Publications

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Continued exploration of the coordination behavior of derivatives of 2-benzophenone-based ligands with metal alkoxides ([M(OR)4]) was undertaken from the reaction of 2-(2-hydroxy-4-methoxybenzoyl)benzoic acid (H2-OBzA) with a series of Group 4 precursors. The products of these reactions were identified as: [(OR)2Ti(-(c,c-OBzA))]2 (OR = OCHMe2 (OPri; 1 •2tol); OCMe3 (OBu t; 2 •THF); OCH2CMe3 (ONep; 3)), [[(OPri)3Ti(-OPri)Ti(OPri) 2]2(-(c,-OBzA))2]2 (4), [(ONep)3Zr(-ONep)2Zr(ONep)2] 2(-(c,-OBzA)2) (5 •tol), [(py)(OBut) 3Zr]2(-(c,c-OBzA)) (6), [(OBut) 2Hf(-OBut)]2(-(c,η1-OBzA)) (7) where c = chelating or η2; = bridging or η1, η1(O,O); and c = bridging chelating or η1,η1(O,O); η2: η1. The metal centers for each of these compounds adopt a pseudo-octahedral geometry employing the OBzA ligand in numerous binding modes. The different functional oxygens (carboxylate, hydroxyl, and carbonyl) were employed in a variety of coordination modes for 1-7. The complexity of these OBzA-modified compounds is driven by a combination of the coordination behavior of the OBzA moieties, the size of the metal cation, and the pendant chain of the OR ligand. Solution NMR indicates a complex structure exists in solution that was considered to be consistent with the solid-state structure. © 2014 Taylor & Francis.

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An evaluation of calcium tungsten oxide (CaWO4) nanoparticles' properties was conducted using the powders generated from an all-alkoxide solvothermal (SOLVO) route. The reaction involved a toluene/pyridine mixture of tungsten(V) ethoxide ([W(OEt)5]) with calcium bis(trimethyl silyl) amide ([Ca(N(Si(CH3)3)2]) modified in situ by a series of alcohols (H-OR) including neo-pentanol (H-OCH2C(CH 3)3 or H-ONep) or sterically varied aryl alcohols (H-OC6H3R2-2,6 where R = CH3 (H-DMP), CH(CH3)2 (H-DIP), C(CH3)3 (DBP))]. Attempts to identify the intermediates generated from this series of reactions led to the crystallographic identification of [(OEt) 4W(μ-OEt)2Ca(DBP)2] (1). Each different SOLVO generated "initial" powder was found by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD) to be nanomaterials roughly assigned as the scheelite phase (PDF 00-041-1431); however, these initial powders displayed no luminescent behavior as determined by photoluminescence (PL) measurements. Thermal processing of these powders at 450, 650, and 750 C yielded progressively larger and more crystalline scheelite nanoparticles. Both PL and cathodoluminescent (CL) emission (422-425 and 429 nm, respectively) were observed for the nanomaterials processed at 750 C. Ion beam induced luminescence (IBIL, 478 nm) appeared to be in agreement with these PL and CL measurements. Further processing of the materials at 1000 C, led to a coalescence of the particles and significant improvement in the observed PL (445 nm) and CL measurements; however, the IBIL spectrum of this material was significantly altered upon exposure. These data suggest that the smaller nanoparticles were more stable to radiation effects possibly due to the lack of energy deposits based on the short track length; whereas the larger particles appear to suffer from radiation induced structural defects. © 2013 American Chemical Society.

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As alternative energy generating devices (i.e., solar, wind, etc) are added onto the electrical energy grid (AC grid), irregularities in the available electricity due to natural occurrences (i.e., clouds reducing solar input or wind burst increasing wind powered turbines) will be dramatically increased. Due to their almost instantaneous response, modern flywheel-based energy storage devices can act a mechanical mechanism to regulate the AC grid; however, improved spin speeds will be required to meet the necessary energy levels to balance these green energy variances. Focusing on composite flywheels, we have investigated methods for improving the spin speeds based on materials needs. The so-called composite flywheels are composed of carbon fiber (C-fiber), glass fiber, and a glue (resin) to hold them together. For this effort, we have focused on the addition of fillers to the resin in order to improve its properties. Based on the high loads required for standard meso-sized fillers, this project investigated the utility of ceramic nanofillers since they can be added at very low load levels due to their high surface area. The impact that TiO2 nanowires had on the final strength of the flywheel material was determined by a three-point-bend test. The results of the introduction of nanomaterials demonstrated an increase in strength of the flywheels C-fiber-resin moiety, with an upper limit of a 30% increase being reported. An analysis of the economic impact concerning the utilization of the nanowires was undertaken and after accounting for new-technology and additional production costs, return on improved-nanocomposite investment was approximated at 4-6% per year over the 20-year expected service life. Further, it was determined based on the 30% improvement in strength, this change may enable a 20-30% reduction in flywheel energy storage cost ($/kW-h).

