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1

Effect of pyrolytic carbon content on microstructure and tribological properties of C/C-SiC brake composites fabricated by isothermal chemical vapor infiltration  

NASA Astrophysics Data System (ADS)

Four types of C/C-SiC composites were prepared by isothermal chemical vapor infiltration (ICVI) of SiC on C/C preforms of different densities. Tribological properties of the composites were evaluated by using MM-1000 testing machine. The results indicated that the friction behaviors of the composites are a strong function of the content of pyrolytic carbon (in matrix). Moreover, friction film was formed on the surface and increased with pyrolytic carbon content. Debris originated of particulate and film-type have been observed after friction testing with ratio and size determined by the content of pyrolytic carbon.

Shi, Qilong; Xiao, Peng

2012-01-01

2

Nondestructive activation analysis of sample of lunar surface material returned by Luna 16 automatic station. [chemical composition  

NASA Technical Reports Server (NTRS)

The composition of a sample of lunar surface material returned by the Luna 16 automatic station from the Sea of Fertility was studied, using nondestructive activation analysis. The structure of the returned surface material is inhomogeneous; the surficial material is thin, quite homogeneous, and the granularity increases with depth. Based on grain size, the sample was separated into five zones. The activation analysis was conducted on a sample taken from the friable surficial layer, zone A. The content of Al, Mn, Na, Cr, Co, Fe, and Sc was determined by nondestructive activation analysis of the sample. In determining Cr, Co, Fe, and Sc, the sample was irradiated for 24 hours and cooled for 10 days. Gamma spectra of the samples were recorded with a semiconductor Ge(Li)-detector and a multichannel analyzer, and measurement data were processed with an electronic computer.

Chayko, M.; Sabo, E.

1974-01-01

3

Use of radiation effects for a controlled change in the chemical composition and properties of materials by intentional addition or substitution of atoms of a certain kind  

SciTech Connect

This study is a continuation of works [1-12] dealing with the field developed by the authors, namely, to widen the possibilities of radiation methods for a controlled change in the atomic composition and properties of thin-film materials. The effects under study serve as the basis for the following two methods: selective atom binding and selective atom substitution. Such changes in the atomic composition are induced by irradiation by mixed beams consisting of protons and other ions, the energy of which is sufficient for target atom displacements. The obtained experimental data demonstrate that the changes in the chemical composition of thin-film materials during irradiation by an ion beam of a complex composition take place according to mechanisms that differ radically from the well-known mechanisms controlling the corresponding chemical reactions in these materials. These radical changes are shown to be mainly caused by the accelerated ioninduced atomic displacements in an irradiated material during irradiation; that is, they have a purely radiation nature. The possibilities of the new methods for creating composite structures consisting of regions with a locally changed chemical composition and properties are demonstrated for a wide class of materials.

Gurovich, B. A.; Prikhod'ko, K. E., E-mail: kirill@irmrnt.kiae.ru; Kuleshova, E. A.; Maslakov, K. I.; Komarov, D. A. [National Research Center Kurchatov Institute (Russian Federation)

2013-06-15

4

Chemical composition and enzymatic digestibility of sugarcane clones selected for varied lignin content  

PubMed Central

Background The recalcitrance of lignocellulosic materials is a major limitation for their conversion into fermentable sugars. Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish this recalcitrance. In this study, we assessed the success of a sugarcane breeding program in selecting sugarcane plants with low lignin content, and report the chemical composition and agronomic characteristics of eleven experimental hybrids and two reference samples. The enzymatic digestion of untreated and chemically delignified samples was evaluated to advance the performance of the sugarcane residue (bagasse) in cellulosic-ethanol production processes. Results The ranges for the percentages of glucan, hemicellulose, lignin, and extractive (based on oven-dry biomass) of the experimental hybrids and reference samples were 38% to 43%, 25% to 32%, 17% to 24%, and 1.6% to 7.5%, respectively. The samples with the smallest amounts of lignin did not produce the largest amounts of total polysaccharides. Instead, a variable increase in the mass of a number of components, including extractives, seemed to compensate for the reduction in lignin content. Hydroxycinnamic acids accounted for a significant part of the aromatic compounds in the samples, with p-coumaric acid predominating, whereas ferulic acid was present only in low amounts. Hydroxycinnamic acids with ester linkage to the hemicelluloses varied from 2.3% to 3.6%. The percentage of total hydroxycinnamic acids (including the fraction linked to lignin through ether linkages) varied from 5.0% to 9.2%, and correlated to some extent with the lignin content. These clones released up to 31% of glucose after 72 hours of digestion with commercial cellulases, whereas chemically delignified samples led to cellulose conversion values of more than 80%. However, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment. Conclusion Some of the experimental sugarcane hybrids did have the combined characteristics of high biomass and high sucrose production with low lignin content. Conversion of glucan to glucose by commercial cellulases was increased in the samples with low lignin content. Chemical delignification further increased the cellulose conversion to values of more than 80%. Thus, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment.

2011-01-01

5

Composite-Material Tanks with Chemically Resistant Liners  

NASA Technical Reports Server (NTRS)

Lightweight composite-material tanks with chemically resistant liners have been developed for storage of chemically reactive and/or unstable fluids . especially hydrogen peroxide. These tanks are similar, in some respects, to the ones described in gLightweight Composite-Material Tanks for Cryogenic Liquids h (MFS-31379), NASA Tech Briefs, Vol. 25, No. 1 (January, 2001), page 58; however, the present tanks are fabricated by a different procedure and they do not incorporate insulation that would be needed to prevent boil-off of cryogenic fluids. The manufacture of a tank of this type begins with the fabrication of a reusable multisegmented aluminum mandrel in the shape and size of the desired interior volume. One or more segments of the mandrel can be aluminum bosses that will be incorporated into the tank as end fittings. The mandrel is coated with a mold-release material. The mandrel is then heated to a temperature of about 400 F (approximately equal to 200 C) and coated with a thermoplastic liner material to the desired thickness [typically approxiamtely equal to 15 mils (approximately equal to 0.38 mm)] by thermal spraying. In the thermal-spraying process, the liner material in powder form is sprayed and heated to the melting temperature by a propane torch and the molten particles land on the mandrel. The sprayed liner and mandrel are allowed to cool, then the outer surface of the liner is chemically and/or mechanically etched to enhance bonding of a composite overwrap. The etched liner is wrapped with multiple layers of an epoxy resin reinforced with graphite fibers; the wrapping can be done either by manual application of epoxy-impregnated graphite cloth or by winding of epoxy-impregnated filaments. The entire assembly is heated in an autoclave to cure the epoxy. After the curing process, the multisegmented mandrel is disassembled and removed from inside, leaving the finished tank. If the tank is to be used for storing hydrogen peroxide, then the liner material should be fluorinated ethylene/propylene (FEP), and one or more FEP O ring(s) should be used in the aluminum end fitting(s). This choice of materials is dictated by experimental observations that pure aluminum and FEP are the only materials suitable for long-term storage of hydrogen peroxide and that other materials tend to catalyze the decomposition of hydrogen peroxide to oxygen and water. Other thermoplastic liner materials that are suitable for some applications include nylon 6 and polyethylene. The processing temperatures for nylon 6 are lower than those for FEP. Nylon 6 is compatible with propane, natural gas, and other petroleum-based fuels. Polyethylene is compatible with petroleum- based products and can be used for short-term storage of hydrogen peroxide.

DeLay, Thomas K.

2004-01-01

6

Chemical Composition  

NASA Astrophysics Data System (ADS)

Measurements of the chemical compositions of materials and the levels of certain substances in them are vital when assessing and improving public health, safety and the environment, are necessary to ensure trade equity, and are required when monitoring and improving industrial products and services. Chemical measurements play a crucial role in most areas of the economy, including healthcare, food and nutrition, agriculture, environmental technologies, chemicals and materials, instrumentation, electronics, forensics, energy, and transportation.

May, Willie; Cavanagh, Richard; Turk, Gregory; Winchester, Michael; Travis, John; Smith, Melody; Derose, Paul; Choquette, Steven; Kramer, Gary; Sieber, John; Greenberg, Robert; Lindstrom, Richard; Lamaze, George; Zeisler, Rolf; Schantz, Michele; Sander, Lane; Phinney, Karen; Welch, Michael; Vetter, Thomas; Pratt, Kenneth; Scott, John; Small, John; Wight, Scott; Stranick, Stephan

7

Chemical Composition of Wild-2 Dust Collected by Stardust  

NASA Astrophysics Data System (ADS)

The Stardust spacecraft collected dust from Comet Wild-2 in two forms: material distributed along tracks in aerogel capture cells and residue in impact craters. To analyze the chemical composition of these samples the tracks produced in the aerogel were extracted as keystones containing complete tracks. Twenty-six tracks were analyzed using an X-Ray Microprobe, providing x-ray fluorescence chemical analysis for elements having K-lines at energies high enough to permit escape from the overlying aerogel (S and the heavier elements, including the moderately-volatile trace elements Cu, Zn, and Ga). Two of these tracks were then split open, exposing the interior for analysis by TOF-SIMS (which allowed detection of the lighter elements, e.g., Mg and Al). Neither Si nor O could be determined for samples captured in the aerogel, since these are the major elements in the aerogel itself. The residue in craters in the Al-foil were analyzed by SEM-EDX and TOF-SIMS. The crater residues provide information on the important light elements (Mg and Si). By combining the results from the craters and the tracks, a comprehensive chemical analysis of the Wild-2 dust was possible. Preliminary Examination of the material indicates that: 1) For particles collected in the aerogel, a significant fraction of the incident mass is frequently deposited along the entry track, suggesting the individual Wild-2 dust particles that hit the aerogel were relatively weak aggregates. 2) The chemical composition of the terminal particle in the track is frequently significantly different from the composition of the material deposited along the track, 3) Most of the elements measured show variations in their Fe-normalized abundances of more than two orders-of-magnitude in both the terminal particles and the material deposited along track walls, indicating that the Wild-2 dust is compositionally heterogeneous at the size scale of the largest particles analyzed, not simply a well-mixed aggregate of sub-micron grains, 4) The mean content of the refractory, rock-forming elements (Mg, Ca, Si, Cr, Fe, and Ni) averaged over the whole tracks and/or the crater residues in the Wild-2 grains are approximately chondritic, and, 5) There is an apparent enrichment over CI in some of the moderately-volatile minor elements (Cu, Zn, and Ga) in the Wild-2 dust.

Flynn, G. J.

2006-12-01

8

Propolis from northern California and Oregon: chemical composition, botanical origin, and content of allergens.  

PubMed

Propolis is a beehive product that bees manufacture by mixing their own wax with vegetable resins collected from different species of trees and bushes. The chemical composition of propolis is very variable because it depends on the flora locally available, and specimens from different geographical and climatic areas display unique properties. In this paper, the results of the chemical characterization of some propolis specimens collected in northern California and in Oregon are presented. Their chemical compositions show that all specimens contain resins from poplars of the Tacamahaca section (balsam poplars)--characteristic of the western part of the North American continent. Nevertheless, some of the specimens are of mixed origin because they also contain resins from poplars of the Aigeiros section (cottonwoods)--also present in this part of the world. Propolis causes allergies in sensitive human individuals, which are due to the presence of certain esters. The contents of known propolis allergenic esters--phenylethyl caffeate, 1,1-dimethylallyl caffeate, benzyl cinnamate, and benzyl salicylate--have been investigated in these specimens and found to depend on the botanical origin. PMID:24772818

Aliboni, Andrea

2014-01-01

9

Content and chemical form of mercury and selenium in soil, sludge, and fertilizer materials  

Microsoft Academic Search

The content and chemical from of Hg and Se were determined for several samples of municipal sewage sludge and sludge ash, garden soil having a history of sludge and residential compost application, and selected fertilizer materials (peat moss, cow manure, residential compost, composted municipal refuse and sewage sludge, Miloganite). Municipal sewage sludge had the highest levels of total Hg (averaging

Chris J. Cappon

1984-01-01

10

Toxicological characterization of chemicals produced from laser irradiation of graphite composite materials  

SciTech Connect

One of the major potential hazards associated with laser machining of graphite composite materials is the toxic fumes and gases that are generated. When exposed to the intense energy of the laser beam, the organic polymer matrix of the composite material may decompose into various toxic by-products. To advance the understanding of the laser machining process from a health and safety viewpoint, this particular study consisted of the following steps: collect and analyze gaseous by-products generated during laser machining; collect particulates generated during laser machining and chemically extract them to determine the chemical species that may have absorbed or recondensed onto these particles; and review and evaluate the toxicity of the identified chemical species.

Kwan, J.

1990-11-01

11

Effect of various buffer-layer structures on the material quality and dislocation density of high composition Al/sub x/Ga/sub 1/. sqrt. /sub x/As laser material grown by metalorganic chemical vapor deposition  

SciTech Connect

The effect of various types of buffer layers on the generation and propagation of dislocations in epitaxial layers of high composition (x = 0.85) Al/sub x/Ga/sub 1/..sqrt../sub x/As grown by metalorganic chemical vapor deposition (MOCVD) on horizontal Bridgman (HB) and liquid-encapsulated Czochralski (LEC) substrates is examined. Bulk epilayers of high composition (x = 0.85) Al/sub x/Ga/sub 1/..sqrt../sub x/As and graded-barrier quantum-well laser structures with confining layers of the same composition were grown simultaneously on high-qualitylow etch-pit density (EPD) HB substrates and comparatively lower qualityhigh EPD LEC substrates with one of four types of compositionally graded andor superlattice buffer-layer structures. The bulk material was characterized by delineation and measurement of surface EPD and the observation of overall surface morphology. Data are also presented on the device characteristics of graded-barrier quantum-well laser diodes grown with these same buffer layers in order to determine the correlation between dislocation density and laser threshold current. The various buffer-layer structures were seen to be effective in reducing the defect density and improving the surface morphology of high composition epilayers grown on both HB and LEC substrates. The threshold-current density of the laser diodes, however, was independent of both the type of prelayer andor substrate utilized

Givens, M.E.; Coleman, J.J.; Zmudzinski, C.A.; Bryan, R.P.; Emanuel, M.A.; Miller, L.M.

1988-05-15

12

Nanograined WC-Co Composite Powders by Chemical Vapor Synthesis  

NASA Astrophysics Data System (ADS)

Nanograined tungsten carbide (WC) Co composite powders were prepared by a chemical vapor synthesis (CVS) process that has previously been used for preparing the aluminides of titanium and nickel and other metallic and intermetallic powders at the University of Utah. To determine the optimum condition for producing nanograined WC-Co composite powders, the effects of carburization temperature, CH4 to WCl6 ratio, CH4 to H2 ratio, CoCl2 contents, and residence time of WC on the powder composition and particle size were investigated. The reduction and carburization of the vaporized chlorides by CH4-H2 mixtures produced nanograined WC and Co composite powder, which sometimes contained small levels of W2C, W, or the ? (Co3W3C) phase. The presence of these incompletely carburized phases can be tolerated because they can be fully carburized during the subsequent sintering process. These phases can also be fully carburized by a separate post-treatment. The products were characterized by using X-ray diffraction (XRD) and a transmission electron microscope (TEM). As a result, nanograined WC-Co composite with the particle size less than 30 nm was obtained.

Ryu, Taegong; Sohn, H. Y.; Han, Gilsoo; Kim, Young-Ugk; Hwang, Kyu Sup; Mena, M.; Fang, Zhigang Z.

2008-02-01

13

Chemical preparation of manganese dioxide\\/polypyrrole composites and their use as cathode active materials for rechargeable lithium batteries  

Microsoft Academic Search

Chemical preparation of composite powders of polypyrrole and either α-MnOâ, β-MnOâ, or spinel LiMnâOâ has been successfully achieved by injecting liquid pyrrole into an acidic medium containing suspended manganese dioxide powder as an oxidizing agent. The content of manganese dioxide in the composites increased with increasing amount of suspended manganese dioxide in the polymerization bath. The maximum content of manganese

Ali H. Gemeay; Hiroshi Nishiyama; Susumu Kuwabata; Hiroshi Yoneyama

1995-01-01

14

Metal inserts in structural composite materials manufactured by RTM  

Microsoft Academic Search

Load transfer on a structural composite part can be carried out by means of metal inserts. Apart from their detachable features, their introduction in a composite material is not without consequence. This paper examines the impact of the inserts in a structural composite material obtained by the Resin Transfer Moulding process. Numerical flow simulations, using RTMFLOT software developed by the

B. Ferret; M. Anduze; C. Nardari

1998-01-01

15

Thermal and Chemical Characterization of Composite Materials. MSFC Center Director's Discretionary Fund Final Report, Project No. ED36-18  

NASA Technical Reports Server (NTRS)

The purpose of this research effort was to: (1) provide a concise and well-defined property profile of current and developing composite materials using thermal and chemical characterization techniques and (2) optimize analytical testing requirements of materials. This effort applied a diverse array of methodologies to ascertain composite material properties. Often, a single method of technique will provide useful, but nonetheless incomplete, information on material composition and/or behavior. To more completely understand and predict material properties, a broad-based analytical approach is required. By developing a database of information comprised of both thermal and chemical properties, material behavior under varying conditions may be better understood. THis is even more important in the aerospace community, where new composite materials and those in the development stage have little reference data. For example, Fourier transform infrared (FTIR) spectroscopy spectral databases available for identification of vapor phase spectra, such as those generated during experiments, generally refer to well-defined chemical compounds. Because this method renders a unique thermal decomposition spectral pattern, even larger, more diverse databases, such as those found in solid and liquid phase FTIR spectroscopy libraries, cannot be used. By combining this and other available methodologies, a database specifically for new materials and materials being developed at Marshall Space Flight Center can be generated . In addition, characterizing materials using this approach will be extremely useful in the verification of materials and identification of anomalies in NASA-wide investigations.

Stanley, D. C.; Huff, T. L.

2003-01-01

16

Optically transparent polyelectrolyte-silica composite materials: Preparation, characterization, and application in optical chemical sensing  

SciTech Connect

A series of polyelectrolyte-containing silica composite materials have been prepared by sol-gel processing. These optically transparent composites have been characterized by scanning electron microscopy and UV-visible spectrophotometry. These materials can be processed into monolithic disks and thin films. The thicknesses of spin-coated films of these materials on glass can be varied from 0.13 to 3.5 {mu}m as determined by an optical interferences method. These materials are ion exchangeable and less brittle than the parent silica glass due to the incorporation of the organic polyelectrolyte. These new composites retain the nanoscale porosity and optical transparency into the ultraviolet of the parent silica sol-gel glasses, making them attractive host matrixes for the immobilization of ionizable dye molecules and chemical reagents. An optical pH sensing platform (0.9 x 2.5 cm) based on the electrostatic immobilization of HPTS (8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt) in a PDMDAAC (poly(diallyldimethylammonium chloride))-silica composite film was fabricated and evaluated. The results clearly demonstrate that this platform is easy to construct with high batch reproducibility and can be regenerated by simple solution ion exchange. The platform is usable in both the modes of absorption and fluorescence, making it versatile. Having a fast response time (ca. {approximately}2 s to more than 2 units of pH change), the platform is also highly resistant to dye leaching and storage degradation over a period of months. 49 refs., 9 figs., 2 tabs.

Shi, Yining; Seliskar, C.J. [Univ. of Cincinnati, OH (United States)] [Univ. of Cincinnati, OH (United States)

1997-03-01

17

The effects of space radiation on a chemically modified graphite-epoxy composite material  

NASA Technical Reports Server (NTRS)

The effects of the space environment on the engineering properties and chemistry of a chemically modified T300/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F/24 C) and elevated temperature (250 F/121 C) on 4-ply unidirectional laminates. From these tests, inplane engineering and strength properties (E sub 1, E sub 2, Nu sub 12, G sub 12, X sub T, Y sub T) were determined. Cyclic tests were also performed to characterize energy dissipation changes due to irradiation and elevated temperature. Large diameter graphite fibers were tested to determine the effects of radiation on their stiffness and strength. No significant changes were observed. Dynamic-mechanical analysis demonstrated that the glass transition temperature was reduced by 50 F(28 C) after irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated material. The chemical modification of the epoxy did not aid in producing a material which was more radiation resistant than the standard T300/934 graphite-epoxy system. Irradiation was found to cause crosslinking and chain scission in the polymer. The latter produced low molecular weight products which plasticize the material at elevated temperatures and cause apparent material stiffening at low stresses at room temperature.

Reed, S. M.; Herakovich, C. T.; Sykes, G. F.

1986-01-01

18

Development of chemical vapor composite (CVC) ceramic materials. Status report, April 1995--June 1997  

SciTech Connect

The objective of the 94 DOE Chemical Vapor Composites (CVC) ceramics materials grant is to develop a reliable and flexible process to produce, in a single step, ceramic composites to final shape. This report is a brief summary of activities in the development of the CVC ceramics materials. Equipment has been designed and built to fabricate CVC silicon carbides with fibers such as Nextel, Nicalon, and carbon. Materials and shapes have been fabricated and characterized as to physical and mechanical properties and microstructure. Details will be given in the final report.

NONE

1997-07-25

19

Multi-functional composite materials for catalysis and chemical mechanical planarization  

NASA Astrophysics Data System (ADS)

Composite materials formed from two or more functionally different materials offer a versatile avenue to create a tailored material with well defined traits. Within this dissertation research, multi-functional composites were synthesized based on organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermo-responsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. Upon UV irradiation, short-lived electron-hole pairs are generated, which produce oxidative species that degrade simple organic contaminants. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. Although after prolonged periods of UV irradiation (˜8-13 hrs), the titania-microgels also degrade, regeneration of the microcomposites was straightforward via the addition of polymer microgels with no loss in photocatalytic activity of the reformed microcomposites. The second objective within this dissertation involved the systematic development of abrasive microcomposite particles containing well dispersed nanoparticles of ceria in an organic/inorganic hybrid polymeric particle for use in chemical mechanical polishing/planarization (CMP). A challenge in IC fabrication involves the defect-free planarization of silicon oxide films for successful multi-layer deposition. Planarization studies conducted with the microcomposites prepared in this research, yield very smooth, planar surfaces with removal rates that rival those of inorganic oxides slurries typically used in industry. The density and size of these ceria-microgel particles could be controlled by varying the temperature or composition during synthesis, leading to softer or harder polishing when desired.

Coutinho, Cecil A.

20

Material circulation model including chemical differentiation within the mantle and secular variation of temperature and composition of the mantle  

NASA Astrophysics Data System (ADS)

It is 20 years since Allègre [Tectonophys 81 (1982) 109] proposed chemical geodynamics as an integrated study of the chemical and physical structure and evolution of the solid Earth. Accumulation of geochemical data of modern magmatic rocks (e.g. [Annu. Rev. Earth Planet. Sci. 14 (1986) 493] and whole mantle tomography (e.g. [J. Geophys. Res. 97 (1992) 4809]) allow us to understand present-day mantle dynamics, and consider more recent geodynamics models (e.g. [Earth Planet. Sci. Lett. 90 (1988) 297]). However, complete investigation of geodynamics requires addressing not only the present-day structure of the earth and its elemental distributions, but also the historical evolution of the earth [Earth Planet. Sci. Lett. 86 (1987) 175], but no current tectonic models include the latter object. Recent remarkable progress of geology, petrology and geochemistry of Precambrian orogenic belts brings about decoding of the Archean tectonics and evolution of the solid earth through geologic time. Especially, understanding the thermal and compositional evolution of the mantle is essential for decoding the whole history of the Earth, because the mantle constitutes more than 85% of the earth. However, there are two inherent problems that require explanation; post-magmatic alteration, and interpretation of the tectonic setting of the magmatism. We eliminated elemental movements during alteration by comparison with whole rock compositions and with major and rare earth element compositions of relict igneous clinopyroxenes (Cpx). The tectonic setting of mafic magmatism was estimated by an independent method of the composition of greenstones; application of the concept of accretionary geology to the Archean greenstone belts. And we found MORB-affinity greenstones from five different-aged greenstone belts. The potential temperature and FeO content of the upper mantle were estimated by comparison of the most primitive MORB from 3.8 to 1.9 Ga with recent melting experiments. The result indicates that the upper mantle had higher FeO content (10 wt.%), and that the FeO content was constant until early Proterozoic, and then decreased. Segregation of iron grains from subducted oceanic crust during slab penetration into the lower mantle is plausible to decrease the FeO content in the mantle. If the produced metallic iron sinks and accumulates on the core, the metallic iron layer would be about 57 km thick. The potential mantle temperature of the upper mantle was about 1480 °C in the Archean and was hotter by ca. 150-200 °C than the modern mantle. The temperature decreased not monotonously but episodically. In addition, recent ultra-high pressure experiments presumed chemical differentiation within the mantle, dehydration or slab melting of subducted oceanic crust beneath a subduction zone, segregation of iron grains from slab materials during slab penetration [Science 273 (1996) 1522], and partial melting of subducted oceanic crust on the core-mantle boundary [Phys. Earth Planet. Inter. (2002)]. This work proposes a global material circulation model, which includes three chemical differentiations within the mantle and the secular change of temperature and composition of the mantle.

Komiya, Tsuyoshi

2004-08-01

21

Chemical Compatibility and Oxidation Resistance of Potential Matrix and Reinforcement Materials in Ceramic Composites for Ultra-High Temperature Applications.  

National Technical Information Service (NTIS)

The mutual chemical composition and compatibilities of some of the potential matrix and reinforcement phases of ceramic composite materials have been investigated in the temperature range 1600-2200 C. The oxidative stabilities of hot pressed, particulate ...

G. M. Mehrotra

1991-01-01

22

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and ThermoChemical Properties  

Microsoft Academic Search

Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter, but also inorganic material. These species, e.g. iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and

Henrike Bladt; Johannes Schmid; Elena D. Kireeva; Olga B. Popovicheva; Natalia M. Perseantseva; Mikhail A. Timofeev; Katja Heister; Johannes Uihlein; Natalia P. Ivleva; Reinhard Niessner

2012-01-01

23

Optimum conditions for composites fiber coating by chemical vapor infiltration  

Microsoft Academic Search

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration. For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size,

Stewart K. Griffiths; R. H. Nilson

1998-01-01

24

Effects of space radiation on a chemically modified graphite-epoxy composite material. Interim report  

Microsoft Academic Search

The effects of the space environment on the engineering properties and chemistry of a chemically modified T300\\/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F\\/24

S. M. Reed; C. T. Herakovich; G. F. Sykes

1986-01-01

25

High toughness, 3D textile, SiC\\/SiC composites by chemical vapor infiltration  

Microsoft Academic Search

Three dimensional, textile, Hi-Nicalon, silicon carbide fiber-reinforced, silicon carbide composites with high toughness and reliability were fabricated by chemical vapor infiltration. The mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.5 g cm?3 after the three dimensional silicon carbide perform has been infiltrated for 30 h. The values

Yongdong Xu; Laifei Cheng; Litong Zhang; Hongfeng Yin; Xiaowei Yin

2001-01-01

26

Preparation of ceramic fiber-ceramic matrix composites by a faster chemical vapor infiltration process  

SciTech Connect

A new, faster process was developed for the fabrication of ceramic fiber-reinforced, ceramic-matrix composites by chemical vapor infiltration. Process and equipment improvements led to the fabrication of preforms with a higher fiber content, and infiltration improvements led to reduced infiltration run times and increased infiltrated densities. These improvements have produced composites with not only higher flexural strengths but also high strain values. The high strain values have been a goal of this work. 23 refs., 8 figs.

Caputo, A.J.; Lackey, W.J.; Stinton, D.P.

1985-01-01

27

Composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A. (Knoxville, TN); Woodward, Jonathan (Solihull, GB); Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN)

2012-02-07

28

The correlationship between the metabolizable energy content, chemical composition and color score in different sources of corn DDGS  

PubMed Central

Background This study was conducted to evaluate the apparent metabolizable energy (AME) and true metabolizable energy (TME) contents in 30 sources of corn distillers dried grains with solubles (DDGS) in adult roosters, and establish the prediction equations to estimate the AME and TME value based on its chemical composition and color score. Methods Twenty-eight sources of corn DDGS made from several processing plants in 11 provinces of China and others imported from the United States. DDGS were analyzed for their metabolizable energy (ME) contents, measured for color score and chemical composition (crude protein, crude fat, ash, neutral detergent fiber, acid detergent fiber), to predict the equation of ME in DDGS. A precision-fed rooster assay was used, each DDGS sample was tube fed (50 g) to adult roosters. The experiment was conducted as a randomized incomplete block design with 3 periods. Ninety-five adult roosters were used in each period, with 90 being fed the DDGS samples and 5 being fasted to estimate basal endogenous energy losses. Results Results showed that the AME ranged from 5.93 to 12.19 MJ/kg, TME ranged from 7.28 to 13.54 MJ/kg. Correlations were found between ME and ash content (-0.64, P?content of DDGS based on chemical composition and color score was AME?=?6.57111?+?0.51475 GE - 0.10003 NDF?+?0.13380 ADF?+?0.07057 fat - 0.57029 ash - 0.02437 L (R2?=?0.70). The best-fit regression equation for TME content of DDGS was TME?=?7.92283?+?0.51475 GE - 0.10003 NDF?+?0.13380 ADF?+?0.07057 fat - 0.57029 ash - 0.02437 L (R2?=?0.70). Conclusions This experiment suggested that measuring the chemical composition and color score of a corn DDGS sample may provide a quality parameter for identifying corn DDGS sources energy digestibility and metabolizable energy content.

2013-01-01

29

(210)Pb content in natural gas pipeline residues ("black-powder") and its correlation with the chemical composition.  

PubMed

The present work was carried out to assess the (210)Pb content in "black-powder" found in pigging operations on gas pipelines in Brazil, in particular, on the Campos Basin gas pipeline. Additionally, the chemical composition of such deposits was determined and an eventual correlation with (210)Pb concentration evaluated. Typical "black-powder" generated in the natural gas pipeline from Campos Basin oilfield contains mainly iron oxide ( approximately 81%) and residual organic matter ( approximately 9%). The (210)Pb content ranges from 4.9 to 0.04k Bqkg(-1) and seems to be inversely correlated with the distance to the platforms. On the other hand, (226)Ra concentration is higher on the pipeline branch between the platform and the onshore installations. (228)Ra was only observed in few samples, in particular, in the samples with the highest (226)Ra content. PMID:15885858

Godoy, José Marcus; Carvalho, Franciane; Cordilha, Aloisio; Matta, Luiz Ernesto; Godoy, Maria Luiza

2005-01-01

30

Controlling dynamic mechanical properties and degradation of composites for bone regeneration by means of filler content.  

PubMed

Bone tissue is a dynamic composite system that adapts itself, in response to the surrounding daily (cyclic) mechanical stimuli, through an equilibrium between growth and resorption processes. When there is need of synthetic bone grafts, the biggest issue is to support bone regeneration without causing mechanically-induced bone resorption. Apart from biological properties, such degradable materials should initially support and later leave room to bone formation. Further, dynamic mechanical properties comparable to those of bone are required. In this study we prepared composites comprising calcium phosphate and L-lactide/D-lactide copolymer in various content ratios using the extrusion method. We evaluated the effect of the inorganic filler amount on the polymer phase (i.e. on the post-extrusion intrinsic viscosity). We then studied their in vitro degradation and dynamic mechanical properties (in dry and humid conditions). By increasing the filler content, we observed significant decrease of the intrinsic viscosity of the polymer phase during the extrusion process. Composites containing higher amounts of apatite had faster degradation, and were also mechanically stiffer. But, due to the lower intrinsic viscosity of their polymer phase, they had larger damping properties. Besides this, higher amounts of apatite also rendered the composites more hydrophilic letting them absorb more water and causing them the largest decrease in stiffness. These results show the importance of filler content in controlling the properties of such composites. Further, in this study we observed that the viscoelastic properties of the composite containing 50wt% apatite were comparable to those of dry human cortical bone. PMID:23455172

Barbieri, Davide; de Bruijn, Joost D; Luo, Xiaoman; Farè, Silvia; Grijpma, Dirk W; Yuan, Huipin

2013-04-01

31

TGA-DTA and chemical composition study of raw material of Bikaner region for electrical porcelain  

NASA Astrophysics Data System (ADS)

Porcelains are vitrified and a fine grained ceramic product, used either glazed or unglazed and is often manufactured from a tri-axial body mix of clays, quartz and alkaline feldspar. Physical properties associated with porcelain include those of permeability, high strength, hardness, glassiness, durability, whiteness, translucence, resonance, brittleness, high resistance to the passage of electricity, high resistance to thermal shock and high elasticity[1,2]. Porcelain insulators are made from three raw materials; clay; feldspar and quartz. For porcelain manufacture the clay is categorized in two groups; ball clay and kaolin, each of which plays an important role, either in the preparation of the product or in the properties of the finished products. The following research highlights the importance that suits these materials for their contributions to the final properties of the product. Keeping this view a TGA-DTA and chemical composition of these raw materials were observed and these materials are found suitable for production of Electrical Porcelain.

Tak, S. K.; Shekhawat, M. S.; Mangal, R.

2013-06-01

32

Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems  

NASA Astrophysics Data System (ADS)

Solids of nearly solar composition have interacted with aqueous fluids on carbonaceous asteroids, icy moons, and trans-neptunian objects. These processes altered mineralogy of accreted materials together with compositions of aqueous and gaseous phases. We evaluated chemistry of aqueous solutions coexisted with CI-type chondritic solids through calculations of chemical equilibria in closed water-rock-gas systems at different compositions of initial fluids, water/rock mass ratios (0.1-1000), temperatures (<350 °C), and pressures (<2 kbars). The calculations show that fluid compositions are mainly affected by solubilities of solids, the speciation of chlorine in initial water-rock mixtures, and the occurrence of Na-bearing secondary minerals such as saponite. The major species in modeled alkaline solutions are Na+, Cl-, CO32-,HCO3-, K+, OH-, H2, and CO2. Aqueous species of Mg, Fe, Ca, Mn, Al, Ni, Cr, S, and P are not abundant in these fluids owing to low solubility of corresponding solids. Typical NaCl type alkaline fluids coexist with saponite-bearing mineralogy that usually present in aqueously altered chondrites. A common occurrence of these fluids is consistent with the composition of grains emitted from Enceladus. Na-rich fluids with abundant CO32-,HCO3-, and OH- anions coexist with secondary mineralogy depleted in Na. The Na2CO3 and NaHCO3 type fluids could form via accretion of cometary ices. NaOH type fluids form in reduced environments and may locally occur on parent bodies of CR carbonaceous chondrites. Supposed melting of accreted HCl-bearing ices leads to early acidic fluids enriched in Mg, Fe and other metals, consistent with signs of low-pH alteration in chondrites. Neutralization of these solutions leads to alkaline Na-rich fluids. Sulfate species have negligible concentrations in closed systems, which remain reduced, especially at elevated pressures created by forming H2 gas. Hydrogen, CO2, and H2O dominate in the gaseous phase, though the abundance of methane cannot be fairly estimated.

Zolotov, Mikhail Yu.

2012-08-01

33

SOx removal by calcined MgAlFe hydrotalcite-like materials: effect of the chemical composition and the cerium incorporation method.  

PubMed

Sulfur oxides are one of the most hazardous atmospheric pollutants since they contribute directly to acid rain formation. Consequently, stringent environmental regulations limit atmospheric SOx emissions, motivating research on efficient ways to reduce them. To supply an alternative to reduce these emissions in fluid catalytic cracking units, this study discloses efficient SOx reducing materials based on calcined MgAlFe hydrotalcite-like compounds (HT's). Thus, HT materials were synthesized by several methods including cerium addition. The adsorption of SO2 was carried out by contacting the calcined solid with a mixture of SO2 (1%) in air at 650 degrees C. It was demonstrated that the isomorphic incorporation of iron increased its reduction capability which was reflected in higher reduction rates and metal sulfate reduction grade at 550 degrees C. Moreover, when cerium was present in the iron-containing materials the saturation rate was improved, because cerium oxide promotes the oxidation of SO2 to SO3. The way cerium is incorporated influences the SO2 adsorption capacity. PMID:16475357

Cantú, Manuel; López-Salinas, Esteban; Valente, Jaime S; Montiel, Ramon

2005-12-15

34

Grained composite materials prepared by combustion synthesis under mechanical pressure  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

35

Composite Materials  

NASA Technical Reports Server (NTRS)

Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

1985-01-01

36

Gaining Improved Chemical Composition by Exploitation of Compton-to-Rayleigh Intensity Ratio in XRF Analysis.  

PubMed

The high specificity of the coherent (Rayleigh), as well as incoherent (Compton) X-ray scattering to the mean atomic number of a specimen to be analyzed by X-ray fluorescence (XRF), is exploited to gain more information on the chemical composition. Concretely, the evaluation of the Compton-to-Rayleigh intensity ratio from XRF spectra and its relation to the average atomic number of reference materials via a calibration curve can reveal valuable information on the elemental composition complementary to that obtained from the reference-free XRF analysis. Particularly for matrices of lower mean atomic numbers, the sensitivity of the approach is so high that it can be easily distinguished between specimens of mean atomic numbers differing from each other by 0.1. Hence, the content of light elements which are "invisible" for XRF, particularly hydrogen, or of heavier impurities/additives in light materials can be calculated "by difference" from the scattering calibration curve. The excellent agreement between such an experimental, empirical calibration curve and a synthetically generated one, on the basis of a reliable physical model for the X-ray scattering, is also demonstrated. Thus, the feasibility of the approach for given experimental conditions and particular analytical questions can be tested prior to experiments with reference materials. For the present work a microfocus X-ray source attached on an SEM/EDX (scanning electron microscopy/energy dispersive X-ray spectroscopy) system was used so that the Compton-to-Rayleigh intensity ratio could be acquired with EDX spectral data for improved analysis of the elemental composition. PMID:24950635

Hodoroaba, Vasile-Dan; Rackwitz, Vanessa

2014-07-15

37

Composite Materials  

NSDL National Science Digital Library

This is an activity (located on page 3 of PDF) about composites, materials made of 2 or more different components. Learners will be challenged to build the best mud bricks, one of the earliest examples of composites. From a supply of various building components, which the learners will examine for their different properties, they will build mud bricks, then dry them and put them through several tests. *Bricks must bake in the sun for 2-3 days prior to testing. Resource contains information about how this activity relates to carbon nanotubes and links to video, DragonflyTV Nano: Hockey Sticks.

Twin Cities Public Television, Inc.

2008-01-01

38

Chemical composition and some trace element contents in coals and coal ash from Tamnava-Zapadno Polje Coal Field, Serbia  

SciTech Connect

The chemical compositions and trace element contents (Zn, Cu, Co, Cr, Ni, Pb, Cd, As, B, Hg, Sr, Se, Be, Ba, Mn, Th, V, U) in coal and coal ash samples from Tamnava-Zapadno Polje coal field in Serbia were studied. The coal from this field belongs to lignite. This high volatility coal has high moisture and low S contents, moderate ash yield, and high calorific value. The coal ash is abundant in alumosilicates. Many trace elements such as Ni > Cd > Cr > B > As > Cu > Co > Pb > V > Zn > Mn in the coal and Ni > Cr > As > B > Cu > Co = Pb > V > Zn > Mn in the coal ash are enriched in comparison with Clarke concentrations.

Vukasinovic-Pesic, V.; Rajakovic, L.J. [University of Montenegro, Podgorica (Montenegro)

2009-07-01

39

Deoiled asphalt as carbon source for preparation of various carbon materials by chemical vapor deposition  

Microsoft Academic Search

Various carbon materials, including vapor grown carbon fibers (VGCFs) and carbon trees, were synthesized by chemical vapor deposition in argon atmosphere, using deoiled asphalt as carbon source and ferrocene as catalyst. Pure carbon microbeads (CMBs) were also obtained by this method in the absence of ferrocene. The influence of different growth parameters, such as ferrocene content, reaction temperature, retention time

Xuguang Liu; Yongzhen Yang; Xian Lin; Bingshe Xu; Yan Zhang

2006-01-01

40

Integration of calcium and chemical looping combustion using composite CaO/CuO-based materials.  

PubMed

Calcium looping cycles (CaL) and chemical looping combustion (CLC) are two new, developing technologies for reduction of CO(2) emissions from plants using fossil fuels for energy production, which are being intensively examined. Calcium looping is a two-stage process, which includes oxy-fuel combustion for sorbent regeneration, i.e., generation of a concentrated CO(2) stream. This paper discuss the development of composite materials which can use copper(II)-oxide (CuO) as an oxygen carrier to provide oxygen for the sorbent regeneration stage of calcium looping. In other words, the work presented here involves integration of calcium looping and chemical looping into a new class of postcombustion CO(2) capture processes designated as integrated CaL and CLC (CaL-CLC or Ca-Cu looping cycles) using composite pellets containing lime (CaO) and CuO together with the addition of calcium aluminate cement as a binder. Their activity was tested in a thermogravimetric analyzer (TGA) during calcination/reduction/oxidation/carbonation cycles. The calcination/reduction typically was performed in methane (CH(4)), and the oxidation/carbonation stage was carried out using a gas mixture containing both CO(2) and O(2). It was confirmed that the material synthesized is suitable for the proposed cycles; with the very favorable finding that reduction/oxidation of the oxygen carrier is complete. Various schemes for the Ca-Cu looping process have been explored here that would be compatible with these new composite materials, along with some different possibilities for flow directions among carbonator, calciner, and air reactor. PMID:22022778

Manovic, Vasilije; Anthony, Edward J

2011-12-15

41

A new method to quantitatively evaluate the chemical composition of waterlogged wood by means of attenuated total reflectance Fourier transform infrared (ATR FT-IR) measurements carried out on wet material.  

PubMed

Wood degradation in waterlogged conditions, although slow, is relevant in some specific contexts, such as in the case of cultural heritage preservation (e.g., ancient shipwrecks found under the water table). This decay process induces the selective depletion of the biopolymers constituting wood cell walls and mainly of their structural polysaccharides (both cellulose and hemicelluloses). Assessment of residual composition of cell walls is normally carried out using conventional chemical analyses, which, however, require elevated amounts of material. The present work reports on a new approach to quantitatively determine the residual chemical composition of wood (in terms of amount of lignin and holocellulose) and therefore its extent of degradation. This was accomplished by acquiring attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectra on material still in waterlogged conditions, which was simply placed in optical contact with the ATR crystal. Data for the calibration set were obtained by means of wet analyses, and the calibration model was based on multivariate statistical analysis through partial least square regression. Acquired spectra showed signals higher and better resolved than for dry wood. Calibration was selected after comparing two different normalization procedures and after processing signals of two different spectral ranges. Furthermore, the exclusion of some outliers led to a substantial improvement in the error parameters (R(2) and root mean square error of cross validation) associated with the calibration model, thus allowing for the selection of the best model. The stability of this best model was also established by means of the leave-more-out method. Finally, a procedure of external validation confirmed that the proposed model also could be applied to similar (for instance, belonging to Pinaceae) wood remains from other excavations. PMID:23643045

Pizzo, Benedetto; Pecoraro, Elisa; Macchioni, Nicola

2013-05-01

42

Impact damage detection of composite materials by fiber Bragg gratings  

Microsoft Academic Search

Usage of fiber-optic Bragg gratings (FBG) for strain measurement is well-known technique in structural health monitoring (SHM). However, this technique based on shift of spectral peak, suffers from different spurious signals, particularly caused by thermal effect. We present here a method for impact damage detection of composite materials based on FBG without thermal disturbance. This method is based on the

Zoran Djinovic; Michael Scheerer; Milos Tomic

2011-01-01

43

Chemical composition and fatty acid content of some spices and herbs under Saudi Arabia conditions.  

PubMed

Some Saudi herbs and spices were analyzed. The results indicated that mustard, black cumin, and cress seeds contain high amount of fat 38.45%, 31.95% and 23.19%, respectively, as compared to clove (16.63%), black pepper (5.34%) and fenugreek (4.51%) seeds. Cress, mustard, black cumin and black pepper contain higher protein contents ranging from 26.61 to 25.45%, as compared to fenugreek (12.91%) and clove (6.9%). Crude fiber and ash content ranged from 6.36 to 23.6% and from 3.57 to 7.1%, respectively. All seeds contain high levels of potassium (ranging from 383 to 823 ?mg/100 g), followed by calcium (ranging from 75 to 270 ?mg/100 g), Magnesium (ranged from 42 to 102 ?mg/100 g) and iron (ranged from 20.5 to 65 ?mg/100 g). However, zinc, manganese and copper were found at low levels. The major fatty acids in cress and mustard were linolenic acid (48.43%) and erucic acid (29.81%), respectively. The lenoleic acid was the major fatty acid in black cumin, fenugreek, black pepper and clove oils being 68.07%, 34.85%, 33.03% and 44.73%, respectively. Total unsaturated fatty acids were 83.24, 95.62, 86.46, 92.99, 81.34 and 87.82% for cress, mustard, black cumin, fenugreek, black pepper and clove, respectively. The differences in the results obtained are due to environmental factors, production areas, cultivars used to produce seeds and also due to the different methods used to prepare these local spices. PMID:23319888

Al-Jasass, Fahad Mohammed; Al-Jasser, Mohammed Saud

2012-01-01

44

Superconducting properties, microstructure and chemical composition of MgB2 sheathed materials  

NASA Astrophysics Data System (ADS)

The superconducting properties, the microstructure and the chemical composition of sheathed MgB2 tapes and of one wire, all synthesized by the powder-in-tube method, were investigated. At 4.2 K critical current densities up to 105 A cm-2 (0 T) and 1.5 × 104 A cm-2 (2.5 T) were obtained by transport measurements in the wire and the tapes, respectively. In the MgB2 matrix of all samples, oxygen was identified and mole fractions of 0-10 at% were determined by electron probe microanalysis. It was found by scanning electron microscopy that only the tapes showed boron-rich secondary phases about 10 µm in size. Comparing different tapes, the critical currents increase with the aspect ratio and decrease with the oxygen mole fraction in the MgB2 material. In the tapes, aspect ratios were inhomogeneous and critical current densities at low fields were limited by insufficient thermal stabilization. For understanding the internal oxidation in the MgB2 tapes, one tape was investigated by analytical transmission electron microscopy (TEM). The combination of energy-dispersive x-ray spectroscopy and electron spectroscopic imaging in the TEM yielded phase maps of this sample. It showed a heterogeneous microstructure, MgB2 grain sizes ranged between 20 nm and 1 µm. Oxygen was primarily bound in 20 nm-1 µm MgO precipitates and secondary phases, and no boron oxides could be evidenced. Randomly distributed 50 nm-1 µm boron-rich secondary phases (MgB4+delta, MgB7+gamma) embedded in the MgB2 matrix were identified. The possible reasons for the oxidation of the superconducting matrix are discussed.

Eyidi, D.; Eibl, O.; Wenzel, T.; Nickel, K. G.; Schlachter, S. I.; Goldacker, W.

