Preparation of nanoporous metal foam from high nitrogen transition metal complexes

DOEpatents

Tappan, Bryce C.; Huynh, My Hang V.; Hiskey, Michael A.; Son, Steven F.; Oschwald, David M.; Chavez, David E.; Naud, Darren L.

2006-11-28

Nanoporous metal foams are prepared by ignition of high nitrogen transition metal complexes. The ammonium salts of iron(III) tris[bi(tetrazolato)-amine], cobalt(III) tris(bi(tetrazolato)amine), and high nitrogen compounds of copper and silver were prepared as loose powders, pressed into pellets and wafers, and ignited under an inert atmosphere to form nanoporous metal foam monoliths having very high surface area and very low density.

Structural applications of metal foams considering material and geometrical uncertainty

NASA Astrophysics Data System (ADS)

Moradi, Mohammadreza

Metal foam is a relatively new and potentially revolutionary material that allows for components to be replaced with elements capable of large energy dissipation, or components to be stiffened with elements which will generate significant supplementary energy dissipation when buckling occurs. Metal foams provide a means to explore reconfiguring steel structures to mitigate cross-section buckling in many cases and dramatically increase energy dissipation in all cases. The microstructure of metal foams consists of solid and void phases. These voids have random shape and size. Therefore, randomness ,which is introduced into metal foams during the manufacturing processes, creating more uncertainty in the behavior of metal foams compared to solid steel. Therefore, studying uncertainty in the performance metrics of structures which have metal foams is more crucial than for conventional structures. Therefore, in this study, structural application of metal foams considering material and geometrical uncertainty is presented. This study applies the Sobol' decomposition of a function of many random variables to different problem in structural mechanics. First, the Sobol' decomposition itself is reviewed and extended to cover the case in which the input random variables have Gaussian distribution. Then two examples are given for a polynomial function of 3 random variables and the collapse load of a two story frame. In the structural example, the Sobol' decomposition is used to decompose the variance of the response, the collapse load, into contributions from the individual input variables. This decomposition reveals the relative importance of the individual member yield stresses in determining the collapse load of the frame. In applying the Sobol' decomposition to this structural problem the following issues are addressed: calculation of the components of the Sobol' decomposition by Monte Carlo simulation; the effect of input distribution on the Sobol' decomposition

Metal-doped organic foam and method of making same. [Patent application

DOEpatents

Rinde, J.A.

Organic foams having a low density and very small cell size and method for producing same in either a metal-loaded or unloaded (nonmetal loaded) form are described. Metal-doped foams are produced by soaking a polymer gel in an aqueous solution of desired metal salt, soaking the gel successively in a solvent series of decreasing polarity to remove water from the gel and replace it with a solvent of lower polarity with each successive solvent in the series being miscible with the solvents on each side and being saturated with the desired metal salt, and removing the last of the solvents from the gel to produce the desired metal-doped foam having desired density cell size, and metal loading. The unloaded or metal-doped foams can be utilized in a variety of applications requiring low density, small cell size foam. For example, rubidium-doped foam made in accordance with the invention has utility in special applications, such as in x-ray lasers.

Metal oxide nanostructures with hierarchical morphology

DOEpatents

Ren, Zhifeng; Lao, Jing Yu; Banerjee, Debasish

2007-11-13

The present invention relates generally to metal oxide materials with varied symmetrical nanostructure morphologies. In particular, the present invention provides metal oxide materials comprising one or more metallic oxides with three-dimensionally ordered nanostructural morphologies, including hierarchical morphologies. The present invention also provides methods for producing such metal oxide materials.

Metallic Nanostructures Based on DNA Nanoshapes

PubMed Central

Shen, Boxuan; Tapio, Kosti; Linko, Veikko; Kostiainen, Mauri A.; Toppari, Jari Jussi

2016-01-01

Metallic nanostructures have inspired extensive research over several decades, particularly within the field of nanoelectronics and increasingly in plasmonics. Due to the limitations of conventional lithography methods, the development of bottom-up fabricated metallic nanostructures has become more and more in demand. The remarkable development of DNA-based nanostructures has provided many successful methods and realizations for these needs, such as chemical DNA metallization via seeding or ionization, as well as DNA-guided lithography and casting of metallic nanoparticles by DNA molds. These methods offer high resolution, versatility and throughput and could enable the fabrication of arbitrarily-shaped structures with a 10-nm feature size, thus bringing novel applications into view. In this review, we cover the evolution of DNA-based metallic nanostructures, starting from the metallized double-stranded DNA for electronics and progress to sophisticated plasmonic structures based on DNA origami objects. PMID:28335274

Microwave-aided synthesis and applications of gold and nickel nanoporous metal foams

NASA Astrophysics Data System (ADS)

Lu, Zhifeng

In the field of nanoscience, nanoporous metal foams are a representative type of nanostructured materials, representing the ultimate form factor of a metal. They possess the hybrid properties of metal and nanoarchitectures, including the following properties such as good electrical and thermal conductivity, catalytic activity and high surface area, ultralow density, high strength-to-weight ratio. The outstanding properties bring the nanoporous metal foams to a wide range of applications, especially in the field of sensor system, energy storage and chemical catalyst. A new method of synthesis developed recently is presented for nanoporous metal foams of gold and nickel. The goal of this study is for the synthesis process of NMFs of and some applications in research and realistic life. Gold NMFs were produced by mixing gold chloride with ethylene glycol, ethanol, and reducing agent, and heating at 150 °C for 5 min with a CEM microwave. Both hydrazine and sodium borohydride were applied as the reducing agent for this redox reaction. Nickel NMFs were produced through the similar procedure with a little difference in the heating condition of 50 W, instead of 150 °C, with either hydrazine or sodium borohydride as the reducing agent. Gold NMFs were applied in surface-enhanced Raman spectroscopy (SERS) as a substrate. It is presented that with the presence of gold NMFs, the detection of the rhodamine 6G (R6G), a model analyte, can be enhanced significantly. The limit of detection for rhodamine 6G was found to be 5.2 x 10 -7 M in this research. Nickel NMFs was applied to degrade methyl orange (MO). An aqueous MO solution will turn nearly colorless after only 10 h of mixing with 0.025 g of nickel NMFs at room temperature under dark condition. In order to study the kinetics of the degradation reaction, MO solution with different initial concentration were used. This application of Ni NMFs is applicable as waste treatment of industrial water and to protect the environment.

Simulated Tip Rub Testing of Low-Density Metal Foam

NASA Technical Reports Server (NTRS)

Bowman, Cheryl L.; Jones, Michael G.

2009-01-01

Preliminary acoustic studies have indicated that low-density, open-cell, metal foams may be suitable acoustic liner material for noise suppression in high by-pass engines. Metal foam response under simulated tip rub conditions was studied to assess whether its durability would be sufficient for the foam to serve both as a rub strip above the rotor as well as an acoustic treatment. Samples represented four metal alloys, nominal cell dimensions ranging from 60 to 120 cells per inch (cpi), and relative densities ranging from 3.4 to 10 percent. The resulting rubbed surfaces were relatively smooth and the open cell structure of the foam was not adversely affected. Sample relative density appeared to have significant influence on the forces induced by the rub event. Acoustic responses of various surface preparations were measured using a normal incidence tube. The results of this study indicate that the foam s open-cell structure was retained after rubbing and that the acoustic absorption spectra variation was minimal.

Metal nanostructures: from clusters to nanocatalysis and sensors

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2017-12-01

The properties of metal clusters and nanostructures composed of them are reviewed. Various existing methods for the generation of intense beams of metal clusters and their subsequent conversion into nanostructures are compared. Processes of the flow of a buffer gas with active molecules through a nanostructure are analyzed as a basis of using nanostructures for catalytic applications. The propagation of an electric signal through a nanostructure is studied by analogy with a macroscopic metal. An analysis is given of how a nanostructure changes its resistance as active molecules attach to its surface and are converted into negative ions. These negative ions induce the formation of positively charged vacancies inside the metal conductor and attract the vacancies to together change the resistance of the metal nanostructure. The physical basis is considered for using metal clusters and nanostructures composed of them to create new materials in the form of a porous metal film on the surface of an object. The fundamentals of nanocatalysis are reviewed. Semiconductor conductometric sensors consisting of bound nanoscale grains or fibers acting as a conductor are compared with metal sensors conducting via a percolation cluster, a fractal fiber, or a bunch of interwoven nanofibers formed in superfluid helium. It is shown that sensors on the basis of metal nanostructures are characterized by a higher sensitivity than semiconductor ones, but are not selective. Measurements using metal sensors involve two stages, one of which measures to high precision the attachment rate of active molecules to the sensor conductor, and in the other one the surface of metal nanostructures is cleaned from the attached molecules using a gas discharge plasma (in particular, capillary discharge) with a subsequent chromatography analysis for products of cleaning.

Thermal-hydraulic performance of metal foam heat exchangers under dry operating conditions

DOE PAGES

Nawaz, Kashif; Bock, Jessica; Jacobi, Anthony M.

2017-03-14

High porosity metal foams with novel thermal, mechanical, electrical, and acoustic properties are being more widely adopted for application. Due to their large surface-area-to-volume ratio and complex structure which induces better fluid mixing, boundary layer restarting and wake destruction, they hold promise for heat transfer applications. In this study, the thermal-hydraulic performance of open-cell aluminum metal foam heat exchanger has been evaluated. The impact of flow conditions and metal foam geometry on the heat transfer coefficient and gradient have been investigated. Metal foam heat exchanger with same geometry (face area, flow depth and fin dimensions) consisting of four different typemore » of metal foams have been built for the study. Experiments are conducted in a closed-loop wind tunnel at different flow rate under dry operating condition. Metal foams with a smaller pore size (40 PPI) have a larger heat transfer coefficient compared to foams with a larger pore size (5 PPI). However, foams with larger pores result in relatively smaller pressure gradients. Current thermal-hydraulic modeling practices have been reviewed and potential issues have been identified. Permeability and inertia coefficients are determined and compared to data reported in open literature. Finally, on the basis of the new experimental results, correlations are developed relating the foam characteristics and flow conditions through the friction factor f and the Colburn j factor.« less

Thermal-hydraulic performance of metal foam heat exchangers under dry operating conditions

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

Nawaz, Kashif; Bock, Jessica; Jacobi, Anthony M.

High porosity metal foams with novel thermal, mechanical, electrical, and acoustic properties are being more widely adopted for application. Due to their large surface-area-to-volume ratio and complex structure which induces better fluid mixing, boundary layer restarting and wake destruction, they hold promise for heat transfer applications. In this study, the thermal-hydraulic performance of open-cell aluminum metal foam heat exchanger has been evaluated. The impact of flow conditions and metal foam geometry on the heat transfer coefficient and gradient have been investigated. Metal foam heat exchanger with same geometry (face area, flow depth and fin dimensions) consisting of four different typemore » of metal foams have been built for the study. Experiments are conducted in a closed-loop wind tunnel at different flow rate under dry operating condition. Metal foams with a smaller pore size (40 PPI) have a larger heat transfer coefficient compared to foams with a larger pore size (5 PPI). However, foams with larger pores result in relatively smaller pressure gradients. Current thermal-hydraulic modeling practices have been reviewed and potential issues have been identified. Permeability and inertia coefficients are determined and compared to data reported in open literature. Finally, on the basis of the new experimental results, correlations are developed relating the foam characteristics and flow conditions through the friction factor f and the Colburn j factor.« less

Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

NASA Technical Reports Server (NTRS)

Yasensky, John; Christiansen, Eric L.

2007-01-01

A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

Experimental investigation of solidification in metal foam enhanced phase change material

NASA Astrophysics Data System (ADS)

Beyne, W.; Bağci, O.; Huisseune, H.; Canière, H.; Danneels, J.; Daenens, D.; De Paepe, M.

2017-10-01

A major challenge for the use of phase change materials (PCMs) in thermal energy storage (TES) is overcoming the low thermal conductivity of PCM’s. The low conductivity gives rise to limited power during charging and discharging TES. Impregnating metal foam with PCM, however, has been found to enhance the heat transfer. On the other hand, the effect of foam parameters such as porosity, pore size and material type has remained unclear. In this paper, the effect of these foam parameters on the solidification time is investigated. Different samples of PCM-impregnated metal foam were experimentally tested and compared to one without metal foam. The samples varied with respect to choice of material, porosity and pore size. They were placed in a rectangular cavity and cooled from one side using a coolant flowing through a cold plate. The other sides of the rectangular cavity were Polymethyl Methacrylate (PM) walls exposed to ambient. The temperature on the exterior walls of the cavity was monitored as well as the coolant flow rate and its temperature. The metal foam inserts reduced the solidification times by at least 25 %. However, the difference between the best performing and worst performing metal foam is about 28 %. This shows a large potential for future research.

Forming foam structures with carbon foam substrates

DOEpatents

Landingham, Richard L.; Satcher, Jr., Joe H.; Coronado, Paul R.; Baumann, Theodore F.

2012-11-06

The invention provides foams of desired cell sizes formed from metal or ceramic materials that coat the surfaces of carbon foams which are subsequently removed. For example, metal is located over a sol-gel foam monolith. The metal is melted to produce a metal/sol-gel composition. The sol-gel foam monolith is removed, leaving a metal foam.

Geometrical characterization of perlite-metal syntactic foam

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

Borovinšek, Matej, E-mail: matej.borovinsek@um.si

This paper introduces an improved method for the detailed geometrical characterization of perlite-metal syntactic foam. This novel metallic foam is created by infiltrating a packed bed of expanded perlite particles with liquid aluminium alloy. The geometry of the solidified metal is thus defined by the perlite particle shape, size and morphology. The method is based on a segmented micro-computed tomography data and allows for automated determination of the distributions of pore size, sphericity, orientation and location. The pore (i.e. particle) size distribution and pore orientation is determined by a multi-criteria k-nearest neighbour algorithm for pore identification. The results indicate amore » weak density gradient parallel to the casting direction and a slight preference of particle orientation perpendicular to the casting direction. - Highlights: •A new method for identification of pores in porous materials was developed. •It was applied on perlite-metal syntactic foam samples. •A porosity decrease in the axial direction of the samples was determined. •Pore shape analysis showed a high percentage of spherical pores. •Orientation analysis showed that more pores are oriented in the radial direction.« less

Formation of 3D graphene foams on soft templated metal monoliths

NASA Astrophysics Data System (ADS)

Tynan, Michael K.; Johnson, David W.; Dobson, Ben P.; Coleman, Karl S.

2016-07-01

Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy.Graphene foams are leading contenders as frameworks for polymer thermosets, filtration/pollution control and for use as an electrode material in energy storage devices, taking advantage of graphene's high electrical conductivity and the porous structure of the foam. Here we demonstrate a simple synthesis of a macroporous 3D graphene material templated from a dextran/metal salt gel, where the metal was cobalt, nickel, copper, and iron. The gel was annealed to form a metal oxide foam prior to a methane chemical vapour deposition (CVD). Cobalt metal gels were shown to afford the highest quality material as determined by electron microscopy (SEM and TEM) and Raman spectroscopy. Electronic supplementary information (ESI) available: Raman, EDX, PXRD, TGA, electrical conductivity data and SEM. See DOI: 10.1039/c6nr02455f

Improved Sand-Compaction Method for Lost-Foam Metal Casting

NASA Technical Reports Server (NTRS)

Bakhtiyarov, Sayavur I.; Overfelt, Ruel A.

2008-01-01

An improved method of filling a molding flask with sand and compacting the sand around a refractory-coated foam mold pattern has been developed for incorporation into the lost-foam metal-casting process. In comparison with the conventional method of sand filling and compaction, this method affords more nearly complete filling of the space around the refractory-coated foam mold pattern and more thorough compaction of the sand. In so doing, this method enables the sand to better support the refractory coat under metallostatic pressure during filling of the mold with molten metal.

A combined NDE/FEA approach to evaluate the structural response of a metal foam

NASA Astrophysics Data System (ADS)

Ghosn, Louis J.; Abdul-Aziz, Ali; Raj, Sai V.; Rauser, Richard W.

2007-04-01

Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of

Foamed-metal-based catalytic afterburners in automotive exhaust systems

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

Pestryakov, A.N.; Ametov, V.A.

1994-08-10

Properties of exhaust afterburning catalysts based on porous cellular materials (foamed metals) have been investigated. Catalysts containing oxides of base metals provide a two-to-threefold reduction of CO emission. Platinum-containing foamed catalysts lower the toxicity of exhaust by 85-90%. A favorable effect is demonstrated by the combined use of afterburners and a motor oil additive based on ultradispersed copper.

Numerical Simulations of Particle Deposition in Metal Foam Heat Exchangers

NASA Astrophysics Data System (ADS)

Sauret, Emilie; Saha, Suvash C.; Gu, Yuantong

2013-01-01

Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.

Foam-Metal Liner Attenuation of Low-Speed Fan Noise

NASA Technical Reports Server (NTRS)

Sutliff, Daniel L.; Jones, Michael G.

2008-01-01

A foam-metal liner for attenuation of fan noise was developed for and tested on a low speed fan. This type of liner represents a significant advance over traditional liners due to the possibility for placement in close proximity to the rotor. An advantage of placing treatment in this region is the modification of the acoustic near field, thereby inhibiting noise generation mechanisms. This can result in higher attenuation levels than can be achieved by liners located in the nacelle inlet. In addition, foam-metal liners could potentially replace the fan rub-strip and containment components, ultimately reducing engine components and thus weight, which can result in a systematic increase in noise reduction and engine performance. Foam-metal liners have the potential to reduce fan noise by 4 dB based on this study.

Electrochemical properties of a lithium-impregnated metal foam anode for thermal batteries

NASA Astrophysics Data System (ADS)

Choi, Yu-Song; Yu, Hye-Ryeon; Cheong, Hae-Won

2015-02-01

Lithium-impregnated metal foam anodes (LIMFAs) are fabricated and investigated. The LIMFAs are prepared by the impregnation of lithium into molten-salt-coated nickel metal foam. A single cell with the LIMFA exhibits a specific capacity of 3009 As g-1. For comparison, a single cell with a LiSi alloy anode is also discharged, demonstrating a specific capacity of 1050 As g-1. These significant improvements can be attributed to the large amount of lithium impregnated into the metal foam as well as the molten lithium holding capability of the foam. Due to their excellent electrochemical properties, LIMFAs are suitable for use in thermal batteries.

Synthesis and Characterization of Polymer-Metal Nanostructured Membranes

DTIC Science & Technology

ions creating unique polymer -metal nanostructured membranes. A comprehensive materials characterization study was performed to understand their...fluoropolymers were also investigated. First the polymer -metal nanostructure of Nafion with several counter-ions was studied upon supercritical fluid CO2...processing. Then, novel fluorinated block copolymers were synthesized using atom transfer radical polymerization (ATRP) and their resulting nanostructure was

49 CFR 178.356 - Specification 20PF phenolic-foam insulated, metal overpack.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Specification 20PF phenolic-foam insulated, metal overpack. 178.356 Section 178.356 Transportation Other Regulations Relating to Transportation (Continued... Specification 20PF phenolic-foam insulated, metal overpack. ...

49 CFR 178.356 - Specification 20PF phenolic-foam insulated, metal overpack.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Specification 20PF phenolic-foam insulated, metal overpack. 178.356 Section 178.356 Transportation Other Regulations Relating to Transportation PIPELINE AND... Specification 20PF phenolic-foam insulated, metal overpack. ...

Engineering metallic nanostructures for plasmonics and nanophotonics

PubMed Central

Lindquist, Nathan C; Nagpal, Prashant; McPeak, Kevin M; Norris, David J; Oh, Sang-Hyun

2012-01-01

Metallic nanostructures now play an important role in many applications. In particular, for the emerging fields of plasmonics and nanophotonics, the ability to engineer metals on nanometric scales allows the development of new devices and the study of exciting physics. This review focuses on top-down nanofabrication techniques for engineering metallic nanostructures, along with computational and experimental characterization techniques. A variety of current and emerging applications are also covered. PMID:22790420

Engineering metallic nanostructures for plasmonics and nanophotonics

NASA Astrophysics Data System (ADS)

Lindquist, Nathan C.; Nagpal, Prashant; McPeak, Kevin M.; Norris, David J.; Oh, Sang-Hyun

2012-03-01

Metallic nanostructures now play an important role in many applications. In particular, for the emerging fields of plasmonics and nanophotonics, the ability to engineer metals on nanometric scales allows the development of new devices and the study of exciting physics. This review focuses on top-down nanofabrication techniques for engineering metallic nanostructures, along with computational and experimental characterization techniques. A variety of current and emerging applications are also covered.

Foamed lightweight materials made from mixed scrap metal waste powder and sewage sludge ash.

PubMed

Wang, Kuen-Sheng; Chiou, Ing-Jia

2004-10-01

The porous properties and pozzolanic effects of sewage sludge ash (SSA) make it possible to produce lightweight materials. This study explored the effects of different metallic foaming agents, made from waste aluminium products, on the foaming behaviours and engineering characteristics, as well as the microstructure of sewage sludge ash foamed lightweight materials. The results indicated that aluminium powder and mixed scrap metal waste powder possessed similar chemical compositions. After proper pre-treatment, waste aluminium products proved to be ideal substitutes for metallic foaming agents. Increasing the amount of mixed scrap metal waste by 10-15% compared with aluminium powder would produce a similar foaming ratio and compressive strength. The reaction of the metallic foaming agents mainly produced pores larger than 10 microm, different from the hydration reaction of cement that produced pores smaller than 1 microm mostly. To meet the requirements of the lightweight materials characteristics and the compressive strength, the amount of SSA could be up to 60-80% of the total solids. An adequate amount of aluminium powder is 0.5-0.9% of the total solids. Increasing the fineness of the mixed scrap metal waste powder could effectively reduce the amount required and improve the foaming ratio.

Low-Speed Fan Noise Attenuation from a Foam-Metal Liner

NASA Technical Reports Server (NTRS)

Sutliff, Daniel L.; Jones, Michael G.

2011-01-01

A foam-metal liner for attenuation of fan noise was developed for and tested on a low-speed fan. This type of liner represents a significant advance over traditional liners, due to the possibility of placement in close proximity to the rotor. An advantage of placing treatment in this region is that the acoustic near field is modified, thereby inhibiting the noise-generation mechanism. This can result in higher attenuation levels than could be achieved by liners located in the nacelle inlet. In addition, foam-metal liners could potentially replace the fan rub strip and containment components, ultimately reducing engine components and thus weight, which can result in a systematic increase in noise reduction and engine performance. Foam-metal liners have the potential to reduce fan noise by 4 dB based on this study.

Nanostructured pseudocapacitive materials decorated 3D graphene foam electrodes for next generation supercapacitors.

PubMed

Patil, Umakant; Lee, Su Chan; Kulkarni, Sachin; Sohn, Ji Soo; Nam, Min Sik; Han, Suhyun; Jun, Seong Chan

2015-04-28

Nowadays, advancement in performance of proficient multifarious electrode materials lies conclusively at the core of research concerning energy storage devices. To accomplish superior capacitance performance the requirements of high capacity, better cyclic stability and good rate capability can be expected from integration of electrochemical double layer capacitor based carbonaceous materials (high power density) and pseudocapacitive based metal hydroxides/oxides or conducting polymers (high energy density). The envisioned three dimensional (3D) graphene foams are predominantly advantageous to extend potential applicability by offering a large active surface area and a highly conductive continuous porous network for fast charge transfer with decoration of nanosized pseudocapacitive materials. In this article, we review the latest methodologies and performance evaluation for several 3D graphene based metal oxides/hydroxides and conducting polymer electrodes with improved electrochemical properties for next-generation supercapacitors. The most recent research advancements of our and other groups in the field of 3D graphene based electrode materials for supercapacitors are discussed. To assess the studied materials fully, a careful interpretation and rigorous scrutiny of their electrochemical characteristics is essential. Auspiciously, both nano-structuration as well as confinement of metal hydroxides/oxides and conducting polymers onto a conducting porous 3D graphene matrix play a great role in improving the performance of electrodes mainly due to: (i) active material access over large surface area with fast charge transportation; (ii) synergetic effect of electric double layer and pseudocapacitive based charge storing.

Process for the preparation of metal-containing nanostructured films

NASA Technical Reports Server (NTRS)

Lu, Yunfeng (Inventor); Wang, Donghai (Inventor)

2006-01-01

Metal-containing nanostructured films are prepared by electrodepositing a metal-containing composition within the pores of a mesoporous silica template to form a metal-containing silica nanocomposite. The nanocomposite is annealed to strengthen the deposited metal-containing composition. The silica is then removed from the nanocomposite, e.g., by dissolving the silica in an etching solution to provide a self-supporting metal-containing nanostructured film. The nanostructured films have a nanowire or nanomesh architecture depending on the pore structure of the mesoporous silica template used to prepare the films.

Metal nanostructures for non-enzymatic glucose sensing.

PubMed

Tee, Si Yin; Teng, Choon Peng; Ye, Enyi

2017-01-01

This review covers the recent development of metal nanostructures in electrochemical non-enzymatic glucose sensing. It highlights a variety of nanostructured materials including noble metals, other transition metals, bimetallic systems, and their hybrid with carbon-based nanomaterials. Particularly, attention is devoted to numerous approaches that have been implemented for improving the sensors performance by tailoring size, shape, composition, effective surface area, adsorption capability and electron-transfer properties. The correlation of the metal nanostructures to the glucose sensing performance is addressed with respect to the linear concentration range, sensitivity and detection limit. In overall, this review provides important clues from the recent scientific achievements of glucose sensor nanomaterials which will be essentially useful in designing better and more effective electrocatalysts for future electrochemical sensing industry. Copyright © 2016 Elsevier B.V. All rights reserved.

Understanding the biological responses of nanostructured metals and surfaces

NASA Astrophysics Data System (ADS)

Lowe, Terry C.; Reiss, Rebecca A.

2014-08-01

Metals produced by Severe Plastic Deformation (SPD) offer distinct advantages for medical applications such as orthopedic devices, in part because of their nanostructured surfaces. We examine the current theoretical foundations and state of knowledge for nanostructured biomaterials surface optimization within the contexts that apply to bulk nanostructured metals, differentiating how their microstructures impact osteogenesis, in particular, for Ultrafine Grained (UFG) titanium. Then we identify key gaps in the research to date, pointing out areas which merit additional focus within the scientific community. For example, we highlight the potential of next-generation DNA sequencing techniques (NGS) to reveal gene and non-coding RNA (ncRNA) expression changes induced by nanostructured metals. While our understanding of bio-nano interactions is in its infancy, nanostructured metals are already being marketed or developed for medical devices such as dental implants, spinal devices, and coronary stents. Our ability to characterize and optimize the biological response of cells to SPD metals will have synergistic effects on advances in materials, biological, and medical science.

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

PubMed Central

Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S. D.; Vukovic, Zorica; de Hosson, Jeff Th. M.; ten Brinke, Gerrit; Loos, Katja

2014-01-01

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

Gyroid nickel nanostructures from diblock copolymer supramolecules.

