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1

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

2

Mechanical Spectroscopy of Nanostructured Composite Materials  

NASA Astrophysics Data System (ADS)

The thermo-mechanical behavior of different nano-structured composite materials, which were processed within the SAPHIR European Integrated Project, has been characterized by mechanical spectroscopy. The obtained results show clearly that creep resistance of fine grain ceramics such as zirconia can be improved by carbon nano-tube (CNT) reinforcements. On the other hand the elastic modulus and the damping capacity of aluminum matrix composites were increased by SiC nano-particle additions. It has also been observed that CNT additions are responsible for a better thermal stability of polymer such as ABS (Acrylonitrile-Butadiene-Styrene) used in automotive industry.

Mari, Daniele; Schaller, Robert; Mazaheri, Mehdi

2011-07-01

3

Nanostructured Composite Materials for High Temperature Thermoelectric Energy Conversion.  

National Technical Information Service (NTIS)

The goals of this project were to synthesize, characterize and model bulk nanostructured composite materials for thermoelectric energy conversion applications. The objective was to produce materials which demonstrate an increase in intrinsic thermoelectri...

C. J. O'Connor

2012-01-01

4

Composite, Nanostructured, Super-Hydrophobic Material.  

National Technical Information Service (NTIS)

A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite materia...

B. R. D'Urso J. T. Simpson

2005-01-01

5

Hydrogen storage properties of magnesium based nanostructured composite materials  

Microsoft Academic Search

In this work, nanostructured composite materials Mg–Ni, Mg–Ni–La, Mg–Ni–Ce and Mg–LaNi5 have been synthesized using the mechanical alloying process. The new materials produced have been investigated by X-ray diffraction (XRD), transition electron microscope (TEM), scanning electron microscope (SEM) and electron energy dispersion spectrum (EDS) for their phase compositions, crystal structure, grain size, particle morphology and the distribution of catalyst element.

Ming Au

2005-01-01

6

Nanostructured materials  

NASA Astrophysics Data System (ADS)

Interest in the physics of condensed matter at size scales larger than that of atoms and smaller than that of bulk solids has grown rapidly over the past two decades owing to the increasing realization that the properties of these mesoscopic atomic ensembles are different than those of conventional solids. As a consequence, interest in artificially assembling materials from nanometer sized building blocks, whether layers or clusters of atoms, arose from discoveries that by controlling the sizes in the range of 1-100 nm and the assembly of such constituents one could begin to alter and prescribe the properties of the assembled nanostructures. Nature had already learned the value of nanostructuring, since many examples of naturally formed nanostructures can be found in biological systems from sea shells to the human body. Nanostructured materials are modulated over nanometer length scales in from zero to three dimensions. They can be assembled with modulation dimensionalities of zero (atom clusters or filaments), one (multilayers), two (ultrafine-grained overlayers or coatings or buried layers), and three (nanophase materials), or also with intermediate dimensionalities. Thus, nanocomposite materials containing multiple phases can range from the most conventional case in which a nanoscale phase is embedded in a phase of conventional sizes to the case in which all the constituent phases are of nanoscale dimensions. All nanostructured materials share three features: atomic domains (grains, layers or phases) spatially confined to less than 100 nm in at least one dimension, significant atom fractions associated with interfacial environments, and interactions between their constituent domains.

Siegel, R. W.

1994-11-01

7

Morphology of nanostructured materials  

Microsoft Academic Search

Here we shall discuss the importance of grazing incidence X-ray scattering tech- niques in studying morphology of nanostructured materials confined in thin films and multi- layers. In these studies, the shapes, sizes, and structures of nanostructured materials and their distribution in composites are investigated. These studies are important for understanding properties that may deviate considerably from the known bulk properties.

M. K. Sanyal; A. Datta; S. Hazra

2002-01-01

8

Nanostructured Shape Memory Alloys: Adaptive Composite Materials and Components.  

National Technical Information Service (NTIS)

Methods for fabricating adaptive composite materials and components using shape memory alloy (SMA) constituents were investigated using a variety of fabrication techniques, including mechanical rolling methods. Both SMA- polymer and SMA-metal composites w...

A. B. Ellis J. H. Perepezko W. C. Crone

2007-01-01

9

Fabrication of a nanostructured gold-polymer composite material  

NASA Astrophysics Data System (ADS)

A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl4 as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent for both the AP and the water solution of HAuCl4. It was found that oxidative polymerization of AP leads to the formation of poly-AP with a diameter of 50±10nm, while the reduction of AuCl4- results in the formation of gold nanoparticles (˜ 2nm). The gold nanoparticles were uniformly dispersed and highly stabilized throughout the macromolecular chain that formed a uniform metal-polymer composite material. The resultant composite material was characterized by means of different techniques, such as UV-vis, IR and Raman spectroscopy, which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the composite material.

Mallick, K.; Witcomb, M.; Scurrell, M.

2006-07-01

10

Fabrication of a nanostructured gold-polymer composite material  

Microsoft Academic Search

.  A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl4 as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent\\u000a for both the AP and the water solution of HAuCl4. It was found that

K. Mallick; M. Witcomb; M. Scurrell

2006-01-01

11

Modeling of nanostructured polymer-metal composite for thermal interface material applications  

Microsoft Academic Search

Previous studies have discovered a unique type of nanostructured polymer-metal composite for thermal interface material with effective thermal conductivity of 8 W\\/mK. It is a promising result but extensive efforts are still required to further enhance the thermal conductivity. Therefore, this paper will try to help the process with modeling and simulation. Calculations reveal the alignment of the fibers have

Zhili Hu; Björn Carlberg; Cong Yue; Xingming Guo; Johan Liu

2009-01-01

12

Nano-particulate dispersion and reinforcement of nanostructured composite materials  

NASA Astrophysics Data System (ADS)

This research investigated the feasibility of reinforcing polymer composites using 30 nm SiC nanoparticles in a vinyl ester resin. The SiC nanoparticles were examined using transmission electron microscopy and thermogravimetric analysis. Gamma-methacryloxy propyl trimethoxy silane (MPS) was chosen as the coupling agent. Both mixing procedures with (1) the nanoparticles pretreated with a dilute MPS solution in an acid 5% (v/v) water-ethanol mixture and (2) the MPS sonicated as an integral blend with the filled vinyl ester, were attempted. Fourier transform infrared spectroscopy was used to study the silanol condensation between MPS and the SiC nanoparticles. The results show that ultrasonic mixing did not fully disperse the particles. Hence the composite strength did not improve although the modulus increased. The use of MPS improved the dispersion quality and hence the composite strength. The rheological behavior of SiC nanoparticle-filled vinyl ester resin systems was evaluated in terms of the Bingham, power law, Herschel-Bulkley, and Casson models. Even when the particle loading was less then 4% by weight, the viscosity of the nanoparticle suspension was found to increase much more than that of a microparticle suspension. This phenomenon may be the result of association between nanoparticles and polymer molecules, effectively making the nanoparticles larger. The resulting reduction in the mobility of polymer molecules also led to delayed curing. The maximum particle loading corresponding to infinite viscosity was determined as 0.1 volume fraction using the (1 - eta r-1/2) - ? dependence. The experimental optimum fractional weight per cent of the dispersants (wt. % dispersant/wt. % SiC) was found to be around 40% for 30 nm SiC nanoparticles, which is in close agreement with the theoretically calculated monolayer coverage dosage of 67%.

Yong, Virginia Hiu-Hung

2005-12-01

13

Nanostructured materials  

Microsoft Academic Search

Interest in the physics of condensed matter at size scales larger than that of atoms and smaller than that of bulk solids has grown rapidly over the past two decades owing to the increasing realization that the properties of these mesoscopic atomic ensembles are different than those of conventional solids. As a consequence, interest in artificially assembling materials from nanometer

R SIEGEL

1994-01-01

14

Nanoprobes, nanostructured materials and solid state materials  

Microsoft Academic Search

Novel templates have been developed to prepare nanostructured porous materials through nonsurfactant templated pathway. And new applications of these materials, such as drug delivery and molecular imprinting, have been explored. The relationship between template content and pore structure has been investigated. The composition and pore structures were studied in detail using IR, TGA, SEM, TEM, BET and XRD. The obtained

Houping Yin

2005-01-01

15

Advanced Nanostructured Magnetic Materials.  

National Technical Information Service (NTIS)

A combined experimental and theoretical investigation of advanced nanostructured magnetic materials has been carried out. Novel physical systems have been synthesized and studied including: hard/soft nanocomposites, magnetic nanowires, thermally processed...

D. J. Sellmyer R. Skomski Y. Liu

2004-01-01

16

Structure and properties of composite materials with polymer matrix reinforced Nd–Fe–B hard magnetic nanostructured particles  

Microsoft Academic Search

Investigation results of the polymer matrix hard magnetic composite materials with nanostructured particles of the powdered rapid quenched Nd–Fe–B strip are presented at this paper. The Nd–Fe–B powder was mixed with powders of iron, aluminum, CuSn10 casting copper alloy with tin, high-alloy X2CrNiMo17-12-2 steel. Epoxy resin has been used as the matrix (2.5wt.%). The composites were unilaterally and uniaxially pressed

L. A. Dobrza?ski; M. Drak

17

Nanostructured LiMPO4 (M = Fe, Mn, Co, Ni) - carbon composites as cathode materials for Li-ion battery  

NASA Astrophysics Data System (ADS)

Nanostructured materials are considered to be strong candidates for fundamental advances in efficient storage and/or conversion. In nanostructured materials transport kinetics and surface processes play determining roles. This work describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO4, M = Fe, Mn, Co, Ni) coated on nanostructured carbon supports (unordered nanofibers, foams). The composites have been prepared by coating the carbon structures in aqueous (or polyols) solutions containing lithium, metal ions and phosphates. After drying out, the composites have been thermally treated at different temperatures (between 600-780°C) for 5-12 hours under nitrogen. The formation of the olivine structured phase was confirmed by the X-ray diffraction analysis on powders prepared under very similar conditions. The surface investigation revealed the formation of an homogeneous coating of the olivine phase on the carbon structures. The electrochemical performance on the composites showed a dramatic improvement of the discharge specific capacity (measured at a discharge rate of C/25 and room temperature) compared to the prepared powders. The delivered values were 105 mAhg-1 for M = Fe, 100 mAhg-1 for M = Co, 70 mAhg-1 for M = Mn and 30 mAhg-1 for M = Ni respectively.

Dimesso, L.; Spanheimer, C.; Nguyen, T. T. D.; Hausbrand, R.; Jaegermann, W.

2012-10-01

18

Nanostructured Shape Memory Alloys: Composite Materials with Shape Memory Alloy Constituents.  

National Technical Information Service (NTIS)

Composite materials are critical for many engineering applications because of the resultant properties that arise from the combination of dissimilar constituent materials. A particularly exciting class of constituent materials is shape memory alloys (SMAs...

W. C. Crone A. B. Ellis J. H. Perepezko

2004-01-01

19

Palladium Nanoparticles in Poly(o?phenylenediamine): Synthesis of a Nanostructured ‘Metal?Polymer’ Composite Material  

Microsoft Academic Search

We report here on an in?situ synthetic method for the preparation of a metal?polymer composite material. This technique offers a route to achieving an intimate contact between the polymer and the metal nanoparticles. Very small palladium nanoparticles (?3 nm) are uniformly dispersed and highly stabilized throughout the macromolecular chain, forming a uniform metal?polymer composite material. The resultant composite material was characterized

Kaushik Mallick; Mike J. Witcomb; Mike S. Scurrell

2006-01-01

20

Nano-structured phosphorus composite as high-capacity anode materials for lithium batteries.  

PubMed

More than LiP service: The adsorption of red phosphorus into porous carbon provides a composite anode material for lithium-ion batteries. The amorphous nano phosphorus, in the carbon matrix, shows highly reversible lithium storage with high coulombic efficiencies and stable cycling capacity of 750 mAh per gram composite. PMID:22865705

Wang, Li; He, Xiangming; Li, Jianjun; Sun, Wenting; Gao, Jian; Guo, Jianwei; Jiang, Changyin

2012-08-02

21

Nanostructured, electroactive and bioapplicable materials  

NASA Astrophysics Data System (ADS)

Novel nanostructured porous sol-gel materials, nanocomposites, electroactive and bioapplicable materials have been successfully developed for a wide range of perceivable applications. Several versatile nonsurfactant templated sol-gel pathways have been developed to prepare nanostructured porous materials and composites with different morphologies (e.g., monoliths, nanospheres, nanoparticles, and thin films), structures, compositions and properties. The synthetic conditions were systematically studied and optimized. The template effects on pore structure as well as synthetic process, especially template removal steps, have been investigated. The composition and pore structures were thoroughly studied with various spectroscopic and microscopic methods such as IR, TGA, SEM, TEM, BET and XRD. The obtained mesoporous materials usually exhibit high surface area, large pore volume and narrowly distributed pore diameter. The porosity can be fine tuned simply by adjusting the template concentration. The convenient synthesis as well as the distinctive structure and physical-chemical properties render these sol-gel materials great suitability for a wide range of potential applications, such as chemical and biological sensors, catalysts, drug delivery and functional coatings. Biocompatible and electroactive nanocomposites have been prepared through a biological agent (i.e., collagen) templated chemical polymerization of aniline monomers. The resultant polyaniline-collagen complexes exhibit well controlled doping-dedoping electroactivity and much enhanced solubility. Demonstrated with cell growth studies, the polyaniline-collagen complexes show improved biocompatibility in comparison to polyaniline. The new materials can be used to fabricate scaffolds, with which the effect of electrical stimuli on cell growth and differentiation can be evaluated with the hope of ultimately using electrical signal to stimulate controllable cell and tissue regeneration. Aniline derivative substituted quinoline ligand compounds and their complexes have been prepared and investigated as potential electroluminescent materials.

Cheng, Shan

22

Nanostructured Zr and Ti-based composite materials with high strength and enhanced plasticity  

Microsoft Academic Search

Multicomponent composite materials with the compositions Zr66Nb13Cu8Ni6.8Al6.2 and Ti66Nb13Cu8Ni6.8Al6.2 were produced by copper mold casting, and their microstructure and their room-temperature mechanical properties were investigated. The specific alloys were developed to circumvent the limited ductility of Zr- and Ti-based bulk metallic glasses by the formation of a heterogeneous microstructure consisting of a nanocrystalline matrix and ductile dendritic bcc precipitates. Comparing

U. Kuehn; N. Mattern; A. Gebert; M. Kusy; M. Bostroem; U. Siegel; L. Schultz

2005-01-01

23

Material composition - Pinning strength correlation in Nb thin films with focused ion beam-milled washboard nanostructures  

NASA Astrophysics Data System (ADS)

An analysis of the interrelated changes in the material composition and the pinning strength in nanostructured Nb (1 1 0) thin films is presented. The nanopatterns were prepared by focused ion beam milling of an array of uniaxial grooves. They induce a washboard-like pinning potential landscape for vortices in the mixed state. By applying different magnetic fields, the most likely pinning sites along which the flux lines move through the samples have been selected. By this, either the background isotropic pinning of the pristine film or the enhanced isotropic pinning originating from the nanoprocessing has been probed. The enhanced pinning strength in the processed films has been found to correlate with the content of Ga implanted into the films during the nanopatterning.

Dobrovolskiy, Oleksandr V.; Begun, Evgeniya; Huth, Michael; Shklovskij, Valerij A.

2013-11-01

24

Nanostructured Li?S-C composites as cathode material for high-energy lithium/sulfur batteries.  

PubMed

With a theoretical capacity of 1166 mA·h·g(-1), lithium sulfide (Li(2)S) has received much attention as a promising cathode material for high specific energy lithium/sulfur cells. However, the insulating nature of Li(2)S prevents the achievement of high utilization (or high capacity) and good rate capability. Various efforts have been made to ameliorate this problem by improving the contact between Li(2)S and electronic conductors. In the literature, however, a relatively high capacity was only obtained with the Li(2)S content below 50 wt %; therefore, the estimated cell specific energy values are often below 350 W·h·kg(-1), which is insufficient to meet the ever-increasing requirements of newly emerging technologies. Here, we report a cost-effective way of preparing nanostructured Li(2)S-carbon composite cathodes by high-energy dry ball milling of commercially available micrometer-sized Li(2)S powder together with carbon additives. A simple but effective electrochemical activation process was used to dramatically improve the utilization and reversibility of the Li(2)S-C electrodes, which was confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. We further improved the cycling stability of the Li(2)S-C electrodes by adding multiwalled carbon nanotubes to the nanocomposites. With a very high specific capacity of 1144 mA·h·g(-1) (98% of the theoretical value) obtained at a high Li(2)S content (67.5 wt %), the estimated specific energy of our cell was ?610 W·h·kg(-1), which is the highest demonstrated so far for the Li/Li(2)S cells. The cells also maintained good rate capability and improved cycle life. With further improvement in capacity retention, nanostructured Li(2)S-C composite cathodes may offer a significant opportunity for the development of rechargeable cells with a much higher specific energy. PMID:23190038

Cai, Kunpeng; Song, Min-Kyu; Cairns, Elton J; Zhang, Yuegang

2012-12-03

25

An investigation of electromagnetic response of composite polymer materials containing carbon nanostructures within the range of frequencies 10 MHz - 1.1 THz  

NASA Astrophysics Data System (ADS)

Electromagnetic characteristics of composite polymer materials based on multilayer carbon nanotubes (MCNTs) and nano-onion carbon structures in a polymethylmethacrylate (PMMA) matrix are investigated. The purpose is to identify a functional relationship between the size, kind, type of processing, concentration of nanotubes and electromagnetic characteristics of composite materials within the frequency range 10 MHz - 1.1 THz. Use is made of the coaxial waveguide, resonator, and quasi-optical methods. The spectra of reflection and transmission coefficients are reported. The composite materials based on carbon nanostructures are shown to actively interact with electromagnetic radiation in a wide range of frequencies.

Suslyaev, V. I.; Kuznetsov, V. L.; Zhuravlev, V. A.; Mazov, I. N.; Korovin, E. Yu.; Moseenkov, S. I.; Dorozhkin, K. V.

2013-01-01

26

Nanostructure Titania Reinforced Conducting Polymer Composites  

NASA Astrophysics Data System (ADS)

Composites of polyaniline with synthesized nanostructured titania (TiO2) and polyaniline with commercial TiO2 have been in situ synthesized by oxidative chemical polymerization method. Sulfuric acid was used as dopant during the polymerization process. Sol-gel precipitates of nanostructured titania were synthesized by hydrolyzing the mixture of titanium chloride (TiCl3) and colloidal transparent solution of starch. Composite materials were subjected for comparison to spectroscopic and X-ray diffraction analysis. Strong coupling/interaction of titania with the imine nitrogen in polyaniline confirmed by FTIR spectral analysis. XRD shows the composite of synthesized titania with polyaniline have broaden peak as compared to that of commercial titania with polyaniline indicating particle size in the range of nanometer scale which is supported by 40 nm particle size of the synthesized titania from TEM picture. Increase in conductivity with increasing temperature was observed in both the composite materials.

Kondawar, S. B.; Thakare, S. R.; Khati, V.; Bompilwar, S.

27

Nanostructured conductive polymeric materials  

NASA Astrophysics Data System (ADS)

Conductive polymer composites (CPCs) are a suitable alternative to metals in many applications due to their light-weight, corrosion resistance, low cost, ease of processing and design flexibility. CPCs have been formulated using different types of conductive fillers. In this PhD thesis, the focus is on CPCs for electrostatic discharge (ESD) protection and electromagnetic interference (EMI) attenuation. Despite the versatility of conductive fillers, carbon black (CB) has been the dominant filler to make CPCs for ESD protection applications because CB/polymer composites have a cost advantage over all other CPCs. For EMI shielding, stainless steel fibres and metal coated fibers are the preferred fillers, however CPCs made of those fibers are not the dominant EMI shielding materials. Metal coated and polymer plated polymers are the most widely used EMI shielding options. The limited use of CPCs in the EMI shielding market is because the high filler loading required to formulate a composite with an adequate level of shielding remarkably increases the composite price. In order to increase the competitiveness of CPCs, percolation threshold should be minimized as much as possible and composites with high EMI shielding capabilities at low filler loading should be formulated because all conductive fillers are expensive compared to polymers. In this thesis, two different methodologies to reduce percolation threshold in CPCs have been successfully developed and a CPC with exceptional EMI shielding capability has been formulated using copper nanowires as conductive filler. The first percolation threshold reduction technique is based on the selective localization of CB at the interface of immiscible polymer blend. The technique requires adding a copolymer that prefers the blend's interface and for which CB nanoparticles has the highest affinity. The second method is based on producing a CPC powder and then using this powder as a conductive filler to produce composite by dry mixing with pure polymer powder followed by compression molding. The EMI shielding material was developed using copper nanowires. CuNW/Polystyrene composites exhibit EMI shielding effectiveness exceeding that of metal microfillers and carbon nanotube/polymer composites and approaching that of coating techniques have been formulated by solution processing and dry mixing.

Al-Saleh, Mohammed H.

28

Synthesis and characterization of LiFePO 4 \\/3-dimensional carbon nanostructure composites as possible cathode materials for Li-ion batteries  

Microsoft Academic Search

Composites of three-dimensional (3D) carbon nanostructures coated with olivine-structured lithium iron phosphates (LiFePO4) as cathode materials for lithium ion batteries have been prepared through a Pechini-assisted reversed polyol process for\\u000a the first time. The coating has been successfully performed on nonfunctionalized commercially available 3D carbon used as\\u000a catalysts. Thermal analysis revealed no phase transitions till crystallization occurred at 579 °C. Morphological

Lucangelo Dimesso; Christina Spanheimer; Susanne Jacke; Wolfram Jaegermann

2011-01-01

29

Nanostructured Energetic Materials.  

National Technical Information Service (NTIS)

This paper reports synthesis of metastable intermolecular composite (MIC) containing CuO nanorods, nanowires combined with aluminum nanoparticles. These composites were prepared using ultrasonic mixing and self-assembly approach. The combustion wave speed...

K. Gangopadhyay R. V. Shende S. Apperson S. Hasan S. Subramanian

2006-01-01

30

Acetylcholinesterase voltammetric biosensors based on carbon nanostructure-chitosan composite material for organophosphate pesticides  

Microsoft Academic Search

A sensitive biosensor for chloropyrifos (CPF), an organophosphorus pesticide, was developed by immobilizing acetylcholinesterase (AChE) through covalent bonding to an oxidized exfoliated graphite nanoplatelet (xGnPs)–chitosan cross-linked composite. Because of the increased surface area and the conductive properties of the nanomaterial, AChE developed a high affinity for acetylthiocholine (ATCI) and formed thiocholine with a fast response. The response of the sensor

Alina C Ion; Ion Ion; Alina Culetu; Dragos Gherase; Carmen A. Moldovan; Rodica Iosub; Adrian Dinescu

2010-01-01

31

Synthesis, characterization, and properties of low-dimensional nanostructured materials  

Microsoft Academic Search

Nanometer scale structures represent an exciting and rapidly expanding area of research. Studies on new physical\\/chemical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology, crystal and microstructure, and composition. Thus, controlled synthesis of nanomaterials is the essential aspect of nanotechnology. This thesis describes the development of simple and

Xianluo Hu

2007-01-01

32

Nanostructured materials for water desalination  

NASA Astrophysics Data System (ADS)

Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.

Humplik, T.; Lee, J.; O'Hern, S. C.; Fellman, B. A.; Baig, M. A.; Hassan, S. F.; Atieh, M. A.; Rahman, F.; Laoui, T.; Karnik, R.; Wang, E. N.

2011-07-01

33

Nanoprobes, nanostructured materials and solid state materials  

NASA Astrophysics Data System (ADS)

Novel templates have been developed to prepare nanostructured porous materials through nonsurfactant templated pathway. And new applications of these materials, such as drug delivery and molecular imprinting, have been explored. The relationship between template content and pore structure has been investigated. The composition and pore structures were studied in detail using IR, TGA, SEM, TEM, BET and XRD. The obtained mesoporous materials have tunable diameters in the range of 2--12 nm. Due to the many advantages of this nonsurfactant templated pathway, such as environment friendly and biocompatibility, controlled release of antibiotics in the nanoporous materials were studied. The in vitro release properties were found to depend on the silica structures which were well tuned by varying the template content. A controlled long-term release pattern of vancomycin was achieved when the template content was 30 wt% or lower. Nanoscale electrochemical probes with dimensions as small as 50 nm in diameter and 1--2 mum in length were fabricated using electron beam deposition on the apex of conventional micron size electrodes. The electroactive region was limited to the extreme tip of the nanoprobe by coating with an insulating polymer and re-opening of the coating at the extreme tip. The novel nanoelectrodes thus prepared were employed to probe neurons in mouse brain slice and the results suggest that the nanoprobes were capable of recording neuronal excitatory postsynaptic potential signals. Interesting solid state chemistry was found in oxygenated iron phthalocyanine. Their Mossbauer spectra show the formation of four oxygenated species apart from the unoxygenated parent compound. The oxygen-bridged compounds formed in the solid matrix bear no resemblance to the one formed by solution chemistry. Tentative assignment of species has been made with the help of Mossbauer and IR spectroscopy. An effort to modify aniline trimer for potential nanoelectronics applications and to investigate the formation of "nano-pancake" shape aggregation was also reported.

Yin, Houping

34

Preparation and characterization of nanostructured MWCNT-TiO{sub 2} composite materials for photocatalytic water treatment applications  

SciTech Connect

Nanoscale composite materials containing multi-walled carbon nanotubes (MWCNT) and titania were prepared by using a modified sol-gel method. The composites were comprehensively characterized by thermogravimetric analysis, nitrogen adsorption-desorption isotherm, powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. The analysis revealed the presence of titania crystallites of about 7.5 nm aggregated together with MWCNT in particles of 15-20 nm of diameter. The photoactivity of the prepared materials, under UV or visible irradiation, was tested using the conversion of phenol from model aqueous solutions as probe reaction. A synergy effect on the photocatalytic activities observed for the composite catalysts was discussed in terms of a strong interphase interaction between carbon and TiO{sub 2} phases by comparing the different roles of MWCNT in the composite materials.

Wang Wendong [Laboratorio de Catalise e Materiais, Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n 4200-465 Porto (Portugal); Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Serp, Philippe; Kalck, Philippe [Laboratoire de Chimie de Coordination UPR 8241 CNRS, Ecole Nationale Superieure d'Ingenieurs en Arts Chimiques Et Technologiques, 118 Route de Narbonne Toulouse Cedex 31077 (France); Silva, Claudia Gomes [Laboratorio de Catalise e Materiais, Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n 4200-465 Porto (Portugal); Faria, Joaquim Luis [Laboratorio de Catalise e Materiais, Departamento de Engenharia Quimica, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n 4200-465 Porto (Portugal)], E-mail: jlfaria@fe.up.pt

2008-04-01

35

Electrical breakdown characteristic of nanostructured W?Cu contacts materials  

Microsoft Academic Search

Nanostructured (NS) W?Cu composite powder was prepared by mechanical alloying (MA), and nanostructured bulk of W?Cu contact\\u000a material was fabricated by hot press sintering in an electrical vacuum furnace. The microstructure, electric conductivity,\\u000a hardness and break down voltage of NS W?Cu alloys were measured and compared to those of conventional W?Cu alloys prepared\\u000a by powder metallurgy. The experimental results show

Wang Junbo; Chen Wen'ge; Ding Binjun

2006-01-01

36

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

37

Composite material  

SciTech Connect

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

38

Preparation and characterization of nanostructured MWCNT-TiO 2 composite materials for photocatalytic water treatment applications  

Microsoft Academic Search

Nanoscale composite materials containing multi-walled carbon nanotubes (MWCNT) and titania were prepared by using a modified sol–gel method. The composites were comprehensively characterized by thermogravimetric analysis, nitrogen adsorption–desorption isotherm, powder X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis absorption spectroscopy. The analysis revealed the presence of titania crystallites of about

Wendong Wang; Philippe Serp; Philippe Kalck; Cláudia Gomes Silva; Joaquim Luís Faria

2008-01-01

39

Nanostructures  

NSDL National Science Digital Library

This page from Foothill-De Anza Community College provides a list of nanostructures. For each structure, its properties, structure, process, and application are detailed. Additionally, most pages include a picture, video, and references. The structures include aerogels, biomolecules, carbon, composite materials, ferrofluids, and many others.

2012-11-06

40

Copper-micrometer-sized diamond nanostructured composites  

NASA Astrophysics Data System (ADS)

Reinforcement of a copper matrix with diamond enables tailoring the properties demanded for thermal management applications at high temperature, such as the ones required for heat sink materials in low activated nuclear fusion reactors. For an optimum compromise between thermal conductivity and mechanical properties, a novel approach based on multiscale diamond dispersions is proposed: a Cu-nanodiamond composite produced by milling is used as a nanostructured matrix for further dispersion of micrometer-sized diamond (?Diamond). A series of Cu-nanodiamond mixtures have been milled to establish a suitable nanodiamond fraction. A refined matrix with homogeneously dispersed nanoparticles was obtained with 4 at.% ?Diamond for posterior mixture with microdiamond and subsequent consolidation. Preliminary consolidation by hot extrusion of a mixture of pure copper and ?Diamond has been carried out to define optimal processing parameters. The materials produced were characterized by x-ray diffraction, scanning and transmission electron microscopy and microhardness measurements.

Nunes, D.; Livramento, V.; Shohoji, N.; Fernandes, H.; Silva, C.; Correia, J. B.; Carvalho, P. A.

2011-12-01

41

Inflammatory Response to Implanted Nanostructured Materials  

Microsoft Academic Search

Nanostructured materials are implanted for dynamic application in therapies such as drug delivery, tissue engineering, biosensing,\\u000a and imaging. The interaction between nanostructured materials and the tissues of the body can be used to alter cellular attachment\\u000a and motility, detect analytes in vivo, and simulate tissue organization. These interactions may also lead to a variety of\\u000a adverse immune responses, such as

Kristy M. Ainslie; Rahul G. Thakar; Daniel A. Bernards; Tejal A. Desai

42

Nanostructured multifunctional electromagnetic materials from the guest-host inorganic-organic hybrid ternary system of a polyaniline-clay-polyhydroxy iron composite: preparation and properties.  

PubMed

A nanostructured electromagnetic polyaniline-polyhydroxy iron-clay composite (PPIC) was prepared by oxidative radical emulsion polymerization of aniline in the presence of polyhydroxy iron cation (PIC) intercalated clays. Morphological observation through SEM, TEM, and AFM suggested the formation of self-assembled nanospheres of PIC with self-assembled PANI engulfed over PIC, and the presence of iron in PPIC was confirmed by the EDS analysis. XRD studies revealed that PPIC are comprised of exfoliated clay layers with PIC in the distorted spinel structure. Magnetic property measurements showed that saturation magnetization increased from 7.3 x 10(-3) to 2.5 emu/g upon varying the amount of PHIC content from 0 to 10%. Electrical conductivity measurements with the same composition were observed to be in the range of 3.0 x 10(-2) to 1.1 S/cm. Thermal stability studies using TGA in combination with DTG suggested that PPICs were thermally stable up to 350 degrees C. The interaction among clay layers, PIC, and PANI chains in PPIC were manifested from the studies made by FTIR and DSC analysis. The prospects for the direct application of this material are developing low-cost chemical sensors and also processable electromagnetic interference shielding materials for high technological applications. PMID:20136090

Reena, Viswan L; Pavithran, Chorappan; Verma, Vivek; Sudha, Janardhanan D

2010-03-01

43

Thermal transport in nanostructured materials  

NASA Astrophysics Data System (ADS)

This dissertation presents the experimental study and theoretical analysis of thermal transport in crystalline nanostructured materials. Traditionally, alloys are known to have the lowest thermal conductivity of crystalline solids, which is often known as the "alloy limit." In this dissertation it is shown that by using epitaxially embedded nanoparticles in alloys, it is possible to reduce the thermal conductivity below the alloy limit over a wide temperature range. The materials studied in this dissertation include In0.53Ga 0.47As containing epitaxially embedded ErAs nanoparticles that are few nanometers in size, ErAs:InGaAs/InGaAlAs superlattices, and TiN/GaN multilayers. Thermal conductivity measurements have been done on these samples from 40 to 800 K using the 3o method. The experiments clearly show that by embedding ErAs nanoparticles, the thermal conductivity can be reduced below that of In0.53Ga0.47As alloy over a wide temperature range. The alloy limit was beaten regardless of whether the ErAs nanoparticles were incorporated into the In0.53Ga0.47As either randomly, or in an ordered manner resulting in ErAs/In0.53Ga0.47As superlattices. Both the size and the spacing between ErAs nanoparticles are critical for thermal conductivity reduction. The theoretical analysis developed here is focused on explaining why and how randomly distributed polydispersed ErAs nanoparticles reduce the thermal transport in In0.53Ga0.47As. Predictions of thermal conductivity are based on a Callaway model that accounts for phonon scattering by nanoparticles. This is achieved by generalizing the model for predicting phonon mean free paths due to alloy scattering and incorporating a statistical size distribution of nanoparticles. The theoretical analysis suggests that while point defects in alloys scatter short wavelength phonons most efficiently, the nanoparticles provide an additional efficient scattering mechanism for the mid to long wavelength phonons. In randomly distributed ErAs in In0.53Ga0.47As, a broad range of the phonon spectrum is thereby blocked due to the size distribution of the ErAs nanoparticles. It is concluded that by varying size distribution and concentration of nanoparticles, one can tune thermal transport of material. The thermal conductivity of ErAs:InGaAs/InGaAlAs superlattices with different carrier concentrations was measured to study the effect of electronic contribution to thermal conductivity. Preliminary results of TiN/GaN multilayer suggest that combinations of coherent and incoherent phonon transport may exist in this structure.

Kim, Woo Chul

44

Nanostructured Si–C composite anodes for lithium-ion batteries  

Microsoft Academic Search

Nanostructured Si–C composite materials were prepared by dispersing nanocrystalline Si in carbon aerogel and subsequent carbonization. Through this process, nanosize Si was homogeneously distributed in a carbon matrix. The Si–C composites exhibit a reversible lithium storage capacity of 1450 mAh\\/g when used as anodes in lithium-ion cells. The nanostructured Si–C composite electrodes demonstrated good cyclability. The Si–C composites could provide

G. X Wang; J. H Ahn; Jane Yao; Steve Bewlay; H. K Liu

2004-01-01

45

Supercritical carbon dioxide approach to nanostructured materials  

NASA Astrophysics Data System (ADS)

Supercritical fluid technology is a novel and emerging strategy to generate nanomaterials in small areas, within high-aspect-ratio structures, on complicated surfaces and poor wettable substrates with high uniformity, high homogeneity and minimum environmental problems. In this dissertation, several strategies were developed for thin film deposition and nanocomposite fabrication. In developing supercritical fluid immersion deposition (SFID), supercritical or near supercritical CO2 was used as a new solvent for immersion deposition, a galvanic displacement process traditionally carried out in aqueous HF solutions containing metal ions, to selectively develop Pd, Cu, Ag and other metal films on featured and non-featured Si substrates. Annealing of thin palladium films deposited by SFID can lead to the formation of palladium silicide in small features on Si substrates. Deposition of metal films on germanium substrates was also achieved through SFID. Through hydrogen reduction of metal-beta-diketone complexes in supercritical CO2, a rapid, convenient and environmentally benign approach has been developed to synthesize a variety of nanostructured materials: (1) Metal (Pd, Ni and Cu) nanowires and nanorods sheathed within multi-walled carbon nanotube (MWCNT) templates; (2) nanoparticles of palladium, rhodium and ruthenium decorated onto functionalized MWCNTs. These highly dispersed nanoparticles are expected to exhibit promising catalytic properties for a variety of chemical or electrochemical reactions; (3) Cu, Pd or Cu-Pd alloy nanocrystals deposited onto SiO2 nanowires (NWs), SiO2 microfibers, or SiC NWs. Different types of nanostructures were achieved, including nanocrystal-NW, spherical aggregation-NW, shell-NW composites and "mesoporous" metals supported by the framework of NWs.

Ye, Xiang-Rong

46

Nanostructured materials for solar energy conversion  

Microsoft Academic Search

This review article deals with the motivation for using nanostructured materials in the field of solar energy conversion. We discuss briefly some recent fundamental observations on supported nanoclusters and optical properties of embedded metallic nanoclusters in a dielectric matrix. An overview on current research and existing applications in this field is given. Nanocomposite thin films developed for the application as

P. Oelhafen; A. Schüler

2005-01-01

47

Engineering soft nanostructured functional materials via orthogonal chemistry  

Microsoft Academic Search

Nanostructured amphiphilic block copolymers, graft copolymers, polymeric thermally responsive molecular brushes and polymer\\u000a stars are only few examples of macromolecular architectures accessible either via controlled\\/living radical polymerization\\u000a (CLRP) techniques or the combination of CLRP mechanisms with efficient post-polymerization routes including click chemistry.\\u000a Precise control over the composition, molecular weight and functionalities is a prerequisite for soft polymeric materials\\u000a to self-organize

Daniel Gromadzki

2010-01-01

48

Engineering hybrid nanostructures of active materials: Applications as electrode materials in lithium ion rechargeable batteries  

Microsoft Academic Search

Aiming to significantly improve the electrochemical properties of electroactive materials for lithium ion batteries, three novel hybrid nanostructures were developed in this thesis. These include nanostructure A: V2O 5 coated on polymer electrolyte-grafted carbon black, nanostructure B: electrode materials incorporated into an electronically conductive carbon web, and nanostructure C: electrode materials dispersed in a conductive porous carbon matrix. Nanocomposites possessing

Huan Huang

2003-01-01

49

Nanostructure material for supercapacitor application  

SciTech Connect

Transition metal nitrides and carbonitride materials were fabricated via sol-gel technology. The transition metal amides were synthesized by two methods: chemical route and electrolysis. The transition metal amides were then further polymerized, sintering to high temperature in an inert or reduced atmosphere. Transition metal nitrides and carbonitrides powders with surface area up to 160 m{sup 2}/g were obtained. The resultant electrode material showed high specific capacitance as crystalline ruthenium oxide.

Huang, Y.; Chu, C.T.; Wei, Q.; Zheng, H.

2000-07-01

50

Molecular simulations of deformation, failure and fracture of nanostructured materials  

NASA Astrophysics Data System (ADS)

The performance of materials depends on their properties, which in turn depend on the atomic structure, composition, microstructure, defects and interfaces. With our continuing thrust to build light-weight structures without compromising any or their material properties, recent paradigm of synthesizing and processing advanced materials emphasizes the so called bottom-up approach, an approach that involves tailored assembly of atoms and molecules, from the atomic or molecular scale to the macroscopic scale. Nanostructured materials, often characterized by their length scale being close to the atomic scale, have attracted a great interest by their potential to demonstrate phenomenal properties compared to conventional materials. Experimental results on nano materials, however, showed a diverse pool of results. Processing difficulties, unavailability of characterization tools and techniques, and mostly our immature knowledge in this field are often considered as the reasons why there is such a disparity between prediction and reality. The main focus of this thesis is to provide quantitative evidence on the stability, deformation and fracture mechanism of materials at the nanoscale. Using a computational method called Molecular Dynamics (MD), various nanoscale phenomena related to the stability of freestanding thin films, the fracture mechanism of crystalline nanostructures, deformation of polymer nanocomposites, and the strength of thin adhesive joints have been addressed in this work. A new approach has been developed to illustrate the underlying mechanism for the morphology-induced stability of freestanding films. The study on fracture of nanocrystalline materials focuses on the thermodynamic origins of defect formation in materials, their evolution and response to mechanical forces. Atomistic evidences have been provided to exemplify that polymer based multi-phased nanostructures are highly affected by the local structural change in polymers at their interfaces which eventually bring size dependent material behavior at the nanoscale. For instance, the atomistic simulations on nanocomposites and thin adhesives demonstrate why materials become size dependent at the nano scale.

Adnan, Ashfaq

51

Nanostructured carbonaceous materials from molecular precursors.  

PubMed

Nanostructured carbonaceous materials, that is, carbon materials with a feature size on the nanometer scale and, in some cases, functionalized surfaces, already play an important role in a wide range of emerging fields, such as the search for novel energy sources, efficient energy storage, sustainable chemical technology, as well as organic electronic materials. Furthermore, such materials might offer solutions to the challenges associated with the on-going depletion of nonrenewable energy resources or climate change, and they may promote further breakthroughs in the field of microelectronics. However, novel methods for their preparation will be required that afford functional carbon materials with controlled surface chemistry, mesoscopic morphology, and microstructure. A highly promising approach for the synthesis of such materials is based on the use of well-defined molecular precursors. PMID:20661971

Hoheisel, Tobias N; Schrettl, Stephen; Szilluweit, Ruth; Frauenrath, Holger

2010-09-01

52

Metal-polymer composites comprising nanostructures and applications thereof  

SciTech Connect

Metal-polymer composites, and methods of making and use thereof, said composites comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.

Wang, Hsing-Lin (Los Alamos, NM); Jeon, Sea Ho (Dracut, MA); Mack, Nathan H. (Los Alamos, NM)

2012-04-03

53

Metal-polymer composites comprising nanostructures and applications thereof  

SciTech Connect

Metal-polymer composites, and methods of making and use thereof, said composites comprising a thermally-cured dense polyaniline substrate; an acid dopant; and, metal nanostructure deposits wherein the deposits have a morphology dependent upon the acid dopant.

Wang, Hsing-Lin (Los Alamos, NM); Jeon, Sea Ho (Dracut, MA); Mack, Nathan H. (Los Alamos, NM)

2011-08-02

54

Arc Plasma Synthesis of Nanostructured Materials: Techniques and Innovations  

SciTech Connect

Arc plasma aided synthesis of nanostructured materials has the potential of producing complex nano phase structures in bulk quantities. Successful implementation of this potential capability to industrial scale nano generation needs establishment of a plasma parameter control regime in terms of plasma gas, flow pattern, pressure, local temperature and the plasma fields to obtain the desired nano phase structures. However, there is a need to design innovative in situ experiments for generation of an extensive database and subsequently to correlate plasma parameters to the size, shape and phase of the generated nanostructures. The present paper reviews the various approaches utilized in the field of arc plasma nanosynthesis in general and in the authors' laboratories in particular. Simple plasma diagnostics and monitoring schemes have been used in conjunction with nano materials characterization tools to explore the possibility of controlling the size, shape, yield and phase composition of the arc generated nanostructures through plasma control. Case studies related to synthesis of AlN, Al2O3, TiO2, ZrO2, ZnO), magnetic (e.g. {gamma}-Fe2O3, Fe3O4) and single elemental materials (e.g. carbon nanotubes) are presented.

Das, A. K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Bhoraskar, S. V. [Department of Physics, University of Pune, Pune 411007 (India); Kakati, M.; Karmakar, Soumen [Centre of Plasma Physics, Tepesia, Sonapur 782 402 (India)

2008-10-23

55

Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques.  

National Technical Information Service (NTIS)

The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles ...

T. C. Clancy T. S. Gates

2005-01-01

56

Dissociation of formaldehyde in nanostructured carbon materials  

NASA Astrophysics Data System (ADS)

Chemical reactions are frequently carried out in nano-structured media, such as micellar or colloidal solutions, nano-porous media, hydrogels or organogels, or in systems involving nano-particles. Nanostructured environments have been shown to enhance reaction rates through a variety of catalytic effects, such as high surface area, interactions with the nano-structure or confinement. However, at present there is little understanding of the role of the nano-structured material in such reactions and the mechanisms involved are subject of ongoing scientific debate. In this work, we have used state-of-the-art electronic structure techniques to study the prototypical example of the reaction of formaldehyde dissociation (H_2CO arrow H2 + CO) within various configurations of a graphitic pore. Using the Nudged Elastic Band (NEB) method for transition states analysis, we have found that the activation en ergy of the dissociation can be influenced by the presence of a graphitic pore. In particular, while a graphene surface reduces the activation barrier for the reaction, this catalytic effect is enhanced by the presence of two planar sheets, which mimic the geometry of a nano-pore. This can likewise induce a decrease of the activation energy, thus making the reaction more energetically favor able. The reaction activation energy has a dependence on the width of the pore (distance between sheets). A decrease is seen to a point of decreasing width, then a change in the favorable reaction path occurs. It is also found the presence of a vacancy can drastically change the reaction path. These conclusions will be discussed in terms of the charge transfer mechanism seen in the catalytic process.

George, Aaron; Santiso, Erik; Buongiorno Nardelli, Marco; Gubbins, K. E.

2004-11-01

57

Nanostructured electrode materials for lithium ion batteries  

Microsoft Academic Search

This thesis discusses two aspects of nanograined electrode materials for lithium batteries. Firstly the size and surface effects in nanosized lithium intercalation materials is explored. Nanosized intercalation materials are modelled using Monte Carlo simulations of finite sized lattice gases. This study shows that finite size intercalation materials can have marked differences in their voltage-composition behaviour compared to their bulk counterparts.

Mark Nikolas Obrovac

2001-01-01

58

Nanostructured energetic materials derived from sol-gel chemistry  

SciTech Connect

Initiation and detonation properties are dramatically affected by an energetic material's microstructural properties. Sol-gel chemistry allows intimacy of mixing to be controlled and dramatically improved over existing methodologies. One material goal is to create very high power energetic materials which also have high energy densities. Using sol-gel chemistry we have made a nanostructured composite energetic material. Here a solid skeleton of fuel, based on resorcinol-formaldehyde, has nanocrystalline ammonium perchlorate, the oxidizer, trapped within its pores. At optimum stoichiometry it has approximately the energy density of HMX. Transmission electron microscopy indicated no ammonium perchlorate crystallites larger than 20 nm while near-edge soft x-ray absorption microscopy showed that nitrogen was uniformly distributed, at least on the scale of less than 80 nm. Small-angle neutron scattering studies were conducted on the material. Those results were consistent with historical ones for this class of nanostructured materials. The average skeletal primary particle size was on the order of 2.7 nm, while the nanocomposite showed the growth of small 1 nm size crystals of ammonium perchlorate with some clustering to form particles greater than 10 nm.

