa. After sintering, the samples were annealed at 1300 °C for 10 h in air. The densities of sintered samples were higher than 97.0% T.D. The electrical conductivities of the SiO2–Al2O3 ceramics in N2 atmosphere (>99.99%) were measured in the temperature range of 500° to 800 °C by using ac bridge circuit at 120 Hz to 1 MHz and dc circuit at 1 V. The electrical conductivities at 800 °C were 3.4 × 10−7 to 4.3 × 10−6 S cm−1, and decreased with increasing Al2O3 content. The SiO2–Al2O3 ceramics were mixed conductors of oxygen ions and electrons in nitrogen atmosphere. The activation energies of ionic and electronic conductivities were 102 to 143 kJ/mole and 102 to 123 kJ/mole, respectively.

Hillebrandite (dicalcium silicate hydrate) was produced by a hydrothermal process. Its crystal structure and microstructures were investigated by conventional TEM and HREM. Most hillebrandite fibers showed their elongation to be parallel to the b axis and tended to lie on the {001} cleavage planes. Selected area diffraction patterns frequently displayed continuous streaking, and corresponding dark-field images revealed stacking disorders perpendicular to the fiber axis. The morphology, stacking disorders, and extinction conditions of {hkO} reflections and hillebrandite resembled those of the minerals wollastonite (CaSiO3) and pectolite (Ca2NaH[SiO3]3). Periodic (100) faulting with a displacement vector 1/2 b is suggested to be the major origin of the streaking and the systematic absences in hillebrandite.

This paper addresses the observed grain size with dependence of the dielectric behavior for Pb(Mg1/3Nb2/3)O3: PbTiO3 ceramics grain sizes ≥ 1.0 μm. A combined transmission electron microscopy (TEM) analysis and dielectric characterization are modeled with a modified brick wall approach. From this model, it is possible to extrapolate information such as single crystal values of dielectric maximum, Kmax, the diffuseness coefficient, δ, and the average intergranular thickness for relaxor ceramics. The calculated intergranular thickness agrees well with TEM observations, ≍2.0 nm. This semi-empirical method may be potentially useful in development work of relaxor ceramics to predict the optimized dielectric properties obtainable within microstructural restrictions.

Pure and conducting RuO2 thin films were successfully deposited on Si, SiO2/Si, and quartz substrates at temperatures as low as 550 °C by a hot wall metal-organic chemical vapor deposition (MOCVD). Bis(cyclopentadienyl)ruthenium, Ru(C5H5)2, was used as the precursor. An optimized MOCVD process for conducting RuO2 thin films was established. Film structure was dependent on MOCVD process parameters such as bubbler temperature, dilute gas flow rates, deposition temperature, and total pressure. Either pure RuO2, pure Ru, or a RuO2 + Ru mixture was obtained under different deposition conditions. As-deposited pure RuO2 films were specular, crack-free, and well adhered on the substrates. The Auger electron spectroscopy depth profile showed good composition uniformity across the bulk of the films. The MOCVD RuO2 thin films exhibited a resistivity as low as 60 μω-cm. In addition, the reflectance of RuO2 in the NIR region had a metallic character.

Raman spectra are reported for fresnoite-type [Ba2Ti(Si, Ge)2O8] materials. Single crystal and glasses of the endmember compositions, Ba2TiSi2O8 (BTS) and Ba2TiGe2O8 (BTG), along with crystalline powders along the pseudobinary join, Ba2TiSi−xGe2−xO8, are discussed. The polarized single-crystal Raman spectra of BTS show the vibrational bands of the Si2O7 and TiO5 molecular groups. The v (Si–O–Si) mode is found at 666 cm−1, and is relatively weak. The strongest bands in the BTS single crystal spectra are found at 858 cm−1 and 873 cm−1. These are attributed to the v (SiO3) modes and the stretching of a short Ti–O bond, with mixing between them evident. The BTG single crystal polarized Raman spectra show the vs(Ge–O–Ge) mode at 521 cm−1, and a strong band at 841 cm−1 assigned to the stretch of the short Ti–O bond. The angular dependence of the TO-LO splitting is cataloged for the A1(z) stretching modes. The vibrational characteristics of both BTS and BTG are dominated by the molecular groups, and do not show behavior indicative of a sheet structure composed of TiO5 and (Si, Ge)2O7 groups. Raman investigation of the crystalline powders points to the presence of Si2O7, Ge2O7, and SiGeO7 groups within the nonendmember compositions. The BTG glass spectra show correspondence with the BTG crystalline Raman spectra; the vs(Ge–O–Ge) mode occurs at 518 cm−1 in the glass. Fivefold coordinated titanium may be present in the BTG glass, as revealed by a very strong band at 824 cm−1 in the I spectrum. BTS glass spectra also show some similarity with the BTS crystalline spectrum; the strongest band is found at 836 cm−1 in the I glass spectrum. Through comparison with other titania-silicate glasses, we conclude that the BTS glass has a structure similar to the crystalline phase.