PubMed

Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S D; Vukovic, Zorica; de Hosson, Jeff Th M; ten Brinke, Gerrit; Loos, Katja

2014-04-28

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

Prospective of employing high porosity open-cell metal foams in passive cryogenic radiators for space applications

NASA Astrophysics Data System (ADS)

Tisha, Dixit; Indranil, Ghosh

2017-02-01

Passive cryogenic radiators work on the principle of dissipating heat to the outer space purely by radiation. High porosity open-cell metal foams are a relatively new class of extended surfaces. These possess the advantages of high surface area density and low weight, characteristics which the space industry looks for. In case of radiative heat transfer, the porous nature of metal foams permits a deeper penetration of the incident radiation. Consequently, the heat transfer area participating in radiative heat exchange increases thereby enhancing the heat transfer rate. However, effective heat conduction in between the foam struts reduces as a result of the void spaces. These two conflicting phenomenon for radiation heat transfer in metal foams have been studied in this work. Similar to the foam conduction-convection heat transfer analysis, a conduction-radiation heat transfer model has been developed for metal foams in analogy with the conventional solid fin theory. Metal foams have been theoretically represented as simple cubic structures. A comparison of the radiative heat transfer through metal foams and solid fins attached to a surface having constant temperature has been presented. Effect of changes in foam characteristic properties such as porosity and pore density have also been studied.

Advanced Micro/Nanostructures for Lithium Metal Anodes

PubMed Central

Zhang, Rui; Li, Nian‐Wu; Cheng, Xin‐Bing; Yin, Ya‐Xia

2017-01-01

Owning to their very high theoretical capacity, lithium metal anodes are expected to fuel the extensive practical applications in portable electronics and electric vehicles. However, unstable solid electrolyte interphase and lithium dendrite growth during lithium plating/stripping induce poor safety, low Coulombic efficiency, and short span life of lithium metal batteries. Lately, varies of micro/nanostructured lithium metal anodes are proposed to address these issues in lithium metal batteries. With the unique surface, pore, and connecting structures of different nanomaterials, lithium plating/stripping processes have been regulated. Thus the electrochemical properties and lithium morphologies have been significantly improved. These micro/nanostructured lithium metal anodes shed new light on the future applications for lithium metal batteries. PMID:28331792

Method and apparatus for ion sequestration and a nanostructured metal phosphate

DOEpatents

Mattigod, Shas V [Richland, WA; Fryxell, Glen E [Kennewic, WA; Li, Xiaohong [Richland, WA; Parker, Kent E [Kennewick, WA; Wellman, Dawn M [West Richland, WA

2010-04-06

A nanostructured substance, a process for sequestration of ionic waste, and an ion-sequestration apparatus are disclosed in the specification. The nanostructured substance can comprise a Lewis acid transition metal bound to a phosphate, wherein the phosphate comprises a primary structural component of the substance and the Lewis acid transition metal is a reducing agent. The nanostructured substance has a Brunner-Emmet-Teller (BET) surface area greater than or equal to approximately 100 m.sup.2/g, and a distribution coefficient for an analyte, K.sub.d, greater than or equal to approximately 5000 ml/g. The process can comprise contacting a fluid and a nanostructured metal phosphate. The apparatus can comprise a vessel and a nanostructured metal phosphate. The vessel defines a volume wherein a fluid contacts the nanostructured metal phosphate.

Forming and Bending of Metal Foams

NASA Astrophysics Data System (ADS)

Nebosky, Paul; Tyszka, Daniel; Niebur, Glen; Schmid, Steven

2004-06-01

This study examines the formability of a porous tantalum foam, known as trabecular metal (TM). Used as a bone ingrowth surface on orthopedic implants, TM is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. This research aims to develop bend and stretch forming as a cost-effective alternative to net machining and EDM for manufacturing thin parts made of TM. Experimentally, bending about a single axis using a wiping die was studied by observing cracking and measuring springback. It was found that die radius and clearance strongly affect the springback properties of TM, while punch speed, embossings, die radius and clearance all influence cracking. Depending on the various combinations of die radius and clearance, springback factor ranged from .70-.91. To examine the affect of the foam microstructure, bending also was examined numerically using a horizontal hexagonal mesh. As the hexagonal cells were elongated along the sheet length, elastic springback decreased. This can be explained by the earlier onset of plastic hinging occurring at the vertices of the cells. While the numerical results matched the experimental results for the case of zero clearance, differences at higher clearances arose due to an imprecise characterization of the post-yield properties of tantalum. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams.

Microstructure based model for sound absorption predictions of perforated closed-cell metallic foams.

PubMed

Chevillotte, Fabien; Perrot, Camille; Panneton, Raymond

2010-10-01

Closed-cell metallic foams are known for their rigidity, lightness, thermal conductivity as well as their low production cost compared to open-cell metallic foams. However, they are also poor sound absorbers. Similarly to a rigid solid, a method to enhance their sound absorption is to perforate them. This method has shown good preliminary results but has not yet been analyzed from a microstructure point of view. The objective of this work is to better understand how perforations interact with closed-cell foam microstructure and how it modifies the sound absorption of the foam. A simple two-dimensional microstructural model of the perforated closed-cell metallic foam is presented and numerically solved. A rough three-dimensional conversion of the two-dimensional results is proposed. The results obtained with the calculation method show that the perforated closed-cell foam behaves similarly to a perforated solid; however, its sound absorption is modulated by the foam microstructure, and most particularly by the diameters of both perforation and pore. A comparison with measurements demonstrates that the proposed calculation method yields realistic trends. Some design guides are also proposed.

The dynamic properties of sandwich structures based on metal-ceramic foams.

DOT National Transportation Integrated Search

2014-01-01

The present research program has studied the fracture properties of closed pore metal-ceramic foams for their potential applications as core systems in sandwich structures. The composite foams were created at Fireline, Inc. (Youngstown, OH) using the...

Understanding photoluminescence of metal nanostructures based on an oscillator model.

PubMed

Cheng, Yuqing; Zhang, Weidong; Zhao, Jingyi; Wen, Te; Hu, Aiqin; Gong, Qihuang; Lu, Guowei

2018-08-03

Scattering and absorption properties of metal nanostructures have been well understood based on the classic oscillator theory. Here, we demonstrate that photoluminescence of metal nanostructures can also be explained based on a classic model. The model shows that inelastic radiation of an oscillator resembles its resonance band after external excitation, and is related to the photoluminescence from metallic nanostructures. The understanding based on the classic oscillator model is in agreement with that predicted by a quantum electromagnetic cavity model. Moreover, by correlating a two-temperature model and the electron distributions, we demonstrate that both one-photon and two-photon luminescence of the metal nanostructures undergo the same mechanism. Furthermore, the model explains most of the emission characteristics of the metallic nanostructures, such as quantum yield, spectral shape, excitation polarization and power dependence. The model based on an oscillator provides an intuitive description of the photoluminescence process and may enable rapid optimization and exploration of the plasmonic properties.

Numerical study of metal foam heat sinks under uniform impinging flow

NASA Astrophysics Data System (ADS)

Andreozzi, A.; Bianco, N.; Iasiello, M.; Naso, V.

2017-01-01

The ever-increasing demand for performance improvement and miniaturization of electronics has led to a significant generation of waste heat that must be dissipated to ensure a reliable device operation. The miniaturization of the components complicates this task. In fact, reducing the heat transfer area, at the same required heat rate, it is necessary to increase the heat flux, so that the materials operate in a temperature range suitable to its proper functioning. Traditional heat sinks are no longer capable of dissipating the generated heat and innovative approaches are needed to address the emerging thermal management challenges. Recently, heat transfer in open-cell metal foams under an impinging jet has received attention due to the considerable heat transfer potential of combining two cooling technologies: impinging jet and porous medium. This paper presents a numerical study on Finned Metal Foam (FMF) and Metal Foam (MF) heat sinks under impinging air jet cooling. The analysis is carried out by means of the commercial software COMSOL Multiphysics®. The purpose is to analyze the thermal performance of the metal foam heat sink, finned or not, varying its geometric parameters. Results are presented in terms of predicted dissipated heat rate, convective heat transfer coefficient and pressure losses.

Assessment of Soft Vane and Metal Foam Engine Noise Reduction Concepts

NASA Technical Reports Server (NTRS)

Jones, Michael G.; Parrott, Tony L.; Sutliff, Daniel L.; Hughes, Chris

2009-01-01

Two innovative fan-noise reduction concepts developed by NASA are presented - soft vanes and over-the-rotor metal foam liners. Design methodologies are described for each concept. Soft vanes are outlet guide vanes with internal, resonant chambers that communicate with the exterior aeroacoustic environment via a porous surface. They provide acoustic absorption via viscous losses generated by interaction of unsteady flows with the internal solid structure. Over-the-rotor metal foam liners installed at or near the fan rotor axial plane provide rotor noise absorption. Both concepts also provide pressure-release surfaces that potentially inhibit noise generation. Several configurations for both concepts are evaluated with a normal incidence tube, and the results are used to guide designs for implementation in two NASA fan rigs. For soft vanes, approximately 1 to 2 dB of broadband inlet and aft-radiated fan noise reduction is achieved. For over-the-rotor metal foam liners, up to 3 dB of fan noise reduction is measured in the low-speed fan rig, but minimal reduction is measured in the high-speed fan rig. These metal foam liner results are compared with a static engine test, in which inlet sound power level reductions up to 5 dB were measured. Brief plans for further development are also provided.

Method for producing nanostructured metal-oxides

DOEpatents

Tillotson, Thomas M.; Simpson, Randall L.; Hrubesh, Lawrence W.; Gash, Alexander

2006-01-17

A synthetic route for producing nanostructure metal-oxide-based materials using sol-gel processing. This procedure employs the use of stable and inexpensive hydrated-metal inorganic salts and environmentally friendly solvents such as water and ethanol. The synthesis involves the dissolution of the metal salt in a solvent followed by the addition of a proton scavenger, which induces gel formation in a timely manner. Both critical point (supercritical extraction) and atmospheric (low temperature evaporation) drying may be employed to produce monolithic aerogels and xerogels, respectively. Using this method synthesis of metal-oxide nanostructured materials have been carried out using inorganic salts, such as of Fe.sup.3+, Cr.sup.3+, Al.sup.3+, Ga.sup.3+, In.sup.3+, Hf.sup.4+, Sn.sup.4+, Zr.sup.4+, Nb.sup.5+, W.sup.6+, Pr.sup.3+, Er.sup.3+, Nd.sup.3+, Ce.sup.3+, U.sup.3+ and Y.sup.3+. The process is general and nanostructured metal-oxides from the following elements of the periodic table can be made: Groups 2 through 13, part of Group 14 (germanium, tin, lead), part of Group 15 (antimony, bismuth), part of Group 16 (polonium), and the lanthanides and actinides. The sol-gel processing allows for the addition of insoluble materials (e.g., metals or polymers) to the viscous sol, just before gelation, to produce a uniformly distributed nanocomposites upon gelation. As an example, energetic nanocomposites of Fe.sub.xO.sub.y gel with distributed Al metal are readily made. The compositions are stable, safe, and can be readily ignited to thermitic reaction.

Engineered Metallic Nanostructures: Fabrication, Characterization, and Applications

NASA Astrophysics Data System (ADS)

Bohloul, Arash

Metallic nanostructures have garnered a great deal of attention due to their fascinating optical properties, which differ from the bulk metal. They have been proven to exceed expectations in wide variety of applications including chemical and biological sensing. Nevertheless, high-throughput and low cost nanofabrication techniques are required to implant metallic nanostructures in widespread applications. With that vision, this thesis presents a versatile and reliable method for scalable fabrication of gold nanostructures. In this approach, a plasma-treated ordered array of polystyrene nanospheres acts as an initial mask. The key step in this process is the vapor-deposition of nickel as a sacrificial mask. Thereby, gold nanostructures are directly formed on the substrate through the nickel mask. This is an easy, powerful, and straightforward method that offers several degrees of freedom to precisely control the shape and size of nanostructures. We made a library of nanostructures including gold nanocrescents, double crescents, nanorings, and nanodisks with the ability to tune the size in the range of 150 to 650 nm. The fabricated nanostructures are highly packed and uniformly cover the centimeter scale substrate. The optical properties of metallic nanostructures were extensively studied by a combination of UV-Vis-NIR and Fourier transform infrared (FTIR) spectroscopies, and correlation between optical response and geometrical parameters were investigated. In the next part of this thesis, highly sensitive surface enhanced infrared absorption (SEIRA) analysis was demonstrated on gold nanocrescent arrays. Theoretical modeling was confirmed that these substrates provide highly dense and strong hot-spots over the substrate, which is required for surface enhanced spectroscopic studies. Gold nanocrescent arrays exhibit highly tunable plasmon resonance to cover desired molecular vibrational bands. These substrates experimentally illustrated 3 orders of magnitude

A Comprehensive Review of One-Dimensional Metal-Oxide Nanostructure Photodetectors

PubMed Central

Zhai, Tianyou; Fang, Xiaosheng; Liao, Meiyong; Xu, Xijin; Zeng, Haibo; Yoshio, Bando; Golberg, Dmitri

2009-01-01

One-dimensional (1D) metal-oxide nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating size and dimensionality dependence of nanostructure properties for potential applications. The construction and integration of photodetectors or optical switches based on such nanostructures with tailored geometries have rapidly advanced in recent years. Active 1D nanostructure photodetector elements can be configured either as resistors whose conductions are altered by a charge-transfer process or as field-effect transistors (FET) whose properties can be controlled by applying appropriate potentials onto the gates. Functionalizing the structure surfaces offers another avenue for expanding the sensor capabilities. This article provides a comprehensive review on the state-of-the-art research activities in the photodetector field. It mainly focuses on the metal oxide 1D nanostructures such as ZnO, SnO2, Cu2O, Ga2O3, Fe2O3, In2O3, CdO, CeO2, and their photoresponses. The review begins with a survey of quasi 1D metal-oxide semiconductor nanostructures and the photodetector principle, then shows the recent progresses on several kinds of important metal-oxide nanostructures and their photoresponses and briefly presents some additional prospective metal-oxide 1D nanomaterials. Finally, the review is concluded with some perspectives and outlook on the future developments in this area. PMID:22454597

Heat Transfer in Metal Foam Heat Exchangers at High Temperature

NASA Astrophysics Data System (ADS)

Hafeez, Pakeeza

Heat transfer though open-cell metal foam is experimentally studied for heat exchanger and heat shield applications at high temperatures (˜750°C). Nickel foam sheets with pore densities of 10 and 40 pores per linear inch (PPI), have been used to make the heat exchangers and heat shields by using thermal spray coating to deposit an Inconel skin on a foam core. Heat transfer measurements were performed on a test rig capable of generating hot gas up to 1000°C. The heat exchangers were tested by exposing their outer surface to combustion gases at a temperature of 550°C and 750°C while being cooled by air flowing through them at room temperature at velocities up to 5 m/s. The temperature rise of the air, the surface temperature of the heat exchangers and the air temperature inside the heat exchanger were measured. The volumetric heat transfer coefficient and Nusselt number were calculated for different velocities. The heat transfer performance of the 40PPI sample brazed with the foil is found to be the most efficient. Pressure drop measurements were also performed for 10 and 40PPI metal foam. Thermographic measurements were done on 40PPI foam heat exchangers using a high temperature infrared camera. A high power electric heater was used to produce hot air at 300°C that passed over the foam heat exchanger while the cooling air was blown through it. Heat shields were made by depositing porous skins on metal foam and it was observed that a small amount of coolant leaking through the pores notably reduces the heat transfer from the hot gases. An analytical model was developed based assuming local thermal non-equilibrium that accounts for the temperature difference between solid and fluid phase. The experimental results are found to be in good agreement with the predicted values of the model.

Complex-Morphology Metal-Based Nanostructures: Fabrication, Characterization, and Applications

PubMed Central

Gentile, Antonella; Ruffino, Francesco; Grimaldi, Maria Grazia

2016-01-01

Due to their peculiar qualities, metal-based nanostructures have been extensively used in applications such as catalysis, electronics, photography, and information storage, among others. New applications for metals in areas such as photonics, sensing, imaging, and medicine are also being developed. Significantly, most of these applications require the use of metals in the form of nanostructures with specific controlled properties. The properties of nanoscale metals are determined by a set of physical parameters that include size, shape, composition, and structure. In recent years, many research fields have focused on the synthesis of nanoscale-sized metallic materials with complex shape and composition in order to optimize the optical and electrical response of devices containing metallic nanostructures. The present paper aims to overview the most recent results—in terms of fabrication methodologies, characterization of the physico-chemical properties and applications—of complex-morphology metal-based nanostructures. The paper strongly focuses on the correlation between the complex morphology and the structures’ properties, showing how the morphological complexity (and its nanoscale control) can often give access to a wide range of innovative properties exploitable for innovative functional device production. We begin with an overview of the basic concepts on the correlation between structural and optical parameters of nanoscale metallic materials with complex shape and composition, and the possible solutions offered by nanotechnology in a large range of applications (catalysis, electronics, photonics, sensing). The aim is to assess the state of the art, and then show the innovative contributions that can be proposed in this research field. We subsequently report on innovative, versatile and low-cost synthesis techniques, suitable for providing a good control on the size, surface density, composition and geometry of the metallic nanostructures. The main

Ultra-low density metallic foams synthesized by contact glow discharge electrolysis (CGDE) for laser experiments

NASA Astrophysics Data System (ADS)

Rocher, Sandrine; Botrel, Ronan; Durut, Frédéric; Chicanne, Cédric; Theobald, Marc; Vignal, Vincent

2018-02-01

The goal of this work is to realize metallic foams synthesized by contact glow discharge electrolysis with specific characteristics. In this paper, we show the results of our studies, consisting in investigating parameters that influence the foams characteristics. Thus, the morphology of metallic foams is examined through scanning electron microscopy (SEM) observations with the acid nature. Moreover, the evolution of the mass and the volume of metallic foams with two experimental parameters (overvoltage and gold concentration) is also investigated. The acid nature affects the foams microscopic structure highlighted by the SEM observations, but for now no valid explanation to this behaviour was found. We prove that the mass deposited on the electrode is dependent on the ionic salt concentration, whereas the overvoltage only affects the foam overall density. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea.

Thin metal nanostructures: synthesis, properties and applications

PubMed Central

Fan, Zhanxi; Huang, Xiao; Tan, Chaoliang

2015-01-01

Two-dimensional nanomaterials, especially graphene and single- or few-layer transition metal dichalcogenide nanosheets, have attracted great research interest in recent years due to their distinctive physical, chemical and electronic properties as well as their great potentials for a broad range of applications. Recently, great efforts have also been devoted to the controlled synthesis of thin nanostructures of metals, one of the most studied traditional materials, for various applications. In this minireview, we review the recent progress in the synthesis and applications of thin metal nanostructures with a focus on metal nanoplates and nanosheets. First of all, various methods for the synthesis of metal nanoplates and nanosheets are summarized. After a brief introduction of their properties, some applications of metal nanoplates and nanosheets, such as catalysis, surface enhanced Raman scattering (SERS), sensing and near-infrared photothermal therapy are described. PMID:28553459

Pulsed photonic fabrication of nanostructured metal oxide thin films

NASA Astrophysics Data System (ADS)

Bourgeois, Briley B.; Luo, Sijun; Riggs, Brian C.; Adireddy, Shiva; Chrisey, Douglas B.

2017-09-01

Nanostructured metal oxide thin films with a large specific surface area are preferable for practical device applications in energy conversion and storage. Herein, we report instantaneous (milliseconds) photonic synthesis of three-dimensional (3-D) nanostructured metal oxide thin films through the pulsed photoinitiated pyrolysis of organometallic precursor films made by chemical solution deposition. High wall-plug efficiency-pulsed photonic irradiation (xenon flash lamp, pulse width of 1.93 ms, fluence of 7.7 J/cm2 and frequency of 1.2 Hz) is used for scalable photonic processing. The photothermal effect of subsequent pulses rapidly improves the crystalline quality of nanocrystalline metal oxide thin films in minutes. The following paper highlights pulsed photonic fabrication of 3-D nanostructured TiO2, Co3O4, and Fe2O3 thin films, exemplifying a promising new method for the low-cost and high-throughput manufacturing of nanostructured metal oxide thin films for energy applications.

Nanostructured Metal Oxides and Sulfides for Lithium-Sulfur Batteries.

PubMed

Liu, Xue; Huang, Jia-Qi; Zhang, Qiang; Mai, Liqiang

2017-05-01

Lithium-sulfur (Li-S) batteries with high energy density and long cycle life are considered to be one of the most promising next-generation energy-storage systems beyond routine lithium-ion batteries. Various approaches have been proposed to break down technical barriers in Li-S battery systems. The use of nanostructured metal oxides and sulfides for high sulfur utilization and long life span of Li-S batteries is reviewed here. The relationships between the intrinsic properties of metal oxide/sulfide hosts and electrochemical performances of Li-S batteries are discussed. Nanostructured metal oxides/sulfides hosts used in solid sulfur cathodes, separators/interlayers, lithium-metal-anode protection, and lithium polysulfides batteries are discussed respectively. Prospects for the future developments of Li-S batteries with nanostructured metal oxides/sulfides are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conducting nanotubes or nanostructures based composites, method of making them and applications

NASA Technical Reports Server (NTRS)

Gupta, Mool C. (Inventor); Yang, Yonglai (Inventor); Dudley, Kenneth L. (Inventor); Lawrence, Roland W. (Inventor)

2013-01-01

An electromagnetic interference (EMI) shielding material includes a matrix of a dielectric or partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.

Highly porous nanostructured copper foam fiber impregnated with an organic solvent for headspace liquid-phase microextraction.

PubMed

Saraji, Mohammad; Ghani, Milad; Rezaei, Behzad; Mokhtarianpour, Maryam

2016-10-21

A new headspace liquid-phase microextraction technique based on using a copper foam nanostructure substrate followed by gas chromatography-flame ionization detection was developed for the determination of volatile organic compounds in water and wastewater samples. The copper foam with highly porous nanostructured walls was fabricated on the surface of a copper wire by a rapid and facile electrochemical process and used as the extractant solvent holder. Propyl benzoate was immobilized in the pores of the copper foam coating and used for the microextraction of benzene, toluene, ethylbenzene and xylenes. The experimental parameters such as the type of organic solvent, desorption temperature, desorption time, salt concentration, sample temperature, equilibrium time and extraction time, were investigated and optimized. Under the optimum conditions, the method detection limit was between 0.06 and 0.25μgL -1 . The relative standard deviation of the method for the analytes at 4-8μgL -1 concentration level ranged from 7.9 to 11%. The fiber-to-fiber reproducibility for three fibers prepared under the same condition was 9.3-12%. The enrichment factor was in the range of 615-744. Different water samples were analyzed for the evaluation of the method in real sample analysis. Relative recoveries for spiked tap, river and wastewater samples were in the range of 85-94%. Finally, the extraction efficiency of the method was compared with those of headspace single drop microextraction and headspace SPME with the commercial fibers. Copyright © 2016 Elsevier B.V. All rights reserved.

Hybrid nanostructures of metal/two-dimensional nanomaterials for plasmon-enhanced applications.

PubMed

Li, Xuanhua; Zhu, Jinmeng; Wei, Bingqing

2016-06-07

Hybrid nanostructures composed of graphene or other two-dimensional (2D) nanomaterials and plasmonic metal components have been extensively studied. The unusual properties of 2D materials are associated with their atomically thin thickness and 2D morphology, and many impressive structures enable the metal nanomaterials to establish various interesting hybrid nanostructures with outstanding plasmonic properties. In addition, the hybrid nanostructures display unique optical characteristics that are derived from the close conjunction of plasmonic optical effects and the unique physicochemical properties of 2D materials. More importantly, the hybrid nanostructures show several plasmonic electrical effects including an improved photogeneration rate, efficient carrier transfer, and a plasmon-induced "hot carrier", playing a significant role in enhancing device performance. They have been widely studied for plasmon-enhanced optical signals, photocatalysis, photodetectors (PDs), and solar cells. In this review, the developments in the field of metal/2D hybrid nanostructures are comprehensively described. Preparation of hybrid nanostructures is first presented according to the 2D material type, as well as the metal nanomaterial morphology. The plasmonic properties and the enabled applications of the hybrid nanostructures are then described. Lastly, possible future research in this promising field is discussed.

Hollow metal nanostructures for enhanced plasmonics (Conference Presentation)

NASA Astrophysics Data System (ADS)

Genç, Aziz; Patarroyo, Javier; Sancho-Parramon, Jordi; Duchamp, Martial; Gonzalez, Edgar; Bastus, Neus G.; Houben, Lothar; Dunin-Borkowski, Rafal; Puntes, Victor F.; Arbiol, Jordi

2016-03-01

Complex metal nanoparticles offer a great playground for plasmonic nanoengineering, where it is possible to cover plasmon resonances from ultraviolet to near infrared by modifying the morphologies from solid nanocubes to nanoframes, multiwalled hollow nanoboxes or even nanotubes with hybrid (alternating solid and hollow) structures. We experimentally show that structural modifications, i.e. void size and final morphology, are the dominant determinants for the final plasmonic properties, while compositional variations allow us to get a fine tuning. EELS mappings of localized surface plasmon resonances (LSPRs) reveal an enhanced plasmon field inside the voids of hollow AuAg nanostructures along with a more homogeneous distributions of the plasmon fields around the nanostructures. With the present methodology and the appropriate samples we are able to compare the effects of hybridization at the nanoscale in hollow nanostructures. Boundary element method (BEM) simulations also reveal the effects of structural nanoengineering on plasmonic properties of hollow metal nanostructures. Possibility of tuning the LSPR properties of hollow metal nanostructures in a wide range of energy by modifying the void size/shell thickness is shown by BEM simulations, which reveals that void size is the dominant factor for tuning the LSPRs. As a proof of concept for enhanced plasmonic properties, we show effective label free sensing of bovine serum albumin (BSA) with some of our hollow nanostructures. In addition, the different plasmonic modes observed have also been studied and mapped in 3D.

A Comprehensive Review of Glucose Biosensors Based on Nanostructured Metal-Oxides

PubMed Central

Rahman, Md. Mahbubur; Saleh Ahammad, A. J.; Jin, Joon-Hyung; Ahn, Sang Jung; Lee, Jae-Joon

2010-01-01

Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors. PMID:22399911

Pore-level numerical analysis of the infrared surface temperature of metallic foam

NASA Astrophysics Data System (ADS)

Li, Yang; Xia, Xin-Lin; Sun, Chuang; Tan, He-Ping; Wang, Jing

2017-10-01

Open-cell metallic foams are increasingly used in various thermal systems. The temperature distributions are significant for the comprehensive understanding of these foam-based engineering applications. This study aims to numerically investigate the modeling of the infrared surface temperature (IRST) of open-cell metallic foam measured by an infrared camera placed above the sample. Two typical approaches based on Backward Monte Carlo simulation are developed to estimate the IRSTs: the first one, discrete-scale approach (DSA), uses a realistic discrete representation of the foam structure obtained from a computed tomography reconstruction while the second one, continuous-scale approach (CSA), assumes that the foam sample behaves like a continuous homogeneous semi-transparent medium. The radiative properties employed in CSA are directly determined by a ray-tracing process inside the discrete foam representation. The IRSTs for different material properties (material emissivity, specularity parameter) are computed by the two approaches. The results show that local IRSTs can vary according to the local compositions of the foam surface (void and solid). The temperature difference between void and solid areas is gradually attenuated with increasing material emissivity. In addition, the annular void space near to the foam surface behaves like a black cavity for thermal radiation, which is ensued by copious neighboring skeletons. For most of the cases studied, the mean IRSTs computed by the DSA and CSA are close to each other, except when the material emissivity is highly weakened and the sample temperature is extremely high.