2003-07-01

45

SiC whisker/Si3N4 composites by a chemical mixing process  

SciTech Connect

A chemical mixing process has been developed for making SiC whisker/Si3N4 composites. The process involves in situ synthesis of SiC whiskers in Si3N4 powder by partial carbothermal reduction of silicon nitride in an argon atmosphere. The effects of reaction conditions and starting raw materials on the formation of SiC whiskers were studied. It has been demonstrated that the morphologies of the in situ synthesized whiskers can be modified by varying carbon-source materials and reaction conditions, and the amount of SiC formed in the product can be adjusted by changing the starting Si3N4-to-C ratio. The chemically mixed composite materials were densified by hot pressing with Y2O3 and Al2O3 as sintering aids. 12 refs.

Wang, Hongyu; Fischman, G.S.

1991-10-01

46

FY98 Final Report Initial Interfacial Chemical Control for Enhancement of Composite Material Strength  

Microsoft Academic Search

The U.S. Army Armament Research Development and Engineering Center (ARDEC) sponsored this research project to support the development of new self-assembled monolayer fiber coatings. These coatings can greatly increase the bond strength between the fiber and the resin matrix of a composite material. Composite ammunition components molded from such materials will exhibit higher strength than current materials, and will provide

GE Fryxell; KL Alford; KL Simmons; WD Samuels

1999-01-01

47

Associating Physical and Chemical Properties to Evaluate Buffer Materials by Th and U Sorption  

SciTech Connect

The physical and chemical properties of buffer materials to be used for a radwaste disposal repository should be evaluated prior to use. In a conventional approach, independent studies of physical and/or chemical characteristics are conducted. This study investigated the relationship between the plastic index (PI) and distribution ratio (Rd) of buffer materials composed of varying ratios of quartz sand and bentonite. Thorium (Th) and Uranium (U) were the nuclides of interest, and both synthetic groundwater and seawater were used as the liquid phases to simulate conditions representative of deep geological disposal within an island. Atterberg tests were used to determine PI values, and batch sorption experiments were employed to measure Rd values. The results show that Th reached maximum sorption behavior when the bentonite content exceeded 30 % of the mixture. Contrariwise, the sorption of U increased linearly with bentonite content, up to bentonite contents of 100%, and this correlation was present regardless of the liquid phase used. A further result is that U has a better additivity with respect to Rd than Th in both synthetic groundwater and synthetic seawater. These results will allow a determination of more effective buffer material composition, and improved estimates of the overall Rd of the buffer material mixture from the Rd of each mineral component.

Jan, Yi-Lin; Chen, Tzu-Yun; Cheng, Hwai-Ping; Hsu, Chun-Nan; Tseng, Chia-Liang; Wei,Yuan-Yaw; Yang, Jen-Yan; Ke, Cheng-Hsiung; Chuang, Jui-Tang; Teng, Shi-Ping

2003-02-27

48

Optimum conditions for composites fiber coating by chemical vapor infiltration  

SciTech Connect

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration (CVI). For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size, and properties of the reactant and product gases. It does not depend on the preform specific surface area, effective diffusivity or preform thickness, nor on the gas-phase yield of the deposition reaction. Further, this optimum pressure is unaltered by the additional constraint of a prescribed deposition uniformity. Optimum temperatures are obtained using an analytical expression for the optimum value along with numerical solutions to the governing transport equations. These solutions account for both diffusive and advective transport, as well as both ordinary and Knudsen diffusion. Sample calculations are presented for coating preform fibers with boron nitride.

Griffiths, S.K.; Nilson, R.H.

1997-04-01

49

Optimum conditions for composites fiber coating by chemical vapor infiltration  

SciTech Connect

A combined analytical and numerical method is employed to optimize process conditions for composites fiber coating by chemical vapor infiltration. For a first-order deposition reaction, the optimum pressure yielding the maximum deposition rate at a preform center is obtained in closed form and is found to depend only on the activation energy of the deposition reaction, the characteristic pore size, and properties of the reactant and product gases. It does not depend on the preform specific surface area, effective diffusivity or preform thickness, nor on the gas-phase yield of the deposition reaction. Further, this optimum pressure is unaltered by the additional constraint of a prescribed deposition uniformity. Optimum temperatures are obtained using an analytical expression for the optimum value along with numerical solutions to the governing transport equations. These solutions account for both diffusive and advective transport, as well as both ordinary and Knudsen diffusion. Sample calculations are presented for coating preform fibers with boron nitride.

Griffiths, S.K.; Nilson, R.H. [Sandia National Labs., Livermore, CA (United States)

1998-04-01

50

Effect of chemical degradation followed by toothbrushing on the surface roughness of restorative composites  

PubMed Central

Objectives The aim of the present study was to assess the effect of the exposure to food-simulating liquids prior to brushing simulation on the surface roughness of five composite materials (Quixfil, Filtek Supreme, Esthet-X, Filtek Z250, Tetric Ceram). Material and methods Twenty cylinders (5 mm diameter and 4 mm height) of each composite were randomly allocated to 4 groups (n=5), according to the food-simulating liquid in which they were immersed for 7 days at 37ºC: artificial saliva, heptane, citric acid, and ethanol. After this period, the top surface of composite cylinders was submitted to 7,500 brushing cycles (200 g load). Measurements of the surface roughness (Ra, µm) were carried out before and after the exposure to the chemicals/brushing simulation. Changes on the morphology of composite surfaces were observed through scanning electron microscopy (SEM). Results The statistical analysis (ANOVA with cofactor / Tukey's test, ?=5%) detected a significant interaction between solutions and composite resins. Esthet-X, Filtek Z250 and Tetric Ceram were not affected by the food-simulating liquids/toothbrushing. Citric acid and ethanol increased the surface roughness of Quixfil and Filtek Supreme, respectively. SEM images corroborate the surface roughness findings, demonstrating the negative effect from chemical solutions and mechanical abrasion. Conclusions The surface roughness of composite resin materials are differently affected by the food-simulating solutions, depending on the immersion media.

VOLTARELLI, Fernanda Regina; dos SANTOS-DAROZ, Claudia Batitucci; ALVES, Marcelo Correa; CAVALCANTI, Andrea Nobrega; MARCHI, Giselle Maria

2010-01-01

51

The effect of reheating conditions and chemical composition on ? ferrite content in austenitic stainless steel slabs  

Microsoft Academic Search

The specimens, selected from different locations of as-cast 304 stainless steel slab, were annealed according to the temperature profiles, which simulated the industrial re-heating process before hot rolling. Annealing, following thermal cycles with maximum temperatures between 1230 and 1270°C for a total time of 1 h, reduced the d ferrite content, increased the size of the individual ferrite island and

J. Y. Cho; F. Czerwinski; J. A. Szpunar

2000-01-01

52

/Al-4Cu Composite Material Produced by Squeeze Casting Method  

NASA Astrophysics Data System (ADS)

The wear behavior of a weight fraction of particles with up to 30 wt.% in situ AlB2 flakes reinforced in Al-4Cu matrix alloy composites and fabricated by a squeeze casting method was investigated in a pin-on-disk abrasion test instrument against different SiC abrasives at room conditions. Wear tests were performed under the load of 10 N against SiC abrasive papers of 80, 100, and 120 mesh grits. The effects of sliding speed, AlB2 flake content, and abrasive grit sizes on the abrasive wear properties of the matrix alloy and composites have been evaluated. The main wear mechanisms were identified using an optical microscope. The results showed that in situ AlB2 flake reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding speed and the abrasive grit size. The wear resistances of the composites were considerably bigger than those of the matrix alloy and increased with increases in in situ AlB2 flake contents.

Ficici, Ferit

2014-05-01

53

Fabrication of fiber reinforced ceramic composites by chemical vapor infiltration  

SciTech Connect

Ceramic fiber-ceramic matrix composites were prepared using the chemical vapor deposition (CVD) process. Our major goal of significantly reducing the infiltration times was accomplished. We have conceived a process, fabricated hardware, and demonstrated on a laboratory scale a process which permits CVD infiltration of an SiC fibrous preform with either an Si/sub 3/N/sub 4/ or SiC matrix in 2 to 12 h. The process should be applicable to infiltration of fibrous preforms prepared by slurry molding, stacking of layers of cloth, or filament winding. Two types of composites (SiC-Si/sub 3/N/sub 4/ and SiC-SiC) have been produced at densities of about 2.0 Mg/m/sup 3/ which was near the desired range. A scheme has also been conceived whereby the new infiltration process could be used for fabrication of tubes or hollow cylinders. This is an important advance since the ability to fabricate tubes or hollow cylinders would offer the hope that the process could be used for fabrication of toughened, high-strength heat exchanger tubes, heat engine cylinder liners and valve guides. 19 references, 7 figures, 1 table.

Caputo, A.J.; Lackey, W.J.

1984-01-01

54

The chemical composition and the content of volatile oil: potential factors that can contribute to the oxidative stability of Nigella sativa L. crude oil.  

PubMed

The crude oil of Nigella sativa L. (Black cumin) has well-known nutraceutical and pharmaceutical properties. The oil is prone to rapid oxidative deterioration because of its high content of poly-unsaturated fatty acids. In the current investigation, different cold-pressed crude oils of N. sativa were examined for their composition of fatty acids and oxidative stability. The data obtained were correlated with the chemical composition and content of volatile oils, which correspond to each crude oil. Results indicated that different crude oils have the same fatty acid composition, and linoleic acid was the major constituent (60.0-61.7%). Though, the oxidative stability index of the crude oils was different ranging from 2.5 hr to 26.9 hr, as revealed by the Rancimate test at 100°C and airflow rate of 20 ml/min. The results showed that there is a straightforward correlation between the volatile oil content and the oxidative stability of the corresponding parent crude oil. In addition, high ?-terpinene content in the constitution of volatile oil can also be another contributing factor for enhancing the oxidative stability of the crude oil. The data presented here draw attention to some important factors that may guide the nutraceutical and food supplement processors in their screening for the highest quality of Nigella crude oils with maximum health benefits. PMID:22432633

Edris, Amr E

2011-03-01

55

Radon diffusion coefficients in 360 waterproof materials of different chemical composition.  

PubMed

This paper summarises the results of radon diffusion coefficient measurements in 360 common waterproof materials available throughout Europe. The materials were grouped into 26 categories according to their chemical composition. It was found that the diffusion coefficients of materials used for protecting houses against radon vary within eight orders from 10(-15) to 10(-8) m(2) s(-1). The lowest values were obtained for bitumen membranes with an Al carrier film and for ethylene vinyl acetate membranes. The highest radon diffusion coefficient values were discovered for sodium bentonite membranes, rubber membranes made of ethylene propylene diene monomer and polymer cement coatings. The radon diffusion coefficients for waterproofings widely used for protecting houses, i.e. flexible polyvinyl chloride, high-, low-density polyethylene, polypropylene and bitumen membranes, vary in the range from 3 × 10(-12) to 3 × 10(-11) m(2) s(-1). Tests were performed which confirmed that the radon diffusion coefficient is also an effective tool for verifying the air-tightness of joints. PMID:21450700

Jiránek, M; Kotrbatá, M

2011-05-01

56

Explorating coupled production of dissolved organic material and methyl mercury in a tidal wetland using the intrinsic chemical composition of the organic material  

NASA Astrophysics Data System (ADS)

Elevated methyl mercury (MeHg) levels found in biota of the San Francisco Estuary have been attributed to methylation processes in the peat-rich tidal wetlands of the Estuary, where the concentration of dissolved organic matter (DOM) is tightly coupled to that of MeHg (r2=0.95). We sought to understand the geochemical processes that contribute to MeHg production by examining the composition of the co-occurring DOM. We measured spectral absorbance and fluorescence properties of DOM, as well as intrinsic chemical properties such as isotopic composition, lignin content, carbohydrate content, and bulk chemical functionality (by CPMAS-NMR). Carbon quality parameters independent of concentration such as specific UV absorbance, lignin abundance, aromatic content, biodegradability, and others were closely coupled to MeHg concentrations. This coupling, combined with the hydrologic forcing within the wetland, suggest that the zones of MeHg production are biogeochemically related to the zones of DOM release, thus providing a means to examine the underlying processes. The observed relationships were robust through the winter, spring, and fall seasons, despite a three- fold variation in MeHg and DOM concentration. The pattern of variation suggests sources of DOM and MeHg within peat pore waters rather than within the litter layer or water column. The various relationships with individual parameters will be discussed.

Bergamaschi, B. A.; Fleck, J. A.; Downing, B.; Stephenson, M.; Hernes, P. J.; Boss, E.

2007-12-01

57

Ultrafine-microstructure composites prepared by chemical vapor deposition. Final report, January 1987-December 1989  

SciTech Connect

In recent years material requirements have become more strict and sophisticated for many novel applications such as space vehicles, ultrasonic jets, ceramic heat engines, high performance cutting tools, etc. It is of great interest to prepare advanced ceramics that possess high temperature stability and strength. A major difficulty exists, however, as the traditional brittleness of ceramics often causes catastrophic failures, thus, limiting their wide usage. Dispersed phase ceramic composites appear to be one solution to this problem. The composites usually possess superior mechanical properties (e.g., fracture toughness, strength, resistance to wear and erosion, hardness, etc.) compared to those of single phase ceramics. The performance of dispersed phase ceramic composites is strongly related to their microstructures. Chemical vapor deposition (CVD) offers an alternative avenue of preparing ceramic composite in the form of coatings by either simultaneous deposition of multiple phases (i.e., codeposition) or by alternately depositing several phases. The major advantage of preparing phase ceramic composites by CVD is that mechanical as well as chemical, electrical, optical and thermal properties of the composites can be favorably tailored by controlling their composition and microstructure. The desired microstructure can be achieved by optimization of CVD process variables such as temperature, pressure, reagent concentration, substrate type, reactor geometry, etc. (KT)

Lackey, W.J.; Freeman, G.B.; Hanigofsky, J.A.; Thompson, J.R.; Gerard, G.J.

1989-12-01

58

Genetic alteration of soybean oil composition by a chemical mutagen  

Microsoft Academic Search

Soybean (Glycine max [L.] Merr. cv. Century) seeds were treated with ethylmethanesulfonate (EMS) and the M2 progeny were evaluated for fatty acid composition of the oil. Treatment with EMS significantly increased the variability\\u000a in content of each of the fatty acids in comparison with those of the Century control. There was a strong inverse relationship\\u000a between oleic and linoleic acids

J. R. Wilcox; J. F. Cavins; N. C. Nielsen

1984-01-01

59

Fabrication of fiber reinforced ceramic composites by chemical vapor infiltration  

Microsoft Academic Search

Ceramic fiber-ceramic matrix composites were prepared using the chemical vapor deposition (CVD) process. Our major goal of significantly reducing the infiltration times was accomplished. We have conceived a process, fabricated hardware, and demonstrated on a laboratory scale a process which permits CVD infiltration of an SiC fibrous preform with either an SiâNâ or SiC matrix in 2 to 12 h.

A. J. Caputo; W. J. Lackey

1984-01-01

60

Microbial growth on fiber reinforced composite materials  

Microsoft Academic Search

Microorganisms may be responsible for physical and chemical changes in composite materials. Inoculation of a fungal consortium to pre-sterilized coupons of five composites resulted in deep penetration into the interior of all materials at a temperature of approximately 22°C within 5 weeks. Scanning electron microscopy (SEM) showed that the inoculated composites were etched by the microorganisms. None of the five

Ji-Dong Gu; T. Ford; K. Thorp; R. Mitchell

1996-01-01

61

What controls the composition of weathered materials transported by large river systems (Invited)  

NASA Astrophysics Data System (ADS)

The critical zone of the Earth is a complex reactor where physical, biological and chemical processes interact to transform the crustal rocks into weathered materials. The river system is selectively transporting materials according to the intensity of physical erosion and the transport capacity of the river system it self. The main advantage of rivers is that they integrate the diversity of processes playing a role in the critical zone. However, using rivers to establish the fluxes of weathered material produced at the atmosphere-hydrosphere-geosphere interface requires a better understanding of the role of parameters such as the nature of the bedrock, the chemical weathering regimes, the physical conditions of transport and their interplay. Although all materials produced by chemical weathering should be exported out of the fluvial system, we are far from understanding the timescales and processes that operate between the top soil and the sea. We will present new results on the chemical and isotopic composition of suspended sediments and bedload sediments from the Amazon river system. Suspended sediments have been sampled along cross sections of the Amazon, Madeira and Solimoes rivers, at different depth in order to cover the whole range of physical conditions of transport. A considerable variability of composition is observed that clearly shows that surface suspended sediments, usually sampled, only poorly represent the chemical composition of the weathered material transported by the river. New estimates of chemical fluxes of material delivered to the ocean by the first largest river of the world can therefore be estimated. The results show that the composition of river sediments is not only controlled by present day chemical weathering conditions in the drainage basin, but also by the chemical history of the bedrock, and thus crustal recycling processes. There is a good correlation between grain size and the chemical composition of the Amazon river suspended sediments and this correlation can be extended to other large river systems such as the Ganges and Brahmaputra system. This new approach of considering the whole spectrum of grain size transported in river systems leads to revisit the classical notions of « weathering-limited » and « transport-limited » regimes of erosion.

Gaillardet, J.; Bouchez, J.; France-Lanord, C.; Maurice, L.

2009-12-01

62

Fatigue Crack Measurement in Composite Materials by Ultrasonic Methods  

NASA Technical Reports Server (NTRS)

The nondestructive detection of intra-ply microcracking in unlined pressure vessels fabricated from composite materials is critical to ensuring mission success. Microcracking in composite structures due to combined fatigue and cryogenic thermal loading can be very troublesome to detect in-service and when it begins to link through the thickness can cause leakage and failure of the structure. These leaks may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. The work presented herein develops a method and an instrument to locate and measure intraply fatigue cracking through the thickness of laminated composite material by means of correlation with ultrasonic resonance. Resonant ultrasound spectroscopy provides measurements which are, sensitive to both the microscopic and macroscopic properties of an object. Elastic moduli, acoustic attenuation, and geometry can all be probed. The approach is based on the premise of half-wavelength resonance. The method injects a broadband ultrasonic wave into the test structure using a swept frequency technique. This method provides dramatically increased energy input into the test article, as compared to conventional spike pulsed ultrasonics. This relative energy increase improves the ability to measure finer details in the materials character, such as micro-cracking and porosity. As the micro-crack density increases, more interactions occur with the higher frequency (small wavelength) components of the signal train causing the spectrum to shift toward lower frequencies. Preliminary experiments have verified a measurable effect on the resonance spectrum of the ultrasonic data to detect microcracking. Methods involving self organizing neural networks and other clustering algorithms show that the resonance ultrasound signatures from composites vary with the degree of microcracking and can be separated and identified.

Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.; Watson, Jason M.; Thom, Robert (Technical Monitor)

2002-01-01

63

Chemical Fingerprinting of Materials Developed Due to Environmental Issues  

NASA Technical Reports Server (NTRS)

Instrumental chemical analysis methods are developed and used to chemically fingerprint new and modified External Tank materials made necessary by changing environmental requirements. Chemical fingerprinting can detect and diagnose variations in material composition. To chemically characterize each material, fingerprint methods are selected from an extensive toolbox based on the material's chemistry and the ability of the specific methods to detect the material's critical ingredients. Fingerprint methods have been developed for a variety of materials including Thermal Protection System foams, adhesives, primers, and composites.

Smith, Doris A.; McCool, A. (Technical Monitor)

2000-01-01

64

Ultrafine-microstructure composites prepared by chemical vapor deposition. Annual report, January-December 1987  

SciTech Connect

The goal is to develop an analytical model that predicts the experimental conditions that permit the preparation of ultrafine-microstructure ceramic composites by chemical vapor deposition (CVD). The model is to be based on classical thermodynamics, mass transport, kinetic, nucleation, and growth theory. The model will be validated for two dispersed-phase composite systems. One system will be boron nitride plus aluminum nitride; the other hafnium diboride plus silicon carbide. The BN + AlN system is of interest for radomes, windows, and tribological applications while HfB2 + SiC offers potential as a high-temperature oxidation-resistant material including oxidation protective coatings for carbon-carbon composites. Thermodynamic analyses of the BN + AlN and the HfB/sub 2/ + SiC systems were completed. These computerized studies indicate that both composite systems can be prepared by codeposition using commercially available, conventional reagents.

Lackey, W.J.; Freeman, G.B.; Smith, A.W.; Thompson, J.R.; Gerard, G.J.

1987-12-01

65

Microstructure and properties of multiphase and functionally graded materials prepared by chemical vapor deposition  

SciTech Connect

The synthesis of multiphase and functionally graded materials by chemical vapor deposition is discussed from a perspective of controlling their composition and microstructure at a nano-scale level, and ultimately, tailoring their material properties. Prior research is briefly reviewed to address the current state of this novel material concept. Recent experimental results relating to controlling the selected properties of two multiphase systems, TiN + MoS{sub 2} and NiAl + Al{sub 2}O{sub 3}, are described to illustrate this concept`s potential merits and challenges for use in realistic applications.

Lee, W.Y.

1996-05-01

66

Contents and composition of organic matter in subsurface soils affected by land use and soil mineralogy  

NASA Astrophysics Data System (ADS)

Land use and mineralogy affect the ability of surface as well as subsurface soils to sequester organic carbon and their contribution to mitigate the greenhouse effect. This study aimed to investigate the long-term impact of land use (i.e., arable and forest) and soil mineralogy on contents and composition of soil organic matter (SOM) from subsurface soils. Seven soils different in mineralogy (Albic and Haplic Luvisol, Colluvic and Haplic Regosol, Haplic and Vertic Cambisol, Haplic Stagnosol) were selected within Germany. Soil samples were taken from forest and adjacent arable sites. First, particulate and water soluble organic matter were separated from the subsurface soil samples. From the remaining solid residues the OM(PY) fractions were separated, analyzed for its OC content (OCPY) and characterized by FTIR spectroscopy. For the arable subsurface soils multiple regression analyses indicate significant positive relationships between the soil organic carbon contents and the contents of i) exchangeable Ca and oxalate soluble Fe, and Alox contents. Further for the neutral arable subsurface soils the contents OCPY weighted by its C=O contents were found to be related to the contents of Ca indicating interactions between OM(PY) and Ca cations. For the forest subsurface soils (pH <5) the OCPY contents were positively related with the contents of Na-pyrophosphate soluble Fe and Al. For the acidic forest subsurface soils such findings indicate interactions between OM(PY) and Fe3+ and Al3+ cations. The effects of land use and soil mineralogy on contents and composition of SOM and OM(PY) will be discussed.

Ellerbrock, Ruth H.; Kaiser, Michael

2010-05-01

67

HDPE-HA composites synthetized by in situ polymerization with different filler content  

NASA Astrophysics Data System (ADS)

In Situ ethylene polymerization was used to synthesize high density polyethylene - hydroxyapatite (HDPE-HA) composites, employing Cp2ZrCl2/MAO as catalytic system. A good dispersion of HA into the HDPE matrix was obtained when the following synthesis conditions were combined: high stirring velocities (2000 rpm), low quantities of solvent (100 mL), and 10 °C. Under these conditions different filler content was used to synthetized HDPE-HA composites. An interaction between HA and HDPE was obtained by FTIR. On the other hand, thermal analysis indicated that no significant differences were observed between HDPE and the composites.

Hermán, V.; Karam, A.; Albano, C.; Romero, K.; González, G.

2012-07-01

68

Carotenoid composition and content of legumes, tubers and starchy roots by HPLC  

Microsoft Academic Search

As part of a series of studies on the analytical and nutritional aspects of carotenoids and retinoids in foods, seventeen types of legumes and their products and 9 tubers and starchy roots were studied for their carotenoid composition and content by HPLC. All samples were saponified and subsequently chromatographed using a reverse -phase HPLC method previously developed in this laboratory

Tee E-Siong; Goh Ah-Heng; Khor Swan-Choo

69

Effects of increasing concentrations of corn distiller's dried grains with solubles on the egg production, internal quality of eggs, chemical composition and nutrients content of egg yolk  

Microsoft Academic Search

The objective of this study was to determine the effects of feeding high levels of corn distiller's dried grains with solubles (DDGS) on egg production, internal quality of eggs, chemical composition and important nutrients content of egg yolk. Four diets were formulated to contain 0, 17, 35 or 50% corn DDGS in a corn and soybean meal base. A total

Hongyu Sun

2011-01-01

70

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

71

Thermomechanical properties of chemically modified graphene\\/poly(methyl methacrylate) composites made by in situ polymerization  

Microsoft Academic Search

The morphology and thermomechanical properties of composites of poly(methyl methacrylate) (PMMA) and chemically modified graphene (CMG) fillers were investigated. For composites made by in situ polymerization, large shifts in the glass transition temperature were observed with loadings as low as 0.05wt.% for both chemically-reduced graphene oxide (RG-O) and graphene oxide (G-O)-filled composites. The elastic modulus of the composites improved by

Jeffrey R. Potts; Sun Hwa Lee; Todd M. Alam; Jinho An; Meryl D. Stoller; Richard D. Piner; Rodney S. Ruoff

2011-01-01

72

Characterization of the chemical composition of polyisobutylene-based oil-soluble dispersants by fluorescence.  

PubMed

A novel methodology based on fluorescence quenching measurements is introduced to determine quantitatively the amine content of polyisobutylene succinimide (PIBSI) dispersants used as engine oil-additives. To this end, a series of five PIBSI dispersants were prepared by reacting 2 mol equiv of polyisobutylene succinic anhydride (PIBSA) with 1 mol equiv of hexamethylenediamine (HMDA), diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine to yield the corresponding b-PIBSI dispersants. After having demonstrated that the presence of hydrogen bonds between the polyamine linker and the succinimide carbonyls of the dispersants prevents the quantitative analysis of the (1)H NMR and FTIR spectra of the dispersants to determine their chemical composition, alternative procedures based on gel permeation chromatography (GPC) and fluorescence quenching were implemented to estimate the amine content of the b-PIBSI dispersants. Taking advantage of the doubling in size that occurs when 2 mol of PIBSA are reacted with 1 mol of HMDA, a combination of GPC and FTIR was employed to follow how the chemical composition and molecular weight distribution of the polymers produced evolved with the reaction of PIBSA and HMDA mixed at different molar ratios. These experiments provided the PIBSA-to-HMDA molar ratio yielding the largest b-PIBSI dispersants and this molar ratio was then selected to prepare the four other dispersants. Having prepared five b-PIBSI dispersants with well-defined secondary amine content, the fluorescence of the succinimide groups was found to decrease with increasing number of secondary amines present in the polyamine linker. This result suggests that fluorescence quenching provides a valid method to determine the chemical composition of b-PIBSI dispersants which is otherwise difficult to characterize by standard (1)H NMR and FTIR spectroscopies. PMID:24628080

Pirouz, Solmaz; Wang, Yulin; Chong, J Michael; Duhamel, Jean

2014-04-10

73

Combinatorial approach for ferroelectric material libraries prepared by liquid source misted chemical deposition method  

PubMed Central

Combinatorial approach for discovering novel functional materials in the huge diversity of chemical composition and processing conditions has become more important for breakthrough in thin film electronic and energy-conversion devices. The efficiency of combinatorial method depends on the preparation of a reliable high-density composition thin-film library. The physico-chemical properties of each sample on the library should be similar to those of the corresponding samples prepared by one-by-one conventional methods. We successfully developed the combinatorial liquid source misted chemical deposition (LSMCD) method and demonstrated its validity in screening the chemical composition of Bi3.75LaxCe0.25-xTi3O12 (BLCT) for high remanent polarization (Pr). LSMCD is a cheap promising combinatorial screening tool. It can control the composition up to ppm level and produce homogeneous multicomponent library. LSMCD method allows us to prepare BLCT thin-film library at the variation of 0.4 mol% of La. Maximum 2Pr is 35 ?C/cm?2 at x = 0.21. The intensity of (117) XRD peak is quantitatively related to 2Pr. Newly developed scanning piezoelectric deformation measurement for nano-sized samples using scanning probe microscope (SPM) is also found out to be reliable for determining the relative ranking of Pr value rapidly.

Kim, Ki Woong; Jeon, Min Ku; Oh, Kwang Seok; Kim, Tai Suk; Kim, Yun Seok; Woo, Seong Ihl

2007-01-01

74

High performance 3D textile Hi-Nicalon SiC\\/SiC composites by chemical vapor infiltration  

Microsoft Academic Search

Three dimensional textile Hi-Nicalon silicon carbide fiber reinforced silicon carbide composites with high toughness and reliability were fabricated by chemical vapor infiltration. The mechanical properties of the composite materials were investigated under bending, shear, and impact loading. The density of the composites was 2.5 g cm?3 after the three dimension silicon carbide perform has been infiltrated for 30 h. The

Yongdong Xu; Laifei Cheng; Litong Zhang; Xiaowei Yin; Hongfeng Yin

2001-01-01

75

Use of near infrared spectroscopy for estimating meat chemical composition, quality traits and fatty acid content from cattle fed sunflower or flaxseed.  

PubMed

This study tested the ability of near infrared reflectance spectroscopy (NIRS) to predict meat chemical composition, quality traits and fatty acid (FA) composition from 63 steers fed sunflower or flaxseed in combination with high forage diets. NIRS calibrations, tested by cross-validation, were successful for predicting crude protein, moisture and fat content with coefficients of determination (R(2)) (RMSECV, g·100g(-1) wet matter) of 0.85 (0.48), 0.90 (0.60) and 0.86 (1.08), respectively, but were not reliable for meat quality attributes. This technology accurately predicted saturated, monounsaturated and branched FA and conjugated linoleic acid content (R(2): 0.83-0.97; RMSECV: 0.04-1.15mg·g(-1) tissue) and might be suitable for screening purposes in meat based on the content of FAs beneficial to human health such as rumenic and vaccenic acids. Further research applying NIRS to estimate meat quality attributes will require the use on-line of a fibre-optic probe on intact samples. PMID:24976561

Prieto, N; López-Campos, O; Aalhus, J L; Dugan, M E R; Juárez, M; Uttaro, B

2014-10-01

76

Development of a new, faster process for the fabrication of ceramic fiber-reinforced ceramic composites by chemical vapor infiltration  

SciTech Connect

A new, faster process was developed for the fabrication of ceramic fiber-reinforced, ceramic-matrix composites by chemical vapor infiltration. Process and equipment improvements led to the fabrication of preforms with a higher fiber content, and infiltration improvements led to reduced infiltration run times and increased infiltrated densities. These improvements have produced composites with not only higher flexural strengths but also high strain values.

Caputo, A.J.; Lackey, W.J.; Stinton, D.P.

1985-01-01

77

Chemical composition of organic matter in extremely acid, lignite-containing lake sediments impacted by fly ash contamination.  

PubMed

In the Lusatian lignite mining district of eastern Germany, extremely acid lakes developed during ground water rising after exploitation of lignite in open-cast mines. The reasons of plant colonization (Juncus bulbosus L.) of some lakes exhibiting moderate pH values while others remain extremely acid and unvegetated are unknown. Alkalinity gain may be achieved by addition of alkaline materials and/or decomposition of organic matter. Our objective was to examine fly ash deposition and the resulting changes in organic matter composition in the uppermost 0 to 5 cm of the sediment sampled from vegetated and unvegetated lakes. Bulk soil and particle size fractions were analyzed for elemental composition, magnetic susceptibility, and chemical structure of the organic matter by 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. The lignite content of the samples was estimated by 14C activity measurements. The pH values decreased with increasing depth and the changes in pH were found to be correlated with changes in magnetic susceptibility. Carbon and nitrogen contents were found to decrease with increasing depth. The C to N ratios are consistent with the (i) the presence of decomposing plant residues and/or microbial material such as algae in the upper 0 to 5 cm of the sediment and (ii) the dominance of lignite in the layers below this depth as confirmed by 14C activity measurements. The structural analyses of the particle size separates from the 0- to 5-cm depth were consistent with the presence of organic matter derived from plant material. This study confirms that fly ash is an important source of alkalinity in the upper 0 to 5 cm of the sediment that enhanced plant growth and led to enrichment of the sediment with organic matter derived from plant material. PMID:15074815

Chabbi, A; Rumpel, C

2004-01-01

78

Regulating continent growth and composition by chemical weathering  

USGS Publications Warehouse

Continents ride high above the ocean floor because they are underlain by thick, low-density, Si-rich, and Mg-poor crust. However, the parental magmas of continents were basaltic, which means they must have lost Mg relative to Si during their maturation into continents. Igneous differentiation followed by lower crustal delamination and chemical weathering followed by subduction recycling are possible solutions, but the relative magnitudes of each process have never been quantitatively constrained because of the lack of appropriate data. Here, we show that the relative contributions of these processes can be obtained by simultaneous examination of Mg and Li (an analog for Mg) on the regional and global scales in arcs, delaminated lower crust, and river waters. At least 20% of Mg is lost from continents by weathering, which translates into >20% of continental mass lost by weathering (40% by delamination). Chemical weathering leaves behind a more Si-rich and Mg-poor crust, which is less dense and hence decreases the probability of crustal recycling by subduction. Net continental growth is thus modulated by chemical weathering and likely influenced by secular changes in weathering mechanisms. ?? 2008 by The National Academy of Sciences of the USA.

Lee, C. -T. A.; Morton, D. M.; Little, M. G.; Kistler, R.; Horodyskyj, U. N.; Leeman, W. P.; Agranier, A.

2008-01-01

79

Policosanol content and composition in perilla seeds.  

PubMed

Policosanols, long-chain alcohols, have many beneficial physiological activities. Contents and compositions in perilla seeds (Perilla frutescens) produced in Korea and China were determined. Waxy materials were extracted from perilla seeds using hot hexane. Yield of the waxy materials from perilla seeds was 72.1 mg/100 g of dry weight. Contents and compositions of the waxy materials and policosanols were identified and quantified by TLC, HPLC, and GC. Major components of the waxy materials from Korean and Chinese perilla seeds were policosanols (25.5 and 34.8%, respectively), hydrocarbons (18.8 and 10.5%), wax esters, steryl esters and aldehydes (53.0 and 49.8%), acids (1.7 and 2.1%), and triacylglycerols (1.0 and 2.9%), determined by HPLC. For comparison, waxy materials of sesame seeds were also analyzed. Yield of the waxy materials from sesame seeds were 8.6 mg/100 g. Less than 5% policosanols were detected in the waxy materials extracted from sesame seeds produced in Korea and China. Wax esters or steryl esters accounted for 93-95% of the sesame waxy materials. Policosanols in the perilla seeds were composed of 67-68% octacosanol, 16-17% hexacosanol, 6-9% triacontanol, and others. PMID:16848517

Adhikari, Prakash; Hwang, Keum Taek; Park, Jae Nam; Kim, Choong Ki

2006-07-26

80

Optimization model coupling both chemical compositions and high-temperature characteristics of sintering materials for sintering burden  

NASA Astrophysics Data System (ADS)

We developed a mathematical optimization model coupling chemical compositions and high-temperature characteristics of sintering materials, targeting the best quality and lowest cost. The simplex algorithm was adopted to solve this model. Four kinds of imported iron ores, two kinds of Chinese iron ore concentrates, and two kinds of fluxes were selected to verify both the model and the algorithm. The results confirmed the possibility of considering both chemical compositions and high-temperature characteristics of iron ores in the optimization model. This model provides a technical roadmap to obtain a precise mathematical correlation between the lowest cost and the grade of iron in sinters based on the condition of given raw materials, which can provide a reference to adjust the grade of iron in the sintering process for enterprise.

Li, Ke-jiang; Zhang, Jian-liang; Liu, Zheng-jian; Su, Bu-xin; Kong, Ling-tan; Yang, Tian-jun

2014-03-01

81

The Effects of Cladding Chemical Composition on Corrosion Behavior of High Burnup BWR Fuel (Corrosion Properties of Low Iron and Low Silicon Content Cladding)  

SciTech Connect

A pool-side oxide thickness measurement campaign for a number of high burnup fuels in some Japanese commercial BWRs has been conducted, in order to study a higher oxide thickness phenomenon observed on a high burnup 9x9 fuel Type B, which was fabricated by NFI and was irradiated in a BWR of TEPCO. The results showed that the combination of cladding chemical composition, irradiation period and coolant environment affected the corrosion behavior of fuel cladding. Cladding with low iron and low silicon content, which has been shown to have inferior corrosion properties, is no longer used for the fuel assemblies loaded in operating Japanese BWRs today and in the future, so this kind of cladding corrosion phenomenon will not occur. This paper describes the results of the oxide thickness measurement, which was performed as a joint study by TEPCO and NFI. (authors)

Otsuka, Yasuyuki; Abe, Moriyasu [Tokyo Electric Power Company (TEPCO), 1-1-3, Uchisaiwai-cho, Chiyoda-ku, Tokyo 100-8560 (Japan); Kakiuchi, Kazuo; Fukuda, Takuji; Ohira, Koichi; Itagaki, Noboru [Nuclear Fuel Industries, Ltd. (NFI), 3135-41, Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1196 (Japan)

2007-07-01

82

Improved fiber-reinforced SiC composites fabricated by chemical vapor infiltration  

SciTech Connect

Fabrication of fiber-reinforced composites by a patented chemical vapor infiltration process has continued. Modifications to the process used for infiltration of unidirectional preforms resulted in more uniform matrix deposition throughout the preform and improved mechanical properties of the composites. Infiltration of improved cloth preforms containing more uniform porosity resulted in composites with fewer and smaller voids.

Stinton, D.P.; Caputo, A.J.; Lowden, R.A.; Besmann, T.M.

1986-01-01

83

Mechanical and chemical consequences of through thickness thermal gradients in polyimide matrix composite materials  

Microsoft Academic Search

Composite material parts may be exposed during their service life to through thickness temperature gradients where the difference between the inner and outer faces may exceed 150°C. The effect of these conditions on 4,4?-bismaleimidodiphenylmethane and diallylbisphenol-A based BMI resin reinforced with glass fabrics was investigated as a function of location through the laminate thickness. It was found that a gradient

E. Drukker; A. K. Green; G. Marom

2003-01-01

84

Chemical composition and mineralogy of borate from Rio Grande deposit, Uyuni (Bolivia) as raw materials for industrial applications  

NASA Astrophysics Data System (ADS)

Bolivia has large tailings as a result of the historic and present-day Sn mining activity developed extensively in that country. Tailings produced in these mining activities have an appropriate composition to reprocess them and make silicate glass and glass-ceramics, obtaining the valorization of wastes and reducing the visual and chemical impact. Reprocessing the wastes to make glass and glass-ceramics prevents the leaching of heavy metals from those wastes because they are retained in the structure of the glass. Furthermore, an option to increase the economic value of these glasses is the introduction of boron and other additives to produce borosilicate glass. In this study a characterization of the Rio Grande borate deposit for its use in the manufacture of borosilicate glass is presented. Mineralogy was determined by X-ray diffraction (XRD), and Fourier transforms infrared spectroscopy (FTIR); textures were observed by scanning electron microscopy (SEM) and chemical composition was determined by inductively coupled plasma mass spectrometry (ICP-MS). The Rio Grande borate deposit is located in an area of about 50 km2 close to the south of the Salar of Uyuni, in the Río Grande de Lípez Delta. Borates occur in the contact between fluvio-deltaic and lacustrine sediments from water raising the surface by capillarity. The borates crop out in an extent area but towards the west they are covered by fluvio-deltaic sediments, which can be up to 2 m thick. These borates occur as lenses 50-100 m in diameter and layers up to 1 m thick. They usually form brittle nodules with a cotton-ball texture. Chemical composition of the Rio Grande borates is CaO, 11.82-13.83 wt%; Na2O, 13.50-19.35 wt%; K2O, 0.05- 1.04 wt%; MgO, 0.42-1.46 wt%; B2O3, 36.21-42.60 wt%; SiO2, up to 0.53 wt% and SO2, up to 0.60 wt%. Trace elements are low: Sr content is between 151-786 ppm, Al 12-676 ppm, Mn between 1-17 ppm, As 2-10 ppm and Fe between 9-376 ppm. The most abundant borate mineral in this deposit is ulexite (NaCaB5.5H20), halite can reach up to 17 wt% and gypsum up to 1.2 wt.%. Calcite occurs in minor contents. Ulexite exhibits a fibrous morphology with fibers oriented parallel each other. Purity of borates from the Rio Grande deposits makes them suitable for the most restrictive applications. Chemistry of these borates is in accordance with the necessary composition for obtaining borosilicate glasses. Acknowledgements: This work was partly financed by the project AECID: A3/042750/11, and the SGR 2009SGR-00444.

Guillen Vargas, Julio; Arancibia, Jony Roger Hans; Alfonso, Pura; Garcia-Valles, Maite; Parcerisa, David; Martinez, Salvador

2014-05-01

85

Defining the chemical role of H2O in mantle melts: Effect of melt composition and H2O content on the activity of SiO2  

NASA Astrophysics Data System (ADS)

Quantifying the influence of volatiles (H2O, CO2) on the chemistry of mantle melts is a critical aspect of understanding the petrogenesis of arc magmas. A significant amount of experimental work done on the effect of H2O on the solidii of various mantle compositions, as well as on multiple saturation points of various primitive melts, has shown that H2O stabilizes olivine with respect to orthopyroxene. Or, in other words, at constant activity of SiO2, the presence of H2O decreases the activity coefficient of SiO2 in the melt, potentially leading to mantle melts that have suprisingly high SiO2 contents (Carmichael, 2002). Quantification and modelling of this behavior in hydrous silicate melts in equilibrium with the mantle have proven problematic, due mainly to a relatively small set of experiments that allow this type of thermodynamic analysis, and because of the experimental and analytical difficulties of dealing with hydrous high P-T samples (e.g. quench to a glass, rapid melt-solid reaction on quench, electron beam sensitivity of resulting glass, volatile content determination, etc). A further complication in the existing data includes co-variance of important experimental parameters (e.g. T and H2O content), making robust statistical regression analysis difficult and potentially misleading. We present here results of high P-T experiments conducted at a single pressure and temperature (1.0 GPa, 1200 deg C) that have the specific goal of quantifying the effect of H2O, as well as other melt components, on the activity coefficient of SiO2 in mantle melts. Using a "sandwich" type experiment, basaltic melts are saturated with an olivine plus orthopyroxene mineral assemblage with varying H2O and CO2 contents. The resulting samples have their bulk solid phase and glass compositions determined using EPMA, and the volatile content of the glass is determined by FTIR. The activity of SiO2 is then calculated using the olivine and orthopyroxene compositions. This value is then used, along with the mole fraction of SiO2 that is measured in the glass, to calculate an activity coefficient for SiO2 in that particular melt. The results show that for two starting compositions, H2O clearly has a strong negative effect on the activity coefficient of SiO2, consistent with some earlier intepretations. Further work is being conducted on differing starting compositions, as well as increasing the range of volatile contents, in order to better quantify their influence on this important chemical parameter of mantle melts. Ultimately, these experiments will help determine whether hydrous arc lavas, including high-Mg andesites, can be attributed to a primitive mantle origin, or whether other magmatic processes are necessary to generate their observed bulk compositions. It will also quantify the amount of H2O necessary to generate such magmas, giving insight into the potential H2O content present in the sub-arc mantle source regions, and allowing a more precise estimate of volatile fluxes in volcanic arc settings.

Moore, G.; Roggensack, K.

2007-12-01

86

Material Removal By Chemical Mechanical Polishing-A Review  

NASA Astrophysics Data System (ADS)

Polishing, the most expensive machining processes, in terms time and labor costs depending on the required surface finish, optic size, and amount of surface roughness from preceding machining operations. A material could remain on the polishing system for hours to days. Thus, attempting to understand the underlying mechanisms and basic science associated with the polishing process is crucial to, in turn, develop methods and procedures to reduce cost, trim schedule, and bolster performance. With an increased need for low surface roughness optics, as in x-ray and enhanced ultra-violet applications, it is imperative to understand the impacts of changing system variables. This paper reviews mechanism of chemical-mechanical polishing (CMP),to provide some interlinking data that can be used to many fundamental aspects of the CMP mechanism ,in turn can predict process responses, e.g., material removal rate, non-uniformity across the wafer, dielectric erosion and metal dishing. This review will provide a new platform for further investigation in CMP mechanism of material removal.

Sivanandini, M.; Dhami, S. S.; Pabla, B. S.

2012-10-01

87

Chemical composition and physicochemical properties of barley dietary fiber by chemical modification.  

PubMed

Chemical modification of dietary fiber (DF), extracted from whole grain barley, was carried out to obtain cross-linked (CL) DF, carboxymethyl (CM) DF, and hydroxypropyl (HP) DF. The DF components, physicochemical properties, and subsequent influence on the in vitro digestibility of wheat starch gels were comparatively investigated. The redistribution of fiber components from chemically modified DF was observed. An increase in the total DF (TDF) content of CL- and HP-DF was observed, which was mainly due to an increase of insoluble DF. Carboxymethylation led to an appreciable increase of soluble DF (1.17-6.20%) but TDF contents slightly decreased. Chemical modification of barley DF led to increases in arabinose (7.1-11.5%) and xylose (10.7-17.5%), but glucose contents decreased (67.4-79.9%). The treatments, especially carboxymethylation, effectively (P<0.05) increased hydration properties (e.g. water solubility, swelling power, and water absorption index). Substitution of 5% wheat starch with CL-, and HP-DF led to decreased in vitro digestibility in comparison to the control starch. Our results suggest that chemical modification improve the DF characteristics of barley and to exploit its potential application as a functional ingredient in fiber-rich products. PMID:23817090

Park, Ka Hwa; Lee, Kwang Yeon; Lee, Hyeon Gyu

2013-09-01

88

[An experimental study on transcoronary chemical ablation: comparison of ventricular tachyarrhythmias induced by chemical ablation according to different chemical materials].  

