New molecular composite materials can be prepared based on an inorganic oxide network and an organic polymer. The polymeric component generally requires low process temperatures, due to the presence of the organic backbone or side groups. A sol-gel process therefore is suitable for synthesizing the inorganic component by dissolving soluble polymers into sol-gel precursor solutions in order to obtain ceramic and polymeric solid phases. In this work polyorganophosphazenes were used because they have many technologically interesting properties (chemical, optical, electrical, mechanical). The methods to obtain covalent bonds between polymer and inorganic network and to obtain homogeneous, transparent hybrid materials without phase separation were studied. It was possible to avoid phase separation by preparing phosphazenes containing free hydroxyl functions and by adequately choosing the experimental conditions.

We report the microstructure of magnetically melt-textured Dy-123 samples, as observed by polarized light metallography. The phase dimensions, morphology, orientation, nature, and distribution are outlined. Grain, twin structure pattern, and grain boundary are characterized. The relationship among cracking, secondary phases, and tetragonal-orthorhombic phase transformation is discussed. The results are obtained by observing a “not-too-well-ordered” region. This leads to definite conclusions on the relationship between crack spacing and 211 distribution, and to some confirmation of the growth mechanism and on macro- and microcrack origins. From the present observations, the effect of the oxygenation process and the quantification of the tensile stress in the materials can also be obtained.

The effects of mechanical milling (MM) on the phase transformation of graphite carbon were investigated using high resolution electron microscopy (HREM), x-ray diffraction, and differential thermal analysis (DTA). Amorphization of graphite as a result of prolonged high-energy ball milling was directly observed with HREM. The exothermic peak in the DTA trace of the ∼200 h ball-milled sample indicated a crystallization onset temperature of about 670 °C and crystallization activation energy of 234 kJ/mole.

X-ray diffraction has been used to measure the strain relaxation in passivated Al–0.5% Cu lines at 200 °C after cooling directly from an anneal at the passivation deposition temperature of 380 °C. Fits to the measured X, Y, and Z components of strain are summed to obtain the hydrostatic component, which exhibits a decay over time. Three mechanisms are considered to explain the decay of the hydrostatic strain in the metal line: Cu precipitation from the solid solution, the presence and growth of voids in the lines, and time-dependent deformation of the passivation. Calculations of the effect of Cu precipitation from the solid solution demonstrate that it plays an insignificant role in the relaxation. A high-voltage scanning electron microscope is used to image the presence and growth of voids through the passivation. The time scale of the growth of stress-induced voids is not the same as the hydrostatic relaxation, indicating that voiding is not solely responsible for the observed relaxation. The relaxation of the line is modeled using a time-dependent finite element model, allowing elastic compliance of the passivation. The magnitude of the calculated relaxation agrees with the measurements. It is suggested that a combination of voiding and passivation compliance is responsible for the measured hydrostatic strain relaxation in the metal line.

A new corrosion resistant coating, being designed for possible replacement of chromate conversion coatings on aluminum alloys, was investigated for composition, structure, and solubility using a variety of techniques. The stoichiometry of the material, prepared by immersion of 1100 Al alloy into a lithium carbonate-lithium hydroxide solution, was approximately Li2Al4CO3(OH)12 · 3H2O. Processing time was shown to be dependent upon the bath pH, and consistent coating formation required supersaturation of the coating bath with aluminum. The exact crystal structure of this hydrotalcite material, hexagonal or monoclinic, was not determined. It was shown that both the bulk material and coatings with the same nominal composition and crystal structure could be formed by precipitation from an aluminum supersatured solution of lithium carbonate.