Foam and gel methods for the decontamination of metallic surfaces

DOEpatents

Nunez, Luis; Kaminski, Michael Donald

2007-01-23

Decontamination of nuclear facilities is necessary to reduce the radiation field during normal operations and decommissioning of complex equipment. In this invention, we discuss gel and foam based diphosphonic acid (HEDPA) chemical solutions that are unique in that these solutions can be applied at room temperature; provide protection to the base metal for continued applications of the equipment; and reduce the final waste form production to one step. The HEDPA gels and foams are formulated with benign chemicals, including various solvents, such as ionic liquids and reducing and complexing agents such as hydroxamic acids, and formaldehyde sulfoxylate. Gel and foam based HEDPA processes allow for decontamination of difficult to reach surfaces that are unmanageable with traditional aqueous process methods. Also, the gel and foam components are optimized to maximize the dissolution rate and assist in the chemical transformation of the gel and foam to a stable waste form.

Nanostructured metal sulfides for energy storage

NASA Astrophysics Data System (ADS)

Rui, Xianhong; Tan, Huiteng; Yan, Qingyu

2014-08-01

Advanced electrodes with a high energy density at high power are urgently needed for high-performance energy storage devices, including lithium-ion batteries (LIBs) and supercapacitors (SCs), to fulfil the requirements of future electrochemical power sources for applications such as in hybrid electric/plug-in-hybrid (HEV/PHEV) vehicles. Metal sulfides with unique physical and chemical properties, as well as high specific capacity/capacitance, which are typically multiple times higher than that of the carbon/graphite-based materials, are currently studied as promising electrode materials. However, the implementation of these sulfide electrodes in practical applications is hindered by their inferior rate performance and cycling stability. Nanostructures offering the advantages of high surface-to-volume ratios, favourable transport properties, and high freedom for the volume change upon ion insertion/extraction and other reactions, present an opportunity to build next-generation LIBs and SCs. Thus, the development of novel concepts in material research to achieve new nanostructures paves the way for improved electrochemical performance. Herein, we summarize recent advances in nanostructured metal sulfides, such as iron sulfides, copper sulfides, cobalt sulfides, nickel sulfides, manganese sulfides, molybdenum sulfides, tin sulfides, with zero-, one-, two-, and three-dimensional morphologies for LIB and SC applications. In addition, the recently emerged concept of incorporating conductive matrices, especially graphene, with metal sulfide nanomaterials will also be highlighted. Finally, some remarks are made on the challenges and perspectives for the future development of metal sulfide-based LIB and SC devices.

Monopropellant engine investigation for space shuttle reaction control system. Volume 3: Improvement of metal foam for catalyst retention

NASA Technical Reports Server (NTRS)

1975-01-01

The retention of granular catalyst in a metal foam matrix was demonstrated to greatly increase the life capability of hydrazine monopropellant reactors. Since nickel foam used in previous tests was found to become degraded after long-term exposure the cause of degradation was examined and metal foams of improved durability were developed. The most durable foam developed was a rhodium-coated nickel foam. An all-platinum foam was found to be incompatible in a hot ammonia (hydrazine) environment. It is recommended to scale up the manufacturing process for the improved foam to produce samples sufficiently large for space shuttle APU gas generator testing.

Metal sulfide and rare-earth phosphate nanostructures and methods of making same

DOEpatents

Wong, Stanislaus; Zhang, Fen

2014-05-13

The present invention provides a method of producing a crystalline metal sulfide nanostructure. The metal is a transitional metal or a Group IV metal. In the method, a porous membrane is placed between a metal precursor solution and a sulfur precursor solution. The metal cations of the metal precursor solution and sulfur ions of the sulfur precursor solution react, thereby producing a crystalline metal sulfide nanostructure.

Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

DOEpatents

Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

2015-06-02

Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

Thermal management improvement of an air-cooled high-power lithium-ion battery by embedding metal foam

NASA Astrophysics Data System (ADS)

Mohammadian, Shahabeddin K.; Rassoulinejad-Mousavi, Seyed Moein; Zhang, Yuwen

2015-11-01

Effect of embedding aluminum porous metal foam inside the flow channels of an air-cooled Li-ion battery module was studied to improve its thermal management. Four different cases of metal foam insert were examined using three-dimensional transient numerical simulations. The effects of permeability and porosity of the porous medium as well as state of charge were investigated on the standard deviation of the temperature field and maximum temperature inside the battery in all four cases. Compared to the case of no porous insert, embedding aluminum metal foam in the air flow channel significantly improved the thermal management of Li-ion battery cell. The results also indicated that, decreasing the porosity of the porous structure decreases both standard deviation of the temperature field and maximum temperature inside the battery. Moreover, increasing the permeability of the metal foam drops the maximum temperature inside the battery while decreasing this property leads to improving the temperature uniformity. Our results suggested that, among the all studied cases, desirable temperature uniformity and maximum temperature were achieved when two-third and the entire air flow channel is filled with aluminum metal foam, respectively.

Chemical Sensors Based on Metal Oxide Nanostructures

NASA Technical Reports Server (NTRS)

Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

2006-01-01

This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

Geometrically induced surface polaritons in planar nanostructured metallic cavities

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

Davids, P. S.; Intravia, F; Dalvit, Diego A.

2014-01-14

We examine the modal structure and dispersion of periodically nanostructured planar metallic cavities within the scattering matrix formulation. By nanostructuring a metallic grating in a planar cavity, artificial surface excitations or spoof plasmon modes are induced with dispersion determined by the periodicity and geometric characteristics of the grating. These spoof surface plasmon modes are shown to give rise to new cavity polaritonic modes at short mirror separations that modify the density of modes in nanostructured cavities. The increased modal density of states form cavity polarirons have a large impact on the fluctuation induced electromagnetic forces and enhanced hear transfer atmore » short separations.« less

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

2004-01-01

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

Effect of Microstructural Parameters on the Relative Densities of Metal Foams

NASA Technical Reports Server (NTRS)

Raj, S. V.; Kerr, Jacob A.

2010-01-01

A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and 314 stainless steel metal foams with different relative densities and pores per inch (p.p.i.) were undertaken in the present investigation to determine the effect of microstructural parameters on the relative densities of metal foams. Several elements of the microstructure, such as longitudinal and transverse cell sizes, cell areas and perimeters, ligament dimensions, cell shapes and volume fractions of closed and open cells, were measured. The cross-sections of the foam ligaments showed a large number of shrinkage cavities, and their circularity factors and average sizes were determined. The volume fractions of closed cells increased linearly with increasing relative density. In contrast, the volume fractions of the open cells and ligaments decreased with increasing relative density. The relative densities and p.p.i. were not significantly dependent on cell size, cell perimeter and ligament dimensions within the limits of experimental scatter. A phenomenological model is proposed to rationalize the present microstructural observations.

From Stochastic Foam to Designed Structure: Balancing Cost and Performance of Cellular Metals

PubMed Central

Lehmhus, Dirk; Vesenjak, Matej

2017-01-01

Over the past two decades, a large number of metallic foams have been developed. In recent years research on this multi-functional material class has further intensified. However, despite their unique properties only a limited number of large-scale applications have emerged. One important reason for this sluggish uptake is their high cost. Many cellular metals require expensive raw materials, complex manufacturing procedures, or a combination thereof. Some attempts have been made to decrease costs by introducing novel foams based on cheaper components and new manufacturing procedures. However, this has often yielded materials with unreliable properties that inhibit utilization of their full potential. The resulting balance between cost and performance of cellular metals is probed in this editorial, which attempts to consider cost not in absolute figures, but in relation to performance. To approach such a distinction, an alternative classification of cellular metals is suggested which centers on structural aspects and the effort of realizing them. The range thus covered extends from fully stochastic foams to cellular structures designed-to-purpose. PMID:28786935

49 CFR 178.358 - Specification 21PF fire and shock resistant, phenolic-foam insulated, metal overpack.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Specification 21PF fire and shock resistant, phenolic-foam insulated, metal overpack. 178.358 Section 178.358 Transportation Other Regulations Relating...) Materials § 178.358 Specification 21PF fire and shock resistant, phenolic-foam insulated, metal overpack. ...

Physicochemical and Electrophysical Properties of Metal/Semiconductor Containing Nanostructured Composites

NASA Astrophysics Data System (ADS)

Gerasimov, G. N.; Gromov, V. F.; Trakhtenberg, L. I.

2018-06-01

The properties of nanostructured composites based on metal oxides and metal-polymer materials are analyzed, along with ways of preparing them. The effect the interaction between metal and semiconductor nanoparticles has on the conductivity, photoconductivity, catalytic activity, and magnetic, dielectric, and sensor properties of nanocomposites is discussed. It is shown that as a result of this interaction, a material can acquire properties that do not exist in systems of isolated particles. The transfer of electrons between metal particles of different sizes in polymeric matrices leads to specific dielectric losses, and to an increase in the rate and a change in the direction of chemical reactions catalyzed by these particles. The interaction between metal-oxide semiconductor particles results in the electronic and chemical sensitization of sensor effects in nanostructured composite materials. Studies on creating molecular machines (Brownian motors), devices for magnetic recording of information, and high-temperature superconductors based on nanostructured systems are reviewed.

Intertwined nanocarbon and manganese oxide hybrid foam for high-energy supercapacitors.

PubMed

Wang, Wei; Guo, Shirui; Bozhilov, Krassimir N; Yan, Dong; Ozkan, Mihrimah; Ozkan, Cengiz S

2013-11-11

Rapid charging and discharging supercapacitors are promising alternative energy storage systems for applications such as portable electronics and electric vehicles. Integration of pseudocapacitive metal oxides with single-structured materials has received a lot of attention recently due to their superior electrochemical performance. In order to realize high energy-density supercapacitors, a simple and scalable method is developed to fabricate a graphene/MWNT/MnO2 nanowire (GMM) hybrid nanostructured foam, via a two-step process. The 3D few-layer graphene/MWNT (GM) architecture is grown on foamed metal foils (nickel foam) via ambient pressure chemical vapor deposition. Hydrothermally synthesized α-MnO2 nanowires are conformally coated onto the GM foam by a simple bath deposition. The as-prepared hierarchical GMM foam yields a monographical graphene foam conformally covered with an intertwined, densely packed CNT/MnO2 nanowire nanocomposite network. Symmetrical electrochemical capacitors (ECs) based on GMM foam electrodes show an extended operational voltage window of 1.6 V in aqueous electrolyte. A superior energy density of 391.7 Wh kg(-1) is obtained for the supercapacitor based on the GMM foam, which is much higher than ECs based on GM foam only (39.72 Wh kg(-1) ). A high specific capacitance (1108.79 F g(-1) ) and power density (799.84 kW kg(-1) ) are also achieved. Moreover, the great capacitance retention (97.94%) after 13 000 charge-discharge cycles and high current handability demonstrate the high stability of the electrodes of the supercapacitor. These excellent performances enable the innovative 3D hierarchical GMM foam to serve as EC electrodes, resulting in energy-storage devices with high stability and power density in neutral aqueous electrolyte. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Development of Metal Oxide Chemical Sensing Nanostructures

NASA Technical Reports Server (NTRS)

Hunter, G. W.; VanderWal,R. L.; Xu, J. C.; Evans, L. J.; Berger, G. M.; Kulis, M. J.

2008-01-01

This paper discusses sensor development based on metal oxide nanostructures and microsystems technology. While nanostructures such as nanowires show significant potential as enabling materials for chemical sensors, a number of significant technical challenges remain. This paper discusses development to address each of these technical barriers: 1) Improved contact and integration of the nanostructured materials with microsystems in a sensor structure; 2) Control of nanostructure crystallinity to allow control of the detection mechanism; and 3) Widening the range of gases that can be detected by fabricating multiple nanostructured materials. A sensor structure composed of three nanostructured oxides aligned on a single microsensor has been fabricated and tested. Results of this testing are discussed and future development approaches are suggested. It is concluded that while this work lays the foundation for further development, these are the beginning steps towards realization of repeatable, controlled sensor systems using oxide based nanostructures.

Metal-polymer composites comprising nanostructures and applications thereof

DOEpatents

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

2011-08-02

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.

Metal-polymer composites comprising nanostructures and applications thereof

DOEpatents

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

2012-04-03

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.

Metal sulfide and rare-earth phosphate nanostructures and methods of making same

DOEpatents

Wong, Stanislaus; Zhang, Fen

2016-06-28

The present invention provides a method of producing a crystalline rare earth phosphate nanostructure. The method comprising: providing a rare earth metal precursor solution and providing a phosphate precursor solution; placing a porous membrane between the metal precursor solution and the phosphate precursor solution, wherein metal cations of the metal precursor solution and phosphate ions of the phosphate precursor solution react, thereby producing a crystalline rare earth metal phosphate nanostructure.

Electrodes synthesized from carbon nanostructures coated with a smooth and conformal metal adlayer

DOEpatents

Adzic, Radoslav; Harris, Alexander

2014-04-15

High-surface-area carbon nanostructures coated with a smooth and conformal submonolayer-to-multilayer thin metal films and their method of manufacture are described. The preferred manufacturing process involves the initial oxidation of the carbon nanostructures followed by a surface preparation process involving immersion in a solution with the desired pH to create negative surface dipoles. The nanostructures are subsequently immersed in an alkaline solution containing a suitable quantity of non-noble metal ions which adsorb at surface reaction sites. The metal ions are then reduced via chemical or electrical means. The nanostructures are exposed to a solution containing a salt of one or more noble metals which replace adsorbed non-noble surface metal atoms by galvanic displacement. The process can be controlled and repeated to obtain a desired film coverage. The resulting coated nanostructures may be used, for example, as high-performance electrodes in supercapacitors, batteries, or other electric storage devices.

Methods of making metal oxide nanostructures and methods of controlling morphology of same

DOEpatents

Wong, Stanislaus S; Hongjun, Zhou

2012-11-27

The present invention includes a method of producing a crystalline metal oxide nanostructure. The method comprises providing a metal salt solution and providing a basic solution; placing a porous membrane between the metal salt solution and the basic solution, wherein metal cations of the metal salt solution and hydroxide ions of the basic solution react, thereby producing a crystalline metal oxide nanostructure.

Room-Temperature Chemical Welding and Sintering of Metallic Nanostructures by Capillary Condensation.

PubMed

Yoon, Sung-Soo; Khang, Dahl-Young

2016-06-08

Room-temperature welding and sintering of metal nanostructures, nanoparticles and nanowires, by capillary condensation of chemical vapors have successfully been demonstrated. Nanoscale gaps or capillaries that are abundant in layers of metal nanostructures have been found to be the preferred sites for the condensation of chemically oxidizing vapor, H2O2 in this work. The partial dissolution and resolidification at such nanogaps completes the welding/sintering of metal nanostructures within ∼10 min at room-temperature, while other parts of nanostructures remain almost intact due to negligible amount of condensation on there. The welded networks of Ag nanowires have shown much improved performances, such as high electrical conductivity, mechanical flexibility, optical transparency, and chemical stability. Chemically sintered layers of metal nanoparticles, such as Ag, Cu, Fe, Ni, and Co, have also shown orders of magnitude increase in electrical conductivity and improved environmental stability, compared to nontreated ones. Pertinent mechanisms involved in the chemical welding/sintering process have been discussed. Room-temperature welding and sintering of metal nanostructures demonstrated here may find widespread application in diverse fields, such as displays, deformable electronics, wearable heaters, and so forth.

Metal Fluorides, Metal Chlorides and Halogenated Metal Oxides as Lewis Acidic Heterogeneous Catalysts. Providing Some Context for Nanostructured Metal Fluorides.

PubMed

Lennon, David; Winfield, John M

2017-01-28

Aspects of the chemistry of selected metal fluorides, which are pertinent to their real or potential use as Lewis acidic, heterogeneous catalysts, are reviewed. Particular attention is paid to β-aluminum trifluoride, aluminum chlorofluoride and aluminas γ and η, whose surfaces become partially fluorinated or chlorinated, through pre-treatment with halogenating reagents or during a catalytic reaction. In these cases, direct comparisons with nanostructured metal fluorides are possible. In the second part of the review, attention is directed to iron(III) and copper(II) metal chlorides, whose Lewis acidity and potential redox function have had important catalytic implications in large-scale chlorohydrocarbons chemistry. Recent work, which highlights the complexity of reactions that can occur in the presence of supported copper(II) chloride as an oxychlorination catalyst, is featured. Although direct comparisons with nanostructured fluorides are not currently possible, the work could be relevant to possible future catalytic developments in nanostructured materials.

Activity Tests of Macro-Meso Porous Catalysts over Metal Foam Plate for Steam Reforming of Bio-Ethanol.

PubMed

Park, No-Kuk; Jeong, Yong Han; Kang, Misook; Lee, Tae Jin

2018-09-01

The catalytic activity of a macro-mesoporous catalyst coated on a metal foam plate in the reforming of bio-ethanol to synthesis gas was investigated. The catalysts were prepared by coating a support with a noble metal and transition metal. The catalytic activity for the production of synthetic gas by the reforming of bio-ethanol was compared according to the support material, reaction temperature, and steam/carbon ratio. The catalysts coated on the metal foams were prepared using a template method, in which macro-pores and meso-pores were formed by mixing polymer beads. In particular, the thermodynamic equilibrium composition of bio-ethanol reforming with the reaction temperature and steam/carbon ratio to produce synthetic gas was examined using the HSC (Enthalpy-Entropy-Heat capacity) chemistry program in this study. The composition of hydrogen and carbon monoxide in the reformate gas produced by steam reforming over the Rh/Ni-Ce-Zr/Al2O3-based pellet type catalysts and metal foam catalysts that had been coated with the Rh/Al-Ce-Zr-based catalysts was investigated by experimental activity tests. The activity of the metal foam catalyst was higher than that of the pellet type catalyst.

Mesoporous magnetic secondary nanostructures as versatile adsorbent for efficient scavenging of heavy metals

PubMed Central

Bhattacharya, Kakoli; Parasar, Devaborniny; Mondal, Bholanath; Deb, Pritam

2015-01-01

Porous magnetic secondary nanostructures exhibit high surface area because of the presence of plentiful interparticle spaces or pores. Mesoporous Fe3O4 secondary nanostructures (MFSNs) have been studied here as versatile adsorbent for heavy metal scavenging. The porosity combined with magnetic functionality of the secondary nanostructures has facilitated efficient heavy metal (As, Cu and Cd) remediation from water solution within a short period of contact time. It is because of the larger surface area of MFSNs due to the porous network in addition to primary nanostructures which provides abundant adsorption sites facilitating high adsorption of the heavy metal ions. The brilliance of adsorption property of MFSNs has been realized through comprehensive adsorption studies and detailed kinetics. Due to their larger dimension, MFSNs help in overcoming the Brownian motion which facilitates easy separation of the metal ion sorbed secondary nanostructures and also do not get drained out during filtration, thus providing pure water. PMID:26602613

Metal Foam Analysis: Improving Sandwich Structure Technology for Engine Fan and Propeller Blades

NASA Technical Reports Server (NTRS)

Fedor, Jessica L.

2004-01-01

The Life Prediction Branch of the NASA Glenn Research Center is searching for ways to construct aircraft and rotorcraft engine fan and propeller blades that are lighter and less costly. One possible design is to create a sandwich structure composed of two metal faces sheets and a metal foam core. The face sheets would carry the bending loads and the foam core would have to resist the transverse shear loads. Metal foam is ideal because of its low density and energy absorption capabilities, making the structure lighter, yet still stiff. The material chosen for the face sheets and core was 17-4PH stainless steel, which is easy to make and has appealing mechanical properties. This material can be made inexpensively compared to titanium and polymer matrix composites, the two current fan blade alternatives. Initial tests were performed on design models, including vibration and stress analysis. These tests revealed that the design is competitive with existing designs; however, some problems were apparent that must be addressed before it can be implemented in new technology. The foam did not hold up as well as expected under stress. This could be due to a number of issues, but was most likely a result of a large number of pores within the steel that weakened the structure. The brazing between the face sheets and the foam was also identified as a concern. The braze did not hold up well under shear stress causing the foam to break away from the face sheets. My role in this project was to analyze different options for improving the design. I primarily spent my time examining various foam samples, created with different sintering conditions, to see which exhibited the most favorable characteristics for our purpose. Methods of analysis that I employed included examining strut integrity under a microscope, counting the number of cells per inch, measuring the density, testing the microhardness, and testing the strength under compression. Shear testing will also be done to examine

Centrifugation-Assisted Fog-Collecting Abilities of Metal-Foam Structures with Different Surface Wettabilities.

PubMed

Ji, Keju; Zhang, Jun; Chen, Jia; Meng, Guiyun; Ding, Yafei; Dai, Zhendong

2016-04-20

The collection of water from fog is a simple and sustainable means of obtaining freshwater for human and animal consumption. Herein, we address the use of metal foam in fog collection and present a novel fog-collecting device fabricated from copper foam. This device, which can also be used in other liquid-gas separation applications, is a 3D extension of biologically inspired 1D and 2D materials. The network structure of the 3D material effectively increased the contact area and interaction time of the skeleton structure and fog compared to those of traditional 2D fog-collecting materials. The main aspects investigated in this study were the influences of the inertial centrifugal force generated by rotating the metal-foam samples and the use of samples with different surface wettabilities on the fog-collecting performance. Superhydrophilic and superhydrophobic samples were found to have higher collection efficiencies at low and high rotational speeds, respectively, and a maximum efficiency of 86% was achieved for superhydrophobic copper foam (20 pores per inch) rotated at 1500 rpm.

Integrated simulation of continuous-scale and discrete-scale radiative transfer in metal foams

NASA Astrophysics Data System (ADS)

Xia, Xin-Lin; Li, Yang; Sun, Chuang; Ai, Qing; Tan, He-Ping

2018-06-01

A novel integrated simulation of radiative transfer in metal foams is presented. It integrates the continuous-scale simulation with the direct discrete-scale simulation in a single computational domain. It relies on the coupling of the real discrete-scale foam geometry with the equivalent continuous-scale medium through a specially defined scale-coupled zone. This zone holds continuous but nonhomogeneous volumetric radiative properties. The scale-coupled approach is compared to the traditional continuous-scale approach using volumetric radiative properties in the equivalent participating medium and to the direct discrete-scale approach employing the real 3D foam geometry obtained by computed tomography. All the analyses are based on geometrical optics. The Monte Carlo ray-tracing procedure is used for computations of the absorbed radiative fluxes and the apparent radiative behaviors of metal foams. The results obtained by the three approaches are in tenable agreement. The scale-coupled approach is fully validated in calculating the apparent radiative behaviors of metal foams composed of very absorbing to very reflective struts and that composed of very rough to very smooth struts. This new approach leads to a reduction in computational time by approximately one order of magnitude compared to the direct discrete-scale approach. Meanwhile, it can offer information on the local geometry-dependent feature and at the same time the equivalent feature in an integrated simulation. This new approach is promising to combine the advantages of the continuous-scale approach (rapid calculations) and direct discrete-scale approach (accurate prediction of local radiative quantities).

Low density metal hydride foams

DOEpatents

Maienschein, Jon L.; Barry, Patrick E.

1991-01-01

Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.

Nanostructured nonprecious metal catalysts for oxygen reduction reaction.

PubMed

Wu, Gang; Zelenay, Piotr

2013-08-20

Platinum-based catalysts represent a state of the art in the electrocatalysis of oxygen reduction reaction (ORR) from the point of view of their activity and durability in harnessing the chemical energy via direct electrochemical conversion. However, because platinum is both expensive and scarce, its widespread implementation in such clean energy applications is limited. Recent breakthroughs in the synthesis of high-performance nonprecious metal catalysts (NPMCs) make replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility. In this Account, we discuss how we can obtain highly promising M-N-C (M: Fe and/or Co) catalysts by simultaneously heat-treating precursors of nitrogen, carbon, and transition metals at 800-1000 °C. The activity and durability of resulting catalysts depend greatly on the selection of precursors and synthesis chemistry. In addition, they correlate quite well with the catalyst nanostructure. While chemists have presented no conclusive description of the active catalytic site for this class of NPMCs, they have developed a designed approach to making active and durable materials, focusing on the catalyst nanostructure. The approach consists of nitrogen doping, in situ carbon graphitization, and the usage of graphitic structures (possibly graphene and graphene oxides) as carbon precursors. Various forms of nitrogen, particularly pyridinic and quaternary, can act as n-type carbon dopants in the M-N-C catalysts, assisting in the formation of disordered carbon nanostructures and donating electrons to the carbon. The CNx structures are likely a crucial part of the ORR active site(s). Noteworthy, the ORR activity is not necessarily governed by the amount of nitrogen, but by how the nitrogen is incorporated into the nanostructures. Apart from the possibility of a direct participation in the active site, the transition metal often plays an important role in the in situ formation of various

Comparison of sound absorbing performances of copper foam and iron foam with the same parameters

NASA Astrophysics Data System (ADS)

Yang, X. C.; Shen, X. M.; Xu, P. J.; Zhang, X. N.; Bai, P. F.; Peng, K.; Yin, Q.; Wang, D.

2018-01-01

Sound absorbing performances of the copper foam and the iron foam with the same parameters were investigated by the AWA6128A detector according to standing wave method. Two modes were investigated, which included the pure metal foam mode and the combination mode with the settled thickness of metal foam. In order to legibly compare the sound absorbing coefficients of the two metal foams, the detected sound frequency points were divided into the low frequency range (100 Hz ~ 1000 Hz), the middle frequency range (1000 Hz ~ 3200 Hz), and the high frequency range (3500 Hz ~ 6000 Hz). Sound absorbing performances of the two metal foams in the two modes were discussed within the three frequency ranges in detail. It would be calculated that the average sound absorbing coefficients of copper foam in the pure metal foam mode were 12.6%, 22.7%, 34.6%, 43.6%, 51.1%, and 56.2% when the thickness was 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm. meanwhile, in the combination mode, the average sound absorbing coefficients of copper foam with the thickness of 10 mm were 30.6%, 34.8%, 36.3%, and 35.8% when the cavity was 5 mm, 10 mm, 15 mm, and 20 mm. In addition, those of iron foam in the pure metal foam mode were 13.4%, 20.1%, 34.4%, 43.1%, 49.6%, and 56.1%, and in the combination mode were 25.6%, 30.5%, 34.3%, and 33.4%.

Metal oxide nanostructures and their gas sensing properties: a review.

PubMed

Sun, Yu-Feng; Liu, Shao-Bo; Meng, Fan-Li; Liu, Jin-Yun; Jin, Zhen; Kong, Ling-Tao; Liu, Jin-Huai

2012-01-01

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

Metal Oxide Nanostructures and Their Gas Sensing Properties: A Review

PubMed Central

Sun, Yu-Feng; Liu, Shao-Bo; Meng, Fan-Li; Liu, Jin-Yun; Jin, Zhen; Kong, Ling-Tao; Liu, Jin-Huai

2012-01-01

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called “small size effect”, yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given. PMID:22736968

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Care for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

2004-01-01

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. Traditionally, these components have been fabricated using expensive materials such as light weight titanium alloys, polymeric composite materials and carbon-carbon composites. The present study investigates the use of P sandwich foam fan blade made up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The stiffness of the sandwich structure is increased by separating the two face sheets by a foam core. The resulting structure possesses a high stiffness while being lighter than a similar solid construction. Since the face sheets carry the applied bending loads, the sandwich architecture is a viable engineering concept. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of the sandwich structure for a fan blade application. A vibration analysis for natural frequencies and P detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of skin thickness and core volume %re presented with a comparison to a solid titanium blade.