PubMed

The purpose of this study was to compare heart rate, appearance rate and duration of ventricular tachycardia (VT) by transcoronary chemical ablation using 95% ethanol and 1% aethoxysclerol respectively. After the balloon which was guided to the left or right coronary artery with PTCA technique in anesthetized dogs was inflated, chemical ablation was performed using ethanol (n = 5) or aethoxysclerol (n = 5). These chemicals were administered at 0.05 ml/sec with total dose of 0.50-1.50 ml. A quadripolar electrode catheter was used to record the intracardiac electrogram. VT occurred in all dogs (100%) after the administration of both ethanol and aethoxysclerol. In one dog using ethanol, VT developed into ventricular fibrillation, resulting in death. In dogs using aethoxysclerol, the heart rate and duration of VT were significantly lower and shorter than in those using ethanol (p < 0.05). There were no significant differences determined histologically in the ablated lesions caused by these different chemicals. We conclude that the severity of VT induced in all subjects by chemical ablation is different according to the materials applied, and that aethoxysclerol seems to be safer in comparison with ethanol. PMID:8484054

Ikeda, T; Ninomiya, K; Sugi, K; Enjoji, Y; Abe, R; Yabuki, S; Yamaguchi, T; Takahashi, K; Naoe, S

1993-05-01

89

Chemical Composition by the APXS along the Downhill Traverse of the Mars Exploration Rover Spirit at Gusev Crater  

NASA Technical Reports Server (NTRS)

The Alpha Particle X-ray Spectrometer (APXS) onboard the Mars Exploration Rover Spirit continues to determine the elemental composition of samples at Gusev Crater. Starting around sol 600 the rover descended Husband Hill, which is part of the Columbia Hills, visited the inner basin with a large dune field, called 'El Dorado', and parked at Low Ridge to conserve energy during the martian winter. Many unique samples were discovered by the instruments onboard Spirit during her downhill traverse. Here, we report only on the chemical data obtained by the APXS. The compositions of some of the soil samples are comparable to the mean soil determined along the earlier traverse. However, a light-toned subsurface sample (disturbed by the rover wheels), called Dead Sea Samra , showed the highest sulfur content of all soil samples, the lowest Na, Mg, Al, Cl, K, Ca, Ti, Mn, and Zn, among the lowest Si and P, and among the highest Cr, Fe and Ni. Assuming ferric sulfate as a major mineral, large amounts of a pure silica phase must be present. Color and quantity of Dead Sea Samra resemble somewhat an earlier soil called Paso Robles , though the latter is a mixture of sulfates with phosphate-rich soil. Manganese in Dead Sea Samra is so low that the Fe/Mn ratio exceeds 300, a value that has never been found previously on Mars (Fe/Mn ratio of 46 for Gusev basalts), indicating that only Fe(3+) occurs. The dune field El Dorado contained granulated material that exhibited the highest Mg and Ni concentrations and the lowest S and Cl compared to all other soils implying an enrichment of olivine-rich sands. Two outcrops, called Algonquin and Comanche , revealed compositions that differ significantly from those of earlier outcrops as they have the highest concentrations of Mg, Fe, and Ni (except for Ni in Independence) and the lowest of Al, K (detection limit), Ca, and Ti of all brushed and almost all abraded rocks. Normative estimates assign them the highest olivine contents ever found for martian rocks and a very mafic nature based on their high Mg/(Mg+Fe) and low Al, Ca and Na. Their significantly high Ni contents point to a different source than the Gusev plains basalts. The elemental compositions of samples encountered during the downhill traverse revealed a larger chemical diversity of the Columbia Hills than the uphill trek already published.

Bruckner, J.; Dreibus, G.; Gellert, R.; Clark, B.C.; Cohen, B.; McCoy, T.; Ming, D.W.; Mittlefehldt, D.W.; Yen, A.; Athena Science Team

2006-01-01

90

Numerical simulation of isothermal chemical vapor infiltration process in fabrication of carbon-carbon composites by finite element method  

Microsoft Academic Search

The chemical vapor infiltration process in fabrication of carbon-carbon composites is highly inefficient and requires long\\u000a processing time. These limitations add considerably to the cost of fabrication and restrict the application of this material.\\u000a Efforts have been made to study the CVI process in fabrication of carbon-carbon composites by computer simulation and predict\\u000a the process parameters, density, porosity, etc. According

Kezhi Li; Hejun Li; Kaiyu Jiang; Xianghui Hou

2000-01-01

91

Effects of coal rank on the chemical composition and toxicological activity of coal liquefaction materials  

SciTech Connect

This report presents data from the chemical analysis and toxicological testing of coal liquefaction materials from the EDS and H-Coal processes operated using different ranks of coal. Samples of recycle solvent from the bottoms recycle mode of the EDS direct coal liquefaction process derived from bituminous, sub-bituminous, and lignite coals were analyzed. In addition, the H-Coal heavy fuel oils derived from bituminous and sub-bituminous coals were analyzed. Chemical methods of analysis included adsoprtion column chromatography, high-resolution gas chromatography, gas chromatography/mass spectrometry, and low-voltage probe-inlet mass spectrometry. The toxicological activity of selected samples was evaluated using the standard microbial mutagenicity assay, an initiation/promotion assay for mouse-skin tumorigenicity, and a static bioassy with Daphnia magna for aquatic toxicity of the water-soluble fractions. 22 refs., 16 figs., 14 tabs.

Wright, C.W.; Dauble, D.D.

1986-05-01

92

Properties of a surface contaminated by gaseous products of polymer composition materials under vacuum conditions  

NASA Astrophysics Data System (ADS)

Optical properties and chemical composition of a surface that is contaminated by molecular flows consisting of gaseous products of polymer composition materials (e.g., EKOM-2 enamel) are experimentally studied. The polymer materials are irradiated using a short-wavelength source with a luminous intensity of 6 × 10-4 W/cm2 sr in the wavelength interval 90-320 nm in a vacuum chamber that is evacuated to a pressure of 10-4-10-3 Pa. An analytical solution is obtained for the problem of radiation fluxes in scattering and absorbing medium of precipitate on a mirror surface, and a relation of model absorption and scattering coefficients for optical radiation in such medium and transport coefficients of the Gurevich theory of turbid medium is demonstrated.

Kalashnikov, E. V.; Kalashnikova, S. N.; Tomeev, K. A.

2014-02-01

93

Chemical composition and biological value of spray dried porcine blood by-products and bone protein hydrolysate for young chickens  

Microsoft Academic Search

1. The chemical composition of spray dried porcine blood by-products is characterised by wide variation in crude protein contents. In spray dried porcine blood plasma (SDBP) it varied between 670–780?g\\/kg, in spray dried blood cells (SDBC) between 830–930?g\\/kg, and in bone protein hydrolysate (BPH) in a range of 740–780?g\\/kg. Compared with fish meal, these feeds are poor in Met and

D. Jamroz; A. Wiliczkiewicz; J. Orda; J. Skorupi?ska; M. S?upczy?ska; J. Kuryszko

2011-01-01

94

Chemical composition topography in RE hexaboride crystals obtained by various solution-melt methods  

NASA Astrophysics Data System (ADS)

An extensive step-by-step study of the chemical composition of rare-earth metal (RE) hexaboride single crystals and their solid solutions has done. The EDX and WDX methods were used for this study. The composition topography of the surface has been investigated in two directions: along the length and breadth of the crystals. It was done for two times: after separation from the Al matrix and after an additional etching and polishing. There was a considerable dispersion of data in the crystals obtained using the solution-melt methods (the conventional and the immiscibility gap method), and also the liquid-phase method (floating zone). An assumption that the direction of growth of single crystals is opposite to the direction of monotonic change of the boron content has been suggested. We have concluded that all single crystals of RE hexaboride grown by different methods are significantly different on composition. This conclusion was made due to the respective relative position of the stoichiometry line and the homogeneity region of the compound which crystals have been obtained.

Gurin, Vladimir; Konovalov, Mihail; Kuzanyan, Armen; Petrosyan, Vahagn; Burkhardt, Ulrich; Grin, Juri

2012-11-01

95

Fabrication of composite alloy cladding material by brazing process  

Microsoft Academic Search

In this paper, hard cladding material used for low-carbon steel was developed at 1150°C by using a brazing process so as to improve surface abrasiveness of common steel castings. The macrohardness of the cladding material after heat treatment was up to HRC50–69. Copper-based alloy was used as the brazing alloy in this technique. The microstructure of the cladding material was

Xia Zhou; Guohui Qu; Jiyang Zhou; Xiwen Wang

2005-01-01

96

Biosorption of heavy metal ions from aqueous solutions by short hemp fibers: Effect of chemical composition.  

PubMed

Sorption potential of waste short hemp fibers for Pb(2+), Cd(2+) and Zn(2+) ions from aqueous media was explored. In order to assess the influence of hemp fiber chemical composition on their heavy metals sorption potential, lignin and hemicelluloses were removed selectively by chemical modification. The degree of fiber swelling and water retention value were determined in order to evaluate the change in accessibility of the cell wall components to aqueous solutions due to the fiber modification. The effects of initial ion concentration, contact time and cosorption were studied in batch sorption experiments. The obtained results show that when the content of either lignin or hemicelluloses is progressively reduced by chemical treatment, the sorption properties of hemp fibers are improved. Short hemp fibers are capable of sorbing metal ions (Pb(2+), Cd(2+) and Zn(2+)) from single as well as from ternary metal ion solutions. The maximum total uptake capacities for Pb(2+), Cd(2+) and Zn(2+) ions from single solutions are the same, i.e. 0.078mmol/g, and from ternary mixture 0.074, 0.035 and 0.035mmol/g, respectively. PMID:18778893

Pejic, Biljana; Vukcevic, Marija; Kostic, Mirjana; Skundric, Petar

2009-05-15

97

Composite Materials Handbook  

NSDL National Science Digital Library

From the US Army Research Laboratory, Materials Sciences Corporation, and University of Delaware Center for Composite Materials, the Composite Materials Handbook provides the "information and guidance necessary to design and fabricate end items from composite materials." Along with current information on the material properties of these composite materials, the handbook also includes data development and usage guidelines. The information has been divided into three areas: polymer, metal, and ceramic matrix composites. The Polymer Matrix Composites Handbook (three volumes including Guidelines for Characterization of Structural Materials; Material Properties; and Materials Usage, Design, and Analysis) and the Metal Matrix Composites Handbook (one volume, .pdf) are available here. The Ceramic Matrix Composites Handbook has yet to be completed. Users may also download Quick Composites Data in spreadsheet format.

98

Computing Equilibrium Chemical Compositions  

NASA Technical Reports Server (NTRS)

Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

Mcbride, Bonnie J.; Gordon, Sanford

1995-01-01

99

Water defluoridation by aluminium oxide-manganese oxide composite material.  

PubMed

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water. PMID:24956783

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

100

The effect of varying Al2O3 percentage in hydroxyapatite/Al2O3 composite materials: morphological, chemical and cytotoxic evaluation.  

PubMed

Hydroxyapatite (HA) and HA-alumina (HA/Al2O3) composites, with Al2O3 contents of 5, 10, 20, and 30%, were synthesized using a wet precipitation method and sintered at 900 and 1300 degrees C. We investigated the effect of sintering temperature and relative concentration of HA and Al2O3 on the chemical composition, surface morphology, and cytotoxicity of the composite powders. The XRD results show that in the 1300 degrees C composites, HA partially decomposed into CaO which combined with Al2O3 to form different calcium aluminates. For the 900 degrees C composites the CaO phase was not detected, though a Ca/P ratio larger than 1.67 measured by XPS suggests that CaO was present in trace amounts. SEM-EDX analysis indicated that the HA microstructure was affected by the sintering temperature, and this HA is present on the surface of Al2O3 particles. The cytotoxicity of the composites was assessed indirectly using the MTT assay. The short-term effect of leachables was quantified by exposing a L929 mouse fibroblast cell line to the degradation products released by the composites after immersion in the cell culture medium. Degradation products were less toxic to L-929 at lower extract concentrations (10, 50%) than at 100% concentration. Cell viability was also influenced by leachable size. PMID:17584892

Epure, L M; Dimitrievska, S; Merhi, Y; Yahia, L 'H

2007-12-15

101

Biosorption of heavy metal ions from aqueous solutions by short hemp fibers: Effect of chemical composition  

Microsoft Academic Search

Sorption potential of waste short hemp fibers for Pb2+, Cd2+ and Zn2+ ions from aqueous media was explored. In order to assess the influence of hemp fiber chemical composition on their heavy metals sorption potential, lignin and hemicelluloses were removed selectively by chemical modification. The degree of fiber swelling and water retention value were determined in order to evaluate the

Biljana Pejic; Marija Vukcevic; Mirjana Kostic; Petar Skundric

2009-01-01

102

Silicon carbide whisker reinforced silicon carbide composites by chemical vapor infiltration  

Microsoft Academic Search

Silicon carbide (SiC) whisker reinforced SiC ceramic matrix composites were prepared by chemical vapor infiltration. Microstructure and mechanical properties of the composites were investigated. The fracture toughness of the composites was improved to 5.65–7.21MPam1\\/2, and its flexural strength value was between 196MPa and 305MPa, depending on the relative density. The pullout of rough whisker, crack deflection and whisker bridging are

Yunfeng Hua; Litong Zhang; Laifei Cheng; Jing Wang

2006-01-01

103

Histopathology of Human Coronary Atherosclerosis by Quantifying Its Chemical Composition With Raman Spectroscopy  

Microsoft Academic Search

Background—Lesion composition, rather than size or volume, determines whether an atherosclerotic plaque will progress, regress, or rupture, but current techniques cannot provide precise quantitative information about lesion composition. We have developed a technique to assess the pathological state of human coronary artery samples by quantifying their chemical composition with near-infrared Raman spectroscopy. Methods and Results—Coronary artery samples (n5165) obtained from

Tjeerd J. Romer; James F. Brennan III; Maryann Fitzmaurice; Michael L. Feldstein; Geurt Deinum; Jonathan L. Myles; John R. Kramer; Robert S. Lees; Michael S. Feld

104

Determination of isoflavone content in soy, red clover, and kudzu dietary supplement materials by liquid chromatography-particle beam/electron ionization mass spectrometry.  

PubMed

Increased consumption of dietary supplements brings about important requirements of analytical methods to allow accurate and precise measurements of the chemical composition of these botanical materials. Presented here is the isoflavone content in proposed National Institute of Standards and Technology standard reference materials (SRMs) determined by LC-particle beam/electron ionization MS. Botanical materials (soy, red clover, and kudzu) are characterized for the content of a suite of five isoflavones (puerarin, daidzein, genistein, formononetin, and biochanin A). These compounds are of interest due to correlations with certain health benefits. An RP chromatographic separation was first optimized using UV-Vis spectrophotometric detection. The LC output was then introduced to an electron ionization source using a particle beam interface on an Extrel Benchmark MS system. The separation was carried out using a commercial C18 column and a linear gradient using water and methanol (both containing 0.1% trifluoroacetic acid as mobile phases A and B, at a flow rate of 1.0 mL/min over 40 min. LOD values for the isoflavones were determined to be at the ng level. Quantitation was performed using an internal standard (IS) approach with 7-hydroxy-4-chromone as the IS compound. The levels of isoflavones in the botanical products were determined for the proposed SRMs. PMID:24282927

Burdette, Carolyn Q; Marcus, R Kenneth

2013-01-01

105

Modification of nanoparticle-organic composite electronic materials for improved chemical sensors.  

SciTech Connect

Molecular electronic based chemical vapor sensors were assembled using noble metal nanoparticles and short conjugated phenylene ethynylene (PE) based molecules. Sacrificial capping ligands on the nanoparticles were replaced by tighter binding PE ligands. The films were assembled between pairs of electrodes by iteratively exposing the substrates to solutions of the nanoparticles and PE crosslinking bridging ligands. Some of the conjugated bridging molecules contained an electron deficient phenol to provide a simple platform for developing sensor applications. The phenol is calculated to have a significant change in its HOMO/LUMO gap in the presence of specific analytes. Judicious combination of nanoparticle size and ligand structure provides a film in which the organic bridging ligands dramatically affect film conductance. Specifically, {pi}-conjugated ligands lower resistance more in films with smaller particles. Thus the sensing mechanism of these films is not based on the typical swelling mechanism but rather on the modulation of the molecular electronic structure of the conducting PE bridging ligands. Interdigitated Au electrodes built on quartz substrates were first silanized with tetrakis(dimethylamino)silane. The remaining amino functionalities were displaced with 1,8-octanedithiol (ODT) to give a thiolated surface capable of binding nanoparticles. The substrate was then incubated in a solution of dodecylamine-capped nanoparticles. The film thickness was increased via alternating exposure to solutions of bifunctional crosslinking molecules and nanoparticles (Figure 1). Nanoparticles and assembled films were characterized by TEM and AFM prior to electrical characterization. After verifying the selectivity of this new attachment chemistry, a novel robotic sample preparation was employed to build nanoparticle films of different thickness on prepared electrodes. By preparing the nanoparticle films using a robot, many problems with irregularities of the deposited films were eliminated. This sample preparation system was designed with the capability to measure the resistivity of the nanoparticle films after assembly of each layer. Using such a sample preparation system is vital for developing mass-produced sensors from nanoparticle films. The robotic system was used to deposit and measure the electrical properties of Pt and Au nanoparticles linked with different ligands such as ODT and meta-PE diisocyanide. Figure 2 is a plot showing the resistance vs. film layer for several combinations of nanoparticles and linker-ligands. The data shows that the resistance of the film drops and eventually saturates as additional nanoparticle layers are deposited. There is also an inversion in the resistance per layer that depends on the nanoparticle's type and the ligand used to crosslink the film. This data is significant because it shows how the selection of certain nanoparticle properties (such as size and material) and selection of an appropriate linking ligand can be used to tune the conductance of a film composed of nanoparticles. It is well known that smaller nanoparticles have a higher charging potential. This coupled with the inherent variability of organic molecules ensures that a film in which the organic molecules dominate conductivity can be achieved. In addition to the experiments above, nanoparticle films were assembled using cross-linkers that can be modified by an analyte. Figure 3 shows a typical I(V) curve for a Au nanoparticle film crosslinked with a phenylene ethynylene based electron deficient phenol. There is a clear reversible change in the resistance of the film when exposed first to acid and then base. The generation of a new response mechanism for nanoparticle films greatly increases the scope of organic/nanoparticle films for sensor applications. Their crosslinked nature increases their robustness and allows for use in both aqueous as well as organic solutions. In summary, we have developed a novel reproducible sample preparation system for the deposition of crosslinked nanoparticle films on a variety of sub

Howell, Stephen Wayne; Dirk, Shawn M.; Wheeler, David A.

2005-03-01

106

Composite structural materials  

NASA Technical Reports Server (NTRS)

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R. G.; Wiberley, S. E.

1985-01-01

107

Composite structural materials  

SciTech Connect

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

Loewy, R.G.; Wiberley, S.E.

1985-08-01

108

Nondestructive evaluation of composite materials by electrical resistance measurement  

NASA Astrophysics Data System (ADS)

This dissertation investigates electrical resistance measurement for nondestructive evaluation of carbon fiber (CF) reinforced polymer matrix composites. The method involves measuring the DC electrical resistance in either the longitudinal or through thickness direction. The thermal history and thermal properties of thermoplastic/CF composites were studied by longitudinal and through-thickness resistance measurements. The resistance results were consistent with differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) results. The resistance measurements gave more information on the melting of the polymer matrix than TMA. They were more sensitive to the glass transition of the polymer matrix than DSC. The through-thickness resistance decreased as autohesion progressed. The activation energy of autohesion was 21.2 kJ/mol for both nylon-6 and polyphenylene sulfide (PPS)/CF composites. Adhesive bonding and debonding were monitored in real-time by measurement of the through-thickness resistance between the adherends in an adhesive joint during heating and subsequent cooling. Debonding occurred during cooling when the pressure or temperature during prior bonding was not sufficiently high. A long heating time below the melting temperature (T m) was found to be detrimental to subsequent PPS adhesive joint development above Tm, due to curing reactions below Tm and consequent reduced mass flow response above Tm. A high heating rate (small heating time) enhanced the bonding more than a high pressure. The longitudinal resistance measurement was used to investigate the effects of temperature and stress on the interface between a concrete substrate and its epoxy/CF composite retrofit. The resistance of the retrofit was increased by bond degradation, whether the degradation was due to heat or stress. The degradation was reversible. Irreversible disturbance in the fiber arrangement occurred slightly as thermal or load cycling occurred, as indicated by the resistance decreasing cycle by cycle. This dissertation also addresses the use of the electrical resistance method to observe thermal and mechanical damage in real time. A temperature increase caused the interlaminar contact resistance to decrease reversibly within each thermal cycle, while thermal damage caused the resistance to decrease abruptly and irreversibly, due to matrix molecular movement and the consequent increase in the chance of fibers of one lamina touching those of an adjacent lamina. The through-thickness volume resistivity irreversibly and gradually decreased upon mechanical damage, which was probably fiber-matrix debonding. Moreover, it reversibly and abruptly increased upon matrix micro-structural change, which occurred reversibly near the peak stress of a stress cycle.

Mei, Zhen

109

Chemical recycling of scrap composites  

NASA Technical Reports Server (NTRS)

There are no well-developed technologies for recycling composite materials other than grinding to produce fillers. New approaches are needed to reclaim these valuable resources. Chemical or tertiary recycling, conversion of polymers into low molecular weight hydrocarbons for reuse as chemicals or fuels, is emerging as the most practical means for obtaining value from waste plastics and composites. Adherent Technologies is exploring a low-temperature catalytic process for recycling plastics and composites. Laboratory results show that all types of plastics, thermosets as well as thermoplastics, can be converted in high yields to valuable hydrocarbon products. This novel catalytic process runs at 200 C, conversion times are rapid, the process is closed and, thus, nonpolluting, and no highly toxic gas or liquid products have been observed so no negative environmental impact will result from its implementation. Tests on reclamation of composite materials show that epoxy, imide, and engineering thermoplastic matrices can be converted to low molecular weight hydrocarbons leaving behind the reinforcing fibers for reuse as composite reinforcements in secondary, lower-performance applications. Chemical recycling is also a means to dispose of sensitive or classified organic materials without incineration and provides a means to eliminate or reduce mixed hazardous wastes containing organic materials.

Allred, Ronald E.; Salas, Richard M.

1994-01-01

110

Ultrafine microstructure composites prepared by chemical vapor deposition. Annual report, January-December 1988  

SciTech Connect

The authors succeeded in preparing dispersed-phase composite coatings which consist of a boron nitride matrix containing aluminum nitride. Chemical vapor deposition (CVD) offers an alternate avenue of preparing ceramic composites by simultaneous deposition of multiple phases (i.e., codeposition). The major advantage of preparing dispersed-phase ceramic composites by CVD is that mechanical as well as chemical, electrical, optical, and thermal properties of the composites can be favorably tailored by controlling the composite composition and microstructure. Dispersed phase composites containing BN+ALN were deposited by CVD. The phases were either amorphous or crystalline depending on the deposition temperature and reagent concentration. One type of deposit which consisted of a turbostratic BN matrix containing oriented single crystal whiskers of ALN was very hard. A qualitative model based on statistical-mechanical nucleation theory and a hypothesized competition between growth of BN and ALN phases was successful in describing the relationship between operating conditions and the resulting microstructure of dispersed phase ceramic (BN+ALN) composites prepared by CVD. This study has provided a fundamental basis for developing more quantitative models, which will integrate the underlying principles of thermodynamics, kinetics, transport phenomena, nucleation and crystal growth theory.

Lackey, W.J.; Freeman, G.B.; Hanigofsky, J.A.; Thompson, J.R.; Gerard, G.J.

1988-12-01

111

Seasonal Variability and Chemical Composition of Carbon Export by the Yukon River, Alaska  

NASA Astrophysics Data System (ADS)

The flow and chemical composition of Arctic rivers are highly variable and reflect the mix of sources and flow paths of surface and ground water contributing to them during any particular season. Annual Yukon River carbon (C) export is dominated by the spring flush, with more than 50% of organic C and 30% of inorganic C exports occurring during May and June. As part of the US National Science Foundation's Arctic Great Rivers Observatory Project, which is studying the six largest rivers discharging to the Arctic Ocean, we measured Yukon River flow and water chemistry at high frequency during the critical periods immediately preceding, during, and following ice melt in 2009 - 2011. Springtime flows had high dissolved organic carbon (DOC) concentrations that rose quickly with water discharge at ice out and decreased with flow into summer. Waters collected near peak flow had high specific ultraviolet absorbance (SUVA) values and high aromatic C content. The rising limb of the spring flush hydrograph also had the greatest bioavailable DOC (BDOC) content, relative to the remainder of the year. The bulk of the DOC exported in spring was of terrestrial plant origin and 14C modern, with respiration carbon dioxide collected from BDOC incubations having similar 14C content to that of the bulk DOC. Interestingly, FT-ICR MS characterization of the DOC exported during the spring flush indicated the presence of labile, atmospherically deposited DOC components having apparent fossil fuel combustion origin, similar to those identified in direct glacial runoff. The importance of the spring flush period and of DOC exports to the total C budget of the Yukon River will also be discussed in the context of seasonal patterns of water discharge, watershed C yields, and of dissolved, particulate, and gaseous inorganic and organic C concentration and flux.

Striegl, R.; Aiken, G.; Butman, D.; Dornblaser, M.; Raymond, P.; Schuster, P.; Spencer, R.; Stubbins, A.; Wickland, K.

2012-04-01

112

Chemical composition of Mars  

USGS Publications Warehouse

The composition of Mars has been calculated from the cosmochemical model of Ganapathy and Anders (1974) which assumes that planets and chondrites underwent the same 4 fractionation processes in the solar nebula. Because elements of similar volatility stay together in these processes, only 4 index elements (U, Fe, K and Tl or Ar36) are needed to calculate the abundances of all 83 elements in the planet. The values chosen are U = 28 ppb, K = 62 ppm (based on K U = 2200 from orbital ??-spectrometry and on thermal history calculations by Tokso??z and Hsui (1978) Fe = 26.72% (from geophysical data), and Tl = 0.14 ppb (from the Ar36 and Ar40 abundances measured by Viking). The mantle of Mars is an iron-rich [Mg/(Mg + Fe) = 0.77] garnet wehrlite (?? = 3.52-3.54 g/cm3), similar to McGetchin and Smyth's (1978) estimate but containing more Ca and Al. It is nearly identical to the bulk Moon composition of Morgan et al. (1978b). The core makes up 0.19 of the planet and contains 3.5% S-much less than estimated by other models. Volatiles have nearly Moon-like abundances, being depleted relative to the Earth by factors of 0.36 (K-group, Tcond = 600-1300 K) or 0.029 (Tl group, Tcond < 600 K). The water abundance corresponds to a 9 m layer, but could be higher by as much as a factor of 11. Comparison of model compositions for 5 differentiated planets (Earth, Venus, Mars, Moon, and eucrite parent body) suggests that volatile depletion correlates mainly with size rather than with radial distance from the Sun. However, the relatively high volatile content of shergottites and some chondrites shows that the correlation is not simple; other factors must also be involved. ?? 1979.

Morgan, J. W.; Anders, E.

1979-01-01

113

Composite structural materials  

NASA Technical Reports Server (NTRS)

Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

114

Tough Composite Materials  

NASA Technical Reports Server (NTRS)

Papers and working group summaries are presented which address composite material behavior and performance improvement. Topic areas include composite fracture toughness and impact characterization, constituent properties and interrelationships, and matrix synthesis and characterization.

Vosteen, L. F. (compiler); Johnson, N. J. (compiler); Teichman, L. A. (compiler)

1984-01-01

115

Preparation of composite particles coated with two kinds of solid powders by semi-chemical recycle method  

Microsoft Academic Search

Polymer microspheres coated with two kinds of solid powders were prepared by the semi-chemical recycle method of waste plastics.\\u000a Magnetite (Fe3O4) and silicon carbide (SiC) were added as solid powders so as to give thermal and electric conductivity and magnetization.\\u000a Waste expanded polystyrene was used as raw materials of polymer matrix of composite particles. In the experiment, the oil\\u000a phase

M. Tanaka; Y. Taguchi; N. Sawatari; N. Saito

2006-01-01

116

Chemical composition of smoke produced by high-frequency electrosurgery in a closed gaseous environment  

Microsoft Academic Search

Background: High-frequency (HF) electrocoagulation and cutting procedures produce smoke by high-temperature pyrolysis of tissues. As\\u000a distinct from the experience of conventional surgery, electrosurgical smoke is produced in a closed gaseous environment during\\u000a laparoscopic operations. As a result, toxic chemicals may be absorbed into the circulation. The effects of this absorption\\u000a are not known. Furthermore, the chemical composition of electrosurgical smoke

C. Hensman; D. Baty; R. G. Willis; A. Cuschieri

1998-01-01

117

Rapid determination of methanol content in paper materials by alkaline extraction, coupled with headspace analysis.  

PubMed

This study reports on a rapid method for the determination of methanol in paper-based materials by alkaline extraction, coupled with headspace analysis. Methanol partition equilibria between solid-liquid phases and vapor-liquid phases were conducted in two separate containers, from which an equation for calculating the total methanol content in the original paper sample was derived. It was found that the extraction equilibrium of methanol from solid sample could be achieved within 5min at room temperature using a high-speed disintegrator, and a subsequent neutralization step is an effective way to prevent methanol from being regenerated at high temperature during headspace equilibration. The results showed that the relative standard deviations for reproducibility tests were in the range of 1.86-6.03%, and the recoveries were in the range of 92.3-107%. The present method is simple and practical; it can be an efficient tool for quantifying the methanol content in paper-based materials and thus play an important role in the investigation of methanol migration behavior in food and beverage packaging. PMID:24861784

Zhang, Chun-Yun; Li, Ling-Ling; Chai, Xin-Sheng; Barnes, Donald G

2014-07-11

118

[EDXRF study on the chemical composition and raw material recipe of Jindezhen porcelains in the five dynasties].  

PubMed

Early crafts of porcelain making in Jindezhen were an important issue in ceramic history of China. The chemical composition of white porcelain and celadon samples excavated from Xianghu Kiln in the five dynasties was analyzed using energy dispersive X-ray fluorescence (EDXRF). Raw material recipes of the samples were discussed. The results showed that white porcelain bodies of Xianghu Kiln in the Five Dynasties were made from porcelain stone, while celadon bodies were made from porcelain stone and Zijin clay. Glaze ash and glaze stone were both used in the formula of white porcelain and celadon glaze, and the amount of glaze ash in the celadon was higher than that in the white porcelain samples. PMID:22827103

zhang, Mao-lin; Zhou, Jian; Li, Qi-jiang; Wu, Jun-ming; Gan, Ke

2012-05-01

119

Chemical Composition of Martian Rocks  

NASA Astrophysics Data System (ADS)

In situ analyses of martian surface rocks (and soils) provided data about the chemical composition of several landing sites. One of the used techniques is the alpha-induced x-ray emission applied by the Alpha Particle X-Ray Spectrometer (APXS) onboard the current Mars Exploration Rovers (MER) Spirit and Opportunity and onboard the preceding Mars Pathfinder Rover Sojourner (MPF Mission). These measurements encompass the determination of major, minor, and (for the MER APXS) trace elements, such as Ni, Zn, and Br, as well as Cu, Pb, Sr, Y, Ga, and Ge. The obtained data indicate a remarkable compositional difference between the rocks at the different landing sites, whereas most soils including those measured by the Viking landers are chemically similar. Initially, the only chemical data of Mars were obtained by the study of a class of meteorites that turned out to be martian, which was furthermore confirmed by the discovery of a rock (by rover Opportunity) that is chemically related to those meteorites. The rocks at the Pathfinder landing site turned out to be richer in Si and K than the martian meteorites and all rocks encountered at the MER sites. At Gusev crater (the first MER landing site), two geological regions were encountered along the rover Spirit's traverse: the plains and the hills. Rocks in the plains resemble primitive basalts, while rocks located in the Columbia Hills revealed different types. Several rock classes could be cataloged based on their chemical composition. Most of the hills rocks are significantly weathered and enriched in mobile elements, such as P, Zn, S, Cl, and Br. On the other hand, a suite of ultramafic rocks was discovered for the first time on Mars. The rocks at Meridiani Planum (the second MER landing site) are salt-rich siliciclastic sediments. All rocks showed much higher S contents than the soils. High concentrations of Cl and Br were also discovered at various samples. Huge quantities of spherules were found on top of soils and outcrops along the rover's traverse. APXS measurements revealed that these spherules contain high amounts of iron that is mainly present as the mineral hematite (determined by Mössbauer spectrometry). The formation of hematite is typically, but not exclusively, an indicator for aqueous activities under oxidizing conditions. The in situ measurements at both MER landing sites point to a variety of sedimentary processes and various types of alteration processes; hence, they show clear evidence of ancient aqueous environments that discontinued long time, ago. The combination of in situ measurements and element correlations obtained by the martian meteorites implies an ancient basaltic crust with high abundances of incompatible elements (K, Rb, Nd, U, and Th) and volatile elements (S, Cl). Compared to the Earth's mantle, the martian mantle contains about twice as much Fe, is richer in moderately volatile elements like K, and has a much higher abundance of phosphorus. In conjunction with chemical data obtained from orbit, such as gamma-ray spectrometry carried out by the Mars Odyssey spacecraft, a global estimation of the composition of the martian surface is obtained and, furthermore, crustal composition can be derived.

Brueckner, J.

2007-05-01

120

Chemical Compatibility of Nonmetallic Materials.  

National Technical Information Service (NTIS)

This TOP(Test Operations Procedure) provides procedures for evaluating the cemical compatibility of the nonmetallic materials, by immersion in various chemicals. Physical properties of the material to be tested are measured before and after immersion to d...

1985-01-01

121

Composite structural materials  

NASA Technical Reports Server (NTRS)

A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

122

Digestion kinetics of neutral detergent fiber and chemical composition within some selected by-product feedstuffs  

Microsoft Academic Search

Nine by-product feedstuffs (BPF) obtained from three different sources were evaluated for nutrient composition, estimated nonstructural carbohydrate (NSC) and TDN content, and total extent and rate of digestion of DM and NDF. The nine BPF evaluated included: beet pulp (BP), rice bran (RB), almond hulls (AH), citrus pulp (CT), bakery waste (BW), wheat mill run (WMR), brewers' grains (BG), distillery

E. J. DePeters; J. G. Fadel; A. Arosemena

1997-01-01

123

Development of chemical vapor composite, CVC materials. Status report, October, 1994--March, 1995  

SciTech Connect

A powder/fiber sensor and controller for CVC reactors was successfully designed, fabricated, tested, and modified. A carbon fiber feeder and controller for a CVC SiC reactor was designed and fabricated but has not yet been tested. SiC material was fabricated using SiC powder ranging in size from 30 to 40 microns. SiC was also fabricated using multiple SiC powders off 10, 30, or 90 microns. Still other SiC materials were fabricated using platelets of 30 or 40 microns. The strength of this SiC material was low due to impurities in the material; ways to eliminate material impurities are currently being thoroughly investigated. Data was assembled on the operation and performance of a typical furnace using a metal fan.

NONE

1995-11-01

124

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1984-01-01

125

Frying stability of high oleic sunflower oils as affected by composition of tocopherol isomers and linoleic acid content.  

PubMed

The influence of linoleic acid content and tocopherol isomeric composition on the frying performance of high oleic sunflower oil was evaluated during a 14-day restaurant style frying operation. At equal linoleic acid content, no significant difference was observed between high oleic sunflower oil containing only ?-tocopherol and the sample containing a mixture of ?-, ?-, and ?-isomers as measured by the amount of total polar components, oligomers, anisidine value, and free fatty acids. On the contrary, at similar tocopherol isomeric composition, high oleic sunflower oil containing lower amount of linoleic acid showed superior frying stability compared to the sample with a higher content of linoleic acid, suggesting that the frying performance of high oleic sunflower oil is dictated primarily by the level of linoleic acid, with the tocopherol isomeric composition of the oil having no significant influence. In all oil samples, the loss of ?-tocopherol was higher than the corresponding loss of ?-tocopherol. PMID:23870970

Aladedunye, Felix; Przybylski, Roman

2013-12-01

126

Densification of unidirectional carbon–carbon composites by isothermal chemical vapor infiltration  

Microsoft Academic Search

The aim of this research was to investigate the densification of cylindrical unidirectional C–C composites by isothermal chemical vapor infiltration. Several different preforms with different fiber volume fractions were prepared, and it was found that the preforms with the lower fiber volume fraction have a more rapid rate of densification and the final density is higher. The problem of infiltrating

He-Jun Li; Xiang-Hui Hou; Yi-Xi Chen

2000-01-01

127

Fabrication of fiber-reinforced ceramic composites by chemical vapor infiltration  

SciTech Connect

Ceramic fiber-ceramic matrix composites are of interest because of their potentially higher strength and toughness. A vacuum forming technique was used to fabricate low-density structures from SiC fibers. These fibrous structures were then infiltrated by chemical vapor deposition. Matrices of Si/sub 3/N/sub 4/ and SiC have been deposited.

Caputo, A.J.; Lackey, W.J.

1984-10-01

128

Energy absorption and exposure buildup factors for some polymers and tissue substitute materials: photon energy, penetration depth and chemical composition dependence.  

PubMed

The gamma ray energy absorption and exposure buildup factors have been calculated by using the five parameter geometric progression (GP) fitting formula for some polymers and tissue substitute materials in the energy region 0.015-15 MeV up to a penetration depth of 40 mean free paths. From the results, it is worth noting that significant variations occur in gamma ray buildup factors for the given polymers and tissue substitute materials depending on photon energy, penetration depth and chemical composition of the materials. Also, it was observed that there are significant variations between energy absorption (EABF) and exposure (EBF) buildup factors which may be due to the variations in chemical composition of the materials used. Finally, it is expected that the presented buildup factor data may be helpful in (a) estimating the effective dose to be given to patients in radiation therapy and diagnostics, hence allowing corrections to be made to the intensity of radiation, as it is somewhat problematic to evaluate the real absorbed dose in critical organs due to the probability of photon buildup somewhere inside the medium; (b) estimating the health hazards arising from the exposure of the human body to radiation, thus it will be helpful in controlling the exposure of the human body to radiation. PMID:21346285

Kurudirek, Murat; Özdemir, Yüksel

2011-03-01

129

Effect of Sericin on Mechanical Behavior of Composite Material Reinforced by Silk Woven Fabric  

NASA Astrophysics Data System (ADS)

Recent, attention has been given to shift from glass fibers and carbon fibers to natural fibers for FRP composites for the goal of protecting the environment. This paper concerned with the application of silk fabric for composite materials. Polypropylene (PP) was used for the matrix material and the silk fabric composites were molded using a compression molding method. Especially, the effect of sericin on mechanical behaviors of composite materials was discussed. Good adhesion between silk and PP was obtained by removing the sericin existing around the fibroin. The tensile modulus of composite decreased with decreasing the sericin because of the flexibility of silk fibers without sericin. In particular, the higher Izod impact value was obtained for the composites containing the silk fibers without sericin.

Kimura, Teruo; Ino, Haruhiro; Hanada, Koji; Katori, Sigetaka

130

Erosion of composite materials  

NASA Technical Reports Server (NTRS)

A model for describing the response of uncoated and coated fiber reinforced composites subjected to repeated impingements of liquid (rain) droplets is presented. The model is based on the concept that fatigue is the dominant factor in the erosion process. Algebraic expressions are provided which give the incubation period, the rate of mass loss past the incubation period, and the total mass loss of the material during rain impact. The influence of material properties on erosion damage and the protection offered by different coatings are discussed and the use of the model in the design in the design of structures and components is illustrated.

Springer, G. S.

1980-01-01

131

A multicontinuum progressive damage model for composite materials motivated by the kinetic theory of fracture  

NASA Astrophysics Data System (ADS)

A conventional composite material for structural applications is composed of stiff reinforcing fibers embedded in a relatively soft polymer matrix, e.g. glass fibers in an epoxy matrix. Although composites have numerous advantages over traditional materials, the presence of two vastly different constituent materials has confounded analysts trying to predict failure. The inability to accurately predict the inelastic response of polymer based composites along with their ultimate failure is a significant barrier to their introduction to new applications. Polymer based composite materials also tend to exhibit rate and time dependent failure characteristics. Lack of knowledge about the rate dependent response and progressive failure of composite structures has led to the current practice of designing these structures with static properties. However, high strain rate mechanical properties can vary greatly from the static properties. The objective of this research is to develop a finite element based failure analysis tool for composite materials that incorporates strain rate hardening effects in the material failure model. The analysis method, referred to as multicontinuum theory (MCT) retains the identity of individual constituents by treating them as separate but linked continua. Retaining the constituent identities allows one to extract continuum phase averaged stress/strain fields for the constituents in a routine structural analysis. Time dependent failure is incorporated in MCT by introducing a continuum damage model into MCT. In addition to modeling time and rate dependent failure, the damage model is capable of capturing the nonlinear stress-strain response observed in composite materials.

Schumacher, Shane Christian

2002-01-01

132

Composite structural materials  

NASA Technical Reports Server (NTRS)

The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

Ansell, G. S.; Wiberley, S. E.

1978-01-01

133

Processing of plastic waste and scrap tires into chemical raw materials, especially by pyrolysis  

Microsoft Academic Search

An account of the occurrence of pyrolyzable material and the state of development of pyrolysis processes in the USA and Japan is followed by a description of laboratory and pilot-scale experiments designed to exploit the raw material content of pyrolyzable substances rather than the heating value. Plastic waste and scrap tires can be pyrolyzed to give up to 40 percent

Walter Kaminsky

1976-01-01

134

Coprecipitated, copper-based, alumina-stabilized materials for carbon dioxide capture by chemical looping combustion.  

PubMed

Chemical looping combustion (CLC) has emerged as a carbon dioxide capture and storage (CCS) process to produce a pure stream of CO(2) at very low costs when compared with alternative CCS technologies, such as scrubbing with amines. From a thermodynamic point of view, copper oxide is arguably the most promising candidate for the oxygen carrier owing to its exothermic reduction and oxidation reactions and high oxygen-carrying capacity. However, the low melting point of pure copper of only 1085 °C has so far prohibited the synthesis of copper-rich oxygen carriers. This paper is concerned with the development of copper-based and Al(2)O(3)-stabilized oxygen carriers that contain a high mass fraction of CuO, namely, 82.4 wt %. The oxygen carriers were synthesized by using a coprecipitation technique. The synthesized oxygen carriers were characterized in detail with regards to their morphological properties, chemical composition, and surface topography. It was found that both the precipitating agent and the pH at which the precipitation was performed strongly influenced the structure and chemical composition of the oxygen carriers. In addition, XRD analysis confirmed that, for the majority of the precipitation conditions investigated, CuO reacted with Al(2)O(3) to form fully reducible CuAl(2)O(4). The redox characteristics of the synthesized materials were evaluated at 800 °C by using methane as the fuel and air for reoxidation. It was found that the oxygen-carrying capacity of the synthesized oxygen carriers was strongly influenced by both the precipitating agent and the pH at which the precipitation was performed; however, all oxygen carriers tested showed a stable cyclic oxygen-carrying capacity. The oxygen carriers synthesized at pH 5.5 using NaOH or Na(2)CO(3) as the precipitating agents were the best oxygen carriers synthesized owing to their high and stable oxygen transfer and uncoupling capacities. The excellent redox characteristics of the best oxygen carrier were interpreted in light of the detailed morphological characterization of the synthesized material and a synthesis-structure-performance relationship was developed. PMID:22744876

Imtiaz, Qasim; Kierzkowska, Agnieszka Marta; Müller, Christoph Rüdiger

2012-08-01

135

Polysulfone-polypyrrole ionic conductive composite membranes synthesized by phase inversion with chemical reaction  

Microsoft Academic Search

New polymeric composite membranes polysulfone-polypyrrole has been prepared by a new technique consisting in phase inversion accompanied by chemical reaction. The membranes were synthesised from polysulfone\\/pyrrole-N, N'-dimethylformamide\\/ methanol system by phase inversion followed by remaining pyrrole in membrane pores polymerization in the presence of iron chloride. The obtained membrane was characterized by Fourrier transformed infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA),

C. Muscalu; R. David; S. A. Garea; A. C. Nechifor; D. I. Vaireanu; S. I. Voicu; G. Nechifor

2009-01-01

136

[Study on the chemical compositions of VOCs emitted by cooking oils based on GC-MS].  

PubMed

Volatile organic compounds (VOCs) are key precursors of ozone and secondary organic aerosols in air, and the differences in the compositions of VOCs lead to their different contribution to atmospheric reaction. Cooking oil fume is one of the important sources of atmospheric VOCs, and its chemical compositions are distinct under different conditions of oil types, food types, cooking methods and heating temperatures etc. In this study, the production of cooking oil fume was simulated by heating typical pure vegetable oils (peanut oil, sunflower oil, soybean oil, olive oil and blend oil) at different temperatures in beakers to investigate the chemical compositions of VOCs. The emitted VOCs were sampled with a Tenax adsorption tube and analyzed using GC-MS after thermal desorption. According to spectral library search and map analysis, using area normalized semi-quantitative method, preliminary qualitative and quantitative tests were conducted for the specific components of VOCs under different conditions. PMID:24640897

He, Wan-Qing; Nie, Lei; Tian, Gang; Li, Jing; Shao, Xia; Wang, Min-Yan

2013-12-01

137

Composite material and method for production of improved composite material  

NASA Technical Reports Server (NTRS)

A laminated composite material with improved interlaminar strength and damage tolerance having short rods distributed evenly throughout the composite material perpendicular to the laminae. Each rod is shorter than the thickness of the finished laminate, but several times as long as the thickness of each lamina. The laminate is made by inserting short rods in layers of prepreg material, and then stacking and curing prepreg material with rods inserted therethrough.

Farley, Gary L. (Inventor)

1996-01-01

138

C/SiC Multilayer Coating for the Oxidation Resistance of C-C Composite by Low Pressure Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Functionally graded materials (FGM) consisting of C and SiC were deposited between the carbon fiber reinforced carbon (C-C) composites and the SiC coating layer by low pressure chemical vapor deposition (LPCVD) method to reduce the thermal stress. The compositions of the graded layers could be easily controlled to various steps by manipulating the input ratio of CH3SiCl3 to C2H2. The residual stresses for the designed compositional distribution were calculated by finite element method (FEM). The designed FGM layers were coated experimentally on the C-C composites and the oxidation behavior of the composites was investigated.

Kim, J. I.; Kim, W. J.; Choi, D. J.; Park, J. Y.; Ryu, W. S.

139

Effect of fruit ripening on content and chemical composition of oil from three oil palm cultivars (Elaeis guineensis Jacq.) grown in Colombia.  

PubMed

A series of physical and chemical changes occur as oil palm fruits ripen in the bunch. We evaluated changes in lipid content in the mesocarp and fruits, and the chemical composition of fatty acids (FA), triacylglycerol (TAG), tocols, and carotenes of the lipids extracted from fruits of three commercial tenera cultivars, namely, Deli×La Me?, Deli×Ekona, and Deli×Avros, planted in two different geographical regions in Colombia, during the ripening process 12, 14, 16, 18, 20, 22, and 24 weeks after anthesis (WAA). It was found that 12 WAA the mesocarp contained less than 6% of total lipids. Oil content increased rapidly after 16 WAA, reaching the maximum oil content of 55% in fresh mesocarp and 47% in fresh fruits at 22 WAA, which was found the optimal time for harvesting. Changes in FA and TAG showed that total polyunsaturated fatty acids (PUFA) and triunsaturated triacylglycerols (TUTAG) decreased, while total saturated fatty acids (SFA) and disaturated triacylglycerols (DSTAG) increased, over the ripening period. Changes in FA were mainly observed in palmitic, oleic, linoleic, and linolenic acids, and in POP, POO, POL, and OLL for the TAGs evaluated. Levels of tocols changed depending on whether they were tocopherols or tocotrienols. In the earliest stages tocopherols were predominant but decreased rapidly from 6600 mg kg(-1) of oil at 14 WAA to 93 mg kg(-1) of oil at 22 WAA. Tocotrienols appeared at the same time as oil synthesis started, and became the main source of total tocols, equivalent to 87% in total lipids extracted. PMID:21894914

Prada, Fausto; Ayala-Diaz, Iván M; Delgado, Wilman; Ruiz-Romero, Rodrigo; Romero, Hernán M

2011-09-28

140

Dispersion of crystalline powder materials in gaseous media of different chemical compositions  

NASA Astrophysics Data System (ADS)

The process of grinding of rutile and barite crystalline powders in a laboratory ball mill in different types of gaseous media (air, nitrogen, helium) has been investigated. Comparative evaluations of the intensity of the dispersion of these minerals have been performed and the particle sizes of powders obtained in different modes of their dispersion have been measured. A sharp increase in the intensity of this process in the helium medium as compared to the air and nitrogen media has been revealed and ultrafine-grained particles of barite powders have been obtained. The results of the performed investigations have demonstrated that the helium medium can be recommended for producing nanoparticles of powder materials in modern types of ball and bead mills with a drastic decrease in the time and energy consumptions required for their preparation.

