I1I. SUPPLENIEN TARY NO &ES

Alumina aerogels were prepared through the addition of propylene oxide to aqueous or ethanolic solutions of hydrated aluminum salts, AlCl 3 •6H 2 O or Al(NO 3) 3 •9H 2 O, followed by drying with supercritical CO 2. This technique affords low-density (60-130 kg/m 3), high surface area (600-700 m 2 /g) alumina aerogel monoliths without the use of alkoxide precursors. The dried alumina aerogels were characterized using elemental analysis, highresolution transmission electron microscopy, powder X-ray diffraction, solid state NMR, acoustic measurements and nitrogen adsorption/desorption analysis. Powder X-ray diffraction and TEM analysis indicated that the aerogel prepared from hydrated AlCl 3 in water or ethanol possessed microstructures containing highly reticulated networks of pseudoboehmite fibers, 2-5 nm in diameter and of varying lengths, while the aerogels prepared from hydrated Al(NO 3) 3 in ethanol were amorphous with microstructures comprised of interconnected spherical particles with diameters in the 5-15 nm range. The difference in microstructure resulted in each type of aerogel displaying distinct physical and mechanical properties. In particular, the alumina aerogels with the weblike microstructure were far more mechanically robust than those with the colloidal network, based on acoustic measurements. Both types of alumina aerogels can be transformed to γ-Al 2 O 3 through calcination at 800 o C without a significant loss in surface area or monolithicity.

Three‐dimensional printing of viscoelastic inks to create porous, elastomeric architectures with mechanical properties governed by the ordered arrangement of their sub‐millimeter struts is reported. Two layouts are patterned, one resembling a “simple cubic” (SC)‐like structure and another akin to a “face‐centered tetragonal” (FCT) configuration. These structures exhibit markedly distinct load response with directionally dependent behavior, including negative stiffness. More broadly, these findings suggest the ability to independently tailor mechanical response in cellular solids via micro‐architected design. Such ordered materials may one day replace random foams in mechanical energy absorption applications.

We have studied pressure-induced chemical reactions in carbon monoxide using both a diamond-anvil cell and a modified large volume press. Our spectroscopic data reveal that carbon monoxide disproportionates into molecular CO 2 and a solid lactone-type polymer; photochemically above 3.2 GPa, thermochemically above 5 GPa at 300K, or at 3 GPa and ~2000K as achieved by laser heating. The solid product can be recovered at ambient conditions with a high degree of conversion, measured to be up to 95% of the original CO. Its fundamental chemical structure includes β-lactone and conjugated C=C, which can be considered a severely modified polymeric carbon suboxide with open ladders and smaller five-membered rings. The polymer is metastable at ambient conditions, spontaneously liberating CO 2 gases exothermically. We find that the recovered polymer has a high energy density, 1-8 KJ/g, and is very combustible. We estimate the density of recovered CO polymer to be at least 1.65 g/cm 3 .2

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% of the framework Nb(V) can be substituted with Ti(IV) or Zr(IV). This class of molecular sieves is easily converted to perovskite through low-temperature heat treatment (500-600 degrees C). This report provides a detailed account of how the charge imbalance of this Nb(V)-M(IV) substitution is compensated. X-ray powder diffraction with Rietveld refinement, infrared spectroscopy, thermogravimetric analysis, (23)Na MAS NMR, and (1)H MAS NMR were used to determine how the framework anionic charge is cation-balanced over a range of framework compositions. All spectroscopic evidence indicated a proton addition for each M(IV) substitution. Evidences for variable proton content included (1) increasing OH observed by (1)H MAS NMR with increasing M(IV) substitution, (2) increased infrared band broadening indicating increased H-bonding with increasing M(IV) substitution, (3) increased TGA weight loss (due to increased OH content) with increasing M(IV) substitution, (4) no variance in population on the sodium sites (indicated by Rietveld refinement) with variable composition, and (5) no change in the (23)Na MAS NMR spectra with variable composition. Also observed by infrared spectroscopy and (23)Na MAS NMR was increased disorder on the Nb(V)/M(IV) framework sites with increasing M(IV) substitution, evidenced by broadening of these spectral features. These spectroscopic studies, along with ion exchange experiments, also revealed the effect of the Nb(V)/M(IV) framework substitution on materials properties. Namely, the temperature of conversion to NaNb(1-x)M(IV)(x)O(3) (M = Ti, Zr) perovskite increased with increasing Ti in the framework and decreased with increasing Zr in the framework. This suggested that Ti stabilizes the SOMS framework and Zr destabilizes the SOMS framework. Finally, comparing ion exchange properties of a SOMS material with minimal (2%) Ti to a SOMS material with maximum (20%) Ti revealed the divalent cation selectivity of these materials which was reported previously is a function of the M(IV) substitution in the framework. A thorough investigation of this class of SOMS materials has revealed the importance of understanding the influence of heterovalent substitutions in microporous frameworks on material properties.