Analysis of periodically patterned metallic nanostructures for infrared absorber

NASA Astrophysics Data System (ADS)

Peng, Sha; Yuan, Ying; Long, Huabao; Liu, Runhan; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

With rapid advancement of infrared detecting technology in both military and civil domains, the photo-electronic performances of near-infrared detectors have been widely concerned. Currently, near-infrared detectors demonstrate some problems such as low sensitivity, low detectivity, and relatively small array scale. The current studies show that surface plasmons (SPs) stimulated over the surface of metallic nanostructures by incident light can be used to break the diffraction limit and thus concentrate light into sub-wavelength scale, so as to indicate a method to develop a new type of infrared absorber or detector with very large array. In this paper, we present the design and characterization of periodically patterned metallic nanostructures that combine nanometer thickness aluminum film with silicon wafer. Numerical computations show that there are some valleys caused by surface plasmons in the reflection spectrum in the infrared region, and both red shift and blue shift of the reflection spectrum were observed through changing the nanostructural parameters such as angle α and diameters D. Moreover, the strong E-field intensity is located at the sharp corner of the nano-structures.

Optical response of nanostructured metal/dielectric composites and multilayers

NASA Astrophysics Data System (ADS)

Smith, Geoffrey B.; Maaroof, Abbas I.; Allan, Rodney S.; Schelm, Stefan; Anstis, Geoffrey R.; Cortie, Michael B.

2004-08-01

The homogeneous optical response in conducting nanostructured layers, and in insulating layers containing dense arrays of self assembled conducting nanoparticles separated by organic linkers, is examined experimentally through their effective complex indices (n*, k*). Classical effective medium models, modified to account for the 3-phase nanostructure, are shown to explain (n*, k*) in dense particulate systems but not inhomogeneous layers with macroscopic conductance for which a different approach to homogenisation is discussed. (n*, k*) data on thin granular metal films, thin mesoporous gold, and on thin metal layers containing ordered arrays of voids, is linked to properties of the surface plasmon states which span the nanostructured film. Coupling between evanescent waves at either surface counterbalanced by electron scattering losses must be considered. Virtual bound states for resonant photons result, with the associated transit delay leading to a large rise in n* in many nanostructures. Overcoating n-Ag with alumina is shown to alter (n*, k*) through its impact on the SP coupling. In contrast to classical optical homogenisation, effective indices depend on film thickness. Supporting high resolution SEM images are presented.

Controlled synthesis of different metal oxide nanostructures by direct current arc discharge.

PubMed

Su, Yanjie; Zhang, Jing; Zhang, Liling; Zhang, Yafei

2013-02-01

Direct current (DC) arc discharge method gives high temperature in a short time, which has been widely used to prepare carbon nanotubes. We use this simple approach to synthesize metal oxide nanostructures (MgO, SnO2) without any catalyst. Different morphologies (nanowires, nanobelts, nanocubes, and nanodisks) of metal oxide nanostructures can be controllably synthesized by changing the content of air in buffer gas. The growth mechanisms for these nanostructures are discussed in detail. Oxygen partial pressure is supposed to be one of the most important key factors. The methodology might be used to synthesize similar nanostructures of other functional oxide materials and non-oxide materials.

The Laser ablation of a metal foam: The role of electron-phonon coupling and electronic heat diffusivity

NASA Astrophysics Data System (ADS)

Rosandi, Yudi; Grossi, Joás; Bringa, Eduardo M.; Urbassek, Herbert M.

2018-01-01

The incidence of energetic laser pulses on a metal foam may lead to foam ablation. The processes occurring in the foam may differ strongly from those in a bulk metal: The absorption of laser light, energy transfer to the atomic system, heat conduction, and finally, the atomistic processes—such as melting or evaporation—may be different. In addition, novel phenomena take place, such as a reorganization of the ligament network in the foam. We study all these processes in an Au foam of average porosity 79% and an average ligament diameter of 2.5 nm, using molecular dynamics simulation. The coupling of the electronic system to the atomic system is modeled by using the electron-phonon coupling, g, and the electronic heat diffusivity, κe, as model parameters, since their actual values for foams are unknown. We show that the foam coarsens under laser irradiation. While κe governs the homogeneity of the processes, g mainly determines their time scale. The final porosity reached is independent of the value of g.

Synthesis of branched metal nanostructures with controlled architecture and composition

NASA Astrophysics Data System (ADS)

Ortiz, Nancy

On account of their small size, metal nanoparticles are proven to be outstanding catalysts for numerous chemical transformations and represent promising platforms for applications in the fields of electronics, chemical sensing, medicine, and beyond. Many properties of metal nanoparticles are size-dependent and can be further manipulated through their shape and architecture (e.g., spherical vs. branched). Achieving morphology control of nanoparticles through solution-based techniques has proven challenging due to limited knowledge of morphology development in nanosyntheses. To overcome these complications, a systematic examination of the local ligand environment of metal precursors on nanostructure formation was undertaken to evaluate its contribution to nanoparticle nucleation rate and subsequent growth processes. Specifically, this thesis will provide evidence from ex situ studies---Transmission Electron Microscopy (TEM) and UV-visible spectroscopy (UV-Vis)---that support the hypothesis that strongly coordinated ligands delay burst-like nucleation to generate spherical metal nanoparticles and ligands with intermediate binding affinity regulate the gradual reduction of metal precursors to promote aggregated assembly of nanodendrites. These ex situ studies were coupled with a new in situ perspective, providing detailed understanding of metal precursor transformation, its direct relation to nanoparticle morphology development, and the ligand influence towards the formation of structurally complex metal nanostructures, using in situ synchrotron X-ray Diffraction (XRD) and Ultra Small-Angle X-ray Scattering (USAXS). The principles extracted from the study of monometallic nanostructure formation were also found to be generally applicable to the synthesis of bimetallic nanostructures, e.g., Pd-Pt architectures, with either core-shell or alloyed structures that were readily achieved by ligand selection. These outcomes provide a direct connection between fundamental

Detonation Propagation through Nitromethane Embedded Metal Foam

NASA Astrophysics Data System (ADS)

Lieberthal, Brandon; Maines, Warren R.; Stewart, D. Scott

2015-11-01

There is considerable interest in developing a better understanding of dynamic behaviors of multicomponent systems. We report results of Eulerian hydrodynamic simulations of shock waves propagating through metal foam at approximately 20% relative density and various porosities using a reactive flow model in the ALE3D software package. We investigate the applied pressure and energy of the shock wave and its effects on the fluid and the inert material interface. By varying pore sizes, as well as metal impedance, we predict the overall effects of heterogeneous material systems at the mesoscale. In addition, we observe a radially expanding blast front in these heterogeneous models and apply the theory of Detonation Shock Dynamics to the convergence behavior of the lead shock.

Development of steel foam processing methods and characterization of metal foam

NASA Astrophysics Data System (ADS)

Park, Chanman

2000-10-01

Steel foam was synthesized by a powder metallurgical route, resulting in densities less than half that of steel. Process parameters for foam synthesis were investigated, and two standard powder formulations were selected consisting of Fe-2.5% C and 0.2 wt% foaming agent (either MgCO3 or SrCO3). Compression tests were performed on annealed and pre-annealed foam samples of different density to determine mechanical response and energy absorption behavior. The stress-strain response was strongly affected by annealing, which reduced the carbon content and converted much of the pearlitic structure to ferrite. Different powder blending methods and melting times were employed and the effects on the geometric structure of steel foam were examined. Dispersion of the foaming agent affected the pore size distribution of the expanded foams. With increasing melt time, pores coalesced, leading to the eventual collapse of the foam. Inserting interlayer membranes in the powder compacts inhibited coalescence of pores and produced foams with more uniform cell size and distribution. The closed-cell foam samples exhibited anisotropy in compression, a phenomenon that was caused primarily by the ellipsoidal cell shapes within the foam. Yield strengths were 3x higher in the transverse direction than in the longitudinal direction. Yield strength also showed a power-law dependence on relative density (n ≅ 1.8). Compressive strain was highly localized and occurred in discrete bands that extended transverse to the loading direction. The yield strength of foam samples showed stronger strain rate dependence at higher strain rates. The increased strain rate dependence was attributed to microinertial hardening. Energy absorption was also observed to increase with strain rate. Measurements of cell wall curvature showed that an increased mean curvature correlated with a reduced yield strength, and foam strengths generally fell below predictions of Gibson-Ashby theory. Morphological defects

Design of Experiments for the Thermal Characterization of Metallic Foam

NASA Technical Reports Server (NTRS)

Crittenden, Paul E.; Cole, Kevin D.

2003-01-01

Metallic foams are being investigated for possible use in the thermal protection systems of reusable launch vehicles. As a result, the performance of these materials needs to be characterized over a wide range of temperatures and pressures. In this paper a radiation/conduction model is presented for heat transfer in metallic foams. Candidates for the optimal transient experiment to determine the intrinsic properties of the model are found by two methods. First, an optimality criterion is used to find an experiment to find all of the parameters using one heating event. Second, a pair of heating events is used to determine the parameters in which one heating event is optimal for finding the parameters related to conduction, while the other heating event is optimal for finding the parameters associated with radiation. Simulated data containing random noise was analyzed to determine the parameters using both methods. In all cases the parameter estimates could be improved by analyzing a larger data record than suggested by the optimality criterion.

Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review

PubMed Central

Arafat, M. M.; Dinan, B.; Akbar, Sheikh A.; Haseeb, A. S. M. A.

2012-01-01

Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research. PMID:22969344

A general strategy toward the rational synthesis of metal tungstate nanostructures using plasma electrolytic oxidation method

NASA Astrophysics Data System (ADS)

Jiang, Yanan; Liu, Baodan; Zhai, Zhaofeng; Liu, Xiaoyuan; Yang, Bing; Liu, Lusheng; Jiang, Xin

2015-11-01

A new method based on conventional plasma electrolytic oxidation (PEO) technology has been developed for the rational synthesis of metal tungstate nanostructures. Using this method, ZnWO4 and NiWO4 nanostructures with controllable morphologies (nanorods, nanosheets and microsheets) and superior crystallinity have been synthesized. It has been found that the morphology diversity of ZnWO4 nanostructures can be selectively tailored through tuning the electrolyte concentration and annealing temperatures, showing obvious advantages in comparison to traditional hydrothermal and sol-gel methods. Precise microscopy analyses on the cross section of the PEO coating and ZnWO4 nanostructures confirmed that the precursors initially precipitated in the PEO coating and its surface during plasma discharge process are responsible for the nucleation and subsequent growth of metal tungstate nanostructures by thermal annealing. The method developed in this work represents a general strategy toward the rational synthesis of metal oxide nanostructures and the formation mechanism of metal tungstate nanostructures fabricated by the PEO method is finally discussed.

On the Feasibility of Very-Low-Density Pure Metal Foams as Bright High-Energy X-ray Sources

NASA Astrophysics Data System (ADS)

Colvin, Jeffrey; Felter, Thomas

2003-10-01

We have used the Busquet approximation (M. Busquet, Phys. Fluids B 5(11), 4191 (1993)) to explore calculationally what the possible x-ray conversion efficiencies into the K-band would be from irradiating very-low-density pure metal foams with tens of kilojoules of 1/3-micron laser light. We will discuss the advantages of pure metal foams as bright high-energy x-ray sources, and some results of this calculational study. We will also present our ideas for how to fabricate pure metal foams with densities of a few milligrams per cubic centimeter. This work was performed under the auspices of the US Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Precise Control Over Morphology and Density of Metal and Transition Metal Nanostructures for Sensing and Energy Related Applications

NASA Astrophysics Data System (ADS)

Tran, Minh

Metallic nanostructures are of great interest due to their applicability in various modern technologies, such as catalysis, sensing, and optoelectronics. In this work, we employed three solution-based methods, including colloidal suspension synthesis, modified galvanic displacement, and electrodeposition, to synthesize nanostructured metals and transition metals, including gold (Au), copper (Cu), platinum (Pt), palladium (Pd), nickel (Ni), and cobalt (Co). Our focus was to establish process-structure-property relationship and explore their applicability in the field of sensing and clean energy generation. More precisely we established relationships between experimental parameters, such as temperature, applied potential, electrolyte pH, reactant concentration, additive, and the number of deposition cycles, and the characteristics of the nanostructures, such as morphology, density, size, and size distribution. Our results indicated that the nanostructures were tunable by adjusting the process parameters. This provided insight into the growth mechanisms of the metallic nanostructures. Since properties of the nanostructures are tunable by controlling the structure, our results provided researchers with additional tools to obtain nanomaterials with desired properties for specific applications. The materials synthesized by our methods were utilized to as substrates for surface enhanced Raman spectroscopy (SERS) and as photocathodes for photoelectrochemical production of hydrogen. The results showed that the performances of our materials were either promising or compatible with those reported in the literature, thus bringing new opportunities to the development of low-cost, high-performance, and flexible nanomaterials for the current and future technologies.

Investigation of low-frequency-oscillating water flow in metal foam with 10 pores per inch

NASA Astrophysics Data System (ADS)

Bağcı, Ö.; Arbak, A.; De Paepe, M.; Dukhan, N.

2018-01-01

In this study, oscillating water flow in metal foam with open cells is investigated experimentally. The metal foam sample has a porosity of 88% and 10 pores. The water was oscillated in the test section with three frequencies between 0.116 Hz and 0.348 Hz, which are considered low for water oscillation, and three flow displacements ranging between 74.35 mm and 111.53 mm. The combinations of frequencies of displacements were studied for their impacts of dimensional and non-dimensional pressure loss quantities. To this purpose, friction factor was correlated as a function of kinetic Reynolds number. The same metal foam sample was studied by exposing it to steady-state water flow to investigate its permeability and drag coefficient in low-velocity flow regimes. The friction factor distribution for oscillating flow was found to be over that found for steady state. The outcomes of the study are important for studying heat transfer under the same flow conditions.

The development of a 3D mesoscopic model of metallic foam based on an improved watershed algorithm

NASA Astrophysics Data System (ADS)

Zhang, Jinhua; Zhang, Yadong; Wang, Guikun; Fang, Qin

2018-06-01

The watershed algorithm has been used widely in the x-ray computed tomography (XCT) image segmentation. It provides a transformation defined on a grayscale image and finds the lines that separate adjacent images. However, distortion occurs in developing a mesoscopic model of metallic foam based on XCT image data. The cells are oversegmented at some events when the traditional watershed algorithm is used. The improved watershed algorithm presented in this paper can avoid oversegmentation and is composed of three steps. Firstly, it finds all of the connected cells and identifies the junctions of the corresponding cell walls. Secondly, the image segmentation is conducted to separate the adjacent cells. It generates the lost cell walls between the adjacent cells. Optimization is then performed on the segmentation image. Thirdly, this improved algorithm is validated when it is compared with the image of the metallic foam, which shows that it can avoid the image segmentation distortion. A mesoscopic model of metallic foam is thus formed based on the improved algorithm, and the mesoscopic characteristics of the metallic foam, such as cell size, volume and shape, are identified and analyzed.

Simulating and discussion on surface plasmon typical optical properties of patterned periodic metallic nanostructures

NASA Astrophysics Data System (ADS)

Liu, Runhan; Yuan, Ying; Long, Huabao; Peng, Sha; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

The intense surface plasmons (SPs) can be generated by patterned metal nano-structure arrays, through coupling incident light onto the functioned metal surface, so as to construct highly constrained surface electromagnetic modes. Therefore, a localized micro-nano-field array with a highly compressed surface electron distribution, can also be shaped and even nano-focused over the surface, which will lead to a lot of special physical effects such as anti-reflection effect, and thus indicate many new potential applications in the field of nano-photonics and -optoelectronics. In this paper, several typical patterned sub-wavelength metal nano-structure arrays were designed according to the process, in which common silicon wafer was employed as the substrate material and aluminum as the metal film with different structural size and arrangement circle. In addition, by adjusting the dielectric constant of metal material appropriately, the power control effect on metallic nanostructure was simulated. The key properties such as the excitation intensity of the surface plasmons were studied by simulating the reflectivity characteristic curves and the electric field distribution of the nanostructure excited by incident infrared beams. It is found that the angle of corners, the arrangement cycle and the metal material properties of the patterned nano-structures can be utilized as key factors to control the excitation intensity of surface plasmons.

Growth of nanostructures with controlled diameter

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

Pfefferle, Lisa; Haller, Gary; Ciuparu, Dragos

2009-02-03

Transition metal-substituted MCM-41 framework structures with a high degree of structural order and a narrow pore diameter distribution were reproducibly synthesized by a hydrothermal method using a surfactant and an anti-foaming agent. The pore size and the mesoporous volume depend linearly on the surfactant chain length. The transition metals, such as cobalt, are incorporated substitutionally and highly dispersed in the silica framework. Single wall carbon nanotubes with a narrow diameter distribution that correlates with the pore diameter of the catalytic framework structure were prepared by a Boudouard reaction. Nanostructures with a specified diameter or cross-sectional area can therefore be predictablymore » prepared by selecting a suitable pore size of the framework structure.« less

Pore-level determination of spectral reflection behaviors of high-porosity metal foam sheets

NASA Astrophysics Data System (ADS)

Li, Yang; Xia, Xin-Lin; Ai, Qing; Sun, Chuang; Tan, He-Ping

2018-03-01

Open cell metal foams are currently attracting attention and their radiative behaviors are of primary importance in high temperature applications. The spectral reflection behaviors of high-porosity metal foam sheets, bidirectional reflectance distribution function (BRDF) and directional-hemispherical reflectivity were numerically investigated. A set of realistic nickel foams with porosity from 0.87 to 0.97 and pore density from 10 to 40 pores per inch were tomographied to obtain their 3-D digital cell network. A Monte Carlo ray-tracing method was employed in order to compute the pore-level radiative transfer inside the network within the limit of geometrical optics. The apparent reflection behaviors and their dependency on the textural parameters and strut optical properties were comprehensively computed and analysed. The results show a backward scattering of the reflected energy at the foam sheet surface. Except in the cases of large incident angles, an energy peak is located almost along the incident direction and increases with increasing incident angles. Through an analytical relation established, the directional-hemispherical reflectivity can be related directly to the porosity of the foam sheet and to the complex refractive index of the solid phase as well as the specularity parameter which characterizes the local reflection model. The computations show that a linear decrease in normal-hemispherical reflectivity occurs with increasing porosity. The rate of this decrease is directly proportional to the strut normal reflectivity. In addition, the hemispherical reflectivity increases as a power function of the incident angle cosine.

Numerical Analysis of a Paraffin/Metal Foam Composite for Thermal Storage

NASA Astrophysics Data System (ADS)

Di Giorgio, P.; Iasiello, M.; Viglione, A.; Mameli, M.; Filippeschi, S.; Di Marco, P.; Andreozzi, A.; Bianco, N.

2017-01-01

In the last decade, the use of Phase Change Materials (PCMs) as passive thermal energy storage has been widely studied both analytically and experimentally. Among the PCMs, paraffins show many advantages, such as having a high latent heat, a low vapour pressure, being chemically inert, stable and non-toxic. But, their thermal conductivity is very low with a high volume change during the melting process. An efficient way to increase their poor thermal conductivity is to couple them with open cells metallic foams. This paper deals with a theoretical analysis of paraffin melting process inside an aluminum foam. A mathematical model is developed by using the volume-averaged governing equations for the porous domain, made up by the PCM embedded into the metal foam. Non-Darcian and buoyancy effects are considered in the momentum equation, while the energy equations are modelled with the Local Thermal Non-Equilibrium (LTNE) approach. The PCM liquefaction is treated with the apparent heat capacity method and the governing equations are solved with a finite-element scheme by COMSOL Multiphysics®. A new method to calculate the coupling coefficients needed for the thermal model has been developed and the results obtained have been validated comparing them to experimental data in literature.

Emerging Science and Research Opportunities for Metals and Metallic Nanostructures

NASA Astrophysics Data System (ADS)

Handwerker, Carol A.; Pollock, Tresa M.

2014-07-01

During the next decade, fundamental research on metals and metallic nanostructures (MMNs) has the potential to continue transforming metals science into innovative materials, devices, and systems. A workshop to identify emerging and potentially transformative research areas in MMNs was held June 13 and 14, 2012, at the University of California Santa Barbara. There were 47 attendees at the workshop (listed in the Acknowledgements section), representing a broad range of academic institutions, industry, and government laboratories. The metals and metallic nanostructures (MMNs) workshop aimed to identify significant research trends, scientific fundamentals, and recent breakthroughs that can enable new or enhanced MMN performance, either alone or in a more complex materials system, for a wide range of applications. Additionally, the role that MMN research can play in high-priority research and development (R&D) areas such as the U.S. Materials Genome Initiative, the National Nanotechnology Initiative, the Advanced Manufacturing Initiative, and other similar initiatives that exist internationally was assessed. The workshop also addressed critical issues related to materials research instrumentation and the cyberinfrastructure for materials science research and education, as well as science, technology, engineering, and mathematics (STEM) workforce development, with emphasis on the United States but with an appreciation that similar challenges and opportunities for the materials community exist internationally. A central theme of the workshop was that research in MMNs has provided and will continue to provide societal benefits through the integration of experiment, theory, and simulation to link atomistic, nanoscale, microscale, and mesoscale phenomena across time scales for an ever-widening range of applications. Within this overarching theme, the workshop participants identified emerging research opportunities that are categorized and described in more detail in the

Nanostructured carbon-metal oxide composite electrodes for supercapacitors: a review

NASA Astrophysics Data System (ADS)

Zhi, Mingjia; Xiang, Chengcheng; Li, Jiangtian; Li, Ming; Wu, Nianqiang

2012-12-01

This paper presents a review of the research progress in the carbon-metal oxide composites for supercapacitor electrodes. In the past decade, various carbon-metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon-metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.

Nanostructured carbon-metal oxide composite electrodes for supercapacitors: a review.

PubMed

Zhi, Mingjia; Xiang, Chengcheng; Li, Jiangtian; Li, Ming; Wu, Nianqiang

2013-01-07

This paper presents a review of the research progress in the carbon-metal oxide composites for supercapacitor electrodes. In the past decade, various carbon-metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon-metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.

Interfacial scanning tunneling spectroscopy (STS) of chalcogenide/metal hybrid nanostructure

NASA Astrophysics Data System (ADS)

Saad, Mahmoud M.; Abdallah, Tamer; Easawi, Khalid; Negm, Sohair; Talaat, Hassan

2015-05-01

The electronic structure at the interface of chalcogenide/metal hybrid nanostructure (CdSe-Au tipped) had been studied by UHV scanning tunneling spectroscopy (STS) technique at room temperature. This nanostructure was synthesized by a phase transfer chemical method. The optical absorption of this hybrid nanostructure was recorded, and the application of the effective mass approximation (EMA) model gave dimensions that were confirmed by the direct measurements using the scanning tunneling microscopy (STM) as well as the high-resolution transmission electron microscope (HRTEM). The energy band gap obtained by STS agrees with the values obtained from the optical absorption. Moreover, the STS at the interface of CdSe-Au tipped hybrid nanostructure between CdSe of size about 4.1 ± 0.19 nm and Au tip of size about 3.5 ± 0.29 nm shows a band bending about 0.18 ± 0.03 eV in CdSe down in the direction of the interface. Such a result gives a direct observation of the electron accumulation at the interface of CdSe-Au tipped hybrid nanostructure, consistent with its energy band diagram. The presence of the electron accumulation at the interface of chalcogenides with metals has an important implication for hybrid nanoelectronic devices and the newly developed plasmon/chalcogenide photovoltaic solar energy conversion.

Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents.

PubMed

Štengl, Václav; Henych, Jiří; Janoš, Pavel; Skoumal, Miroslav

2016-01-01

Metal oxides have very important applications in many areas of chemistry, physics and materials science; their properties are dependent on the method of preparation, the morphology and texture. Nanostructured metal oxides can exhibit unique characteristics unlike those of the bulk form depending on their morphology, with a high density of edges, corners and defect surfaces. In recent years, methods have been developed for the preparation of metal oxide powders with tunable control of the primary particle size as well as of a secondary particle size: the size of agglomerates of crystallites. One of the many ways to take advantage of unique properties of nanostructured oxide materials is stoichiometric degradation of chemical warfare agents (CWAs) and volatile organic compounds (VOC) pollutants on their surfaces.

Nanostructural self-organization and dynamic adaptation of metal-polymer tribosystems

NASA Astrophysics Data System (ADS)

Mashkov, Yu. K.

2017-02-01

The results of investigating the effect of nanosize modifiers of a polymer matrix on the nanostructural self-organization of polymer composites and dynamic adaptation of metal-polymer tribosystems, which considerably affect the wear resistance of polymer composite materials, have been analyzed. It has been shown that the physicochemical nanostructural self-organization processes are developed in metal-polymer tribosystems with the formation of thermotropic liquid-crystal structures of the polymer matrix, followed by the transition of the system to the stationary state with a negative feedback that ensures dynamic adaptation of the tribosystem to given operating conditions.

49 CFR 178.358 - Specification 21PF fire and shock resistant, phenolic-foam insulated, metal overpack.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Specification 21PF fire and shock resistant, phenolic-foam insulated, metal overpack. 178.358 Section 178.358 Transportation Other Regulations Relating... Class 7 (Radioactive) Materials § 178.358 Specification 21PF fire and shock resistant, phenolic-foam...

Negative refraction of acoustic waves using a foam-like metallic structure

NASA Astrophysics Data System (ADS)

Hladky-Hennion, A.-C.; Vasseur, J. O.; Haw, G.; Croënne, C.; Haumesser, L.; Norris, A. N.

2013-04-01

A phononic crystal (PC) slab made of a single metallic phase is shown, theoretically and experimentally, to display perfect negative index matching and focusing capability when surrounded with water. The proposed PC slab is a centimeter scale hollow metallic foam-like structure in which acoustic energy is mediated via the metal lattice. The negative index property arises from an isolated branch of the dispersion curves corresponding to a mode that can be coupled to incident acoustic waves in surrounding water. This band also intercepts the water sound line at a frequency in the ultrasonic range. The metallic structure is consequently a candidate for the negative refraction of incident longitudinal waves.

Nanostructured transition metal oxides useful for water oxidation catalysis

DOEpatents

Frei, Heinz M; Jiao, Feng

2013-12-24

The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

Tuning and synthesis of metallic nanostructures by mechanical compression

DOEpatents

Fan, Hongyou; Li, Binsong

2015-11-17

The present invention provides a pressure-induced phase transformation process to engineer metal nanoparticle architectures and to fabricate new nanostructured materials. The reversible changes of the nanoparticle unit cell dimension under pressure allow precise control over interparticle separation in 2D or 3D nanoparticle assemblies, offering unique robustness for interrogation of both quantum and classic coupling interactions. Irreversible changes above a threshold pressure of about 8 GPa enables new nanostructures, such as nanorods, nanowires, or nanosheets.

Metal oxide nanostructures: preparation, characterization and functional applications as chemical sensors.

PubMed

Zappa, Dario; Bertuna, Angela; Comini, Elisabetta; Kaur, Navpreet; Poli, Nicola; Sberveglieri, Veronica; Sberveglieri, Giorgio

2017-01-01

Preparation and characterization of different metal oxide (NiO, WO 3 , ZnO, SnO 2 and Nb 2 O 5 ) nanostructures for chemical sensing are presented. p-Type (NiO) and n-type (WO 3 , SnO 2 , ZnO and Nb 2 O 5 ) metal oxide nanostructures were grown on alumina substrates using evaporation-condensation, thermal oxidation and hydrothermal techniques. Surface morphologies and crystal structures were investigated through scanning electron microscopy and Raman spectroscopy. Furthermore, different batches of sensors have been prepared, and their sensing performances towards carbon monoxide and nitrogen dioxide have been explored. Moreover, metal oxide nanowires have been integrated into an electronic nose and successfully applied to discriminate between drinking and contaminated water.