Simpson, R L; Tillotson, T M; Hrubesh, L W; Gash, A E

2000-03-15

59

Nanostructured materials for applications in heterogeneous catalysis.  

PubMed

In this review, a brief survey is offered on the main nanotechnology synthetic approaches available to heterogeneous catalysis, and a few examples are provided of their usefulness for such applications. We start by discussing the use of colloidal, reverse micelle, and dendrimer chemistry in the production of active metal and metal oxide nanoparticles with well-defined sizes, shapes, and compositions, as a way to control the surface atomic ensembles available for selective catalysis. Next we introduce the use of sol-gel and atomic layer deposition chemistry for the production and modification of high-surface-area supports and active phases. Reference is then made to the more complex active sites that can be created or carved on such supports by using organic structure-directing agents. We follow with an examination of the ability to achieve multiple functionality in catalysis via the design of dumbbells, core@shell, and other complex nanostructures. Finally, we consider the mixed molecular-nanostructure approach that can be used to develop more demanding catalytic sites, by derivatizing the surface of solids or tethering or immobilizing homogeneous catalysts or other chemical functionalities. We conclude with a personal and critical perspective on the importance of fully exploiting the synergies between nanotechnology and surface science to optimize the search for new catalysts and catalytic processes. PMID:23072831

Zaera, Francisco

2013-04-01

60

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.

61

Final Technical Progress Report NANOSTRUCTURED MAGNETIC MATERIALS  

SciTech Connect

This report describes progress made during the final phase of our DOE-funded program on Nanostructured Magnetic Materials. This period was quite productive, resulting in the submission of three papers and presentation of three talks at international conferences and three seminars at research institutions. Our DOE-funded research efforts were directed toward studies of magnetism at surfaces and interfaces in high-quality, well-characterized materials prepared by Molecular Beam Epitaxy (MBE) and sputtering. We have an exceptionally well-equipped laboratory for these studies, with: Thin film preparation equipment; Characterization equipment; Equipment to study magnetic properties of surfaces and ultra-thin magnetic films and interfaces in multi-layers and superlattices.

Charles M. Falco

2012-09-13

62

Supramolecular materials: Self-organized nanostructures  

SciTech Connect

Miniaturized triblock copolymers have been found to self-assemble into nanostructures that are highly regular in size and shape. Mushroom-shaped supramolecular structures of about 200 kilodaltons form by crystallization of the chemically identical blocks and self-organize into films containing 100 or more layers stacked in a polar arrangement. The polar supramolecular material exhibits spontaneous second-harmonic generation from infrared to green photons and has an adhesive tape-like character with nonadhesive-hydrophobic and hydrophilic-sticky opposite surfaces. The films also have reasonable shear strength and adhere tenaciously to glass surfaces on one side only. The regular and finite size of the supramolecular units is believed to be mediated by repulsive forces among some of the segments in the triblock molecules. A large diversity of multifunctional materials could be formed from regular supramolecular units weighing hundreds of kilodaltons. 21 refs., 10 figs.

Stupp, S.I.; LeBonheur, V.; Walker, K. [Univ. of Illinois, Urbana-Champaign, IL (United States)] [and others

1997-04-18

63

Nanostructures in Physical Materials Chemistry: An Exploratory Laboratory  

Microsoft Academic Search

The blend of nanotechnology and material science is often beyond the scope of undergraduate laboratories. Through undergraduate research, graphite-intercalated compounds have been incorporated in the production of carbon-based nanostructures. Based on this work a series of exploratory exercises were designed for the undergraduate physical chemistry laboratory emphasizing nanostructure material science. This rapidly expanding area of science and technology can be

Thomas J. Manning; Amy Feldman; Michael Anderson; Leri Atwater; Brent Lesile; Derek Lovingood; Anna Lee McRae; Rob Stapleton; Kim Riddle; Jun Lui; Thomas Vickers; Naresh Dalal; Lambertus J. van de Burgt

2001-01-01

64

Composite Structural Materials.  

National Technical Information Service (NTIS)

The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved perf...

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

1982-01-01

65

Core-Shell and Segmented Polymer-Metal Composite Nanostructures  

PubMed Central

Composite nanostructures (~200 nm wide and several ?m long) of metal and polyaniline (PANI) in two new variations of core-shell (PANI-Au) and segmented (Au-PANI and Ni-Au-PANI) architectures were fabricated electrochemically within anodized aluminum oxide (AAO) membranes. Control over the structure of these composites (including the length of the gold shells in the core-shell structures) was accomplished by adjusting the time and rate of electrodeposition, and the pH of the solution from which the materials were grown. Exposure of the core-shell structures to oxygen plasma removed the PANI and yielded aligned gold nanotubes. In the segmented structures, a self-assembled monolayer (SAM) of thioaniline nucleated the growth of PANI on top of metal nanorods, and acted as an adhesion layer between the metal and PANI components.

Lahav, Michal; Weiss, Emily; Xu, Qiaobing; Whitesides, George M.

2008-01-01

66

DBR PSi\\/PMMA composite materials for smart patch application  

Microsoft Academic Search

New nanostructured composite materials based on porous silicon (PSi) have been developed as a smart patch type for drug delivery applications. Distributed Bragg reflector (DBR) PSi films and caffeine-impregnated polymethyl methacrylate (PMMA) are used to produce flexible and stable composite materials in which the porous silicon matrix is covered with polymer. DBR PSi films and the composite films display a

Youngdae Koh; Seunghyun Jang; Jihoon Kim; Sungsoo Kim; Young Chun Ko; Sungdong Cho; Honglae Sohn

2008-01-01

67

Nanostructured Materials for Environmental Remediation of Organic Contaminants in Water  

Microsoft Academic Search

Nanostructured materials have opened new avenues in various scientific fields and are providing novel opportunities in environmental science. The increased surface area-to-volume ratio of nanoparticles, quantum size effects, and the ability to tune surface properties through molecular modification make nanostructures ideal for many environmental remediation applications. We describe herein the fabrication of metal and semiconductor nanoparticles for environmental remediation applications,

Sherine O. Obare; Gerald J. Meyer

2004-01-01

68

Mechanics of composite materials  

SciTech Connect

This book contains the following papers: crack growth resistance of TiB{sub 2} particulate/SiC matrix composite; constitutive relations of flexible composites under elastic deformation; determination of two kinds of composite plasticity: inclusions plastic vs. matrix plastic; 3-D analysis of transient interlaminar thermal stress of laminated composites; effect of seawater on the fracture toughness of pultruded rods; evaluation of new failure criterion for fibrous composite materials; and bridged cracks in fiber-reinforced composites.

Dvorak, G.J. (Inst. Center for Composite Materials and Structures, Rensselaer Polytechnic Inst. (US)); Laws, N. (Dept. of Mechanical Engineering, Univ. of Pittsburgh, PA (US))

1988-01-01

69

Wear corrosion properties of nano-structured SiC–nickel composite coatings obtained by electroplating  

Microsoft Academic Search

Advances in materials performance often require the development of composite systems. Coated materials could be one form to use. The abrasion and corrosion resistance of components can be greatly increased by protective coatings and this is a growing industry of considerable economic importance. These paper aims with a comparative wear corrosion study of pure nickel and Ni–SiC nano-structured composite coating.

Lidia Benea; Pier Luigi Bonora; Alberto Borello; Stefano Martelli

2001-01-01

70

Fundamental Understanding and Theoretical Design of Novel Nanostructured Semiconductor Materials.  

National Technical Information Service (NTIS)

This research was for the fundamental understanding and theoretical design of novel nanostructured semiconductor materials with a potential impact in the areas of thermoelectrics, solar energy, and the role of impurities and embedded nanoparticles. The mo...

A. J. Freeman H. Peng J. Medvedeva J. Song M. S. Park

2012-01-01

71

TOPICAL REVIEW: Lyotropic liquid crystal directed synthesis of nanostructured materials  

NASA Astrophysics Data System (ADS)

This review introduces and summarizes lyotropic liquid crystal (LLC) directed syntheses of nanostructured materials consisting of porous nanostructures and zero-dimensional (0-D), one-dimensional (1-D) and two-dimensional (2-D) nanostructures. After a brief introduction to the liquid crystals, the LLCs used to prepare mesoporous materials are discussed; in particular, recent advances in controlling mesostructures are summarized. The LLC templates directing the syntheses of nanoparticles, nanorods, nanowires and nanoplates are also presented. Finally, future development in this field is discussed.

Wang, Cuiqing; Chen, Dairong; Jiao, Xiuling

2009-04-01

72

Polyaniline nanostructures expedient as working electrode materials in supercapacitors  

NASA Astrophysics Data System (ADS)

Granular type polyaniline (PANi), PANi nanofibers (NFs), and PANi nanotubes (NTs) expedient as working electrode materials for supercapacitors are synthesized. The synthesis procedure used in this work facilitates not only the synthesis of solid powders of the PANi nanostructures, but also thin films constituted by the same PANi nanostructures in the same experiment. PANi NFs are found to exhibit faster electrode kinetics and better capacitance when compared to PANi NTs and granular PANi. Specific capacitance and energy storage per unit mass of PANi NFs are 239.47 Fg-1 (at 0.5 Ag-1) and 43.2 Wh kg-1, respectively. Electrical conductivity of PANi NFs is also better when compared to the other two nanostructures. Properties of the three PANi nanostructures are explicated in correlation with crystallinity, intrinsic oxidation state, doping degree, BET surface area, and ordered mesoporosity pertaining to the nanostructures.

Gedela, Venkata Ramana; Srikanth, Vadali Venkata Satya Siva

2013-08-01

73

Nanostructured hybrid materials from aqueous polymer dispersions  

Microsoft Academic Search

Organic–inorganic (O–I) hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of

Valter Castelvetro; Cinzia De Vita

2004-01-01

74

Hollow Nanostructured Anode Materials for Li-Ion Batteries  

PubMed Central

Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li+ transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability.

2010-01-01

75

Hollow Nanostructured Anode Materials for Li-Ion Batteries  

NASA Astrophysics Data System (ADS)

Hollow nanostructured anode materials lie at the heart of research relating to Li-ion batteries, which require high capacity, high rate capability, and high safety. The higher capacity and higher rate capability for hollow nanostructured anode materials than that for the bulk counterparts can be attributed to their higher surface area, shorter path length for Li+ transport, and more freedom for volume change, which can reduce the overpotential and allow better reaction kinetics at the electrode surface. In this article, we review recent research activities on hollow nanostructured anode materials for Li-ion batteries, including carbon materials, metals, metal oxides, and their hybrid materials. The major goal of this review is to highlight some recent progresses in using these hollow nanomaterials as anode materials to develop Li-ion batteries with high capacity, high rate capability, and excellent cycling stability.

Liu, Jun; Xue, Dongfeng

2010-10-01

76

Nanotechnology and health safety--toxicity and risk assessments of nanostructured materials on human health.  

PubMed

The field of nanotechnology has recently emerged as the most commercially viable technology of this century because of its wide-ranging applications in our daily lives. Man-made nanostructured materials such as fullerenes, nanoparticles, nanopowders, nanotubes, nanowires, nanorods, nanofibers, quantum dots, dendrimers, nanoclusters, nanocrystals, and nanocomposites are globally produced in large quantities due to their wide potential applications, e.g., in skincare and consumer products, healthcare, electronics, photonics, biotechnology, engineering products, pharmaceuticals, drug delivery, and agriculture. Human exposure to these nanostructured materials is inevitable, as they can enter the body through the lungs or other organs via food, drink, and medicine and affect different organs and tissues such as the brain, liver, kidney, heart, colon, spleen, bone, blood, etc., and may cause cytotoxic effects, e.g., deformation and inhibition of cell growth leading to various diseases in humans and animals. Since a very wide variety of nanostructured materials exits, their interactions with biological systems and toxicity largely depend upon their properties, such as size, concentration, solubility, chemical and biological properties, and stability. The toxicity of nanostructured materials could be reduced by chemical approaches such by surface treatment, functionalization, and composite formation. This review summarizes the sources of various nanostructured materials and their human exposure, biocompatibility in relation to potential toxicological effects, risk assessment, and safety evaluation on human and animal health as well as on the environment. PMID:18019130

Singh, Surya; Nalwa, Hari Singh

2007-09-01

77

Nanostructured Materials Integrated in Microfabricated Optical Devices  

SciTech Connect

This project combined nanocomposite materials with microfabricated optical device structures for the development of microsensor arrays. For the nanocomposite materials we have designed, developed, and characterized self-assembling, organic/inorganic hybrid optical sensor materials that offer highly selective, sensitive, and reversible sensing capability with unique hierarchical nanoarchitecture. Lipid bilayers and micellar polydiacetylene provided selective optical response towards metal ions (Pb(II), Hg(II)), a lectin protein (Concanavalin A), temperature, and organic solvent vapor. These materials formed as composites in silica sol-gels to impart physical protection of the self-assembled structures, provide a means for thin film surface coatings, and allow facile transport of analytes. The microoptical devices were designed and prepared with two- and four-level diffraction gratings coupled with conformal gold coatings on fused silica. The structure created a number of light reflections that illuminated multiple spots along the silica surface. These points of illumination would act as the excitation light for the fluorescence response of the sensor materials. Finally, we demonstrate an integrated device using the two-level diffraction grating coupled with the polydiacetylene/silica material.

SASAKI, DARRYL Y.; LAST, JULIE A.; BONDURANT, BRUCE; WAGGONER, TINA A.; BRINKER, C. JEFFREY; KEMME, SHANALYN A.; WENDT, JOEL R.; CARTER, TONY; SAMORA, SALLY; WARREN, MIAL E.; SINCLAIR, MICHAEL B.; YANG, YI

2002-12-01

78

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

79

Synthesis, characterization, and properties of low-dimensional nanostructured materials  

NASA Astrophysics Data System (ADS)

Nanometer scale structures represent an exciting and rapidly expanding area of research. Studies on new physical/chemical properties and applications of nanomaterials and nanostructures are possible only when nanostructured materials are made available with desired size, morphology, crystal and microstructure, and composition. Thus, controlled synthesis of nanomaterials is the essential aspect of nanotechnology. This thesis describes the development of simple and versatile solution-based approaches to synthesize low-dimensional nanostructures. The first major goal of this research is to design and fabricate morphology-controlled alpha-Fe 2O3 nanoarchitectures in aqueous solution through a programmed microwave-assisted hydrothermal route, taking advantage of microwave irradiation and hydrothermal effects. Free-standing alpha-Fe2O3 nanorings are prepared by hydrolysis of FeCl3 in the presence of phosphate ions. The as-formed architecture of alpha-Fe2O 3 nanorings is an exciting new member in the family of iron oxide nanostructures. Our preliminary results demonstrate that sensors made of the alpha-Fe 2O3 nanorings exhibit high sensitivity not only for bio-sensing of hydrogen peroxide in a physiological solution but also for gas-sensing of alcohol vapor at room temperature. Moreover, monodisperse alpha-Fe 2O3 nanocrystals with continuous aspect-ratio tuning and fine shape control are achieved by controlling the experimental conditions. The as-formed alpha-Fe2O3 exhibits shape-dependent infrared optical properties. The growth process of colloidal alpha-Fe 2O3 crystals in the presence of phosphate ions is discussed. In addition, through an efficient microwave-assisted hydrothermal process, self-assembled hierarchical alpha-Fe2O3 nanoarchitectures are synthesized on a large scale. The second major goal of this research is to develop convenient microwave-hydrothermal approaches for the fabrication of carbon-based nanocomposites: (1) A one-pot solution-phase route, namely microwave-assisted hydrothermal reduction/carbonization (MAHRC), is developed to prepare coaxial Ag/amorphous-carbon (a-C) nanocables. The as-grown Ag/C nanocables can self-assemble in an end-to-end fashion. (2) A novel Se/C nanocomposite with core-shell structures is prepared. The new material consists of a trigonal-Se (t-Se) core and an amorphous-C (a-C) shell. The Se/C composite can be converted to hollow carbon capsules by thermal treatment. (3) A Fe 3O4/C nanocomposite is synthesized by a green wet-chemical approach. The product possesses porous microstructures and exhibits superparamagnetic behavior. The third major goal of this research is develop facile solution-based methods for preparing carbonaceous nano test tubes, thin films of metal iodides, and spherical selenium spheres: (1) Carbonaceous nano test tubes are fabricated by a facile "decoring" route using a core-sheath Te carbon nanocomposite as the precursor. The as-formed carbonaceous material looks like a "test tube" with an average diameter of about 120 nm and lengths up to 5 mum. (2) Tetrahedral-shaped CuI crystals were formed on a variety of copper substrates (e.g. grids, flat/porous foils, and macro-/nano- wires) via an interfacial reaction between a copper substrate and iodine in water at room temperature. This preparation approach can also be used to grow PbI2 and AgI nano- and micro-crystals with different morphologies on corresponding substrates. (3) Colloidal trigonal selenium (t-Se) microspheres are synthesized through a mild hydrothermal reduction reaction, using glucose as a reducing regent and water as an environmentally friendly solvent. Importantly, the resulting t-Se microspheres inherit functional groups from the starting materials and possess hydrophilic and biocompatible surfaces.

Hu, Xianluo

80

Nanostructured electrode materials for lithium ion batteries  

NASA Astrophysics Data System (ADS)

This thesis discusses two aspects of nanograined electrode materials for lithium batteries. Firstly the size and surface effects in nanosized lithium intercalation materials is explored. Nanosized intercalation materials are modelled using Monte Carlo simulations of finite sized lattice gases. This study shows that finite size intercalation materials can have marked differences in their voltage-composition behaviour compared to their bulk counterparts. The finite size of the lattices tends to cause a rounding-off of voltage plateaus, while surface effects cause extra plateaus to appear in voltage curves and can also cause phase transitions to occur at different voltages than they do in the bulk. Attempts at making real nanosized intercalation materials proved difficult by standard laboratory methods. A nanograined lithium manganese oxide was prepared in aqueous solution, however. This material has an interesting microstructure, being composed of 7 nm grains which self-assemble into 50 nm squares and rectangles. The voltage behaviour of this material is similar to that of lithium rich LiMn2O4 spinel, but has capacity between 3.3 V and 3.8 V, where no capacity exists in bulk LiMn2O 4. The voltage plateaus of this material are also sloped and rounded off. It is unclear if these effects are caused by surface and size effects or by lattice defects in the structure. The second focus of the thesis explores the mechanism and applications of displacement electrodes for secondary lithium cells. Such electrodes do not intercalate lithium, but undergo a reversible displacement reaction during cycling. It was found that non-intercalating transition metal oxide electrodes are displaced by lithium on the first discharge to form a nanocomposite of lithia and reduced transition metal. During charge lithium is removed from this composite, while concurrently the transition metal enters the oxygen lattice of the lithia. This process is thought to resemble an ion-exchange mechanism. It is also shown that a nanocomposite of lithia and transition metal made by ball-milling contains electrochemically active lithium. Such materials have a huge capacity (˜500 mAh/g) compared to conventional intercalation cathodes. These composites might find application in lithium batteries as high capacity cathode materials or as an additive to provide a source of lithium for conventional anodes which suffer from irreversible capacity or for cathodes that can uptake more lithium than they contain as made. Finally, the ion-exchange mechanism discussed for displacement type electrodes was attempted outside of the cell by reacting Li2O with transition metal ions in nonaqueous solvents. Although a reaction occurred, it was difficult to tell if an ion exchange type reaction took place or if a water impurity was the cause of the reaction. Nevertheless such a reaction was shown to take place very slowly in solution, if it occurs at all. Because of this, binary lithium compounds other than Li2O in which the reaction does take place more quickly, such as Li2S, are suggested as better candidates for electrochemical displacement type electrodes.

Obrovac, Mark Nikolas

2001-08-01

81

Composite Material Switches  

NASA Astrophysics Data System (ADS)

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

2002-09-01

82

Composite materials with giant anisotropy and negative index of refraction  

Microsoft Academic Search

We demonstrate that a nanostructured plasmonic composite material can show negative index of refraction at infrared and optical frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed material is intrinsically non-magnetic (mu ? 1), its performance is not limited to proximity of a

Viktor A. Podolskiy; Leo A. Alekseyev; Evgenii E. Narimanov

2005-01-01

83

Physical properties investigation of nanostructured materials and their applications  

Microsoft Academic Search

Nanostructured materials provide the essential foundation of nanotechnology, some special properties of these materials resulted in many novel applications in various areas of applied science and engineering. Nanoparticles and carbon nanotubes (CNTs) are the nanomaterials that have been found most valuable. First, I will address physical properties of nanoparticles. Optical, chemical and other physical properties of gold\\/silver nanoparticles have been

Yi Zhang

2008-01-01

84

Nanostructured polymer microcomposites: A distinct class of insulating materials  

Microsoft Academic Search

Experimental evidence was produced and gathered to demonstrate the distinct nature of nanostructured polymer microcomposites. The case of a polymer composite consisting of a high-content of micrometric quartz with a small adjunct of nanoclay is discussed. Emphasis is put on dielectric behavior studies while some results on thermal characteristics are presented. Overall results strongly support the potential of this class

M. F. Frechette; R. Y. Larocque; M. Trudeau; R. Veillette; R. Rioux; S. Pelissou; S. Besner; M. Javan; K. Cole; M.-T. T. That; D. Desgagnes; J. Castellon; S. Agnel; A. Toureille; G. Platbrood

2008-01-01

85

Nanostructured Silicon as an Active Optoelectronic Material  

Microsoft Academic Search

\\u000a This review paper charts the progress made over the last decade in realising a variety of optoelectronic devices using nanostructured\\u000a porous silicon. Although waveguides, modulators and detectors are covered, emphasis is given to visible light-emitting diodes\\u000a whose efficiency is now 1%. Although their performance is still inadequate for optical interconnect applications, two promising\\u000a approaches for further major advances are concluded

L. T. Canham

86

PHOTONICS AND NANOTECHNOLOGY Laser nanostructuring of materials surfaces  

NASA Astrophysics Data System (ADS)

This paper reviews results of experimental and theoretical studies of surface micro- and nanostructuring of metals and other materials irradiated directly by short and ultrashort laser pulses. Special attention is paid to direct laser action involving melting of the material (with or without ablation), followed by ultrarapid surface solidification, which is an effective approach to producing surface nanostructures. Theoretical analysis of recrystallisation kinetics after irradiation by ultrashort laser pulses makes it possible to determine the volume fraction of crystallised phase and the average size of forming crystalline structures as functions of laser treatment regime and thermodynamic properties of the material. The present results can be used to optimise pulsed laser treatment regime in order to ensure control nanostructuring of metal surfaces.

Zavestovskaya, I. N.

2010-12-01

87

Preparation and properties on hollow nano-structured smoke material  

NASA Astrophysics Data System (ADS)

In recent years, the weapon systems of laser guidance and infrared (IR) imaging guidance have been widely used in modern warfare because of their high precision and strong anti-interference. Notwithstanding, military smoke, as a rapid and effective passive jamming means, can effectively counteract the attack of enemy precision-guided weapons by scattering and absorbability. Conventional smoke has good attenuation capability only to visible light (0.4-0.76 ?m), but hardly any effect to other electromagnetic wave band. The weapon systems of laser guidance and IR imaging guidance usually work in broad band, including near IR (1-3 ?m), middle IR (3-5 ?m), far IR (8-14 ?m), and so on. Accordingly, exploiting and using new efficient obscurant materials, which is one of the important factors that develop smoke technology, have become a focus and attracted more interests around the world. Then nano-structured materials that are developing very quickly have turned into our new choice. Hollow nano-structured materials (HNSM) have many special properties because of their nano-size wall-thickness and sub-micron grain-size. After a lot of HNSM were synthesized in this paper, their physical and chemical properties, including grain size, phase composition, microstructure, optical properties and resistivity were tested and analysed. Then the experimental results of the optical properties showed that HNSM exhibit excellent wave-absorbing ability in ultraviolet, visible and infrared regions. On the basis of the physicochemmical properties, HNSM are firstly applied in smoke technology field. And the obscuration performance of HNSM smoke was tested in smoke chamber. The testing waveband included 1.06?m and 10.6?m laser, 3-5?m and 8-14?m IR radiation. Then the main parameters were obtained, including the attenuation rate, the transmission rate, the mass extinction coefficient, the efficiency obscuring time, and the sedimentation rate, etc. The main parameters of HNSM smoke were contrasted in detail with graphite powder smoke agent. The results showed that HNSM smoke possesses better obscuration capability compared with the smoke performance of conventional materials (such as HC, RP, oil, carbon black, and graphite powder). Therefore, they are new smoke obscurant materials which can effectively interfere with broadband electromagnetic radiation, including 1.06 ?m and 10.6 ?m laser, 3-5 ?m and 8-14 ?m IR waveband.

Liu, Xiang-cui; Dai, Meng-yan; Fang, Guo-feng; Shi, Wei-dong; Cheng, Xiang; Liu, Hai-feng; Zhang, Tong

2013-09-01

88

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

89

Synthesis of nanostructured materials in inverse miniemulsions and their applications.  

PubMed

Polymeric nanogels, inorganic nanoparticles, and organic-inorganic hybrid nanoparticles can be prepared via the inverse miniemulsion technique. Hydrophilic functional cargos, such as proteins, DNA, and macromolecular fluoresceins, may be conveniently encapsulated in these nanostructured materials. In this review, the progress of inverse miniemulsions since 2000 is summarized on the basis of the types of reactions carried out in inverse miniemulsions, including conventional free radical polymerization, controlled/living radical polymerization, polycondensation, polyaddition, anionic polymerization, catalytic oxidation reaction, sol-gel process, and precipitation reaction of inorganic precursors. In addition, the applications of the nanostructured materials synthesized in inverse miniemulsions are also reviewed. PMID:24056795

Cao, Zhihai; Ziener, Ulrich

2013-09-12

90

Synthesis of nanostructured materials in inverse miniemulsions and their applications  

NASA Astrophysics Data System (ADS)

Polymeric nanogels, inorganic nanoparticles, and organic-inorganic hybrid nanoparticles can be prepared via the inverse miniemulsion technique. Hydrophilic functional cargos, such as proteins, DNA, and macromolecular fluoresceins, may be conveniently encapsulated in these nanostructured materials. In this review, the progress of inverse miniemulsions since 2000 is summarized on the basis of the types of reactions carried out in inverse miniemulsions, including conventional free radical polymerization, controlled/living radical polymerization, polycondensation, polyaddition, anionic polymerization, catalytic oxidation reaction, sol-gel process, and precipitation reaction of inorganic precursors. In addition, the applications of the nanostructured materials synthesized in inverse miniemulsions are also reviewed.

Cao, Zhihai; Ziener, Ulrich

2013-10-01

91

Scaling laws for van der Waals interactions in nanostructured materials  

NASA Astrophysics Data System (ADS)

Van der Waals interactions have a fundamental role in biology, physics and chemistry, in particular in the self-assembly and the ensuing function of nanostructured materials. Here we utilize an efficient microscopic method to demonstrate that van der Waals interactions in nanomaterials act at distances greater than typically assumed, and can be characterized by different scaling laws depending on the dimensionality and size of the system. Specifically, we study the behaviour of van der Waals interactions in single-layer and multilayer graphene, fullerenes of varying size, single-wall carbon nanotubes and graphene nanoribbons. As a function of nanostructure size, the van der Waals coefficients follow unusual trends for all of the considered systems, and deviate significantly from the conventionally employed pairwise-additive picture. We propose that the peculiar van der Waals interactions in nanostructured materials could be exploited to control their self-assembly.

Gobre, Vivekanand V.; Tkatchenko, Alexandre

2013-08-01

92

Potential applications of nanostructured materials in nuclear waste management.  

SciTech Connect

This report summarizes the results obtained from a Laboratory Directed Research & Development (LDRD) project entitled 'Investigation of Potential Applications of Self-Assembled Nanostructured Materials in Nuclear Waste Management'. The objectives of this project are to (1) provide a mechanistic understanding of the control of nanometer-scale structures on the ion sorption capability of materials and (2) develop appropriate engineering approaches to improving material properties based on such an understanding.

Braterman, Paul S. (The University of North Texas, Denton, TX); Phol, Phillip Isabio; Xu, Zhi-Ping (The University of North Texas, Denton, TX); Brinker, C. Jeffrey; Yang, Yi (University of New Mexico, Albuquerque, NM); Bryan, Charles R.; Yu, Kui; Xu, Huifang (University of New Mexico, Albuquerque, NM); Wang, Yifeng; Gao, Huizhen

2003-09-01

93

Hybrid silicon-carbon nanostructured composites as superior anodes for lithium ion batteries  

Microsoft Academic Search

We have successfully fabricated a hybrid silicon-carbon nanostructured composite with large area (about 25.5 in2) in a simple fashion using a conventional sputtering system. When used as the anode in lithium ion batteries, the uniformly\\u000a deposited amorphous silicon (a-Si) works as the active material to store electrical energy, and the pre-coated carbon nanofibers\\u000a (CNFs) serve as both the electron conducting

Po-Chiang Chen; Jing Xu; Haitian Chen; Chongwu Zhou

2011-01-01

94

Synthesis and chemical modification of carbon nanostructures for materials applications  

NASA Astrophysics Data System (ADS)

This dissertation explores the structure, chemical reactivities, electromagnetic response, and materials properties of various carbon nanostructures, including single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphite, and graphene nanoribbons (GNRs). Efficient production and modification of these unique structures, each with their own distinct properties, will make them more accessible for applications in electronics, materials, and biology. A method is reported for controlling the permittivity from 1--1000 MHz of SWCNT-polymer composites (0.5 wt%) for radio frequency applications including passive RF antenna structures and EMI shielding. The magnitude of the real permittivity varied between 20 and 3.3, decreasing as higher fractions of functionalized-SWCNTs were added. The microwave absorbing properties and subsequent heating of carbon nanotubes were used to rapidly cure ceramic composites. With less than 1 wt% carbon nanotube additives and 30--40 W of directed microwave power (2.45 GHz), bulk composite samples reached temperatures above 500°C within 1 min. Graphite oxide (GO) polymer nanocomposites were developed at 1, 5, and 10 wt% for the purpose of evaluating the flammability reduction and materials properties of the resulting systems. Microscale oxygen consumption calorimetry revealed that addition of GO reduced the total heat release in all systems, and GO-polycarbonate composites demonstrated very fast self-extinguishing times in vertical open flame tests. A simple solution-based oxidative process using potassium permanganate in sulfuric acid was developed for producing nearly 100% yield of graphene nanoribbons (GNRs) by lengthwise cutting and unraveling of MWCNT sidewalls. Subsequent chemical reduction of the GNRs resulted in restoration of electrical conductivity. The GNR synthetic conditions were investigated in further depth, and an improved method which utilized a two-acid reaction medium was found to produce GNRs with fewer defects and/or holes on the basal plane and higher aspect ratio. Two different covalent functionalization methods for GNRs based on diazonium chemistry were developed. The resulting functionalized GNRs (f-GNRs) are readily soluble in organic solvents which increase their solution processability. The f-GNRs were also found to be in a reduced state, with minimal sp2 carbon disruption, while also keeping the ribbon shape.

Higginbotham, Amanda Lynn

95

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

96

Compositional ordering and stability in nanostructured, bulk thermoelectric alloys.  

SciTech Connect

Thermoelectric materials have many applications in the conversion of thermal energy to electrical power and in solid-state cooling. One route to improving thermoelectric energy conversion efficiency in bulk material is to embed nanoscale inclusions. This report summarize key results from a recently completed LDRD project exploring the science underpinning the formation and stability of nanostructures in bulk thermoelectric and the quantitative relationships between such structures and thermoelectric properties.

Hekmaty, Michelle A.; Faleev, S.; Medlin, Douglas L.; Leonard, F.; Lensch-Falk, J.; Sharma, Peter Anand; Sugar, J. D.

2009-09-01

97

Formation and characterization of metal-polymer nanostructured composites  

Microsoft Academic Search

Nanostructured metal (Pd, Sn, Cu)-polymer (poly-para-xylylene) and metal-oxide-polymer composites reveal synergism of properties of the initial components, which gives rise to specific electrical, mechanical, and optical properties related to an ordered distribution of nanoparticles over the matrix volume. Methods where polymerisation and formation of the nanoparticles are performed simultaneously are very promising. This paper reports on the experimental set-up for

S. A. Zavyalov; A. N. Pivkina; J. Schoonman

2002-01-01

98

Magneto-optical stokes polarimetry and nanostructured magnetic materials.  

PubMed

Stokes parameters fully characterize the polarization state of light in an experimentally accessible manner. Photoelastic modulator (PEM) based Stokes polarimetry offers a very high sensitivity which is particularly suitable for the investigation of the magneto-optical properties of nanostructured magnetic materials. In this paper, we shall describe a robust methodology recently developed by us that utilizes a dual PEM setup. As an example of its application, we report on the magneto-optical characteristics of focused Ga ion beam patterned Fe films. We have investigated Ga ion irradiation of single-layer polycrystalline Fe films deposited on Si3N4 substrates, which allows us to study the effects of ion implantation with minimum added complications. Complemented by structural and other characterization techniques, the absolute measurement of magneto-optical effects through the determination of Stokes parameters has enabled us to effectively separate the various contributions from film thinning due to sputtering, structural modifications and compositional changes caused by Ga incorporation. A comparison is also made between the magneto-optical behavior of patterned thin films and that of anodic aluminum oxide embedded magnetic nanowire arrays. PMID:22629897

Cook, P J; Zhang, J; Liu, Y; Guan, W; Wang, N; Qin, L; Shen, T H; Jones, G A; Grundy, P J

2012-02-01

99

Nanostructured functional materials prepared by atom transfer radical polymerization  

Microsoft Academic Search

Atom transfer radical polymerization (ATRP) is the most extensively studied controlled\\/living radical polymerization (CRP) method, with the interest originating primarily in its simplicity and broad applicability, and in the ability to prepare previously inaccessible well-defined nanostructured polymeric materials. This review illustrates the range of well-defined advanced functional materials that can be prepared by ATRP. We detail the precise synthesis of

Krzysztof Matyjaszewski; Nicolay V. Tsarevsky

2009-01-01

100

Functional block copolymers: nanostructured materials with emerging applications.  

PubMed

Recent advances in polymer synthesis have significantly enhanced the ability to rationally design block copolymers with tailored functionality. The self-assembly of these macromolecules in the solid state or in solution allows the formation of nanostructured materials with a variety of properties and potential functions. This Review illustrates recent progress in the field of block copolymer materials by highlighting selected emerging applications. PMID:22806974

Schacher, Felix H; Rupar, Paul A; Manners, Ian

2012-07-16

101

Magnetism of nanostructured permanent-magnet materials  

NASA Astrophysics Data System (ADS)

Sm2Co17-type high-temperature permanent magnets with composition Sm(Co, Fe, Cu, Ti)z are investigated. The effects of Ti (or Zr), Cu, Fe and z value, as well as the effect of heat treatment on the magnetic properties are reported. Ti is found a necessity to form the cellular microstructure with grain size less than 100 nm. The Cu-rich Sm(Co, Cu)5 phase forms the grain-boundary which pins the magnetic domain-wall motion. Low Cu content makes the high-temperature coercivity vary in an abnormal way. A record-high high-temperature coercivity of 12.3 kOe at 500°C has been obtained. Granular SmCoz (z = 3--7.5) and Sm-Co-Cu-Ti thin films were produced by thermal processing of sputtered Sm-Co single layers and SmCo 5/(CuTi) multilayers. Inplane anisotropy was found in SmCoz for the composition range of z < 5.5, whereas for z > 5.5 the films exhibits three-dimensional random anisotropy. Sm-Co-Cu-Ti films were sputtered onto Si substrates with a Cr underlayer and coverlayer. X-ray diffraction patterns show that the hexagonal 1:5 phase forms after annealing. Electron micrographs of the processed films show that grains with diameters of 5 to 10 nm are embedded in a matrix. Both the grains and the matrix phase exhibit the CaCu5 Structure. The hysteresis loops show that these films have large coercivities of up to 50.4 kOe. FePt single layer and FePt/Fe multilayer thin films are prepared by magnetron sputtering. The single-phase behavior of the hysteresis loops of FePt/Fe multilayers indicates the existence of exchange coupling in these materials. An energy product of 19 MGOe has been obtained. Nanocrystalline Sm12(Co, Cu, Ti)88 powders are produced by mechanical alloying and are investigated using X-ray diffraction analysis and magnetization measurements. Different heat treatments are performed to investigate the influence on the magnetic properties and crystal structures. The intrinsic coercivity of the powders increases with an increasing amount of Cu. Short annealing time produces a metastable 1:7 phase with high crystalline anisotropy that results in large coercivity. A room temperature coercivity of 22 kOe was obtained in Sm12Co76Cu9Ti 3 powder. Sm-Co binary alloys are also investigated. A coercivity of 41 kOe is obtained in Sm2Co7. The magnetization reversal mechanism is analyzed in both Sm-Co-Cu-Ti and Sm-Co alloys. (Abstract shortened by UMI.)

Zhou, Jian

102

Formation of nanostructured MnO/Co/solid-electrolyte interphase ternary composites as a durable anode material for lithium-ion batteries.  

PubMed

Nanoporous MnO frameworks with highly dispersed Co nanoparticles were produced from MnCO3 precursors prepared in a gel matrix. The MnO frameworks that contain 20 mol% Co exhibited excellent cycle performance as an anode material for Li-ion batteries. The solid-electrolyte interphase (SEI) formed in the frameworks through the electrochemical reaction mediates the active materials, such as MnO, Mn, and Li2O, during the conversion reaction in the charge-discharge cycle. The Co nanoparticles and SEI provide the electron and Li-ion conductive networks, respectively. The ternary nanocomposites of the MnO framework, metallic Co nanoparticles, and embedded SEI are categorized as durable anode materials for Li-ion batteries. PMID:23401355

Dang, Feng; Oaki, Yuya; Kokubu, Takao; Hosono, Eiji; Zhou, Haoshen; Imai, Hiroaki

2013-02-07

103

Novel thermal properties of nanostructured materials.  

SciTech Connect

A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. For example, an approximately 20% improvement in effective thermal conductivity is observed when 5 vol.% CuO nanoparticles are added to water. Even more importantly, the heat transfer coefficient of water under dynamic flow conditions is increased more than 15% with the addition of less than 1 vol.% CuO particles. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers. Yttria-stabilized zirconia (YSZ) thin films are being produced by metal-organic chemical vapor deposition techniques. Preliminary results have indicated that the thermal conductivity is reduced by approximately a factor-of-two at room temperature in 10 nm grain-sized YSZ compared to coarse-grained or single crystal YSZ.

Eastman, J. A.

1999-01-13

104

Applications of ultrasound to the synthesis of nanostructured materials.  

PubMed

Recent advances in nanostructured materials have been led by the development of new synthetic methods that provide control over size, morphology, and nano/microstructure. The utilization of high intensity ultrasound offers a facile, versatile synthetic tool for nanostructured materials that are often unavailable by conventional methods. The primary physical phenomena associated with ultrasound that are relevant to materials synthesis are cavitation and nebulization. Acoustic cavitation (the formation, growth, and implosive collapse of bubbles in a liquid) creates extreme conditions inside the collapsing bubble and serves as the origin of most sonochemical phenomena in liquids or liquid-solid slurries. Nebulization (the creation of mist from ultrasound passing through a liquid and impinging on a liquid-gas interface) is the basis for ultrasonic spray pyrolysis (USP) with subsequent reactions occurring in the heated droplets of the mist. In both cases, we have examples of phase-separated attoliter microreactors: for sonochemistry, it is a hot gas inside bubbles isolated from one another in a liquid, while for USP it is hot droplets isolated from one another in a gas. Cavitation-induced sonochemistry provides a unique interaction between energy and matter, with hot spots inside the bubbles of approximately 5000 K, pressures of approximately 1000 bar, heating and cooling rates of >10(10) K s(-1); these extraordinary conditions permit access to a range of chemical reaction space normally not accessible, which allows for the synthesis of a wide variety of unusual nanostructured materials. Complementary to cavitational chemistry, the microdroplet reactors created by USP facilitate the formation of a wide range of nanocomposites. In this review, we summarize the fundamental principles of both synthetic methods and recent development in the applications of ultrasound in nanostructured materials synthesis. PMID:20401929

Bang, Jin Ho; Suslick, Kenneth S

2010-03-12

105

Nanostructuring, compositional fluctuations, and atomic ordering in the thermoelectric materials AgPb(m)SbTe(2+m). The myth of solid solutions.  

PubMed

The nature of the thermoelectric materials Ag(1-x)Pb(m)SbTe(m+2) or LAST-m materials (LAST for Lead Antimony Silver Tellurium) with different m values at the atomic as well as nanoscale was studied with powder/single-crystal X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy. Powder diffraction patterns of different members (m = 0, 6, 12, 18, infinity) are consistent with pure phases crystallizing in the NaCl-structure-type (Fmm) and the proposition that the LAST family behaved as solid solutions between the PbTe and AgSbTe2 compounds. However, electron diffraction and high resolution transmission electron microscopy studies suggest the LAST phases are inhomogeneous at the nanoscale with at least two coexisting sets of well-defined phases. The minority phase which is richer in Ag and Sb is on the nanosized length scale, and it is endotaxially embedded in the majority phase which is poorer in Ag and Sb. Moreover, within each nanodomain we observe extensive long range ordering of Ag, Pb, and Sb atoms. The long range ordering can be confirmed by single crystal X-ray diffraction studies. Indeed, data collections of five different single crystals were successfully refined in space groups of lower symmetry than Fmm including P4/mmm and Rm. The results reported here provide experimental evidence for a conceptual basis that could be employed when designing high performance thermoelectric materials and dispel the decades long belief that the systems (AgSbTe2)(1-x)(PbTe)x are solid solutions. PMID:15969596

Quarez, Eric; Hsu, Kuei-Fang; Pcionek, Robert; Frangis, N; Polychroniadis, E K; Kanatzidis, Mercouri G

2005-06-29

106

Combination of lightweight elements and nanostructured materials for batteries.  

PubMed

In a society that increasingly relies on mobile electronics, demand is rapidly growing for both primary and rechargeable batteries that power devices from cell phones to vehicles. Existing batteries utilize lightweight active materials that use electrochemical reactions of ions such as H(+), OH(-) and Li(+)/Mg(2+) to facilitate energy storage and conversion. Ideal batteries should be inexpensive, have high energy density, and be made from environmentally friendly materials; batteries based on bulk active materials do not meet these requirements. Because of slow electrode process kinetics and low-rate ionic diffusion/migration, most conventional batteries demonstrate huge gaps between their theoretical and practical performance. Therefore, efforts are underway to improve existing battery technologies and develop new electrode reactions for the next generation of electrochemical devices. Advances in electrochemistry, surface science, and materials chemistry are leading to the use of nanomaterials for efficient energy storage and conversion. Nanostructures offer advantages over comparable bulk materials in improving battery performance. This Account summarizes our progress in battery development using a combination of lightweight elements and nanostructured materials. We highlight the benefits of nanostructured active materials for primary zinc-manganese dioxide (Zn-Mn), lithium-manganese dioxide (Li-Mn), and metal (Mg, Al, Zn)-air batteries, as well as rechargeable lithium ion (Li-ion) and nickel-metal hydride (Ni-MH) batteries. Through selected examples, we illustrate the effect of structure, shape, and size on the electrochemical properties of electrode materials. Because of their numerous active sites and facile electronic/ionic transfer and diffusion, nanostructures can improve battery efficiency. In particular, we demonstrate the properties of nanostructured active materials including Mg, Al, Si, Zn, MnO(2), CuV(2)O(6), LiNi(0.8)Co(0.2)O(2), LiFePO(4), Fe(2)O(3), Co(3)O(4), TiS(2), and Ni(OH)(2) in battery applications. Electrochemical investigations reveal that we generally attain larger capacities and improved kinetics for electrode materials as their average particle size decreases. Novel nanostructures such as nanowires, nanotubes, nanourchins, and porous nanospheres show lower activation energy, enhanced reactivity, improved high-rate charge/discharge capability, and more controlled structural flexibility than their bulk counterparts. In particular, anode materials such as Si nanospheres and Fe(2)O(3) nanotubes can deliver reversible capacity exceeding 500 mA.h/g. (Graphite used commercially has a theoretical capacity of 372 mA x h/g.) Nanocomposite cathode materials such as NiP-doped LiFePO(4) and metal hydroxide-coated Ni(OH)(2) nanotubes allow us to integrate functional components, which enhance electrical conductivity and suppress volume expansion. Therefore, shifting from bulk to nanostructured electrode materials could offer a revolutionary opportunity to develop advanced green batteries with large capacity, high energy and power density, and long cycle life. PMID:19354236

Chen, Jun; Cheng, Fangyi

2009-06-16

107

Magnetism of nanostructured permanent-magnet materials  

Microsoft Academic Search

Sm2Co17-type high-temperature permanent magnets with composition Sm(Co, Fe, Cu, Ti)z are investigated. The effects of Ti (or Zr), Cu, Fe and z value, as well as the effect of heat treatment on the magnetic properties are reported. Ti is found a necessity to form the cellular microstructure with grain size less than 100 nm. The Cu-rich Sm(Co, Cu)5 phase forms

Jian Zhou

2002-01-01

108

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

109

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

110

Nanostructured electrocatalyst for fuel cells : silica templated synthesis of Pt/C composites.  

SciTech Connect

Platinum-based electrocatalysts are currently required for state-of-the-art fuel cells and represent a significant portion of the overall fuel cell cost. If fuel cell technology is to become competitive with other energy conversion technologies, improve the utilization of precious metal catalysts is essential. A primary focus of this work is on creating enhanced nanostructured materials which improve precious-metal utilization. The goal is to engineer superior electrocatalytic materials through the synthesis, development and investigation of novel templated open frame structures synthesized in an aerosol-based approach. Bulk templating methods for both Pt/C and Pt-Ru composites are evaluated in this study and are found to be limited due to the fact that the nanostructure is not maintained throughout the entire sample. Therefore, an accurate examination of structural effects was previously impossible. An aerosol-based templating method of synthesizing nanostructured Pt-Ru electrocatalysts has been developed wherein the effects of structure can be related to electrocatalytic performance. The aerosol-based templating method developed in this work is extremely versatile as it can be conveniently modified to synthesize alternative materials for other systems. The synthesis method was able to be extended to nanostructured Pt-Sn for ethanol oxidation in alkaline media. Nanostructured Pt-Sn electrocatalysts were evaluated in a unique approach tailored to electrocatalytic studies in alkaline media. At low temperatures, nanostructured Pt-Sn electrocatalysts were found to have significantly higher ethanol oxidation activity than a comparable nanostructured Pt catalyst. At higher temperatures, the oxygen-containing species contribution likely provided by Sn is insignificant due to a more oxidized Pt surface. The importance of the surface coverage of oxygen-containing species in the reaction mechanism is established in these studies. The investigations in this work present original studies of anion exchange ionomers as entrapment materials for rotating disc electrode (RDE) studies in alkaline media. Their significance is linked to the development of membrane electrode assemblies (MEAs) with the same ionomer for a KOH-free alkaline fuel cell (AFC).