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This report addresses recent developments concerning the identification and handling of potential peroxide forming (PPF) and peroxide yielded derivative (PYD) chemicals. PPF chemicals are described in terms of labeling, shelf lives, and safe handling requirements as required at SNL. The general peroxide chemistry concerning formation, prevention, and identification is cursorily presented to give some perspective to the generation of peroxides. The procedure for determining peroxide concentrations and the proper disposal methods established by the Hazardous Waste Handling Facility are also provided. Techniques such as neutralization and dilution are provided for the safe handling of any PYD chemicals to allow for safe handling. The appendices are a collection of all available SNL documentation pertaining to PPF/PYD chemicals to serve as a single reference.

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The first step in an attempt to isolate Sc° from a W° crucible was explored by soaking the samples in a series of organic (HOAc) and inorganic (HCl, H₂SO₄, H₃PO₄, HNO₃) acids. All samples, except the HOAc, yielded a powder. The weight loss suggests that HNO₃ is the most efficient solvent; however, the powders were tentatively identified by PXRD and found to contain both W and Sc by-products. The higher weight loss may also indicate dissolution of the Wo crucible, which was further evidenced upon visual inspection of the crucible. The H₃PO₄ acid soak yielded the cleanest removal of Sc from the crucible. More work to understand the separation of the Sc° from the W° crucible is necessary but the acid routes appear to hold promise under not as of yet established criteria.

Scintillating nanomaterials are being investigated as replacements for fragile, difficult to synthesize single crystal radiation detectors, but greater insight into their structural stability when exposed to extreme environments is needed to determine long-term performance. An initial study using high-Z cadmium tungstate (CdWO4) nanorods and an in-situ ion irradiation transmission electron microscope (I3TEM) was performed to determine the feasibility of these extreme environment experiments. The I3TEM presents a unique capability that permits the real time characterization of nanostructures exposed to various types of ion irradiation. In this work, we investigated the structural evolution of CdWO4 nanorods exposed to 50 nA of 3 MeV copper (3+) ions. During the first several minutes of exposure, the nanorods underwent significant structural evolution. This appears to occur in two steps where the nanorods are first segmented into smaller sections followed by the sintering of adjacent particles into larger nanostructures. An additional study combined in-situ ion irradiation with electron tomography to record tilt series after each irradiation dose; which were then processed into 3D reconstructions to show radiation damage to the material over time. Analyses to understand the mechanisms and structure-property relationships involved are ongoing. © 2012 SPIE.

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During this task, Silane functionalized TiO2 and HK3Ti4O4(SiO4)3 were sent to Goodyear (GY) for testing. These materials were characterized based on their interaction with the model elastomer, squalene. The Van der Waals interactions and Hamaker Constants for ZnO particles in squalene and rubber materials were characterized and it was determined that a 10-20 nm spacing was necessary between primary filler particles to maintain a stable nanocomposite. Contact angle measurements on the ZnO and ZnO-silane materials indicated that the solvent should wet the particles, and solvophobic attractions should not be present. These studies showed that the surface modification with sulfosilane coupling agents was successful, and high levels of dispersion of the particles remained possible. Further, a novel surface charging phenomenon where negative surface charging is developed in the squalene environment was observed and corroborated by measurements of particle size and of the surface modified materials in squalene. This impacts the dispersion of the particles according to the traditional colloidal interpretation of electrostatic repulsive forces between particles. Additionally, thin nanocomposite fibers were developed using electrospinning. The size and shape of the oxides did not change during the electrospinning process, although the shape of the fiber and the distribution of the particles, particularly for ZnO, was not ideal. There was an obvious increase in elastic modulus and hardness from the addition of the oxides, but differentiating the oxides, and particularly the surfactants, was difficult. The A-1289 lead to the greatest dispersion of the filler particles, while the A-1589 and the NXT produced clustered particle aggregates. This agrees with previous study of these materials in low molecular weight squalene solvent studies reported earlier. The behavior of the nanoparticle ZnO and the microparticle silica is different as well, with the ZnO being contained within the elastomer, and the SiO2 forming monolayers at the surface of the elastomer. The dynamic mechanical analysis did not show clear trends between the surface modification and the aggregate structure. In the silica particles, the NXT led to the least particle interaction, followed by the A-1289 and highest particle interaction found for the A-1589. For the nanosized ZnO, the best dispersion was found for the A-1589, with both the A-1289 and NXT exhibiting frequency dependent responses.