A practical approach for solving disposal of rubber waste: Leachability of heavy metals from foamed concrete containing rubber powder waste (RPW)

NASA Astrophysics Data System (ADS)

Kadir, Aeslina Abdul; Hassan, Mohd Ikhmal Haqeem; Sarani, Noor Amira; Yatim, Fatin Syahirah Mohamed; Jaini, Zainorizuan Mohd

2017-09-01

Enormous disposal of rubber wastes has become an issue with the facts that all tires have its own life span. Inefficient disposal method of RPW from used tire can cause environmental impact as the heavy metals content in tire can easily leach out thus causing contamination to the soil and waterways. The goals of this study is to identify the heavy metals content of rubber powder waste (RPW) and to determine the potential of leachability of heavy metals from foamed concrete containing different percentages of RPW. Therefore, this study is focused on the leachability of RPW incorporated in foamed concrete. Different percentages of RPW were incorporated in foamed concrete (0%, 6%, 12% and 18%) for the investigation. Leachability tests were done by using toxicity characteristic leaching procedure (TCLP) on crushed samples of foamed concrete incorporated with RPW and were analyzed by using inductive coupled plasma mass spectrometry (ICP-MS). The results from XRF indicated that RPW is high in metals such as Zn, Cu, Ba and Co. The highest concentration of heavy metals in raw RPW is Zn with 51403 ppm which is exceeded USEPA (2010) maximum contaminant level (MCL) of Zn with only 5 ppm. After RPW had been incorporated into a foamed concrete, the results demonstrated that the Zn, Cu, Ba and Co heavy metals were less leached and complied with USEPA standard. The incorporation of RPW into foamed concrete in this study demonstrated that it could be a potential alternative raw material for concrete thus enhancing the possibility of its reuse in safe and sustainable way.

Fibroblastic interactions with high-porosity Ti-6Al-4V metal foam.

PubMed

Cheung, Serene; Gauthier, Maxime; Lefebvre, Louis-Philippe; Dunbar, Michael; Filiaggi, Mark

2007-08-01

A novel metallic Ti-6Al-4V foam in development at the National Research Council of Canada was investigated for its ability to foster cell attachment and growth using a fibroblast cell culture model. The foam was manufactured via a powder metallurgical process that could produce interconnected porosity greater than 70%. Cell attachment was assessed after 6 and 24 h, while proliferation was examined after 3 and 7 days. Ingrown fibroblasts displayed a number of different morphologies; some fibroblasts were spread thinly in close apposition with the irregular surface, or more often had several anchorage points and extended in three dimensions as they spanned pore space. It was also demonstrated that fibroblasts were actively migrating through the porous scaffold over a 14-day period. In a 60-day extended culture, fibroblasts were bridging and filling macropores and had extensively infiltrated the foams. Overall, it was established that this foam was supportive of cell attachment and proliferation, migration through the porous network, and that it was capable of sustaining a large cell population.

Application of carbon foam for heavy metal removal from industrial plating wastewater and toxicity evaluation of the adsorbent.

PubMed

Lee, Chang-Gu; Song, Mi-Kyung; Ryu, Jae-Chun; Park, Chanhyuk; Choi, Jae-Woo; Lee, Sang-Hyup

2016-06-01

Electroplating wastewater contains various types of toxic substances, such as heavy metals, solvents, and cleaning agents. Carbon foam was used as an adsorbent for the removal of heavy metals from real industrial plating wastewater. Its sorption capacity was compared with those of a commercial ion-exchange resin (BC258) and a heavy metal adsorbent (CupriSorb™) in a batch system. The experimental carbon foam has a considerably higher sorption capacity for Cr and Cu than commercial adsorbents for acid/alkali wastewater and cyanide wastewater. Additionally, cytotoxicity test showed that the newly developed adsorbent has low cytotoxic effects on three kinds of human cells. In a pilot plant, the carbon foam had higher sorption capacity for Cr (73.64 g kg(-1)) than for Cu (14.86 g kg(-1)) and Ni (7.74 g kg(-1)) during 350 h of operation time. Oxidation pretreatments using UV/hydrogen peroxide enhance heavy metal removal from plating wastewater containing cyanide compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

Collaboration with Williams International to Demonstrate the Characteristics of a Foam-Metal-Liner Installed Over-the-Rotor of a Turbofan Engine

NASA Technical Reports Server (NTRS)

Sutliff, Daniel; Elliott, Dave; Jones, Mike; Hartley, Tom

2008-01-01

A Williams International FJ44-3A 3000-lb thrust class turbofan engine was used as a demonstrator for foam-metal liner installed in close proximity to the fan. Two foam metal liner designs were tested and compared to the hardwall. Traditional Single-Degree-of-Freedom liner designs were also evaluated to provide a comparison. Normalized information on farfield acoustics is presented in this paper. The results show that up to 5 dB PWL overall attenuation was achieved in the forward quadrant. In general, the foam-metal liners performed better when the fan tip speed was below sonic.

New technique for heterogeneous vapor-phase synthesis of nanostructured metal layers from low-dimensional volatile metal complexes

NASA Astrophysics Data System (ADS)

Badalyan, A. M.; Bakhturova, L. F.; Kaichev, V. V.; Polyakov, O. V.; Pchelyakov, O. P.; Smirnov, G. I.

2011-09-01

A new technique for depositing thin nanostructured layers on semiconductor and insulating substrates that is based on heterogeneous gas-phase synthesis from low-dimensional volatile metal complexes is suggested and tried out. Thin nanostructured copper layers are deposited on silicon and quartz substrates from low-dimensional formate complexes using a combined synthesis-mass transport process. It is found that copper in layers thus deposited is largely in a metal state (Cu0) and has the form of closely packed nanograins with a characteristic structure.

Surface plasmon microscopy with low-cost metallic nanostructures for biosensing I

NASA Astrophysics Data System (ADS)

Lindquist, Nathan; Oh, Sang-Hyun; Otto, Lauren

2012-02-01

The field of plasmonics aims to manipulate light over dimensions smaller than the optical wavelength by exploiting surface plasmon resonances in metallic films. Typically, surface plasmons are excited by illuminating metallic nanostructures. For meaningful research in this exciting area, the fabrication of high-quality nanostructures is critical, and in an undergraduate setting, low-cost methods are desirable. Careful optical characterization of the metallic nanostructures is also required. Here, we present the use of novel, inexpensive nanofabrication techniques and the development of a customized surface plasmon microscopy setup for interdisciplinary undergraduate experiments in biosensing, surface-enhanced Raman spectroscopy, and surface plasmon imaging. A Bethel undergraduate student performs the nanofabrication in collaboration with the University of Minnesota. The rewards of mentoring undergraduate students in cooperation with a large research university are numerous, exposing them to a wide variety of opportunities. This research also interacts with upper-level, open-ended laboratory projects, summer research, a semester-long senior research experience, and will enable a large range of experiments into the future.

Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

2004-01-01

The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful

Using graphitic foam as the bonding material in metal fuel pins for sodium fast reactors

NASA Astrophysics Data System (ADS)

Karahan, Aydın; Kazimi, Mujid S.

2013-10-01

The study evaluates the possible use of graphite foam as the bonding material between U-Pu-Zr metallic fuel and steel clad for sodium fast reactor applications using FEAST-METAL fuel performance code. Furthermore, the applicability of FEAST-METAL to the advanced fuel designs is demonstrated. Replacing the sodium bond with a chemically stable foam material would eliminate fuel clad metallurgical interactions, and allow for fuel swelling under low external stress. Hence, a significant improvement is expected for the steady state and transient performance. FEAST-METAL was used to assess the thermo-mechanical behavior of the new fuel form and a reference metallic fuel pin. Nearly unity conversion ratio, 75% smear density U-15Pu-6Zr metallic fuel pin with sodium bond, and T91 cladding was selected as a reference case. It was found that operating the reference case at high clad temperatures (600-660 °C) results in (1) excessive clad wastage formation/clad thinning due to lanthanide migration and formation of brittle phases at clad inner surface, and (2) excessive clad hoop strain at the upper axial section due mainly to the occurrence of thermal creep. The combination of these two factors may lead to cladding breach. The work concludes that replacing the sodium bond with 80% porous graphite foam and reducing the fuel smear density to 70%, it is likely that the fuel clad metallurgical interaction would be eliminated while the fuel swelling is allowed without excessive fuel clad mechanical interaction. The suggested design appears as an alternative for a high performance metallic fuel design for sodium fast reactors.

Synthesis and characterization of transition metal oxide/sulfide nanostructures for electrochemical applications

NASA Astrophysics Data System (ADS)

Yilmaz, Gamze

This thesis is essentially oriented to develop low-cost nanostructured transition metal (nickel and vanadium) oxides and sulfides with high energy density, power density and electrochemical stability via strategies of structural design, hybridization, functionalization and surface engineering. Metal oxide and metal oxide/sulfide hybrid nanostructures in several designs, including hierarchical porous nanostructures, hollow polyhedrons, nanocubes, nanoframes, octopod nanoframes, and nanocages, were synthesized to study the contribution of structural design, compositional engineering, functionalization and surface engineering to the electrochemical properties of the materials. Modulated compositional and structural features disclosed the opportunities of large accessible active sites, facile ion transport, robustness and enhanced electrical conductivity. The best electrochemical performance with merits of highest energy density (38.9 Wh kg-1), power density (7.4 kW kg-1) and electrochemical stability (90.9% after 10000 cycles) was obtained for nickel cobalt layered double hydroxide/cobalt sulfide (NiCo-LDH/Co9S8) hybrid hollow polyhedron structure.

Metallic nanospheres embedded in nanowires initiated on nanostructures and methods for synthesis thereof

DOEpatents

Zaidi, Saleem [Albuquerque, NM; Tringe, Joseph W [Walnut Creek, CA; Vanamu, Ganesh [Sunnyvale, CA; Prinja, Rajiv [Albuquerque, NM

2012-01-10

A nanostructure includes a nanowire having metallic spheres formed therein, the spheres being characterized as having at least one of about a uniform diameter and about a uniform spacing there between. A nanostructure in another embodiment includes a substrate having an area with a nanofeature; and a nanowire extending from the nanofeature, the nanowire having metallic spheres formed therein, the spheres being characterized as having at least one of about a uniform diameter and about a uniform spacing there between. A method for forming a nanostructure is also presented. A method for reading and writing data is also presented. A method for preparing nanoparticles is also presented.

Investigation the foam dynamics capacity of SDS in foam generator by affecting the presence of organic and inorganic contaminant

NASA Astrophysics Data System (ADS)

Haryanto, Bode; Siswarni, M. Z.; Sianipar, Yosef C. H.; Sinaga, Tongam M. A.; Bestari, Imam

2017-05-01

The effect of negative charge SDS monomer on its foam capacity with the presence of contaminants was investigated in foam generator. Generally, surfactant with higher concentration has higher foam capacity. The higher concentration will increase the number of monomer then increase the micelles in liquid phase. Increasing the number of monomer with the negative charge is a potential to increase interaction with metal ion with positive charge in solution. The presence of inorganic compound as metal ion with positive charge and organic compound (colloid) as particle of coffee impacting to generate the foam lamella with monomer is evaluated. Foam dynamic capacity of only SDS with variation of CMC, 1 x; 2 x; 3 x have the height 7.5, 8.0 and 8.3 cm respectively with the different range time were investigated. The Height of foam dynamic capacity with the presence of 20 ppm Cd2+ ion contaminant was 8.0, 8.3 and 8.4 cm at the same CMC variation of SDS. The presence of metal ion contaminant within the foam was confirmed by AAS. The black coffee particles and oil as contaminant decreased the foam capacity significantly in comparing to metal ions.

Panelized wall system with foam core insulation

DOEpatents

Kosny, Jan [Oak Ridge, TN; Gaskin, Sally [Houston, TX

2009-10-20

A wall system includes a plurality of wall members, the wall members having a first metal panel, a second metal panel, and an insulating core between the first panel and the second panel. At least one of the first panel and the second panel include ridge portions. The insulating core can be a foam, such as a polyurethane foam. The foam can include at least one opacifier to improve the k-factor of the foam.

Nanoimprint methods for the fabrication of macroscopic plasmonically active metal nanostructures

NASA Astrophysics Data System (ADS)

Nagel, Robin D.; Filser, Simon; Zhang, Tianyue; Manzi, Aurora; Schönleber, Konrad; Lindsly, James; Zimmermann, Josef; Maier, Thomas L.; Scarpa, Giuseppe; Krischer, Katharina; Lugli, Paolo

2017-02-01

In this article, we present a refined nanostructuring method, lift-off nanoimprint lithography (LO-NIL), which allows the deposition of high-quality metal nanostructures due to a bilayer resist process and compare it to nano-transfer printing (nTP), a purely additive metal printing technique. LO-NIL and nTP are used as accurate methods for the fabrication of ordered plasmonic metal nanostructure arrays on semiconducting substrates over large areas using the example of gold nanodisks on silicon. The possibility of feature size adjustment in LO-NIL during the fabrication process is especially useful for tuning plasmonic resonance peaks between the visible and the mid-infrared range as well as fine-tuning of these resonances. In UV-VIS-NIR spectroscopic measurements, a significant blueshift in the plasmonic resonance was found for nTP samples compared to the ones fabricated with the lift-off technique. It was concluded that this shift originates from a metal/substrate interface roughness resulting in a change in the dielectric properties of this layer. This finding was verified with finite difference time-domain simulations where a similar trend was found for a model with an assumed thin air gap in this interface. In cyclic voltammetry measurements under illumination, a reduced overpotential by almost 400 mV for CO2 reduction and hydrogen evolution was found for LO-NIL samples.

Predicting Mechanical Properties of Metal Matrix Syntactic Foams Reinforced with Ceramic Spheres

DTIC Science & Technology

2012-01-01

predicting the properties of interest listed above. Kiser et al. [12] extended a metal foam model to account for ceramic reinforcement to predict the...Daoud A. J Alloys Compd. 2009; 487:618. 11. Drury WJ, Rickles SA, Sanders Jr TH, Cochran JK. In Light-Weight Alloys for Aerospace Applications, ed. Loe

High-harmonic generation by field enhanced femtosecond pulses in metal-sapphire nanostructure

PubMed Central

Han, Seunghwoi; Kim, Hyunwoong; Kim, Yong Woo; Kim, Young-Jin; Kim, Seungchul; Park, In-Yong; Kim, Seung-Woo

2016-01-01

Plasmonic high-harmonic generation (HHG) drew attention as a means of producing coherent extreme ultraviolet (EUV) radiation by taking advantage of field enhancement occurring in metallic nanostructures. Here a metal-sapphire nanostructure is devised to provide a solid tip as the HHG emitter, replacing commonly used gaseous atoms. The fabricated solid tip is made of monocrystalline sapphire surrounded by a gold thin-film layer, and intended to produce EUV harmonics by the inter- and intra-band oscillations of electrons driven by the incident laser. The metal-sapphire nanostructure enhances the incident laser field by means of surface plasmon polaritons, triggering HHG directly from moderate femtosecond pulses of ∼0.1 TW cm−2 intensities. The measured EUV spectra exhibit odd-order harmonics up to ∼60 nm wavelengths without the plasma atomic lines typically seen when using gaseous atoms as the HHG emitter. This experimental outcome confirms that the plasmonic HHG approach is a promising way to realize coherent EUV sources for nano-scale near-field applications in spectroscopy, microscopy, lithography and atto-second physics. PMID:27721374

Endurance of Damping Properties of Foam-Filled Tubes

PubMed Central

Strano, Matteo; Marra, Alessandro; Mussi, Valerio; Goletti, Massimo; Bocher, Philippe

2015-01-01

The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools. PMID:28793425

Endurance of Damping Properties of Foam-Filled Tubes.

PubMed

Strano, Matteo; Marra, Alessandro; Mussi, Valerio; Goletti, Massimo; Bocher, Philippe

2015-07-07

The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools.

Benzyl Alcohol-Mediated Versatile Method to Fabricate Nonstoichiometric Metal Oxide Nanostructures.

PubMed

Qamar, Mohammad; Adam, Alaaldin; Azad, Abdul-Majeed; Kim, Yong-Wah

2017-11-22

Nanostructured metal oxides with cationic or anionic deficiency find applications in a wide range of technological areas including the energy sector and environment. However, a facile route to prepare such materials in bulk with acceptable reproducibility is still lacking; many synthesis techniques are still only bench-top and cannot be easily scaled-up. Here, we report that the benzyl alcohol (BA)-mediated method is capable of producing a host of nanostructured metal oxides (MO x , where M = Ti, Zn, Ce, Sn, In, Ga, or Fe) with inherent nonstoichiometry. It employs multifunctional BA as a solvent, a reducing agent, and a structure-directing agent. Depending on the oxidation states of metal, elemental or nonstoichiometric oxide forms are obtained. Augmented photoelectrochemical oxidation of water under visible light by some of these nonstoichiometric oxides highlights the versatility of the BA-mediated synthesis protocol.

Nanopatterning the electronic properties of gold surfaces with self-organized superlattices of metallic nanostructures.

PubMed

Didiot, Clement; Pons, Stephane; Kierren, Bertrand; Fagot-Revurat, Yannick; Malterre, Daniel

2007-10-01

The self-organized growth of nanostructures on surfaces could offer many advantages in the development of new catalysts, electronic devices and magnetic data-storage media. The local density of electronic states on the surface at the relevant energy scale strongly influences chemical reactivity, as does the shape of the nanoparticles. The electronic properties of surfaces also influence the growth and decay of nanostructures such as dimers, chains and superlattices of atoms or noble metal islands. Controlling these properties on length scales shorter than the diffusion lengths of the electrons and spins (some tens of nanometres for metals) is a major goal in electronics and spintronics. However, to date, there have been few studies of the electronic properties of self-organized nanostructures. Here we report the self-organized growth of macroscopic superlattices of Ag or Cu nanostructures on Au vicinal surfaces, and demonstrate that the electronic properties of these systems depend on the balance between the confinement and the perturbation of the surface states caused by the steps and the nanostructures' superlattice. We also show that the local density of states can be modified in a controlled way by adjusting simple parameters such as the type of metal deposited and the degree of coverage.

The foamed structures in numerical testing

NASA Astrophysics Data System (ADS)

John, Antoni; John, Małgorzata

2018-01-01

In the paper numerical simulation of the foamed metal structures using numerical homogenization algorithm is prescribed. From the beginning, numerical model of heterogeneous porous simplified structures of typical foamed metal, based on the FEM was built and material parameters (coefficients of elasticity matrix of the considered structure) were determined with use of numerical homogenization algorithm. During the work the different RVE models of structure were created and their properties were compared at different relative density, different numbers and the size and structure of the arrangement of voids. Finally, obtained results were used in modeling of typical elements made from foam metals structures - sandwich structure and profile filled with metal foam. Simulation were performed for different dimensions of cladding and core. Additionally, the test of influence material orientation (arrangement of voids in RVE element) on the maximum stresses and displacement during bending test was performed.

Physical and Mechanical Properties of W-Ni-Fe-Co Metal Foam Modified by Titanium Tungsten Carbide Alloying

NASA Astrophysics Data System (ADS)

Ishchenko, A. N.; Tabachenko, A. N.; Afanas'eva, S. A.; Belov, N. N.; Biryukov, Yu. A.; Burkin, V. V.; D'yachkovskii, A. S.; Rogaev, K. S.; Skosyrskii, A. B.; Yugov, N. T.

2018-02-01

The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.

Optimal Design of Functionally Graded Metallic Foam Insulations

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.; Sankar, Bhavani; Venkataraman, Satchi; Zhu, Huadong

2002-01-01

The focus of our work has been on developing an insight into the physics that govern the optimum design of thermal insulation for use in thermal protection systems of launch vehicle. Of particular interest was to obtain optimality criteria for designing foam insulations that have density (or porosity) distributions through the thickness for optimum thermal performance. We investigate the optimum design of functionally graded thermal insulation for steady state heat transfer through the foam. We showed that the heat transfer in the foam has competing modes, of radiation and conduction. The problem assumed a fixed inside temperature of 400 K and varied the aerodynamic surface heating on the outside surface from 0.2 to 1.0 MW/sq m. The thermal insulation develops a high temperature gradient through the thickness. Investigation of the model developed for heat conduction in foams showed that at high temperatures (as on outside wall) intracellular radiation dominates the heat transfer in the foam. Minimizing radiation requires reducing the pore size, which increases the density of the foam. At low temperatures (as on the inside wall), intracellular conduction (of the metal and air) dominates the heat transfer. Minimizing conduction requires increasing the pore size. This indicated that for every temperature there was an optimum value of density that minimized the heat transfer coefficient. Two optimization studies were performed. One was to minimize the heat transmitted though a fixed thickness insulation by varying density profiles. The second was to obtain the minimum mass insulation for specified thickness. Analytical optimality criteria were derived for the cases considered. The optimality condition for minimum heat transfer required that at each temperature we find the density that minimizes the heat transfer coefficient. Once a relationship between the optimum heat transfer coefficient and the temperature was found, the design problem reduced to the solution of a

An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation

NASA Astrophysics Data System (ADS)

Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard

2014-03-01

Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.

Effects of process parameters on properties of porous foams formed by laser-assisted melting of steel powder (AISI P21)/foaming agent (ZrH2) mixture

NASA Astrophysics Data System (ADS)

Seo, Ja-Ye; Lee, Ki-Yong; Shim, Do-Sik

2018-01-01

This paper describes the fabrication of lightweight metal foams using the directed energy deposition (DED) method. DED is a highly flexible additive manufacturing process wherein a metal powder mixed with a foaming agent is sprayed while a high-power laser is used to simultaneously melt the powder mixture into layered metal foams. In this study, a mixture of a carbon steel material (P21 powder) and a widely used foaming agent, ZrH2, is used to fabricate metal foams. The effects of various process parameters, such as the laser power, powder feed rate, powder gas flow rate, and scanning speed, on the deposition characteristics (porosity, pore size, and pore distribution) are investigated. The synthesized metal foams exhibit porosities of 10% or lower, and a mean pore area of 7 × 105 μm2. It is observed that the degree of foaming increases in proportion to the laser power to a certain extent. The results also show that the powder feed rate has the most pronounced effect on the porosity of the metal foams, while the powder gas flow rate is the most suitable parameter for adjusting the size of the pores formed within the foams. Further, the scanning speed, which determines the amounts of energy and powder delivered, has a significant effect on the height of the deposits as well as on the properties of the foams. Thus, during the DED process for fabricating metal foams, the pore size and distribution and hence the foam porosity can be tailored by varying the individual process parameters. These findings should be useful as reference data for the design of processes for fabricating porous metallic materials that meet the specific requirements for specialized parts.

Commercial Applications of Metal Foams: Their Properties and Production

PubMed Central

García-Moreno, Francisco

2016-01-01

This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector. PMID:28787887

Metal-Organic-Framework-Derived Carbon Nanostructure Augmented Sonodynamic Cancer Therapy.

PubMed

Pan, Xueting; Bai, Lixin; Wang, Hui; Wu, Qingyuan; Wang, Hongyu; Liu, Shuang; Xu, Bolong; Shi, Xinghua; Liu, Huiyu

2018-06-01

Sonodynamic therapy (SDT) can overcome the critical issue of depth-penetration barrier of photo-triggered therapeutic modalities. However, the discovery of sonosensitizers with high sonosensitization efficacy and good stability is still a significant challenge. In this study, the great potential of a metal-organic-framework (MOF)-derived carbon nanostructure that contains porphyrin-like metal centers (PMCS) to act as an excellent sonosensitizer is identified. Excitingly, the superior sonosensitization effect of PMCS is believed to be closely linked to the porphyrin-like macrocycle in MOF-derived nanostructure in comparison to amorphous carbon nanospheres, due to their large highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap for high reactive oxygen species (ROS) production. The nanoparticle-assisted cavitation process, including the visualized formation of the cavitation bubbles and microjets, is also first captured by high-speed camera. High ROS production in PMCS under ultrasound is validated by electron spin resonance and dye measurement, followed by cellular destruction and high tumor inhibition efficiency (85%). This knowledge is important from the perspective of understanding the structure-dependent SDT enhancement of a MOF-derived carbon nanostructure. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures.

PubMed

Fang, Jixiang; Zhang, Lingling; Li, Jiang; Lu, Lu; Ma, Chuansheng; Cheng, Shaodong; Li, Zhiyuan; Xiong, Qihua; You, Hongjun

2018-02-06

Metal species have a relatively high mobility inside mesoporous silica; thus, it is difficult to introduce the metal precursors into silica mesopores and suppress the migration of metal species during a reduction process. Therefore, until now, the controlled growth of metal nanocrystals in a confined space, i.e., mesoporous channels, has been very challenging. Here, by using a soft-enveloping reaction at the interfaces of the solid, liquid, and solution phases, we successfully control the growth of metallic nanocrystals inside a mesoporous silica template. Diverse monodispersed nanostructures with well-defined sizes and shapes, including Ag nanowires, 3D mesoporous Au, AuAg alloys, Pt networks, and Au nanoparticle superlattices are successfully obtained. The 3D mesoporous AuAg networks exhibit enhanced catalytic activities in an electrochemical methanol oxidation reaction. The current soft-enveloping synthetic strategy offers a robust approach to synthesize diverse mesoporous metal nanostructures that can be utilized in catalysis, optics, and biomedicine applications.

Orbital foamed material extruder

NASA Technical Reports Server (NTRS)

Tucker, Dennis S. (Inventor)

2009-01-01

This invention is a process for producing foamed material in space comprising the steps of: rotating the material to simulate the force of gravity; heating the rotating material until it is molten; extruding the rotating, molten material; injecting gas into the extruded, rotating, molten material to produce molten foamed material; allowing the molten foamed material to cool to below melting temperature to produce the foamed material. The surface of the extruded foam may be heated to above melting temperature and allowed to cool to below melting temperature. The extruded foam may also be cut to predetermined length. The starting material may be metal or glass. Heating may be accomplished by electrical heating elements or by solar heating.

Shrinkage deformation of cement foam concrete

NASA Astrophysics Data System (ADS)

Kudyakov, A. I.; Steshenko, A. B.

2015-01-01

The article presents the results of research of dispersion-reinforced cement foam concrete with chrysotile asbestos fibers. The goal was to study the patterns of influence of chrysotile asbestos fibers on drying shrinkage deformation of cement foam concrete of natural hardening. The chrysotile asbestos fiber contains cylindrical fiber shaped particles with a diameter of 0.55 micron to 8 microns, which are composed of nanostructures of the same form with diameters up to 55 nm and length up to 22 microns. Taking into account the wall thickness, effective reinforcement can be achieved only by microtube foam materials, the so- called carbon nanotubes, the dimensions of which are of power less that the wall pore diameter. The presence of not reinforced foam concrete pores with perforated walls causes a decrease in its strength, decreases the mechanical properties of the investigated material and increases its shrinkage. The microstructure investigation results have shown that introduction of chrysotile asbestos fibers in an amount of 2 % by weight of cement provides the finely porous foam concrete structure with more uniform size closed pores, which are uniformly distributed over the volume. This reduces the shrinkage deformation of foam concrete by 50%.