Stechel, Ellen Beth; Switzer, Elise E.; Fujimoto, Cy H.; Atanassov, Plamen Borissov; Cornelius, Christopher James; Hibbs, Michael R.

2007-09-01

111

Thermoelectric energy conversion using nanostructured materials  

NASA Astrophysics Data System (ADS)

High performance thermoelectric materials in a wide range of temperatures are essential to broaden the application spectrum of thermoelectric devices. This paper presents experiments on the power and efficiency characteristics of lowand mid-temperature thermoelectric materials. We show that as long as an appreciable temperature difference can be created over a short thermoelectric leg, good power output can be achieved. For a mid-temperature n-type doped skutterudite material an efficiency of over 11% at a temperature difference of 600 °C could be achieved. Besides the improvement of thermoelectric materials, device optimization is a crucial factor for efficient heat-to-electric power conversion and one of the key challenges is how to create a large temperature across a thermoelectric generator especially in the case of a dilute incident heat flux. For the solar application of thermoelectrics we investigated the concept of large thermal heat flux concentration to optimize the operating temperature for highest solar thermoelectric generator efficiency. A solar-to-electric power conversion efficiency of ~5% could be demonstrated. Solar thermoelectric generators with a large thermal concentration which minimizes the amount of thermoelectric nanostrucutured bulk material shows great potential to enable cost-effective electrical power generation from the sun.

Chen, Gang; Kraemer, Daniel; Muto, Andrew; McEnaney, Kenneth; Feng, Hsien-Ping; Liu, Wei-Shu; Zhang, Qian; Yu, Bo; Ren, Zhifeng

2011-05-01

112

Materials: A class of porous metallic nanostructures  

NASA Astrophysics Data System (ADS)

Colloidal crystals are ordered arrays of particles in the nanometre-to-micrometre size range. Useful microstructured materials can be created by replicating colloidal crystals in a durable matrix that preserves their key feature of long-range periodic structure. For example, colloidal crystals have been used to fabricate structures from inorganic oxides, polymers, diamond and glassy carbon, and semiconductor quantum dots, and some structures have photonic properties or are patterned on different hierarchical length scales. By using colloidal crystals as templates, we have synthesized a new class of metallic materials with long-range nano-scale ordering and hierarchical porosity.

Velev, O. D.; Tessier, P. M.; Lenhoff, A. M.; Kaler, E. W.

1999-10-01

113

Magnetic Cluster States in Nanostructured Materials  

SciTech Connect

The goal of this work is to fabricate model nanomaterials with different types of disorder and use atomic-scale characterization and macroscopic magnetization measurements to understand better how specific types of disorder affects macroscopic magnetic behavior. This information can be used to produce magnetic nanomaterials with specific properties for applications such as permanent magnets, soft magnetic material for motors and biomedical applications.

Diandra Leslie-Pelecky

2008-06-13

114

Fabrication and characterization of nanostructured III-V thermoelectric materials  

NASA Astrophysics Data System (ADS)

Approximately two thirds of all fossil fuel used is lost as heat. Thermoelectric materials, which convert heat into electrical energy, may provide a solution to partially recover some of this lost energy. To date, most commercial thermoelectric materials are too inefficient to be a viable option for most waste heat applications. This research proposes to investigate the fabrication and characterization of nanostructured III-V semiconductor thermoelectric materials with the goal of increasing the performance of existing technology. In order to improve thermoelectric material efficiency, either the lattice thermal conductivity must be lowered or the thermoelectric power factor must be increased. This research will focus on the latter by modifying the density of states of the semiconductor material and studying the effect of quantum confinement on the material's thermoelectric properties. Using focused ion beam milling, nanostructured cantilevers are fabricated from single crystal wafers. An all around gate dielectric and electrode are deposited to create a depletion region along the outer core of the cantilever, thus creating an inner conductive core. The Seebeck coefficient can then be measured as a function of confinement by varying the gate voltage. This technique can be applied to various material systems to investigate the effects of confinement on their thermoelectric properties.

Novotny, Clint; Sharifi, Fred

2013-09-01

115

Materials: A class of porous metallic nanostructures  

Microsoft Academic Search

Colloidal crystals are ordered arrays of particles in the nanometre-to-micrometre size range. Useful microstructured materials can be created by replicating colloidal crystals in a durable matrix that preserves their key feature of long-range periodic structure. For example, colloidal crystals have been used to fabricate structures from inorganic oxides, polymers, diamond and glassy carbon, and semiconductor quantum dots, and some structures

O. D. Velev; P. M. Tessier; A. M. Lenhoff; E. W. Kaler

1999-01-01

116

Nanostructured Materials for Portable and Stationary Energy Storage  

NASA Astrophysics Data System (ADS)

Storing energy electrochemically involves electronic and ionic processes and chemical transformation inside and at the interface of materials. The ability to understand and design nanostructures and their interfaces afford the great opportunities for controlling these fundamental processes, which can ultimately lead to high performance energy storage devices. Here I will present several exciting examples on designing nanostructures and their interfaces to realize high performance energy storage devices. One example is on designing nanowires and heterostructured nanowires for ultrahigh capacity storage of lithium ions in silicon anodes and sulfur cathodes. The challenges associated with large volume expansion, electron and ion transport, and solid-electrolyte-interphase (SEI) have been addressed. Another example is to design open framework stucture of nanocrystals, which facility facile insertion of sodium and potassium ions. The high power, high energy efficiency and low-cost aqueous batteries can be enabled for grid scale stationary storage.

Cui, Yi

2012-02-01

117

High-strength, thermally-stable nanostructured materials  

NASA Astrophysics Data System (ADS)

The properties of two technologically important precipitation-treatable alloys - Al 6061 and Inconel 718, that are deformed to large plastic strains at room temperature by machining, are presented. The strong effect of prior density of precipitates on the consequent microstructure refinement during chip formation was determined by deforming Al 6061 of different tempers to varying levels of strain, by varying the tool rake angle. Chips cut from peak-aged 6061, consisting of a fine dispersion of precipitates, produced the finest microstructure and are composed of sub-100 nm grains. On the other hand, coarser precipitate distributions in over-aged 6061 and an absence of precipitates in solution-treated 6061 resulted in much coarser microstructures. Thermal stability of such nanostructured chips with different levels of strain and precipitate distributions is analyzed by studying evolution of Vickers micro-hardness and microstructure after different heat treatments. Chips produced from the peak-aged temper and over-aged temper soften following heat treatment while those from the solution-treated state first, gain strength before softening. The results are rationalized based on prior studies of the characteristics and kinetics of precipitation and coarsening in Al-Mg-Si systems. It is then demonstrated that precipitate-stabilized nanostructured materials synthesized from a prototypical alloy system - Inconel 718, are extremely stable even after prolonged heat treatment for 240 hours at temperatures as high as one-half of the melting point. This extraordinary thermal stability is traced to the retention of a fine dispersion of precipitates in a nanostructured matrix even after extended heat treatment. It is anticipated that general design principles garnered from understanding of the causal phenomena determining strengthening and thermal stability, can lead to the development of alloy systems for the manufacture of high-strength, thermally-stable nanostructured materials.

Shankar, Ravi

118

Composite-hydroxide-mediated approach for the synthesis of nanostructures of complex functional-oxides.  

PubMed

We demonstrate a generic approach for the synthesis of single-crystal complex oxide nanostructures of various structure types, such as perovskites, spinels, monoclinic, corundum, CaF(2) structured, tetragonal, and even metal hydroxides. The method is based on a reaction between a metallic salt and a metallic oxide in a solution of composite-hydroxide eutectic at approximately 200 degrees C and normal atmosphere without using an organic dispersant or capping agent. The synthesis technique is cost-effective, one-step, easy to control, and is performed at low temperature and normal atomospheric pressure. The technique can be expanded to many material systems, and it provides a general, simple, convenient, and innovative strategy for the synthesis of nanostructures of complex oxides with important scientific and technological applications in ferroelectricity, ferromagnetism, colossal magnetoresistance, fuel cell, optics, and more. PMID:16834445

Liu, Hong; Hu, Chenguo; Wang, Zhong Lin

2006-07-01

119

Molecularly Designed Ultrafine/Nanostructured Materials, volume 351  

NASA Astrophysics Data System (ADS)

Nanostructured materials are usually defined as having some length scale smaller than 100 nm in at least one dimension. An important subset of this group of materials is powders with particle size less than 100 nm, and polycrystalline materials, made by consolidating these powders in such a way as to retain a grain size below this limit. The choice of 100 nm stems from the fact that many physical, optical, and magnetic properties have characteristic lengths in this range. As grain or particle size is reduced below this characteristic length, the properties associated with these phenomena are radically altered. A frequently cited example is the freezing out of mechanisms for generating glissile dislocations. Another reason for expecting remarkable properties in nanostructured polycrystalline materials is the very high proportion of atoms at, or near, grain boundaries (as high as fifty percent or greater for grain sizes below five or ten nanometers). This leads, for example, to very rapid diffusion coupled with very short diffusion distances.

Gonsalves, Kenneth E.; Chow, Gan-Moog; Xiao, Tongsan D.; Cammarata, Robert C.

1994-04-01

120

A new approach to the fabrication of ``smart`` near-surface nanostructure composites  

SciTech Connect

A new method for the formation of smart near-surface nanoscale composites has been developed. In this approach, small precipitates of active phases are embedded in the near-surface region of the material that is to be modified by a combination of ion implantation and thermal processing. The dispersion, concentration, and microstructure of the nanocrystals formed in the substrate material can be tailored through a careful choice of processing parameters - making this approach well suited to high value added, high technology applications. The applicability of this approach to forming smart surfaces on otherwise inactive materials was established in the case of VO{sup 2} precipitates which were embedded in Al{sub 2}O{sub 3} single crystals to create a medium suitable for optical applications--including optical data storage. Most recently, this concept has been extended to the fabrication of magnetic field sensitive nanostructured surfaces by forming magnetostrictive precipitates of materials such as Ni or RFe{sub 2} (with R = Tm, Tb, Sm) that are embedded in various single crystal oxide hosts. These nanostructured, active surface composites have been characterized using XRD, RBS, TEM, and magneto-optical techniques.

Gea, L.; Honda, S.; Boatner, L.A.; Haynes, T.E.; Sales, B.C.; Modine, F.A.; Meldrum, A.; Budai, J.D. [Oak Ridge National Lab., TN (United States). Solid State Div.; Beckers, L. [Forshungzentrum Juelich (Germany)

1998-01-01

121

Fabrication of bioinspired nanostructured materials via colloidal self-assembly  

NASA Astrophysics Data System (ADS)

Through millions of years of evolution, nature creates unique structures and materials that exhibit remarkable performance on mechanicals, opticals, and physical properties. For instance, nacre (mother of pearl), bone and tooth show excellent combination of strong minerals and elastic proteins as reinforced materials. Structured butterfly's wing and moth's eye can selectively reflect light or absorb light without dyes. Lotus leaf and cicada's wing are superhydrophobic to prevent water accumulation. The principles of particular biological capabilities, attributed to the highly sophisticated structures with complex hierarchical designs, have been extensively studied. Recently, a large variety of novel materials have been enabled by natural-inspired designs and nanotechnologies. These advanced materials will have huge impact on practical applications. We have utilized bottom-up approaches to fabricate nacre-like nanocomposites with "brick and mortar" structures. First, we used self-assembly processes, including convective self-assembly, dip-coating, and electrophoretic deposition to form well oriented layer structure of synthesized gibbsite (aluminum hydroxide) nanoplatelets. Low viscous monomer was permeated into layered nanoplatelets and followed by photo-curing. Gibbsite-polymer composite displays 2 times higher tensile strength and 3 times higher modulus when compared with pure polymer. More improvement occurred when surface-modified gibbsite platelets were cross-linked with the polymer matrix. We observed ˜4 times higher strength and nearly 1 order of magnitude higher modulus than pure polymer. To further improve the mechanical strength and toughness of inorganicorganic nanocomposites, we exploited ultrastrong graphene oxide (GO), a single atom thick hexagonal carbon sheet with pendant oxidation groups. GO nanocomposite is made by co-filtrating GO/polyvinyl alcohol suspension on 0.2 im pore-sized membrane. It shows ˜2 times higher strength and ˜15 times higher ultimate strains than nacre and pure GO paper (also synthesized by filtration). Specifically, it exhibits ˜30 times higher fracture energy than filtrated graphene paper and nacre, ˜100 times tougher than filtrated GO paper. Besides reinforced nanocomposites, we further explored the self-assembly of spherical colloids and the templating nanofabrication of moth-eye-inspired broadband antireflection coatings. Binary crystalline structures can be easily accomplished by spin-coating double-layer nonclose-packed colloidal crystals as templates, followed by colloidal templating. The polymer matrix between self-assembled colloidal crystal has been used as a sacrificial template to define the resulting periodic binary nanostructures, including intercalated arrays of silica spheres and polymer posts, gold nanohole arrays with binary sizes, and dimple-nipple antireflection coatings. The binary-structured antireflection coatings exhibit better antireflective properties than unitary coatings. Natural optical structures and nanocomposites teach us a great deal on how to create high performance artificial materials. The bottom-up technologies developed in this thesis are scalable and compatible with standard industrial processes, promising for manufacturing high-performance materials for the benefits of human beings.

Huang, Wei-Han

122

Developments in nanostructured LiMPO4 (M = Fe, Co, Ni, Mn) composites based on three dimensional carbon architecture.  

PubMed

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. This review describes recent developments in the synthesis and characterization of composites which consist of lithium metal phosphates (LiMPO(4), M = Fe, Co, Ni, Mn) coated on nanostructured carbon architectures (unordered and ordered carbon nanotubes, amorphous carbon, carbon foams). The major goal of this review is to highlight new progress in using different three dimensional nanostructured carbon architectures as support for the phosphate based cathode materials (e.g.: LiFePO(4), LiCoPO(4)) of high electronic conductivity to develop lithium batteries with high energy density, high rate capability and excellent cycling stability resulting from their huge surface area and short distance for mass and charge transport. PMID:22491511

Dimesso, L; Förster, C; Jaegermann, W; Khanderi, J P; Tempel, H; Popp, A; Engstler, J; Schneider, J J; Sarapulova, A; Mikhailova, D; Schmitt, L A; Oswald, S; Ehrenberg, H

2012-04-10

123

Energy Absorption of Composite Materials.  

National Technical Information Service (NTIS)

This paper results of a study on the energy absorption characteristics of selected composite material systems and compares the results with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphi...

G. L. Farley

1983-01-01

124

Nanostructure multilayer materials for capacitor energy storage for EH vehicles  

SciTech Connect

Acceleration and regenerative breaking for electric and hybrid vehicles require high power capacitors to complement energy sources. Large, flat nanostructure multilayer capacitors (NMCS) can provide load balancing capacitance in EHVs of the future. Additional uses include snubber capacitors for power electronics such as motor drives, energy discharge capacitors for lasers, and numerous industrial and military electronics applications [1]. In the present work, we demonstrate the effectiveness of LLNL`s multilayer materials technology by fabricating NMC test films with high energy and power density.

Barbee, T.W. Jr.; Johnson, C.W.

1995-02-01

125

High thermoelectric performance via hierarchical compositionally alloyed nanostructures.  

PubMed

Previous efforts to enhance thermoelectric performance have primarily focused on reduction in lattice thermal conductivity caused by broad-based phonon scattering across multiple length scales. Herein, we demonstrate a design strategy which provides for simultaneous improvement of electrical and thermal properties of p-type PbSe and leads to ZT ~ 1.6 at 923 K, the highest ever reported for a tellurium-free chalcogenide. Our strategy goes beyond the recent ideas of reducing thermal conductivity by adding two key new theory-guided concepts in engineering, both electronic structure and band alignment across nanostructure-matrix interface. Utilizing density functional theory for calculations of valence band energy levels of nanoscale precipitates of CdS, CdSe, ZnS, and ZnSe, we infer favorable valence band alignments between PbSe and compositionally alloyed nanostructures of CdS1-xSex/ZnS1-xSex. Then by alloying Cd on the cation sublattice of PbSe, we tailor the electronic structure of its two valence bands (light hole L and heavy hole ?) to move closer in energy, thereby enabling the enhancement of the Seebeck coefficients and the power factor. PMID:23647245

Zhao, Li-Dong; Hao, Shiqiang; Lo, Shih-Han; Wu, Chun-I; Zhou, Xiaoyuan; Lee, Yeseul; Li, Hao; Biswas, Kanishka; Hogan, Timothy P; Uher, Ctirad; Wolverton, C; Dravid, Vinayak P; Kanatzidis, Mercouri G

2013-05-06

126

One-dimensional nanostructures as electrode materials for lithium-ion batteries with improved electrochemical performance  

Microsoft Academic Search

One-dimensional (1D) nanosize electrode materials of lithium iron phosphate (LiFePO4) nanowires and Co3O4–carbon nanotube composites were synthesized by the hydrothermal method. The as-prepared 1D nanostructures were structurally characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. We tested the electrochemical properties of LiFePO4 nanowires as cathode and Co3O4–carbon nanotubes as anode in lithium-ion cells, via cyclic voltammetry and

Guoxiu Wang; Xiaoping Shen; Jane Yao

2009-01-01

127

Micro- and Nanostructured Materials for Active Devices and Molecular Electronics  

SciTech Connect

Traditional single layer barrier coatings are not adequate in preventing degradation of the performance of organic molecular electronic and other active devices. Most advanced devices used in display technology now consist of micro and nanostructured small molecule, polymer and inorganic coatings with thin high reactive group 1A metals. This includes organic electronics such as organic light emitting devices (OLED). The lifetimes of these devices rapidly degrades when they are exposed to atmospheric oxygen and water vapor. Thin film photovoltaics and batteries are also susceptible to degradation by moisture and oxygen. Using in-line coating techniques we apply a composite nanostructured inorganic/polymer thin film barrier that restricts moisture and oxygen permeation to undetectable levels using conventional permeation test equipment. We describe permeation mechanisms for this encapsulation coating and flat panel display and other device applications. Permeation through the multilayer barrier coating is defect and pore limited and can be described by Knudsen diffusion involving a long and tortuous path. Device lifetime is also enhanced by the long lag times required to reach the steady state flux regime. Permeation rates in the range of 10-6 cc,g/m2/d have been achieved and OLED device lifetimes. The structure is robust, yet flexible. The resulting device performance and lifetimes will also be described. The barrier film can be capped with a thin film of transparent conductive oxide yielding an engineered nanostructured device for next generation, rugged, lightweight or flexible displays. This enables, for the first time, thin film encapsulation of emissive organic displays.

Martin, Peter M.; Graff, Gordon L.; Gross, Mark E.; Burrows, Paul E.; Bennett, Wendy D.; Mast, Eric S.; Hall, Michael G.; Bonham, Charles C.; Zumhoff, Mac R.; Williford, Rick E.

2003-10-01

128

Evaluation of different conductive nanostructured particles as filler in smart piezoresistive composites  

PubMed Central

This work presents a comparison between three piezoresistive composite materials based on nanostructured conductive fillers in a polydimethylsiloxane insulating elastomeric matrix for sensing applications. Without any mechanical deformation upon an applied bias, the prepared composites present an insulating electric behavior, while, when subjected to mechanical load, the electric resistance is reduced exponentially. Three different metal fillers were tested: commercial nickel and copper spiky-particles and synthesized highly-pointed gold nanostars. These particles were chosen because of their high electrical conductivity and especially for the presence of nanosized sharp tips on their surface. These features generate an enhancement of the local electric field increasing the tunneling probability between the particles. Different figures of merit concerning the morphology of the fillers were evaluated and correlated with the corresponding functional response of the composite.

2012-01-01

129

Nanostructuring of semiconductor materials and metallic thin films using femtosecond laser and scanning probe microscope  

Microsoft Academic Search

Ultra-short pulsed-laser radiation has been shown to be an effective tool for controlled material processing and surface nano\\/micro-modification because of minimal thermal and mechanical damage. Nanostructuring of a variety of materials is gaining widespread importance owing to ever-increasing applications of nanostructures in numerous fields. This study demonstrates that controllable surface nanostructuring can be achieved by effectively utilizing the local field

Anant Chimmalgi; Taeyul Choi; David Hwang; Constantine P. Grigoropoulos

2003-01-01

130

A study on thermoelectric properties of nanostructured bulk materials  

NASA Astrophysics Data System (ADS)

Solid-state cooling and power generation based on thermoelectric effects are attractive for a wide range of applications in power generation, waste heat recovery, air-conditioning, and refrigeration. There have been persistent efforts on improving figure of merit (ZT) since 1950's, but the ZTs of dominant commercial bulk materials have been remained at ˜1. To improve ZT to a higher value, we have been pursuing an approach based on random nanostructures, based on the idea that the thermal conductivity reduction that is responsible for ZT enhancement in superlattices can be realized in such nanostructures. In this dissertation I will discuss synthesis and characterization of various nanopowders prepared by chemical as well as high-energy ball milling methods. The solid dense samples from nanopowders were prepared by direct current induced hot press (DC hot press) technique. The thermoelectric properties of the hot pressed samples have been studied in detail. In our study, ZT values of ˜1.4 and ˜1.2 have been achieved in bulk p- and n-type bismuth telluride alloys respectively. More importantly, in the range of 20--250°C, ZT is above 0.8 with a peak ZT of 1.4 at 100°C in p-type sample, which makes it not only very useful for cooling but also very efficient for power generation with hot side close to 250°C, an efficiency not attainable before due to a reduction in ZT to below 0.25 at that temperature. Power generation efficiency and cooling performance using our hot-pressed samples show better performance than the commercially available samples of these materials. These bulk materials were made by DC hot press technique using nanopowders prepared by high energy ball milling. Microstructure studies and theoretical analysis indicated that the improvement mainly comes from a lower phonon contribution to thermal conductivity due to increased boundaries and defect states. Lead telluride, lead selenide and their alloys using a similar approach have also been studied. In p- and n-type alloys of PbSnTe and AgPbSbTe, ZTs higher than the state-of-the-art PbTe alloys are obtained. The discovery points a new direction to achieve higher ZT in other thermoelectric bulk materials, which we believe will change the thermoelectric energy conversion technology landscape. With the data we obtained, it is clear that a nanoparticle based thermoelectric materials hold significant promise. We already have demonstrated enhanced ZT values in various nanostructured materials and demonstrated the feasibility of the approach. We believe that continued investigation in this area should let us achieve superlattice-like figures of merit, based on these results.

Poudel, Bed

131

Nanomanufacturing : nano-structured materials made layer-by-layer.  

SciTech Connect

Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

Cox, James V.; Cheng, Shengfeng; Grest, Gary Stephen; Tjiptowidjojo, Kristianto (University of New Mexico); Reedy, Earl David, Jr.; Fan, Hongyou; Schunk, Peter Randall; Chandross, Michael Evan; Roberts, Scott A.

2011-10-01

132

Scalable synthesis of TiO2/graphene nanostructured composite with high-rate performance for lithium ion batteries.  

PubMed

A simple and scalable method is developed to synthesize TiO(2)/graphene nanostructured composites as high-performance anode materials for Li-ion batteries using hydroxyl titanium oxalate (HTO) as the intermediate for TiO(2). With assistance of a surfactant, amorphous HTO can condense as a flower-like nanostructure on graphene oxide (GO) sheets. By calcination, the HTO/GO nanocomposite can be converted to TiO(2)/graphene nanocomposite with well preserved flower-like nanostructure. In the composite, TiO(2) nanoparticles with an ultrasmall size of several nanometers construct the porous flower-like nanostructure which strongly attached onto conductive graphene nanosheets. The TiO(2)/graphene nanocomposite is able to deliver a capacity of 230 mA h g(-1) at 0.1 C (corresponding to a current density of 17 mA g(-1)), and demonstrates superior high-rate charge-discharge capability and cycling stability at charge/discharge rates up to 50 C in a half cell configuration. Full cell measurement using the TiO(2)/graphene as the anode material and spinel LiMnO(2) as the cathode material exhibit good high-rate performance and cycling stability, indicating that the TiO(2)/graphene nanocomposite has a practical application potential in advanced Li-ion batteries. PMID:23185962

Xin, Xing; Zhou, Xufeng; Wu, Jinghua; Yao, Xiayin; Liu, Zhaoping

2012-11-29

133

Thermal Characterization of Nanostructures and Advanced Engineered Materials  

NASA Astrophysics Data System (ADS)

Continuous downscaling of Si complementary metal-oxide semiconductor (CMOS) technology and progress in high-power electronics demand more efficient heat removal techniques to handle the increasing power density and rising temperature of hot spots. For this reason, it is important to investigate thermal properties of materials at nanometer scale and identify materials with the extremely large or extremely low thermal conductivity for applications as heat spreaders or heat insulators in the next generation of integrated circuits. The thin films used in microelectronic and photonic devices need to have high thermal conductivity in order to transfer the dissipated power to heat sinks more effectively. On the other hand, thermoelectric devices call for materials or structures with low thermal conductivity because the performance of thermoelectric devices is determined by the figure of merit Z=S2sigma/K, where S is the Seebeck coefficient, K and sigma are the thermal and electrical conductivity, respectively. Nanostructured superlattices can have drastically reduced thermal conductivity as compared to their bulk counterparts making them promising candidates for high-efficiency thermoelectric materials. Other applications calling for thin films with low thermal conductivity value are high-temperature coatings for engines. Thus, materials with both high thermal conductivity and low thermal conductivity are technologically important. The increasing temperature of the hot spots in state-of-the-art chips stimulates the search for innovative methods for heat removal. One promising approach is to incorporate materials, which have high thermal conductivity into the chip design. Two suitable candidates for such applications are diamond and graphene. Another approach is to integrate the high-efficiency thermoelectric elements for on-spot cooling. In addition, there is strong motivation for improved thermal interface materials (TIMs) for heat transfer from the heat-generating chip to heat-sinking units. This dissertation presents results of the experimental investigation and theoretical interpretation of thermal transport in the advanced engineered materials, which include thin films for thermal management of nanoscale devices, nanostructured superlattices as promising candidates for high-efficiency thermoelectric materials, and improved TIMs with graphene and metal particles as fillers providing enhanced thermal conductivity. The advanced engineered materials studied include chemical vapor deposition (CVD) grown ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on Si substrates, directly integrated nanocrystalline diamond (NCD) films on GaN, free-standing polycrystalline graphene (PCG) films, graphene oxide (GOx) films, and "pseudo-superlattices" of the mechanically exfoliated Bi2Te3 topological insulator films, and thermal interface materials (TIMs) with graphene fillers.

Goyal, Vivek Kumar

134

Composite material heat pipe radiator  

Microsoft Academic Search

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness

Nelson J. Gernert; David B. Sarraf; Richard J. Guenther

1996-01-01

135

Nanostructuring superconductors by ion beams: A path towards materials engineering  

NASA Astrophysics Data System (ADS)

The paper deals with nanostructuring of superconducting materials by means of swift heavy ion beams. The aim is to modify their structural, optical and electromagnetic properties in a controlled way, to provide possibility of making them functional for specific applications. Results are presented concerning flux pinning effects (implantation of columnar defects with nanosize cross section to enhance critical currents and irreversibility fields), confined flux-flow and vortex guidance, design of devices by locally tailoring the superconducting material properties, analysis of disorder-induced effects in multi-band superconductors. These studies were carried out on different kinds of superconducting samples, from single crystals to thin films, from superconducting oxides to magnesium diboride, to recently discovered iron-based superconductors.

Gerbaldo, Roberto; Ghigo, Gianluca; Gozzelino, Laura; Laviano, Francesco; Amato, Antonino; Rovelli, Alberto; Cherubini, Roberto

2013-07-01

136

Joining of composite materials  

SciTech Connect

This Conference Proceedings contains 9 papers, of which one is abstracted separately, describing the latest achievement in effective methods of joining of composite structures. Most composite systems do not deform plastically and thus cannot alleviate stress concentration. The papers cover the design, analysis, testing and inspection of joined interfaces. Data are given for both mechanically fastened and adhesively bonded joints.

Kedward, K.T.

1981-01-01

137

Materials for Hydrogen Storage: From Complex Hydrides to Functionalized Nanostructures  

NASA Astrophysics Data System (ADS)

The world wide effort for a transition to renewable and clean (i.e. carbon-free) form of energy has resulted in an upsurge of interest in harnessing and utilizing Hydrogen. Apart from being the most abundant element in the universe, hydrogen offers many advantages over other fuels: it is non-toxic, clean to use, and packs more energy per mass than any other fuel. Hydrogen energy production, storage and distribution constitute a multi-disciplinary area of research. Coming to the material issues for solid state storage of hydrogen, the most desirable criteria are high storage capacity, satisfactory kinetics, and optimal thermodynamics. Complex hydrides involving light metals, such as Alanates, Imides, Borates, Amidoboranes etc. show impressive gravimetric efficiencies, although the hydrogen desorption temperatures turn out to be rather high. Apart from complex hydrides, there are other kinds of novel materials that have been investigated, e.g. carbon based materials activated with nano-catalysts, clathrate hydrates, metal-organic complexes, and more recently nanostructured cages viz. fullerenes and nanotubes decorated with simple or transition metals that serve to attract hydrogen in molecular form. In this talk, after giving a broad overview on hydrogen economy, I shall focus on first-principles design of materials for hydrogen storage, from complex hydrides to various kinds of functinalized nanostructures, and discuss the recent results obtained in our laboratory [1-6]. Some outstanding issues and challenges, like how to circumvent the problem of metal clustering on surface, or how to bring down the hydrogen desorption temperature etc. will be discussed.

Das, G. P.

2011-07-01

138

Synthesis of nanostructured polymer materials with different morphologies: Nanoporous ordered networks and hollow capsules  

Microsoft Academic Search

Nanostructured polymer materials with interesting morphological variation, which include three dimensionally interconnected uniform nanoporous network arrays (volume- and surface-templated ordered arrays) and hollow core spheres were synthesized by inducing different polymerization process of phenol and formaldehyde as a precursor over silica templates (ordered silica colloidal crystals or individual silica particles). The pore sizes of the resulting nanostructured polymer materials can

Suk Bon Yoon; Soonki Kang; Jong-Sung Yu

2006-01-01

139

Multifunctional upconversion-magnetic hybrid nanostructured materials: synthesis and bioapplications.  

PubMed

The combination of nanotechnology and biology has developed into an emerging research area: nano-biotechnology. Upconversion nanoparticles (UCNPs) have attracted a great deal of attention in bioapplications due to their high chemical stability, low toxicity, and high signal-to-noise ratio. Magnetic nanoparticles (MNPs) are also well-established nanomaterials that offer controlled size, ability to be manipulated externally, and enhancement of contrast in magnetic resonance imaging (MRI). As a result, these nanoparticles could have many applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Because of the potential benefits of multimodal functionality in biomedical applications, researchers would like to design and fabricate multifunctional upconversion-magnetic hybrid nanostructured materials. The hybrid nanostructures, which combine UCNPs with MNPs, exhibit upconversion fluorescence alongside superparamagnetism property. Such structures could provide a platform for enhanced bioimaging and controlled drug delivery. We expect that the combination of unique structural characteristics and integrated functions of multifunctional upconversion-magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nano-bioapplications. PMID:23650477

Li, Xiaomin; Zhao, Dongyuan; Zhang, Fan

2013-03-21

140

Multifunctional Upconversion-Magnetic Hybrid Nanostructured Materials: Synthesis and Bioapplications  

PubMed Central

The combination of nanotechnology and biology has developed into an emerging research area: nano-biotechnology. Upconversion nanoparticles (UCNPs) have attracted a great deal of attention in bioapplications due to their high chemical stability, low toxicity, and high signal-to-noise ratio. Magnetic nanoparticles (MNPs) are also well-established nanomaterials that offer controlled size, ability to be manipulated externally, and enhancement of contrast in magnetic resonance imaging (MRI). As a result, these nanoparticles could have many applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Because of the potential benefits of multimodal functionality in biomedical applications, researchers would like to design and fabricate multifunctional upconversion-magnetic hybrid nanostructured materials. The hybrid nanostructures, which combine UCNPs with MNPs, exhibit upconversion fluorescence alongside superparamagnetism property. Such structures could provide a platform for enhanced bioimaging and controlled drug delivery. We expect that the combination of unique structural characteristics and integrated functions of multifunctional upconversion-magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nano-bioapplications.

Li, Xiaomin; Zhao, Dongyuan; Zhang, Fan

2013-01-01

141

Nano-Structured Li3V2(PO4)3 /Carbon Composite for High Rate Lithium Ion Batteries  

SciTech Connect

Nanostructured Li3V2(PO4)3 /carbon composite (Li3V2(PO4)3/C) is successfully prepared by incorporating precursor solution into expanded pore structure of highly mesoporous carbon. XRD, SEM and TEM are used to characterize the composite structure. The particles sizes of the samples are centered at ~ 20 nm and well dispersed in the carbon matrix. When cycled in a voltage range of 3-4.3 V, Li3V2(PO4)3/C cathode delivers a reversible capacity of 122 mAh g-1 at 1C-rate and maintains a specific discharge capacity of 83 mAh g-1 even at 32 C-rate. Therefore, nanostructured Li3V2(PO4)3 and mesoporous carbon composite has a great potential to be used as cathode material for high power lithium-ion batteries.

Pan, Anqiang; Liu, Jun; Zhang, Jiguang; Xu, Wu; Cao, Guozhong H.; Nie, Zimin; Arey, Bruce W.; Liang, Shu-quan

2010-09-22

142

Multiwavelength anomalous diffraction and diffraction anomalous fine structure to study composition and strain of semiconductor nanostructures. MAD and DAFS for studying Semiconductor Nanostructures  

NASA Astrophysics Data System (ADS)

The aim of this paper is to illustrate the use of Multi-Wavelength Anomalous Diffraction (MAD) and Diffraction Anomalous Fine Structure (DAFS) spectroscopy for the study of structural properties of semiconductor nanostructures. We give a brief introduction on the basic principles of these techniques providing a detailed bibliography. Then we focus on the data reduction and analysis and we give specific examples of their application on three different kinds of semiconductor nanostructures: Ge/Si nanoislands, AlN capped GaN/AlN Quantum Dots and AlGaN/AlN Nanowires. We show that the combination of MAD and DAFS is a very powerful tool to solve the structural problem of these materials of high technological impact. In particular, the effects of composition and strain on diffraction are disentangled and composition can be determined in a reliable way, even at the interface between nanostructure and substrate. We show the great possibilities of this method and give the reader the basic tools to undertake its use.

Favre-Nicolin, V.; Proietti, M. G.; Leclere, C.; Katcho, N. A.; Richard, M.-I.; Renevier, H.

2012-06-01

143

Reversibly assembled cellular composite materials.  

PubMed

We introduce composite materials made by reversibly assembling a three-dimensional lattice of mass-produced carbon fiber-reinforced polymer composite parts with integrated mechanical interlocking connections. The resulting cellular composite materials can respond as an elastic solid with an extremely large measured modulus for an ultralight material (12.3 megapascals at a density of 7.2 milligrams per cubic centimeter). These materials offer a hierarchical decomposition in modeling, with bulk properties that can be predicted from component measurements and deformation modes that can be determined by the placement of part types. Because site locations are locally constrained, structures can be produced in a relative assembly process that merges desirable features of fiber composites, cellular materials, and additive manufacturing. PMID:23950496

Cheung, Kenneth C; Gershenfeld, Neil

2013-08-15

144

Repeatable Hydrogen Storage using Nano-structured Graphite Materials  

NASA Astrophysics Data System (ADS)

Repeatable hydrogen adsorption and desorption with nano-structured graphite material (NSG) was confirmed using a high-accuracy volumetric measuring apparatus at room temperature [1]. The NSG was prepared from commercially obtained graphite powder with a purity of 99.997% (GoodFellow Cambridge Ltd.) using a mechanical milling process at a pressure of 2.0 x 10-4 Pa. The untreated graphite adsorbed 0.02wt% of hydrogen, while 0.20 - 0.25wt% of hydrogen can be repeatedly adsorbed by the NSG. Measurements of the hydrogen adsorption rate at constant pressure and pore-size distribution suggest that the hydrogen molecules are adsorbed through a diffusion process into pores with a diameter less than 1 nm. [1] H.Kajiura et al., APL82(2003)1929.

Kajiura, Hisashi; Kadono, Koji; Tsutsui, Shigemitsu; Murakami, Yousuke

2004-03-01

145

Mechanics of composite materials  

Microsoft Academic Search

The book presents a comprehensive account of the basic theory of the mechanical behavior of heterogeneous materials. Basic results of continuum mechanics concerning elasticity theory, viscoelasticity theory, plasticity theory and Eshelby's formula are summarized, and the stiffness or effective moduli of materials containing spherical inclusions and cylindrical and lamellar systems are examined in detail. Laminates are discussed, and the analysis,

R. M. Christensen

1979-01-01

146

Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO2), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO2), where lithium ions are inserted/deinserted into/out of the TiO2 crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs.

Wu, Hao Bin; Chen, Jun Song; Hng, Huey Hoon; Wen (David) Lou, Xiong

2012-03-01

147

Biotechnology and Composite Materials.  

National Technical Information Service (NTIS)

Biotechnology, in general terms, is the science and engineering of using living organisms for making useful products such as pharmaceuticals, foods, fuels, chemicals, materials or in waste treatment processes and clinical and chemical analyses. It encompa...

B. C. Woolsey R. Narayan R.C. Schiavone

1993-01-01

148

Forming nanostructured cubic trialuminide\\/carbide composites by mechanical milling followed by thermal processing  

Microsoft Academic Search

Milling titanium trialuminide and titanium powders with an organic process control agent (PCA) followed by annealing forms nanostructured (Al,Cr)3Ti\\/Ti2AlC composites. Composition of charge, milling time and PCA control final microstructure. Product is useful as thermal spray feedstock for oxidation and wear resistant composite coatings.

J. J. Le Claire; E. A. Laitila; D. E. Mikkola

2004-01-01

149

A nanostructured composite based on polyaniline and gold nanoparticles: synthesis and gas sensing properties  

NASA Astrophysics Data System (ADS)

Nanostructured composite materials based on polyaniline (PANI) and gold nanoparticles have been prepared by means of an osmosis based method. Several morphologies have been obtained for the pristine nanoPANI and for nanoPANI-Au composite, ranging from amorphous to sponge-like and spherical shapes. On the basis of this morphological investigation, different materials with high surface area have been selected and tested as chemical interactive materials for room temperature gas and vapor sensing. The resistive sensor devices have been exposed to different vapor organic compounds (VOCs) of interest in the fields of environmental monitoring and biomedical applications, such as toluene, acetic acid, ethanol, methanol, acetonitrile, water, ammonia and nitrogen dioxide. The effect of doping with H2SO4 has been studied for both nanoPANI and nanoPANI-Au samples. In particular, nanoPANI-Au showed sensitivity to ammonia (up to 10 ppm) higher than that to other VOCs or interfering analytes. The facile preparation method and the improved properties achieved for the polyaniline-gold composite materials are significant in the nanomaterials field and have promise for applications in ammonia vapor monitoring.

Venditti, Iole; Fratoddi, Ilaria; Vittoria Russo, Maria; Bearzotti, Andrea

2013-04-01

150

A nanostructured composite based on polyaniline and gold nanoparticles: synthesis and gas sensing properties.  

PubMed

Nanostructured composite materials based on polyaniline (PANI) and gold nanoparticles have been prepared by means of an osmosis based method. Several morphologies have been obtained for the pristine nanoPANI and for nanoPANI-Au composite, ranging from amorphous to sponge-like and spherical shapes. On the basis of this morphological investigation, different materials with high surface area have been selected and tested as chemical interactive materials for room temperature gas and vapor sensing. The resistive sensor devices have been exposed to different vapor organic compounds (VOCs) of interest in the fields of environmental monitoring and biomedical applications, such as toluene, acetic acid, ethanol, methanol, acetonitrile, water, ammonia and nitrogen dioxide. The effect of doping with H2SO4 has been studied for both nanoPANI and nanoPANI-Au samples. In particular, nanoPANI-Au showed sensitivity to ammonia (up to 10 ppm) higher than that to other VOCs or interfering analytes. The facile preparation method and the improved properties achieved for the polyaniline-gold composite materials are significant in the nanomaterials field and have promise for applications in ammonia vapor monitoring. PMID:23518508

Venditti, Iole; Fratoddi, Ilaria; Russo, Maria Vittoria; Bearzotti, Andrea

2013-03-22

151

Fracture mechanics of composite materials  

Microsoft Academic Search

The above circumstances lead to models based on a discussion of the structure of a composite being used most frequently in the fracture mechanics of composite materials. In view of the stochastic properties of the elements in the structure, especially the dispersion in the strength of the fibers, stochastic fracture models are widely used [4-7]. Nevertheless, there has been no

V. V. Bolotin

1981-01-01

152

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

153

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

154

High strain sustaining, nitrile rubber based, large-area, superhydrophobic, nanostructured composite coatings  

Microsoft Academic Search

Elastomeric superhydrophobic nanostructured composite coatings scalable to large areas are prepared by spray casting particle-polymer dispersions. The dispersions consist of nanostructured carbon black particles along with submicrometer-sized poly(tetrafluoroethylene) particles dispersed in nitrile rubber solution in acetone, with the goal to attain superhydrophobicity with minimal content of particle fillers. The coatings are applied on various flexible substrates, which are subsequently stretched

Thomas M. Schutzius; Manish K. Tiwari; Ilker S. Bayer; Constantine M. Megaridis

2011-01-01

155

Nanostructured Composite Electrodes for Lithium Batteries (Final Technical Report)  

Microsoft Academic Search

The objective of this study was to explore new ways to create nanostructured electrodes for rechargeable lithium batteries. Of particular interests are unique nanostructures created by electrochemical deposition, etching and combustion chemical vapor deposition (CCVD). Three-dimensional nanoporous Cu6Sn5 alloy has been successfully prepared using an electrochemical co-deposition process. The walls of the foam structure are highly-porous and consist of numerous

Meilin Liu; James Gole

2006-01-01

156

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

157

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. 10 figs.

Dunmead, S.D.; Holt, J.B.; Kingman, D.D.; Munir, Z.A.

1988-10-21

158

Nanostructured Magnetic Materials, Final Report, July 1, 2009-June 30, 2011.  

National Technical Information Service (NTIS)

This report describes progress made during the final phase of our DOE-funded program on Nanostructured Magnetic Materials. This period was quite productive, resulting in the submission of three papers and presentation of three talks at international confe...

A. Schwartz C. M. Falco

2012-01-01

159

Composition, nanostructure, and optical properties of silver and silver-copper lusters  

SciTech Connect

Lusters are composite thin layers of coinage metal nanoparticles in glass displaying peculiar optical properties and obtained by a process involving ionic exchange, diffusion, and crystallization. In particular, the origin of the high reflectance (golden-shine) shown by those layers has been subject of some discussion. It has been attributed to either the presence of larger particles, thinner multiple layers or higher volume fraction of nanoparticles. The object of this paper is to clarify this for which a set of laboratory designed lusters are analysed by Rutherford backscattering spectroscopy, transmission electron microscopy, x-ray diffraction, and ultraviolet-visible spectroscopy. Model calculations and numerical simulations using the finite difference time domain method were also performed to evaluate the optical properties. Finally, the correlation between synthesis conditions, nanostructure, and optical properties is obtained for these materials.

Pradell, Trinitat; Pavlov, Radostin S. [Center for Research in NanoEngineering, Universitat Politecnica de Catalunya and Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Campus Baix Llobregat, ESAB, Esteva Terrades 8, 08860 Castelldefels, Barcelona (Spain); Carolina Gutierrez, Patricia; Climent-Font, Aurelio [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid, 28049 Madrid, Spain and Departamento de Fisica Aplicada, C-XII, Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Molera, Judit [GRTD, Escola Politecnica Superior, Universitat de Vic. C. de la Laura, 13, 08500 Vic (Spain)

2012-09-01

160

Nanostructured composites obtained by ATRP sleeving of bacterial cellulose nanofibers with acrylate polymers.  

