In Situ Observation of Calcium Aluminate Inclusions Dissolution into Steelmaking Slag

NASA Astrophysics Data System (ADS)

Miao, Keyan; Haas, Alyssa; Sharma, Mukesh; Mu, Wangzhong; Dogan, Neslihan

2018-06-01

The dissolution rate of calcium aluminate inclusions in CaO-SiO2-Al2O3 slags has been studied using confocal scanning laser microscopy (CSLM) at elevated temperatures: 1773 K, 1823 K, and 1873 K (1500 °C, 1550 °C, and 1600 °C). The inclusion particles used in this experimental work were produced in our laboratory and their production technique is explained in detail. Even though the particles had irregular shapes, there was no rotation observed. Further, the total dissolution time decreased with increasing temperature and decreasing SiO2 content in the slag. The rate limiting steps are discussed in terms of shrinking core models and diffusion into a stagnant fluid model. It is shown that the rate limiting step for dissolution is mass transfer in the slag at 1823 K and 1873 K (1550 °C and 1600 °C). Further investigations are required to determine the dissolution mechanism at 1773 K (1500 °C). The calculated diffusion coefficients were inversely proportional to the slag viscosity and the obtained values for the systems studied ranged between 5.64 × 10-12 and 5.8 × 10-10 m2/s.

Process for removing sulfur from sulfur-containing gases: high calcium fly-ash

DOEpatents

Rochelle, Gary T.; Chang, John C. S.

1991-01-01

The present disclosure relates to improved processes for treating hot sulfur-containing flue gas to remove sulfur therefrom. Processes in accordance with the present invention include preparing an aqueous slurry composed of a calcium alkali source and a source of reactive silica and/or alumina, heating the slurry to above-ambient temperatures for a period of time in order to facilitate the formation of sulfur-absorbing calcium silicates or aluminates, and treating the gas with the heat-treated slurry components. Examples disclosed herein demonstrate the utility of these processes in achieving improved sulfur-absorbing capabilities. Additionally, disclosure is provided which illustrates preferred configurations for employing the present processes both as a dry sorbent injection and for use in conjunction with a spray dryer and/or bagfilter. Retrofit application to existing systems is also addressed.

The influence of high temperatures on selected properties of calcium aluminous composites

NASA Astrophysics Data System (ADS)

KoÅáková, Dana; KoÅ¥átková, Jaroslava; Čáchová, Monika; Vejmelková, Eva; Čechmánek, René; Reiterman, Pavel; Černý, Robert

2017-07-01

The article compares different types of aluminate cements with the reference Portland cement, used in refractory composites. The rate of influence of elevated temperatures (400 °C and 1000 °C) is studied. The investigated parameters are basic physical characteristics and mechanical properties. Results show the best behaviour of the mixture containing Portland cement for the reference state (in the means of all studied parameters); which however after exposition to 1000 °C has the worst performance. Both aluminate cements behave better after heating, which proves its suitability for refractory composites. It is concluded, that the mixture with Gorkal cement achieves the best results.

Phase relations of aluminous silica to 120 GPa and lowermost mantle dynamics

NASA Astrophysics Data System (ADS)

Tronnes, R. G.; Andrault, D.; Konopkova, Z.; Morgenroth, W.; Liermann, H.-P.

2012-04-01

Al-content. Due to the presence of the Al-rich Ca-ferrite phase (near the MgAl2O4-NaAlSiO4-join) in natural basaltic compositions, the Al-solubility limits for the silica-dominated phases in basaltic lithologies may be similar to those in the binary system SiO2-AlO1.5. Phase transitions in response to increasing pressure are generally associated with densification. Because of the strong partitioning of light and voluminous AlO1.5 into seifertite, however, the densification effect is more than offset by the lighter alumina component. The unit cell data of ref. [1] indicate a volume increase of about 3.8% associated with the transition. The associated density reduction would be strongly dependent on the substitution mechanism. O-vacancy and cation (3Si4+ → 4Al3+) substitutions yield density reductions of 5.4% and 1.9%, respectively [1]. The large density reduction accompanying the seifertite transition may limit the role of gravitational accretion of evolved MORB to the LLSVPs. Segregation of Fe-rich picritic, komatiitic or peridotitic rocks with no separate silica phase may be more likely. Deep-mantle cumulates and solidified melts of peridotitic to komatiitic composition were mostly produced in the Hadean and early Archean, indicating that the antipodal and near-equatorial LLSVPs, stabilized by Earth's rotation, could also represent ancient structures.

Hydration of Portland cement with additions of calcium sulfoaluminates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Saout, Gwenn, E-mail: gwenn.le-saout@mines-ales.fr; Lothenbach, Barbara; Hori, Akihiro

2013-01-15

The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C-S-H has amore » similar composition as in OPC with no additional Al to Si substitution. As in CSA-OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.« less

Synthesis of nano grade hollow silica sphere via a soft template method.

PubMed

Tsai, Ming-Shyong; Li, Miao Ju; Yen, Fu-Hsu

2008-06-01

The nano grade hollow silica sphere (HSS) was synthesized by a novel soft template method. We found that the precipitate of aluminate had a porous structure that could be the soft template for HSS. After mixing the colloidal silica with the aluminate precipitate, the bubble trapped in this porous structure could form the nano grade HSS. The aluminate precipitate was removed by adjusting the pH of the slurry to approximately 1. The outside diameter, the specific surface, and the mean pore size diameter of the forming HSS were 60-90 nm, 571 m2/g, and 3 nm, respectively. The formed HSS was collected by modifying the surface with Si(OCH3)3CHCH2 (VTMO) and then filtrating the precipitated gel in the n-butanol and ethanol solvent system.

Cell behavior of human mesenchymal stromal cells in response to silica/collagen based xerogels and calcium deficient culture conditions.

PubMed

Wagner, Alena-Svenja; Glenske, Kristina; Henß, Anja; Kruppke, Benjamin; Rößler, Sina; Hanke, Thomas; Moritz, Andreas; Rohnke, Marcus; Kressin, Monika; Arnhold, Stefan; Schnettler, Reinhard; Wenisch, Sabine

2017-07-04

Herein, we aim to elucidate osteogenic effects of two silica-based xerogels with different degrees of bioactivity on human bone-derived mesenchymal stromal cells by means of scanning electron microscopy, quantitative PCR enhanced osteogenic effects and the formation of an extracellular matrix which could be ascribed to the sample with lower bioactivity. Given the high levels of bioactivity, the cells revealed remarkable sensitivity to extremely low calcium levels of the media. Therefore, additional experiments were performed to elucidate cell behavior under calcium deficient conditions. The results refer to capacity of the bone-derived stromal cells to overcome calcium deficiency even though proliferation, migration and osteogenic differentiation capabilities were diminished. One reason for the differences of the cellular response (on tissue culture plates versus xerogels) to calcium deficiency seems to be the positive effect of silica. The silica could be detected intracellularly as shown by time of flight-secondary ion mass spectrometry after cultivation of primary cells for 21 days on the surfaces of the xerogels. Thus, the present findings refer to different osteogenic differentiation potentials of the xerogels according to the different degrees of bioactivity, and to the role of silica as a stimulator of osteogenesis. Finally, the observed pattern of connexin-based hemichannel gating supports the assumption that connexin 43 is a key factor for calcium-mediated osteogenesis in bone-derived mesenchymal stromal cells.

Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

NASA Astrophysics Data System (ADS)

Bouhadja, M.; Jakse, N.; Pasturel, A.

2014-06-01

Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al2O3)1-x(SiO2)x, glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO5 structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution of the glass-transition temperature as well as of the fragility as a function of silica content along the three joins.

Synthesis of silver-containing calcium aluminate particles and their effects on a MTA-based endodontic sealer.

PubMed

Almeida, Luiza Helena S; Moraes, Rafael R; Morgental, Renata D; Cava, Sérgio S; Rosa, Wellington Luiz O; Rodrigues, Patrícia; Ribeiro, Anderson S; Só, Marcus; Pappen, Fernanda G

2018-05-19

To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A+Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer. Pure C3A and C3A+Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P<0.05). The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A+Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca +2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag. The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Capping a Pulpotomy with Calcium Aluminosilicate Cement: Comparison to Mineral Trioxide Aggregates

PubMed Central

Kramer, Phillip R.; Woodmansey, Karl F.; White, Robert; Primus, Carolyn M.; Opperman, Lynne A.

2014-01-01

Introduction Calcium aluminate cements have shown little affinity for bacterial growth, low toxicity, and immunogenicity when used as a restoration material, but calcium aluminate cements have not been tested in vivo in pulpotomy procedures. Methods To address this question, a calcium aluminate cement (Quick-Set) was tested along with 2 mineral trioxide aggregates, ProRoot MTA and MTA Plus. These cements were used as a capping agent after pulpotomy. Control rats had no pulpotomy, or the pulpotomy was not capped. Proinflammatory cytokines interleukin (IL)-1β and IL-1α were measured, and histology was performed at 30 and 60 days after capping. The nociceptive response was determined by measuring the lengthening of the rat's meal duration. Results and Conclusions: IL-1β and IL-1α concentrations were reduced in the capped teeth, but no differences were observed among the 3 cements. Dentinal bridging could be detected at both 30 and 60 days with each of the 3 cements, and the pulps were still vital 60 days after capping. Meal duration significantly shortened after placement of the 3 different cements, indicating a nociceptive response, but there were no differences among the materials. Calcium aluminate cements had similar properties to mineral trioxide aggregates and is a viable option for pulpotomy procedures. PMID:25146026

DNA adsorption onto glass surfaces

NASA Astrophysics Data System (ADS)

Carlson, Krista Lynn

Streaming potential measurements were performed on microspheres of silica, lime silicate (SLS) and calcium aluminate (CA) glasses containing silica and iron oxide (CASi and CAFe). The silicate based glasses exhibited acidic surfaces with isoelectric points (IEP) around a pH of 3 while the calcium aluminates displayed more basic surfaces with IEP ranging from 8--9.5. The surface of the calcium aluminate microspheres containing silica reacted with the background electrolyte, altering the measured zeta potential values and inhibiting electrolyte flow past the sample at ˜ pH 4 due to formation of a solid plug. DNA adsorption experiments were performed using the microspheres and a commercially available silicate based DNA isolation filter using a known quantity of DNA suspended in a chaotropic agent free 0.35 wt% Tris(hydroxymethyl)aminomethane (Tris) buffer solution. The microspheres and commercial filter were also used to isolate DNA from macrophage cells in the presence of chaotropic agents. UV absorbance at ˜260 nm and gel electrophoresis were used to quantify the amount and size of the DNA strands that adsorbed to the microsphere surfaces. In both experiments, the 43--106 microm CAFe microspheres adsorbed the largest quantity of DNA. However, the 43--106 microm SLS microspheres isolated more DNA from the cells than the <43 microm CAFe microspheres, indicating that microsphere size contributes to isolation ability. The UV absorbance of DNA at ˜260 nm was slightly altered due to the dissolution of the calcium aluminate glasses during the adsorption process. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) determined that calcium and aluminum ions leached from the CA and CAFe microsphere surfaces during these experiments. Circular dichroism (CD) spectroscopy showed that the leached ions had no effect on the conformation of the DNA, and therefore would not be expected to interfere in downstream applications such as DNA replication. The 0.35 wt

Striking role of non-bridging oxygen on glass transition temperature of calcium aluminosilicate glass-formers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouhadja, M.; Jakse, N.; Pasturel, A.

2014-06-21

Molecular dynamics simulations are used to study the structural and dynamic properties of calcium aluminosilicate, (CaO-Al{sub 2}O{sub 3}){sub 1−x}(SiO{sub 2}){sub x}, glass formers along three joins, namely, R = 1, 1.57, and 3, in which the silica content x can vary from 0 to 1. For all compositions, we determined the glass-transition temperature, the abundances of the non-bridging oxygen, triclusters, and AlO{sub 5} structural units, as well as the fragility from the temperature evolution of the α-relaxation times. We clearly evidence the role played by the non-bridging oxygen linked either to Al atoms or Si atoms in the evolution ofmore » the glass-transition temperature as well as of the fragility as a function of silica content along the three joins.« less

Calcium aluminates hydration in presence of amorphous SiO{sub 2} at temperatures below 90 deg. C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivas Mercury, J.M.; Turrillas, X.; Aza, A.H. de

2006-10-15

The hydration behaviour of Ca{sub 3}Al{sub 2}O{sub 6}, Ca{sub 12}Al{sub 14}O{sub 33} and CaAl{sub 2}O{sub 4} with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-} {sub x} (OH){sub 4} {sub x} ) and gibbsite, Al(OH){sub 3}, were identified, likewise amorphous phases like Al(OH) {sub x} , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-} {sub x} (OH){sub 4} {sub x} (0{<=}3-x{<=}0.334), which was themore » main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca{sub 3}Al{sub 2}(SiO{sub 4}){sub 3-} {sub x} (OH){sub 4} {sub x} (0{<=}3-x{<=}0.334), was identified besides gibbsite, Al(OH){sub 3}, as a crystalline stable hydration products in Ca{sub 3}Al{sub 2}O{sub 6}, Ca{sub 12}Al{sub 14}O{sub 33} and CaAl{sub 2}O{sub 4} hydrated with added amorphous silica between 40 and 90 deg. C.« less

Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

NASA Astrophysics Data System (ADS)

Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

Model of Inclusion Evolution During Calcium Treatment in the Ladle Furnace

NASA Astrophysics Data System (ADS)

Tabatabaei, Yousef; Coley, Kenneth S.; Irons, Gordon A.; Sun, Stanley

2018-04-01

Calcium treatment of steel is typically employed to modify alumina inclusions to liquid calcium aluminates. However, injected calcium also reacts with the dissolved sulfur to form calcium sulfide. The current work aims to develop a kinetic model for the evolution of oxide and sulfide inclusions in Al-killed alloyed steel during Ca treatment in the ladle refining process. The model considers dissolution of the calcium from the calcium bubbles into the steel and reduction of calcium oxide in the slag to dissolved calcium. A steel-inclusion kinetic model is used for mass transfer to the inclusion interface and diffusion within the calcium aluminate phases formed on the inclusion. The inclusion-steel kinetic model is then coupled with a previously developed steel-slag kinetic model. The coupled inclusion-steel-slag kinetic model is applied to the chemical composition changes in molten steel, slag, and evolution of inclusions in the ladle. The result of calculations is found to agree well with an industrial heat for species in the steel as well as inclusions during Ca treatment.

Studies on sintering additives for hydroxyapatite, and controlled porosity structures of calcium aluminates and polypropylene-tricalcium phosphate for bone graft applications

NASA Astrophysics Data System (ADS)

Kalita, Samar Jyoti

Tissue engineering has made a significant contribution in developing new biomaterials that can restore the structural features and physiological functions of natural tissues. Various materials, such as metals, ceramics, polymers and composites have been developed for their use in hard tissue engineering applications. Part A of this thesis describes my research on HAp ceramics. HAp, a bioactive ceramic, is known for its osteoconductivity, but shows poor mechanical performance. This program aimed at improving mechanical performance of synthetic HAp by introducing small quantities of various sintering additives. A range of oxide-based sintering additives were selected and prepared. Dense compacts were prepared using a uniaxial press with an average green density of 1.6 g/cc. Results showed that some of these sintering additives improved densification, hardness and compression strength of synthetic HAp compared to the pure composition. A maximum bulk density of 3.06 g/cc was achieved for 2.5 wt% addition of MgO. A Microhardness of 4.9 GPa (505 HV) was measured for 2.5 wt% addition of BaO, and the highest compression strength (220MPa) was reported for 2.5 wt% addition of CaO. Cytotoxicity and cell proliferation studies with a modified human osteoblast (HOB) cell-line (OPC1) proved most of these materials non-toxic and biocompatible. Microscopic observation revealed that bone cells were attached and grew well on most of these ceramic matrices. Part B describes my work on development of controlled porosity polypropylene-tricalcium phosphate composite scaffolds via the fused deposition modeling (FDM) process. Hg-porosimetry was performed to determine pore size and their distribution. Uniaxial compression testing performed on samples with 36 vol% porosity and pore size of 160 mum showed the best compressive strength of 12.7 MPa. Part C includes my research on development of "3-D honeycomb" porous calcium aluminate structures via the indirect FDM process. Samples of 29% and

Nanofiltration Results: Membrane Removal of Calcium, Magnesium, Sodium, Silica, Lithium, Chlorine, and Sulfate from Simulated Geothermal Brines

DOE Data Explorer

Jay Renew

2016-02-06

Results from a nanofiltration study utilizing simulated geothermal brines. The data includes a PDF documenting the process used to remove Calcium, Magnesium, Sodium, Silica, Lithium, Chlorine, and Sulfate from simulated geothermal brines. Three different membranes were evaluated. The results were analyzed using inductively coupled plasma mass spectrometry (ICP-MS).

Novel mechanism for the modification of Al2O3-based inclusions in ultra-low carbon Al-killed steel considering the effects of magnesium and calcium

NASA Astrophysics Data System (ADS)

Guo, Jing; Cheng, Shu-sen; Guo, Han-jie; Mei, Ya-guang

2018-03-01

Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al2O3-based inclusions during secondary refining. The results showed that Al2O3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO-MgO-Al2O3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3wt% and the temperature is higher than 1843 K.

Structure of liquid tricalcium aluminate

NASA Astrophysics Data System (ADS)

Drewitt, James W. E.; Barnes, Adrian C.; Jahn, Sandro; Kohn, Simon C.; Walter, Michael J.; Novikov, Alexey N.; Neuville, Daniel R.; Fischer, Henry E.; Hennet, Louis

2017-02-01

The atomic-scale structure of aerodynamically levitated and laser-heated liquid tricalcium aluminate (Ca3Al2O6 ) was measured at 2073(30) K by using the method of neutron diffraction with Ca isotope substitution (NDIS). The results enable the detailed resolution of the local coordination environment around calcium and aluminum atoms, including the direct determination of the liquid partial structure factor, SCaCa(Q ) , and partial pair distribution function, gCaCa(r ) . Molecular dynamics (MD) simulation and reverse Monte Carlo (RMC) refinement methods were employed to obtain a detailed atomistic model of the liquid structure. The composition Ca3Al2O6 lies at the CaO-rich limit of the CaO:Al2O3 glass-forming system. Our results show that, although significantly depolymerized, liquid Ca3Al2O6 is largely composed of AlO4 tetrahedra forming an infinite network with a slightly higher fraction of bridging oxygen atoms than expected for the composition. Calcium-centered polyhedra exhibit a wide distribution of four- to sevenfold coordinated sites, with higher coordinated calcium preferentially bonding to bridging oxygens. Analysis of the MD configuration reveals the presence of ˜10 % unconnected AlO4 monomers and Al2O7 dimers in the liquid. As the CaO concentration increases, the number of these isolated units increases, such that the upper value for the glass-forming composition of CaO:Al2O3 liquids could be described in terms of a percolation threshold at which the glass can no longer support the formation of an infinitely connected AlO4 network.

Kinetics of pack aluminization of nickel

NASA Technical Reports Server (NTRS)

Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

1978-01-01

The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye

2014-02-15

Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape.more » The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.« less

Chlordetect: Commercial Calcium Aluminate Based Conductimetric Sensor for Chloride Presence Detection

PubMed Central

Torres-Luque, Magda; Sánchez-Silva, Mauricio

2017-01-01

Chloride presence affects different environments (soil, water, concrete) decreasing their qualities. In order to assess chloride concentration this paper proposes a novel sensor for detecting and measuring it. This sensor is based on electric changes of commercial monocalcium aluminate (CA) when it interacts with chloride aqueous solutions. CA is used as a dielectric material between two coplanar capacitors. The geometry proposed for this sensor allows to assess the chloride content profile, or to make four times the same measurement. Besides, the experimental design gives us the possibility of study not just the chloride effect, but also the time and some geometric effects due to the sensor design. As a result, this sensor shows a limit of detection, sensitivity, and response time: 0.01 wt % Cl− and 0.06 wt % Cl−, and 2 min, respectively, comparable with other non invasive techniques as optical fibre sensors. PMID:28902147

Alkali Silica Reaction In The Presence Of Metakaolin - The Significant Role of Calcium Hydroxide

NASA Astrophysics Data System (ADS)

Zapała-Sławeta, Justyna

2017-10-01

Reducing the internal corrosion, which is the result of reactions between alkalis and reactive aggregates is especially important in ensuring durability properties of concrete. One of the methods of inhibiting the reaction is using some mineral additives which have pozzolanic properties. This paper presents the efficacy of high-reactivity metakaolin in reducing expansion due to alkali-silica reaction. It was demonstrated that metakaolin in the amount from 5% to 20% by mass of Portland cement reduce linear expansion of mortar bars with opal aggregate. Nevertheless, the safe expansion level in the specimens, classified as non-destructive to concrete, was recorded for the mortars prepared with 20% addition of metakaolin. Depletion of free calcium hydroxide content was considered as one of the most beneficial effects of metakaolin in controlling alkali silica reaction. Based on thermogravimetric analysis (TGA) performed on mortar bars with and without metakaolin the differences in portlandite content were determined. Microstructural observation of the specimens containing metakaolin indicated the presence of a reaction products but fewer in number than those forming in the mortars without mineral additives.

Prediction of the explosion effect of aluminized explosives

NASA Astrophysics Data System (ADS)

Zhang, Qi; Xiang, Cong; Liang, HuiMin

2013-05-01

We present an approach to predict the explosion load for aluminized explosives using a numerical calculation. A code to calculate the species of detonation products of high energy ingredients and those of the secondary reaction of aluminum and the detonation products, velocity of detonation, pressure, temperature and JWL parameters of aluminized explosives has been developed in this study. Through numerical calculations carried out with this code, the predicted JWL parameters for aluminized explosives have been compared with those measured by the cylinder test. The predicted JWL parameters with this code agree with those measured by the cylinder test. Furthermore, the load of explosion for the aluminized explosive was calculated using the numerical simulation by using the JWL equation of state. The loads of explosion for the aluminized explosive obtained using the predicted JWL parameters have been compared with those using the measured JWL parameters. Both of them are almost the same. The numerical results using the predicted JWL parameters show that the explosion air shock wave is the strongest when the mass fraction of aluminum powder in the explosive mixtures is 30%. This result agrees with the empirical data.

Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F

PubMed Central

Pyatina, Tatiana; Sugama, Toshifumi; Moon, Juhyuk; James, Simon

2016-01-01

An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. This work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersive X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm) and greater compressive strength after 300 °C curing. Mechanical properties of the set cements were not compromised by the retarder. PMID:28773543

Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F

DOE PAGES

Pyatina, Tatiana; Sugama, Toshifumi; Moon, Juhyuk; ...

2016-05-27

An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. Here, this work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersivemore » X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm) and greater compressive strength after 300 °C curing. Lastly, mechanical properties of the set cements were not compromised by the retarder.« less

Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F.

PubMed

Pyatina, Tatiana; Sugama, Toshifumi; Moon, Juhyuk; James, Simon

2016-05-27

An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. This work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersive X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm) and greater compressive strength after 300 °C curing. Mechanical properties of the set cements were not compromised by the retarder.

Reduction of calcium flux from the extracellular region and endoplasmic reticulum by amorphous nano-silica particles owing to carboxy group addition on their surface.

PubMed

Onodera, Akira; Yayama, Katsutoshi; Morosawa, Hideto; Ishii, Yukina; Tsutsumi, Yasuo; Kawai, Yuichi

2017-03-01

Several studies have reported that amorphous nano-silica particles (nano-SPs) modulate calcium flux, although the mechanism remains incompletely understood. We thus analyzed the relationship between calcium flux and particle surface properties and determined the calcium flux route. Treatment of Balb/c 3T3 fibroblasts with nano-SPs with a diameter of 70 nm (nSP70) increased cytosolic calcium concentration, but that with SPs with a diameter of 300 or 1000 nm did not. Surface modification of nSP70 with a carboxy group also did not modulate calcium flux. Pretreatment with a general calcium entry blocker almost completely suppressed calcium flux by nSP70. Preconditioning by emptying the endoplasmic reticulum (ER) calcium stores slightly suppressed calcium flux by nSP70. These results indicate that nSP70 mainly modulates calcium flux across plasma membrane calcium channels, with subsequent activation of the ER calcium pump, and that the potential of calcium flux by nano-SPs is determined by the particle surface charge.

On the kinetics of pack aluminization

NASA Technical Reports Server (NTRS)

Gupta, B. K.; Sarkhel, A. K.; Seigle, L. L.

1975-01-01

A theory of pack aluminization has been formulated by combining gaseous and solid-state diffusion rates. This theory relates the surface composition of the coating and therefore, in principle, the phase morphology and the growth rate of the coating, to pack operating parameters such as pack aluminum density, type of activator, temperature and others. Experimental data on the aluminization of unalloyed nickel in pure aluminum packs obtained to date are in good agreement with the predictions of the theory.

Effects of dietary ammonium chloride and variations in calcium to phosphorus ratio on silica urolithiasis in sheep.

PubMed

Stewart, S R; Emerick, R J; Pritchard, R H

1991-05-01

Ammonium chloride was added to diets varying in Ca content to evaluate its potential in preventing silica urolith formation in sheep. A 2 x 2 factorial experiment involved wether lambs with ad libitum access to a diet of 50% grass hay and 50% ground oats plus supplement. The basal diet contained on a DM basis 3.3% SiO2, .31% Ca, .22% P, 11.6% CP, and 26% ADF. Treatments (38 to 39 lambs/treatment) consisted of a control (C), limestone to increase dietary calcium to .6% (L), 1% ammonium chloride (A), and L + A (LA). After a 118-d experimental period, siliceous kidney deposits were found only in C and L, with silica making up 93% to 95% of the urolithic ash. Urolith incidences were 13% (C) and 18% (L), respectively. The lack of urolith development in lambs fed A and LA (ammonium chloride effect, P less than .01) and a trend toward a lower urolith incidence in C vs L (P less than .02) support the hypothesis that acid-forming effects of the diet and a reduction in the dietary Ca to P ratio reduce silica urolith formation.

Impact of welan gum on tricalcium aluminate-gypsum hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma Lei, E-mail: malei198713@163.com; Zhao Qinglin, E-mail: zhaoqinglin@whut.edu.cn; Yao Chukang

The retarding effect of welan gum on tricalcium aluminate-gypsum hydration, as a partial system of ordinary Portland cement (OPC) hydration, was investigated with several methods. The tricalcium aluminate-gypsum hydration behavior in the presence or absence of welan gum was researched by field emission gun scanning electron microscopy, X-ray diffraction and zeta potential analysis. Meanwhile, we studied the surface electrochemical properties and adsorption characteristics of welan gum by utilizing a zeta potential analyzer and UV-VIS absorption spectrophotometer. By adding welan gum, the morphology change of ettringite and retardation of hydration stages in tricalcium aluminate-gypsum system was observed. Moreover, we detected themore » adsorption behavior and zeta potential inversion of tricalcium aluminate and ettringite, as well as a rapid decrease in the zeta potential of tricalcium aluminate-gypsum system. The reduction on nucleation rate of ettringite and hydration activity of C{sub 3}A was also demonstrated. Thus, through the adsorption effect, welan gum induces a retarding behavior in tricalcium aluminate-gypsum hydration. Highlights: Black-Right-Pointing-Pointer Adsorption characteristics of welan gum on C{sub 3}A and ettringite have been studied. Black-Right-Pointing-Pointer C{sub 3}A-gypsum hydration behavior and the hydration products are examined in L/S = 3. Black-Right-Pointing-Pointer Welan gum retards the process of C{sub 3}A-gypsum hydration. Black-Right-Pointing-Pointer The addition of welan gum changes the nucleation growth of ettringite.« less

Duplex aluminized coatings

NASA Technical Reports Server (NTRS)

Gedwill, M. A.; Grisaffe, S. J. (Inventor)

1975-01-01

The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses.

PubMed

López-Delgado, Aurora; Tayibi, Hanan; Pérez, Carlos; Alguacil, Francisco José; López, Félix Antonio

2009-06-15

A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO-Al(2)O(3)-SiO(2) system at 1500 degrees C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H(2), NH(3), CH(4), H(2)S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al(2)O(3) ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62GPa and the linear thermal expansion coefficient, alpha, varied between (62 and 139)x10(-7)K(-1). Several glasses showed a high hydrolytic resistance in deionised water at 98 degrees C.

Possibilities of using aluminate cements in high-rise construction

NASA Astrophysics Data System (ADS)

Kaddo, Maria

2018-03-01

The article describes preferable ways of usage of alternative binders for high-rise construction based on aluminate cements. Possible areas of rational use of aluminate cements with the purpose of increasing the service life of materials and the adequacy of the durability of materials with the required durability of the building are analyzed. The results of the structure, shrinkage and physical and mechanical properties of concrete obtained from dry mixes on the base of aluminate cements for self-leveling floors are presented. To study the shrinkage mechanism of curing binders and to evaluate the role of evaporation of water in the development of shrinkage was undertaken experiment with simple unfilled systems: gypsum binder, portland cement and «corrosion resistant high alumina cement + gypsum». Principle possibility of binder with compensated shrinkage based on aluminate cement, gypsum and modern superplasticizers was defined, as well as cracking resistance and corrosion resistance provide durability of the composition.

Releasing effects in flame photometry: Determination of calcium

USGS Publications Warehouse

Dinnin, J.I.

1960-01-01

Strontium, lanthanum, neodymium, samarium, and yttrium completely release the flame emission of calcium from the depressive effects of sulfate, phosphate, and aluminate. Magnesium, beryllium, barium, and scandium release most of the calcium emission. These cations, when present in high concentration, preferentially form compounds with the depressing anions when the solution is evaporated rapidly in the flame. The mechanism of the interference and releasing effects is explained on the basis of the chemical equilibria in the evaporating droplets of solution and is shown to depend upon the nature of the compounds present in the aqueous phase of the solution. The need for background correction techniques is stressed. The releasing effect is used in the determination of calcium in silicate rocks without the need for separations.

Calcium silicate hydrates: Solid and liquid phase composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lothenbach, Barbara, E-mail: Barbara.lothenbach@empa.ch; Nonat, André

This paper presents a review on the relationship between the composition, the structure and the solution in which calcium silicate hydrate (C–S–H) is equilibrated. The silica chain length in C–S–H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space, preferentially at low calcium concentrations and thus by low Ca/Si C–S–H. Aluminium uptake in C–S–H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si, aluminium substitutes silica in the bridging position, at Ca/Si > 1 aluminium is bound in TAH.more » Recently developed thermodynamic models are closely related to the structure of C–S–H and tobermorite, and able to model not only the solubility and the chemical composition of the C–S–H, but also to predict the mean silica chain length and the uptake of aluminium.« less

Eigenvalue Detonation of Combined Effects Aluminized Explosives

NASA Astrophysics Data System (ADS)

Capellos, C.; Baker, E. L.; Nicolich, S.; Balas, W.; Pincay, J.; Stiel, L. I.

2007-12-01

Theory and performance for recently developed combined—effects aluminized explosives are presented. Our recently developed combined-effects aluminized explosives (PAX-29C, PAX-30, PAX-42) are capable of achieving excellent metal pushing, as well as high blast energies. Metal pushing capability refers to the early volume expansion work produced during the first few volume expansions associated with cylinder and wall velocities and Gurney energies. Eigenvalue detonation explains the observed detonation states achieved by these combined effects explosives. Cylinder expansion data and thermochemical calculations (JAGUAR and CHEETAH) verify the eigenvalue detonation behavior.

Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orosco, Pablo, E-mail: porosco@unsl.edu.ar; Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis Chacabuco y Pedernera, San Luis; Barbosa, Lucía

2014-11-15

Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl{sub 2}–N{sub 2} flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al{sub 2}O{sub 3} (alumina) in chlorine atmosphere was developed and the results were compared with thosemore » obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl{sub 2} atmosphere of the MgO–Al{sub 2}O{sub 3} mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C.« less

The Management of Silica in Los Alamos National Laboratory Tap Water - A Study of Silica Solubility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wohlberg, C.; Worland, V.P.; Kozubal, M.A.

1999-07-01

Well water at Los Alamos National Laboratory (LANL) has a silica (SiO{sub 2}) content of 60 to 100 mg/L, with 4 mg/L of magnesium, 13 mg/L calcium and lesser concentrations of other ions. On evaporation in cooling towers, when the silica concentration reaches 150 to 220 mg/L, silica deposits on heat transfer surfaces. When the high silica well water is used in the reprocessing of plutonium, silica remains in solution at the end of the process and creates a problem of removal from the effluent prior to discharge or evaporation. The work described in this Report is divided into twomore » major parts. The first part describes the behavior of silica when the water is evaporated at various conditions of pH and in the presence of different classes of anions: inorganic and organic. In the second part of this work it was found that precipitation (floccing) of silica was a function of solution pH and mole ratio of metal to silica.« less

The influence of pozzolanic materials on the mechanical stability of aluminous cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collepardi, M.; Monosi, S.; Piccioli, P.

1995-07-01

High alumina cement is particularly suitable for manufacturing sulphate resistant concretes and in particular cement mixes which are able resist the sear water aggression. High alumina cement paste, in the presence of silica fume, shows an increasing strength trend even at 20 C and 40 C, since this pozzolan causes the formation of gehlenite hydrate (C{sub 2}ASH{sub 8}) and therefore strongly reduces the transformation of hexagonal aluminate hydrates (CAH{sub 10}, C{sub 2}AH{sub 8}) into the cubic hydrate (C{sub 3}AH{sub 6}) which is responsible for the strength loss of high-alumina cement mixes at higher temperatures (>20 C). On the contrary, flymore » ash is not suitable for reducing the transformation of hexagonal hydrates into the cubic phase. Consequently, the strength at 20 C and 40 C of the fly ash-high alumina cement mixes decrease as well as the high alumina cement pastes in the absence of pozzolan.« less

Method of processing aluminous ores

DOEpatents

Loutfy, Raouf O.; Keller, Rudolf; Yao, Neng-Ping

1981-01-01

A method of producing aluminum chloride from aluminous materials containing compounds of iron, titanium and silicon comprising reacting the aluminous materials with carbon and a chlorine-containing gas at a temperature of about 900.degree. K. to form a gaseous mixture containing chlorides of aluminum, iron, titanium and silicon and oxides of carbon; cooling the gaseous mixture to a temperature of about 400.degree. K. or lower to condense the aluminum chlorides and iron chlorides while titanium chloride and silicon chloride remain in the gas phase to effect a separation thereof; heating the mixture of iron chlorides and aluminum chlorides to a temperature of about 800.degree. K. to form gaseous aluminum chlorides and iron chlorides; passing the heated gases into intimate contact with aluminum sulfide to precipitate solid iron sulfide and to form additional gaseous aluminum chlorides; and separating the gaseous aluminum chloride from the solid iron sulfide.

Effect of Zirconia Nanoparticles in Epoxy-Silica Hybrid Adhesives to Join Aluminum Substrates.

PubMed

Figueroa-Lara, José de Jesús; Torres-Rodríguez, Miguel; Gutiérrez-Arzaluz, Mirella; Romero-Romo, Mario

2017-09-27

This research presents the interaction of the epoxy polymer diglicydil ether of bisphenol-A (DGEBA) with silica (SiO₂) nanoparticles plus zirconia (ZrO₂) nanoparticles obtained via the sol-gel method in the synthesis of an epoxy-silica-zirconia hybrid adhesive cured with polyamide. ZrO₂ nanoparticles were added to the epoxy-silica hybrid adhesive produced in situ to modify the apparent shear strength of two adhesively bonded aluminum specimens. The results showed that the addition of different amounts of ZrO₂ nanoparticles increased the shear strength of the adhesively bonded aluminum joint, previously treated by sandblasting, immersion in hot water and silanized with a solution of hydrolyzed 3-glycidoxipropyltrimethoxysilane (GPTMS). The morphology and microstructure of the nanoparticles and aluminum surfaces were examined by scanning electron microscopy (SEM), and elemental analysis was performed with the Energy-dispersive X-ray spectroscopy (EDS) detector; the chemical groups were investigated during the aluminum surface modification using Fourier transform infrared spectroscopy (FTIR).

Effect of Zirconia Nanoparticles in Epoxy-Silica Hybrid Adhesives to Join Aluminum Substrates

PubMed Central

Figueroa-Lara, José de Jesús; Torres-Rodríguez, Miguel

2017-01-01

This research presents the interaction of the epoxy polymer diglicydil ether of bisphenol-A (DGEBA) with silica (SiO2) nanoparticles plus zirconia (ZrO2) nanoparticles obtained via the sol-gel method in the synthesis of an epoxy-silica-zirconia hybrid adhesive cured with polyamide. ZrO2 nanoparticles were added to the epoxy-silica hybrid adhesive produced in situ to modify the apparent shear strength of two adhesively bonded aluminum specimens. The results showed that the addition of different amounts of ZrO2 nanoparticles increased the shear strength of the adhesively bonded aluminum joint, previously treated by sandblasting, immersion in hot water and silanized with a solution of hydrolyzed 3-glycidoxipropyltrimethoxysilane (GPTMS). The morphology and microstructure of the nanoparticles and aluminum surfaces were examined by scanning electron microscopy (SEM), and elemental analysis was performed with the Energy-dispersive X-ray spectroscopy (EDS) detector; the chemical groups were investigated during the aluminum surface modification using Fourier transform infrared spectroscopy (FTIR). PMID:28953243

Quenchable water-rich, aluminous post-stishovite: implications for seismic anomalies in the mid-mantle

NASA Astrophysics Data System (ADS)

Myhill, R.; Frost, D. J.; Panero, W. R.; Boffa Ballaran, T.; Miyajima, N.; Bureau, H.; Raepsaet, C.; Siersch, N.; Kohn, S. C.

2016-12-01

At mid-mantle pressures, stishovite undergoes a displacive phase transition to the calcium chloride structure. It has been argued that softening accompanying this phase transition leads to very low seismic velocities and that silica-rich materials in the lower mantle may therefore be effective scatterers of seismic energy. The post-stishovite phase is also a promising candidate for water storage in the lower mantle, as it is both stable at very high temperatures and isostructural with the high pressure hydrous phases delta-AlOOH and Phase H. Pure SiO2 post-stishovite is unquenchable, making ex-situ characterisation impossible. In this study, we exploit the stabilisation of the post-stishovite structure due to alumina incorporation to synthesise and quench large crystals of post-stishovite. Single crystals are characterised by X-ray diffraction, TEM and Raman spectroscopy, and water contents are analysed with elastic recoil detection and FTIR. We show that water contents in our post-stishovite crystals are consistent with an SiO2-AlOOH solid solution, containing 3-7 times more water per atom of aluminium than stishovite. Our results suggest that almost 1 wt % H2O could be incorporated into post-stishovite crystals in lower mantle mafic rocks. We use ab-initio simulations to investigate the effect of pressure on the mechanism of hydroxyl incorporation into aluminous stishovite and post-stishovite. Finally, we discuss the potential for post-stishovite to affect seismic velocities in the lower mantle. In addition to the scattering potential of the phase transition, patchy low velocity layers in the mid-mantle might represent regions where hydrous melts are reacting with post-stishovite. In the lowermost mantle, transformation of post-stishovite to seifertite could result in the formation of a hydrous melt that might explain seismologically observed ultra low velocity zones.

40 CFR 721.10423 - Complex strontium aluminate, rare earth doped (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... earth doped (generic). 721.10423 Section 721.10423 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.10423 Complex strontium aluminate, rare earth doped... substances identified generically as complex strontium aluminate, rare earth doped (PMNs P-12-22, P-12-23, P...

Shock Initiation Characteristics of an Aluminized DNAN/RDX Melt-Cast Explosive

NASA Astrophysics Data System (ADS)

Cao, Tong-Tang; Zhou, Lin; Zhang, Xiang-Rong; Zhang, Wei; Miao, Fei-Chao

2017-10-01

Shock sensitivity is one of the key parameters for newly developed, 2,4-dinitroanisole (DNAN)-based, melt-cast explosives. For this paper, a series of shock initiation experiments were conducted using a one-dimensional Lagrangian system with a manganin piezoresistive pressure gauge technique to evaluate the shock sensitivity of an aluminized DNAN/cyclotrimethylenetrinitramine (RDX) melt-cast explosive. This study fully investigated the effects of particle size distributions in both RDX and aluminum, as well as the RDX's crystal quality on the shock sensitivity of the aluminized DNAN/RDX melt-cast explosive. Ultimately, the shock sensitivity of the aluminized DNAN/RDX melt-cast explosives increases when the particle size decreases in both RDX and aluminum. Additionally, shock sensitivity increases when the RDX's crystal quality decreases. In order to simulate these effects, an Ignition and Growth (I&G) reactive flow model was calibrated. This calibrated I&G model was able to predict the shock initiation characteristics of the aluminized DNAN/RDX melt-cast explosive.

Atom probe tomography of intermetallic phases and interfaces formed in dissimilar joining between Al alloys and steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemmens, B.

While Si additions to Al are widely used to reduce the thickness of the brittle intermetallic seam formed at the interface during joining of Al alloys to steel, the underlying mechanisms are not clarified yet. The developed approach for the site specific atom probe tomography analysis revealed Si enrichments at grain and phase boundaries between the θ (Fe{sub 4}Al{sub 13}) and η (Fe{sub 2}Al{sub 5}) phase, up to about ten times that of the concentration in Al. The increase in Si concentration could play an important role for the growth kinetics of the intermetallic phases formed for example in hot-dipmore » aluminizing of steel. - Highlights: •Si additions to Al reduce thickness of intermetallic seam in joining with steel. •Approach developed for the site specific APT analysis of the intermetallic seam •Si enrichment at grain and phase boundaries possibly affects growth of intermetallics.« less

Corrosion of Spiral Rib Aluminized Pipe

DOT National Transportation Integrated Search

2012-08-01

Large diameter, corrugated steel pipes are a common sight in the culverts that run alongside many Florida roads. Spiral-ribbed aluminized pipe (SRAP) has been widely specified by the Florida Department of Transportation (FDOT) for runoff drainage. Th...

Crystal structure control of aluminized clay minerals on the mobility of caesium in contaminated soil environments

NASA Astrophysics Data System (ADS)

Dzene, Liva; Ferrage, Eric; Viennet, Jean-Christophe; Tertre, Emmanuel; Hubert, Fabien

2017-02-01

Radioactive caesium pollution resulting from Fukushima Dai-ichi and Chernobyl nuclear plant accidents involves strong interactions between Cs+ and clays, especially vermiculite-type minerals. In acidic soil environments, such as in Fukushima area, vermiculite is subjected to weathering processes, resulting in aluminization. The crystal structure of aluminized clays and its implications for Cs+ mobility in soils remain poorly understood due to the mixture of these minerals with other clays and organic matter. We performed acidic weathering of a vermiculite to mimic the aluminization process in soils. Combination of structure analysis and Cs+ extractability measurements show that the increase of aluminization is accompanied by an increase in Cs+ mobility. Crystal structure model for aluminized vermiculite is based on the interstratification of unaltered vermiculite layers and aluminized layers within the same particle. Cs+ in vermiculite layers is poorly mobile, while the extractability of Cs+ is greatly enhanced in aluminized layers. The overall reactivity of the weathered clay (cation exchange capacity, Cs+ mobility) is then governed by the relative abundance of the two types of layers. The proposed layer model for aluminized vermiculite with two coexisting populations of caesium is of prime importance for predicting the fate of caesium in contaminated soil environments.

Sandia National Laboratories Small-Scale Sensitivity Testing (SSST) Report: Calcium Nitrate Mixtures with Various Fuels.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, Jason Joe

Based upon the presented sensitivity data for the examined calcium nitrate mixtures using sugar and sawdust, contact handling/mixing of these materials does not present hazards greater than those occurring during handling of dry PETN powder. The aluminized calcium nitrate mixtures present a known ESD fire hazard due to the fine aluminum powder fuel. These mixtures may yet present an ESD explosion hazard, though this has not been investigated at this time. The detonability of these mixtures will be investigated during Phase III testing.

Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces.

PubMed

Smith, Benjamin J; Rawal, Aditya; Funkhouser, Gary P; Roberts, Lawrence R; Gupta, Vijay; Israelachvili, Jacob N; Chmelka, Bradley F

2011-05-31

Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state (1)H, (13)C, (29)Si, and (27)Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications.

Spin transition of ferric iron in the calcium-ferrite type aluminous phase: Fe 3+ Spin Transition in the CF Phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ye; Qin, Fei; Wu, Xiang

2017-08-01

We investigated Fe-free and Fe-bearing CF phases using nuclear forward scattering and X-ray diffraction coupled with diamond anvil cells up to 80 GPa at room temperature. Octahedral Fe3+ ions in the Fe-bearing CF phase undergo a high-spin to low-spin transition at 25–35 GPa, accompanied by a volume reduction of ~2.0% and a softening of bulk sound velocity up to 17.6%. Based on the results of this study and our previous studies, both the NAL and CF phases, which account for 10–30 vol % of subducted MORB in the lower mantle, are predicted to undergo a spin transition of octahedral Fe3+more » at lower mantle pressures. Spin transitions in these two aluminous phases result in an increase of density of 0.24% and a pronounced softening of bulk sound velocity up to 2.3% for subducted MORB at 25–60 GPa and 300 K. The anomalous elasticity region expands and moves to 30–75 GPa at 1200 K and the maximum of the VΦ reduction decreases to ~1.8%. This anomalous elastic behavior of Fe-bearing aluminous phases across spin transition zones may be relevant in understanding the observed seismic signatures in the lower mantle.« less

Optimization of a Strontium Aluminate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bone, Alexandria N.

2017-08-01

Strontium aluminate with Eu 2+ and Dy 3+ has been at the forefront of emerging applications for storage phosphors since its discovery in 1996. In this study, the emission intensity and luminescence lifetime of SrAl 2O 4: Eu 2+, Dy 3+ were enhanced by partial substitution of Ca 2+ into Sr 2+ sites in the matrix.

Software framework for the upcoming MMT Observatory primary mirror re-aluminization

NASA Astrophysics Data System (ADS)

Gibson, J. Duane; Clark, Dusty; Porter, Dallan

2014-07-01

Details of the software framework for the upcoming in-situ re-aluminization of the 6.5m MMT Observatory (MMTO) primary mirror are presented. This framework includes: 1) a centralized key-value store and data structure server for data exchange between software modules, 2) a newly developed hardware-software interface for faster data sampling and better hardware control, 3) automated control algorithms that are based upon empirical testing, modeling, and simulation of the aluminization process, 4) re-engineered graphical user interfaces (GUI's) that use state-of-the-art web technologies, and 5) redundant relational databases for data logging. Redesign of the software framework has several objectives: 1) automated process control to provide more consistent and uniform mirror coatings, 2) optional manual control of the aluminization process, 3) modular design to allow flexibility in process control and software implementation, 4) faster data sampling and logging rates to better characterize the approximately 100-second aluminization event, and 5) synchronized "real-time" web application GUI's to provide all users with exactly the same data. The framework has been implemented as four modules interconnected by a data store/server. The four modules are integrated into two Linux system services that start automatically at boot-time and remain running at all times. Performance of the software framework is assessed through extensive testing within 2.0 meter and smaller coating chambers at the Sunnyside Test Facility. The redesigned software framework helps ensure that a better performing and longer lasting coating will be achieved during the re-aluminization of the MMTO primary mirror.

Characterizing AISI 1045 steel surface duplex-treated by alternating current field enhanced pack aluminizing and nitriding

NASA Astrophysics Data System (ADS)

Xie, Fei; Zhang, Ge; Pan, Jianwei

2018-02-01

Thin cases and long treating time are shortcomings of conventional duplex treatment of aluminizing followed by nitriding (DTAN). Alternating current field (ACF) enhanced DTAN was carried out on AISI 1045 steel by applying an ACF to treated samples and treating agents with a pair of electrodes for overcoming those shortcomings. By investigating cases' structures, phases, composition and hardness distributions of differently treated samples, preliminary studies were made on characterizations of the ACF enhanced duplex treatment to AISI 1045 steel. The results show that, with the help of the ACF, the surface Al-rich phase Al5Fe2 formed in conventional pack aluminizing can be easily avoided and the aluminizing process is dramatically promoted. The aluminizing case can be nitrided either with conventional pack nitriding or ACF enhanced pack nitriding. By applying ACF to pack nitriding, the diffusion of nitrogen into the aluminizing case is promoted. AlN, Fe2∼3N and solid solution of N in iron are efficiently formed as a result of reactions of N with the aluminizing case. A duplex treated case with an effective thickness of more than 170 μm can be obtained by the alternating current field enhanced 4 h pack aluminizing plus 4 h pack nitriding.