Klyavin, O. V.; Drinberg, A. S.; Chernov, Yu. M.; Shpeizman, V. V.

2012-05-01

141

Direct determination of the lipid content in starch–lipid composites by time-domain NMR  

Microsoft Academic Search

Starch–lipid composites, prepared by excess steam jet cooking aqueous mixtures of starch and lipid, are used in a broad range of applications for which their performance can depend upon accurately knowing the amount of the lipid contributed by the composites. A rapid and non-destructive method based on time-domain nuclear magnetic resonance spectroscopy (TD-NMR) was evaluated to quantitate soybean oil (SBO)

James A. Kenar

2007-01-01

142

Composite Materials: An Educational Need.  

ERIC Educational Resources Information Center

Described is the need to incorporate the concepts and applications of advanced composite materials into existing chemical engineering programs. Discussed are the justification for, and implementation of topics including transport phenomena, kinetics and reactor design, unit operations, and product and process design. (CW)

Saliba, Tony E.; Snide, James A.

1990-01-01

143

40 CFR Table Z-1 to Subpart Z of... - Default Chemical Composition of Phosphate Rock by Origin  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Default Chemical Composition of Phosphate Rock by Origin Z Table Z-1 to Subpart Z of Part 98 Protection...Subpart Z of Part 98âDefault Chemical Composition of Phosphate Rock by Origin Origin Total carbon(percent by weight)...

2013-07-01

144

Evaluation of Basic Electrical Parameters of Silver-Based Contact Materials of Different Chemical Composition and Manufacturing Technology  

Microsoft Academic Search

The paper outlines the manufacturing technology of different silver-metal and silver-metal oxide composite materials to be used in contacts of low-voltage switches. There were conducted tests of the electrical properties of contacts made of eight different composite materials and hard silver. There was determined their resistance to arc erosion and static welding. There were also measured changes of contact resistance

E. Walczuk; P. Borkowski; S. Ksie?z?arek; W. Missol; Z. Rdzawski; K. Durst

2010-01-01

145

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

146

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1988-06-20

147

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1984-01-01

148

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

1989-01-01

149

Composite structural materials  

NASA Technical Reports Server (NTRS)

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Loewy, R.; Wiberley, S. E.

1986-01-01

150

Process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition  

DOEpatents

A chemical vapor deposition (CVD) process for preparing fiber-reinforced ceramic composites. A specially designed apparatus provides a steep thermal gradient across the thickness of a fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

Lackey, Jr., Walter J. (Oak Ridge, TN); Caputo, Anthony J. (Knoxville, TN) [Knoxville, TN

1986-01-01

151

Computational scheme for ab-initio predictions of chemical compositions interfaces realized by deposition growth  

NASA Astrophysics Data System (ADS)

We present a novel computational scheme to predict chemical compositions at interfaces as they emerge in a growth process. The scheme uses the Gibbs free energy of reaction associated with the formation of interfaces with a specific composition as predictor for their prevalence. It explicitly accounts for the growth conditions by rate-equation modeling of the deposition environment. The Bell-Evans-Polanyi principle motivates our emphasis on an effective nonequilibrium thermodynamic description inspired by chemical reaction theory. We illustrate the scheme by characterizing the interface between TiC and alumina. Equilibrium thermodynamics favors a nonbinding interface, being in conflict with the wear-resistant nature of TiC/alumina multilayer coatings. Our novel scheme predicts that deposition of a strongly adhering interface is favored under realistic conditions.

Rohrer, Jochen; Hyldgaard, Per

2011-09-01

152

Production and application of chemical fibers with special properties for manufacturing composite materials and goods of different usage  

NASA Technical Reports Server (NTRS)

The development of modern technologies demands the creation of new nonmetallic, fibrous materials with specific properties. The fibers and materials developed by NII 'Chimvolokno', St. Petersburg, can be divided into two groups. The first group includes heat-resistant fibers, fire-resistant fibers, thermotropic fibers, fibers for medical application, and textile structures. The second group contains refractory fibers, chemoresistant and antifriction fibers, fibers on the basis of polyvinyl alcohol, microfiltering films, and paperlike and nonwoven materials. In cooperation with NPO 'Chimvolokno' MYTITSHI, we developed and started producing heat-resistant high-strength fibers on the base of polyhetarearilin and aromatic polyimides (SVM and terlon); heat-resistant fibers on the base of polyemede (aramid); fire-retardant fibers (togilen); chemoresistant and antifriction fibers on the basis of homo and copolymers of polytetrafluoroethylene (polyfen and ftorin); and water soluble, acetylated, and high-modulus fibers from polyvinyl alcohol (vylen). Separate reports will deal with textile structures and thermotropic fibers, as well as with medical fibers. One of the groups of refractory fibers carbon fibers (CF) and the corresponding paperlike nonwoven materials are discussed in detail. Also, composite materials (CM) and their base, which is the subject of the author's research since 1968, is discussed.

Levit, R.

1993-01-01

153

Combinatorial synthesis of inorganic or composite materials  

DOEpatents

Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials or, alternatively, allowing the components to interact to form at least two different materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, nonbiological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

Goldwasser, Isy (Palo Alto, CA); Ross, Debra A. (Mountain Ranch, CA); Schultz, Peter G. (La Jolla, CA); Xiang, Xiao-Dong (Danville, CA); Briceno, Gabriel (Baldwin Park, CA); Sun, Xian-Dong (Fremont, CA); Wang, Kai-An (Cupertino, CA)

2010-08-03

154

Modelling of local modification of chemical composition generated by artificial beam injection in stratosphere  

NASA Astrophysics Data System (ADS)

The physical/chemical processes that are occurring in the middle atmosphere, are very complex and knowledge of them are obviously poor. At the same time the understanding of these processes is necessary, in particular, for an explanation of ozone dynamics and influencing on it of the different factors, for example, impurities of anthropogenous nature. In the present activity the capability of creation of noticeable local disturbances of concentration of ozone and other minor neutral components in stratosphere si theoretically modeled for artificial injection of high energy electron beams from a high-altitude balloon. With the help of numerical simulations (31 reactions) the quantitative assessments of expected effect for different altitudes (range of 35-45 km) and different values of eddy diffusion factor are obtained and presented. It is shown the considered means has a number of advantages in comparison with method of artificial action on stratosphere ozone by VHF generation of ionized area in atmosphere. At first, it is much more friend and precisely to conduct diagnostic of effect, which one arises due to "in -situ" onboard measurements from a balloon. Secondly, it is possible to inject any impurities (freons) to study directly in stratosphere their affect on ozone. The method, tendered here, requires considerably smaller material costs and can be realized already now. Based on presented modeling results it is important to note that in our method an integral disturbance in stratosphere (full quantity of created molecules of ozone, nitric oxides etc.) is rather insignificant, as the effect is localized near to injected electron beam. Therefore there is no hazard of deposition of unchecked injury to environment. At the same time realization of tendered experiment will allow essentially to deepen our representations about composite physical/chemical processes occurring in middle atmosphere (stratosphere).

Oraevsky, V.; Ruzhin, Y.; Borisov, N.; Nesterov, I.

155

Synthesis of nanostructured carbon materials by open-air laser-induced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Elemental carbon in the sp2 hybridization state can form a great variety of graphitic and amorphous structures. Carbon nanotube is a well-known form of graphitic carbon that has remarkable mechanical, electronic and electrochemical properties with applications ranging from reinforced composite materials to micro-scale electronic devices. Pyrolytic carbon film with turbostratic structure is a form of amorphous carbon that possesses excellent barrier properties against diffusion of moisture and hydrogen, and is used as hermetic coating for optical fibers operating under harsh environments. Current deposition techniques for these novel carbon materials are limited in production rate, quality and reproducibility, thereby restricting their usage for advanced applications. In this dissertation, an open-air laser-induced chemical vapor deposition technique is proposed and investigated for the rapid growth of high quality carbon nanotubes and nanometer thick pyrolytic carbon films. The first part of the thesis focuses on the open-air synthesis of carbon nanotubes on stationary and moving fused quartz substrates. The second part will study the deposition of pyrolytic carbon film on various optical components including optical fibers. Optical microscopy, high-resolution transmission and scanning electron microscopy, Raman and Auger electron spectroscopy, as well as x-ray energy-dispersive spectrometry, scanning white-light interferometry and thermal pyrometry are used to investigate the deposition rate, morphology, microstructure and chemical composition of the deposited carbon materials.

Kwok, Kinghong

156

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2001-01-01

157

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2002-01-01

158

Mechanics of Composite Materials  

Microsoft Academic Search

The mechanical behavior of composites is traditionally evaluated on both microscopic and macroscopic scale to take into account inhomogeneity. Micromechanics attempts to quantify the interactions of fiber and matrix (reinforcement and resin) on a microscopic scale on par with the diameter of a single fiber. Macromechanics treats composites as homogeneous materials, with mechanical properties representative of the laminate as a

Robert M. Jones

1999-01-01

159

Composite structural materials  

NASA Technical Reports Server (NTRS)

Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1982-01-01

160

Aerogel composites using chemical vapor infiltration  

Microsoft Academic Search

A new method to produce novel composite materials based on the use of aerogels as a starting material is described. Using chemical vapor infiltration, a variety of solid materials were thermally deposited into the open pore structure of aerogel. The resulting materials possess new and unusual properties including photoluminescence, magnetism and altered optical properties. An important characteristic of this preparation

Arlon J. Hunt; Michael R. Ayers; Wanqing Cao

1995-01-01

161

Carbon\\/silicon carbide composites prepared by chemical vapor infiltration combined with silicon melt infiltration  

Microsoft Academic Search

In order to reduce processing costs and improve the thermal stability of three-dimensional carbon fiber-reinforced silicon carbide composites, a chemical vapor infiltration combined with silicon melt infiltration method was developed for fabricating composites. According to the size of the pores in the preform, chemical vapor infiltration (CVI) and silicon melt infiltration (SMI) were mainly used to infiltrate small pores between

Yongdong Xu; Laifei Cheng; Litong Zhang

1999-01-01

162

Chemical composition of soils and plant species in the Polar Urals as influenced by rock type  

Microsoft Academic Search

The concentrations of chemical elements in tundra soils and plants of ultramafic and acid rocks were investigated in the Polar Urals. The close dependence of the soil concentrations of elements on the granulometric composition of the soils was shown and also the relationship of their chemical composition with that of the underlying bedrock including the predominance of magnesium over calcium

Maria N. Kataeva; Natalya V. Alexeeva-Popova; Irina V. Drozdova; Alla I. Beljaeva

2004-01-01

163

Spatial-Time Variability of Particulate Material Content and its Composition on the East Siberian Shelf: from Mesoscale to Interannual Variability  

NASA Astrophysics Data System (ADS)

Here we present the data obtained in the Russia-US cruises (FEBRAS, NOAA, NSF, and Russian Foundation for Basic Research, RFBR, funded) in 2000, 2003-2005, and in the International Siberian Shelf Study-2008 (ISSS-2008, supported by the Wallenberg Foundation, FEBRAS, NOAA, and RFBR) which characterized a spatial and inter-annual variability in distribution of particulate material (PM), and its organic carbon and stable isotopes content. The role of the coastal zone in lateral transport and fate of terrestrial organic carbon in the East Siberian Arctic Shelf (ESAS) is still not studied well because most recent activities were focused on onshore geomorphologic and geochemical features, while biogeochemical and sedimentation consequences of coastal erosion and riverine runoff in the sea were not studied sufficiently. Dynamics of PM and its composition was studied twice along the Lena river in summer-fall of 2003. Spatial-time dynamics of PM composition (POC and isotopes) along with its mineralogical composition is considered in connection with changing river runoff and wind patterns. It has been found that not the rivers (Lena, Yana, Indigirka, Kolyma), but the coastal erosion is a dominant source of terrestrial particulate organic carbon (POC) into the ESAS. That supports the hypothesis about the dominant role of coastal erosion in the offshore transport of terrestrial organic carbon and sedimentation in the ESAS proposed by Semiletov (DAN, 1999). The PM concentration sharp gradient was found across the frontal zone between 'freshened/high PM' and 'Pacific/low PM' waters. Position of the frontal zone varies significantly from year to year. It is mainly attributed to the difference in atmospheric circulation patterns driven the Arctic Ocean circulation. During storms and surges the PM concentration in the same area increased up to 10-times and higher (up to 80-242 mg/l) in 2000 and 2005 comparing the 2003 and 2004. Values of total PM and other environmental parameters were integrated vertically and spatially for the 'comparison' area using approach proposed by Shakhova et al. (GRL, 2005) to make the first quantitative PM burden estimation (2003 vs 2004).

Dudarev, O.; Charkin, A.; Shakhova, N. E.; Semiletov, I. P.; Gustafsson, O. M.; Vonk, J.; Sanchez-Garcia, L.

2013-12-01

164

Composite Aluminum-Copper Sheet Material by Friction Stir Welding and Cold Rolling  

NASA Astrophysics Data System (ADS)

An aluminum alloy and a pure copper material were butt-joined by friction stir welding and subsequently cold rolled. The cold-rolling operation proved to be very advantageous because small voids present after friction stir welding were closed, the interface area per material thickness was enlarged, a thin intermetallic layer was partitioned, and the joint was strengthened by strain hardening. Tensile test specimens fractured in the heat-affected zone in the aluminum material; tensile strengths of the joints exceeded the tensile strengths of the base materials and were as high as 335 MPa. During soft annealing of the composite material, a 6-8-?m-thick intermetallic layer was grown at the interface. Nevertheless, tensile fracture still occurred in the heat-affected zone of the aluminum material. Electrical resistivity of the joint was smaller than resistivity of the aluminum material. Production of such composite material would result in coiled sheet material that could be subjected to further treatments such as electroplating and forming operations in an efficient and economically viable manner. The new composite material is promising for emerging automotive and industrial electrical applications.

Kahl, S.; Osikowicz, W.

2013-08-01

165

Magnesite-Spinel products from fused materials with by-products from chemical processes  

Microsoft Academic Search

Conclusions The feasibility was demonstrated of producing chrome-containing magnesia spinel from a mixture of the by-products of chemical processes and magnesite. The composition of this spinel is similar to that of spinel fused from a mixture of commercial alumina, magnesite, and chromite. The fused spinel from the by-products contains a large proportion of SiO2 and correspondingly less FeO + Fe2O3

Ya. Z. Shapiro; É. V. Degtyareva; G. R. Kotel'nikov; A. N. Bushin; V. I. Ponomarenko

1974-01-01

166

Aqueous chemical wash compositions  

SciTech Connect

This patent describes an aqueous, substantially unfoamed chemical wash composition having properties making it suitable for use as a pre-flush in well cementing operations and/or for removal of drilling mud from a borehole at a temperature of from about 150/sup 0/F to about 270/sup 0/F, the wash a. being predominantly composed of water, b. containing an active surfactant component comprising a combination of (1) from about 0.1 to about 1.5 weight percent (total weight basis) of a water soluble anionic surfactant; (2) from about 0.1 to about 1.5 weight percent (total weight basis) of a nonionic surfactant; and (3) from about 0.05 to about 0.54 weight percent (total weight basis) of at least one water soluble amphoteric surfactant, and c. having dispersed therein a heterogeneous mixture of distinct particles comprising both a first particulate oil soluble resin which is friable and a second particulate oil soluble resin which is pliable and where the size of the friable resin particles ranges from about 0.5 to about 300 microns and the size of the pliable resin particles ranges from about 0.05 to about 30 microns. The amount of the friable-pliable resin mixture is sufficient to impart effective fluid loss control to the chemical wash composition.

Bannister, C.E.

1987-07-21

167

One-step growth of graphene–carbon nanotube hybrid materials by chemical vapor deposition  

Microsoft Academic Search

Graphene–carbon nanotube (CNT) hybrid materials were synthesized by simple one-step chemical vapor deposition (CVD) using ethanol as precursor. On a copper foil decorated with silicon nanparticles (Si NPs), a graphene film grows uniformly on the substrate while CNTs sprout out from Si NPs to form a network on top. The density of CNTs can be controlled by the CVD growth

Xiaochen Dong; Bing Li; Ang Wei; Xiehong Cao; M. B. Chan-Park; Hua Zhang; Lain-Jong Li; Wei Huang; Peng Chen

2011-01-01

168

Thermo-chemical fuel removal from porous materials by oxygen and nitrogen dioxide  

NASA Astrophysics Data System (ADS)

Thermo-chemical removal (TCR), or baking in reactive gases, is a candidate method to control the co-deposit related tritium inventory in fusion devices. TCR can be understood as reaction–diffusion processes in a porous material. O2-TCR was applied to 150–550 nm thick a-C:D layers with similar textures. A linear relation between the integral TCR rate and the layer thickness, as predicted by the understanding, was observed in the experiment, i.e. the time to remove the hydrogen inventory is independent of its initial amount. TCR with nitrogen dioxide (NO2) at temperatures of 200–350 °C was conducted with a set of a-C:D and W–C–H layers. At 350 °C NO2 removed ? 15% porosity a-C:D within 3 min. The O retention in remaining a-C:D was ? 1017 O cm?2. An activation energy of ? 0.78 eV for reactions of NO2 with D and C was determined. The results were applied for predictions of the TCR effectivity in ITER. The treatment of W–C–H led to O uptake (O/W ? 2–3), while W and C contents remained unchanged.

Möller, S.; Alegre, D.; Kreter, A.; Petersson, P.; Esser, H. G.; Samm, U.

2014-04-01

169

Resin composite restorative materials.  

PubMed

This paper surveys the most important developments in resin-based dental composites and focuses on the deficits (e.g. polymerization shrinkage) and strengths of the materials and their clinical implications. Moreover, differences between composite categories, such as hybrid, nanohybrid, microfilled, packable, ormocer-based, silorane-based, polyacid-modified composites (compomers) and flowable composites are highlighted, especially in view of their mechanical behaviour. In addition to the classical dimethacrylate-based composites, special attention is given to alternative monomers, such as siloranes, ormocers or high-molecular-weight dimethacrylate monomers (e.g. dimer acid-based dimethacrylates and tricyclodecane (TCD)-urethane), analysing their advantages, behaviour and abilities. Finally, the paper attempts to establish the needs and wishes of clinicians for further development of resin-based composites. PMID:21564116

Ilie, N; Hickel, R

2011-06-01

170

Chemical composition of Luna 16 lunar regolith  

NASA Technical Reports Server (NTRS)

Data on the chemical composition of regolith returned by the Luna 16 automatic station and two fragments of basalts from the lower layer of the core are presented. Spark mass spectrometric, primary X-ray spectral, emission spectral, and atomic absorption methods were used in the analysis. The regolith of mare provinces were shown to be a mixture of material of various origins. The source of the material of the mare regolith was principally basalts of the corresponding lunar lava maria. The regolith is genetically related to it. This follows from a comparison of the chemical composition, mineralogical, and petrochemical features of the basesalts and the regolith from the Sea of Fertility, Sea of Tranquillity, and Ocean of Storms, respectively.

Vinogradov, A. P.; Chupakhin, M. S.; Belyayev, Y. I.

1974-01-01

171

Highly birefringent polymer microstructured optical fibers embedded in composite materials  

NASA Astrophysics Data System (ADS)

Composite structures are made from two or more constituent materials with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing highly birefringent polymer microstructured optical fibers into the composite material. These new fibers can consist of only two polymer materials (PMMA and PC) with similar value of the Young modulus as the composite material so any stresses induced in the composite material can be easily measured by the proposed embedded fiber optic sensors.

Lesiak, P.; SzelÄ g, M.; Kuczkowski, M.; Doma?ski, A. W.; Woli?ski, T. R.

2013-05-01

172

Chemical studies of H chondrites-10 : contents of thermally labile trace elements are unaffected by late heating.  

SciTech Connect

We have used radiochemical neutron activation analysis (RNAA) to determine 15 trace elements, including 10 moderately and highly volatile ones - Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, Tl, In (in increasing volatility order) - in 6 H chondrite falls with low 3He contents. These plus prior RNAA data provide a compositional database of 92 H4-6 chondrite falls. Three suites of samples can be identified from their noble gas contents: 44 with 'normal' contents, and, therefore, 'normal' orbits and cosmic ray exposure histories; 8 that lost radiogenic gases, presumably by shock late in their histories; and 17 that lost cosmogenic gases by heating during close solar approach. We used the standard multivariate statistical techniques of linear discriminant analysis and logistic regression to compare contents of the 10 moderately and highly volatile trace elements, listed above, in these 3 suites. We found no significant differences. This contrasts sharply with similar comparisons involving random falls and H4-6 chondrites that landed on Earth at specific time intervals. Apparently, contents of volatile trace elements in H4-6 chondrites were established early in their histories and they are so retentively sited that loss during later heating episodes did not occur.

Wang, M.-S.; Wolf, S. F.; Lipschutz, M. E.; Chemical Engineering; Purdue Univ.

1999-09-01

173

Nanostructured composite reinforced material  

DOEpatents

A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

Seals, Roland D. (Oak Ridge, TN); Ripley, Edward B. (Knoxville, TN); Ludtka, Gerard M. (Oak Ridge, TN)

2012-07-31

174

Energetic composites and method of providing chemical energy  

DOEpatents

A method for providing chemical energy and energetic compositions of matter consisting of thin layers of substances which will exothermically react with one another. The layers of reactive substances are separated by thin layers of a buffer material which prevents the reactions from taking place until the desired time. The reactions are triggered by an external agent, such as mechanical stress or an electric spark. The compositions are known as metastable interstitial composites (MICs). This class of compositions includes materials which have not previously been capable of use as energetic materials. The speed and products of the reactions can be varied to suit the application.

Danen, Wayne C. (Los Alamos, NM) [Los Alamos, NM; Martin, Joe A. (Espanola, NM) [Espanola, NM

1997-01-01

175

Modified Composite Materials Workshop  

NASA Technical Reports Server (NTRS)

The reduction or elimination of the hazard which results from accidental release of graphite fibers from composite materials was studied at a workshop. At the workshop, groups were organized to consider six topics: epoxy modifications, epoxy replacement, fiber modifications, fiber coatings and new fibers, hybrids, and fiber release testing. Because of the time required to develop a new material and acquire a design data base, most of the workers concluded that a modified composite material would require about four to five years of development and testing before it could be applied to aircraft structures. The hybrid working group considered that some hybrid composites which reduce the risk of accidental fiber release might be put into service over the near term. The fiber release testing working group recommended a coordinated effort to define a suitable laboratory test.

Dicus, D. L. (compiler)

1978-01-01

176

Chemical composition and some anti-nutrient content of raw and processed bitter vetch (Vicia ervilia) seed for use as feeding stuff in poultry diet.  

PubMed

An experiment was conducted to determine chemical composition of raw and treated bitter vetch seed for use in poultry diets. Processing methods were: soaked in water for 12 h, then autoclaved and dried (SA); coarsely ground, soaked in water for 24 h, autoclaved and dried (GSA); coarsely ground, soaked in water for 47 h with exchange of water every 12 h, cooked and dried (GSC); coarsely ground, soaked in solution of 1% acetic acid for 24 h at 60 degrees C and dried (GAA). Raw bitter vetch seed was contained 94.52, 26.56, 0.4, 58.86, 3.38, 5.32, 12.28 and 14.20 percent DM, CP, EE, NFE, Ash, CF, ADF and NDF, respectively. Its GE, AME, AMEn, TME and TMEn values were 18.10, 13.15, 14.38, 14.10 and 14.69 MJ/kg, respectively. Results indicated that bitter vetch is a good source of Fe (340 ppm) and Cu (46.7 ppm). It s amino acid profile was suitable and methionine was the first limiting amino acid when compared with broiler and layer chicks requirements. Its canavanine and tannin content were 0.78 and 6.7 mg/kgDM, respectively. Processing methods improved CP and in some cases AMEn. All processing methods especially GSC resulted in a significant (P < 0.05) reduction in canavanine and tannin. PMID:19052906

Sadeghi, Gh; Pourreza, J; Samei, A; Rahmani, H

2009-01-01

177

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1983-01-01

178

High-reinforcement-content metal matrix composites  

SciTech Connect

This article describes how aluminum-based composites with high volume percentages of nonmetallic reinforcement materials can challenge applications traditionally met by ferrous materials. Discontinuously reinforced metal matrix composites (MMC) have a wide range of potential automotive applications. These extend from structural uses, including wear-resistant components such as disc-brake rotors, through high-specific-stiffness components such as robot arms and disc-brake calipers, to high-specific-strength components such as connecting rods. In addition, composites with silicon carbide (SiC) filler have low density, high thermal conductivity, and low coefficient of thermal expansion (CTE) that makes them useful for controlling temperatures in electronic devices.

NONE

1995-06-01

179

Vibrational damping of composite materials  

NASA Astrophysics Data System (ADS)

The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss factor and modulus could be tailored by changing the angle, were produced and investigated. The addition of particles between composite prepreg layers to increase damping was studied. Electroviscoelastic materials that drastically changed properties such as loss factor and modulus with an applied voltage were manufactured and tested.

Biggerstaff, Janet M.

180

Microstructure and mechanical properties of three-dimensional carbon\\/silicon carbide composites fabricated by chemical vapor infiltration  

Microsoft Academic Search

Three-dimensional carbon\\/silicon carbide composites were fabricated by chemical vapor infiltration, and the microstructure and mechanical properties were investigated. For the composites (CSiC) with no pyrolytic carbon interfacial layer, the mechanical properties (flexural strength, flexural elastic modulus, shear strength and fracture toughness) are increased with density of the composites. High density (p = 2.1 g cm?3) CSiC composites exhibit high fracture

Yongdong Xu; Litong Zhang; Laifei Cheng; Dantao Yan

1998-01-01

181

Characterization of Al 2O 3–Al nano-composite powder prepared by a wet chemical method  

Microsoft Academic Search

A wet chemical method was used to prepare Al2O3-coated Al nano-size-composite powders using Al, aluminum nitrate and ammonia as the starting materials. TEM, SEM, TG\\/DSC, zeta potential, XPS, X-ray were used to characterize the composite powders. Results showed that a uniform thin Al(OH)3 layer can formed on the surface of Al particles. After calcined at 1000°C for 2h, the thin

Hong-xia Lu; Jie Hu; Chang-ping Chen; Hong-wei Sun; Xing Hu; De-lin Yang

2005-01-01

182

Variability of the essential oil content and composition of chamomile (Matricaria recutita L.) affected by weather conditions.  

PubMed

In our study we examined the variability of the essential oil content and composition of chamomile (Matricaria recutita L.) during three years (2005-2007). Twenty-eight populations of wild origin and 4 registered cultivars ('Soroksári 40', 'Lutea', 'Goral' and 'Bona') were evaluated in open field experiments. It could be established that the experimental populations represented different genetic potential for essential oil accumulation and composition. The best populations of wild growing origin from the Somogy-region and four cultivars produced the highest essential oil contents (above 0.6 g/100g) in each year. Additionally, the quality of the characteristic main compound of the oil determining the "chemotype", according to Schilcher, was found to be stable during the three years period. However, the actual chemosyndroms are significantly influenced by the weather conditions. In the three years' experiment, the moderately warm and relatively wet year of 2006 produced the highest contents of essential oil and also that of its alpha-bisabolol component. Although bisabolol oxide A also showed a high variability through the years, its direct connection with weather conditions could not be proved. A moderate variability was established for the proportions of chamazulene, and the lowest one for bisabolol-oxide B. Considerable genotype-weather interaction was supposed, especially for the essential oil content and for the ratio of bisabolol-oxide A. PMID:20420329

Gosztola, Beáta; Sárosi, Szilvia; Németh, Eva

2010-03-01

183

Orthopedic Composite Materials.  

National Technical Information Service (NTIS)

The program was designed as a pilot project to establish new techniques for making orthopedic prosthetic materials. The basic idea was to make metal supported ceramic composites, so that the metal provided strength (and an element of ductility) and the re...

B. J. Shaw

1972-01-01

184

Introduction to Advanced Composite Materials  

NSDL National Science Digital Library

This presentation provides an introduction to composite materials and curriculum guidelines. Topics include applications of composites, advantages and disadvantages, and advice for developing a curriculum on advanced composite materials. This document is available for download as a PDF.

Stuart, Joe

2012-10-15

185

A comparison of composition and emulsifying properties of MFGM materials prepared from different dairy sources by microfiltration.  

PubMed

Milk fat globule membrane (MFGM), due to its specific nature and composition, is known as material possessing advantageous nutritional as well as technological properties. In this study MFGM materials were produced from several dairy sources such as buttermilk (BM), butter serum (BS) and buttermilk whey (BMW) by microfiltration (MF). The obtained materials, depending on the sources, were called BM-MFGM, BS-MFGM and BMW-MFGM, respectively. The compositions of starting materials and the isolated MFGM materials as well as their emulsifying properties were analyzed and compared. As expected, the MF resulted in enrichment of polar lipids (PLs), major components of MFGM. On dry matter basis, BM-MFGM and BS-MFGM were about 2.5 times higher in PLs compared to their beginning materials while BMW-MFGM was about 8.3 times compared to buttermilk powder (BMP). Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the microfiltered products still contained a high amount of non-MFGM proteins such as caseins, ?-lactoglobulin, and ?-lactalbumin. Emulsions of 35% soya oil in water were prepared with the mentioned materials using a homogenizer at various pressures. Generally, emulsions prepared with BMP and butter serum powder had significantly higher particle sizes than those prepared with the MFGM materials. This result along with microscopy observation and viscosity measurement indicated the presence of aggregated particles in the former emulsions, probably as a result of lack of surface-active components. The differences in composition, especially in content of PLs and proteins of the materials were the main reasons for the differences in their emulsifying behaviors. PMID:23751553

Miocinovic, Jelena; Le, Thien Trung; Fredrick, Eveline; Van der Meeren, Paul; Pudja, Predrag; Dewettinck, Koen

2013-06-10

186

Chemical composition of Nigella sativa L. seed extracts obtained by supercritical carbon dioxide.  

PubMed

Chemical composition of black cumin (Nigella sativa L.) seed extracts obtained by supercritical carbon dioxide at two different conditions that result in total extract (28 MPa/50°C, SFE 1) and major volatile part (12 MPa/40°C, SFE 2) and essential oil obtained by hydrodistillation of SFE-1 (HD SFE). SFE have been carried out to characterize the compounds and the variation of quinones and phenolics. The extracts were analysed by GC and GC-MS and the presence of phenolic compounds was further confirmed by 2D HSQCT (1)H and (13)C NMR spectroscopy. Forty-seven volatile compounds were detected where sixteen compounds were reported for the first time in the oil of this seed. Moreover, thymoquinone (TQ), dithymoquinone (DTQ), thymohydroquinone (THQ) and thymol (THY) were the major phenolic compounds. It can be concluded that the chemical composition of extracts obtained by SC CO2 extraction of the seeds showed better recovery of phenolic compounds than HD SFE and proved the occurrence of thermally labile or photosensitive bioactive volatiles of four major quinonic phenol compounds. PMID:23572692

Tiruppur Venkatachallam, Suresh Kumar; Pattekhan, Hajimalang; Divakar, Soundar; Kadimi, Udaya Sankar

2010-12-01

187

Variation of chemical composition with age in human femoral head cartilage  

Microsoft Academic Search

The chemical composition of intact femoral head cartilage was investigated with age. Full-depth cartilage showed a decrease in water content and an increase in keratan sulphate and noncollagenous material with age. When analyzed through the depth of the cartilage, keratan sulphate was shown to appear first in the deep zones and later in the surface, while water content was lost

M F Venn

1978-01-01

188

Effect of nitrogen content and additional straw on changes in chemical composition, volatile losses, and ammonia emissions from dairy manure during long-term storage.  

PubMed

Twelve 200-L barrels were used to determine the effects of N content and straw addition on changes in chemical composition and volatile losses measured by mass balance of dairy manure during a 136-d storage period. In addition, on d 0, 3, 6, 12, 28, 56, and 136, rate of NH?-N emission was measured, and core samples were collected to characterize fermentation pattern. High N (3.06% N, HN) and low N (2.75% N, LN) manures were obtained from cows fed diets with 17.2 and 15.2% crude protein (dry matter basis), respectively. On d 0, manure scraped from a freestall barn floor was diluted with water to 10% dry matter and loaded in barrels with (+S) or without (-S) mixing 22g of chopped wheat straw per kilogram of undiluted manure. Data were analyzed as a randomized complete block with a 2×2 factorial arrangement of treatments and 3 replications. We observed no interaction between treatments for the reported measurements, but several day-of-storage by treatment interactions were found. Throughout storage, total NH?-N (TAN, NH?-N + NH??-N; 71.9 vs. 104.3 mg/dL), pH (6.40 vs. 6.74), and total volatile fatty acids (TVFA, starting on d 12) were lower for LN relative to HN manure. In the presence of straw, crust formation occurred between d 12 and 28, and pH became lower and TVFA became higher starting on d 56, compared with no straw. Treatments did not influence loss of organic matter, organic N, organic C, or N, which averaged 31, 29, 26, and 20%, respectively. However, neutral detergent fiber loss was 44% higher for +S relative to -S manure. Consistent reductions in the C:N ratio indicated proportionally higher volatile C loss than volatile N loss during storage. Overall rate of NH?-N emission was 36% lower for LN than for HN manure. In the presence of straw, rate of NH?-N emission did not differ until after crust formation, but was 67% lower on d 56 and 95% lower on d 136, when it was barely detectable, compared with manure with no straw. Manure pH was highly correlated with TVFA:TAN ratio (r=-0.78), and rate of NH?-N emission was correlated with pH, TVFA:TAN, TVFA, and TAN (r=0.47, -0.44, -0.23, and 0.28, respectively). In this trial, both microbial fermentation and crust formation influenced NH?-N emission rate and other measured responses, highlighting the importance of long-term sampling to evaluate treatment effects in manure storage studies. PMID:22612981

Aguerre, M J; Wattiaux, M A; Hunt, T; Lobos, N E

2012-06-01

189

Treatment of chemical warfare agents by zero-valent iron nanoparticles and ferrate(VI)/(III) composite.  

PubMed

Nanoscale zero-valent iron (nZVI) particles and a composite containing a mixture of ferrate(VI) and ferrate(III) were prepared by thermal procedures. The phase compositions, valence states of iron, and particle sizes of iron-bearing compounds were determined by combination of X-ray powder diffraction, Mössbauer spectroscopy and scanning electron microscopy. The applicability of these environmentally friendly iron based materials in treatment of chemical warfare agents (CWAs) has been tested with three representative compounds, sulfur mustard (bis(2-chlorethyl) sulfide, HD), soman ((3,3'-imethylbutan-2-yl)-methylphosphonofluoridate, GD), and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX). Zero-valent iron, even in the nanodimensional state, had a sluggish reactivity with CWAs, which was also observed in low degrees of CWAs degradation. On the contrary, ferrate(VI)/(III) composite exhibited a high reactivity and complete degradations of CWAs were accomplished. Under the studied conditions, the estimated first-order rate constants (? 10(-2)s(-1)) with the ferrate(VI)/(III) composite were several orders of magnitude higher than those of spontaneous hydrolysis of CWAs (10(-8)-10(-6)s(-1)). The results demonstrated that the oxidative technology based on application of ferrate(VI) is very promising to decontaminate CWAs. PMID:22119195

Zboril, Radek; Andrle, Marek; Oplustil, Frantisek; Machala, Libor; Tucek, Jiri; Filip, Jan; Marusak, Zdenek; Sharma, Virender K

2012-04-15

190

Production and Application of Chemical Fibers with Special Properties for Manufacturing Composite Materials and Goods of Different Usage.  

National Technical Information Service (NTIS)

The development of modern technologies demands the creation of new nonmetallic, fibrous materials with specific properties. The fibers and materials developed by NII 'Chimvolokno', St. Petersburg, can be divided into two groups. The first group includes h...

R. Levit

1993-01-01

191

Oxygen isotopic compositions of asteroidal materials returned from Itokawa by the Hayabusa mission.  

PubMed

Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid. PMID:21868668

Yurimoto, Hisayoshi; Abe, Ken-ichi; Abe, Masanao; Ebihara, Mitsuru; Fujimura, Akio; Hashiguchi, Minako; Hashizume, Ko; Ireland, Trevor R; Itoh, Shoichi; Katayama, Juri; Kato, Chizu; Kawaguchi, Junichiro; Kawasaki, Noriyuki; Kitajima, Fumio; Kobayashi, Sachio; Meike, Tatsuji; Mukai, Toshifumi; Nagao, Keisuke; Nakamura, Tomoki; Naraoka, Hiroshi; Noguchi, Takaaki; Okazaki, Ryuji; Park, Changkun; Sakamoto, Naoya; Seto, Yusuke; Takei, Masashi; Tsuchiyama, Akira; Uesugi, Masayuki; Wakaki, Shigeyuki; Yada, Toru; Yamamoto, Kosuke; Yoshikawa, Makoto; Zolensky, Michael E

2011-08-26

192

Comparison of self repair in various composite matrix materials  

NASA Astrophysics Data System (ADS)

In a comparison of self repair in graphite composites (for airplane applications) versus epoxy and vinyl ester composites (for building structures or walls) 1 the type of damage that the fiber/matrix is prone to experience is a prime factor in determining which materials self repair well and 2 the flow of energy during damage determines what kinds of damage that can be self repaired well. 1) In brittle composites, repair was successful throughout the composite due to matrix cracking which allowed for optimum chemical flow, whereas in toughened composites that did not crack, the repair chemical flows into a few layers of the composite. 2) If the damage energy is stopped by the composite and goes laterally, it causes delamination which will be repaired; however if the damage energy goes through the composite as with a puncture, then there will be limited delamination, less chemical release and less self repair.

Dry, Carolyn

2014-04-01

193

Multilayer Electroactive Polymer Composite Material  

NASA Technical Reports Server (NTRS)

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2011-01-01

194

Static properties and moisture content properties of polyester fabrics modified by plasma treatment and chemical finishing  

NASA Astrophysics Data System (ADS)

Low temperature plasma treatment has been conducted in textile industry and has some success in the dyeing and finishing processes. In this paper, an attempt was made to apply low temperature plasma treatment to improve the anti-static property of polyester fabric. The polyester fabrics were treated under different conditions using low temperature plasma. An Orthogonal Array Testing Strategy was employed to determine the optimum treatment condition. After low temperature plasma treatment, the polyester fabrics were evaluated with different characterisation methods. Under the observation of scanning electron microscope, the surface structure of low temperature plasma-treated polyester fabric was seriously altered. This provided more capacity for polyester to capture moisture and hence increase the dissipation of static charges. The relationship between moisture content and half-life decay time for static charges was studied and the results showed that the increment of moisture content would result in shortening the time for the dissipation of static charges. Moreover, there was a great improvement in the anti-static property of the low temperature plasma-treated polyester fabric after comparing with that of the polyester fabric treated with commercial anti-static finishing agent.

Kan, C. W.; Yuen, C. W. M.

2008-01-01

195

Ski Technology And Composite Materials  

NSDL National Science Digital Library

The following resource is from Lessonopoly, which has created student activities and lesson plans to support the video series, Science of the Olympic Winter Games, created by NBC Learn and the National Science Foundation. Featuring exclusive footage from NBC Sports and contributions from Olympic athletes and NSF scientists, the series will help teach your students valuable scientific concepts. Students will learn the basic engineering issues related to ski design. They will learn about composite materials and polymer materials. Also, students will create and test a composite material.

2010-01-01

196

Matrix Composition Regulates Three-Dimensional Network Formation by Endothelial Cells and Mesenchymal Stem Cells in Collagen/Fibrin Materials  

PubMed Central

Co-cultures of endothelial cells (EC) and mesenchymal stem cells (MSC) in three-dimensional (3D) protein hydrogels can be used to recapitulate aspects of vasculogenesis in vitro. MSC provide paracrine signals that stimulate EC to form vessel-like structures, which mature as the MSC transition to the role of mural cells. In this study, vessel-like network formation was studied using 3D collagen/fibrin (COL/FIB) matrices seeded with embedded EC and MSC and cultured for 7 days. The EC:MSC ratio was varied from 5:1, 3:2, 1:1, 2:3 and 1:5. The matrix composition was varied at COL/FIB compositions of 100/0 (pure COL), 60/40, 50/50, 40/60 and 0/100 (pure FIB). Vasculogenesis was markedly decreased in the highest EC:MSC ratio, relative to the other cell ratios. Network formation increased with increasing fibrin content in composite materials, although the 40/60 COL/FIB and pure fibrin materials exhibited the same degree of vasculogenesis. EC and MSC were co-localized in vessel-like structures after 7 days and total cell number increased by approximately 70%. Mechanical property measurements showed an inverse correlation between matrix stiffness and network formation. The effect of matrix stiffness was further investigated using gels made with varying total protein content and by crosslinking the matrix using the dialdehyde glyoxal. This systematic series of studies demonstrates that matrix composition regulates vasculogenesis in 3D protein hydrogels, and further suggests that this effect may be caused by matrix mechanical properties. These findings have relevance to the study of neovessel formation and the development of strategies to promote vascularization in transplanted tissues.

Rao, Rameshwar R.; Peterson, Alexis W.; Ceccarelli, Jacob; Putnam, Andrew J.; Stegemann, Jan P.

2013-01-01

197

Phase composition and morphology of TaC coating on carbon fibers by chemical vapor infiltration  

Microsoft Academic Search

Chemical vapor infiltration was applied to deposit TaC thin film on carbon fibers using TaCl5–Ar–C3H6–H2 source. The influence of temperature, pressure and addition of H2 on phase composition and morphology of the coating had been studied. The results showed that the composition of the coating changes with temperature. The films are mainly composed of TaC and C when deposited at

Zhao-ke Chen; Xiang Xiong; Bai-yun Huang; Guo-dong Li; Feng Zheng; Peng Xiao; Hong-bo Zhang; Jian Yin

2008-01-01

198

Aligned carbon nanotube-reinforced silicon carbide composites produced by chemical vapor infiltration  

Microsoft Academic Search

A chemical vapor infiltration (CVI) technique was used to overcome most of the challenges involved in fabricating exceptionally-tough CNT\\/SiC composites. Nanotube pullout and sequential breaking and slippage of the walls of the CNTs during failure were consistently observed for all fractured CNT\\/SiC samples. These energy absorbing mechanisms result in the fracture strength of the CNT\\/SiC composites about an order of

Zhanjun Gu; Yingchao Yang; Kaiyuan Li; Xinyong Tao; Gyula Eres; Jane Y. Howe; Litong Zhang; Xiaodong Li; Zhengwei Pan

2011-01-01

199

Dense, finely, grained composite materials  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

200

Aligned Carbon Nanotube Reinforced Silicon Carbide Composites by Chemical Vapor Infiltration  

SciTech Connect

Owing to their exceptional stiffness and strength1 4, carbon nanotubes (CNTs) have long been considered to be an ideal reinforcement for light-weight, high-strength, and high-temperature-resistant ceramic matrix composites (CMCs)5 10. However, the research and development in CNT-reinforced CMCs have been greatly hindered due to the challenges related to manufacturing including poor dispersion, damages during dispersion, surface modification, densification and sintering, weak tube/matrix interfaces, and agglomeration of tubes at the matrix grain boundaries5,11. Here we report the fabrication of high-quality aligned CNT/SiC composites by chemical vapor infiltration (CVI), a technique that is being widely used to fabricate commercial continuous-filament CMCs12 15. Using the CVI technique most of the challenges previously encountered in the fabrication of CNT composites were readily overcome. Nanotube pullouts, an important toughening mechanism for CMCs, were consistently observed on all fractured CNT/SiC samples. Indeed, three-point bending tests conducted on individual CNT/SiC nanowires (diameters: 50 200 nm) using an atomic force microscope show that the CNT-reinforced SiC nanowires are about an order of magnitude tougher than the bulk SiC. The tube/matrix interface is so intimate and the SiC matrix is so dense that a ~50-nm-thick SiC coating can effectively protect the inside nanotubes from being oxidized at 1600 C in air. The CVI method may be extended to produce nanotube composites from a variety of matrix

Gu, Zhan Jun [University of Georgia, Athens, GA; Yang, Ying Chao [University of South Carolina, Columbia; Li, Kai Yuan [University of Georgia, Athens, GA; Tao, Xin Yong [University of South Carolina, Columbia; Eres, Gyula [ORNL; Howe, Jane Y [ORNL; Zhang, Li Tong [Northwestern Polytechnical University, Xi'an, China; Li, Xiao Dong [University of South Carolina, Columbia; Pan, Zhengwei [ORNL

2011-01-01

201

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

Baucom, Robert M.

1991-01-01

202

Preparation and characterization of 5-sulphosalicylic acid doped tetraethoxysilane composite ion-exchange material by sol-gel method.  

PubMed

In this manuscript, we report the preparation and characterization of sulphosalicylic doped tetraethoxysilane (SATEOS), composite material by sol-gel method as a new ion exchanger for the removal of Ni(II) from aqueous solution. The fine granular material was prepared by acid catalyzed condensation polymerization through sol-gel mechanism in the presence of cationic surfactant. The material has an ion exchange capacity of 0.64 mequiv./g(dry) for sodium ions, 0.60 mequiv./g(dry) for potassium ions, 1.84 mequiv./g(dry) for magnesium ions, 1.08 mequiv./g(dry) for calcium ions and 1.36 mequiv./g(dry) for strontium ions. Its X-ray diffraction studies suggest that it is crystalline in nature. The material has been characterized by SEM, IR, TGA and DTG so as to identify the various functional groups and ion exchange sites present in this material. Quantum chemical computations at DFT/B3LYP/6-311G (d,p) level on model systems were performed to substantiate the structural conclusions based ion instrumental techniques. Investigations into the elution behaviour, ion exchange reversibility and distribution capacities of this material towards certain environmentally hazardous metal ions are also performed. The material shows good chemical stability towards acidic conditions and exhibits fast elution of exchangeable H(+) ions under neutral conditions. This material shows remarkable selectivity for Ni(II) and on the basis of its Kd value (4×10(2) in 0.01M HClO4) some binary separations of Ni(II) from other metal ions are performed. PMID:23774782

Rehman, Suhail-ul; Islam, Nasarul; Ahad, Sozia; Fatima, Syed Zeeshan; Pandith, Altaf Hussain

2013-09-15

203

Chemical composition and some anti-nutrient content of raw and processed bitter vetch ( Vicia ervilia ) seed for use as feeding stuff in poultry diet  

Microsoft Academic Search

An experiment was conducted to determine chemical composition of raw and treated bitter vetch seed for use in poultry diets.\\u000a Processing methods were: soaked in water for 12 h, then autoclaved and dried (SA); coarsely ground, soaked in water for 24 h,\\u000a autoclaved and dried (GSA); coarsely ground, soaked in water for 47 h with exchange of water every 12 h, cooked and dried

G. H. Sadeghi; J. Pourreza; A. Samei; H. Rahmani

2009-01-01

204

Morphology and chemical composition analysis of inorganic nanosheets by the field-emission scanning electron microscope system.  

