Alumina xerogels were prepared by a two step hydrolysis in non-aqueous media. This synthesis produced high surface area materials with controlled amount of pentacoordinated aluminum. The effect of heat treatment and of the preparation procedure on the physical characteristics of the powder was determined by nitrogen adsorption and X-Ray diffraction, whereas the aluminum coordination was studied by 27Al MAS NMR. The pore size distribution and the pentahedral aluminum content (up to 700°C) are closely related to the degree of condensation of the prehydrolysed oligomer species.

Composites of amine terminated butadieneacrylonitrile (ATBN) and montmorillonite (MMT) were prepared by ion exchange between the onium salt of the polymer and the interlamellar cation of the mineral following two different preparation approaches. The first carried out the ion exchange in situ and used dioxane, a better solvent for the polymer, and the second administered the onium salt to MMT using dimethylsulfoxide (DMSO). Elemental analysis and IR spectroscopy indicated that all the ionic sites of the mineral have been occupied by polymer end groups. The d (001) spacing and the span between the internal lamelar surface were only expanded to about 14 Å and 5 Å, respectively, suggesting horizontal packing of the polymer molecules. TEM of microtome sections prepared from compression molded composites revealed that the lamellae, laminated with polymers assembled into multiplets of about 5 nm for both preparations. The multiplets clustered into mineral rich domains whose average size was 250 nm for the DMSO preparation. Finer clusters (70 nm) were obtained by the first method. This three fold decrease in the average domain size was attributed to the strong solvation power of dioxane in the binary solvent and to the locale of ion exchange.

Progress has been made towards the development of inorganic-organic multilayered films modeled after Hofmann clathrate compounds. Cobalt-bipyridine multilayers were grown layer by layer on a silicon substrate. The resulting films were characterized using ellipsometry, grazing angle X-ray diffraction, Auger electron spectroscopy and EPMA (Electron Probe Micro- Analysis). Results indicate that moderately well ordered layers have been synthesized, but cross-linking with M(CN)42(M = Ni, Pd, or Pt) to simulate the model structure does not significantly occur.

Several new crystalline bimetallic alkoxide precursors for barium titanates processing have been prepared: {[Ba(Solv)2]2[Ti(OAr)6]2} (1) (Solv = coordinated solvent molecule, Ar = aryl group), [Ba(CH2OHCH2OH)4(H20)][Ti(OCH2CH2O)3] (2), Ba[Ti2(OR)9]2 (3) (R = methyl, ethyl, and n-propyl), and [Ba(BzOH)Ti2O(OBz)8]2 (4) (Bz = benzyl). These precursors have been characterized by elemental analysis, IR, NMR, and single-crystal X-ray diffraction techniques. Compound 1 is well-suited for sol-gel processing of BaTiO3 powders and thin films under a variety of conditions. The facile preparation of 2 using relatively inexpensive starting materials makes it a viable alternative for the synthesis of BaTiO3 fine powders. Both compounds 3 and 4 are fairly moisture-sensitive; hydrolysis of these precursors under acidic conditions affords the formation of gels instead of precipitates. The reactivity of 3 toward hydrolysis can be tailored by varying the alkyl group.

Silica aerogels are sol-gel derived nanostructured materials with high porosities up to 99.8%. The nanostructures of silica aerogels are investigated by BET, SEM, SAXS techniques. A typical fractal structure is found especially for base-catalyzed aerogels. That is the aerogels are made of particles of size a, these particles form the branching and interconnecting networks up to an average cluster size ξ, At length scales above ξ, the material is an homogeneous assembly of such clusters; between a and ξ, the structure is fractal. Meanwhile, the effects of catalysis and aging on the structures are investigated and discussed. The reasons why SCD technique should be used are also deeply discussed.

Incoherent inelastic neutron scattering (IINS) measurements of hydrogen bound to Ir6 clusters in the nanoscale pores of zeolite NaY and similar clusters in KL zeolite are reported. On the basis of hydrogen uptake measurements and the observation of peaks in the IINS spectra, we infer that hydrogen is bound to the metal nanoclusters in the zeolite pores. The HINS data for both zeolites are similar and consistent with the presence of IrH2 species.

We have investigated the local structural and magnetic properties of Fe in nanostructured Fe-Cr-Mo-V-C M50 type steel. Experimental techniques which we used include XAFS and NMR. NMR results on as-synthesized M50 type steel shows that the material contains a small amount of bcc Fe plus some other highly disordered phase(s). XAFS measurements indicate that the near neighbor coordinations around Fe are not simply well ordered bcc or fcc Fe and that the sample doesn't have long range crystalline order. XAFS measurements on the consolidated sample show that Fe is predominantly in the form of bcc Fe with good long range order.