Multicale modeling of the detonation of aluminized explosives using SPH-MD-QM method

NASA Astrophysics Data System (ADS)

Peng, Qing; Wang, Guangyu; Liu, Gui-Rong; de, Suvranu

Aluminized explosives have been applied in military industry since decades ago. Compared with ideal explosives, aluminized explosives feature both fast detonation and slow metal combustion chemistry, generating a complex multi-phase reactive flow. Here, we introduce a sequential multiscale model of SPH-MD-QM to simulate the detonation behavior of aluminized explosives. At the bottom level, first-principles quantum mechanics (QM) calculations are employed to obtain the training sets for fitting the ReaxFF potentials, which are used in turn in the reactive molecular dynamics (MD) simulations in the middle level to obtain the chemical reaction rates and equations of states. At the up lever, a smooth particle hydrodynamics (SPH) method incorporated ignition and growth model and afterburning model has been used for the simulation of the detonation and combustion of the aluminized explosive. Simulation is compared with experiment and good agreement is observed. The proposed multiscale method of SPH-MD-QM could be used to optimize the performance of aluminized explosives. The authors would like to acknowledge the generous financial support from the Defense Threat Reduction Agency (DTRA) Grant No. HDTRA1-13-1-0025 and the Office of Naval Research Grants ONR Award No. N00014-08-1-0462 and No. N00014-12-1-0527.

Transition of Blast Furnace Slag from Silicate Based to Aluminate Based: Sulfide Capacity

NASA Astrophysics Data System (ADS)

Yan, Zhiming; Lv, Xuewei; Pang, Zhengde; He, Wenchao; Liang, Dong; Bai, Chenguang

2017-10-01

The effect of Al2O3 and Al2O3/SiO2 ratio on the sulfide capacity of the molten aluminosilicate CaO-SiO2-Al2O3-MgO-TiO2 slag system with high Al2O3 content was measured at 1773 K (1500 °C) using a metal-slag equilibration method. The sulfide capacity between silicate-based and aluminate-based slag was also compared based on the thermodynamic analysis and structural characteristics of melts. At a fixed CaO/SiO2 ratio of 1.20, the sulfide capacity decreases with increasing Al2O3 content primarily due to the decrease of free oxygen (FO) and the activity of O2-. Increasing the Al2O3/SiO2 ratio from 0.47 to 0.79 causes a significant increase in the sulfide capacity of the slags, and a slight increase is found when the Al2O3/SiO2 ratio is more than 0.79. The effect of the substitution of silica by alumina on the sulfide capacity of the slags was not only due to an increase in the activity of basic oxides ( a_{{{O}^{2 - } }} ) but also to a decrease in the stability of sulfide ( γ_{{{S}^{2 - } }} ). Moreover, a_{{{O}^{2 - } }} and γ_{{{S}^{2 - } }} increase in a similar degree, and the weaker binding electronegativity of Al3+ with oxygen atoms results in a slight increase in the final sulfide capacity in the aluminate-based slag system with Al2O3 ↔ SiO2 substitution. Five different sulfide capacity models were employed to predict the sulfide capacity, and the iso-sulfide capacity distribution diagram based on the Young's model was obtained in the high Al2O3 corner of the diagram.

Corrosion of Spiral Rib Aluminized Pipe : [Summary

DOT National Transportation Integrated Search

2012-01-01

Large diameter, corrugated steel pipes are a common sight in the culverts that run alongside many Florida roads. Spiral-ribbed aluminized pipe (SRAP) has been widely specified by the Florida Department of Transportation (FDOT) for runoff drainage. Th...

Method of preparing a sintered lithium aluminate structure for containing electrolyte

DOEpatents

Sim, James W.; Kinoshita, Kimio

1981-01-01

A porous sintered tile is formed of lithium aluminate for retaining molten lectrolyte within a fuel cell. The tile is prepared by reacting lithium hydroxide in aqueous solution with alumina particles to form beta lithium aluminate particles. The slurry is evaporated to dryness and the solids dehydrated to form a beta lithium aluminate powder. The powder is compacted into the desired shape and sintered at a temperature in excess of 1200 K. but less than 1900 K. to form a porous integral structure that is subsequently filled with molten electrolyte. A tile of this type is intended for use in containing molten alkali metal carbonates as electolyte for use in a fuel cell having porous metal or metal oxide electrodes for burning a fuel gas such as hydrogen and/or carbon monoxide with an oxidant gas containing oxygen.

Coagulation chemistries for silica removal from cooling tower water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyman, May Devan; Altman, Susan Jeanne; Stewart, Tom

2010-02-01

The formation of silica scale is a problem for thermoelectric power generating facilities, and this study investigated the potential for removal of silica by means of chemical coagulation from source water before it is subjected to mineral concentration in cooling towers. In Phase I, a screening of many typical as well as novel coagulants was carried out using concentrated cooling tower water, with and without flocculation aids, at concentrations typical for water purification with limited results. In Phase II, it was decided that treatment of source or make up water was more appropriate, and that higher dosing with coagulants deliveredmore » promising results. In fact, the less exotic coagulants proved to be more efficacious for reasons not yet fully determined. Some analysis was made of the molecular nature of the precipitated floc, which may aid in process improvements. In Phase III, more detailed study of process conditions for aluminum chloride coagulation was undertaken. Lime-soda water softening and the precipitation of magnesium hydroxide were shown to be too limited in terms of effectiveness, speed, and energy consumption to be considered further for the present application. In Phase IV, sodium aluminate emerged as an effective coagulant for silica, and the most attractive of those tested to date because of its availability, ease of use, and low requirement for additional chemicals. Some process optimization was performed for coagulant concentration and operational pH. It is concluded that silica coagulation with simple aluminum-based agents is effective, simple, and compatible with other industrial processes.« less

Preparation and Characterization of Hydroxyapatite-Silica Composite Nanopowders

NASA Astrophysics Data System (ADS)

Latifi, S. M.; Fathi, M. H.; Golozar, M. A.

One of the most important objectives in the field of biomaterials science and engineering is development of new materials as bone substitutes. Silica (SiO2) has an important role in the biomineralization and biological responses. The aim of this research was to prepare and characterize hydroxyapatite-silica (HA-SiO2) composite nanopowder with different content of silica. Hydroxyapatite-silica composite nanopowders with 20 and 40 wt% silica were prepared using a sol-gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as a source of hydroxyapatite; also, tetraethylorthosilicate and methyltriethoxisilane as a source of silica. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for characterization and evaluation of the products. The results indicated the presence of nanocrystalline hydroxyapatite phase beside amorphous silica phase in prepared composite nanopowders. Moreover, by increasing the content of silica in composite nanopowders, the crystallinity will be decreased,and the ability of the product as a bone substitute material might be controlled by changing the content of the ingredients and subsequently its structure.

The influences of calcia silica contents to the compressive strength of the Al-7000 aluminium foam

NASA Astrophysics Data System (ADS)

Sutarno; Soepriyanto, S.; Korda, A. A.; Dirgantara, T.

2016-08-01

This experiment evaluated the effect of calcia alumina and alumina silica that formed as side products involved in metal mixture of aluminium foam. These compounds are formed from additional calcium carbonate and silica in the mixture. Calcium carbonate (CaCO3) roles as a blowing agent source of carbon dioxide (CO2). The formation of calcia alumina (CaO.Al2O3) is desired to improve the viscosity and to strengthen of cell wall of aluminium foam. However, Al-7000 aluminium foam showed a decrease tendency of compressive strength probably due to existence of alumina silica (3Al2O3.SiO2) in the metal mixture. In this case, the silica that thermally combines with alumina compound may degrade the metal mixture of aluminium foam structure.

Reinforcement of natural rubber hybrid composites based on marble sludge/Silica and marble sludge/rice husk derived silica

PubMed Central

Ahmed, Khalil; Nizami, Shaikh Sirajuddin; Riza, Nudrat Zahid

2013-01-01

A research has been carried out to develop natural rubber (NR) hybrid composites reinforced with marble sludge (MS)/Silica and MS/rice husk derived silica (RHS). The primary aim of this development is to scrutinize the cure characteristics, mechanical and swelling properties of such hybrid composite. The use of both industrial and agricultural waste such as marble sludge and rice husk derived silica has the primary advantage of being eco-friendly, low cost and easily available as compared to other expensive fillers. The results from this study showed that the performance of NR hybrid composites with MS/Silica and MS/RHS as fillers is extremely better in mechanical and swelling properties as compared with the case where MS used as single filler. The study suggests that the use of recently developed silica and marble sludge as industrial and agricultural waste is accomplished to provide a probable cost effective, industrially prospective, and attractive replacement to the in general purpose used fillers like china clay, calcium carbonate, and talc. PMID:25685484

Biomimetic silica encapsultation of living cells

NASA Astrophysics Data System (ADS)

Jaroch, David Benjamin

Living cells perform complex chemical processes on size and time scales that artificial systems cannot match. Cells respond dynamically to their environment, acting as biological sensors, factories, and drug delivery devices. To facilitate the use of living systems in engineered constructs, we have developed several new approaches to create stable protective microenvironments by forming bioinspired cell-membrane-specific silica-based encapsulants. These include vapor phase deposition of silica gels, use of endogenous membrane proteins and polysaccharides as a site for silica nucleation and polycondensation in a saturated environment, and protein templated ordered silica shell formation. We demonstrate silica layer formation at the surface of pluripotent stem-like cells, bacterial biofilms, and primary murine and human pancreatic islets. Materials are characterized by AFM, SEM and EDS. Viability assays confirm cell survival, and metabolite flux measurements demonstrate normal function and no major diffusion limitations. Real time PCR mRNA analysis indicates encapsulated islets express normal levels of genetic markers for β-cells and insulin production. The silica glass encapsulant produces a secondary bone like calcium phosphate mineral layer upon exposure to media. Such bioactive materials can improve device integration with surrounding tissue upon implantation. Given the favorable insulin response, bioactivity, and long-term viability observed in silica-coated islets, we are currently testing the encapsulant's ability to prevent immune system recognition of foreign transplants for the treatment of diabetes. Such hybrid silica-cellular constructs have a wide range of industrial, environmental, and medical applications.

Determination of performance of non-ideal aluminized explosives.

PubMed

Keshavarz, Mohammad Hossein; Mofrad, Reza Teimuri; Poor, Karim Esmail; Shokrollahi, Arash; Zali, Abbas; Yousefi, Mohammad Hassan

2006-09-01

Non-ideal explosives can have Chapman-Jouguet (C-J) detonation pressure significantly different from those expected from existing thermodynamic computer codes, which usually allows finding the parameters of ideal detonation of individual high explosives with good accuracy. A simple method is introduced by which detonation pressure of non-ideal aluminized explosives with general formula C(a)H(b)N(c)O(d)Al(e) can be predicted only from a, b, c, d and e at any loading density without using any assumed detonation products and experimental data. Calculated detonation pressures show good agreement with experimental values with respect to computed results obtained by complicated computer code. It is shown here how loading density and atomic composition can be integrated into an empirical formula for predicting detonation pressure of proposed aluminized explosives.

A drift chamber constructed of aluminized mylar tubes

NASA Astrophysics Data System (ADS)

Baringer, P.; Jung, C.; Ogren, H. O.; Rust, D. R.

1987-03-01

A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls.

Research on Equation of State For Detonation Products of Aluminized Explosive

NASA Astrophysics Data System (ADS)

Yue, Jun-Zheng; Duan, Zhuo-Ping; Zhang, Zhen-Yu; Ou, Zhuo-Cheng

2017-10-01

The secondary reaction of the aluminum powder contained in an aluminized explosive is investigated, from which the energy loss resulted from the quantity reduce of the gaseous products is demonstrated. Moreover, taking the energy loss into account, the existing improved Jones-Wilkins-Lee (JWL) equation of state for detonation products of aluminized explosive is modified. Furthermore, the new modified JWL equation of state is implemented into the dynamic analysis software (DYNA)-2D hydro-code to simulate numerically the metal plate acceleration tests of the Hexogen (RDX)-based aluminized explosives. It is found that the numerical results are in good agreement with previous experimental data. In addition, it is also demonstrated that the reaction rate of explosive before the Chapman-Jouget (CJ) state has little influence on the motion of the metal plate, based on which a simple approach is proposed to simulate numerically the products expansion process after the CJ state.

Continuous Modeling of Calcium Transport Through Biological Membranes

NASA Astrophysics Data System (ADS)

Jasielec, J. J.; Filipek, R.; Szyszkiewicz, K.; Sokalski, T.; Lewenstam, A.

2016-08-01

In this work an approach to the modeling of the biological membranes where a membrane is treated as a continuous medium is presented. The Nernst-Planck-Poisson model including Poisson equation for electric potential is used to describe transport of ions in the mitochondrial membrane—the interface which joins mitochondrial matrix with cellular cytosis. The transport of calcium ions is considered. Concentration of calcium inside the mitochondrion is not known accurately because different analytical methods give dramatically different results. We explain mathematically these differences assuming the complexing reaction inside mitochondrion and the existence of the calcium set-point (concentration of calcium in cytosis below which calcium stops entering the mitochondrion).

Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, A.K., E-mail: anjan.k.chatterjee@gmail.co

2009-11-15

In the family of aluminous cements the potential of strontium aluminate, the strontium-barium aluminate and the barium aluminate cements have been sporadically and incoherently studied over several decades in various parts of the world and more particularly in the East European countries without much wide-spread commercial success. Attempts had also been made to extend the exploratory studies to the (Ca, Sr, Ba)O-Al{sub 2}O{sub 3}-ZrO{sub 2}-HfO{sub 2} system to synthesize super-refractory binders. In fact, the above compositions, prima facie, seem to have the potential of arriving at cementitious formulations that, apart from being super-refractory, may as well be highly resistant tomore » seawater, X-rays and gamma radiation. Looking at these potentials, quite a few experimental studies have been carried out under the guidance and supervision of the present author. The present paper is an endeavour to collate the data on some of these systems both from the published literature as well as from the author's findings. The prime motive has been to review and re-assess the prospects of manufacturing a range of new aluminous binders with superior properties.« less

Eigenvalue Detonation of Combined Effects Aluminized Explosives

NASA Astrophysics Data System (ADS)

Capellos, Christos; Baker, Ernest; Balas, Wendy; Nicolich, Steven; Stiel, Leonard

2007-06-01

This paper reports on the development of theory and performance for recently developed combined effects aluminized explosives. Traditional high energy explosives used for metal pushing incorporate high loading percentages of HMX or RDX, whereas blast explosives incorporate some percentage of aluminum. However, the high blast explosives produce increased blast energies, with reduced metal pushing capability due to late time aluminum reaction. Metal pushing capability refers to the early volume expansion work produced during the first few volume expansions associated with cylinder wall velocities and Gurney energies. Our Recently developed combined effects aluminized explosives (PAX-29C, PAX-30, PAX-42) are capable of achieving excellent metal pushing and high blast energies. Traditional Chapman-Jouguet detonation theory does not explain the observed detonation states achieved by these combined effects explosives. This work demonstrates, with the use of cylinder expansion data and thermochemical code calculations (JAGUAR and CHEETAH), that eigenvalue detonation theory explains the observed behavior.

Biomimetic mineral self-organization from silica-rich spring waters.

PubMed

García-Ruiz, Juan Manuel; Nakouzi, Elias; Kotopoulou, Electra; Tamborrino, Leonardo; Steinbock, Oliver

2017-03-01

Purely inorganic reactions of silica, metal carbonates, and metal hydroxides can produce self-organized complex structures that mimic the texture of biominerals, the morphology of primitive organisms, and that catalyze prebiotic reactions. To date, these fascinating structures have only been synthesized using model solutions. We report that mineral self-assembly can be also obtained from natural alkaline silica-rich water deriving from serpentinization. Specifically, we demonstrate three main types of mineral self-assembly: (i) nanocrystalline biomorphs of barium carbonate and silica, (ii) mesocrystals and crystal aggregates of calcium carbonate with complex biomimetic textures, and (iii) osmosis-driven metal silicate hydrate membranes that form compartmentalized, hollow structures. Our results suggest that silica-induced mineral self-assembly could have been a common phenomenon in alkaline environments of early Earth and Earth-like planets.

Role of Tartaric Acid in Chemical, Mechanical and Self-Healing Behaviors of a Calcium-Aluminate Cement Blend with Fly Ash F under Steam and Alkali Carbonate Environments at 270 °C

PubMed Central

Pyatina, Tatiana; Sugama, Toshifumi

2017-01-01

Tartaric acid (TA) changes short-term mechanical behavior and phase composition of sodium-metasilicate activated calcium-aluminate cement blend with fly ash, type F, when used as a set control additive to allow sufficient pumping time for underground well placement. The present work focuses on TA effect on self-healing properties of the blend under steam or alkali carbonate environments at 270 °C applicable to geothermal wells. Compressive strength recoveries and cracks sealing were examined to evaluate self-healing of the cement after repeated crush tests followed by two consecutive healing periods of 10 and 5 days at 270 °C. Optical and scanning electron microscopes, X-ray diffraction, Fourier Transform infrared and EDX measurements along with thermal gravimetric analyses were used to identify phases participating in the healing processes. Samples with 1% mass fraction of TA by weight of blend demonstrated improved strength recoveries and crack plugging properties, especially in alkali carbonate environment. This effect was attributed to silicon-rich (C,N)-A-S-H amorphous phase predominant in TA-modified samples, high-temperature stable zeolite phases along with the formation of tobermorite-type crystals in the presence of tartaric acid. PMID:28772701

Role of Tartaric Acid in Chemical, Mechanical and Self-Healing Behaviors of a Calcium-Aluminate Cement Blend with Fly Ash F under Steam and Alkali Carbonate Environments at 270°C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyatina, Tatiana; Sugama, Toshifumi

Tartaric acid (TA) changes short-term mechanical behavior and phase composition of sodium-metasilicate activated calcium-aluminate cement blend with fly ash, type F, when used as a set control additive to allow sufficient pumping time for underground well placement. The present work focuses on TA effect on self-healing properties of the blend under steam or alkali carbonate environments at 270°C applicable to geothermal wells. Compressive strength recoveries and cracks sealing were examined to evaluate self-healing of the cement after repeated crush tests followed by two consecutive healing periods of 10 and 5 days at 270°C. Optical and scanning electron microscopes, X-ray diffraction,more » Fourier Transform infrared and EDX measurements along with thermal gravimetric analyses were used to identify phases participating in the healing processes. Samples with 1% mass fraction of TA by weight of blend demonstrated improved strength recoveries and crack plugging properties, especially in alkali carbonate environment. This effect was attributed to silicon-rich (C,N)-A-S-H amorphous phase predominant in TA-modified samples, high-temperature stable zeolite phases along with the formation of tobermorite-type crystals in the presence of tartaric acid.« less

Role of Tartaric Acid in Chemical, Mechanical and Self-Healing Behaviors of a Calcium-Aluminate Cement Blend with Fly Ash F under Steam and Alkali Carbonate Environments at 270°C

DOE PAGES

Pyatina, Tatiana; Sugama, Toshifumi

2017-03-25

Tartaric acid (TA) changes short-term mechanical behavior and phase composition of sodium-metasilicate activated calcium-aluminate cement blend with fly ash, type F, when used as a set control additive to allow sufficient pumping time for underground well placement. The present work focuses on TA effect on self-healing properties of the blend under steam or alkali carbonate environments at 270°C applicable to geothermal wells. Compressive strength recoveries and cracks sealing were examined to evaluate self-healing of the cement after repeated crush tests followed by two consecutive healing periods of 10 and 5 days at 270°C. Optical and scanning electron microscopes, X-ray diffraction,more » Fourier Transform infrared and EDX measurements along with thermal gravimetric analyses were used to identify phases participating in the healing processes. Samples with 1% mass fraction of TA by weight of blend demonstrated improved strength recoveries and crack plugging properties, especially in alkali carbonate environment. This effect was attributed to silicon-rich (C,N)-A-S-H amorphous phase predominant in TA-modified samples, high-temperature stable zeolite phases along with the formation of tobermorite-type crystals in the presence of tartaric acid.« less

Heterogeneous Nucleation of Dicalcium Phosphate Dihydrate on Modified Silica Surfaces

PubMed Central

Miller, Carrie; Komunjer, Ljepša; Hlady, Vladimir

2012-01-01

Heterogeneous nucleation of dicalcium phosphate dihydrate, CaHPO4•2H2O (DCPD) was studied on untreated planar fused silica and on three modified silica surfaces: octadecylsilyl (OTS) modified silica, human serum albumin treated OTS silica, and UV-oxidized 3-mercaptopropyltriethoxysilyl (MTS) modified silica. The supersaturation ratio of calcium and phosphate solution with respect to DCPD was kept below ~10. The nucleated crystals were observed 24 hours and one week after initial contact between supersaturated solutions and substrate surfaces using bright field and reflectance interference contrast microscopy. No DCPD crystals nucleated on albumin-treated OTS-silica. Majority of the DCDP crystals formed on the other modified silica surfaces appeared to be morphologically similar irrespective of the nature of nucleating substrate. Reflectance interference contrast microscopy provided a proof that the majority of the crystals on these substrates do not develop an extended contact with the substrate surface. The images showed that the most extended contact planes were between the DCPD crystals and MTS modified silica surface. The crystals nucleated on OTS-treated and untreated silica surfaces showed only few or none well-developed contact planes. PMID:25264399

Treatment of cooling tower blowdown water containing silica, calcium and magnesium by electrocoagulation.

PubMed

Liao, Z; Gu, Z; Schulz, M C; Davis, J R; Baygents, J C; Farrell, J

2009-01-01

This research investigated the effectiveness of electrocoagulation using iron and aluminium electrodes for treating cooling tower blowdown (CTB) waters containing dissolved silica (Si(OH)(4)), Ca(2 + ) and Mg(2 + ). The removal of each target species was measured as a function of the coagulant dose in simulated CTB waters with initial pH values of 5, 7, and 9. Experiments were also performed to investigate the effect of antiscaling compounds and coagulation aids on hardness ion removal. Both iron and aluminum electrodes were effective at removing dissolved silica. For coagulant doses < or =3 mM, silica removal was a linear function of the coagulant dose, with 0.4 to 0.5 moles of silica removed per mole of iron or aluminium. Iron electrodes were only 30% as effective at removing Ca(2 + ) and Mg(2 + ) as compared to silica. There was no measurable removal of hardness ions by aluminium electrodes in the absence of organic additives. Phosphonate based antiscaling compounds were uniformly effective at increasing the removal of Ca(2 + ) and Mg(2 + ) by both iron and aluminium electrodes. Cationic and amphoteric polymers used as coagulation aids were also effective at increasing hardness ion removal.

Aluminate effect on desilication product phase transformation

NASA Astrophysics Data System (ADS)

Peng, Hong; Vaughan, James

2018-06-01

It remains a grand challenge in the treatment of bauxite residue to physically separate zeolite (also known as the DeSilication Product, DSP) from other unleached mineral phases owing to their fine sizes, typically less than 2 μm in diameter. In this study, the effect of aluminate concentration on DSP phase transformation was investigated from synthetic NaOH-NaAl(OH)4-Na2SiO3-H2O solution at 90 °C. The results show how at relatively low aluminate concentrations of 0.125 and 0.25 M NaAl(OH)4(aq), larger zeolite crystals of up to 60 μm in diameter are formed during homogenous precipitation from aqueous solution. The precipitation process involves the conversion of zeolite LTA to sodalite via the formation of an intermediate phase, octahedral LTN. Initial amorphous solids precipitate as aggregates in which cubic zeolite LTA nucleation occurs. As the reaction proceeds, truncated octahedral LTN appears with the cubic zeolite LTA and finally sodalite crystallizes on the LTA-LTN aggregates resulting in coarsened particles.

High Temperature Oxidation of Hot-Dip Aluminized T92 Steels

NASA Astrophysics Data System (ADS)

Abro, Muhammad Ali; Hahn, Junhee; Lee, Dong Bok

2018-03-01

The T92 steel plate was hot-dip aluminized, and oxidized in order to characterize the high-temperature oxidation behavior of hot-dip aluminized T92 steel. The coating consisted of Al-rich topcoat with scattered Al3Fe grains, Al3Fe-rich upper alloy layer with scattered (Al, Al5Fe2, AlFe)-grains, and Al5Fe2-rich lower alloy layer with scattered (Al5Fe2, AlFe)-grains. Oxidation at 800 °C for 20 h formed (α-Al2O3 scale)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer), while oxidation at 900 °C for 20 h formed (α-Al2O3 scale plus some Fe2O3)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer) from the surface. During oxidation, outward migration of all substrate elements, inward diffusion of oxygen, and back and forth diffusion of Al occurred according to concentration gradients. Also, diffusion transformed and broadened AlFe and AlFe3 layers dissolved with some oxygen and substrate alloying elements. Hot-dip aluminizing improved the high-temperature oxidation resistance of T92 steel through preferential oxidation of Al at the surface.

High Temperature Oxidation of Hot-Dip Aluminized T92 Steels

NASA Astrophysics Data System (ADS)

Abro, Muhammad Ali; Hahn, Junhee; Lee, Dong Bok

2018-05-01

The T92 steel plate was hot-dip aluminized, and oxidized in order to characterize the high-temperature oxidation behavior of hot-dip aluminized T92 steel. The coating consisted of Al-rich topcoat with scattered Al3Fe grains, Al3Fe-rich upper alloy layer with scattered (Al, Al5Fe2, AlFe)-grains, and Al5Fe2-rich lower alloy layer with scattered (Al5Fe2, AlFe)-grains. Oxidation at 800 °C for 20 h formed (α-Al2O3 scale)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer), while oxidation at 900 °C for 20 h formed (α-Al2O3 scale plus some Fe2O3)/(AlFe layer)/(AlFe3 layer)/(α-Fe(Al) layer) from the surface. During oxidation, outward migration of all substrate elements, inward diffusion of oxygen, and back and forth diffusion of Al occurred according to concentration gradients. Also, diffusion transformed and broadened AlFe and AlFe3 layers dissolved with some oxygen and substrate alloying elements. Hot-dip aluminizing improved the high-temperature oxidation resistance of T92 steel through preferential oxidation of Al at the surface.

DEVELOPMENT OF A CALCIUM-BASED SORBENT FOR HOT GAS CLEANUP

DOE Office of Scientific and Technical Information (OSTI.GOV)

T.D. Wheelock; L.K. Doraiswamy; K. Constant

1999-10-01

The development and testing of potential calcium-based sorbents for hot gas cleanup continued. One of the most promising materials combines powdered limestone and a calcium aluminate cement by two step pelletization followed by steam curing. Reasonably strong pellets are produced with good adsorption characteristics by incorporating 20 wt.% cement in the core and 40 wt.% cement in the shell. The resulting 4.76 mm diameter pellets are capable of withstanding a crushing force approaching 11.5 N/mm before breaking and are also capable of removing H{sub 2}S from dilute, hot gas streams. The pellets are also regenerable and reusable. Another promising materialmore » combines calcium carbonate powder and finely ground calcined alumina in tablet form. The small tablets are prepared by mixing the materials with water to form a thick paste which is then molded and dried. The tablets are hardened by calcining at either 1000 to 1100 C. The resulting tablets are strong and capable of removing H{sub 2}S from a dilute, hot gas stream.« less

On the kinetics of the pack - Aluminization process

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.

1976-01-01

An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

Reuse of ornamental rock-cutting waste in aluminous porcelain.

PubMed

Silva, M A; Paes, H R; Holanda, J N F

2011-03-01

Large amounts of solid wastes are discarded in the ornamental rocks industry. This work investigates the incorporation of ornamental rock-cutting waste as a raw material into an aluminous porcelain body, replacing natural feldspar material by up to 35 wt.%. Formulations containing rock-cutting waste were pressed and sintered at 1350 °C. The porcelain pieces were tested to determine their properties (linear shrinkage, water absorption, apparent density, mechanical strength, and electrical resistivity). Development of the microstructure was followed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The results showed that ornamental rock-cutting waste could be used in aluminous porcelains, in the range up to 10 wt.%, as a partial replacement for traditional flux material, resulting in a valid route for management of this abundant waste. Copyright © 2010 Elsevier Ltd. All rights reserved.

Fabrication of polystyrene/gold nanotubes and nanostructure-controlled growth of aluminate.

PubMed

Zhu, Haifeng; Ai, Sufen; He, Qiang; Cui, Yue; Li, Junbai

2007-07-01

Direct adsorption of gold nanoparticles in the inner of alumina template and following immersion of polystyrene (PS) dichloromethane solution in the template resulted in the fabrication of composite nanotubes of PS and gold nanoparticles. Several methods have been used to characterize the tubular structure. Nanostructured sodium aluminates were formed when the anodic alumina oxide membrane was dissolved by the sodium hydroxide. A "flower" shape was found after etching the template while the synthesis process was recorded as function of a time. The results demonstrate that the shape and size of the aluminates nanostructure can be controlled by etching time and the pore diameter of the alumina membrane.

Quantitative description of yttrium aluminate ceramic composition by means of Er+3 microluminescence spectrum

NASA Astrophysics Data System (ADS)

Videla, F. A.; Tejerina, M. R.; Moreira-Osorio, L.; Conconi, M. S.; Orzi, D. J. O.; Flores, T.; Ponce, L. V.; Bilmes, G. M.; Torchia, G. A.

2018-05-01

The composition of erbium-doped yttrium aluminate ceramics was analyzed by means of confocal luminescence spectroscopy, EDX, and X-ray diffraction. A well-defined linear correlation was found between a proposed estimator computed from the luminescence spectrum and the proportion of ceramic phases coexisting in different samples. This result shows the feasibility of using erbium luminescence spectroscopy to perform a quantitative determination of different phases of yttrium aluminates within a micrometric region in nanograined ceramics.

Precision Joining Center

NASA Astrophysics Data System (ADS)

Powell, J. W.; Westphal, D. A.

1991-08-01

A workshop to obtain input from industry on the establishment of the Precision Joining Center (PJC) was held on July 10-12, 1991. The PJC is a center for training Joining Technologists in advanced joining techniques and concepts in order to promote the competitiveness of U.S. industry. The center will be established as part of the DOE Defense Programs Technology Commercialization Initiative, and operated by EG&G Rocky Flats in cooperation with the American Welding Society and the Colorado School of Mines Center for Welding and Joining Research. The overall objectives of the workshop were to validate the need for a Joining Technologists to fill the gap between the welding operator and the welding engineer, and to assure that the PJC will train individuals to satisfy that need. The consensus of the workshop participants was that the Joining Technologist is a necessary position in industry, and is currently used, with some variation, by many companies. It was agreed that the PJC core curriculum, as presented, would produce a Joining Technologist of value to industries that use precision joining techniques. The advantage of the PJC would be to train the Joining Technologist much more quickly and more completely. The proposed emphasis of the PJC curriculum on equipment intensive and hands-on training was judged to be essential.

Study of optical properties of cerium ion doped barium aluminate phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lohe, P. P., E-mail: prachiti.lohe2012@gmail.com; Omanwar, S. K.; Bajaj, N. S.

2016-05-06

In the recent years due to their various optical and technological applications aluminate materials have attracted attention of several researchers. When these materials are doped with rare earth ions they show properties favorable for many optical applications such as high quantum efficiencies. These materials are used in various applications such as lamp phosphors, optically and thermoluminescence dosimeter etc Barium aluminate BaAl{sub 2}O{sub 4} doped with Ce is well known long lasting phosphor. This paper reports synthesis of BaAl{sub 2}O{sub 4}: Ce phosphor prepared by a simple combustion synthesis. The samples were characterized for the phase purity, chemical bonds and luminescentmore » properties.« less

Releasing-addition method for the flame-photometric determination of calcium in thermal waters

USGS Publications Warehouse

Rowe, J.J.

1963-01-01

Study of the interferences of silica and sulfate in the flame-photometric determination of calcium in thermal waters has led to the development of a method requiring no prior chemical separations. The interference effects of silica, sulfate, potassium, sodium, aluminum, and phosphate are overcome by an addition technique coupled with the use of magnesium as a releasing agent. ?? 1963.

Calcium silicate-based drug delivery systems.

PubMed

Zhu, Ying-Jie; Guo, Xiao-Xuan; Sham, Tsun-Kong

2017-02-01

Compared with other inorganic materials such as silica, metal oxides, noble metals and carbon, calcium silicate-based materials, especially nanostructured calcium silicate materials, have high biocompatibility, bioactivity and biodegradability, high specific surface area, nanoporous/hollow structure, high drug-loading capacity, pH-responsive drug release behavior and desirable drug release properties, and thus they are promising for the application in drug delivery. Calcium silicate-based drug delivery systems have a long drug-release time, which can significantly prolong the therapeutic effect of drugs. Another advantage of calcium silicate-based drug delivery systems is their pH-responsive drug release property, which can act as an ideal platform for targeted drug delivery. Areas covered: In recent years, studies have been carried out on calcium silicate-based drug delivery systems, and important results and insights have been documented. This article is not intended to offer a comprehensive review on the research on calcium silicate-based drug delivery systems, but presents some examples reported in the literature, and includes new insights obtained by tracking the interactions between drug molecules and calcium silicate carriers on the molecular level using the synchrotron-based X-ray spectroscopy. Expert opinion: Finally, our opinions on calcium silicate-based drug delivery systems are provided, and several research directions for the future studies are proposed.

Ion microprobe analyses of aluminous lunar glasses - A test of the 'rock type' hypothesis

NASA Technical Reports Server (NTRS)

Meyer, C., Jr.

1978-01-01

Previous soil survey investigations found that there are natural groupings of glass compositions in lunar soils and that the average major element composition of some of these groupings is the same at widely separated lunar landing sites. This led soil survey enthusiasts to promote the hypothesis that the average composition of glass groupings represents the composition of primary lunar 'rock types'. In this investigation the trace element composition of numerous aluminous glass particles was determined by the ion microprobe method as a test of the above mentioned 'rock type' hypothesis. It was found that within any grouping of aluminous lunar glasses by major element content, there is considerable scatter in the refractory trace element content. In addition, aluminous glasses grouped by major elements were found to have different average trace element contents at different sites (Apollo 15, 16 and Luna 20). This evidence argues that natural groupings in glass compositions are determined by regolith processes and may not represent the composition of primary lunar 'rock types'.

Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroefl, Ch.; Gruber, M.; Plank, J., E-mail: sekretariat@bauchemie.ch.tum.de

2012-11-15

UHPC is fluidized particularly well when a blend of MPEG- and APEG-type PCEs is applied. Here, the mechanism for this behavior was investigated. Testing individual cement and micro silica pastes revealed that the MPEG-PCE disperses cement better than silica whereas the APEG-PCE fluidizes silica particularly well. This behavior is explained by preferential adsorption of APEG-PCE on silica while MPEG-PCEs exhibit a more balanced affinity to both cement and silica. Adsorption data obtained from individual cement and micro silica pastes were compared with those found for the fully formulated UHPC containing a cement/silica blend. In the UHPC formulation, both PCEs stillmore » exhibit preferential and selective adsorption similar as was observed for individual cement and silica pastes. Preferential adsorption of PCEs is explained by their different stereochemistry whereby the carboxylate groups have to match with the steric position of calcium ions/atoms situated at the surfaces of cement hydrates or silica.« less

Soft-Templating Synthesis of Mesoporous Silica-Based Materials for Environmental Applications

NASA Astrophysics Data System (ADS)

Gunathilake, Chamila Asanka

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 °C) and elevated (60-120 °C) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 °C via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60-120 °C. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per gram

Formation of copper aluminate spinel and cuprous aluminate delafossite to thermally stabilize simulated copper-laden sludge.

PubMed

Hu, Ching-Yao; Shih, Kaimin; Leckie, James O

2010-09-15

The study reported herein indicated the stabilization mechanisms at work when copper-laden sludge is thermally treated with gamma-alumina and kaolinite precursors, and evaluated the prolonged leachability of their product phases. Four copper-containing phases - copper oxide (CuO), cuprous oxide (Cu(2)O), copper aluminate spinel (CuAl(2)O(4)), and cuprous aluminate delafossite (CuAlO(2)) - were found in the thermal reactions of the investigated systems. These phases were independently synthesized for leaching by 0.1M HCl aqueous solution, and the relative leachabilities were found to be CuAl(2)O(4)

Silica removal from steamflood produced water: South Texas Tar Sands Pilot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, S.A.; Cathey, S.R.; Yost, M.E.

1984-09-01

Steamflood produced waters commonly contain suspended solids, oil, hardness, sulfide, and silica. Removal of these contaminants would make many of these waters suitable candidates for recycling as steam feedwater. Reuse of steamflood produced waters will increase steamer feedwater supplies, as well as reduce water disposal requirements. This paper describes a field pilot study of silica removal from steamflood produced water in the South Texas Tar Sands region. A hot-lime precipitation process was used to reduce dissolved silica concentrations from 400 mg/l to less than 50 mg/l SiO/sub 2/ in Mary R. Saner Ranch produced water. Most water systems using hot-limemore » precipitation for silica removal call for the addition of magnesium salts, as well as lime, to enhance silica removal. In this field study, however, magnesium salt addition did not improve silica removal efficiency. Hydrated lime ((Ca(OH)/sub 2/), alone, was sufficient to attain the desired silica residual, 50 mg/l SiO/sub 2/. The dissolved silica adsorbed onto the CaCO/sub 3/ crystals formed by lime reacting with the alkalinity present in the produced water. Required lime dosage was approximately 900 mg/lCa(OH)/sub 2/. Residual silica concentrations were found to be strongly related to both precipitator pH and calcium ion concentration. Therefore, on-line pH and hardness monitoring may be used to estimate and control residual silica concentration. A 50,000-BPD (7,900 m/sup 3//d) produced water treating plant has been designed using results from this pilot study.« less

Lithium aluminate/zirconium material useful in the production of tritium

DOEpatents

Cawley, W.E.; Trapp, T.J.

A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Lithium aluminate/zirconium material useful in the production of tritium

DOEpatents

Cawley, W.E.; Trapp, T.J.

1984-10-09

A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Lithium aluminate/zirconium material useful in the production of tritium

DOEpatents

Cawley, William E.; Trapp, Turner J.

1984-10-09

A composition is described useful in the production of tritium in a nuclear eactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Prolonged toxicity characteristic leaching procedure for nickel and copper aluminates.

PubMed

Shih, Kaimin; Tang, Yuanyuan

2011-04-01

The toxicity characteristic leaching procedure (TCLP) is a regulatory testing method widely employed to evaluate the environmental friendliness of waste materials. TCLP analysis provides a fast, easy and economical way to determine the mobility of waste pollutants under simulated landfill conditions. Recent studies on metal stabilization have reported the potential for nickel and copper aluminates to form in thermal treatment conditions, and suggested a more reliable method of stabilizing hazardous metals, particularly when products are to be reused. There is thus an urgent need for a convenient and effective method of quantifying metal leachability and identifying the metal leaching behavior of sparingly soluble materials. In this study, standard TCLP analysis was modified into a prolonged leaching experiment to investigate the leaching behavior of nickel and copper oxides (NiO and CuO) and their aluminates (NiAl(2)O(4), CuAl(2)O(4) and CuAlO(2)). The results demonstrate the difficulty of differentiating the leachability of highly insoluble phases, such as NiO and NiAl(2)O(4), using the standard TCLP. The prolonged TCLP method, however, confirmed NiAl(2)O(4) to have a lower degree of intrinsic leachability than NiO and that it could be expected to undergo congruent dissolution under landfill conditions. For the more soluble copper system, the aluminates were still found to possess a much lower degree of leachability, and their leaching behavior to follow an incongruent dissolution pattern. The results of this study prove prolonged TCLP analysis to be a convenient and effective way to evaluate the environmental friendliness of metal waste and to identify the leaching behavior of waste materials.

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

PubMed

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. Copyright © 2014 Elsevier Ltd. All rights reserved.

Live neighbor-joining.

PubMed

Telles, Guilherme P; Araújo, Graziela S; Walter, Maria E M T; Brigido, Marcelo M; Almeida, Nalvo F

2018-05-16

In phylogenetic reconstruction the result is a tree where all taxa are leaves and internal nodes are hypothetical ancestors. In a live phylogeny, both ancestral and living taxa may coexist, leading to a tree where internal nodes may be living taxa. The well-known Neighbor-Joining heuristic is largely used for phylogenetic reconstruction. We present Live Neighbor-Joining, a heuristic for building a live phylogeny. We have investigated Live Neighbor-Joining on datasets of viral genomes, a plausible scenario for its application, which allowed the construction of alternative hypothesis for the relationships among virus that embrace both ancestral and descending taxa. We also applied Live Neighbor-Joining on a set of bacterial genomes and to sets of images and texts. Non-biological data may be better explored visually when their relationship in terms of content similarity is represented by means of a phylogeny. Our experiments have shown interesting alternative phylogenetic hypothesis for RNA virus genomes, bacterial genomes and alternative relationships among images and texts, illustrating a wide range of scenarios where Live Neighbor-Joining may be used.

Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

PubMed

Borges, Endler M

2015-04-01

Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed. © Crown copyright 2014.

Pulse joining cartridges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

Pulse joining cartridges

DOEpatents

Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

2016-08-23

A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

PubMed

Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

2012-12-18

The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

Distribution of biogenic silica and quartz in recent deep-sea sediments

NASA Astrophysics Data System (ADS)

Leinen, Margaret; Cwienk, Douglas; Heath, G. Ross; Biscaye, Pierre E.; Kolla, V.; Thiede, Jørn; Dauphin, J. Paul

1986-03-01

All available quartz and biogenic silica concentrations from deep-sea surface sediments were intercalibrated, plotted, and contoured on a calcium-carbonate-free basis. The maps show highest concentrations of biogenic silica (opal) along the west African coast, along equatorial divergences in all oceans, and at the Polar Front in the southern Indian Ocean. These are all areas where upwelling is strong and there is high biological productivity. Quartz in pelagic sediments deposited far from land is generally eolian in origin. Its distribution reflects dominant wind systems in the Pacific, but in much of the Atlantic and Indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes.

Quantitative analysis for the determination of aluminum percentage and detonation performance of aluminized plastic bonded explosives by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Rezaei, A. H.; Keshavarz, M. H.; Kavosh Tehrani, M.; Darbani, S. M. R.

2018-06-01

The aluminized plastic-bonded explosive (PBX) is a composite material in which solid explosive particles are dispersed in a polymer matrix, which includes three major components, i.e. polymeric binder, metal fuel (aluminum) and nitramine explosive. This work introduces a new method on the basis of the laser-induced breakdown spectroscopy (LIBS) technique in air and argon atmospheres to investigate the determination of aluminum content and detonation performance of aluminized PBXs. Plasma emissions of aluminized PBXs are recorded where atomic lines of Al, C and H as well as molecular bands of AlO and CN are identified. The experimental results demonstrate that a good discrimination and separation between the aluminized PBXs is possible using LIBS and principle component analysis, although they have similar atomic composition. Relative intensity of the AlO/Al is used to determine aluminum percentage of the aluminized PBXs. The obtained quantitative calibration curve using the relative intensity of the AlO/Al is better than the resulting calibration curve using only the intensity of Al. By using the LIBS method and the measured intensity ratio of CN/C, an Al content of 15% is found to be the optimum value in terms of velocity of detonation of the RDX/Al/HTPB standard samples.

Calcium-based biomaterials for diagnosis, treatment, and theranostics.

PubMed

Qi, Chao; Lin, Jing; Fu, Lian-Hua; Huang, Peng

2018-01-22

Calcium-based (CaXs) biomaterials including calcium phosphates, calcium carbonates, calcium silicate and calcium fluoride have been widely utilized in the biomedical field owing to their excellent biocompatibility and biodegradability. In recent years, CaXs biomaterials have been strategically integrated with imaging contrast agents and therapeutic agents for various molecular imaging modalities including fluorescence imaging, magnetic resonance imaging, ultrasound imaging or multimodal imaging, as well as for various therapeutic approaches including chemotherapy, gene therapy, hyperthermia therapy, photodynamic therapy, radiation therapy, or combination therapy, even imaging-guided therapy. Compared with other inorganic biomaterials such as silica-, carbon-, and gold-based biomaterials, CaXs biomaterials can dissolve into nontoxic ions and participate in the normal metabolism of organisms. Thus, they offer safer clinical solutions for disease theranostics. This review focuses on the state-of-the-art progress in CaXs biomaterials, which covers from their categories, characteristics and preparation methods to their bioapplications including diagnosis, treatment, and theranostics. Moreover, the current trends and key problems as well as the future prospects and challenges of CaXs biomaterials are also discussed at the end.

Joining of dissimilar materials

DOEpatents

Tucker, Michael C; Lau, Grace Y; Jacobson, Craig P

2012-10-16

A method of joining dissimilar materials having different ductility, involves two principal steps: Decoration of the more ductile material's surface with particles of a less ductile material to produce a composite; and, sinter-bonding the composite produced to a joining member of a less ductile material. The joining method is suitable for joining dissimilar materials that are chemically inert towards each other (e.g., metal and ceramic), while resulting in a strong bond with a sharp interface between the two materials. The joining materials may differ greatly in form or particle size. The method is applicable to various types of materials including ceramic, metal, glass, glass-ceramic, polymer, cermet, semiconductor, etc., and the materials can be in various geometrical forms, such as powders, fibers, or bulk bodies (foil, wire, plate, etc.). Composites and devices with a decorated/sintered interface are also provided.

Chrysler Upset Protrusion Joining Techniques for Joining Dissimilar Metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Logan, Stephen

The project goal was to develop and demonstrate a robust, cost effective, and versatile joining technique, known as Upset Protrusion Joining (UPJ), for joining challenging dissimilar metal com-binations, especially those where one of the metals is a die cast magnesium (Mg) component. Since two of the key obstacles preventing more widespread use of light metals (especially in high volume automotive applications) are 1) a lack of robust joining techniques and 2) susceptibility to galvanic corrosion, and since the majority of the joint combinations evaluated in this project include die cast Mg (the lightest structural metal) as one of the twomore » materials being joined, and since die casting is the most common and cost effective process for producing Mg components, then successful project completion provides a key enabler to high volume application of lightweight materials, thus potentially leading to reduced costs, and encouraging implementation of lightweight multi-material vehicles for significant reductions in energy consumption and reduced greenhouse gas emissions. Eco-nomic benefits to end-use consumers are achieved primarily via the reduction in fuel consumption. Unlike currently available commercial processes, the UPJ process relies on a very robust mechanical joint rather than intermetallic bonding, so the more cathodic material can be coated prior to joining, thus creating a robust isolation against galvanic attack on the more anodic material. Additionally, since the UPJ protrusion is going through a hole that can be pre-drilled or pre-punched prior to coating, the UPJ process is less likely to damage the coating when the joint is being made. Further-more, since there is no additional cathodic material (such as a steel fastener) used to create the joint, there is no joining induced galvanic activity beyond that of the two parent materials. In accordance with its originally proposed plan, this project has successfully developed process variants of UPJ to

Pozzolanic activity and durability of nano silica, micro silica and silica gel contained concrete

NASA Astrophysics Data System (ADS)

Al Ghabban, Ahmed; Al Zubaidi, Aseel B.; Fakhri, Zahraa

2018-05-01

This paper aims to investigate the influence of replacement of cement with nano silica, micro silica and silica gel admixtures on pozzolanic activity, the replacement ratio was10% for all admixture, silica gel used in two forms (beads and crushed powder). Also, the water absorption test was investigated for obtaining the durability properties of concrete, in specimens for this test admixtures were added in four different dosages 1%, 2%, 3% and 4% by weight of the cementitious material into the concrete mixture. Experimental investigations of modified concrete were conducted after 28 days of water curing. Results showed that mixes of nano silica and crushed silica gel showed a higher pozzolanic activity index. For the water absorption test, all mixes incorporating nano silica, micro silica and silica gel showed lower absorption than control mixes best result were noticed with crushed silica gel and nano silica mixes. DTA analysis confirms the results for both poisonous activity and water absorption.