Nanocrystalline copper powder was produced by a NaBH4 reduction of CuCl in a simple solution phase room temperature reaction. Uniaxial hot pressing in a closed tungsten die was used to compact powder into dense specimens. Samples were analyzed by x-ray diffraction, precision densitometry, electron microscopy, energy dispersive x-ray analysis, and selected area diffraction. Mechanical properties of the consolidated samples were determined by microhardness measurements, three-point bending of rectangular specimens, and compression tests. Yield strength measured for nanocrystalline Cu in the present work was over two times that reported in literature for Cu with comparable grain size and over five times that of conventional Cu. Restricted grain growth observed in the hot-pressed samples and improved mechanical properties are attributed to the presence of boron. A unique method of obtaining homogeneous in situ nanosized reinforcements to strengthen the grain boundaries in nanocrystalline materials is identified.

Gold particles smaller than 2 nm in diameter were grown in glass. Their optical absorption spectrum did not show the usual plasma absorption band for gold particles; this band was spread by the small particle size. The absorption spectrum was calculated from the bulk optical properties of gold, modified for the small particle size; there was good agreement between calculated and measured spectra. The smallest particles containing from 20 to 40 gold atoms showed a λ−4 dependence of absorption on wavelength λ. This result implies that the absorption in these particles was entirely from free electrons at wavelengths above 0.3 μm.

The fracture strength and toughness of alumina can be increased by lamination with strategically placed nickel layers and with a modified Ni/Al2O3 interface through tape casting. In order to examine the potential of this type of laminated composite in high temperature applications, the laminates were tested at elevated temperatures. This paper describes how a modified tortuous interface, instead of a smooth interface, increases the creep resistance of the laminates. Interface modification can control high temperature laminate behavior and is critical to successful composite design.

A fast-firing technique for the sintering of lead magnesium niobate relaxor ceramics at relatively low temperature has been described. In this process, the samples containing excess PbO (up to 5 wt. %) are directly introduced into a furnace maintained at a temperature of 950 °C and kept there for 15–80 min, followed by a postsintering annealing treatment at 800 °C for 10 h. The importance of fast heating as well as annealing treatment has been justified. The sintered samples are near-phase-pure perovskite materials showing high bulk densities (>94%), uniform and dense microstructure, and satisfactory dielectric properties (Kmax > 13,000). The technique is simple and economic, does not require any controlled atmosphere, and minimizes hazards from lead volatilization.

Thin films of BaxSr1−xTiO3 (x = 0.7, 0.8, 0.9, and 1.0) were prepared by metalorganic decomposition (MOD). The relative permittivity, dissipation, polarization, resistivity, and grain size of these films were studied as a function of composition and temperature. Ferroelectric hysteresis loops were observed for all values of x and were found to be independent of measurement temperature though strongly dependent upon grain size.

A bismuth-deficient pyrochlore phase has been observed in both powder and film samples fired at 775 °C. The estimated stoichiometry of this pyrochlore (based on calculated diffraction patterns) was Sr0.2(Sr0.5Bi0.7)Ta2O6.75. This bismuth-deficient pyrochlore phase may be considered deleterious to the formation of the SrBi2Ta2O9“SBT” ferroelectric compound since a significant presence of this pyrochlore compound implies a large deviation from the desired cation ratios. Additionally, films prepared on platinized silicon substrates indicate the SBT phase formation may be encouraged by the substrate; there appears to be some 00l preferential orientation for stoichiometric SBT thin films.

Thin diamond film coated WC-Co cutting tool inserts were produced using arc-jet and hot-filament chemical vapor deposition. The diamond films were characterized using SEM, XRD, and Raman spectroscopy to examine crystal structure, fracture mode, thickness, crystalline orientation, diamond quality, and residual stress. The performance of the tools was evaluated by comparing the wear resistance of the materials to brazed polycrystalline diamond-tipped cutting tool inserts (PCD) while machining A390 aluminum (18% silicon). Results from the experiments carried out in this study suggest that the wear resistance of the thin diamond films is primarily related to the grain boundary strength, crystal orientation, and the density of microdefects in the diamond film.