Incredible antibacterial activity of noble metal functionalized magnetic core-zeolitic shell nanostructures.

PubMed

Padervand, M; Janatrostami, S; Karanji, A Kiani; Gholami, M R

2014-02-01

Functionalized magnetic core-zeolitic shell nanostructures were prepared by hydrothermal and coprecipitation methods. The products were characterized by Vibrating Sample Magnetometer (VSM), X-ray powder diffraction (XRD), Fourier Transform Infrared (FTIR) spectra, nitrogen adsorption-desorption isotherms, and Transmission Electron Microscopy (TEM). The growth of mordenite nanoparticles on the surface of silica coated nickel ferrite nanoparticles in the presence of organic templates was also confirmed. Antibacterial activity of the prepared nanostructures was investigated by the inactivation of Escherichia coli as a gram negative bacterium. A new mechanism was proposed for inactivation of E. coli over the prepared samples. In addition, the Minimum Inhibitory Concentration (MIC) and reuse ability were studied. TEM images of the destroyed cell wall after the treatment time were performed to illustrate the inactivation mechanism. According to the experimental results, the core-shell nanostructures which were modified by organic agents and then functionalized with noble metal nanoparticles were the most active. The interaction of the noble metals with the organic components on the surface of nanostructures was studied theoretically and the obtained results were used to interpret the experimental results. © 2013. Published by Elsevier B.V. All rights reserved.

Quantum dot behavior in transition metal dichalcogenides nanostructures

NASA Astrophysics Data System (ADS)

Luo, Gang; Zhang, Zhuo-Zhi; Li, Hai-Ou; Song, Xiang-Xiang; Deng, Guang-Wei; Cao, Gang; Xiao, Ming; Guo, Guo-Ping

2017-08-01

Recently, transition metal dichalcogenides (TMDCs) semiconductors have been utilized for investigating quantum phenomena because of their unique band structures and novel electronic properties. In a quantum dot (QD), electrons are confined in all lateral dimensions, offering the possibility for detailed investigation and controlled manipulation of individual quantum systems. Beyond the definition of graphene QDs by opening an energy gap in nanoconstrictions, with the presence of a bandgap, gate-defined QDs can be achieved on TMDCs semiconductors. In this paper, we review the confinement and transport of QDs in TMDCs nanostructures. The fabrication techniques for demonstrating two-dimensional (2D) materials nanostructures such as field-effect transistors and QDs, mainly based on e-beam lithography and transfer assembly techniques are discussed. Subsequently, we focus on electron transport through TMDCs nanostructures and QDs. With steady improvement in nanoscale materials characterization and using graphene as a springboard, 2D materials offer a platform that allows creation of heterostructure QDs integrated with a variety of crystals, each of which has entirely unique physical properties.

How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics

PubMed Central

De Schampheleire, Sven; De Jaeger, Peter; De Kerpel, Kathleen; Ameel, Bernd; Huisseune, Henk; De Paepe, Michel

2016-01-01

This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. PMID:28787894

Building one-dimensional oxide nanostructure arrays on conductive metal substrates for lithium-ion battery anodes.

PubMed

Jiang, Jian; Li, Yuanyuan; Liu, Jinping; Huang, Xintang

2011-01-01

Lithium ion battery (LIB) is potentially one of the most attractive energy storage devices. To meet the demands of future high-power and high-energy density requirements in both thin-film microbatteries and conventional batteries, it is challenging to explore novel nanostructured anode materials instead of conventional graphite. Compared to traditional electrodes based on nanostructure powder paste, directly grown ordered nanostructure array electrodes not only simplify the electrode processing, but also offer remarkable advantages such as fast electron transport/collection and ion diffusion, sufficient electrochemical reaction of individual nanostructures, enhanced material-electrolyte contact area and facile accommodation of the strains caused by lithium intercalation and de-intercalation. This article provides a brief overview of the present status in the area of LIB anodes based on one-dimensional nanostructure arrays growing directly on conductive inert metal substrates, with particular attention to metal oxides synthesized by an anodized alumina membrane (AAM)-free solution-based or hydrothermal methods. Both the scientific developments and the techniques and challenges are critically analyzed.

Drag reduction using metallic engineered surfaces with highly ordered hierarchical topographies: nanostructures on micro-riblets

NASA Astrophysics Data System (ADS)

Kim, Taekyung; Shin, Ryung; Jung, Myungki; Lee, Jinhyung; Park, Changsu; Kang, Shinill

2016-03-01

Durable drag-reduction surfaces have recently received much attention, due to energy-saving and power-consumption issues associated with harsh environment applications, such as those experienced by piping infrastructure, ships, aviation, underwater vehicles, and high-speed ground vehicles. In this study, a durable, metallic surface with highly ordered hierarchical structures was used to enhance drag-reduction properties, by combining two passive drag-reduction strategies: an air-layer effect induced by nanostructures and secondary vortex generation by micro-riblet structures. The nanostructures and micro-riblet structures were designed to increase slip length. The top-down fabrication method used to form the metallic hierarchical structures combined laser interference lithography, photolithography, thermal reflow, nanoimprinting, and pulse-reverse-current electrochemical deposition. The surfaces were formed from nickel, which has high hardness and corrosion resistance, making it suitable for use in harsh environments. The drag-reduction properties of various metal surfaces were investigated based on the surface structure: a bare surface, a nanostructured surface, a micro-riblet surface, and a hierarchically structured surface of nanostructures on micro-riblets.

Strain compatibility tests for sprayed foam cryogenic insulation

NASA Technical Reports Server (NTRS)

Hill, W. L.; Kimberlin, D. O.

1970-01-01

Mechanical stress applied to foam-coated aluminum alloy specimens maintained at cryogenic temperature simulates actual use conditions of the foam insulation. The testing reveals defects in the polyurethane foam or in the foam to metal bond.

Metal oxide nanostructures for gas detection

NASA Astrophysics Data System (ADS)

Maziarz, Wojciech; Pisarkiewicz, Tadeusz; Rydosz, Artur; Wysocka, Kinga; Czyrnek, Grzegorz

2013-07-01

Currently, most of gas sensors on the market are produced in thin or thick film technologies with the use of ceramic substrates. It is expected that the miniature sensors needed in portable applications will be based on one-dimensional structures due to their low power consumption, fast and stable time response, small dimensions and possibility of embedding in integrated circuit together with signal conditioning electronics. The authors manufactured resistance type gas sensors based on ZnO and WO3 nanostructures. ZnO:Al nanorods with good cristallinity were obtained with electrodeposition method, while ZnO:Al nanofibres with varying diameters were obtained by electrospinning method. The sensors were built as a nanowire network. WO3 films with nanocrystalline surface were manufactured by deposition of a three layer WO3/W/WO3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. In effect a uniform nanostructurized metal oxide layer was formed. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional conductometric type sensors.

Porous Media Approach for Modeling Closed Cell Foam

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.

2006-01-01

In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is

High Sensitivity Gas Detection Using a Macroscopic Three-Dimensional Graphene Foam Network

PubMed Central

Yavari, Fazel; Chen, Zongping; Thomas, Abhay V.; Ren, Wencai; Cheng, Hui-Ming; Koratkar, Nikhil

2011-01-01

Nanostructures are known to be exquisitely sensitive to the chemical environment and offer ultra-high sensitivity for gas-sensing. However, the fabrication and operation of devices that use individual nanostructures for sensing is complex, expensive and suffers from poor reliability due to contamination and large variability from sample-to-sample. By contrast, conventional solid-state and conducting-polymer sensors offer excellent reliability but suffer from reduced sensitivity at room-temperature. Here we report a macro graphene foam-like three-dimensional network which combines the best of both worlds. The walls of the foam are comprised of few-layer graphene sheets resulting in high sensitivity; we demonstrate parts-per-million level detection of NH3 and NO2 in air at room-temperature. Further, the foam is a mechanically robust and flexible macro-scale network that is easy to contact (without Lithography) and can rival the durability and affordability of traditional sensors. Moreover, Joule-heating expels chemisorbed molecules from the foam's surface leading to fully-reversible and low-power operation. PMID:22355681

Emerging Science and Research Opportunities for Metals and Metallic Nanostructures: A Report on the NSF MMN Workshop

NASA Astrophysics Data System (ADS)

Pollock, Tresa; Handwerker, Carol

In the next decade, fundamental research in metals and metallic nanostructures (MMN) has the potential to continue to transform science into innovative materials, devices, and systems. This talk summarizes the findings of a workshop to identify emerging and potentially transformative research areas in MMN. The metals and metallic nanostructures (MMNs) workshop aimed to identify significant research trends, scientific fundamentals, and recent breakthroughs that can enable new or enhanced MMN performance, either alone or in a more complex materials system, for a wide range of applications. Additionally, the role that MMN research can play in high-priority research and development (R&D) areas such as the U.S. Materials Genome Initiative, the National Nanotechnology Initiative, the Advanced Manufacturing Initiative, and other similar initiatives that exist internationally was assessed. The workshop also addressed critical issues related to materials research instrumentation and the cyberinfrastructure for materials science research and education, as well as science, technology, engineering, and mathematics (STEM) workforce development, with emphasis on the United States but with an appreciation that similar challenges and opportunities for the materials community exist internationally.

Do dielectric nanostructures turn metallic in high-electric dc fields?

PubMed

Silaeva, E P; Arnoldi, L; Karahka, M L; Deconihout, B; Menand, A; Kreuzer, H J; Vella, A

2014-11-12

Three-dimensional dielectric nanostructures have been analyzed using field ion microscopy (FIM) to study the electric dc field penetration inside these structures. The field is proved to be screened within a few nanometers as theoretically calculated taking into account the high-field impact ionization process. Moreover, the strong dc field of the order of 0.1 V/Å at the surface inside a dielectric nanostructure modifies its band structure leading to a strong band gap shrinkage and thus to a strong metal-like optical absorption near the surface. This metal-like behavior was theoretically predicted using first-principle calculations and experimentally proved using laser-assisted atom probe tomography (APT). This work opens up interesting perspectives for the study of the performance of all field-effect nanodevices, such as nanotransistor or super capacitor, and for the understanding of the physical mechanisms of field evaporation of dielectric nanotips in APT.

Chemically Modified Metal Oxide Nanostructure for Photoelectrochemical Water Splitting

NASA Astrophysics Data System (ADS)

Wang, Gongming

Hydrogen gas is chemical fuel with high energy density, and represents a clean, renewable and carbon-free burning fuel, which has the potential to solve the more and more urgent energy crisis in today's society. Inspired by natural photosynthesis, artificial photosynthesis to generate hydrogen energy has attracted a lot of attentions in the field of chemistry, physics and material. Photoelectrochemical water splitting based on semiconductors represents a green and low cost method to generate hydrogen fuel. However, the current overall efficiency of solar to hydrogen is quite low, due to some intrinsic limitations such as bandgap, diffusion distance, carrier lifetime and photostability of semiconductors. Although nanostructured semiconductors can improve their photoelectrochemical water splitting performance to some extent, by increasing electrolyte accessible area and shortening minority carrier diffusion distance, nanostructure engineering cannot change their intrinsic electronic properties. Recent development in chemically modified nanostructures such as surface catalyst decoration, element doping, plasmonic modification and interfacial hetero-junction design have led to significant advancement in the photoelectrochemical water splitting, by improving surface reaction kinetics and charge separation, transportation and collection efficiency. In this thesis, I will give a detailed discussion on the chemically modified metal oxide nanostructures for photoelectrocemical hydrogen generation, with a focus on the element doping, hydrogen treatment and catalyst modification. I have demonstrated nitrogen doping on ZnO and Ti doping on hematite can improve their photoelectrochemical performance. In addition, we found hydrogen treatment is a general and effective method to improve the photocatalytic performance, by increasing their carrier desities. Hydrogen treatment has been demonstrated on TiO2, WO3 and BiVO4. In the end, we also used electrochemical catalyt to modify

The control of ultrasonic transmission by the metamaterials structure of electrorheological fluid and metal foam

NASA Astrophysics Data System (ADS)

Li, Linlin; Wang, Mingzhong; Wang, Jiahui; Zhao, Xiaopeng

2017-11-01

A metamaterial structure formed by foamed metal and starch and oil-based electrorheological (ER) fluid is designed in this paper. Experiments show that the metamaterial structure exhibits a regulation effect on the amplitude and phase of the transmitted waves of 35-80 kHz ultra-wideband ultrasonic waves in water. With the increase of the electric field, the transmission amplitude and phase of the ultrasonic wave increases, whereas the control ability of the same gradient electric field decreases. The amplitude of the transmission controlled by the metamaterial structure and electric field increases at first, and then decreases with the increase in volume fraction of the ER fluid. Thus, it is thought that the interaction between the microstructure produced by the rheological properties of the ER fluid and the porous foam metal affects the propagation of the acoustic wave.

Soft Nanoimprint Lithography for Direct Printing of Crystalline Metal Oxide Nanostructures

NASA Astrophysics Data System (ADS)

Kothari, Rohit; Beaulieu, Michael; Watkins, James

2015-03-01

We demonstrate a solution-based soft nanoimprint lithography technique to directly print dimensionally-stable crystalline metal oxide nanostructures. A patterned PDMS stamp is used in combination with a UV/thermal cure step to imprint a resist containing high concentrations of crystalline nanoparticles in an inorganic/organic binder phase. The as-imprinted nanostructures are highly crystalline and therefore undergo little shrinkage (less than 5% in some cases) upon thermal annealing. High aspect ratio nanostructures and sub-100 nm features are easily realized. Residual layer free direct imprinting (no etching) was achieved by choosing the resist with the appropriate surface energy to ensure dewetting at stamp-substrate interface. The technique was further extended to stack the nanostructures by deploying a layer-by-layer imprint strategy. The method is scalable and can produce large area device quality nanostructures in a rapid fashion at a low cost. CeO2, ITO and TiO2 nanopatterns are illustrated for their potential use in fuel cell electrodes, solar cell electrodes and photonic devices, respectively.

Hybrid Deployable Foam Antennas and Reflectors

NASA Technical Reports Server (NTRS)

Rivellini, Tommaso; Willis, Paul; Hodges, Richard; Spitz, Suzanne

2006-01-01

Hybrid deployable radio antennas and reflectors of a proposed type would feature rigid narrower apertures plus wider adjoining apertures comprising reflective surfaces supported by open-cell polymeric foam structures (see figure). The open-cell foam structure of such an antenna would be compressed for compact stowage during transport. To initiate deployment of the antenna, the foam structure would simply be released from its stowage mechanical restraint. The elasticity of the foam would drive the expansion of the foam structure to its full size and shape. There are several alternatives for fabricating a reflective surface supported by a polymeric foam structure. One approach would be to coat the foam with a metal. Another approach would be to attach a metal film or a metal-coated polymeric membrane to the foam. Yet another approach would be to attach a metal mesh to the foam. The hybrid antenna design and deployment concept as proposed offers significant advantages over other concepts for deployable antennas: 1) In the unlikely event of failure to deploy, the rigid narrow portion of the antenna would still function, providing a minimum level of assured performance. In contrast, most other concepts for deploying a large antenna from compact stowage are of an "all or nothing" nature: the antenna is not useful at all until and unless it is fully deployed. 2) Stowage and deployment would not depend on complex mechanisms or actuators, nor would it involve the use of inflatable structures. Therefore, relative to antennas deployed by use of mechanisms, actuators, or inflation systems, this antenna could be lighter, cheaper, amenable to stowage in a smaller volume, and more reliable. An open-cell polymeric (e.g., polyurethane) foam offers several advantages for use as a compressible/expandable structural material to support a large antenna or reflector aperture. A few of these advantages are the following: 3) The open cellular structure is amenable to compression to a very

Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

NASA Astrophysics Data System (ADS)

Sapkota, Keshab R.

Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

Headgroup interactions and ion flotation efficiency in mixtures of a chelating surfactant, different foaming agents, and divalent metal ions.

PubMed

Svanedal, Ida; Boija, Susanne; Norgren, Magnus; Edlund, Håkan

2014-06-10

The correlation between interaction parameters and ion flotation efficiency in mixtures of chelating surfactant metal complexes and different foaming agents was investigated. We have recently shown that chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) forms strong coordination complexes with divalent metal ions, and this can be utilized in ion flotation. Interaction parameters for mixed micelles and mixed monolayer formation for Mg(2+) and Ni(2+) complexes with the chelating surfactant 4-C12-DTPA and different foaming agents were calculated by Rubingh's regular solution theory. Parameters for the calculations were extracted from surface tension measurements and NMR diffusometry. The effects of metal ion coordination on the interactions between 4-C12-DTPA and the foaming agents could be linked to a previously established difference in coordination chemistry between the examined metal ions. As can be expected from mixtures of amphoteric surfactants, the interactions were strongly pH-dependent. Strong correlation was found between interaction parameter β(σ) for mixed monolayer formation and the phase-transfer efficiency of Ni(2+) complexes with 4-C12-DTPA during flotation in a customized flotation cell. In a mixture of Cu(2+) and Zn(2+), the significant difference in conditional stability constants (log K) between the metal complexes was utilized to selectively recover the metal complex with the highest log K (Cu(2+)) by ion flotation. Flotation experiments in an excess concentration of metal ions confirmed the coordination of more than one metal ion to the headgroup of 4-C12-DTPA.

Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures

PubMed Central

Huang, Jin; Wan, Qing

2009-01-01

This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. PMID:22303154

Enthalpy-based multiple-relaxation-time lattice Boltzmann method for solid-liquid phase-change heat transfer in metal foams.

PubMed

Liu, Qing; He, Ya-Ling; Li, Qing

2017-08-01

In this paper, an enthalpy-based multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed for solid-liquid phase-change heat transfer in metal foams under the local thermal nonequilibrium (LTNE) condition. The enthalpy-based MRT-LB method consists of three different MRT-LB models: one for flow field based on the generalized non-Darcy model, and the other two for phase-change material (PCM) and metal-foam temperature fields described by the LTNE model. The moving solid-liquid phase interface is implicitly tracked through the liquid fraction, which is simultaneously obtained when the energy equations of PCM and metal foam are solved. The present method has several distinctive features. First, as compared with previous studies, the present method avoids the iteration procedure; thus it retains the inherent merits of the standard LB method and is superior to the iteration method in terms of accuracy and computational efficiency. Second, a volumetric LB scheme instead of the bounce-back scheme is employed to realize the no-slip velocity condition in the interface and solid phase regions, which is consistent with the actual situation. Last but not least, the MRT collision model is employed, and with additional degrees of freedom, it has the ability to reduce the numerical diffusion across the phase interface induced by solid-liquid phase change. Numerical tests demonstrate that the present method can serve as an accurate and efficient numerical tool for studying metal-foam enhanced solid-liquid phase-change heat transfer in latent heat storage. Finally, comparisons and discussions are made to offer useful information for practical applications of the present method.

Enthalpy-based multiple-relaxation-time lattice Boltzmann method for solid-liquid phase-change heat transfer in metal foams

NASA Astrophysics Data System (ADS)

Liu, Qing; He, Ya-Ling; Li, Qing

2017-08-01

In this paper, an enthalpy-based multiple-relaxation-time (MRT) lattice Boltzmann (LB) method is developed for solid-liquid phase-change heat transfer in metal foams under the local thermal nonequilibrium (LTNE) condition. The enthalpy-based MRT-LB method consists of three different MRT-LB models: one for flow field based on the generalized non-Darcy model, and the other two for phase-change material (PCM) and metal-foam temperature fields described by the LTNE model. The moving solid-liquid phase interface is implicitly tracked through the liquid fraction, which is simultaneously obtained when the energy equations of PCM and metal foam are solved. The present method has several distinctive features. First, as compared with previous studies, the present method avoids the iteration procedure; thus it retains the inherent merits of the standard LB method and is superior to the iteration method in terms of accuracy and computational efficiency. Second, a volumetric LB scheme instead of the bounce-back scheme is employed to realize the no-slip velocity condition in the interface and solid phase regions, which is consistent with the actual situation. Last but not least, the MRT collision model is employed, and with additional degrees of freedom, it has the ability to reduce the numerical diffusion across the phase interface induced by solid-liquid phase change. Numerical tests demonstrate that the present method can serve as an accurate and efficient numerical tool for studying metal-foam enhanced solid-liquid phase-change heat transfer in latent heat storage. Finally, comparisons and discussions are made to offer useful information for practical applications of the present method.

On the size-dependent magnetism and all-optical magnetization switching of transition-metal silicide nanostructures

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

Glushkov, G. I.; Tuchin, A. V.; Popov, S. V.

Theoretical investigations of the electronic structure, synthesis, and all-optical magnetization switching of transition-metal silicide nanostructures are reported. The magnetic moment of the nanostructures is studied as a function of the silicide cluster size and configuration. The experimentally demonstrated magnetization switching of nanostructured nickel silicide by circularly polarized light makes it possible to create high-speed storage devices with high density data recording.

Self-organized synthesis of silver dendritic nanostructures via an electroless metal deposition method

NASA Astrophysics Data System (ADS)

Qiu, T.; Wu, X. L.; Mei, Y. F.; Chu, P. K.; Siu, G. G.

2005-09-01

Unique silver dendritic nanostructures, with stems, branches, and leaves, were synthesized with self-organization via a simple electroless metal deposition method in a conventional autoclave containing aqueous HF and AgNO3 solution. Their growth mechanisms are discussed in detail on the basis of a self-assembled localized microscopic electrochemical cell model. A process of diffusion-limited aggregation is suggested for the formation of the silver dendritic nanostructures. This nanostructured material is of great potential to be building blocks for assembling mini-functional devices of the next generation.

The Process of Nanostructuring of Metal (Iron) Matrix in Composite Materials for Directional Control of the Mechanical Properties

PubMed Central

Zemtsova, Elena

2014-01-01

We justified theoretical and experimental bases of synthesis of new class of highly nanostructured composite nanomaterials based on metal matrix with titanium carbide nanowires as dispersed phase. A new combined method for obtaining of metal iron-based composite materials comprising the powder metallurgy processes and the surface design of the dispersed phase is considered. The following stages of material synthesis are investigated: (1) preparation of porous metal matrix; (2) surface structuring of the porous metal matrix by TiC nanowires; (3) pressing and sintering to give solid metal composite nanostructured materials based on iron with TiC nanostructures with size 1–50 nm. This material can be represented as the material type “frame in the frame” that represents iron metal frame reinforcing the frame of different chemical compositions based on TiC. Study of material functional properties showed that the mechanical properties of composite materials based on iron with TiC dispersed phase despite the presence of residual porosity are comparable to the properties of the best grades of steel containing expensive dopants and obtained by molding. This will solve the problem of developing a new generation of nanostructured metal (iron-based) materials with improved mechanical properties for the different areas of technology. PMID:24695459

The process of nanostructuring of metal (iron) matrix in composite materials for directional control of the mechanical properties.

PubMed

Zemtsova, Elena; Yurchuk, Denis; Smirnov, Vladimir

2014-01-01

We justified theoretical and experimental bases of synthesis of new class of highly nanostructured composite nanomaterials based on metal matrix with titanium carbide nanowires as dispersed phase. A new combined method for obtaining of metal iron-based composite materials comprising the powder metallurgy processes and the surface design of the dispersed phase is considered. The following stages of material synthesis are investigated: (1) preparation of porous metal matrix; (2) surface structuring of the porous metal matrix by TiC nanowires; (3) pressing and sintering to give solid metal composite nanostructured materials based on iron with TiC nanostructures with size 1-50 nm. This material can be represented as the material type "frame in the frame" that represents iron metal frame reinforcing the frame of different chemical compositions based on TiC. Study of material functional properties showed that the mechanical properties of composite materials based on iron with TiC dispersed phase despite the presence of residual porosity are comparable to the properties of the best grades of steel containing expensive dopants and obtained by molding. This will solve the problem of developing a new generation of nanostructured metal (iron-based) materials with improved mechanical properties for the different areas of technology.

Inverse metal-assisted chemical etching produces smooth high aspect ratio InP nanostructures.

PubMed

Kim, Seung Hyun; Mohseni, Parsian K; Song, Yi; Ishihara, Tatsumi; Li, Xiuling

2015-01-14

Creating high aspect ratio (AR) nanostructures by top-down fabrication without surface damage remains challenging for III-V semiconductors. Here, we demonstrate uniform, array-based InP nanostructures with lateral dimensions as small as sub-20 nm and AR > 35 using inverse metal-assisted chemical etching (I-MacEtch) in hydrogen peroxide (H2O2) and sulfuric acid (H2SO4), a purely solution-based yet anisotropic etching method. The mechanism of I-MacEtch, in contrast to regular MacEtch, is explored through surface characterization. Unique to I-MacEtch, the sidewall etching profile is remarkably smooth, independent of metal pattern edge roughness. The capability of this simple method to create various InP nanostructures, including high AR fins, can potentially enable the aggressive scaling of InP based transistors and optoelectronic devices with better performance and at lower cost than conventional etching methods.

A review on chemiresistive room temperature gas sensors based on metal oxide nanostructures, graphene and 2D transition metal dichalcogenides.

PubMed

Joshi, Nirav; Hayasaka, Takeshi; Liu, Yumeng; Liu, Huiliang; Oliveira, Osvaldo N; Lin, Liwei

2018-03-10

Room-temperature (RT) gas sensing is desirable for battery-powered or self-powered instrumentation that can monitor emissions associated with pollution and industrial processes. This review (with 171 references) discusses recent advances in three types of porous nanostructures that have shown remarkable potential for RT gas sensing. The first group comprises hierarchical oxide nanostructures (mainly oxides of Sn, Ni, Zn, W, In, La, Fe, Co). The second group comprises graphene and its derivatives (graphene, graphene oxides, reduced graphene oxides, and their composites with metal oxides and noble metals). The third group comprises 2D transition metal dichalcogenides (mainly sulfides of Mo, W, Sn, Ni, also in combination with metal oxides). They all have been found to enable RT sensing of gases such as NOx, NH 3 , H 2 , SO 2 , CO, and of vapors such as of acetone, formaldehyde or methanol. Attractive features also include high selectivity and sensitivity, long-term stability and affordable costs. Strengths and limitations of these materials are highlighted, and prospects with respect to the development of new materials to overcome existing limitations are discussed. Graphical Abstract The review summarizes the most significant progresses related to room temperature gas sensing by using hierarchical oxide nanostructures, graphene and its derivatives and 2D transition metal dichalcogenides, highlighting the peculiar gas sensing behavior with enhanced selectivity, sensitivity and long-term stability.

ε-MnO2 nanostructures directly grown on Ni foam: a cathode catalyst for rechargeable Li-O2 batteries.

PubMed

Hu, Xiaofei; Han, Xiaopeng; Hu, Yuxiang; Cheng, Fangyi; Chen, Jun

2014-04-07

A sponge-like ε-MnO2 nanostructure was synthesized by direct growth of ε-MnO2 on Ni foam through a facile electrodeposition route. When applied as a self-supporting, binder-free cathode material for rechargeable nonaqueous lithium-oxygen batteries, the ε-MnO2/Ni electrode exhibits considerable high-rate capability (discharge capacity of ∼6300 mA h g(-1) at a current density of 500 mA g(-1)) and enhanced cyclability (exceeding 120 cycles) without controlling the discharge depth. The superior performance is proposed to be associated with the 3D nanoporous structures and abundant oxygen defects as well as the absence of side reactions related to carbon-based conductive additives and binders.