Growth of hydroxyapatite in a biocompatible mesoporous ordered silica.

PubMed

Díaz, A; López, T; Manjarrez, J; Basaldella, E; Martínez-Blanes, J M; Odriozola, J A

2006-03-01

A novel biomaterial (HA-SBA-15) has been developed based on the growth of calcium phosphate hydroxyapatite (HA) nanoparticles within an organized silica structure (SBA-15). Characterization of the material was carried out using a combination of X-ray diffraction, X-ray fluorescence, transmission electron microscopy, N2 adsorption-desorption isotherms and nuclear magnetic resonance. Transmission electron microscopy observations and N2 porosimetry revealed the crystallization of hydroxyapatite nanoparticles inside the mesopore cavities of the silica structure. Specific surface areas of 760 m2 g(-1) and 260 m2 g(-1) were measured for the SBA-15 and the HA-SBA-15 material, respectively. The hydroxyl groups present in the silica nanostructure surface have brought about cationic defects in the silicium sites, mainly with those of tetrahedral symmetry, and promoted the formation of siloxanes. 29Si MAS-NMR analysis shows a significant reduction of the silanol groups concentration with HA growing within the base (SBA-15) material. Studies and brain tissue biocompatibility tests were carried out. Histopathological studies on the SBA-15 implant material showed no changes to the tissue nearby. The results confirmed the synthesis of a silica-based composite containing HA nanoparticles with the potential for biomedical applications.

Steam stable mesoporous silica MCM-41 stabilized by trace amounts of Al.

PubMed

Tompkins, Jordan T; Mokaya, Robert

2014-02-12

Evaluation of low and ultralow Al content (Si/Al between 50 and 412) aluminosilicate Al-MCM-41 materials synthesized via three contrasting alumination routes, namely, direct mixed-gel synthesis, post-synthesis wet grafting, and post-synthesis dry grafting, indicates that trace amounts of Al introduced via dry grafting can stabilize mesoporous silica MCM-41 to steaming at 900 °C for 4 h. It was found that trace amounts of Al (Si/Al > 400) introduced via so-called dry grafting of Al stabilize the virtually purely siliceous MCM-41 to steaming, whereas Al incorporated via other methods that involve aqueous media such as direct mixed gel synthesis or wet grafting of Al offer only limited protection at low Al content. It is particularly remarkable that a post-synthesis dry grafted Al-MCM-41 material possessing trace amounts of Al (i.e., Si/Al ratio of 412) and surface area and pore volume of 1112 m(2)/g and 1.20 cm(3)/g, respectively, retains 90% (998 m(2)/g) of the surface area and 85% (1.03 cm(3)/g) of the pore volume after exposure to steaming at 900 °C for 4 h. Under similar steam treatment conditions, the mesostructure of pure silica Si-MCM-41 is virtually destroyed and undergoes a 93% reduction in surface area (958 m(2)/g to 69 m(2)/g) and 88% decrease in pore volume (0.97 cm(3)/g to 0.12 cm(3)/g). The steam stable ultralow (i.e., trace) Al containing MCM-41 materials is found to be virtually similar to mesoporous pure silica Si-MCM-41 with hardly any detectable acidity. The improvement in steam stability arises from not only the presence of trace amounts of Al, but also from an apparent increase in the level of silica condensation that is specific to dry grafted alluminosilicate MCM-41 materials. The more highly condensed framework has fewer silanol groups and therefore is more resistant to hydrolysis under steaming conditions.

Calcium leaching behavior of cementitious materials in hydrochloric acid solution.

PubMed

Yang, Huashan; Che, Yujun; Leng, Faguang

2018-06-11

The calcium leaching behavior of cement paste and silica fume modified calcium hydroxide paste, exposed to hydrochloric acid solution, is reported in this paper. The kinetic of degradation was assessed by the changes of pH of hydrochloric acid solution with time. The changes of compressive strength of specimens in hydrochloric acid with time were tested. Hydration products of leached specimens were also analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscope (AFM). Tests results show that there is a dynamic equilibrium in the supply and consumption of calcium hydroxide in hydrochloric acid solution, which govern the stability of hydration products such as calcium silicate hydrate (C-S-H). The decrease of compressive strength indicates that C-S-H are decomposed due to the lower concentration of calcium hydroxide in the pore solution than the equilibrium concentration of the hydration products. Furthermore, the hydration of unhydrated clinker delayed the decomposition of C-S-H in hydrochloric acid solution due to the increase of calcium hydroxide in pore solution of cementitious materials.

CFRTP and stainless steel laser joining: Thermal defects analysis and joining parameters optimization

NASA Astrophysics Data System (ADS)

Jiao, Junke; Xu, Zifa; Wang, Qiang; Sheng, Liyuan; Zhang, Wenwu

2018-07-01

Experiments with different joining parameters were carried out on fiber laser welding system to explore the mechanism of CFRTP/stainless steel joining and the influence of the parameters on the joining quality. The thermal defect and the microstructure of the joint was tested by SEM, EDS. The joint strength and the thermal defect zone width was measured by the tensile tester and the laser confocal microscope, respectively. The influence of parameters such as the laser power, the joining speed and the clamper pressure on the stainless steel surface thermal defect and the joint strength was analyzed. The result showed that the thermal defect on the stainless steel surface would change metal's mechanical properties and reduce its service life. A chemical bonding was found between the CFRTP and the stainless steel besides the physical bonding and the mechanical bonding. The highest shear stress was obtained as the laser power, the joining speed and the clamper pressure is 280 W, 4 mm/s and 0.15 MPa, respectively.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bizzozero, Julien, E-mail: julien.bizzozero@gmail.com; Scrivener, Karen L.

This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

A New Method for Determining the Equation of State of Aluminized Explosive

NASA Astrophysics Data System (ADS)

Zhou, Zheng-Qing; Nie, Jian-Xin; Guo, Xue-Yong; Wang, Qiu-Shi; Ou, Zhuo-Cheng; Jiao, Qing-Jie

2015-01-01

The time-dependent Jones—Wilkins—Lee equation of state (JWL-EOS) is applied to describe detonation state products for aluminized explosives. To obtain the time-dependent JWL-EOS parameters, cylinder tests and underwater explosion experiments are performed. According to the result of the wall radial velocity in cylinder tests and the shock wave pressures in underwater explosion experiments, the time-dependent JWL-EOS parameters are determined by iterating these variables in AUTODYN hydrocode simulations until the experimental values are reproduced. In addition, to verify the reliability of the derived JWL-EOS parameters, the aluminized explosive experiment is conducted in concrete. The shock wave pressures in the affected concrete bodies are measured by using manganin pressure sensors, and the rod velocity is obtained by using a high-speed camera. Simultaneously, the shock wave pressure and the rod velocity are calculated by using the derived time-dependent JWL equation of state. The calculated results are in good agreement with the experimental data.

Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

PubMed Central

Estokova, Adriana; Kovalcikova, Martina; Luptakova, Alena; Prascakova, Maria

2016-01-01

Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure. PMID:28773452

Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

NASA Astrophysics Data System (ADS)

Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.

2016-02-01

Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

Dissolution enhancement of a model poorly water-soluble drug, atorvastatin, with ordered mesoporous silica: comparison of MSF with SBA-15 as drug carriers.

PubMed

Maleki, Aziz; Hamidi, Mehrdad

2016-01-01

The purpose of this study was to develop mesoporous silica materials incorporated with poorly water-soluble drug atorvastatin calcium (AC) in order to improve drug dissolution, and intended to be orally administrated. A comparison between 2D-hexagonal silica nanostructured SBA-15 and mesocellular siliceous foam (MSF) with continuous 3D pore system on drug release rate was investigated. AC-loaded mesoporous silicas were characterized thorough N2 adsorption-desorption analysis, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and dynamic light scattering (DLS). Results demonstrated a successful incorporation of AC into the silica-based hosts. The results taken from the drug release tests were also analyzed using different parameters, namely similarity factor (f2), difference factor (f1), dissolution efficiency (DE%), mean dissolution rate (MDR) and dissolution time (tm%). It confirmed a significant enhancement in the release profile of atorvastatin calcium with SBA-15, and MSF as drug carrier. Moreover, in comparison with SBA-15, MSF showed faster release rate of AC in enzyme-free simulated gastric fluid (pH 1.2). We believed that our findings can help the use of mesoporous silica materials in improving bioavailability of poorly water-soluble drugs.

Organic-Silica Interactions in Saline: Elucidating the Structural Influence of Calcium in Low-Salinity Enhanced Oil Recovery.

PubMed

Desmond, J L; Juhl, K; Hassenkam, T; Stipp, S L S; Walsh, T R; Rodger, P M

2017-09-08

Enhanced oil recovery using low-salinity solutions to sweep sandstone reservoirs is a widely-practiced strategy. The mechanisms governing this remain unresolved. Here, we elucidate the role of Ca 2+ by combining chemical force microscopy (CFM) and molecular dynamics (MD) simulations. We probe the influence of electrolyte composition and concentration on the adsorption of a representative molecule, positively-charged alkylammonium, at the aqueous electrolyte/silica interface, for four electrolytes: NaCl, KCl, MgCl 2 , and CaCl 2 . CFM reveals stronger adhesion on silica in CaCl 2 compared with the other electrolytes, and shows a concentration-dependent adhesion not observed for the other electrolytes. Using MD simulations, we model the electrolytes at a negatively-charged amorphous silica substrate and predict the adsorption of methylammonium. Our simulations reveal four classes of surface adsorption site, where the prevalence of these sites depends only on CaCl 2 concentration. The sites relevant to strong adhesion feature the O - silica site and Ca 2+ in the presence of associated Cl - , which gain prevalence at higher CaCl 2 concentration. Our simulations also predict the adhesion force profile to be distinct for CaCl 2 compared with the other electrolytes. Together, these analyses explain our experimental data. Our findings indicate in general how silica wettability may be manipulated by electrolyte concentration.

Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

PubMed

Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

2014-02-01

The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

Tableting properties of silica aerogel and other silicates.

PubMed

Hentzschel, C M; Alnaief, M; Smirnova, I; Sakmann, A; Leopold, C S

2012-04-01

In solid oral dosage forms silicates are commonly used as glidants in low concentration. However, due to their large specific surface area, silicates may also be used as carrier materials for drugs. Moreover, silicates allow amorphisation of drugs by co-grinding or processing with supercritical fluids. The aim of this study was to investigate the physical and the tableting properties of Silica Aerogel (special type of silica with an extremely large specific surface area), Neusilin(®) US2 (magnesium aluminometasilicate), Florite(®) (calcium silicate) and Aerosil(®) 200 (colloidal silica). Powder blends of Avicel(®) PH102 (microcrystalline cellulose) and different amounts of the respective silicate were compacted and analyzed for their tabletability (tensile strength vs. compaction pressure) as well as their Heckel plot. With Neusilin(®) the tabletability appeared to be independent of the silicate concentration, whereas with Florite(®) an increasing silicate concentration led to a higher tensile strength. In contrast, the addition of Silica Aerogel and Aerosil(®) resulted in a decrease of the tensile strength. With Aerosil(®) a maximum tolerable concentration of 20% [w/w] was determined. Plastic deformation of all powder blends decreased with increasing silicate concentration. This effect was most pronounced with Aerosil(®) and least with Florite(®). Tablets with acceptable tensile strength were obtained with all plain silicates except for Aerosil(®). Therefore, these silicates may be used in tablet formulations, e.g. as carrier materials for liquid or amorphous drugs.

75 FR 51002 - Pure Magnesium In Granular Form from the People's Republic of China: Initiation of Changed...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-18

.... SUPPLEMENTARY INFORMATION: Background On November 19, 2001, the Department published in the Federal Register an... are: lime, calcium metal, calcium silicon, calcium carbide, calcium carbonate, carbon, slag coagulants, fluorspar, nephaline syenite, feldspar, aluminum, alumina (Al2O3), calcium aluminate, soda ash, hydrocarbons...

In situ alkali-silica reaction observed by x-ray microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurtis, K.E.; Monteiro, P.J.M.; Brown, J.T.

1997-04-01

In concrete, alkali metal ions and hydroxyl ions contributed by the cement and reactive silicates present in aggregate can participate in a destructive alkali-silica reaction (ASR). This reaction of the alkalis with the silicates produces a gel that tends to imbibe water found in the concrete pores, leading to swelling of the gel and eventual cracking of the affected concrete member. Over 104 cases of alkali-aggregate reaction in dams and spillways have been reported around the world. At present, no method exists to arrest the expansive chemical reaction which generates significant distress in the affected structures. Most existing techniques availablemore » for the examination of concrete microstructure, including ASR products, demand that samples be dried and exposed to high pressure during the observation period. These sample preparation requirements present a major disadvantage for the study of alkali-silica reaction. Given the nature of the reaction and the affect of water on its products, it is likely that the removal of water will affect the morphology, creating artifacts in the sample. The purpose of this research is to observe and characterize the alkali-silica reaction, including each of the specific reactions identified previously, in situ without introducing sample artifacts. For observation of unconditioned samples, x-ray microscopy offers an opportunity for such an examination of the alkali-silica reaction. Currently, this investigation is focusing on the effect of calcium ions on the alkali-silica reaction.« less

Exposure to crystalline silica in abrasive blasting operations where silica and non-silica abrasives are used.

PubMed

Radnoff, Diane L; Kutz, Michelle K

2014-01-01

Exposure to respirable crystalline silica is a hazard common to many industries in Alberta but particularly so in abrasive blasting. Alberta occupational health and safety legislation requires the consideration of silica substitutes when conducting abrasive blasting, where reasonably practicable. In this study, exposure to crystalline silica during abrasive blasting was evaluated when both silica and non-silica products were used. The crystalline silica content of non-silica abrasives was also measured. The facilities evaluated were preparing metal products for the application of coatings, so the substrate should not have had a significant contribution to worker exposure to crystalline silica. The occupational sampling results indicate that two-thirds of the workers assessed were potentially over-exposed to respirable crystalline silica. About one-third of the measurements over the exposure limit were at the work sites using silica substitutes at the time of the assessment. The use of the silica substitute, by itself, did not appear to have a large effect on the mean airborne exposure levels. There are a number of factors that may contribute to over-exposures, including the isolation of the blasting area, housekeeping, and inappropriate use of respiratory protective equipment. However, the non-silica abrasives themselves also contain silica. Bulk analysis results for non-silica abrasives commercially available in Alberta indicate that many contain crystalline silica above the legislated disclosure limit of 0.1% weight of silica per weight of product (w/w) and this information may not be accurately disclosed on the material safety data sheet for the product. The employer may still have to evaluate the potential for exposure to crystalline silica at their work site, even when silica substitutes are used. Limited tests on recycled non-silica abrasive indicated that the silica content had increased. Further study is required to evaluate the impact of product recycling

Mineral contents and their solubility on calcium carbonat calcite nanocrystals from cockle shell powder (Anadara granosa Linn)

NASA Astrophysics Data System (ADS)

Widyastuti, S.; Pramushinta, I. A.

2018-03-01

Prepared and characterized calcium carbonat calcite nanocrystals improves solubility. Calcium carbonat calcite nanocrystals were synthesized using precipitation method from the waste of blood clam cockle shells (Anadara granosa Linn). This study was conducted to analyze mineral composition of nanocrystals calcium carbonat calcite cockle (Anadara granosa) shell for calcium fortification of food applications and to evaluate the solubilities of Calsium and Phospor. The sample of nanocrystals from cockle shells was evaluated to determine the content of 11 macro-and micro-elements. These elements are Calcium (Ca), Magnesium (Mg), Sodium (Na), Phosphorus (P), Potassium (K), Ferrum (Fe), Copper (Cu), Nickel (Ni), Zink (Zn), Boron (B) and Silica (Si)). Cockleshell powders were found to contain toxic elements below detectable levels. The solubilities of Calcium and Phospor were p<0.05.

A safer disposal of hazardous phosphate coating sludge by formation of an amorphous calcium phosphate matrix.

PubMed

Navarro-Blasco, I; Duran, A; Pérez-Nicolás, M; Fernández, J M; Sirera, R; Alvarez, J I

2015-08-15

Phosphate coating hazardous wastes originated from the automotive industry were efficiently encapsulated by an acid-base reaction between phosphates present in the sludge and calcium aluminate cement, yielding very inert and stable monolithic blocks of amorphous calcium phosphate (ACP). Two different compositions of industrial sludge were characterized and loaded in ratios ranging from 10 to 50 wt.%. Setting times and compressive strengths were recorded to establish the feasibility of this method to achieve a good handling and a safe landfilling of these samples. Short solidification periods were found and leaching tests showed an excellent retention for toxic metals (Zn, Ni, Cu, Cr and Mn) and for organic matter. Retentions over 99.9% for Zn and Mn were observed even for loadings as high as 50 wt.% of the wastes. The formation of ACP phase of low porosity and high stability accounted for the effective immobilization of the hazardous components of the wastes. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of calcium hydroxide, alkali dilution and calcium concentration in mitigating the alkali silica reaction using palm oil fuel ash

NASA Astrophysics Data System (ADS)

Asrah, Hidayati; Mirasa, Abdul Karim; Bolong, Nurmin

2018-02-01

This study investigated the mechanism of how POFA mitigated the ASR expansion. Two types of POFA; the UPOFA and GPOFA with different fineness were used to replace the cement at 20% and 40% and their effects on the mortar bar expansion, calcium hydroxide, alkali dilution, and calcium concentration were investigated. The results showed that UPOFA has a significant ability to mitigate the ASR, even at a lower level of replacement (20%) compared to GPOFA. The mechanism of UPOFA in mitigating the ASR expansion was through a reduction in the calcium hydroxide content, which produced low calcium concentration within the mortar pore solution. Low pore solution alkalinity signified that UPOFA had good alkali dilution effect. Meanwhile, a higher dosage of GPOFA was required to mitigate the ASR expansion. An increase in the pore solution alkalinity of GPOFA mortar indicated higher penetration of alkalis from the NaOH solution, which reduced the alkali dilution effect. However, this was compensated by the increase in the cement dilution effect at higher GPOFA replacement, which controlled the mortar bar expansion below the ASTM limit.

Joined concentric tubes

DOEpatents

DeJonghe, Lutgard; Jacobson, Craig; Tucker, Michael; Visco, Steven

2013-01-01

Tubular objects having two or more concentric layers that have different properties are joined to one another during their manufacture primarily by compressive and friction forces generated by shrinkage during sintering and possibly mechanical interlocking. It is not necessary for the concentric tubes to display adhesive-, chemical- or sinter-bonding to each other in order to achieve a strong bond. This facilitates joining of dissimilar materials, such as ceramics and metals.

Elastomeric Thermal Insulation Design Considerations in Long, Aluminized Solid Rocket Motors

NASA Technical Reports Server (NTRS)

Martin, Heath T.

2017-01-01

An all-new sounding rocket was designed at NASA's Marshall Space Flight Center that featured an aft finocyl, aluminized solid propellant grain and silica-filled ethylene-propylene-diene monomer (SFEPDM) internal insulation. Upon the initial static firing of the first of this new design, the solid rocket motor (SRM) case failed thermally just upstream of the aft closure early in the burn time. Subsequent fluid modeling indicated that the high-velocity combustion-product jets emanating from the fin-slots in the propellant grain were likely inducing a strongly swirling flow, thus substantially increasing the severity of the convective environment on the exposed portion of the SFEPDM insulation in this region. The aft portion of the fin-slots in another of the motors were filled with propellant to eliminate the possibility of both direct jet impingement on the exposed SFEPDM and the appearance of strongly swirling flow in the aft region of the motor. When static-fired, this motor's case still failed in the same axial location, and, though somewhat later than for the first static firing, still in less than 1/3rd of the desired burn duration. These results indicate that the extreme material decomposition rates of the SFEPDM in this application are not due to gas-phase convection or shear but rather to interactions with burning aluminum or alumina slag. Further comparisons with between SFEPDM performance in this design and that in other hot-fire tests provide insight into the mechanisms of SFEPDM decomposition in SRM aft domes that can guide the upcoming redesign effort, as well as other future SRM designs. These data also highlight the current limitations of modeling elastomeric insulators solely with diffusion-controlled, gas-phase thermochemistry in SRM regions with significant viscous shear and/or condense-phase impingement or flow.

RhBMP-2 loaded 3D-printed mesoporous silica/calcium phosphate cement porous scaffolds with enhanced vascularization and osteogenesis properties

NASA Astrophysics Data System (ADS)

Li, Cuidi; Jiang, Chuan; Deng, Yuan; Li, Tao; Li, Ning; Peng, Mingzheng; Wang, Jinwu

2017-01-01

A major limitation in the development of effective scaffolds for bone regeneration has been the limited vascularization of the regenerating tissue. Here, we propose the development of a novel calcium phosphate cement (CPC)-based scaffold combining the properties of mesoporous silica (MS) with recombinant human bone morphogenic protein-2 (rhBMP-2) to facilitate vascularization and osteogenesis. Specifically, the development of a custom MS/CPC paste allowed the three-dimensional (3D) printing of scaffolds with a defined macroporous structure and optimized silicon (Si) ions release profile to promote the ingrowth of vascular tissue at an early stage after implantation in support of tissue viability and osteogenesis. In addition, the scaffold microstructure allowed the prolonged release of rhBMP-2, which in turn significantly stimulated the osteogenesis of human bone marrow stromal cells in vitro and of bone regeneration in vivo as shown in a rabbit femur defect repair model. Thus, the combination MS/CPC/rhBMP-2 scaffolds might provide a solution to issues of tissue necrosis during the regeneration process and therefore might be able to be readily developed into a useful tool for bone repair in the clinic.

System and process for aluminization of metal-containing substrates

DOEpatents

Chou, Yeong-Shyung; Stevenson, Jeffry W.

2017-12-12

A system and method are detailed for aluminizing surfaces of metallic substrates, parts, and components with a protective alumina layer in-situ. Aluminum (Al) foil sandwiched between the metallic components and a refractory material when heated in an oxidizing gas under a compression load at a selected temperature forms the protective alumina coating on the surface of the metallic components. The alumina coating minimizes evaporation of volatile metals from the metallic substrates, parts, and components in assembled devices that can degrade performance during operation at high temperature.

System and process for aluminization of metal-containing substrates

DOEpatents

Chou, Yeong-Shyung; Stevenson, Jeffry W

2015-11-03

A system and method are detailed for aluminizing surfaces of metallic substrates, parts, and components with a protective alumina layer in-situ. Aluminum (Al) foil sandwiched between the metallic components and a refractory material when heated in an oxidizing gas under a compression load at a selected temperature forms the protective alumina coating on the surface of the metallic components. The alumina coating minimizes evaporation of volatile metals from the metallic substrates, parts, and components in assembled devices during operation at high temperature that can degrade performance.

Microstructure of amorphous aluminum hydroxide in belite-calcium sulfoaluminate cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Fei; Yu, Zhenglei; Yang, Fengling

Belite-calcium sulfoaluminate (BCSA) cement is a promising low-CO{sub 2} alternative to ordinary Portland cement. Herein, aluminum hydroxide (AH{sub 3}), the main amorphous hydration product of BCSA cement, was investigated in detail. The microstructure of AH{sub 3} with various quantities of gypsum was investigated via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The AH{sub 3} with various morphologies were observed and confirmed in the resulting pastes. Particular attention was paid to the fact that AH{sub 3} always contained a small amount of Ca according to the results of EDS analysis. The AH{sub 3} was then characterized via highmore » resolution transmission electron microscopy (HRTEM). The results of HRTEM indicated that Ca arose from nanosized tricalcium aluminate hexahydrate which existed in the AH{sub 3}.« less

Driving Ability of HMX based Aluminized Explosive Affected by the Reaction Degree of Aluminum Powder

NASA Astrophysics Data System (ADS)

Duan, Yingliang

2017-06-01

Due to the time scale of aluminum reaction, the detonation process of the aluminized explosive becomes very complex, and there is less agreement on the reaction mechanism of aluminum powder. If the reaction of aluminum occurs in the reaction zone, the energy released will further strengthen the work ability of detonation wave. So it is very important for characterizing the detonation parameters and detonation driving ability to accurately understand the role of aluminum powder in the reaction zone. In this paper, detonation driving process of HMX based aluminized explosive was studied by cylinder test, obtaining the expansion track of cylinder wall. In order to further research the reaction degree (λ) of aluminum in the reaction zone, the thermodynamic program VHL was used to calculate the detonation process at different reaction degrees, obtaining the parameters of detonation products thermodynamic state. Using the dynamic software LS-DYNA and the JWL equation of state by fitting the pressure and relative volume relationship, the cylinder test was simulated. Compared with the experimental results, when the reaction degree is 20%, the driving ability is found to be in agreement with measured ones. It is concluded that the driving ability of HMX based aluminized explosive can be more accurately characterized by considering the reaction degree of aluminum powder in the reaction zone.

Physico-chemical mechanisms involved in the acceleration of the hydration of calcium sulfoaluminate cement by lithium ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cau Dit Coumes, Céline, E-mail: celine.cau-dit-coumes@cea.fr; Dhoury, Mélanie; Champenois, Jean-Baptiste

This work investigates the influence of lithium ions on the hydration at 25 °C of two calcium sulfoaluminate (CSA) cements comprising 0 or 10% gypsum. Small concentrations of lithium salts (LiOH, LiNO{sub 3}) accelerate the early hydration of both CSA cements either in paste or in diluted and stirred suspension. The effect of the lithium cation is much stronger than its counter-ion. Hydration is accelerated by an increase in the lithium concentration up to 30 μmol Li/g of the used CSA cement (with a high ye'elimite content), and then levels off. The postulated mechanism relies on a fast precipitation ofmore » amorphous Li-containing Al(OH){sub 3}, which acts as seeds for accelerating the precipitation of amorphous Al(OH){sub 3} that speeds up the whole hydration process. This process seems to be closely related to the one involved in the acceleration of the hydration of calcium aluminate cement by lithium ions.« less

Duct Joining System

DOEpatents

Proctor, John P.

2001-02-27

A duct joining system for providing an air-tight seal and mechanical connection for ducts and fittings is disclosed. The duct joining system includes a flexible gasket affixed to a male end of a duct or fitting. The flexible gasket is affixed at an angle relative to normal of the male end of the duct. The female end of the other duct includes a raised bead in which the flexible gasket is seated when the ducts are properly joined. The angled flexible gasket seated in the raised bead forms an air-tight seal as well as fastens or locks the male end to the female end. Alternatively, when a flexible duct is used, a band clamp with a raised bead is clamped over the female end of the flexible duct and over the male end of a fitting to provide an air tight seal and fastened connection.

Duct joining system

DOEpatents

Proctor, John P.; deKieffer, Robert C.

2001-01-01

A duct joining system for providing an air-tight seal and mechanical connection for ducts and fittings is disclosed. The duct joining system includes a flexible gasket affixed to a male end of a duct or fitting. The flexible gasket is affixed at an angle relative to normal of the male end of the duct. The female end of the other duct includes a raised bead in which the flexible gasket is seated when the ducts are properly joined. The angled flexible gasket seated in the raised bead forms an air-tight seal as well as fastens or locks the male end to the female end. Alternatively, when a flexible duct is used, a band clamp with a raised bead is clamped over the female end of the flexible duct and over the male end of a fitting to provide an air tight seal and fastened connection.

Charge division in a small proportional chamber constructed with aluminized mylar tubes

NASA Astrophysics Data System (ADS)

Biino, C.; Mussa, R.; Palestini, S.; Pastrone, N.; Pesando, L.

1988-09-01

A tracking detector composed of aluminized mylar drift tubes is under development for the Fermilab experiment 760. A prototype chamber has been constructed. Results on the longitudinal coordinate determined by charge division are given. Spatial resolution values below 2 mm (rms) were found, corresponding to <1% of the chamber length. Results on chamber ageing are also discussed.

Boundary conditions for diffusion in the pack-aluminizing of nickel.

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.; Menon, N. B.

1973-01-01

The surface compositions of nickel specimens coated for various lengths of time in aluminizing packs at 2000 F were studied, in order to obtain information about the kinetics of the pack-cementation process in the formation of aluminide coatings. The results obtained indicate that the surface compositions of the coated nickel specimens are independent of time, at least for time between 0.5 and 20 hrs. Another important observation is that the specimens gained weight during the coating process.

Welding and joining: A compilation

NASA Technical Reports Server (NTRS)

1975-01-01

A compilation is presented of NASA-developed technology in welding and joining. Topics discussed include welding equipment, techniques in welding, general bonding, joining techniques, and clamps and holding fixtures.

Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

PubMed Central

Lechner, Carolin C.; Becker, Christian F. W.

2015-01-01

Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed. PMID:26295401

Chemistry of silica scale mitigation for RO desalination with particular reference to remote operations.

PubMed

Milne, Nicholas A; O'Reilly, Tom; Sanciolo, Peter; Ostarcevic, Eddy; Beighton, Mark; Taylor, Kelvin; Mullett, Mark; Tarquin, Anthony J; Gray, Stephen R

2014-11-15

Silica scaling in reverse osmosis of groundwater is a significant issue in water stressed areas due to the limitations that scaling imposes on water recovery. While calcium and magnesium scaling potential can be significantly reduced by the use of ion exchange or other softening processes, the silica scaling potential typically remains. Improving the recovery of reverse osmosis by limiting the potential for silica scale is important in ensuring maximum water recovery. This is particularly important for mining and natural gas industries that are located in remote regions. The remote nature of these sites imposes three major restrictions on the silica scale mitigation process. Firstly, the generation of poorly dewaterable sludges must be avoided. Also, the quality of any reverse osmosis (RO) permeate must be able to meet the end use requirements, particularly for boilers. Finally, silica removal should not impact upon other potentially useful or valuable components within the brine, and should not make the disposal of the unusable waste brine components more difficult. Reduction of scaling potential can be achieved in three main ways: operating RO at high pH after hardness has been removed, operating at low pH, and reducing the silica concentration either in pretreatment or by using an interstage technique. Operating at high pH has the initial requirement of hardness removal to prevent scaling and this could be an issue on some sites. Hardness removal operations that use ion exchange resins may be challenged by water chemistry and the operational costs associated with high chemical regeneration costs. Operating at low pH may be more desirable than high pH operation as this can help to reduce the risk of scale formation from calcium or magnesium salts. The drawback comes from the cost of acid, particularly for high-alkalinity waters. There are numerous silica removal techniques including chemical dosing of lime, or aluminium or iron salts, electrocoagulation

Joining engineering ceramics

NASA Astrophysics Data System (ADS)

Loehman, Ronald E.

Methods for joining ceramics are outlined with attention given to their fundamental properties, and some examples of ceramic bonding in engineering ceramic systems are presented. Ceramic-ceramic bonds using no filler material include diffusion and electric-field bonding and ceramic welding, and bonds with filler materials can be provided by Mo-Mn brazing, microwave joining, and reactive nonmetallic liquid bonding. Ceramic-metal joints can be effected with filler material by means of the same ceramic-ceramic processes and without filler material by means of use of molten glass or diffusion bonding. Key properties of the bonding processes include: bonds with discontinuous material properties, energies that are positive relative to the bulk material, and unique chemical and mechanical properties. The processes and properties are outlined for ceramic-metal joints and for joining silicon nitride, and the factors that control wetting, adhesion, and reaction on the atomic scale are critical for establishing successful joints.

Welding and Joining of Titanium Aluminides

PubMed Central

Cao, Jian; Qi, Junlei; Song, Xiaoguo; Feng, Jicai

2014-01-01

Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials. PMID:28788113

The effect of explosive percentage on underwater explosion energy release of hexanitrohexaazaisowurtzitane and octogen based aluminized explosives

NASA Astrophysics Data System (ADS)

Jiao, Qingjie; Wang, Qiushi; Nie, Jianxin; Guo, Xueyong; Zhang, Wei; Fan, Wenqi

2018-03-01

To control the explosion energy output by optimizing explosive components is a key requirement in a number of different application areas. The effect of different Al/O Ratio on underwater explosion of aluminized explosives has been studied detailedly. However, the effect of explosive percentage in the same Al/O Ratio is rarely researched, especially for Hexanitrohexaazaisowurtzitane (CL-20) based aluminized explosives. In this study, we performed the underwater explosion experiments with 1.2-kilogram explosives in order to investigate the explosion energy released from CL-20 and Octogen (HMX) based aluminized explosives. The percentage of the explosive varied from 5% to 30% and it is shown that: the shockwave peak pressure (pm) grows gradually; shock wave energy (Es) continues increasing, bubble energy (Eb) increases then decreases peaking at 15% for both formulas, and the total energy (E) and energy release rate (η) peak at 20% for CL-20 and 15% for HMX. This paper outlines the physical mechanism of Eb change under the influence of an aluminium initial reaction temperature and reaction active detonation product percentage coupling. The result shows that CL-20 is superior as a new high explosive and has promising application prospects in the regulation of explosive energy output for underwater explosives.

Optimization of soil stabilization with class C fly ash.

DOT National Transportation Integrated Search

1987-01-01

Previous Iowa DOT sponsored research has shown that some Class : C fly ashes are cementitious (because calcium is combined as calcium : aluminates) while other Class C ashes containing similar amounts of : elemental calcium are not (1). Fly ashes fro...

Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cau Dit Coumes, Celine; Courtois, Simone; Peysson, Sandrine

Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL{sup -1}. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement-waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 deg. Cmore » by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CSA) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CSA cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale.« less

Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams

NASA Astrophysics Data System (ADS)

Yuan, Zheng

Antifoams are utilized as an industrial additive to control undesired foam during processing. This study focuses on the impact of silica on the antifoam stability. Antifoam stability refers to the ability to maintain efficiency in foam destruction after prolonged shelf storage. Common antifoams are a mixture of hydrophobic silica particles and silicone oil. Based on the general mechanisms of antifoam action discussed in Chapter 1, silica particles play a significant role in foam destruction. Silica particles contribute to foam control by facilitating the entry and the penetration depth of oil-silica globules into surfactant-water films (foam bubble walls). The size, morphology and hydrophobicity of silica can be manipulated to generate optimal antifoam globules. For example, the two silicas with good shelf life performance (8375 and 9512) had the largest silica particles and both showed a tendency to aggregate in toluene solution. We conclude that improved shelf life is related to the propensity of PDMS oil to adsorb on silica, which leads to aggregation and particle size increase. We measured the time-evolution of dynamic light scattering (DLS) from 3-vol% antifoam dissolved in toluene (Chapter 2). For the sample with the largest hydrodynamic radius (9512) the scattered intensity decreased significantly after applying ultrasonic dispersion. Decreasing intensity also occurred for 8375 albeit at later times. The decrease of intensity is attributed to the growth and precipitation of oil-silica globules. The concentration dependence of light scattering confirmed the growth-precipitation hypothesis. FT-IR (Chapter 3) was consistent with precipitation due to oil adsorption, but the data were not definitive. Chapter 4 examines the time-evolution of silica structures by static light scattering and X-ray scattering. The combined data are consistent with a hierarchical structure for silica. Agglomeration occurred fastest for 9512, which is consistent with DLS observations

Water-sensitive positron trapping modes in nanoporous magnesium aluminate ceramics

NASA Astrophysics Data System (ADS)

Filipecki, J.; Ingram, A.; Klym, H.; Shpotyuk, O.; Vakiv, M.

2007-08-01

The water-sensitive positron trapping modes in nanoporous MgAl2O4 ceramics with a spinel structure are studied. It is shown that water-sorption processes in magnesium aluminate ceramics leads to corresponding increase in positron trapping rates of extended defects located near intergranual boundaries. This catalytic affect has reversible nature, being strongly dependent on sorption water fluxes in ceramics. The fixation of all water-dependent positron trapping inputs allow to refine the most significant changes in positron trapping rate of extended defects.

Mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells following their exposure to a discoloration-free calcium aluminosilicate cement.

PubMed

Niu, Li-Na; Pei, Dan-Dan; Morris, Matthew; Jiao, Kai; Huang, Xue-Qing; Primus, Carolyn M; Susin, Lisiane F; Bergeron, Brian E; Pashley, David H; Tay, Franklin R

2016-10-01

An experimental discoloration-free calcium aluminosilicate cement has been developed with the intention of maximizing the beneficial attributes of tricalcium silicate cements and calcium aluminate cements. The present study examined the effects of this experimental cement (Quick-Set2) on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available tricalcium silicate cement (white mineral trioxide aggregate (ProRoot(®) MTA); WMTA). The osteogenic potential of hDPSCs exposed to the cements was examined using qRT-PCR for osteogenic gene expressions, Western blot for osteogenic-related protein expressions, alkaline phosphatase enzyme activity, Alizarin red S staining, Fourier transform infrared spectroscopy and transmission electron microscopy of extracellular calcium deposits. Results of the six assays indicated that osteogenic differentiation of hDPSCs was significantly enhanced after exposure to the tricalcium silicate cement or the experimental calcium aluminosilicate cement, with the former demonstrating better mineralogenic stimulation capacity. The better osteogenic stimulating effect of the tricalcium silicate cement on hDPSCs may be due to its relatively higher silicate content, or higher OH(-) and Ca(2+) release. Further investigations with the use of in vivo animal models are required to validate the potential augmenting osteogenic effects of the experimental discoloration-free calcium aluminosilicate cement. Published by Elsevier Ltd.

Affordable, Robust Ceramic Joining Technology (ARCJoint) Developed

NASA Technical Reports Server (NTRS)

Steele, Gynelle C.

2001-01-01

Affordable, Robust Ceramic Joining Technology (ARCJoint) is a method for joining high temperature- resistant ceramic pieces together, establishing joints that are strong, and allowing joining to be done in the field. This new way of joining allows complex shapes to be formed by joining together geometrically simple shapes. The joining technology at NASA is one of the enabling technologies for the application of silicon-carbide-based ceramic and composite components in demanding and high-temperature applications. The technology is being developed and tested for high-temperature propulsion parts for aerospace use. Commercially, it can be used for joining ceramic pieces used for high temperature applications in the power-generating and chemical industries, as well as in the microelectronics industry. This innovation could yield big payoffs for not only the power-generating industry but also the Silicon Valley chipmakers. This technology, which was developed at the NASA Glenn Research Center by Dr. Mrityunjay Singh, is a two-step process involving first using a paste to join together ceramic pieces and bonding them by heating the joint to 110 to 120 C for between 10 and 20 min. This makes the joint strong enough to be handled for the final joining. Then, a silicon-based substance is applied to the joint and heated to 1400 C for 10 to 15 min. The resulting joint is as strong as the original ceramic material and can withstand the same high temperatures.

Interaction of fullerene (C60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications.

PubMed

Chen, Kai Loon; Elimelech, Menachem

2008-10-15

The deposition kinetics of fullerene (C60) nanoparticles onto bare silica surfaces and surfaces precoated with humic acid and alginate are investigated over a range of monovalent (NaCI) and divalent (CaCl2) salt concentrations using a quartz crystal microbalance. Because simultaneous aggregation of the fullerene nanoparticles occurs, especially at higher electrolyte concentrations, we normalize the observed deposition rates by the corresponding favorable (transport-limited) deposition rates to obtain the attachment efficiencies, alpha. The deposition kinetics of fullerene nanoparticles onto bare silica surfaces are shown to be controlled by electrostatic interactions and van der Waals attraction, consistent with the classical particle deposition behavior where both favorable and unfavorable deposition regimes are observed. The presence of dissolved humic acid and alginate in solution leads to significantly slower deposition kinetics due to steric repulsion. Precoating the silica surfaces with humic acid and alginate exerts similar steric stabilization in the presence of NaCl. In the presence of CaCl2, the deposition kinetics of fullerene nanoparticles onto both humic acid- and alginate-coated surfaces are relatively high, even at relatively low (0.3 mM) calcium concentration. This behavior is attributed to the macromolecules undergoing complex formation with calcium ions, which reduces the charge and steric influences of the adsorbed macromolecular layers.

The Join-Up Meeting

NASA Technical Reports Server (NTRS)

Cameron, W. Scott

2002-01-01

I recently took on a new assignment and, as is my norm, I scheduled a series of one-hour, 1:1 join-up meetings with the various lead personnel on the team and their hierarchy. During one of these meetings, the person I was meeting with informed me how pleasantly surprised she was that I had scheduled this meeting as very few individuals took the time anymore to have them. I was shocked. I was taught that establishing a 1:1 relationship with the people on your team is critical to the project's success. This was the first time I'd heard anything like this about join-up meetings. I filed this feedback away. Later I was talking to my project manager-mentor, and he indicated he had finished his join-up meetings with every person in his new organization. He also indicated his predecessor had conducted few, if any, join-up meetings. Again, I was shocked. When I reflected on these two experiences, I realized a very negative trend might be emerging in our fast-paced, schedule-driven, 500-e-mail-per-day, cell-phone -ringing, 24/7 -communication, multi-tasking work lives: NO FACE TIME! Face time is what you spend with people to talk about the project you are working on, their expectations of you, your expectations of them, your hierarchy's expectations about each of you, and/or-last but certainly not least-what each of you plans on achieving during the project. A 1:1, face-to-face, join-up meeting is the only way I know to build solid trust between the project manager and the team members and their hierarchy.

Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Go

Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgymore » (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition

Porous electrolyte retainer for molten carbonate fuel cell. [lithium aluminate

DOEpatents

Singh, R.N.; Dusek, J.T.

1979-12-27

A porous tile for retaining molten electrolyte within a fuel cell is prepared by sintering particles of lithium aluminate into a stable structure. The tile is assembled between two porous metal plates which serve as electrodes with fuels gases such as H/sub 2/ and CO opposite to oxidant gases such as O/sub 2/ and CO/sub 2/. The tile is prepared with a porosity of 55 to 65% and a pore size distribution selected to permit release of sufficient molten electrolyte to wet but not to flood the adjacent electrodes.

[In vitro toxicity of naturally occurring silica nanoparticles in C1 coal in bronchial epithelial cells].

PubMed

Li, Guangjian; Huang, Yunchao; Liu, Yongjun; Guo, Lv; Zhou, Yongchun; Yang, Kun; Chen, Ying; Zhao, Guangqiang; Lei, Yujie

2012-10-01

China's Xuan Wei County in Yunnan Province have the world's highest incidence of lung cancer in nonsmoking women-20 times higher than the rest of China. Previous studies showed, this high lung cancer incidence may be associated with the silica particles embedded in the production combustion from the C1 coal. The aim of this study is to separate the silica particles from production combustion from the C1 bituminous coal in Xuan Wei County of Yunnan Province, and study in vitro toxicity of naturally occurring silica particles on BEAS-2B. ①Separating the silica particles from combustion products of C1 bituminous coal by physical method, observing the morphology by Scanning Electron Microscope, analysis elements by SEM-EDX, observed the single particle morphology by Transmission Electron Microscope, analyed its particle size distribution by Laser particle size analyzer, the surface area of silica particles were determined by BET nitrogen adsorption analysis; ②Cell viability of the experimental group (silica; naturally occurring), control group (silica; industrial produced and crystalline silica) was detected by assay used the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, and the reactive oxygen species (ROS), lactate dehydrogenase (LDH) were determined after 24 h-72 h exposed to these particles. ①The physical method can separate silica particles from production combustion from the C1 bituminous coal, which have different size, and from 30 nm to 120 nm particles accounted for 86.8%, different morphology, irregular surface area and containing trace of aluminum, calcium and iron and other elements; ②Under the same concentration, the experiment group have higher toxicity on BEAS-2B than control groups. Physical method can separate silica particles from production combustion from the C1 bituminous coal and not change the original morphology and containing trace; ②Naturally occurring silica nanoparticles have irregular morphology

Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene, dextran sulfate, and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ioutsi, A. N.; Shapovalova, E. N.; Ioutsi, V. A.; Mazhuga, A. G.; Shpigun, O. A.

2017-12-01

New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

Thermal Properties of Double-Aluminized Kapton at Low Temperatures

NASA Technical Reports Server (NTRS)

Tuttle, J.; DiPirro, M.; Canavan, E.; Hait, T.

2007-01-01

Double-aluminized kapton (DAK) is commonly used in multi-layer insulation blankets in cryogenic systems. NASA plans to use individual DAK sheets in lightweight deployable shields for satellites carrying instruments. A set of these shields will reflect away thermal radiation from the sun, the earth, and the instrument's warm side and allow the instrument's cold side to radiate its own heat to deep space. In order to optimally design such a shield system, it is important to understand the thermal characteristics of DAK down to low temperatures. We describe experiments which measured the thermal conductivity and electrical resistivity down to 4 Kelvin and the emissivity down to 10 Kelvin.

Evaluating the Upset Protrusion Joining (UPJ) Method to Join magnesium Castings to Dissimilar Metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Logan, Stephen D.

2015-08-19

This presentation discusses advantages and best practices for incorporating magnesium in automotive component applications to achieve substantial mass reduction, as well as some of the key challenges with respect to joining, coating, and galvanic corrosion, before providing an introduction and status update of the U.S. Department of Energy and Department of Defense jointly sponsored Upset Protrusion Joining (UPJ) process development and evaluation project. This update includes sharing performance results of a benchmark evaluation of the self-pierce riveting (SPR) process for joining dissimilar magnesium (Mg) to aluminum (Al) materials in four unique coating configurations before introducing the UPJ concept and comparingmore » performance results of the joints made with the UPJ process to those made with the SPR process.« less

Method of winning aluminum metal from aluminous ore

DOEpatents

Loutfy, Raouf O.; Keller, Rudolf; Yao, Neng-Ping

1981-01-01

Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (AlS) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

Synthesis of nanostructured porous silica coatings on titanium and their cell adhesive and osteogenic differentiation properties.

PubMed

Inzunza, Débora; Covarrubias, Cristian; Von Marttens, Alfredo; Leighton, Yerko; Carvajal, Juan Carlos; Valenzuela, Francisco; Díaz-Dosque, Mario; Méndez, Nicolás; Martínez, Constanza; Pino, Ana María; Rodríguez, Juan Pablo; Cáceres, Mónica; Smith, Patricio

2014-01-01

Nanostructured porous silica coatings were synthesized on titanium by the combined sol-gel and evaporation-induced self-assembly process. The silica-coating structures were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and nitrogen sorptometry. The effect of the nanoporous surface on apatite formation in simulated body fluid, protein adsorption, osteoblast cell adhesion behavior, and osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) is reported. Silica coatings with highly ordered sub-10 nm porosity accelerate early osteoblast adhesive response, a favorable cell response that is attributed to an indirect effect due to the high protein adsorption observed on the large-specific surface area of the nanoporous coating but is also probably due to direct mechanical stimulus from the nanostructured topography. The nanoporous silica coatings, particularly those doped with calcium and phosphate, also promote the osteogenic differentiation of hBMSCs with spontaneous mineral nodule formation in basal conditions. The bioactive surface properties exhibited by the nanostructured porous silica coatings make these materials a promising alternative to improve the osseointegration properties of titanium dental implants and could have future impact on the nanoscale design of implant surfaces. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.

1998-01-01

Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FER Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

Using Underwater Explosion and Cylinder Expansion Tests to Calibrate Afterburn Models for Aluminized Explosives

NASA Astrophysics Data System (ADS)

Wedberg, Rasmus

2017-06-01

The study explores the combined use of underwater performance tests and cylinder expansion tests in order to parameterize detonation models for aluminized explosives which exhibit afterburning. The approach is suggested to be used in conjunction with thermochemical computation. A formulation containing RDX and aluminum powder is considered and several charges with varying masses are submerged and detonated. Pressure gauges are employed at horizontal distances scaling with the charge diameter, and the specific shock wave energy is shown to increase with charge mass. This is attributed to the combustion of aluminum particles after the Chapman-Jouguet plane. Cylinder expansion tests are carried out using Photon Doppler Velocimetry to register the wall expansion velocity. The tests are modeled using a multi-material arbitrary Lagrangian-Eulerian approach with the Guirguis-Miller model describing detonation with afterburning. The equation of state and afterburn rate law parameters are adjusted such that the model reproduces the results from the cylinder expansion and underwater tests. The approach seems promising, and might be valuable for aluminized explosive formulations intended to be used in a variety of confinement conditions. Swedish Armed Forces.

