In this work, the synthesis and physiochemical characterization of titanium oxide nanoparticle-graphene oxide (TiO 2 -GO) and titanium oxide nanoparticle-reduced graphene oxide (TiO 2 -RGO) composites was undertaken. TiO 2 -GO materials were prepared via the hydrolysis of TiF 4 at 60 °C for 24 h in the presence of an aqueous dispersion of graphene oxide (GO). The reaction proceeded to yield an insoluble material that is composed of TiO 2 and GO. Composites were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, N 2 adsorption-desorption, and thermal gravimetric analysis/differential thermal analysis (TGA/DTA). This approach yielded highly faceted anatase nanocrystals with petal-like morphologies on and embedded between the graphene sheets. At higher GO concentrations with no stirring of the reaction media, a long-range ordered assembly for TiO 2 -GO sheets was observed due to self-assembly. GO-TiO 2 composites formed colloidal dispersions at low concentrations (∼0.75 mg/mL) in water and ethanol but were not amenable to forming graphene papers via filtration through Anodisc membranes (0.2 µM pore diameter) due to their high titania concentration. Zeta potential measurements and particle size distributions from dynamic light scattering (DLS) experiments on these materials explain the stability of the TiO 2 -GO colloidal solutions. Chemical and thermal methods were also used to reduce TiO 2 -GO to give TiO 2 -RGO materials.

Here we report on the application of sol-gel template synthesis to the investigation of size-induced ferroelectric phase transitions in lead titanate (PbTiO 3 ) nanotubes and nanofibers. A 0.8 M chelate solgel, made from titanium(IV) tertabutoxide and lead(II) trihydrate acetate, was applied to two different templates. Nanotubes were formed within 200-nm-pore Whatman anodisc aluminum oxide membranes, and nanofibers were prepared using 50-, 100-, and 200-nm Whatman track-etched polycarbonate membranes. Transmission electron microscopy images revealed that the tubes comprised grains of e20 nm and the fibers comprised individual grains e200 nm in width when a 200-nm pore size template is used. An examination of how the grain/crystallite size and aspect ratio of one-dimensional morphologies affect the ferroelectric phase transition was monitored through the comparison of bulk powders and the nanostructured materials using electron diffraction, X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry.

Select members of a series of structurally characterized calcium aryloxides (Ca(OAr)2) were found to influence the morphologies and phases of the final calcium ceramic nanomaterials produced, independent of the process route investigated. The Ca(OAr)2 were synthesized using an amide alcohol exchange route between [Ca(μ-NR2)(NR2)]2 (R = Si(CH3)3) and the appropriate aryl alcohol [H-OAr = H-OC6H4(R)-2 where R = CH(CH3)2 (H-oPP), C(CH3)3 (H-oBP); H-OC6H3(R)2-2,6 where R = CH3 (H-DMP), CH(CH3)2 (H-DIP), and C(CH3)3 (H-DBP)] along with triphenyl silanol (H-TPS = OSi(C6H5)3], in toluene (tol) or tetrahydrofuran (THF). The resulting products were isolated as H+[(μ3-O)Ca2(μ-oPP)2(oPP)(THF)3]2·THF]- (1), Ca(oBP)2(THF)4 (2), H+[(μ3-O)Ca2(μ-DMP)2(DMP)(THF)3]2 - (3), {2[Ca(DIP)2(THF)3]·Ca(DIP)2(THF)4}·THF (4a), [Ca(μ-DIP)(DIP)(THF)2]2 (4b), Ca(DBP)2(THF)3 (5), [Ca(μ-DBP)(DBP)]2 (6), and Ca(TPS)2(THF)4 (7). The coordination of the Ca atoms ranged from trigonal planar to octahedral, forming mono-, di-, and tetranuclear species based on the steric bulk of the ligand and coordination of Lewis basic THF. Solution NMR indicated that these compounds retain their structure in solution, except for 5, which was found to be disrupted to form a monomer. Vaterite or portlandite nanomaterials were isolated from 3 or 4a, respectively, independent of the processing route (solvothermal or solution precipitation). The morphology variations were interpreted based on the “precursor structure argument”, and the phase variation was attributed to the “precursor's decomposition pathway”. Full details of the synthesis and characterization of 1−7 as well as the nanomaterials generated therefrom are discussed.

For the first time tungsten based nanoparticles (WNPs) of scheelite (MWO 4 ; M = Ca, Sr, Ba, Pb), wolframite (MWO 4 (9) where Mes = C 6 H 2 (CH 3 ) 3 -2,4,6, ONep = OCH 2 CMe 3 , Et = CH 2 CH 3 , and py = pyridine. Through these routes, the WNP morphologies were found to be manipulated by the processing conditions, while precursor selection influenced the final phase observed. For the solution precipitation route, 1 yielded (5 × 100 nm) W 18 O 49 rods while stochiometeric reactions between 1 and (2 -9) generated homogenous sub 30 nm nano-dots, -diamonds, -rods, and -wires for the MWO 4 systems. For the solvothermal route, 1 was found to produce wires of WO 3 with aspect ratios of 20 while (1 & 2) formed 10 -60 nm CaWO 4 nanodots. Room temperature photoluminescent (PL) emission properties of select WNPs were also examined with fluorescence spectroscopy (λ ex = 320 nm). Broad PL emissions = 430, 420, 395, 420 nm were;