PubMed

Novel nanostructured composite materials based on bacterial cellulose membranes (BC) and acrylate polymers were prepared by in situ atom transfer radical polymerization (ATRP). BC membranes were functionalized with initiating sites, by reaction with 2-bromoisobutyryl bromide (BiBBr), followed by atom transfer radical polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA), catalyzed by copper(I) bromide and N,N,N',N?,N?-pentamethyldiethylenetriamine (PMDETA), using two distinct initiator amounts and monomer feeds. The living characteristic of the system was proven by the growth of PBA block from the BC-g-PMMA membrane. The BC nanofiber sleeving was clearly demonstrated by SEM imaging, and its extent can be tuned by controlling the amount of initiating sites and the monomer feed. The ensuing nanocomposites showed high hydrophobicity (contact angles with water up to 134°), good thermal stability (initial degradation temperature in the range 241-275 °C), and were more flexible that the unmodified BC membranes. PMID:23692287

Lacerda, Paula S S; Barros-Timmons, Ana M M V; Freire, Carmen S R; Silvestre, Armando J D; Neto, Carlos P

2013-05-21

161

Nanostructure control of graphene-composited TiO2 by a one-step solvothermal approach for high performance dye-sensitized solar cells  

NASA Astrophysics Data System (ADS)

We present a one-step solvothermal approach to prepare uniform graphene-TiO2 nanocomposites with delicately controlled TiO2 nanostructures, including ultra-small 2 nm nanoparticles, 12 nm nanoparticles and nanorods. Using three composites as photoanode materials, the effect of nanostructure of graphene-composited TiO2 on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO2-graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%.We present a one-step solvothermal approach to prepare uniform graphene-TiO2 nanocomposites with delicately controlled TiO2 nanostructures, including ultra-small 2 nm nanoparticles, 12 nm nanoparticles and nanorods. Using three composites as photoanode materials, the effect of nanostructure of graphene-composited TiO2 on the performance of dye-sensitized solar cells was investigated, and results showed that the ultra-small 2 nm TiO2-graphene composite based photoanode exhibited the highest power conversion efficiency of 7.25%. Electronic supplementary information (ESI) available: Detailed experimental procedures, AFM images, SEM images, J-V curves for optimization, and tables containing EDX results, BET results and calculation data. See DOI: 10.1039/c1nr11300c

He, Ziming; Guai, Guanhong; Liu, Jing; Guo, Chunxian; Chye Loo, Joachim Say; Li, Chang Ming; Tan, Timothy Thatt Yang

2011-11-01

162

Organic photonic devices utilizing nano-structured materials  

NASA Astrophysics Data System (ADS)

The characteristics of organic photonic devices with various kinds of geometrical nano-structures at the interface between organic materials, and also between the organic layer and metal electrode are investigated. A cutoff frequency of more than 20 MHz was observed for single-layer heterostructure organic photodetector (OPD) by applying a reverse bias electric field under the illumination of the red repetition pulse light. The mixed-layer heterostructure OPD with high photocurrent and high speed photoresponse is suitable for the application of optical link devices. An organic light-emitting diode (OLED) with a partial doping layer at the interface of heterostructure device can be expected to improve the modulation characteristics. The existence of interface between the organic layer and Cs or CsF results in low turn-on voltage for OLEDs. To achieve the efficient electron injection, it is necessary to exist Cs layer just on the organic layer. The efficient electron injection and the low turn-on voltage result from the coexistence of MgAg and CsF at the position of approximately 1 nm from organic layer. The poly(3-hexylthiophene) device with a cathode fabricated from Ag nanoparticles shows a photoresponse and a red emission in the reverse and forward bias regions, respectively. We demonstrated the possibility of polymer OLEDs using a cathode fabricated from Ag nanoparticles by wet processing.

Kajii, H.; Morimune, T.; Maki, H.; Hino, Y.; Kin, Z.; Ohmori, Y.

2006-03-01

163

Thermoelectric figure of merit for bulk nanostructured composites with distributed parameters  

SciTech Connect

The effective properties of composites whose structure includes nanocontacts between bulk-phase macrocrystallites are considered. A model for such a nanostructured composite is constructed. Effective values of the thermoelectric power, thermal and electrical conductivities, and thermoelectric figure of merit are calculated in the mean-field approximation.

Snarskii, A. A. [National Technical University 'Kyiv Polytechnic Institute' (Ukraine); Sarychev, A. K. [Russian Academy of Sciences, Institute for Theoretical and Applied Electromagnetics (Russian Federation); Bezsudnov, I. V., E-mail: biv@akuan.ru ['Nauka-Service' Scientific and Production Company (Russian Federation); Lagarkov, A. N. [Russian Academy of Sciences, Institute for Theoretical and Applied Electromagnetics (Russian Federation)

2012-05-15

164

Bioactivity and structural properties of nanostructured bulk composites containing Nb2O5 and natural hydroxyapatite  

NASA Astrophysics Data System (ADS)

In this work, we investigate the bioactivity and structural properties of nanostructured bulk composites that are composed of Nb2O5 and natural hydroxyapatite (HAp) and are produced by mechanical alloying and powder metallurgy. X-ray diffraction and Raman spectroscopy data showed that the milling process followed by a heat treatment at 1000 °C induced chemical reactions along with the formation of the CaNb2O6, PNb9O25 and Ca3(PO4)2 phases. Rietveld refinement indicated significant changes in each phase weight fraction as a function of HAp concentration. These changes influenced the in vitro bioactivity of the material. XRD and FTIR analyses indicated that the composites exhibited bioactivity characteristics by forming a carbonated apatite layer when the composites were immersed in a simulated body fluid. The formed layers had a maximum thickness of 13 ?m, as measured by confocal Raman spectroscopy and as confirmed by scanning electron microscopy. The results of this work suggest that the tested bulk composites are promising biomaterials for use in implants.

Bonadio, T. G. M.; Sato, F.; Medina, A. N.; Weinand, W. R.; Baesso, M. L.; Lima, W. M.

2013-06-01

165

Complex nanostructured materials from segmented copolymers prepared by ATRP  

Microsoft Academic Search

:   The development of new controlled\\/living radical polymerization processes, such as Atom Transfer Radical Polymerization (ATRP)\\u000a and other techniques such as nitroxide mediated polymerization and degenerative transfer processes, including RAFT, opened\\u000a the way to the use of radical polymerization for the synthesis of well-defined, complex functional nanostructures. The development\\u000a of such nanostructures is primarily dependent on self-assembly of well-defined segmented

T. Kowalewski; R. D. McCullough; K. Matyjaszewski

2003-01-01

166

Investigation of the dynamics of radiolytic formation of ZnO nanostructured materials by pulse radiolysis  

NASA Astrophysics Data System (ADS)

ZnO nanostructures have been synthesized by radiolytic methods. A Cobalt-60 ?-source and a 7 MeV linear electron accelerator (LINAC) was used for the radiolysis experiments. Reducing agent like hydrated electron (eaq-), which is produced in radiolysis of water, was used to synthesize ZnO nanostructure materials from zinc salt. 1 M tert-butanol was used to quench the primary oxidizing radical like hydroxyl radical (OH) radiolytic water solution. Doses of about 80 130 kGy were used to perform radiolysis experiments in the present investigation. Time-resolved pulse radiolysis has been used to monitor the transient species involved in the formation of ZnO nanostructures by monitoring at different wavelengths. A scheme for the formation of the ZnO nanostructured materials by the radiolytic method has been described. The formation of ZnO nanostructures was confirmed by X-ray diffraction (XRD) measurements. Dynamic light scattering (DLS) measurements indicated that the size of the nanostructures is in the range of 6 8 nm, which is in agreement with that obtained from XRD. It is interesting to note that ZnO nanostructured materials, as prepared by the radiolytic method, exhibit strong room-temperature fluorescence.

Rath, M. C.; Sunitha, Y.; Ghosh, H. N.; Sarkar, S. K.; Mukherjee, T.

2009-02-01

167

Composite containing coated fibrous material  

SciTech Connect

This patent describes a process for producing a composite containing at least about 10% by volume of boron nitride coated fibrous material and having a porosity of less than about 20% by volume. It comprises: forming a slurry of infiltration-promoting material and organic binding material in a liquid medium; depositing a coating of boron nitride on fibrous material leaving no significant portion thereof exposed; depositing a silicon-wettable coating on the boron nitride-coated fibrous material leaving no significant portion of the boron nitride exposed; providing the resulting coated fibrous material substantially as a layer; casting the slurry onto the coated fibrous material in an amount sufficient to form a tape therewith; evaporating the liquid medium forming a tape; firing the tape to remove the organic binding material producing a porous body; providing an infiltrant comprised of boron and silicon containing elemental boron in solution in silicon in an amount of at least about 0.1% by weight of elemental silicon; contacting the porous body with infiltrant associated infiltrating means whereby the infiltrant is infiltrated into the porous body; heating the resulting assembly in a partial vacuum to a temperature at which the infiltrant is molten and infiltrating the molten infiltrant into the porous body to produce an infiltrated product; and cooling the product producing the composite.

Singh, R.N.; Gaddipati, A.R.

1989-12-26

168

Joining of polymer composite materials  

SciTech Connect

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

Magness, F.H.

1990-11-01

169

Modern Carbon Composite Brake Materials  

Microsoft Academic Search

Carbon-carbon composites used in friction systems are becoming increasingly popular in aircrafts owing to their combination of low weight and high performance. Their current acceptance as brake materials is somewhat restrained due to two factors: cost and performance variations. Many manufacturers are taking steps toward improving their cost efficiency by utilizing lower cost precursor fibers and processing methodologies. At the

Christopher Byrne

2004-01-01

170

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

171

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.

172

Hydrothermal carbon-based nanostructured hollow spheres as electrode materials for high-power lithium-sulfur batteries.  

PubMed

Carbon hollow spheres were produced using a sustainable approach, i.e. hydrothermal carbonization, using monosaccharides as carbon precursors and silica nanoparticles as hard-templates. Hydrothermal carbonization is an eco-efficient and cost-effective route to synthesize nanostructured carbonaceous materials from abundant biomass-derived molecules. After further thermal treatment under an inert atmosphere and removal of the silica-based core by chemical etching, porous hollow spheres depicting 5-8 nm thin shells were obtained. Subsequently, carbon-sulfur composites were synthesized via a melt diffusion method and used as nanostructured composites for cathodes in lithium-sulfur (Li-S) cells. The morphology of the hollow spheres was controlled and optimized to achieve improved electrochemical properties. Both high specific energies and high specific powers were obtained, due to the unique nanostructure of the hollow spheres. These results revealed that using optimized carbonaceous materials, it is possible to design sustainable Li-S cells showing promising electrochemical properties. PMID:23493908

Brun, Nicolas; Sakaushi, Ken; Yu, Linghui; Giebeler, Lars; Eckert, Jürgen; Titirici, Magdalena M

2013-03-15

173

Nanostructured energetic materials using sol–gel methodologies  

Microsoft Academic Search

We have utilized a sol–gel synthetic approach in preparing nano-sized transition metal oxide components for new energetic nanocomposites. Nanocomposites of Fe2O3\\/Al(s), are readily produced from a solution of Fe(III) salt by adding an organic epoxide and a powder of the fuel metal. These materials can be processed to aerogel or xerogel monolithic composite solids. High resolution transmission electron microscopy (HRTEM)

T. M. Tillotson; A. E. Gash; R. L. Simpson; L. W. Hrubesh; J. H. Satcher; J. F. Poco

2001-01-01

174

Synthesis and applications of bioinspired inorganic nanostructured materials  

NASA Astrophysics Data System (ADS)

Although the study of biominerals may be traced back many centuries, it is only recently that biological principles have been applied to synthetic systems in processes termed "biomimetic" and "bioinspired" to yield materials syntheses that are otherwise not possible and may also reduce the expenditure of energy and/or eliminate toxic byproducts. Many investigators have taken inspiration from interesting and unusual minerals formed by organisms, in a process termed biomineralisation, to tailor the nanostructure of inorganic materials not necessarily found biogenically. However, the fields of nanoparticle synthesis and biomineralisation remain largely separate, and this thesis is an attempt to apply new studies on biomineralisation to nanomaterials science. Principally among the proteins that influence biomineralisation is a group comprised largely of negatively charged aspartic acid residues present in serum. This study is an investigation determining the ability of these serum proteins and other anolagous biomolecules to stabilise biologically relevant amorphous minerals and influence the formation of a variety of materials at the nanoscale. Three different materials were chosen to demonstrate this effect; gold was templated into nanosized single crystals by the action of bioorganic molecules, and the utility of these nanoparticles as a biosensor was explored. The influence of bioorganic molecules on the phase selection and crystal size restriction of titanium dioxide, an important semiconductor with many applications, was explored. The use of bioorganically derived nanoparticles of titanium dioxide was then demonstrated as a highly efficient photocatalyst. Finally, calcium carbonate, a prevalent biomineral was shown to form highly ordered structures over a variety of length scales and different crystalline polymorphs under the influence of a templating protein. In addition, an alternative route to producing calcium phosphate nanoparticle dispersions by mechanical filtration was explored and use as a transfection vector was optimised in two cell lines. Several significant achievements are presented: (i) the assessment of the relative ability of serum, serum derived proteins and their analogues to stabilize the amorphous state, (ii) the formation of single crystalline gold templated by an antibody, (iii) the formation of highly photocatalytically active nanoparticulate anatase by a phosphorylated cyclic esther, (iv) the formation of conical structures at the air liquid interface by the templating ability of a protein and (v) the optimisation of calcium phosphate nanoparticle mediated transfection in two cell lines by mechanical filtration.

Bassett, David C.

175

Composite materials and their use in structures  

Microsoft Academic Search

This book attempts to provide a basic fundamental understanding of the physical and mathematical aspects of the materials system and structures comprised of composite materials. The introduction discusses the nature and scope of composite materials, the strengthening processes used in the manufacture of alloys, and the needs for composite materials. Then various types of fiber-reinforced materials are examined, first by

J. R. Vinson; T. W. Chou

1975-01-01

176

Nanostructured Nb reinforced NiTi shape memory alloy composite with high strength and narrow hysteresis  

NASA Astrophysics Data System (ADS)

An in-situ nanostructured Nb reinforced NiTi shape-memory alloy composite was fabricated by mechanical reduction of an as-cast Nb-NiTi eutectic alloy. The composite exhibits large elastic strain, high strength, narrow hysteresis, and high mechanical energy storage density and efficiency during tensile cycling. In situ synchrotron high-energy X-ray diffraction revealed that these superior properties were attributed to the strong coupling between nanostructured Nb and NiTi matrix during deformation. Furthermore, this study offers a good understanding of the deformation behavior of the nanoscale reinforcement embedded in the metal matrix deformed by stress-induced phase transformation.

Hao, Shijie; Cui, Lishan; Jiang, Daqiang; Yu, Cun; Jiang, Jiang; Shi, Xiaobin; Liu, Zhenyang; Wang, Shan; Wang, Yandong; Brown, Dennis E.; Ren, Yang

2013-06-01

177

Nanostructured energetic materials using sol-gel methodologies  

SciTech Connect

The fundamental differences between energetic composites and energetic materials made from a monomolecular approach are the energy density attainable and the energy release rates. For the past 4 years, we have been exploiting sol-gel chemistry as a route to process energetic materials on a microstructural scale. At the last ISA conference, we described four specific sol-gel approaches to fabricating energetic materials and presented our early work and results on two methods - solution crystallization and powder addition. Here, we detail our work on a third approach, energetic nanocomposites. Synthesis of thermitic types of energetic nanocomposites are presented using transition and main group metal-oxide skeletons. Results on characterization of structure and performance will also be given.

Tillotson, T M; Simpson, R L; Hrubesh, L W; Gash, A E; Thomas, I M; Poco, J F

2000-09-27

178

Gold nanostructures: a class of multifunctional materials for biomedical applications.  

PubMed

Gold nanostructures have proven to be a versatile platform for a broad range of biomedical applications, with potential use in numerous areas including: diagnostics and sensing, in vitro and in vivo imaging, and therapeutic techniques. These applications are possible because of the highly favorable properties of gold nanostructures, many of which can be tailored for specific applications. In the first part of this tutorial review, we will discuss the most critical properties of gold nanostructures for biomedical applications: surface chemistry, localized surface plasmon resonance (LSPR), and morphology. In the second part of the review, we will discuss how these properties can be harnessed for a selection of biomedical applications, aiming to give the reader an overview of general strategies as well as highlight some recent advances in this field. PMID:20818451

Cobley, Claire M; Chen, Jingyi; Cho, Eun Chul; Wang, Lihong V; Xia, Younan

2010-09-06

179

Modeling and characterization of the elastic behavior of interfaces in nanostructured materials: From an atomistic description to a continuum approach  

NASA Astrophysics Data System (ADS)

Steady technological progresses in all fields of nanoscale technology and probe technology have enabled the synthesis, the assembly, the development, the characterization and the improvement of nanostructured materials. The lack of understanding of their macroscopic behavior is a major roadblock for inserting these materials into engineering applications. Partially due to these rapid advances in nano-scale and nano-structured materials, there has been a resurgence of interest in surface elastic properties such as surface energy, surface stresses, and surface elastic stiffness. Because of the large surface-to-volume ratio in nano-materials, surface elastic properties become more prominent. They have strong influence on the overall thermo-mechanical behavior of the nano-materials. In this dissertation, an innovative approach combining continuum mechanics and atomistic simulations is exposed to develop a nanomechanics theory for modeling and predicting the macroscopic behavior of nanomaterials. This nanomechanics theory exhibits the simplicity of the continuum formulation while taking into account the discrete atomic structure and interaction near surfaces/interfaces. There are four primary objectives to this dissertation. First, theory of interfaces is revisited to better understand its behavior and effects on the overall behavior of nanostructures. Second, atomistic tools are provided in order to efficiently determine the properties of free surfaces and interfaces. Interface properties are reported in this work, with comparison to both theoretical and experimental characterizations of interfaces. Specifically, we report surface elastic properties of groups 10--11 transition metals as well as properties for low-CSL grain boundaries in copper. Third, we propose a continuum framework that casts the atomic level information into continuum quantities that can be used to analyze, model and simulate macroscopic behavior of nanostructured materials. In particular, we study the effects of surface free energy on the effective modulus of nano-particles, nano-wires and nano-films as well as nanostructured crystalline materials and propose a general framework valid for any shape of nanostructural elements/nano-inclusions (integral forms) that characterizes the size-dependency of the elastic properties. This approach bridges the gap between discrete systems (atomic level interactions) and continuum mechanics. Finally this continuum outline is used to understand the effects of surfaces on the overall behavior of nano-size structural elements (particles, films, fibers, etc.) and nanostructured materials. More specifically we will discuss the impact of surface relaxation, surface elasticity and non-linearity of the underlying bulk on the properties nanostructured materials. In terms of engineering applications, this approach proves to be a useful tool for multi-scale modeling of heterogeneous materials with nanometer scale microstructures and provides insights on surface properties for several material systems; these will be very useful in many fields including surface science, tribology, fracture mechanics, adhesion science and engineering, and more. It will accelerate the insertion of nano-size structural elements, nano-composite and nanocrystalline materials into engineering applications.

Dingreville, Remi

180

Reliable contact fabrication on nanostructured Bi2Te3-based thermoelectric materials.  

PubMed

A cost-effective and reliable Ni-Au contact on nanostructured Bi2Te3-based alloys for a solar thermoelectric generator (STEG) is reported. The use of MPS SAMs creates a strong covalent binding and more nucleation sites with even distribution for electroplating contact electrodes on nanostructured thermoelectric materials. A reliable high-performance flat-panel STEG can be obtained by using this new method. PMID:23531997

Feng, Shien-Ping; Chang, Ya-Huei; Yang, Jian; Poudel, Bed; Yu, Bo; Ren, Zhifeng; Chen, Gang

2013-03-27

181

Investigation of the dynamics of radiolytic formation of ZnO nanostructured materials by pulse radiolysis  

Microsoft Academic Search

ZnO nanostructures have been synthesized by radiolytic methods. A Cobalt-60 gamma-source and a 7 MeV linear electron accelerator (LINAC) was used for the radiolysis experiments. Reducing agent like hydrated electron (eaq-), which is produced in radiolysis of water, was used to synthesize ZnO nanostructure materials from zinc salt. 1 M tert-butanol was used to quench the primary oxidizing radical like

M. C. Rath; Y. Sunitha; H. N. Ghosh; S. K. Sarkar; T. Mukherjee

2009-01-01

182

Investigation of the dynamics of radiolytic formation of ZnO nanostructured materials by pulse radiolysis  

Microsoft Academic Search

ZnO nanostructures have been synthesized by radiolytic methods. A Cobalt-60 ?-source and a 7MeV linear electron accelerator (LINAC) was used for the radiolysis experiments. Reducing agent like hydrated electron (eaq?), which is produced in radiolysis of water, was used to synthesize ZnO nanostructure materials from zinc salt. 1M tert-butanol was used to quench the primary oxidizing radical like hydroxyl radical

M. C. Rath; Y. Sunitha; H. N. Ghosh; S. K. Sarkar; T. Mukherjee

2009-01-01

183

Bimetallic Janus nanostructures via programmed shell growth  

NASA Astrophysics Data System (ADS)

We report the synthesis of compositionally asymmetric, core-Janus shell plasmonic nanostructures comprised of Au and Ag. Kinetic control was employed to achieve asymmetric shell growth on Au nanoparticles acting as cores. Subsequent differential surface functionalization of these nanostructures enabled programmed shell growth resulting in core-Janus shell nanostructures. UV/vis extinction spectra reveal that the localized surface plasmon resonance of the nanostructures depends on the composition and distribution of the components, providing additional handles to tune the optical properties of metal nanostructures. The core-Janus shell nanostructures demonstrated here are highly Raman-active making them attractive candidates for Raman-based biosensing and bioimaging applications.We report the synthesis of compositionally asymmetric, core-Janus shell plasmonic nanostructures comprised of Au and Ag. Kinetic control was employed to achieve asymmetric shell growth on Au nanoparticles acting as cores. Subsequent differential surface functionalization of these nanostructures enabled programmed shell growth resulting in core-Janus shell nanostructures. UV/vis extinction spectra reveal that the localized surface plasmon resonance of the nanostructures depends on the composition and distribution of the components, providing additional handles to tune the optical properties of metal nanostructures. The core-Janus shell nanostructures demonstrated here are highly Raman-active making them attractive candidates for Raman-based biosensing and bioimaging applications. Electronic supplementary information (ESI) available: Materials and methods. See DOI: 10.1039/c3nr34321a

Gandra, Naveen; Portz, Christopher; Singamaneni, Srikanth

2013-02-01

184

Tuning the composition and nanostructure of Pt/Ir films via anodized aluminum oxide templated atomic layer deposition.  

SciTech Connect

Nanostructured metal films have been widely studied for their roles in sensing, catalysis, and energy storage. In this work, the synthesis of compositionally controlled and nanostructured Pt/Ir films by atomic layer deposition (ALD) into porous anodized aluminum oxide templates is demonstrated. Templated ALD provides advantages over alternative synthesis techniques, including improved film uniformity and conformality as well as atomic-scale control over morphology and composition. Nanostructured Pt ALD films are demonstrated with morphological control provided by the Pt precursor exposure time and the number of ALD cycles. With these approaches, Pt films with enhanced surface areas, as characterized by roughness factors as large as 310, are reproducibly synthesized. Additionally, nanostructured Ptlr alloy films of controlled composition and morphology are demonstrated by templated ALD, with compositions varying systematically from pure Pt to pure Ir. Lastly, the application of nanostructured Pt films to electrochemical sensing applications is demonstrated by the non-enzymatic sensing of glucose.

Comstock, D. J.; Christensen, S. T.; Elam, J. W.; Pellin, M. J.; Hersam, M. C.; Northwestern Univ.

2010-09-23

185

Nanostructured Materials Synthesis Using Hypersonic Plasma Particle Deposition  

NASA Astrophysics Data System (ADS)

We (Work performed with P. H. McMurry, J. V. R. Heberlein, N. Rao and H. J. Lee) report a new deposition process in which ultrafine particles nucleate in a thermal plasma undergoing a supersonic expansion and are deposited on a substrate by hypersonic impaction. The objective of this process is to produce nanostructured material at high rates without having to collect and process a loose powder. Preliminary experiments in which silicon was synthesized by injecting vapor-phase silicon tetrachloride into an argon-hydrogen plasma produced in 20 minutes a deposit measuring approximately 1.3 mm thick and 5 mm in diameter, for a linear growth rate of about 1 um/s. In these experiments the plasma was generated by a DC torch operating at 200 A and 40 V. Flow rates were: argon, 35 slm; hydrogen, 4 slm; and SiCl_4, 0.2 slm. In previous experiments with similar operating conditions footnote N Rao, B. Micheel, D. Hansen, C. Fandrey, M. Bench, S. Girshick, J. Heberlein and P. McMurry, J. Mater. Res. 10, 2973 (1995); N. Rao, S. Girshick, J. Heberlein, P. McMurry, S. Jones, D. Hansen and B. Micheel, Plasma Chem. Plasma Process. 15, 581 (1995), the expansion of this mixture through a converging nozzle produced a silicon aerosol with a number-mean particle diameter of about 10 nm. In the present experiments the boron nitride nozzle was lengthened from 5 mm to 10 mm. The pressure was 66 kPa (500 torr) upstream of the nozzle and 0.3 kPa (2.5 torr) in the deposition chamber, driving a hypersonic flow which is capable of depositing particles down to about 3 nm in diameter by inertial impaction. The particle deposition process was recorded by a telemicroscope video camera, and deposits were characterized by scanning electron microscopy, x-ray diffraction, atomic force microscopy, and energy-dispersive x-ray analysis. The grain size of the deposit is expected to depend on substrate temperature, an effect which we are presently studying.

Girshick, Steven L.

1996-10-01

186

A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties.  

PubMed

Textiles can provide a suitable substrate to grow micro-organisms especially at appropriate humidity and temperature in contact to human body. Recently, increasing public concern about hygiene has been driving many investigations for anti-microbial modification of textiles. However, using many anti-microbial agents has been avoided because of their possible harmful or toxic effects. Application of inorganic nano-particles and their nano-composites would be a good alternative. This review paper has focused on the properties and applications of inorganic nano-structured materials with good anti-microbial activity potential for textile modification. The discussed nano-structured anti-microbial agents include TiO(2) nano-particles, metallic and non-metallic TiO(2) nano-composites, titania nanotubes (TNTs), silver nano-particles, silver-based nano-structured materials, gold nano-particles, zinc oxide nano-particles and nano-rods, copper nano-particles, carbon nanotubes (CNTs), nano-clay and its modified forms, gallium, liposomes loaded nano-particles, metallic and inorganic dendrimers nano-composite, nano-capsules and cyclodextrins containing nano-particles. This review is also concerned with the application methods for the modification of textiles using nano-structured materials. PMID:20417070

Dastjerdi, Roya; Montazer, Majid

2010-03-30

187

Nonlinear optical spectroscopy and imaging of photonic materials and nanostructures  

NASA Astrophysics Data System (ADS)

We investigated the nonlinear optical susceptibilities, the nonlinear absorption coefficients and the nonlinear transmission properties of various photonic glasses and crystals. The enhancement of the nonlinear absorption coefficient due to Two-Photon Absorption (TPA) in structural and optical defects in fused silica materials was explored. The correlation between the presence of defects and the increase in TPA was then used to propose a novel in situ 2-D mapping technique for defect detection when growing Potassium Dihydrogen Phosphate (KDP) crystals and their analogs. Open and close aperture Z-scans were also performed on various CdS quantum dots embedded in different generations, G4, G5 and G6, dendrimer films using picosecond and femtosecond pulses between 350 nm and 1 mum. The measured values of the third order nonlinear coefficient were among the highest off-resonance nonlinearities reported for organic and/or hybrid composites materials. We have shown that the nonlinear response in these materials is also a function of the dynamics of the excited states involved and that measurements of the nonlinear optical coefficient with pulses of different duration are directly correlated to the dynamics of the excited states. Finally, the nonlinear optical properties of hybrid systems based on single-wall carbon nanotubes were investigated at different laser pulse durations. These materials show interesting nonlinear transmission properties which makes them perfect candidates for optical limiting applications.

Etienne, Michael

188

Nanostructuring of semiconductor materials and metallic thin films using femtosecond laser and scanning probe microscope  

NASA Astrophysics Data System (ADS)

Ultra-short pulsed-laser radiation has been shown to be an effective tool for controlled material processing and surface nano/micro-modification because of minimal thermal and mechanical damage. Nanostructuring of a variety of materials is gaining widespread importance owing to ever-increasing applications of nanostructures in numerous fields. This study demonstrates that controllable surface nanostructuring can be achieved by effectively utilizing the local field enhancement in the near field of a SPM probe tip irradiated with femtosecond laser pulses. Results of nanostructuring of various metallic and semiconductor thin film samples utilizing an 800nm femtosecond laser system in conjunction with a commercial SPM in ambient air are presented. Additionally, results from a companion micro-ablation study on gold thin films and numerical Finite Difference Time Domain (FDTD) simulation results for the spatial distribution of the laser field intensity beneath the tip are presented in an effort to achieve better understanding of the laser-material interaction. Flexibility in the choice of the substrate material and the processing environment, high spatial resolution (~10-12nm) and possibility of high processing rates by massive integration of the tips make this method an effective nanostructuring tool. Potential applications of this method include nanolithography, mask repair, nanodeposition, high-density data storage, as well as various nano-biotechnology related applications.

Chimmalgi, Anant; Choi, Taeyul; Hwang, David; Grigoropoulos, Constantine P.

2003-06-01

189

Switching of the natural nanostructure in Bi2Te3 materials by ion irradiation.  

PubMed

In Bi(2)Te(3) materials the natural nanostructure (nns) with a wavelength of 10 nm can be reproducibly switched ON and OFF by Ar(+) ion irradiation at 1.5 and 1 keV. Controlled formation of the nns in Bi(2)Te(3) materials has potential for reducing its thermal conductivity and could increase the thermoelectric figure of merit. PMID:22718358

Aabdin, Zainul; Peranio, Nicola; Eibl, Oliver

2012-06-21

190

Properties of Five Toughened Matrix Composite Materials.  

National Technical Information Service (NTIS)

The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and un...

R. J. Cano M. B. Dow

1992-01-01

191

Composite, Ordered Material Having Sharp Surface Features.  

National Technical Information Service (NTIS)

A composite material having sharp surface features includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wh...

B. R. D'Urso J. T. Simpson

2005-01-01

192

Low-temperature relaxation processes in a Cu-Nb nanostructured fiber composite  

Microsoft Academic Search

The elastic and dissipative properties of nanostructured superconducting fiber composites Cu-32 vol.% Nb at frequencies of the order of 70 kHz are investigated in the temperature range 2-320 K. The composites, prepared by the method of intensive plastic deformation, consist of a fragmented copper matrix uniformly filled with niobium fibers having diameters of 200-500 nm. It is found that the

E. N. Vatazhuk; P. P. Pal-Val; L. N. Pal-Val; V. D. Natsik; M. A. Tikhonovsky; A. A. Kupriyanov

2009-01-01

193

Integration of mechanical alloying and equal channel angular extrusion for production of nanostructured materials  

NASA Astrophysics Data System (ADS)

The main objective of this study is to develop the technology to produce nanostructured materials with superior mechanical and chemical behavior. The focus of this research is mainly on two issues: (1) Use of mechanical alloying (MA) to produce nanostructured titanium silicide (Ti5Si 3) in powder form. (2) Use of equal channel angular extrusion (ECAE) for consolidation of mechanically alloyed powder in bulk form by preserving the fine scale structure. Nanostructured materials are a special group of materials with grain size less than 100 nanometers (nm), with a high percentage of atoms located at their grain boundaries. Due to the special structural arrangement of atoms, nanostructured materials are capable of developing much higher strength and stronger resistance to chemical attack, as compared to materials with conventional structure (grain size ranging from micrometers to millimeters). Because of their extraordinary mechanical and chemical properties, nanostructured materials have attracted a lot of attention in industry today. However, progress made to date in the production of these materials is limited to laboratory quantities and thin layers for surface coatings. In order that engineered nanostructured materials exhibit such superior properties, the essential requirement is that these materials should be in the bulk-processed condition and in larger quantities, suitable for industrial applications. This research achieves this by integrating the mechanical alloying process for production of nanostructured powders, and equal channel angular extrusion process to consolidate these powders and preserve their fine structure in bulk form. MA is a high-energy ball milling process used to produce nanocrystalline and amorphous materials in powder form. The design of experiments statistical method (23 factorial design) is applied to optimize this process to produce nanostructured titanium silicide (Ti5Si3) in powder form. ECAE is a process that produces intense and uniform plastic deformation caused by simple shear of the material. This process has proven to be an effective method for forming nanocrystalline materials in bulk form. A 4 x 2factorial design was used to optimize the ECAE process. Finite element analysis and other modeling studies are presented to support the experimental work performed. X-ray diffraction (XRD) was used to determine the grain size of the material in powder form and the final product. Vickers method is used to measure the microhardness. The main interest was on the production of nanostructured titanium silicide, a material with many applications in aerospace, transportation, oil industry etc. The titanium silicide material in powder form with grain size of 1 mum (micrometer) was subjected to a mechanical alloying process, which resulted in a nanostructured powder with a grain size of less than nm. To avoid the high temperature involvement used in traditional powder consolidation methods, which in turn causes the coarsening of grains, the nanostructured powder was consolidated using the ECAE process. The final product possessed a Vickers microhardness as high as 1500, and a grain size of less than 10 nm.

Kaculi, Xhemal

194

A RESEARCH REVIEW ARTICLE ON COMPOSITE MATERIAL  

PubMed Central

The search of aesthetic dental material is on. Composites are a material of choice in this category. Composite have developed over past few years and increased use of material is in demand. This article gives us a brief knowledge of existing and newer composites.

CHOKSI, DIPTI; IDNANI, BARKHA

2013-01-01

195

Functionalization of gold and carbon nanostructured materials using gamma-ray irradiation  

NASA Astrophysics Data System (ADS)

Gold nanoparticles were successfully attached to the surface sites of carbon nanotubes (CNT). Both nanostructured materials were functionalized by ?-ray irradiation without chemical treatments for creating active sites. UV-visible absorption spectra of the un-irradiated and gamma ray-irradiated nanomaterials are also studied. The absorption spectrum of the irradiated CNT shows a new strong peak located at 700 nm, which might act as the active site on the surface of CNT, the result being an attachment of gold nanoparticles. This approach provides an efficient method to attach other nanostructures to carbon nanotubes for using them in different applications such as medicine and synthesis of catalytic materials.

Salah, Numan; Habib, Sami S.; Khan, Zishan H.; Al-Hamedi, Salim; Djouider, Fathi

2009-11-01

196

Composite material heat pipe radiator  

SciTech Connect

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness (0.076 mm). The thin liner transitioned to heavier-walled ends which allowed the tubing to be sealed using conventional welding. More specifically, the heat pipe was 1.14 m long, 24 mm in diameter and had a mass of 0.165 kg. Water was the working fluid. The heat pipe was tested in a Thermacore thermal vacuum chamber under hot and cold wall operating conditions. The heat load dissipated ranged from 10 to 60 watts. Heat pipe operating temperatures varied from 278 K to 403 K. After testing, the heat pipe was delivered to NASA JSC where future thermal vacuum chamber tests are planned. {copyright} {ital 1996 American Institute of Physics.}

Gernert, N.J.; Sarraf, D.B. [Thermacore, Inc., 780 Eden Road, Lancaster, Pennsylvania 17601 (United States); Guenther, R.J. [Battelle, Pacific Northwest Laboratories, Richland, Washington 99352 (United States); Hurlbert/, K.M. [NASA Johnson Space Center, 2101 NASA Road, 1 Houston, Texas 77058-3696 (United States); EC3

1996-03-01

197

Nanostructured multilayered thin film barriers for Mg{sub 2}Si thermoelectric materials  

SciTech Connect

The Mg{sub 2}Si-based alloys are promising candidates for thermoelectric energy conversion in the middle-high temperature range in order to replace lead compounds. The main advantages of silicide-based thermoelectrics are the nontoxicity and the abundance of their constituent elements in the earth crust. The drawback of such kind of materials is their oxygen sensitivity at high temperature that entails their use under vacuum or inert atmosphere. In order to limit the corrosion phenomena, nanostructured multilayered molybdenum silicide-based materials were deposited via RF magnetron sputtering onto stainless steel, alumina and silicon (100) to set up the deposition process and then onto Mg{sub 2}Si pellets. XRD, EDS, FE-SEM and electrical measurements at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of the deposited coatings. At the end, the mechanical behavior of the system thin film/Mg{sub 2}Si-substrate as a function of temperature and the barrier properties for oxygen protection after thermal treatment in air at high temperature were qualitatively evaluated by FE-SEM.

Battiston, S.; Boldrini, S.; Fiameni, S.; Agresti, F.; Famengo, A.; Fabrizio, M.; Barison, S. [CNR - IENI, Corso Stati Uniti 4, 35127 Padova (Italy)

2012-06-26

198

Microstructure and mechanical properties of 7075 aluminum alloy nanostructured composites processed by mechanical milling and indirect hot extrusion  

SciTech Connect

Nanostructured composites of 7075 aluminum alloy and carbon coated silver nanoparticles were produced by mechanical milling and indirect hot extrusion. The milling products were obtained in a high energy SPEX ball mill, and then were compacted by uniaxial load and pressure-less sintered under argon atmosphere. Finally, the sintered product was hot extruded. Carbon coated silver nanoparticles were well distributed in the matrix of the extruded material. Tensile tests were carried out to corroborate the hypothesis that second phase particles, well dispersed in the matrix, improve the strength of the material. High resolution transmission electron microscopy was employed to locate and make sure that the silver nanoparticles were homogeneously and finely dispersed. Highlights: Black-Right-Pointing-Pointer 7075 Al nanostructured composites can be produced by mechanical milling. Black-Right-Pointing-Pointer Carbon coated silver nanoparticles are well dispersed into aluminum matrix. Black-Right-Pointing-Pointer Ductile Ag-C NP's improve the mechanical properties of the 7075 Al-alloy. Black-Right-Pointing-Pointer Ag-C NP's content has an important effect in the particle and crystallite size. Black-Right-Pointing-Pointer Ag-C NP's keep their morphology after milling and conformation processes.

Flores-Campos, R., E-mail: ruben.flores@itesm.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No. 120, CP 31109, Chihuahua, Chih., Mexico (Mexico); Tecnologico de Monterrey Campus Saltillo, Departamento de Ingenieria, Prol. Juan de la Barrera No. 1241 Ote., Col. Cumbres, CP 25270, Saltillo, Coah., Mexico (Mexico); Estrada-Guel, I., E-mail: ivanovich.estrada@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No. 120, CP 31109, Chihuahua, Chih., Mexico (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No. 120, CP 31109, Chihuahua, Chih., Mexico (Mexico); Martinez-Sanchez, R., E-mail: roberto.martinez@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No. 120, CP 31109, Chihuahua, Chih., Mexico (Mexico); Herrera-Ramirez, J.M., E-mail: martin.herrera@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No. 120, CP 31109, Chihuahua, Chih., Mexico (Mexico)

2012-01-15

199

Green energy storage materials: advanced nanostructured materials for lithium-ion batteries  

NASA Astrophysics Data System (ADS)

The projected doubling of world energy consumption in the next fifty years requires certain measures to meet this demand. The ideal energy provider is reliable, efficient, with low emissions source - wind, solar, etc. The low carbon footprint of renewables is an added benefit, which makes them especially attractive during this era of environmental consciousness. Unfortunately, the intermittent nature of energy from these renewables is not suitable for the commercial and residential grid application, unless the power delivery is 24/7, with minimum fluctuation. This requires intervention of efficient electrical energy storage technology to make power generation from renewable practical. The progress to higher energy and power density especially for battery technology will push material to the edge of stability and yet these materials must be rendered safe, stable and with reliable operation throughout their long life. A major challenge for chemical energy storage is developing the ability to store more energy while maintaining stable electrode-electrolyte interface. A structural transformation occurs during charge-discharge cycle, accompanied by a volume change, degrading the microstructure over-time. The need to mitigate this volume and structural change accompanying charge-discharge cycle necessitates going to nanostructured and multifunctional materials that have the potential of dramatically enhancing the energy density and power density.

Tripathi, Alok Mani; Chandrasekar, M. S.; Mitra, Sagar

2011-05-01

200

Chemically modified and nanostructured porous silicon as a drug delivery material and device  

Microsoft Academic Search

This thesis describes the fabrication, chemical modification, drug release, and toxicity studies of nanostructured porous silicon for the purposes of developing a smart drug delivery device. The first chapter is an introductory chapter, presenting the chemical and physical properties of porous silicon, the concepts and issues of current drug delivery devices and materials, and how porous silicon can address the

Emily Jessica Anglin

2007-01-01

201

Nanostructured composite layers of mussel adhesive protein and ceria nanoparticles.  

PubMed

Mussel adhesive proteins are known for their high affinity to a range of different surfaces, and they therefore appear as ideal candidates for producing thin inorganic-organic composite films with high robustness. In this work we explore the possibility of making cohesive films utilizing layer-by-layer deposition of the highly positively charged mussel adhesive protein, Mefp-1, and negatively charged ceria nanoparticles. This particular material combination was chosen due to recent findings that such films provide good corrosion protection. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used for following the film formation process in situ on silica surfaces. A close to linear growth of the film with number of deposited layers was found for up to 18 deposition steps, the highest number of depositions investigated in this work. The Mefp-1 concentration during film deposition affected the film properties, where a higher protein concentration resulted in a stiffer film. It was also found that the added mass could be amplified by using a Mefp-1 solution containing small aggregates. The surface nanomechanical properties of dried multilayer films were investigated using peak force QNM (quantitative nanomechanical mapping) in air. Homogeneous surface coverage was found under all conditions explored, and the Young's modulus of the outer region of the coating increased when a higher Mefp-1 concentration was used during film deposition. The nature of the outermost surface layer was found to significantly affect the surface nanomechanical properties. The abrasion resistance of the coating was measured by using controlled-force contact mode AFM. PMID:23815752

Krivosheeva, Olga; Sababi, Majid; Dedinaite, Andra; Claesson, Per M

2013-07-18

202

International Conference (4th) on Nanostructured Materials Held in Stockholm, Sweden on 14-19 June 1998. Book of Abstracts.  

National Technical Information Service (NTIS)

The art of developing functionalized nanostructured materials exploiting unusual interfacial properties has not only produced new hitherto unknown man-made materials but almost seem to lead to the world of self assembled systems' - a step closer to mimick...

B. H. Kear R. W. Siegel T. Tsakalakos

1998-01-01

203

Polyolefin composites containing a phase change material  

DOEpatents

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein, said polyolefin being thermally form stable; the composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Salyer, Ival O. (Dayton, OH)

1991-01-01

204

Microstructure and tribological behaviour of nano-structured metal matrix composite boride coatings synthesized by combined laser and sol–gel technology  

Microsoft Academic Search

Hard nano-structured metal matrix composite (MMC) boride coatings have been synthesized by laser melting of pre-placed powder mixture paste of B4C+sol–gel derived nano-particulate TiO2 on AISI 1050 (EN43) medium carbon steel and AISI 316L stainless steel substrates. Different coating\\/processing gas conditions were employed to understand the influence of graphite and nitrogen gas interactions with the coating material at high temperatures.

A. Roy Choudhury; Tamer Ezz; Satyajit Chatterjee; Lin Li

2008-01-01

205

Thin film dielectric composite materials  

DOEpatents

A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

Jia, Quanxi (Los Alamos, NM); Gibbons, Brady J. (Los Alamos, NM); Findikoglu, Alp T. (Los Alamos, NM); Park, Bae Ho (Los Alamos, NM)

2002-01-01

206

Comparative evaluation of biocompatibility of dense nanostructured and microstructured Hydroxyapatite/Titania composites.  

PubMed

This work deals with the biocompatibility of dense nano- and micro-structured Hydroxyapatite/Titania composites prepared by two step and conventional sintering, respectively. By application of two step sintering, it was shown that the final grain size of HA-15 wt.% TiO2 is maintained lower than 100 nm while by the application of conventional sintering it reaches higher than 100 nm. Biocompatibility of the dense bulks was evaluated by cell attachment and proliferation experiments. Cell morphology, and viability on each nano- and micro-structured Hydroxyapatite/Titania composites were examined at different time points. The nanostructured HA/Titania dense bulk exhibited higher cell viability than a microstructured one. In addition, the effects of ionic products from nano- and micro-structured bulk dissolution on osteoblasts were studied. The MTT test confirmed that the products from nanostructured HA/Titania dense bulk significantly promoted osteoblast proliferation within a certain concentration range. PMID:23498255

Farzin, A; Ahmadian, M; Fathi, M H

2013-01-28

207

Novel applications exploiting the thermal properties of nanostructured materials.  

SciTech Connect

A new class of heat transfer fluids, termed nanofluids, has been developed by suspending nanocrystalline particles in liquids. Due to the orders-of-magnitude larger thermal conductivities of solids compared to those of liquids such as water, significantly enhanced thermal properties are obtained with nanofluids. The use of nanofluids could impact many industrial sectors, including transportation, energy supply and production, electronics, textiles, and paper production by, for example, decreasing pumping power needs or reducing heat exchanger sizes. In contrast to the enhancement in effective thermal transport rates that is obtained when nanoparticles are suspended in fluids, nanocrystalline coatings are expected to exhibit reduced thermal conductivities compared to coarse-grained coatings. Reduced thermal conductivities are predicted to arise because of a reduction in the mean free path of phonons due to presence of grain boundaries. This behavior, combined with improved mechanical properties, makes nanostructured zirconia coatings excellent candidates for future applications as thermal barriers.

Eastman, J. A.

1998-11-20

208

Nanostructured material surfaces--preparation, effect on cellular behavior, and potential biomedical applications: a review.  

PubMed

Nanostructures play important roles in vivo, where nanoscaled features of extracellular matrix (ECM) components influence cell behavior and resultant tissue formation. This review summarizes some of the recent developments in fostering new concepts and approaches to nanofabrication, such as top-down and bottom-up and combinations of the two. As in vitro investigations demonstrate that man-made nanotopography can be used to control cell reactions to a material surface, its potential application in implant design and tissue engineering becomes increasingly evident. Therefore, we present recent progress in directing cell fate in the field of cell mechanics, which has grown rapidly over the last few years, and in various tissue-engineering applications. The main focus is on the initial responses of cells to nanostructured surfaces and subsequent influences on cellular functions. Specific examples are also given to illustrate the potential nanostructures may have for biomedical applications and regenerative medicine. PMID:22161281

Guduru, Deepak; Niepel, Marcus; Vogel, Jürgen; Groth, Thomas

2011-10-01

209

Thermal evaporation furnace with improved configuration for growing nanostructured inorganic materials.  

