The mass spectral fragment ion yields and total electron yields have been measured for the polymers poly(butene-1 sulfone) [PBS] and poly(1,4-phenylene ether sulfone) [PPES] around the sulfur 2p (LII) edge, using synchrotron radiation from the Canadian Synchrotron Radiation Facility [CSRF]. Ionization of the sulfur 2p orbitals of PBS produced a sharp decrease in the neutral yields of SO2 and 1-butene. Decreases in the SO2 and 1-butene neutral yield shapes “mirrored” the structure present in the total electron yield. Ionization of the sulfur 2p orbital does not appear to produce any enhanced cleavage of the C–S bonds in the polymer backbone. A G(olefin)/G(SO2) ratio of 0.96 ± 0.15 was determined at 21 °C from mass spectrometry, consistent with a depropagation reaction mechanism. PPES showed a much different behavior than PBS about the sulfur 2p edge, with no detectable yield of SO2.

Rheological behavior, properties of colloidal solids consolidated by filtration, and their structure change during drying were studied with aqueous suspensions of a mullite powder of nanometer size and two kinds of alumina powders of submicrometer sizes. The rheological properties of non-Newtonian flow suspensions were analyzed by a power law equation of S = K γn, where S is the shear stress, γ the shear rate, and K and n (O ⋚ n ⋚ 1) constants. The critical solids content (Vc) at n = O (indicating colloidal solids) depended greatly on the zeta potential of particles in suspensions, and dominated the densities of dried green compacts (Vg) of submicrometer sized powders. In a nanometer sized powder, the densities of dried green compacts were dependent on both Vc value and the solid contents of suspensions. Phase diagrams of one-component colloidal systems were constructed by plotting the Vc and Vg values against the zeta potential of particles. These phase diagrams indicate that the colloidal solids range (surrounded by Vc and a minimum Vg lines) is narrow for nanometer sized powder and wide for submicrometer sized powder. The solids content range of dried green compacts was very narrow for submicrometer sized powder but relatively wide for nanometer sized powder due to the low flexibility of colloidal structure during drying.

SiO2−GeO2 and Al2O3−TiO2 mixed oxide powders were synthesized using a counterflow diffusion flame burner. SiCl4, GeCl4, Al(CH3)3, and TiCl4 were used as source materials for the formation of oxide particles in hydrogen-oxygen flames. In situ particle sizes were determined using dynamic light-scattering. Powders were collected using two different methods, a thermophoretic method (particles are collected onto carbon coated TEM grids) and an electrophoretic method (particles are collected onto stainless steel strips). Their size, morphology, and crystalline form were examined using a transmission electron microscope and an x-ray diffractometer. A photomultiplier at 90° to the argon ion laser beam was used to measure the light-scattering intensity. The formation of the mixed oxides was investigated using Si to Ge and Al to Ti ratios of 3:5 and 1:1, respectively. Heterogeneous nucleation of the SiO2 on the surface of the GeO2 was observed. In Al2O3−TiO2 mixtures, both oxide particles form at the same temperature. X-ray diffraction analysis of particles sampled at temperatures higher than 1553 K showed the presence of rutile, γ–Al2O3, and aluminum titanate. Although the particle formation process for SiO2−GeO2 is very different from that for Al2O3−TiO2, both mixed oxides result in very uniform mixtures.

Acoustic emission (AE) behavior at scratch test has been studied for TiN coatings that deposited in an ion plating system. The AE intensity of the coatings measured by the scratch test depended not only on the adhesion of a coating-substrate interface but also on the intrinsic properties of a deposited film. In this work, a careful separation of coating parameters was investigated to clarify the relationship between the AE intensity and the intrinsic properties of coated films. For identical coating conditions, the AE intensity increased with coating thickness since the elastic energy released during the scratching is proportional to film thickness. It has been found that the coatings prepared at higher substrate temperature and/or at higher substrate bias voltage had a larger crystallite size and lower internal stress. With increasing bias voltage and substrate temperature, the AE intensity of TiN coatings decreased. An explanation for this behavior has been proposed in terms of the internal stress and the toughness of the deposited films.