The effect of CO2 at low temperature and pressure on solutions supersaturated with silica in the presence of limestone and dolomite

USGS Publications Warehouse

Lovering, T.G.; Patten, L.E.

1962-01-01

The effect of 1 atm of CO2 over initially neutral solutions supersaturated with silica, at room temperature, as contrasted with 1 atm of air was determined over a period of 5 months, together with changes brought about by the introduction of calcite and dolomite to these solutions in the form of either chips or finely ground powder. In the absence of CO2 all solutions quickly reached equilibrium and no silica precipitated. In the presence of CO2 approximately two-thirds of the silica precipitated as silica gel within the first 2 months; the amount of silica precipitated was not affected by the presence of limestone or dolomite. Silica gel precipitated as a fine powder in the presence of finely ground calcite and dolomite, but as a cloudy gelatinous mass in the presence of coarse chips of dolomite and calcite, and in the absence of either calcite or dolomite. Preferential leaching of calcium from dolomite took place, both in the presence of air and in the presence of CO2, but was more pronounced in the presence of air. There was no evidence of physical replacement of either limestone or dolomite by precipitated silica. ?? 1962.

Willmore energy for joining of carbon nanostructures

NASA Astrophysics Data System (ADS)

Sripaturad, P.; Alshammari, N. A.; Thamwattana, N.; McCoy, J. A.; Baowan, D.

2018-06-01

Numerous types of carbon nanostructure have been found experimentally, including nanotubes, fullerenes and nanocones. These structures have applications in various nanoscale devices and the joining of these structures may lead to further new configurations with more remarkable properties and applications. The join profile between different carbon nanostructures in a symmetric configuration may be modelled using the calculus of variations. In previous studies, carbon nanostructures were assumed to deform according to perfect elasticity, thus the elastic energy, depending only on the axial curvature, was used to determine the join profile consisting of a finite number of discrete bonds. However, one could argue that the relevant energy should also involve the rotational curvature, especially when its size is comparable to the axial curvature. In this paper, we use the Willmore energy, a natural generalisation of the elastic energy that depends on both the axial and rotational curvatures. Catenoids are absolute minimisers of this energy and pieces of these may be used to join various nanostructures. We focus on the cases of joining a fullerene to a nanotube and joining two fullerenes along a common axis. By comparing our results with the earlier work, we find that both energies give similar joining profiles. Further work on other configurations may reveal which energy provides a better model.

Dissociation of intracellular lysosomal rupture from the cell death caused by silica

PubMed Central

Kane, AB; Stanton, RP; Raymond, EG; Dobson, ME; Knafelc, ME; Farber, JL

1980-01-01

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane

Torsional Shear Strength Tests for Glass-Ceramic Joined Silicon Carbide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferraris, Monica; Ventrella, Andrea; Salvo, Milena

2014-03-17

A torsion test on hour-glass-shaped samples with a full joined or a ring-shaped joined area was chosen in this study to measure shear strength of glass-ceramic joined silicon carbide. Shear strength of about 100 MPa was measured for full joined SiC with fracture completely inside their joined area. Attempts to obtain this shear strength with a ring-shaped joined area failed due to mixed mode fractures. However, full joined and ring-shaped steel hour-glasses joined by a glass-ceramic gave the same shear strength, thus suggesting that this test measures shear strength of joined components only when their fracture is completely inside theirmore » joined area.« less

Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

NASA Technical Reports Server (NTRS)

Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

2010-01-01

Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the

Influence of Synthesis Mode of Supplement Based on Calcium Hydrosylicates on the Structure and Properties of Lime Compositions

NASA Astrophysics Data System (ADS)

Loganina, V. I.; Pyshkina, I. S.

2017-11-01

It was proposed to use synthesized calcium hydrosilicates in finishing lime dry mixes as a modifying supplement. The effect of substances containing amorphous silica which are used for synthesis on the activity of the modifying supplement was established. The effect of the synthesis mode of supplement on the structure formation of lime compositions was illustrated. It was found that the injection of supplements of hydrosilicates accelerates the increase of mechanical strength. The efficiency of the modifying supplements of amorphous silica, such as diatomite, in the synthesis was shown.

Conjoint Forming - Technologies for Simultaneous Forming and Joining

NASA Astrophysics Data System (ADS)

Groche, P.; Wohletz, S.; Mann, A.; Krech, M.; Monnerjahn, V.

2016-03-01

The market demand for new products optimized for e. g. lightweight applications or smart components leads to new challenges in production engineering. Hybrid structures represent one promising approach. They aim at higher product performance by using a suitable combination of different materials. The developments of hybrid structures stimulate the research on joining of dissimilar materials. Since they allow for joining dissimilar materials without external heating technologies based on joining by plastic deformation seem to be of special attractiveness. The paper at hand discusses the conjoint forming approach. This approach combines forming and joining in one process. Two or more workpieces are joined while at least one workpiece is plastically deformed. After presenting the fundamental joining mechanisms, the conjoint forming approach is discussed comprehensively. Examples of conjoint processes demonstrate the effectiveness and reveal the underlying phenomena.

Prospects of joining multi-material structures

NASA Astrophysics Data System (ADS)

Sankaranarayanan, R.; Hynes, N. Rajesh Jesudoss

2018-05-01

Spring up trends and necessities make the pipelines for the brand new Technologies. The same way, Multimaterial structures emerging as fruitful alternatives for the conventional structures in the manufacturing sector. Especially manufacturing of transport vehicles is placing a perfect platform for these new structures. Bonding or joining technology plays a crucial role in the field of manufacturing for sustainability. These latest structures are purely depending on such joining technologies so that multi-material structuring can be possible practically. The real challenge lies on joining dissimilar materials of different properties and nature. Escalation of thermoplastic usage in large structural components also faces similar ambiguity for joining multi-material structures. Adhesive bonding, mechanical fastening and are the answering technologies for multi-material structures. This current paper analysis the prospects of these bonding technologies to meet the challenges of tomorrow.

Evaluations of Silica Aerogel-Based Flexible Blanket as Passive Thermal Control Element for Spacecraft Applications

NASA Astrophysics Data System (ADS)

Hasan, Mohammed Adnan; Rashmi, S.; Esther, A. Carmel Mary; Bhavanisankar, Prudhivi Yashwantkumar; Sherikar, Baburao N.; Sridhara, N.; Dey, Arjun

2018-03-01

The feasibility of utilizing commercially available silica aerogel-based flexible composite blankets as passive thermal control element in applications such as extraterrestrial environments is investigated. Differential scanning calorimetry showed that aerogel blanket was thermally stable over - 150 to 126 °C. The outgassing behavior, e.g., total mass loss, collected volatile condensable materials, water vapor regained and recovered mass loss, was within acceptable range recommended for the space applications. ASTM tension and tear tests confirmed the material's mechanical integrity. The thermo-optical properties remained nearly unaltered in simulated space environmental tests such as relative humidity, thermal cycling and thermo-vacuum tests and confirmed the space worthiness of the aerogel. Aluminized Kapton stitched or anchored to the blanket could be used to control the optical transparency of the aerogel. These outcomes highlight the potential of commercial aerogel composite blankets as passive thermal control element in spacecraft. Structural and chemical characterization of the material was also done using scanning electron microscopy, Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy.

Method of winning aluminum metal from aluminous ore

DOEpatents

Loutfy, R.O.; Keller, R.; Yao, N.P.

Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (A1S) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

In-network processing of joins in wireless sensor networks.

PubMed

Kang, Hyunchul

2013-03-11

The join or correlated filtering of sensor readings is one of the fundamental query operations in wireless sensor networks (WSNs). Although the join in centralized or distributed databases is a well-researched problem, join processing in WSNs has quite different characteristics and is much more difficult to perform due to the lack of statistics on sensor readings and the resource constraints of sensor nodes. Since data transmission is orders of magnitude more costly than processing at a sensor node, in-network processing of joins is essential. In this paper, the state-of-the-art techniques for join implementation in WSNs are surveyed. The requirements and challenges, join types, and components of join implementation are described. The open issues for further research are identified.

In-Network Processing of Joins in Wireless Sensor Networks

PubMed Central

Kang, Hyunchul

2013-01-01

The join or correlated filtering of sensor readings is one of the fundamental query operations in wireless sensor networks (WSNs). Although the join in centralized or distributed databases is a well-researched problem, join processing in WSNs has quite different characteristics and is much more difficult to perform due to the lack of statistics on sensor readings and the resource constraints of sensor nodes. Since data transmission is orders of magnitude more costly than processing at a sensor node, in-network processing of joins is essential. In this paper, the state-of-the-art techniques for join implementation in WSNs are surveyed. The requirements and challenges, join types, and components of join implementation are described. The open issues for further research are identified. PMID:23478603

Crystal structures and optical properties of new quaternary strontium europium aluminate luminescent nanoribbons

DOE PAGES

Li, Xufan; Budai, John D.; Liu, Feng; ...

2014-11-12

We report the synthesis and characterizations of three series of quaternary strontium europium aluminate (Sr-Eu-Al-O; SEAO) luminescent nanoribbons that show blue, green, and yellow luminescence from localized Eu2+ luminescent centers. These three series of SEAO nanoribbons are: blue luminescent, tetragonal Sr1-xEuxAl6O10 (01-xEu xAl 2O 4 (01-xEu xAl 2O 4 (0

UV-visible-NIR light generation through frequency upconversion in Tm3+-doped low silica calcium aluminosilicate glasses using multiple excitation around 1.2 μm

NASA Astrophysics Data System (ADS)

Trindade, C. M.; Rego-Filho, F. G.; Astrath, N. G. C.; Jacinto, C.; Gouveia-Neto, A. S.

2018-04-01

Intense ultraviolet upconversion emission was produced in single Tm3+-doped OH--free low silica calcium aluminosilicate glasses. A new excitation route based upon multi-Stokes Raman emissions generated in an optical fiber pumped at 1.064 μm, and exploiting the absorption band around 1.2 μm by means of the 3H5 thulium excited state, was used. Furthermore, the other bands of the stimulated Raman scattering spectrum resonantly enhances all the upconversion processes, resulting in efficient ultraviolet (295 nm, 360 nm), blue (456 nm, 480 nm), red (650 nm, 667 nm), and near-infrared (800 nm) emissions. The population of the 1P0, 1D2, 1G4, 3F2 and 3H4 excited-state emitting levels was accomplished through stepwise multi-photon absorption. Results indicate competing cross-relaxation processes involving Tm3+ ion-pairs producing UV emission population quenching Simplified energy-level diagram of Tm3+- doped sample excited using multi-stokes emissions. The λp indication describes all excitation wavelengths, represented by a single arrow for the sake of simplicity.

Calcium silicates synthesised from industrial residues with the ability for CO2 sequestration.

PubMed

Morales-Flórez, Victor; Santos, Alberto; López, Antonio; Moriña, Isabel; Esquivias, Luis

2014-12-01

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry. © The Author(s) 2014.

Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation. Revised

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.; Hall, Rachelle L.

1998-01-01

Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FEP. Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

Hexamethyldisilazane Removal with Mesoporous Materials Prepared from Calcium Fluoride Sludge.

PubMed

Kao, Ching-Yang; Lin, Min-Fa; Nguyen, Nhat-Thien; Tsai, Hsiao-Hsin; Chang, Luh-Maan; Chen, Po-Han; Chang, Chang-Tang

2018-05-01

A large amount of calcium fluoride sludge is generated by the semiconductor industry every year. It also requires a high amount of fuel consumption using rotor concentrators and thermal oxidizers to treat VOCs. The mesoporous adsorbent prepared by calcium fluoride sludge was used for VOCs treatment. The semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s) due to the formation of silicon dioxide, which blocks porous adsorbents. The adsorption of HMDS (Hexamethyldisiloxane) was tested with mesoporous silica materials synthesized from calcium fluoride (CF-MCM). The resulting samples were characterized by XRD, XRF, FTIR, N2-adsorption-desorption techniques. The prepared samples possessed high specific surface area, large pore volume and large pore diameter. The crystal patterns of CF-MCM were similar with Mobil composite matter (MCM-41) from TEM image. The adsorption capacity of HMDS with CF-MCM was 40 and 80 mg g-1, respectively, under 100 and 500 ppm HMDS. The effects of operation parameters, such as contact time and mixture concentration, on the performance of CF-MCM were also discussed in this study.

Effect of phase composition of calcium silicate phosphate component on properties of brushite based composite cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sopcak, T., E-mail: tsopcak@imr.saske.sk; Medvecky, L.; Giretova, M.

The composite cement mixtures were prepared by mixing brushite (B) with, the amorphous hydrated calcium silicate phosphate (CSPH) or annealed calcium silicate phosphate (CSP composed of Si-saturated hydroxyapatite, wollastonite and silica) phases and water as liquid component. The contents of the silicate-phosphate phase in composites were 10.30 and 50 wt%. The significant effect of both the Ca/P ratio and different solubility of calcium silicate phosphate component in starting cement systems on setting time and phase composition of the final composite cements was demonstrated. The compressive strength of the set cements increased with the filler addition and the highest value (~more » 48 MPa) exhibited the 50CSP/B cement composite. The final setting times of the composite cements decreased with the CSPH addition from about 25 to 17 min in 50CSHP/B and setting time of CSP/B composites was around 30 min. The higher content of silica in cements caused the precipitation of fine hydroxyapatite particles in the form of nanoneedles or thin plates perpendicularly oriented to sample surface. The analysis of in vitro cement cytotoxicity demonstrated the strong reduction in cytotoxicity of 10CSPH/B composite with time of cultivation (a low cytotoxicity after 9 days of culture) contrary to cements with higher calcium silicate-phosphate content. These results were attributed to the different surface topography of composite substrates and possible stimulation of cell proliferation by the slow continuously release of ions from 10CSPH/B cement. - Highlights: • Ca/P ratio and solubility of calcium silicate-phosphate components affect the self-setting properties of cements. • Strong relationship between the composite in vitro cytotoxicity and surface microtopography was demonstrated. • Plate-like morphology of coarser particles allowed cells to better adhere and proliferate as compared with nanoneedles.« less

Na(+) and Ca(2+) effect on the hydration and orientation of the phosphate group of DPPC at air-water and air-hydrated silica interfaces.

PubMed

Casillas-Ituarte, Nadia N; Chen, Xiangke; Castada, Hardy; Allen, Heather C

2010-07-29

Hydration and orientation of the phosphate group of dipalmitoylphosphatidylcholine (DPPC) monolayers in the liquid-expanded (LE) phase and the liquid-condensed (LC) phase in the presence of sodium ions and calcium ions was investigated with vibrational sum frequency generation (SFG) spectroscopy at the air-aqueous interface in conjunction with surface pressure measurements. In the LE phase, both sodium and calcium affect the phosphate group hydration. In the LC phase, however, sodium ions affect the phosphate hydration subtly, while calcium ions cause a marked dehydration. Silica-supported DPPC monolayers prepared by the Langmuir-Blodgett method reveal similar hydration behavior relative to that observed in the corresponding aqueous subphase for the case of water and in the presence of sodium ions. However, in the presence of calcium ions the phosphate group dehydration is greater than that from the corresponding purely aqueous CaCl(2) subphase. The average tilt angles from the surface normal of the PO(2)(-) group of DPPC monolayers on the water surface and on the silica substrate calculated from SFG data are found to be 59 degrees +/- 3 degrees and 72 degrees +/- 5 degrees , respectively. Orientation of the phosphate group is additionally affected by the presence of ions. These findings show that extrapolation of results obtained from model membranes from liquid surfaces to solid supports may not be warranted since there are differences in headgroup organization on the two subphases.

Properties of lithium aluminate for application as an OSL dosimeter

NASA Astrophysics Data System (ADS)

Twardak, A.; Bilski, P.; Marczewska, B.; Lee, J. I.; Kim, J. L.; Gieszczyk, W.; Mrozik, A.; Sądel, M.; Wróbel, D.

2014-11-01

Several samples of undoped and carbon or copper doped lithium aluminate (LiAlO2) were prepared in an attempt to achieve a material, which can be applicable in optically stimulated luminescence (OSL) dosimetry. All investigated samples are highly sensitive to ionizing radiation and show good reproducibility. The undoped and copper doped samples exhibit sensitivity several times higher than that of Al2O3:C, while sensitivity of the carbon doped samples is lower. The studied samples exhibit significant fading, but dynamics of signal loss is different for differently doped samples, what indicates a possibility of improving this characteristic by optimizing dopant composition.

Joining of Gamma Titanium Aluminides

DTIC Science & Technology

2002-09-01

AFRL-ML-WP-TR-2003-4036 JOINING OF GAMMA TITANIUM ALUMINIDES LTC William A. Baeslack, III Metals Branch (AFRL/MLLM) Metals, Ceramics, and...GAMMA TITANIUM ALUMINIDES 5c. PROGRAM ELEMENT NUMBER 62102F 5d. PROJECT NUMBER MO2R 5e. TASK NUMBER 10 6. AUTHOR(S) LTC William A...comparatively discusses the results of research and development performed on the joining of gamma titanium aluminides during the past two decades. Although

Ethylene glycol contamination effects on first surface aluminized mirrors

NASA Astrophysics Data System (ADS)

Dunlop, Patrick; Probst, Ronald G.; Evatt, Matthew; Reddell, Larry; Sprayberry, David

2016-07-01

The Dark Energy Spectroscopic Instrument (DESI) is under construction for installation on the Mayall 4 Meter telescope. The use of a liquid cooling system is proposed to maintain the DESI prime focus assembly temperature within ±1°C of ambient. Due to concerns of fluid deposition onto optical surfaces from possible leaks, systematic tests were performed of the effects on first surface aluminized mirrors of ethylene glycol and two other candidate coolants. Objective measurement of scattering and reflectivity was an important supplement to visual inspection. Rapid cleanup of a coolant spill followed by a hand wash of the mirror limited surface degradation to the equivalent of a few months of general environmental exposure. Prolonged exposure to corrosive coolants dissolved the aluminum, necesitating mirror recoating.

Silica extraction from geothermal water

DOEpatents

Bourcier, William L; Bruton, Carol J

2014-09-23

A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

Aluminization and mirror removal of the Magellan 6.5-meter telescope

NASA Astrophysics Data System (ADS)

Perez, Frank S.

1994-06-01

The Magellan Project 6.5-meter telescope is a collaboration of the Carnegie Institution of Washington and the University of Arizona. The telescope will be located on Cerro Manqui, at the Las Campanas Observatory, Chile. At the beginning of the Magellan Project several schemes were investigated for realuminizing the primary mirror. We have chosen to leave the primary mirror in its cell with the mirror support system intact. Two major advantages of leaving the mirror in its cell are that it does not have to be lifted or handled and the support system does not have to be removed or reinstalled for aluminization.

Joining a Gym

MedlinePlus

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Join or be excluded from biomedicine? JOINS and Post-colonial Korea.

PubMed

Ma, Eunjeong

2015-04-01

This paper discusses re-emergence of Korean medicine(s) in the global context with a focus on a natural drug JOINS, a highly contentious drug regarding its legal status. By following through its life world, the paper contends that the drug is the embodiment of the postcolonial anxiety that crosses the intersections between the aspiring nation and globalizing strategies of the bio-pharmaceutical industry. JOINS is a natural drug prescribed to alleviate the symptoms of degenerative arthritis. SK Chemicals, Ltd., a giant domestic pharmaceutical company developed the drug by utilizing the knowledge of traditional pharmacopeia and put it on the market in 2001. In the domestic market, the drug is treated as a prescription drug, implying that Western medicine-trained doctors (as opposed to Korean medicine doctors) are entitled to prescribe drugs. It also indicates that the drug has undergone a series of lab tests such as toxicity, efficacy, and clinical trials in compliance with regulatory guidelines. However, the domestic standards are not rigorous enough to satisfy international standards, so that it is exported as a nutritional supplement abroad. The government, the pharmaceutical industry, and the Western medicine profession are happy with how the drug stands domestically and internationally. Rather, it is Korean doctors who try to disrupt the status quo and reclaim their rights to traditional knowledge, who have been alienated from the pharmaceuticalization of traditional knowledge. Thus, the JOINS tablet embodies the complex web of modern Korean society, professional interests, the pharmaceutical industry, and globalization.

Advanced concepts in joining by conventional processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, G.R.; Fasching-James, A.A.; Onsoien, M.I.

1994-12-31

Innovations which can be made to conventional arc welding processes so that advanced materials can be more efficiently joined are considered. Three examples are discussed: (1) GTA welding of iron aluminides, (2) GMA welding of advanced steels, and (3) SMA welding of structural steels. Advanced materials present new challenges for the materials joining specialist. The three examples discussed in this paper demonstrate, however, that modest but creative alterations of conventional GTAW, GMAW, or SMAW processes can provide new and better controls for solving advanced materials joining problems.

Biochemical evolution. I. Polymerization On internal, organophilic silica surfaces of dealuminated zeolites and feldspars.

PubMed

Smith, J V

1998-03-31

Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars.

Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars

PubMed Central

Smith, Joseph V.

1998-01-01

Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars. PMID:9520372

Nickel stabilization efficiency of aluminate and ferrite spinels and their leaching behavior.

PubMed

Shih, Kaimin; White, Tim; Leckie, James O

2006-09-01

Stabilization efficiencies of spinel-based construction ceramics incorporating simulated nickel-laden waste sludge were evaluated and the leaching behavior of products investigated. To simulate the process of immobilization, nickel oxide was mixed alternatively with gamma-alumina, kaolinite, and hematite. These tailoring precursors are commonly used to prepare construction ceramics in the building industry. After sintering from 600 to 1480 degrees C at 3 h, the nickel aluminate spinel (NiAl204) and the nickel ferrite spinel (NiFe204) crystallized with the ferrite spinel formation commencing about 200-300 degrees C lower than for the aluminate spinel. All the precursors showed high nickel incorporation efficiencies when sintered at temperatures greater than 1250 degrees C. Prolonged leach tests (up to 26 days) of product phases were carried out using a pH 2.9 acetic acid solution, and the spinel products were invariably superior to nickel oxide for immobilization over longer leaching periods. The leaching behavior of NiAl2O4 was consistent with congruent dissolution without significant reprecipitation, but for NiFe2O4, ferric hydroxide precipitation was evident. The major leaching reaction of sintered kaolinite-based products was the dissolution of cristobalite rather than NiAl2O4. This study demonstrated the feasibility of transforming nickel-laden sludge into spinel phases with the use of readily available and inexpensive ceramic raw materials, and the successful reduction of metal mobility under acidic environments.

Damage thresholds of silica fibers in holmium:YAG laser energy delivery for medical applications

NASA Astrophysics Data System (ADS)

Marolda, Matthew D.; Perrault, Donald F., Jr.; Pankratov, Michail M.; Shapshay, Stanley M.

1993-07-01

Pulsed Holmium:YAG (Ho:YAG) laser has been approved for some clinical applications and is under investigation for others. There is little published evidence on the durability or damage parameters for the fibers used in delivering energy from pulsed Ho:YAG laser. This study makes an initial attempt to investigate the damage threshold of different silica fibers under various conditions. Three types of fibers supplied by different manufacturers underwent laboratory testing. The overall finding of the study is that a new `perfect' fiber sustains no damage when fired without a target in air or in saline at energies up to 1.5 J/pulse and repetition rate up to 10 Hz. This study suggests that one may need to chose a fiber according to the clinical procedure to be performed: in cases where only soft tissue is to be manipulated - - any fiber may fare well, in cases where bone or calcified tissue is to be lased -- one may need fiber with aluminized or other hard coating. We also conclude that only professional refinishing with the removal of all exposed core-cladding material can insure trouble free performance.

Explosive Spot Joining of Metals

NASA Technical Reports Server (NTRS)

Bement, Laurence J. (Inventor); Perry, Ronnie B. (Inventor)

1997-01-01

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebend, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires. and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity. angular collision between the mating surfaces. This collision creates surface melts and collision bonding resulting in electron-sharing linkups.

Recycled asphalt pavement - fly ash geopolymers as a sustainable pavement base material: Strength and toxic leaching investigations.

PubMed

Hoy, Menglim; Horpibulsuk, Suksun; Rachan, Runglawan; Chinkulkijniwat, Avirut; Arulrajah, Arul

2016-12-15

In this research, a low-carbon stabilization method was studied using Recycled Asphalt Pavement (RAP) and Fly Ash (FA) geopolymers as a sustainable pavement material. The liquid alkaline activator (L) is a mixture of sodium silicate (Na 2 SiO 3 ) and sodium hydroxide (NaOH), and high calcium FA is used as a precursor to synthesize the FA-RAP geopolymers. Unconfined Compressive Strength (UCS) of RAP-FA blend and RAP-FA geopolymer are investigated and compared with the requirement of the national road authorities of Thailand. The leachability of the heavy metals is measured by Toxicity Characteristic Leaching Procedure (TCLP) and compared with international standards. The Scanning Electron Microscopy (SEM) analysis of RAP-FA blend indicates the Calcium Aluminate (Silicate) Hydrate (C-A-S-H) formation, which is due to a reaction between the high calcium in RAP and high silica and alumina in FA. The low geopolymerization products (N-A-S-H) of RAP-FA geopolymer at NaOH/Na 2 SiO 3 =100:0 are detected at the early 7days of curing, hence its UCS is lower than that of RAP-FA blend. The 28-day UCS of RAP-FA geopolymers at various NaOH/Na 2 SiO 3 ratios are significantly higher than that of the RAP-FA blend, which can be attributed to the development of geopolymerization reactions. With the input of Na 2 SiO 3 , the highly soluble silica from Na 2 SiO 3 reacted with leached silica and alumina from FA and RAP and with free calcium from FA and RAP; hence the coexistence of N-A-S-H gel and C-A-S-H products. Therefore, the 7-day UCS values of RAP-FA geopolymers increase with decreasing NaOH/Na 2 SiO 3 ratio. TCLP results demonstrated that there is no environmental risk for both RAP-FA blends and RAP-FA geopolymers in road construction. The geopolymer binder reduces the leaching of heavy metal in RAP-FA mixture. The outcomes from this research will promote the move toward increased applications of recycled materials in a sustainable manner in road construction. Copyright © 2016

Effect of Air and Vacuum Storage on the Tensile Properties of X-Ray Exposed Aluminized-FEP

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Gummow, Jonathan D.

2000-01-01

Metallized Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), a common spacecraft thermal control material, from the exterior layer of the Hubble Space Telescope (HST) has become embrittled and suffers from extensive cracking. Teflon samples retrieved during Hubble servicing missions and from the Long Duration Exposure Facility (LDEF) indicate that there may be continued degradation in tensile properties over time. An investigation has been conducted to evaluate the effect of air and vacuum storage on the mechanical properties of x-ray exposed FEP. Aluminized-FEP (Al-FEP) tensile samples were irradiated with 15.3 kV Cu x-rays and stored in air or under vacuum for various time periods. Tensile data indicate that samples stored in air display larger decreases in tensile properties than for samples stored under vacuum. Air-stored samples developed a hazy appearance, which corresponded to a roughening of the aluminized surface. Optical property changes were also characterized. These findings indicate that air exposure plays a role in the degradation of irradiated FEP, therefore proper sample handling and storage is necessary with materials retrieved from space.

JOINING DISSIMILAR MATERIALS USING FRICTION STIR SCRIBE TECHNIQUE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep

2016-09-01

Development of robust and cost effective method of joining dissimilar materials can provide a critical pathway to enable widespread use of multi-material design and components in mainstream industrial applications. The use of multi-material components such as Steel-Aluminum, Aluminum-Polymer allows design engineers to optimize material utilization based on service requirements and often lead weight and cost reductions. However producing an effective joint between materials with vastly different thermal, microstructural and deformation response is highly problematic using conventional joining and /or fastening methods. This is especially challenging in cost sensitive high volume markets that largely rely on low–cost joining solutions. Friction Stirmore » Scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like Magnesium and Aluminum to high temperature materials like Steels and Titanium. Additionally viable joints between polymer composites and metal can also be made using this method. This paper will present state of the art, progress made and challenges associated with this innovative derivative of Friction Stir welding in reference to joining dissimilar metals and polymer/metal combinations.« less

Joining Dissimilar Materials Using Friction Stir Scribe Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upadhyay, Piyush; Hovanski, Yuri; Jana, Saumyadeep

2016-10-03

Development of a robust and cost-effective method of joining dissimilar materials could provide a critical pathway to enable widespread use of multi-material designs and components in mainstream industrial applications. The use of multi-material components such as steel-aluminum and aluminum-polymer would allow design engineers to optimize material utilization based on service requirements and could often lead to weight and cost reductions. However, producing an effective joint between materials with vastly different thermal, microstructural, and deformation responses is highly problematic using conventional joining and/or fastening methods. This is especially challenging in cost sensitive, high volume markets that largely rely on low costmore » joining solutions. Friction stir scribe technology was developed to meet the demands of joining materials with drastically different properties and melting regimes. The process enables joining of light metals like magnesium and aluminum to high temperature materials like steel and titanium. Viable joints between polymer composites and metal can also be made using this method. This paper will present the state of the art, progress made, and challenges associated with this innovative derivative of friction stir welding in reference to joining dissimilar metals and polymer/metal combinations.« less

A two-phase model for aluminized explosives on the ballistic and brisance performance

NASA Astrophysics Data System (ADS)

Kim, Wuhyun; Gwak, Min-cheol; Lee, Young-hun; Yoh, Jack J.

2018-02-01

The performance of aluminized high explosives is considered by varying the aluminum (Al) mass fraction in a heterogeneous mixture model. Since the time scales of the characteristic induction and combustion of high explosives and Al particles differ, the process of energy release behind the leading detonation wave front occurs over an extended period of time. For simulating the performance of aluminized explosives with varying Al mass fraction, HMX (1,3,5,7-tetrahexmine-1,3,5,7-tetrazocane) is considered as a base explosive when formulating the multiphase conservation laws of mass, momentum, and energy exchanges between the HMX product gases and Al particles. In the current study, a two-phase model is utilized in order to determine the effects of the Al mass fraction in a condensed phase explosive. First, two types of confined rate stick tests are considered to investigate the detonation velocity and the acceleration ability, which refers to the radial expansion velocity of the confinement shell. The simulation results of the confined rate stick test are compared with the experimental data for the Al mass fraction range of 0%-25%, and the optimal Al mass fraction is provided, which is consistent with the experimental observations. Additionally, a series of plate dent test simulations are conducted, the results of which show the same tendency as those of the experimental tests with varying Al mass fractions.

Design synthesis and optimization of joined-wing transports

NASA Technical Reports Server (NTRS)

Gallman, John W.; Smith, Stephen C.; Kroo, Ilan M.

1990-01-01

A computer program for aircraft synthesis using a numerical optimizer was developed to study the application of the joined-wing configuration to transport aircraft. The structural design algorithm included the effects of secondary bending moments to investigate the possibility of tail buckling and to design joined wings resistant to buckling. The structural weight computed using this method was combined with a statistically-based method to obtain realistic estimates of total lifting surface weight and aircraft empty weight. A variety of 'optimum' joined-wing and conventional aircraft designs were compared on the basis of direct operating cost, gross weight, and cruise drag. The most promising joined-wing designs were found to have a joint location at about 70 percent of the wing semispan. The optimum joined-wing transport is shown to save 1.7 percent in direct operating cost and 11 percent in drag for a 2000 nautical mile transport mission.

Aerodynamic and structural studies of joined-wing aircraft

NASA Technical Reports Server (NTRS)

Kroo, Ilan; Smith, Stephen; Gallman, John

1991-01-01

A method for rapidly evaluating the structural and aerodynamic characteristics of joined-wing aircraft was developed and used to study the fundamental advantages attributed to this concept. The technique involves a rapid turnaround aerodynamic analysis method for computing minimum trimmed drag combined with a simple structural optimization. A variety of joined-wing designs are compared on the basis of trimmed drag, structural weight, and, finally, trimmed drag with fixed structural weight. The range of joined-wing design parameters resulting in best cruise performance is identified. Structural weight savings and net drag reductions are predicted for certain joined-wing configurations compared with conventional cantilever-wing configurations.

Joining of porous silicon carbide bodies

DOEpatents

Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

1990-05-01

A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

Influence of Chloride-Ion Adsorption Agent on Chloride Ions in Concrete and Mortar.

PubMed

Peng, Gai-Fei; Feng, Nai-Qian; Song, Qi-Ming

2014-04-30

The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride ion content in mortar was tested. The experimental results reveal that the Cl agent could adsorb chloride ions effectively, which had penetrated into concrete and mortar. When the Cl agent was used at a dosage of 6% by mass of cementitious materials in mortar, the resistance to the penetration of chloride ions could be improved greatly, which was more pronounced when a combination of the Cl agent and fly ash or slag was employed. Such an effect is not the result of the low permeability of the mortar, but might be a result of the interaction between the Cl agent and the chloride ions penetrated into the mortar. There are two possible mechanisms for the interaction between the Cl agent and chloride ion ingress. One is the reaction between calcium aluminate hydrate in the Cl agent and chloride ions to form Friedel's salt, and the other one is that calcium aluminate hydrate reacts with calcium nitrite to form AFm during the early-age hydration of mortar and later the NO₂ - in AFm is replaced by chloride ions, which then penetrate into the mortar, also forming Friedel's salt. More research is needed to confirm the mechanisms.

Influence of Chloride-Ion Adsorption Agent on Chloride Ions in Concrete and Mortar

PubMed Central

Peng, Gai-Fei; Feng, Nai-Qian; Song, Qi-Ming

2014-01-01

The influence of a chloride-ion adsorption agent (Cl agent in short), composed of zeolite, calcium aluminate hydrate and calcium nitrite, on the ingress of chloride ions into concrete and mortar has been experimentally studied. The permeability of concrete was measured, and the chloride ion content in mortar was tested. The experimental results reveal that the Cl agent could adsorb chloride ions effectively, which had penetrated into concrete and mortar. When the Cl agent was used at a dosage of 6% by mass of cementitious materials in mortar, the resistance to the penetration of chloride ions could be improved greatly, which was more pronounced when a combination of the Cl agent and fly ash or slag was employed. Such an effect is not the result of the low permeability of the mortar, but might be a result of the interaction between the Cl agent and the chloride ions penetrated into the mortar. There are two possible mechanisms for the interaction between the Cl agent and chloride ion ingress. One is the reaction between calcium aluminate hydrate in the Cl agent and chloride ions to form Friedel’s salt, and the other one is that calcium aluminate hydrate reacts with calcium nitrite to form AFm during the early-age hydration of mortar and later the NO2− in AFm is replaced by chloride ions, which then penetrate into the mortar, also forming Friedel’s salt. More research is needed to confirm the mechanisms. PMID:28788625

Mass dependence of calcium isotope fractionations in crown-ether resin chromatography.

PubMed

Fujii, Yasuhiko; Nomura, Masao; Kaneshiki, Tositaka; Sakuma, Yoichi; Suzuki, Tatsuya; Umehara, Saori; Kishimoto, Tadahumi

2010-06-01

Benzo 18-crown-6-ether resin was synthesised by the phenol condensation polymerisation process in porous silica beads, of which particle diameter was ca 60micro Calcium adsorption chromatography was performed with the synthesised resin packed in a glass column. The effluent was sampled in fractions, and the isotopic abundance ratios of (42)Ca, (43)Ca, (44)Ca, and (48)Ca against (40)Ca were measured by a thermo-ionisation mass spectrometer. The enrichment of heavier calcium isotopes was observed at the front boundary of calcium adsorption chromatogram. The mass dependence of mutual separation of calcium isotopes was analysed by using the three-isotope-plots method. The slopes of three-isotope-plots indicate the relative values of mutual separation coefficients for concerned isotopic pairs. The results have shown the normal mass dependence; isotope fractionation is proportional to the reduced mass difference, (M - M')/MM', where M and M' are masses of heavy and light isotope, respectively. The mass dependence clarifies that the isotope fractionations are originated from molecular vibration. The observed separation coefficient epsilon is 3.1x10(-3) for the pair of (40)Ca and (48)Ca. Productivity of enriched (48)Ca by crown-ether-resin was discussed as the function of the separation coefficient and the height equivalent to the theoretical plate.

Joined-wing research airplane feasibility study

NASA Technical Reports Server (NTRS)

Wolkovitch, J.

1984-01-01

The joined wing is a new type of aircraft configuration which employs tandem wings arranged to form diamond shapes in plan view and front view. Wind-tunnel tests and finite-element structural analyses have shown that the joined wing provides the following advantages over a comparable wing-plus-tail system; lighter weight and higher stiffness, higher span-efficiency factor, higher trimmed maximum lift coefficient, lower wave drag, plus built-in direct lift and direct sideforce control capability. To verify these advantages at full scale a manned research airplane is required. A study has therefore been performed of the feasibility of constructing such an airplane, using the fuselage and engines of the existing NAA AD-1 oblique-wing airplane. Cost and schedule constraints favored converting the AD-1 rather than constructing a totally new airframe. By removing the outboard wing panels the configuration can simulate wings joined at 60, 80, or 100 percent of span. For maximum versatility the aircraft has alternative control surfaces (such as ailerons and elevators on the front and/or rear wings), and a removeable canard to explore canard/joined-wing interactions at high-lift conditions. Design, performance, and flying qualities are discussed.

Preliminary design optimization of joined-wing aircraft

NASA Technical Reports Server (NTRS)

Gallman, John W.; Kroo, Ilan M.; Smith, Stephen C.

1990-01-01

The joined wing is an innovative aircraft configuration that has a its tail connected to the wing forming a diamond shape in both top and plan view. This geometric arrangement utilizes the tail for both pitch control and as a structural support for the wing. Several researchers have studied this configuration and predicted significant reductions in trimmed drag or structural weight when compared with a conventional T-tail configuration. Kroo et al. compared the cruise drag of joined wings with conventional designs of the same lifting-surface area and structural weight. This study showed an 11 percent reduction in cruise drag for the lifting system of a joined wing. Although this reduction in cruise drag is significant, a complete design study is needed before any economic savings can be claimed for a joined-wing transport. Mission constraints, such as runway length, could increase the wing area and eliminate potential drag savings. Since other design codes do not accurately represent the interaction between structures and aerodynamics for joined wings, we developed a new design code for this study. The aerodynamic and structural analyses in this study are significantly more sophisticated than those used in most conventional design codes. This sophistication was needed to predict the aerodynamic interference between the wing and tail and the stresses in the truss-like structure. This paper describes these analysis methods, discusses some problems encountered when applying the numerical optimizer NPSOL, and compares optimum joined wings with conventional aircraft on the basis of cruise drag, lifting surface weight, and direct operating cost (DOC).

A Modeling Approach for Plastic-Metal Laser Direct Joining

NASA Astrophysics Data System (ADS)

Lutey, Adrian H. A.; Fortunato, Alessandro; Ascari, Alessandro; Romoli, Luca

2017-09-01

Laser processing has been identified as a feasible approach to direct joining of metal and plastic components without the need for adhesives or mechanical fasteners. The present work sees development of a modeling approach for conduction and transmission laser direct joining of these materials based on multi-layer optical propagation theory and numerical heat flow simulation. The scope of this methodology is to predict process outcomes based on the calculated joint interface and upper surface temperatures. Three representative cases are considered for model verification, including conduction joining of PBT and aluminum alloy, transmission joining of optically transparent PET and stainless steel, and transmission joining of semi-transparent PA 66 and stainless steel. Conduction direct laser joining experiments are performed on black PBT and 6082 anticorodal aluminum alloy, achieving shear loads of over 2000 N with specimens of 2 mm thickness and 25 mm width. Comparison with simulation results shows that consistently high strength is achieved where the peak interface temperature is above the plastic degradation temperature. Comparison of transmission joining simulations and published experimental results confirms these findings and highlights the influence of plastic layer optical absorption on process feasibility.

Ignition threshold of aluminized HMX-based PBXs

NASA Astrophysics Data System (ADS)

Miller, Christopher; Zhou, Min

2017-06-01

We report the results of micromechanical simulations of the ignition of aluminized HMX-based PBX under loading due to impact by thin flyers. The conditions analyzed concern loading pulses on the order of 20 nanoseconds to 0.8 microseconds in duration and impact piston velocities on the order of 300-1000 ms-1. The samples consist of a stochastically similar bimodal distribution of HMX grains, an Estane binder, and 50 μm aluminum particles. The computational model accounts for constituent elasto-vicoplasticity, viscoelasticity, bulk compressibility, fracture, interfacial debonding, fracture, internal contact, bulk and frictional heating, and heat conduction. The analysis focuses on the development of hotspots under different material settings and loading conditions. In particular, the ignition threshold in the form of the James relation and the corresponding ignition probability are calculated for the PBXs containing 0%, 6%, 10%, and 18% aluminum by volume. It is found that the addition of aluminum increases the ignition threshold, causing the materials to be less sensitive. Dissipation and heating mechanism changes responsible for this trend are delineated. Support by DOE NNSA SSGF is gratefully acknowledged.

Crystalline Silica

Cancer.gov

Learn about crystalline silica (quartz dust), which can raise your risk of lung cancer. Crystalline silica is present in certain construction materials such as concrete, masonry, and brick and also in commercial products such as some cleansers, cosmetics, pet litter, talcum powder, caulk, and paint.

Toroid Joining Gun. [thermoplastic welding system using induction heating

NASA Technical Reports Server (NTRS)

Buckley, J. D.; Fox, R. L.; Swaim, R J.

1985-01-01

The Toroid Joining Gun is a low cost, self-contained, portable low powered (100-400 watts) thermoplastic welding system developed at Langley Research Center for joining plastic and composite parts using an induction heating technique. The device developed for use in the fabrication of large space sructures (LSST Program) can be used in any atmosphere or in a vacuum. Components can be joined in situ, whether on earth or on a space platform. The expanded application of this welding gun is in the joining of thermoplastic composites, thermosetting composites, metals, and combinations of these materials. Its low-power requirements, light weight, rapid response, low cost, portability, and effective joining make it a candidate for solving many varied and unique bonding tasks.

Impact initiation of reactive aluminized fluorinated acrylic nanocomposites

DOE PAGES

White, Bradley W.; Crouse, Christopher A.; Spowart, Jonathan E.; ...

2016-04-18

The initiation of aluminized fluorinated acrylic (AlFA) nanocomposites during modified Taylor impact tests was investigated. Samples were impacted against a steel or sapphire anvil at a nominal velocity of 150 m/s. A framing camera was used to capture head-on and side-profile impact images for the sapphire window and steel plate rigid anvils, respectively. Correlations were drawn between both experimental setups to determine the initiation locations and reaction times. Reactions were found to initiate at an intermediate radius on the impact face of the pellet at a time near full compaction. From simulations, the highest strains and temperatures were found atmore » radii similar to those observed in experiments at the time of ignition. Off-normal impacts produced higher localized straining and temperatures on one-half of the pellet. As a result, the copper projectile, used for delivery, was revealed to aid in a shear assisted reaction by helping to drive the pellet material outward as the projectile deformed radially.« less

Impact initiation of reactive aluminized fluorinated acrylic nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Bradley W.; Crouse, Christopher A.; Spowart, Jonathan E.

The initiation of aluminized fluorinated acrylic (AlFA) nanocomposites during modified Taylor impact tests was investigated. Samples were impacted against a steel or sapphire anvil at a nominal velocity of 150 m/s. A framing camera was used to capture head-on and side-profile impact images for the sapphire window and steel plate rigid anvils, respectively. Correlations were drawn between both experimental setups to determine the initiation locations and reaction times. Reactions were found to initiate at an intermediate radius on the impact face of the pellet at a time near full compaction. From simulations, the highest strains and temperatures were found atmore » radii similar to those observed in experiments at the time of ignition. Off-normal impacts produced higher localized straining and temperatures on one-half of the pellet. As a result, the copper projectile, used for delivery, was revealed to aid in a shear assisted reaction by helping to drive the pellet material outward as the projectile deformed radially.« less

Raman Spectroscopy of Water-rich Stishovite and Dense High-Pressure Silica up to 55 GPa

NASA Astrophysics Data System (ADS)

Nisr, C.; Shim, S. H.; Leinenweber, K. D.; Chizmeshya, A. V.

2017-12-01

Recent studies have shown that mineral phases such as δ-AlOOH, (Mg,Si)OOH, (Mg,Si,Al)OOH, (Al,Si)O2 and SiO2 with rutile-type or modified rutile-type crystal structures can store large amounts of water and be stable at high pressure and high temperature relevant to the Earth's lower mantle. The Al-H charge coupled substitution has been proposed to explain the large storage capacity of these phases. However, the substitution cannot explain the large water storage found in pure stishovite (Spektor et al., 2011). Instead, an octahedral version of hydrogarnet-like substitution has been proposed for the incorporation of hydrogen in pure stishovite. We have performed Raman spectroscopy measurements on pure hydrous stishovite with 3.2 wt% water up to 55 GPa. At ambient pressure, we found that the OH stretching mode frequencies range between those of low-water aluminous stishovite and δ-AlOOH, suggesting an intermediate strength of hydrogen bonding between these two phases. In the lattice mode range, we observe modes similar to the IR-active modes of anhydrous stishovite after decompression to 1 bar, suggesting Si defects in the crystal structure that activate the inactive modes. Our data show a series of changes at pressures between 24 and 28 GPa, supporting our observation of a phase transition (likely to the CaCl2 type) in X-Ray diffraction measurements (Nisr et al., 2017, JGR). We found that the OH mode of hydrous stishovite has a positive frequency shift with an increase in pressure. The behavior is the opposite to that found in δ-AlOOH, indicating that the OH incorporation mechanism in hydrous silica is different from that of aluminous low-water stishovite and δ-AlOOH, likely through direct substitution (Si ⇄ 4H+). Because the mantle hydrous phases would have complex compositions, our study suggests that the direct substitution should also be considered together with the Al substitution for the deep mantle storage of water.

Method of joining metallic and composite components

NASA Technical Reports Server (NTRS)

Semmes, Edmund B. (Inventor)

2010-01-01

A method is provided for joining a metallic member to a structure made of a composite matrix material. One or more surfaces of a portion of the metallic member that is to be joined to the composite matrix structure is provided with a plurality of outwardly projecting studs. The surface including the studs is brought into engagement with a portion of an uncured composite matrix material so that fibers of the composite matrix material intertwine with the studs, and the metallic member and composite structure form an assembly. The assembly is then companion cured so as to join the metallic member to the composite matrix material structure.

Effect of silica fume on the characterization of the geopolymer materials

NASA Astrophysics Data System (ADS)

Khater, Hisham M.

2013-12-01

The influence of silica fume (SF) addition on properties of geopolymer materials produced from alkaline activation of alumino-silicates metakaolin and waste concrete produced from demolition works has been studied through the measurement of compressive strength, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM) analysis. Alumino-silicate materials are coarse aggregate included waste concrete and fired kaolin (metakaolin) at 800°C for 3 h, both passing a sieve of 90 μm. Mix specimens containing silica fume were prepared at water/binder ratios in a range of 0.30 under water curing. The used activators are an equal mix of sodium hydroxide and silicate in the ratio of 3:3 wt.%. The control geopolymer mix is composed of metakaolin and waste concrete in an equal mix (50:50, wt.%). Waste concrete was partially replaced by silica fume by 1 to 10 wt.%. The results indicated that compressive strengths of geopolymer mixes incorporating SF increased up to 7% substitution and then decreased up to 10% but still higher than that of the control mix. Results indicated that compressive strengths of geopolymer mixes incorporating SF increases up to 7% substitution and then decreases up to 10% but still higher than the control mix, where 7% SF-digested calcium hydroxide (CH) crystals, decreased the orientation of CH crystals, reduced the crystal size of CH gathered at the interface, and improved the interface more effectively.

