Electric fields generate transverse flows near electrodes that sweep colloidal particles into densely packed assemblies. We interpret this behavior in terms of electrohydrodynamic motion stemming from distortions of the field by the particles that alter the body force distribution in the electrode charge polarization layer. A scaling analysis shows how the action of the applied electric field generates fluid motion that carries particles toward one another. The resulting fluid velocity is proportional to the square of the applied field and decreases inversely with frequency. Experimental measurements of the particle aggregation rate accord with the electrohydrodynamic theory over a wide range of voltages and frequencies.

The patterning of ceramic thin films is of great interest for use in MEMS and other applications. However, the complex chemistries of certain materials make the use of traditional photolithography techniques prohibitive. In this paper, a number of low-cost, high throughput techniques for the patterning of ceramic thin films derived from chemical solution precursors, such as sol-gels and ceramic slurries, are presented. A particular emphasis is placed on methods that are derived from soft lithographic methods using elastomer molds. Two categories of techniques are discussed: first, the focus is on methods that rely on the principles of confinement within the physical features of the mold to define the pattern on the substrate surface. Then, subtractive patterning techniques that rely on transferring a pattern to a spin-cast, large-area continuous thin film are described. While most techniques have been demonstrated with fidelities on the order of 100 nm, their inability to precisely register and align the patterns as part of a hierarchical fabrication scheme have thus far hindered their commercial implementation.

Asimple method is described for controlling the organization of proteins on surfaces using two-dimensional arrays of micron-sized colloidal particles. Suspensions of colloids functionalized with proteins are deposited onto coverslips coated with gold using a combination of gravitational settling and applied electrical fields. Varying settling time and particle concentration controls the density of particles on the substrate. Surface coverage ranged from an essentially continuous coating of protein on close-packed arrays to domains of protein separated by distances as large as 16 ím. Colloidal particle arrays were also patterned into 500 µm islands on substrates using elastomeric lift-off membranes. The applicability of this approach to the promotion of fibroblast cell adhesion and spreading was demonstrated using particles coated with the cell adhesion protein fibronectin. Behavior of adherent cells varied with particle density. This method provides a general strategy for controlling the organization of functional proteins at surfaces on three length scales: the size of individual colloidal particles, the spacing between particles, and the organization of particles in patterned arrays.

The patterning of sol-gel-derived thin films by micromolding in capillaries can produce unintended topographical deviations from the shape of the original mold that may limit the utility of the technique in potential applications. During drying and heat treatment, nonuniform shrinkage across the film due to the densification of the gel matrix results in “double-peak” film topographies whereby the film thickness is greater at the lateral edges than in the middle. Using the same framework used to understand the imbibition and wetting of the sol-gel in the capillary channels, we developed a mechanism to explain the formation of the double-peak profile. As a model system, patterned Pb(Zr_0.52Ti_0.48)O₃ thin films were studied. Atomic force microscopic characterization was used to quantify the effect of the rate of gelation on the topography of the patterned thin films. Modifications to the channel mold design eliminate the peak formation, producing more homogeneous patterns that better replicate the features of the mold.

In order to achieve the revolutionary new defense capabilities offered by materials science and engineering, innovative management to reduce the risks associated with translating research results will be needed along with the R&D. While payoff is expected to be high from the promising areas of materials research, many of the benefits are likely to be evolutionary. Nevertheless, failure to invest in more speculative areas of research could lead to undesired technological surprises. Basic research in physics, chemistry, biology, and materials science will provide the seeds for potentially revolutionary technologies later in the 21st century.

Binary colloidal suspensions are assembled into planar superlattices using ac electric fields. Either
triangular or square-packed arrays form, depending on the frequency and relative particle concentrations.
The frequency dependence is striking since superlattices develop at low and high frequencies
but not at intermediate frequencies. We explain the low frequency behavior <3 kHz in terms of
induced-dipole repulsion balanced by attraction resulting from electrohydrodynamic (EHD) flow. At
high frequencies (20–200 kHz), EHD flow is negligible but aggregation occurs since dipole-dipole
interactions become attractive.