Polycrystalline films of barium titanate (BaTiO3) have been synthesized on titanium (Ti) substrates by the galvanostatic anodization of Ti in a solution of 0.4 M Ba(OH)2. Crystalline films are formed at temperatures under 100 °C within 10 min at a current density of 25 mA/cm2 at atmospheric pressure. Crystallinity of the films is found to increase with both current density and time of reaction. At 90 °C, a film of 1 μm thickness is formed after 10 min; grain sizes up to 0.5 μm are obtained. Microstructure of the films is found to be critically dependent on the pretreatment of the titanium anode. Capacitance measurements on the film yield a dielectric constant of 200 with a minimum tan delta of 0.09 at 10 kHz. On the basis of the voltage-time curves, it is interpreted that an amorphous intermediate is formed which crystallizes to form perovskite BaTiO3.

Polyparaphenylene (PPP)-based carbons heat-treated at temperatures (THT) from 600 °C up to 3000 °C have been characterized both structurally and in terms of their physical properties. Special attention is given to PPP heat-treated at 700 °C (denoted by PPP-700), since samples heat-treated to this temperature were observed to have exceptionally high lithium affinities when electrochemically doped with Li. At low THT below 700 °C, it is found that the local structure of PPP-based samples can be characterized mostly in terms of a disordered polymer. As a result of heat treatment to high temperature, PPP-based carbon shows graphitization behavior with regard to x-ray diffraction d002 (graphite c-axis d-spacing) development and to the increase of the Raman IG/ID intensity ratio (where IG and ID are the integrated intensities of the 1580 cm−1 and 1360 cm−1 Raman modes, respectively), as is found in so-called graphitizing carbons. However, development of the c-axis crystallite size (Lc) is restricted to very small values, in the range of so-called nongraphitizing carbons, while the a-axis crystallite size (La) attains values up to roughly 120 Å for heat treatments near 3000 °C. These structural properties of PPP-based carbons are consistent with the observed electrical characteristics and their dependence on THT. Low temperature magnetic susceptibility measurements were analyzed, along with Raman spectra, allowing for the characterization of disorder in terms of localized spin states for several heat-treated PPP samples. By interpreting the results of these various characterization techniques, we are able to present an insightful perspective on the nature of PPP-based carbons and the role of PPP-700 as an effective lithium host material for secondary battery applications.

Thin films of NiFe2O4 were deposited on SrTiO3 (001) and Y0.15Zr0.85O2 (yttria-stabilized zirconia) (001) and (011) substrates by 90°-off-axis sputtering. Ion channeling, x-ray diffraction, and transmission electron microscopy studies reveal that films grown at 600 °C consist of ∼300 Å diameter grains separated by thin regions of highly defective or amorphous material. The development of this microstructure is attributed to the presence of rotated or displaced crystallographic domains and is comparable to that observed in other materials grown on mismatched substrates (e.g., GaAs/Si or Ba2YCu3O7/MgO). Postdeposition annealing at 1000 °C yields films that are essentially single crystal. The magnetic properties of the films are strongly affected by the structural changes; unannealed films are not magnetically saturated even in an applied field of 55 kOe, while the annealed films have properties comparable to those of bulk, single crystal NiFe2O4. Homoepitaxial films grown at 400 °C also are essentially single crystal.

Copper sulfide (CuS) powder precipitated from a chemical bath containing Cu(II) chloride and thiourea and annealed in air at 150 °C for 1 h was dispersed in a poly(acrylic acid) aqueous solution (with additional water or propylene glycol as a dispersive agent) and cast on glass slides. Upon evaporation of the solvent, coatings of ∼50 μm in thickness of a CuS-poly(acrylic acid) composite are formed. Measurement of sheet resistance (R□) indicates a percolation threshold of electrical conduction at a weight fraction [wf is wt. % of CuS to poly(acrylic acid) + CuS] of about 40%; the composite undergoes a transition from insulator (R□ ∼ 1013 Ω) to conductive state (R□ ∼ 102 Ω). The morphology and thermal stability of the composite depend on the choice of the dispersive agent for the CuS powder; smoother and thermally stable (up to a temperature of 250 °C) coatings are obtained when propylene glycol is used. The results on x-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy studies are given to indicate the structure and bonding mechanisms and their dependence on temperature and dispersive agents.