PubMed

Nanosheets can be used as building blocks to fabricate versatile nanostructured materials. In this paper, morphology of the Cs(4)W(11)O(36) and Nb(3)O(8) and TaO(3) sheets with different layers are analyzed by different field-emission scanning electron microscopes (FE-SEMs). Chemical composition of the single-layered Cs(4)W(11)O(36) with thickness of about 2 nm, and multilayered Nb(3)O(8) nanosheets with thickness of less than 14 nm are analyzed by both the Si(Li) solid-state detector and transition edge sensor (TES) microcalorimeter, successfully. The effects of energy resolution, accelerating voltage and substrate on the quantitative analysis are discussed briefly. PMID:19150970

Li, Qinghui; Ono, Yuki; Homma, Yoshikazu; Nakai, Izumi; Fukuda, Katsutoshi; Sasaki, Takayoshi; Tanaka, Keiichi; Nakayama, Satoshi

2009-01-01

205

True chemical composition profiles at polymer interphases: recovery from measurements distorted by instrumental broadening.  

PubMed

The determination of chemical composition profiles at polymer interphases is an important issue at the moment of elucidating the physical mechanisms that operate in polymer diffusion processes and for calculating diffusion parameters. Several techniques are available to measure these profiles, the most common being forward recoil spectroscopy, Rutherford backscattering spectrometry, nuclear reaction analysis, confocal Raman microspectroscopy (CRM), and scanning infrared microscopy. However, all these techniques are affected by the limited resolution of the experimental setup, which in practice produces a rounding effect on the sharp corners of the composition profile; this may lead to incorrect conclusions regarding the measurements. In this work an inverse technique is proposed to correct this undesirable effect in the profiles. The inversion is performed on a model of the measuring process, which includes the instrumental broadening function, a quantitative representation of the limited resolution. The proposed methodology was tested using numerically generated experiments and genuine experimental runs obtained from CRM measurements at interphases of polymer bilayers. In all cases, the recovered profiles were close to the expected ones. In the truly experimental results diffusion tails are observed behind and ahead of the diffusion front before the numerical treatment of the data. These tails may be caused by a genuine mass diffusion or by an artifact. After the numerical treatment the tails disappear and a sharp interphase is recovered, a result one expects for the polymer pairs under study. PMID:14661834

Tomba, Pablo; Eliçabe, Guillermo

2003-08-01

206

Liquid Helium Composite Regenerator Material.  

National Technical Information Service (NTIS)

A cryogenic composite material designed for application to gap regenerators in cyclic cryocoolers operating below 10 K is investigated. The material is a composite of helium self-loaded into a metallic extended surface structure whose dispersion form is s...

T. R. Knowles

1987-01-01

207

Multifunctional Autonomically Healing Composite Material.  

National Technical Information Service (NTIS)

A composite material, contains a polymer, a polymerizer, a corresponding catalyst for the polymerizer, and a plurality of capsules. The polymerizer is in the capsules. The composite material is self-healing.

J. S. Moore N. R. Sottos P. H. Geubelle S. R. Sriram S. R. White

2005-01-01

208

CHARACTERIZATION AND PROPERTIES OF ALUMINUM COMPOSITE MATERIALS PREPARED BY POWDER METALLURGY TECHNIQUES USING CERAMIC SOLID WASTES  

Microsoft Academic Search

This work provides preliminary results of aluminum metal matrix composites (MMCs) reinforced with granulated slag (GS) and electric arc furnace dust (EAFD). The present work concerns the synthesis and properties of Al\\/GS and Al\\/EAFD composites based on powder metallurgy techniques. The hardness and compressive strength of the sintering compacts were determined to compare the mechanical properties of the composite material

L. Ma. Flores-Vélez; J. Chávez; L. Hernández; O. Domínguez

2001-01-01

209

Carbon Fibre Composite Materials Produced by Gamma Radiation Induced Curing of Epoxy Resins  

NASA Astrophysics Data System (ADS)

It is well known that ionizing radiation can initiate polymerization of suitable monomers for many applications. In this work an epoxy difunctional monomer has been used as matrix of a carbon fibre composite in order to produce materials through gamma radiation, for aerospace and advanced automotive applications. Radiation curing has been performed at different absorbed doses and, as comparison, also thermal curing of the same monomer formulations has been done. Furthermore some irradiated samples have been also subjected to a post irradiation thermal curing in order to complete the polymerization reactions. The properties of the cured materials have been studied by moisture absorption isotherms, dynamic mechanical thermal analysis and mechanical flexural tests.

Dispenza, C.; Alessi, S.; Spadaro, G.

2008-08-01

210

Barium content of benthic foraminifera controlled by bottom-water composition  

Microsoft Academic Search

THE carbon isotope ratio (delta13C) and cadmium content (Cd\\/Ca) of benthic foraminifera shells have been used to reconstruct deep-water circulation patterns of the glacial oceans1-7. These tracers co-vary with phosphorus in the modern ocean because they are nearly quantitatively regenerated from sinking biological debris in the upper water column. Hence they can be used to reconstruct the distribution of labile

D. Lea; E. Boyle

1989-01-01

211

Chemical compatibility and oxidation resistance of potential matrix and reinforcement materials in ceramic composites for ultra-high temperature applications. Final report, 30 Sep 87-31 Jan 90  

Microsoft Academic Search

The mutual chemical composition and compatibilities of some of the potential matrix and reinforcement phases of ceramic composite materials have been investigated in the temperature range 1600-2200 C. The oxidative stabilities of hot pressed, particulate composites containing 50:50 volume percent of each compound in a material combination have been studied in the temperature range 1000-16000 C. The material combinations investigated

Mehrotra

1991-01-01

212

Preparation and Characterization of Chemically Synthesized Hybrid Composites for Bone Tissue Regeneration  

NASA Astrophysics Data System (ADS)

The aim of this study concerns the development of bioresorbable composite materials for bone repair and regeneration. Hydroxyapatite loaded composites were synthesized by a colloidal non-aqueous chemical precipitation technique at room temperature. This study describes the synthesis and characterization of HA/PCL composite material, in order to verify the interaction between the ceramic and the polymer phases by a morphological investigation.

Raucci, M. G.; Guarino, V.; Ambrosio, L.

2008-08-01

213

Detection of Defects in Composite Pyrotechnic Materi als and Products by IR NDT Methods  

Microsoft Academic Search

Pyrotechnic composite materials are widely used in milita ry and civil applications as solid composite (heterogeneous) propellants and gas-generators in rocket motors. Non- destructive testing (NDT) methods are used to detect defect s which can disturb in reliable and safe functioning of these materials and products or distinc tly decrease the level of their performance characteristics. These defects are caused

Waldemar SWIDERSKI; Maciej MISZCZAK

214

NASA technology utilization survey on composite materials  

NASA Technical Reports Server (NTRS)

NASA and NASA-funded contractor contributions to the field of composite materials are surveyed. Existing and potential non-aerospace applications of the newer composite materials are emphasized. Economic factors for selection of a composite for a particular application are weight savings, performance (high strength, high elastic modulus, low coefficient of expansion, heat resistance, corrosion resistance,), longer service life, and reduced maintenance. Applications for composites in agriculture, chemical and petrochemical industries, construction, consumer goods, machinery, power generation and distribution, transportation, biomedicine, and safety are presented. With the continuing trend toward further cost reductions, composites warrant consideration in a wide range of non-aerospace applications. Composite materials discussed include filamentary reinforced materials, laminates, multiphase alloys, solid multiphase lubricants, and multiphase ceramics. New processes developed to aid in fabrication of composites are given.

Leeds, M. A.; Schwartz, S.; Holm, G. J.; Krainess, A. M.; Wykes, D. M.; Delzell, M. T.; Veazie, W. H., Jr.

1972-01-01

215

Chemical Composition of Cigarette Smoke.  

National Technical Information Service (NTIS)

Cigarette smoke is a concentrated aerosol of liquid particles suspended in an atmosphere consisting mainly of nitrogen, oxygen, and carbon dioxide. While the precise chemical composition of the particulate and gaseous phases is dependent on the characteri...

M. R. Guerin

1979-01-01

216

Comparison of the structural and chemical composition of two unique micro/nanostructures produced by femtosecond laser interactions on nickel  

NASA Astrophysics Data System (ADS)

The structural and chemical composition of two unique microstructures formed on nickel, with nanoscale features, produced using femtosecond laser surface processing (FLSP) techniques is reported in this paper. These two surface morphologies, termed mounds and nanoparticle-covered pyramids, are part of a larger class of self-organized micro/nanostructured surfaces formed using FLSP. Cross-sections of the structures produced using focused ion beam milling techniques were analyzed with a transmission electron microscope. Both morphologies have a solid core with a layer of nanoparticles on the surface. Energy dispersive X-ray spectroscopy by scanning transmission electron microscopy studies reveal that the nanoparticles are a nickel oxide, while the core material is pure nickel.

Zuhlke, Craig A.; Anderson, Troy P.; Alexander, Dennis R.

2013-09-01

217

Effect of Yarn Sizes on the Tensile Damage Evolution of a C/SiC Composite Fabricated by Chemical Vapor Infiltration  

NASA Astrophysics Data System (ADS)

The damage evolutions of C/SiC composites fabricated by chemical vapor infiltration with two different sizes of yarns were compared by cyclic tensile load/unload tests accompanied with the acoustic emission (AE) monitoring. The results show that an inflexion was observed in both the evolution of hysteresis characteristics and the corresponding AE curve for composite with fine yarns, which is, however, absent for composite with coarse yarns, suggesting that the former is much closer to the tough material than the latter one. Felicity effect was observed for both composites, which is more pronounced for the composite with coarse yarns due to the large yarn sizes leading to more matrix debris inside the yarns.

Wang, Yiqiang; Zhang, Litong; Cheng, Laifei

2011-04-01

218

The chemical composition of Martian soil and rocks returned by the mobile alpha proton X-ray spectrometer: preliminary results from the X-ray mode.  

PubMed

The alpha proton x-ray spectrometer (APXS) on board the rover of the Mars Pathfinder mission measured the chemical composition of six soils and five rocks at the Ares Vallis landing site. The soil analyses show similarity to those determined by the Viking missions. The analyzed rocks were partially covered by dust but otherwise compositionally similar to each other. They are unexpectedly high in silica and potassium, but low in magnesium compared to martian soils and martian meteorites. The analyzed rocks are similar in composition to terrestrial andesites and close to the mean composition of Earth's crust. Addition of a mafic component and reaction products of volcanic gases to the local rock material is necessary to explain the soil composition. PMID:9388173

Rieder, R; Economou, T; Wänke, H; Turkevich, A; Crisp, J; Brückner, J; Dreibus, G; McSween, H Y

1997-12-01

219

Hydrogen storage in different carbon materials: Influence of the porosity development by chemical activation  

NASA Astrophysics Data System (ADS)

The hydrogen adsorption capacity of different types of carbon nanofibers (platelet, fishbone and ribbon) and amorphous carbon have been measured as a function of pressure and temperature. The results showed that the more graphitic carbon materials adsorbed less hydrogen than more amorphous materials. After a chemical activation process, the hydrogen storage capacities of the carbon materials increased markedly in comparison with the non-activated ones. BET surface area of amorphous carbon increased by a factor of 3.5 and the ultramicropore volume doubled, thus increasing the hydrogen adsorption by a factor of 2. However, BET surface area in platelet CNFs increased by a factor of 3 and the ultramicropore volume by a factor of 6, thus increasing the hydrogen storage by a factor of 4.5. The dependency of hydrogen storage capacity of carbon materials on the BET surface area was evaluated using both a condensation model and experimental results. Comparison of data suggests that the hydrogen adsorption capacity clearly depends on the pore structure and so, on the accessibility to the internal surface.

Jiménez, Vicente; Ramírez-Lucas, Ana; Sánchez, Paula; Valverde, José Luís; Romero, Amaya

2012-01-01

220

Method of forming a chemical composition  

DOEpatents

A method of forming a chemical composition such as a chemical hydride is described and which includes the steps of selecting a composition having chemical bonds and which is capable of forming a chemical hydride; providing a source of hydrogen; and exposing the selected composition to an amount of ionizing radiation to encourage the changing of the chemical bonds of the selected composition, and chemically reacting the selected composition with the source of hydrogen to facilitate the formation of a chemical hydride.

Bingham, Dennis N. (Idaho Falls, ID) [Idaho Falls, ID; Wilding, Bruce M. (Idaho Falls, ID) [Idaho Falls, ID; Klingler, Kerry M. (Idaho Falls, ID) [Idaho Falls, ID; Zollinger, William T. (Idaho Falls, ID) [Idaho Falls, ID; Wendt, Kraig M. (Idaho Falls, ID) [Idaho Falls, ID

2007-10-09

221

Electromagnetic Properties of a New Ferrite-Ceramic Composite Material  

Microsoft Academic Search

NiCuZn ferrite-CaCu3Ti4O12 composite materials which possess both capacitive and inductive properties for suppressing electromagnetic interference (EMI) were synthesized by a solid-state reaction. As the CaCu3Ti4O12 content increases from 1 to 30 wt%, the epsiv' of the composites measured at 100 Hz increases from 35 to 12 000 while the mu' of the composites measured at 100 kHz decreases from 1800

Ying He; Huaiwu Zhang; Weiwei Ling; Chunhong Mu; Yuanxun Li; Jian Shen

2009-01-01

222

Chemical composition of the continental crust as revealed by studies in East China  

NASA Astrophysics Data System (ADS)

We report abundances of sixty-three major, trace, and rare earth elements in the upper crust in five tectonic units (the interior and southern margin of the North China craton, the North and South Qinling orogenic belts, and the Yangtze craton) of central East China and the study area as a whole. The estimates are based on sampling of 11,451 individual rock samples over an area of 950,000 km 2 , from which 905 large composite samples were prepared and analyzed by thirteen methods. Some of the trace elements (i.e., Ag, As, Ge, Mo, Pd, Pt, Sb, Se, Sn, W) have never been subjected to systematic analysis in previous regional crustal composition studies. The middle, lower, and total crust compositions of the tectonic units are also estimated from studies of exposed crustal cross-sections and granulite xenoliths and by correlation of seismic data from eleven regional seismic refraction profiles with lithologies. The proposed granodioritic total crust composition has the following ratios of element pairs exhibiting similar compatibility, that are identical or close to the primitive mantle values: Zr/Hf = 37, Nb/Ta = 17.5, Ba/Th = 87, K/Pb = 0.12 × 10 4 , Rb/Cs = 25, Ba/Rb = 8.94, Sn/Sm = 0.31, Se/Cd = 1.64, La/As = 10.3, Ce/Sb = 271, Pb/Bi = 57, Rb/Tl = 177, Er/Ag = 52, Cu/Au = 3.2×10 4 , Sm/Mo = 7.5, Nd/W = 40, Cl/Li = 10.8, F/Nd = 21.9, and La/B = 1.8. The ( ) value is calculated at ~5. The upper crust composition is less evolved and higher in TiO 2 , total FeO, Co, Cr, Ni, Sc and V, and lower in Na 2 O, K 2 O and Nb, Ta, Rb, Th, U, and Zr, than previous estimates based on shield samplings. Because usually the uppermost layer of the crust, where mafic volcanics tend to concentrate, has been removed from Precambrian shields, and since our study involves Phanerozoic orogenic belts, the results are suggested to be better representative of the upper crust in a general sense. Trace elements associated with mineralization (e.g., B, Cl, Se, As, Bi, Pd, W, Th, Cs, Ta, Tl, Hg, Au, and Pb) show considerable inter-unit variations by a factor of 2-5 in the upper crust. In addition, the North Qinling paleoactive margin is characterized by anomalous enrichment in Th, U, and Pb in particular and has a marked lower value (3.3) compared to the two cratons and the South Qinling paleopassive margin ( = 4.5-6.2). Each tectonic unit has a relatively homogenous middle crust composition which is broadly similar to the composition of the total crust. The lower crust in East China can be divided into two layers both seismically and chemically. The upper lower crust is characterized by Vp = 6.7 km s -1 and an intermediate composition and the lowermost crust by Vp = 7.1 km s -1 and a mafic composition. The bulk lower crust is still intermediate in composition with 58% SiO 2 due to the dominance of the upper lower crust. P-wave velocities of both the lower and total crusts in East China are slower by 0.2-0.4 km s -1 compared to various global estimates. Correspondingly, the total crust shows an more evolved composition and is characterized by a significant negative Eu anomaly (Eu/Eu * = 0.80), low (10.4), and high (3.0) ratios. The obtained SiO 2 is 64% on a volatile-free basis. The near arc magma ratio implies that intraplate crustal growth contributes < 10% of the continental crust. The relative deficits in Eu, Sr, and transition metals (Cr, Ni, Co, V, and Ti) in the derived crustal compositions of East China, along with slower crustal velocity and thin crustal thickness for the Paleozoic to Mesozoic Qinling-Dabie-Sulu orogenic belt, strongly suggest that lower crust delamination of eclogites, as represented by those from the Dabie-Sulu belt, had played an important role in modification of the East China crust during the Phanerozoic era.

Shan, Gao; Luo, Ting-Chuan; Zhang, Ben-Ren; Zhang, Hong-Fei; Han, Yin-Wen; Zhao, Zi-Dan; Hu, Yi-Ken

1998-06-01

223

Chemical composition of the continental crust as revealed by studies in East China  

NASA Astrophysics Data System (ADS)

We report abundances of sixty-three major, trace, and rare earth elements in the upper crust in five tectonic units (the interior and southern margin of the North China craton, the North and South Qinling orogenic belts, and the Yangtze craton) of central East China and the study area as a whole. The estimates are based on sampling of 11,451 individual rock samples over an area of 950,000 km 2, from which 905 large composite samples were prepared and analyzed by thirteen methods. Some of the trace elements (i.e., Ag, As, Ge, Mo, Pd, Pt, Sb, Se, Sn, W) have never been subjected to systematic analysis in previous regional crustal composition studies. The middle, lower, and total crust compositions of the tectonic units are also estimated from studies of exposed crustal cross-sections and granulite xenoliths and by correlation of seismic data from eleven regional seismic refraction profiles with lithologies. The proposed granodioritic total crust composition has the following ratios of element pairs exhibiting similar compatibility, that are identical or close to the primitive mantle values: Zr/Hf = 37, Nb/Ta = 17.5, Ba/Th = 87, K/Pb = 0.12 × 10 4, Rb/Cs = 25, Ba/Rb = 8.94, Sn/Sm = 0.31, Se/Cd = 1.64, La/As = 10.3, Ce/Sb = 271, Pb/Bi = 57, Rb/Tl = 177, Er/Ag = 52, Cu/Au = 3.2×10 4, Sm/Mo = 7.5, Nd/W = 40, Cl/Li = 10.8, F/Nd = 21.9, and La/B = 1.8. The ? ( 238U/ 204Pb) value is calculated at ˜5. The upper crust composition is less evolved and higher in TiO 2, total FeO, Co, Cr, Ni, Sc and V, and lower in Na 2O, K 2O and Nb, Ta, Rb, Th, U, and Zr, than previous estimates based on shield samplings. Because usually the uppermost layer of the crust, where mafic volcanics tend to concentrate, has been removed from Precambrian shields, and since our study involves Phanerozoic orogenic belts, the results are suggested to be better representative of the upper crust in a general sense. Trace elements associated with mineralization (e.g., B, Cl, Se, As, Bi, Pd, W, Th, Cs, Ta, Tl, Hg, Au, and Pb) show considerable inter-unit variations by a factor of 2-5 in the upper crust. In addition, the North Qinling paleoactive margin is characterized by anomalous enrichment in Th, U, and Pb in particular and has a marked lower ? value (3.3) compared to the two cratons and the South Qinling paleopassive margin (? = 4.5-6.2). Each tectonic unit has a relatively homogenous middle crust composition which is broadly similar to the composition of the total crust. The lower crust in East China can be divided into two layers both seismically and chemically. The upper lower crust is characterized by Vp = 6.7 km s -1 and an intermediate composition and the lowermost crust by Vp = 7.1 km s -1 and a mafic composition. The bulk lower crust is still intermediate in composition with 58% SiO 2 due to the dominance of the upper lower crust. P-wave velocities of both the lower and total crusts in East China are slower by 0.2-0.4 km s -1 compared to various global estimates. Correspondingly, the total crust shows an more evolved composition and is characterized by a significant negative Eu anomaly (Eu/Eu? = 0.80), low Sr/Nd (10.4), and high La/Nb (3.0) ratios. The obtained SiO 2 is 64% on a volatile-free basis. The near arc magma La/Nb ratio implies that intraplate crustal growth contributes <10% of the continental crust. The relative deficits in Eu, Sr, and transition metals (Cr, Ni, Co, V, and Ti) in the derived crustal compositions of East China, along with slower crustal velocity and thin crustal thickness for the Paleozoic to Mesozoic Qinling-Dabie-Sulu orogenic belt, strongly suggest that lower crust delamination of eclogites, as represented by those from the Dabie-Sulu belt, had played an important role in modification of the East China crust during the Phanerozoic era.

Gao, Shan; Luo, Ting-Chuan; Zhang, Ben-Ren; Zhang, Hong-Fei; Han, Yin-wen; Zhao, Zi-Dan; Hu, Yi-Ken

1998-06-01

224

Process for preparing a chemical compound enriched in isotope content  

DOEpatents

A process to prepare a chemical enriched in isotope content which includes: (a) A chemical exchange reaction between a first and second compound which yields an isotopically enriched first compound and an isotopically depleted second compound; (b) the removal of a portion of the first compound as product and the removal of a portion of the second compound as spent material; (c) the conversion of the remainder of the first compound to the second compound for reflux at the product end of the chemical exchange reaction region; (d) the conversion of the remainder of the second compound to the first compound for reflux at the spent material end of the chemical exchange region; and the cycling of the additional chemicals produced by one conversion reaction to the other conversion reaction, for consumption therein. One of the conversion reactions is an oxidation reaction, and the energy that it yields is used to drive the other conversion reaction, a reduction. The reduction reaction is carried out in a solid polymer electrolyte electrolytic reactor. The overall process is energy efficient and yields no waste by-products.

Michaels, Edward D. (Spring Valley, OH)

1982-01-01

225

Elastomer actuators: systematic improvement in properties by use of composite materials  

NASA Astrophysics Data System (ADS)

Dielectric elastomer actuators (DEAs) have attracted increasing attention over the last few years owing to their outstanding properties, e.g. their large actuation strains, high energy density, and pliability, which have opened up a wide spectrum of potential applications in fields ranging from microengineering to medical prosthetics. There is consequently a huge demand for new elastomer materials with improved properties to enhance the performance of DEAs and to overcome the limitations associated with currently available materials, such as the need for high activation voltages and the poor long-term stability. The electrostatic pressure that activates dielectric elastomers can be increased by higher permittivity of the elastomer and thus may lead to lower activation voltages. This has led us to consider composite elastomeric dielectrics based on thermoplastic elastomers or PDMS, and conductive polyaniline or ceramic (soft doped PZT) powder fillers. The potential of such materials and strategies to counter the adverse effects of increased conductivity and elastic modulus are discussed.

Molberg, Martin; Leterrier, Yves; Plummer, Christopher J. G.; Löwe, Christiane; Opris, Dorina M.; Clemens, Frank; Månson, Jan-Anders E.

2010-03-01

226

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

Micromechanical Combined Stress Analysis (MICSTRAN) computer code provides materials engineers with easy-to-use personal-computer-based software tool to calculate overall properties of composite, given properties of fibers and matrix. Computes overall thermoelastic parameters and stresses by micromechanical analysis. Written in FORTRAN 77.

Naik, Rajiv A.

1994-01-01

227

Chemical analysis and biological testing of materials from the EDS coal liquefaction process: a status report  

SciTech Connect

Representative process materials were obtained from the EDS pilot plant for chemical and biological analyses. These materials were characterized for biological activity and chemical composition using a microbial mutagenicity assay and chromatographic and mass spectrometric analytical techniques. The two highest boiling distillation cuts, as well as process solvent (PS) obtained from the bottoms recycle mode operation, were tested for initiation of mouse skin tumorigenicity. All three materials were active; the crude 800/sup 0 +/F cut was substantially more potent than the crude bottoms recycle PS or 750 to 800/sup 0/F distillate cut. Results from chemical analyses showed the EDS materials, in general, to be more highly alkylated and have higher hydroaromatic content than analogous SRC II process materials (no in-line process hydrogenation) used for comparison. In the microbial mutagenicity assays the N-PAC fractions showed greater activity than did the aliphatic hydrocarbon, hydroxy-PAH, or PAH fractions, although mutagenicity was detected in certain PAH fractions by a modified version of the standard microbial mutagenicity assay. Mutagenic activities for the EDS materials were lower, overall, than those for the corresponding materials from the SRC II process. The EDS materials produced under different operational modes had distinguishable differences in both their chemical constituency and biological activity. The primary differences between the EDS materials studied here and their SRC II counterparts used for comparison are most likely attributable to the incorporation of catalytic hydrogenation in the EDS process. 27 references, 28 figures, 27 tables.

Later, D.W.; Pelroy, R.A.; Wilson, B.W.

1984-05-01

228

Structure, composition, and chemical reactivity of carbon nanotubes by selective nitrogen doping  

Microsoft Academic Search

Carbon nanotubes (CNTs) doped with a range of nitrogen contents (0–10at.%) were prepared via a floating catalyst CVD method using ferrocene, NH3, and xylene or pyridine. XPS and Raman microscopy were used to assess quantitatively the compositional and structural properties of the nitrogen-doped carbon nanotubes (N-CNTs). XPS analysis indicates a shift in and broadening of the C1s spectra track with

Stephen Maldonado; Stephen Morin; Keith J. Stevenson

2006-01-01

229

Space radiation effects on composite matrix materials - Analytical approaches  

NASA Technical Reports Server (NTRS)

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.

1979-01-01

230

Chemical processing of lunar materials  

NASA Technical Reports Server (NTRS)

The paper highlights recent work on the general problem of processing lunar materials. The discussion covers lunar source materials, refined products, motivations for using lunar materials, and general considerations for a lunar or space processing plant. Attention is given to chemical processing through various techniques, including electrolysis of molten silicates, carbothermic/silicothermic reduction, carbo-chlorination process, NaOH basic-leach process, and HF acid-leach process. Several options for chemical processing of lunar materials are well within the state of the art of applied chemistry and chemical engineering to begin development based on the extensive knowledge of lunar materials.

Criswell, D. R.; Waldron, R. D.

1979-01-01

231

Variations in T2* and Fat Content of Murine Brown and White Adipose Tissues by Chemical-Shift MRI  

PubMed Central

Purpose To compare T2* relaxation times and proton density fat-fraction (PDFF) values between brown (BAT) and white (WAT) adipose tissue in lean and ob/ob mice. Materials and Methods A group of lean male mice (n=6), and two groups of ob/ob male mice placed on similar four-week (n=6) and eight-week (n=8) ad libitum diets, were utilized. The animals were imaged at 3 Tesla using a T2*-corrected chemical-shift based water-fat MRI method that provides simultaneous estimation of T2* and PDFF on a voxel-wise basis. Regions of interest were drawn within the interscapular BAT and gonadal WAT depots on co-registered T2* and PDFF maps. Measurements were assessed using analysis of variance, Bonferroni-adjusted t-test for multi-group comparisons, and the Tukey post-hoc test. Results Significant differences (p<0.01) in BAT T2* and PDFF were observed between the lean and ob/ob groups. The ob/ob animals exhibited longer BAT T2* and greater PDFF than lean animals. However, only BAT PDFF was significantly different (p<0.01) between the two ob/ob groups. When comparing BAT to WAT within each group, T2* and PDFF values were consistently lower in BAT than WAT (p<0.01). The difference was most prominent in the lean animals. In both ob/ob groups, BAT exhibited very WAT-like appearances and properties on the MRI images. Conclusion T2* and PDFF are lower in BAT than WAT. This is likely due to variations in tissue composition. The values were consistently lower in lean mice than in ob/ob mice, suggestive of the former’s greater demand for BAT thermogenesis and reflective of leptin hormone deficiencies and diminished BAT metabolic activity in the latter.

Hu, Houchun H.; Hines, Catherine D.G.; Smith, Daniel L.; Reeder, Scott B.

2011-01-01

232

Modeling of chemical vapor infiltration process for fabrication of carbon–carbon composites by finite difference methods  

Microsoft Academic Search

A finite difference (FD)-based method is proposed to describe the chemical vapor infiltration (CVI) processes for fabrication of carbon–carbon composites. The continuous, unsteady-state CVI processing can be divided into many discrete steady-state depositions by this model. Long cylindroid unidirectional carbon–carbon composites are prepared using the isothermal CVI technique to verify the accuracy of the FD methods. Experimental research shows that

Xianghui Hou; Hejun Li; Yixi Chen; Kezhi Li

1999-01-01

233

Fabrication of SiC fiber reinforced SiC composite by chemical vapor infiltration for excellent mechanical properties  

Microsoft Academic Search

The process optimization for the forced-flow\\/thermal gradient chemical vapor infiltrated SiC based composites with an advanced SiC fiber(Tyranno SA) was carried out. The new SiC\\/SiC composites had a lower porosity and the uniform distribution of pores compared with conventional CVI. The uniform interphases between SiC fibers and matrix could be obtained by reversing the gas-flow direction mid-way through the coating

N. Igawa; T. Taguchi; T. Nozawa; L. L. Snead; T. Hinoki; J. C. McLaughlin; Y. Katoh; S. Jitsukawa; A. Kohyama

2005-01-01

234

Alumina fiber/alumina matrix composites prepared by a chemical vapor infiltration technique  

SciTech Connect

Ceramic/ceramic composites made of alumina fibers embedded in an alumina matrix were obtained from fibrous alumina preforms (fiber volume = 0.12 to 0.40) using a chemical vapor infiltration technique based on gaseous alumina precursors (AlCl3-H2-CO2). Low deposition temperatures (950 to 1000 C) and total pressures (2 to 3 kPa) must be used to preferentially deposit alumina within the pores rather than on the external surface of the preform. Different fiber orientations were studied: i.e. randomly oriented short fibers and one- and two-dimensional preforms. Densification was performed down to residual open porosity of the order of 10 to 15 percent. For a one-dimensional alpha-alumina fiber composite (residual porosity about 10 percent), flexural strengths of 250 MPa and about 100 MPa were obtained at room temperature and 1200 C, respectively. Most composites exhibited brittle failure at room temperature. 20 references.

Colmet, R.; Lhermitte-Sebire, I.; Naslain, R.

1986-04-01

235

Chemical characterization of torbanites by transmission micro-FTIR spectroscopy: Origin and extent of compositional heterogeneities  

NASA Astrophysics Data System (ADS)

Four Permian to Carboniferous torbanites of various geographical origins were examined by transmission micro-FTIR spectroscopy on doubly polished thin sections (10-25 ?m). Several types of heterogeneities (different types of organic matrix; yellow and orange Botryococcus braunii colonies) were identified and chemically characterized. Important differences were noted between the organic constituents of the matrix and the algal bodies, regarding the intensity of OH, C?O, and aromatic C?C absorptions. The previous IR studies of torbanites on bulk samples therefore afforded substantially biased information on the composition of B. braunii fossil colonies, on their oil potential, and on the maturity of such kerogens. Micro-FTIR spectra indicate that the organic matrix corresponds neither to an extensive breaking up of colonies nor to humic substances. This matrix is highly heterogeneous; two types were identified in the Autun sample (chiefly corresponding to degraded algal and bacterial constituents, respectively). A precise characterization of the organic matrix was made difficult, however, in Pumpherston torbanite, due to intimate mixing with minerals. The co-occurrence of yellow and orange colonies, with contrasted micro-FTIR features, in Autun torbanite neither reflects radiolysis processes nor differences in maturation and/or source algae. A specific spatial relation was observed between these two types of algal bodies and the organo-mineral matrix, thus revealing differences in colony microenvironment after deposition. The orange colonies are likely derived, in agreement with their micro-FTIR spectra and their spatial correlation with the matrix, from sedimentological and/or matrix-catalysed diagenetic transformations of some yellow colonies. This first application of micro-FTIR to kerogens confirmed the utility of this nondestructive, in situ pin-point method. Although torbanites have been extensively studied, all the analytical methods so far used only provided bulk information. Further insight into torbanite composition, origin and evolution can be obtained via micro-FTIR spectroscopy.

Landais, Patrick; Rochdi, Aïcha; Largeau, Claude; Derenne, Sylvie

1993-06-01

236

Multi-scaled polymer-based composite materials synthesized by mechanical alloying  

Microsoft Academic Search

Multi-scaled composite materials are of great importance, because they exhibit higher mechanical properties than those attained using conventional fillers or polymer blends. In this work, multi-scaled composite materials based on ultra-high-molecular weight polyethylene (UHMWPE), quasicrystals, polyimide and bronze are investigated for use in the moving parts of machines, gears, bearings, and sliding elements. The main object is to investigate the

S. D. Kaloshkin; L.-J. Vandi; V. V. Tcherdyntsev; E. V. Shelekhov; V. D. Danilov

2009-01-01

237

Characterization of the failure process in composite materials by the Fiber Bundle Model  

NASA Astrophysics Data System (ADS)

Our aim in this paper is to investigate the time distribution of the monomer intact fiber of a bundle model of fibers subject to a constant external load. Breaking process is created by thermally induced stress fluctuations followed by load redistribution with the local load-sharing rule (LLS) which subsequently leads to an avalanche of breakings. The results showed that the maximum number of the intact fiber monomer (MNIFM) was observed at time t1 proportional to the materials failure time tf independently of the temperature value (t1? 1/3 tf). So, this parameter can characterize clearly the avalanche phenomenon observed in the failure process of the composite materials. Moreover, we have found that MNIFM presents a Gaussian variation with the applied load and exhibits a power law with the size of the system. The MNIFM temperature dependence was also investigated in this study.

Hader, A.; Achik, I.; Lahyani, A.; Sbiaai, K.; Boughaleb, Y.

2014-07-01

238

Chemical Compositions by Using LC-MS/MS and GC-MS and Biological Activities of Sedum sediforme (Jacq.) Pau.  

PubMed

In this research, the chemical composition and biological activities of various extracts obtained from whole parts of Sedum sediforme (Jacq.) Pau were compared. The amounts of total phenolic and flavonoid components in crude extracts were determined by expression as pyrocatechol and quercetin equivalents, respectively. All of the extracts (petroleum ether, acetone, methanol, and water) obtained from S. sediforme showed strong antioxidant activity in four tested methods. Particularly, the IC50 values of the methanol extract, which was the richest in terms of total phenolic and flavonoid contents, were found to be lower than those of ?-tocopherol and BHT in ?-carotene bleaching (9.78 ± 0.06 ?g/mL), DPPH free radical scavenging (9.07 ± 0.07 ?g/mL), and ABTS cation radical scavenging (5.87 ± 0.03 ?g/mL) methods. Furthermore, the methanol extract of S. sediforme showed higher inhibition activity than galanthamine against acetyl- and butyryl-cholinesterase enzymes. Also, acetone and methanol extracts exhibited moderate antimicrobial activity against Candida albicans. The main constituents of fatty acid and essential oil were identified as palmitic acid (C16:0) (28.8%) and ?-selinene (20.4%), respectively, by GC-MS. In the methanol extract of S. sediforme, quercetin, rutin, naringenin, and protocatechuic, p-coumaric, caffeic, and chlorogenic acids were detected and quantified by LC-MS/MS. Results of the current study showed that the methanol extract of S. sediforme may also be used as a food supplement. PMID:24773044

Erta?, Abdulselam; Bo?a, Mehmet; Y?lmaz, Mustafa Abdullah; Ye?il, Yeter; Ha?imi, Nesrin; Kaya, Meryem ?eyda; Temel, Hamdi; Kolak, Ufuk

2014-05-21

239

Leaf Xanthophyll content and composition in sun and shade determined by HPLC  

Microsoft Academic Search

As a part of our investigations to test the hypothesis that zeaxanthin formed by reversible de-epoxidation of violaxanthin serves to dissipate any excessive and potentially harmful excitation energy we determined the influence of light climate on the size of the xanthophyll cycle pool (violaxanthin + antheraxanthin + zeaxanthin) in leaves of a number of species of higher plants. The maximum

Susan S. Thayer; Olle Björkman

1990-01-01

240

Chemical vapor infiltration of non-oxide ceramic matrix composites  

SciTech Connect

Continuous fiber ceramic composites are enabling new, high temperature structural applications. Chemical vapor infiltration methods for producing these composites are being investigated, with the complexity of filament weaves and deposition chemistry merged with standard heat and mass transport relationships. Silicon carbide- based materials are, by far, the most mature, and are already being used in aerospace applications. This paper addresses the state-of-the-art of the technology and outlines current issues.

Besmann, T.M.; Stinton, D.P.; Lowden, R.A.

1993-12-31

241

Policosanol contents and compositions of wheat varieties.  

PubMed

Policosanol (PC) is the common name for a mixture of high molecular weight (20-36 carbon) aliphatic primary alcohols, which are constituents of plant epicuticular waxes. Wheat germ oil has been reported to improve human physical fitness, and this effect is attributed to its high PC, specifically its high octacosanol (OC) content. Although the PC composition of wheat leaves has been studied extensively, information on PC content and composition of wheat grain fractions is scarce. The objective of this study was to examine the PC contents and compositions of wheat grain fractions of 31 varieties grown in Oklahoma. PC compositions of the samples were identified using a gas chromatograph coupled with a mass spectrometer. The PC content of wheat bran was higher than that of the germ, shorts, and flour. The Trego and Intrada varieties had the highest PC content among the 31 wheat varieties studied. Tetracosanol (C24), hexacosanol (C26), and OC (C28) were the major PC components in all varieties. This study showed that wheat varieties grown under identical growing conditions and management differ significantly in PC content and composition. PMID:15998118

Irmak, Sibel; Dunford, Nurhan Turgut

2005-07-13

242

Variation in Miscanthus chemical composition and implications for conversion by pyrolysis and thermo-chemical bio-refining for fuels and chemicals.  

PubMed

Different species and genotypes of Miscanthus were analysed to determine the influence of genotypic variation and harvest time on cell wall composition and the products which may be refined via pyrolysis. Wet chemical, thermo-gravimetric (TGA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) methods were used to identify the main pyrolysis products and determine the extent to which genotypic differences in cell wall composition influence the range and yield of pyrolysis products. Significant genotypic variation in composition was identified between species and genotypes, and a clear relationship was observed between the biomass composition, yields of pyrolysis products, and the composition of the volatile fraction. Results indicated that genotypes other than the commercially cultivated Miscanthus x giganteus may have greater potential for use in bio-refining of fuels and chemicals and several genotypes were identified as excellent candidates for the generation of genetic mapping families and the breeding of new genotypes with improved conversion quality characteristics. PMID:21035327

Hodgson, E M; Nowakowski, D J; Shield, I; Riche, A; Bridgwater, A V; Clifton-Brown, J C; Donnison, I S

2011-02-01

243

Analysis of neutron diffraction peak broadening caused by internal stresses in composite materials  

SciTech Connect

Neutron diffraction is an essential tool in the study of internal stresses in composite materials. In most work only the peak shifts caused by the related elastic strains are considered, but other valuable information exists in the form of peak shape changes. The conditions under which the pure diffraction profile of the composite (i.e. the profile when all sources of broadening not caused by the residual stresses are removed) represents the probability distribution of the peak shifts corresponding to the strains are examined. It is shown that in these conditions, the pure diffraction profile has no attributes of particle size broadening (and vice versa), thereby providing a test for the validity of results interpreted in this way. The experimental derivation of measured strain distributions in Al{sub 2}O{sub 3}/SiCp composites using neutron diffraction is described. No apparent particle size broadening was detected, demonstrating the validity of the results, which also satisfied other tests for consistency.

Todd, R.I.; Borsa, C.; Derby, B. [Univ. of Oxford (United Kingdom). Dept. of Materials; Bourke, M.A.M. [Los Alamos National Lab., NM (United States)

1994-07-01

244

Material composition optimization for heat-resisting FGMs by artificial neural network  

Microsoft Academic Search

Unless the material composition field in functionally graded materials (FGM) is assumed a priori, an explicit relation between the objective function and the design variables is almost hard to derive. This implicitness naturally leads to the use of finite difference scheme for the sensitivity analysis in the numerical optimization, but which requires the remarkably long CPU time when the objective

J. R. Cho; S. W. Shin

2004-01-01

245

Fatigue Crack and Porosity Measurement in Composite Materials by Thermographic and Ultrasonic Methods  

NASA Technical Reports Server (NTRS)

Contents include the following: 1. Purpose. Detect thermo-mechanically induced intra-ply fatigue microcracking and manufactured porosity in unlined composite pressure vessels. 2. Defect descriptions. Porosity, microcracking. 3. Thermography. Overview of technique. Strengths and Weaknesses. Examples of its use for porosity detection. 4. Resonant ultrasound spectroscopy. Overview of technique. Strengths and Weaknesses. Examples of its use for microcracking detection. Conclusions.

Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.

2003-01-01

246

Micromanufacturing Of Hard To Machine Materials By Physical And Chemical Ablation Processes  

NASA Astrophysics Data System (ADS)

Miniaturization leads to high requirements to the applied manufacturing processes especially in respect to the used hard to machine materials and the aims of structure size and geometrical accuracy. Traditional manufacturing processes reach their limits here. One alternative for these provide thermal and chemical ablation processes. These processes are applied for the production of different microstructures in different materials like hardened steel, carbides and ceramics especially for medical engineering and tribological applications.

Schubert, A.; Edelmann, J.; Gross, S.; Zeidler, H.; Meichsner, G.; Hackert, M.; Wolf, N.; Schneider, J.

2011-01-01

247

Measurement of complex Young moduli of composite materials by time-gated microwaves  

NASA Astrophysics Data System (ADS)

The complex Young's modulus of composite materials made of glass/fibers and epoxy matrix is deduced from the measurement of velocities and amplitude of acoustic waves generated by microwaves. A magnetron working at 10 GHz delivers a pulse of 1.2 ?s with a power of 5 kilowatts. Acoustic rod modes are generated at both interfaces of the sample that is placed in a waveguide. The acoustic wave generation is due to the rapid thermal expansion caused by microwave absorption. From a unidirectional model the acceleration at any position in the sample can be computed. An accelerometer acquired the acoustic waveform in a low frequency domain (5-25 kHz) at an end of the rod. The comparison between experimental and theoretical accelerations permits to solve the inverse problem of determination of the viscoelastic properties of the rod. The samples are cut out of a plate in various directions to measure the viscoelastic properties along the fibers or in the perpendicular direction. A comparison between complex Young's moduli measured at low and ultrasonic frequencies will be presented and leads to some comments about the attenuation along the fibers in composite materials. .

Hosten, Bernard; Bacon, Christophe

2000-05-01

248

Determination of chemical composition of siderite in concretions by wavelength-dispersive X-ray spectrometry following selective dissolution.  

PubMed

Determination of chemical composition of siderite (Fe, Me)CO(3) (where Me=Mg, Ca, Mn) present in siderite concretion is developed. An accurate and precise determination of Mg, Ca, Mn and Fe in siderite required complete separation of this mineral from other materials, e.g. calcite, quartz. For this purpose, selective dissolution in acetic acid (HAc) was applied. HAc concentration from 0.1 to 1 mol L(-1) and extraction time from 0.5 to 8h were investigated. In each step of investigation of selective dissolution, the X-ray diffraction measurements (XRD) of the residues was performed and also calcium (complexometric titration) and iron (XRF) in solution were determined. HAc of concentration 0.25 mol L(-1) and extraction time of 2h was adopted for siderite separation because in these conditions the siderite was not dissolved and, simultaneously, calcite was completely dissolved. In the next step, the nondissolved sample was digested in hydrochloric acid. The solution of the separated siderite was pipetted onto membrane filter and Mg, Ca, Mn and Fe were determined by wavelength-dispersive X-ray fluorescence (WDXRF) spectrometry. The calibration was performed using 11 certified reference materials of iron ores. Matrix effects were corrected using empirical coefficient model for intermediate-thickness samples. PMID:19064098

Sitko, Rafa?; Zawisza, Beata; Krzykawski, Tomasz; Malicka, Ewa

2009-01-15

249

Effect of ceramic coating by aerosol deposition on abrasion resistance of a resin composite material.  

PubMed

Aerosol deposition (AD coating) is a novel technique to coat solid substances with a ceramic film. The purpose of the present study was to investigate the effect of AD coating on abrasion resistance of a resin composite material. A 5-microm-thick aluminum oxide layer was created on the polymerized resin composite. The specimen was cyclically abraded using a toothbrush abrasion simulator for 100,000 cycles. Abraded surface was then measured with a profilometer to determine the average roughness (Ra) and maximum roughness (Rmax). It was found that abrasion cycling increased the Ra value of the No-AD-coating group, but decreased the Ra and Rmax values of the AD coating group. Moreover, the AD coating group showed significantly smaller Ra and Rmax values after 100,000 abrasion cycles as compared to the No-coating control group. Microscopic observation supported these findings. In conclusion, the resistance of the resin composite against toothbrush abrasion was improved by AD coating. PMID:17338303

Taira, Yohsuke; Hatono, Hironori; Mizukane, Masahiro; Tokita, Masahiro; Atsuta, Mitsuru

2006-12-01

250

Effects of Annealing on Material Characteristics of Diamond-Like Carbon Film Formed by Focused-Ion-Beam Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

The effects of annealing on the material characteristics of a diamond-like carbon (DLC) thin film fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated. The elementary analysis, using Rutherford backscattering spectrometry and elastic recoil detection analysis, and measurement of hardness and Young’s modulus, using a nanoindentation technique, were performed on the FIB-CVD DLC thin film by annealing for 1 h in the temperature range from room temperature to 1273 K. Elementary analysis indicated that the Ga content in the FIB-CVD DLC film used as an ion source began to decrease considerably at 523 K and the H content also began to decrease at 773 K. On the other hand, the hardness and Young’s modulus of the FIB-CVD DLC film were found to decrease beyond 773 K. This decrease in hardness is ascribed to the variation in H content rather than in Ga content in the film.