Micropatterning of Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films with line features as small as
350 nm was demonstrated through capillary molding of organometallic solutions within
the continuous channels of an elastomeric mold. Despite the large stresses that develop
during the evaporation of the solvent, pyrolysis of the organics, and the densification
and crystallization of the inorganic gel, the patterned crystalline PZT films were
crack-free and mechanically robust. Flawless regions as large as 1 cm2 were obtained.
The cross-sectional shape of the patterned PZT lines was trapezoidlike. Single
perovskite PZT grains that formed during annealing at 600–700 °C completely filled
the cross-sectional area of the patterned lines. Lead acetate, zirconium propoxide, and
titanium isopropoxide were used as the starting materials. Substrates used included
silver tape, stainless steel plate, silicon wafer, and platinum-coated silicon wafer.

We have examined experimentally and theoretically the resonance frequency of a lead zirconate titanate ~PZT!/brass unimorph disk transducer with a water ~ice! layer on the brass surface. We showed that the flexural resonance frequency decreased with the presence of a water layer and the decrease in resonance frequency increased with an increasing water amount. Upon lowering the temperature, the freezing transition of the deposited water layer was detected when the resonance frequency of the transducer increased abruptly at the freezing temperature. In contrast to water, an ice layer increased the resonance frequency and the increase in the resonance frequency increased with the ice layer thickness. Theoretically, an analytic expression for the flexural resonance frequency of a unimorph transducer in the presence of an ice ~water! layer on the brass surface was obtained in terms of the Young’s moduli, densities, and thickness of the PZT, brass, and ice ~water layers. The theoretical predictions were shown to agree with the experimental results.

An alumina ceramic 12.5x12.5x5.0 mm microreactor was constructed using a modified stereolithography process. The design was based on a ‘‘Swiss roll’’ concept of double spiral-shaped channels to facilitate a high level of heat transfer between the reactants and combustion products and wall surface contact of the flow through the microreactor body. Self-sustained combustion of hydrogen and air mixtures was demonstrated over a wide range of fuel/air mixtures and flow rates for equivalence ratios from 0.2 to 1.0 and chemical energy inputs from 2 to 16 W. Depositing platinum on gamma alumina on the internal walls enabled catalytic ignition at or near room temperature and self-sustained operation at temperatures to 300 C. Catalyst degradation was observed at higher operating temperatures and reignition capabilities were lost. However, sustained operation could be obtained at wall temperatures in excess of 300 C, apparently stabilized by a combination of surface and gas-phase reaction phenomena. A global energy balance model was developed to analyze overall reactor performance characteristics. The reactor design and operating temperature range have potential applications as a heat source for thermoelectric and pyroelectric power generation at small scales compatible with microelectromechanical systems applications.

The effect of a transverse tensile stress on the electric-fieldinduced 90°-domain reorientation in tetragonal lead zirconate titanate (PZT) near the morphotropic phase boundary was investigated in situ using X-ray diffraction (XRD). The XRD intensity ratio, I(002)/I(200), which represents the ratio of the volume of the c-domains to that of the a-domains on the PZT surface, was examined as a function of the electric field at various stress levels. It was found that a transverse tensile stress changes the electric-field dependence of I(002)/I(200), especially at higher electric fields. Without a transverse tensile stress, I(002)/I(200) began to saturate at E 800 kV/m. With a transverse tensile stress of 75 MPa, I(002)/I(200) increased with an upward curvature with the electric field, indicating that the transverse tensile stress enhanced the field-induced 90°- domain reorientation, and increased the effective piezoelectric coefficients at larger electric fields. At E 900 kV/m, the estimated d31,domain changed from 200 1012 V/m at zero stress, to 350 1012 V/m at 75 MPa.

A number of biological materials owe their unusual structural characteristics and mechanical properties to long-range order induced by the lamination of â-sheet proteins between layers of inorganic mineral.1 In such composites, both the protein layer and the mineral layer adopt structures different from those they assume in isolation. Interactions between such layers and the ordered structures that result from these interactions enable nature to produce biomaterials that are simultaneously hard, strong, and tough.