3D porous and ultralight carbon hybrid nanostructure fabricated from carbon foam covered by monolayer of nitrogen-doped carbon nanotubes for high performance supercapacitors

NASA Astrophysics Data System (ADS)

He, Shuijian; Hou, Haoqing; Chen, Wei

2015-04-01

3D porous and self-supported carbon hybrids are promising electrode materials for supercapacitor application attributed to their prominent properties such as binder-free electrode fabrication process, excellent electric conductivity and high power density etc. We present here a facile chemical vapor deposition method to fabricate a novel 3D flexible carbon hybrid nanostructure by growing a monolayer of nitrogen-doped carbon nanotubes on the skeleton of carbon foam (N-CNTs/CF) with Fe nanoparticle as catalyst. With such 3D porous, flexible and ultralight carbon nanostructure as binder-free electrode material, large surface area is available and fast ionic transport is facilitated. Moreover, the carbon-based network can provide excellent electronic conductivity. The electrochemical studies demonstrate that the supercapacitor constructed from the N-CNTs/CF hybrid exhibit high power density of 69.3 kW kg-1 and good stability with capacitance retention ration above 95% after cycled at 50 A g-1 for 5000 cycles. Therefore, the prepared porous N-CNTs/CF nanostructure is expected to be a type of excellent electrode material for electrical double layer capacitors.

A Thrombus Generation Model Applied to Aneurysms Treated with Shape Memory Polymer Foam and Metal Coils

NASA Astrophysics Data System (ADS)

Horn, John; Ortega, Jason; Hartman, Jonathan; Maitland, Duncan

2015-11-01

To prevent their rupture, intracranial aneurysms are often treated with endovascular metal coils which fill the aneurysm sac and isolate it from the arterial flow. Despite its widespread use, this method can result in suboptimal outcomes leading to aneurysm recurrence. Recently, shape memory polymer foam has been proposed as an alternative aneurysm filler. In this work, a computational model has been developed to predict thrombus formation in blood in response to such cardiovascular implantable devices. The model couples biofluid and biochemical phenomena present as the blood interacts with a device and stimulates thrombus formation. This model is applied to simulations of both metal coil and shape memory polymer foam treatments within an idealized 2D aneurysm geometry. Using the predicted thrombus responses, the performance of these treatments is evaluated and compared. The results suggest that foam-treated aneurysms may fill more quickly and more completely with thrombus than coil-filled aneurysms, potentially leading to improved long-term aneurysm healing. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Multidimensional Anodized Titanium Foam Photoelectrode for Efficient Utilization of Photons in Mesoscopic Solar Cells.

PubMed

Kang, Jin Soo; Choi, Hyelim; Kim, Jin; Park, Hyeji; Kim, Jae-Yup; Choi, Jung-Woo; Yu, Seung-Ho; Lee, Kyung Jae; Kang, Yun Sik; Park, Sun Ha; Cho, Yong-Hun; Yum, Jun-Ho; Dunand, David C; Choe, Heeman; Sung, Yung-Eun

2017-09-01

Mesoscopic solar cells based on nanostructured oxide semiconductors are considered as a promising candidates to replace conventional photovoltaics employing costly materials. However, their overall performances are below the sufficient level required for practical usages. Herein, this study proposes an anodized Ti foam (ATF) with multidimensional and hierarchical architecture as a highly efficient photoelectrode for the generation of a large photocurrent. ATF photoelectrodes prepared by electrochemical anodization of freeze-cast Ti foams have three favorable characteristics: (i) large surface area for enhanced light harvesting, (ii) 1D semiconductor structure for facilitated charge collection, and (iii) 3D highly conductive metallic current collector that enables exclusion of transparent conducting oxide substrate. Based on these advantages, when ATF is utilized in dye-sensitized solar cells, short-circuit photocurrent density up to 22.0 mA cm -2 is achieved in the conventional N719 dye-I 3 - /I - redox electrolyte system even with an intrinsically inferior quasi-solid electrolyte. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of shape memory polymer foam versus bare metal coil treatments in an in vivo porcine sidewall aneurysm model.

PubMed

Horn, John; Hwang, Wonjun; Jessen, Staci L; Keller, Brandis K; Miller, Matthew W; Tuzun, Egemen; Hartman, Jonathan; Clubb, Fred J; Maitland, Duncan J

2017-10-01

The endovascular delivery of platinum alloy bare metal coils has been widely adapted to treat intracranial aneurysms. Despite the widespread clinical use of this technique, numerous suboptimal outcomes are possible. These may include chronic inflammation, low volume filling, coil compaction, and recanalization, all of which can lead to aneurysm recurrence, need for retreatment, and/or potential rupture. This study evaluates a treatment alternative in which polyurethane shape memory polymer (SMP) foam is used as an embolic aneurysm filler. The performance of this treatment method was compared to that of bare metal coils in a head-to-head in vivo study utilizing a porcine vein pouch aneurysm model. After 90 and 180 days post-treatment, gross and histological observations were used to assess aneurysm healing. At 90 days, the foam-treated aneurysms were at an advanced stage of healing compared to the coil-treated aneurysms and showed no signs of chronic inflammation. At 180 days, the foam-treated aneurysms exhibited an 89-93% reduction in cross-sectional area; whereas coiled aneurysms displayed an 18-34% area reduction. The superior healing in the foam-treated aneurysms at earlier stages suggests that SMP foam may be a viable alternative to current treatment methods. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1892-1905, 2017. © 2016 Wiley Periodicals, Inc.

Fabrication of transition metal-containing nanostructures via polymer templates for a multitude of applications

NASA Astrophysics Data System (ADS)

Lu, Jennifer Qing

Nanostructures such as carbon nanotubes and semiconducting nanowires offer great technological promise due to their remarkable properties. The lack of a rational synthesis method prevents fabricating these nanostructures with desirable and consistent properties at predefined locations for device applications. In this thesis, employing polymer templates, a variety of highly ordered catalytically active transition metal nanostructures, ranging from single metallic nanoparticles of Fe, Co, Ni, Au and bimetallic nanoparticles of Ni/Fe and Co/Mo to Fe-rich silicon oxide nanodomains with uniform and tunable size and spacing have been successfully synthesized. These nanostructures have been demonstrated to be excellent catalyst systems for the synthesis of carbon nanotube and silicon nanowire. High quality, small diameter carbon nanotubes and nanowires with narrow size distribution have been successfully attained. Because these catalytically active nanostructures are uniformly distributed and do not agglomerate at the growth temperatures, uniform, high density and high quality carbon nanotube mats have been obtained. Since this polymer template approach is fully compatible with conventional top-down photolithography, lithographically selective growth of carbon nanotubes on a surface or suspended carbon nanotubes across trenches have been produced by using existing semiconductor processing. We have also shown the feasibility of producing carbon nanotubes and silicon nanowires at predefined locations on a wafer format and established a wafer-level carbon nanotube based device fabrication process. The ability of the polymer template approach to control catalyst systems at the nano-, micro- and macro-scales paves a pathway for commercialization of these 1D nanostructure-enabled devices. Beside producing well-defined, highly ordered discrete catalytically active metal-containing nanostructures by the polymer template approach, Au and Ag nanotextured surfaces have also been

Facile synthesis of nanostructured transition metal oxides as electrodes for Li-ion batteries

NASA Astrophysics Data System (ADS)

Opra, Denis P.; Gnedenkov, Sergey V.; Sokolov, Alexander A.; Minaev, Alexander N.; Kuryavyi, Valery G.; Sinebryukhov, Sergey L.

2017-09-01

At all times, energy storage is one of the greatest scientific challenge. Recently, Li-ion batteries are under special attention due to high working voltage, long cycle life, low self-discharge, reliability, no-memory effect. However, commercial LIBs usage in medium- and large-scale energy storage are limited by the capacity of lithiated metal oxide cathode and unsafety of graphite anode at high-rate charge. In this way, new electrode materials with higher electrochemical performance should be designed to satisfy a requirement in both energy and power. As it known, nanostructured transition metal oxides are promising electrode materials because of their elevated specific capacity and high potential vs. Li/Li+. In this work, the perspective of an original facile technique of pulsed high-voltage plasma discharge in synthesis of nanostructured transition metal oxides as electrodes for lithium-ion batteries has been demonstrated.

A general synthesis strategy for the multifunctional 3D polypyrrole foam of thin 2D nanosheets

NASA Astrophysics Data System (ADS)

Xue, Jiangli; Mo, Maosong; Liu, Zhuming; Ye, Dapeng; Cheng, Zhihua; Xu, Tong; Qu, Liangti

2018-06-01

A 3D macroporous conductive polymer foam of thin 2D polypyrrole (PPy) nanosheets is developed by adopting a novel intercalation of guest (monomer Py) between the layers of the lamellar host (3D vanadium oxide foam) template-replication strategy. The 3D PPy foam of thin 2D nanosheets exhibits diverse functions including reversible compressibility, shape memory, absorption/adsorption and mechanically deformable supercapacitor characteristics. The as-prepared 3D PPy foam of thin nanosheets is highly light weight with a density of 12 mg·cm-3 which can bear the large compressive strain up to 80% whether in wet or dry states; and can absorb organic solutions or extract dye molecules fast and efficiently. In particular, the PPy nanosheet-based foam as a mechanically deformable electrode material for supercapacitors exhibits high specific capacitance of 70 F·g-1 at a fast charge-discharge rate of 50 mA·g-1, superior to that of any other typical pure PPy-based capacitor. We envision that the strategy presented here should be applicable to fabrication of a wide variety of organic polymer foams and hydrogels of low-dimensional nanostructures and even inorganic foams and hydrogels of low-dimensional nanostructures, and thus allow for exploration of their advanced physical and chemical properties.

Self-Assembly of Metal Oxides into Three-Dimensional Nanostructures: Synthesis and Application in Catalysis

EPA Science Inventory

Nanostructured metal (Fe, Co, Mn, Cr, Mo) oxides were fabricated under microwave irradiation conditions in pure water without using any reducing or capping reagent. The metal oxides self-assembled into octahedron, spheres, triangular rods, pine, and hexagonal snowflake-like thre...

RISK REDUCTION VIA GREENER SYNTHESIS OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES

EPA Science Inventory

Aqueous preparation of nanoparticles using vitamins B2 and C which can function both as reducing and capping agents are described. Bulk and shape-controlled synthesis of noble nanostructures via microwave (MW)-assisted spontaneous reduction of noble metal salts using a-D-glucose,...

Application and future of solid foams

NASA Astrophysics Data System (ADS)

Bienvenu, Yves

2014-10-01

To conclude this series of chapters on solid foam materials, a review of industrial current applications and of mid-term market perspectives centred on manmade foams is given, making reference to natural cellular materials. Although the polymeric foam industrial development overwhelms the rest and finds applications on many market segments, more attention will be paid to the emerging market of inorganic-especially metallic-foams (and cellular materials) and their applications, present or upcoming. It is shown that the final applications of solid foams are primarily linked to transport and the present-day development of the different classes of solid foams is contrasted between functional applications and structural applications. xml:lang="fr"

Metal-Coated Cenospheres Obtained via Magnetron Sputter Coating: A New Precursor for Syntactic Foams

NASA Astrophysics Data System (ADS)

Shishkin, A.; Hussainova, I.; Kozlov, V.; Lisnanskis, M.; Leroy, P.; Lehmhus, D.

2018-05-01

Syntactic foams (SFs) and metal matrix syntactic foams (MMSFs) represent an advanced type of metal matrix composites (MMCs) based on hollow microspheres as particulate reinforcement. In general, SF and MMSFs allow tailoring of properties through choice of matrix, reinforcement, and volume fraction of the latter. A further handle for property adjustment is surface modification of the reinforcing particles. The present study introduces cenospheres for use as filler material in SF and MMSFs and as lightweight filler with electromagnetic interference shielding properties in civil engineering, which have been surface coated by means of physical vapor deposition, namely vibration-assisted sputter coating using a magnetron sputtering system. Altogether four types of such cenosphere-based composite powders (CPs) with an original particle size range of 50-125 µm (average particle size d50 75 µm) were studied. Surface films deposited on these were composed of Cu, stainless steel, Ti, and Ti-TiN double layers. For Cu coatings, the deposited metal film thickness was shown to be dependent on the sputtering energy. Scanning electron microscope backscattering images revealed nonporous films uniform in thickness directly after sputtering. Film thickness varied between 0.15 µm and 2.5 µm, depending on coating material and sputtering parameters. From these materials, samples were produced without addition of metal powders, exhibiting metal contents as low as 8-10 wt.% based on the coating alone. Obtained samples had an apparent density of 1.1-1.9 g/cm3 and compressive strengths ranging from 22 MPa to 135 MPa.

Structural Engineering of Carbon and Metal Nanostructures for Antibacterial Applications

NASA Astrophysics Data System (ADS)

Rojas-Andrade, Mauricio D.

Antibiotic resistance is a particularly alarming issue in world health today, as the rise and prevalence of antibiotic-resistant microorganisms significantly increases death rates and costs of treatment in even the most developed nations. According to the World Health Organization, many countries around the world have observed last-resort antibiotics to be ineffective in over half of patients afflicted by common pathogenic bacteria such as Escherichia coli and Staphylococcus Aureus, necessitating the search for novel antibacterial agents. Recently, nanostructured materials have been utilized for this application, with promising results observed for a wide variety of different compositions and morphologies. This has prompted significant research efforts toward the understanding of the antimicrobial activities of nanostructured materials in order to determine the nature of their unique cytotoxic mechanisms and consequently, the root of their antibacterial efficacy. This dissertation presents the antibacterial activities of novel carbon and metal nanostructures, focusing on the connection between their structural characteristics and their mechanisms of cytotoxicity. In the first chapter, the antibacterial activity of silver nanostructures synthesized by a green, photochemical method is reported. By utilizing high-resolution transmission microscopy (HRTEM) and x-ray diffraction (XRD), a correlation between the surface morphology and crystal structure of silver nanostructures to their antibacterial activity is established. Silver nanostructures structures composed of (111) faceted surfaces are proposed to be more cytotoxic towards bacterial cells due to slow oxidation and fast dissolution kinetics outside and inside bacterial cells respectively. This chapter develops the foundation for silver nanostructure toxicity, with the fundamental mechanisms being applicable to all metal nanostructures. In chapter 2, the antibacterial activities of Ag, Cu, and bimetallic, Ag

Nanoscale Seebeck effect at hot metal nanostructures

NASA Astrophysics Data System (ADS)

Ly, Aboubakry; Majee, Arghya; Würger, Alois

2018-02-01

We theoretically study the electrolyte Seebeck effect in the vicinity of a heated metal nanostructure, such as the cap of an active Janus colloid in an electrolyte, or gold-coated interfaces in optofluidic devices. The thermocharge accumulated at the surface varies with the local temperature, thus modulating the diffuse part of the electric double layer. On a conducting surface with non-uniform temperature, the isopotential condition imposes a significant polarization charge within the metal. Surprisingly, this does not affect the slip velocity, which takes the same value on insulating and conducting surfaces. Our results for specific-ion effects agree qualitatively with recent observations for Janus colloids in different electrolyte solutions. Comparing the thermal, hydrodynamic, and ion diffusion time scales, we expect a rich transient behavior at the onset of thermally powered swimming, extending to microseconds after switching on the heating.

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

PubMed

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

2012-04-21

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 (SnO(2)), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO(2)), where lithium ions are inserted/deinserted into/out of the TiO(2) 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.

GREENER PRODUCTION OF NOBLE METAL NANOSTRUCTURES AND NANOCOMPOSITES: RISK REDUCTION AND APPLICATIONS

EPA Science Inventory

The synthesis of nanometal/nano metal oxide/nanostructured polymer and their stabilization (through dispersant, biodegradable polymer) involves the use of natural renewable resources such plant material extract, biodegradable polymers, sugars, vitamins and finally efficient and s...

Plasmon-enhanced electron scattering in nanostructured thin metal films revealed by low-voltage scanning electron microscopy

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

Mikhailovskii, V., E-mail: v.mikhailovskii@spbu.ru; IRC for Nanotechnology, Research Park, St.-Petersburg State University; Petrov, Yu.

2016-06-17

The drastic enhancement of backscattered electrons (BSE) yield from nanostructured thin metal film which exceeded well the one from massive metal was observed at accelerating voltages below 400 V. The dependences of BSE signal from nanostructured gold film on accelerating voltage and on retarding grid potential applied to BSE detector were investigated. It was shown that enhanced BSE signal was formed by inelastic scattered electrons coming from the gaps between nanoparticles. A tentative explanation of the mechanism of BSE signal enhancement was suggested.

Microstructure and Mechanical Behavior of Amorphous Al-Cu-Ti Metal Foams Synthesized by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Li, Maoyuan; Lu, Lin; Dai, Zhen; Hong, Yiqiang; Chen, Weiwei; Zhang, Yuping; Qiao, Yingjie

Amorphous Al-Cu-Ti metal foams were prepared by spark plasma sintering (SPS) process with the diameter of 10mm. The SPS process was conducted at the pressure of 200 and 300MPa with the temperature of 653-723K, respectively. NaCl was used as the space-holder, forming almost separated pores with the porosity of 65 vol%. The microstructure and mechanical behavior of the amorphous Al-Cu-Ti metal foams were systematically investigated. The results show that the crystallinity increased at elevated temperatures. The effect of pressure and holding time on the crystallization was almost negligible. The intermetallic compounds, i.e. Al-Ti, Al-Cu and Al-Cu-Ti were identified from X-ray diffraction (XRD) patterns. It was found that weak adhesion and brittle intermetallic compounds reduced the mechanical properties, while lower volume fraction and smaller size of NaCl powders improved the mechanical properties.

Synthesis and properties of transition-metal arsenide nanostructures: From superparamagnetism to superconductivity

NASA Astrophysics Data System (ADS)

Desai, Prachi

This dissertation study focuses on developing new protocols for synthesis of nanostructured transition-metal pnictides including superconducting LiFeAs and studying their structure- property relationship. Nanostructured materials are known to differ in properties compared to their bulk counterparts owing to enhanced surface area and increased packing efficiency in devices. Synthetic chemistry skills and nanofabrication techniques like wet chemistry, electrodeposition, solvothermal, hydrothermal and lithography, are extremely useful for creating nanostructures of these functional materials. This is a challenging task simply because maintaining the phase composition same as that of the bulk material along with achieving nanostructures (nanoparticles, nanowires, nanopillars etc.) simultaneously is not easy. Papers I and II showcase novel synthesis methods for E based pnictides [EPn where E = 1st row transition elements and Pn = P, As etc.]. The superparamagnetism of transition-metal pnictides (e.g. FeAs, CoAs) nanomaterials obtained by this method have interesting magnetic features like high blocking temperatures and inter-particle magnetic exchange. Paper III, shows the concept of generalized protocol of EAs synthesis and discusses the principles behind this method. This protocol has been tested for applicability to not only FeAs, but also MnAs, CoAs and CrAs systems. Generalization of this method along with the discovery of superparamagnetic behavior in FeAs is one of the key findings of this research work. Alongside, paper IV shows the formation of Co3O4 nanowires through solid-solid conversion route aided by sacrificial templates.

Electrode Plate For An Eletrlchemical Cell And Having A Metal Foam Type Support, And A Method Of Obtaining Such An Electrode

DOEpatents

Verhoog, Roelof; Precigout, Claude; Stewart, Donald

1996-05-21

The electrode plate includes an active portion that is pasted with active material, and a plate head that is made up of three layers of compressed metal foam comprising: a non-pasted portion of height G of the support of the electrode plate; and two strips of non-pasted metal foam of height R on either side of the non-pasted portion of height G of the support and also extending for an overlap height h.sub.2 over the pasted portion of the support. The plate head includes a zone of reduced thickness including a portion that is maximally compressed, and a transitional portion between said maximally compressed portion and the remainder of the electrode which is of thickness e.sub.2. A portion of said plate head forms a connection tab. The method of obtaining the electrode consists in simultaneously rolling all three layers of metal foam in the plate head, and then in cutting matter away from the plates so as to obtain respective connection tabs.

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression.

PubMed

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-02-17

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results.

DNA nanostructure-directed assembly of metal nanoparticle superlattices

NASA Astrophysics Data System (ADS)

Julin, Sofia; Nummelin, Sami; Kostiainen, Mauri A.; Linko, Veikko

2018-05-01

Structural DNA nanotechnology provides unique, well-controlled, versatile, and highly addressable motifs and templates for assembling materials at the nanoscale. These methods to build from the bottom-up using DNA as a construction material are based on programmable and fully predictable Watson-Crick base pairing. Researchers have adopted these techniques to an increasing extent for creating numerous DNA nanostructures for a variety of uses ranging from nanoelectronics to drug-delivery applications. Recently, an increasing effort has been put into attaching nanoparticles (the size range of 1-20 nm) to the accurate DNA motifs and into creating metallic nanostructures (typically 20-100 nm) using designer DNA nanoshapes as molds or stencils. By combining nanoparticles with the superior addressability of DNA-based scaffolds, it is possible to form well-ordered materials with intriguing and completely new optical, plasmonic, electronic, and magnetic properties. This focused review discusses the DNA structure-directed nanoparticle assemblies covering the wide range of different one-, two-, and three-dimensional systems.

A general synthesis strategy for the multifunctional 3D polypyrrole foam of thin 2D nanosheets

NASA Astrophysics Data System (ADS)

Xue, Jiangli; Mo, Maosong; Liu, Zhuming; Ye, Dapeng; Cheng, Zhihua; Xu, Tong; Qu, Liangti

2018-05-01

A 3D macroporous conductive polymer foam of thin 2D polypyrrole (PPy) nanosheets is developed by adopting a novel intercalation of guest (monomer Py) between the layers of the lamellar host (3D vanadium oxide foam) template-replication strategy. The 3D PPy foam of thin 2D nanosheets exhibits diverse functions including reversible compressibility, shape memory, absorption/adsorption and mechanically deformable supercapacitor characteristics. The as-prepared 3D PPy foam of thin nanosheets is highly light weight with a density of 12 mg·cm-3 which can bear the large compressive strain up to 80% whether in wet or dry states; and can absorb organic solutions or extract dye molecules fast and efficiently. In particular, the PPy nanosheet-based foamas a mechanically deformable electrode material for supercapacitors exhibits high specific capacitance of 70 F·g-1 at a fast charge-discharge rate of 50 mA·g-1, superior to that of any other typical pure PPy-based capacitor. We envision that the strategy presented here should be applicable to fabrication of a wide variety of organic polymer foams and hydrogels of low-dimensional nanostructures and even inorganic foams and hydrogels of low-dimensional nanostructures, and thus allow for exploration of their advanced physical and chemical properties.

Designing deoxidation inhibiting encapsulation of metal oxide nanostructures for fluidic and biological applications

NASA Astrophysics Data System (ADS)

Ghosh, Moumita; Ghosh, Siddharth; Seibt, Michael; Schaap, Iwan A. T.; Schmidt, Christoph F.; Mohan Rao, G.

2016-12-01

Due to their photoluminescence, metal oxide nanostructures such as ZnO nanostructures are promising candidates in biomedical imaging, drug delivery and bio-sensing. To apply them as label for bio-imaging, it is important to study their structural stability in a bio-fluidic environment. We have explored the effect of water, the main constituent of biological solutions, on ZnO nanostructures with scanning electron microscopy (SEM) and photoluminescence (PL) studies which show ZnO nanorod degeneration in water. In addition, we propose and investigate a robust and inexpensive method to encapsulate these nanostructures (without structural degradation) using bio-compatible non-ionic surfactant in non-aqueous medium, which was not reported earlier. This new finding is an immediate interest to the broad audience of researchers working in biophysics, sensing and actuation, drug delivery, food and cosmetics technology, etc.

Nanostructured Metal Oxide Sorbents for the Collection and Recovery of Uranium from Seawater

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

Chouyyok, Wilaiwan; Warner, Cynthia L.; Mackie, Katherine E.

2016-02-07

The ability to collect uranium from seawater offers the potential for a long-term green fuel supply for nuclear energy. However, extraction of uranium, and other trace minerals, is challenging due to the high ionic strength and low mineral concentrations in seawater. Herein we evaluate the use of nanostructured metal oxide sorbents for the collection and recovery of uranium from seawater. Chemical affinity, chemical adsorption capacity and kinetics of preferred sorbent materials were evaluated. High surface area manganese and iron oxide nanomaterials showed excellent performance for uranium collection from seawater. Inexpensive nontoxic carbonate solutions were demonstrated to be an effective andmore » environmental benign method of stripping the uranium from the metal oxide sorbents. Various formats for the utilization of the nanostructured metals oxide sorbent materials are discussed including traditional and nontraditional methods such as magnetic separation. Keywords: Uranium, nano, manganese, iron, sorbent, seawater, magnetic, separations, nuclear energy« less

Two-photon reduction: a cost-effective method for fabrication of functional metallic nanostructures

NASA Astrophysics Data System (ADS)

Tabrizi, Sahar; Cao, YaoYu; Lin, Han; Jia, BaoHua

2017-03-01

Metallic nanostructures have underpinned plasmonic-based advanced photonic devices in a broad range of research fields over the last decade including physics, engineering, material science and bioscience. The key to realizing functional plasmonic resonances that can manipulate light at the optical frequencies relies on the creation of conductive metallic structures at the nanoscale with low structural defects. Currently, most plasmonic nanostructures are fabricated either by electron beam lithography (EBL) or by focused ion beam (FIB) milling, which are expensive, complicated and time-consuming. In comparison, the direct laser writing (DLW) technique has demonstrated its high spatial resolution and cost-effectiveness in three-dimensional fabrication of micro/nanostructures. Furthermore, the recent breakthroughs in superresolution nanofabrication and parallel writing have significantly advanced the fabrication resolution and throughput of the DLW method and made it one of the promising future nanofabrication technologies with low-cost and scalability. In this review, we provide a comprehensive summary of the state-of-the-art DLW fabrication technology for nanometer scale metallic structures. The fabrication mechanisms, different material choices, fabrication capability, including resolution, conductivity and structure surface smoothness, as well as the characterization methods and achievable devices for different applications are presented. In particular, the development trends of the field and the perspectives for future opportunities and challenges are provided at the end of the review. It has been demonstrated that the quality of the metallic structures fabricated using the DLW method is excellent compared with other methods providing a new and enabling platform for functional nanophotonic device fabrication.

Diffusion and surface alloying of gradient nanostructured metals

PubMed Central

Lu, Ke

2017-01-01

Gradient nanostructures (GNSs) have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed. PMID:28382244

Surface Charge Transfer Doping via Transition Metal Oxides for Efficient p-Type Doping of II-VI Nanostructures.

PubMed

Xia, Feifei; Shao, Zhibin; He, Yuanyuan; Wang, Rongbin; Wu, Xiaofeng; Jiang, Tianhao; Duhm, Steffen; Zhao, Jianwei; Lee, Shuit-Tong; Jie, Jiansheng

2016-11-22

Wide band gap II-VI nanostructures are important building blocks for new-generation electronic and optoelectronic devices. However, the difficulty of realizing p-type conductivity in these materials via conventional doping methods has severely handicapped the fabrication of p-n homojunctions and complementary circuits, which are the fundamental components for high-performance devices. Herein, by using first-principles density functional theory calculations, we demonstrated a simple yet efficient way to achieve controlled p-type doping on II-VI nanostructures via surface charge transfer doping (SCTD) using high work function transition metal oxides such as MoO 3 , WO 3 , CrO 3 , and V 2 O 5 as dopants. Our calculations revealed that these oxides were capable of drawing electrons from II-VI nanostructures, leading to accumulation of positive charges (holes injection) in the II-VI nanostructures. As a result, Fermi levels of the II-VI nanostructures were shifted toward the valence band regions after surface modifications, along with the large enhancement of work functions. In situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy characterizations verified the significant interfacial charge transfer between II-VI nanostructures and surface dopants. Both theoretical calculations and electrical transfer measurements on the II-VI nanostructure-based field-effect transistors clearly showed the p-type conductivity of the nanostructures after surface modifications. Strikingly, II-VI nanowires could undergo semiconductor-to-metal transition by further increasing the SCTD level. SCTD offers the possibility to create a variety of electronic and optoelectronic devices from the II-VI nanostructures via realization of complementary doping.