Kanda, Kazuhiro; Igaki, Jun-ya; Saikubo, Akihiko; Kometani, Reo; Suzuki, Tsuneo; Niihara, Koichi; Saitoh, Hidetoshi; Matsui, Shinji

2008-09-01

251

Material circulation model including chemical differentiation within the mantle and secular variation of temperature and composition of the mantle  

Microsoft Academic Search

It is 20 years since Allègre [Tectonophys 81 (1982) 109] proposed chemical geodynamics as an integrated study of the chemical and physical structure and evolution of the solid Earth. Accumulation of geochemical data of modern magmatic rocks (e.g. [Annu. Rev. Earth Planet. Sci. 14 (1986) 493] and whole mantle tomography (e.g. [J. Geophys. Res. 97 (1992) 4809]) allow us to

Tsuyoshi Komiya

2004-01-01

252

Chemical composition of cigarette smoke  

Microsoft Academic Search

Cigarette smoke is a concentrated aerosol of liquid particles suspended in an atmosphere consisting mainly of nitrogen, oxygen, and carbon dioxide. While the precise chemical composition of the particulate and gaseous phases is dependent on the characteristics of the cigarette and the manner in which it is smoked, both phases contain tens of hundreds of individual constitutents. Notable among potentially

Guerin

1979-01-01

253

[Mechanism of pigment content on infrared emissivity of composite coatings].  

PubMed

Polyurethane (PU)/flaky metal composite coatings were prepared by using PU and flaky metal powders as adhesives and pigments, respectively. The infrared emissivity of coatings with different metal content was measured by infrared emissometer, and the microstructure of PU/flaky metal composite coatings was observed by scanning electron microscopy. The results of infrared emissivity measurement indicate that the emissivity changes significantly with increasing metal content and presents a "U" type. The results of microstructure observation indicate that PU/flaky metal composite coatings have one-dimensional photonic structural characteristics. According to the microstructure characteristics, the optical reflection spectra of one-dimensional photonic structure in PU/flaky metal composite coatings with different metal content were simulated, and the results show that "U" type variation of emissivity with increasing metal content is derived from the blueshift of reflection peak wavelength with increasing metal content of one-dimensional photonic structure in coatings. PMID:23285860

Zhang, Wei-Gang; Xu, Guo-Yue; Xu, Fei-Feng; Ding, Ru-Ya; Tan, Shu-Juan

2012-10-01

254

Controlling charge transport in blue organic light-emitting devices by chemical functionalization of host materials  

SciTech Connect

Generation of white light from OLEDs for general lighting applications requires a highly efficient blue component. However, a stable and power efficient blue OLED component with simple device architecture remains a significant challenge partly due to lack of appropriate host materials. Here we report the photophysical and device properties of ambipolar host phosphine oxide based materials. In this work, we studied the effect of the structural modification made to phosphine oxide-based hosts on the charge balance. We observed significant changes in charge transport within the host occurred upon small modifications to their chemical structure. As a result, an alteration of the chemical design of these materials allows for the control of charge balance of the OLED.

Polikarpov, Evgueni; Koech, Phillip K.; Wang, Liang; Swensen, James S.; Cosimbescu, Lelia; Rainbolt, James E.; Von Ruden, Amber L.; Gaspar, Daniel J.; Padmaperuma, Asanga B.

2011-01-18

255

Molar mass, chemical-composition, and functionality-type distributions of poly(2-oxazoline)s revealed by a variety of separation techniques.  

PubMed

Detailed characterization of synthetic polymers often required multiple advanced separation technologies since the various molecular distributions present, e.g. polymer molar mass, chemical composition, functionality distributions, etc. are generally mutually dependent. The complexity of polymeric materials necessitates the use of a variety of analytical methods, either in conjunction or in integrated ("hyphenated") systems. Poly(2-oxazoline) homo- and copolymers with two different side groups rendering the systems hydrophobic, i.e. phenyl and dec-9-enyl substituents, synthesized by living cationic ring-opening polymerization, were investigated. The average chemical composition obtained by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) corresponded well with the theoretical composition. The chemical-composition distribution was studied with gradient elution liquid chromatography (GELC) using water and tetrahydrofuran as mobile-phase components. Statistical copolymer samples - in contrast to their block copolymer analogues - revealed two well-separated peaks in GELC. By combining GELC with size-exclusion chromatography (SEC) it was confirmed that the GELC separation was not based on differences in the molar mass. A more likely explanation of the GELC results is the presence of an ionic fraction in the samples of statistical copolymers resulting from either chain-transfer reactions or termination by addition of water. This hypothesis was confirmed with capillary electrophoresis. PMID:23068763

Chojnacka, Aleksandra; Kempe, Kristian; van de Ven, Henrik C; Englert, Christoph; Hoogenboom, Richard; Schubert, Ulrich S; Janssen, Hans-Gerd; Schoenmakers, Peter

2012-11-23

256

Energetic Analysis of Drying Biological Materials with High Moisture Content by Using Microwave Energy  

Microsoft Academic Search

One of the most important parameters in the drying process is the efficiency of energy transfer. Although it is well known that the absorbed component of the referred energy in the dehydration process under microwave conditions is theoretically lower—especially during the falling rate period of drying—by an order of magnitude than that of convective drying, the real efficiency of energy

Zoltán Kurják; Attila Barhács; János Beke

2012-01-01

257

Evaluation of body composition and nitrogen content of renal patients on chronic dialysis as determined by total body neutron activation  

SciTech Connect

Total body protein (nitrogen), body cell mass (potassium), fat, and water were measured in 15 renal patients on maintenance hemodialysis (MHD). Total body nitrogen was measured by means of prompt ..gamma.. neutron activation analysis; total body water was determined with tritium labeled water; total body potassium was measured by whole body counting. The extracellular water was determined by a technique utilizing the measurement of total body chloride and plasma chloride. When compared with corresponding values of a control group of the same age, sex, and height, the protein content, body cell mass, and total body fat of the MHD patients were within the normal range. The only significant change was an increase in the extracellular water/body cell mass ratio in the male MHD patients compared to the control. The lack of significant difference of the nitrogen values of the MHD patients compared to matched controls suggests that dialysis minimizes any residual effects of uremic toxicity or protein-calorie malnutrition. These findings further suggest that there is a need to reevaluate the traditional anthropometric and biochemical standards of nutritional status for MHD patients. It was concluded that it is particularly important to measure protein stores of MHD patients with low protein intake to ascertain nutritional status. Finally, in vivo measurement of total body nitrogen and potassium for determination of body composition provides a simple, direct, and accurate assessment of the nutritional status of MHD patients.

Cohn, S.H.; Brennan, B.L.; Yasumura, S.; Vartsky, D.; Vaswani, A.N.; Ellis, K.J.

1983-07-01

258

Composition control of Hf1-xSixO2 films deposited on Si by chemical-vapor deposition using amide precursors  

Microsoft Academic Search

Hafnium silicate (Hf1-xSixO2) films were deposited by metalorganic chemical-vapor deposition with composition x ranging from 0 to 1 using amide precursors in an organic solvent. The liquid precursors, tetrakis(diethylamido)hafnium, Hf[N(C2H5)2]4, and tetrakis(dimethylamido)silicon, Si[N(CH3)2]4, are compatible when mixed in solution, have high elemental purity, and exhibit a low halogen content. Thin oxide films were deposited with these precursors over a range

B. C. Hendrix; A. S. Borovik; C. Xu; J. F. Roeder; T. H. Baum; M. J. Bevan; M. R. Visokay; J. J. Chambers; A. L. P. Rotondaro; H. Bu; L. Colombo

2002-01-01

259

Effects of feed gas composition and catalyst thickness on carbon nanotube and nanofiber synthesis by plasma enhanced chemical vapor deposition.  

PubMed

Many engineering applications require carbon nanotubes with specific characteristics such as wall structure, chirality and alignment. However, precise control of nanotube properties grown to application specifications remains a significant challenge. Plasma-enhanced chemical vapor deposition (PECVD) offers a variety of advantages in the synthesis of carbon nanotubes in that several important synthesis parameters can be controlled independently. This paper reports an experimental study of the effects of reacting gas composition (percentage methane in hydrogen) and catalyst film thickness on carbon nanotube (CNT) growth and a computational study of gas-phase composition for the inlet conditions of experimentally observed carbon nanotube growth using different chemical reaction mechanisms. The simulations seek to explain the observed effects of reacting gas composition and to identify the precursors for CNT formation. The experimental results indicate that gas-phase composition significantly affects the synthesized material, which is shown to be randomly aligned nanotube and nanofiber mats for relatively methane-rich inlet gas mixtures and non-tubular carbon for methane-lean incoming mixtures. The simulation results suggest that inlet methane-hydrogen mixture coverts to an acetylene-methane-hydrogen mixture with minor amounts of ethylene, hydrogen atom, and methyl radical. Acetylene appears to be the indicator species for solid carbon formation. The simulations also show that inlet methane-hydrogen mixture does not produce enough gas-phase precursors needed to form quality CNTs below 5% CH4 concentrations in the inlet stream. PMID:18681048

Garg, R K; Kim, S S; Hash, D B; Gore, J P; Fisher, T S

2008-06-01

260

Chemical vapor deposition and infiltration processes of carbon materials  

Microsoft Academic Search

The chemical vapor deposition (CVD) and the chemical vapor infiltration (CVI) processes of carbon materials are reviewed starting from the historical aspects and including the latest developments in the preparation of C\\/C composites. Our presentation is based on an analysis of the different types of reactors, of the composite materials with different types of pyrocarbon as matrices and a comparison

P Delhaes

2002-01-01

261

Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites  

NASA Astrophysics Data System (ADS)

In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called "interphase" between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC-TiC)n interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC-TiC)n films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

Jacques, S.; Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P.

2013-06-01

262

Novel composite materials synthesized by the high-temperature interaction of pyrrole with layered oxide matrices  

Microsoft Academic Search

The initial goal of the research presented herein was to develop the very first synthetic metal---high-temperature superconductor ceramic composite material, in the specific form of a polypyrrole---Bi2Sr2CaCu 2O8+delta nanocomposite. In the course of scientific investigation, this scope was broadened to encompass structurally and compositionally similar layered bismuthates and simpler layered oxides. The latter substrates were prepared through novel experimental procedures

Alexandru Cezar Pavel

2006-01-01

263

Chemical composition and antibacterial activity of Cordia verbenacea extracts obtained by different methods.  

PubMed

The present study describes the chemical composition and the antibacterial activity of extracts from Cordia verbenacea DC (Borraginaceae), a traditional medicinal plant that grows widely along the southeastern coast of Brazil. The extracts were obtained using different extraction techniques: high-pressure operations and low-pressure methods. The high-pressure technique was applied to obtain C. verbenacea extracts using pure CO(2) and CO(2) with co-solvent at pressures up to 30MPa and temperatures of 30, 40 and 50 degrees C. Organic solvents such as n-hexane, ethyl acetate, ethanol, acetone and dichloromethane were used to obtain extracts by low-pressure processes. The antibacterial activity of the extracts was also subjected to screening against four strains of bacteria using the agar dilution method. The extraction yields were up to 5.0% w/w and up to 8.6% w/w for supercritical fluid extraction with pure CO(2) and with ethyl acetate as co-solvent, respectively, while the low-pressure extraction indicates yields up to 24.0% w/w in the soxhlet extraction using water and aqueous mixture with 50% ethanol as solvents. The inhibitory activity of the extracts in gram-positive bacteria was significantly higher than in gram-negative. The quantification and the identification of the extracts recovered were accomplished using GC/MS analysis. The most important components identified in the extract were artemetin, beta-sitosterol, alpha-humulene and beta-caryophyllene, among others. PMID:19683436

Michielin, Eliane M Z; Salvador, Ana A; Riehl, Carlos A S; Smânia, Artur; Smânia, Elza F A; Ferreira, Sandra R S

2009-12-01

264

Development of rice husks-plastics composites for building materials.  

PubMed

In this paper, a new effective recycling method for rice husks and waste expanded polystyrene is developed by using a combination of both wastes. A styrene solution of waste expanded polystyrene is used as a binder for rice husks-plastics composites. The composites are prepared with various mix proportions by a hot press molding method, and tested for apparent density, water absorption, expansion in thickness, and dry and wet flexural strengths. From the test results, the apparent density of the composites is increased with increasing binder content and filler-binder ratio. Their flexural strength and wet flexural strengths reach maximums at a binder content of 30.0% and a filler-binder ratio of 1.0. Their water absorption and expansion in thickness are decreased with increasing binder content and filler-binder ratio. Since the composites have a high flexural strength and water resistance, their uses as building materials are expected. PMID:16256327

Choi, Nak-Woon; Mori, Ippei; Ohama, Yoshihiko

2006-01-01

265

Regulation of responsiveness of phosphorescence toward dissolved oxygen concentration by modulating polymer contents in organic-inorganic hybrid materials.  

PubMed

Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the dissolved oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the dissolved oxygen concentration in water can be modulated by changing the percentage of the contents in the material. PMID:24794749

Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki

2014-06-15

266

Chemical composition of hard-coal pitches  

SciTech Connect

The chemical compositions of the pitches from seven coke and chemicals enterprises working on various charges and their ..gamma.. and ..beta.. components with a quantitative estimation of the individual substances has been investigated by the GLC method. The amount of components of the initial pitches identified ranged between 63 and 78 mass.%, of the ..gamma..-fraction 70-78 mass.%, and of the ..beta..-fraction 47-59 mass.%. The hydrocarbon compositions of the pitches were practically identical, i.e., they did not appear on the composition of the charge.

Chistyakov, A.N.; Denisenko, V.I.

1982-01-01

267

Methods of selecting raw material composition for asphalt production  

Microsoft Academic Search

It is recommended that raw material for oxidation should be prepared by mixing two components with certain boiling ranges and chemical-group compositions. The heavy component may be a residue obtained by high-vacuum distillation of a long residuum, or it may be an asphalt produced in the propane deasphalting of a reduced crude. The light component may be a long residuum,

R. S. Akhmetova; E. P. Glozman

1974-01-01

268

Synthesis of nanostructured carbon materials by open-air laser-induced chemical vapor deposition  

Microsoft Academic Search

Elemental carbon in the sp2 hybridization state can form a great variety of graphitic and amorphous structures. Carbon nanotube is a well-known form of graphitic carbon that has remarkable mechanical, electronic and electrochemical properties with applications ranging from reinforced composite materials to micro-scale electronic devices. Pyrolytic carbon film with turbostratic structure is a form of amorphous carbon that possesses excellent

Kinghong Kwok

2005-01-01

269

STUDY OF CHEMICAL COMPOSITION AND ELECTRONIC STRUCTURE OF HIGH-MELTING COMPOUNDS OF ZIRCONIUM BY ELECTRONIC AES  

Microsoft Academic Search

Changes in chemical composition and electronic structure of surface layers of ZrCx and ZrNy in areas of ho- mogeneity (0.51 < xC1.0, 0.765 ys I.0) under the action of sample heating by electron bombardment within the temperature range 300 K dThC 2300 K have been studied using layer-by- layer analysis of sample surface by AES. Till now study of zirconium

I. A. Brytov; A. S. Wander; V. S. Neshpor

1984-01-01

270

Performance of composite catalysts in palm oil cracking for the production of liquid fuels and chemicals  

Microsoft Academic Search

A composite material containing zeolite ZSM-5 and mesoporous molecular sieve was prepared by coating ZSM-5 crystals with a layer of mesoporous molecular sieve using cetyltrimethylammonium chloride as template. The ratio of mesophase was varied from 10 to 40 wt.% and the alumina content in the mesophase was varied from 0 to 15 wt.%. The synthesized composite materials were characterized using

Farouq A. A Twaiq; A. R Mohamad; Subhash Bhatia

2004-01-01

271

Mechanisms in damping of mechanical vibration by piezoelectric ceramic-polymer composite materials  

Microsoft Academic Search

The piezoelectric ceramic (piezoceramic) component of a polymer-piezoelectric ceramic composite converts mechanical energy\\u000a into electrical energy and this electrical energy is dissipated as heat in a load resistance, R\\u000a x, simulated by a shunted resistance, but provided in practice by a conductive polymer composite matrix. The composite therefore\\u000a dissipates the input mechanical energy via the damping mechanism provided by piezoelectric

H. H. Law; P. L. Rossiter; L. L. Koss; G. P. Simon

1995-01-01

272

Effect of the chemical composition on the work function of gold substrates modified by binary self-assembled monolayers.  

PubMed

This study demonstrated that the work function (?) of Au substrates can be fine-tuned by using series ratios of binary self-assembled monolayers (SAMs). By using pure amine- and carboxylic acid-bearing alkanethiol SAM on gold substrates, ? of Au changed from 5.10 to 5.16 and 5.83, respectively, as determined by ultra-violet photoelectron spectrometry (UPS). The shift in ? due to the use of different functional groups was rationalized by considering the dipole moments of the molecules anchored on the Au surface. A series of binary SAMs were fabricated by mixing carboxylic acid- and amine-terminated alkanethiols in the deposition solution. By mixing these functional groups in SAMs, a linear correlation between ? with respect to chemical composition (hence the effective dipole moment on the Au surface) was observed. It was found that arbitrary ? between extremes (5.16 and 5.83) controlled by respective functional groups can be obtained by changing the chemical composition of SAMs. The Scanning Kelvin Probe (SKP) was also used to measure the contact potential difference (CPD) between SAMs and referencing Au on a patterned substrate prepared by photo-lithography. It was found that the CPD of SAMs with different chemical compositions correlates to their ?. However, the magnitude of the CPD was smaller than the difference in ? measured by UPS that was possibly due to the adsorption of contaminants in air. PMID:21258709

Lee, Szu-Hsian; Lin, Wei-Chun; Chang, Chi-Jen; Huang, Chih-Chieh; Liu, Chi-Ping; Kuo, Che-Hung; Chang, Hsun-Yun; You, Yun-Wen; Kao, Wei-Lun; Yen, Guo-Ji; Kuo, Ding-Yuan; Kuo, Yu-Ting; Tsai, Meng-Hung; Shyue, Jing-Jong

2011-03-14

273

An Overview of Recent Development in Composite Catalysts from Porous Materials for Various Reactions and Processes  

PubMed Central

Catalysts are important to the chemical industry and environmental remediation due to their effective conversion of one chemical into another. Among them, composite catalysts have attracted continuous attention during the past decades. Nowadays, composite catalysts are being used more and more to meet the practical catalytic performance requirements in the chemical industry of high activity, high selectivity and good stability. In this paper, we reviewed our recent work on development of composite catalysts, mainly focusing on the composite catalysts obtained from porous materials such as zeolites, mesoporous materials, carbon nanotubes (CNT), etc. Six types of porous composite catalysts are discussed, including amorphous oxide modified zeolite composite catalysts, zeolite composites prepared by co-crystallization or overgrowth, hierarchical porous catalysts, host-guest porous composites, inorganic and organic mesoporous composite catalysts, and polymer/CNT composite catalysts.

Xie, Zaiku; Liu, Zhicheng; Wang, Yangdong; Yang, Qihua; Xu, Longya; Ding, Weiping

2010-01-01

274

Cadmium Chemical Form in Mine Waste Materials by X-ray Absorption Spectroscopy  

SciTech Connect

This study examines the molecular form of cadmium (Cd) present in mine wastes by X-ray Absorption Spectroscopy (XAS; Cd>20 mg/kg) using the K-edge of Cd at the Photon Factory Advanced Ring (PF-AR), NW10A beam line at KEK-Tsukuba-Japan. Mine waste materials and zinc concentrate were analyzed for Cd by ICPMS prior to undertaking XAS (range 21-452 mg/kg). Model compounds (CdO, Cd(OH){sub 2}, CdCO{sub 3}, Cdacetate, CdS, Cdstearate, CdDEDTC) and samples were examined in solid form at 20 K. The XANES spectra showed similar E max values for both model compounds and samples. The EXAFS showed that Cd-S in CdS, gives a flatter spectrum in the extended region compared to Cd-O found with CdCO{sub 3}, CdO and Cd Stearate. Linear combination fitting with model Cd compounds did not give clear assignments of composition, indicating that more detailed EXAFS spectra is required as mineral forms containing Cd were present rather than simple Cd compounds such as CdCO{sub 3}. The Cd bond for a single shell model in mine waste sample matrices appears to be either Cd-O or Cd-S, or a combination of both. Comparison of molecular data from the XAS studies with bioaccessibility data giving a prediction of bioavailability for mine waste materials provides useful information about the significance of the cadmium form as a contaminant for health risk assessment purposes.

Diacomanolis, V.; Ng, J. C. [University of Queensland, National Research Centre for Environmental Toxicology, Coopers Plains, QLD, 4008 (Australia); Sadler, R. [School of Public Health, Griffith University, Brisbane, QLD (Australia); Harris, H. H. [School of Chemistry and Physics, University of Adelaide, Adelaide, SA (Australia); Nomura, M. [Photon Factory, Institute of Material Structure Science, Tsukuba (Japan); Noller, B. N. [University of Queensland, Centre For Mined Land Rehabilitation, St Lucia 4072 QLD (Australia)

2010-06-23

275

Chemical composition, morphology and optical properties of zinc sulfide coatings deposited by low-energy electron beam evaporation  

NASA Astrophysics Data System (ADS)

The research determines the features of formation, morphology, chemical composition and optical properties of the coatings deposited by the method, proposed for the first time, of the exposure of mechanical mixture of zinc and sulfur powders to low-energy electron beam evaporation. The findings show that the deposited coatings are characterized by high chemical and structural homogeneity in thickness. The study considers the influence of substrate temperature and thickness of the deposited layer on the morphology and the width of the formed ZnS thin layers band gap. Also was shown the possibility to form ZnS coatings with this method using the mixture of zinc and copper sulfide powders.

Ragachev, A. V.; Yarmolenko, M. A.; Rogachev, A. A.; Gorbachev, D. L.; Zhou, Bing

2014-06-01

276

Improved process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition  

SciTech Connect

A specially designed apparatus provides a steep thermal gradient across the thickness of fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

Lackey, W.J. Jr.; Caputo, A.J.

1984-09-07

277

Comparative chemical composition of the essential oils obtained by microwave-assisted hydrodistillation and hydrodistillation from Agrimonia pilosa LEDEB. Collected in three different regions of China.  

PubMed

Conventional hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) were performed to obtain the volatile oils of Agrimonia pilosa Ledeb. harvested in three different regions of China, which were subsequently characterized by GC-FID and GC/MS analyses. Compared with HD, MAHD was advantageous in terms of energy savings and extraction time (60 vs. 240?min for MAHD and HD, resp.). The chemical composition varied among the different oils obtained, and the variations in the contents of the main constituents of the oils were irregular. Hence, these variations affected both the quantity and composition of the oils. The oil yields (0.15-0.21%) were affected by the method of extraction and the region of harvest, with the maximum amount of oil obtained by MAHD for the plants collected in Hubei (HB) and the minimum yield obtained by HD for the plants from Zhejing (ZJ). Hexadecanoic acid constituted the major compound of the essential oils, with the highest content found in the oil obtained by HD for plants from HB (41.18%) and the lowest one found in the oil obtained by MAHD from plants from ZJ (11.83%). Microwave irradiation did not adversely affect the composition of the essential oils. The findings show that MAHD is a modern, green, and fast technology. PMID:22422533

Wang, Hongwu; Liu, Yanqing; Wei, Shoulian; Yan, Zijun; Jin, Xing

2012-03-01

278

Regional variation in content, composition and organization of porcine epithelial barrier lipids revealed by thin-layer chromatography and transmission electron microscopy  

Microsoft Academic Search

Epidermis and oral epithelia provide permeability barriers that limit penetration of potentially harmful agents. Barrier function is determined by lipids in the superficial epithelial layers and varies regionally by more than 10-fold. The purpose of this study was to determine whether differences in lipid content, composition or organization could account for this variation in barrier function. Stratum corneum from skin,

S. Law; P. W. Wertz; D. C. Swartzendruber; C. A. Squier

1995-01-01

279

Microstructure and tensile behavior of multiply needled C\\/SiC composite fabricated by chemical vapor infiltration  

Microsoft Academic Search

The microstructure and tensile behavior of a multiply needled C\\/SiC composite fabricated by chemical vapor infiltration were investigated. Results showed that the tensile stress–strain curves exhibited a typical nonlinear behavior and can be divided into three regions: a very small initial linear region followed by a large nonlinear region and finally a quasi-linear region. Needling process caused a crimp around

Jingjiang Nie; Yongdong Xu; Litong Zhang; Laifei Cheng; Junqiang Ma

2009-01-01

280

Chemical Composition of the Essential Oils of Cinnamomum loureirii Nees. From China Obtained by Hydrodistillation and Microwave-assisted Hydrodistillation  

Microsoft Academic Search

The essential oils of the bark of young branches of Cinnamomum loureirii Nees. from China were isolated by hydrodistillation (HD) and microwave-assisted hydrodistillation (MHD) in yields of 5.8% and 6.1%, respectively. The chemical composition of the oils was examined by GC and GC\\/MS. Twenty components in the HD oil and 21 components in the MHD oil were identifed, representing 95.2%

Rong Li; Ying Wang; Zi-Tao Jiang; Shan Jiang

2010-01-01

281

Composite structural materials. [aircraft structures  

NASA Technical Reports Server (NTRS)

The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1980-01-01

282

Novel composite materials synthesized by the high-temperature interaction of pyrrole with layered oxide matrices  

NASA Astrophysics Data System (ADS)

The initial goal of the research presented herein was to develop the very first synthetic metal---high-temperature superconductor ceramic composite material, in the specific form of a polypyrrole---Bi2Sr2CaCu 2O8+delta nanocomposite. In the course of scientific investigation, this scope was broadened to encompass structurally and compositionally similar layered bismuthates and simpler layered oxides. The latter substrates were prepared through novel experimental procedures that enhanced the chance of yielding nanostructured morphologies. The designed novel synthesis approaches yielded a harvest of interesting results that may be further developed upon their dissemination in the scientific community. High-temperature interaction of pyrrole with molybdenum trioxide substrates with different crystalline phases and morphologies led to the formation of the first members of a new class of heterogeneous microcomposites characterized by incomplete occupancy by the metal oxide core of the volume encapsulated by the rigid, amorphous permeable polymeric membrane that reproduces the volume of the initial grain of precursor substrate. The method may be applied for various heterogeneous catalyst substrates for the precise determination of the catalytically active crystallographic planes. In a different project, room-temperature, templateless impregnation of molybdenum trioxide substrates with different crystalline phases and morphologies by a large excess of silver (I) cations led to the formation of 1-D nanostructured novel Ag-Mo-O ternary phase in what may be the simplest experimental procedure available to date that has yielded a 1-D nanostructure, regardless the nature of the constituent material. Interaction of this novel ternary phase with pyrrole vapors at high reaction temperatures led to heterogeneous nanostructured composites that exhibited a silver nanorod core. Nanoscrolls of vanadium pentoxide xerogel were synthesized through a novel, facile reflux-based method that employed very acidic pH levels and long reaction times. The nanoscrolls proved to be an excellent precursor for the synthesis of reduced vanadium oxide nanosheets by the redox intercalation of long chain monoamine molecules. In a related development, the very first synthetic metal---mixed-valence polyoxovanadate salt hybrid material was synthesized in the form of a polypyrrole---tetrammonium hexavanadate microcomposite by a redox simultaneous co-precipitation in an aqueous solution. The novel material displayed good mechanical properties towards solid lubricant applications and tunable electronic conductivity. Nanocomposites of polypyrrole---layered bismuthates were produced by the topotactic intercalation of pyrrole and its subsequent in situ polymerization. Insulating and superconducting layered bismuthates were used in a similar experimental procedure that used pre-intercalated iodine species as sacrificial topotactic oxidizing agents. A novel method of iodine intercalation by a solution-based transport procedure was used in the process. Interaction of pyrrole with layered bismuthates at high reaction temperatures led to the formation of polymer-covered metal nanorods as a result of intrinsic lattice templating effect. The successful synthesis of the 1-D heterogeneous nanostructures represents the first example in which nanocomposites were used as precursors. Appropriate doping of the initial layered ceramic substrates led to polymer-covered metal alloy nanorods.

Pavel, Alexandru Cezar

283

Spectral Analysis by XANES Reveals that GPNMB Influences the Chemical Composition of Intact Melanosomes  

SciTech Connect

GPNMB is a unique melanosomal protein. Unlike many melanosomal proteins, GPNMB has not been associated with any forms of albinism, and it is unclear whether GPNMB has any direct influence on melanosomes. Here, melanosomes from congenic strains of C57BL/6J mice mutant for Gpnmb are compared to strain-matched controls using standard transmission electron microscopy and synchrotron-based X-ray absorption near-edge structure analysis (XANES). Whereas electron microscopy did not detect any ultrastructural changes in melanosomes lacking functional GPNMB, XANES uncovered multiple spectral phenotypes. These results directly demonstrate that GPNMB influences the chemical composition of melanosomes and more broadly illustrate the potential for using genetic approaches in combination with nano-imaging technologies to study organelle biology.

T Haraszti; C Trantow; A Hedberg-Buenz; M Grunze; M Anderson

2011-12-31

284

Proximate composition and energy content of beef steaks as influenced by USDA quality grade and degree of doneness.  

PubMed

This study evaluated the influence of various degrees of doneness on proximate composition and energy content of beef. Ten steaks were obtained from each of five USDA Prime, five USDA Choice, and five USDA Select strip loins and assigned to one of five degree of doneness treatments (two sets of treatments per strip loin): raw, medium rare (63 °C), medium (71 °C), well done (77 °C), and very well done (82 °C). After cooking, steaks were dissected into separable tissue components consisting of lean, fat, and refuse. Lean tissue was used to obtain proximate analyses of protein, moisture, fat, and ash. Degree of doneness did influence (P<0.05) the nutrient composition of beef steaks. As the degree of doneness increased, percent fat and protein increased, while percent moisture decreased. Cooking steaks to a higher degree of doneness resulted in a higher caloric value when reported per 100g basis. PMID:21663807

Smith, A M; Harris, K B; Haneklaus, A N; Savell, J W

2011-10-01

285

Chemical composition and tissue energy density of the cuttlefish ( Sepia apama ) and its assimilation efficiency by Diomedea albatrosses  

Microsoft Academic Search

The cuttlefish Sepia apama Gray (Mollusca: Cephalopoda) is a seasonally abundant food resource exploited annually by moulting albatrosses throughout\\u000a winter and early spring in the coastal waters of New South Wales, Australia. To assess its nutritional value as albatross\\u000a forage, we analysed S. apama for water, lipid protein, ash contents, energy density and amino acid composition. Because albatrosses consistently consume

H. Battam; M. Richardson; A. W. T. Watson; W. A. Buttemer

2010-01-01

286

Experimental study of electromagnetic emission signals generated by crack generation in composite materials  

NASA Astrophysics Data System (ADS)

The formation of a crack is accompanied by the generation of an electromagnetic field. A differential equation was derived and solved to describe the transformation of the field parameters into an electric signal, provided capacitive sensors are used. In the next stage, an analysis of spurious external electromagnetic and acoustic fields was carried out, and measures to suppress their effects were designed. The issue of amplifying extremely low electromagnetic signals generated during the crack formation was dealt with, too. The mentioned analyses resulted in the design of a method to detect and evaluate electromagnetic emission (EME) signals and acoustic emission (AE) signals, which accompany mechanical stressing of materials and structures. Based on the results of such analyses, an automated double-channel measuring apparatus was used for signal data acquisition, saving and processing. The operation of the apparatus was successfully tested by processing a large set of measurement results obtained from a composite material called 'extren'. Our experimental results confirmed the correctness of both the EME and AE measurement methods, and measuring apparatus design. Our measurement results make it possible to track the behaviour of cracks, localize them and evaluate some of their basic parameters.

Koktavy, P.

2009-01-01

287

Manufacturing Method for Photo-Voltaic Materials by Chemical Spray Pulverization.  

National Technical Information Service (NTIS)

Acetonitrile has been shown to be a suitable carrier solvent for the preparation of thin layers of cuprous sulphide by chemical atomization. A reactive spraying apparatus for monodispersed mist has been developed. It is claimed to be indispensable for est...

M. Savelli J. Lahaye J. Vedel

1983-01-01

288

The tooth attachment mechanism defined by structure, chemical composition and mechanical properties of collagen fibers in the periodontium  

PubMed Central

In this study, a comparison between structure, chemical composition and mechanical properties of collagen fibers at three regions within a human periodontium, has enabled us to define a novel tooth attachment mechanism. The three regions include 1) the enthesis region: insertion site of periodontal ligament fibers (collagen fibers) into cementum at the root surface, 2) bulk cementum and 3) the cementum dentin junction (CDJ). Structurally, continuity in collagen fibers was observed from the enthesis, through bulk cementum and CDJ. At the CDJ the collagen fibers split into individual collagen fibrils and intermingled with the extracellular matrix of mantle dentin. Under wet conditions, the collagen fibers at the three regions exhibited significant swelling suggesting a composition rich in polyanionic molecules such as glycosaminoglycans. Additionally, site-specific indentation illustrated a comparable elastic modulus between collagen fibers at the enthesis (1 – 3 GPa) and the CDJ (2 – 4 GPa). However, the elastic modulus of collagen fibers within bulk cementum was higher (4 – 7 GPa) suggesting presence of extrafibrillar mineral. It is known that the tooth forms a fibrous joint with the alveolar bone which is termed a gomphosis. Although narrower in width than the periodontal ligament space, the hygroscopic CDJ can also be termed as a gomphosis; a fibrous joint between cementum and root dentin capable of accommodating functional loads similar to that between cementum and alveolar bone. From an engineering perspective, it is proposed that a tooth contains two fibrous joints that accommodate the masticatory cyclic loads. These joints are defined by the attachment of dissimilar materials via graded stiffness interfaces, such as; 1) alveolar bone attached to cementum with the PDL and 2) cementum to root dentin with the CDJ. Thus, through variations in concentrations of basic constituents, distinct regions with characteristic structures and graded properties allow for attachment and the load bearing characteristics of a tooth.

Ho, Sunita P.; Marshall, Sally J.; Ryder, Mark I.; Marshall, Grayson W.

2008-01-01

289

Wear of hard materials by hard particles  

SciTech Connect

Hard materials, such as WC-Co, boron carbide, titanium diboride and composite carbide made up of Mo2C and WC, have been tested in abrasion and erosion conditions. These hard materials showed negligible wear in abrasion against SiC particles and erosion using Al2O3 particles. The WC-Co materials have the highest wear rate of these hard materials and a very different material removal mechanism. Wear mechanisms for these materials were different for each material with the overall wear rate controlled by binder composition and content and material grain size.

Hawk, Jeffrey A.

2003-10-01

290

Cell Attachment to Hydrogel-Electrospun Fiber Mat Composite Materials  

PubMed Central

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials.

Han, Ning; Johnson, Jed K.; Bradley, Patrick A.; Parikh, Kunal S.; Lannutti, John J.; Winter, Jessica O.

2012-01-01

291

Cell attachment to hydrogel-electrospun fiber mat composite materials.  

PubMed

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials. PMID:24955629

Han, Ning; Johnson, Jed K; Bradley, Patrick A; Parikh, Kunal S; Lannutti, John J; Winter, Jessica O

2012-01-01

292

Flaw Detection for Composite Materials Improved by Advanced Thermal Image Reconstruction Techniques  

NASA Technical Reports Server (NTRS)

The development of advanced composite materials for use in space and propulsion components has seen considerable growth over the past few years. In addition to improvements that have been made in material properties and processing techniques, similar growth must be seen in the development of methods for the detection of flaws, either generated in service or during manufacturing. Thermal imaging techniques have proven to be successful for the nondestructive evaluation (NDE) of composite materials, but their detection capabilities decrease as flaw depth increases. The purpose of this research is to investigate advanced thermal imaging methods and thermal image processing technologies to increase the maximum depth below surface that a flaw can be detected and improve the contrast between flawed regions and sound regions.

Martin, Richard E.; Gyekenyesi, Andrew L.

2003-01-01

293

Carbon composites reinforced by graphite grains  

NASA Astrophysics Data System (ADS)

A new kind of composites - graphite grain/carbon (G/C) composites prepared by thermal gradient chemical vapor infiltration technology and elementary properties are investigated, and the microstructure evaluated. It is observed that pores among graphite grains are filled with pyrocarbon effectively, therefore, G/C composites with high density can be obtained. These composites offer the high temperature properties of carbon material, and excellent mechanical properties and isotropy.

Zhao, Jian-guo; Li, Ke-zhi; Li, He-jun; Wang, Chuang; Feng, Feng

2008-04-01

294

Fabrication of ceramic-ceramic composites by chemical vapor deposition. [SiC-TiSi/sub 2/  

SciTech Connect

Toughened ceramic composites were produced by the simultaneous chemical vapor deposition of two phases. Fracture toughness values were nearly double the value of SiC when CH/sub 3/SiCl/sub 3/ and TiCl/sub 4/ vapors were used to produce SiC-TiSi/sub 2/ composites. Other systems consisting of SiC and the metal or metal carbides of Ni, Cr, W, and Mo were examined. Equilibrium thermodynamic analyses of these systems were performed as a function of the chemical vapor deposition variables: temperature, total pressure, and reactant concentration. These calculations confirmed that the volatile species used early in this work (organometallic compounds of Ni and Cr and the fluorides of W and Mo) were not suitable for the production of toughened composites. Additional work is under way to produce composites from the oxychlorides or carbonyls of Ni and Cr or the chlorides or oxychlorides of W and Mo. Thermodynamic calculations also indicated that SiC and TiC should be codeposited when CH/sub 3/SiCl/sub 3/, TiCl/sub 4/, and a hydrocarbon are used as the coating gases. Much additional work remains to produce SiC-TiC composites and to control the morphology of the TiSi/sub 2/ dispersed phase so that optimum fracture toughness values can be obtained.

Stinton, D.P.; Lackey, W.J.; Lauf, R.J.; Besmann, T.M.

1984-01-01

295

Chemical composition and biological value of spray dried porcine blood by-products and bone protein hydrolysate for young chickens.  

PubMed

The chemical composition of spray dried porcine blood by-products is characterised by wide variation in crude protein contents. In spray dried porcine blood plasma (SDBP) it varied between 670-780?g/kg, in spray dried blood cells (SDBC) between 830-930?g/kg, and in bone protein hydrolysate (BPH) in a range of 740-780?g/kg. Compared with fish meal, these feeds are poor in Met and Lys. Moreover, in BPH deep deficits of Met, Cys, Thr and other amino acids were found. The experiment comprised 7 dietary treatments: SDBP, SDBC, and BPH, each at an inclusion rate of 20 or 40?g/kg diet, plus a control. The addition of 20 or 40?g/kg of the analysed meals into feeds for very young chickens (1-28?d post hatch) significantly decreased the body weight (BW) of birds. Only the treatments with 40?g/kg of SDBP and SDBC showed no significant difference in BW as compared with the control. There were no significant differences between treatments and type of meal for feed intake, haematocrit and haemoglobin concentrations in blood. Addition of bone protein and blood cell meals to feed decreased the IgG concentration in blood and caused shortening of the femur and tibia bones. However, changes in the mineral composition of bones were not significantly affected by the type of meal used. The blood by-products, which are rich in microelements, improved retention of Ca and Cu only. In comparison to control chickens, significantly better accretion of these minerals was found in treatments containing 20?g/kg of SDBP or 40?g/kg of SDBC. Great variability in apparent ileal amino acid digestibility in chickens was determined. In this respect, some significant differences related to the type of meal fed were confirmed for Asp, Pro, Val, Tyr and His. In general, the apparent ileal digestibility of amino acids was about 2-3 percentage units better in chickens fed on diets containing the animal by products than in control birds. PMID:22029787

Jamroz, D; Wiliczkiewicz, A; Orda, J; Skorupi?ska, J; S?upczy?ska, M; Kuryszko, J

2011-10-01

296

Thermal Shock Properties of a 2D-C/SiC Composite Prepared by Chemical Vapor Infiltration  

NASA Astrophysics Data System (ADS)

The thermal shock properties of a two-dimensional carbon fiber-reinforced silicon carbide composite with a multilayered self-healing coating (2D-C/SiC) were investigated in air. The composite was prepared by low-pressure chemical vapor infiltration. 2D-C/SiC specimens were thermally shocked for different cycles between 900 and 300 °C. The thermal shock resistance was characterized by residual tensile properties and mass variation. The change of the surface morphology and microstructural evolution of the composite were examined by a scanning electron microscope. In addition, the phase evolution on the surfaces was identified using an X-ray diffractometer. It is found that the composite retains its tensile strength within 20 thermal shock cycles. However, the modulus of 2D-C/SiC decreases gradually with increasing thermal shock cycles. Extensive pullout of fibers on the fractured surface and peeling off of the coating suggest that the damage caused by the thermal shock involves weakening of the bonding strength of coating/composite and fiber/matrix. In addition, the carbon fibers in the near-surface zone were oxidized through the matrix cracks, and the fiber/matrix interfaces delaminated when the composite was subjected to a larger number of thermal shock cycles.

Zhang, Chengyu; Wang, Xuanwei; Wang, Bo; Liu, Yongsheng; Han, Dong; Qiao, Shengru; Guo, Yong

2013-06-01

297

Compositional and chemical modifications of V 2O 5 and NaVO 3 induced by N 2+ bombardment  

NASA Astrophysics Data System (ADS)

The chemical and compositional changes induced by 0.5-5 keV N 2+ bombardment of V 2O 5 and NaVO 3 have been studied by XPS. Both the atomic concentrations and the chemical states of the different constituents reach a steady state at an irradiation dose < 10 17{N 2+}/{cm 2}. As in Ar + bombardment of these targets, the vanadium is reduced to lower oxidation states. The reactive nature of the N 2+ species is however reflected by the opening of a chemical channel for oxygen removal (possibly by NO x formation) and retention of 10-20% of the impinging nitrogen in the targets mainly as vanadium nitride, VN.

Mezentzeff, P.; Lifshitz, Y.; Rabalais, J. W.

1990-01-01

298

Cometary coma chemical composition (C4) mission. [Abstract only  

NASA Technical Reports Server (NTRS)

Cometary missions are of enormous fundamental importance for many different space science disciplines, including exobiology. Comets are presumed relics of the earliest, most primitive material in the solar nebula and are related to the planetesimals. They undoubtedly provided a general enrichment of volatiles to the inner solar system (contributing to atmospheres and oceans) and may have been key to the origin of life. A Discovery class, comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, was selected for further study by NASA earlier this year. The C4 Mission is a highly focused and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission, concentrating exclusively on measurements which will lead to an understanding of the chemical composition and make-up of the cometary nucleus. The scientific goals of the Cometary Coma Chemical Composition (C4) Mission are to rendezvous with a short-period comet and (1) to determine the elemental, chemical, and isotopic composition of the nucleus and (2) to characterize the chemical and isotopic nature of its atmosphere. Further, it is a goal to obtain preliminary data on the development of the coma (dust and gas composition) as a function of time and orbital position.

Carle, G. C.; Clark, B. C.; Niemann, H. B.; Alexander, M.; Knocke, P. C.; O'Hara, B. J.

1994-01-01

299

Fabrication of thermochromic composite using monodispersed VO 2 coated SiO 2 nanoparticles prepared by modified chemical solution deposition  

Microsoft Academic Search

Monodispersed thermochromic VO2 particles were fabricated by VO2 coating onto monodispersed SiO2 nanoparticles with the modified chemical solution deposition technique using vanadium isopropoxide solution and monodispersed SiO2 particle suspension solution. The average size of the resultant VO2–SiO2 particle was 57nm and the coating thickness of the VO2 layer was 6nm. A thermochromic composite was fabricated using the VO2–SiO2 particles and

Hisao Suzuki; Kenji Yamaguchi; Hidetoshi Miyazaki

2007-01-01

300

Analysis of fatty acid content and composition in microalgae.  

PubMed

A method to determine the content and composition of total fatty acids present in microalgae is described. Fatty acids are a major constituent of microalgal biomass. These fatty acids can be present in different acyl-lipid classes. Especially the fatty acids present in triacylglycerol (TAG) are of commercial interest, because they can be used for production of transportation fuels, bulk chemicals, nutraceuticals (?-3 fatty acids), and food commodities. To develop commercial applications, reliable analytical methods for quantification of fatty acid content and composition are needed. Microalgae are single cells surrounded by a rigid cell wall. A fatty acid analysis method should provide sufficient cell disruption to liberate all acyl lipids and the extraction procedure used should be able to extract all acyl lipid classes. With the method presented here all fatty acids present in microalgae can be accurately and reproducibly identified and quantified using small amounts of sample (5 mg) independent of their chain length, degree of unsaturation, or the lipid class they are part of. This method does not provide information about the relative abundance of different lipid classes, but can be extended to separate lipid classes from each other. The method is based on a sequence of mechanical cell disruption, solvent based lipid extraction, transesterification of fatty acids to fatty acid methyl esters (FAMEs), and quantification and identification of FAMEs using gas chromatography (GC-FID). A TAG internal standard (tripentadecanoin) is added prior to the analytical procedure to correct for losses during extraction and incomplete transesterification. PMID:24121679

Breuer, Guido; Evers, Wendy A C; de Vree, Jeroen H; Kleinegris, Dorinde M M; Martens, Dirk E; Wijffels, René H; Lamers, Packo P

2013-01-01

301

Sorption of Metal Oxoanions by Composite Biosorbents of Waste Material of Brown Seaweeds Ascophyllum nodosum and PAN  

Microsoft Academic Search

Two different composite sorbents of chemically modified dealginaded seaweed Ascophyllum nodosum (DS-2 and DS-3) were used for the selective removal of metal (W, Mo, and V) oxoanions. All experiments were carried out by dynamic column sorption. The effects of the pH, flow rate and the concentration of the accompanying anions in the feed solution were studied. Sorption of tungstate, molybdate

Eva Mištová; Helena Parschová; Lud?k Jelínek; Zd?n?k Mat?jka; Ferdinand Šebesta

2010-01-01

302

Modeling of SiC-matrix composite formation by isothermal chemical vapor infiltration  

Microsoft Academic Search

In this paper, a model of the isothermal chemical vapor infiltration (ICVI) is developed. The fibrous substrate (preform) is considered as a complex porous medium with two systems of parallel pores oriented along the preform thickness. One of them is associated with pores formed by fibers in a bundle; another is a system of inter-bundle pores. The model accounts for

V. I. Kulik; A. V. Kulik; M. S. Ramm; Yu. N. Makarov

2004-01-01

303

Composite materials and method of making  

DOEpatents

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

304

Invariant Properties of Composite Materials.  