Nacre (mother-of-pearl) from mollusc shells is a biologically formed lamellar ceramic. The inelastic deformation of this material has been experimentally examined, with a focus on understanding the underlying mechanisms. Slip along the lamellae tablet interface has been ascertained by testing in compression with the boundaries oriented at 45° to the loading axis. The steady-state shear resistance tss has been determined and inelastic strain shown to be as high as 8%. The inelastic deformation was realized by massive interlamellae shearing. Testing in tension parallel to the tablets indicates inelastic strain of about 1%, occurring at a steady-state stress, sss » 110 MPa. The strain was associated with the formation of multiple dilatation bands at the intertablet boundaries accompanied by interlamellae sliding. Nano-asperities on the aragonite tablets and their interposing topology provide the resistance to interfacial sliding and establish the level of the stress needed to attain the inelastic strain. Detailed mechanisms and their significance for the design of robust ceramics are discussed.

We examined the static axial displacement of a ceramic d31-gradient flextensional transducer both experimentally and theoretically. Two lead zirconate titanate systems, (PZT)/PZT and PZT/ZnO, were studied. The PZT/PZT transducers consisted of two PZT layers of different d31 coefficients. The PZT/ZnO transducers consisted of a PZT and a ZnO layer. The PZT/PZT transducers were of an inner-type dome structure. The PZT/ZnO transducers were either flat, or had an inner- or outer-type dome structure by varying the thickness ratio between the two layers or the Sb2O3 content in the ZnO layer. An inner (outer)-type transducer has the large-d31 layer on the inside (outside) of the dome structure. For the PZT/PZT transducers, the axial displacement varied with the thickness ratio and reached a maximum when the two layers had similar thickness, in agreement with the calculations. With a conductive nonpiezoelectric layer, the PZT/ZnO transducers had higher axial displacements, which varied with the thickness ratio and the Sb2O3 content, than the PZT/PZT transducers. With 6 wt% Sb2O3, the transducers were flat and the measured displacements at various thickness ratios were similar to the calculated values. With 4 wt% Sb2O3, the transducers were of an outer type. The measured axial displacements were about twice the calculated values, suggesting an enhanced d31 value because of the tensile bending stress in the PZT layer. The scaled axial displacements of the PZT/ZnO transducers with 4 wt% Sb2O3 were comparable to that of the Rainbow transducers. With 8 wt% Sb2O3, the displacements of transducers with thin PZT layers (<0.3 mm) were lower than the calculated values because of increased conductivity in the PZT layer.

The aim of this paper is to dissect the hierarchical structures of BaTiO3 particles into primary, secondary, tertiary, and quaternary structural levels and to thoroughly review the corresponding structureferroelectricity relationships at all levels. This analytical framework is of growing importance for the fundamental understanding of the ferroelectric properties of BaTiO3 in microelectronic devices, especially as their structural levels are all approaching the same scale in the process of miniaturization. The identification of the most influential structure among others and the deduction of a meaningful structure-ferroelectricity relationship depend on a thorough understanding of the relationships.

The inelastic deformation of nacre that leads to its structural robustness has been characterized in a recent experimental study. This article develops a model for the inelastic behavior, measured in tension, along the axis of the aragonite plates. The model is based on observations for abalone nacre that the inelasticity is associated with periodic dilatation bands. These bands contain coordinated separations at the periphery of the plates. The separations open as the material strains. The response is attributed to nanoscale asperities on the surfaces of the plates. The model calculates the stresses needed to displace the plates, resisted by elastic contacts at the asperities. The results are compared with the measured stress/strain curves.