Nanocrystalline copper produced by a solution-phase chemistry approach and compacted by hot pressing was subjected to room temperature deformation. Uniaxial compression and rolling were used to deform the samples to °90% reduction in thickness. Samples were subjected to several heat treatments to study microstructure and property evolution as a function of heat treatment. Thermal response of the as-pressed and deformed nanocrystalline Cu was also studied by differential scanning calorimetry. Optical metallography, scanning and transmission electron microscopy, and selected area diffraction were used to characterize microstructures after heat treatments. Samples exhibited an endotherm upon heating at 322 °C which was reversible upon cooling. This was attributed to either dissolution and formation of Cu–B precipitates or the diffusion of B from the grain boundaries to the bulk and back to the grain boundaries. Exaggerated recrystallization occurs in the temperature range of 399–422 °C. Samples maintained high dislocation density, deformation bands, and fine grain size up to 322 °C. Beyond the recrystallization temperature, grains grew at a faster rate to submicron or micron levels. The strain hardening observed in the samples of the present study is attributed to the presence of boron. Two mechanisms are suggested for the role of B: (i) segregation of B to the grain boundaries leading to strengthening of grain boundaries, and (ii) formation of Cu–B nanoprecipitates leading to precipitation strengthening.

Two experimental techniques for the quantitative measurement of residual stress in thin polycrystalline diamond coatings have been developed. The x-ray low-incident-beam-angle-diffraction (LIBAD) allows one to measure the lattice strain with well-defined in-depth information, while micro-Raman spectroscopy permits one to accurately measure the frequencies of the zone-center optical phonons of diamond which are related to the lattice strain. The interpretation of the measured information in terms of residual stress is outlined for both techniques. The residual stress data obtained by either method in thin CVD diamond coatings were found to be in excellent agreement. The sign and magnitude of the balanced biaxial stress in the coating plane depend mainly on the substrate material used for the diamond deposition. Compressive stress was present in diamond coatings deposited on WC-Co substrates, whereas tensile stress was found in those on SiAlON substrates.

Bi2Nbx V1−xO5.5 ceramics with x ranging from 0.01 to 0.5 have been prepared. The crystal system transforms from an orthorhombic to tetragonal at x 3= 0.1 and it persists until x = 0.5. Scanning electron microscopic (SEM) investigations carried out on thermally etched Bi2NbxV1−xO5.5 ceramics confirm that the grain size decreases markedly (18 μm to 4 μm) with increasing x. The shift in the Curie temperature (725 K) toward lower temperatures, with increasing x, is established by Differential Scanning Calorimetry (DSC). The dielectric constants as well as the loss tangent (tan δ) decrease with increasing x at room temperature.

An aqueous, all nitrate, solution-based preparation of BaTiO3 is reported here. Rapid freezing of a barium and titanyl nitrate solution, followed by low temperature sublimitation of the solvent, yielded a freeze-dried nitrate precursor which was thermally processed to produce BaTiO3. XRD revealed that 10 min at temperatures ≧600 °C resulted in the formation of phase pure nanocrystalline BaTiO3. TEM revealed that the material was uniform and nanocrystalline (10–15 nm). The high surface to volume ratio inherent in these small particles stabilized the cubic phase of BaTiO3 at room temperature. It was also found that the average particle size of the BaTiO3 produced was highly dependent upon calcination temperature and only slightly dependent upon annealing time. This result suggests a means of selection of particle size of the product through judicious choice of calcination temperature. The experimental details of the freeze-dried precursor preparation, thermal processing of the precursor, product formation, and product morphology are discussed.