A series of investigations were carried out to evaluate the topographic and structural effects of ion implantation on monolithic Si3N4 ceramic surfaces. Implantations were performed with N2, Ne, or Ar in the fluence range of 2.0 × 1016 to 4 × 1017 particles/cm2 and implant voltages of 125 to 200 keV, depending on the mass of the implanted species. Single crystal Si and SiC were also examined for comparative purposes. Noble gases produced blisters on Si3N4 and significant increases in surface expansion. TEM examination of the Si3N4 blister shell showed a distribution of small bubbles, ranging in size from 5 to 300 nm, depending upon the type of Si3N4, and a transformation of the original crystalline structure into an amorphous phase. Analysis of the blister shell, using electron energy loss spectrometry (EELS) and energy dispersive x-ray spectrometry (EDXS) showed that a significant quantity of the implanted Ar was still present in the blister (skin).

We report on the microstructural analyses of chemically prepared Pb(Zr0.53Ti0.47)O3 (PZT 53/47) films. Although several techniques were used to analyze films, transmission electron microscopy (TEM) was emphasized. Phase evolution of these films, fabricated using hybrid metallo-organic decomposition (HMD), was determined by processing films at temperatures ranging from 500 °C to 650 °C. Our films, when observed with an optical microscope, appeared to consist of two distinct phases: (1) a featureless matrix and (2) 1–2 μm diameter “rosettes”. PZT films fired at 500 °C consisted of a pyrochlore containing phase (featureless matrix) and contained no perovskite, whereas films fired at 600 °C were ferroelectric and were approximately 90% perovskite (rosettes) by volume. Our TEM analysis showed that the pyrochlore-containing phase consisted of interpenetrating nanocrystalline pyrochlore and amorphous phases, both with dimensions on the order of 5 nm. For PZT films processed at 650 °C, the perovskite phase was observed in two forms: (1) large (≍2 μm) rosette structures containing 30 nm pores and (2) dense equiaxed particles on the order of 100 nm. We propose that phase evolution—with increasing temperature of HMD PZT 53/47 films—consists of the following steps: (1) phase separation, probably occurring in solution, (2) pyrochlore crystallization, (3) heterogeneous nucleation of perovskite PZT, and (4) homogeneous nucleation of perovskite PZT.

Using the measured elastic constants of TiN and NbN single crystals with cubic symmetry, the effective elastic constants of single-crystal TiN/NbN superlattice films with tetragonal symmetry, namely c11, c12, c13, c33, c44, and c66 have been calculated for various thickness ratios of the layers. Using a line-focus acoustic microscope, measurements of surface acoustic waves (SAWs) have been carried out on single-crystal TiN/NbN superlattice films grown on the (001) plane of cubic crystal MgO substrates. The phase velocities measured as functions of the angle of propagation display the expected anisotropic nature of cubic crystals. Dispersion curves of SAWs propagating along the symmetry axes have been obtained by measuring wave velocities for various film thicknesses and frequencies. The SAW dispersion curves calculated from the effectiveelastic constants and the effective mass density of the superlattice films show very good agreement with experimental results. The results of this paper exhibit no anomalous dependence of the elastic constants on the superlattice period of TiN/NbN superlattices.

Ba(Mg1/3Nb2/3)O3 powders were prepared through an alkoxide-hydroxide route. Their sintering behavior and crystallographic structures were investigated, and microwave properties of the obtained ceramics were also measured. Crystalline powder with approximately 0.5 μm in particle size was obtained by the reaction of Ba(OH)2−8H2O and Mg–Nb double alkoxide, Mg[Nb(OEt)6]2, in ethanol-acetone solution. A powder compact sintered at 1350 °C for 2 h showed >99% of relative density and >0.9 of ordering degree of the B site. The Q value of Ba(Mg1/3Nb2/3)O3 ceramics was sensitive to sintering conditions due to the formation of an impurity phase. The ceramics sintered at 1350 °C for 5 h showed a dielectric constant ∊ of 32 and Q value of > 13 000 at 11.8 GHz. The temperature coefficient of resonant frequency τf was 23.9 ppm/°C at 9.8 GHz.