We have examined both experimentally and theoretically a piezoelectric unimorph cantilever as a liquid viscosity-and-density sensor. The fabricated piezoelectric unimorph consisted of a PbO•ZrO2•TiO2 ~PZT! layer on a thin stainless-steel plate. In addition to a driving electrode, a sensing electrode was placed on top of the PZT layer, permitting the direct measurement of the resonance frequency. The cantilever was tested using water–glycerol solutions of different compositions. In all three of the tested modes, the resonance frequency decreased while the width of the resonance peak increased with increasing glycerol content. To account for the liquid effect, we consider the cantilever as a sphere of radius R oscillating in a liquid. By including the high and low frequency terms in the induced mass and the damping coefficient of the liquid, we show that for a given liquid density and viscosity the oscillating-sphere model predicts a resonance frequency and peak width that closely agree with experiment. Furthermore, the viscosity and the density of a liquid have been determined simultaneously using the experimentally measured resonance frequency and peak width as inputs to the oscillating-sphere model. The calculated liquid viscosity and density closely agreed with the known values, indicating that our cantilever-based sensor is effective in determining viscosity and density, simultaneously. We also show that scaling analysis predicts an increase in the width of the resonance peak with decreasing cantilever size, an observation in agreement with the large peak widths observed for microcantilevers.

A method for assembling patterned cryst. arrays of colloidal particles using UV illumination of an optically-sensitive semiconducting anode while using the anode to apply an electronic field to the colloidal particles. The UV illumination increases c.d., and consequently, the flow of the colloidal particles. As a result, colloidal particles can be caused to migrate from nonilluminated areas of the anode to illuminated areas of the anode. Selective illumination of the anode can also be used to permanently affix colloidal crystals to illuminated areas of the anode while not affixing them to nonilluminated areas of the anode. [on SciFinder(R)]

A modification of the traditional unimorph flextensional actuator is provided by replacing the metal shim with an elec. conducting oxide. Comprised of Pb zirconate titanate (PZT) and ZnO that is co-sintered, the laminate composite obtains large axial displacements while maintaining moderate axial loads. The varistor properties of ZnO dictate that the conductance increases several orders of magnitude when a crit. elec. field is applied. The versatility of the processing over other actuator system facilitates miniaturization, while maintaining comparable performance characteristics. Functional gradients in the material properties are created in the green body by layering thin tape cast sheets. The unique PZT-ZnO composite not only controls the piezoelec. gradient, but permits control of the sintering kinetics leading to the processing of either flat or highly domed structures. [on SciFinder(R)]

The ceramic particles from plastically deformable aq. ceramic slurrys have on their surface a closely-packed anionic surfactant bilayer or an anionic/nonionic surfactant bilayer. Optionally, ceramic particles have on their surface a closely-packed cationic surfactant bilayer or a cationic/nonionic surfactant bilayer. Slurries prepg. includes (a) dispersing ceramic particles in an amt. of water to form an aq. ceramic slurry, (b) adding an anionic surfactant or a mixt. of an anionic and nonionic surfactant, and (c) adjusting the pH value to adsorb on the ceramic particle surface a closely-packed anionic surfactant bilayer or anionic/nonionic surfactant bilayer. [on SciFinder(R)]

For a wide range of technological applications the need for optically transparent, monolithic, mesoporous silicates is readily apparent. Potential areas of utility include filtration,catalysis, and optoelectronics among many others. This laboratory has previously reported on the synthesis of such materials that are formed through the addition of tetramethoxysilane to a liquid crystal solution of hexanol, cetylpyridinium chloride, and 0.2 M hydrochloric acid, and our investigation into the properties of these materials is a continuing process. We have achieved defect and fracture free material of suitable size (0.5 cm x 3 cm diameter disks) via supercritical drying of the silicate under ethanol or CO2. The dried materials are remarkably similar to ordinary glass in strength, texture, and clarity. They possess pore volumes of ca. 1.0 cm3/g, with BET surface areas >1000 m2/g. We can re-infiltrate the dried monolith with hydroxyethylacrylate, a photo-polymerizable monomer, to create an inorganic/organic nanocomposite. There is fracturing upon re-infiltration, but preliminary tests show that the polymerization proceeds despite the mechanical failure. These findings suggest many possible applications for these unique nanocomposites.

