A model is presented to explain the formation and morphologies of surfactant-silicate mesostructures. Three processes are identified: multidentate binding silicate oligomers cationic surfactant, preferential polymerization in interface region, charge density matching between surfactant silicate. The explains present experimental data, including transformation lamellar hexagonal mesophases, provides a guide for predicting conditions that favor lamellar, hexagonal, or cubic Model Q(230)...

Alumina aerogels were prepared through the addition of propylene oxide to aqueous or ethanolic solutions hydrated aluminum salts, AlCl3·6H2O Al(NO3)3·9H2O, followed by drying with supercritical CO2. This technique affords low-density (60−130 kg/m3), high-surface-area (600−700 m2/g) alumina aerogel monoliths without use alkoxide precursors. The dried characterized using elemental analysis, high-resolution transmission electron microscopy, powder X-ray diffraction, solid-state NMR, acoustic...

Three‐dimensional printing of viscoelastic inks to create porous, elastomeric architectures with mechanical properties governed by the ordered arrangement their sub‐millimeter struts is reported. Two layouts are patterned, one resembling a “simple cubic” (SC)‐like structure and another akin “face‐centered tetragonal” (FCT) configuration. These structures exhibit markedly distinct load response directionally dependent behavior, including negative stiffness. More broadly, these findings...

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to successful storage sequestered CO2 in gas and oil reservoirs. As a first step, we investigate reaction rates mechanistic pathways for cement mineral growth absence by coupling water chemistry XRD NMR spectroscopic data. We find semi-crystalline calcium (alumino-)silicate hydrate (Al-CSH) forms as precursor solid tobermorite. Rate constants tobermorite were found be k = 0.6 (+/- 0.1) x...

Abstract 3D printing of polymeric foams by direct-ink-write is a recent technological breakthrough that enables the creation versatile compressible solids with programmable microstructure, customizable shapes, and tunable mechanical response including negative elastic modulus. However, in many applications success these printed materials as viable replacement for traditional stochastic critically depends on their performance micro-architectural stability while deployed under long-term...

The dynamic and equilibrium water vapor sorption properties of Sylgard-184, a commercially available poly(dimethylsiloxane) elastomer (PDMS), were determined via gravimetric analysis from 30 to 70 °C. Described here is methodology for quantitatively assessing how diffuses ad/absorbs into polymeric materials that are traditionally considered hydrophobic. PDMS frequently chosen their moisture barrier properties; our results, however, demonstrate able penetrate the material over range...

We have studied pressure-induced chemical reactions in carbon monoxide using both a diamond anvil cell and modified large volume press. Our spectroscopic data reveal that disproportionates into molecular CO2 solid lactone-type polymer; photochemically above 3.2 GPa, thermochemically 5 GPa at 300 K, or 3 ∼2000 K as achieved by laser heating. The product can be recovered ambient conditions with high degree of conversion, measured to up 95% the original CO. Its fundamental structure includes...

We present a robust and general method for embedding nanoparticles, such as quantum dots (QD) or colloidal gold (Au) nanocrystals, into highly water-soluble thin silica shell doped with paramagnetic gadolinium (Gd3+) ions without negatively impacting the optical properties of QD Au nanoparticle cores. The ultrathin has been covalently linked to Gd3+ chelator, tetraazacyclododecanetetraacetic acid (DOTA). resulting complex diameter 8 15 nm is soluble in high ionic strength buffers at pH...

Abstract We report the synthesis and characterization of novel elastomeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) as both cross‐linker filler within a polydimethylsiloxane (PDMS) polymer matrix. These composites were prepared through reaction octasilane‐POSS (OS‐POSS) with vinyl‐terminated PDMS chains using hydrosilylation chemistry. In addition, larger super‐POSS cross‐linkers, consisting two pendant hepta(isobutyl)POSS molecules attached to central core,...

We present a new approach for modelling macrodispersivity in spatially variable velocity fields, such as exist geologically heterogeneous formations. Considering spectral representation of the velocity, it is recognized that numerical models usually capture low-wavenumber effects, while large-wavenumber associated with subgrid block variability, are suppressed. While this suppression avoidable if heterogeneity captured at minute detail, goal impossible to achieve all but most trivial cases....

Sandia octahedral molecular sieves (SOMS) is an isostructural, variable composition class of ion exchangers with the general formula Na(2)Nb(2-x)M(IV)(x)O (6-x)(OH)(x).H(2)O (M(IV) = Ti, Zr; x 0.04-0.40) where up to 20% framework Nb(V) can be substituted Ti(IV) or Zr(IV). This easily converted perovskite through low-temperature heat treatment (500-600 degrees C). report provides a detailed account how charge imbalance this Nb(V)-M(IV) substitution compensated. X-ray powder diffraction...

Bacteria often reside in communities where the cells have secreted sticky, polymeric compounds that allow them to attach surfaces. This sessile lifestyle, referred as a biofilm, affords within these tolerance of antibiotics and antimicrobial treatments. Biofilms bacterium Pseudomonas aeruginosa been implicated cystic fibrosis are capable colonizing medical implant devices, such heart valves catheters, treatment infection requires removal infected device. mode growth is stark contrast...

Aqueous solutions of 100 parts per billion (ppb) uranium at pH 7 were treated with granulated activated carbon (GAC) that had been modified various formulations hydrophobic aerogels. The composite materials found to be superior in removing from a stock solution compared GAC alone evaluated by ASTM D 3860-98 method for batch testing. testing results using Freundlich adsorption model. best performing material has parameters n = 2.87 and Kf 1169 1.00, 20 alone. formed mixing (CH3O)4Si the...

We have measured changes in transverse relaxation times (T2e), residual dipolar couplings (〈Ωd2〉), and the mean-squared fluctuations (〈δΩd2〉), associated with cross-link density a complex silica-filled polydiphenylpolysiloxane/polydimethylsiloxane (PDPS/PDMS) block copolymer composite material. The crosslinks were induced by both chemical modification of base polymer radiolytic aging. detected H1 NMR responses from chains directly interacting silica filler (〈δΩd2〉≫2×106 rad2 sec−2), network...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA New Family of Octahedral Molecular Sieves: Sodium Ti/ZrIV NiobatesMay Nyman, Akhilesh Tripathi, John B. Parise, Robert S. Maxwell, William T. A. Harrison, and Tina M. NenoffView Author Information M.S. 0755, Sandia National Laboratories P.O. Box 5800, Albuquerque, Mexico 87185-0755 Department Chemistry Geosciences, State University York Stony Brook, 11794-2100 Lawrence Livermore Laboratory 808, L-226, Livermore, California 94551 Chemistry,...

DC745 is a commercially available silicone elastomer consisting of dimethyl, methyl−phenyl, and vinyl−methyl siloxane monomers cross-linked with peroxide vinyl specific curing agent. It generally considered to age gracefully be resistant chemical thermally harsh environments. However, little data exist on the radiation resistance this commonly used elastomer. We report static 1H NMR studies residual dipolar couplings in solid elastomers subject exposure ionizing γ radiation. spin-echo shows...