PubMed

A tubular furnace specifically designed for growing nanostructured materials is presented in this work. The configuration allows an accurate control of evaporation temperature, substrate temperature, total pressure, oxygen partial pressure, volumetric flow and source-substrate distance, with the possibility of performing both downstream and upstream depositions. In order to illustrate the versatility of the equipment, the furnace was used for growing semiconducting oxide nanostructures under different deposition conditions. Highly crystalline indium oxide nanowires with different morphologies were synthesized by evaporating mixtures of indium oxide and graphite powders with different mass ratios at temperatures between 900 °C and 1050 °C. The nanostructured layers were deposited onto oxidized silicon substrates with patterned gold catalyst in the temperature range from 600 °C to 900 °C. Gas sensors based on these nanowires exhibited enhanced sensitivity towards oxygen, with good response and recovery times. PMID:21721724

Joanni, E; Savu, R; Valadares, L; Cilense, M; Zaghete, M A

2011-06-01

210

Computer simulation of radiation-induced nanostructure formation in amorphous materials  

NASA Astrophysics Data System (ADS)

In this study, 3D simulations based on a theoretical model were developed to investigate radiation-induced nanostructure formation in amorphous materials. Model variables include vacancy production and recombination rates, ion sputtering effects, and redeposition of sputtered atoms. In addition, a phase field model was developed to predict vacancy diffusion as a function of free energies of mixing and interfacial energies. The distribution profile of the vacancy production rate along the depth of an irradiated matrix was considered as a near Gaussian approximation according to Monte-Carlo TRIM code calculations. Dynamic processes responsible for nanostructure evolution were simulated by updating the vacancy concentration profile over time. Simulated morphologies include cellular nanoholes, nanowalls, nanovoids, and nanofibers, with the resultant morphology dependant upon the incident ion species and ion fluence. These simulated morphologies are consistent with experimental observations achieved under comparable experimental conditions. Our model provides a distinct numerical approach to accurately predicting morphological results for ion-irradiation-induced nanostructures.

Li, Kun-Dar; Perez-Bergquist, Alejandro; Wang, Lumin

2009-09-01

211

Wear behavior of light-cured resin composites with bimodal silica nanostructures as fillers.  

PubMed

To enhance wear behavior of resin composites, bimodal silica nanostructures including silica nanoparticles and silica nanoclusters were prepared and proposed as fillers. The silica nanoclusters, a combination of individually dispersed silica nanoparticles and their agglomerations, with size distribution of 0.07-2.70?m, were fabricated by the coupling reaction between amino and epoxy functionalized silica nanoparticles, which were obtained by the surface modification of silica nanoparticles (~70nm) using 3-aminopropyl triethoxysilane (APTES) and 3-glycidoxypropyl trimethoxysilane (GPS) as coupling agents, respectively. Silica nanoparticles and nanoclusters were then silanized with 3-methacryloxypropyl trimethoxysilane (?-MPS) to prepare composites by mixing with bisphenol A glycerolate dimethacrylate (Bis-GMA) and tri (ethylene glycol) dimethacrylate (TEGDMA). Experimental composites with various filler compositions were prepared and their wear behaviors were assessed in this work. The results suggested that composites with increasing addition of silica nanoparticles in co-fillers possessed lower wear volume and smoother worn surface. Particularly, the composite 53:17 with the optimum weight ratio of silica nanoparticles and silica nanoclusters presented the excellent wear behavior with respect to that of the commercial Esthet-X, although the smallest wear volume was achieved by Z350 XT. The introduction of bimodal silica nanostructures as fillers might provide a new sight for the design of resin composites with significantly improved wear resistance. PMID:24094185

Wang, Ruili; Bao, Shuang; Liu, Fengwei; Jiang, Xiaoze; Zhang, Qinghong; Sun, Bin; Zhu, Meifang

2013-08-09

212

Carbon nanostructured materials for applications in nano-medicine, cultural heritage, and electrochemical biosensors.  

PubMed

This review covers applications of pristine and functionalized single-wall carbon nanotubes (SWCNTs) in nano-medicine, cultural heritage, and biosensors. The physicochemical properties of these engineered nanoparticles are similar to those of ultrafine components of airborne pollution (UF) and might have similar adverse effects. UF may impair cardiovascular autonomic control (inducing a high-risk condition for adverse cardiovascular effects), cause mammalian embryo toxicity, and increase geno-cytotoxic risk. SWCNTs coated with a biopolymer, for example polyethylenimine (PEI), become extremely biocompatible, hence are useful for in-vivo and in-vitro drug delivery and gene transfection. It is also possible to successfully immobilize a human enteric virus on PEI/SWCNT composites, suggesting application as a carrier in non-permissive media. The effectiveness of carbon nanostructured materials in the cleaning, restoration, and consolidation of deteriorated historical surfaces has been widely shown by the use of carbon nanomicelles to remove black dendritic crust from stone surfaces. The nanomicelles, here, have the twofold role of delivery and controlled release of the cleaning agents. The high biocompatibility of functionalized SWCNTs with enzymes and proteins is a fundamental feature used in the assembly of electrochemical biosensors. In particular, a third-generation protoporphyrin IX-based biosensor has been assembled for amperometric detection of nitrite, an environmental pollutant involved in the biodeterioration and black encrustation of historical surfaces. PMID:23064705

Valentini, F; Carbone, M; Palleschi, G

2012-10-13

213

Electrical properties of composites with tin tin oxide core shell nanostructure and their sensing behaviour  

Microsoft Academic Search

Metallic tin having a dendritic structure was grown within a silica-based gel by an electrodeposition technique. The dendrites were shown to consist of nanoparticles with a median diameter of 31 nm. By giving a controlled oxidation treatment to the composite, a tin core-tin oxide shell nanostructure was induced. The shell thicknesses varied from 1.5 to 4.0 nm depending on the

B. N. Pal; D. Chakravorty

2005-01-01

214

In situ formed Ti–Cu–Ni–Sn–Ta nanostructure-dendrite composite with large plasticity  

Microsoft Academic Search

A group of Ti–Cu–Ni–Sn–Ta multicomponent alloys is prepared by copper mold casting and arc melting, respectively, in which nanostructured (or ultrafine-grained) matrix-dendrite composites can be obtained. With increasing Ti and Ta contents, the volume fraction of the dendritic phase increases. The grain size of the matrix phase depends on the preparation method, and is 30–70 nm for as-cast 2–3 mm

G He; W Löser; J Eckert

2003-01-01

215

Flexure Tests of Three Fibrous Composite Materials.  

National Technical Information Service (NTIS)

Carbon and glass/ester composites were tested for flexural stiffness and strength. The test specimens were prepared from three types of composite materials: carbon fiber cloth/vinylester, glassfiber cloth/vinylester, and glassfiber/polyester in prepreg fo...

L. Knutsson H. Bjermert

1980-01-01

216

Using simultaneous deposition and rapid growth to produce nanostructured composite films of AlN/TiN by chemical vapor deposition  

SciTech Connect

Brittleness has been the major obstacle in using ceramics. Previous research has shown, however, that ceramic materials that have small grain size show plasticity. The authors therefore propose two methods to produce nanostructured ceramic films by chemical vapor deposition (CVD): (1) high-speed deposition and (2) simultaneous deposition of insoluble materials (contained in a mixture of insoluble solids). These methods were successfully applied to aluminum nitride/titanium nitride (AlN/TiN) films produced by CVD. The AlN/TiN nanostructured composite films were synthesized by atmospheric-pressure CVD (APCVD), using aluminum chloride (AlCl{sub 3}), titanium chloride (TiCl{sub 4}), and ammonia (NH{sub 3}) as reactant gases at temperatures ranging from 923 to 1123 K in a horizontal tubular reactor. For the high-speed deposition strategy, the authors obtained growth rates as high as 1.2 mm/h. Using either method, they were able to attain AlN/TiN composite films that had a grain size of 8 nm (AlN crystals) and 6 nm (TiN crystals), showing that these methods are effective in producing nanostructured composite films by CVD. Measurements of the fracture toughness of the prepared materials indicated that these strategies can be used to improve the ductility of ceramics.

Liu, Y.J.; Egashira, Yasuyuki; Komiyama, Hiroshi [Univ. of Tokyo (Japan). Dept. of Chemical System Engineering; Kim, H.J. [Toyohashi Univ. of Technology (Japan). Dept. of Ecological Engineering; Kimura, Hisamichi [Tohoku Univ., Sendai (Japan). Inst. of Materials Research

1996-05-01

217

Nanostructure and mineral composition of trabecular bone in the lateral femoral neck: implications for bone fragility in elderly women.  

PubMed

Despite interest in investigating age-related hip fractures, the determinants of decreased bone strength in advanced age are not clear enough. Hitherto it has been obscure how the aging process affects the femoral neck nanostructure and composition, particularly in the lateral subregion of the femoral neck, which is considered as a fracture-initiating site. The femoral bone samples used in this study were obtained at autopsy in 10 women without skeletal disease (five younger: aged 20-40 years, and five elderly: aged 73-94 years). Atomic force microscopy (AFM) was applied to explore the mineral grain size in situ in young vs. old trabecular bone samples from the lateral femoral neck. The chemical compositions of the samples were determined using inductively coupled plasma optical emission spectroscopy and direct current argon arc plasma optical emission spectrometry. Our AFM study revealed differences in trabecular bone nanostructure between young and elderly women. The mineral grain size in the trabeculae of the old women was larger than that in the young (median: 95 vs. 59nm), with a particular bimodal distribution: 45% were small grains (similar to the young) and the rest were larger. Since chemical analyses showed that levels of calcium and phosphorus were unchanged with age, our study suggests that during aging the existing bone mineral is reorganized and forms larger aggregates. Given the mechanical disadvantage of large-grained structures (decreased material strength), the observed nanostructural differences contribute to our understanding of the increased fragility of the lateral femoral neck in aged females. Moreover, increasing data on mineral grains in natural bone is essential for advancing calcium-phosphate ceramics for bone tissue replacement. PMID:21658479

Milovanovic, Petar; Potocnik, Jelena; Stoiljkovic, Milovan; Djonic, Danijela; Nikolic, Slobodan; Neskovic, Olivera; Djuric, Marija; Rakocevic, Zlatko

2011-05-27

218

Structure and function of oxide nanostructures: catalytic consequences of size and composition.  

PubMed

Redox and acid-base properties of dispersed oxide nanostructures change markedly as their local structure and electronic properties vary with domain size. These changes give rise to catalytic behavior, site structures, and reaction chemistries often unavailable on bulk crystalline oxides. Turnover rates for redox and acid catalysis vary as oxide domains evolve from isolated monomers to two-dimensional oligomers, and ultimately into clusters with bulk-like properties. These reactivity changes reflect the ability of oxide domains to accept or redistribute electron density in kinetically-relevant reduction steps, in the formation of temporary acid sites via reductive processes, and in the stabilization of cationic transition states. Reduction steps are favored by low-lying empty orbitals prevalent in larger clusters, which also favor electron delocalization, stable anions, and strong Brønsted acidity. Isomerization of xylenes and alkanes, elimination reactions of alkanols, and oxidation of alkanes to alkenes on V, Mo, Nb, and W oxide domains are used here to demonstrate the remarkable catalytic diversity made available by changes in domain size. The reactive and disordered nature of small catalytic domains introduces significant challenges in their synthesis and their structural and mechanistic characterization, which require in situ probes and detailed kinetic analysis. The local structure and electronic properties of these materials must be probed during catalysis and their catalytic function be related to specific kinetically-relevant steps. Structural uniformity can be imposed on oxide clusters by the use of polyoxometalate clusters with thermodynamically stable and well-defined size and connectivity. These clusters provide the compositional diversity and the structural fidelity required to develop composition-function relations from synergistic use of experiments and theory. In these clusters, the valence and electronegativity of the central atom affects the acid strength of the polyoxometalate clusters and the rate constants for acid catalyzed elementary steps via the specific stabilization of cationic transition states in isomerization and elimination reactions. PMID:18766228

Macht, Josef; Iglesia, Enrique

2008-07-09

219

Optical sensor using functionalized composite materials  

US Patent & Trademark Office Database

The invention relates to a method for sensing the presence of at least one analyte in a medium, comprising disposing in the medium a functionalized composite material such that the at least one analyte is absorbed by the functionalized composite material, the functionalized composite material having at least one optical property that is modulated by absorption of the at least one analyte; and measuring modulation of the at least one optical property of the functionalized composite material; wherein modulation of the at least one optical property of the functionalized composite material is indicative of the presence of the analyte in the medium. The invention also relates to an optical sensor for sensing the presence of at least one analyte in a medium, and a functionalized composite material having at least one optical property that is modulated upon absorption of one or more analyte.

2010-08-17

220

Mechanical Behavior of Nanostructured Materials at High Strain Rates. Computer Simulation  

NASA Astrophysics Data System (ADS)

In this paper, we present the new model of mechanical behavior of nanostructural materials (NsM) and nanocrystalline materials (NM) in wide range of strain rates. The model was used for computer simulation of shock wave dynamics in NsM ?-Ti, Al, Cu, g and NM Al2O3, ZrO2-Y2O3 ceramics. The inelastic strain causes by the deformation mechanisms at micro- and meso- scale levels. The results testify to distinctions of the mechanical behavior nanostructural and a course-grained ceramic materials and a metal alloys at shock wave loading. The model predicts that the shear stress of NM and NsM at high strain rates is less than ones of course-grained materials due to contributions to inelastic deformation of the grain boundary sliding.

Skripnyak, Vladimir

2005-07-01

221

A review of nanostructured lithium ion battery materials via low temperature synthesis.  

PubMed

Nanostructured materials afford us new opportunities to improve the current technology for synthesizing Li ion batteries. Generating nanomaterials with new properties via an inexpensive approach offers a tremendous potential for realizing high performance Li-ion batteries. In this review, I mainly summarize some of the recent progress made, and describe the patents awarded on synthesizing nanostructured cathode materials for these batteries via low temperature wet- chemistry methods. From an economical view, such syntheses, especially hydrothermal synthesis, may offer the opportunities for significantly lowering the cost of manufacturing battery materials, while conferring distinct environmental advantages. Recent advances in in-situ (real time) X-ray diffraction for studying hydrothermal synthesis have great potential for bettering the rational design of advanced lithium-electrode materials. The development of this technique also will be discussed. PMID:22747718

Chen, Jiajun

2013-01-01

222

Optical resonances in a composite asymmetric plasmonic nanostructure  

NASA Astrophysics Data System (ADS)

The optical properties of a composite metamaterial, composed of asymmetric split-ring resonators (SRR) inserted into the periodic circular holes, have been investigated both experimentally and theoretically. Transmission peaks and dip associated with the localized plasmon excitations have been found: the peaks originate from the resonances of the smaller or bigger SRR, and the dip stems from the strong coupling between them. To understand the results, a composite LC circuit model has been employed.

Huang, Wan-Xia; Wang, Qian-Jin; Yin, Xiao-Gang; Huang, Cheng-Ping; Huang, Huang; Wang, Yu-Min; Zhu, Yong-Yuan

2011-06-01

223

Dynamic compaction of particulate composite materials  

NASA Astrophysics Data System (ADS)

This paper describes the mechanical alloying + dynamic compaction flowchart for producing composites with particulate reinforcements. The combinations of components tested included aluminum silicon carbide, aluminum boron carbide, copper silicon carbide, and copper silica. Mechanical alloying produced granules of composite with reinforcements uniformly distributed in the matrix material. Dynamic compaction of mechanically alloyed granules was shown to produce high quality composite materials with crack-free structure. As the standard methods for explosive treatment lead to crack formation in bulk composites, this work included the development of a tool for treating composite materials.

Popov, V. A.; Staudhammer, K. P.; Goulbin, V. N.

2006-08-01

224

Improvement of physical characteristics of petroleum waxes by using nano-structured materials  

Microsoft Academic Search

Layered double hydroxides (LDHs) are a class of synthetic two-dimensional nano-structured anionic clays whose structure can be described as nano-layered ordered material. This study aims to use nano-layered materials as a host for organic guests having required functional groups such as azo-compounds to alter LDH surface properties from hydrophilic to hydrophobic and increase sorption capacity for sulfur and aromatic compounds

Osama Saber; Nermen Hefny; Abdullah A. Al Jaafari

2011-01-01

225

Effect of aspect ratio and water contamination on the electric properties of nanostructured insulating materials  

Microsoft Academic Search

Organically-modified nanofiller clays can have significantly different aspect ratios as well as accumulate a relatively large amount of water in the composite bulk due to the contribution of the filler itself and the interaction between filler and polymer matrix. This paper investigates the effect of water absorption in a nanostructured thermoplastic polymer, namely ethylene-vinyl-acetate (EVA), on electrical property modifications considering

Davide Fabiani; Gian Carlo Montanari; Luigi Testa

2010-01-01

226

Thermal conduction phenomena in carbon nanotubes and related nanostructured materials  

NASA Astrophysics Data System (ADS)

The extremely high thermal conductivities of carbon nanotubes have motivated a wealth of research. Progress includes innovative conduction metrology based on microfabricated platforms and scanning thermal probes as well as simulations exploring phonon dispersion and scattering using both transport theory and molecular dynamics. This article highlights these advancements as part of a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays of nanotubes or disordered nanotube mats. Nanotube length, diameter, and chirality strongly influence the thermal conductivities of individual nanotubes and the transition from primarily diffusive to ballistic heat transport with decreasing temperature. A key experimental challenge, for both individual nanotubes and aligned films, is the separation of intrinsic and contact resistances. Molecular dynamics simulations have studied the impacts of specific types of imperfections on the nanotube conductance and its variation with length and chirality. While the properties of aligned films fall short of predictions based on individual nanotube data, improvements in surface engagement and postfabrication nanotube quality are promising for a variety of applications including mechanically compliant thermal contacts.

Marconnet, Amy M.; Panzer, Matthew A.; Goodson, Kenneth E.

2013-07-01

227

Nanostructured manganese oxides as lithium battery cathode materials  

Microsoft Academic Search

We have designed and synthesized a novel nanocrystalline manganese oxide with a nanofibrous morphology by employing an electrodeposition process in the presence of a non-ionic surfactant. This unique nanoporous\\/nanocrystalline material effectively accommodates the structural transformation during lithium insertion and avoids deleterious morphological changes as observed in battery materials composed of large particles. Consequently, the material exhibits outstanding cycling stability in

Ping Liu; Se-Hee Lee; Yanfa Yan; C. Edwin Tracy; John A. Turner

2006-01-01

228

Composite Materials with Improved Properties in Compression.  

National Technical Information Service (NTIS)

Preparation of composite materials which have high strength in compression. Scientific approach is to prepare novel polymeric coupling agents. These will permit formation of multiple flexible covalent bonds between fibers as well as to matrix materials. I...

W. P. Weber

1993-01-01

229

Multifunctional iron-based metal oxide nanostructured materials: Synthesis, characterization, and properties  

NASA Astrophysics Data System (ADS)

Iron-based metal oxides, such as iron oxides, iron-containing perovskites, and iron-containing perovskite composites or solid solutions, are promising materials for the design and synthesis of technologically important multifunctional materials. They are noteworthy for their unique and diverse properties including electronic, magnetic, and elastic ones. Stimulated by interest in the bulk properties of these materials as well as scientific potential and applications at the nanoscale, iron-based metal oxide nanostructured (FeMONS) materials are being considered as an interesting model system to investigate fundamental properties and for a host of potential applications as diverse as additives, catalysts, electronic devices, magnetic recording media, information storage, spintronics, and sensors. Recent research on a multiferroic system, such as BiFeO3, reveals that there are unique couplings among the independent physical properties including ferroelectricity, ferromagnetism, and ferroelasticity. Developing approaches to designing as well as investigating properties of new synthetic formulations of these transition metal oxide nanomaterials has been the recent focus of much of our efforts in this group. Multiferroic bismuth ferrite (BiFeO 3) nanoparticles have been synthesized employing a facile sol-gel method and their size-dependent magnetic properties have been studied and correlated with: (i) increased suppression of the known spiral spin structure (period length of ˜62 nm) with decreasing nanoparticle size and (ii) uncompensated spins and strain anisotropies at the surface. Moreover, BiFeO 3 nanotubes have been generated using a modified template methodology and extensively characterized. Furthermore, solid solutions of BiFeO 3 and typical perovskites, such as BaTiO3 and SrTiO 3, have been prepared employing a molten salt method and the study has been extended to properties associated with their inherent compositions. Single-crystalline Bi2Fe4O9 nanocubes have been fabricated utilizing a molten salt method and the role of various experimental parameters has been examined towards predictive control of shape and size. Single-crystalline iron oxide (a-Fe2O3) rhombohedra have been generated using environmentally friendly protocols and transformed into aggregates of magnetic nanocomposites of Fe and Fe3O4.

Park, Tae-Jin

230

Self-sensing structural composite materials  

Microsoft Academic Search

Self-sensing was attained in lightweight structural composite materials, including those with polymer (epoxy), carbon and ceramic (Si3N 4) matrices. Either a volume of the composite or the interlaminar interface in the composite was used as the sensor. The use of the interlaminar interface as a sensor is a new approach, which was found to be effective in continuous carbon fiber

Shoukai Wang

2002-01-01

231

Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.  

PubMed

A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis. PMID:23478269

Villani, M; Rimoldi, T; Calestani, D; Lazzarini, L; Chiesi, V; Casoli, F; Albertini, F; Zappettini, A

2013-03-12

232

The interaction between lining materials and composite resin restorative materials.  

PubMed

The effects of four lining materials, Dycal, Procal, Cavitec and Poly F cement on Adaptic and Concise have been investigated in vitro. The parameters studied were surface roughness, hardness and colour both with and without an intermediate (or bonding) resin being present between the restorative material and the liner. The effects of the four liners on the composites varied both between the lining materials themselves and with the composite resin. Two materials, Procal and Dycal, had little interaction with the composites, provided an intermediate resin was used with the latter. Cavitec appeared to have an adverse reaction with the composites and Poly F, whilst having no effect on the colour of the composites, did increase surface roughness. The adverse effects of linig materials were ascribed to minor constituents, particularly methyl salicylate, present in the formulation. PMID:6453213

Lingard, G L; Davies, E H; Von Fraunhofer, J A

1981-03-01

233

Stress distribution in antifriction composite materials  

Microsoft Academic Search

The optimum shape of hard inclusions in a composite material, irrespective of the magnitude of load and mode of its application to the surface, is a spheroid or ellipsoid of revolution. The characteristic linear size of a hard inclusion should be greater than the calculated diameter of a single spot of contact. If a composite material is to exhibit high

L. V. Zabolotnyi

1979-01-01

234

Electromagnetic shielding effectiveness of composite material  

Microsoft Academic Search

The purpose of this paper is to present an engineering study of the electromagnetic shielding effectiveness of composite materials used in space applications. The objective of the study is to identify and quantify the important electrical characteristics of composite materials proposed as substitutes for conventional metal-based structural elements of spacecraft. Current design practices utilized by various developers of spacecraft, particularly

Patrick J. Serna; Gary H. Liechty

1999-01-01

235

Structure and properties of hybrid composite materials  

NASA Astrophysics Data System (ADS)

The structure and interfacial interaction are studied in the hybrid aluminum-matrix composite materials fabricated by reactive casting combined with mechanical mixing of fillers with a metallic melt. The following types of hardening are considered: hardening by ceramic particles and by the phases formed as isolated inclusions or coatings on ceramic particles during in situ reactions. The hardness and tribological properties of the composite materials as functions of their compositions are discussed.

Chernyshova, T. A.; Kobeleva, L. I.; Bolotova, L. K.; Katin, I. V.

2013-03-01

236

Composite Dielectric Materials for Electrical Switching  

SciTech Connect

Composites that consist of a dielectric host containing a particulate conductor as a second phase are of interest for electrical switching applications. Such composites are "smart" materials that can function as either voltage or current limiters, and the difference in fimction depends largely upon whether the dielectric is filled to below or above the percolation threshold. It also is possible to combine current and voltage limiting in a single composite to make a "super-smart" material.

Modine, F.A.

1999-04-25

237

Theoretical analysis of electric, magnetic and magnetoelectric properties of nano-structured multiferroic composites  

NASA Astrophysics Data System (ADS)

Electric, magnetic and magnetoelectric properties of the nano-structured multiferroic composites were studied by using an energy formulation with the consideration of the surface, interface, and size effect. Coupled thermodynamic evolution equations with respect to the spontaneous polarization and magnetization were established, in which the elastic fields in the matrix and inclusions were solved based on the Eshelby's equivalent inclusion concept and the Mori-Tanaka method. Physical properties of the composite, such as the spontaneous order parameters, piezoelectric/piezomagnetic properties, and the magnetoelectric coupling effect are highly dependent on the stress state and the microstructures of the nano-composites. Magnetoelectric coupling voltage coefficient was unstable in the vicinity of the critical size and disappeared below the critical size. The model is versatile enough for various composite structures.

Lu, Xiaoyan; Li, Hui; Wang, Biao

2011-10-01

238

CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS  

Microsoft Academic Search

Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D adsorption than that of H, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content

S. Xiao; L. Heung

2010-01-01

239

Antireflection effects at nanostructured material interfaces and the suppression of thin-film interference.  

PubMed

Thin-film interference is a well-known effect, and it is commonly observed in the colored appearance of many natural phenomena. Caused by the interference of light reflected from the interfaces of thin material layers, such interference effects can lead to wavelength and angle-selective behavior in thin-film devices. In this work, we describe the use of interfacial nanostructures to eliminate interference effects in thin films. Using the same principle inspired by moth-eye structures, this approach creates an effective medium where the index is gradually varying between the neighboring materials. We present the fabrication process for such nanostructures at a polymer-silicon interface, and experimentally demonstrate its effectiveness in suppressing thin-film interference. The principle demonstrated in this work can lead to enhanced efficiency and reduce wavelength/angle sensitivity in multilayer optoelectronic devices. PMID:23676429

Yang, Qiaoyin; Zhang, Xu A; Bagal, Abhijeet; Guo, Wei; Chang, Chih-Hao

2013-05-15

240

Nano-structured Materials in New and Existing Buildings: To Improved Performance and Saving of Energy  

NASA Astrophysics Data System (ADS)

Improving well-being in buildings, in relation to energy conservation, represents a great challenge. In southern Italy a basic problem is that of keeping buildings cool in the summer months. This problem affects not only newly-erected buildings, but also the large number of existing buildings, some of which are of historical importance. Nano-technology represents an excellent opportunity to harness the salvage of existing buildings to the living requirements of contemporary society. The use of nano-structured materials in newly-erected buildings will lead to improved performance and a considerable saving of energy. Above all, the use of nano-structured materials in existing buildings will provide the possibility of intervention in these buildings and help improve, for example, insulation or lighting, without invasive intervention and consequent damage to the building itself.

Scalisi, F.

241

Design of Geopolymeric Materials Based on Nanostructural Characterization and Modeling.  

National Technical Information Service (NTIS)

Geopolymers, a class of largely X-ray amorphous aluminosilicate binder materials, have been studied extensively over the past several decades, but largely from an empirical standpoint. The primary aim of this investigation has been to apply a more science...

G. C. Lukey J. S. van Deventer J. L. Provis P. Duxson

2006-01-01

242

Multifunctional Materials Based on Self Assembly of Molecular Nanostructures.  

National Technical Information Service (NTIS)

In this program we developed an important class of multifunctional and self assembling materials based on the use of triblock molecular structures that had both luminescent chromophores and dipole moments. The objective was to integrate self assembly, enc...

S. I. Stupp

2001-01-01

243

Nanostructured Functional Inorganic Materials Templated by Natural Substances  

Microsoft Academic Search

\\u000a Naturally-produced sophisticated hierarchal structures and the astonishing properties of biological substances are difficult\\u000a to obtain artificially, even with the most technologically advanced synthetic methodologies. As the needs for the development\\u000a of advanced materials with improved performance characteristics become increasingly important, the potential of natural substances\\u000a for material design and fabrication is being actively explored. The combination of versatile synthetic chemical

Yuanqing Gu; Jianguo Huang

244

On the origin of sensing properties of the nanostructured layers of semiconducting metal oxide materials  

Microsoft Academic Search

A model for the electronic states in the nanostructured metal oxide based semiconductor materials (NSSM) explaining the mechanism of their sensing properties is suggested. It is shown that as the nanoparticle diameter a decreases down to critical size aCR?80–100nm, the redistribution of electrons from bulk donors to the surface vacancies (“surface electron traps”) takes place. This leads to a significant

N. P. Zaretskiy; L. I. Menshikov; A. A. Vasiliev

245

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

246

Latent heat nano composite building materials  

Microsoft Academic Search

Heat storage for heating and cooling of buildings reduces the conventional energy consumption with a direct impact on CO2 emissions. The goal of this study was to find the physico-chemical fundamentals for tailoring phase change material (PCM)-epoxy composites as building materials depending on phase change temperature and latent heat using the optimal geometry for each application. Thus, some nano-composite materials

M. Constantinescu; L. Dumitrache; D. Constantinescu; E. M. Anghel; V. T. Popa; A. Stoica; M. Olteanu

2010-01-01

247

NANOSTRUCTURED CERAMICS AND COMPOSITES FOR REFRACTORY APPLICATIONS IN COAL GASIFICATION  

SciTech Connect

A class of ceramics, capable of exhibiting low coefficients of thermal expansion and catalytic properties was investigated. Investigations were directed towards nanoengineering of NZP ceramics and NZP-based composites by chemical means by controlling their compositions and processing variables. NaZr{sub 2}(PO{sub 4}){sub 3} (NZP) was synthesized by combining water-soluble precursors leading to the precipitation of a gel that was dried, calcined, pressed into pellets, then fired at 850 C. Without chemical additives, the resulting ceramic comprised pores ranging in size from approximately 25 to 50 nm and a surface area of about 30m{sup 2}/g. Hydroxyapatite, which has a needle-like morphology, was mechanically mixed with the calcined gel to template NZP crystallization. What resulted was a coarsening of the pore structure and a decrease in surface area. When copper nitrate was added to the solution during synthesis, the resulting ceramic underwent shrinkage upon firing as well as an increase in strength. HAp and copper additions combined resulted in 40% volume shrinkage and a doubling of the tensile strength to 16MPa. A very different type of porosity was achieved when silica was partly substituted for phosphorous in the NZP structure. Na{sub 3}Zr{sub 2}(Si{sub 2}P)O{sub 12} (NASCION) was synthesized in the same manner as NZP, but the fired ceramic possessed a reticulated pore structure comprising large cavities ranging in size from 5 to 50 {micro}m. The NASCION ceramic either shrank or expanded upon firing depending on when the silica was added during synthesis. When the silica precursor (amorphous, precipitated silica) was added before the calcining step, the pressed pellets expanded during firing, whereas they shrank when the silica was added after the gel was calcined. The observed dilation increased with increasing calcining temperature and particle size, up to 26%. The contraction of the ceramic when fired increased with increasing calcining temperature and a greater surface area of the gel. Direct addition of Silica fiber was only modestly beneficial. Fiber addition combined with controlled densification resulted in the greatest improvement in strength. Ion exchange properties of NASICON were established for Cs, Pb, and Cd. It was found that the extent of ion exchange depended on ion size and that Cd could be fully exchanged into NASICON. Catalytic activity of Cu and Ag substituted compositions were determined and it was found that Ag substitution reduced the temperature at which carbon black could be oxidized. However, Ag substitution results in the formation of zircon. Ion conductivity of NASCION was determined and it was found to compare well with other ionic conductors.

Paul Brown

2005-01-31

248

Polymeric Bicontinuous Microemulsions as Templates for Nanostructured Materials  

NASA Astrophysics Data System (ADS)

Ternary blends of two homopolymers and a diblock copolymer can self-assemble into interpenetrating, three dimensionally-continuous networks with a characteristic length scale of ˜ 100 nm. In this thesis, it is shown that these liquid phases, known as polymeric bicontinuous microemulsions (B?E), can be designed as versatile precursors to nanoporous materials having pores with uniform sizes of ˜ 100 nm. The model blends from which the porous materials are derived are composed of polyethylene (PE) and a sacrificial polyolefin. The liquid B?E structure is captured by crystallization of the PE, and a three-dimensionally continuous pore network with a narrow pore size distribution is generated by selective extraction of the sacrificial component. The original B?E structure is retained in the resultant nanoporous PE. This monolithic material is then used as a template in the synthesis of other nanoporous materials for which structural control at the nm scale has traditionally been difficult to achieve. These materials, which include a high-temperature ceramic, polymeric thermosets, and a conducting polymer, are produced by a simple nanocasting process, providing an inverse replica of the PE template. On account of the B?E structure of the template, the product materials also possess three-dimensionally continuous pore networks with narrow size distributions centered at ˜ 100 nm. The PE template is further used as a template for the production of hierarchically structured inorganic and polymeric materials by infiltration of mesostructured compounds into its pore network. In the former case, a hierarchically porous SiO2 material is demonstrated, simultaneously possessing two discrete, bicontinuous pore networks with sizes differing by over an order of magnitude. Finally, the templating procedures are extended to thin films supported on substrates and novel conductive polymer films are synthesized. The work described herein represents an unprecedented suite of nanoporous materials with well-defined pore structures prepared from a single PE template. They are anticipated to have potential application in diverse technological areas, including catalysis, separations, sensors, and electronic devices.

Jones, Brad Howard

249

Recent developments in nanostructured thermoelectric materials and devices  

Microsoft Academic Search

Thermal management is a critical issue for microelectronic and microphotonic devices. The efficiency of actual thermoelectric devices is determined by the thermoelectric figure of merit Z. Because Z has unit of inverse temperature, nondimensional figure-of-merit ZT that appears often in device analysis is commonly used. The best ZT materials are found in heavily doped semiconductors which has ZT ? 1.

Ronggui Yang; Gang Chen

2004-01-01

250

NANOSTRUCTURED MATERIAL DESIGN FOR HG, AS, AND SE CAPTURE  

EPA Science Inventory

The goal of this research project is to identify potential materials that can be used as multipollutant sorbents using a hierarchy of computational modeling approaches. Palladium (Pd) and gold (Au) alloys were investigated and the results show that the addition of a small amou...

251

Nanostructured materials for advanced energy conversion and storage devices  

Microsoft Academic Search

New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments

Antonino Salvatore Aricò; Peter Bruce; Bruno Scrosati; Jean-Marie Tarascon; Walter van Schalkwijk

2005-01-01

252

Thermal properties of graphene and nanostructured carbon materials  

Microsoft Academic Search

Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability

Alexander A. Balandin

2011-01-01

253

Using biological inspiration to engineer functional nanostructured materials.  

PubMed

Humans have always looked to nature for design inspiration, and material design on the molecular level is no different. Here we explore how this idea applies to nanoscale biomimicry, specifically examining both recent advances and our own work on engineering lipid and polymer membrane systems with cellular processes. PMID:17192981

Wendell, David W; Patti, Jordan; Montemagno, Carlo D

2006-11-01

254

Spectral representation theory of graded composite materials  

NASA Astrophysics Data System (ADS)

In graded composite materials, the physical properties can vary continuously in space and it may give different physical phenomena when compared with homogeneous materials. The Bergman-Milton spectral representation is a rigorous mathematical formalism to express the effective dielectric constant of nongraded composite materials [1]. In this study, we consider a material (rather than microsture [2]) graded composites, and generalize the Bergman-Milton spectral representation to extract the spectral density function for the effective dielectric constant of this graded composite material in the frequency domain [3]. Analytic and numerical solution will be presented for graded films and graded spheres. [1] D. J. Bergman, Phys. Rev. B 14, 4304 (1976). [2] J. P. Huang, K. W. Yu, G. Q. Gu, M. Karttunen, Phys. Rev. E 67, 051405 (2003). [3] L. Gao, J. P. Huang, K.W. Yu, Eur. Phys. J. B 36, 475 (2003).

Chan, K. L.; Kwok, C. M.; Yu, K. W.

2008-03-01

255

Autophagous spacecraft composite materials for orbital propulsion  

Microsoft Academic Search

We are developing structural polymer composite materials that can be converted into fuels and combusted with oxidizers for orbital propulsion of spacecraft. We have identified candidate materials and demonstrated sustained combustion with nitrogen tetroxide (NTO) as an oxidizer. To improve reaction chemistry we have evaluated several energetic additives. Detailed material compatibility tests were conducted to identify stable combinations of structural

Prakash Joshi; Bernard L. Upschulte; Alan H. Gelb; B. David Green; Dean M. Lester; Ingvar Wallace; W. David Starrett; David W. Marshall

2002-01-01

256

Nanostructure and Composition of Tribo-Boundary Films Formed in Ionic Liquid Lubrication  

SciTech Connect

Since the idea of using ionic liquids (ILs) as lubricants was raised in 2001, many studies have been conducted in this area and results have demonstrated superior lubricating performance for a variety of ionic liquids. It is widely believed that tribochemical reactions occur between the metal surface and the IL during the wear process to form a protective tribo-boundary film on the contact area that reduces friction and wear. However, the study of this critical boundary film has been limited to top surface two-dimensional topography examination and chemical analysis in the literature. A more comprehensive characterization is needed to help understand the film formation process and the lubricating mechanism. This study demonstrated a multi-technique three-dimensional approach to characterize the IL-formed boundary films, including top surface morphology examination, cross section nanostructure characterization, and layered chemical analysis. Characterization was carried out on both ferrous and aluminum surfaces lubricated by an ammonium IL. The focused-ion-beam (FIB) technique enabled TEM/EDS examination on the cross section of the boundary film to provide direct measurement of the film thickness, visualization of the nanostructure, and analysis of composition. In addition, composition-depth profiles were generated using XPS aided by ion-sputtering to reveal the composition change at different levels of the boundary film to investigate the film formation process.

Qu, Jun [ORNL; Chi, Miaofang [ORNL; Meyer III, Harry M [ORNL; Blau, Peter Julian [ORNL; Dai, Sheng [ORNL; Luo, Huimin [ORNL

2011-01-01

257

The influence of the composition of nanostructural PSZ powders on ceramics wear  

Microsoft Academic Search

The results of tribological testing of ceramics with the composition ZrO2 + Al2O3, ZrO2 + Y2O3, and ZrO2 + Y2O3 + Al2O3 made of nanostructural powders are presented. The nanopowders have been obtained by chemical precipitation from solutions\\u000a of zirconium and yttrium chloride salts. The studies have been carried out as applied to machine parts: drawing dies and bearing\\u000a plugs.

V. G. Lapteva; V. V. Alisin; L. I. Kuksenova; Yu. I. Sherbakov; I. A. Khrennikova

2011-01-01

258

Effective load transfer by a chromium carbide nanostructure in a multi-walled carbon nanotube/copper matrix composite  

NASA Astrophysics Data System (ADS)

Multi-walled carbon nanotube (MWCNT) reinforced copper (Cu) matrix composites, which exhibit chromium (Cr) carbide nanostructures at the MWCNT/Cu interface, were prepared through a carbide formation using CuCr alloy powder. The fully densified and oriented MWCNTs dispersed throughout the composites were prepared using spark plasma sintering (SPS) followed by hot extrusion. The tensile strengths of the MWCNT/CuCr composites increased with increasing MWCNTs content, while the tensile strength of MWCNT/Cu composite decreased from that of monolithic Cu. The enhanced tensile strength of the MWCNT/CuCr composites is a result of possible load-transfer mechanisms of the interfacial Cr carbide nanostructures. The multi-wall failure of MWCNTs observed in the fracture surface of the MWCNT/CuCr composites indicates an improvement in the load-bearing capacity of the MWCNTs. This result shows that the Cr carbide nanostructures effectively transferred the tensile load to the MWCNTs during fracture through carbide nanostructure formation in the MWCNT/Cu composite.

Cho, Seungchan; Kikuchi, Keiko; Kawasaki, Akira; Kwon, Hansang; Kim, Yangdo

2012-08-01

259

Effective load transfer by a chromium carbide nanostructure in a multi-walled carbon nanotube/copper matrix composite.  

PubMed

Multi-walled carbon nanotube (MWCNT) reinforced copper (Cu) matrix composites, which exhibit chromium (Cr) carbide nanostructures at the MWCNT/Cu interface, were prepared through a carbide formation using CuCr alloy powder. The fully densified and oriented MWCNTs dispersed throughout the composites were prepared using spark plasma sintering (SPS) followed by hot extrusion. The tensile strengths of the MWCNT/CuCr composites increased with increasing MWCNTs content, while the tensile strength of MWCNT/Cu composite decreased from that of monolithic Cu. The enhanced tensile strength of the MWCNT/CuCr composites is a result of possible load-transfer mechanisms of the interfacial Cr carbide nanostructures. The multi-wall failure of MWCNTs observed in the fracture surface of the MWCNT/CuCr composites indicates an improvement in the load-bearing capacity of the MWCNTs. This result shows that the Cr carbide nanostructures effectively transferred the tensile load to the MWCNTs during fracture through carbide nanostructure formation in the MWCNT/Cu composite. PMID:22797555

Cho, Seungchan; Kikuchi, Keiko; Kawasaki, Akira; Kwon, Hansang; Kim, Yangdo

2012-07-13

260

Sensors as probes for the environmental dynamics of nanostructured materials  

NASA Astrophysics Data System (ADS)

The last decade has witnessed an explosion of interests in the science and technology of engineered nanomaterials. The primary drive for most nanotechnology research and development is to synthesize new nanomaterials and to identify novel applications for them. Nanomaterials offer new possibilities for the development of novel sensing and monitoring technologies. Nanosensors can be classified under two main categories: (1) sensors that are used to measure nanoscale properties; and (2) sensors that are themselves nanoscale or have nanoscale materials or components. The first category can enhance our understanding of the fate and transport of engineered nanomaterials in environmental and biological systems. This is an area of critical interest in risk assessment. The second category can eventually result in lower material cost, reduced weight and power consumption. This presentation will focus on category 1 sensor for fullerenes and metal nanoparticles.

Sadik, Wunmi

2012-02-01

261

Electrosorption capacitance of nanostructured carbon-based materials  

Microsoft Academic Search

The fundamental mechanism of electrosorption of ions developing a double layer inside nanopores was studied via a combination of experimental and theoretical studies. A novel graphitized-carbon monolithic material has proven to be a good electrical double-layer capacitor that can be applied in the separation of ions from aqueous solutions. An extended electrical double-layer model indicated that the pore size distribution

Chia-Hung Hou; Chengdu Liang; Sotira Yiacoumi; Sheng Dai; Costas Tsouris

2006-01-01

262

EE FY00 report: nanostructure multilayer materials for capacitors  

SciTech Connect

Only two intrinsic approaches to increasing the density of energy stored in capacitors are known: (1) Increase the Dielectric Constant while maintaining the breakdown filed; and (2) Increase the breakdown field for a given dielectric constant material. The maximum energy density, E{sub 0} (Joules/cm{sup 3}) that can be stored in the dielectric of a capacitor is given by: E{sub 0} = 1/2 k {var_epsilon}{sub 0} V{sub b}{sup 2} (Joules/cm{sup 3} dielectric). Where k is the relative permittivity (dielectric constant), {var_epsilon}{sub 0} is the permittivity of free space (8.894 x 10{sup -14} F/cm) and V{sub b} the dielectric material breakdown field. In this project we have successfully developed capacitor structures using dielectric materials with 3 < k < 50 that exhibit high breakdown fields. The observed performance of these capacitors as characterized by the energy stored per unit volume of dielectric at V{sub b} are compared on the basis of the breakdown field in Figure 1.

Barbee, T W Jr

2000-10-26

263

Nanostructured high-energy cathode materials for advanced lithium batteries  

NASA Astrophysics Data System (ADS)

Nickel-rich layered lithium transition-metal oxides, LiNi1-xMxO2 (M?=?transition metal), have been under intense investigation as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. However, the commercial deployment of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures. Here, we report a nickel-rich lithium transition-metal oxide with a very high capacity (215?mA?h?g-1), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle. Using this nano-functional full-gradient approach, we are able to harness the high energy density of the nickel-rich core and the high thermal stability and long life of the manganese-rich outer layers. Moreover, the micrometre-size secondary particles of this cathode material are composed of aligned needle-like nanosize primary particles, resulting in a high rate capability. The experimental results suggest that this nano-functional full-gradient cathode material is promising for applications that require high energy, long calendar life and excellent abuse tolerance such as electric vehicles.

Sun, Yang-Kook; Chen, Zonghai; Noh, Hyung-Joo; Lee, Dong-Ju; Jung, Hun-Gi; Ren, Yang; Wang, Steve; Yoon, Chong Seung; Myung, Seung-Taek; Amine, Khalil

2012-11-01

264

Nanostructured high-energy cathode materials for advanced lithium batteries.  

PubMed

Nickel-rich layered lithium transition-metal oxides, LiNi(1-x)M(x)O(2) (M = transition metal), have been under intense investigation as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. However, the commercial deployment of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures. Here, we report a nickel-rich lithium transition-metal oxide with a very high capacity (215 mA h g(-1)), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle. Using this nano-functional full-gradient approach, we are able to harness the high energy density of the nickel-rich core and the high thermal stability and long life of the manganese-rich outer layers. Moreover, the micrometre-size secondary particles of this cathode material are composed of aligned needle-like nanosize primary particles, resulting in a high rate capability. The experimental results suggest that this nano-functional full-gradient cathode material is promising for applications that require high energy, long calendar life and excellent abuse tolerance such as electric vehicles. PMID:23042415

Sun, Yang-Kook; Chen, Zonghai; Noh, Hyung-Joo; Lee, Dong-Ju; Jung, Hun-Gi; Ren, Yang; Wang, Steve; Yoon, Chong Seung; Myung, Seung-Taek; Amine, Khalil

2012-10-07

265

Delamination Growth in Composite Materials.  

National Technical Information Service (NTIS)

The Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) specimens are employed to characterize MODE I and MODE II interlaminar fracture resistance of graphite/epoxy (CYCOM 982) and graphite/PEEK (APC2) composites. Sizing of test specimen geomet...

