Nano-crystalline, zirconium oxide and oxyhydroxide particulates were produced using a novel, continuous, flow-through hydrothermal technology which was previously developed at the Pacific Northwest National Laboratory. Homogeneous aqueous solutions containing 0. LM ZrO(NO3)2, 0.2-0.5M urea, and in some cases 0.025-0.10M NaF were pumped at pressures of 6000-8000 psi through a heated stainless steel reaction tube at 340-350°C. Flow at pressure was maintained using a nozzle at the down-stream end of the reaction tube. In this process, termed Rapid Thermal Decomposition of precursors in Solution (RTDS), the formation of zirconium oxide and oxyhydroxide nano-crystals (diameters of generally less than 15-nm) occurred during the solution's brief residence time (<15 seconds) in the reaction tube, yielding aqueous slurries of agglomerated particulates upon exiting the nozzle. Powders were separated from these slurries, washed, then dried. RTDS powder prepared from 0.1M ZrO(NO3)2and 0.5M urea had a surface area of 210 m2/g and was determined to be a mixture of predominantly nano-crystalline (<10 nm crystallite diameter) cubic ZrO2 with the balance being monoclinic ZrO2. This powder was subsequently calcined to 500°C, pressed into a pellet at 20,000 psi and sintered at 500°C for one hour to yield a mechanically stable porous support with a measured surface area of 125 m2/g. In contrast, RTDS powder prepared from 0.1M ZrO(NO3)2, 0.5M urea, and 0.1M NaF was determined to be pure monoclinic ZrO2with a surface area of 58 m2/g.

The conditions of nanodispersed particles precipitation from a gas flow on the surface cooled to cryogenic temperatures are analyzed. The range of allowable values of precipitation surface temperature has been defined in dependence of dispersed flow characteristics. The method can be used both for catching of nanopowders, and for gas cleaning from aerosol and dust particles for ecological purposes.

Nanostructured a-Fe2O3 powders were generated by rapid expansion of supercritical fluid solutions (RESS, T=773 K, P=100 MPa) and by rapid thermal decomposition of precursors in solution ( RTDS, T=623 K, P=100 MPa) on lab RESS-setup from 0,040 M and 0,10 M aqueous solutions of Fe(NO3)3. The size of subcrystallites is about 22-29 nm. Comparison of reactivity of α-Fe2O3 powders in a model solid state reaction between a-Fe2O3 powders (generated by RESS from 0,040 M solution) and Li2CO3 (mole ratio 1:1) with literature data on a-Fe2O3 powders produced by other methods shows that its reactivity is markedly higher. A basic essence possibility of zinc ferrite ZnFe2O4 formation immediately at the stage of the rapid expansion (T=773K; P=100 MPa) of a supercritical aqueous solution of zinc and iron nitrates (molar ratio Zn:Fe=1:2; C=0. 1 M) was shown.

Vanadium pentoxide hydrate was pillared with ultrafine titanium dioxide particles to form expanded layered structure (∼20 A) and thereby forming microporous substance (diameter =∼10 A). Porous structure formation and adsorption of some toxic gases (CO and NO) were discussed.

Monodisperse silica-tin oxide particles of the core-shell type were prepared via a sol-gel process without formation of agglomerates. After synthesis of silica cores the surface was coated with tin oxide by controlled hydrolysis and condensation of tin(IV) tertiary butoxide. Particle properties were characterized by electron microscopy, dynamic light scattering, N2-sorption (BET), zeta potential and X-ray fluorescence analysis. As a consequence of the variable content of tin oxide numerous possible applications arise, for example introducing X-ray opacity in dental filling materials. In order to use such particles as fillers, an additional surface functionalization with 3-methacryloxypropyltrimethoxysilane was created matching the C=C-functional groups of the polymer resins, e.g. ORMOCER*s. Characterization methods such as diffuse reflectance infrared Fourier transform spectroscopy and elemental analysis were used to confirm the surface coverage.

Hybrids of quaternary ammonium-modified montmorillonites and polypropylene were prepared by melting intercalation. Results of mechanical property measurements show that, tensile strength, modulus and impact strength of PP composites are greatly enhanced simultaneously by a small addition amount of modified montmorillonites.

The structure and mechanical properties of Y-TZP nanoceramics produced by ultrasonic (US) action on nanostructured ZrO2 – 5.4wt% Y2O3 powder have been analyzed. The influence of powder US-treatment on elastic aftereffect of a compact, uniformity of ceramics volumetric shrinkage, on ceramic nanostructure forming and as a result on its density, hardness, impact strength was shown. The optimum of power level of US-action was defined.