Effects of Leaching Behavior of Calcium Ions on Compression and Durability of Cement-Based Materials with Mineral Admixtures

PubMed Central

Cheng, An; Chao, Sao-Jeng; Lin, Wei-Ting

2013-01-01

Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume) on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials. PMID:28809247

Multicolor printing plate joining

NASA Technical Reports Server (NTRS)

Waters, W. J. (Inventor)

1984-01-01

An upper plate having ink flow channels and a lower plate having a multicolored pattern are joined. The joining is accomplished without clogging any ink flow paths. A pattern having different colored parts and apertures is formed in a lower plate. Ink flow channels each having respective ink input ports are formed in an upper plate. The ink flow channels are coated with solder mask and the bottom of the upper plate is then coated with solder. The upper and lower plates are pressed together at from 2 to 5 psi and heated to a temperature of from 295 F to 750 F or enough to melt the solder. After the plates have cooled and the pressure is released, the solder mask is removed from the interior passageways by means of a liquid solvent.

Serpentinization processes: Influence of silica

NASA Astrophysics Data System (ADS)

Huang, R.; Sun, W.; Ding, X.; Song, M.; Zhan, W.

2016-12-01

Serpentinization systems are highly enriched in molecular hydrogen (H2) and hydrocarbons (e.g. methane, ethane and propane). The production of hydrocarbons results from reactions between H2 and oxidized carbon (carbon dioxide and carbon monoxide), which possibly contribute to climate changes during early history of the Earth. However, the influence of silica on the production of H2 and hydrocarbons was poorly constrained. We performed experiments at 311-500 °C and 3.0 kbar using mechanical mixtures of silica and olivine in ratios ranging from 0 to 40%. Molecular hydrogen (H2), methane, ethane and propane were formed, which were analyzed by gas chromatography. It was found that silica largely decreased H2 production. Without any silica, olivine serpentinization produced 94.5 mmol/kg H2 after 20 days of reaction time. By contrast, with the presence of 20% silica, H2 concentrations decreased largely, 8.5 mmol/kg. However, the influence of silica on the production of hydrocarbons is negligible. Moreover, with the addition of 20%-40% silica, the major hydrous minerals are talc, which was quantified according to an established standard curve calibrated by infrared spectroscopy analyses. It shows that silica greatly enhances olivine hydration, especially at 500 °C. Without any addition of silica, reaction extents were <5% at 17 days during olivine serpentinization at 500 °C and 3.0 kbar. By contrast, with the presence of 50% silica, olivine was completely transformed to talc within 9 days. This study indicates that silica impedes the oxidation of ferrous iron into ferric iron, and that rates of olivine hydration in natural geological settings are much faster with silica supply.

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Science.gov Websites

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Joining of advanced materials by superplastic deformation

DOEpatents

Goretta, Kenneth C.; Routbort, Jules L.; Gutierrez-Mora, Felipe

2008-08-19

A method for utilizing superplastic deformation with or without a novel joint compound that leads to the joining of advanced ceramic materials, intermetallics, and cermets. A joint formed by this approach is as strong as or stronger than the materials joined. The method does not require elaborate surface preparation or application techniques.

Joining of advanced materials by superplastic deformation

DOEpatents

Goretta, Kenneth C.; Routbort, Jules L.; Gutierrez-Mora, Felipe

2005-12-13

A method for utilizing superplastic deformation with or without a novel joint compound that leads to the joining of advanced ceramic materials, intermetallics, and cermets. A joint formed by this approach is as strong as or stronger than the materials joined. The method does not require elaborate surface preparation or application techniques.

Combustion Synthesis of Magnesium Aluminate

NASA Astrophysics Data System (ADS)

Kale, M. A.; Joshi, C. P.; Moharil, S. V.

2011-10-01

In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl6O10 has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

Cr6+-containing phases in the system CaO-Al2O3-CrO42--H2O at 23 °C

NASA Astrophysics Data System (ADS)

Pöllmann, Herbert; Auer, Stephan

2012-01-01

Synthesis and investigation of lamellar calcium aluminium hydroxy salts was performed to study the incorporation of chromate ions in the interlayer of lamellar calcium aluminium hydroxy salts. Different AFm-phases (calcium aluminate hydrate with alumina, ferric oxide, mono-anion phase) containing chromate were synthesized. These AFm-phases belong to the group of layered double hydroxides (LDHs). 3CaO·Al2O3·CaCrO4·nH2O and C3A·1/2Ca(OH)2·1/2CaCrO4·12H2O were obtained as pure phases and their different distinct interlayer water contents and properties determined. Solid solution of chromate-containing phases and tetracalcium-aluminate-hydrate (TCAH) were studied. The uptake of chromate into TCAH from solutions was proven. Chromate contents in solution decrease to <0.2 mg/l.

Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

NASA Astrophysics Data System (ADS)

Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

2015-02-01

The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress-strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

Enabling Dissimilar Material Joining Using Friction Stir Scribe Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hovanski, Yuri; Upadyay, Piyush; Kleinbaum, Sarah

2017-04-05

One challenge in adapting welding processes to dissimilar material joining is the diversity of melting temperatures of the different materials. Although the use of mechanical fasteners and adhesives have mostly paved the way for near-term implementation of dissimilar material systems, these processes only accentuate the need for low-cost welding processes capable of joining dissimilar material components regardless of alloy, properties, or melting temperature. Friction stir scribe technology was developed to overcome the challenges of joining dissimilar material components where melting temperatures vary greatly, and properties and/or chemistry are not compatible with more traditional welding processes. Although the friction stir scribemore » process is capable of joining dissimilar metals and metal/polymer systems, a more detailed evaluation of several aluminum/steel joints is presented herein to demonstrate the ability to both chemically and mechanically join dissimilar materials.« less

Formation Mechanism of CaS-Bearing Inclusions and the Rolling Deformation in Al-Killed, Low-Alloy Steel with Ca Treatment

NASA Astrophysics Data System (ADS)

Xu, Guang; Jiang, Zhouhua; Li, Yang

2016-08-01

The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.

Investigation of laundering and dispersion approaches for silica and calcium phosphosilicate composite nanoparticles synthesized in reverse micelles

NASA Astrophysics Data System (ADS)

Tabakovic, Amra

Nanotechnology, the science and engineering of materials at the nanoscale, is a booming research area with numerous applications in electronic, cosmetic, automotive and sporting goods industries, as well as in biomedicine. Composite nanoparticles (NPs) are of special interest since the use of two or more materials in NP design imparts multifunctionality on the final NP constructs. This is especially relevant for applications in areas of human healthcare, where the use of dye or drug doped composite NPs is expected to improve the diagnosis and treatment of cancer and other serious illnesses. Since the physicochemical properties of NP suspensions dictate the success of these systems in biomedical applications, especially drug delivery of chemotherapeutics, synthetic routes which offer precise control of NP properties, especially particle diameter and colloidal stability, are utilized to form a variety of composite NPs. Formation of NPs in reverse, or water-in-oil, micelles is one such synthetic approach. However, while the use of reverse micelles to form composite NPs offers precise control over NP size and shape, the post-synthesis laundering and dispersion of synthesized NP suspensions can still be a challenge. Reverse micelle synthetic approaches require the use of surfactants and low dielectric constant solvents, like hexane and cyclohexane, as the oil phase, which can compromise the biocompatibility and colloidal stability of the final composite NP suspensions. Therefore, appropriate dispersants and solvents must be used during laundering and dispersion to remove surfactant and ensure stability of synthesized NPs. In the work presented in this dissertation, two laundering and dispersion approaches, including packed column high performance liquid chromatography (HPLC) and centrifugation (sedimentation and redispersion), are investigated for silver core silica (Ag-SiO2) and calcium phosphosilicate (Caw(HxPO4)y(Si(OH)zOa) b · cH2O, CPS) composite NP suspensions

A validated densitometric method for analysis of atorvastatin calcium and metoprolol tartarate as bulk drugs and in combined capsule dosage forms.

PubMed

Patole, Sm; Khodke, As; Potale, Lv; Damle, Mc

2011-01-01

A simple, accurate and precise high-performance thin-layer chromatographic method has been developed for the estimation of Atorvastatin Calcium and Metoprolol Tartarate simultaneously from a capsule dosage form. The method employed Silica gel 60F (254s)precoated plates as stationary phase and a mixture of Chloroform: Methanol: Glacial acetic acid (dil.) :: (9:1.5:0.2 ml %v/v) as mobile phase. Densitometric scanning was performed at 220 nm using Camag TLC scanner 3. The method was linear in the drug concentrations' range of 500 to 2500 ng/spot for Atorvastatin Calcium, also for Metoprolol Tartarate with correlation coefficient of 0.984 for Atorvastatin Calcium and 0.995 for Metoprolol Tartarate respectively. The retention factor for Atorvastatin Calcium was 0.45 ± 0.04 and for Metoprolol Tartarate was 0.25 ± 0.02. The method was validated as per ICH (International Conference on Harmonisation) Guidelines, proving its utility in estimation of Atorvastatin Calcium and Metoprolol Tartarate in combined dosage form.

Drug Release as a function of bioactivity, incubation regime, liquid, and initial load: Release of bortezomib from calcium phosphate-containing silica/collagen xerogels.

PubMed

Kruppke, Benjamin; Hose, Dirk; Schnettler, Reinhard; Seckinger, Anja; Rößler, Sina; Hanke, Thomas; Heinemann, Sascha

2018-04-01

The ability of silica-/collagen-based composite xerogels to act as drug delivery systems was evaluated by taking into account the initial drug concentration, bioactivity of the xerogels, liquid, and incubation regime. The proteasome inhibitor bortezomib was chosen as a model drug, used for the systemic treatment of multiple myeloma. Incubation during 14 days in phosphate-buffered saline (PBS) or simulated body fluid (SBF) showed a weak initial burst and was identified to be of first order with subsequent release being independent from the initial load of 0.1 or 0.2 mg bortezomib per 60 mg monolithic sample. Faster drug release occurred during incubation in SBF compared to PBS, and during static incubation without changing the liquid, compared to dynamic incubation with daily liquid changes. Drug-loaded xerogels with hydroxyapatite as a third component exhibited enhanced bioactivity retarding drug release, explained by formation of a surface calcium phosphate layer. The fastest release of 50% of the total drug load was observed for biphasic xerogels after 7 days during dynamic incubation in SBF. As a result, the presented concept is suitable for the intended combination of the advantageous bone substitution properties of xerogels and local application of drugs exemplified by bortezomib. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1165-1173, 2018. © 2017 Wiley Periodicals, Inc.

P- T phase relations of silicic, alkaline, aluminous liquids: new results and applications to mantle melting and metasomatism

NASA Astrophysics Data System (ADS)

Draper, David S.; Green, Trevor H.

1999-07-01

We report new experimental results obtained under nominally anhydrous conditions at 1.0-1.5 GPa on a synthetic melt whose composition is typical of extreme-composition xenolith glasses. These results demonstrate that part of this extreme compositional range is in equilibrium with a lherzolitic assemblage (olivine, orthopyroxene, and clinopyroxene on the liquidus), extending our earlier findings [D.S. Draper, T.H. Green P- T phase relations of silicic, alkaline, aluminous mantle-xenolith glasses under anhydrous and C-O-H fluid-saturated conditions, J. Petrol. 38 (1997) 1187-1224] showing saturation with harzburgite minerals (olivine and orthopyroxene on the liquidus). The new results strengthen the view that such liquids can readily coexist with upper mantle rocks. Our results also bear on the current debate regarding the nature of low-degree mantle melts between proponents of the diamond-aggregate technique [who argue for comparatively silica- and alkali-rich low-degree melts; e.g., M.B. Baker, M.M. Hirschmann, M.S. Ghiorso, E.M. Stolper, Compositions of near-solidus peridotite melts from experiments and thermodynamic calculations, Nature 375 (1995) 308-311; M.B. Baker, M.M. Hirschmann, L.E. Wasylenki, E.M. Stolper, M.S. Ghiorso, Quest for low-degree mantle melts, Nature 381 (1996) 286] and those favoring the sandwich technique [who question the value of the diamond-aggregate work and argue that near-solidus melts must be nepheline- and olivine-normative; T.J. Falloon, D.H. Green, H.St.C. O'Neill, C.G. Ballhaus, Quest for low-degree mantle melts, Nature 381 (1996) 285; T.J. Falloon, D.H. Green, H.St.C. O'Neill, W.O. Hibberson, Experimental tests of low degree peridotite partial melt compositions: implications for the nature of anhydrous near-solidus peridotite melts at 1 GPa, Earth Planet. Sci. Lett. 152 (1997) 149-162]. Our results support aspects of both views. The sandwich-technique view is supported, for example, because all our liquids coexisting with mantle

Deleterious role of trace elements - Silica and lead in the development of chronic kidney disease.

PubMed

Mascarenhas, Starlaine; Mutnuri, Srikanth; Ganguly, Anasuya

2017-06-01

Chronic-Kidney-Disease of Unknown-etiology (CKDu) has been reported in developing-countries like Sri-Lanka, India and Central-America without sparing the Indian sub-district (namely Canacona) located in south-Goa. The disease etiology is unlinked to common causes of diabetes and hypertension and assumed to be environmentally induced due to its asymptomatic-nature and occurrence in groundwater relying communities. This study aimed to understand environmental risk-factors underlying CKDu-etiology using Indian sub-district (Canacona) as case-study. Biochemical-analysis of CKDu-affected and non-affected individual's blood and detailed hydro-geochemical analyses of CKDu-affected and non-affected region's groundwater (drinking-water)were conducted. Trace geogenic-element-silica was highly dominant in affected-region's groundwater, thus its nephrotoxic-potential was analysed via in-vitro cytotoxicity-assays on human-kidney-cell-lines. All CKDu-affected-subjects showed increased-levels of serum-urea (52.85 mM),creatinine (941.5 μM),uric-acid (1384.5 μM), normal blood-glucose (4.65 mM), being distinct biomarkers of environmentally-induced CKD-'chronic-tubulo-interstitial-nephritis'. Affected-subjects reported high blood-lead levels (1.48 μM)suggesting direct-nephrotoxicity resulting in impaired blood-clearance and also exhibits indirect-nephrotoxicity by disrupting calcium-homeostasis causing skeletal-disorders and prolonged-consumption of NSAID's (pain-alleviation), indirectly causing renal-damage. Affected-region's groundwater was acidic (pH-5.6), resulting in borderline-lead (9.98 μgL -1 ) and high-silica (115.5 mgL -1 )contamination. Silica's bio-availability (determining its nephrotoxicity) was enhanced at groundwater's acidic-pH and Ca-Mg-deficient-composition (since these cations complex with silica reducing bioavailability). Silica exhibited renal-proximal-tubular-cytotoxicity on long-term exposure comparable with affected-region's groundwater silica

Evaluating the Upset Protrusion Joining (UPJ) Method to Join Magnesium Castings to Dissimilar Metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Logan, Stephen

2016-02-24

This presentation discusses advantages and best practices for incorporating magnesium in automotive component applications to achieve substantial mass reduction, as well as some of the key challenges with respect to joining, coating, and galvanic corrosion, before providing an introduction and status update of the U.S. Department of Energy and Department of Defense jointly sponsored Upset Protrusion Joining (UPJ) process development and evaluation project. This update includes sharing performance results of a benchmark evaluation of the self-pierce riveting (SPR) process for joining dissimilar magnesium (Mg) to aluminum (Al) materials in four unique coating configurations before introducing the UPJ concept and comparingmore » performance results of the joints made with the UPJ process to those made with the SPR process. Key results presented include: The benchmark SPR process can produce good joints in the MgAM60B-Al 6013 joint configuration with minimal cracking in the Mg coupons if the rivet is inserted from the Mg side into the Al side; Numerous bare Mg to bare Al joints made with the SPR process separated after only 6-wks of accelerated corrosion testing due to fracture of the rivet as a result of hydrogen embrittlement; For the same joint configurations, UPJ demonstrated substantially higher pre-corrosion joint strengths and post-corrosion joint strengths, primarily because of the larger diameter protrusion compared to smaller SPR rivet diameter and reduced degradation due to accelerated corrosion exposure; As with the SPR process, numerous bare Mg to bare Al joints made with the UPJ process also separated after 6-wks of accelerated corrosion testing, but unlike the SPR experience, the UPJ joints experienced degradation of the boss and head because of galvanic corrosion of the Mg casting, not hydrogen embrittlement of the steel rivet; In the configuration where both the Mg and Al were pretreated with Alodine 5200 prior to joining and the complete assembly

Enabling Dissimilar Material Joining Using Friction Stir Scribe Technology

DOE PAGES

Hovanski, Yuri; Upadyay, Piyush; Kleinbaum, Sarah; ...

2017-04-05

One challenge in adapting welding processes to dissimilar material joining is the diversity of melting temperatures of the different materials. Although the use of mechanical fasteners and adhesives have mostly paved the way for near-term implementation of dissimilar material systems, these processes only accentuate the need for low-cost welding processes capable of impartially joining dissimilar material components regardless of alloy, properties, or melting temperature. Friction stir scribe technology was developed to overcome the challenges of joining dissimilar material components where melting temperatures vary greatly, and properties and/or chemistry are not compatible with more traditional welding processes. Finally, although the frictionmore » stir scribe process is capable of joining dissimilar metals and metal/polymer systems, a more detailed evaluation of several aluminum/steel joints is presented herein to demonstrate the ability to both chemically and mechanically join dissimilar materials.« less

Immobilization of LiCl-Li 2 O pyroprocessing salt wastes in chlorosodalite using glass-bonded hydrothermal and salt-occlusion methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riley, Brian J.; Peterson, Jacob A.; Kroll, Jared O.

In this study, salt occlusion and hydrothermal processes were used to make chlorosodalite through reaction with a high-LiCl salt simulating a waste stream following pyrochemical treatment of oxide-based used nuclear fuel. Some products were reacted with glass binders to increase chlorosodalite yield through alkali ion exchange and aide in densification. Hydrothermal processes included reaction of the salt simulant in an acid digestion vessel with either zeolite 4A or sodium aluminate and colloidal silica. Chlorosodalite yields in the crystalline products were nearly complete in the glass-bonded materials at values of 100 mass% for the salt-occlusion method, up to 99.0 mass% formore » the hydrothermal synthesis with zeolite 4A, and up to 96 mass% for the hydrothermal synthesis with sodium aluminate and colloidal silica. These results show promise for using chemically stable chlorosodalite to immobilize oxide reduction salt wastes.« less

Immobilization of LiCl-Li2O pyroprocessing salt wastes in chlorosodalite using glass-bonded hydrothermal and salt-occlusion methods

NASA Astrophysics Data System (ADS)

Riley, Brian J.; Peterson, Jacob A.; Kroll, Jared O.; Frank, Steven M.

2018-04-01

In this study, hydrothermal and salt-occlusion processes were used to make chlorosodalite through reactions with a high-LiCl salt simulating a waste stream generated from pyrochemical treatment of oxide-based used nuclear fuel. Some products were reacted with glass binders to increase chlorosodalite yield through alkali ion exchange and to aid in densification. Hydrothermal processes included reaction of the salt simulant in an autoclave with either zeolite 4A or sodium aluminate and colloidal silica. Chlorosodalite yields in the crystalline products were nearly complete in the glass-bonded materials at values of 100 mass% for the salt-occlusion method, up to 99.0 mass% for the hydrothermal synthesis with zeolite 4A, and up to 96 mass% for the hydrothermal synthesis with sodium aluminate and colloidal silica. These results show promise for using chemically stable chlorosodalite to immobilize oxide reduction salt wastes.

Low temperature joining of ceramic composites

DOEpatents

Barton, Thomas J.; Anderson, Iver E.; Ijadi-Maghsoodi, Sina; Nosrati, Mohammad; Unal, Ozer

1999-01-12

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or cermaic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix.

Low temperature joining of ceramic composites

DOEpatents

Barton, Thomas J.; Anderson, Iver E.; Ijadi-Maghsoodi, Sina; Nosrati, Mohammad; Unal, Ozer

1999-07-13

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or ceramic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix.

Low temperature joining of ceramic composites

DOEpatents

Barton, Thomas J.; Anderson, Iver E.; Ijadi-Maghsoodi, Sina; Nosrati, Mohammad; Unal, Ozer

2001-04-10

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or cermaic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix.

Low temperature joining of ceramic composites

DOEpatents

Barton, T.J.; Anderson, I.E.; Ijadi-Maghsoodi, S.; Nosrati, M.; Unal, O.

1999-07-13

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or ceramic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 C to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix. 3 figs.

Low temperature joining of ceramic composites

DOEpatents

Barton, T.J.; Anderson, I.E.; Ijadi-Maghsoodi, S.; Nosrati, M.; Unal, O.

1999-01-12

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or ceramic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix. 3 figs.

Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niu, Z.; Yang, L.; Kabisatpathy, S.

2009-03-24

A sol-gel process has been developed to incorporate bionanoparticles, such as turnip yellow mosaic virus, cowpea mosaic virus, tobacco mosaic virus, and ferritin into silica, while maintaining the integrity and morphology of the particles. The structures of the resulting materials were characterized by transmission electron microscopy, small angle X-ray scattering, and N{sub 2} adsorption-desorption analysis. The results show that the shape and surface morphology of the bionanoparticles are largely preserved after being embedded into silica. After removal of the bionanoparticles by calcination, mesoporous silica with monodisperse pores, having the shape and surface morphology of the bionanoparticles replicated inside the silica,more » was produced,. This study is expected to lead to both functional composite materials and mesoporous silica with structurally well-defined large pores.« less

Modification of Alumina and Spinel Inclusions by Calcium in Liquid Steel

NASA Astrophysics Data System (ADS)

Verma, Neerav

2011-12-01

Steel Cleanliness plays a crucial role in determining steel properties such as toughness, ductility, formability, corrosion resistance and surface quality. The production of clean steel often involves the elimination or chemical and morphological modification of oxide and sulfide inclusions. Along with deteriorating the steel properties, solid inclusions can affect steel castability through nozzle clogging. Nozzle clogging occurs when solid inclusions accumulate in the caster pouring system such as the ladle shroud or submerged entry nozzle (SEN). Thus, it is important to understand how to achieve desired inclusion characteristics (shape, size and chemistry) through the steelmaking process. Among the various practices adopted in industries to counteract the effect of solid inclusions, modification of solid inclusions to liquid or partially liquid state through calcium treatment is one of the methods. Calcium can be used because it has a strong ability to form oxides and sulfides. In Al-killed steels, the most common inclusions are alumina (Al2O3) inclusions, which are solid at steelmaking temperatures. On calcium treatment, solid alumina inclusions are converted to calcium aluminates, which have liquidus temperatures lower than steelmaking temperature (1600°C) [14]. It has been found that alumina inclusions may contain some MgO and such inclusions are termed alumina magnesia spinels (Al2O3.xMgO) [18]. These spinels are more stable than alumina and it has been suggested that they might be more difficult to modify [18]. But, some authors have proposed that MgO can actually help in the liquefaction of inclusions, and have demonstrated successful modification of spinels by Ca treatment [20, 21]. In the present research, the mechanism of transformation of alumina and spinel inclusions upon calcium treatment was studied by characterizing transient evolution of inclusions. A vacuum induction was used for melting, making additions (Al, Al-Mg and CaSi2) and sampling. The

Holographic optical assembly and photopolymerized joining of planar microspheres

DOE PAGES

Shaw, L. A.; Chizari, S.; Panas, R. M.; ...

2016-07-27

The aim of this research is to demonstrate a holographically driven photopolymerization process for joining colloidal particles to create planar microstructures fixed to a substrate, which can be monitored with real-time measurement. Holographic optical tweezers (HOT) have been used to arrange arrays of microparticles prior to this work; here we introduce a new photopolymerization process for rapidly joining simultaneously handled microspheres in a plane. Additionally, we demonstrate a new process control technique for efficiently identifying when particles have been successfully joined by measuring a sufficient reduction in the particles’ Brownian motion. Furthermore, this technique and our demonstrated joining approach enablemore » HOT technology to take critical steps toward automated additive fabrication of microstructures.« less

Optical and spectroscopic investigation on Calcium Borotellurite glass system

NASA Astrophysics Data System (ADS)

Paz, E. C.; Lodi, T. A.; Gomes, B. R. A.; Melo, G. H. A.; Pedrochi, F.; Steimacher, A.

2016-05-01

In this work, the glass formation in Calcium Borotellurite (CBTx) system and their optical properties were studied. Six glass samples were prepared by melt-quenching technique and the samples obtained are transparent, lightly yellowish, without any visible crystallites. The results showed that TeO2 addition increases the density, the electronic polarizability and, consequently, the refractive index. The increase of electronic polarizability and optical basicity suggest that TeO2 addition increases the non-bridging oxygen (NBO) concentration. The increase of TeO2 shifts the band edge to longer wavelength owing to increase in non-bridging oxygen ions, resulting in a linear decrease of optical energy gap. The addition of TeO2 increases the temperature coefficient of the optical path length (dS/dT) in room temperature, which are comparable to phosphate and lower than Low Silica Calcium Alumino Silicate (LSCAS) glasses. The values of dS/dT present an increase as a function of temperature for all the samples measured. The results suggest that CBTx is a good candidate for rare-earth doping and several optical applications.

Sodium Aluminate Concentration Effects on Microstructure and Corrosion Behavior of the Plasma Electrolytic Oxidation Coatings on Pure Titanium

NASA Astrophysics Data System (ADS)

Molaei, Maryam; Fattah-Alhosseini, Arash; Gashti, Seyed Omid

2018-01-01

Sodium aluminate (NaAlO2) concentration was varied in order to understand the influence of the chemical composition of electrolyte on the spark characteristics, microstructure, and corrosion behavior of plasma electrolytic oxidation (PEO) coatings. For this purpose, PEO coatings were formed on the pure titanium substrate surface using solutions of four diverse sodium aluminate concentrations (6, 8, 10, and 12 g/L). The PEO process was carried out at constant time and voltage (180 seconds and 420 V). Studying the microstructures of samples by scanning electron microscope (SEM) and their corrosion behavior in 3.5 wt pct NaCl solutions indicated that the increase in NaAlO2 concentration (up to 10 g/L) led to an increase in uniformity and compactness, thus decreasing the size of micro-pores and increment of corrosion resistance. However, at a certain level of NaAlO2 concentration (12 g/L), large and severe sparks were created on the surface of the sample during the process, worsening the corrosion resistance and microstructure of coating.

Performance Evaluation of Nose Cap to Silica Tile Joint of RLV-TD under the Simulated Flight Environment using Plasma Wind Tunnel Facility

NASA Astrophysics Data System (ADS)

Pillai, Aravindakshan; Krishnaraj, K.; Sreenivas, N.; Nair, Praveen

2017-12-01

Indian Space Research Organisation, India has successfully flight tested the reusable launch vehicle through launching of a demonstration flight known as RLV-TD HEX mission. This mission has given a platform for exposing the thermal protection system to the real hypersonic flight thermal conditions and thereby validated the design. In this vehicle, the nose cap region is thermally protected by carbon-carbon followed by silica tiles with a gap in between them for thermal expansion. The gap is filled with silica fibre. Base material on which the C-C is placed is made of molybdenum. Silica tile with strain isolation pad is bonded to aluminium structure. These interfaces with a variety of materials are characterised with different coefficients of thermal expansion joined together. In order to evaluate and qualify this joint, model tests were carried out in Plasma Wind Tunnel facility under the simultaneous simulation of heat flux and shear levels as expected in flight. The thermal and flow parameters around the model are determined and made available for the thermal analysis using in-house CFD code. Two tests were carried out. The measured temperatures at different locations were benign in both these tests and the SiC coating on C-C and the interface were also intact. These tests essentially qualified the joint interface between C-C and molybdenum bracket and C-C to silica tile interface of RLV-TD.

[Early prenatal diagnosis of diprosopic syncephalic joined twins].

PubMed

Picaud, A; Nlome-Nze, A R; Engongha-Beka, T; Ogowet-Igumu, N

1990-06-01

The authors summarize the case of diprosopic syncephalic joined twins diagnosed at 22 weeks of pregnancy by ultrasonography performed because of hydramnios. The rate of separation anomalies of monozygotic twins is assessed by a review of the literature: from 1 to twenty to fifty thousands for joined twins to 1 per cent fifty thousand to fifteen millions for diprosopus. The etiology is the result of a late division of the egg between D12 and D16. Often an encephalic diprosopic joined twins cause elevated levels of maternal serum alpha protein. Early ultrasonography permits to consider a vaginal therapeutic abortion.

Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel.

PubMed

Cerkauskaite, Ausra; Drevinskas, Rokas; Rybaltovskii, Alexey O; Kazansky, Peter G

2017-04-03

We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

Explosive Joining for the Mars Sample Return Mission

NASA Technical Reports Server (NTRS)

Bement, Laurence J.; Sanok, Joseph T.

2000-01-01

A unique, small-scale, ribbon explosive joining process is being developed as an option for closing and sealing a metal canister to allow the return of a pristine sample of the Martian surface and atmosphere to Earth. This joining process is accomplished by an explosively driven, high-velocity, angular collision of the metal, which melts and effaces the oxide films from the surfaces to allow valence electron sharing to bond the interface. Significant progress has been made through more than 100 experimental tests to meet the goals of this ongoing developmental effort. The metal of choice, aluminum alloy 6061, has been joined in multiple interface configurations and in complete cylinders. This process can accommodate dust and debris on the surfaces to be joined. It can both create and sever a joint at its midpoint with one explosive input. Finally, an approach has been demonstrated that can capture the back blast from the explosive.

Effects of radiation on lithium aluminate samples properties

NASA Astrophysics Data System (ADS)

Botter, F.; Lefevre, F.; Rasneur, B.; Trotabas, M.; Roth, E.

1986-11-01

The irradiation behaviour of lithium aluminate, a candidate material for a fusion reactor blanket, has been investigated. About 130 samples of 7.5% 6Li content γ-LiAlO 2 have been loaded in a 6 level device, and were irradiated for 25.7 FPD in the core of the Osiris reactor at Saclay at the end of 1984, within an experiment named ALICE 1. The properties of several textural groups have been examined before and after irradiation and the correlation of the results observed as a function of the irradiation conditions is given. No significant variation of the properties, as a whole, was shown at 400°C under fluences of 4.7 × 10 20 n cm -2 fast neutrons ( > 1 MeV) and 1.48 × 10 20 n cm -2 thermal neutrons. At 600°C, under the highest flux, weight losses less than 1%, and decreases of 2 to 8% of the sound velocity were measured. Generally, neither swelling nor breakage, except those due to combined mechanical and thermal shocks, were observed.

Joining of graphene flakes by low energy N ion beam irradiation

NASA Astrophysics Data System (ADS)

Wu, Xin; Zhao, Haiyan; Pei, Jiayun; Yan, Dong

2017-03-01

An approach utilizing low energy N ion beam irradiation is applied in joining two monolayer graphene flakes. Raman spectrometry and atomic force microscopy show the joining signal under 40 eV and 1 × 1014 cm-2 N ion irradiation. Molecular dynamics simulations demonstrate that the joining phenomenon is attributed to the punch-down effect and the subsequent chemical bond generation between the two sheets. The generated chemical bonds are made up of inserted ions (embedded joining) and knocked-out carbon atoms (saturation joining). The electronic transport properties of the joint are also calculated for its applications.

Palladium-Catalyzed Carbon-Fluorine and Carbon-Hydrogen Bond Alumination of Fluoroarenes and Heteroarenes.

PubMed

Chen, Wenyi; Hooper, Thomas N; Ng, Jamues; White, Andrew J P; Crimmin, Mark R

2017-10-02

Through serendipitous discovery, a palladium bis(phosphine) complex was identified as a catalyst for the selective transformation of sp 2 C-F and sp 2 C-H bonds of fluoroarenes and heteroarenes to sp 2 C-Al bonds (19 examples, 1 mol % Pd loading). The carbon-fluorine bond functionalization reaction is highly selective for the formation of organoaluminium products in preference to hydrodefluorination products (selectivity=4.4:1 to 27:1). Evidence is presented for a tandem catalytic process in which hydrodefluorination is followed by sp 2 C-H alumination. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acyl silicates and acyl aluminates as activated intermediates in peptide formation on clays

NASA Technical Reports Server (NTRS)

White, D. H.; Kennedy, R. M.; Macklin, J.

1984-01-01

Glycine reacts with heating on dried clays and other minerals to give peptides in much better yield than in the absence of mineral. This reaction was proposed to occur by way of an activated intermediate such as an acyl silicate or acyl aluminate analogous to acyl phosphates involved in several biochemical reactions including peptide bond synthesis. The proposed mechanism has been confirmed by trapping the intermediate, as well as by direct spectroscopic observation of a related intermediate. The reaction of amino acids on periodically dried mineral surfaces represents a widespead, geologically realistic setting for prebiotic peptide formation via in situ activation.

A Review of Similar and Dissimilar Micro-joining of Nitinol

NASA Astrophysics Data System (ADS)

Deepan Bharathi Kannan, T.; Ramesh, T.; Sathiya, P.

2016-04-01

NiTinol belongs to a class of smart materials which has a wide range of applications in the field of automotive, aerospace, biomedical, robotics, etc., owing to the growing trend in miniaturization of components. Micro-joining is becoming one of the important and familiar processes in the fabrication of miniaturized components. Recently, effective micro-joining of thin sheets has been gaining a lot of interest among researchers. In this article, the research and progress in micro-joining of NiTinol to itself and other metals are reviewed at different aspects. To date, laser welding, tungsten inert gas welding, and resistance welding have been used to a large extent in investigating the weldability of NiTinol alloys. Some important welding parameters used in micro joining by various researchers and their effects on weld qualities are detailed in this review. Metallurgical aspects, mechanical properties and corrosion aspects of micro-joined NiTinol sheets/wires are discussed. The aim of this report is to review the recent progress in micro-joining of NiTinol and to provide a basis for follow-on research.

Water solubility in aluminous orthopyroxene and the origin of Earth's asthenosphere.

PubMed

Mierdel, Katrin; Keppler, Hans; Smyth, Joseph R; Langenhorst, Falko

2007-01-19

Plate tectonics is based on the concept of rigid lithosphere plates sliding on a mechanically weak asthenosphere. Many models assume that the weakness of the asthenosphere is related to the presence of small amounts of hydrous melts. However, the mechanism that may cause melting in the asthenosphere is not well understood. We show that the asthenosphere coincides with a zone where the water solubility in mantle minerals has a pronounced minimum. The minimum is due to a sharp decrease of water solubility in aluminous orthopyroxene with depth, whereas the water solubility in olivine continuously increases with pressure. Melting in the asthenosphere may therefore be related not to volatile enrichment but to a minimum in water solubility, which causes excess water to form a hydrous silicate melt.

Organically Modified Silicas on Metal Nanowires

PubMed Central

2010-01-01

Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

Macroporous Silica with Thick Framework for Steam-Stable and High-Performance Poly(ethyleneimine)/Silica CO2 Adsorbent.

PubMed

Min, Kyungmin; Choi, Woosung; Choi, Minkee

2017-06-09

Poly(ethyleneimine) (PEI)/silica has been widely studied as a solid adsorbent for post-combustion CO 2 capture. In this work, a highly macroporous silica (MacS), synthesized by secondary sintering of fumed silica, is compared with various mesoporous silicas with different pore structures as a support for PEI. The silicas with large pore diameter and volume enabled high CO 2 adsorption kinetics and capacity, because pore occlusion by the supported PEI was minimized. The steam stability of the silica structures increased with the silica wall thickness owing to suppressed framework ripening. The silicas with low steam stability showed rapid leaching of PEI, which indicated that the PEI squeezed out of the collapsed silica pores leached more readily. Consequently, MacS that had an extra-large pore volume (1.80 cm 3  g -1 ) and pore diameter (56.0 nm), and a thick wall (>10 nm), showed the most promising CO 2 adsorption kinetics and capacity as well as steam stability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of calcium and magnesium in the concrete tubes of the sandcastle worm.

PubMed

Sun, ChengJun; Fantner, Georg E; Adams, Jonathan; Hansma, Paul K; Waite, J Herbert

2007-04-01

Sandcastle worms Phragmatopoma californica build mound-like reefs by sticking together large numbers of sand grains with cement secreted from the building organ. The cement consists of protein plus substantial amounts of calcium and magnesium, which are not invested in any mineral form. This study examined the effect of calcium and magnesium depletion on the structural and mechanical properties of the cement. Divalent ion removal by chelating with EDTA led to a partial collapse of cement architecture and cement dislodgement from silica surfaces. Mechanical properties examined were sand grain pull-out force, tube resistance to compression and cement adhesive force. EDTA treatment reduced sand grain pull-out forces by 60% and tube compressive strength by 50% relative to controls. EDTA lowered both the maximal adhesive force and energy dissipation of cement by up to an order of magnitude. The adhesiveness of calcium- and magnesium-depleted cement could not be restored by re-exposure to the ions. The results suggest that divalent ions play a complex and multifunctional role in maintaining the structure and stickiness of Phragmatopoma cement.

Newly Branded Energy Systems Integration Group Joins International

Science.gov Websites

research fellow at NREL. Likewise, UVIG sees opportunity in partnering with iiESI. The international Group Joins International Institute for Energy Systems Integration Newly Branded Energy Systems Integration Group Joins International Institute for Energy Systems Integration March 22, 2018 The world of

Micro-stress dominant displacive reconstructive transition in lithium aluminate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Qiwei; Yan, Xiaozhi; Zhang, Leilei

It is supposed that diffusive reconstructive transitions usually take place under hydrostatic pressure or low stresses, and displacive reconstructive phase transitions easily occur at nonhydrostatic pressure. Here, by in-situ high pressure synchrotron X-ray diffraction and single-crystal Raman scattering studies on lithium aluminate at room temperature, we show that the reconstructive transition mechanism is dependent on the internal microscopic stresses rather than the macroscopic stresses. In this case, even hydrostatic pressure can favor the displacive transition if the compressibility of crystal is anisotropic. During hydrostatic compression, γ-LiAlO{sub 2} transforms to δ-LiAlO{sub 2} at about 4 GPa, which is much lower than thatmore » in previous nonhydrostatic experiments (above 9 GPa). In the region where both phases coexist, there are enormous microscopic stresses stemming from the lattice mismatch, suggesting that this transition is displacive. Furthermore, the atomic picture is drawn with the help of the shear Raman modes.« less

Transport of colloidal silica in unsaturated sand: Effect of charging properties of sand and silica particles.

PubMed

Fujita, Yosuke; Kobayashi, Motoyoshi

2016-07-01

We have studied the transport of colloidal silica in various degrees of a water-saturated Toyoura sand column, because silica particles are widely used as catalyst carriers and abrasive agents, and their toxicity is reported recently. Since water-silica, water-sand, and air-water interfaces have pH-dependent negative charges, the magnitude of surface charge was controlled by changing the solution pH. The results show that, at high pH conditions (pH 7.4), the deposition of colloidal silica to the sand surface is interrupted and the silica concentration at the column outlet immediately reaches the input concentration in saturated conditions. In addition, the relative concentration of silica at the column outlet only slightly decreases to 0.9 with decreasing degrees of water saturation to 38%, because silica particles are trapped in straining regions in the soil pore and air-water interface. On the other hand, at pH 5 conditions (low pH), where sand and colloid have less charge, reduced repulsive forces result in colloidal silica attaching onto the sand in saturated conditions. The deposition amount of silica particles remarkably increases with decreasing degrees of water saturation to 37%, which is explained by more particles being retained in the sand column associated with the air-water interface. In conclusion, at higher pH, the mobility of silica particles is high, and the air-water interface is inactive for the deposition of silica. On the other hand, at low pH, the deposition amount increases with decreasing water saturation, and the particle transport is inhibited. Copyright © 2016 Elsevier Ltd. All rights reserved.

The joined wing - An overview. [aircraft tandem wings in diamond configurations

NASA Technical Reports Server (NTRS)

Wolkovitch, J.

1985-01-01

The joined wing is a new type of aircraft configuration which employs tandem wings arranged to form diamond shapes in plan view and front view. Wind-tunnel tests and finite-element structural analyses have shown that the joined wing provides the following advantages over a comparable wing-plus-tail system; lighter weight and higher stiffness, higher span-efficiency factor, higher trimmed maximum lift coefficient, lower wave drag, plus built-in direct lift and direct sideforce control capability. A summary is given of research performed on the joined wing. Calculated joined wing weights are correlated with geometric parameters to provide simple weight estimation methods. The results of low-speed and transonic wind-tunnel tests are summarized, and guidelines for design of joined-wing aircraft are given. Some example joined-wing designs are presented and related configurations having connected wings are reviewed.

An Overview of Orbital Detections of Hydrated Silica and Silica-Rich Rocks on Mars

NASA Astrophysics Data System (ADS)

Sun, V. Z.; Milliken, R.

2016-12-01

Early predictions of high-silica phases on Mars have been confirmed by numerous orbital observations throughout the past 15 years and supported by recent rover and meteorite investigations. Orbital spectroscopy at visible-near-IR (CRISM/OMEGA) and thermal IR (TES/THEMIS) wavelengths has established the presence of aqueously formed hydrated silica across the planet as well as regional silica-rich rocks of igneous origin. TES data provided the first indications of widespread silica enrichment in the northern lowlands, which were debated to represent either andesite or altered basalt on the basis of spectral and geologic arguments. Since then, more localized occurrences of primary silicic lithologies have suggested that igneous processes on Mars may have been more diverse and complex than previously recognized. CRISM and OMEGA data also reveal numerous occurrences of hydrated silica on the Martian surface, likely reflecting primary chemical precipitates or secondary processes such as aqueous alteration or diagenesis. These detections have been associated with fluvial landforms, volcanic settings, uplifted central peak rocks, and mobile sediments, suggesting a variety of formation mechanisms. These silica phases and their colocation with other alteration products such as clays and sulfates reveal aqueous environments that may have been acidic, alkaline, or alternatingly both through space and time. Although there is an apparent prevalence of geochemically immature silica (e.g., glass or opal-A) indicating limited aqueous alteration, several instances of more mature silica (e.g., opal-CT or quartz) point to locales that may have experienced periods of prolonged water-rock interaction. This presentation will give an overview of the distribution and variety of these high-silica phases as seen from orbital datasets and discuss their implications for the magmatic and aqueous history of Mars.

Control over Silica Particle Growth and Particle–Biomolecule Interactions Facilitates Silica Encapsulation of Mammalian Cells with Thickness Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Robert K.; Harper, Jason C.; Tartis, Michaelann S.

Over the past 20 years, many strategies utilizing sol–gel chemistry to integrate biological cells into silica-based materials have been reported. One such strategy, Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition, shows promise as an efficient encapsulation technique due to the ability to vary the silica encapsulation morphology obtained by this process through variation of SG-CViL reaction conditions. In this report, we develop SG-CViL as a tunable, multi-purpose silica encapsulation strategy by investigating the mechanisms governing both silica particle generation and subsequent interaction with phospholipid assemblies (liposomes and living cells). Using Dynamic Light Scattering (DLS) measurements, linear and exponential silica particlemore » growth dynamics were observed which were dependent on deposition buffer ion constituents and ion concentration. Silica particle growth followed a cluster–cluster growth mechanism at acidic pH, and a monomer-cluster growth mechanism at neutral to basic pH. Increasing silica sol aging temperature resulted in higher rates of particle growth and larger particles. DLS measurements employing PEG-coated liposomes and cationic liposomes, serving as model phospholipid assemblies, revealed that electrostatic interactions promote more stable liposome–silica interactions than hydrogen bonding and facilitate silica coating on suspension cells. However, continued silica reactivity leads to aggregation of silica-coated suspension cells, revealing the need for cell isolation to tune deposited silica thickness. As a result, utilizing these mechanistic study insights, silica was deposited onto adherent HeLa cells under biocompatible conditions with micrometer-scale control over silica thickness, minimal cell manipulation steps, and retained cell viability over several days.« less

Control over Silica Particle Growth and Particle–Biomolecule Interactions Facilitates Silica Encapsulation of Mammalian Cells with Thickness Control

DOE PAGES

Johnston, Robert K.; Harper, Jason C.; Tartis, Michaelann S.

2017-07-13

Over the past 20 years, many strategies utilizing sol–gel chemistry to integrate biological cells into silica-based materials have been reported. One such strategy, Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition, shows promise as an efficient encapsulation technique due to the ability to vary the silica encapsulation morphology obtained by this process through variation of SG-CViL reaction conditions. In this report, we develop SG-CViL as a tunable, multi-purpose silica encapsulation strategy by investigating the mechanisms governing both silica particle generation and subsequent interaction with phospholipid assemblies (liposomes and living cells). Using Dynamic Light Scattering (DLS) measurements, linear and exponential silica particlemore » growth dynamics were observed which were dependent on deposition buffer ion constituents and ion concentration. Silica particle growth followed a cluster–cluster growth mechanism at acidic pH, and a monomer-cluster growth mechanism at neutral to basic pH. Increasing silica sol aging temperature resulted in higher rates of particle growth and larger particles. DLS measurements employing PEG-coated liposomes and cationic liposomes, serving as model phospholipid assemblies, revealed that electrostatic interactions promote more stable liposome–silica interactions than hydrogen bonding and facilitate silica coating on suspension cells. However, continued silica reactivity leads to aggregation of silica-coated suspension cells, revealing the need for cell isolation to tune deposited silica thickness. As a result, utilizing these mechanistic study insights, silica was deposited onto adherent HeLa cells under biocompatible conditions with micrometer-scale control over silica thickness, minimal cell manipulation steps, and retained cell viability over several days.« less

21 CFR 182.1711 - Silica aerogel.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having...

21 CFR 182.1711 - Silica aerogel.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having...

Behavior of macroporous vinyl silica and silica monolithic columns in high pressure gas chromatography.

PubMed

Maniquet, Adrien; Bruyer, Nicolas; Raffin, Guy; Baco-Antionali, Franck; Demesmay, Claire; Dugas, Vincent; Randon, Jérôme

2017-06-30

80% vinyltrimethoxysilane-based hybrid silica monoliths (80-VTMS), which have been initially developed for separation in reversed-phase liquid chromatography, have been investigated in high pressure gas chromatography separations (carrier gas pressure up to 60bar) and compared to silica monolithic columns. The behavior of both silica and 80-VTMS monolithic columns was investigated using helium, nitrogen and carbon dioxide as carrier gas. The efficiency of 80-VTMS monolithic columns was shown to vary differently than silica monolithic columns according to the temperature and the carrier gas used. Carrier gas nature was a significant parameter on the retention for both silica and vinyl columns in relation to its adsorption onto the stationary phase in such high pressure conditions. The comparison of retention and selectivity between 80-VTMS monoliths and silica was performed under helium using the logarithm of the retention factor according to the number of carbon atoms combined to Kovats indexes. The very good performances of these columns were demonstrated, allowing the separation of 8 compounds in less than 1min. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanisms of optical losses in the 5D4 and 5D3 levels in Tb3+ doped low silica calcium aluminosilicate glasses

NASA Astrophysics Data System (ADS)

dos Santos, J. F. M.; Terra, I. A. A.; Astrath, N. G. C.; Guimarães, F. B.; Baesso, M. L.; Nunes, L. A. O.; Catunda, T.

2015-02-01

Trivalent Tb-doped materials exhibit strong emission in the green and weak emission in the UV-blue levels. Usually, this behavior is attributed to the cross relaxation (CR) process. In this paper, the luminescence properties of Tb3+-doped low silica calcium aluminosilicate glasses are analyzed for UV (λexc = 325 nm) and visible (488 nm) excitations. Under 325 nm excitation, the intensity of green luminescence increases proportionally to Tb3+ concentration. However, the blue luminescence intensity is strongly reduced with the increase of concentration from 0.5-15.0 wt. %. In the case of 488 nm excitation, a saturation behavior of the green emission is observed at intensities two orders of magnitude smaller than expected for bleaching of the ground state population. Using a rate equation model, we showed that this behavior can be explained by an excited state absorption cross section two orders of magnitude larger than the ground state absorption. The blue emission is much weaker than expected from our rate equations (325 nm and 488 nm excitation). We concluded that only the CR process cannot explain the overall feature of measured luminescence quenching in the wide range of Tb3+ concentrations. Cooperative upconversion from a pair of excited ions (5D3:5D3 or 5D3:5D4) and other mechanisms involving upper lying states (4f5d, charge transfer, host matrix, defects, etc.) may play a significant role.

Fluxing agent for metal cast joining

DOEpatents

Gunkel, Ronald W.; Podey, Larry L.; Meyer, Thomas N.