National Technical Information Service (NTIS)

Invariant properties of the elastic coefficient matrices of laminated composite plates are presented. The use of these invariants in materials evaluation and design optimization is discussed. Simple formulas, based upon micromechanics results, are derived...

N. J. Pagano S. W. Tsai

1968-01-01

305

Chemical composition and tissue energy density of the cuttlefish (Sepia apama) and its assimilation efficiency by Diomedea albatrosses.  

PubMed

The cuttlefish Sepia apama Gray (Mollusca: Cephalopoda) is a seasonally abundant food resource exploited annually by moulting albatrosses throughout winter and early spring in the coastal waters of New South Wales, Australia. To assess its nutritional value as albatross forage, we analysed S. apama for water, lipid protein, ash contents, energy density and amino acid composition. Because albatrosses consistently consume S. apama parts preferentially in the order of head, viscera and mantle, we analysed these sections separately, but did not identify any nutritional basis for this selective feeding behaviour. The gross energy value of S. apama bodies was 20.9 kJ/g dry mass, but their high water content (>83%; cf <70% for fish) results in a relatively low energy density of 3.53 kJ/g. This may contribute to a need to take large meals, which subsequently degrade flight performance. Protein content was typically >75% dry mass, whereas fat content was only about 1%. Albatrosses feed on many species of cephalopods and teleost fish, and we found the amino acid composition of S. apama to be comparable to a range of species within these taxa. We used S. apama exclusively in feeding trials to estimate the energy assimilation efficiency for Diomedea albatrosses. We estimated their nitrogen-corrected apparent energy assimilation efficiency for consuming this prey to be 81.82 ± 0.72% and nitrogen retention as 2.90 ± 0.11 g N kg(-1) d(-1). Although S. apama has a high water content and relatively low energy density, its protein composition is otherwise comparable to other albatross prey species. Consequently, the large size and seasonal abundance of this prey should ensure that albatrosses remain replete and adequately nourished on this forage while undergoing moult. PMID:20640855

Battam, H; Richardson, M; Watson, A W T; Buttemer, W A

2010-11-01

306

[Stability evaluation of chemical compositions of Rhizoma gastrodiae with 60Co-? irradiation by high performance liquid chromatography].  

PubMed

The main chromatographic fingerprint peaks of Rhizoma gastrodiae were established for evaluating the stability of chemical compositions of Rhizoma gastrodiae with 60Co-gamma irradiation to control the dosage of 60Co-gamma irradiation sterilization by high performance liquid chromatography (HPLC). Eight Rhizoma gastrodiae samples were analyzed. The chromatographic fingerprints of Rhizoma gastrodiae were constructed with 14 common fingerprint peaks, and its 10 main peaks were identified using the similarity evaluation system of chromatographic fingerprints of traditional Chinese medicine (version 2004 A) recommended by State Food and Drug Administration of China. The relative standard deviations of the peak areas of the 10 main peaks were used to evaluate the stability of corresponding chemical compositions of Rhizoma gastrodiae with 60Co-gamma irradiation. The results showed that the compositions of 3 of the 10 main peaks were influenced and a good relationship was obtained between the influence and 60Co-gamma irradiation doses for the eight Rhizoma gastrodiae samples. Some chemical components of Rhizoma gastrodiae weren't steady after 60Co-gamma irradiation, so a low dosage should be selected for 60Co-gamma irradiation sterilization. PMID:22500449

Yang, Xiaorong; Huang, Min; Liu, Sujun; Song, Jiuhua

2011-12-01

307

Highly bioactive silver and silver\\/titania composite films grown by chemical vapour deposition  

Microsoft Academic Search

This paper describes how photocatalytically active films of TiO2, grown by thermal CVD, may be functionally and structurally modified by deposition of nano-structured silver via a novel flame assisted CVD process. The resulting composite films are shown to be highly durable, highly photocatalytically active and are also shown to possess strong antibacterial behaviour.The deposition control, arising from the described approach,

L. A. Brook; P. Evans; H. A. Foster; M. E. Pemble; A. Steele; D. W. Sheel; H. M. Yates

2007-01-01

308

Chemical composition of Hanford Tank SY-102  

SciTech Connect

The US Department of Energy established the Tank Waste Remediation System (TWRS) to safely manage and dispose of the radioactive waste, both current and future, stored in double-shell and single-shell tanks at the Hanford sites. One major program element in TWRS is pretreatment which was established to process the waste prior to disposal using the Hanford Waste Vitrification Plant. In support of this program, Los Alamos National Laboratory has developed a conceptual process flow sheet which will remediate the entire contents of a selected double-shelled underground waste tank, including supernatant and sludge, into forms that allow storage and final disposal in a safe, cost-effective and environmentally sound manner. The specific tank selected for remediation is 241-SY-102 located in the 200 West Area. As part of the flow sheet development effort, the composition of the tank was defined and documented. This database was built by examining the history of liquid waste transfers to the tank and by performing careful analysis of all of the analytical data that have been gathered during the tank`s lifetime. In order to more completely understand the variances in analytical results, material and charge balances were done to help define the chemistry of the various components in the tank. This methodology of defining the tank composition and the final results are documented in this report.

Birnbaum, E.; Agnew, S.; Jarvinen, G.; Yarbro, S.

1993-12-01

309

Carbon materials for chemical capacitive energy storage.  

PubMed

Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed. PMID:21953940

Zhai, Yunpu; Dou, Yuqian; Zhao, Dongyuan; Fulvio, Pasquale F; Mayes, Richard T; Dai, Sheng

2011-11-01

310

Measurement of material properties of individual layers for composite films by a pull-in method  

NASA Astrophysics Data System (ADS)

There has been an increasing need for MEMS devices with composite films in recent years. This paper presents an improved model of pull-in voltage by finite-difference method (FDM) for a composite fixed-fixed beam, which takes influence of lateral residual stresses of each layer into account. Young's modulus and residual stresses of each layer for composite beam can then be extracted by these pull-in voltages. And fixed-fixed surface machined beams with multi-cup style anchor were fabricated to be suitable to the model of pull-in voltage. Validation and accuracy of the extracting method have been verified by FEM simulation and experiments.

Nie, Meng; Huang, Qing-An; Li, Weihua

2006-04-01

311

Modulating Materials by Orthogonally Oriented ?-Strands: Composites of Amyloid and Silk Fibroin Fibrils.  

PubMed

Amyloid fibrils and silk fibroin (SF) fibrils are proteinaceous aggregates occurring either naturally or as artificially reconstituted fibrous systems, in which the constituent ?-strands are aligned either orthogonally or parallel to the fibril main axis, conferring complementary physical properties. Here, it is shown how the combination of these two classes of protein fibrils with orthogonally oriented ?-strands results in composite materials with controllable physical properties at the molecular, mesoscopic, and continuum length scales. PMID:24845975

Ling, Shengjie; Li, Chaoxu; Adamcik, Jozef; Shao, Zhengzhong; Chen, Xin; Mezzenga, Raffaele

2014-07-01

312

Grinding of aluminium silicon carbide metal matrix composite materials by electrolytic in-process dressing grinding  

Microsoft Academic Search

The grinding cost of metal matrix composite materials is more due to low removal rates and high rates of wear of super abrasive\\u000a wheels. This electrolytic in-process dressing (ELID) technique uses a metal-bonded grinding wheel that is electrolytically\\u000a dressed during the grinding process for abrasives that protrude continuously from super abrasive wheels. This research carries\\u000a out ELID grinding using various

A. M. Shanawaz; S. Sundaram; U. T. S. Pillai; P. Babu Aurtherson

313

Effect of Rhizobium inoculation, organic and chemical fertilizers on proximate composition, in vitro protein digestibility, tannin and sulphur content of faba beans  

Microsoft Academic Search

A field experiment was carried out to investigate the effect of Rhizobium inoculation, sulphur, nitrogen and chicken manure on proximate analysis, in vitro protein digestibility (IVPD) tannin and sulphur content of faba beans. The results showed that Rhizobium inoculation, sulphur, nitrogen and chicken manure treatments significantly (P ? 0.05) increased protein, IVPD and tannin content. Ash, moisture, fat and crude

Elsiddig A. E. Elsheikh; Abdulhafiz A. Elzidany

1997-01-01

314

Investigation of the relationship between chemical composition and size distribution of airborne particles by partial least squares and positive matrix factorization  

Microsoft Academic Search

(1) Two multivariate data analysis methods, partial least square (PLS) and positive matrix factorization (PMF), were used to analyze aerosol size distribution data and composition data. The relationships between the size distribution data and composition data were investigated by PLS. Three latent variables summarized chemical composition data and most variations in size distribution data especially for large particles and proved

Liming Zhou; Philip K. Hopke; Charles O. Stanier; Spyros N. Pandis; John M. Ondov; J. Patrick Pancras

2005-01-01

315

Dual Bioactivities of Essential Oil Extracted from the Leaves of Artemisia argyi as an Antimelanogenic versus Antioxidant Agent and Chemical Composition Analysis by GC/MS  

PubMed Central

The study was aimed at investigating the antimelanogenic and antioxidant properties of essential oil when extracted from the leaves of Artemisia argyi, then analyzing the chemical composition of the essential oil. The inhibitory effect of the essential oil on melanogenesis was evaluated by a mushroom tyrosinase activity assay and B16F10 melanoma cell model. The antioxidant capacity of the essential oil was assayed by spectrophotometric analysis, and the volatile chemical composition of the essential oil was analyzed with gas chromatography-mass spectrometry (GC/MS). The results revealed that the essential oil significantly inhibits mushroom tyrosinase activity (IC50 = 19.16 mg/mL), down-regulates B16F10 intracellular tyrosinase activity and decreases the amount of melanin content in a dose-dependent pattern. Furthermore, the essential oil significantly scavenged 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and 2,2?-azino-bis (3-ethylbenzthiazoline- 6-sulphonic acid) ABTS radicals, showed an apparent reduction power as compared with metal-ion chelating activities. The chemicals constituents in the essential oil are ether (23.66%), alcohols (16.72%), sesquiterpenes (15.21%), esters (11.78%), monoterpenes (11.63%), ketones (6.09%), aromatic compounds (5.01%), and account for a 90.10% analysis of its chemical composition. It is predicted that eucalyptol and the other constituents, except for alcohols, in the essential oil may contribute to its antioxidant activities. The results indicated that essential oil extracted from A. argyi leaves decreased melanin production in B16F10 cells and showed potent antioxidant activity. The essential oil can thereby be applied as an inhibitor of melanogenesis and could also act as a natural antioxidant in skin care products.

Huang, Huey-Chun; Wang, Hsiao-Fen; Yih, Kuang-Hway; Chang, Long-Zen; Chang, Tsong-Min

2012-01-01

316

Left Handed Materials Using Magnetic Composites.  

National Technical Information Service (NTIS)

A left-handed composite material which includes a mixture of a ferromagnetic material and a dielectric material. The direction of magnetization of the ferromagnetic material, and its volume fraction are controlled such that the composite material exhibits...

J. Q. Xiao S. T. Chui

2003-01-01

317

Spectral analysis by XANES reveals that GPNMB influences the chemical composition of intact melanosomes  

PubMed Central

Summary GPNMB is a unique melanosomal protein. Unlike many melanosomal proteins, GPNMB has not been associated with any forms of albinism and it is unclear whether GPNMB has any direct influence on melanosomes. Here, melanosomes from congenic strains of C57BL/6J mice mutant for Gpnmb are compared to strain-matched controls using standard transmission electron microscopy and synchrotron-based X-ray absorption near-edge structure analysis (XANES). Whereas electron microscopy did not detect any ultrastructural changes to melanosomes lacking functional GPNMB, XANES uncovered multiple spectral phenotypes. These results directly demonstrate that GPNMB influences the chemical composition of melanosomes, and more broadly illustrate the potential for using genetic approaches in combination with nano-imaging technologies to study organelle biology. Significance Of the large number of proteins known to be present in melanosomes, the majority are not known to visibly influence melanosome appearance. It remains largely unknown what role, if any, most of these proteins may have in pigment cell biology. This work demonstrates an approach for discovering previously undetectable melanosomal phenotypes through a combined use of synchrotron-based spectromicroscopy and genetics. Specifically, we demonstrate that GPNMB influences the carbon absorption spectra of melanosomes. A similar strategy might also be applied to discover new features of a wide range of additional organelles important to human health and disease.

Haraszti, Tamas; Trantow, Colleen M.; Hedberg-Buenz, Adam; Grunze, Michael; Anderson, Michael G.

2010-01-01

318

In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning  

DOEpatents

A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

Kim, Choong Paul (Northridge, CA); Hays, Charles C. (Pasadena, CA); Johnson, William L. (Pasadena, CA)

2007-07-17

319

Chemical composition of burnt smell caused by accidental fires: environmental contaminants.  

PubMed

The chemical composition of the odors typical of fires has recently been deciphered. Basically the constituents are mixtures of acetophenone, benzyl alcohol, hydroxylated derivatives of benzaldehyde, methoxylated and/or alkylated phenols and naphthalene. This finding makes it possible to develop objective, practical analytic measurement methods for the burnt smell as a contribution to improving fire damage assessment and remediation monitoring. With the aid of an artificially produced burnt smell and a panel of testers the odor detection threshold of a test mixture was determined olfactometrically to 2 ?g m?³. Using a defined burnt-smell atmosphere in a test chamber, analytical methods with active sampling, the adsorbents XAD 7 and TENAX TA, and GC/MS measurement were then optimized and tested with a view to being able to carry out sensitive quantitative measurement of burnt smells. A further practical method with particular application to the qualitative characterization of this odor is based on the use of a new SPME (solid-phase microextraction) field sampler with DVB/CAR/PDMS (divinylbenzene/Carboxen™/polydimethylsiloxane) fibers. PMID:20947130

Heitmann, K; Wichmann, H; Bahadir, M; Gunschera, J; Schulz, N; Salthammer, T

2011-01-01

320

Structural health monitoring of smart composite materials by using EFPI and FBG sensors  

Microsoft Academic Search

Structural health monitoring (SHM) including the real-time cure monitoring and non-destructive evaluation (NDE) in-service is very important and definitely demanded for safely working of high performance composite structures in situ. It is very difficult to carry out by using conventional methods. A unique opportunity was provided to real-time monitor the health status of composite structures by using embedded fiber optic

Jinsong Leng; Anand Asundi

2003-01-01

321

Chemically treated fillers and polymeric compositions containing same  

US Patent & Trademark Office Database

Described are fillers, e.g., inorganic oxides, that have been chemically treated to have a carbon content of greater than 1 weight percent, a mercapto content of at least 0.15 weight percent, a Silane Conversion Index of at least 0.3 and a Standard Reinforcement Index of 4 or more. Polymeric compositions that contain such treated fillers are also described.

2003-11-18

322

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.  

SciTech Connect

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70 degC. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 degC lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

2012-02-01

323

Chemical composition and protein quality of buckwheat ( Fagopyrum esculentum Moench )  

Microsoft Academic Search

The chemical composition and protein quality of two varieties of buckwheat were measured and compared with the values of wheat. The protein quality was based on amino acid composition and true protein digestibility, biological value, net protein utilization, and utilizable protein obtained in N-balance experiments with rats. The protein content in buckwheat was approximately 12% and thus very much the

Bjørn O. Eggum; Ivan Kreft; Branka Javornik

1980-01-01

324

226Ra and 228Ra in scale and sludge samples and their correlation with the chemical composition.  

PubMed

In order to contribute to a future waste management policy related to the presence of technologically enhanced natural occurring radioactive material (TENORM) in the Brazilian petroleum industry, the present work presents the chemical composition and the (226)Ra and (228)Ra content of sludge and scales generated during the offshore E and P petroleum activities in the Campos Basin, the primary offshore oil production region in Brazil. The (226)Ra and (228)Ra content on 36 sludge and scales samples were determined by gamma-spectrometry. Based on X-ray diffractometry results, a chemical analysis schema for these samples was developed. The results have shown that scales are 75% barium and strontium sulfates, with a mean (226)Ra and (228)Ra content of 106 kBq kg(-1) and 78 kBq kg(-1), respectively. On the other hand, sludge samples have a much more complex chemical composition than the scales. The (226)Ra and (228)Ra content in sludge also varies much more than the content observed in the scales samples and ranged from 0.36 to 367 kBq kg(-1) and 0.25 to 343 kBq kg(-1), respectively. PMID:12957550

Godoy, José Marcus; da Cruz, Rosana Petinatti

2003-01-01

325

Risks and reliability of manufacturing processes as related to composite materials for spacecraft structures  

NASA Technical Reports Server (NTRS)

Fabricating primary aircraft and spacecraft structures using advanced composite materials entail both benefits and risks. The benefits come from much improved strength-to-weight ratios and stiffness-to-weight ratios, potential for less part count, ability to tailor properties, chemical and solvent resistance, and superior thermal properties. On the other hand, the risks involved include high material costs, lack of processing experience, expensive labor, poor reproducibility, high toxicity for some composites, and a variety of space induced risks. The purpose of this project is to generate a manufacturing database for a selected number of materials with potential for space applications, and to rely on this database to develop quantitative approaches to screen candidate materials and processes for space applications on the basis of their manufacturing risks including costs. So far, the following materials have been included in the database: epoxies, polycyanates, bismalemides, PMR-15, polyphenylene sulfides, polyetherimides, polyetheretherketone, and aluminum lithium. The first four materials are thermoset composites; the next three are thermoplastic composites, and the last one is is a metal. The emphasis of this database is on factors affecting manufacturing such as cost of raw material, handling aspects which include working life and shelf life of resins, process temperature, chemical/solvent resistance, moisture resistance, damage tolerance, toxicity, outgassing, thermal cycling, and void content, nature or type of process, associate tooling, and in-process quality assurance. Based on industry experience and published literature, a relative ranking was established for each of the factors affecting manufacturing as listed above. Potential applications of this database include the determination of a delta cost factor for specific structures with a given process plan and a general methodology to screen materials and processes for incorporation into the current conceptual design optimization of future spacecrafts as being coordinated by the Vehicle Analysis Branch where this research is being conducted.

Bao, Han P.

1995-01-01

326

Content, format, gender and grade level differences in elementary students' ability to read science materials as measured by the cloze procedure  

NASA Astrophysics Data System (ADS)

Present instructional trends in science indicate a need to reexamine a traditional concern in science education: the readability of science textbooks. An area of reading research not well documented is the effect of color, visuals, and page layout on readability of science materials. Using the cloze readability method, the present study explored the relationships between page format, grade level, sex, content, and elementary school students ability to read science material. Significant relationships were found between cloze scores and both grade level and content, and there was a significant interaction effect between grade and sex in favor of older males. No significant relationships could be attributed to page format and sex. In the area of science content, biological materials were most difficult in terms of readability followed by earth science and physical science. Grade level data indicated that grade five materials were more difficult for that level than either grade four or grade six materials were for students at each respective level. In eight of nine cases, the science text materials would be classified at or near the frustration level of readability. The implications for textbook writers and publishers are that science reading materials need to be produced with greater attention to readability and known design principles regarding visual supplements. The implication for teachers is that students need direct instruction in using visual materials to increase their learning from text material. Present visual materials appear to neither help nor hinder the student to gain information from text material.

Williams, Richard L.; Yore, Larry D.

327

Birefringent nanostructured composite materials  

NASA Astrophysics Data System (ADS)

We use a very efficient recursive method to calculate the effective optical response of materials made up of arbitrarily shaped dielectric inclusions arranged in periodic 2D arrays within a metal matrix with a lattice constant much smaller than the wavelength of the incident light, so that we may neglect retardation. The starting point of the calculation is a digitized image of the system. The geometrical shape of the inclusions and their orientation in the 2D array induce a birefringent optical response of the whole metamaterial that can be tailored to specific needs.

Mendoza, Bernardo S.; Mochán, W. Luis

2012-03-01

328

Nanophase and Composite Optical Materials  

NASA Technical Reports Server (NTRS)

This talk will focus on accomplishments, current developments, and future directions of our work on composite optical materials for microgravity science and space exploration. This research spans the order parameter from quasi-fractal structures such as sol-gels and other aggregated or porous media, to statistically random cluster media such as metal colloids, to highly ordered materials such as layered media and photonic bandgap materials. The common focus is on flexible materials that can be used to produce composite or artificial materials with superior optical properties that could not be achieved with homogeneous materials. Applications of this work to NASA exploration goals such as terraforming, biosensors, solar sails, solar cells, and vehicle health monitoring, will be discussed.

2003-01-01

329

Chemical compatibility of cartridge materials  

NASA Technical Reports Server (NTRS)

The objectives were to determine the chemical compatibility of titanium-zirconium-molybdenum (TZM) with GaAs and CdZnTe, and Inconel with HgCdTe and HgZnTe. At the present time, no other studies regarding the compatibility of these crystal components and their respective cartridge materials have been performed. This study was to identify any possible problems between these materials to insure proper containment of possibly hazardous fumes during crystal growth experiments. In this study, the reaction zone between the materials was studied and the amount of degradation to the system was measured. Detailed results are presented.

Ambrose, Bryan; Wilcox, R. C.; Zee, R. H.

1992-01-01

330

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.  

PubMed Central

A putative yeast sn-2 acyltransferase gene (SLC1-1), reportedly a variant acyltransferase that suppresses a genetic defect in sphingolipid long-chain base biosynthesis, has been expressed in a yeast SLC deletion strain. The SLC1-1 gene product was shown in vitro to encode an sn-2 acyltransferase capable of acylating sn-1 oleoyl-lysophosphatidic acid, using a range of acyl-CoA thioesters, including 18:1-, 22:1-, and 24:0-CoAs. The SLC1-1 gene was introduced into Arabidopsis and a high erucic acid-containing Brassica napus cv Hero under the control of a constitutive (tandem cauliflower mosaic virus 35S) promoter. The resulting transgenic plants showed substantial increases of 8 to 48% in seed oil content (expressed on the basis of seed dry weight) and increases in both overall proportions and amounts of very-long-chain fatty acids in seed triacylglycerols (TAGs). Furthermore, the proportion of very-long-chain fatty acids found at the sn-2 position of TAGs was increased, and homogenates prepared from developing seeds of transformed plants exhibited elevated lysophosphatidic acid acyltransferase (EC 2.3.1.51) activity. Thus, the yeast sn-2 acyltransferase has been shown to encode a protein that can exhibit lysophosphatidic acid acyltransferase activity and that can be used to change total fatty acid content and composition as well as to alter the stereospecific acyl distribution of fatty acids in seed TAGs.

Zou, J; Katavic, V; Giblin, E M; Barton, D L; MacKenzie, S L; Keller, W A; Hu, X; Taylor, D C

1997-01-01

331

Oxygen and Magnesium Isotopic Compositions of Asteroidal Materials Returned from Itokawa by the Hayabusa Mission  

NASA Technical Reports Server (NTRS)

The Hayabusa spacecraft made two touchdowns on the surface of Asteroid 25143 Itokawa on November 20th and 26th, 2005. The Asteroid 25143 Itokawa is classified as an S-type asteroid and inferred to consist of materials similar to ordinary chondrites or primitive achondrites [1]. Near-infrared spectroscopy by the Hayabusa spacecraft proposed that the surface of this body has an olivine-rich mineral assemblage potentially similar to that of LL5 or LL6 chondrites with different degrees of space weathering [2]. The spacecraft made the reentry into the Earth s atmosphere on June 12th, 2010 and the sample capsule was successfully recovered in Australia on June 13th, 2010. Although the sample collection processes on the Itokawa surface had not been made by the designed operations, more than 1,500 grains were identified as rocky particles in the sample curation facility of JAXA, and most of them were judged to be of extraterrestrial origin, and definitely from Asteroid Itokawa on November 17th, 2010 [3]. Although their sizes are mostly less than 10 microns, some larger grains of about 100 microns or larger were also included. The mineral assembly is olivine, pyroxene, plagioclase, iron sulfide and iron metal. The mean mineral compositions are consistent with the results of near-infrared spectroscopy from Hayabusa spacecraft [2], but the variations suggest that the petrologic type may be smaller than the spectroscopic results. Several tens of grains of relatively large sizes among the 1,500 grains will be selected by the Hayabusa sample curation team for preliminary examination [4]. Each grain will be subjected to one set of preliminary examinations, i.e., micro-tomography, XRD, XRF, TEM, SEM, EPMA and SIMS in this sequence. The preliminary examination will start from the last week of January 2011. Therefore, samples for isotope analyses in this study will start from the last week of February 2011. By the time of the LPSC meeting we will have measured the oxygen and magnesium isotopic composition of several grains. We will present the first results from the isotope analyses that will have been performed.

Yurimoto, H; Abe, M.; Ebihara, M.; Fujimura, A.; Hashizume, K.; Ireland, T. R.; Itoh, S.; Kawaguchi, K.; Kitajima, F.; Mukai, T.; Nagao, K.; Nakamura, T.; Naraoka, H.; Noguchi, T.; Okazaki, R.; Sakamoto, N.; Seto, Y.; Tsuchiyama, A.; Uesugi, M.; Yada, T.; Yoshikawa, M.; Zolensky, M.

2011-01-01

332

Fatigue Crack and Porosity Measurement in Composite Materials by Thermographic and Ultrasonic Methods  

NASA Technical Reports Server (NTRS)

Many nondestructive methods exist for the detection of localized material anomalies in an otherwise good composite structure. The problem arises when the material system as a whole has degraded during service or was improperly manufactured. Porosity and intra-ply microcracking are two such conditions that in unlined composite pressure vessels can be very troublesome to detect and when linked through the thickness can be critical to mission success. These leak paths may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. Research sought nondestructive methods for quantifying porosity and microcracking in composite tankage. Both thermographic and resonance ultrasound methods have been utilized with artificial neural network and statistical approaches to analyze the data. Resonant ultrasound spectroscopy provides measurements, which are sensitive to fine details in the materials character, such as micro-cracking and porosity. Here, the higher frequency (shorter wavelength) components of the signal train provide more significant interaction with the defects causing the spectral characteristics to shift toward lower amplitudes at the higher frequencies. As the density of the defects increases more interactions occur and more drastic amplitude changes are observed. From a thermal perspective, the higher the defect density the lower the through thickness thermal diffusivity will be. Utilizing a point heat source, and thermographically recording the heat profile with time, diffusivity calculations can be made which in turn can be related to the relative quality of the material. Preliminary experiments to verify the measurable effect on the resonance spectrum of the ultrasonic data to detect microcracking and for porosity detection thermographically are presented. Methods involving supervised and unsupervised artificial neural networks as well as other clustering algorithms are developed for signal identification.

Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.; Watson, Jason M.; Thom, Robert (Technical Monitor)

2002-01-01

333

Method for making composite material  

US Patent & Trademark Office Database

A method for fabricating a composite material includes providing a free-standing carbon nanotube structure having a plurality of carbon nanotubes, introducing at least two reacting materials into the carbon nanotube structure to form a reacting layer, activating the reacting materials to grow a plurality of nanoparticles, wherein the nanoparticles are spaced from each other and coated on a surface of each of the carbon nanotubes of the carbon nanotube structure.

2012-10-30

334

Composite material impregnation unit  

NASA Technical Reports Server (NTRS)

This memorandum presents an introduction to the NASA multi-purpose prepregging unit which is now installed and fully operational at the Langley Research Center in the Polymeric Materials Branch. A description of the various impregnation methods that are available to the prepregger are presented. Machine operating details and protocol are provided for its various modes of operation. These include, where appropriate, the related equations for predicting the desired prepreg specifications. Also, as the prepregger is modular in its construction, each individual section is described and discussed. Safety concerns are an important factor and a chapter has been included that highlights the major safety features. Initial experiences and observations for fiber impregnation are described. These first observations have given great insight into the areas of future work that need to be addressed. Future memorandums will focus on these individual processes and their related problems.

Wilkinson, S. P.; Marchello, J. M.; Johnston, N. J.

1993-01-01

335

In vitro release kinetics and physical, chemical and mechanical characterization of a POVIAC®/CaCO3/HAP-200 composite.  

PubMed

Coralline calcium-hydroxyapatite and calcium carbonate from Porites Porites coral were added to a polymeric matrix based on polyvinyl acetate (POVIAC(®)), to obtain a novel bone substitute composite as well as a system for the controlled drug (cephalexin) release. Composite samples with different compositions were characterized by physical-chemical and mechanical methods. Furthermore, the in vitro release profile of cephalexin and the kinetic behavior of its release from these composites were analyzed by appropriate mathematical models. It was shown that there is no chemical interaction between the inorganic filler and the polymer matrix, each conserving the original properties of the raw materials. The compressive mechanical strength and Young modulus of the composite with 17.5% of POVIAC(®), has better mechanical properties than those of cancellous bone. The variation of POVIAC(®) content can affect the cephalexin release kinetic in the composite. The cephalexin release mechanism from the composites can be considered as the result of the joint contribution of a prevailing Fickian diffusion and of polymer chain relaxation. It was also demonstrated that cephalexin is occluded inside the composites and not on their surface. PMID:22201028

Aragón, Javier; González, Ramón; Fuentes, Gastón; Palin, Luca; Croce, Gianluca; Viterbo, Davide

2012-02-01

336

Chemical composition of volatile oils from the pericarps of Indian sandalwood (Santalum album) by different extraction methods.  

PubMed

The chemical composition of volatile compounds from pericarp oils of Indian sandalwood, Santalum album L., isolated by hydrodistillation and solvent extraction, were analyzed by GC and GC-MS. The pericarps yielded 2.6 and 5.0% volatile oil by hydrodistillation and n-hexane extraction, and they were colorless and yellow in color, respectively. A total of 66 volatile components were detected. The most prominent compounds were palmitic and oleic acids, representing about 40-70% of the total oil. Many fragrant constituents and biologically active components, such as alpha- and beta-santalol, cedrol, esters, aldehydes, phytosterols, and squalene were present in the pericarp oils. This is the first report of the volatile composition of the pericarps of any Santalum species. PMID:22428257

Zhang, Xin Hua; da Silva, Jaime A Teixeira; Jia, Yong Xia; Zhao, Jie Tang; Ma, Guo Hua

2012-01-01

337

Space processing of composite materials  

NASA Technical Reports Server (NTRS)

Materials and processes for the testing of aluminum-base fiber and particle composites, and of metal foams under extended-time low-g conditions were investigated. A wetting and dispersion technique was developed, based on the theory that under the absence of a gas phase all solids are wetted by liquids. The process is characterized by a high vacuum environment and a high temperature cycle. Successful wetting and dispersion experiments were carried out with sapphire fibers, whiskers and particles, and with fibers of silicon carbide, pyrolytic graphite and tungsten. The developed process and facilities permit the preparation of a precomposite which serves as sample material for flight experiments. Low-g processing consists then merely in the uniform redistribution of the reinforcements during a melting cycle. For the preparation of metal foams, gas generation by means of a thermally decomposing compound was found most adaptable to flight experiments. For flight experiments, the use of compacted mixture of the component materials limits low-g processing to a simple melt cycle.

Steurer, W. H.; Kaye, S.

1975-01-01

338

Ablation properties of C\\/C composites with various needled preforms prepared by isothermal chemical vapor infiltration  

Microsoft Academic Search

The ablation properties of C\\/C composites with four different needled preforms prepared by isothermal chemical vapor infiltration\\u000a (ICVI), which are super-thin mat lay-up, 0\\/90 weftless fabric lay-up, 0\\/45 weftless fabric lay-up and 0\\/45 twill fabric\\u000a lay-up, were quantitatively evaluated by performing the ablation tests with an engine torch. And their ablation discrepancies\\u000a were analyzed according to the surface characteristic, porosity

Su-fang Tang; Dao-ling Wang; Jing-yi Deng; Wen-chuan Liu; Ke Yang

2007-01-01

339

Chemical constraints on fly ash glass compositions  

SciTech Connect

The major oxide content and mineralogy of 75 European fly ashes were examined, and the major element composition of the glass phase was obtained for each. Correlation of compositional trends with the glass content of the ash was explored. Alkali content was deduced to have a major influence on glass formation, and this in turn could be related to the probable chemistry of clay minerals in the source coals. Maximal glass content corresponded to high aluminum content in the glass, and this is in accordance with the theoretical mechanism of formation of aluminosilicate glasses, in which network-modifying oxides are required to promote tetrahedral coordination of aluminum in glass chain structures. Iron oxide was found to substitute for alkali oxides where the latter were deficient, and some indications of preferred eutectic compositions were found. The work suggests that the proportion of the glass phase in the ash can be predicted from the coal mineralogy and that the utility of a given ash for processing into geopolymers or zeolites is determined by its source. 23 refs., 7 figs., 1 tab.

John H. Brindle; Michael J. McCarthy [University of Dundee, Dundee (United Kingdom). Division of Civil Engineering

2006-12-15

340

Energy Absorption of Composite Materials  

Microsoft Academic Search

This paper presents results of a study on the energy absorption characteristics of selected composite material systems and compares the results with aluminum. Com posite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite\\/epoxy (Gr\\/E), Kevlar® epoxy (K\\/E) and glass\\/epoxy (Gl\\/E). Chamfering and notching one end of the composite tube specimen reduced the peak load

Gary L. Farley

1983-01-01

341

Chemical composition and morphology of renal stones.  

PubMed

Two issues related to nephrolithiasis are explored: (1) does the chemical composition and morphology of renal calculi in South Poland overlap with the studies from other countries? and (2) are there possibilities to evaluate in vivo chemical composition of stones using computed tomography? The study was conducted on 108 renal stones. X-ray fluorescence, X-ray diffraction and Fourier transformed infrared spectroscopy were used to determine the chemical composition. The morphology of the stones was examined using micro computed tomography. The stone chemical composition in South Poland indicate that calcium oxalate monohydrate was overwhelmingly dominant (84%) followed by hydroxyapatite (8%) and struvite (6%). The occurrence of uric acid stones was very low (2%). The relative frequency of various stone types is similar in South Poland to other industrialized countries. The studied renal stones were characterized by a large variability in the concentrations of both major and trace elements. The maximum/minimum concentration ratio exceeds two orders of magnitude. Significant morphological differences have been observed between different types of stones. The stones were composed of oxalate polyhedrons stuck together or had the phosphate core overlaid with layers oxalate and organic mater. The use of CT to identify stone type seems to be limited. PMID:24858554

Wrobel, Andrzej; Rokita, Eugeniusz; Taton, Grzegorz; Thor, Piotr

2013-01-01

342

Fracture problems in composite materials  

NASA Technical Reports Server (NTRS)

A series of fracture problems in composite materials are identified, their methods of solution are briefly discussed, and some sample results are presented. The main problem of interest is the determination of the stress state in the neighborhood of localized imperfections such as cracks and inclusions which may exist in the composite. Particular emphasis is placed on the evaluation of quantities such as the stress intensity factors, the power of the stress singularity, and the strain energy release rate, which may be used directly or indirectly in connection with an appropriate fracture criterion for the prediction of fracture initiation and propagation load levels. The topics discussed include a crack in layered composites, a crack terminating at and going through a bi-material interface, a penny-shaped crack in a filament-reinforced elastic matrix, and inclusion problems in bonded materials.

Erdogan, F.

1972-01-01

343

Designing high hard block Content TPU resins for composite application  

NASA Astrophysics Data System (ADS)

Thermoplastic Polyurethanes (TPU) are linear block copolymers typically constructed of statistically alternating soft (SS) and hard (HS) segments. Due to their numerous industrial applications these materials have received considerable attention. We have recently investigated the phase behavior and morphology of a set of high hard block content polyurethanes. Using mainly calorimetry, scattering and microscopy techniques we were able to elucidate the origins of all the thermal events observed through differential scanning calorimetry and propose a new morphological model of the structure and the phase behavior of these high hard block content polyurethanes [A. Saiani et al. Macromolecules, 34, 9059-9068 (2001); 37, 1411-1421 (2004); 40, 7252-7262 (2007)]. We have now shown that these new materials can potentially be used as resins for designing fiber based composites and investigated the effect of processing on conditions the final properties of the composites

Saiani, Alberto; Nedolisa, Chinemelum; Lindsay, Christopher I.

2013-03-01

344

Effect of film composition on the performance of interdigitated electrode methods used for chemically amplified photoresist characterization: methods for analyzing photoresist materials containing base quencher  

NASA Astrophysics Data System (ADS)

Previously, a method which utilizes interdigitated electrode (IDE) sensors to collect capacitance versus exposure dose data for thin films containing a photoacid generator (PAG) and polymer and subsequently calculate the Dill C photoreaction rate constant for the photoacid generator has been presented. This paper discusses a method for extending such IDE methods to calculate the Dill C rate constant for a photoacid generator in a film containing a polymer, photoacid generator, and base quencher. This three component formulation more closely resembles the composition of commercial chemically amplified photoresists. It is shown that by using a data normalization approach, the IDE data can be successfully analyzed to compute accurate Dill C values for a PAG in the presence of base quencher and to estimate the concentration of base quencher in the film. The technique also thus allows for measurement of the impact of the presence of base quencher on the photoreaction rate constant of the photoacid generator.

Berger, Cody; Henderson, Clifford L.

2005-05-01

345

Analytical and numerical study of the densification of carbon\\/carbon composites by a film-boiling chemical vapor infiltration process  

Microsoft Academic Search

The film-boiling chemical vapor infiltration (CVI) process is a fast process developed for composite material fabrication, and especially carbon\\/carbon composites. In order to help define optimal conditions, a local 1D model has been developed to study the densification front which establishes itself during the processing of a carbon\\/carbon fibrous preform. The model features heat conduction, precursor gas diffusion, densification reactions

Nathalie Nadeau; Gérard L. Vignoles; Claude-Michel Brauner

2006-01-01

346

Delicate refinement of surface nanotopography by adjusting TiO2 coating chemical composition for enhanced interfacial biocompatibility.  

PubMed

Surface topography and chemistry have significant influences on the biological performance of biomedical implants. Our aim is to produce an implant surface with favorable biological properties by dual modification of surface chemistry and topography in one single simple process. In this study, because of its chemical stability, excellent corrosion resistance, and biocompatibility, titanium oxide (TiO2) was chosen to coat the biomedical Ti alloy implants. Biocompatible elements (niobium (Nb) and silicon (Si)) were introduced into TiO2 matrix to change the surface chemical composition and tailor the thermophysical properties, which in turn leads to the generation of topographical features under specific thermal history of plasma spraying. Results demonstrated that introduction of Nb2O5 resulted in the formation of Ti0.95Nb0.95O4 solid solution and led to the generation of nanoplate network structures on the composite coating surface. By contrast, the addition of SiO2 resulted in a hairy nanostructure and coexistence of rutile and quartz phases in the coating. Additionally, the introduction of Nb2O5 enhanced the corrosion resistance of TiO2 coating, whereas SiO2 did not exert much effect on the corrosion behaviors. Compared to the TiO2 coating, TiO2 coating doped with Nb2O5 enhanced primary human osteoblast adhesion and promoted cell proliferation, whereas TiO2 coatings with SiO2 were inferior in their bioactivity, compared to TiO2 coatings. Our results suggest that the incorporation of Nb2O5 can enhance the biological performance of TiO2 coatings by changing the surface chemical composition and nanotopgraphy, suggesting its potential use in modification of biomedical TiO2 coatings in orthopedic applications. PMID:23957368

Zhao, Xiaobing; Wang, Guocheng; Zheng, Hai; Lu, Zufu; Zhong, Xia; Cheng, Xingbao; Zreiqat, Hala

2013-08-28

347

Pedagogical Content Knowledge in Teaching Material  

ERIC Educational Resources Information Center

The scope of this article is to understand to what extent Computer Science teachers can find support for their Pedagogical Content Knowledge (PCK) in teaching material. We report the results of a study in which PCK is used as framework to develop a research instrument to examine three high school computer science textbooks, with special focus on…

Saeli, Mara; Perrenet, Jacob; Jochems, Wim M. G.; Zwaneveld, Bert

2012-01-01

348

Bacterial Community Composition in the Gut Content and Ambient Sediment of Sea Cucumber Apostichopus japonicus Revealed by 16S rRNA Gene Pyrosequencing  

PubMed Central

The composition of the bacterial communities in the contents of the foregut and hindgut of the sea cucumber Apostichopus japonicus and in the ambient surface sediment was surveyed by 16S rRNA gene 454-pyrosequencing. A total of 188,623 optimized reads and 15,527 operational taxonomic units (OTUs) were obtained from the ten gut contents samples and four surface sediment samples. The sequences in the sediments, foregut contents, and hindgut contents were assigned to 38.0±4.7, 31.2±6.2 and 27.8±6.5 phyla, respectively. The bacterial richness and Shannon diversity index were both higher in the ambient sediments than in the gut contents. Proteobacteria was the predominant phylum in both the gut contents and sediment samples. The predominant classes in the foregut, hindgut, and ambient sediment were Holophagae and Gammaproteobacteria, Deltaproteobacteria and Gammaproteobacteria, and Gammaproteobacteria and Deltaproteobacteria, respectively. The potential probiotics, including sequences related to Bacillus, lactic acid bacteria (Lactobacillus, Lactococcus, and Streptococcus) and Pseudomonas were detected in the gut of A. japonicus. Principle component analysis and heatmap figure showed that the foregut, hindgut, and ambient sediment respectively harbored different characteristic bacterial communities. Selective feeding of A. japonicus may be the primary source of the different bacterial communities between the foregut contents and ambient sediments.

Gao, Fei; Li, Fenghui; Tan, Jie; Yan, Jingping; Sun, Huiling

2014-01-01

349

Bacterial Community Composition in the Gut Content and Ambient Sediment of Sea Cucumber Apostichopus japonicus Revealed by 16S rRNA Gene Pyrosequencing.  

PubMed

The composition of the bacterial communities in the contents of the foregut and hindgut of the sea cucumber Apostichopus japonicus and in the ambient surface sediment was surveyed by 16S rRNA gene 454-pyrosequencing. A total of 188,623 optimized reads and 15,527 operational taxonomic units (OTUs) were obtained from the ten gut contents samples and four surface sediment samples. The sequences in the sediments, foregut contents, and hindgut contents were assigned to 38.0±4.7, 31.2±6.2 and 27.8±6.5 phyla, respectively. The bacterial richness and Shannon diversity index were both higher in the ambient sediments than in the gut contents. Proteobacteria was the predominant phylum in both the gut contents and sediment samples. The predominant classes in the foregut, hindgut, and ambient sediment were Holophagae and Gammaproteobacteria, Deltaproteobacteria and Gammaproteobacteria, and Gammaproteobacteria and Deltaproteobacteria, respectively. The potential probiotics, including sequences related to Bacillus, lactic acid bacteria (Lactobacillus, Lactococcus, and Streptococcus) and Pseudomonas were detected in the gut of A. japonicus. Principle component analysis and heatmap figure showed that the foregut, hindgut, and ambient sediment respectively harbored different characteristic bacterial communities. Selective feeding of A. japonicus may be the primary source of the different bacterial communities between the foregut contents and ambient sediments. PMID:24967593

Gao, Fei; Li, Fenghui; Tan, Jie; Yan, Jingping; Sun, Huiling

2014-01-01

350

Impact response of composite materials  

NASA Technical Reports Server (NTRS)

Composite materials composed of carbon fibers and resin matrices offer great promise in reducing the weight of aerospace structures. However they remain extremely vulnerable to out of plane impact loads, which lead to severe losses in strength and stiffness. The results of an experimental program, undertaken to investigate the low velocity impact damage tolerance of composite materials is presented. The objectives were to identify key neat resin/composite properties that lead to enhancement of composite impact damage tolerance and to find a small scale test that predicts compression after impact properties of panels. Five materials were selected for evaluation. These systems represented different classes of material behavior such as brittle epoxy, modified epoxies, and amorphous and semicrystalling thermoplastics. The influence of fiber properties on the impact performance was also studied in one material, i.e., in polyether ether ketone (PEEK). Several 24 and 48 ply quasi-isotropic and 24 ply orthotropic laminates were examined using an instrumented drop weight impactor. Correlations with post impact compression behavior were made.

Tiwari, S. N.; Srinivasan, K.

1991-01-01

351

Templated Chemically Deposited Semiconductor Optical Fiber Materials  

NASA Astrophysics Data System (ADS)

Chemical deposition is a powerful technology for fabrication of planar microelectronics. Optical fibers are the dominant platform for telecommunications, and devices such as fiber lasers are forming the basis for new industries. High-pressure chemical vapor deposition (HPCVD) allows for conformal layers and void-free wires of precisely doped crystalline unary and compound semiconductors inside the micro-to-nanoscale-diameter pores of microstructured optical fibers (MOFs). Drawing the fibers to serve as templates into which these semiconductor structures can be fabricated allows for geometric design flexibility that is difficult to achieve with planar fabrication. Seamless coupling of semiconductor optoelectronic and photonic devices with existing fiber infrastructure thus becomes possible, facilitating all-fiber technological approaches. The deposition techniques also allow for a wider range of semiconductor materials compositions to be exploited than is possible by means of preform drawing. Gigahertz bandwidth junction-based fiber devices can be fabricated from doped crystalline semiconductors, for example. Deposition of amorphous hydrogenated silicon, which cannot be drawn, allows for the exploitation of strong nonlinear optical function in fibers. Finally, crystalline compound semiconductor fiber cores hold promise for high-power infrared light-guiding fiber devices and subwavelength-resolution, large-area infrared imaging.

Sparks, Justin R.; Sazio, Pier J. A.; Gopalan, Venkatraman; Badding, John V.

2013-07-01

352

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

Research related to growth of an imbedded through-width delamination (ITWD) in a compression loaded composite structural element is presented. Composites with widely different interlaminar fracture resistance were examined, viz., graphite/epoxy (CYCOM 982) and graphite/PEEK (APC-2). The initial part of the program consisted of characterizing the material in tension, compression and shear mainly to obtain consistent material properties for analysis, but also as a check of the processing method developed for the thermoplastic APC-2 material. The characterization of the delamination growth in the ITWD specimen, which for the unidirectional case is essentially a mixed Mode 1 and 2 geometry, requires verified mixed-mode growth criteria for the two materials involved. For this purpose the main emphasis during this part of the investigation was on Mode 1 and 2 fracture specimens, namely the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimens.

Gillespie, J. W., Jr.; Carlson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1985-01-01

353

Radiopacity of experimental composite resins containing radiopaque materials.  