Nanophase NiAl powders were synthesized by solid state reaction via ball milling of elemental Ni and Al powders under an argon atmosphere for 0-8 h, 16 h, 24 h, and 48 h. Structural characterization of the nanophase NiAI was performed by x-ray diffraction and transmission electron microscopy. The oxidation behavior of the powders was studied by thermogravimetric analysis. It was found that the Ni + Al = NiAl solid state reaction took place between 4 and 5 hours of mechanical alloying. After 5 h or more of mechanical alloying, the phase of the ball milled particles was the B2 structure, with average grain sizes which decreased with increasing mechanical alloying times. The relationship between the long-range-order parameters and mechanical alloying time was studied. After 5 h, 6 h, 8 h, 16 h, 24 h, and 48 h mechanical alloying, the long-range-order parameter was determined to be approximately 0.82, 0.75, 0.75, 0.75, 0.71, and 0.63, respectively. Iron contamination was observed, resulting from wear of the steel vial and balls. In the mechanically alloyed NiAl nanoparticles, edge dislocations, shear bands, subgrains, distorted regions, and a large number of grain boundaries were observed.

Barium titanate ultrafine particles are prepared by hydrothermal method at low temperature. Their phase structures and photoluminescence (PL) properties are examined by X-ray diffraction and Raman spectroscopy. The critical size of the cubic-tetragonal phase transition is about 48 nm and the lattice parameter ratio c/a equals 1.003. Strong photoluminescence is observed with central frequency located at 695 nm. The spectral behaviors at different annealing times and temperatures are studied. We attribute them to the semiconducting hexagonal phase embeded in the nanophase cubic BaTiO3to form trap centers and cause PL process.

Electron diffraction patterns and high-resolution transmission electron microscope (HREM) images show that the dominant phase in tungsten carbide thin films grown by plasma enhanced chemical vapor deposition is WC(1−x). The f.c.c crystal structure and the unit cell size of WC(1−x) have been determined via electron powder diffraction. The two largest and most dominant spacings in HREM images are the {111} and {002} spacings of WC(1−x). Cross lattice fringes along the two most densely populated zones of WC(1−x) are seen. The sizes and aspect ratios of nano-crystals have been measured from HREM images. Stereo analysis of individual nano-crystals has been done. Confirmation of the 3-D structure of WC(1−x) via spacings larger than 0.15 nm will require a tilt larger than 35° between images.

Glassy epoxy-clay nanocomposites (Tg ≈ 82 °C) have been prepared by the reaction of diglycidyl ether of bisphenol A and a polyoxyalkylene amine curing agent in the presence of organo cation exchanged smectite (montmorillonite) clays. Commercially available AMS and CWC montmorillonites purified on the industrial scale (Nanocor, Inc.) afforded nanocomposites with performance properties comparable to those obtained from montmorillonite purified by laboratory methods. We provide the first evidence for clay nanolayer reinforcement of a glassy epoxy matrix under compressive strain. Compression stress - strain experiments revealed substantial improvements in the modulus and yield strength when the clay nanolayers were exfoliated in the glassy matrix. However, no improvement in the modulus or yield strength was observed when the clay component was merely intercalated by the epoxy matrix, signifying that nanolayer exfoliation is an essential feature of reinforcement. Furthermore, the mechanical properties of epoxy-clay nanocomposites prepared with the C18H37NH3+ - exchanged forms of the AMS and CWC clays have been tested by dynamic mechanical analysis and thermal mechanical analysis. The nanocomposites exhibit improved dynamic storage modulus above and below the glass transition temperature, as well as lower coefficients of thermal expansivity compared to the pure polymer. In addition, the solvent resistant properties of the nanocomposites are substantially improved compared to the pristine polymer.

This paper discusses the potential of mechanochemical activation of low grade raw materials with carbonaceous inclusions to achieve high-quality building ceramics. The procedure proposed enabled us to produce clay-coated quartz powders thus facilitating further processing steps of semidry pressing and firing of the bricks, tiles and flagstones.

The polyimide hybrids that have been most widely studied by the authors contain a silica phase produced from tetraethoxysilane by the sol-gel method. Despite the expected strong interactions, through H-bonds, between the polyamic acid precursor for the polyimide and the large number of hydroxyl groups from the silica phase, it is rather difficult to prevent phase separation and rapid coarsening of the morphology upon removal of the solvent from the original solution mixture. These systems can be compatibilized, however, with the selective use of functionalized trialkoxysilane coupling agents, such as glycidyl and isocyanate types.