2002-11-05

A method of joining an aluminum cast member to an aluminum component. The method includes the steps of coating a surface of an aluminum component with flux comprising cesium fluoride, placing the flux coated component in a mold, filling the mold with molten aluminum alloy, and allowing the molten aluminum alloy to solidify thereby joining a cast member to the aluminum component. The flux preferably includes aluminum fluoride and alumina. A particularly preferred flux includes about 60 wt. % CsF, about 30 wt. % AlF.sub.3, and about 10 wt. % Al.sub.2 O.sub.3.

Calcium bioavailability and kinetics of calcium ascorbate and calcium acetate in rats.

PubMed

Cai, Jianwei; Zhang, Qinmin; Wastney, Meryl E; Weaver, Connie M

2004-01-01

The objective was to investigate the bioavailability and mechanism of calcium absorption of calcium ascorbate (ASC) and calcium acetate (AC). A series of studies was performed in adult Sprague-Dawley male rats. In the first study, each group of rats (n = 10/group) was assigned to one of the five test meals labeled with (45)Ca: (i) 25 mg calcium as heated ASC or (ii) unheated ASC, (iii) 25 mg calcium as unheated AC, (iv) 3.6 mg Ca as unheated ASC, or (v) unheated AC. Femur uptake indicated better calcium bioavailability from ASC than AC at both calcium loads. A 5-min heat treatment partly reduced bioavailability of ASC. Kinetic studies were performed to further investigate the mechanism of superior calcium bioavailability from ASC. Two groups of rats (n = 10/group) received oral doses of 25 mg Ca as ASC or AC. Each dose contained 20 micro Ci (45)Ca. Two additional groups of rats (n = 10/group) received an intravenous injection (iv) of 10 micro Ci (45)Ca after receiving an unlabeled oral dose of 25 mg calcium as ASC or AC. Sequential blood samples were collected over 48 hrs. Urine and fecal samples were collected every 12 hrs for 48 hrs and were analyzed for total calcium and (45)Ca content. Total calcium and (45)Ca from serum, urine, and feces were fitted by a compartment kinetics model with saturable and nonsaturable absorption pathways by WinSAAM (Windows-based Simulation Analysis and Modeling). The difference in calcium bioavailability between the two salts was due to differences in saturable rather than passive intestinal absorption and not to endogenous secretion or calcium deposition rate. The higher bioavailability of calcium ascorbate was due to a longer transit time in the small intestine compared with ASC.

Universal connectors for joining stringers

NASA Technical Reports Server (NTRS)

Harrison, Jr., Ernest (Inventor)

1987-01-01

This invention is a lightweight, universal connector that joins stringers at various angles. The connectors 10 are fabricated from fiber-epoxy resin strips that wrap around stringers 30 and have ends, tabs 16 and 18, which extend in one general direction. The inside surface of the first tab 16 lies on a plane defined by the stringers being joined, and the second tab 18 is separated from the first tab 16 by a distance equal to their thickness. Stringers 30 of different shapes and sizes are joined by alternately bonding the first tab 16 of one connector between the first 16 and second 18 tabs of another connector. Tee-joints are formed by using web elements 41 and 42 which each partially wrap around a stringer 3010 and have tabs 411 and 421 which are offset, and are bonded between tabs 16 and 18 of universal connectors 109 and 1010 bonded to another stringer 309. Sharp corners are trimmed from the tabs so that a gusset area remains between the stringers for support. Acute angle through obtuse angle joints are formed by trimming those edges of the tabs which lie against the stringers. A specific application of the invention is a Walker 60, utilized by handicapped individuals, fabricated from composite materials that is 40% lighter than similar metallic structures.

Larnite powders and larnite/silica aerogel composites as effective agents for CO2 sequestration by carbonation.

PubMed

Santos, A; Ajbary, M; Morales-Flórez, V; Kherbeche, A; Piñero, M; Esquivias, L

2009-09-15

This paper presents the results of the carbonation reaction of two sample types: larnite (Ca(2)SiO(4)) powders and larnite/silica aerogel composites, the larnite acting as an active phase in a process of direct mineral carbonation. First, larnite powders were synthesized by the reaction of colloidal silica and calcium nitrate in the presence of ethylene glycol. Then, to synthesize the composites, the surface of the larnite powders was chemically modified with 3-aminopropyltriethoxysilane (APTES), and later this mixture was added to a silica sol previously prepared from tetraethylorthosilicate (TEOS). The resulting humid gel was dried in an autoclave under supercritical conditions for the ethanol. The textures and chemical compositions of the powders and composites were characterized.The carbonation reaction of both types of samples was evaluated by means of X-ray diffraction and thermogravimetric analysis. Both techniques confirm the high efficiency of the reaction at room temperature and atmospheric pressure. A complete transformation of the silicate into carbonate resulted after submitting the samples to a flow of pure CO(2) for 15 min. This indicates that for this reaction time, 1t of larnite could eliminate about 550 kg of CO(2). The grain size, porosity, and specific surface area are the factors controlling the reaction.

Oxidation of a Silica-Containing Material in a Mach 0.3 Burner Rig

NASA Technical Reports Server (NTRS)

Nguyen, QuynhGiao N.; Cuy, Michael D.; Gray, Hugh R. (Technical Monitor)

2002-01-01

A primarily silica-containing material with traces of organic compounds, as well as aluminum and calcium additions, was exposed to a Mach 0.3 burner rig at atmospheric pressure using jet fuel. The sample was exposed for 5 continuous hours at 1370 C. Post exposure x-ray diffraction analyses indicate formation of cristobalite, quartz, NiO and Spinel (Al(Ni)CR2O4). The rig hardware is composed of a nickel-based superalloy with traces of Fe. These elements are indicated in the energy dispersive spectroscopy (EDS) results. This material was studied as a candidate for high temperature applications under an engine technology program.

Fused silica GRISMs manufactured by hydrophilic direct bonding at moderate heating

NASA Astrophysics Data System (ADS)

Kalkowski, G.; Grabowski, K.; Harnisch, G.; Flügel-Paul, T.; Zeitner, U.; Risse, S.

2017-12-01

For high-resolution spectroscopy in space, GRISM elements—obtained by patterning gratings onto a prism surface—find increasing applications. We report on GRISM manufacturing by joining the individual functional elements—prisms and gratings—to suitable components by the technology of hydrophilic direct bonding. Fused silica was used as a substrate material and binary gratings were fabricated by standard e-beam lithography and dry etching. Alignment of the grating dispersion direction to the prism angle was realized by passive adjustment on dedicated bonding gear matched to the substrate geometry. Materials adapted bonds of high transmission, stiffness, and strength were obtained after heat treatment at temperatures of about 200 °C in vacuum. Examples for bonding uncoated as well as coated grating surfaces are given. The results illustrate the great potential of hydrophilic glass direct bonding for manufacturing transmission optics to be used in space or other heavy duty applications.

Aeroelastic tailoring and structural optimization of joined-wing configurations

NASA Astrophysics Data System (ADS)

Lee, Dong-Hwan

2002-08-01

Methodology for integrated aero-structural design was developed using formal optimization. ASTROS (Automated STRuctural Optimization System) was used as an analyzer and an optimizer for performing joined-wing weight optimization with stress, displacement, cantilever or body-freedom flutter constraints. As a pre/post processor, MATLAB was used for generating input file of ASTROS and for displaying the results of the ASTROS. The effects of the aeroelastic constraints on the isotropic and composite joined-wing weight were examined using this developed methodology. The aeroelastic features of a joined-wing aircraft were examined using both the Rayleigh-Ritz method and a finite element based aeroelastic stability and weight optimization procedure. Aircraft rigid-body modes are included to analyze of body-freedom flutter of the joined-wing aircraft. Several parametric studies were performed to determine the most important parameters that affect the aeroelastic behavior of a joined-wing aircraft. The special feature of a joined-wing aircraft is body-freedom flutter involving frequency interaction of the first elastic mode and the aircraft short period mode. In most parametric study cases, the body-freedom flutter speed was less than the cantilever flutter speed that is independent of fuselage inertia. As fuselage pitching moment of inertia was increased, the body-freedom flutter speed increased. When the pitching moment of inertia reaches a critical value, transition from body-freedom flutter to cantilever flutter occurred. The effects of composite laminate orientation on the front and rear wings of a joined-wing configuration were studied. An aircraft pitch divergence mode, which occurred because of forward movement of center of pressure due to wing deformation, was found. Body-freedom flutter and cantilever-like flutter were also found depending on combination of front and rear wing ply orientations. Optimized wing weight behaviors of the planar and non

Laser beam joining of material combinations for automotive applications

NASA Astrophysics Data System (ADS)

Schubert, Emil; Zerner, Ingo; Sepold, Gerd

1997-08-01

An ideal material for automotive applications would combine the following properties: high corrosion resistance, high strength, high stiffness and not at least a low material price. Today a single material is not able to meet all these requirements. Therefore, in the future different materials will be placed where they meet the requirements best. The result of this consideration is a car body with many different alloys and metals, which have to be joined to one another. BIAS is working on the development of laser based joining technologies for different material combinations, especially for thin sheets used in automotive applications. One result of the research is a joining technology for an aluminum-steel-joint. Using a Nd:YAG laser the problem of brittle intermetallic phases between these materials was overcome. Using suitable temperature-time cycles, elected by a FEM-simulation, the thickness of intermetallic phases was kept below 10 micrometers . This technology was also applied to coated steels, which were joined with different aluminum alloys. Further it is demonstrated that titanium alloys, e.g. used for racing cars, can also be joined with aluminum alloys.

Identification of Candidate Zero Maintenance Paving Materials. Volume 1

DTIC Science & Technology

1977-05-01

an anhydrous calcium sulfoaluminate as a way to control ettringite-formarion reactions and patented it as an invention on 18 October 1961. Another... Sulfoaluminates of Calcium as Stable and Meta- stable Phases and Study of Portion of the Five-Component System CaO-SO 3 -Al0 3-Na20-H 2O at 25C. Ph. D...Berkeley, Jun 1972. 242. , "Effect of Lime on Hydration of Pastes Containing Gypsum and Calcium Aluminates or Calcium Sulfoaluminate ," Journal, American

Epoxy Grout With Silica Thickener

NASA Technical Reports Server (NTRS)

Mcclung, C. E.

1984-01-01

Grout cures quickly, even in presence of hydraulic oil. Grout is mixture of aggregate particles, finely-divided silica, epoxy resin, and triethylenetetramine curing agent, with mixture containing about 85 percent silica and aggregate particle sand 15 percent resin and curing agent. Silica is thickening agent and keeps grout from sagging.

Improved Joining of Metal Components to Composite Structures

NASA Technical Reports Server (NTRS)

Semmes, Edmund

2009-01-01

Systems requirements for complex spacecraft drive design requirements that lead to structures, components, and/or enclosures of a multi-material and multifunctional design. The varying physical properties of aluminum, tungsten, Invar, or other high-grade aerospace metals when utilized in conjunction with lightweight composites multiply system level solutions. These multi-material designs are largely dependent upon effective joining techAn improved method of joining metal components to matrix/fiber composite material structures has been invented. The method is particularly applicable to equipping such thin-wall polymer-matrix composite (PMC) structures as tanks with flanges, ceramic matrix composite (CMC) liners for high heat engine nozzles, and other metallic-to-composite attachments. The method is oriented toward new architectures and distributing mechanical loads as widely as possible in the vicinities of attachment locations to prevent excessive concentrations of stresses that could give rise to delaminations, debonds, leaks, and other failures. The method in its most basic form can be summarized as follows: A metal component is to be joined to a designated attachment area on a composite-material structure. In preparation for joining, the metal component is fabricated to include multiple studs projecting from the aforementioned face. Also in preparation for joining, holes just wide enough to accept the studs are molded into, drilled, or otherwise formed in the corresponding locations in the designated attachment area of the uncured ("wet') composite structure. The metal component is brought together with the uncured composite structure so that the studs become firmly seated in the holes, thereby causing the composite material to become intertwined with the metal component in the joining area. Alternately, it is proposed to utilize other mechanical attachment schemes whereby the uncured composite and metallic parts are joined with "z-direction" fasteners. The

Characterization, Operation and Analysis of Test Motors Containing Aluminized Hybrid Fuels

NASA Technical Reports Server (NTRS)

Kibbey, Timothy P.; Cortopassi, Andrew C.; Boyer, J. Eric

2017-01-01

NASA Marshall Space Flight Center's Materials and Processes Department, with support from the Propulsion Systems Department, has renewed the development and maintenance of a hybrid test bed for exposing ablative thermal protection materials to an environment similar to that seen in solid rocket motors (SRM). The Solid Fuel Torch (SFT), operated during the Space Shuttle program, utilized gaseous oxygen for oxidizer and an aluminized hydroxyl-terminated polybutadiene (HTPB) fuel grain to expose a converging section of phenolic material to a 400 psi, 2-phase flow combustion environment. The configuration allows for up to a 2 foot long, 5 inch diameter fuel grain cartridge. Wanting to now test rubber insulation materials with a turn-back feature to mimic the geometry of an aft dome being impinged by alumina particles, the throat area has now been increased by several times to afford flow similarity. Combined with the desire to maintain a higher operating pressure, the oxidizer flow rate is being increased by a factor of 10. Out of these changes has arisen the need to characterize the fuel/oxidizer combination in a higher mass flux condition than has been previously tested at MSFC, and at which the literature has little to no reporting as well. Testing for fuel regression rate comprised a two-level, full factorial design available over Aluminum loading level, mass flow rate, pressure, and diameter. The data taken significantly surpasses the previous available data on regression rate of aluminized HTPB fuel burning with gaseous oxygen. It encompasses higher mass fluxes, and appears to generate more consistent data. The good test article and facility design and testing work of the Penn State HPCL combined with careful analysis of the data and good planning has made this possible. This should be able to assist with developing rate laws that are useful both for research planning and for developing flight system sizing relationships that can help optimize hybrid rocket

The phagocytosis and toxicity of amorphous silica.

PubMed

Costantini, Lindsey M; Gilberti, Renée M; Knecht, David A

2011-02-02

Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37 °C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both cases. However, the result suggests a mechanistic difference

Metal-silica sol-gel materials

NASA Technical Reports Server (NTRS)

Stiegman, Albert E. (Inventor)

2002-01-01

The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

PubMed

Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

2016-02-01

This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring.

PubMed

Chen, Fang; Hableel, Ghanim; Zhao, Eric Ruike; Jokerst, Jesse V

2018-07-01

The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine. Copyright © 2018 Elsevier Inc. All rights reserved.

What Is Crystalline Silica?

MedlinePlus

... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

Joining Tubes With Adhesive

NASA Technical Reports Server (NTRS)

Bateman, W. A.

1984-01-01

Cylindrical tubes joined together, end to end, by method employing adhesive, tapered ends, and spacing wires. Tapered joint between tubular structural elements provides pressure between bonding surfaces during adhesive curing. Spacing wires prevent adhesive from being scraped away when one element inserted in other. Method developed for assembling structural elements made of composite materials.

Multifunctional mesoporous silica catalyst

DOEpatents

Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

2015-03-31

The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

Study of the pluronic-silica interaction in synthesis of mesoporous silica under mild acidic conditions.

PubMed

Sundblom, Andreas; Palmqvist, Anders E C; Holmberg, Krister

2010-02-02

The interaction between silica and poly(ethylene oxide) (PEO) in water may appear trivial and it is generally stated that hydrogen bonding is responsible for the attraction. However, a literature search shows that there is not a consensus with respect to the mechanism behind the attractive interaction. Several papers claim that only hydrogen bonding is not sufficient to explain the binding. The silica-PEO interaction is interesting from an academic perspective and it is also exploited in the preparation of mesoporous silica, a material of considerable current interest. This study concerns the very early stage of synthesis of mesoporous silica under mild acidic conditions, pH 2-5, and the aim is to shed light on the interaction between silica and the PEO-containing structure directing agent. The synthesis comprises two steps. An organic silica source, tetraethylorthosilicate (TEOS), is first hydrolyzed and Pluronic P123, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, is subsequently added at different time periods following the hydrolysis of TEOS. It is shown that the interaction between the silica and the Pluronic is dependent both on the temperature and on the time between onset of TEOS hydrolysis and addition of the copolymer. The results show that the interaction is mainly driven by entropy. The effect of the synthesis temperature and of the time between hydrolysis and addition of the copolymer on the final material is also studied. The material with the highest degree of mesoorder was obtained when the reaction was performed at 20 degrees C and the copolymer was added 40 h after the start of TEOS hydrolysis. It is claimed that the reason for the good ordering of the silica is that whereas particle formation under these conditions is fast, the rate of silica condensation is relatively low.

Silica coatings on clarithromycin.

PubMed

Bele, Marjan; Dmitrasinovic, Dorde; Planinsek, Odon; Salobir, Mateja; Srcic, Stane; Gaberscek, Miran; Jamnik, Janko

2005-03-03

Pre-crystallized clarithromycin (6-O-methylerythromycin A) particles were coated with silica from the tetraethyl orthosilicate (TEOS)-ethanol-aqueous ammonia system. The coatings had a typical thickness of 100-150 nm and presented about 15 wt.% of the silica-drug composite material. The properties of the coatings depended on reactant concentration, temperature and mixing rate and, in particular, on the presence of a cationic surfactant (cetylpyridinium chloride). In the presence of cetylpyridinium chloride the silica coatings slightly decreased the rate of pure clarithromycin dissolution.

Joined ceramic product

DOEpatents

Henager, Jr., Charles W [Kennewick, WA; Brimhall, John L [West Richland, WA

2001-08-21

According to the present invention, a joined product is at least two ceramic parts, specifically bi-element carbide parts with a bond joint therebetween, wherein the bond joint has a metal silicon phase. The bi-element carbide refers to compounds of MC, M.sub.2 C, M.sub.4 C and combinations thereof, where M is a first element and C is carbon. The metal silicon phase may be a metal silicon carbide ternary phase, or a metal silicide.

The Effect of Various Acids to the Gelation Process to the Silica Gel Characteristic Using Organic Silica

NASA Astrophysics Data System (ADS)

Rahman, NA; Widiyastuti, W.; Sigit, D.; Ajiza, M.; Sujana, W.

2018-01-01

Bagasse ash is solid waste of cane sugar industry which contain of silica more than 51%. Some previous study of silica gel from bagasse ash have been conducted often and been applied. This study concerns about the effect of various acid used in the process of gelation to the characteristic of silica gel produced. Then, this silica gel will be used as adsorbent. As that, the silica gel must fulfill the requirements of adsorbent, as have good pores characteristics, fit in mesoporous size so that adsorbent diffusion process is not disturbed. A fitted pores size of silica gel can be prepared by managing acid concentration used. The effect of acid, organic acid (tartaric acid) and inorganic acid (hydrochloric acid), is investigated in detail. The acid is added into sodium silicate solution in that the gel is formed, the pores structures can be investigated with BET, the crystal form is analyzed with XRD and the pore structure is analyzed visually with SEM. By managing the acid concentration added, it gets the effect of acid to the pore structure of silica gel. The bigger concentration is, the bigger the pore’s size of silica gel produced.

Space Environmental Effects Testing and Characterization of the Candidate Solar Sail Material Aluminized Mylar

NASA Technical Reports Server (NTRS)

Edwards, D. L.; Hubbs, W. S.; Wertz, G. E.; Alstatt, R.; Munafo, Paul (Technical Monitor)

2001-01-01

The usage of solar sails as a propellantless propulsion system has been proposed for many years. The technical challenges associated with solar sails are fabrication of ultralightweight films, deploying the sails and controlling the spacecraft. Integral to all these challenges is the mechanical property integrity of the sail while exposed to the harsh environment of space. This paper describes testing and characterization of a candidate solar sail material, Aluminized Mylar. This material was exposed to a simulated Geosynchronous Transfer Orbit (GTO) and evaluated by measuring thermooptical and mechanical property changes. Testing procedures and results are presented.

The Phagocytosis and Toxicity of Amorphous Silica

PubMed Central

Costantini, Lindsey M.; Gilberti, Renée M.; Knecht, David A.

2011-01-01

Background Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Methodology/Principal Findings Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Conclusions/Significance Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both

Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

PubMed Central

Wilson, Rosamund J; Copley, J Brian

2017-01-01

Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Findings Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Conclusion Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance. PMID:28182142

Come Join the Band

ERIC Educational Resources Information Center

Olson, Cathy Applefeld

2011-01-01

A growing number of students in Blue Springs, Missouri, are joining the band, drawn by a band director who emphasizes caring and inclusiveness. In the four years since Melissia Goff arrived at Blue Springs High School, the school's extensive band program has swelled. The marching band alone has gone from 100 to 185 participants. Also under Goff's…

A Combined Brazing and Aluminizing Process for Repairing Turbine Blades by Thermal Spraying Using the Coating System NiCrSi/NiCoCrAlY/Al

NASA Astrophysics Data System (ADS)

Nicolaus, M.; Möhwald, K.; Maier, H. J.

2017-10-01

The repair and maintenance of components in the aerospace industry play an increasingly important role due to rising manufacturing costs. Besides welding, vacuum brazing is a well-established repair process for turbine blades made of nickel-based alloys. After the coating of the worn turbine blade has been removed, the manual application of the nickel-based filler metal follows. Subsequently, the hot gas corrosion-protective coating is applied by thermal spraying. The brazed turbine blade is aluminized to increase the hot gas corrosion resistance. The thermal spray technology is used to develop a two-stage hybrid technology that allows shortening the process chain for repair brazing turbine blades and is described in the present paper. In the first step, the coating is applied on the base material. Specifically, the coating system employed here is a layer system consisting of nickel filler metal, NiCoCrAlY and aluminum. The second step represents the combination of brazing and aluminizing of the coating system which is subjected to a heat treatment. The microstructure, which results from the combined brazing and aluminizing process, is characterized and the relevant diffusion processes in the coating system are illustrated. The properties of the coating and the ramifications with respect to actual applications will be discussed.

Application of the joined wing to tiltrotor aircraft

NASA Technical Reports Server (NTRS)

Wolkovitch, Julian; Wainfan, Barnaby; Ben-Harush, Yitzhak; Johnson, Wayne

1989-01-01

A study was made to determine the potential speed improvements and other benefits resulting from the application of the joined wing concept to tiltrotor aircraft. Using the XV-15 as a baseline, the effect of replacing the cantilever wing by a joined-wing pair was studied. The baseline XV-15 cantilever wing has a thickness/chord ratio of 23 percent. It was found that this wing could be replaced by a joined-wing pair of the same span and total area employing airfoils of 12 percent thickness/chord ratio. The joined wing meets the same static strength requirements as the cantilever wing, but increases the limiting Mach Number of the aircraft from M=0.575 to M=0.75, equivalent to an increase of over 100 knots in maximum speed. The joined wing configuration studied is lighter than the cantilever and has approximately 11 percent less wing drag in cruise. Its flutter speed of 245 knots EAS is not high enough to allow the potential Mach number improvement to be attained at low altitude. The flutter speed can be raised either by employing rotors which can be stopped and folded in flight at speeds below 245 knots EAS, or by modifying the airframe to reduce adverse coupling with the rotor dynamics. Several modifications of wing geometry and nacelle mass distribution were investigated, but none produced a flutter speed above 260 knots EAS. It was concluded that additional research is required to achieve a more complete understanding of the mechanism of rotor/wing coupling.

Growth, structural, spectroscopic and optical characterization of barium doped calcium tartrate

NASA Astrophysics Data System (ADS)

Verma, Seema; Raina, Bindu; Gupta, Vandana; Bamzai, K. K.

2018-05-01

Barium doped calcium tartrates synthesized by controlled diffusion using silica gel technique at ambient temperature was characterized by single crystal X-ray diffraction which establishes monoclinic crystal system with volume of the unit cell 923.97(10) Ǻ3 and the space group being P21. UV - Vis characterization gives various linear optical constants like absorption, transmittance, reflectance, band gap, extinction coefficient, urbach energy, complex dielectric constant, optical and electrical conductivity. These constants are considered to be essential in characterizing materials that are used in various applications like fabrication of optoelectronic devices. FTIR spectrum establishes the presence of various bands of functional groups expected from metal tartrate with water of crystallization.

Efficient and Scalable Graph Similarity Joins in MapReduce

PubMed Central

Chen, Yifan; Zhang, Weiming; Tang, Jiuyang

2014-01-01

Along with the emergence of massive graph-modeled data, it is of great importance to investigate graph similarity joins due to their wide applications for multiple purposes, including data cleaning, and near duplicate detection. This paper considers graph similarity joins with edit distance constraints, which return pairs of graphs such that their edit distances are no larger than a given threshold. Leveraging the MapReduce programming model, we propose MGSJoin, a scalable algorithm following the filtering-verification framework for efficient graph similarity joins. It relies on counting overlapping graph signatures for filtering out nonpromising candidates. With the potential issue of too many key-value pairs in the filtering phase, spectral Bloom filters are introduced to reduce the number of key-value pairs. Furthermore, we integrate the multiway join strategy to boost the verification, where a MapReduce-based method is proposed for GED calculation. The superior efficiency and scalability of the proposed algorithms are demonstrated by extensive experimental results. PMID:25121135

Efficient and scalable graph similarity joins in MapReduce.

PubMed

Chen, Yifan; Zhao, Xiang; Xiao, Chuan; Zhang, Weiming; Tang, Jiuyang

2014-01-01

Along with the emergence of massive graph-modeled data, it is of great importance to investigate graph similarity joins due to their wide applications for multiple purposes, including data cleaning, and near duplicate detection. This paper considers graph similarity joins with edit distance constraints, which return pairs of graphs such that their edit distances are no larger than a given threshold. Leveraging the MapReduce programming model, we propose MGSJoin, a scalable algorithm following the filtering-verification framework for efficient graph similarity joins. It relies on counting overlapping graph signatures for filtering out nonpromising candidates. With the potential issue of too many key-value pairs in the filtering phase, spectral Bloom filters are introduced to reduce the number of key-value pairs. Furthermore, we integrate the multiway join strategy to boost the verification, where a MapReduce-based method is proposed for GED calculation. The superior efficiency and scalability of the proposed algorithms are demonstrated by extensive experimental results.

Ceramic-to-Metal Joining for High Temperature, High Pressure Heat Exchangers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mako, Frederick; Mako III, Frederick

2016-12-05

Designed and tested silicon carbide to metal joining and silicon carbide joining technology under high temperature and high pressure conditions. Determined that the joints maintained integrity and remained helium gas tight. These joined parts have been tested for mechanical strength, fracture toughness and hermeticity. A component testing chamber was designed and built and used for testing the joint integrity.

Sample Desorption/Onization From Mesoporous Silica

DOEpatents

Iyer, Srinivas; Dattelbaum, Andrew M.

2005-10-25

Mesoporous silica is shown to be a sample holder for laser desorption/ionization of mass spectrometry. Supported mesoporous silica was prepared by coating an ethanolic silicate solution having a removable surfactant onto a substrate to produce a self-assembled, ordered, nanocomposite silica thin film. The surfactant was chosen to provide a desired pore size between about 1 nanometer diameter and 50 nanometers diameter. Removal of the surfactant resulted in a mesoporous silica thin film on the substrate. Samples having a molecular weight below 1000, such as C.sub.60 and tryptophan, were adsorbed onto and into the mesoporous silica thin film sample holder and analyzed using laser desorption/ionization mass spectrometry.

Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

PubMed Central

Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward

2013-01-01

To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate PTHrP secretion and milk calcium transport with calcium availability. To test this idea genetically, we bred BLG-Cre mice with CaSR-floxed mice to ablate the CaSR specifically from mammary epithelial cells only at the onset of lactation (CaSR-cKO mice). Loss of the CaSR in the lactating mammary gland did not disrupt alveolar differentiation or milk production. However, it did increase the secretion of PTHrP into milk and decreased the transport of calcium from the circulation into milk. CaSR-cKO mice did not show accelerated bone resorption, but they did have a decrease in bone formation. Loss of the mammary gland CaSR resulted in hypercalcemia, decreased PTH secretion, and increased renal calcium excretion in lactating mothers. Finally, loss of the mammary gland CaSR resulted in decreased calcium accrual by suckling neonates, likely due to the combination of increased milk PTHrP and decreased milk calcium. These results demonstrate that the mammary gland CaSR coordinates maternal bone and calcium metabolism, calcium transport into milk, and neonatal calcium accrual during lactation. PMID:23782944

Joining Forces. A Team Approach to Secondary School Development.

ERIC Educational Resources Information Center

Miller, Rima; Corcoran, Thomas B.

This manual is designed to guide the implementation of the Joining Forces Program, a comprehensive improvement process for secondary schools. Implementation of the program requires the cooperative effort of the local school district, state and local education associations, and the administration and staff of participating schools. Joining Forces…

Thermally stable silica-coated hydrophobic gold nanoparticles.

PubMed

Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

2009-01-01

We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

Silica nanoparticle stability in biological media revisited.

PubMed

Yang, Seon-Ah; Choi, Sungmoon; Jeon, Seon Mi; Yu, Junhua

2018-01-09

The stability of silica nanostructure in the core-silica shell nanomaterials is critical to understanding the activity of these nanomaterials since the exposure of core materials due to the poor stability of silica may cause misinterpretation of experiments, but unfortunately reports on the stability of silica have been inconsistent. Here, we show that luminescent silver nanodots (AgNDs) can be used to monitor the stability of silica nanostructures. Though relatively stable in water and phosphate buffered saline, silica nanoparticles are eroded by biological media, leading to the exposure of AgNDs from AgND@SiO 2 nanoparticles and the quenching of nanodot luminescence. Our results reveal that a synergistic effect of organic compounds, particularly the amino groups, accelerates the erosion. Our work indicates that silica nanostructures are vulnerable to cellular medium and it may be possible to tune the release of drug molecules from silica-based drug delivery vehicles through controlled erosion.

Liquid-solid joining of bulk metallic glasses

NASA Astrophysics Data System (ADS)

Huang, Yongjiang; Xue, Peng; Guo, Shu; Wu, Yang; Cheng, Xiang; Fan, Hongbo; Ning, Zhiliang; Cao, Fuyang; Xing, Dawei; Sun, Jianfei; Liaw, Peter K.

2016-07-01

Here, we successfully welded two bulk metallic glass (BMG) materials, Zr51Ti5Ni10Cu25Al9 and Zr50.7Cu28Ni9Al12.3 (at. %), using a liquid-solid joining process. An atomic-scale metallurgical bonding between two BMGs can be achieved. The interface has a transition layer of ~50 μm thick. The liquid-solid joining of BMGs can shed more insights on overcoming their size limitation resulting from their limited glass-forming ability and then promoting their applications in structural components.

Liquid-solid joining of bulk metallic glasses

PubMed Central

Huang, Yongjiang; Xue, Peng; Guo, Shu; Wu, Yang; Cheng, Xiang; Fan, Hongbo; Ning, Zhiliang; Cao, Fuyang; Xing, Dawei; Sun, Jianfei; Liaw, Peter K.

2016-01-01

Here, we successfully welded two bulk metallic glass (BMG) materials, Zr51Ti5Ni10Cu25Al9 and Zr50.7Cu28Ni9Al12.3 (at. %), using a liquid-solid joining process. An atomic-scale metallurgical bonding between two BMGs can be achieved. The interface has a transition layer of ~50 μm thick. The liquid-solid joining of BMGs can shed more insights on overcoming their size limitation resulting from their limited glass-forming ability and then promoting their applications in structural components. PMID:27471073

Liquid-solid joining of bulk metallic glasses.

PubMed

Huang, Yongjiang; Xue, Peng; Guo, Shu; Wu, Yang; Cheng, Xiang; Fan, Hongbo; Ning, Zhiliang; Cao, Fuyang; Xing, Dawei; Sun, Jianfei; Liaw, Peter K

2016-07-29

Here, we successfully welded two bulk metallic glass (BMG) materials, Zr51Ti5Ni10Cu25Al9 and Zr50.7Cu28Ni9Al12.3 (at. %), using a liquid-solid joining process. An atomic-scale metallurgical bonding between two BMGs can be achieved. The interface has a transition layer of ~50 μm thick. The liquid-solid joining of BMGs can shed more insights on overcoming their size limitation resulting from their limited glass-forming ability and then promoting their applications in structural components.

Liquid-solid joining of bulk metallic glasses

DOE PAGES

Huang, Yongjiang; Xue, Peng; Guo, Shu; ...

2016-07-29

Here, we successfully welded two bulk metallic glass (BMG) materials, Zr 51Ti 5Ni 10Cu 25Al 9 and Zr 50.7Cu 28Ni 9Al 12.3 (at. %), using a liquid-solid joining process. An atomic-scale metallurgical bonding between two BMGs can be achieved. The interface has a transition layer of ~50 μm thick. In conclusion, the liquid-solid joining of BMGs can shed more insights on overcoming their size limitation resulting from their limited glass-forming ability and then promoting their applications in structural components.

Interface modification based ultrashort laser microwelding between SiC and fused silica.

PubMed

Zhang, Guodong; Bai, Jing; Zhao, Wei; Zhou, Kaiming; Cheng, Guanghua

2017-02-06

It is a big challenge to weld two materials with large differences in coefficients of thermal expansion and melting points. Here we report that the welding between fused silica (softening point, 1720°C) and SiC wafer (melting point, 3100°C) is achieved with a near infrared femtosecond laser at 800 nm. Elements are observed to have a spatial distribution gradient within the cross section of welding line, revealing that mixing and inter-diffusion of substances have occurred during laser irradiation. This is attributed to the femtosecond laser induced local phase transition and volume expansion. Through optimizing the welding parameters, pulse energy and interval of the welding lines, a shear joining strength as high as 15.1 MPa is achieved. In addition, the influence mechanism of the laser ablation on welding quality of the sample without pre-optical contact is carefully studied by measuring the laser induced interface modification.

Chitosan-silica complex membranes from sulfonic acid functionalized silica nanoparticles for pervaporation dehydration of ethanol-water solutions.

PubMed

Liu, Ying-Ling; Hsu, Chih-Yuan; Su, Yu-Huei; Lai, Juin-Yih

2005-01-01

Nanosized silica particles with sulfonic acid groups (ST-GPE-S) were utilized as a cross-linker for chitosan to form a chitosan-silica complex membranes, which were applied to pervaporation dehydration of ethanol-water solutions. ST-GPE-S was obtained from reacting nanoscale silica particles with glycidyl phenyl ether, and subsequent sulfonation onto the attached phenyl groups. The chemical structure of the functionalized silica was characterized with FTIR, (1)H NMR, and energy-dispersive X-ray. Homogeneous dispersion of the silica particles in chitosan was observed with electronic microscopies, and the membranes obtained were considered as nanocomposites. The silica nanoparticles in the membranes served as spacers for polymer chains to provide extra space for water permeation, so as to bring high permeation rates to the complex membranes. With addition of 5 parts per hundred of functionalized silica into chitosan, the resulting membrane exhibited a separation factor of 919 and permeation flux of 410 g/(m(2) h) in pervaporation dehydration of 90 wt % ethanol aqueous solution at 70 degrees C.

Development of a procedure for forming assisted thermal joining of tubes

NASA Astrophysics Data System (ADS)

Chen, Hui; Löbbe, Christian; Staupendahl, Daniel; Tekkaya, A. Erman

2018-05-01

With the demand of lightweight design in the automotive industry, not only the wall-thicknesses of tubular components of the chassis or spaceframe are continuously decreased. Also the thicknesses of exhaust system parts are reduced to save material and mass. However, thinner tubular parts bring about additional challenges in joining. Welding or brazing methods, which are utilized in joining tubes with specific requirements concerning leak tightness, are sensitive to the gap between the joining partners. Furthermore, a large joining area is required to ensure the durability of the joint. The introduction of a forming step in the assembled state prior to thermal joining can define and control the gap for subsequent brazing or welding. The mechanical pre-joint resulting from the previously described calibration step also results in easier handling of the tubes prior to thermal joining. In the presented investigation, a spinning process is utilized to produce force-fit joints of varying lengths and diameter reduction and form-fit joints with varying geometrical attributes. The spinning process facilitates a high formability and geometrical flexibility, while at the achievable precision is high and the process forces are low. The strength of the joints is used to evaluate the joint quality. Finally, a comparison between joints produced by forming with subsequent brazing and original tube is conducted, which presents the high performance of the developed procedure for forming assisted thermal joining.

Removal of dissolved and colloidal silica

DOEpatents

Midkiff, William S.

2002-01-01

Small amorphous silica particles are used to provide a relatively large surface area upon which silica will preferentially adsorb, thereby preventing or substantially reducing scaling caused by deposition of silica on evaporative cooling tower components, especially heat exchange surfaces. The silica spheres are contacted by the cooling tower water in a sidestream reactor, then separated using gravity separation, microfiltration, vacuum filtration, or other suitable separation technology. Cooling tower modifications for implementing the invention process have been designed.

Near-infrared light-controlled regulation of intracellular calcium to modulate macrophage polarization.

PubMed

Kang, Heemin; Zhang, Kunyu; Wong, Dexter Siu Hong; Han, Fengxuan; Li, Bin; Bian, Liming

2018-04-21

Macrophages are multifunctional immune cells with diverse physiological functions such as fighting against infection, influencing progression of pathologies, maintaining homeostasis, and regenerating tissues. Macrophages can be induced to adopt distinct polarized phenotypes, such as classically activated pro-inflammatory (M1) phenotypes or alternatively activated anti-inflammatory and pro-healing (M2), to execute diverse and dynamic immune functions. However, unbalanced polarizations of macrophage can lead to various pathologies, such as atherosclerosis, obesity, tumor, and asthma. Thus, the capability to remotely control macrophage phenotypes is important to the success of treating many pathological conditions involving macrophages. In this study, we developed an upconversion nanoparticle (UCNP)-based photoresponsive nanocarrier for near-infrared (NIR) light-mediated control of intracellular calcium levels to regulate macrophage polarization. UCNP was coated with mesoporous silica (UCNP@mSiO 2 ), into which loaded calcium regulators that can either supply or deplete calcium ions. UCNP@mSiO 2 was chemically modified through serial coupling of photocleavable linker and Arg-Gly-Asp (RGD) peptide-bearing molecular cap via cyclodextrin-adamantine host-guest complexation. The RGD-bearing cap functioned as the photolabile gating structure to control the release of calcium regulators and facilitated the cellular uptake of UCNP@mSiO 2 nanocarrier. The upconverted UV light emission from the UCNP@mSiO 2 under NIR light excitation triggered the cleavage of cap and intracellular release of calcium regulators, thereby allowing temporal regulation on the intracellular calcium levels. Application of NIR light through skin tissue promoted M1 or M2 polarization of macrophages, by elevating or depleting intracellular calcium levels, respectively. To the best of our knowledge, this is the first demonstration of NIR light-mediated remote control on macrophage polarization. This

Cellular membrane trafficking of mesoporous silica nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, I-Ju

This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulfmore » some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to

Silica removal in industrial effluents with high silica content and low hardness.

PubMed

Latour, Isabel; Miranda, Ruben; Blanco, Angeles

2014-01-01

High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%.

Finite element thermal analysis for PMMA/st.st.304 laser direct joining

NASA Astrophysics Data System (ADS)

Hussein, Furat I.; Salloomi, Kareem N.; Akman, E.; Hajim, K. I.; Demir, A.

2017-01-01

This work is concerned with building a three-dimensional (3D) ab-initio models that is capable of predicting the thermal distribution of laser direct joining processes between Polymethylmethacrylate (PMMA) and stainless steel 304(st.st.304). ANSYS® simulation based on finite element analysis (FEA) was implemented for materials joining in two modes; laser transmission joining (LTJ) and conduction joining (CJ). ANSYS® simulator was used to explore the thermal environment of the joints during joining (heating time) and after joining (cooling time). For both modes, the investigation is carried out when the laser spot is at the middle of the joint width, at 15 mm from the commencement point (joint edge) at traveling time of 3.75 s. Process parameters involving peak power (Pp=3 kW), pulse duration (τ=5 ms), pulse repetition rate (PRR=20 Hz) and scanning speed (v=4 mm/s) are applied for both modes.

Silica based hybrid materials for drug delivery and bioimaging.

PubMed

Bagheri, Elnaz; Ansari, Legha; Abnous, Khalil; Taghdisi, Seyed Mohammad; Charbgoo, Fahimeh; Ramezani, Mohammad; Alibolandi, Mona

2018-05-10

Silica hybrid materials play an important role in improvement of novel progressive functional nanomaterials. Study in silica hybrid functional materials is supported by growing interest in providing intelligent materials that combine best of the inorganic silica structure along with organic or biological realms. Hybrid silica materials do not only provide fantastic opportunities for the design of novel materials for research but their represented unique properties open versatile applications specifically in nanomedicine since it was recognized by US FDA as a safe material for human trials. By combining various materials with different characteristics along with silica NPs as building blocks, silica-based hybrid vehicles were developed. In this regard, silica-based hybrid materials have shown great capabilities as unique carriers for bioimaging and/or drug delivery purposes. In the aforementioned hybrid systems, silica was preferred as a main building block of the hybrid structure, which is easily functionalized with different materials, bio-molecules and targeting ligands while providing biocompatibility for the system. This review will cover a full description of different hybrids of silica nanoparticles including silica-polymer, silica-protein, silica-peptide, silica-nucleic acid, silica-gold, silica-quantum dot, and silica-magnetic nanoparticles and their applications as therapeutic or imaging systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Embedded Heaters for Joining or Separating Plastic Parts

NASA Technical Reports Server (NTRS)

Bryant, Melvin A., III

2004-01-01

A proposed thermal-bonding technique would make it possible to join or separate thermoplastic parts quickly and efficiently. The technique would eliminate the need for conventional welding or for such conventional fastening components as bolted flanges or interlocking hooks. The technique could be particularly useful in the sign industry (in which large quantities of thermoplastics are used) or could be used to join plastic pipes. A thin sheet of a suitable electrically conductive material would be formed to fit between two thermoplastic parts to be joined (see figure). The electrically conductive sheet and the two parts would be put together tightly, then an electrical current would be sent through the conductor to heat the thermoplastic locally. The magnitude of the current and the heating time would be chosen to generate just enough heat to cause the thermoplastic to adhere to both sides of the electrically conductive sheet. Optionally, the electrically conductive sheet could contain many small holes to provide purchase or to increase electrical resistance to facilitate the generation of heat. After thermal bonding, the electrically conductive sheet remains as an integral part of the structure. If necessary, the electrically conductive sheet can be reheated later to separate the joined thermoplastic parts.

Laser hybrid joining of plastic and metal components for lightweight components

NASA Astrophysics Data System (ADS)

Rauschenberger, J.; Cenigaonaindia, A.; Keseberg, J.; Vogler, D.; Gubler, U.; Liébana, F.

2015-03-01

Plastic-metal hybrids are replacing all-metal structures in the automotive, aerospace and other industries at an accelerated rate. The trend towards lightweight construction increasingly demands the usage of polymer components in drive trains, car bodies, gaskets and other applications. However, laser joining of polymers to metals presents significantly greater challenges compared with standard welding processes. We present recent advances in laser hybrid joining processes. Firstly, several metal pre-structuring methods, including selective laser melting (SLM) are characterized and their ability to provide undercut structures in the metal assessed. Secondly, process parameter ranges for hybrid joining of a number of metals (steel, stainless steel, etc.) and polymers (MABS, PA6.6-GF35, PC, PP) are given. Both transmission and direct laser joining processes are presented. Optical heads and clamping devices specifically tailored to the hybrid joining process are introduced. Extensive lap-shear test results are shown that demonstrate that joint strengths exceeding the base material strength (cohesive failure) can be reached with metal-polymer joining. Weathering test series prove that such joints are able to withstand environmental influences typical in targeted fields of application. The obtained results pave the way toward implementing metalpolymer joints in manufacturing processes.

Laser-Induced Fluorescence Photogrammetry for Dynamic Characterization of Transparent and Aluminized Membrane Structures

NASA Technical Reports Server (NTRS)

Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.; Pappa, Richard S.

2003-01-01

Photogrammetry has proven to be a valuable tool for static and dynamic profiling of membrane based inflatable and ultra-lightweight space structures. However, the traditional photogrammetric targeting techniques used for solid structures, such as attached retro-reflective targets and white-light dot projection, have some disadvantages and are not ideally suited for measuring highly transparent or reflective membrane structures. In this paper, we describe a new laser-induced fluorescence based target generation technique that is more suitable for these types of structures. We also present several examples of non-contact non-invasive photogrammetric measurements of laser-dye doped polymers, including the dynamic measurement and modal analysis of a 1m-by-1m aluminized solar sail style membrane.

Process for Preparing Epoxy-Reinforced Silica Aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B (Inventor)

2016-01-01

One-pot reaction process for preparing epoxy-reinforced monolithic silica aerogels comprising the reaction of at least one silicon compound selected from the group consisting of alkoxysilanes, orthosilicates and combination thereof in any ratio with effective amounts of an epoxy monomer and an aminoalkoxy silane to obtain an epoxy monomer-silica sol in solution, subsequently preparing an epoxy-monomer silica gel from said silica sol solution followed by initiating polymerization of the epoxy monomer to obtain the epoxy-reinforced monolithic silica aerogel.

Peptide-laden mesoporous silica nanoparticles with promoted bioactivity and osteo-differentiation ability for bone tissue engineering.

PubMed

Luo, Zuyuan; Deng, Yi; Zhang, Ranran; Wang, Mengke; Bai, Yanjie; Zhao, Qiang; Lyu, Yalin; Wei, Jie; Wei, Shicheng

2015-07-01

Combination of mesoporous silica materials and bioactive factors is a promising niche-mimetic solution as a hybrid bone substitution for bone tissue engineering. In this work, we have synthesized biocompatible silica-based nanoparticles with abundant mesoporous structure, and incorporated bone-forming peptide (BFP) derived from bone morphogenetic protein-7 (BMP-7) into the mesoporous silica nanoparticles (MSNs) to obtain a slow-release system for osteogenic factor delivery. The chemical characterization demonstrates that the small osteogenic peptide is encapsulated in the mesoporous successfully, and the nitrogen adsorption-desorption isotherms suggest that the peptide encapsulation has no influence on mesoporous structure of MSNs. In the cell experiment, the peptide-laden MSNs (p-MSNs) show higher MG-63 cell proliferation, spreading and alkaline phosphatase (ALP) activity than the bare MSNs, indicating good in vitro cytocompatibility. Simultaneously, the osteogenesis-related proteins expression and calcium mineral deposition disclose enhanced osteo-differentiation of human mesenchymal stem cells (hMSCs) under the stimulation of the p-MSNs, confirming that BFP released from MSNs could significantly promote the osteogenic differentiation of hMSCs, especially at 500μg/mL of p-MSNs concentration. The peptide-modified MSNs with better bioactivity and osteogenic differentiation make it a potential candidate as bioactive material for bone repairing, bone regeneration, and bio-implant coating applications. Copyright © 2015 Elsevier B.V. All rights reserved.

High-energy electron beams for ceramic joining

NASA Astrophysics Data System (ADS)

Turman, Bob N.; Glass, S. J.; Halbleib, J. A.; Helmich, D. R.; Loehman, Ron E.; Clifford, Jerome R.

1995-03-01

Joining of structural ceramics is possible using high melting point metals such as Mo and Pt that are heated with a high energy electron beam, with the potential for high temperature joining. A 10 MeV electron beam can penetrate through 1 cm of ceramic, offering the possibility of buried interface joining. Because of transient heating and the lower heat capacity of the metal relative to the ceramic, a pulsed high power beam has the potential for melting the metal without decomposing or melting the ceramic. We have demonstrated the feasibility of the process with a series of 10 MeV, 1 kW electron beam experiments. Shear strengths up to 28 MPa have been measured. This strength is comparable to that reported in the literature for bonding silicon nitride (Si3N4) to molybdenum with copper-silver-titanium braze, but weaker than that reported for Si3N4 - Si3N4 with gold-nickel braze. The bonding mechanism appears to be formation of a thin silicide layer. Beam damage to the Si3N4 was also assessed.