Molybdenum hexacarbonyl in hexadecane was irradiated with high intensity ultrasound under argon at 90°C to yield face centered cubic molybdenum carbide, Mo2C. After thermal treatment, oxygen and excess carbon were removed to give stoichiometric Mo2C. SEM micrographs showed that the surface was extremely porous. TEM micrographs showed that the solid was an aggregate of particles with diameters of ≈ 2 nm. This material has a very high surface area, 188 m2/g as determined by BET gas adsorption. Catalytic studies have been conducted on the dehydrogenation of cyclohexane and the hydrogenolysis of ethane. The sonochemically prepared Mo2C shows good catalytic activity for the dehydrogenation of cyclohexane with 100% selectivity for formation of benzene without hydrogenolysis to methane. The material revealed poor catalytic activity for the hydrogenolysis of ethane.

The inert gas condensation (IGC) technique was employed to synthesize non-agglomerated nanoparticles of ZrO2 and Y2O3 with different average particle sizes ranging from 4 to 14 run. The sintering behaviors (in air and vacuum) of single phase n-ZrO2 (monoclinic crystal structure) and Y2O3-ZrO2 mixture (Y-TZP) were studied in terms of densification rate and final sintering temperature. There was a strong correlation between densification characteristics and properties of the starting powder compacts such as average particle size, particle and pore size distributions. n-ZrO2 was sintered to full density in air at temperatures as low as 1125°C (0.47 Tm) and in vacuum at 975 °C (0.42 Tm). Although the grain sizes in the fully sintered samples were well below 100 nm, the grains had grown by a factor of 10 as compared to the initial particle size. Therefore, a pressureassisted sintering technique was employed to further reduce the densification temperature and final grain size. Threshold effects in this process are also discussed.

Although plagued by a lack of ductility, titanium aluminides are among the most promising intermetallics under development. Significant improvements in ductility may be obtained from nanostructured intermetallics. Nanosize particles of TiAl3 have been prepared by heat-treatment of chemically synthesized precursor (compound 1). Nanosized TiAl3 has been characterized by chemical analysis, XRD, EDS, NMR, and HREM.

Spray Conversion Processing was used to synthesize high volume fractions (0.52 - 0.74) of nanograined (Fe, Mo)6C carbide dispersions in iron, starting from water soluble precursors. The essential features of the process are, (1) preparation of a chemically homogeneous precursor powder, and (2) thermochemical conversion of the precursor powder to the desired nanostructured composite powder through controlled gas-solid reactions. The thermodynamic and kinetic features of the gas-solid reactions, and the influence of various processing parameters on the structures developed, are discussed. The powders were consolidated to near theoretical density by pressureless sintering and hot pressing. All the consolidated samples had bicontinuous structures. Compared to M2 high speed tool steels, these high volume fraction carbide strengthened iron alloys display superior hardness values up to 500°C.

Nanocrystalline iron powders were produced by means of the gas condensation. Pure nitrogen, or oxygen, or air, was introduced into the as-made powders before they were taken from the chamber. Various atmospheres produced varied layer structures around the iron particles. A high resolution transmission electron microscope was used to analyze the crystal structure and vibrating-sample magnetometer was used to measure the magnetic properties of nanocrystalline iron particles. The results showed that a layer of amorphous or nanocrystalline structure was formed initially on the surface of iron particles. This thin amorphous layer crystallized into Fe304 after annealing under electron irradiation when the introduced atmosphere was pure oxygen or air. However, it formed a passivated layer of ζ-Fe2N when nitrogen was introduced. The exchange anisotropy between the iron core and the superficial iron oxide or nitride shell was observed as the sample was cooled in an applied field of 10 kOe from room temperature to 5 K. The shift of the hysteresis loop caused by exchange anisotropy was 16% for the nitride shell and 8% for the oxide shell.

To develop novel polypeptide-based thin films, a series of star polypeptides modified with nonlinear optical chromophores has been synthesized. Using amino-substituted tetraphenyl porphyrin as an initiator, the N-carboxy anhydride of γ-benzyl L-glutamic acid was polymerized onto the porphyrin at a monomer to initiator ratio 20:1. The resulting four-branch star was modified with a selection of dyes. Dyes that modified both the N-terminus and benzyl side chain were used. We demonstrated feasibility of insertion of a metal ion into the polypeptide porphyrin core. The polypeptide series was characterized by UV/VIS, FTIR, and CD. The UV/VIS data suggested ease of modification of both the N-terminus and side chains. The FTLR and CD data show the resulting polypeptides were ∝-helical. The results demonstrate the feasibility of modifying the optical properties of a porphyrin by three approaches: insertion of metal, attachment of dye to N-terminus or modification of γ-benzyl L-glutamate side chain.

To develop novel optical thin films, we have prepared self-assembled polypeptide films by an electrostatic process. The films were placed on a glass slide previously silanized by an amino silane and given a positive charge by immersion in aqueous acid. Subsequent immersion of the slide in aqueous anionic solutions of either poly(L-glutamic acid), congo red, copper phthalocyanine tetrasulfonic acid or p-nitroaniline-modified poly(L-glutamic acid) resulted in deposition of the anions on the surface. Following anionic immersion, the slides were dipped into a cationic poly(L-lysine) solution. Alternate dipping into anionic and cationic solutions yielded multilayers. The thin films were characterized by optical absorption and circular dichroism. The optical density increased with dipping cycles. Circular dichroism measurements of the thin films showed induced dichroism of the congo red and phthalocyanine-containing films, suggesting formation of a locally ordered dye-polypeptide complex. Solution circular dichroism measurements of the polypeptides indicated a coil conformation, while poly(Lglutamic acid)/poly(L-lysine) complexes showed circular dichroism spectrum characteristic of a β-sheet.