Composites of SiC–Al2O3 and SiC–mullite are unstable at high temperatures. The reactions occurring within the composites between 1700 and 1850 °C in stagnant inert atmospheres were characterized. Gaseous products cause excessive weight losses which cannot be attributed to passive oxidation. These losses can be successfully retarded by processing under high pressures. Compatible phases were determined by x-ray analysis for mixtures lying in the section SiC–Al4C3−Al2O3−SiO2. The reactions produced condensed phases of Al2OC and Al4O4C as well as gaseous SiO and CO. The condensed phases have high vapor pressures above 1700 °C. The effect of these reactions on densification of composites by firing at different temperatures for various periods under different pressures was studied. Dense materials prepared under high pressures at 1825 °C were tested at 1700 °C under normal pressure in argon, where active oxidation is expected, and weight losses were insignificant.

Ultrafine amorphous Si/C/N ternary powders have been prepared in a CO2 laser assisted process. We demonstrate the possibility to drive the C/N ratio in the powder by properly choosing the experimental conditions and the gaseous reactant ratio in the initial mixture containing silane, dimethylamine, and ammonia. A kinetic model that accounts for reaching the equilibrium between the gaseous reaction intermediates and the solid products is proposed.

The reaction kinetics involved in the continuous precipitation of monodispersed spherical yttrium basic carbonate particles was studied. The amount of powder produced was a linear function of H2CO3 generated by the decomposition of urea in mildly acidic solutions. A model equation, containing an empirical constant F, was derived to describe the conversion yield as a function of reactant concentrations, reaction time, and temperature. The calculated and experimental data agree well for both the batch and continuous processes.

A high precision gravimetric method was used to investigate the adsorption of nitrogen (N2) and carbon tetrachloride (CCl4), respectively, at 77 and 298 K, onto various industrial minerals. The solids investigated include silica isomorphs, blast furnace slags, an Y-zeolite, and several naturally occurring fibrous minerals. The adsorption isotherms were analyzed to derive surface areas, BET constants (C), and surface fractal parameters (D). The latter were obtained through an approach recently suggested by Avnir and Jaroniec,1 using multilayer adsorption data; D values obtained for the various gas-solid systems investigated cover the range 2.1–3.0. A systematic comparison between D values inferred from N2 and CCl4 adsorption data shows that the CCl4 molecule probes the surface roughness in a more discriminate fashion than N2. In most cases, the differences between D(N2) and D(CCl4) appear to reflect changes due to sample preparation more than intrinsic differences amongst the various solids.

Modification of substrates by controlled deposition of nanometer-size particulates (nanoclusters) is an efficient means of fabricating materials designed for applications in which specific surface interactions play a vital role (e.g., molecular catalysis and microelectronics). We have found that highly dispersed nanoclusters form on thin films of poly(siloxaneimide) (PSI) copolymers supported on copper transmission electron microscopy (TEM) grids when subjected to long anneals at elevated temperatures. In this note, we report on the composition and source of these anomalous nanoclusters, as determined by a variety of electron microscopical techniques. Spectra obtained with parallel electron energy-loss spectroscopy (PEELS) indicate that these particulates, which typically measure 4–18 nm in diameter, are composed of copper with a mean valence of +1. Electron microdiffraction patterns reveal that the nanoclusters are polycrystalline, possessing lattice spacings similar to those of Cu2O. Mechanistic routes of formation are suggested based on experimental design, and factors influencing formation are also described.

We have examined the bonding arrangements in Na–P–O–F and Na–Al–P–O–F glasses using 19F, 27Al, and 31P solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. For the Al-free series of glasses, the 19F NMR spectra are dominated by peaks near +90 ppm, representative of F terminating P-chains. The formation of these bonds has little effect on the 31P chemical shifts, indicating that F preferentially replaces bridging oxygen on the phosphate tetrahedra, consistent with previous NMR studies of crystalline fluorophosphates and other spectroscopic studies of fluorophosphate glass. For the Na–Al–P–O–F glasses, 27Al NMR detects only octahedral Al-sites, the 19F NMR spectra include a second peak near −12 ppm due to F bonded to Al, and the 31P NMR spectra contain signals due to Q1-sites with one or more Al next-nearest neighbors. The relative intensity of the two 19F peaks correlates well with previous spectroscopic studies and shows that a greater fraction of F–P bonds forms when the base glass is remelted in NH4HF2.