J. W. Gillespie L. A. Carlsson R. B. Pipes R. Rothschilds B. Trethewey

1986-01-01

266

Surface Anchoring of Nematic Phase on Carbon Nanotubes: Nanostructure of Ultra-High Temperature Materials  

SciTech Connect

Nuclear energy is a dependable and economical source of electricity. Because fuel supply sources are available domestically, nuclear energy can be a strong domestic industry that can reduce dependence on foreign energy sources. Commercial nuclear power plants have extensive security measures to protect the facility from intruders [1]. However, additional research efforts are needed to increase the inherent process safety of nuclear energy plants to protect the public in the event of a reactor malfunction. The next generation nuclear plant (NGNP) is envisioned to utilize a very high temperature reactor (VHTR) design with an operating temperature of 650-1000�°C [2]. One of the most important safety design requirements for this reactor is that it must be inherently safe, i.e., the reactor must shut down safely in the event that the coolant flow is interrupted [2]. This next-generation Gen IV reactor must operate in an inherently safe mode where the off-normal temperatures may reach 1500�°C due to coolant-flow interruption. Metallic alloys used currently in reactor internals will melt at such temperatures. Structural materials that will not melt at such ultra-high temperatures are carbon/graphtic fibers and carbon-matrix composites. Graphite does not have a measurable melting point; it is known to sublime starting about 3300�°C. However, neutron radiation-damage effects on carbon fibers are poorly understood. Therefore, the goal of this project is to obtain a fundamental understanding of the role of nanotexture on the properties of resulting carbon fibers and their neutron-damage characteristics. Although polygranular graphite has been used in nuclear environment for almost fifty years, it is not suitable for structural applications because it do not possess adequate strength, stiffness, or toughness that is required of structural components such as reaction control-rods, upper plenum shroud, and lower core-support plate [2,3]. For structural purposes, composites consisting of strong carbon fibers embedded in a carbon matrix are needed. Such carbon/carbon (C/C) composites have been used in aerospace industry to produce missile nose cones, space shuttle leading edge, and aircraft brake-pads. However, radiation-tolerance of such materials is not adequately known because only limited radiation studies have been performed on C/C composites, which suggest that pitch-based carbon fibers have better dimensional stability than that of polyacrylonitrile (PAN) based fibers [4]. The thermodynamically-stable state of graphitic crystalline packing of carbon atoms derived from mesophase pitch leads to a greater stability during neutron irradiation [5]. The specific objectives of this project were: (i) to generating novel carbonaceous nanostructures, (ii) measure extent of graphitic crystallinity and the extent of anisotropy, and (iii) collaborate with the Carbon Materials group at Oak Ridge National Lab to have neutron irradiation studies and post-irradiation examinations conducted on the carbon fibers produced in this research project.

Ogale, Amod A

2012-04-27

267

A Direct Route towards Assembly of Nanoparticle-Carbon Nanotube Composite Materials  

SciTech Connect

The exploration of nanoparticle-structured thin films as sensing materials desires maximum accessibility of analytes and effective mass transport within the nanostructure. This paper explores the viability of creating nanoparticle-carbon nanotube (CNTs) as composite interfacial materials to enhance such properties. We report findings of an investigation of the assembly of monolayer-protected gold nanoparticles on multi-walled CNTs. A simple and effective route has been demonstrated for assembling nanoparticles of 2-5 nm core sizes onto CNTs with controllable coverage and interparticle spatial properties. The composite nanomaterials can be dispersed in organic solvent and cast on interdigitated microelectrode surface. The skeleton-like nanocomposite materials have been examined for chemiresistor sensing of volatile organic compounds. The response profiles and sensitivities of the nanocomposites determined for the sorption of a series of vapors have been shown to exhibit different or enhanced sensing properties in comparison with similar but nanotube-free nanoparticle assemblies. The observation of these results can be attributed to a combination of three factors, the increased accessibility of analytes to the nanostructure, the enhanced mass transport characteristics, and the unique electronic properties of the nanocomposite materials. Implications of the findings to the design of nanostructured sensing materials are also discussed.

Han, Li; Wu, Wendy; Kirk, F.L.; Luo, Jin; Maye, Mathew M.; Kariuki, Nancy N.; Lin, Yuehe; Wang, Chong M.; Zhong, Chuan-Jian

2004-07-06

268

Manufacturing technology of the composite materials: nanocrystalline material - polymer type  

Microsoft Academic Search

Purpose: This paper presents the material and technological solution which makes it possible to obtain the nanocrystalline, ferromagnetic powder material of Fe73.5Cu1Nb3Si13.5B9 alloy after its thermal nanocrystallization with the succeeding high-energy milling. Another aspect was to develop the technology to obtain the nanocrystalline composite materials made by binding the obtained powder material with the high density low- pressures polyethylene (PEHD)

B. Zi?bowicz; D. Szewieczek; L. A. Dobrza?ski

269

Oxidative Dehydrogenation Properties of Novel Nanostructured Polyoxovanadate Based Materials  

Microsoft Academic Search

\\u000a Abstract  A comparative study of the catalytic oxidative dehydrogenation of propane by a novel polyoxovanadate based open-framework\\u000a material (Co-POV)—[Co3V18O42(H2O)12(XO4)]·24H2O (X = V, S), which is composed of nanometer size vanadium oxide clusters interlinked by cobalt oxide {–O–Co–O–} motifs, showed\\u000a that Co-POV has superior catalytic property as compared to its individual metal oxide constituents, vanadium oxide and cobalt\\u000a oxide, and their mixture, with high

M. Ishaque Khan; Kadir Aydemir; M. Rafiq H. Siddiqui; Abdulrahman A. Alwarthan; Christopher L. Marshall

2011-01-01

270

Near-term nanotechnology: the molecular fabrication of nanostructured materials  

NASA Astrophysics Data System (ADS)

The remarkably short timescales commonly predicted for achieving full molecular nanotechnology (MNT) are not realistic, as an enormous investment must be made up-front for a distant and ill-defined payoff. The reason is that technology, per se, is not an economic driver; economics instead drives technology. Hence, markets that could motivate the ongoing, incremental development of MNT must be sought. Such markets exist: they fundamentally consist of the molecular assembly of nano structured materials such as semipermeable membranes, catalysts, perfect crystalline fibres, and others. Although in theory atomically precise, such materials have no molecular moving parts and thus will be both easier to build and more robust. Some of these applications (e.g. catalysis), moreover, have huge, mature markets. Once a demand is established, further incremental development of primitive molecular assemblers, or `molecular looms', might then justify the analogies with the explosive development of computer hardware over the last few decades. Finally, the fact that many such applications are likely to be rendered obsolete by full MNT is irrelevant to their interim value as technology drivers.

Gillett, Stephen L.

1996-09-01

271

Muorganic/inorganic nanostructured materials: Towards synergistic mechanical and optical properties  

NASA Astrophysics Data System (ADS)

This study utilizes the "bricks" and "mortar" approach to assemble representative organic and inorganic nanostructures into functional hybrid nanomaterials. Zero-dimensional spherical nanoparticles, one-dimensional silver nanowires, and two-dimensional silver nanoplates represent the inorganic functional nanostructured "bricks". Functional-group bearing polystyrene2-polyethyleneoxide1 (PS2-PEO 1) star polymer, poly(allylamine hydrochloride), and poly(styrene sulfonate) were employed as the "mortar". Mechanical, optical, and electrical properties of the resulting organic/inorganic microstructures were investigated to establish structure-property relationships. Beyond the design, fabrication, and characterization of these novel hybrid nanomaterials two potential applications have been explored: (1) ultra-thin composite film-based pressure sensor and (2) single nanoparticle SERS-based chemical sensors. One-dimensional silver nanowires (diameter = 80 +/- 5 nm, length = 6 +/- 2 microm) were sandwiched into layer-by-layer (LbL) polyelectrolyte film to yield a series of robust freestanding ultrathin structures (< 100 nm thick). The sandwich architecture allows facile control over volume fraction of silver nanowires (2.5 ? ? ? 22.5%), and hence their composite Young's moduli. Furthermore, the composite film was found to be conductive (110--660 S/cm) within the range of volume fraction in par with percolation threshold predicted for a two-dimensional film. Subsequently, an array of silver nanowires was unidirectionally aligned by means of Langmuir-Blodgett (LB) technique. The unidirectionally oriented silver nanowires were sandwiched into LbL film to give an anisotropic nanocomposite film with much stiffer (fivefold) mechanical response in the direction of nanowire orientation. In addition to their tailored mechanical and electrical properties, these films are robust and can be easily transferred onto various microfabricated substrates. To fabricate these nanostructures, two experimental techniques were developed to characterize the micromechanical properties of the nanocomposite film and array of one-dimensional metallic nanostructures: interferometry of bulged film and buckling of array of highly-oriented nanowires, respectively. Next, using the same silver nanowire building block a different design of organic/inorganic hybrid nanostructures was explored. With the aid of a three-arm (X-PEO)1-(PS1-Y)2 star polymer linker, spherical gold nanoparticles were assembled onto a silver nanowire surface. We demonstrated that such hybrid, silver-gold nanowires resembling nanocobs, possess significant SERS ability and can serve as bright anisotropic SERS-markers for Raman-based chemical sensor. The influence of core nanostructure geometries (1-D silver nanowire versus 2-D silver nanoplates) were subsequently investigated for their single-nanoparticle hybrid SERS-enhancing ability and control over optical plasmon absorption within the visible and near infrared range. In the latter design, an improved design of SERS-nanostructure was explored by replacing the three-arm star polymer with polyelectrolyte "mortar" which can absorb chemical analytes into the intra-particle "hot-spots".

Gunawidjaja, Ray

272

A Statistical Theory of Composite Materials Strength  

Microsoft Academic Search

A statistical tensile failure theory of composite materials with uniaxially oriented fibers is proposed. In the theory, the strength of fibers is assumed to be a statistical quantity and the fibers around a broken fiber are supposed to be subjected to localized stress concentra tions. The number of broken fibers in a layer of composite as a function of average

Yuntian Zhu; Benlian Zhou; Guanhu He; Zongguang Zheng

1989-01-01

273

Carbon-Carbon Materials and Composites.  

National Technical Information Service (NTIS)

Carbon-fiber-reinforced carbon matrix (carbon-carbon) composites have received increasing emphasis over the past 15 years. These materials have been used primarily in the aerospace and automotive industries. Carbon-carbon composites can be made in a wide ...

D. D. Edie J. D. Buckley

1992-01-01

274

Self-healing structural composite materials  

Microsoft Academic Search

A self-healing fiber-reinforced structural polymer matrix composite material is demonstrated. In the composite, a microencapsulated healing agent and a solid chemical catalyst are dispersed within the polymer matrix phase. Healing is triggered by crack propagation through the microcapsules, which then release the healing agent into the crack plane. Subsequent exposure of the healing agent to the chemical catalyst initiates polymerization

M. R. Kessler; N. R. Sottos; S. R. White

2003-01-01

275

Method to fabricate layered material compositions  

SciTech Connect

A new class of processes suited to the fabrication of layered material compositions is disclosed. Layered material compositions are typically three-dimensional structures which can be decomposed into a stack of structured layers. The best known examples are the photonic lattices. The present invention combines the characteristic features of photolithography and chemical-mechanical polishing to permit the direct and facile fabrication of, e.g., photonic lattices having photonic bandgaps in the 0.1-20.mu. spectral range.

Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

2002-01-01

276

Laser welding of discontinuously reinforced composite materials  

NASA Astrophysics Data System (ADS)

The features of metal composite materials fusion welding are examined and the main defects arising at argon-arc, electron-beam and laser welding of alloys Al-Be-Mg, Fe-Cu-Pb and Al-Pb are revealed. The defects formation mechanisms are indicated and technological welding methods of metal composite materials are developed. These methods allow to prevent defects formation and obtain the welds with required mechanical properties and quality.

Shiganov, I. N.

1999-01-01

277

Dynamic compressive behavior of thick composite materials  

Microsoft Academic Search

The effect of strain rate on the compressive behavior of thick carbon\\/epoxy composite materials was investigated. Falling weight impact and split Hopkinson pressure bar systems were developed for dynamic characterization of composite materials in compression at strain rates up to 2000 s–1. Strain rates below 10 s–1 were generated using a servohydraulic testing machine. Strain rates between 10 s–1 and

H. M. Hsiao; I. M. Daniel; R. D. Cordes

1998-01-01

278

Raman Imaging of Micro- and Nano-Structured Materials  

NASA Astrophysics Data System (ADS)

Raman microscopy has emerged as a powerful technique to characterize anisotropic materials with a submicrometer resolution. The use of polarized light allows one to get precise information about the local organization of the relevant molecular groups through the determination of the most probable distribution function. Such a polarized analysis can be conducted under a confocal microscope but caution must be considered because of the use of high numerical aperture objectives. The molecular orientation can be effectively correlated with the topography of the sample when atomic force microscopy experiments are conducted on the same object. In this chapter, we present 2D and 3D Raman imaging results that have been conducted on mesostructured polymer surfaces and on functionalized metallic surfaces that can serve as SERS platforms. In addition, we compare the results obtained on semiconductor nanowires in confocal Raman conditions or benefiting from local tip enhancement.

Guieu, Valérie; Lagugné-Labarthet, François

279

Nanostructured material for advanced energy storage : magnesium battery cathode development.  

SciTech Connect

Magnesium batteries are alternatives to the use of lithium ion and nickel metal hydride secondary batteries due to magnesium's abundance, safety of operation, and lower toxicity of disposal. The divalency of the magnesium ion and its chemistry poses some difficulties for its general and industrial use. This work developed a continuous and fibrous nanoscale network of the cathode material through the use of electrospinning with the goal of enhancing performance and reactivity of the battery. The system was characterized and preliminary tests were performed on the constructed battery cells. We were successful in building and testing a series of electrochemical systems that demonstrated good cyclability maintaining 60-70% of discharge capacity after more than 50 charge-discharge cycles.

Sigmund, Wolfgang M. (University of Florida, Gainesville, FL); Woan, Karran V. (University of Florida, Gainesville, FL); Bell, Nelson Simmons

2010-11-01

280

Nanostructure multilayer dielectric materials for capacitors and insulators  

DOEpatents

A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}) in alternating layers to form a nano-laminate. 1 fig.

Barbee, T.W. Jr.; Johnson, G.W.

1998-04-21

281

Composite materials: composition, properties and clinical applications. A literature review.  

PubMed

Various composite materials are available today for direct restorative techniques. The most well-known materials are the hybrid composites. This technology, based on methacrylates and different types of filler coupled with silanes, has been continuously improved. Disadvantages such as polymerisation shrinkage, bacterial adhesion and side effects due to monomer release still remain. The aim of material development is to eliminate or at least reduce these negative factors by adapting the individual components of the material. With ormocers, the methacrylate has been partially replaced by an inorganic network. According to recent studies, the biocompatibility was not improved in all cases. The development of compomer was an attempt to combine the positive properties of glassionomers with composite technology. This has only partially succeeded, because the fluoride release is low. In an in-situ study, a caries protective effect could be shown at least in the first days following filling placement with concurrent extra-oral demineralisation. By replacing the chain-monomers in the composite matrix by ring-shaped molecules, a new approach to reduce polymerisation shrinkage was investigated. A new group of materials, the siloranes, has been developed. Siloranes are hydrophobic and need to be bonded to the dental hard tissue using a special adhesive system. Long-term clinical studies are still needed to prove the superiority of this new group of materials over modern hybrid composites. PMID:21243545

Zimmerli, Brigitte; Strub, Matthias; Jeger, Franziska; Stadler, Oliver; Lussi, Adrian

2010-01-01

282

Shock wave interactions with nano-structured materials: a molecular dynamics approach  

NASA Astrophysics Data System (ADS)

Porous materials have long been known to be effective in blast mitigation strategies. Nano-structured materials appear to have an even greater potential for blast mitigation because of their high surface-to-volume ratio, a geometric factor which substantially attenuates shock wave propagation. A molecular dynamics approach was used to explore the effects of this remarkable property on the behavior of traveling shocks impacting on solid materials. The computational setup included a moving piston, a gas region, and a target solid wall with and without a porous structure. The materials involved were represented by realistic interaction potentials. The results indicate that the presence of a nano-porous material layer in front of the target wall reduced the stress magnitude and the energy deposited inside the solid by about 30 %, while at the same time substantially decreasing the loading rate.

Al-Qananwah, A. K.; Koplik, J.; Andreopoulos, Y.

2013-02-01

283

Evaluation of Hybrid Composite Materials.  

National Technical Information Service (NTIS)

An examination of the available fiber prepregs clearly suggests that the higher stiffness and strength materials such as boron and graphite have higher price levels than the lower stiffness and strength prepregs such as Kevlar-49 and S-Glass. A logical ou...

S. V. Kulkarni B. W. Rosen H. C. Boehm

1975-01-01

284

High capacitive performance of nanostructured Mn-Ni-Co oxide composites for supercapacitor  

SciTech Connect

Nanostructured Mn-Ni-Co oxide composites (MNCO) were prepared by thermal decomposition of the precursor obtained by chemical co-precipitation of Mn, Ni and Co salts. The chemical composition and morphology were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The electrochemical capacitance of MNCO electrode was examined by cyclic voltammetry, impedance and galvanostatic charge-discharge measurements. The results showed that MNCO electrode exhibited the good electrochemical characteristics. A maximum capacitance value of 1260 F g{sup -1} could be obtained within the potential range of -0.1 to 0.4 V versus saturated calomel electrode (SCE) in 6 mol L{sup -1} KOH electrolyte.

Luo Jianmin [Institute of Applied Chemistry, Xinjiang University, Urumqi 830046 (China); Gao Bo [College of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Zhang Xiaogang [College of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)], E-mail: azhangxg@163.com

2008-05-06

285

3-D textile reinforcements in composite materials  

SciTech Connect

Laminated composite materials have been used in structural applications since the 1960s. However, their high cost and inability to accommodate fibers in the laminate`s thickness direction greatly reduce their damage tolerance and impact resistance. The second generation of materials--3-D textile reinforced composites--offers significant cost reduction, and by incorporating reinforcement in the thickness direction, dramatically increases damage tolerance and impact resistance. However, methods for predicting mechanical properties of 3-D textile reinforced composite materials tend to be more complex. These materials also have disadvantages--particularly in regard to crimps in the yarns--that require more research. Textile preforms, micro- and macromechanical modeling, manufacturing processes, and characterization all need further development. As researchers overcome these problems, this new generation of composites will emerge as a highly competitive family of materials. This book provides a state-of-the-art account of this promising technology. In it, top experts describe the manufacturing processes, highlight the advantages, identify the main applications, analyze methods for predicting mechanical properties, and detail various reinforcement strategies, including grid structure, knitted fabric composites, and the braiding technique. Armed with the information in this book, readers will be prepared to better exploit the advantages of 3-D textile reinforced composites, overcome its disadvantages, and contribute to the further development of the technology.

Miravete, A. [Univ. of Zaragoza (Spain)

1999-11-01

286

Nonmetallic materials and composites at low temperatures  

Microsoft Academic Search

This book presents articles by leading scientists who explore the cryogenic behavior of such materials as epoxies, polyethylenes, polymers, various composites, and glasses. Examines the thermal and dielectric properties of these materials, as well as their elasticity, cohesive strength, resistance to strain and fracturing, and applications. Topics include thermal properties of crystalline polymers; thermal conductivity in semicrystalline polymers; ultrasonic absorption

G. Hartwig; D. Evans

1982-01-01

287

Prediction of Crushing Stress in Composite Materials  

Microsoft Academic Search

A simple mathematical model for predicting the crushing stress of composite materials was derived and presented in this article. The present knowledge of fracture mechanics and strength of materials are used as the basis for the model. The fracture mechanics part of the analysis was based on energy release rate approach; the energy release rate, G, of the proposed model

S. Goh; H. Ku; S. L. Ang

2008-01-01

288

Improvements in 3-omega measurement of thermal conductivity for nanostructured materials  

NASA Astrophysics Data System (ADS)

Nanostructured materials have reduced thermal conductivity in order to enhance the thermoelectric figure of merit (ZT). The 3? method is widely used for vertical thermal conductivity measurements in the nanostructure materials, especially layered materials. The challenge for this method is to measure the small 3? voltage at the third harmonic, above the comparably large ? voltage from the sample at the fundamental frequency, complicated by the nonlinear signal from other components in the measurement circuit. We carefully study the 3? method [Cahill, Rev. Sci. lnstrum. 61 (2), 802 (1990)] and develop a strategy to increase the signal to noise ratio of the data, for more accurate results. We also investigate an alternate sample preparation geometry for the 3? measurement, so that the heat flow is vertical and linear through the thin film instead of cylindrical as is standard for this method. This results in a direct measurement of the vertical thermal conductivity in such an anisotropic material. New geometries for measuring lateral thermal conductivity will also be proposed and explored.

Zhou, Chuanle; Grayson, M.; Koblmueller, G.

2011-03-01

289

Large scale atomistic approaches to thermal transport and phonon scattering in nanostructured materials  

NASA Astrophysics Data System (ADS)

Decreasing the thermal conductivity of bulk materials by nanostructuring and dimensionality reduction, or by introducing some amount of disorder represents a promising strategy in the search for efficient thermoelectric materials [1]. For example, considerable improvements of the thermoelectric efficiency in nanowires with surface roughness [2], superlattices [3] and nanocomposites [4] have been attributed to a significantly reduced thermal conductivity. In order to accurately describe thermal transport processes in complex nanostructured materials and directly compare with experiments, the development of theoretical and computational approaches that can account for both anharmonic and disorder effects in large samples is highly desirable. We will first summarize the strengths and weaknesses of the standard atomistic approaches to thermal transport (molecular dynamics [5], Boltzmann transport equation [6] and Green's function approach [7]) . We will then focus on the methods based on the solution of the Boltzmann transport equation, that are computationally too demanding, at present, to treat large scale systems and thus to investigate realistic materials. We will present a Monte Carlo method [8] to solve the Boltzmann transport equation in the relaxation time approximation [9], that enables computation of the thermal conductivity of ordered and disordered systems with a number of atoms up to an order of magnitude larger than feasible with straightforward integration. We will present a comparison between exact and Monte Carlo Boltzmann transport results for small SiGe nanostructures and then use the Monte Carlo method to analyze the thermal properties of realistic SiGe nanostructured materials. This work is done in collaboration with Davide Donadio, Francois Gygi, and Giulia Galli from UC Davis.[4pt] [1] See e.g. A. J. Minnich, M. S. Dresselhaus, Z. F. Ren, and G. Chen, Energy Environ. Sci. 2, 466 (2009).[0pt] [2] A. I. Hochbaum et al, Nature 451, 163 (2008).[0pt] [3] R. Venkatasubramanian, E. Siivola, T. Colpitts, and B. O'Quinn, Nature 413, 597 (2001).[0pt] [4] B. Poudel et al, Science 320, 634 (2008).[0pt] [5] See e.g. Y. He, D. Donadio, and G. Galli, Nano Lett. 11, 3608 (2011).[0pt] [6] See e.g. A. Ward and D. A. Broido, Phys. Rev. B 81, 085205 (2010).[0pt] [7] See e.g. I. Savic, N. Mingo, and D. A. Stewart, Phys. Rev. Lett. 101, 165502 (2008).[0pt] [8] I. Savic, D.Donadio, F.Gygi, and G.Galli (in preparation).[0pt] [9] See e.g. J. E. Turney, E. S. Landry, A. J. H. McGaughey, and C. H. Amon, Phys. Rev. B, 79, 064301 (2009).

Savic, Ivana

2012-02-01

290

Highly sensitive ethanol chemical sensor based on Ni-doped SnO? nanostructure materials.  

PubMed

Due to potential applications of semiconductor transition doped nanostructure materials and the important advantages of synthesis in cost-effective and environmental concerns, a significant effort has been consummated for improvement of Ni-doped SnO(2) nanomaterials using hydrothermal technique at room conditions. The structural and optical properties of the low-dimensional (average diameter, 52.4 nm) Ni-doped SnO(2) nanostructures were demonstrated using various conventional techniques such as UV/visible spectroscopy, FT-IR spectroscopy, X-ray powder diffraction (XRD), and Field-emission scanning electron microscopy (FE-SEM). The calcined doped material is an attractive semiconductor nanoparticle for accomplishment in chemical sensing by simple I-V technique, where toxic chemical (ethanol) is used as a target chemical. Thin-film of Ni-doped SnO(2) nanostructure materials with conducting coating agents on silver electrodes (AgE, surface area, 0.0216 cm(2)) revealed higher sensitivity and repeatability. The calibration plot is linear (R, 0.8440) over the large dynamic range (1.0 nM-1.0 mM), where the sensitivity is approximately 2.3148 ?A cm(-2) mM(-1) with a detection limit of 0.6 nM, based on signal/noise ratio in short response time. Consequently on the basis of the sensitive communication among structures, morphologies, and properties, it is exemplified that the morphologies and the optical characteristics can be extended to a large scale in doping nanomaterials and proficient chemical sensors applications. PMID:21831627

Rahman, Mohammed M; Jamal, Aslam; Khan, Sher Bahadar; Faisal, M

2011-07-20

291

Reactive Ballistic Deposition of Nanostructured Model Materials for Electrochemical Energy Conversion and Storage  

SciTech Connect

Finely structured, supported thin films offer a host of opportunities for fundamental and applied research. Nanostructured materials often exhibit physical properties which differ from their bulk counterparts due to the increased importance of the surface in determining the thermodynamics and behavior of the system. Thus, control of the characteristic size, porosity, morphology, and surface area presents opportunities to tailor new materials which are useful platforms for elucidating the fundamental processes related to energy conversion and storage. The ability to produce high purity materials with direct control of relevant film parameters such as porosity, film thickness, and film morphology is of immediate interest in the fields of electrochemistry, photocatalysis, and thermal catalysis. Studies of various photoactive materials have introduced questions concerning the effects of film architecture and surface structure on the performance of the materials, while recent work has demonstrated that nanostructured, mesoporous, or disordered materials often deform plastically, making them robust in applications where volumetric expansion and phase transformations occur, such as in materials for lithium-ion batteries. Moreover, renewed emphasis has been placed on the formation of semi-conductive electrodes with controlled pore-size and large surface areas for the study and application of pseudo-capacitance and cation insertion processes for electrical energy storage. Understanding how the performance of such materials depends on morphology, porosity, and surface structure and area requires a synthesis technique which provides for incremental variations in structure and facilitates assessment of the performance with the appropriate analytical tools, preferably those that provide both structural information and kinetic insight into photoelectrochemical processes.

Flaherty, David W.; Hahn, Nathan T.; May, Robert A.; Berglund, Sean P.; Lin, Yong-Mao; Stevenson, Keith J.; Dohnalek, Zdenek; Kay, Bruce D.; Mullins, C. Buddie

2012-03-20

292

Advanced composite materials for optomechanical systems  

NASA Astrophysics Data System (ADS)

Polymer matrix composites (PMCs) have been well established in optomechanical systems for several decades. The other three classes of composites; metal matrix composites (MMCs), ceramic matrix composites (CMCs), and carbon matrix composites (CAMCs) are making significant inroads. The latter include carbon/carbon (C/C) composites (CCCs). The success of composites has resulted in increasing use in consumer, industrial, scientific, and aerospace/defense optomechanical applications. Composites offer significant advantages over traditional materials, including high stiffnesses and strengths, near-zero and tailorable coefficients of thermal expansion (CTEs), tailorable thermal conductivities (from very low to over twice that of copper), and low densities. In addition, they lack beryllium's toxicity problems. Some manufacturing processes allow parts consolidation, reducing machining and joining operations. At present, PMCs are the most widely used composites. Optomechanical applications date from the 1970s. The second High Energy Astrophysical Observatory spacecraft, placed in orbit in 1978, had an ultrahigh-modulus carbon fiber-reinforced epoxy (carbon/epoxy) optical bench metering structure. Since then, fibers and matrix materials have advanced significantly, and use of carbon fiber-reinforced polymers (CFRPs) has increased steadily. Space system examples include the Hubble Space Telescope metering truss and instrument benches, Upper Atmosphere Research Satellite (UARS), James Webb Space Telescope and many others. Use has spread to airborne applications, such as SOFIA. Perhaps the most impressive CFRP applications are the fifty-four 12m and twelve 7m moveable ground-based ALMA antennas. The other three classes of composites have a number of significant advantages over PMCs, including no moisture absorption or outgassing of organic compounds. CCC and CMC components have flown on a variety of spacecraft. MMCs have been used in space, aircraft, military and industrial applications. In this paper, we review key PMC, MMC, CCC, and CMC optomechanical system materials, including properties, advantages, disadvantages, applications and future developments. These topics are covered in more detail in SPIE short courses SC218 and SC1078.

Zweben, Carl

2013-09-01

293

Deformational methods of material nanostructuring: Premises, history, state of the art, and prospects  

NASA Astrophysics Data System (ADS)

Brief history of origin and development of methods of deformational nanostructuring of materials (DNM) also referred to as methods of severe plastic deformation (SPD) are presented. Principles and efficiencies of the most widespread DNM methods — torsion under quasi-hydrostatic pressure (THP), equal channel angular pressing (ECAP), and hydrostatic isothermal forging (HIF) — are analyzed. Results of pioneer research of the structure and properties of nanomaterials produced by these methods are given. Prospects for the DNM application in industrial technologies of metal treatment and product manufacturing are indicated.

Mulyukov, R. R.; Nazarov, A. A.; Imaev, R. M.

2008-05-01

294

The Challenges and Opportunities of Measuring Properties of Nanoparticles and Nanostructured Materials: Importance of a Multi-Technique Approach  

SciTech Connect

Nanostructured materials are increasingly subject to nearly every type of chemical and physical analysis possible. Because of their small feature size there is a significant focus on tools with high spatial resolution. Since, in addition, because of their high surface area, it is natural to characterize nanomaterials using tools designed to analyze surfaces. Regardless of the approach, nanostructured materials present a variety of obstacles to useful analysis. Specimen handling, contamination, environmental conditions and time can be important for analysis of many materials but are of increased concern for nanomaterials. Impacts of shape and stability of nanostructured materials are less explored. In a program focused on iron nanoparticles we use a combination of tools for routine analysis including XPS, TEM, and XRD and apply other methods as needed to obtain essential information.

Baer, Donald R.; Engelhard, Mark H.; Wang, Chong M.; Lea, Alan S.; Pecher, Klaus H.

2006-04-26

295

Atomistic Monte Carlo simulations of heat transport in Si and SiGe nanostructured materials  

NASA Astrophysics Data System (ADS)

Efficient thermoelectric energy conversion depends on the design of materials with low thermal conductivity and/or high electrical conductivity and Seebeck coefficient [1]. Semiconducting nanostructured materials are promising candidates to exhibit high thermoelectric efficiency, as they may have much lower thermal conductivity than their bulk counterparts [1]. Atomistic simulations capable of handling large samples and describing accurately phonon dispersions and lifetimes at the nanoscale could greatly advance our understanding of heat transport in such materials [2]. We will present an atomistic Monte Carlo method to solve the Boltzmann transport equation [3] that enables the computation of the thermal conductivity of large systems with both empirical and first principles Hamiltonians (e.g. up to several thousand atoms in the case of Tersoff potentials). We will demonstrate how this new approach allows one to rationalize trends in the thermal conductivity of a range of Si and SiGe based nanostructures, as a function of size, dimensionality and morphology [3]. [1] See e.g. A. J. Minnich et al. Energy Environ. Sci. 2, 466 (2009). [2] Y. He, I. Savic, D. Donadio, and G. Galli, accepted in Phys. Chem. Chem. Phys. [3] I. Savic, D. Donadio, F. Gygi, and G. Galli, submitted.

Savic, Ivana; Donadio, Davide; Murray, Eamonn; Gygi, Francois; Galli, Giulia

2013-03-01

296

Vertically Aligned Nanostructured Arrays of Inorganic Materials: Synthesis, Distinctive Physical Phenomena, and Device Integration  

NASA Astrophysics Data System (ADS)

The manifestation of novel physical phenomena upon scaling materials to finite size has inspired new device concepts that take advantage of the distinctive electrical, mechanical, and optical, properties of nanostructures. The development of fabrication approaches for the preparation of their 1D nanostructured form, such as nanowires and nanotubes, has contributed greatly to advancing fundamental understanding of these systems, and has spurred the integration of these materials in novel electronics, photonic devices, power sources, and energy scavenging constructs. Significant progress has been achieved over the last decade in the preparation of ordered arrays of carbon nanotubes, II---VI and III---V semiconductors, and some binary oxides such as ZnO. In contrast, relatively less attention has been focused on layered materials with potential for electrochemical energy storage. Here, we describe the catalyzed vapor transport growth of vertical arrays of orthorhombic V2O 5 nanowires. In addition, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to precisely probe the alignment, uniformity in crystal growth direction, and electronic structure of single-crystalline V2O5 nanowire arrays prepared by a cobalt-catalyzed vapor transport process. The dipole selection rules operational for core-level electron spectroscopy enable angle-dependant NEXAFS spectroscopy to be used as a sensitive probe of the anisotropy of these systems and provides detailed insight into bond orientation and the symmetry of the frontier orbital states. The experimental spectra are matched to previous theoretical predictions and allow experimental verification of features such as the origin of the split-off conduction band responsible for the n-type conductivity of V2O5 and the strongly anisotropic nature of vanadyl-oxygen-derived (V=O) states thought to be involved in catalysis. We have also invested substantial effort in obtaining shape and size control of metal oxide materials to obtain a fundamental understanding of the influence of finite size and surface restructuring on electronic instabilities in the proximity of the Fermi level. We present here a novel synthetic approach that takes advantage of the intrinsic octahedral symmetry of rock-salt-structured VO to facilitate the growth of six-armed nanocrystallites of related, technologically more important binary vanadium oxide V2O5 . The prepared nanostructures exhibit clear six-fold symmetry and most notably show remarkable retention of electronic structure. The latter has been evidenced through extensive X-ray absorption spectroscopy measurements. We have further designed a facile, generalizable, and entirely scalable approach for the fabrication of vertically aligned arrays of Fe2O 3/polypyrrole core---shell nanostructures and polypyrrole nanotubes. Our "all electrochemical" approach is based on the fabrication of ?-Fe 2O3 nanowire arrays by the simple heat treatment of commodity low carbon steel substrates, followed by electropolymerization of conformal polypyrrole sheaths around the nanowires. Subsequently, electrochemical etching of the nanowires yields large-area vertically aligned polypyrrole nanotube arrays on the steel substrate. The developed methodology is generalizable to functionalized pyrrole monomers and represents a significant practical advance of relevance to the technological implementation of conjugated polymer nanostructures in electrochromics, electrochemical energy storage, and sensing. As another variation of this general synthetic route, we have extended the practice of our simple oxidative process for the fabrication of large-area ZnO nanostructures, specifically highly aligned nanowire arrays integrated onto galvanized steel substrates which via a simple device design and additive piezoelectric nanopower generation were measured across the array substrates. The nanomaterial syntheses and device fabrication approaches developed here will enable facile integration of piezoelectric nanogenerators on to structural components.

Velazquez, Jesus Manuel

297

Crack—Interface Interaction in Composite Materials  

Microsoft Academic Search

The presence of cracks has a major impact on the reliability of advanced materials, like fiber or particle reinforced composites\\u000a or laminated composites. This paper presents different aspects of the interaction between crack and interface: stress field\\u000a and fracture parameters for a crack approaching the interface and the crack deflection versus penetration for a crack with\\u000a the tip on the

Liviu Marsavina; Tomasz Sadowski

298

Nanostructured glass-crystal materials with lead sulfide for passive Q switching of IR lasers  

NASA Astrophysics Data System (ADS)

New results are obtained from an investigation of the formation processes of nanostructured material accompanying the heat treatment of silicate glasses containing lead sulfide dissolved during synthesis. Important morphological features of the material have been detected—close-to-monodisperse distribution of PbS nanocrystals (NCs) over size and partial spatial ordering of the NCs. The heat-treatment regimes developed for the initial glasses make it possible to obtain high-quality samples that demonstrate narrow absorption lines of the PbS NCs for the 2-2.5-µm spectral region. The fundamental physical limitation of the subsequent broadening (?>2.5 µm) of the working range of passive Q switches using such materials is the impossibility of implementing the regime of strong size quantization of electron-hole pairs when the radius of the NCs is comparable with the Bohr radii of electrons and holes.

Onushchenko, A. A.; Zhilin, A. A.; Petrovski?, G. T.; Raaben, É. L.; Gaponenko, M. S.; Malyarevich, A. M.; Yumashev, K. V.; Golubkov, V. V.

2006-09-01

299

Health monitoring method for composite materials  

DOEpatents

An in-situ method for monitoring the health of a composite component utilizes a condition sensor made of electrically conductive particles dispersed in a polymeric matrix. The sensor is bonded or otherwise formed on the matrix surface of the composite material. Age-related shrinkage of the sensor matrix results in a decrease in the resistivity of the condition sensor. Correlation of measured sensor resistivity with data from aged specimens allows indirect determination of mechanical damage and remaining age of the composite component.

Watkins, Jr., Kenneth S. (Dahlonega, GA); Morris, Shelby J. (Hampton, VA)

2011-04-12

300

Preparation and in vitro evaluation of nanostructured TiO 2\\/TCP composite coating by plasma electrolytic oxidation  

Microsoft Academic Search

Porous and nanostructured TiO2\\/tricalcium phosphate (TCP) composite coating on titanium substrate was prepared by plasma electrolytic oxidation (PEO). The microstructure and phase composition of the coating were characterized using scanning electron microscopy and X-ray diffraction. Its bioactivity was evaluated by simulated body fluid (SBF) immersion tests. MG63 cells were cultured on the surface of the coating to investigate its cytocompatibility.

Hongjie Hu; Xuanyong Liu; Chuanxian Ding

2010-01-01

301

Simultaneous synthesis and consolidation of nanostructured TaSi 2–Si 3N 4 composite by pulsed current activated combustion  

Microsoft Academic Search

Dense nanostructured 4TaSi2–Si3N4 composite was synthesized by pulsed current activated combustion synthesis (PCACS) method within 3min in one step from mechanically activated powders of TaN and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense 4TaSi2–Si3N4 composite with relative density of up to 98% was produced under simultaneous

Hyun-Kuk Park; Jeong-Hwan Park; Jin-Kook Yoon; In-Yong Ko; Jung-Mann Doh; In-Jin Shon

2009-01-01

302

General strategy for designing core-shell nanostructured materials for high-power lithium ion batteries.  

PubMed

Because of its extreme safety and outstanding cycle life, Li(4)Ti(5)O(12) has been regarded as one of the most promising anode materials for next-generation high-power lithium-ion batteries. Nevertheless, Li(4)Ti(5)O(12) suffers from poor electronic conductivity. Here, we develop a novel strategy for the fabrication of Li(4)Ti(5)O(12)/carbon core-shell electrodes using metal oxyacetyl acetonate as titania and single-source carbon. Importantly, this novel approach is simple and general, with which we have successfully produce nanosized particles of an olivine-type LiMPO(4) (M = Fe, Mn, and Co) core with a uniform carbon shell, one of the leading cathode materials for lithium-ion batteries. Metal acetylacetonates first decompose with carbon coating the particles, which is followed by a solid state reaction in the limited reaction area inside the carbon shell to produce the LTO/C (LMPO(4)/C) core-shell nanostructure. The optimum design of the core-shell nanostructures permits fast kinetics for both transported Li(+) ions and electrons, enabling high-power performance. PMID:23092272

Shen, Laifa; Li, Hongsen; Uchaker, Evan; Zhang, Xiaogang; Cao, Guozhong

2012-10-25

303

Nanostructured nickel-free austenitic stainless steel composites with different content of hydroxyapatite  

NASA Astrophysics Data System (ADS)

The aim of this work is to show that Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite can be synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). Hydroxyapatite was introduced into stainless steel because it is intensively studied for bone repair and replacement applications. Nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels. Therefore it's combination with hydroxyapatite that has high biocompatibility and ability to bond to bone could have improved properties, as well.To confirm nanocrystalline structure of obtained material and reveal topographical features of the surface, small-angle X-ray analysis (SAXS) and atomic force microscopy (AFM) were used. Results are consistent and the mean grain size of the obtained materials do not exceed 100 nm.

Tulinski, Maciej; Jurczyk, Mieczyslaw

2012-11-01

304

Natural frequency behavior of damaged composite materials  

NASA Astrophysics Data System (ADS)

Attention is given to characterizing the effect of material system, geometry, and stacking sequence on the vibration response of damaged plates of fiber-reinforced composite. Plate layups are fashioned from various composite materials and subjected to four damage cycles, and a signal analyzer is employed to study the frequency response function (FRF) of the materials. The materials employed include the AS4/3501-6, IM7/E7T1-2, and IM7/977-2 families, and numerical analyses are used for comparison. Frequencies are obtained from the experimentally established FRFs, and natural frequencies tend to decrease in the presence of extensive localized damage. The fiber is argued to dominate the response of the plate, and the experimental data are confirmed in some cases by the results of finite-element calculations.

Duggan, M. B.; Ochoa, O. O.

1992-11-01

305

Composite Materials: Properties as Influenced by Phase Geometry  

Microsoft Academic Search

This book deals with the mechanical and physical behavior of composites as influenced by composite geometry. The monograph provides a comprehensive introduction for researchers and students to modern composite materials research with a special emphasis on the influence of geometry to materials properties. Composite Materials enables the reader to a better understanding of the behavior of natural composites, improvement of

Lauge F. Nielsen

2005-01-01

306

Modeling of laser interactions with composite materials.  

PubMed

We develop models of laser interactions with composite materials consisting of fibers embedded within a matrix. A ray-trace model is shown to determine the absorptivity, absorption depth, and optical power enhancement within the material, as well as the angular distribution of the reflected light. We also develop a macroscopic model, which provides physical insight and overall results. We show that the parameters in this model can be determined from the ray trace model. PMID:23669848

Boley, Charles D; Rubenchik, Alexander M

2013-05-10

307

Study of the compatibility between light-cured repair materials and composite materials by holographic interferometry  

Microsoft Academic Search

Based on current trends in research on techniques for repairing composite materials, this paper focuses on the compatibility between a light-cured repair material and composite materials. The repair material used in this study is intended to find applicability in techniques for repairing damaged composite materials. Test pieces of the composite material were excited by a sinusoidal acoustic source at a

Linfeng Guo; Zhimin Zhao; Mingjuan Gao

2005-01-01

308

Interlaminar fracture and damage of composite materials  

Microsoft Academic Search

Interlaminar fracture behavior of composite materials under static and cyclic loadings was studied. The fracture energy is evaluated by compliance, beam and area methods. The comparison results show that the initial fracture energy could be evaluated either by beam or area method while the crack growth resistance could be calculated by compliance method. Increases in the critical load and fracture

1988-01-01

309

Physics in ``Polymers, Composites, and Sports Materials  

Microsoft Academic Search

The undergraduate science course described uses the themes of polymers and composites, as used in sports materials, to teach some key concepts in introductory chemistry and physics. The course is geared towards students who are interested in science, but are still completing prerequisite mathematics courses required for science majors. Each class is built around a laboratory activity. Atoms, molecules and

Eric Hagedorn; Milijana Suskavcevic

2007-01-01

310

Crashworthy capability of composite material structures  

Microsoft Academic Search

Considerable research interest has been directed towards the use of composite materials for crashworthiness applications, because they can be designed to provide impact energy absorption capabilities which are superior to those of metals when compared on a weight basis. This review draws together information from a variety of sources to compare the findings of researchers in this field.The anisotropy of

A. G Mamalis; M. Robinson; D. E. Manolakos; G. A. Demosthenous; M. B. Ioannidis; J. Carruthers

1997-01-01

311

Characterization of self-healing composite materials  

Microsoft Academic Search

Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Researchers at the University of Illinois Urbana Champaign have recently developed a method to reverse the effects of, or heal, damage in the epoxy matrix. Their in-situ self-healing system uses embedded microcapsules and a catalyst that trigger

Kevin John Ford

2006-01-01

312

Thermoplastic Composite Materials for Aerospace Applications  

NASA Astrophysics Data System (ADS)

Mechanical and thermo-physical properties of composites materials with thermoplastic matrix (PEEK/IM7, TPI/IM7 and PPS/IM7) used for aerospace applications have been analyzed as function of two different process techniques: compression molding and fiber placement process ``hot gas assisted.''

Casula, G.; Lenzi, F.; Vitiello, C.

2008-08-01

313

Damping Analysis of Sandwich Composite Materials  

Microsoft Academic Search

The article presents an analysis of the damping of sandwich composites, made of PVC foam cores and laminated skins. Damping parameters are investigated using beam test specimens and an impulse technique. Damping modeling is developed using a finite element analysis which evaluated the different energies dissipated in the material directions of the core and the layers of the skins. The

Mustapha Assarar; Abderrahim El Mahi; Jean-Marie Berthelot

2009-01-01

314

Magnetic Composite Materials and Arbitrary - Relationships  

Microsoft Academic Search

This theoretical study addresses fabricating composite conducting materials with an effective arbitrary B-H relationship in the quasi-static field approximation, exhibiting new magnetic properties. The experimental results demonstrate the possibility of having linear artificial structures with negative effective magnetic permeability. The equivalent circuital model confirms the theoretical and experimental analysis. In particular, following the circuital approach we show how to obtain

Bernardo Tellini; Mauro Bologna

2010-01-01

315

Candida albicans adhesion to composite resin materials.  

PubMed

The adhesion of Candida albicans to dental restorative materials in the human oral cavity may promote the occurrence of oral candidosis. This study aimed to compare the susceptibility of 14 commonly used composite resin materials (two compomers, one ormocer, one novel silorane, and ten conventional hybrid composites) to adhere Candida albicans. Differences in the amount of adhering fungi should be related to surface roughness, hydrophobicity, and the type of matrix. Cylindrical specimens of each material were made according to the manufacturers' instructions. Surface roughness R (a) was assessed by perthometer measurements and the degree of hydrophobicity by computerized contact angle analysis. Specimens were incubated with a reference strain of C. albicans (DMSZ 1386), and adhering fungi were quantified by using a bioluminometric assay in combination with an automated plate reader. Statistical differences were analyzed by the Kruskal-Wallis test and Mann-Whitney U test. Spearman's rank correlation coefficients were calculated to assess correlations. Median R (a) of the tested composite resin materials ranged between 0.04 and 0.23 microm, median contact angles between 69.2 degrees and 86.9 degrees . The two compomers and the ormocer showed lower luminescence intensities indicating less adhesion of fungi than all tested conventional hybrid composites. No conclusive correlation was found between surface roughness, hydrophobicity, and the amount of adhering C. albicans. PMID:18810508

Bürgers, Ralf; Schneider-Brachert, Wulf; Rosentritt, Martin; Handel, Gerhard; Hahnel, Sebastian

2008-09-23

316

Applicability of ferrimagnetic hosts to nanostructured negative index of refraction (left-handed) materials  

Microsoft Academic Search

There has been considerable interest generated by the demonstration of (epsilon) < 0, (mu) < 0 composite materials. These negative index of refraction materials, a subset of the class of materials labeled 'left-handed', possess two different arrays of resonant structures which separately give rise to negative (epsilon) and (mu) over the appropriate microwave frequency interval. Any attempt to significantly increase

Graeme Dewar

2002-01-01

317

Slow crack propagation in composite restorative materials.  