Ceramic-polymer composites produced by natural organisms are known to have properties far beyond those that can be achieved in present technological materials [1]. The mollusk shell, for example, starting with relatively weak structural ingredients calcium carbonate and chitin is one such ceramic-polymer composite. In nacre, the overall composite is more than 95 volume percent calcium carbonate, with the remainder an organic matrix of protein and chitin. The inorganic phase consists of highly oriented aragonite platelets forming the bricks and the organic matrix forming the mortar in between [1]. Even though nacre consists of a high amount of the inorganic component, it has excellent fracture toughness and high strength. Studies have been conducted to understand the factors which control the nucleation and orientation of crystallization [2-4]. However, very limited knowledge about the ceramic polymer interfaces, structure, chemistry and whether the interfacial interaction involves ion-binding is known.

Nanocrystalline cerium oxide was synthesized by magnetron sputtering of a metallic target, followed by controlled post-oxidation. The resulting cerium oxide clusters were <10 nm in size, and highly non-stoichiometric in nature. The oxygen deficiency of such materials was associated with the unusual catalytic activity in oxidation and redox reactions. This paper compares the surface chemistry of nanocrystalline CeO2−x with stoichiometric CeO2. It further explores the promoting effect of Cu-doping on surface reduction and oxidation.

The oxidation states of metal cations were examined with X-ray photoelectron spectroscopy after various oxidizing and reducing heat treatments in a connected reaction chamber. Isothermal pulsed reduction and oxidation of the samples were investigated by thermogravimetric analysis. Reduction properties of the different materials are discussed in terms of their microstructure, oxygen deficiency and chemical composition. These studies will help to understand the importance of bulk defects and synergistic effects in multicomponent and multiphase materials for high surface reactivity.

A new class of superlattices consisting of alternating layers of organic and inorganic materials has been prepared from 8-hydroxyquinoline aluminium (Alq), copper phthalocyanine (CuPc), 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) and MgF2 by molecular beam deposition. Small-angle x-ray diffraction data and cross-sectional transmission electron micrograph of the superlattices reveal that the superlattices have layered structure throughout the entire stack. From comparison of the x-ray diffraction patterns, it is found that the interface roughness between organic and MgF2 layers depends on the materials for organic layers. High-angle x-ray diffraction data indicate that there is a structural ordering in the CuPc and PTCDI layers. From the optical absorption and photoluminescence measurements, it is found that the exciton energy of Alq shifts to higher energy with decreasing Alq layer thickness.

By virtue of their shape selectivity and stability, molecular sieves are ideal components for discriminating chemical sensors. In this paper we report the preparation of capacitance type sensors based on aluminum phosphate molecular sieves. Thin films of the molecular sieves AlPO4-5, A1PO 4-H3 and AlPO4-H1, which cover a range of pore dimensions, were deposited on titanium nitride coated silicon wafers by laser ablation. A subsequent hydrothermal treatment followed by a Pd/Au coating and the application of standard photoresist/masking techniques were used to generate the capacitors. The molecular sieves exhibit significant changes in capacitance upon exposure to target molecules, including CO2, CO, N2, H2O and toluene.

We are investigating a method for synthesizing oriented layered thin film structures that exhibit nonlinear optical properties. This method involves self-assembly of metal bisphosphonate multilayers on gold and silicon substrates. Multilayers are characterized via optical ellipsometry, diffuse reflectance and attenuated total reflectance FTIR, and grazing angle X-ray diffraction.

To incorporate nonlinear optical activity into self-assembled films, we use a,w-bisphosphonates containing aromatic π systems sandwiched between donor and acceptor groups. In order to maximize the overall polarizability of the film, the polarizable bisphosphonate molecules must preferentially bind in only one orientation. To accomplish this, one of the terminal phosphonate groups of the molecule is protected (in ester form). After binding the free phosphonic acid end, the terminal ester is converted to a phosphonic acid group by hydrolysis with bromotrimethylsilane (BTMS). Layering is continued by binding a metal layer and repeating the cycle. Films prepared via this route do exhibit second harmonic generation, but apparently incomplete deprotection of each layer leads to increasing disorder with increasing number of layers.

Nanometer sized silicon particles have been produced by ultrasonic dispersion of thin sections of porous silicon in organic solvents. High resolution TEM and FTIR have been used to establish the size range and surface structure/composition of these particles. The larger particles, which range in size from 20 to 50 nm, are made up of a conglomeration of smaller particles with a diameter of a few nanometers. The HRTEM shows an amorphous layer on the surface of many of the clusters. FTIR data suggest this amorphous layer is silicon-dioxide which may also have organic constituents.