Two different chemical processing routes were successfully used for the fabrication of lithium aluminosilicate (LAS) specimens having dense and homogeneous microstructure with an essentially pore-free state. These are (i) sol-gel route using the hydrolysis-condensation reaction of metal alkoxides and (ii) mixed colloidal processing route. Lowering Li content in the sol-gel-derived LAS significantly enhanced densification and retarded the crystallization. The β-spodumene (∼0.8 μm) seeding in the sol-gel-derived LAS modified the sequence of phase transformations and lowered the crystallization temperature by 120 °C. Therefore, combining the epitaxial seeding with the sol-gel process, one can bring down the crystallization temperature to the sintering temperature range (∼800 °C). Similarly, the LAS gel prepared by the mixed colloidal processing route exhibited a noticeable shrinkage over a broad temperature range (600–950 °C) and produced a dense sintered body with an essentially pore-free microstructure.

We report here on the synthesis of new materials termed organoceramics in which polymers are molecularly dispersed within inorganic crystalline phases. These nanocomposite materials may not only have unique morphologies and physical properties but may also lead to new processing methods for ceramic-based materials. In organoceramics polymer molecules could opportunistically occupy sites such as grain boundaries or other two-dimensional defects, nanopores, lattice channels, or interlamellar spaces. Our synthetic approach to get macromolecules to those sites is to nucleate and grow inorganic crystals from homogeneous solutions containing the polymer chains as co-solutes. The new materials discussed in this manuscript were synthesized by growing calcium aluminate crystals in the presence of water soluble polymers and were characterized by x-ray diffraction, scanning electron microscopy, elemental analysis, and diffuse reflectance infrared spectroscopy. The macromolecules used in organoceramic synthesis included poly(vinyl alcohol), poly(dimethyldiallyl ammonium chloride), and poly(dibutyl ammonium iodide). We found that the chemistry of polymer repeats can impact on the spatial distribution of the dispersed organic chains and also on the morphology of organoceramic powders. In the case of the poly(vinyl alcohol) organoceramic the polymer is intercalated in “flattened” conformations in Ca2Al(OH)6[X] ·nH2O, thus increasing the distance between ionic layers from 7.9 Å to ∊ 18 Å (X is a monovalent or divalent anion). Such a layered nanocomposite can be formed only by intercalating the poly(vinyl alcohol) during growth of the Ca2Al(OH)6[X] · nH2O crystal. The synthetic pathway is therefore able to overcome large entropic barriers and incorporate significant amounts of polymer in the organoceramic product, in some cases up to 38% by weight. The particles of this nanocomposite are spheroidal aggregates of thin plate crystals whereas the use of a polycationic polymer in the synthesis leads to rod-like particles in which organic chains may reside in channels of the inorganic crystal.

Cordierite gel powder prepared by the hydrolysis of an alkoxide complex was seeded with crystalline α-cordierite particles. The effects of seeding on the phase transformation and mechanical properties were studied. The unseeded cordierite gel powder crystallized into α-cordierite via μ-cordierite at 1050 °C. The μ-α cordierite transformation caused microcracks which led to poor flexural strengths of about 30 MPa, although the strength of μ-cordierite was 160 MPa. The seeding appeared to promote a direct formation of the α-cordierite from the amorphous state. The development of microcracks due to μ-α cordierite transformation could be prevented by the modified crystallization behavior, resulting in the improved flexural strength of α-cordierite of 190 MPa. The seeding also lowered the crystallization temperature of α-cordierite to 900 °C, which could be attributed to the epitaxial crystallization of the complex-alkoxide-derived cordierite gel powder.