PubMed

The double-torsion test technique was used to study slow crack propagation in a set of dental composite resins including two glass-filled and two microfilled materials. The microstructure within each pair was the same but one of the resins was selfcured and the other photocured. The fracture behavior was dependent on the filler concentration and the presence of absorbed water. Wet materials fractured by slow crack growth in the range of crack velocity studied (10(-7) to 10(-3) m/s), and the microfilled composites, which contain a lower concentration of inorganic filler, had lower stress intensity factors (K1c) than the glass-filled composites tested. Dry specimens of the microfilled materials and the selfcured, glass-filled composite also showed unstable, stick-slip fracture behavior indicative of a crack blunting mechanism which leads to an elevation of the stress intensity factor for crack initiation over K1c for stable crack growth. The plasticizing effect of water increased the viscoelastic response of the materials measured by the slope of curves of slow crack growth. Analysis of fracture surfaces showed that cracks propagated at low velocities (10(-7) to 10(-5) m/s) by the apparent failure of the filler/matrix interfacial bond, and absorbed water affected the strength or fracture resistance of the interface. At high crack velocities the properties of the composite depend on the properties of the polymeric matrix, the filler, and the filler volume fraction, but at low velocities the interface is the controlling factor in the durability of these composites exposed to an aqueous environment. PMID:3584167

Montes-G, G M; Draughn, R A

1987-05-01

318

Electrical properties of composites with tin tin oxide core shell nanostructure and their sensing behaviour  

NASA Astrophysics Data System (ADS)

Metallic tin having a dendritic structure was grown within a silica-based gel by an electrodeposition technique. The dendrites were shown to consist of nanoparticles with a median diameter of 31 nm. By giving a controlled oxidation treatment to the composite, a tin core-tin oxide shell nanostructure was induced. The shell thicknesses varied from 1.5 to 4.0 nm depending on the duration of oxidation. The electrical conductivity of the composite structure was shown to be controlled by a small polaron hopping conduction. The nanoshell comprised SnO and SnO2 phases, respectively, and electrical conduction is believed to arise due to the hopping of electrons between Sn2+ and Sn4+ ions at the interfaces of these two regions. The composite films exhibited a three order of magnitude decrease in resistivity as the relative humidity was varied from 35% to 95%. Electrons from hydroxyl groups of adsorbed water molecules are believed to form localized states at the tin ion sites which cause an increase in electrical conductivity. The nanocomposites also exhibit substantial resistivity changes when exposed to CO, C2H5OH and NO2 gases, respectively. The effect is believed to result from reduction or oxidation of the tin ions by the gas molecules concerned.

Pal, B. N.; Chakravorty, D.

2005-09-01

319

Silicon\\/Graphite Nano-Structured Composites For A High Efficiency Lithium-Ion Batteries Anode  

Microsoft Academic Search

Si\\/C composites have been employed in an attempt to overcome the problems of Si-based negative Li-ion electrodes. The composites\\u000a were produced by coating, followed by a two-step solid state reaction. Electrodes were prepared therefrom by spreading on\\u000a a Cu foil. The materials were characterized by SEM and XRD. The Si phase in the composite shows an enhanced crystalline structure\\u000a compared

T. Stankulov; W. Obretenov; B. Banov; A. Momchilov; A. Trifonova

320

Accelerated aging of polymer composite bridge materials  

NASA Astrophysics Data System (ADS)

Accelerated aging research on samples of composite materials and candidate UV protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory. Durability results and sensor data form test with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards and acceptance criteria for PMC bridges for use in the transportation infrastructure.

Carlson, Nancy M.; Blackwood, Larry G.; Torres, Lucinda L.; Rodriguez, Julio G.; Yoder, Timothy S.

1999-05-01

321

Accelerated Aging of Polymer Composite Bridge Materials  

SciTech Connect

Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

J. G. Rodriguez; L. G. Blackwood; L. L. Torres; N. M. Carlson; T. S. Yoder

1999-03-01

322

Development of collagen-hydroxyapatite nanostructured composites via a calcium phosphate precursor mechanism  

NASA Astrophysics Data System (ADS)

Bone is an interpenetrating inorganic/organic composite that consists of mineralized collagen fibrils, which is hierarchically organized into various structures. The structure of mineralized collagen fibril, in which nano-crystals of hydroxyapatite are embedded within the collagen fibrils, provides remarkable mechanical and bio-resorptive properties. Therefore, there have been many attempts to produce collagen-hydroxyapatite composites having a bone-like structure. However, duplication of even the most fundamental level of bone structure has not been easily achieved by conventional nucleation and growth techniques, which are based on the most widely accepted hypothesis of bone mineralization. In nature, the collagen fibril is mineralized via intrafibrillar mineralization, which produces preferentially oriented hydroxyapatite nano-crystals occupying the interstices in collagen fibrils. Our group has demonstrated that intrafibrillar mineralization can be achieved by using a new method based on the Polymer-Induced Liquid-Precursor (PILP) mineralization process. In the PILP process, a poly-anionic additive can produce an amorphous calcium phosphate precursor which enables us to achieve intrafibrillar mineralization of collagen. It is thought that the precursor is pulled into the interstices of the collagen fibrils via capillary forces, and upon solidification and crystallization of the precursor produces an interpenetrating composite with the nanostructured architecture of bone. In this dissertation, to demonstrate the effectiveness of the PILP process on the intrafibrillar mineralization of collagen fibril, various collagen scaffolds, such as turkey tendon, bovine tendon and synthetic collagen sponge, were mineralized by the PILP process. Various poly-aspartates with different molecular weight were also used for the optimization of the PILP process for the mineralization of the collagen scaffolds. With the systematic researches, we discovered that the molecular weight of poly-aspartic acid affects the degree of intrafibrillar mineralization of collagen scaffolds. High molecular weight poly-aspartic acid could produce a stable and dispersed amorphous precursor, leading to a high degree of intrafibrillar mineralization. The mineral content of the collagen sponge mineralized using high molecular weight poly-aspartic acid was equivalent to the mineral content of bone. According to X-ray diffraction analysis of the mineralized collagen, the size and composition of the intrafibrillar hydroxyapatite produced by the PILP process were almost identical to carbonated hydroxyapatite in bone. The selective area electron diffraction patterns indicated that the [001] direction of hydroxyapatite is roughly aligned along the c-axis of collagen fibril, leading to the formation 002 arcs. Using dark field imaging, it was possible to visualize the preferentially oriented hydroxyapatite in TEM. Thermal analysis of mineralized collagen also showed a reduction in the thermal stability of collagen, which is similar to that observed in the collagen in bone, due to the presence of intrafibrillar hydroxyapatite. Now, we confidently suggest that the PILP process can provide a new way to develop synthetic bone-like composites whose nano-structure is very close to the nano-structure of natural bone. Moreover, we hope that our successful intrafibrillar mineralization of collagen via the precursor mechanism revives discussion of hypothesis of bone mineralization via the amorphous calcium phosphate phase.

Jee, Sang Soo

323

Hydrogel Composite Materials for Tissue Engineering Scaffolds  

NASA Astrophysics Data System (ADS)

Hydrogels are appealing for biomaterials applications due to their compositional similarity with highly hydrated natural biological tissues. However, for structurally demanding tissue engineering applications, hydrogel use is limited by poor mechanical properties. Here, composite materials approaches are considered for improving hydrogel properties while attempting to more closely mimic natural biological tissue structures. A variety of composite material microstructures is explored, based on multiple hydrogel constituents, particle reinforcement, electrospun nanometer to micrometer diameter polymer fibers with single and multiple fiber networks, and combinations of these approaches to form fully three-dimensional fiber-reinforced hydrogels. Natural and synthetic polymers are examined for formation of a range of scaffolds and across a range of engineered tissue applications. Following a discussion of the design and fabrication of composite scaffolds, interactions between living biological cells and composite scaffolds are considered across the full life cycle of tissue engineering from scaffold fabrication to in vivo use. We conclude with a summary of progress in this area to date and make recommendations for continuing research and for advanced hydrogel scaffold development.

Shapiro, Jenna M.; Oyen, Michelle L.

2013-04-01

324

Conductor-polymer composite electrode materials  

DOEpatents

A conductive composite material useful as an electrode, comprises a conductor and an organic polymer which is reversibly electrochemically dopable to change its electrical conductivity. Said polymer continuously surrounds the conductor in intimate electrical contact therewith and is prepared by electrochemical growth on said conductor or by reaction of its corresponding monomer(s) on said conductor which has been pre-impregnated or pre-coated with an activator for said polymerization. Amount of the conductor is sufficient to render the resultant composite electrically conductive even when the polymer is in an undoped insulating state.

Ginley, D.S.; Kurtz, S.R.; Smyrl, W.H.; Zeigler, J.M.

1984-06-13

325

Combustion products from advanced composite materials.  

PubMed

Recent advances in armament and materials applications are beginning to outpace the development of adequate safety characterizations. To avoid unnecessary and restrictive regulations implemented to protect individuals from potential toxic consequences resulting from exposure to combustion products of advanced composite materials (ACM); this laboratory has begun an investigation of combustion characteristics. In this preliminary investigation we have assessed the production of particulate matter and the production of organic compounds contained in both the combustion vapor phase or associated with the particulate matter. The results of these investigations have revealed that a substantial fraction of the particulates appear to be in the respirable range and that a high number of organic compounds and potential toxicants are associated with particulate matter. These findings are the first to describe the production of potentially toxic atmospheres from the combustion of advanced composite materials and indicate the usefulness of further investigations to quantify the risk of exposure to humans. These and forthcoming data will be useful in determining proper protective equipment and precautions required to protect human health during exposures to products from the combustion of advanced composite materials. PMID:9433657

Lipscomb, J C; Kuhlmann, K J; Cline, J M; Larcom, B J; Peterson, R D; Courson, D L

1997-11-01

326

First Principles Investigations of Technologically and Environmentally Important Nano-structured Materials and Devices  

NASA Astrophysics Data System (ADS)

In the course of my PhD I have worked on a broad range of problems using simulations from first principles: from catalysis and chemical reactions at surfaces and on nanostructures, characterization of carbon-based systems and devices, and surface and interface physics. My research activities focused on the application of ab-initio electronic structure techniques to the theoretical study of important aspects of the physics and chemistry of materials for energy and environmental applications and nano-electronic devices. A common theme of my research is the computational study of chemical reactions of environmentally important molecules (CO, CO2) using high performance simulations. In particular, my principal aim was to design novel nano-structured functional catalytic surfaces and interfaces for environmentally relevant remediation and recycling reactions, with particular attention to the management of carbon dioxide. We have studied the carbon-mediated partial sequestration and selective oxidation of carbon monoxide (CO), both in the presence and absence of hydrogen, on graphitic edges. Using first-principles calculations we have studied several reactions of CO with carbon nanostructures, where the active sites can be regenerated by the deposition of carbon decomposed from the reactant (CO) to make the reactions self-sustained. Using statistical mechanics, we have also studied the conditions under which the conversion of CO to graphene and carbon dioxide is thermodynamically favorable, both in the presence and in the absence of hydrogen. These results are a first step toward the development of processes for the carbon-mediated partial sequestration and selective oxidation of CO in a hydrogen atmosphere. We have elucidated the atomic scale mechanisms of activation and reduction of carbon dioxide on specifically designed catalytic surfaces via the rational manipulation of the surface properties that can be achieved by combining transition metal thin films on oxide substrates. We have analyzed the mechanisms of the molecular reactions on the class of catalytic surfaces so designed in an effort to optimize materials parameters in the search of optimal catalytic materials. All these studies are likely to bring new perspectives and substantial advancement in the field of high-performance simulations in catalysis and the characterization of nanostructures for energy and environmental applications. Moving to novel materials for electronics applications, I have studied the structural and vibrational properties of mono and bi-layer graphene. I have characterized the lattice thermal conductivity of ideal monolayer and bi-layer graphene, demonstrating that their behavior is similar to that observed in graphite and indicating that the intra-layer coupling does not affect significantly the thermal conductance. I have also calculated the electron-phonon interaction in monolayer graphene and obtained electron scattering rates associated with all phonon modes and the intrinsic resistivity/mobility of monolayer graphene is estimated as a function of temperature. On another project, I have worked on ab initio molecular dynamic studies of novel Phase Change Materials (PCM) for memory and 3D-integration. We characterized high-temperature, sodium | nickel chloride, rechargeable batteries. These batteries are under consideration for hybrid drive systems in transportation applications. As part of our activities to improve performance and reliability of these batteries, we developed an engineering transport model of the component electrochemical cell. To support that model, we have proposed a reaction kinetics expression for the REDOX (reduction-oxidation) reaction at the porous positive electrode. We validate the kinetics expression with electrochemical measurements. A methodology based on the transistor body effect is used to estimate inversion oxide thicknesses (Tinv) in high-kappa/metal gate, undoped, ultra-thin body SOI FINFETs. The extracted Tinvs are compared to independent capacitance voltage (CV) measurements.

Paul, Sujata

327

High thermal conductivity epoxy-silver composites based on self-constructed nanostructured metallic networks  

NASA Astrophysics Data System (ADS)

We demonstrate epoxy-silver nanoparticle composites with high thermal conductivity ? enabled by self-constructed nanostructured networks (SCNN) forming during the curing process at relatively low temperatures (150 °C). The networks formation mechanism involves agglomeration of the polyvinylpyrrolidone (PVP) coated nanoparticles, PVP removal, and sintering of the nanoparticles at suppressed temperatures induced by their small diameters (20-80 nm). Sintering and the SCNN formation are supported by differential scanning calorimetry and electron microscopy investigations. The formation of SCNN with high aspect ratio structures leads to enhancements in the measured thermal conductivity ? of the composite by more than two orders of magnitude versus the pure epoxy. However, ? enhancements are modest if microparticles (1.8-4.2 ?m) are employed instead of PVP coated nanoparticles. The ? trends are qualitatively explained using a percolating threshold thermal conductivity model for the microcomposites. For the nanocomposites the measured ? is ~14% of the upper limit value predicted by the Hashin and Shtrikman (H-S) theory for an ideally connected network, a measure of the non-ideal network inside the nanocomposites.

Pashayi, Kamyar; Fard, Hafez Raeisi; Lai, Fengyuan; Iruvanti, Sushumna; Plawsky, Joel; Borca-Tasciuc, Theodorian

2012-05-01

328

In-situ TEM - a tool for quantitative observations of deformation behavior in thin films and nano-structured materials  

SciTech Connect

This paper highlights future developments in the field of in-situ transmission electron microscopy, as applied specifically to the issues of deformation in thin films and nanostructured materials. Emphasis is place on the forthcoming technical advances that will aid in extraction of improved quantitative experimental data using this technique.

Stach, E.A.

2001-09-04

329

A novel method for extracting oscillator strength of select rare-earth ion optical transitions in nanostructured dielectric materials  

Microsoft Academic Search

A new technique to obtain the oscillator strength of select rare-earth optical transitions in nanostructured dielectric materials (nanophosphors) is presented. It is based on the experimentally observed nanophosphor lifetime dependence on the embedding medium. A constant oscillator strength and parity-allowed electric dipole transitions of the RE ion emission are assumed. The oscillator strength is obtained from the slope of the

R. E. Muenchausen; L. G. Jacobsohn; B. L. Bennett; E. A. McKigney; J. F. Smith; D. W. Cooke

2006-01-01

330

Titanium composite materials for transportation applications  

NASA Astrophysics Data System (ADS)

Discontinuously reinforced titanium alloys containing in-situ formed TiB needles are emerging as candidate materials for advanced applications. This new family of titanium composites presents technical advantages, and it can be less expensive and easily amenable for net-shape manufacturing relative to titanium metal-matrix composites developed to date. The production of a master compound by a novel and cost-effective process called self-propagating high-temperature synthesis (SHS) has been studied. This master compound could be subsequently used in an investment casting process to obtain TiB-reinforced net-shape titanium-matrix composites. The SHS technique and its features were investigated in depth before a suitable master compound was defined and produced. Cast samples obtained from the addition of the master compound have been produced and the most important issues concerning the processing, microstructure, and mechanical properties are highlighted in this paper.

García de Cortazar, M.; Agote, I.; Silveira, E.; Egizabal, P.; Coleto, J.; Le Petitcorps, Y.

2008-11-01

331

Versatile, high sensitivity, and automatized angular dependent vectorial Kerr magnetometer for the analysis of nanostructured materials.  

PubMed

Magneto-optical Kerr effect (MOKE) magnetometry is an indispensable, reliable, and one of the most widely used techniques for the characterization of nanostructured magnetic materials. Information, such as the magnitude of coercive fields or anisotropy strengths, can be readily obtained from MOKE measurements. We present a description of our state-of-the-art vectorial MOKE magnetometer, being an extremely versatile, accurate, and sensitivity unit with a low cost and comparatively simple setup. The unit includes focusing lenses and an automatized stepper motor stage for angular dependent measurements. The performance of the magnetometer is demonstrated by hysteresis loops of Co thin films displaying uniaxial anisotropy induced on growth, MnIr/CoFe structures exhibiting the so called exchange bias effect, spin valves, and microfabricated flux guides produced by optical lithography. PMID:21529020

Teixeira, J M; Lusche, R; Ventura, J; Fermento, R; Carpinteiro, F; Araujo, J P; Sousa, J B; Cardoso, S; Freitas, P P

2011-04-01

332

Controlling the synthetic pathways of TiO2-derived nanostructured materials.  

PubMed

A comprehensive study of the hydrothermal synthesis of TiO2-derived nanostructured materials, including layered protonic trititanate (H2Ti3O7), metal-ion exchangeable titanate (Na(x)H(2-x)Ti3O7), TiO2(B) and anatase nanotubes and TiO2-anatase nanowires, was conducted. Nanoscaled tubular structures were found to be already present in the samples derived from prolonged hydrothermal process of bulk anatase TiO2 and could be converted to various types of nanotubes, nanowires or nanorodes by post-synthesis treatments. 0.1 M HCI acid wash and air annealing were the two key parameters to select the types of nanotubes/nanowires as the final products. XRD, Raman, TG, and XPS core level and valence band studies were carried out to elucidate our proposed synthetic pathways. PMID:18019163

Lim, San Hua; Ji, Wei; Lin, Jianyi

2007-09-01

333

NDE of polymeric composite material bridge components  

NASA Astrophysics Data System (ADS)

Rapid advancements with respect to utilization of polymeric composite materials for bridge components is occurring. This situation is driven primarily by the potential improvements offered by these materials with respect to long term durability. However, because of the developmental nature of these materials much of the materials characterization has involved short term testing without the synergistic effects of environmental exposure. Efforts to develop nondestructive evaluation procedures, essential for any wide spread use in critical structural applications, have been consequently limited. This paper discuses the effort to develop NDE methods for field inspection of hybrid glass and carbon fiber reinforced vinyl ester pultruded 'double box' I beams that are installed in a small bridge over Tom's Creek, in Blacksburg, Virginia. Integrated structural element sensors, dormant infrared devices, as well as acousto-ultrasonic methods are under development for detecting and monitoring the occurrence and progression of life limiting deterioration mechanisms.

Duke, John C.; Horne, Michael R.

1998-03-01

334

Formation of nanostructured composites with environmentally-dependent electrical properties based on poly(vinylidene fluoride)–polyaniline core–shell latex system  

Microsoft Academic Search

Submicron poly(vinylidene fluoride) (PVDF)\\/polyaniline (PANI) core–shell latex particles are synthesized and examined as an active component in a simple conductometric chemical sensor. The structure and physical properties of these particles and nanostructured composite PVDF–PANI polymer films built of them are characterized with transmission electron, atomic force, and helium ion microscopy techniques, differential scanning calorimetry, and conductivity measurements. The nanostructured composite

Gururaj M. Neelgund; Valery N. Bliznyuk; Alexander A. Pud; Kateryna Yu. Fatyeyeva; Erika Hrehorova; Margaret Joyce

2010-01-01

335

Plasmonic Nanostructures Synthesized by On-Wire Lithography: Smaller Sizes and New Materials and Applications  

NASA Astrophysics Data System (ADS)

On-Wire Lithography (OWL) is a powerful synthetic method for the preparation of nanostructure arrays with highly tunable particle size and interparticle spacing. While a number of different types of materials can be created with OWL, the work in this dissertation focuses on the synthesis of plasmonic gold and silver nanostructure ensembles, where we take advantage of OWL's unique control over geometry for fundamental plasmonic investigations and applications in detection, nanoscale encoding, and authentication. In Chapter 2, previous work on the synthesis of gold nanodisk dimers using OWL for surface-enhanced Raman scattering (SERS) is extended to silver, which leads to an increase in the sensitivity of the structures for SERS. Several challenges in the OWL process for the preparation of controlled and well-defined silver segments are addressed, and the impact the increased sensitivity of silver has on the SERS properties of the dimers for detection and nanoscale encoding of materials are investigated. In Chapter 3, an altered OWL process is presented for the synthesis of smaller metal nanostructure arrays, surpassing the previous limit of 270 nm in diameter. Applying important alterations to the OWL process presented in this chapter, we demonstrate for the first time the ability to synthesize arrays with tailorable diameters down to as small as 35 nm, which has important implications in a number of important applications of OWL due to the enhancement of many nanoscale properties at these length scales. One example presented in this chapter illustrates the ability to study how the plasmon resonances of gold nanorods couple with one another across very short distances in a way that had not been achieved with any other synthesis/fabrication methods. In Chapters 4-6, several applications of the smaller OWL structures are demonstrated for fundamental and applied investigations. In Chapter 4, OWL-synthesized Au nanorod dimer and trimer structures are used to study the interactions of closely spaced plasmonic structures, which leads to new insights about the nature of plasmon coupling. In Chapters 5 and 6, 35 nm diameter Au OWL dimers are applied as unique and powerful SERS substrates for a number of novel applications.

Osberg, Kyle David

336

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

Composite materials are light, strong, corrosion-resistant composites of two or more materials used commonly in manufacturing. This recent report is from the Australian Academy of Science with support from The Cooperative Research Centre for Advanced Composite Structures, Ltd. and the Commonwealth Department of Industry, Science and Resources. It gives information on the history, manufacturing techniques, and efficiency of composite materials. A glossary, reference list, and links to educational sites as well as other composite materials sites are also featured.

2000-01-01

337

The Development of Electrically Conductive Polycaprolactone Fumarate-Polypyrrole Composite Materials for Nerve Regeneration  

PubMed Central

Electrically conductive polymer composites composed of polycaprolactone fumarate and polypyrrole (PCLF-PPy) have been developed for nerve regeneration applications. Here we report the synthesis and characterization of PCLF-PPy and in vitro studies showing PCLF-PPy materials support both PC12 cell and dorsal root ganglia (DRG) neurite extension. PCLF-PPy composite materials were synthesized by polymerizing pyrrole in pre-formed PCLF scaffolds (Mn 7,000 or 18,000 g mol?1) resulting in interpenetrating networks of PCLF-PPy. Chemical compositions and thermal properties were characterized by ATR-FTIR, XPS, DSC, and TGA. PCLF-PPy materials were synthesized with five different anions (naphthalene-2-sulfonic acid sodium salt (NSA), dodecylbenzenesulfonic acid sodium salt (DBSA), dioctyl sulfosuccinate sodium salt (DOSS), potassium iodide (I), and lysine) to investigate effects on electrical conductivity and to optimize chemical composition for cellular compatibility. PCLF-PPy materials have variable electrical conductivity up to 6 mS cm?1 with bulk compositions ranging from 5 to 13.5 percent polypyrrole. AFM and SEM characterization show microstructures with a root mean squared (RMS) roughness of 1195 nm and nanostructures with RMS roughness of 8 nm. In vitro studies using PC12 cells and DRG show PCLF-PPy materials synthesized with NSA or DBSA support cell attachment, proliferation, neurite extension, and are promising materials for future studies involving electrical stimulation.

Runge, M. Brett; Dadsetan, Mahrokh; Baltrusaitis, Jonas; Knight, Andrew M.; Ruesink, Terry; Lazcano, Eric; Lu, Lichun; Windebank, Anthony J.; Yaszemski, Michael J.

2010-01-01

338

Laboratory Blast Simulator for Composite Materials Characterization  

Microsoft Academic Search

\\u000a Blasts and explosives have raised serious concerns in recent years due to the fatal injury and catastrophic damage they have\\u000a caused in the combat zones and due to industrial accidents. Owing to their lightweight and complex damage process, fiber-reinforced\\u000a composite materials have been found to have higher energy absorption capability and to be able to generate less lethal debris\\u000a than

Guojing Li; Dahsin Liu

339

Nonlinear dielectric response of periodic composite materials  

Microsoft Academic Search

This paper addresses the rigorous treatment of the tunability effect (dc electric field driven variation of the permittivity)\\u000a in a high-contrast two dimensional periodic composite (a matrix of a large dielectric constant ferroelectric material with\\u000a linear dielectric inclusions). The theoretical analysis here shows that the trend established for the case of low linear dielectric\\u000a concentrations (that the dilution with a

A. Kolpakov; A. K. Tagantsev; L. Berlyand; A. Kanareykin

2007-01-01

340

Chemically modified and nanostructured porous silicon as a drug delivery material and device  

NASA Astrophysics Data System (ADS)

This thesis describes the fabrication, chemical modification, drug release, and toxicity studies of nanostructured porous silicon for the purposes of developing a smart drug delivery device. The first chapter is an introductory chapter, presenting the chemical and physical properties of porous silicon, the concepts and issues of current drug delivery devices and materials, and how porous silicon can address the issues regarding localized and controlled drug therapies. The second chapter discusses chemical modifications of nanostructured porous Si for stabilizing the material in biologically relevant media while providing an extended release of a therapeutic in vitro. This chapter also demonstrates the utility of the porous silicon optical signatures for effectively monitoring drug release from the system and its applications for development of a self-reporting drug delivery device. In chapter three, the concept of providing a triggered release of a therapeutic from porous silicon microparticles through initiation by an external stimulus is demonstrated. The microparticles are chemically modified, and the release is enhanced by a short application of ultrasound to the particulate system. The effect of ultrasound on the drug release and particle size is discussed. Chapter four presents a new method for sustaining the release of a monoclonal antibody from the porous matrix of porous SiO2. The therapeutic is incorporated into the films through electrostatic adsorption and a slow release is observed in vitro. A new method of quantifying the extent of drug loading is monitored with interferometry. The last chapter of the thesis provides a basic in vivo toxicity study of various porous Si microparticles for intraocular applications. Three types of porous Si particles are fabricated and studied in a rabbit eye model. The toxicity studies were conducted by collaborators at the Shiley Eye Center, La Jolla, CA. This work, demonstrates the feasibility of developing a self-reporting, extended release drug delivery system using porous Si microparticles for intraocular applications.

Anglin, Emily Jessica

341

Characterization of self-healing composite materials  

NASA Astrophysics Data System (ADS)

Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Researchers at the University of Illinois Urbana Champaign have recently developed a method to reverse the effects of, or heal, damage in the epoxy matrix. Their in-situ self-healing system uses embedded microcapsules and a catalyst that trigger a romp reaction in an effort to rebond the microcracks. Several models have been developed in an effort to predict how a composite laminate damages. One model in particular, the Continuous Damage Mechanics model, CDM that has been developed at West Virginia University uses material properties that are easily obtained from standard ASTM and ISO testing methods. The CDM model has been extended at West Virginia University to incorporate the effects of a self-healing system to develop a Continuous Damage and Healing Mechanics model, CDHM. In this work, a testing procedure to characterize the autonomic healing of polymer matrix composites is outlined, as well as the regenerative effects of the self-healing system. The capability of the CDHM model to predict the material properties of the self-healing system is also addressed. The CDHM model is validated with experimental results for various laminates fabricated out of E-glass/epoxy.

Ford, Kevin John

342

Chlorhexidine-releasing methacrylate dental composite materials.  

PubMed

Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release. PMID:15955557

Leung, Danny; Spratt, David A; Pratten, Jonathan; Gulabivala, Kishor; Mordan, Nicola J; Young, Anne M

2005-12-01

343

Development of Micro and Nanostructured Materials for Interfacial Self-Healing  

ERIC Educational Resources Information Center

|Damage in polymeric coatings, adhesives, microelectronic components, and composites spans many length scales. For small scale damage, autonomic self-healing can repair multiple damage modes without manual intervention. In autonomic self-healing materials, a healing response is triggered by damage to the material. Size scale considerations, such…

Blaiszik, Benjamin James

2009-01-01

344

Fibrous composite materials in dentistry and orthopaedics: review and applications  

Microsoft Academic Search

In this report, the usage of fibrous composite materials in dentistry and orthopaedics is reviewed. Furthermore, the authors introduced functionally graded composite dental post, aesthetic composite archwires and brackets, and braided carbon\\/PEEK composite compression bone plate. Functionally graded composite dental post has continuously varied stiffness and this function successfully solved stress concentration at the root. Aesthetic composite archwires made of

K Fujihara; K Teo; R Gopal; P. L Loh; V. K Ganesh; S Ramakrishna; K. W. C Foong; C. L Chew

2004-01-01

345

Dendrimers as building blocks for nanostructured materials: Micro- and mesoporosity in dendrimer-based xerogels  

SciTech Connect

Recently the authors have been exploring the use of dendrimeric building blocks in the construction of new types of nanostructured materials. In principle, this may be accomplished with use of various chemical interactions for linking the dendrimers together. For example, highly charged dendrimers of opposite charge might assemble via electrostatic forces into superlattice structures. Another approach involves the covalent assembly of dendrimer building blocks into network structures using coupling reactions between functional end groups on the dendrimer surface. Spherically shaped dendrimers may be expected to pack into networks possessing interstitial spaces whose size is influenced by the radius of the dendrimer building block. With this approach, it should be possible to generate new classes of porous materials with tunable pore sizes and inclusion properties. For such materials, one might expect that pore diameters would increase, and surface areas decrease, with higher dendrimer generations. In summary, this work has produced dendrimer-based xerogels that exhibit high surface areas, and an interesting observation with respect to the relationship between generation number and surface area has been made. Future work will address the influence of various synthetic conditions on the structures of the gels. Also, the authors intend to investigate the properties of these new materials as molecular sieves, porous membranes, and catalyst supports.

Kriesel, J.W.; Tilley, T.D. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National lab., CA (United States). Chemical Sciences Div.

1999-05-01

346

Material selection and grade optimization applied to aluminum matrix composites  

Microsoft Academic Search

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials\\u000a is assessed with merit parameters. The competition between materials (material selection optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material,

J. Eliasson; R. Sandstroem

1995-01-01

347

A Grammatical Approach for Customization of Laminated Composite Materials  

Microsoft Academic Search

The wide range of properties covered by the manufacturable fiber—matrix combinations of composite materials, along with their directional property characteristics, provides designers with material selection flexibility during designing composite material products. Meeting multiple property goals, however, complicates the design process as both the composite material selection and the component shape formation becomes intricate with the multiple loading conditions, which may

Soumitra Nandi; Zahed Siddique; M. Cengiz Altan

2011-01-01

348

Self-sensing structural composite materials  

NASA Astrophysics Data System (ADS)

Self-sensing was attained in lightweight structural composite materials, including those with polymer (epoxy), carbon and ceramic (Si3N 4) matrices. Either a volume of the composite or the interlaminar interface in the composite was used as the sensor. The use of the interlaminar interface as a sensor is a new approach, which was found to be effective in continuous carbon fiber epoxy-matrix composites for sensing temperature, moisture and damage. In case of temperature sensing, the interlaminar interface functioned as either a thermistor or a thermocouple junction. The thermocouple approach required the fibers in the contacting laminae to be dissimilar, whereas the thermistor approach did not. By using two crossply laminae, a two-dimensional array of sensors was attained and demonstrated to be effective for temperature distribution sensing. By measuring the contact electrical resistivity of the interlaminar interface during shear, the interlaminar shear process was monitored in real time. Study of the electrical conduction across the interlaminar interface led to the observation of apparent negative electrical resistance, which could be controlled by composite design. The use of a volume of a structural composite as the sensor and measurement of the volume electrical resistivity of the volume showed that continuous carbon fiber epoxy-matrix and carbon-matrix composites were effective for the self-sensing of strain and damage, whereas the SiC whisker Si3N 4-matrix composite was effective for the self-sensing of strain only. For the case of the epoxy-matrix composite, it was found that the four-probe method of resistance measurement was effective, whereas the two-probe method was not; it was also found that the though-thickness resistance was a sensitive indicator of matrix damage, while the longitudinal resistance was a less sensitive indicator. Polycrystalline beta-SiC fiber without a carbon core was found to be a piezoresistive strain sensor, but that with a carbon core was not. The consolidation of carbon fiber epoxy-matrix laminae during composite fabrication by lamination was monitored in real time by measurement of the through-thickness electrical resistivity. The consolidation was thus found to be hastened and to occur to a greater extent by increasing the pressure. The consequence of better consolidation remained after curing and subsequent cooling.

Wang, Shoukai

349

Composition-dependent magnetic properties of BiFeO3-BaTiO3 solid solution nanostructures  

Microsoft Academic Search

We report on the Mössbauer spectra and magnetization properties of single-crystalline (BiFeO3)x-(BaTiO3)1-x solid solution nanostructures in the form of nanocubes, measuring approximately 150 to 200 nm on a side, prepared by a molten salt solid-state reaction method in the compositional range wherein 0.5<=x<=1 . Powder x-ray diffraction (XRD) and monochromatic synchrotron XRD studies indicate products of high purity, which undergo

Tae-Jin Park; Georgia C. Papaefthymiou; Arthur J. Viescas; Yongjae Lee; Hongjun Zhou; Stanislaus S. Wong; H. Zhou

2010-01-01

350

Multifunctional iron-based metal oxide nanostructured materials: Synthesis, characterization, and properties  

Microsoft Academic Search

Iron-based metal oxides, such as iron oxides, iron-containing perovskites, and iron-containing perovskite composites or solid solutions, are promising materials for the design and synthesis of technologically important multifunctional materials. They are noteworthy for their unique and diverse properties including electronic, magnetic, and elastic ones. Stimulated by interest in the bulk properties of these materials as well as scientific potential and

Tae-Jin Park

2007-01-01

351

Preparation and electrochemical performances of doughnut-like Ni(OH)2-Co(OH)2 composites as pseudocapacitor materials  

NASA Astrophysics Data System (ADS)

Doughnut-like nanostructured Ni(OH)2-Co(OH)2 composites were prepared by combining hydrothermal and chemical deposition routes. The electrochemical performances of the composites were investigated as pseudocapacitor materials through galvanostatic charge-discharge and cyclic voltammetry tests. The Ni(OH)2-Co(OH)2 composites delivered a specific capacitance of 2193 F g-1 at 2 A g-1 and 1398 F g-1 at 20 A g-1, much higher than those of pristine Ni(OH)2. The enhancement of the overall electrochemical performances is ascribed to the synergetic contribution from nanostructured Ni(OH)2 and electrically conductive CoOOH forming in the charge process.

Li, Jinxiu; Yang, Mei; Wei, Jinping; Zhou, Zhen

2012-07-01

352

Preparation and electrochemical performances of doughnut-like Ni(OH)?-Co(OH)? composites as pseudocapacitor materials.  

PubMed

Doughnut-like nanostructured Ni(OH)(2)-Co(OH)(2) composites were prepared by combining hydrothermal and chemical deposition routes. The electrochemical performances of the composites were investigated as pseudocapacitor materials through galvanostatic charge-discharge and cyclic voltammetry tests. The Ni(OH)(2)-Co(OH)(2) composites delivered a specific capacitance of 2193 F g(-1) at 2 A g(-1) and 1398 F g(-1) at 20 A g(-1), much higher than those of pristine Ni(OH)(2). The enhancement of the overall electrochemical performances is ascribed to the synergetic contribution from nanostructured Ni(OH)(2) and electrically conductive CoOOH forming in the charge process. PMID:22684332

Li, Jinxiu; Yang, Mei; Wei, Jinping; Zhou, Zhen

2012-06-08

353

POLYMER ENGINEERING: Research on composite materials at Liverpool University, Part 2: Energy absorbing composite materials  

Microsoft Academic Search

The ability of a composite material to absorb energy in its bulk rather than at the tip of a crack is very important when such materials are used in the automobile industry, for example to protect passengers from the consequences of high speed impact under crash conditions. Part 2 of this article describes research into the design and fabrication of

D. Hull

1983-01-01

354

Nondestructive evaluation of advanced ceramic composite materials  

SciTech Connect

Nondestructive evaluation techniques were developed to characterize performance degrading conditions in continuous fiber-reinforced silicon carbide/silicon carbide composites. Porosity, fiber-matrix interface bond strength, and physical damage were among the conditions studied. The material studied is formed by chemical vapor infiltration (CVI) of the matrix material into a preform of woven reinforcing fibers. Acoustic, ultrasonic, and vibration response techniques were studied. Porosity was investigated because of its inherent presence in the CVI process and of the resultant degradation of material strength. Correlations between porosity and ultrasonic attenuation and velocity were clearly demonstrated. The ability of ultrasonic transmission scanning techniques to map variations in porosity in a single sample was also demonstrated. The fiber-matrix interface bond was studied because of its importance in determining the fracture toughness of the material. Correlations between interface bonding and acoustic and ultrasonic properties were observed. These results are presented along with those obtained form acoustic and vibration response measurements on material samples subjected to mechanical impact damage. This is the final report on research sponsored by the US Department of Energy, Fossil Energy Advanced Research and Technology Development Materials Program. 10 refs., 24 figs., 2 tabs.

Lott, L.A.; Kunerth, D.C.; Walter, J.B.

1991-09-01

355

Novel nano-structured phosphor materials cast from natural Morpho butterfly scales  

NASA Astrophysics Data System (ADS)

The fabrication of the first nano-structured phosphor materials, cast from scales of the Morpho pleides butterfly, are reported. The structures are obtained by infilling sections of the butterfly wings with precursor phosphor solutions, then drying the samples at 100°C, followed by firing/annealing at 700°C for 30min. During the firing of the resulting solids the natural template is sacrificed and burns off, leaving a cast of the butterfly structure that is composed of the resulting phosphor material. Two different phosphor precursor solutions were used, either the precursor water-based solution for the red Y2O3:Eu3+ phosphor or europium-doped titanium ethoxide solution, which is the precursor for the TiO2:Eu3+ phosphor. In this work we have demonstrated that it is possible to reproduce fine detail in these casts, with structural features having ca. 100?nm dimensions being clearly visible. The casts of two distinct types of scale of the Morpho pleides butterfly were prepared in this work from phosphor materials. One distinct type of scale was rounded whereas the other was dentated, there being a clear difference in spacing between the longitudinal ridges for these two types. As yet, the casts manifest none of the photonic properties of the original butterfly scales. This is thought to be due to the precursor phosphor solutions not penetrating into the lamellar structures that are located between the cross-ribbing in the scales.

Silver, J.; Withnall*, R.; Ireland, T. G.; Fern, G. R.

2005-07-01

356

Three-dimensional nanostructuring by two-photon polymerization of hybrid materials  

NASA Astrophysics Data System (ADS)

Two-photon polymerization (2PP) of photosensitive inorganic-organic hybrid polymers (ORMOCERs, developed at the Frauenhofer Institut für Silicatforschung) is demonstrated as a very promising approach for the fabrication of complicated three-dimensional micro- and nanostructures. These materials are produced by sol-gel synthesis with molecular level mixing of different components. It is remarkable that properties of the hybrid polymers can be tuned from those that are characteristic for organic polymers to those that are similar to inorganic glasses. They have negative resist behaviour and can be used as storage-stable, liquid photo-polymerizable resins. When Ti:sapphire femtosecond laser pulses are tightly focused into the volume of this resin (which is transparent in the infrared) they can initiate two-photon polymerization process transferring liquid into solid state. This process is confined to a highly localized area at the focal point due to the quadratic dependence of the two-photon absorption rate on the laser intensity. When the laser focus is moved through the resin in three dimensions, the polymerization occurs along the trace of the focus. This allows to fabricate any computer-generated 3D structure by direct laser 'recording' into the volume of the ORMOCER. The non-irradiated liquid resin can be dissolved in alcohol leaving the polymerized copy of the computer model. Compared to conventional photo-lithography which is a planar processing, two-photon polymerization is a real three-dimensional volume microfabrication technique. These technologies can be used for rapid prototyping and low-cost fabrication of artificial micro- and nanostructured components which are required for different applications in optics, medicine, and biology. Numerous examples such as photonic crystals, micromechanical and microoptical devices will be demonstrated in this presentation.

Serbin, Jesper J.; Chichkov, Boris N.

2003-04-01

357

Three-dimensional nanostructuring of hybrid materials by two-photon polymerization  

NASA Astrophysics Data System (ADS)

Two-photon polymerization (2PP) of photosensitive inorganic-organic hybrid polymers (ORMOCERs, developed at the Frauenhofer Institut für Silicatforschung) is demonstrated as a very promising approach for the fabrication of complicated three-dimensional micro- and nanostructures. These materials are produced by sol-gel synthesis with molecular level mixing of different components. It is remarkable that properties of the hybrid polymers can be tuned from those that are characteristic for organic polymers to those that are similar to inorganic glasses. They have negative resist behaviour and can be used as storage-stable, liquid photo-polymerizable resins. When Ti:sapphire femtosecond laser pulses are tightly focused into the volume of this resin (which is transparent in the infrared) they can initiate two-photon polymerization process transferring liquid into solid state. This process is confined to a highly localized area at the focal point due to the quadratic dependence of the two-photon absorption rate on the laser intensity. When the laser focus is moved through the resin in three dimensions, the polymerization occurs along the trace of the focus. This allows to fabricate any computer-generated 3D structure by direct laser "recording" into the volume of the ORMOCER. The non-irradiated liquid resin can be dissolved in alcohol leaving the polymerized copy of the computer model. Compared to conventional photo-lithography which is a planar processing, two-photon polymerization is a real three-dimensional volume microfabrication technique. This technology can be used for rapid prototyping and low-cost fabrication of artificial micro- and nanostructured components which are required for different applications in optics, medicine, and biology. Numerous examples such as photonic crystals, micromechanical and microoptical devices are presented.

Serbin, Jesper; Chichkov, Boris N.; Houbertz, Ruth

2003-11-01

358

Synthesis and characterization of nanostructured cathode materials for rechargeable lithium/lithium ion batteries  

NASA Astrophysics Data System (ADS)

The rapidly increasing markets of portable electronic devices and electric/hybrid vehicles have raised worldwide R&D efforts in developing high-energy rechargeable lithium and lithium ion batteries. High performance intercalation cathodes are key to the success of these batteries. The nanotechnology has endowed the electrode materials with a variety of improved features as well as unique characteristics. Synthesis approaches were designed in this thesis work to utilize these advantages and investigate the exceptional phenomena raised by the nanostructured materials. A novel sol-gel method was designed for the synthesis of carbon-coated phase-pure lithium iron phosphate with submicron particle sizes and uniform size distribution. The surface carbon coating was formed in-situ through pyrolysis of the precursor gel, which improved the apparent electronic conductivity of the as prepared material to 10-2 S/cm compared with 10-9-10-10 S/cm of the pristine LiFePO 4. The favorable physical characteristics of the synthesized LiFePO 4 particles and the improved electronic conductivity through the carbon coating led to electrochemical properties comparable to the best performances reported so far. Amorphous manganese oxide cryogels with nanoarchitecture were obtained by freeze-drying Mn (IV) oxide hydrogels. The combination of the advantages of the amorphous structure and the nano-architecture of the materials gave high capacities and excellent rate capabilities. This work led to the finding of a nanocrystalline Li2MnO3-like compound with a surprising electrochemical activity, which is in sharp contrast to the microcrystalline rock-salt Li2MnO3 that has been known to be electrochemically inactive. The study highlights the possibility of qualitative difference in intercalation behavior of nanostructured intercalation compounds compared with their microcrystalline counterparts. Bismuth and copper modified amorphous manganese oxides were synthesized by aqueous coprecipitation methods and investigated as intercalation hosts for rechargeable lithium batteries. The results suggest the promise of achieving high performance intercalation electrodes by enhancing amorphous manganese oxides through cation modification.