A series of alkaline earth modified titanium neo-pentoxide (OCH2CMe3, ONep) derivatives were synthesized through the alcoholysis reaction of [Ti(μ-ONep)(ONep)3]2 and the respective alkaline earth alkoxide (AE(OR)2), where AE(OR)2 = “Ca(ONep)2” (1), Sr5(μ4-O)(μ3-ONep)4(μ-ONep)4(HONep)(py)4 (2), or [Ba2(μ3-ONep)(μ-ONep)2(ONep)(HONep)3(py)]2 (3), in pyridine (py) in a 1:1 cation stoichiometry. For each AE cation, the following mixed-cation species were identified by single-crystal X-ray diffraction as (py)2AE[Ti(μ-ONep)2(ONep)3]2, where AE = Ca (1a), Sr (2a), and Ba (3a). For each species, two square bipyramidal titanium moieties bridge to the single octahedrally bound AE metal center through four μ-ONep ligands. Two terminal py ligands on the AE and three terminal ONep ligands on Ti complete their coordination. Compounds 1a−3a were used to synthesize nanoparticles of AETiO3 using solution precipitation (methyl-imidazole:water) and solvothermal (benzyl alcohol) routes. For comparison, we processed stoichiometeric mixtures of the individual precursors under identical conditions as noted for 1−3. The nanoparticles (5−50 nm) synthesized varied in phase from carbonates to perovskites depending on the cation and the synthetic conditions used. On the basis of the comparison of routes, stoichiometric mixtures were better in generating single-phase AETiO3 from the MeIm/H2O route after calcination, whereas, through solovothermal synthesis routes, single-source and stoichiometric mixtures both gave favorable crystalline results for Sr and Ba.

A series of polysulfone and polyacrylate-based zwitterionic coatings were prepared on epoxy-primed aluminum substrata and characterized for their antifouling (AF) and fouling-release (FR) properties towards marine bacteria, microalgae and barnacles. The zwitterionic polymer coatings provided minimal resistance against bacterial biofilm retention and microalgal cell attachment, but facilitated good removal of attached microbial biomass by exposure to water-jet apparatus generated hydrodynamic shearing forces. Increasing the ion content of the coatings improved the AF properties, but required a stronger adhesive bond to the epoxy-primed aluminum substratum to prevent coating swelling and dissolution. Grafted poly(sulfobetaine) (gpSBMA), the most promising zwitterionic coating identified from microfouling evaluations, enabled the removal of four out of five barnacles reattached to its surface without incurring damage to their baseplates. This significant result indicated that gpSBMA relied predominately on its surface chemistry for its FR properties since it was very thin (~1-2 µm) relative to commercial coating standards (>200 µm).

This paper presents the recent trends in the mechanical characterization of composite systems under consideration for Marine Hydro Kinetic (MHK) applications exposed to salt water environments. First, a testing protocol for environmental effects has been developed for resin infused in-house fabricated laminates. Unidirectional ([0] and [90]) mechanical test samples were submerged in synthetic sea water at 40°C and 50°C, with the weight recorded at time intervals over the entire period. Additional witness coupons were submerged to monitor effects of fiber orientation and cure temperature. Next, after conditioning to both full saturation and partial saturation, static compressive and tensile strength properties at temperatures of 0°C, 20°C and 40°C were collected. These results show trends of reduced tensile and compressive strength with increasing moisture and temperature in the 0° (longitudinal) direction. In the 90° (transverse) direction, compression strength decreases but tensile strength is little affected as temperature and moisture increase. Finally, both mechanical and chemical analysis results are presented for samples conditioned in a Salt Fog Chamber for unidirectional, [0] and [90], samples.

In an effort to generate single-source precursors for the production of metal-siloxide (MSiO ) materials, the tris(trimethylsilyl)silanol (H-SST or H-OSi(SiMe) (1) ligand was reacted with a series of group 4 and 5 metal alkoxides. The group 4 products were crystallographically characterized as [Ti(SST)(OR)] (OR = OPr (2), OBu (3), ONep (4)); [Ti(SST)(OBu )] (5); [Zr(SST)(OBu )(py)] (6); [Zr(SST)(OR)] (OR = OBu (7), ONep, (8)); [Hf(SST)(OBu )] (9); and [Hf(SST)(ONep)(py) ] ( n = 1 (10), n = 2 (10a)) where OPr = OCH(CH), OBu = OC(CH), OBu = O(CH)CH, ONep = OCHC(CH), py = pyridine. The crystal structures revealed varied SST substitutions for: monomeric Ti species that adopted a tetrahedral ( T-4) geometry; monomeric Zr compounds with coordination that varied from T-4 to trigonal bipyramidal ( TBPY-5); and monomeric Hf complexes isolated in a TBPY-5 geometry. For the group 5 species, the following derivatives were structurally identified as [V(SST)(py)] (11), [Nb(SST)(OEt)] (12), [Nb(O)(SST)(py)] (13), 2[H][(Nb(μ-O)(SST))(μ-O)] (14), [NbO(OEt)(SST)·1/5NaO] (15), [Ta(SST)(μ-OEt)(OEt)] (16), and [Ta(SST)(OEt)] (17) where OEt = OCHCH. The group 5 monomeric complexes were solved in a TBPY-5 arrangement, whereas the Ta of the dinculear 16 was solved in an octahedral coordination environment. Thermal analyses of these precursors revealed a stepwise loss of ligand, which indicated their potential utility for generating the MSiO materials. The complexes were thermally processed (350-1100 °C, 4 h, ambient atmosphere), but instead of the desired MSiO, transmission electron microscopy analyses revealed that fractions of the group 4 and group 5 precursors had formed unusual metal oxide silica architectures.