Top scientists join Stephen Hawking at Perimeter Institute

NASA Astrophysics Data System (ADS)

Banks, Michael

2009-03-01

Nine leading researchers are to join Stephen Hawking as visiting fellows at the Perimeter Institute for Theoretical Physics in Ontario, Canada. The researchers, who include string theorists Leonard Susskind from Stanford University and Asoka Sen from the Harisch-Chandra Research Institute in India, will each spend a few months of the year at the institute as "distinguished research chairs". They will be joined by another 30 scientists to be announced at a later date.

Laser beam joining of optical fibers in silicon V-grooves

NASA Astrophysics Data System (ADS)

Kaufmann, Stefan; Otto, Andreas; Luz, Gerhard

2000-06-01

The increasing use of optical data transmission systems and the development of new optical components require adjustment-insensitive and reliable joining and assembling techniques. The state of the art includes the utilization of silicon submounts with anisotropically etched V-grooves. Several glass fibers are fixed in these V-grooves with adhesive. Adhesive bonds tend towards degradation under the influence of temperature and moisture. For this reason, the alternative joining processes laser beam welding and laser beam soldering are relevant. The goal is a reliable joining of optical fibers in V-grooves without damage to the fibers or the silicon submount. Because of the anomaly of silicon during phase transformation, a positive joining can be realized by laser beam welding. A melt pool is created through the energy of a Nd:YAG-laser pulse. During solidification, the volume of silicon increases and a bump is formed in the center. Experiments have shown that this phenomenon can be used for joining optical fibers in silicon-V-grooves. With suitable parameters the silicon flows half around the fiber during solidification. For each fiber, several welding points are necessary. Another promising joining method is laser bema soldering. In this case, a second silicon sheet with a solder deposit is placed on the fibers which lie in the V-grooves of the metallized silicon submount. The laser heats the upper silicon until the solder metals by heat conduction.

Quantum-splitting oxide-based phosphors and method of producing the same

DOEpatents

Setlur, Anant Achyut; Srivastava, Alok Mani

2003-09-02

Strontium, calcium, strontium calcium, strontium calcium magnesium, calcium magnesium aluminates, and strontium borates activated with Pr.sup.3+ exhibit characteristics of quantum-splitting phosphors under VUV excitation. A large emission peak at about 405 nm under VUV excitation is used conveniently to identify quantum-splitting phosphors. Improvements may be achieved with addition of fluorides or boric acid as a flux during the preparation of the phosphors. It is also possible to predict improvement in quantum efficiency by observing the ratio of emission intensities at about 480 nm and about 610 nm.

Calcium

MedlinePlus

... You'll also find calcium in broccoli and dark green, leafy vegetables (especially collard and turnip greens, ... can enjoy good sources of calcium such as dark green, leafy vegetables, broccoli, chickpeas, and calcium-fortified ...

Carbothermal transformation of a graphitic carbon nanofiber/silica aerogel composite to a SiC/silica nanocomposite.

PubMed

Lu, Weijie; Steigerwalt, Eve S; Moore, Joshua T; Sullivan, Lisa M; Collins, W Eugene; Lukehart, C M

2004-09-01

Carbon nanofiber/silica aerogel composites are prepared by sol-gel processing of surface-enhanced herringbone graphitic carbon nanofibers (GCNF) and Si(OMe)4, followed by supercritical CO2 drying. Heating the resulting GCNF/silica aerogel composites to 1650 degrees C under a partial pressure of Ar gas initiates carbothermal reaction between the silica aerogel matrix and the carbon nanofiber component to form SiC/silica nanocomposites. The SiC phase is present as nearly spherical nanoparticles, having an average diameter of ca. 8 nm. Formation of SiC is confirmed by powder XRD and by Raman spectroscopy.

Joining of polymer composite materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Magness, F.H.

1990-11-01

Under ideal conditions load bearing structures would be designed without joints, thus eliminating a source of added weight, complexity and weakness. In reality the need for accessibility, repair, and inspectability, added to the size limitations imposed by the manufacturing process and transportation/assembly requirements mean that some minimum number of joints will be required in most structures. The designer generally has two methods for joining fiber composite materials, adhesive bonding and mechanical fastening. As the use of thermoplastic materials increases, a third joining technique -- welding -- will become more common. It is the purpose of this document to provide amore » review of the available sources pertinent to the design of joints in fiber composites. The primary emphasis is given to adhesive bonding and mechanical fastening with information coming from documentary sources as old as 1961 and as recent as 1989. A third, shorter section on composite welding is included in order to provide a relatively comprehensive treatment of the subject.« less

Adsorption of silica colloids onto like-charged silica surfaces of different roughness

DOE PAGES

Dylla-Spears, R.; Wong, L.; Shen, N.; ...

2017-01-17

Particle adsorption was explored in a model optical polishing system, consisting of silica colloids and like-charged silica surfaces. The adsorption was monitored in situ under various suspension conditions, in the absence of surfactants or organic modifiers, using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in surface coverage with particle concentration, particle size, pH, ionic strength and ionic composition were quantified by QCM-D and further characterized ex situ by atomic force microscopy (AFM). A Monte Carlo model was used to describe the kinetics of particle deposition and provide insights on scaling with particle concentration. Transitions from near-zero adsorption tomore » measurable adsorption were compared with equilibrium predictions made using the Deraguin-Verwey-Landau-Overbeek (DLVO) theory. In addition, the impact of silica surface roughness on the propensity for particle adsorption was studied on various spatial scale lengths by intentionally roughening the QCM sensor surface using polishing methods. It was found that a change in silica surface roughness at the AFM scale from 1.3 nm root-mean-square (rms) to 2.7 nm rms resulted in an increase in silica particle adsorption of 3-fold for 50-nm diameter particles and 1.3-fold for 100-nm diameter particles—far exceeding adsorption observed by altering suspension conditions alone, potentially because roughness at the proper scale reduces the total separation distance between particle and surface.« less

Presence of nano-sized silica during in vitro digestion of foods containing silica as a food additive.

PubMed

Peters, Ruud; Kramer, Evelien; Oomen, Agnes G; Rivera, Zahira E Herrera; Oegema, Gerlof; Tromp, Peter C; Fokkink, Remco; Rietveld, Anton; Marvin, Hans J P; Weigel, Stefan; Peijnenburg, Ad A C M; Bouwmeester, Hans

2012-03-27

The presence, dissolution, agglomeration state, and release of materials in the nano-size range from food containing engineered nanoparticles during human digestion is a key question for the safety assessment of these materials. We used an in vitro model to mimic the human digestion. Food products subjected to in vitro digestion included (i) hot water, (ii) coffee with powdered creamer, (iii) instant soup, and (iv) pancake which either contained silica as the food additive E551, or to which a form of synthetic amorphous silica or 32 nm SiO(2) particles were added. The results showed that, in the mouth stage of the digestion, nano-sized silica particles with a size range of 5-50 and 50-500 nm were present in food products containing E551 or added synthetic amorphous silica. However, during the successive gastric digestion stage, this nano-sized silica was no longer present for the food matrices coffee and instant soup, while low amounts were found for pancakes. Additional experiments showed that the absence of nano-sized silica in the gastric stage can be contributed to an effect of low pH combined with high electrolyte concentrations in the gastric digestion stage. Large silica agglomerates are formed under these conditions as determined by DLS and SEM experiments and explained theoretically by the extended DLVO theory. Importantly, in the subsequent intestinal digestion stage, the nano-sized silica particles reappeared again, even in amounts higher than in the saliva (mouth) digestion stage. These findings suggest that, upon consumption of foods containing E551, the gut epithelium is most likely exposed to nano-sized silica. © 2012 American Chemical Society

Silicon Nitride Joining.

DTIC Science & Technology

1984-05-01

and alkaline earth species present in Si3 N or In the glass were found to be deleterious to joint integrity. The results of all ttanamission electron...of Si3 94 ,’ Bulietin, of The American Ceramic Society 58 58-486 (1979). 2 ~ ~ %$ - ~ ~ ’WIN TECHNICAL PROGRESS ’Progress during the third year of the...at temperatures up to 1300*C on Si3 N4 joined with a IaO-Al 2 O3 -Si0 2 glass, -5-9M, and with an yttrium oxynLtrLde glass, SG-14. However, the

Preparation and Characterization of Silica Aerogel Microspheres

PubMed Central

Chen, Qifeng; Wang, Hui; Sun, Luyi

2017-01-01

Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4–20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping densities and specific surface areas of the aerogel microspheres are in the range of 0.112–0.287 g/cm3 and 207.5–660.6 m2/g, respectively. The diameter of the silica aerogel microspheres could be tailored by varying the processing conditions including agitation rate, water/oil ratio, mass ratio of Span 80: Tween 80, and emulsifier concentration. The effects of these parameters on the morphology and textural properties of the synthesized silica aerogel microspheres were systematically investigated. Such silica aerogel microspheres can be used to prepare large-scale silica aerogels at an ambient pressure for applications in separation and high efficiency catalysis, which requires features of high porosity and easy fill and recovery. PMID:28772795

Water Vapor Effects on Silica-Forming Ceramics

NASA Technical Reports Server (NTRS)

Opila, E. J.; Greenbauer-Seng, L. (Technical Monitor)

2000-01-01

Silica-forming ceramics such as SiC and Si3N4 are proposed for applications in combustion environments. These environments contain water vapor as a product of combustion. Oxidation of silica-formers is more rapid in water vapor than in oxygen. Parabolic oxidation rates increase with the water vapor partial pressure with a power law exponent value close to one. Molecular water vapor is therefore the mobile species in silica. Rapid oxidation rates and large amounts of gases generated during the oxidation reaction in high water vapor pressures may result in bubble formation in the silica and nonprotective scale formation. It is also shown that silica reacts with water vapor to form Si(OH)4(g). Silica volatility has been modeled using a laminar flow boundary layer controlled reaction equation. Silica volatility depends on the partial pressure of water vapor, the total pressure, and the gas velocity. Simultaneous oxidation and volatilization reactions have been modeled with paralinear kinetics.

Preparation and Characterization of Silica Aerogel Microspheres.

PubMed

Chen, Qifeng; Wang, Hui; Sun, Luyi

2017-04-20

Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4-20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping densities and specific surface areas of the aerogel microspheres are in the range of 0.112-0.287 g/cm³ and 207.5-660.6 m²/g, respectively. The diameter of the silica aerogel microspheres could be tailored by varying the processing conditions including agitation rate, water/oil ratio, mass ratio of Span 80: Tween 80, and emulsifier concentration. The effects of these parameters on the morphology and textural properties of the synthesized silica aerogel microspheres were systematically investigated. Such silica aerogel microspheres can be used to prepare large-scale silica aerogels at an ambient pressure for applications in separation and high efficiency catalysis, which requires features of high porosity and easy fill and recovery.

Chitosan-silica hybrid porous membranes.

PubMed

Pandis, Christos; Madeira, Sara; Matos, Joana; Kyritsis, Apostolos; Mano, João F; Ribelles, José Luis Gómez

2014-09-01

Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. Copyright © 2014 Elsevier B.V. All rights reserved.

High-Temperature Self-Healing and Re-Adhering Geothermal Well Cement Composites

NASA Astrophysics Data System (ADS)

Pyatina, T.; Sugama, T.; Boodhan, Y.; Nazarov, L.

2017-12-01

Self-healing cementitious materials are particularly attractive for the cases where damaged areas are difficult to locate and reach. High-temperature geothermal wells with aggressive environments impose most difficult conditions on cements that must ensure durable zonal isolation under repeated thermal, chemical and mechanical stresses. The present work evaluates matrix and carbon steel (CS) - cement interface self-healing and re-adhering properties of various inorganic cementitious composites under steam, alkali carbonate or brine environments at 270-300oC applicable to geothermal wells. The composite materials included blends based on Ordinary Portland Cement (OPC) and natural zeolites and alkali or phosphate activated composites of Calcium Aluminate Cement (CAC) with fly ash, class F. Class G cement blend with crystalline silica was used as a baseline. Compressive-strength and bond-strength recoveries were examined to evaluate self-healing and re-adhering properties of the composites after repeated crush tests followed by 5-day healing periods in these environments. The optical and scanning electron microscopes, X-ray diffraction, Fourier Transform infrared, Raman spectroscopy and EDX measurements were used to identify phases participating in the strengths recoveries and cracks filling processes. Amorphous silica-rich- and small-size crystalline phases played an important role in the healing of the tested composites in all environments. Possible ways to enhance self-healing properties of cementitious composites under conditions of geothermal wells were identified.

Joining of aluminum sheet and glass fiber reinforced polymer using extruded pins

NASA Astrophysics Data System (ADS)

Conte, Romina; Buhl, Johannes; Ambrogio, Giuseppina; Bambach, Markus

2018-05-01

The present contribution proposes a new approach for joining sheet metal and fiber reinforced composites. The joining process draws upon a Friction Stir Forming (FSF) process, which is performed on the metal sheet to produce slender pins. These pins are used to pierce through the composite. Joining is complete by forming a locking head out of the part if the pin sticks out of the composite. Pins of different diameters and lengths were produced from EN AW-1050 material, which were joined to glass fiber reinforced polyamide-6. The strength of the joint has been experimentally tested in order to understand the effect of the process temperature on the pins strength and therefore on the joining. The results demonstrate the feasibility of this new technique, which uses no excess material.

Thermoplastic Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge

NASA Technical Reports Server (NTRS)

Roberts, Scott N. (Inventor); Schramm, Joseph P. (Inventor); Hofmann, Douglas C. (Inventor); Johnson, William L. (Inventor); Kozachkov, Henry (Inventor); Demetriou, Marios D. (Inventor)

2015-01-01

Systems and methods for joining BMG Composites are disclosed. Specifically, the joining of BMG Composites is implemented so as to preserve the amorphicity of their matrix phase and the microstructure of their particulate phase. Implementation of the joining method with respect to the construction of modular cellular structures that comprise BMG Composites is also discussed.

Technological Advances in Joining

DTIC Science & Technology

1981-08-01

automotive industry, and similar robots are being equipped to perform many arc welding functions in areas where high production rates must be...nonvacuum electron-beam welding favor the use of this process by the automotive industry. For example, this process has been used to join the component...metal additions were not needed. This process has been also used to weld various assemblies for automotive transmissions (e.g., annulus gear assemblies

Joining of parts via magnetic heating of metal aluminum powders

DOEpatents

Baker, Ian

2013-05-21

A method of joining at least two parts includes steps of dispersing a joining material comprising a multi-phase magnetic metal-aluminum powder at an interface between the at least two parts to be joined and applying an alternating magnetic field (AMF). The AMF has a magnetic field strength and frequency suitable for inducing magnetic hysteresis losses in the metal-aluminum powder and is applied for a period that raises temperature of the metal-aluminum powder to an exothermic transformation temperature. At the exothermic transformation temperature, the metal-aluminum powder melts and resolidifies as a metal aluminide solid having a non-magnetic configuration.

Astronaut Sullivan prepares to join crew in training

NASA Image and Video Library

1984-09-04

41D-3188 (2 September 1984) --- Astronaut Kathryn D. Sullivan, 41-G mission specialist, joins with other members of the seven-person crew prior to a training session in the Shuttle mockup and integration laboratory at the Johnson Space Center. Dr. Sullivan will be the first American woman to perform an extravehicular activity (EVA) in space when she joins Astronaut David C. Leestma for some outside-the-Challenger duty on October 9. The mission is scheduled for an October 5, 1984 launch.

Structural optimization for joined-wing synthesis

NASA Technical Reports Server (NTRS)

Gallman, John W.; Kroo, Ilan M.

1992-01-01

The differences between fully stressed and minimum-weight joined-wing structures are identified, and these differences are quantified in terms of weight, stress, and direct operating cost. A numerical optimization method and a fully stressed design method are used to design joined-wing structures. Both methods determine the sizes of 204 structural members, satisfying 1020 stress constraints and five buckling constraints. Monotonic splines are shown to be a very effective way of linking spanwise distributions of material to a few design variables. Both linear and nonlinear analyses are employed to formulate the buckling constraints. With a constraint on buckling, the fully stressed design is shown to be very similar to the minimum-weight structure. It is suggested that a fully stressed design method based on nonlinear analysis is adequate for an aircraft optimization study.

21 CFR 182.1711 - Silica aerogel.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered...

21 CFR 582.1711 - Silica aerogel.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives § 582.1711 Silica aerogel. (a) Product. Silica...

21 CFR 582.1711 - Silica aerogel.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives § 582.1711 Silica aerogel. (a) Product. Silica...

21 CFR 582.1711 - Silica aerogel.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives § 582.1711 Silica aerogel. (a) Product. Silica...

21 CFR 582.1711 - Silica aerogel.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives § 582.1711 Silica aerogel. (a) Product. Silica...

21 CFR 582.1711 - Silica aerogel.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE General Purpose Food Additives § 582.1711 Silica aerogel. (a) Product. Silica...

Agmatine attenuates silica-induced pulmonary fibrosis.

PubMed

El-Agamy, D S; Sharawy, M H; Ammar, E M

2014-06-01

There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p < 0.001) and reduced glutathione (p < 0.05) activities with significant decrease in the lung malondialdehyde (p < 0.001) content as compared to the silica group. Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects. © The Author(s) 2014.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium pantothenate, calcium chloride double salt... FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

Injectable TEMPO-oxidized nanofibrillated cellulose/biphasic calcium phosphate hydrogel for bone regeneration.

PubMed

Safwat, Engie; Hassan, Mohammad L; Saniour, Sayed; Zaki, Dalia Yehia; Eldeftar, Mervat; Saba, Dalia; Zazou, Mohamed

2018-05-01

Nanofibrillated cellulose, obtained from rice straw agricultural wastes was used as a substrate for the preparation of a new injectable and mineralized hydrogel for bone regeneration. Tetramethyl pyridine oxyl (TEMPO) oxidized nanofibrillated cellulose, was mineralized through the incorporation of a prepared and characterized biphasic calcium phosphate at a fixed ratio of 50 wt%. The TEMPO-oxidized rice straw nanofibrillated cellulose was characterized using transmission electron microscopy, Fourier transform infrared, and carboxylic content determination. The injectability and viscosity of the prepared hydrogel were evaluated using universal testing machine and rheometer testing, respectively. Cytotoxicity and alkaline phosphatase level tests on osteoblast like-cells for in vitro assessment of the biocompatibility were investigated. Results revealed that the isolated rice straw nanofibrillated cellulose is a nanocomposite of the cellulose nanofibers and silica nanoparticles. Rheological properties of the tested materials are suitable for use as injectable material and of nontoxic effect on osteoblast-like cells, as revealed by the positive alkaline phosphate assay. However, nanofibrillated cellulose/ biphasic calcium phosphate hydrogel showed higher cytotoxicity and lower bioactivity test results when compared to that of nanofibrillated cellulose.

Crystalline Silica Primer

USGS Publications Warehouse

,

1992-01-01

substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izvekov, Sergei, E-mail: sergiy.izvyekov.civ@mail.mil; Rice, Betsy M.

2015-12-28

A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching ofmore » the interactions from ab initio MD simulations of liquid silica. The derived shape of the O–Si–O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O–O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O–O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.« less

Permanent wire splicing by an explosive joining process

NASA Technical Reports Server (NTRS)

Bement, Laurence J. (Inventor); Kushnick, Anne C. (Inventor)

1991-01-01

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebent, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires, and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and collision bonding results in electron sharing linkups.

Toroid Joining Gun For Fittings And Couplings

NASA Technical Reports Server (NTRS)

Fox, Robert L.; Swaim, Robert J.; Johnson, Samuel D.; Buckley, John D.; Copeland, Carl E.; Coultrip, Robert H.; Johnston, David F.; Phillips, William M.

1992-01-01

Hand-held gun used to join metal heat-to-shrink couplings. Uses magnetic induction (eddy currents) to produce heat in metal coupling, and thermocouple to measure temperature and signals end of process. Gun, called "toroid joining gun" concentrates high levels of heat in localized areas. Reconfigured for use on metal heat-to-shrink fitting and coupling applications. Provides rapid heating, operates on low power, lightweight and portable. Safe for use around aircraft fuel and has no detrimental effects on surrounding surfaces or objects. Reliable in any environment and under all weather conditions. Gun logical device for taking full advantage of capabilities of new metal heat-to-shrink couplings and fittings.

Production of silver-silica core-shell nanocomposites using ultra-short pulsed laser ablation in nanoporous aqueous silica colloidal solutions

NASA Astrophysics Data System (ADS)

Santagata, A.; Guarnaccio, A.; Pietrangeli, D.; Szegedi, Á.; Valyon, J.; De Stefanis, A.; De Bonis, A.; Teghil, R.; Sansone, M.; Mollica, D.; Parisi, G. P.

2015-05-01

Ultra-short pulsed laser ablation of materials in liquid has been demonstrated to be a versatile technique for nanoparticles production. In a previous paper, it has been described, for the first time, how by laser ablation in a liquid system, silver nanoparticles can be loaded onto SBA-15 and MCM-41 supports which show promising catalytic properties for the oxidation of Volatile Organic Compounds (VOCs). The aim of the present research is to demonstrate the formation of stable silver-silica core-shell nanoparticles by direct laser ablation (Ti:Sa; 800 nm pulse duration: 120 fs repetition rate: 1 kHz, pulse energy: 3.6 mJ, fluence: 9 J cm  -  2) of a Ag target submerged in a static colloidal solution of MCM-41 or SBA-15 silica nanoporous materials. In previous studies, it was discovered that a side and negligible product of the laser ablation process of silver performed in water-silica systems, could be related to the formation of silver-silica core-shell nanoparticles. In order to emphasize this side process some modifications to the laser ablation experimental set-up were performed. Among these, the most important one, in order to favor the production of the core-shell systems, was to keep the liquid silica suspension firm. The laser generated nanomaterials were then analyzed using TEM morphologic characterization. By UV-vis absorption spectra the observed features have been related to components of the colloidal solution as well as to the number of the incident laser pulses. In this manner characterizations on both the process and the resulting suspension have been performed. Significant amount of small sized silver-silica core-shell nanoparticles have been detected in the studied systems. The size distribution, polydispersivity, UV-vis plasmonic bands and stability of the produced silver-silica core-shell nanocomposites have been related to the extent of damage induced in the nanoporous silica structure during the ablation procedure adopted

The Flying Diamond: A joined aircraft configuration design project, volume 1

NASA Technical Reports Server (NTRS)

Ball, Chris; Czech, Joe; Lentz, Bryan; Kobashigawa, Daryl; Oishi, Curtis; Poladian, David

1988-01-01

The results of the analysis conducted on the Joined Wing Configuration study are presented. The joined wing configuration employs a conventional fuselage and incorporates two wings joined together near their tips to form a diamond shape in both plan view and front view. The arrangement of the lifting surfaces uses the rear wing as a horizontal tail and as a forward wing strut. The rear wing has its root at the tip of the vertical stabilizer and is structurally attached to the trailing edge of the forward wing. This arrangement of the two wings forms a truss structure which is inherently resistant to the aerodynamic bending loads generated during flight. This allows for a considerable reduction in the weight of the lifting surfaces. With smaller internal wing structures needed, the Joined Wing may employ thinner wings which are more suitable for supersonic and hypersonic flight, having less induced drag than conventional cantilever winged aircraft. Inherent in the Joined Wing is the capability of the generation of direct lift and side force which enhance the performance parameters.

Steps to Join Green Power Partnership

EPA Pesticide Factsheets

The U.S. EPA's Green Power Partnership is a voluntary partnership program designed to reduce the environmental impact of electricity generation by promoting renewable energy. This page details steps organizations should take to join the Partnership.

Joining of SiC parts by polishing and hipping

DOEpatents

Rossi, Guilio A.; Pelletier, Paul J.

1990-05-15

A method of joining two pre-sintered pieces of silicon carbide is disclosed. It entails polishing the surfaces to be joined to a mirror-finish, fitting the polished surfaces together to form a composite structure, and then subjecting the composite structure to hot isostatic pressing under conditions which are sufficient to form a joint which is essentially indistinguishable from the original silicon carbide pieces.

Modified silica-based heterogeneous catalysts for etherification of glycerol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gholami, Zahra, E-mail: zahra.gholami@petronas.com.my; Abdullah, Ahmad Zuhairi, E-mail: chzuhairi@usm.my; Gholami, Fatemeh, E-mail: fgholami59@gmail.com

2015-07-22

The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product.more » The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca{sub 1.6}La{sub 0.6}/MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%.« less

The Joining-Up Process: Issues in Effective Human Resource Development

ERIC Educational Resources Information Center

Frohman, Alan L.; Kotter, John P.

1975-01-01

Four specific problems associated with ineffective and expensive joining-up which are examined in the article are: (1) mismatched expectations; (2) stifling creativity and challenge; (3) lack of managerial awareness and sensitivity to joining-up issues; and (4) using inappropriate or incomplete screening criteria. Solutions are suggested; a table…

Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

NASA Astrophysics Data System (ADS)

Patel, Binay S.

Epoxies are widely used as underfill resins throughout the microelectronics industry to mechanically couple and protect various components of flip-chip assemblies. Generally rigid materials largely surround underfill resins. Improving the mechanical and thermal properties of epoxy resins to better match those of their rigid counterparts can help extend the service lifetime of flip-chip assemblies. Recently, researchers have demonstrated that silica nanoparticles are effective toughening agents for lightly-crosslinked epoxies. Improvements in the fracture toughness of silica-filled epoxy nanocomposites have primarily been attributed to two toughening mechanisms: particle debonding with subsequent void growth and matrix shear banding. Various attempts have been made to model the contribution of these toughening mechanisms to the overall fracture energy observed in silica-filled epoxy nanocomposites. However, disparities still exist between experimental and modeled fracture energy results. In this dissertation, the thermal, rheological and mechanical behavior of eight different types of silica-filled epoxy nanocomposites was investigated. Each nanocomposite consisted of up to 10 vol% of silica nanoparticles with particle sizes ranging from 20 nm to 200 nm, with a variety of surface treatments and particle structures. Fractographical analysis was conducted with new experimental approaches in order to accurately identify morphological evidence for each proposed toughening mechanism. Overall, three major insights into the fracture behavior of real world silica-filled epoxy nanocomposites were established. First, microcracking was observed as an essential toughening mechanism in silica-filled epoxy nanocomposites. Microcracking was observed on the surface and subsurface of fractured samples in each type of silica-filled epoxy nanocomposite. The additional toughening contribution of microcracking to overall fracture energy yielded excellent agreement between experimental

Silica Precipitation and Lithium Sorption

DOE Data Explorer

Jay Renew

2015-09-20

This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography.

PubMed

Rathnasekara, Renuka; El Rassi, Ziad

2017-07-28

Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF 3 .ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute' differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5'-monophosphates, and weak bases, e.g., nucleobases and nucleosides. Copyright © 2017 Elsevier B.V. All rights reserved.

Flexible Friction Stir Joining Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Zhili; Lim, Yong Chae; Mahoney, Murray

2015-07-23

Reported herein is the final report on a U.S. Department of Energy (DOE) Advanced Manufacturing Office (AMO) project with industry cost-share that was jointly carried out by Oak Ridge National Laboratory (ORNL), ExxonMobil Upstream Research Company (ExxonMobil), and MegaStir Technologies (MegaStir). The project was aimed to advance the state of the art of friction stir welding (FSW) technology, a highly energy-efficient solid-state joining process, for field deployable, on-site fabrications of large, complex and thick-sectioned structures of high-performance and high-temperature materials. The technology innovations developed herein attempted to address two fundamental shortcomings of FSW: 1) the inability for on-site welding andmore » 2) the inability to weld thick section steels, both of which have impeded widespread use of FSW in manufacturing. Through this work, major advance has been made toward transforming FSW technology from a “specialty” process to a mainstream materials joining technology to realize its pervasive energy, environmental, and economic benefits across industry.« less

Multiscale Model for the Templated Synthesis of Mesoporous Silica: The Essential Role of Silica Oligomers

DOE PAGES

Perez-Sanchez, German; Chien, Szu -Chia; Gomes, Jose R. B.; ...

2016-04-04

A detailed theoretical understanding of the synthesis mechanism of periodic mesoporous silica has not yet been achieved. We present results of a multiscale simulation strategy that, for the first time, describes the molecular-level processes behind the formation of silica/surfactant mesophases in the synthesis of templated MCM-41 materials. The parameters of a new coarse-grained explicit-solvent model for the synthesis solution are calibrated with reference to a detailed atomistic model, which itself is based on quantum mechanical calculations. This approach allows us to reach the necessary time and length scales to explicitly simulate the spontaneous formation of mesophase structures while maintaining amore » level of realism that allows for direct comparison with experimental systems. Our model shows that silica oligomers are a necessary component in the formation of hexagonal liquid crystals from low-concentration surfactant solutions. Because they are multiply charged, silica oligomers are able to bridge adjacent micelles, thus allowing them to overcome their mutual repulsion and form aggregates. This leads the system to phase separate into a dilute solution and a silica/surfactant-rich mesophase, which leads to MCM-41 formation. Before extensive silica condensation takes place, the mesophase structure can be controlled by manipulation of the synthesis conditions. Our modeling results are in close agreement with experimental observations and strongly support a cooperative mechanism for synthesis of this class of materials. Furthermore, this work paves the way for tailored design of nanoporous materials using computational models.« less

Individual Factors Motivating People to Join Organized Violent Movements

DTIC Science & Technology

2017-06-09

INDIVIDUAL FACTORS MOTIVATING PEOPLE TO JOIN ORGANIZED VIOLENT MOVEMENTS A thesis presented to the Faculty of the U.S...2016 – JUN 2017 4. TITLE AND SUBTITLE Individual Factors Motivating People to Join Organized Violent Movements 5a. CONTRACT NUMBER 5b. GRANT...NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Command and General Staff College ATTN: ATZL-SWD-GD Fort Leavenworth, KS 66027

Nonlinear Aeroelastic Analysis of Joined-Wing Configurations

NASA Astrophysics Data System (ADS)

Cavallaro, Rauno

Aeroelastic design of joined-wing configurations is yet a relatively unexplored topic which poses several difficulties. Due to the overconstrained nature of the system combined with structural geometric nonlinearities, the behavior of Joined Wings is often counterintuitive and presents challenges not seen in standard layouts. In particular, instability observed on detailed aircraft models but never thoroughly investigated, is here studied with the aid of a theoretical/computational framework. Snap-type of instabilities are shown for both pure structural and aeroelastic cases. The concept of snap-divergence is introduced to clearly identify the true aeroelastic instability, as opposed to the usual aeroelastic divergence evaluated through eigenvalue approach. Multi-stable regions and isola-type of bifurcations are possible characterizations of the nonlinear response of Joined Wings, and may lead to branch-jumping phenomena well below nominal critical load condition. Within this picture, sensitivity to (unavoidable) manufacturing defects could have potential catastrophic effects. The phenomena studied in this work suggest that the design process for Joined Wings needs to be revisited and should focus, when instability is concerned, on nonlinear post-critical analysis since linear methods may provide wrong trend indications and also hide potentially catastrophical situations. Dynamic aeroelastic analyses are also performed. Flutter occurrence is critically analyzed with frequency and time-domain capabilities. Sensitivity to different-fidelity aeroelastic modeling (fluid-structure interface algorithm, aerodynamic solvers) is assessed showing that, for some configurations, wake modeling (rigid versus free) has a strong impact on the results. Post-flutter regimes are also explored. Limit cycle oscillations are observed, followed, in some cases, by flip bifurcations (period doubling) and loss of periodicity of the solution. Aeroelastic analyses are then carried out on a

Silica in alkaline brines

USGS Publications Warehouse

Jones, B.F.; Rettig, S.L.; Eugster, H.P.

1967-01-01

Analysis of sodium carbonate-bicarbonate brines from closed basins in volcanic terranes of Oregon and Kenya reveals silica contents of up to 2700 parts per million at pH's higher than 10. These high concentrations of SiO 2 can be attributed to reaction of waters with silicates, and subsequent evaporative concentration accompanied by a rise in pH. Supersaturation with respect to amorphous silica may occur and persist for brines that are out of contact with silicate muds and undersaturated with respect to trona; correlation of SiO2 with concentration of Na and total CO2 support this interpretation. Addition of moredilute waters to alkaline brines may lower the pH and cause inorganic precipitation of substantial amounts of silica.

Conversion of geothermal waste to commercial products including silica

DOEpatents

Premuzic, Eugene T.; Lin, Mow S.

2003-01-01

A process for the treatment of geothermal residue includes contacting the pigmented amorphous silica-containing component with a depigmenting reagent one or more times to depigment the silica and produce a mixture containing depigmented amorphous silica and depigmenting reagent containing pigment material; separating the depigmented amorphous silica and from the depigmenting reagent to yield depigmented amorphous silica. Before or after the depigmenting contacting, the geothermal residue or depigmented silica can be treated with a metal solubilizing agent to produce another mixture containing pigmented or unpigmented amorphous silica-containing component and a solubilized metal-containing component; separating these components from each other to produce an amorphous silica product substantially devoid of metals and at least partially devoid of pigment. The amorphous silica product can be neutralized and thereafter dried at a temperature from about 25.degree. C. to 300.degree. C. The morphology of the silica product can be varied through the process conditions including sequence contacting steps, pH of depigmenting reagent, neutralization and drying conditions to tailor the amorphous silica for commercial use in products including filler for paint, paper, rubber and polymers, and chromatographic material.

Robust Joining and Assembly Technologies for Ceramic Matrix Composites: Technical Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Mrityunjay, Singh; Gray, Hugh R. (Technical Monitor)

2002-01-01

Fiber reinforced ceramic matrix composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, energy, process, and nuclear industries. The engineering designs require fabrication and manufacturing of complex shaped parts. In many instances, it is more economical to build up complex shapes by Joining simple geometrical shapes. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in ceramic matrix composites will be presented. Various joint design philosophies and design issues in joining of composites will be discussed along with an affordable, robust ceramic joining technology (ARCJoinT). A wide variety of ceramic composites, in different shapes and sizes, have been joined using this technology. Microstructure and mechanical properties of joints will be reported. Current status of various ceramic joining technologies and future prospects for their applications will also be discussed.

Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

NASA Astrophysics Data System (ADS)

Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

2016-05-01

Silica/polyaniline (PANI) core-shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core-shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2015-01-01

Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.

Affordable, Robust Ceramic Joining Technology (ARCJoinT) for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

Ceramic joining is recognized as one of the enabling technologies for the successful utilization of silicon carbide-based monolithic ceramic and fiber reinforced composite components in a number of demanding and high temperature applications in aerospace and ground-based systems. An affordable, robust ceramic joining technology (ARCJoinT) for joining of silicon carbide-based ceramics and fiber reinforced composites has been developed. This technique is capable of producing joints with tailorable thickness and composition. A wide variety of silicon carbide-based ceramics and composites, in different shapes and sizes, have been joined using this technique. The room and high temperature mechanical properties and fractography of ceramic joints have been reported. In monolithic silicon carbide ceramics, these joints maintain their mechanical strength up to 1350 C in air. There is no change in the mechanical strength of joints in silicon carbide matrix composites up to 1200 C in air. In composites, simple butt joints yield only about 20% of the ultimate strength of the parent materials. This technology is suitable for the joining of large and complex shaped ceramic and composite components, and with certain modifications, can be applied to repair of ceramic components damaged in service.

High-T sub c thin films on low microwave loss alkaline-rare-earth-aluminate crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolewski, R.; Gierlowski, P.; Kula, W.

1991-03-01

This paper reports on the alkaline-rare-earth aluminates (K{sub 2}NiF{sub 4}-type perovskites) which are an excellent choice as the substrate material for the growth of high-T{sub c} thin films suitable for microwave and far-infrared applications. The CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals have been grown by Czochralski pulling and fabricated into the form of (001) oriented wafers. The Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O films deposited on these substrates by a single-target magnetron sputtering exhibited very good superconducting and structural properties.

Process optimization of joining by upset bulging with local heating

NASA Astrophysics Data System (ADS)

Rusch, Michael; Almohallami, Amer; Sviridov, Alexander; Bonk, Christian; Behrens, Bernd-Arno; Bambach, Markus

2017-10-01

Joining by upset bulging is a mechanical joining method where axial load is applied to a tube to form two revolving bulges, which clamp the parts to be joined and create a force and form fit. It can be used to join tubes with other structures such as sheets, plates, tubes or profiles of the same or different materials. Other processes such as welding are often limited in joining multi-material assemblies or high-strength materials. With joining by upset bulging at room temperature, the main drawback is the possible initiation of damage (cracks) in the inner buckling zone because of high local stresses and strains. In this paper, a method to avoid the formation of cracks is introduced. Before forming the bulge the tube is locally heated by an induction coil. For the construction steel (E235+N) a maximum temperature of 700 °C was used to avoid phase transformation. For the numerical study of the process the mechanical properties of the tube material were examined at different temperatures and strain rates to determine its flow curves. A parametrical FE model was developed to simulate the bulging process with local heating. Experiments with local heating were executed and metallographic studies of the bulging area were conducted. While specimens heated to 500 °C showed small cracks left, damage-free flanges could be created at 600 and 700 °C. Static testing of damage-free bulges showed improvements in tensile strength and torsion strength compared to bulges formed at room-temperature, while bending and compression behavior remained nearly unchanged. In cyclic testing the locally heated specimens underwent about 3.7 times as many cycles before failure as the specimens formed at room temperature.

Calcium deprivation increases the palatability of calcium solutions in rats.

PubMed

McCaughey, Stuart A; Forestell, Catherine A; Tordoff, Michael G

2005-02-15

Calcium-deprived rats have elevated intakes of CaCl2, other calcium salts, and some non-calcium compounds. We used taste reactivity to examine the effects of calcium deprivation on the palatability of CaCl2 and other solutions. Nine male Sprague-Dawley rats were calcium-deprived by maintenance on a low-calcium diet, and eight replete rats were used as controls. All rats were videotaped during intraoral infusion of the following solutions: 30 and 300 mM CaCl2, 30 mM calcium lactate, 100 and 600 mM NaCl, 30 mM MgCl2, 1 mM quinine.HCl, 2.5 mM sodium saccharin, and deionized water. We counted individual orofacial and somatic movements elicited by the infusions and used them to calculate total ingestive and aversive scores. Relative to controls, calcium-deprived rats gave a significantly larger number of tongue protrusions and had higher total ingestive scores for CaCl2, calcium lactate, NaCl, and MgCl2. Our results suggest that CaCl2, calcium lactate, NaCl, and MgCl2 taste more palatable to rats when they are calcium-deprived than replete, and this may be responsible for the increased intake of these solutions following calcium deprivation.

Size effect of optical silica microsphere pressure sensors

NASA Astrophysics Data System (ADS)

Jiao, Xinbing; Hao, Ruirui; Pan, Qian; Zhao, Xinwei; Bai, Xue

2018-07-01

Two types of optical pressure sensors with silica microspheres are proposed. The size effect of optical silica microsphere pressure sensors is studied by using a single-wavelength laser beam and polarimeters. The silica microspheres with diameters of 1.0 μm, 1.5 μm and 2.0 μm are prepared on garnet substrates by a self-assembly method. The pressure and the optical properties of the silica microspheres are measured by a resistance strain sensor and Thorlabs Stokes polarimeters as a function of the external direct current (DC) voltage. The optical silica microsphere sensor in transmission mode is suitable for pressure measuring. The results show that the pressure increases, while the diameter of the silica microspheres decreases. The maximum internal pressure can reach up to 7.3 × 107 Pa when the diameter of the silica microspheres is 1.0 μm.

Parametric weight evaluation of joined wings by structural optimization

NASA Technical Reports Server (NTRS)

Miura, Hirokazu; Shyu, Albert T.; Wolkovitch, Julian

1988-01-01

Joined-wing aircraft employ tandem wings having positive and negative sweep and dihedral, arranged to form diamond shapes in both plan and front views. An optimization method was applied to study the effects of joined-wing geometry parameters on structural weight. The lightest wings were obtained by increasing dihedral and taper ratio, decreasing sweep and span, increasing fraction of airfoil chord occupied by structural box, and locating the joint inboard of the front wing tip.

Grazers: biocatalysts of terrestrial silica cycling

PubMed Central

Vandevenne, Floor Ina; Barão, Ana Lúcia; Schoelynck, Jonas; Smis, Adriaan; Ryken, Nick; Van Damme, Stefan; Meire, Patrick; Struyf, Eric

2013-01-01

Silica is well known for its role as inducible defence mechanism countering herbivore attack, mainly through precipitation of opaline, biogenic silica (BSi) bodies (phytoliths) in plant epidermal tissues. Even though grazing strongly interacts with other element cycles, its impact on terrestrial silica cycling has never been thoroughly considered. Here, BSi content of ingested grass, hay and faeces of large herbivores was quantified by performing multiple chemical extraction procedures for BSi, allowing the assessment of chemical reactivity. Dissolution experiments with grass and faeces were carried out to measure direct availability of BSi for dissolution. Average BSi and readily soluble silica numbers were higher in faeces as compared with grass or hay, and differences between herbivores could be related to distinct digestive strategies. Reactivity and dissolvability of BSi increases after digestion, mainly due to degradation of organic matrices, resulting in higher silica turnover rates and mobilization potential from terrestrial to aquatic ecosystems in non-grazed versus grazed pasture systems (2 versus 20 kg Si ha−1 y−1). Our results suggest a crucial yet currently unexplored role of herbivores in determining silica export from land to ocean, where its availability is linked to eutrophication events and carbon sequestration through C–Si diatom interactions. PMID:24107532

Ultrasound assisted deposition of silica coatings on titanium

NASA Astrophysics Data System (ADS)

Kaş, Recep; Ertaş, Fatma Sinem; Birer, Özgür

2012-10-01

We present a novel ultrasound assisted method for silica coating of titanium surfaces. The coatings are formed by “smashing” silica nanoparticles onto activated titanium surface in solution using intense ultrasonic field. Homogeneous silica coatings are formed by deposition of dense multiple layers of silica nanoparticles. Since the nanoparticles also grow during the reaction, the layers of the coatings have smaller particles on the substrate and larger particles towards the surface. The thickness of the coatings can be controlled with several experimental parameters. Silica layers with thickness over 200 nm are readily obtained.

Altering the concentration of silica tunes the functional properties of collagen-silica composite scaffolds to suit various clinical requirements.

PubMed

Perumal, Sathiamurthi; Ramadass, Satiesh Kumar; Gopinath, Arun; Madhan, Balaraman; Shanmugam, Ganesh; Rajadas, Jayakumar; Mandal, Asit Baran

2015-12-01

The success of a tissue engineering scaffold depends on a fine balance being achieved between the physicochemical and biological properties. This study attempts to understand the influence of silica concentration on the functional properties of collagen-silica (CS) composite scaffolds for soft tissue engineering applications. Increasing the ratio of silica to collagen (0.25, 0.5, 0.75, 1.0, 1.25, 1.5 and 2.0 w/w) gave a marked advantage in terms of improving the water uptake and compressive modulus of the CS scaffolds, while also enhancing the biological stability and the turnover time. With increase in silica concentration the water uptake and compressive modulus increased concurrently, whereas it was not so for surface porous architecture and biocompatibility which are crucial for cell adhesion and infiltration. Silica:collagen ratio of ≤1 exhibits favourable surface biocompatibility, and any further increase in silica concentration has a detrimental effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rhenium Mechanical Properties and Joining Technology

NASA Technical Reports Server (NTRS)

Reed, Brian D.; Biaglow, James A.

1996-01-01

Iridium-coated rhenium (Ir/Re) provides thermal margin for high performance and long life radiation cooled rockets. Two issues that have arisen in the development of flight Ir/Re engines are the sparsity of rhenium (Re) mechanical property data (particularly at high temperatures) required for engineering design, and the inability to directly electron beam weld Re chambers to C103 nozzle skirts. To address these issues, a Re mechanical property database is being established and techniques for creating Re/C103 transition joints are being investigated. This paper discusses the tensile testing results of powder metallurgy Re samples at temperatures from 1370 to 2090 C. Also discussed is the evaluation of Re/C103 transition pieces joined by both, explosive and diffusion bonding. Finally, the evaluation of full size Re transition pieces, joined by inertia welding, as well as explosive and diffusion bonding, is detailed.

Calcium ionization balance and argon/calcium abundance in solar flares

NASA Astrophysics Data System (ADS)

Antonucci, E.; Marocchi, D.; Gabriel, A. H.; Doschek, G. A.

1987-12-01

An earlier analysis of solar flare calcium spectra from XRP and P78-1 aimed at measuring the calcium ionization balance resulted in an ambiguity due to a line blend between the calcium q line and an Ar XVII line. In the present work the calcium line 'r' is included in the analysis in order to resolve this problem. It is shown that the correct calcium ionization balance is that indicated in the earlier paper as corresponding to an argon/calcium abundance ratio of 0.2. The argon/calcium abundance ratio in the group of solar flares studied is shown to be 0.2 + or - 0.2. It is further argued that while the abundance of heavy elements may be enhanced in energetic flare events, this enhancement is less for argon than for calcium, leading to an argon/calcium ratio smaller than that present in the quiet sun.

[Amorphous silica. Types, health effects of exposure, NDS].

PubMed

Woźniak, H; Wiecek, E

1995-01-01

Maximum allowable concentration (MAC) values for amorphous silica dust have not been identified in the Polish legal regulations up-to-date. In this work the authors review values of allowable (recommended) amorphous silica dust concentrations in other countries. Data on other types of amorphous silica (natural and synthetic) used in industry as well as data on health effects of exposure to these types of dust are presented. The work encompasses 42 entries in the references and one Table which includes the following proposed MAC values: Non-calcinate diatomaceous earth (diatomite) and synthetic silica: Total dust--10 mg/m3 Respirable dust--2 mg/m3 Calcinate diatomaceous earth (diatomite) and fused silica (vitreous silica): Total dust--2 mg/m3 Respirable dust--1 mg/m3.

Calcium Carbonate

MedlinePlus

... Maalox® (as a combination product containing Calcium Carbonate, Simethicone) ... Relief (as a combination product containing Calcium Carbonate, Simethicone) ... Plus (as a combination product containing Calcium Carbonate, Simethicone)

Aligned silica nanowires on the inner wall of bubble-like silica film: the growth mechanism and photoluminescence.

PubMed

Chen, Yiqing; Zhou, Qingtao; Jiang, Haifeng; Su, Yong; Xiao, Haihua; Zhu, Li-Ang; Xu, Liang

2006-02-28

Large area, aligned amorphous silica nanowires grow on the inner wall of bubble-like silica film, which is prepared by thermal evaporation of a molten gallium-silicon alloy in a flow of ammonia. These nanowires are 10-20 nm in diameter and 0.5-1.5 µm in length. The bubble-like silica film functions as a substrate, guiding the growth of silica nanowires by a vapour-solid process. This work helps us to clearly elucidate the growth mechanism of aligned amorphous silica nanowires, ruling out the possibility of liquid gallium acting as a nucleation substrate for the growth of the aligned silica nanowires. A broad emission band from 290 to 600 nm is observed in the photoluminescence (PL) spectrum of these nanowires. There are seven PL peaks: two blue emission peaks at 430 nm (2.88 eV) and 475 nm (2.61 eV); and five ultraviolet emission peaks at 325 nm (3.82 eV), 350 nm (3.54 eV), 365 nm (3.40 eV), 385 nm (3.22 eV) and 390 nm (3.18 eV), which may be related to various oxygen defects.

Friction stir lap joining of automotive aluminium alloy and carbon-fiber-reinforced plastic

NASA Astrophysics Data System (ADS)

Bang, H. S.; Das, A.; Lee, S.; Bang, H. S.

2018-05-01

Multi-material combination such as aluminium alloys and carbon-fiber-reinforced plastics (CFRP) are increasingly used in the aircraft and automobile industries to enhance strength-to-weight ratio of the respective parts and components. Various processes such as adhesive bonding, mechanical fasteners and laser beam joining were employed to join metal alloy and CFRP sheets. However, long processing time of adhesive bonding, extra weight induced by mechanical fasteners and high operating cost of the laser is major limitations of these processes. Therefore, friction stir welding is an alternative choice to overcome those limitations in joining of CFRP and aluminium alloys. In the present work, an attempt is undertaken to join AA5052 alloy and polyamide 66 CFRP sheets by friction stir lap joining technique using pinned and pin-less tools. The joint qualities are investigated extensively at different joining conditions using two different types of tools and surface ground aluminium sheets. The results show that pin-less tool and surface ground aluminium alloy can provide the suitable joint with maximum joint strength around 8 MPa.