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A heteroleptic titanium metal alkoxide (OPy){sub 2}Ti(4MP){sub 2}, where OPy = NC{sub 5}H{sub 4}(CH{sub 2}O)-2 and 4MP = OC{sub 6}H{sub 4}(SH)-4, was investigated as a candidate precursor for the solution-based (sol-gel) synthesis of titanium oxide via the photoactivation of intermolecular linking reactions (e.g., hydrolysis/condensation). The evolution of the electronic structure of the solution-based molecule arising from conventional (dark) chemical reaction kinetics was compared with that of samples exposed to ultraviolet (UV) radiation at wavelengths of {lambda} = 337.1 nm and 405 nm using UV-visible absorption spectroscopy. Photoinduced changes in the spectra were examined as a function of both the incident wavelength of exposure and the total fluence. Experimental results confirm the UV-induced modification of spectral absorption features, attributed to ligand-localized and charge transfer transitions accompanied by structural changes associated with hydrolysis and condensation. The photoenhancement of reaction kinetics in these processes was confirmed by the increased modification of the absorption features in the solution spectra, which saturated more rapidly under UV-illumination than under dark conditions. Similar saturation behaviors were observed for both the 337.1 nm and the 405 nm incident wavelengths with the same total deposited energy density indicating a relative insensitivity of the photoinduced response to excitation energy for the wavelengths and fluences studied.

This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver the sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr{sub 3} ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr{sub 3} is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable.

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The global market for wireless sensor networks in 2010 will be valued close to $10 B, or 200 M units. TPL, Inc. is a small Albuquerque based business that has positioned itself to be a leader in providing uninterruptible power supplies in this growing market with projected revenues expected to exceed $26 M in 5 years. This project focused on improving TPL, Inc.'s patent-pending EnerPak{trademark} device which converts small amounts of energy from the environment (e.g., vibrations, light or temperature differences) into electrical energy that can be used to charge small energy storage devices. A critical component of the EnerPak{trademark} is the supercapacitor that handles high power delivery for wireless communications; however, optimization and miniaturization of this critical component is required. This proposal aimed to produce prototype microsupercapacitors through the integration of novel materials and fabrication processes developed at New Mexico Technology Research Collaborative (NMTRC) member institutions. In particular, we focused on developing novel ruthenium oxide nanomaterials and placed them into carbon supports to significantly increase the energy density of the supercapacitor. These improvements were expected to reduce maintenance costs and expand the utility of the TPL, Inc.'s device, enabling New Mexico to become the leader in the growing global wireless power supply market. By dominating this niche, new customers were expected to be attracted to TPL, Inc. yielding new technical opportunities and increased job opportunities for New Mexico.

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A specially designed specimen holder employing a beryllium dome has been fabricated for collection of X-ray diffraction (XRD) data from highly reactive materials. The specimen holder has a robust O-ring type seal (< 10-9 Torr) and no observed intensity artifacts in the 1° to 150° 2θ range. The design also minimizes specimen displacement errors and allows for analysis of both powders and bulk specimens (i.e., pellets). The simple design makes for straightforward assembly of the holder within the confines of a glove box. XRD analysis of hygroscopic LaBr3 powders collected with this holder are suitable for Rietveld structure refinement, yielding unit cell lattice parameters of a=7.9703(6) Å and c=4.5122(6) Å cell volume= 248.44(6) Å3; Rp =7.70%. © 2008 International Centre for Diffraction Data.