CubicBaTiO3 particles of10nmwere crystallized predominantly within the hydroxylated polybutadiene matrix of a phase separated triblock copolymeric thin film of polystyrene-polybutadiene-polystyrene (Kraton D1102). The barium titanated Kraton thin film had remnants of the cylindrical morphology of a plain Kraton thin film with an interdomain spacing of 23 nm. The procedure of barium titanation consisted of three steps: (1) in situ hydroxylation of the polybutadiene matrix of an annealed Kraton thin film, (2) regioselective deposition of barium titanium methoxypropanoxide (BaTi(OCH2CH(CH2)OCH3)6) on the hydroxylated polybutadiene matrix, and (3) hydrothermal reduction of the organometallic complexes in anNH3/H2Oatmosphere at 80 °C for 24 h. Isolated water clusters in step 3, condensed from theNH3/H2O atmosphere of 1 M NH4OH(aq) at 80 °C in the alkoxide-Kraton films, were believed to have a typical diameter of no more than 23 nm at a pH of 14. They gave a high pH environment to weaken the chelating effectamongalkoxides and the organic matrix and provided a spatial confinement for the localized nucleation and growth of cubic BaTiO3 nanoparticles.

In contrast to extensive studies on hydroxyapatite thin films, very little has been reported on the thin films of carbonated apatite (dahllite). In this report, we describe the synthesis and characterization of a highly crystalline dahllite thin film assembled via a biomimetic pathway. A free-standing continuous precursor film of carbonated calcium phosphate in an amorphous phase was first prepared by a solution-inhibited templating method (template-inhibition) at an air-water interface. A stearic acid surface monolayer acted as the template, while a carbonate-phosphate solution composed a binary inhibition system. The precursor film formed at the air/water interface was heated at 900 °C and transformed into a dense crystalline film that retained the overall shape of the precursor. The crystalline phase was characterized by XRD and IR to be a single-phase carbonate apatite, with carbonate substitutions in both type A (OH-) and type B (PO4 3-) lattice positions.

The depth of photocuring for a model resin system was investigated as a function of photoinitiator concentration. Direct measurements of gel thickness were made from thin films of cross-linked multifunctional methacrylate monomer. The monomer, 2,2-bis{4-[2-hydroxy-3-(methacryloxy)propoxy]phenyl}propane, was polymerized in a solution of trichloroethylene with an ultraviolet laser light source at 325 nm. The monomer solutions were photocured using varying levels of both photonic energy and photoinitiator concentration. An optimal photoinitiator concentration that maximized the gel cure depth was observed. Additionally, two regimes were shown to exist in which the shrinkage (upon solvent removal) was minimized or maximized. A model was developed to probe the physics of the system. Good agreement with experiment was obtained, and the model may be employed to predict both the existence and location of the optimal photoinitiator concentration and the corresponding cure depth. The study showed that photoinitiator plays a significant role in controlling the quality and performance of the formed gel network, with special regard to thickness of cured layers. This has potential application to fields as diverse as industrially cured coatings and dental fillings, and more generally, 3-dimensional rapid prototyping techniques.

Large (in excess of 2 cm in diam.), single crystal YBa2Cu3O7-x [123 YBCO] crystals, where x ≤ 0.6, can be grown in a seventeen step process or some variant thereof from finely ground and well mixed 123 YBCO and 211 YBCO powders with a small amt. of Pt by controlling the rate of cooling from within a compact of the powders using a temp. gradient in the radial and axial planes (independently) of ∼1-20°/in. diam. of compact to nucleate the crystal growth. Crystal growth is also promoted as well using a Sm oxide seed crystal, preferably SmBa2Cu3O7-y, where y ≤ 1.6. After nucleation the compact is cooled slowly at a rate from ∼0.1-1°/h to promote the single crystal development. [on SciFinder(R)]

A bulk high-temp. superconductor single crystal MBa2Cu3O7-x, where M = Y, Sm, Eu, Gd, Dy, Ho, Er, or Yb; and x = ∼0.1 to ∼1.0, are produced by a novel process incorporating: (i) starting powders produced by combustion spray pyrolysis; (ii) a novel setter powder; and/or (iii) a monitored isothermal growth process. [on SciFinder(R)]