Risk of calcium oxalate nephrolithiasis in postmenopausal women supplemented with calcium or combined calcium and estrogen.

PubMed

Domrongkitchaiporn, Somnuek; Ongphiphadhanakul, Boonsong; Stitchantrakul, Wasana; Chansirikarn, Sirinthorn; Puavilai, Gobchai; Rajatanavin, Rajata

2002-02-26

Recent studies showed that postmenopausal women lost less bone mass when supplemented with calcium or estrogen therapy. However, the safety of the treatments in terms of the risk of calcium oxalate stone formation is unknown. We therefore conducted this study to determine the alteration in calcium oxalate supersaturation after calcium supplement or after combined calcium and estrogen therapy in postmenopausal osteoporotic women. Fifty-six postmenopausal women were enrolled in this study. All subjects were more than 10 years postmenopausal with vertebral or femoral osteoporosis by bone mineral density criteria. They were randomly allocated to receive either 625 mg of calcium carbonate (250 mg of elemental calcium) at the end of a meal three times a day (group A, n=26) or calcium carbonate in the same manner plus 0.625 mg/day of conjugated equine estrogen and 5 mg medrogestone acetate from day 1-12 each month (group B, n=30). The age (mean +/- S.E.M.) was 66.3 +/- 1.2 and 65.1 +/- 1.1 years, weight 54.1 +/- 1.2 and 55.3 +/- 2.1 kg, in group A and group B, respectively. Urine specimens (24-h) were collected at baseline and 3 months after treatment for the determination of calcium oxalate saturation by using Tiselius's index (AP(CaOx)) and calcium/citrate ratio. After 3 months of treatment, there was no significant alteration from baseline for urinary excretion of calcium, citrate and oxalate. Urinary phosphate excretion was significantly reduced (6.3 +/- 0.7 vs. 5.1 +/- 0.7 mmol/day for group A and 8.2 +/- 0.9 vs. 5.8 +/- 0.7 mmol/day for group B, P<0.05), whereas net alkaline absorption was significantly elevated (10.1 +/- 3.6 vs. 20.1 +/- 4.4 meq/day for group A and 4.8 +/- 3.2 vs. 19.9 +/- 3.6 meq/day for group B, P<0.05). Calcium/citrate ratio and AP(CaOx) determined at baseline were not different from the corresponding values after treatment in both groups; calcium/citrate: 10.1 +/- 3.1 vs. 10.1 +/- 2.5 for group A and 9.3 +/- 1.8 vs. 11.9 +/- 2.5 for group B and

Health hazards due to the inhalation of amorphous silica.

PubMed

Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

2002-01-01

Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study

Characterization of silica particles modified with γ-methacryloxypropyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Jiang, Jun; Wang, Wang; Shen, Haiying; Wang, Jiamin; Cao, Jinzhen

2017-03-01

The surface of hydrophilic silica particles was modified with different concentrations (2, 4, 6, 8 and 10%) of γ-methacryloxypropyltrimethoxysilane (MPTS). The hydrophobicity and hygroscopicity of unmodified and modified silica were investigated through water contact angle (WCA) tests and dynamic vapor sorption (DVS) method, respectively. The results showed that the surface properties of silica were closely related with the MPTS concentration. Within the range of MPTS concentration applied, 8% MPTS modified silica showed the least aggregation. With the increasing MPTS concentration, the WCAs on modified silica film increased correspondingly, and finally exceeded 90° at 6% and 8% concentrations. The equilibrium moisture contents (EMCs) of modified silica also decreased with the increasing MPTS concentration. The improvement on hydrophobicity can be correlated with the reduction of residual hydroxyl groups (-OH) on modified silica. The self-condensation of MPTS began to occur at concentrations higher than 4%, especially at 8%. Owing to this effect, the modified silica with 8% MPTS showed a slightly higher EMC than 6% MPTS within low relative humidity (RH) range up to 40%. At a higher RH ranging from 40 to 90%, 8% group showed the lowest EMCs because of its highest hydrophobicity and low specific surface area. A mechanism concerning the MPTS modification of silica was also proposed in this study based on the research results.

Silica-Rich Soil Found by Spirit

NASA Technical Reports Server (NTRS)

2007-01-01

NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.

The silica-rich patch, informally named 'Gertrude Weise' after a player in the All-American Girls Professional Baseball League, was exposed when Spirit drove over it during the 1,150th Martian day, or sol, of Spirit's Mars surface mission (March 29, 2007). One of Spirit's six wheels no longer rotates, so it leaves a deep track as it drags through soil. Most patches of disturbed, bright soil that Spirit had investigated previously are rich in sulfur, but this one has very little sulfur and is about 90 percent silica.

This image is a approximately true-color composite of three images taken through different filters by Spirit's panoramic camera on Sol 1,187 (May 6). The track of disturbed soil is roughly 20 centimeters (8 inches) wide.

Spirit's miniature thermal emission spectrometer, which can assess a target's mineral composition from a distance, examined the Gertrude Weise patch on Sol 1,172 (April 20). The indications it found for silica in the overturned soil prompted a decision to drive Spirit close enough to touch the soil with the alpha particle X-ray spectrometer, a chemical analyzer at the end of Spirit's robotic arm. The alpha particle X-ray spectrometer collected data about this target on sols 1,189 and 1,190 (May 8 and May 9) and produced the finding of approximately 90 percent silica.

Silica is silicon dioxide. On Earth, it commonly occurs as the crystalline mineral quartz and is the main ingredient in window glass. The Martian silica at Gertrude Weise is non-crystalline, with no detectable quartz.

In most cases, water is required to produce such a concentrated deposit of silica, according to members of the rover science team. One possible origin for the silica could have been interaction of soil with acidic steam produced by volcanic activity. Another could

Silica-Rich Soil in Gusev Crater

NASA Technical Reports Server (NTRS)

2007-01-01

NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.

The silica-rich patch, informally named 'Gertrude Weise' after a player in the All-American Girls Professional Baseball League, was exposed when Spirit drove over it during the 1,150th Martian day, or sol, of Spirit's Mars surface mission (March 29, 2007). One of Spirit's six wheels no longer rotates, so it leaves a deep track as it drags through soil. Most patches of disturbed, bright soil that Spirit had investigated previously are rich in sulfur, but this one has very little sulfur and is about 90 percent silica.

Spirit's panoramic camera imaged the bright patch through various filters on Sol 1,158 (April 6). This approximately true-color image combines images taken through three different filters. The track of disturbed soil is roughly 20 centimeters (8 inches) wide.

Spirit's miniature thermal emission spectrometer, which can assess a target's mineral composition from a distance, examined the Gertrude Weise patch on Sol 1,172 (April 20). The indications it found for silica in the overturned soil prompted a decision to drive Spirit close enough to touch the soil with the alpha particle X-ray spectrometer, a chemical analyzer at the end of Spirit's robotic arm. The alpha particle X-ray spectrometer collected data about this target on sols 1,189 and 1,190 (May 8 and May 9) and produced the finding of approximately 90 percent silica.

Silica is silicon dioxide. On Earth, it commonly occurs as the crystalline mineral quartz and is the main ingredient in window glass. The Martian silica at Gertrude Weise is non-crystalline, with no detectable quartz.

In most cases, water is required to produce such a concentrated deposit of silica, according to members of the rover science team. One possible origin for the silica could have been interaction of soil with acidic steam

Grassy Silica Nanoribbons and Strong Blue Luminescence

NASA Astrophysics Data System (ADS)

Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

2016-09-01

Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT WITH SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

Synthesis of zinc aluminate with high surface area by microwave hydrothermal method applied in the transesterification of soybean oil (biodiesel)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quirino, M.R.; Oliveira, M.J.C.; Keyson, D.

Highlights: • ZnAl{sub 2}O{sub 4} spinel was synthesized by the microwave hydrothermal method in only 15 or 30 min. • The powders show high specific surface area. • ZAT{sub b}15 showed activity of 52.22% for the conversion of soybean oil into biodiesel. - Abstract: Zinc aluminate is a material with high thermal stability and high mechanical strength that, owing to these properties, is used as a catalyst or support. In this work, zinc aluminate spinel was synthesized by the microwave hydrothermal method in only 15 or 30 min at a low temperature (150 °C) without templates, using only Al(NO{sub 3}){submore » 3}·9H{sub 2}O, Zn(NO{sub 3}){sub 2}·6H{sub 2}O, and urea as precursors and applied in the transesterification of soybean oil. X-ray diffraction analysis showed that ZnAl{sub 2}O{sub 4} had a cubic structure without secondary phases. The nitrogen adsorption measurements (BET) revealed a high surface area (266.57 m{sup 2} g{sup −1}) for the nanopowder synthesized in 15 min. This powder showed activity of 52.22% for the catalytic conversion of soybean oil into biodiesel by transesterification.« less

Studies on densification, mechanical, micro-structural and structure–properties relationship of magnesium aluminate spinel refractory aggregates prepared from Indian magnesite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Chandrima; Ghosh, Arup; Haldar, Manas Kamal, E-mail: manashaldar@cgcri.res.in

The present work intends to study the development of magnesium aluminate spinel aggregates from Indian magnesite in a single firing stage. The raw magnesite has been evaluated in terms of chemical analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. The experimental batch containing Indian magnesite and calcined alumina has been sintered in the temperature range of 1550 °C–1700 °C. The sintered material has been characterized in terms of physico-chemical properties like bulk density, apparent porosity, true density, relative density and thermo-mechanical/mechanical properties like hot modulus of rupture, thermal shock resistance, cold modulus of rupture and structural propertiesmore » by X-ray diffraction in terms of phase identification and evaluation of crystal structure parameters of corresponding phases by Rietveld analysis. The microstructures developed at different temperatures have been analyzed by field emission scanning electron microscope study and compositional analysis of the developed phase has been carried out by energy dispersive X-ray study. - Highlights: • The studies have been done to characterize the developed magnesium aluminate spinel. • The studies reveal correlation between refractory behavior of spinel and developed microstructures. • The studies show the values of lattice parameters of developed phases.« less

All-round joining method with carbon fiber reinforced interface

NASA Astrophysics Data System (ADS)

Miwa, Noriyoshi; Tanaka, Kazunori; Kamiya, Yoshiko; Nishi, Yoshitake

2008-08-01

Carbon fiber reinforced polymer (CFRP) has been recently applied to not only wing, but also fan blades of turbo fan engines. To prevent impact force, leading edge of titanium was often mounted on the CFRP fan blades with adhesive force. In order to enhance the joining strength, a joining method with carbon fiber reinforced interface has been developed. By using nickel-coated carbon fibers, a joining sample with carbon fiber-reinforced interface between CFRP and CFRM has been successfully developed. The joining sample with nickel-coated carbon fiber interface exhibits the high tensile strength, which was about 10 times higher than that with conventional adhesion. On the other hand, Al-welding methods to steel, Cu and Ti with carbon fiber reinforced interface have been successfully developed to lighten the parts of machines of racing car and airplane. Carbon fibers in felt are covered with metals to protect the interfacial reaction. The first step of the welding method is that the Al coated felt is contacted and wrapped with molten aluminum solidified under gravity pressure, whereas the second step is that the felt with double layer of Ni and Al is contacted and wrapped with molten steel (Cu or Ti) solidified under gravity pressure. Tensile strength of Al-Fe (Cu or Ti) welded sample with carbon fiber reinforced interface is higher than those of Al-Fe (Cu or Ti) welded sample.

Winter climate change and fine root biogenic silica in sugar maple trees (Acer saccharum): Implications for silica in the Anthropocene

NASA Astrophysics Data System (ADS)

Maguire, Timothy J.; Templer, Pamela H.; Battles, John J.; Fulweiler, Robinson W.

2017-03-01

Winter temperatures are projected to increase over the next century, leading to reductions in winter snowpack and increased frequency of soil freezing in many northern forest ecosystems. Here we examine biogenic silica (BSi) concentrations in sugar maple (Acer saccharum) fine roots collected from a snow manipulation experiment at Hubbard Brook Experimental Forest (New Hampshire, USA). Increased soil freezing significantly lowered the BSi content of sugar maple fine roots potentially decreasing their capacity to take up water and dissolved nutrients. The reduced silica uptake (8 ± 1 kmol silica km-2) by sugar maple fine roots is comparable to silica export from temperate forest watersheds. We estimate that fine roots account for 29% of sugar maple BSi, despite accounting for only 4% of their biomass. These results suggest that increased frequency of soil freezing will reduce silica uptake by temperate tree roots, thereby changing silica availability in downstream receiving waters.

Production and Application of Olivine Nano-Silica in Concrete

NASA Astrophysics Data System (ADS)

Mardiana, Oesman; Haryadi

2017-05-01

The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

Effects of sandblasting and silica-coating procedures on pure titanium.

PubMed

Kern, M; Thompson, V P

1994-10-01

Silica coating titanium improves chemomechanical bonding. Sandblasting is recommended as a pretreatment to thermal silica coating (Silicoater MD) or as part of a tribochemical silica coating process (Rocatec). This study evaluated the effects of sandblasting and coating techniques on volume loss, surface morphology and composition changes in pure titanium. Volume loss of titanium was similar to values reported for base alloys and does not seem to be critical for the clinical fit of restorations. Embedded alumina particles were found in the titanium after sandblasting and the alumina content increased to a range of 27.5-39.3 wt% as measured by EDS. Following tribochemical silica coating, a layer of small silica particles remained on the surface, increasing the silica content to a range of 17.9-19.5 wt%. Ultrasonic cleaning removed loose alumina or silica particles from the surface, resulting in only slight decreases in alumina or silica contents, suggesting firm attachment of most of the alumina and silica to the titanium surface. Silica content following thermal silica coating treatment increased only slightly from the sandblasted specimen to 1.4 wt%. The silica layer employed by these silica coating methods differs widely in both morphology and thickness. These results provide a basis for explanation of adhesive failure modes in bond strength tests and for developing methods to optimize resin bonding. Clinically, ultrasonic cleaning of sandblasted and tribochemically silica coated titanium should improve resin bonding as loose surface particles are removed without relevant changes in composition.

Effect of the conditions of REM microalloying of steel on the corrosion activity of nonmetallic inclusions

NASA Astrophysics Data System (ADS)

Movenko, D. A.; Kotel'nikov, G. I.; Pavlov, A. V.; Bytsenko, O. A.

2015-11-01

Experimental heats of low-alloy steel are performed under various conditions of rare-earth metal microalloying and aluminum and calcium deoxidation. Electron-probe microanalysis of nonmetallic inclusions and a metallographic investigation of a metal are used to show that, when interacting with water, nonmetallic cerium oxide inclusions do not form hydrates and, correspondingly, are not aggressive. When aluminum, calcium, and cerium additions are sequentially introduced into a melt, a continuous cerium oxide shell forms on calcium aluminates, protects corrosive nonmetallic inclusions against interaction with water, and weakens local metal corrosion.

Study of photoluminescence properties of CaAl{sub 2}O{sub 4}: Eu{sup 2+} prepared by combustion synthesis method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hingwe, V. S., E-mail: vishwas.hingwe@yahoo.in; Omanwar, S. K.; Bajaj, N. S.

2016-05-06

Eu{sup 2+} doped alkaline earth metals such as strontium aluminate, calcium aluminate and barium aluminate prepared by using modified combustion synthesis method at 600°C with Urea as fuel. Crystal structure is determined by using XRD and the sample confirmation by using the FTIR. The effect of the host material on the photoluminescence (PL) and phosphorescence properties were studied by using the Hitachi F-7000 spectrofluorimeter equipped with a 450W Xenon lamp, in the range 200-650 nm. The emission spectra of Eu{sup 2+} range from 450 to 500 nm in the Blue to aqua region and the transition 4f{sup 7}-4f{sup 6} 5d{sup 1}.more » The observed emission in CaAl{sub 2}O{sub 4} is 440 nm.« less

Pumping Iron and Silica Bodybuilding

NASA Astrophysics Data System (ADS)

Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

2016-02-01

The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

Tungsten foil laminate for structural divertor applications - Joining of tungsten foils

NASA Astrophysics Data System (ADS)

Reiser, Jens; Rieth, Michael; Möslang, Anton; Dafferner, Bernhard; Hoffmann, Jan; Mrotzek, Tobias; Hoffmann, Andreas; Armstrong, D. E. J.; Yi, Xiaoou

2013-05-01

This paper is the fourth in our series on tungsten laminates. The aim of this paper is to discuss laminate synthesis, meaning the joining of tungsten foils. It is obvious that the properties of the tungsten laminate strongly depend on the combination of (i) interlayer and (ii) joining technology, as this combination defines (i) the condition of the tungsten foil after joining (as-received or recrystallised) as well as (ii) the characteristics of the interface between the tungsten foil and the interlayer (wettability or diffusion leading to a solid solution or the formation of intermetallics). From the example of tungsten laminates joined by brazing with (i) an eutectic silver copper brazing filler, (ii) copper, (iii) titanium, and (iv) zirconium, the microstructure will be discussed, with special focus on the interface. Based on our assumptions of the mechanism of the extraordinary ductility of tungsten foil we present three syntheses strategies and make recommendations for the synthesis of high temperature tungsten laminates.

Laser-induced Self-organizing Microstructures on Steel for Joining with Polymers

NASA Astrophysics Data System (ADS)

van der Straeten, Kira; Burkhardt, Irmela; Olowinsky, Alexander; Gillner, Arnold

The combination of different materials such as thermoplastic composites and metals is an important way to improve lightweight construction. As direct connections between these materials fail due to their physical and chemical properties, other joining techniques are required. A new joining approach besides fastening and adhesive joining is a laser-based two-step process. Within the first step the metal surface is modified by laser-microstructuring. In order to enlarge the boundary surface and create undercuts, random self-organizing microstructures are generated on stainless steel substrates. In a second process step both joining partners, metal and composite, are clamped together, the steel surface is heated up with laser radiation and through heat conduction the thermoplastic matrix is melted and flows into the structures. After cooling-down a firm joint between both materials is created. The presented work shows the influence of different laser parameters on the generation of the microstructures. The joint strength is investigated through tensile shear strength tests.

Reinforced silver-embedded silica matrix from the cheap silica source for the controlled release of silver ions

NASA Astrophysics Data System (ADS)

Hilonga, A.; Kim, J. K.; Sarawade, P. B.; Kim, H. T.

2009-07-01

In this study, a reinforced silver-embedded silica matrix was designed by utilizing the interaction between the [AlO 4] - tetrahedral and the Ag + in sol-gel process using sodium silicate as a silica precursor. The Ag + mole ratio in each sample was significantly varied to examine the influence of silver concentration on the properties of the final product. Aluminium ions were added to reinforce and improve the chemical durability of silver-embedded silica. A templated sample at Al/Ag = 1 atomic ratio was also synthesized to attempt a possibility of controlling porosity of the final product. Also, a sample neither embedded with silver nor templated was synthesized and characterized to serve as reference. The material at Al/Ag = 1 was found to have a desirable properties, compared to its counterparts, before and even after calcination up to 1000 °C. The results demonstrate that materials with desirable properties can be obtained by this unprecedented method while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2010 CFR

2010-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2012 CFR

2012-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2013 CFR

2013-04-01

... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may...

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT OF CENTER WITH TOP OF SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

Infrared transient-liquid-phase joining of SCS-6/ β21S titanium matrix composite

NASA Astrophysics Data System (ADS)

Blue, Craig A.; Sikka, Vinod K.; Blue, Randall A.; Lin, Ray Y.

1996-12-01

Fiber-reinforced titanium matrix composites (TMCs) are among the advanced materials being considered for use in the aerospace industry due to their light weight, high strength, and high modulus. A rapid infrared joining process has been developed for the joining of composites and advanced materials. Rapid infrared joining has been shown not to have many of the problems associated with conventional joining methods. Two models were utilized to predict the joint evolution and fiber reaction zone growth. Titanium matrix composite, 16-ply SCS-6/ β21S, has been successfully joined with total processing times of approximately 2 minutes, utilizing the rapid infrared joining technique. The process utilizes a 50 °C/s ramping rate, 17- µm Ti-15Cu-15Ni wt pct filler material between the faying surfaces; a joining temperature of 1100 °C; and 120 seconds of time to join the composite material. Joint shear-strength testing of the rapid infrared joints at temperatures as high as 800 °C has revealed no joint failures. Also, due to the rapid cooling of the process, no poststabilization of the matrix material is necessary to prevent the formation of a brittle omega phase during subsequent use of the TMC at intermediate temperatures, 270 °C to 430 °C, for up to 20 hours.

Asymmetric orientation of toluene molecules at oil-silica interfaces

NASA Astrophysics Data System (ADS)

Ledyastuti, Mia; Liang, Yunfeng; Kunieda, Makoto; Matsuoka, Toshifumi

2012-08-01

The interfacial structure of heptane and toluene at oil-silica interfaces has previously been studied by sum frequency generation [Z. Yang et al., J. Phys. Chem. C. 113, 20355 (2009)], 10.1021/jp9043122. It was found that the toluene molecule is almost perpendicular to the silica surface with a tilt angle of about 25°. Here, we have investigated the structural properties of toluene and heptane at oil-silica interfaces using molecular dynamics simulations for two different surfaces: the oxygen-bridging (hydrophobic) and hydroxyl-terminated (hydrophilic) surfaces of quartz (silica). Based on the density profile, it was found that both heptane and toluene oscillate on silica surfaces, with heptane showing more oscillation peaks. Furthermore, the toluene molecules of the first layer were found to have an asymmetric distribution of orientations, with more CH3 groups pointed away from the silica surface than towards the silica surface. These findings are generally consistent with previous experiments, and reveal enhanced molecular structures of liquids at oil-silica interfaces.

Asymmetric orientation of toluene molecules at oil-silica interfaces.

PubMed

Ledyastuti, Mia; Liang, Yunfeng; Kunieda, Makoto; Matsuoka, Toshifumi

2012-08-14

The interfacial structure of heptane and toluene at oil-silica interfaces has previously been studied by sum frequency generation [Z. Yang et al., J. Phys. Chem. C. 113, 20355 (2009)]. It was found that the toluene molecule is almost perpendicular to the silica surface with a tilt angle of about 25°. Here, we have investigated the structural properties of toluene and heptane at oil-silica interfaces using molecular dynamics simulations for two different surfaces: the oxygen-bridging (hydrophobic) and hydroxyl-terminated (hydrophilic) surfaces of quartz (silica). Based on the density profile, it was found that both heptane and toluene oscillate on silica surfaces, with heptane showing more oscillation peaks. Furthermore, the toluene molecules of the first layer were found to have an asymmetric distribution of orientations, with more CH(3) groups pointed away from the silica surface than towards the silica surface. These findings are generally consistent with previous experiments, and reveal enhanced molecular structures of liquids at oil-silica interfaces.

Waveguide bends from nanometric silica wires

NASA Astrophysics Data System (ADS)

Tong, Limin; Lou, Jingyi; Mazur, Eric

2005-02-01

We propose to use bent silica wires with nanometric diameters to guide light as optical waveguide bend. We bend silica wires with scanning tunneling microscope probes under an optical microscope, and wire bends with bending radius smaller than 5 μm are obtained. Light from a He-Ne laser is launched into and guided through the wire bends, measured bending loss of a single bend is on the order of 1 dB. Brief introductions to the optical wave guiding and elastic bending properties of silica wires are also provided. Comparing with waveguide bends based on photonic bandgap structures, the waveguide bends from silica nanometric wires show advantages of simple structure, small overall size, easy fabrication and wide useful spectral range, which make them potentially useful in the miniaturization of photonic devices.

Green synthesis of silica nanoparticles using sugarcane bagasse

NASA Astrophysics Data System (ADS)

Mohd, Nur Kamilah; Wee, Nik Nur Atiqah Nik; Azmi, Alyza A.

2017-09-01

Silica nanoparticles have been great attention as it being evaluated for used in abundant fields and applications. Due to this significance, this research was conducted to synthesis silica nanoparticles using local agricultural waste, sugarcane bagasse. We executed extraction and precipitation process as it involved low cost, less toxic and low energy process compared to other methods. The Infrared (IR) spectra showed the vibration peak of Si-O-Si, which clearly be the evidence for the silica characteristics in the sample. In this research, amorphous silica nanoparticles with spherical morphology with an average size of 30 nm, and specific surface area of 111 m2/g-1 have been successfully synthesized. The XRD patterns showed the amorphous nature of silica nanoparticles. As a comparison, the produced silica nanoparticles from sugarcane bagasse are compared with the respective nanoparticles synthesized using Stöber method.

Differences in the Nature of Active Sites for Methane Dry Reforming and Methane Steam Reforming over Nickel Aluminate Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, Jessica L.; Mangarella, Michael C.; D’Amico, Andrew D.

In this paper, the Pechini synthesis was used to prepare nickel aluminate catalysts with the compositions NiAl 4O 7, NiAl 2O 4, and Ni 2Al 2O 5. The samples have been characterized by N 2 physisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Characterization results indicate unique structural properties and excellent regeneration potential of nickel aluminates. Prepared samples were tested when unreduced and reduced prior to reaction for methane dry reforming and methane steam reforming reactivity. NiAl 2O 4 in the reduced and unreduced statemore » as well as NiAl 4O 7 in the reduced state are active and stable for methane dry reforming due to the presence of 4-fold coordinated oxidized nickel. The limited amount of metallic nickel in these samples minimizes carbon deposition. Finally, on the other hand, the presence of metallic nickel is required for methane steam reforming. Ni 2Al 2O 5 in the reduced and unreduced states and NiAl 2O 4 in the reduced state are found to be active for methane steam reforming due to the presence of sufficiently small nickel nanoparticles that catalyze the reaction without accumulating carbonaceous deposits.« less

Differences in the Nature of Active Sites for Methane Dry Reforming and Methane Steam Reforming over Nickel Aluminate Catalysts

DOE PAGES

Rogers, Jessica L.; Mangarella, Michael C.; D’Amico, Andrew D.; ...

2016-07-20

In this paper, the Pechini synthesis was used to prepare nickel aluminate catalysts with the compositions NiAl 4O 7, NiAl 2O 4, and Ni 2Al 2O 5. The samples have been characterized by N 2 physisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Characterization results indicate unique structural properties and excellent regeneration potential of nickel aluminates. Prepared samples were tested when unreduced and reduced prior to reaction for methane dry reforming and methane steam reforming reactivity. NiAl 2O 4 in the reduced and unreduced statemore » as well as NiAl 4O 7 in the reduced state are active and stable for methane dry reforming due to the presence of 4-fold coordinated oxidized nickel. The limited amount of metallic nickel in these samples minimizes carbon deposition. Finally, on the other hand, the presence of metallic nickel is required for methane steam reforming. Ni 2Al 2O 5 in the reduced and unreduced states and NiAl 2O 4 in the reduced state are found to be active for methane steam reforming due to the presence of sufficiently small nickel nanoparticles that catalyze the reaction without accumulating carbonaceous deposits.« less

Silica and lung cancer: a controversial issue.

PubMed

Pairon, J C; Brochard, P; Jaurand, M C; Bignon, J

1991-06-01

The role of crystalline silica in lung cancer has long been the subject of controversy. In this article, we review the main experimental and epidemiological studies dealing with this problem. Some evidence for a genotoxic potential of crystalline silica has been obtained in the rare in vitro studies published to date. In vivo studies have shown that crystalline silica is carcinogenic in the rat; the tumour types appear to vary according to the route of administration. In addition, an association between carcinogenic and fibrogenic potency has been observed in various animal species exposed to crystalline silica. An excess of lung cancer related to occupational exposure to crystalline silica is reported in many epidemiological studies, regardless of the presence of silicosis. However, most of these studies are difficult to interpret because they do not correctly take into account associated carcinogens such as tobacco smoke and other occupational carcinogens. An excess of lung cancer is generally reported in studies based on silicosis registers. Overall, experimental and human studies suggest an association between exposure to crystalline silica and an excess of pulmonary malignancies. Although the data available are not sufficient to establish a clear-cut causal relationship in humans, an association between the onset of pneumoconiosis and pulmonary malignancies is probable. In contrast, experimental observations have given rise to a pathophysiological mechanism that might account for a putative carcinogenic potency of crystalline silica.

Advances in Solid State Joining of High Temperature Alloys

NASA Technical Reports Server (NTRS)

Ding, Jeff; Schneider, Judy

2011-01-01

Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

Code of Federal Regulations, 2014 CFR

2014-04-01

... SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Special Dietary and Nutritional Additives § 172.330 Calcium pantothenate, calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may be safely used in foods for special...

Protein-directed assembly of arbitrary three-dimensional nanoporous silica architectures.

PubMed

Khripin, Constantine Y; Pristinski, Denis; Dunphy, Darren R; Brinker, C Jeffrey; Kaehr, Bryan

2011-02-22

Through precise control of nanoscale building blocks, such as proteins and polyamines, silica condensing microorganisms are able to create intricate mineral structures displaying hierarchical features from nano- to millimeter-length scales. The creation of artificial structures of similar characteristics is facilitated through biomimetic approaches, for instance, by first creating a bioscaffold comprised of silica condensing moieties which, in turn, govern silica deposition into three-dimensional (3D) structures. In this work, we demonstrate a protein-directed approach to template silica into true arbitrary 3D architectures by employing cross-linked protein hydrogels to controllably direct silica condensation. Protein hydrogels are fabricated using multiphoton lithography, which enables user-defined control over template features in three dimensions. Silica deposition, under acidic conditions, proceeds throughout protein hydrogel templates via flocculation of silica nanoparticles by protein molecules, as indicated by dynamic light scattering (DLS) and time-dependent measurements of elastic modulus. Following silica deposition, the protein template can be removed using mild thermal processing yielding high surface area (625 m(2)/g) porous silica replicas that do not undergo significant volume change compared to the starting template. We demonstrate the capabilities of this approach to create bioinspired silica microstructures displaying hierarchical features over broad length scales and the infiltration/functionalization capabilities of the nanoporous silica matrix by laser printing a 3D gold image within a 3D silica matrix. This work provides a foundation to potentially understand and mimic biogenic silica condensation under the constraints of user-defined biotemplates and further should enable a wide range of complex inorganic architectures to be explored using silica transformational chemistries, for instance silica to silicon, as demonstrated herein.

Robust Joining and Integration of Advanced Ceramics and Composites: Challenges, Opportunities, and Realities

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay

2006-01-01

Advanced ceramics and fiber reinforced composites are under active consideration for use in a wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite components require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition, these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing of high temperature joints in advanced ceramics and ceramic matrix composites will be presented. Silicon carbide based advanced ceramics and fiber reinforced composites in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology. In addition, some examples of metal-ceramic brazing will also be presented. Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and composites will be reported. Various joint design philosophies and design issues in joining of ceramics and composites will be discussed.

Explosive Joining for Nuclear-Reactor Repair

NASA Technical Reports Server (NTRS)

Bement, L. J.; Bailey, J. W.

1983-01-01

In explosive joining technique, adapter flange from fuel channel machined to incorporate a V-notch interface. Ribbon explosive, 1/2 inch (1.3 cm) in width, drives V-notched wall of adapter into bellows assembly, producing atomic-level metallurgical bond. Ribbon charge yields joint with double parent metal strength.

Process for preparing polymer reinforced silica aerogels

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

2011-01-01

Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

Joining of Silicon Carbide-Based Ceramics by Reaction Forming Method

NASA Technical Reports Server (NTRS)

Singh, M.; Kiser, J. D.

1997-01-01

Recently, there has been a surge of interest in the development and testing of silicon-based ceramics and composite components for a number of aerospace and ground based systems. The designs often require fabrication of complex shaped parts which can be quite expensive. One attractive way of achieving this goal is to build up complex shapes by joining together geometrically simple shapes. However, the joints should have good mechanical strength and environmental stability comparable to the bulk materials. These joints should also be able to maintain their structural integrity at high temperatures. In addition, the joining technique should be practical, reliable, and affordable. Thus, joining has been recognized as one of the enabling technologies for the successful utilization of silicon carbide based ceramic components in high temperature applications. Overviews of various joining techniques, i.e., mechanical fastening, adhesive bonding, welding, brazing, and soldering have been provided in recent publications. The majority of the techniques used today are based on the joining of monolithic ceramics with metals either by diffusion bonding, metal brazing, brazing with oxides and oxynitrides, or diffusion welding. These techniques need either very high temperatures for processing or hot pressing (high pressures). The joints produced by these techniques have different thermal expansion coefficients than the ceramic materials, which creates a stress concentration in the joint area. The use temperatures for these joints are around 700 C. Ceramic joint interlayers have been developed as a means of obtaining high temperature joints. These joint interlayers have been produced via pre-ceramic polymers, in-situ displacement reactions, and reaction bonding techniques. Joints produced by the pre-ceramic polymer approach exhibit a large amounts of porosity and poor mechanical properties. On the other hand, hot pressing or high pressures are needed for in-situ displacement

Calcium waves.

PubMed

Jaffe, Lionel F

2008-04-12

Waves through living systems are best characterized by their speeds at 20 degrees C. These speeds vary from those of calcium action potentials to those of ultraslow ones which move at 1-10 and/or 10-20 nm s(-1). All such waves are known or inferred to be calcium waves. The two classes of calcium waves which include ones with important morphogenetic effects are slow waves that move at 0.2-2 microm s(-1) and ultraslow ones. Both may be propagated by cycles in which the entry of calcium through the plasma membrane induces subsurface contraction. This contraction opens nearby stretch-sensitive calcium channels. Calcium entry through these channels propagates the calcium wave. Many slow waves are seen as waves of indentation. Some are considered to act via cellular peristalsis; for example, those which seem to drive the germ plasm to the vegetal pole of the Xenopus egg. Other good examples of morphogenetic slow waves are ones through fertilizing maize eggs, through developing barnacle eggs and through axolotl embryos during neural induction. Good examples of ultraslow morphogenetic waves are ones during inversion in developing Volvox embryos and across developing Drosophila eye discs. Morphogenetic waves may be best pursued by imaging their calcium with aequorins.

Aluminum and stainless steel tubes joined by simple ring and welding process

NASA Technical Reports Server (NTRS)

Townhill, A.

1967-01-01

Duranel ring is used to join aluminum and stainless steel tubing. Duranel is a bimetal made up of roll-bonded aluminum and stainless steel. This method of joining the tubing requires only two welding operations.

Formation of hollow silica nanospheres by reverse microemulsion

NASA Astrophysics Data System (ADS)

Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

2015-05-01

Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and

New Silica Magnetite Sorbent: The Influence of Variations of Sodium Silicate Concentrations on Silica Magnetite Character

NASA Astrophysics Data System (ADS)

Azmiyawati, C.; Pratiwi, P. I.; Darmawan, A.

2018-04-01

The adsorption capacity of an adsorbent is determined by the adsorbent and the adsorbate properties. The character of the adsorbent will play a major role in its ability to adsorb the corresponding adsorbate. Therefore, in this study we looked at the effects of variations of sodium silicate concentrations on the resulting magnetite silica adsorbent properties. The application of silica coating on the magnetite was carried out through a sol-gel process with sodium silicate and HCl precursors. Based on the characterization data obtained, it was found that the silica coating on magnetite can increase the resistance to acid leaching, increase the particle size, but decrease the magnetic properties of the magnetite. Based on Gas Sorption Analyzer (GSA) and X-ray Difraction (XRD) data it can successively be determined that increase in concentration of sodium silicate will increase the surface area and amorphous structure of the Silica Magnetie.

Glass formation and crystallization in the alumina-silica-lanthanum phosphate system for ceramics composites

NASA Astrophysics Data System (ADS)

Guo, Shuling

The formation, structure, and dynamics of glasses in the alumina-silica-lanthanum phosphate system and their crystallization were investigated as a function of composition. These are of interest because of their potential as precursors for synthesizing ceramic-matrix-composites via co-crystallization of lanthanum monazite and either mullite or alumina into finely mixed microstructures. The glasses were characterized by X-Ray Diffraction (XRD), Raman spectroscopy, Differential Scanning Calorimetry (DSC), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Energy Loss Spectrometry (EELS). Glass formation from rapidly quenched liquids was easiest and most consistent for compositions containing silica, such as for mullitemonazite compositions, and more difficult for alumina-monazite compositions. For mullite-monazite glasses, the glass transition temperatures increased linearly from 845°C to 906°C with increasing mullite content. An analysis of the glass structure indicated a network consisting of corner-linked aluminate, silicate and phosphate tetrahedra where aluminum played a central role of separating silicon and phosphorous. It was hypothesized that the glass network consisted of domains of aluminum silicate network edged by phosphate tetrahedra. A maximum in the crystallization temperature was attributed to the complexity of the glass network. At relatively mullite-rich compositions, simultaneous and cooperative crystallization of lanthanum phosphate and mullite correlated with the highest crystallization temperatures, and the lowest activation energies of crystallization. This was preceded by amorphous phase segregation in the glass at lower temperatures. An intermediate phase of lanthanum phosphate was discovered with an orthorhombic unit cell. For compositions of high phosphate contents, lanthanum phosphate precipitated first at about 900°C leaving an essentially pure mullite glass

Silica sol as grouting material: a physio-chemical analysis.

PubMed

Sögaard, Christian; Funehag, Johan; Abbas, Zareen

2018-01-01

At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.

Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process

PubMed Central

Baumgärtner, Benjamin; Möller, Hendrik; Neumann, Thomas

2017-01-01

A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol–gel-processing of silica precursors is used to deposit a silica coating directly on the fiber’s surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine) via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine)) on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine), silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes. PMID:28685115

Preparation of thick silica coatings on carbon fibers with fine-structured silica nanotubes induced by a self-assembly process.

PubMed

Baumgärtner, Benjamin; Möller, Hendrik; Neumann, Thomas; Volkmer, Dirk

2017-01-01

A facile method to coat carbon fibers with a silica shell is presented in this work. By immobilizing linear polyamines on the carbon fiber surface, the high catalytic activity of polyamines in the sol-gel-processing of silica precursors is used to deposit a silica coating directly on the fiber's surface. The surface localization of the catalyst is achieved either by attaching short-chain polyamines (e.g., tetraethylenepentamine) via covalent bonds to the carbon fiber surface or by depositing long-chain polyamines (e.g., linear poly(ethylenimine)) on the carbon fiber by weak non-covalent bonding. The long-chain polyamine self-assembles onto the carbon fiber substrate in the form of nanoscopic crystallites, which serve as a template for the subsequent silica deposition. The silicification at close to neutral pH is spatially restricted to the localized polyamine and consequently to the fiber surface. In case of the linear poly(ethylenimine), silica shells of several micrometers in thickness can be obtained and their morphology is easily controlled by a considerable number of synthesis parameters. A unique feature is the hierarchical biomimetic structure of the silica coating which surrounds the embedded carbon fiber by fibrillar and interconnected silica fine-structures. The high surface area of the nanostructured composite fiber may be exploited for catalytic applications and adsorption purposes.

Calcium - urine

MedlinePlus

Urinary Ca+2; Kidney stones - calcium in urine; Renal calculi - calcium in your urine; Parathyroid - calcium in urine ... A 24-hour urine sample is most often needed: On day 1, urinate into the toilet when you wake up in the morning. ...

Mesoporous silica templated zirconia nanoparticles

NASA Astrophysics Data System (ADS)

Ballem, Mohamed A.; Córdoba, José M.; Odén, Magnus

2011-07-01

Nanoparticles of zirconium oxide (ZrO2) were synthesized by infiltration of a zirconia precursor (ZrOCl2·8H2O) into a SBA-15 mesoporous silica mold using a wet-impregnation technique. X-ray diffractometry and high-resolution transmission electron microscopy show formation of stable ZrO2 nanoparticles inside the silica pores after a thermal treatment at 550 °C. Subsequent leaching out of the silica template by NaOH resulted in well-dispersed ZrO2 nanoparticles with an average diameter of 4 nm. The formed single crystal nanoparticles are faceted with 110 surfaces termination suggesting it to be the preferred growth orientation. A growth model of these nanoparticles is also suggested.

In-situ Raman spectroscopic study of aluminate speciation in H2O-KOH solutions at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Mookherjee, M.; Keppler, H.; Manning, C. E.

2009-12-01

The solubility of corundum in H2O is low even at high pressure and temperatures. Therefore, it is commonly assumed that alumina remains essentially immobile during fluid-rock interaction. However, field and experimental evidence suggests that alumina solubility is strongly enhanced in the presence of silica as well as in alkaline solutions. In order to understand what controls the alumina solubility and how it is enhanced as a function of fluid composition, we conducted Raman-spectroscopic study of Al speciation in aqueous fluids at high pressure and temperature. Experiments were carried out in an externally heated hydrothermal diamond-anvil cell equipped with low-fluorescence diamonds and iridium gaskets. Raman spectra were collected with a Horiba Jobin-Yvon Labram HR spectrometer using the 514 nm line of an argon laser for excitation. In a first series of experiments, the speciation of alumina was studied in a 1 M KOH solution in equilibrium with corundum up to 700 oC and ~1 GPa. The Raman spectra show a prominent band at 618 cm-1 interpreted to arise from Al-O stretching vibrations associated with the tetrahedral [Al(OH)4]1- species. At higher pressure and temperature, an additional vibrational mode appears in the spectra at 374 cm-1 (full width at half maximum ~ 20 cm-1). This feature is tentatively attributed to [(OH)3Al-O-Al(OH)3]2- (Moolenaar et al. 1970, Jour. Phys. Chem., 74, 3629-3636). No evidence for KAl(OH)4 was observed, consistent with piston cylinder experiments at 700 oC and 1 GPa (Wohlers & Manning, 2009, Chem. Geol., 262, 310). Upon cooling from high-pressure and high temperature, slow kinetics of corundum regrowth lead to oversaturation in the solutions, as evidenced by sharp peaks at 930 and 1066 cm-1 observed upon cooling. These features are probably due to colloidal aluminum hydroxide. The results provide the first evidence for aluminate polymerization at high pressure and temperature, and offer insights into the causes for enhancement of

Genetically Encoded Calcium Indicators For Studying Long-Term Calcium Dynamics During Apoptosis

PubMed Central

Garcia, M. Iveth; Chen, Jessica J.; Boehning, Darren

2017-01-01

Intracellular calcium release is essential for regulating almost all cellular functions. Specific spatio-temporal patterns of cytosolic calcium elevations are critical determinants of cell fate in response to pro-apoptotic cellular stressors. As the apoptotic program can take hours or days, measurement of long-term calcium dynamics are essential for understanding the mechanistic role of calcium in apoptotic cell death. Due to the technical limitations of using calcium-sensitive dyes to measure cytosolic calcium little is known about long-term calcium dynamics in living cells after treatment with apoptosis-inducing drugs. Genetically encoded calcium indicators could potentially overcome some of the limitations of calcium-sensitive dyes. Here, we compared the performance of the genetically encoded calcium indicators GCaMP6s and GCaMP6f with the ratiometric dye Fura-2. GCaMP6s performed as well or better than Fura-2 in detecting agonist-induced calcium transients. We then examined the utility of GCaMP6s for continuously measuring apoptotic calcium release over the course of ten hours after treatment with staurosporine. We found that GCaMP6s was suitable for measuring apoptotic calcium release over long time courses and revealed significant heterogeneity in calcium release dynamics in individual cells challenged with staurosporine. Our results suggest GCaMP6s is an excellent indicator for monitoring long-term changes cytosolic calcium during apoptosis. PMID:28073595

Deformation and Forming of Joined Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carsley, John; Hovanski, Yuri; Clarke, Kester D.

2014-09-23

Introductory article to a set of invited papers from the TMS committee on shaping and forming. This paper introduces a set of papers that were prepared to discussing the deformation and forming of joined materials, and to announce an upcoming symposium at the 2015 MS&T meeting in Columbus Ohio.

Method of joining ceramics

DOEpatents

Henager, Jr., Charles H.; Brimhall, John L.

2000-01-01

According to the method of the present invention, joining a first bi-element carbide to a second bi-element carbide, has the steps of: (a) forming a bond agent containing a metal carbide and silicon; (b) placing the bond agent between the first and second bi-element carbides to form a pre-assembly; and (c) pressing and heating the pre-assembly in a non-oxidizing atmosphere to a temperature effective to induce a displacement reaction creating a metal silicon phase bonding the first and second bi-element carbides.

The effect of variable calcium and very low calcium diets on human calcium metabolism. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Chu, J.

1971-01-01

The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

Procedure to prepare transparent silica gels

NASA Technical Reports Server (NTRS)

Barber, Patrick G. (Inventor); Simpson, Norman R. (Inventor)

1987-01-01

This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

The activity of calcium in calcium-metal-fluoride fluxes

NASA Astrophysics Data System (ADS)

Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

1995-08-01

The standard Gibbs energy of reaction Ca (1) + O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: Δ G° = -64,300(±700) + 19.8(±3.5) T J/mol (1373 to 1623 K) The activities of calcium in the CaOsatd-Ca- MF2 ( M: Ca, Ba, Mg) and CaOsatd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF2, BaF2, and MgF2 at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

Fluorine-Based DRIE of Fused Silica

NASA Technical Reports Server (NTRS)

Yee, Karl; Shcheglov, Kirill; Li, Jian; Choi, Daniel

2007-01-01

A process of deep reactive-ion etching (DRIE) using a fluorine-based gas mixture enhanced by induction-coupled plasma (ICP) has been demonstrated to be effective in forming high-aspect-ratio three-dimensional patterns in fused silica. The patterns are defined in part by an etch mask in the form of a thick, high-quality aluminum film. The process was developed to satisfy a need to fabricate high-aspect-ratio fused-silica resonators for vibratory microgyroscopes, and could be used to satisfy similar requirements for fabricating other fused-silica components.

Robust Joining and Integration Technologies for Advanced Metallic, Ceramic, and Composite Systems

NASA Technical Reports Server (NTRS)

Singh, M.; Shpargel, Tarah; Morscher, Gregory N.; Halbig, Michael H.; Asthana, Rajiv

2006-01-01

Robust integration and assembly technologies are critical for the successful implementation of advanced metallic, ceramic, carbon-carbon, and ceramic matrix composite components in a wide variety of aerospace, space exploration, and ground based systems. Typically, the operating temperature of these components varies from few hundred to few thousand Kelvin with different working times (few minutes to years). The wide ranging system performance requirements necessitate the use of different integration technologies which includes adhesive bonding, low temperature soldering, active metal brazing, diffusion bonding, ARCJoinT, and ultra high temperature joining technologies. In this presentation, a number of joining examples and test results will be provided related to the adhesive bonding and active metal brazing of titanium to C/C composites, diffusion bonding of silicon carbide to silicon carbide using titanium interlayer, titanium and hastelloy brazing to silicon carbide matrix composites, and ARCJoinT joining of SiC ceramics and SiC matrix composites. Various issues in the joining of metal-ceramic systems including thermal expansion mismatch and resulting residual stresses generated during joining will be discussed. In addition, joint design and testing issues for a wide variety of joints will be presented.

High-Silica Lamoose Rock

NASA Image and Video Library

2015-07-23

A rock fragment dubbed "Lamoose" is shown in this picture taken by the Mars Hand Lens Imager (MAHLI) on NASA's Curiosity rover. Like other nearby rocks in a portion of the "Marias Pass" area of Mt. Sharp, Mars, it has unusually high concentrations of silica. The high silica was first detected in the area by the Chemistry & Camera (ChemCam) laser spectrometer. This rock was targeted for follow-up study by the MAHLI and the arm-mounted Alpha Particle X-ray Spectrometer (APXS). Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz. High levels of silica could indicate ideal conditions for preserving ancient organic material, if present, so the science team wants to take a closer look. The rock is about 4 inches (10 centimeters) across. It is fine-grained, perhaps finely layered, and etched by the wind. The image was taken on the 1,041st Martian day, or sol, of the mission (July 11, 2015). MAHLI was built by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover. http://photojournal.jpl.nasa.gov/catalog/PIA19828

Size- and structure-dependent toxicity of silica particulates

NASA Astrophysics Data System (ADS)