PubMed

This study aimed to investigate the relationship between the radiopacity of an experimental light-cured composite resin and the amount and type of its radiopaque material: Ti, SrCO3, ZrO2, BaSO4, or Bi2O3. Radiopacity of each material was evaluated in terms of aluminum equivalent thickness using an aluminum step wedge. Then, the half-value layer thickness of the experimental composite resin, which had an aluminium equivalent thickness of 1 mm, was evaluated. It was found that the effects of elemental composition were not identical when evaluated in terms of aluminum equivalent thickness and by half-value layer. Nevertheless, both measurement methods indicated that radiopacity increased with increase in radiopaque material content as well as increase in atomic number of the element. PMID:16279720

Aoyagi, Yujin; Takahashi, Hidekazu; Iwasaki, Naohiko; Honda, Ei-ichi; Kurabayashi, Toru

2005-09-01

354

Influence of sundrying on the chemical composition, aflatoxin content and fungal counts of two pepper varieties — Capsicum annum and Capsicum frutescens  

Microsoft Academic Search

Samples of sundried, matured red pepper,Capsicum annum with a moisture content (MC) of 12.7–26.8 percent had on dry weight basis, vitamin C, 5.0–6.4 mg\\/100 g; crude protein, 0.8–1.2 percent; total soluble solids, 3.3–4.1 percent, and fungal counts of log 4.4–4.5\\/g. Ordinary matured redC. annum had MC, 75.7–78.2 percent vitamin C, 36.1–38.5 mg\\/100 g; crude protein, 2.4–2.8 percent; total soluble solids,

G. O. Adegoke; A. E. Allamu; J. O. Akingbala; A. O. Akanni

1996-01-01

355

The prediction of apparent metabolisable energy content of oil seeds and oil seed by-products for poultry from its chemical components, in vitro analysis or near-infrared reflectance spectroscopy  

Microsoft Academic Search

Regression models including chemical composition, in vitro digestibility and near-infrared reflectance spectroscopy (NIRS) were compared to predict the energy content of several feed ingredients for poultry. The nitrogen-corrected apparent metabolisable energy content (AMEn) and its proportion on total gross energy (AMEn\\/GE) were determined in 52 batches of six protein concentrates; samples were randomly obtained from a poultry feed manufacturing plant

B. Losada; P. García-Rebollar; C. Álvarez; P. Cachaldora; M. A. Ibáñez; J. Méndez; J. C. De Blas

2010-01-01

356

Welds in thermoplastic composite materials  

Microsoft Academic Search

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

N. S. Taylor

1990-01-01

357

Welds in thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Taylor, N. S.

358

Durability of polymer composite materials  

Microsoft Academic Search

The purpose of this research is to examine structural durability of advanced composite materials under critical loading conditions, e.g., combined thermal and mechanical loading and shear fatigue loading. A thermal buckling model of a burnt column, either axially restrained or under an axial applied force was developed. It was predicted that for a column exposed to the high heat flux

Liu Liu

2006-01-01

359

Composite materials prepared by phase inversion deposition of polyacrylonitrile onto porous polyethylene films  

Microsoft Academic Search

Composite ultrafiltration membanes were prepared by deposition of polyacrylonitrile onto a porous polyethylene support by\\u000a the phase inversion procedure. The supports were hydrophilized by treatment in a barrier discharge argon plasma. Methods were\\u000a suggested for controlling the pore size in the polyacrylonitrile layer. The filtration characteristics of the membranes and\\u000a their mechanical properties were determined.

A. S. Olifirenko; E. Yu. Rosova; N. N. Saprykina; A. F. Mitilineos; G. K. Elyashevich

2009-01-01

360

Lunar Skylights and Their Chemical Compositions  

NASA Astrophysics Data System (ADS)

In 2009, the Japanese orbiter, SELenological and Engineering Explorer (SELENE) discovered a skylight on the near side of the moon. Skylights are collapsed ceilings of rilles, thought to be caused by moonquakes, meteoroids, or incomplete formation of these lava tube ceilings. Since then, NASA's Lunar Reconnaissance Orbiter has discovered two more skylights, also located on the near side of the moon. Previous research has shown that the physical characteristics of known rilles, can be used as indicators of the presence of yet undiscovered rille and lava dome locations across the lunar surface. We hypothesize that skylights have a signature chemical composition that is unique, and can be used to predict the location of additional skylights on the surface of the moon. For this study, we compared chemical composition data of the three mare sites containing skylights with the 21 mare sites without skylights. Using the software JMARS for the Moon, we compiled multiple datasets to measure the concentrations of 13 different chemical compounds including calcium, iron oxide, titanium dioxide, and thorium. We then conducted a two-tailed T-test of the data, which generated probability values for the mean differences across all 13 chemical compounds of the maria sites with skylights and the maria sites without skylights. Our results show that there is no statistical difference in chemical composition across all of the maria sites examined. Therefore, we conclude that chemical composition does not predict or indicate potential skylight locations on the moon. Further research on other skylight characteristics, for example depth and surrounding underground lava channels, may shed light on the relationships between mare and skylights locations. Three Skylight Locations Found on Lunar Surface 100m View of Mare Tranquilitatis Skylight

Wong, J.; Torres, J.; FitzHoward, S.; Luu, E.; Hua, J.; Irby, R.

2013-12-01

361

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Bardenheier, R.

1981-01-01

362

Combined studies of chemical composition of urine sediments and kidney stones by means of infrared microspectroscopy.  

PubMed

Results of the structural analysis of urinary sediments by means of infrared spectral microscopy are presented. The results are in good agreement with the results of standard optical microscopy in the case of single-component and crystalline urinary sediments. It is found that for noncrystalline or multicomponent sediments, the suggested spectroscopic method is superior to optical microscopy. The chemical structure of sediments of any molecular origin can be elucidated by this spectroscopic method. The method is sensitive enough to identify solid particles of drugs present in urine. Sulfamethoxazole and traces of other medicines are revealed in this study among the other sediments. We also show that a rather good correlation exists between the type of urinary sediments and the renal stones removed from the same patient. Spectroscopic studies of urinary stones and corresponding sediments from 76 patients suffering from renal stone disease reveal that in 73% of cases such correlation exists. This finding is a strong argument for the use of infrared spectral microscopy to prevent kidney stone disease because stones can be found in an early stage of formation by using the nonintrusive spectroscopic investigation of urinary sediments. Some medical recommendations concerning the overdosing of certain pharmaceuticals can also be derived from the spectroscopic studies of urinary sediments. PMID:23429795

Tamošaityt?, Sandra; Hendrixson, Vaiva; Želvys, Ar?nas; Tyla, Ram?nas; Ku?inskien?, Zita A; Jankevi?ius, Feliksas; Pu?etait?, Milda; Jablonskien?, Valerija; Šablinskas, Valdas

2013-02-01

363

Determination of the composition of the organic matter chemically stabilized by agricultural soil clay minerals: Spectroscopy and Density Fractionation  

NASA Astrophysics Data System (ADS)

The interactions between soil organic matter and clay minerals are considered important processes because of their ability to sequester C in soil for long periods of time, and hence control C in the global C cycle when present. However, differing results have been reported regarding the composition of the soil organic matter - aromatic fractions versus aliphatic fractions - associated with clay minerals. To clarify this critical issue and better understand the C sequestration process in soils, we aimed to determine the nature of the chemically bound natural organic matter on clay surfaces, and to probe the speciation and spatial distribution of C in the soil clay nanoparticles using direct spectroscopic measurements namely solid-state CP-MAS and DP-MAS 13C NMR spectroscopy, x-ray diffraction spectroscopy (XRD), and scanning transmission x-ray microscopy (STXM). We tested the hypotheses that peptides and polysaccharides are stabilized by the smectite-illite clay while the lipids and black carbon are a separate phase; and that they are evenly distributed on clay surfaces. A soil clay fraction (5.5% organic C) was isolated from the surface of a prairie soil (Mollisol) in southwestern Minnesota, characterized by a pH 6.0, 32.5% clay content, and 3.7% organic carbon, using a sonication-sedimentation-siphoning process in distilled water. Then was subjected to density separation combined with low energy ultrasonic dispersion to separate the free organic and black C (light fraction) from the chemically bound C (heavy fraction). The XRD results indicated a dominance of interstratified smectite-illite clays in soil. The 13C-NMR spectra of the soil clay fraction suggested that polysaccharides and polypeptides are the prevailing components of the organic matter associated with the mineral clay, with only a minor component of aromatic C. The light fraction has strong alkyl C-H bands characteristic of fatty acids plus strong C-O bands characteristic of polysaccharides, including the anomeric C band centered at 105 ppm. The aromatic band at 130 ppm and the phenolic C-O band at 150 pm are strong as well indicating the presence of black carbon and lignin-derived components, contrary to the heavy fraction where they are almost absent. STXM results indicated that the proteins are abundant in the soil clay fraction, separate from lipids, and partially associated with saccharides. The black carbon constitutes a separate phase, but is amply present with lipids and lignin-derived compounds in the light fraction. We conclude that (1) the smectite-illite sheets in our soils preferentially retain peptides, and polysaccharides favoring the protection of these normally readily biodegradable fractions relative to the lignin-derived phenolic components; (2) the black carbon constitutes a major component of the light fraction, and is partially attached to the organic matter bonded with the smectitic clays; and (3) the lipids are associated with soil clay fraction as a separate phase, but are not bound to clay minerals.

Oufqir, Sofia; Bloom, Paul; Toner, Brandy; Hatcher, Patrick

2014-05-01

364

Isolation, purification and chemical composition of maize root cap slime  

Microsoft Academic Search

Summary The total root exudate isolated axenically from roots is shown to constitute an extremely heterogenous population of particulate and soluble material. Differences in protein and total sugars contents, and neutral sugar composition throughout stages of total root exudate purification are reported. The importance of controlled collection and purification conditions to ensure valid analysis and composition of purified maize root

Annie Chaboud

1983-01-01

365

Chemical and anatomical compositions of coal precursors  

SciTech Connect

Four cores of peat from various environments in the Florida Everglades and one from the Okefenokee Swamp, Georgia have been studied with the objective of clarifying the roles of cellulose, lignin and other vascular plant polymers as input to coalification. The peat was first separated by set sieving into a coarse fraction consisting of fragments of plant organs and tissues, and a fine fraction containing an amorphous humic matrix mixed with a minority of disrupted cellular material. Microscopic examination, Curie-point pyrolysis/mass spectrometry with multivariate statistical analyses of the data, supplemented by pyrolysis/gas chromatography and PY/GC/MD, revealed substantial differences in the degree of preservation of plant tissues and in chemistry between peats derived from different types of plants. Some ..cap alpha..-cellulose is present in the upper levels of the peats, but the total polysaccharide content decreases markedly with depth, perhaps due in some cases to changes in the source vegetation, but mainly due to selective enzymatic removal of certain monomer units from polymeric lignin, thereby concentrating the structural types remaining (notably structures related to p.coumaryl alcohol). Polymeric aliphatic hydrocarbon structures are present in nearly all samples, but are more abundant at the lower depths. The chemical and morphological differences in peats are likely to be reflected in the coals that may form from them.

Ryan, N.J.

1985-01-01

366

Chemical compatibility of cartridge materials  

NASA Technical Reports Server (NTRS)

This twelve month progress report deals with the chemical compatibility of semiconductor crystals grown in zero gravity. Specifically, it studies the chemical compatibility between TZM, a molybdenum alloy containing titanium and zirconium, and WC 103, a titanium alloy containing Niobium and Hafnium, and Gallium arsenide (GaAs) and Cadmium Zinc Tellurite (CdZnTe). Due to the health hazards involved, three approaches were used to study the chemical compatibility between the semiconductor and cartridge materials: reaction retort, thermogravimetric analysis, and bulk cylindrical cartridge containers. A scanning electron microscope with an energy dispersive X-ray analyzer was used to examine all samples after testing. The first conclusion drawn is that reaction rates with TZM were not nearly as great as they were with WC 103. Second, the total reaction between GaAs and WC 103 was almost twice that with TZM. Therefore, even though WC 103 is easier to fabricate, at least half of the cartridge thickness will be degraded if contact is made with one of the semiconductor materials leading to a loss of strength properties.

Wilcox, Roy C.; Zee, R. H.

1991-01-01

367

Chemical composition, vitamin E content, lipid oxidation, colour and cooking losses in meat from Tudanca bulls finished on semi-extensive or intensive systems and slaughtered at 12 or 14 months.  

PubMed

The effects of production system (SE: pasture based vs. IN: concentrate based) and slaughter age (12 vs. 14 months) on chemical composition, vitamin E and myoglobin contents, lipid oxidation at 0, 3 and 6 days of display, colour and cooking losses at 2 and 7 days postmortem from thirty-three Tudanca calves were studied. SE animals showed lower IMF and greater vitamin E contents (1.2 vs. 2.9% and 4.1 vs. 1.8 ?g/g, respectively). Thiobarbituric acid reactive substances (TBARS) increased (p ? 0.001) with display time and was greater in the IN system. After 6 days display, IN animals presented twofold TBARS values (1.4 vs. 0.8 mg malonaldehyde/kg meat). At 7 days postmortem, SE groups presented greater (p ? 0.05) L* and lower (p ? 0.05) b* and H° than IN groups. Myoglobin increased with age (3.4 to 3.9 mg/g meat), but differences (p ? 0.05) on a* and C* values were observed only between 12 and 14 months at 2 days postmortem. PMID:24211548

Humada, M J; Sañudo, C; Serrano, E

2014-02-01

368

Unusual chemical compositions of noctilucent-cloud particle nuclei  

NASA Technical Reports Server (NTRS)

Two sounding rocket payloads were launched from the ESRO range in Sweden during a noctilucent cloud display. Large numbers of submicron particles were collected, most of which appear to be made up of a high density material coated with a low density material. Typical electron micrographs are shown. Particle chemical compositions have been measured by use of dispersive X-ray analysis equipment attached to an electron microscope and have revealed that most of the high density particle nuclei have atomic weights greater than iron.

Hemenway, C. L.

1973-01-01

369

Chemical composition of essential oil from Calligonum polygonoides Linn.  

PubMed

The essential oil from air dried buds and roots of Calligonum polygonoides Linn., has been extracted from dry steam distillation and analysed for chemical composition by gas chromatography-mass spectrometry. In total, 27 and 10 compounds were analysed qualitatively and quantitatively, accounting for 68.42% and 82.12% total contents of the essential oils of buds and roots, respectively. It contains a complex mixture of terpenoids, hydrocarbons, phenolic compounds, acid derivatives and ketones. The main component of essential oil was ethyl homovanillate (11.79%) in buds and drimenol (29.42%) in roots. PMID:22574752

Samejo, Muhammad Qasim; Memon, Shahabuddin; Bhanger, Muhammad Iqbal; Khan, Khalid Mohammed

2013-04-01

370

Evaluation of momentum effects on material properties of titanium-silicon-nitrogen nanocrystalline composites prepared by pulsed dc reactive sputtering  

NASA Astrophysics Data System (ADS)

The investigation had as a general goal the deposition of thin films that possess high erosion wear resistance. The fabrication technique used for this purpose was an industry-compatible process called reactive sputtering physical vapor deposition (PVD). The study specifically involved depositing Ti-Si-N nc-composite thin films according to generic design principles that specify using a transition metal nitride and a covalent nitride material system in order to produce hard coatings (˜50 GPa Vickers hardness). Thin films were deposited using reactive pulsed, do sputtering to avoid arcing issues and for wider control over the process properties such as the deposition rate and level of bombardment. Two sputter guns used synchronized pulsed do signals, which were asymmetric and bipolar with positive voltages of less than +100 V and negative voltages of -500 to -1000 V. The pulsing frequency was varied in this co-deposition system as a possible means to control the nanocrystalline composite thin film properties by controlling the level of bombardment. The thin films were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to determine the crystallinity of the films. XRD results show the presence of the (111), (220), and (200) orientations with the later being most common. TEM bright-field images show nanocrystals in the 10 to 40 nm range, depending on the pulsing frequency. A columnar morphology (50--120 nm diameters) was observed in the nc-composite films from images taken with a scanning electron microscope. Verification of the TiN and SiN phases was accomplished using XPS to analyze the binding energies of Ti 2p and Si 2p electrons, respectively. Oxygen was detected in the films, (2--9 at.%) depending on pulsing frequency, and it severely worsened the mechanical properties, specifically the hardness, by reacting with some of the silicon in the SiN phase. A maximum Vickers hardness, Hv, of 32 GPa and reduced elastic modulus, Er, of 290 GPa were measured using displacement controlled nanoindentation. Normalized nanoindentation depths of 5, 10 and 15% of the film thickness were performed and showed that normalized indent depths of 10% produced reliable data. Analysis of the plasma properties in situ shows variation in the ionized species, their density, and energy as a function of pulsing frequency. A Langmuir probe and energy-resolved mass spectrometer (Hiden probe) were used to analyze the conditions at the substrate position within the deposition chamber. The major ion constituent in the plasma was N2 + with N+, Ti+, SiN+, and TiN+ comprising the remaining species. The energy analysis of N2+ and N+ show that the energy distribution is bimodal with the majority of ions < 5 eV, while a secondary, less intense peak of 70 to 75 eV exists. This information was used to calculate a universally applicable momentum-per-atom figure of merit at the growing film surface during deposition. The nc-composites deposited at 10 mT N2 show that as the momentum-per-atom increases, so do the Hv and Er. The nc-composites deposited at 5 mT N2 show a negative correlation to the content of (111) orientation in the films, which itself correlates to the momentum-per-atom.

Sunal, Paul Dennis

371

Energy absorption of composite materials  

NASA Technical Reports Server (NTRS)

Results of a study on the energy absorption characteristics of selected composite material systems are presented and the results compared with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite/epoxy (Gr/E), Kevlar (TM)/epoxy (K/E) and glass/epoxy (Gl/E). Chamfering and notching one end of the composite tube specimen reduced the peak load at initial failure without altering the sustained crushing load, and prevented catastrophic failure. Static compression and vertical impact tests were performed on 128 tubes. The results varied significantly as a function of material type and ply orientation. In general, the Gr/E tubes absorbed more energy than the Gl/E or K/E tubes for the same ply orientation. The 0/ + or - 15 Gr/E tubes absorbed more energy than the aluminum tubes. Gr/E and Gl/E tubes failed in a brittle mode and had negligible post crushing integrity, whereas the K/E tubes failed in an accordian buckling mode similar to the aluminum tubes. The energy absorption and post crushing integrity of hybrid composite tubes were not significantly better than that of the single material tubes.

Farley, G. L.

1983-01-01

372

Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review  

NASA Astrophysics Data System (ADS)

The measurement of the sizes and the velocities of droplets relies upon widespread and well-established techniques, but characterizing their temperature and their composition remains challenging. The lack of standard methods is particularly detrimental, given the importance of these parameters for validating models and numerical simulations of many spray processes. Heat and mass transfers are dominant aspects in applications such as spray combustion in IC engines, spray cooling, spray drying, wet scrubbers in which liquid sprays capture gas pollutants and also the preparation of nanoparticles via spray route. This paper provides a review of the main techniques available to optically measure the temperature and chemical compositions of single droplets and sprays. Most of these techniques are based on phenomena related to light interaction with matter. Photoluminescence processes like fluorescence and phosphorescence have temperature and composition dependences which can be exploited, while other methods rely on light scattering by the droplets. In particular, the angular position of the rainbow is very sensitive to the refractive index and then to both the temperature and composition. Less widely used diagnostic methods include Raman scattering, thermochromic liquid crystals, thermographic phosphors, infrared thermography, morphology-dependent resonances and their subsequent effects on the stimulated emission of dye molecules. In this review, the emphasis is mainly placed on two groups of techniques—methods based on laser-induced fluorescence and those based on light scattering—but details about alternative methods will be also provided. The potential of combining fluorescence-based techniques or rainbow refractometry with a droplet sizing measurement technique to derive temperature and composition per size class will be also discussed.

Lemoine, Fabrice; Castanet, Guillaume

2013-07-01

373

226Ra and 228Ra in scale and sludge samples and their correlation with the chemical composition  

Microsoft Academic Search

In order to contribute to a future waste management policy related to the presence of technologically enhanced natural occurring radioactive material (TENORM) in the Brazilian petroleum industry, the present work presents the chemical composition and the 226Ra and 228Ra content of sludge and scales generated during the offshore E and P petroleum activities in the Campos Basin, the primary offshore

José Marcus Godoy; Rosana Petinatti da Cruz

2003-01-01

374

Removal of lipid soluble process chemicals from biological materials by extraction with naturally occurring oils or synthetic substitutes thereof  

SciTech Connect

This patent describes a method of removing lipid soluble process chemicals from biological materials comprising blood plasma and fractions thereof containing the lipid soluble process chemicals. The lipid soluble process chemical is a virus attenuating solvent having a high flash point, a detergent, or a mixture thereof. It comprises bringing the biological materials containing the lipid soluble process chemicals into contact with an effective amount of a naturally occurring oil extracted from a plant or an animal or a synthetic compound of similar chemical structure. Also described is a method of removing lymphokine inducing phorbol esters from lympholkine-containing biological material. It comprises bringing the biological materials containing the phorbol esters into contact with an effective amount of a naturally occurring oil extracted from a plant or an animal or a synthetic compound of similar chemical structure so as to remove 80% or more of the phorbol esters.

Woods, K.R.; Orme, T.W.

1988-12-06

375

Chemical Composition and Heterogeneity of Wild 2 Cometary Particles Determined by Synchrotron X-ray Fluorescence  

SciTech Connect

Seven cometary dust particle tracks in Stardust aerogel were studied using synchrotron X-ray fluorescence methods at the National Synchrotron Light Source (NY) and Advanced Photon Source (IL). Elemental maps were produced for each of the tracks and elemental abundances for 156 individual fragments within these tracks were determined. Whole-track elemental abundances were inferred by summing the elemental masses for the fragments in each track and scaling by the ratio of total Fe in the map and total Fe in the fragments. In general, whole-track and terminal-particle abundances are dissimilar. The total Fe masses ranged from 4 to 2200 pg, corresponding to impactors in the size range of 2.7 to 22 {mu}m if Fe abundances are equal to the chondritic value. Systematic variations in element abundance with fragment distance from the aerogel entry point were generally subtle but were pronounced in one track (C2115,19). In this track, Zn/Fe was about three orders of magnitude higher at the top, Cr/Fe was two orders of magnitude higher at the bottom, and S was relatively uniform. Compositional convergence data showed that typically analysis of {approx}10 fragments was needed to reach convergent whole-track abundance. Zinc was an exception, showing nonconvergent profiles and steps due to the presence of rare, high-Zn fragments. The resulting wholetrack elemental abundances show diverse patterns that are generally chondritic (i.e., within a factor of three of CI abundances) with some exceptions, notably depletions in S and enrichments in the moderately volatile elements Cu, Zn, and Ga. Enrichments in large ion lithophile elements relative to Fe were observed in one track. Correlation matrices showed several strong elemental correlations, notably selenium associated with sulfur (sulfides), a ubiquitous correlation of the first-row transition metals Cr, Mn, and Fe attributed to the presence of pyroxene, and enrichments of gallium associated with calcium, likely affiliated with Mg-Al glass.

Lanzirotti,A.; Sutton, S.; Flynn, G.; Newville, M.; Rao, W.

2008-01-01

376

Correlation of rocket propulsion fuel properties with chemical composition using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry followed by partial least squares regression analysis.  

PubMed

There is an increased need to more fully assess and control the composition of kerosene-based rocket propulsion fuels such as RP-1. In particular, it is critical to make better quantitative connections among the following three attributes: fuel performance (thermal stability, sooting propensity, engine specific impulse, etc.), fuel properties (such as flash point, density, kinematic viscosity, net heat of combustion, and hydrogen content), and the chemical composition of a given fuel, i.e., amounts of specific chemical compounds and compound classes present in a fuel as a result of feedstock blending and/or processing. Recent efforts in predicting fuel chemical and physical behavior through modeling put greater emphasis on attaining detailed and accurate fuel properties and fuel composition information. Often, one-dimensional gas chromatography (GC) combined with mass spectrometry (MS) is employed to provide chemical composition information. Building on approaches that used GC-MS, but to glean substantially more chemical information from these complex fuels, we recently studied the use of comprehensive two dimensional (2D) gas chromatography combined with time-of-flight mass spectrometry (GC×GC-TOFMS) using a "reversed column" format: RTX-wax column for the first dimension, and a RTX-1 column for the second dimension. In this report, by applying chemometric data analysis, specifically partial least-squares (PLS) regression analysis, we are able to readily model (and correlate) the chemical compositional information provided by use of GC×GC-TOFMS to RP-1 fuel property information such as density, kinematic viscosity, net heat of combustion, and so on. Furthermore, we readily identified compounds that contribute significantly to measured differences in fuel properties based on results from the PLS models. We anticipate this new chemical analysis strategy will have broad implications for the development of high fidelity composition-property models, leading to an improved approach to fuel formulation and specification for advanced engine cycles. PMID:24411093

Kehimkar, Benjamin; Hoggard, Jamin C; Marney, Luke C; Billingsley, Matthew C; Fraga, Carlos G; Bruno, Thomas J; Synovec, Robert E

2014-01-31

377

The Effect of Chemical Functionalization on Mechanical Properties of Nanotube/Polymer Composites  

NASA Technical Reports Server (NTRS)

The effects of the chemical functionalization of a carbon nanotube embedded in a nanotube/polyethylene composite on the bulk elastic properties are presented. Constitutive equations are established for both functionalized and non-functionalized nanotube composites systems by using an equivalent-continuum modeling technique. The elastic properties of both composites systems are predicted for various nanotube lengths, volume fractions, and orientations. The results indicate that for the specific composite material considered in this study, most of the elastic stiffness constants of the functionalized composite are either less than or equal to those of the non-functionalized composite.

Odegard, G. M.; Frankland, S. J. V.; Gates, T. S.

2003-01-01

378

Non-contact measurement of CNT compounding ratio in composite material by eddy current method  

Microsoft Academic Search

Carbon nano-tubes (CNT) are new materials which have an excellent mechanical and electric characteristics. Electric conductivity and high rigidity (high strength) can be given to a resin by mixing CNT with a usual resin. The compounding ratio of CNT was estimated by optical observation and resistance measurement by 4 probes method so far. But, both methods are time-consuming. Therefore, the

H. Wakiwaka; M. Kodani; M. Endo; Y. Takahashi

2006-01-01

379

An In Vitro Spectroscopic Analysis to Determine the Chemical Composition of the Precipitate Formed by Mixing Sodium Hypochlorite and Chlorhexidine  

PubMed Central

Introduction The purpose of this in vitro study was to determine the chemical composition of the precipitate formed by mixing sodium hypochlorite (NaOCl) and Chlorhexidine (CHX), and relative molecular weight of the components. Methods Using commercially available chlorhexidine gluconate (CHXg), a 2% solution was formed and mixed in a 1:1 ratio with commercially available NaOCl producing a brown precipitate. The precipitate as well as a mixture of precipitate and pure chlorhexidine diacetate (CHXa) was then analyzed using 1D and 2D NMR spectroscopy. Results The 1D and 2D NMR spectra were fully assigned, in terms of chemical shifts of all proton and carbon atoms in intact CHX. This permitted identification of CHX breakdown products with and without the aliphatic linker present, including lower molecular weight components of CHX that contained a para-substituted benzene that was not para-chloroaniline (PCA). Conclusions Based on this in vitro study, the precipitate formed by NaOCl and CHX is composed of at least two separate molecules, all of which are smaller in size than CHX. Along with native CHX, the precipitate contains two chemical fragments derived from CHX, neither of which are PCA.

Sem, Daniel S.

2014-01-01

380

Fracture of laminated composite materials  

Microsoft Academic Search

Cracks occurring in conventional laminates, or artificially bonded composites, and slip bands appearing in lamellar alloys, or naturally bonded composites, are studied. In this analysis, a mixed mode plane crack is modeled by continuous distributions of both climb and glide dislocations. The requirement that the boundary conditions prescribed on the surfaces of this crack must be satisfied results in dual

Omoike

1984-01-01

381

Adiabatic shear failure of high reinforcement content aluminum matrix composites  

Microsoft Academic Search

Dynamic failure behaviors of high reinforcement content TiB2\\/Al composites were experimentally investigated using split Hopkinson pressure bar (SHPB). The TiB2\\/Al composites showed high flow stresses and good plastic deformation ability at high strain rates. Adiabatic temperature\\u000a rise decreased the flow stresses of TiB2\\/Al composites, which was verified by the prediction of Johnson–Cook model. While the predictions by Cowper–Symonds model\\u000a exhibited

G. H. Wu; D. Z. Zhu; G. Q. Chen; L. T. Jiang; Q. Zhang

2008-01-01

382

Fabrication method for photovoltaic materials by chemical atomisation spray. Final report  

SciTech Connect

Acetonitrile has been shown to be a suitable carrier solvent for the preparation of thin layers of cuprous sulphide by chemical atomisation. A reactive spraying apparatus for monodispersed mist has been developed. It is claimed to be indispensible for establishing a firm relation between the characteristics of the mist and those of the films obtained. The formation of thin layers of cadmium sulphide and stannic oxide on various supports has been studied and the quality of the layers, their adhesion to the support, and the influence of the nature and temperature of the support on the reactions have been investigated. Three laboratories have participated in the evaluation of the physical characteristics of the thin layers.

Savelli, M.; LaHaye, J.; Vadel, J.

1982-09-01

383

Chemical characterization of selected LDEF polymeric materials  

NASA Technical Reports Server (NTRS)

The chemical characterization of selected polymeric materials which received exposure on the LDEF is reported. The specimens examined include silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material, polysulfone matrix resin/graphite fiber reinforced composites, and several high performance polymer films. These specimens came from numerous LDEF locations and, thus, received different environmental exposures. The results of infrared, thermal, x ray photoelectron, and various solution property analyses have shown no significant change at the molecular level in the polymer that survived exposure. However, scanning electron and scanning tunneling microscopies show resin loss and a texturing of the surface of some specimens which resulted in a change in optical properties. The potential effect of a silicon containing molecular contamination on these materials is addressed. The possibility of continued post-exposure degradation of some polymeric films is also proposed.

Young, Philip R.; Slemp, Wayne S.

1992-01-01

384

Bioinspired organic-inorganic composite materials prepared by an alternate soaking process as a tissue reconstitution matrix.  

PubMed

Poly(acrylic acid) (PAAc) grafted poly(ethylene) (PE) (PAAc-g-PE) film-apatite or calcium carbonate (CaCO3) composite materials were prepared by an alternate soaking process, which simply forms apatite or CaCO3 on the polymer materials by alternate soaking in Ca(2+)- and PO(3-)4- or CO(3)2- -containing solutions. X-ray diffraction analysis of the composite films indicated the presence of hydroxyapatite or CaCO3 on the film. Scanning electron microscopic observation revealed that the whole surface of the film was covered by the apatite or CaCO3. Cell compatibility tests of the apatite- or CaCO3-coated film suggested that the greater number of cells adhered on the films and that the cell proliferation properties were extremely greater on the films. PMID:14624523

Ogomi, Daisuke; Serizawa, Takeshi; Akashi, Mitsuru

2003-12-15

385

New types of reinforced composite materials  

Microsoft Academic Search

The physical properties of solids determine their usefulness as structural materials. Metals have some disadvantageous characteristics which reduce their effectiveness in critical engineering applications. These limitations can be overcome by the use of certain types of fibrous reinforced composites which have become available over the last few years. However, these materials in turn have their own inherent limitations, particularly in

J. G. Morley

1976-01-01

386

Understanding chemical trends in rock surface compositions as measured by ChemCam at Gale crater, Mars: The signatures of rock coatings and rinds in LIBS laboratory data  

NASA Astrophysics Data System (ADS)

On Earth, the physical and chemical breakdown of rocky materials occurs through interactions with the atmosphere, soil, biological processes, and aqueous solutions. These interactions produce alteration features on the surfaces of rocks, which record information about the amount and types of fluids with which the rock has interacted. Alteration features can also be indicators of and habitats for microbial life in terrestrial environments. Thus, detecting rock surface alteration is an important part of the NASA Curiosity rover mission to Gale crater, Mars. The ChemCam LIBS instrument onboard Curiosity is uniquely suited to detecting and analyzing rock surface alteration. The LIBS technique uses a pulsed laser microbeam (350-550 ?m) to ablate small amounts of material from a target to form a plasma. Because some material is removed during each laser pulse, it is possible to obtain a depth profile of chemical composition by performing multiple laser pulses on one location. Each pulse returns a spectrum that represents the composition at a specific depth, with each subsequent shot sampling the composition at a slightly greater depth. Laboratory measurements of basalts have shown that each LIBS shot removes at least ~0.3-0.82 ?m/shot, suggesting a removal of ~9-25 ?m of the surface for a standard analysis of 30 shots in rocks of similar hardness. Here we present laboratory LIBS experiments on well-characterized terrestrial rock samples with coatings and rinds with the goal of understanding the signatures of such features in LIBS data from Mars. The terrestrial sample set includes a basalt with a ~0-50 ?m thick Mn-rich rock varnish and a thin (<1 mm) weathering rind and a sandy dolomite with a ~500 ?m thick Ca-rich rind. Both samples were interrogated with hundreds of LIBS shots per location three times on the unweathered interior and three times on the exterior. Results from the basalt show that compositions similar to the bulk rock composition was reached by ~50-70 shots, with the observed chemical changes suggesting both the varnish and at least some rind were penetrated. Results from the sandy dolomite do not show as clear a change from rock exterior to interior as the basalt, but a general chemical trend from exterior to interior was observed in all three depth profiles. Laboratory results suggest that depth profiles of at least 100 shots are useful for clearly identifying coatings and rinds of similar thickness to those found on Earth. However, alteration trends may still be discernible with fewer shots. On Mars, the rock Bathurst Inlet (sol 55), which was shot only 30 times per location, shows what appears to be a near-surface gradient of several elements, most notably Li. Trends similar in nature (if not composition) to the terrestrial sandy dolomite sample were also observed on raised ridge materials such as McGrath_5 (sol 234). Additional martian samples also show trends similar to coatings and rinds measured in the laboratory, suggesting that there may be surface alteration of some rocks in Gale crater.

Lanza, N.; Clegg, S. M.; Wiens, R. C.; Leveille, R. J.; Melikechi, N.; Ollila, A.; Tokar, R. L.; Newsom, H. E.; Blank, J. G.; Bridges, N. T.; Clark, B.; Deans, M. C.; Delapp, D.; Ehlmann, B. L.; Hardgrove, C. J.; Jackson, R.; Lasue, J.; McInroy, R.; Meslin, P.; Mezzacappa, A.; Team, M.

2013-12-01

387

Chemical Softening and Wear of Dental Composites  

Microsoft Academic Search

The purpose of this work was to determine the influence of chemical food-simulating liquids on the wear of various commercial dental composite restoratives. In many cases, pre-conditioning the restoratives in these liquids for one week produced swelling of the polymer matrix and considerable surface damage. The resulting degradation reduced the hardness and enhanced the wear as measured by a pin-and-disc

J. E. McKinney; W. Wu

1985-01-01

388

Chemical vapor infiltration and deposition to produce a silicon carbide–carbon functionally gradient material  

Microsoft Academic Search

Functionally gradient material (FGM) that had a layer in which the chemical composition changed gradually from C to SiC between the C\\/C composite and the surface SiC layer was prepared. The 3D-woven carbon fiber preform was solidified partially by liquid-phase impregnation with a resol-type cresol resin. The preform was further solidified by thermal-gradient chemical vapor infiltration of carbon from propane.

Motoaki Kawase; Teruoki Tago; Michihiro Kurosawa; Hisashi Utsumi; Kenji Hashimoto

1999-01-01

389

A rapid fabrication of C\\/C composites by a thermal gradient chemical vapor infiltration method with vaporized kerosene as a precursor  

Microsoft Academic Search

A thermal gradient, atmospheric pressure chemical vapor infiltration method with simultaneous vaporized kerosene as a precursor for rapid fabrication of C\\/C composites was studied. By this method, carbon felts (bulk density ?0.2gcm?3) were densified to C\\/C composites with density of 1.67 and 1.71gcm?3 when prepared at 1050 and 1150°C for 6h, respectively. X-ray diffraction result indicates that the composites have

Jiping Wang; Junmin Qian; Guanjun Qiao; Zhihao Jin

2007-01-01

390

Detection of adulteration of pumpkin seed oil by analysis of content and composition of specific ?7-phytosterols  

Microsoft Academic Search

A simple and accurate method for the determination of phytosterols by capillary gas chromatography was developed for the\\u000a analysis of the seeds and oil of the pumpkin Cucurbita pepo L., the naked seed variety growing in the southern Styrian parts of Austria. After extraction of the oil and saponification,\\u000a the remaining unsaponifiable material was isolated and purified using silica gel

Alexandra Mandl; Gregor Reich; W. Lindner

1999-01-01

391

Effect of different growth stages of Ziziphora clinopodioides Lam. on its chemical composition  

PubMed Central

Aims: The aim of this study is to monitor the changes in the chemical composition of Ziziphora clinopodioides Lam. throughout nine different growth stages. Materials and Methods: Volatile components such as essential oils were analyzed using the gas chromatography (GC) and GC-mass spectrometry, and the contents of non-volatile components were determined by a visible spectrophotometer. Results: Hydro-distilled essential oil content ranged from a minimum of 1.1% (in the post-flowering stage) to a maximum of 1.8% (in the flowering stage). The essential oils included pulegone, which was the most abundant component (77.48-87.3%), p-menthanone (2.79-12.39%), trans-isopulegone (1.04-2.06%), d-limonene (0.51-3.03%) and eucarvone (1.5-4.48%). The contents of non-volatile components, such as that of total phenolics (TPC), total flavonoids (TFC), total triterpenoids content (TTC) and total free amino acids content (TFAAC) were measured using visible spectrophotometry. In the growing stage, TPC, TFC, TTC and TFAAC were 9.91-12.80 mg/g, 29.84-50.63 mg/g, 0.57-1.41 mg/g and 13.33-28.56 mg/g, respectively. Conclusion: These data can be used as a basis to determine the optimal harvest time of Z. clinopodioide Lam.

Ding, Wenhuan; Yang, Tao; Liu, Feng; Tian, Shuge

2014-01-01

392

New composite thermoelectric materials for energy harvesting applications  

NASA Astrophysics Data System (ADS)

The concept of using nanostructured composite materials to enhance the dimensionless thermoelectric figure of merit ZT relative to that for their counterpart homogeneous alloyed bulk crystalline materials of similar chemical composition is presented in general terms. Specific applications are made to the Si-Ge and Bi2--xSbxTe3 systems for use in high-temperature power generation and cooling applications. The scientific advantages of the nanocomposite approach for the simultaneous increase in the power factor and decrease in the thermal conductivity are emphasized insofar as their simultaneous occurrence is enabled by the independent control of these physical properties through the special properties of their nanostructures. Also emphasized are the practical advantages of using such bulk samples both for thermoelectric property measurements and for providing a straightforward path to scaling up the materials synthesis and integration of such nanostructured materials into practical thermoelectric powergeneration and cooling modules and devices.

Dresselhaus, M. S.; Chen, G.; Ren, Z. F.; Dresselhaus, G.; Henry, A.; Fleurial, J.-P.

2009-04-01

393

Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods  

NASA Astrophysics Data System (ADS)

The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and phthalic anhydride. A simple method to prepare composite surfaces that can change the wettability in response to the temperature change was proposed and evaluated. Composite surfaces prepared by nanoporous alumina templates filled with polymers showed surface morphology and wettability that depend on temperature. This effect is attributed to the significant difference in thermal conductivity and the thermal expansion coefficient between the alumina and the polymers. The reversibility in thermal response depends on the properties of the polymers.

Yoon, Joonsung

394

Abrasive Wear of In Situ AlB2/Al-4Cu Composite Material Produced by Squeeze Casting Method  

NASA Astrophysics Data System (ADS)

The wear behavior of a weight fraction of particles with up to 30 wt.% in situ AlB2 flakes reinforced in Al-4Cu matrix alloy composites and fabricated by a squeeze casting method was investigated in a pin-on-disk abrasion test instrument against different SiC abrasives at room conditions. Wear tests were performed under the load of 10 N against SiC abrasive papers of 80, 100, and 120 mesh grits. The effects of sliding speed, AlB2 flake content, and abrasive grit sizes on the abrasive wear properties of the matrix alloy and composites have been evaluated. The main wear mechanisms were identified using an optical microscope. The results showed that in situ AlB2 flake reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding speed and the abrasive grit size. The wear resistances of the composites were considerably bigger than those of the matrix alloy and increased with increases in in situ AlB2 flake contents.

Ficici, Ferit

2014-04-01

395

Chemical composition of sediments from White Sea, Russian Arctic  

NASA Astrophysics Data System (ADS)

The White Sea, the only Russian inland sea, is located on the north of outlying districts of the European part of Russia, belongs to Arctic Ocean. Area of water of sea occupies about 90 tousend square kilometers. The sea can be divided into some general parts: neck, funnel, basin and 4 Bays: Dvina Bay, Kandalaksha Bay, Mezen Bay and Onega Bay. The purpose of this work was geochemical mapping of the surface sediments of this area. The main tasks were: compilation data base of element composition of the surface sediments, geochemical mapping of each element, research of the anormal concentration of elements on the surface. To detect the content of chemical elements several methods were used: atomic absorption spectrometry (P.P. Shirshov Institute of Oceanology); neutron activation analysis (Vernadsky Institute of Geochemistry and Analytical Chemistry), total and organic carbon analysis, photometric method to detection Si, Al, P (P.P. Shirshov Institute of Oceanology). Bulk composition is one of the fundamental characteristics of sediments and bottom deposites of modern basins. Coarse-grained sediments with portion of pelitic component <50% is spread on the shallow area (Kandalaksha Bay), in areas with high hydrodynamic activity of near-bottom water. Under the conditions of their low activity, fine-grained facies are common(>80%). Character of elements distribution correlates with facial distribution of sediments from White Sea. According to litologic description, bottom surface of Dvina Bay is practically everywhere covered by layer of fine-grained sand. In the border area between Dvina Bay and White Sea basin on terraced subwater slope aleurite politic silts are abundant. They tend to exhange down the slope to clay silts. In Onega Bay fractions of non-deposition are observed. They are characterized by wide spread of thin blanket poorgraded sediments, which are likely to be relic. Relief of Kandalakscha Bay bottom is presented as alternation of abyssal fosses (near 300 m) with silles and elevations (<20 m), and also numerous islands. Thus variety of sediment composition is observed here - from rules and gravels to fine-grained clay silts [1]. The map of distribution of chemical elements was created by using bulk composition data with the help of program ArcView. Mn distribution in sedimentation mass is largely determed by influence of redox diagenesis. Reactive form of Mn dominates over less moving, litogenic form in sedimation mass of White Sea. Litogenic form remains in sediment, reactive form moves into silt near-bottom water, resulting Mn migration both in sediment and near-bottom layer of marine water. Mn oxidizes on the contact with oxygen of marine water and alters into insoluble form MnO2, causing Mn enrichment of surface layer of sediments. Highly movable silt deposit MnO2 and enriched by Mn suspension are moved by underflow and accumulate in bottom depressions and in central part of the sea, which is quite wide from both places of original sedimentation and run off sources [2]. Thus, the interrelation between granulometric composition of sediment and materials concentration can be shown by the example of Mn. Local conditions, leading to accumulation of clastic components, are: 1. Rise of content in sand owning to separation of heavy minerals 2. Rise of content in surface, mainly sandy clay sediments owning to presence of concretions 3. Rise of content in lower bunches roof owning to diagenetic contraction. Authors thank academic Lisitsyn for encourage, Andrey Apletalin for valuable help, and everybody, who helped in field and laboratory research of the White sea sediments. Work was being done under the auspices of Russian foundation of basic research (grants 09-05-10081, 09-05-00658 and 08-05-00860), RSA presidiums program of 17 fundamental researches (project 17.1). References: 1.Kuzmina T., Lein A., Lutchsheva L., Murdmaa I., Novigatsky A., Shevchenko V. Chemical composition of White Sea's sediments // Litology and mineral deposits . 2009. - ? 2. - P 115-132. 2.Nevessky E., Medvedev V. , Kalin

Gamza, Olga; Shevchenko, Vladimir; Novigatsky, Aleksandr

2010-05-01

396

Tough composite materials: Recent developments  

NASA Technical Reports Server (NTRS)

The present volume broadly considers topics in composite fracture toughness and impact behavior characterization, composite system constituent properties and their interrelationships, and matrix systems' synthesis and characterization. Attention is given to the characterization of interlaminar crack growth in composites by means of the double cantilever beam specimen, the characterization of delamination resistance in toughened resin composites, the effect of impact damage and open holes on the compressive strength of tough resin/high strain fiber laminates, the effect of matrix and fiber properties on compression failure mechanisms and impact resistance, the relation of toughened neat resin properties to advanced composite mechanical properties, and constituent and composite properties' relationships in thermosetting matrices. Also treated are the effect of cross-link density on the toughening mechanism of elastomer-modified epoxies, the chemistry of fiber/resin interfaces, novel carbon fibers and their properties, the development of a heterogeneous laminating resin, solvent-resistant thermoplastics, NASA Lewis research in advanced composites, and opportunities for the application of composites in commercial aircraft transport structures.

Vosteen, L. F. (editor); Johnston, N. J. (editor); Teichman, L. A. (editor); Blankenship, C. P. (editor)

1985-01-01

397

Yield and chemical composition of sesame, Sesamum indicum L., as affected by variety and location grown  

Microsoft Academic Search

Summary  Observation nurseries including 24 varieties of sesame were grown at 23 locations in 16 states. Data for yield, oil and protein\\u000a content of the seed, and for iodine value of the oil were obtained from certain locations.\\u000a \\u000a Sesame seems reasonably well adapted on the better soils of most of the southern one-half of the United States. Average seed\\u000a yield for

Murray L. Kinman; S. M. Stark

1954-01-01

398

Changes in chemical composition during the colonisation of citrus pulps by a dairy Penicillium roqueforti strain  

Microsoft Academic Search

Citrus pulps were examined during colonisation with Penicillium roqueforti Pr2. Fungal growth increased the crude protein content from 5.62 to 8.55 (% dry matter) in orange pulp and from 5.77 to 11.89 (% dry matter) in lemon pulp. The ether extract increased respectively from 1.62 to 4.38 (% dry matter) and from 0.97 to 6.78 (% dry matter). The neutral

V Scerra; A Caridi; F Foti; M. C Sinatra; P Caparra

2000-01-01

399

Microstructure and properties of particle reinforced silicon carbide and silicon nitride ceramic matrix composites prepared by chemical vapor infiltration  

Microsoft Academic Search

IntroductionParticle reinforced silicon carbide and silicon nitride ceramic matrix composites were fabricated using designed particle agglomeration and chemical vapor infiltration (CVI) technique. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were employed to observe the microstructures of the preforms and as-infiltrated composites. In the preform, the inter-agglomeration and intra-agglomeration pores had an approximate size of 500–800?m and 5–10?m, respectively.

Yongsheng Liu; Laifei Cheng; Litong Zhang; Yunfeng Hua; Wenbin Yang

2008-01-01

400

CHEMICAL AND STRUCTURAL CHANGES FOR BIMETALLIC MATERIALS OBTAINED BY THE WELDING PROCESS  

Microsoft Academic Search

This paper presents the transformations which take place during the obtaining process of bimetallic materials. As a plating process was used the welding. The added material was a bronze wit