The invention relates to a polarization cell which is coated with glass deposited from a sol-gel used for hyperpolarizing noble gases. The invention also includes a method for hyperpolarizing noble gases utilizing the polarization cell coated with glass deposited from a sol-gel. These polarization cells can also be incorporated into containers used for storage and transport of the hyperpolarized noble gases. [on SciFinder(R)]

Mesoporous aluminosilicate in the hexagonal phase (MCM-41) has been synthesized from fused fly ash solutions and cationic cetyltrimethylammonium bromide (CTAB) surfactants. We provide direct evidence that an MCM-41 aluminosilicate with a homogeneous chemical composition of Si/Al = 13.4 can be prepared with cationic surfactant. Our results indicate that coal combustion byproducts can be utilized for producing mesoporous molecular sieves even though they contain significant amounts of impurities.

The magnetic excitation spectrum of a YBa2Cu3O7 crystal containing 0.5% of nonmagnetic (Zn) impurities has been determined by inelastic neutron scattering. Whereas in the pure system a sharp resonance peak at E similar or equal to 40 meV is observed exclusively below the superconducting transition temperature T-c, the magnetic response in the Zn-substituted system is broadened significantly and vanishes at a temperature much higher than T-c. The energy-integrated spectral weight observed near q = (pi, pi) increases with Zn substitution, and only about half of the spectral weight is removed at T-c.

We have investigated theoretically the elastic and yield behaviors of strongly flocculated colloids by first examining the yield forces between two particles within the framework of Derjaguin-Landau-Verwey-Overbeck (DLVO) interactions. Under highly attractive conditions, i,e,, in the absence of the secondary minimum in the DLVO potential, the radial (tensile) motion between particles is nonelastic because of the lack of an inflection point in the DLVO potential. However, the lateral (shear) motion is shown to be elastic up to a distance y(max), providing a mechanism for the observed elasticity in colloidal gels. If r(0) and s(0) are, respectively, the closest center-to-center and surface-to-surface distances between two particles, y(max) proportional to (1- 0.5 alpha zeta(2))(s(0)r(0))(1/2) where zeta is the zeta potential of the particles and a a defined constant. Moreover, the yield force between two particles is much smaller in the lateral direction than in the radial direction. These results suggest that yielding of a particulate network is likely to occur through the lateral movements between particles. The yield strain can be approximated as that at which all the bonds in a certain direction have a perpendicular displacement >y(max), resulting in epsilon(yield) = y(max)/r(0) proportional to (1 - 0.5 alpha zeta(2))(s(0)/r(0))(1/2) The shear modulus of the network, G', can be deduced by combining the elastic constant of the lateral movement with the existing elastic theory of a particulate network. The yield stress can be approximated as sigma(yield) approximate to G'epsilon(yield) proportional to (1 - 1.5 alpha zeta(2))A/24s(0)(3/2) 1/Rd-3/2 where A is the Hamaker constant and R the particle radius. These predictions are shown to compare favorably with existing experiments.

We study the elastic moduli and structure of boron carbide/aluminum (B4C/Al) multiphase composites using rigorous bounding and experimental characterization techniques. We demonstrate that rigorous bounds on the effective moduli are useful in that they can accurately predict (i) the effective elastic moduli, given the phase moduli and volume fractions, or (ii) the phase moduli (volume fractions), given the effective moduli and phase volume fractions (moduli). Using the best available rigorous bounds on the effective elastic moduli of multiphase composites involving volume-fraction information, we are able to predict the bulk and shear moduli of the AI,BC phase, a reaction product that forms during heat treatment. These theoretical predictions are in very good agreement with recent experimental measurements of the moduli of the AI,BC phase. Moreover, we evaluate more-refined bounds involving three-point structural correlation functions by extracting such information from an image of a sample of the B4C/Al composite. Although experimental data for the effective moduli are unavailable for this sample, our predictions of the effective moduli based on three-point bounds should be quite accurate.