In the present work we have established that compatibilty is achieved only upon exceeding a critical concentration of coupling agent, which increases linearly with the total silica content up to a certain level. This was found to be connected with the ability of the coupling agent to displace the strongly associated solvent molecules with the amic acid units of the polymer chains in order to develop the required level of interactions across the interface between the organic and inorganic components.

Treated silica xerogels with controlled porosity and surface area were prepared by the in-situ treatment of hydrogels with hexamethyldisiloxane in the presence of isopropyl alcohol. The resulting hydrogels were hydrophobic and readily transferred to organic solvents allowing their isolation. The surface area and porosity of the xerogel were controlled by varying the pH, time and temperature used to aggregate the hydrogel prior to treatment. The treated xerogels were evaluated as reinforcing fillers in silicone rubber formulations. When the bases were crosslinked with peroxides, silicone elastomers with acceptable mechanical properties were obtained. The relationship between the surface area, porosity and the type and degree of surface treatment of the xerogel, and its reinforcing ability was studied. In general, the mechanical properties of the elastomer increased as the filler structure increased; however, xerogels with higher surface areas were more difficult to incorporate and gave higher plasticity bases.

Poly(dimethylsiloxane) (PDMS) networks were prepared by tetrafunctionally endlinking hydroxyl-terminated chains with tetraethoxysilane (TEOS). The resulting networks were filled in-situ by hydrolysis-condensation reactions that were either acid or base catalyzed reactions on some novel precursors. These precursors included star-shaped molecules, rings, linear comb-like chains, and pre-hydrolyzed products of silanes such as TEOS. Both monomethoxy and trimethoxy groups were used as hydrolyzable groups on these molecules. The structures of the resulting composites were examined by small-angle X-ray scattering, and their mechanical properties were determined using equilibrium stress-strain measurements in elongation. Novel precursors with monomethoxy functionalities did not generate stable particulates, but those with trimethoxy functionalities did, with some improvements in mechanical properties. Partially-hydrolyzed TEOS provided the best reinforcement of these PDMS elastomers.

Nanocrystalline sulfated zirconia catalysts were prepared using the rapid thermal decomposition of precursors in solution (RTDS) powder formation process. Zirconia gel formation, initial crystallization, and sulfate incorporation occurred during a brief exposure to hydrothermal conditions in the RTDS reactor. The partially crystalline zirconia solid was collected as a suspension, separated by centrifugation, and subjected to calcination to achieve full catalytic activity. Crystallinity, sulfate content, and catalytic activity of the calcined powders toward butane isomerization varied according to the hydrothermal conditions at which the zirconia powders were originally precipitated. The powders were characterized using powder XRD, FTIR, and XAS.

Inorganic membranes prepared by the sol gel method are promising candidates for use as filters in separation processes. Conducting supported membranes and coatings have been produced from redispersable nanoscaled crystalline Sb-doped SnO2 powders with a Sb content up to 5 mole % (with respect to Sn). The crystalline particles are monosized (≅4 nm) and fully redispersable in aqueous solution at pH ≥ 8 with a solid content up to 70 wt. %. By thermal treatment at different temperatures and times, the pore size diameter of the material can be adjusted from 4 to 20 nm with a very narrow pore size distribution (∼ ±1 nm) and a total porosity of 63 %, practically independent of the sintering parameters. Uniaxial pressed substrates present similar characteristics with however larger pore size distribution (±5 nm) and 80 % total porosity. Their resistance decreases with sintering temperature and time down to 4 Ω (800 °C 8 h). Fully dispersed aqueous solutions of the powder (25 wt. %) were used to prepare transparent conducting coatings on glass or ceramics by spin-coating. After thermal treatment (1 hour at 550 °C) single layers 200 nm thick exhibited a typical specific electrical resistance ρ = 2.5·10−2 ωcm with transmission in the visible range measured against air of 90%.

Extrusion freeform fabrication is a 3-D layerwise writing technique for forming objects directly under the control of a CAD program. This method is one of a family of rapid prototyping methods which include stereolithography, selective laser sintering and fused deposition modeling. This system can be used to build shapes, layer by layer, from hydrogels of agarose, polyacrylamide or other cross-linked water-soluble acrylic polymers.

Mineralization can be induced in these gels by first building a part from an aqueous gel slurry containing calcium sulfate powder. This part is then immersed in a carbonate or phosphate solution which diffuses into the gel and precipitates calcite or calcium phosphates as the sulfate slowly dissolves. The resulting material contains 5-10 vol% mineral, 5 vol% agarose and 85-90 vol% water. On drying a bone-like composite is formed. If the original part is not a solid but a mesh of connected struts, the drying step results in a stronger part.