Yang, Jingsi

359

Development of Nano-structured Electrode Materials for High Performance Energy Storage System  

NASA Astrophysics Data System (ADS)

Systematic studies have been done to develop a low cost, environmental-friendly facile fabrication process for the preparation of high performance nanostructured electrode materials and to fully understand the influence factors on the electrochemical performance in the application of lithium ion batteries (LIBs) or supercapacitors. For LIBs, LiNi1/3Co1/3Mn1/3O2 (NCM) with a 1D porous structure has been developed as cathode material. The tube-like 1D structure consists of inter-linked, multi-facet nanoparticles of approximately 100-500nm in diameter. The microscopically porous structure originates from the honeycomb-shaped precursor foaming gel, which serves as self-template during the stepwise calcination process. The 1D NCM presents specific capacities of 153, 140, 130 and 118mAh·g-1 at current densities of 0.1C, 0.5C, 1C and 2C, respectively. Subsequently, a novel stepwise crystallization process consisting of a higher crystallization temperature and longer period for grain growth is employed to prepare single crystal NCM nanoparticles. The modified sol-gel process followed by optimized crystallization process results in significant improvements in chemical and physical characteristics of the NCM particles. They include a fully-developed single crystal NCM with uniform composition and a porous NCM architecture with a reduced degree of fusion and a large specific surface area. The NCM cathode material with these structural modifications in turn presents significantly enhanced specific capacities of 173.9, 166.9, 158.3 and 142.3mAh·g -1 at 0.1C, 0.5C, 1C and 2C, respectively. Carbon nanotube (CNT) is used to improve the relative low power capability and poor cyclic stability of NCM caused by its poor electrical conductivity. The NCM/CNT nanocomposites cathodes are prepared through simply mixing of the two component materials followed by a thermal treatment. The CNTs were functionalized to obtain uniformly-dispersed MWCNTs in the NCM matrix. The electrochemical tests found reduced inner electron resistance and improved rate capability of the nanocomposite cathodes compared to the neat NCM, which were attributed to the 3D spatial conductive network formed by MWCNTs and Super p carbon black in the nanocomposites. The capacity retention ratios after 100 cycles of Li/NCM-CNTs cell were about 81%, much higher than that of Li/NCM cell (˜72%). As for supercapacitor, the annealed GO/CNT films or papers the binder-free electrodes are prepared and use for high performance supercapacitors. The amphiphilic nature of graphene oxide (GO) sheets allows adsorption of CNTs onto their surface in water, capable of forming highly stable dispersion. Thus, the GO/CNT hybrid films or papers are self-assembled via simple casting or vacuum filtration of aqueous dispersion. The hybrid thin film electrode with a moderate CNT content, typically 12.5wt%, give rise to remarkable electrochemical performance with extremely high specific capacitances of 428 and 145 F·g -1 at current densities of 0.5 and 100 A·g-1, respectively, as well as a remarkable retention rate 98% of the initial value after 10,000 charge/discharge cycles. The same as film type electrode, the rGO/CNT sandwich papers gives rise to an excellent specific capacitance of 151 F·g-1 at a current density of 0.5 A·g -1, as well as a remarkable retention ratio of 86 % of the initial value after 6,000 charge/discharge cycles at 5 A·g-1. These improvements arise from the synergistic effects of the increased electronic conductivity and effective surface area associated with large electrochemical active sites. The synergistic effects arising from i) the enlarged surface area of electrodes due to the intercalation of CNTs between the stacked GO sheets with associated large electrochemical active sites and ii) the improved conductivity through the formation of 3D network aided by CNTs, are mainly responsible for these findings. The effects of reduction process are also studied on the supercapacitive behavior of electrodes made from flexible graphene oxide (GO) papers. It is found that the s

Huang, Zhendong

360

Damage and fracture mechanics of composite materials  

NASA Astrophysics Data System (ADS)

The design of structural systems in the aerospace industry has been characterized by a continuing search for strong, yet lightweight, materials to achieve maximum payload capability for minimum weight. In recent years, this search has led to a wide use of fiber reinforced composites, such as carbon, glass and kevelar based composites. Comparison of these new materials with the traditional ones (metals) according to the basic properties, such as density, elastic modulus and also long-time and short-time strength, shows their superiority over traditional materials, when weight is a major design factor, like in the aerospace industry. Most composite materials of interest to aerospace applications have been adequately characterized under static loading conditions. Related work to study their fracture behaviour has been limited. Since most failure mechanisms involve crack growth and/or delamination, design of such components requires knowledge and understanding of their fracture properties. This thesis includes an experimental and analytical investigation of fracture characteristics of composite materials. The post-peak response of notched specimens subjected to uniaxial cyclic loading is established to evaluate the fracture energy associated with progressive matrix damage and subsequent crack growth. A total of 75 uniaxial tension specimens were tested. The experimental work consisted of first testing several un-notched specimens with different thickness (number of layers) to determine the initial and secondary elastic modulus as well as the tensile strength. The investigation studied the effect of the various fracture parameters, including thickness, fiber orientation, and crack width ratio (a/w) on the behaviour of crack propagation, peak load, and post-peak response. The specimens used in this research were prepared using the vacuum bagging technique, with a chosen number of fiber glass cloth layers and fiber orientation. The experimental results provided information regarding the peak load, post-peak response, fracture energy and stress intensity factor of the notched composite materials specimen under repeated loading/unloading cyclicity. The load versus crack opening displacement as well as crack length, fracture toughness and fracture energy versus number of loading cycles are produced for different specimens. Based on the experimental results, concepts of fracture mechanics are applied to evaluate stiffness degradation, fracture toughness and fracture energy evolution associated with crack growth. In addition, a linear elastic fracture mechanics approach combined with continuum damage representation is used to predict the response of specimens (peak load and crack opening displacement). This effort has also generated a new crack band model for computational purposes. A new formula is derived to compute delamination and interlaminar buckling loads using the finite element method. By matching the analytical near crack tip displacement field with the finite element approximation, the crack-axial stress magnitude is established, and therefore an accurate assessment of the buckling load responsible for delamination of composites is accurately evaluated. A comprehensive derivation of the fracture inelastic zone size and shape in anisotropic solids is presented. An adaptation of Hill's failure criterion is used to derive the shape of the inelastic zone. The findings explain the "banded" shape of the damage zone observed during crack growth.

Abdussalam, Saleh Ramadan

361

Composite materials for thermal energy storage  

DOEpatents

A composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These PCM's do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon, siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, D.K.; Burrows, R.W.; Shinton, Y.D.

1985-01-04

362

Dental composites/glass ionomers: the materials.  

PubMed

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1292462

Bowen, R L; Marjenhoff, W A

1992-09-01

363

Orthotropic piezoelectric composite materials actuator and its preliminary application  

Microsoft Academic Search

In this paper, the laminated piezoelectric composite materials with orthotropic properties, the structures, performances of orthotropic piezoelectric actuation elements are studied. Orthotropic piezoelectric composite materials present remarkable differences in two primary directions perpendicular to each other. As actuation chips, the laminated orthotropic piezoelectric composite materials present opposite deformation tendencies in two primary directions, which conforms to the deformation law of

Ying Luo; Guoqi Zhao; Jianzu Gu; Zuting Liu

2002-01-01

364

Lignins as Components of Polymeric Composite Materials  

NASA Astrophysics Data System (ADS)

The results of studies of natural, native, and technical lignins are surveyed. Data are presented on the structures and physicochemical properties of various technical lignins (hydrolytic, sulphite, and sulphate lignins), which constitute the waste of the cellulose-paper and hydrolytic industries. Considerable attention is devoted to the examination of the properties of lignins which are responsible for their employment for the reinforcement of elastomers and the modification of plastics. The methods of utilisation and rational employment of technical lignins in the plastics industry as active ingredients of polymeric composite materials are examined. The importance of sulphate lignins as the most active from the standpoint of structure and properties in relation to the polymer matrix for the creation of highly filled lignin-containing polymeric materials — lignoplastics of the type of poprolin — is specially emphasised. The bibliography includes 160 references.

Lyubeshkina, E. G.

1983-07-01

365

Ferroelectric mesocrystals of bismuth sodium titanate: formation mechanism, nanostructure, and application to piezoelectric materials.  

PubMed

Ferroelectric mesocrystals of Bi0.5Na0.5TiO3 (BNT) with [100]-crystal-axis orientation were successfully prepared using a topotactic structural transformation process from a layered titanate H1.07Ti1.73O4·nH2O (HTO). The formation reactions of BNT mesocrystals in HTO-Bi2O3-Na2CO3 and HTO-TiO2-Bi2O3-Na2CO3 reaction systems and their nanostructures were studied by XRD, FE-SEM, TEM, SAED, and EDS, and the reaction mechanisms were given. The BNT mesocrystals are formed by a topotactic structural transformation mechanism in the HTO-Bi2O3-Na2CO3 reaction system and by a combination mechanism of the topotactic structural transformation and epitaxial crystal growth in the HTO-TiO2-Bi2O3-Na2CO3 reaction system, respectively. The BNT mesocrystals prepared by these methods are constructed from [100]-oriented BNT nanocrystals. Furthermore, these reaction systems were successfully applied to the fabrication of [100]-oriented BNT ferroelectric ceramic materials. A BNT ceramic material with a high degree of orientation, high relative density, and small grain size was achieved. PMID:23978153

Hu, Dengwei; Kong, Xingang; Mori, Kotaro; Tanaka, Yasuhiro; Shinagawa, Kazunari; Feng, Qi

2013-08-26

366

Manufacturing of hard magnetic composite materials Nd-Fe-B  

Microsoft Academic Search

Purpose: This paper presents the material and technological solution which makes it possible obtaining of hard magnetic composite materials: nanocrystalline material - polymer. Design\\/methodology\\/approach: For fabrication of composite materials the Nd-Fe-B powder obtained by melt quenching technique was used and for matrix: epoxy resin (EP) or high density polyethylene (HDPE) (2.5 % wt.). Composite materials were compacted by the one-sided

M. Drak; B. Zi?bowicz; L. A. Dobrza?ski

367

Dealloying to nanoporous silver and its implementation as a template material for construction of nanotubular mesoporous bimetallic nanostructures.  

PubMed

Nanoporous silver (NPS) is fabricated by selectively dissolving Al from AgAl alloys in corrosive electrolytes at room temperature. Electron spectroscopy characterizations demonstrate that the NaOH electrolyte is beneficial to the formation of a three-dimensional bicontinuous porous nanostructure with uniform and tunable pore and ligament dimensions of a few tens of nanometers, while processing in HCl electrolyte easily lead to coarsened porous nanostructures. The high-surface-area Ag nanostructures are demonstrated as novel effective template materials to the construction of nanotubular mesoporous Pt/Ag and Pd/Ag alloy structures, which are realized via room temperature galvanic replacement reactions with H(2)PtCl(6) and K(2)PdCl(4) solutions by adding a high concentration of Cl(-) ions as a coordinating agent. Electrochemical measurements indicate that the resulting hollow and porous bimetallic nanostructures show enhanced electrocatalytic activities and CO-tolerance with better durability toward methanol and formic acid oxidation due to alloying with Ag. PMID:20799316

Xu, Caixia; Li, Yingying; Tian, Fang; Ding, Yi

2010-10-25

368

Ultrafast opto-acoustics applied to the study of material nanostructures  

NASA Astrophysics Data System (ADS)

The propagation of ultra-short sound pulses in water has been studied using an ultrafast opto-acoustic technique. A pulse time-of-flight technique for measuring the depths of deep channels in Si-based nanostructures was demonstrated. We report in these proof-of-concept ultrasonic experiments how spatial profile information of nanostructures can be acquired, where sound pulses propagate down narrow channels in patterned nanostructures. We have been able to detect acoustic echoes for sound propagating along a channel as narrow as 35 nm with depth to width ratios exceeding 10:1.

Grimsley, T. J.; Yang, F.; Che, S.; Antonelli, G. A.; Maris, H. J.; Nurmikko, A. V.

2011-01-01

369

High power 4.7 V nanostructured spinel lithium manganese nickel oxide lithium-ion battery cathode materials  

Microsoft Academic Search

Nanostructured LiMn1.5+deltaNi0.5-deltaO 4 spinel powders were synthesized by a solution based chemistry method called modified Pechini. The impacts of processing parameters such as synthesis temperature, oxygen-partial-pressure and mole ratio of ethylene glycol to citric acid on the morphology, structure and properties of spinel materials have been studied thoroughly via various in-situ and ex-situ characterization techniques. Later, these parameters were tied

Muharrem Kunduraci

2007-01-01

370

Viscoelastic models for polymeric composite materials  

SciTech Connect

An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the macroscopic behavior of the composite (explosive). Of interest here is the determination of an appropriate constitutive law for a polyurethane binder material. A Taylor Cylinder impact test, and uniaxial stress tension and compression tests at various strain rates, have been performed on the polyurethane. Evident from time resolved Taylor Cylinder profiles, the material undergoes very large strains ({gt}100{percent}) and yet recovers its initial configuration. A viscoelastic constitutive law is proposed for the polyurethane and was implemented in the finite element, explicit, continuum mechanics code EPIC. The Taylor Cylinder impact experiment was simulated and the results compared with experiment. Modeling improvements are discussed. {copyright} {ital 1996 American Institute of Physics.}

Bardenhagen, S.G.; Harstad, E.N. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Foster, J.C. Jr. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)]|[Wright Laboratory, Armament Directorate, Eglin AFB, Florida 32542 (United States); Maudlin, P.J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1996-05-01

371

Composition of estuarine colloidal material: organic components  

NASA Astrophysics Data System (ADS)

Colloidal material in the size range 1.2 nm to 0.4 ?m was isolated by ultrafiltration from Chesapeake Bay and Patuxent River waters (U.S.A.). Temperature controlled, stepwise pyrolysis of the freeze-dried material, followed by gas chromatographic-mass spectrometric analyses of the volatile products indicates that the primary organic components of this polymer are carbohydrates and peptides. The major pyrolysis products at the 450°C step are acetic acid, furaldehydes, furoic acid, furanmethanol, diones and lactones characteristic of carbohydrate thermal decomposition. Pyrroles, pyridines, amides and indole (protein derivatives) become more prevalent and dominate the product yield at the 600°C pyrolysis step. Olefins and saturated hydrocarbons, originating from fatty acids, are present only in minor amounts. These results are consistent with the composition of Chesapeake phytoplankton (approximately 50% protein, 30% carbohydrate, 10% lipid and 10% nucleotides by dry weight). The pyrolysis of a cultured phytoplankton and natural particulate samples produced similar oxygen and nitrogencontaining compounds, although the proportions of some components differ relative to the colloidal fraction. There were no lignin derivatives indicative of terrestrial plant detritus in any of these samples. The data suggest that aquatic microorganisms, rather than terrestrial plants, are the dominant source of colloidal organic material in these river and estuarine surface waters.

Sigleo, Anne C.; Hoering, Thomas C.; Helz, George R.

1982-09-01

372

High velocity impact resistance of composite materials  

NASA Astrophysics Data System (ADS)

Composite materials are used in applications that require protection against high velocity impacts by fragment simulating projectiles. In this work, the ballistic performance of two commercially available materials against a fragments simulating projectile (FSP) is studied. The materials used were an aramid fiber with a phenolic matrix and a polyethylene fiber with a thermoplastic film. Impact tests have been carried out, with velocities ranging from 300 m/s to 1260m/s. The projectile used is a 1.1g NATO FSP. Impact velocity and exit velocity are measured, to determine the V{50} and the energy absorbed in cases where perforation occurs. Assessment of the impact damaged area is done using ultrasonic C-scan inspection. Types of damage and damage mechanisms have been identified. Several mechanical tests have been carried out to determine the mechanical properties, at different strain rates. Future work in numerical simulation of impact will be done using commercial code AutodyntinycircledR ftom Century Dynamics.

Justo, Jo; Marquer, A. T.

2003-09-01

373

Aluminium composite materials for multichip modules  

SciTech Connect

This paper reports that, as a result of continued advances in microelectronics, packaging technologies have become ital to the success of advanced designs. Progress in this field has been driven by advances in active device technologies that have resulted in significant miniaturization, increased functional density, and higher operating frequencies. These developments have produced ever-increasing power densities requiring improve thermal management schemes. In particular, multichip modules (MCMs) present challenges because they contain several devices in close proximity. The alternatives to improve cooling schemes-higher junction temperatures and decreased reliability-are clearly unacceptable. Requirements for improved cooling are complicated further in avionics systems by the need to minimize system weight and in automotive systems by the need to provide protection from a more hostile environment while maintaining low cost. These needs are driving materials developments along a number of fonts, as reviewed in Carl Zweben's article in this issue. Unfortunately, no current-generation material can meet all of these challenges. The use of aluminum or copper results in unacceptable expansion stress on silicon- or gallium arsenide-based devices. Kovar is costly to manufacture in complex configurations and ins inherently poor in thermal conductivity. The Cu/W and Cu/Mo blends, either in the form of metallurgical or macroscopic composites, offer good thermal conductivity but are inherently heavy and are manufactured from expensive raw materials.

Premkumar, M.K.; Hunt, W.H. Jr.; Sawtell, R.R. (Innometalx Group, Alcoa Center, PA (US))

1992-07-01

374

Ordered Nanostructured Amphiphile Self-Assembly Materials from Endogenous Nonionic Unsaturated Monoethanolamide Lipids in Water  

SciTech Connect

The self-assembly, solid state and lyotropic liquid crystalline phase behavior of a series of endogenous n-acylethanolamides (NAEs) with differing degrees of unsaturation, viz., oleoyl monoethanolamide, linoleoyl monoethanolamide, and linolenoyl monoethanolamide, have been examined. The studied molecules are known to possess inherent biological function. Both the monoethanolamide headgroup and the unsaturated hydrophobe are found to be important in dictating the self-assembly behavior of these molecules. In addition, all three molecules form lyotropic liquid crystalline phases in water, including the inverse bicontinuous cubic diamond (Q{sub II}{sup D}) and gyroid (Q{sub II}{sup G}) phases. The ability of the NAE's to form inverse cubic phases and to be dispersed into ordered nanostructured colloidal particles, cubosomes, in excess water, combined with their endogenous nature and natural medicinal properties, makes this new class of soft mesoporous amphiphile self-assembly materials suitable candidates for investigation in a variety of advanced multifunctional applications, including encapsulation and controlled release of therapeutic agents and incorporation of medical imaging agents.

Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Moghaddam, Minoo; Seddon, John M.; Drummond, Calum J. (CSIRO/MHT); (ICL)

2010-08-23

375

Polyoxometalate clusters, nanostructures and materials: from self assembly to designer materials and devices.  

PubMed

Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures and several structural types and novel physical properties are examined. In this critical review the synthetic and design approaches to the many polyoxometalate cluster types are presented encompassing all the sub-types of polyoxometalates including, isopolyoxometalates, heteropolyoxometalates, and reduced molybdenum blue systems. As well as the fundamental structure and bonding aspects, the final section is devoted to discussing these clusters in the context of contemporary and emerging interdisciplinary interests from areas as diverse as anti-viral agents, biological ion transport models, and materials science. PMID:17173149

Long, De-Liang; Burkholder, Eric; Cronin, Leroy

2006-10-30

376

Hybrid nanocolloids with programmed three-dimensional shape and material composition  

NASA Astrophysics Data System (ADS)

Tuning the optical, electromagnetic and mechanical properties of a material requires simultaneous control over its composition and shape. This is particularly challenging for complex structures at the nanoscale because surface-energy minimization generally causes small structures to be highly symmetric. Here we combine low-temperature shadow deposition with nanoscale patterning to realize nanocolloids with anisotropic three-dimensional shapes, feature sizes down to 20?nm and a wide choice of materials. We demonstrate the versatility of the fabrication scheme by growing three-dimensional hybrid nanostructures that contain several functional materials with the lowest possible symmetry, and by fabricating hundreds of billions of plasmonic nanohelices, which we use as chiral metafluids with record circular dichroism and tunable chiroptical properties.

Mark, Andrew G.; Gibbs, John G.; Lee, Tung-Chun; Fischer, Peer

2013-09-01

377

Effective thermal conduction in composite materials  

NASA Astrophysics Data System (ADS)

The problem of determining the bounds and/or estimating the effective thermal conductivity ( ? eff) of a composite (multiphase) system given the volume fractions and the conductivities of the components has been investigated. A comparison between the measured data and the results predicted by theoretical models has been made for seven heterogeneous samples. The tested models include those of the effective medium theory (EMT), Hashin and Shtrikman (HS) bounds, and Wiener bounds. These models can be used to characterize macroscopic homogeneous and isotropic multiphase composite materials either by determining the bounds for the effective thermal conductivity and/or by estimating the overall conductivity of the random mixture. It turns out that the most suitable one of these models to estimate ? eff is the EMT model. This model is a mathematical model based on the homogeneity condition which satisfies the existence of a statistically homogeneous medium that encloses inclusions of different phases. Numerical values of thermal conductivity for the samples that satisfy the homogeneity condition imposed by the effective medium theory are in best agreement with the experimentally measured ones.

Suleiman, Bashir M.

2010-04-01

378

Graphene nanoribbon and nanostructured SnO2 composite anodes for lithium ion batteries.  

PubMed

A composite made from graphene nanoribbons (GNRs) and tin oxide (SnO2) nanoparticles (NPs) is synthesized and used as the anode material for lithium ion batteries (LIBs). The conductive GNRs, prepared using sodium/potassium unzipping of multiwall carbon nanotubes, can boost the lithium storage performance of SnO2 NPs. The composite, as an anode material for LIBs, exhibits reversible capacities of over 1520 and 1130 mAh/g for the first discharge and charge, respectively, which is more than the theoretical capacity of SnO2. The reversible capacity retains ~825 mAh/g at a current density of 100 mA/g with a Coulombic efficiency of 98% after 50 cycles. Further, the composite shows good power performance with a reversible capacity of ~580 mAh/g at the current density of 2 A/g. The high capacity, good power performance and retention can be attributed to uniformly distributed SnO2 NPs along the high-aspect-ratio GNRs. The GNRs act as conductive additives that buffer the volume changes of SnO2 during cycling. This work provides a starting point for exploring the composites made from GNRs and other transition metal oxides for lithium storage applications. PMID:23758123

Lin, Jian; Peng, Zhiwei; Xiang, Changsheng; Ruan, Gedeng; Yan, Zheng; Natelson, Douglas; Tour, James M

2013-06-17

379

Review on advanced composite materials boring mechanism and tools  

Microsoft Academic Search

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre\\/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher

Runping Shi; Chengyong Wang

2010-01-01

380

The Investigation on Stability and Structural Properties of Cohesion-Based Nanostructures Material  

NASA Astrophysics Data System (ADS)

Styrene-doped ZrLaOy nanostructures were obtained by sol-gel method low-temperature synthesis. The nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and transmission electron microscopy (TEM) techniques. The observation using SEM and TEM revealed that the ring-shaped nanostructures were very uniform. Further characterization using XRD disclosed that the cohesion of the samples was controllable with annealing temperatures in the range of 800-1500°C. Cohesion property was investigated for the samples. The cohesion increased when increasing the annealing temperature. This was linked to the reinforcement of the oxygen bound on the ZrLaOy nanostructures The shape of nanostructures showed a transformation from a ring-shaped growth mode to a hole-surfaced growth mode with increasing annealing temperature. The styrene-doped ZrLaOy nanostructures with controllable crystallinity will have great potential for various applications in fuel, cells, batteries, electronics devices and chemical sensors.

Bahari, Ali; Gholipur, Reza; Derakhshi, Maryam

2013-10-01

381

The toxicological mode of action and the safety of synthetic amorphous silica-a nanostructured material.  

PubMed

Synthetic amorphous silica (SAS), in the form of pyrogenic (fumed), precipitated, gel or colloidal SAS, has been used in a wide variety of industrial and consumer applications including food, cosmetics and pharmaceutical products for many decades. Based on extensive physico-chemical, ecotoxicology, toxicology, safety and epidemiology data, no environmental or health risks have been associated with these materials if produced and used under current hygiene standards and use recommendations. With internal structures in the nanoscale size range, pyrogenic, precipitated and gel SAS are typical examples of nanostructured materials as recently defined by the International Organisation for Standardisation (ISO). The manufacturing process of these SAS materials leads to aggregates of strongly (covalently) bonded or fused primary particles. Weak interaction forces (van der Waals interactions, hydrogen bonding, physical adhesion) between aggregates lead to the formation of micrometre (?m)-sized agglomerates. Typically, isolated nanoparticles do not occur. In contrast, colloidal SAS dispersions may contain isolated primary particles in the nano-size range which can be considered nano-objects. The size of the primary particle resulted in the materials often being considered as "nanosilica" and in the inclusion of SAS in research programmes on nanomaterials. The biological activity of SAS can be related to the particle shape and surface characteristics interfacing with the biological milieu rather than to particle size. SAS adsorbs to cellular surfaces and can affect membrane structures and integrity. Toxicity is linked to mechanisms of interactions with outer and inner cell membranes, signalling responses, and vesicle trafficking pathways. Interaction with membranes may induce the release of endosomal substances, reactive oxygen species, cytokines and chemokines and thus induce inflammatory responses. None of the SAS forms, including colloidal nano-sized particles, were shown to bioaccumulate and all disappear within a short time from living organisms by physiological excretion mechanisms with some indications that the smaller the particle size, the faster the clearance is. Therefore, despite the new nomenclature designating SAS a nanomaterial, none of the recent available data gives any evidence for a novel, hitherto unknown mechanism of toxicity that may raise concerns with regard to human health or environmental risks. Taken together, commercial SAS forms (including colloidal silicon dioxide and surface-treated SAS) are not new nanomaterials with unknown properties, but are well-studied materials that have been in use for decades. PMID:22349641

Fruijtier-Pölloth, Claudia

2012-02-13

382

Mechanics of composite materials - A unified micromechanical approach  

Microsoft Academic Search

This book presents a unified theory for the prediction of the overall behavior of composite materials. After discussing the fundamentals of the mechanics of composites, several basic composite models are described, together with the micromechanical method of cells for the analysis of elastic composites with aligned continuous or short fibers. The cell method is used to predict the strength and

Jacob Aboudi

1991-01-01

383

Method for preparing polyolefin composites containing a phase change material  

DOEpatents

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein. The composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Salyer, Ival O. (Dayton, OH)

1990-01-01

384

Embedded binary eutectic alloy nanostructures: a new class of phase change materials.  

PubMed

Phase change materials are essential to a number of technologies ranging from optical data storage to energy storage and transport applications. This widespread interest has given rise to a substantial effort to develop bulk phase change materials well suited for desired applications. Here, we suggest a novel and complementary approach, the use of binary eutectic alloy nanoparticles embedded within a matrix. Using GeSn nanoparticles embedded in silica as an example, we establish that the presence of a nanoparticle/matrix interface enables one to stabilize both nanobicrystal and homogeneous alloy morphologies. Further, the kinetics of switching between the two morphologies can be tuned simply by altering the composition. PMID:20698591

Shin, S J; Guzman, J; Yuan, C-W; Liao, Christopher Y; Boswell-Koller, Cosima N; Stone, P R; Dubon, O D; Minor, A M; Watanabe, Masashi; Beeman, Jeffrey W; Yu, K M; Ager, J W; Chrzan, D C; Haller, E E

2010-08-11

385

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

386

Nanostructuring of organic-inorganic hybrid materials for distributed feedback laser resonators by two-photon polymerization.  

PubMed

With two-photon absorption induced polymerization arbitrary three dimensional nano- and microstructures can be patterned directly into photoresists. We report on the fabrication of a low threshold organic semiconductor distributed feedback laser using the technique of two-photon absorption induced polymerization. A surface grating with 400 nm periodicity and 40 nm height modulation was fabricated by two-photon absorption induced polymerization in the organic-inorganic hybrid material ORMOCER. With structuring several stacked layers acting as a planar basis for the nanostructure microscopic substrate tilt can be compensated simply. This enabled us to uniformly nano-structure the surface grating over an area of 200 x 200 microm(2). PMID:19219153

Woggon, Thomas; Kleiner, Thomas; Punke, Martin; Lemmer, Uli

2009-02-16

387

Power Composites: Structural Materials that Generate and Store Electrical Energy.  

National Technical Information Service (NTIS)

We describe progress in the development of a synthetic multifunctional material: namely a fiber composite with both power and structural function. The structural composite contains batteries encased in piezoelectric tubes. When the structure vibrates the ...

D. A. Shockey S. C. Ventura S. C. Narang J. W. Simons B. C. Bourne

2005-01-01

388

Soviet Developments in Composite Materials, January - June 1975.  

National Technical Information Service (NTIS)

Selected Soviet publications on composite materials over a period of 6 months (January to June 1975) are abstracted in this report. The publications cover both experimental and theoretical research on carbon fiber-reinforced plastic composites and carbon ...

J. Kourilo

1976-01-01

389

Developing polymer composite materials: carbon nanotubes or graphene?  

PubMed

The formation of composite materials represents an efficient route to improve the performances of polymers and expand their application scopes. Due to the unique structure and remarkable mechanical, electrical, thermal, optical and catalytic properties, carbon nanotube and graphene have been mostly studied as a second phase to produce high performance polymer composites. Although carbon nanotube and graphene share some advantages in both structure and property, they are also different in many aspects including synthesis of composite material, control in composite structure and interaction with polymer molecule. The resulting composite materials are distinguished in property to meet different applications. This review article mainly describes the preparation, structure, property and application of the two families of composite materials with an emphasis on the difference between them. Some general and effective strategies are summarized for the development of polymer composite materials based on carbon nanotube and graphene. PMID:23813859

Sun, Xuemei; Sun, Hao; Li, Houpu; Peng, Huisheng

2013-07-01

390

Microrobotics using composite materials: the micromechanical flying insect thorax  

Microsoft Academic Search

The use of high performance composite materials provides a substantial performance improvement for microrobotics. Such materials have great beneflts over common MEMs materials such as better frac- ture toughness and fatigue properties than semicon- ductors, and higher stifiness to weight ratios than most metals. Composite structures yield remarkable improvements in microrobotic links and joints, as well as greater performance actuators

Robert J. Wood; Srinath Avadhanula; M. Menon; Ronald S. Fearing

2003-01-01

391

Using of Composite Material in Wind Turbine Blades  

Microsoft Academic Search

The turbines manufactured from the mid 1980s until the late 1990s were mainly constructed using standard components. After that period, special components started being designed and manufactured for turbine use only. One of the best solutions is using composite materials in wind turbine. Most composites are made up of just two materials. One material (the matrix or binder) binds together

Bulent Eker; Aysegul Akdogan; Ali Vardar

2006-01-01

392

Nickel composite magnetostrictive material research for ultrasonic transducer  

Microsoft Academic Search

The immediate objective was to manufacture and test a composite transducer material of the compound SmFe2 in a nickel matrix fabricated by a powder metallurgy technique. The long term objective was the effective utilization of a 'giant' magnetostrictive REFe2 material in a ductile and corrosion resistant composite for use as a transducer core material.

D. T. Peters; E. L. Huston

1977-01-01

393

Fluorescent-Magnetic Hybrid Nanostructures: Preparation, Properties, and Applications in Biology  

Microsoft Academic Search

Research on nanocomposite materials aims at developing nanoscale composites with innovative optical, chemical, and magnetic properties, all combined in one single nanostructure. In this scenario, nanostructures which show simultaneously fluorescent and magnetic features are of particular interest for pharmaceutical and biomedical applications. In this review, we will focus our attention on magnetic-fluorescent nanocomposite based on colloidal iron oxide nanocrystals combined

Alessandra Quarta; Riccardo Di Corato; Liberato Manna; Andrea Ragusa

2007-01-01

394

ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS  

SciTech Connect

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for {sup 236}U/{sup 235}U in SRM950a was determined to be (8.48 {+-} 2.63) x 10{sup -6}, whereas {sup 236}U was not detected in CRM112a. They are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the {sup 238}U/{sup 235}U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

2009-09-03

395

Nanostructured composite thin films with tailored resistivity by atomic layer deposition  

NASA Astrophysics Data System (ADS)

We have developed a new type of thin film composite material comprised of Mo:Al2O3 consisting of conducting metal nanoclusters embedded in an insulating Al2O3 matrix. These nanocomposite thin films were prepared by atomic layer deposition (ALD). Quartz crystal microbalance (QCM) experiments performed with various Mo cycle percentages revealed that the Mo ALD inhibits the Al2O3 ALD and vice versa. Despite this inhibition, the relationship between Mo content in the films and cycle percentage was close to expectations. Depth profiling X-ray photoelectron spectroscopy (XPS) showed that the Mo:Al2O3 films were uniform in composition and contained Al, O, and metallic Mo as expected, but also included significant F and C. Cross sectional TEM revealed the composite film structure to be metallic nanoparticles (2-3nm) embedded uniformly in an amorphous Al2O3 insulating matrix. The resistivity of these composite films could be tailored in the range of 104 -1012 Ohm-cm by adjusting the Mo ALD cycle percentage. These nanocomposite films have been used as resistive coatings in microchannel plate (MCP) fabrication and as charge-drain coatings in micro-electron-optical devices. Here we report the ALD growth characterization, and application of these of Mo:Al2O3, films.

Mane, Anil U.; Elam, Jeffrey W.

2013-09-01

396

Synthesis of nanostructured materials by using metal-cyanide coordination polymers and their lithium storage properties.  

PubMed

Herein, we demonstrate a novel and simple two-step process for preparing LiCoO2 nanocrystals by using a Prussian blue analogue Co3[Co(CN)6]2 as a precursor. The resultant LiCoO2 nanoparticles possess single crystalline nature and good uniformity with an average size of ca. 360 nm. The unique nanostructure of LiCoO2 provides relatively shorter Li(+) diffusion pathways, thus facilitating the fast kinetics of electrochemical reactions. As a consequence, high reversible capacity, excellent cycling stability and rate capability are achieved with these nanocrystals as cathodes for lithium storage. The LiCoO2 nanocrystals deliver specific capacities of 154.5, 135.8, 119, and 100.3 mA h g(-1) at 0.2, 0.4, 1, and 2 C rates, respectively. Even at a high current density of 4 C, a reversible capacity of 87 mA h g(-1) could be maintained. Importantly, a capacity retention of 83.4% after 100 cycles is achieved at a constant discharge rate of 1 C. Furthermore, owing to facile control of the morphology and size of Prussian blue analogues by varying process parameters, as well as the tailored design of multi-component metal-cyanide hybrid coordination polymers, with which we have successfully prepared porous Fe2O3@NixCo3-xO4 nanocubes, one of the potential anode materials for lithium-ion batteries, such a simple and scalable approach could also be applied to the synthesis of other nanomaterials for energy storage devices. PMID:24071706

Nie, Ping; Shen, Laifa; Luo, Haifeng; Li, Hongsen; Xu, Guiyin; Zhang, Xiaogang

2013-09-26

397

Composite materials for extremely large mirrors and optical structures  

NASA Astrophysics Data System (ADS)

Building on our successful production of a world-class dimensionally stable composite optical bench structure for the SOLAR-B space telescope, Mitsubishi Electric is continuing to develop high performance lightweight composites for optical structures including mirrors. A key feature of composite materials is the ability to design the material to optimally meet the application requirements. Thus, various materials with individual characteristics are under development, each providing significant improvement over the state of the art.

Ozaki, Tsuyoshi; Hahn, Steven

2004-07-01

398

Molecular dynamics simulations of the deformation of nano-structured materials  

NASA Astrophysics Data System (ADS)

The strength of nano-layered materials is dictated by dislocation confinement at interfaces, when an external stress is applied. In materials composed of nano-layered duplex structures, several factors influence the maximum value of the externally-applied stress before dislocations can move across the interface, and thus slip confinement is lost. The strengthening effect is a result of elastic modulus mismatch across the interface (the Koehler barrier), lattice resistance mismatch influencing the core structure (the gamma surface effect), and any coherency strains. Recently, it has been experimentally shown that nano-twinned copper can be produced by pulsed electro-plating, and that the strength is several GPa without significant loss of electrical conductivity. The objective of our research is to use large-scale Molecular Dynamics modelling methods to study the mechanisms of dislocation motion in multi-layer nano-structure and the interactions of dislocation with interfaces and twin boundaries. Those methods used the Embedded Atom Method for the calculation of potentials of Cu, Ni. We present here studies of dislocation motion in Cu/Ni nano-layers utilizing Molecular Dynamics (MD) simulations, where we observed that the interfaces act as barriers for dislocation transmission, which accelerate or decelerate the motion of its partials. We present another study of the mechanism of twin boundary migration (TBM) in copper crystals with a nano-twinned structure. We show that the mechanism of twin boundary migration is a consequence of the nucleation and motion of Schockley partial dislocations across the twin boundary. We also studied the size effects on the deformation of nano-twinned copper. The deformation behaviors of nano-twinned Cu with different twin thickness are compared under several loading methods. The stacking fault density and the number of nucleated dislocations are compared for different size lamellae of twin structures. The present simulations reveal the origins of strengthening caused by nano-twins as the restriction of dissociated dislocation loop motion in narrow channels. A Critical twin thickness for the maximum strength in twinned copper is found to be around 4 nm. After the introduction of the background, we presents a literature review on the theory of Molecular Dynamics Modelling and the applications of MD on the Nano-materials. The research progress and results will be discussed next and followed by a Conclusion and Summary.

Li, Lan

399

Orthotic Devices Using Lightweight Composite Materials.  

National Technical Information Service (NTIS)

Potential applications of high strength, lightweight composite technology in the orthotic field were studied. Several devices were designed and fabricated using graphite-epoxy composite technology. Devices included shoe plates, assistive walker devices, a...

E. Harrison

1983-01-01

400

Bulk Nanostructured Materials Obtained by Shock Waves Compaction of Ultrafine Titanium and Aluminum  

NASA Astrophysics Data System (ADS)

Theoretical and experimental Investigations of shock wave consolidation processes of Ti-Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al. The normal and tangential stresses in the cylindrical steel tube (containers of Ti-Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (? 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al. Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

Chikhradze, Nikoloz M.; Politis, Constantin; Chikhradze, Mikheil; Oniashvili, George

401

NANOSTRUCTURED SiC-Ni COMPOSITE COATINGS OBTAINED BY ELECTRODEPOSITION - A TRIBOCORROSION STUDY  

Microsoft Academic Search

The tribocorrosion properties of SiC (20nm) - Ni nanostructured coatings have been studied in pin on disc tribocorrosimeter connected with an electrochemical cell. The objectives of our study in principal is to fully understanding the tribocorrosion process kinetic and mechanism of modified surfaces by co-depositing nano silicon carbide particles with nickel. The samples with coating on a top of a

Lidia BENEA; Viorel IORDACHE; François WENGER; Pierre PONTHIAUX

402

Structure and property evaluation of a vacuum plasma sprayed nanostructured tungsten–hafnium carbide bulk composite  

Microsoft Academic Search

Vacuum plasma spray (VPS) forming of tungsten-based metal matrix nanocomposites (MMCs) has shown to be a cost effective and time saving method for the formation of bulk monolithic nanostructured thermo-mechanical components. Spray drying of powder feedstock appears to have a significant effect on the improved mechanical properties of the bulk nanocomposite. The reported elastic modulus of the nanocomposite nearly doubles

K. E. Rea; V. Viswanathan; A. Kruize; J. Th. M. De Hosson; S. O’Dell; T. McKechnie; S. Rajagopalan; R. Vaidyanathan; S. Seal

2008-01-01

403

Preparation of Composite Materials in Space. Volume 2 Technical Report.  

National Technical Information Service (NTIS)

A study to define promising materials, significant processing criteria, and the related processing techniques and apparatus for the preparation of composite materials in space was conducted. The study also established a program for zero gravity experiment...

W. H. Steurer S. Kaye

1973-01-01

404

HDPE Wood-Plastic Composite Material Model Subject to Damage.  

National Technical Information Service (NTIS)

The information presented in this thesis is part of an ongoing research project being performed at Washington State University to develop wood-plastic composite materials for waterfront structures. Material development has been finished and relevant infor...

G. Lu

2002-01-01

405

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

406

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Dai, Heming

407

Composite tribological materials. (Latest citations from Fluidex). Published Search  

SciTech Connect

The bibliography contains citations concerning the properties, behavior, and uses of composite tribological materials in and on various objects, devices, and equipment. The citations examine friction and wear characteristics, mechanisms, and the performance of these materials and the objects to which they are applied. Composite tribological materials are used, for example, in bearings, gears, and piston rings. Included are self lubricating materials. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1998-02-01

408

Nanostructured materials based on mesoporous silica and mesoporous silica/apatite as osteogenic growth peptide carriers.  

PubMed

The aim of this work was the preparation of inorganic mesoporous materials from silica, calcium phosphate and a nonionic surfactant and to evaluate the incorporation and release of different concentrations of osteogenic growth peptide (OGP) for application in bone regeneration. The adsorption and release of the labeled peptide with 5,6-carboxyfluorescein (OGP-CF) from the mesoporous matrix was monitored by fluorescence spectroscopy. The specific surface area was 880 and 484 m(2) g(-1) for pure silica (SiO) and silica/apatite (SiCaP), respectively; the area influenced the percentage of incorporation of the peptide. The release of OGP-CF from the materials in simulated body fluid (SBF) was dependent on the composition of the particles, the amount of incorporated peptide and the degradation of the material. The release of 50% of the peptide content occurred at around 4 and 30 h for SiCaP and SiO, respectively. In conclusion, the materials based on SiO and SiCaP showed in vitro bioactivity and degradation; thus, these materials should be considered as alternative biomaterials for bone regeneration. PMID:23910362

Mendes, L S; Saska, S; Martines, M A U; Marchetto, R

2013-07-02

409

Environmental effects on composite materials. Volume 3  

SciTech Connect

The present collection of papers, each of which has previously been abstracted in International Aerospace Abstracts, discusses the accelerated environmental testing of composites, moisture solubility and diffusion in epoxy and epoxy-glass composites, the influence of internal and external factors affecting moisture absorption in polymer composites, long-tern moisture absorption in graphite/epoxy angle-ply laminates, the effect of UV light on Kevlar 49-reinforced composites, and temperature and moisture induced deformation in composite sandwich panels. Also discussed are the orthotropic thermoelastic problem of uniform heat flow distributed by a central crack, the effect of microcracks on composite laminate thermal expansion, the stress analysis of wooden structures exposed to elevated temperatures, and the deflection of plastic beams at elevated temperatures.

Springer, G.S.

1988-01-01

410

Environmental effects on composite materials. Volume 3  

Microsoft Academic Search

The present collection of papers, each of which has previously been abstracted in International Aerospace Abstracts, discusses the accelerated environmental testing of composites, moisture solubility and diffusion in epoxy and epoxy-glass composites, the influence of internal and external factors affecting moisture absorption in polymer composites, long-tern moisture absorption in graphite\\/epoxy angle-ply laminates, the effect of UV light on Kevlar 49-reinforced

1988-01-01

411

Materials characterisation and crash modelling of composite-aluminium honeycomb sandwich material  

Microsoft Academic Search

Composite sandwich materials are extensively used in aerospace, motorsport and other applications that require low-weight, high-stiffness materials with high strength and energy absorption. In Formula 1 vehicles, composite-aluminium sandwich materials are used for the energy absorbing structures and the protective cell for the driver. Generally, the loading and failure mechanisms in sandwich composite materials are well understood. However, their behaviour

A. K. Pickett; A. J. Lamb; F. Chaudoye

2009-01-01

412

A New Way to Prepare Nanostructured Materials:  Flame Spraying of Microemulsions  

Microsoft Academic Search

In this report we describe a new method to obtain nanostructured coatings or powders based on the flame decomposition of microcompartmentalized solutions. Metal nanoclusters of well-defined size are obtained by reduction of a metal salt inside the water compartment of water in oil (w\\/o) microemulsions, formed by water in hexane and stabilized by an appropriate surfactant. Metal nanoclusters can be

M. Bonini; U. Bardi; D. Berti; C. Neto; P. Baglioni

2002-01-01

413

The applications of carbon nanostructures and semiconductor materials in the development of biosensors  

Microsoft Academic Search

In recent years, nanomaterials and nanostructures with unique chemical, physical, and mechanical properties have been developed and applied as both sensing matrices and transducers, offering new opportunities for the development of highly sensitive bio-chemical sensors. The chemical and physical characteristics of the electrochemically active carbon nanotubes, nanofibers and fullerenes, as well as their potential applications in biosensors will be first

M. F. Frasco; R. Buiculescu; V. Vamvakaki; N. A. Chaniotakis

2009-01-01

414

Methodology for Evaluating Manufacturability of Composite Materials  

NASA Astrophysics Data System (ADS)

It is widely acknowledged that decisions made in the early design stages have a greater influence on the final product than those made in the later stages. In a conventional design process, composite products are designed without sufficient consideration being given to limitations of composite manufacturing process. Quite often some of composite designs cannot be produced with special performance requirement or cannot be produced at a reasonable cost. To resolve this drawback and achieve the competitive designs for composite product, an integrated knowledge framework that supports the quantitative manufacturability evaluation of composite design proposals was introduced. The essential concept of the composite manufacturability was defined through an in-depth analysis of composite manufacturing process. The evaluation flow was acquired according to the hierarchical indices. A stage-based quality assessment model for the composite multistage process was mainly studies. It relies on the consideration that the final quality of a composite product is mainly determined by some critical stages during a production cycle. Finally, the method is illustrated through a case focusing on the quality issue of void formation in autoclave process.

Cong, Jingjie; Zhang, Boming

2012-06-01

415

Microstructural design of composite materials for crashworthy structural applications  

Microsoft Academic Search

Traditionally, metals are used for crashworthy structural applications, mainly due to their plastic deformation characteristics that enable them to absorb impact energy in a controlled manner. Unlike the metals, polymer composite materials display little plastic deformation characteristics. The use of polymer composites for crashworthy structural applications is a major challenge for the composite community. Current research work clearly suggests that

S Ramakrishna

1997-01-01

416

Characterization and prediction of abrasive wear of powder composite materials  

Microsoft Academic Search

Composite materials produced by powder metallurgy provide a solution in many engineering applications where materials with high abrasion and erosion resistance are required. The actual wear behaviour of the material is associated with many external factors (particle size, velocity, angularity, etc.) and intrinsic material properties (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of such tribomaterials are highly dependent

R. Veinthal; P. Kulu; J. Pirso; H. Käerdi

2009-01-01

417

CFRP\\/titanium hybrid material for improving composite bolted joints  

Microsoft Academic Search

The structural joining remains an essential challenge for the development of composite aerospace structures: every structural interconnection means a disturbance of an optimized structure resulting in an increase in overall structural weight. The lightweight potential of advanced, high-performance fiber composite materials is affected more strongly by mechanical fastening techniques than by conventional metallic materials due to the low shear and

B. Kolesnikov; L. Herbeck; A. Fink

2008-01-01

418

Biomedical applications of polymer-composite materials: a review  

Microsoft Academic Search

An overview of various biomedical applications of polymer-composite materials reported in the literature over the last 30 years is presented in this paper. For the benefit of the readers, general information regarding structure and function of tissues, types and purpose of implants\\/medical devices, and various other materials used, are also briefly presented. Different types of polymer composite that are already

S. Ramakrishna; J. Mayer; E. Wintermantel; Kam W Leong

2001-01-01

419

Thermophysical Analysis of High Modulus Composite Materials for Space Vehicles  

Microsoft Academic Search

High modulus composite materials are used extensively in aerospace vehicles mainly for the purpose of increasing strength and reducing weight. However, thermal properties have become essential design information with the use of composite materials in the thermal design of spacecraft and spacecraft electronics packages. This is because the localized heat from closely packed devices can lead to functional failure of

Ho-Sung Lee

2009-01-01

420

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...

2009-04-01

421

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...