We have examined the static and dynamic electromechanical responses of PZT-brass (piezoelectric-nonpiezoelectric) plate unimorphs of various brass/PZT thickness ratios. The study was performed both experimentally and theoretically. The static measurements showed that, given a PZT layer thickness, there exists a brass/PZT thickness ratio that gives the unimorph the highest static displacement under an applied field. The effects of geometric shape and external loading on the displacement of the unimorphs were also examined. The dynamic measurements showed that, given a PZT layer thickness, the bending-mode resonance frequencies increase with an increasing brass/PZT thickness ratio. These results were in good agreement with the theoretical predictions that were obtained with the plate geometry.

A mullite/mullite nanocomposite powder has been synthesized, composed of nanometer-size 3Al(2)O(3)center dot 2SiO(2) ('3 : 2') mullite precipitates within a matrix of the high alumina 2Al(2)O(3)center dot SiO2 ('2 : 1') mullite. Historically, the transition from the metastable high-alumina phase to the thermodynamically stable '3 : 2' phase of mullite has been thought to be a continuous process, involving a continuous solid solution between the two forms of mullite. In contradiction to this widely held view, our high resolution transmission electron microscopic characterization confirms that a first order phase transition between two distinct mullites occurs. The high degree of interface coherence between the precipitates and the matrix allows us to speculate that the mechanical properties of the matrix could be enhanced by a process similar to the precipitation hardening of metals.

A summary of some recent results of neutron scattering studies of high temperature superconductors is given, with a focus on resonant spin excitations in the superconducting states of YBa2CU3O6+x and Bi2Sr2CaCu2O8+delta. The opportunities offered by advances in neutron scattering instrumentation, such as focusing and polarization techniques, for these experiments are discussed, (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

The microscopic equilibrium structures of adsorbed films of quaternary ammonium surfactants on mica have been investigated by noncontact atomic force microscopy imaging as a function of alkyl chain length and headgroup structure. Spherical and cylindrical surface micelles were observed; these were found to be related to bulk. solution self-assembly and the surfactant packing parameter, v/a(0)l(c). Shape transitions in the surface aggregates were observed on changing the counterion between chloride, bromide, and salicylate.

A process directed to prepg. surfactant-polycryst. inorg. nanostructured materials having designed microscopic patterns. The process includes forming a polycryst. inorg. substrate having a flat surface and placing in contact with the flat surface of the substrate a surface having a predetd. microscopic pattern. An acidified aq. reacting soln. is then placed in contact with an edge of the surface having the predetd. microscopic pattern. The soln. wicks into the microscopic pattern by capillary action. The reacting soln. has an effective amt. of a silica source and an effective amt. of a surfactant to produce a mesoscopic silica film upon contact of the reacting soln. with the flat surface of the polycryst. inorg. substrate and absorption of the surfactant into the surface. Subsequently an elec. field is applied tangentially directed to the surface within the microscopic pattern. The elec. field is sufficient to cause electro-osmotic fluid motion and enhanced rates of fossilization by localized Joule heating. [on SciFinder(R)]

Barium titanate can be hydrothermally synthesized by exposing a titanium source to a Ba(OH)(2) solution. In concentrated solutions, time resolved studies indicated that BaTiO3 particles nucleate, grow and agglomerate to form 'raspberry-like' clusters which gradually rearrange to form single crystal BaTiO3 particles. Polymer films containing barium titanate particles can also be produced by a hydrothermal route. Titanium organometallic precursor is dissolved in polymer solutions and spun-cast into films. BaTiO3 is formed in the polymer matrix upon exposure to Ba(OH)(2) solution at temperatures below 100 degrees C. Two modifications to this approach are described which alter the morphology of the BaTiO3 particles utilizing the tendency of the block copolymer matrix to microphase separate. Patterning of the BaTiO3 by redistribution of the precursor in the block copolymer matrix may provide a method of producing 0-3, 1-3 and 2-2 connectivities.