The CSI: Dognapping Workshop is a culmination of the more than 65 Sandian staff and intern volunteers dedication to exciting and encouraging the next generation of scientific leaders. This 2 hour workshop used a 'theatrical play' and 'hands on' activities that was fun, exciting and challenging for 3rd-5th graders while meeting science curriculum standards. In addition, new pedagogical methods were developed in order to introduce nanotechnology to the public. Survey analysis indicated that the workshop had an overall improvement and positive impact on helping the students to understand concepts from materials science and chemistry as well as increased our interaction with the K-5 community. Anecdotal analyses showed that this simple exercise will have far reaching impact with the results necessary to maintain the United States as the scientific leader in the world. This experience led to the initiation of over 100 Official Junior Scientists.

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The formation of 10-nm ZnO nanopyramids using a simple synthetic route has been isolated from the reaction of Zn(OAc)2·2H2O in 1,4-butanediol followed by ripening at 90°C. This was accomplished by establishing control over the Ostwald ripening process through the use of a carboxylic acid specific adsorbate. Using a variety of analytical methods, it is proposed that the carboxylate groups in the acetate precursor stabilize the {101} habit planes, creating septahedral shapes or nanopyramids. Particle assembly into crystallographically oriented dimers was observed with high specificity, and the association mechanism is suggested to relate to the crystal polarity and the variation in specific adsorption of the carboxylic acid to the surface facets. These materials are a candidate for biological labeling applications in living cells.

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Anhydrous cerium bromide (CeBr3) and cerium doped lanthanum bromide (Ce+3-LaBr3) were obtained by the dehydration of hydrates synthesized by a direct acidification process. The dehydration process involves heating in vacuum through three phase changes - hydrate, amorphous, and crystalline LaBr3. Incomplete removal of the bound water leads to the formation of oxybromides and the partial reduction of the lanthanum at high temperatures. It was found that upon the completion of dehydration (< 200°C) a complete solid solution can be formed between LaBr3 and CeBr3. These two compounds form a simple binary phase diagram. Challenges associated with the dehydration process are discussed.

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A series of cerium alkoxides were synthesized from the reaction of Ce{N[Si(CH3)3]2}3 and the appropriate alcohol: neopentyl alcohol [H-OCH2C(CH3) 3 = H-ONep], tert-butyl alcohol [H-OC(CH3)3 = H-OtBu], o-(tert-butyl)phenol {H-OC6H4[C(CH 3)3]-2 = H-oBP), 2,6-dimethylphenol [H-OC 6H3(CH3)2-2,6 = H-DMP], 2,6-diisopropylphenol {H-OC6H3[CH(CH3) 2]2-2,6 = H-DIP}, 2,6-di-tert-butylphenol {H-OC 6H3[C(CH3)3]2-2,6 = H-DBP}, or 2,6-diphenylphenol [H-OC6H3(C6H 5)2-2,6 = H-DPP] using toluene (tol), tetrahydrofuran (THF) or pyridine (py). The precursors were characterized as [Ce(μ-ONep) 2(ONep)]4 (1), Ce4(μ3-OtBu) 3(μ-OtBu)4(OtBu)5 (2), Ce 3(μ3-OtBu)3(H-OtBu)2(OtBu) 3(H-OtBu)2 (2a), Ce(OBP)3(THF)3 (3), [Ce(μ-DMP)(DMP)2(solv)2]2 [solv = THF (4) and py (4a)], Ce(DIP)3(THF)3 (5), Ce(DPP) 3(THF)2 (6). Once isolated, several of these species were further reacted with a series of sterically varied carboxylic acid modifiers including isobutyric acid [H-O2CCH(CH3)2 = H-OPc] and trimethylacetic acid [H-O2CC(CH3)3 = H-OBc]. The products were isolated as [Ce(OR)(μ-ORc)(μc-ORc) (py)]2 [OR = oBP, OBc: 7; DMP, OPc: 8; DMP, OBc: 9; DIP, OPc: 10]. These compounds were identified by single-crystal X-ray diffraction and powder XRD analyses. Several novel structure types are added to the cerium alkoxide family of compounds. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

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