Adsorption of heavy metals on conventional and nanostructured materials for wastewater treatment purposes: A review.

PubMed

Burakov, Alexander E; Galunin, Evgeny V; Burakova, Irina V; Kucherova, Anastassia E; Agarwal, Shilpi; Tkachev, Alexey G; Gupta, Vinod K

2018-02-01

The problem of water pollution is of a great concern. Adsorption is one of the most efficient techniques for removing noxious heavy metals from the solvent phase. This paper presents a detailed information and review on the adsorption of noxious heavy metal ions from wastewater effluents using various adsorbents - i.e., conventional (activated carbons, zeolites, clays, biosorbents, and industrial by-products) and nanostructured (fullerenes, carbon nanotubes, graphenes). In addition to this, the efficiency of developed materials for adsorption of the heavy metals is discussed in detail along with the comparison of their maximum adsorption capacity in tabular form. A special focus is made on the perspectives of further wider applications of nanostructured adsorbents (especially, carbon nanotubes and graphenes) in wastewater treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

Self-assembly of metal nanostructures on binary alloy surfaces

PubMed Central

Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

2011-01-01

Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

An assessment of polyurethane foam passive samplers for atmospheric metals compared with active samplers.

PubMed

Li, Qilu; Yang, Kong; Li, Jun; Zeng, Xiangying; Yu, Zhiqiang; Zhang, Gan

2018-05-01

In this study, we conducted an assessment of polyurethane foam (PUF) passive sampling for metals combining active sampling. Remarkably, we found that the metals collected in the passive samples differed greatly from those collected in active samples. By composition, Cu and Ni accounted for significantly higher proportions in passive samples than in active samples, leading to significantly higher uptake rates of Cu and Ni. In assessing seasonal variation, metals in passive samples had higher concentrations in summer (excluding Heshan), which differed greatly from the pattern of active samples (winter > summer), indicating that the uptake rates of most metals were higher in summer than in winter. Overall, due to the stable passive uptake rates, we considered that PUF passive samplers can be applied to collect atmospheric metals. Additionally, we created a snapshot of the metal pollution in the Pearl River Delta using principal component analysis of PUF samples and their source apportionment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nanostructured composite reinforced material

DOEpatents

Seals, Roland D [Oak Ridge, TN; Ripley, Edward B [Knoxville, TN; Ludtka, Gerard M [Oak Ridge, TN

2012-07-31

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.

Experimental investigation of thermal characteristics of lithium ion battery using phase change materials combined with metallic foams and fins

NASA Astrophysics Data System (ADS)

Deng, Y. C.; Zhang, H. Y.; Xia, X.

2016-08-01

Phase change materials are of great interest in energy storage and energy management applications due to their high latent heat and excellent cycling stability. In this paper, the thermal characteristics of phase change materials (PCM) for thermal management of cylindrical 18650 lithium-ion battery (LIB) were experimentally investigated. A commercial paraffin wax with a melting temperaturerange between 47 - 53.8oC was used in this study. A metal cylinder with a heater was used to emulate the heat generation from a battery, which was surrounded with the paraffin PCM and containted in a metal housing. The experiment was conducted in an environmental test chamber with controlled ambient temperatures and power inputs. Both the battery temperature and the housing wall temperature were measured during steady-state heating and cyclic heating conditions. Since PCM has low thermal conductivity, thermal enhancement techniques were investigated by adding metal foams (MFs) or combining metallic foam and fins into the PCM to enhance the thermal conductivity. The battery temperatures were measured for all the cases and the results were analyzed and discussed.

The Effect of Matrix Composition on the Deformation and Failure Mechanisms in Metal Matrix Syntactic Foams during Compression

PubMed Central

Kádár, Csilla; Máthis, Kristián; Knapek, Michal; Chmelík, František

2017-01-01

The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results. PMID:28772556

Constitutive modeling of aluminum foam and finite element implementation for crash simulations

NASA Astrophysics Data System (ADS)

Bi, Jing

In the past decades metallic foams have been increasingly used as filler materials in crashworthiness applications due to their relatively low cost and high capacity of energy absorption. Due to the destructive nature of crashes, studies on the performance of metallic foams using physical testing have been limited to examining the crushing force histories and/or folding patterns that are insufficient for crashworthiness designs. For this reason, numerical simulations, particularly nonlinear finite element (FE) analyses, play an important role in designing crashworthy foam-filled structures. An effective and numerically stable model is needed for modeling metallic foams that are porous and encounter large nonlinear deformations in crashes. In this study a new constitutive model for metallic foams is developed to overcome the deficiency of existing models in commercial FE codes such as LS-DYNA. The new constitutive model accounts for volume changes under hydrostatic compression and combines the hydrostatic pressure and von Mises stress into one yield function. The change of the compressibility of the metallic foam is handled in the constitutive model by allowing for shape changes of the yield surface in the hydrostatic pressure-von Mises stress space. The backward Euler method is adopted to integrate the constitutive equations to achieve numerical accuracy and stability. The new foam model is verified and validated by existing experimental data before used in FE simulations of crushing of foam-filled columns that have square and hexagonal cross-sections.

Simulation of the light emission properties of patterned metal-based nanostructures for ultra-high density optical storage

NASA Astrophysics Data System (ADS)

Li, Weijun; Zhu, Yaping; Luo, Jun; Peng, Sha; Lei, Yu; Tong, Qing; Zhang, Xinyu; Xie, Changsheng

2015-10-01

Current researches show that the surface plasmon-polariton modes (SPPMs) in metallic nanostructures can lead to a powerful localization of guided light signals, which is generally as small as a few nanometers and thus far beyond the diffraction limit of electromagnetic waves in dielectric media. In this paper, our attention is paid to the modeling and simulation of particular kinds of patterned metal-based nanostructure fabricated over several common wafers such as typical silicon dioxide. The nanostructures are designed for concentrating and delivering incident light energy into nanoscale regions. In our research, the factors, for instance, optical materials, patterned nano-structures, the distance arrangement between adjacent single nanopattern, and the frequency of incident electromagnetic wave, are taken as variables, and further the CST microwave studio is used to simulate optical behaviors of the devices developed by us. By comparing the transmittance and electric field intensity distribution in small area, the nano-light-emission effects are analyzed, and the conditions for obtaining near-field nanospots have been chosen.

Enhancing Surface Sensing Sensitivity of Metallic Nanostructures using Blue-Shifted Surface Plasmon Mode and Fano Resonance.

PubMed

Lee, Kuang-Li; Chang, Chia-Chun; You, Meng-Lin; Pan, Ming-Yang; Wei, Pei-Kuen

2018-06-27

Improving surface sensitivities of nanostructure-based plasmonic sensors is an important issue to be addressed. Among the SPR measurements, the wavelength interrogation is commonly utilized. We proposed using blue-shifted surface plasmon mode and Fano resonance, caused by the coupling of a cavity mode (angle-independent) and the surface plasmon mode (angle-dependent) in a long-periodicity silver nanoslit array, to increase surface (wavelength) sensitivities of metallic nanostructures. It results in an improvement by at least a factor of 4 in the spectral shift as compared to sensors operated under normal incidence. The improved surface sensitivity was attributed to a high refractive index sensitivity and the decrease of plasmonic evanescent field caused by two effects, the Fano coupling and the blue-shifted resonance. These concepts can enhance the sensing capability and be applicable to various metallic nanostructures with periodicities.

Direct writing of metal nanostructures: lithographic tools for nanoplasmonics research.

PubMed

Leggett, Graham J

2011-03-22

Continued progress in the fast-growing field of nanoplasmonics will require the development of new methods for the fabrication of metal nanostructures. Optical lithography provides a continually expanding tool box. Two-photon processes, as demonstrated by Shukla et al. (doi: 10.1021/nn103015g), enable the fabrication of gold nanostructures encapsulated in dielectric material in a simple, direct process and offer the prospect of three-dimensional fabrication. At higher resolution, scanning probe techniques enable nanoparticle particle placement by localized oxidation, and near-field sintering of nanoparticulate films enables direct writing of nanowires. Direct laser "printing" of single gold nanoparticles offers a remarkable capability for the controlled fabrication of model structures for fundamental studies, particle-by-particle. Optical methods continue to provide a powerful support for research into metamaterials.

Layered manganese oxides-decorated and nickel foam-supported carbon nanotubes as advanced binder-free supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Huang, Ming; Mi, Rui; Liu, Hao; Li, Fei; Zhao, Xiao Li; Zhang, Wei; He, Shi Xuan; Zhang, Yu Xin

2014-12-01

Three-dimensional carbon nanotubes@MnO2 core-shell nanostructures grown on Ni foam for binder-free capacitor electrodes have been fabricated by a floating catalyst chemical vapor deposition process and a facile hydrothermal approach. Ultrathin layered MnO2 nanosheets are uniformly coated on the surface of the carbon nanotubes (CNTs), directly grown on Ni foam. This unique well-designed binder-free electrode exhibits a high specific capacitance (325.5 F g-1 at a current density of 0.3 A g-1), good rate capability (70.7% retention), and excellent cycling stability (90.5% capacitance retention after 5000 cycles), due to the high conductivity of the close contact between CNTs and Ni foam, as well as the moderate specific surface area of the CNTs@MnO2 core-shell nanostructures. The developed synthetic strategy may provide design guidelines for constructing advanced binder-free supercapacitors electrode.

Design, fabrication, and characterization of metallic nanostructures for surface-enhanced Raman spectroscopy and plasmonic applications

NASA Astrophysics Data System (ADS)

Hao, Qingzhen

Metal/dielectric nanostructures have the ability to sustain coherent electron oscillations known as surface plasmons. Due to their capability of localizing and guiding light in sub-wavelength metal nanostructures beyond diffraction limits, surface plasmon-based photonics, or “plasmonics” has opened new physical phenomena and lead to novel applications in metamaterials, optoelectronics, surface enhanced spectroscopy and biological sensing. This dissertation centers on design, fabrication, characterization of metallic nanostructures and their applications in surface-enhanced Raman spectroscopy (SERS) and actively tunable plasmonics. Metal-dielectric nanostructures are the building blocks for photonic metamaterials. One valuable design guideline for metamaterials is the Babinet’s principle, which governs the optical properties of complementary nanostructures. However, most complementary metamaterials are designed for the far infrared region or beyond, where the optical absorption of metal is small. We have developed a novel dual fabrication method, capable of simultaneously producing optically thin complementary structures. From experimental measurements and theoretical simulations, we showed that Babinet’s principle qualitatively holds in the visible region for the optically thin complements. The complementary structure is also a good platform to study subtle differences between nanoparticles and nanoholes in SERS (a surface sensitive technique, which can enhance the conventional Raman cross-section by 106˜108 fold, thus very useful for highly sensitive biochemical sensing). Through experimental measurement and theoretical analysis, we showed that the SERS enhancement spectrum (plot of SERS enhancement versus excitation wavelengths), dominated by local near-field, for nanoholes closely follows their far-field optical transmission spectrum. However, the enhancement spectrum for nanoparticles red-shifts significantly from their far-field optical extinction

Compressive Behaviour and Energy Absorption of Aluminium Foam Sandwich

NASA Astrophysics Data System (ADS)

Endut, N. A.; Hazza, M. H. F. Al; Sidek, A. A.; Adesta, E. T. Y.; Ibrahim, N. A.

2018-01-01

Development of materials in automotive industries plays an important role in order to retain the safety, performance and cost. Metal foams are one of the idea to evolve new material in automotive industries since it can absorb energy when it deformed and good for crash management. Recently, new technology had been introduced to replace metallic foam by using aluminium foam sandwich (AFS) due to lightweight and high energy absorption behaviour. Therefore, this paper provides reliable data that can be used to analyze the energy absorption behaviour of aluminium foam sandwich by conducting experimental work which is compression test. Six experiments of the compression test were carried out to analyze the stress-strain relationship in terms of energy absorption behavior. The effects of input variables include varying the thickness of aluminium foam core and aluminium sheets on energy absorption behavior were evaluated comprehensively. Stress-strain relationship curves was used for energy absorption of aluminium foam sandwich calculation. The result highlights that the energy absorption of aluminium foam sandwich increases from 12.74 J to 64.42 J respectively with increasing the foam and skin thickness.

One-process fabrication of metal hierarchical nanostructures with rich nanogaps for highly-sensitive surface-enhanced Raman scattering.

PubMed

Liu, Gui-qiang; Yu, Mei-dong; Liu, Zheng-qi; Liu, Xiao-shan; Huang, Shan; Pan, Ping-ping; Wang, Yan; Liu, Mu-lin; Gu, Gang

2015-05-08

One-process fabrication of highly active and reproducible surface-enhanced Raman scattering (SERS) substrates via ion beam deposition is reported. The fabricated metal-dielectric-metal (MDM) hierarchical nanostructure possesses rich nanogaps and a tunable resonant cavity. Raman scattering signals of analytes are dramatically strengthened due to the strong near-field coupling of localized surface plasmon resonances (LSPRs) and the strong interaction of LSPRs of metal NPs with surface plasmon polaritons (SPPs) on the underlying metal film by crossing over the dielectric spacer. The maximum Raman enhancement for the highest Raman peak at 1650 cm(-1) is 13.5 times greater than that of a single metal nanoparticle (NP) array. Moreover, the SERS activity can be efficiently tailored by varying the size and number of voids between adjacent metal NPs and the thickness of the dielectric spacer. These findings may broaden the scope of SERS applications of MDM hierarchical nanostructures in biomedical and analytical chemistry.

Cascaded plasmon-plasmon coupling mediated energy transfer across stratified metal-dielectric nanostructures

PubMed Central

Golmakaniyoon, Sepideh; Hernandez-Martinez, Pedro Ludwig; Demir, Hilmi Volkan; Sun, Xiao Wei

2016-01-01

Surface plasmon (SP) coupling has been successfully applied to nonradiative energy transfer via exciton-plasmon-exciton coupling in conventionally sandwiched donor-metal film-acceptor configurations. However, these structures lack the desired efficiency and suffer poor photoemission due to the high energy loss. Here, we show that the cascaded exciton-plasmon-plasmon-exciton coupling in stratified architecture enables an efficient energy transfer mechanism. The overlaps of the surface plasmon modes at the metal-dielectric and dielectric-metal interfaces allow for strong cross-coupling in comparison with the single metal film configuration. The proposed architecture has been demonstrated through the analytical modeling and numerical simulation of an oscillating dipole near the stratified nanostructure of metal-dielectric-metal-acceptor. Consistent with theoretical and numerical results, experimental measurements confirm at least 50% plasmon resonance energy transfer enhancement in the donor-metal-dielectric-metal-acceptor compared to the donor-metal-acceptor structure. Cascaded plasmon-plasmon coupling enables record high efficiency for exciton transfer through metallic structures. PMID:27698422

A Numerical Analysis on a Compact Heat Exchanger in Aluminum Foam

NASA Astrophysics Data System (ADS)

Buonomo, B.; Ercole, D.; Manca, O.; Nardini, S.

2016-09-01

A numerical investigation on a compact heat exchanger in aluminum foam is carried out. The governing equations in two-dimensional steady state regime are written in local thermal non-equilibrium (LTNE). The geometrical domain under investigation is made up of a plate in aluminum foam with inside a single array of five circular tubes. The presence of the open-celled metal foam is modeled as a porous media by means of the Darcy-Forchheimer law. The foam has a porosity of 0.93 with 20 pores per inch and the LTNE assumption is used to simulate the heat transfer between metal foam and air. The compact heat exchanger at different air flow rates is studied with an assigned surface tube temperature. The results in terms of local heat transfer coefficient and Nusselt number on the external surface of the tubes are given. Moreover, local air temperature and velocity profiles in the smaller cross section, between two consecutive tubes, as a function of Reynolds number are showed. The performance evaluation criteria (PEC) is assessed in order to evaluate the effectiveness of the metal foam.

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

NASA Astrophysics Data System (ADS)

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

2012-10-01

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.

Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams

NASA Technical Reports Server (NTRS)

Raj, S. V.

2010-01-01

Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use the three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15 percent and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50 to 57 percent of the cell faces were pentagonal while 24 to 28 percent were quadrilateral and 15 to 22 percent were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with 3 quadrilateral, 6 pentagonal faces and 2 hexagonal faces consistent with the 3-6-2 cell.

Chemically Designed Metallic/Insulating Hybrid Nanostructures with Silver Nanocrystals for Highly Sensitive Wearable Pressure Sensors.

PubMed

Kim, Haneun; Lee, Seung-Wook; Joh, Hyungmok; Seong, Mingi; Lee, Woo Seok; Kang, Min Su; Pyo, Jun Beom; Oh, Soong Ju

2018-01-10

With the increase in interest in wearable tactile pressure sensors for e-skin, researches to make nanostructures to achieve high sensitivity have been actively conducted. However, limitations such as complex fabrication processes using expensive equipment still exist. Herein, simple lithography-free techniques to develop pyramid-like metal/insulator hybrid nanostructures utilizing nanocrystals (NCs) are demonstrated. Ligand-exchanged and unexchanged silver NC thin films are used as metallic and insulating components, respectively. The interfaces of each NC layer are chemically engineered to create discontinuous insulating layers, i.e., spacers for improved sensitivity, and eventually to realize fully solution-processed pressure sensors. Device performance analysis with structural, chemical, and electronic characterization and conductive atomic force microscopy study reveals that hybrid nanostructure based pressure sensor shows an enhanced sensitivity of higher than 500 kPa -1 , reliability, and low power consumption with a wide range of pressure sensing. Nano-/micro-hierarchical structures are also designed by combining hybrid nanostructures with conventional microstructures, exhibiting further enhanced sensing range and achieving a record sensitivity of 2.72 × 10 4 kPa -1 . Finally, all-solution-processed pressure sensor arrays with high pixel density, capable of detecting delicate signals with high spatial selectivity much better than the human tactile threshold, are introduced.

Plasmonic mode interferences and Fano resonances in Metal-Insulator- Metal nanostructured interface

PubMed Central

Nicolas, Rana; Lévêque, Gaëtan; Marae-Djouda, Joseph; Montay, Guillame; Madi, Yazid; Plain, Jérôme; Herro, Ziad; Kazan, Michel; Adam, Pierre-Michel; Maurer, Thomas

2015-01-01

Metal-insulator-metal systems exhibit a rich underlying physics leading to a high degree of tunability of their spectral properties. We performed a systematic study on a metal-insulator-nanostructured metal system with a thin 6 nm dielectric spacer and showed how the nanoparticle sizes and excitation conditions lead to the tunability and coupling/decoupling of localized and delocalized plasmonic modes. We also experimentally evidenced a tunable Fano resonance in a broad spectral window 600 to 800 nm resulting from the interference of gap modes with white light broad band transmitted waves at the interface playing the role of the continuum. By varying the incident illumination angle shifts in the resonances give the possibility to couple or decouple the localized and delocalized modes and to induce a strong change of the asymmetric Fano profile. All these results were confirmed with a crossed comparison between experimental and theoretical measurements, confirming the nature of different modes. The high degree of control and tunability of this plasmonically rich system paves the way for designing and engineering of similar systems with numerous applications. In particular, sensing measurements were performed and a figure of merit of 3.8 was recorded ranking this sensor among the highest sensitive in this wavelength range. PMID:26399425

Optimization of Design and Manufacturing Process of Metal Foam Filled Anti-Intrusion Bars

NASA Astrophysics Data System (ADS)

Villa, Andrea; Strano, Matteo; Mussi, Valerio

2011-05-01

The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding bodies that is partially converted into internal work of the bodies involved in the crash. The aim of this paper is to investigate the performances of a new kind of anti-intrusion bars for automotive use, filled with metallic foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is the evolution of a previous paper presented by the authors at Esaform 2010 and will present new results and findings. It is conducted by evaluating some key technical issues of the manufacturing problem and by conducting experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH2 blowing agent. Bars are tested in three point bending, in order to evaluate their performances in terms of force-displacement response and other specific performance parameters. In order to understand the role of interface between the inner surface of the tube and the external surface of the foam, different kinds of interface are tested.

Detection of trace heavy metal ions in water by nanostructured porous Si biosensors.

PubMed

Shtenberg, Giorgi; Massad-Ivanir, Naama; Segal, Ester

2015-07-07

A generic biosensing platform, based on nanostructured porous Si (PSi), Fabry-Pérot thin films, for label-free monitoring of heavy metal ions in aqueous solutions by enzymatic activity inhibition, is described. First, we show a general detection assay by immobilizing horseradish peroxidase (HRP) within the oxidized PSi nanostructure and monitor its catalytic activity in real time by reflective interferometric Fourier transform spectroscopy. Optical studies reveal the high specificity and sensitivity of the HRP-immobilized PSi towards three metal ions (Ag(+) > Pb(2+) > Cu(2+)), with a detection limit range of 60-120 ppb. Next, we demonstrate the concept of specific detection of Cu(2+) ions (as a model heavy metal) by immobilizing Laccase, a multi-copper oxidase, within the oxidized PSi. The resulting biosensor allows for specific detection and quantification of copper ions in real water samples by monitoring the Laccase relative activity. The optical biosensing results are found to be in excellent agreement with those obtained by the gold standard analytical technique (ICP-AES) for all water samples. The main advantage of the presented biosensing concept is the ability to detect heavy metal ions at environmentally relevant concentrations using a simple and portable experimental setup, while the specific biosensor design can be tailored by varying the enzyme type.

Nanostructuring effect of multi-walled carbon nanotubes on electrochemical properties of carbon foam as constructive electrode for lead acid battery

NASA Astrophysics Data System (ADS)

Kumar, Rajeev; Kumari, Saroj; Mathur, Rakesh B.; Dhakate, Sanjay R.

2015-01-01

In the present study, nanostructuring effect of multi-walled carbon nanotubes (MWCNTs) on electrochemical properties of coal tar pitch (CTP) based carbon foam (CFoam) was investigated. The different weight fractions of MWCNTs were mixed with CTP and foam was developed from the mixture of CTP and MWCNTs by sacrificial template technique and heat treated at 1,400 and 2,500 °C in inert atmosphere. These foams were characterized by scanning electron microscopy, X-ray diffraction, and potentiostat PARSTAT for cyclic voltammetry. It was observed that, bulk density of CFoam increases with increasing MWCNTs content and decreases after certain amount. The MWCNTs influence the morphology of CFoam and increase the width of ligaments as well as surface area. During the heat treatment, stresses exerting at MWCNTs/carbon interface accelerate ordering of the graphene layer which have positive effect on the electrochemical properties of CFoam. The current density increases from 475 to 675 mA/cm2 of 1,400 °C heat treated and 95 to 210 mA/cm2 of 2,500 °C heat-treated CFoam with 1 wt% MWCNTs. The specific capacitance was decreases with increasing the scan rate from 100 to 1,000 mV/s. In case of 1 % MWCNTs content CFoam the specific capacitance at the scan rate 100 mV/s was increased from 850 to 1,250 μF/cm2 and 48 to 340 μF/cm2 of CFoam heat treated at 1,400 °C and 2,500 °C respectively. Thus, the higher value surface area and current density of MWCNTs-incorporated CFoam heat treated to 1,400 °C can be suitable for lead acid battery electrode with improved charging capability.

Composite materials formed with anchored nanostructures

DOEpatents

Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei

2015-03-10

A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

Ceramic nanostructures and methods of fabrication

DOEpatents

Ripley, Edward B [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Morrell, Jonathan S [Knoxville, TN

2009-11-24

Structures and methods for the fabrication of ceramic nanostructures. Structures include metal particles, preferably comprising copper, disposed on a ceramic substrate. The structures are heated, preferably in the presence of microwaves, to a temperature that softens the metal particles and preferably forms a pool of molten ceramic under the softened metal particle. A nano-generator is created wherein ceramic material diffuses through the molten particle and forms ceramic nanostructures on a polar site of the metal particle. The nanostructures may comprise silica, alumina, titania, or compounds or mixtures thereof.

Gradient composite metal-ceramic foam as supportive component for planar SOFCs and MIEC membranes

NASA Astrophysics Data System (ADS)

Smorygo, Oleg; Mikutski, Vitali; Marukovich, Alexander; Sadykov, Vladislav; Usoltsev, Vladimir; Mezentseva, Natalia; Borodinecs, Anatolijs; Bobrenok, Oleg

2011-06-01

A novel approach to the design of planar gradient porous supports for the thin-film SOFCs and MIEC membranes is described. The support's thermal expansion is controlled by the creation of a two-component composite metal-ceramic foam structure. Thin MIEC membranes and SOFCs were prepared on the composite supports by the layerwise deposition of composite functional layers including complex fluorites and perovskites. Lab-scale studies demonstrated promising performance of both MIEC membrane and SOFC.

Numerical investigation on aluminum foam application in a tubular heat exchanger

NASA Astrophysics Data System (ADS)

Buonomo, Bernardo; di Pasqua, Anna; Ercole, Davide; Manca, Oronzio; Nardini, Sergio

2018-02-01

A numerical study has been conducted to examine the thermal and fluiddynamic behaviors of a tubular heat exchanger in aluminum foam. A plate in metal foam with a single array of five circular tubes is the geometrical domain under examination. Darcy-Forchheimer flow model and the thermal non-equilibrium energy model are used to execute two-dimensional simulations on metal foam heat exchanger. The foam is characterized by porosity and (number) pores per inch respectively equal to 0.935 and 20. Different air flow rates are imposed to the entrance of the heat exchanger with an assigned surface tube temperature. The results are provided in terms of local heat transfer coefficient and Nusselt number evaluated on the external surface of the tubes. Furthermore, local air temperature and velocity profiles in the smaller cross section, between two consecutive tubes are given. Finally, the Energy Performance Ratio (EPR) is evaluated in order to demonstrate the effectiveness of the metal foam.

Co-doped titanium oxide foam and water disinfection device

DOEpatents

Shang, Jian-Ku; Wu, Pinggui; Xie, Rong-Cai

2016-01-26

A quaternary oxide foam, comprises an open-cell foam containing (a) a dopant metal, (b) a dopant nonmetal, (c) titanium, and (d) oxygen. The foam has the advantages of a high surface area and a low back pressure during dynamic flow applications. The inactivation of Escherichia coli (E. coli) was demonstrated in a simple photoreactor.

Recent Advances in Metal Chalcogenides (MX; X = S, Se) Nanostructures for Electrochemical Supercapacitor Applications: A Brief Review

PubMed Central

Theerthagiri, Jayaraman; Durai, Govindarajan; Rana, Abu ul Hassan Sarwar; Sangeetha, Kirubanandam; Kuppusami, Parasuraman; Kim, Hyun-Seok

2018-01-01

Supercapacitors (SCs) have received a great deal of attention and play an important role for future self-powered devices, mainly owing to their higher power density. Among all types of electrical energy storage devices, electrochemical supercapacitors are considered to be the most promising because of their superior performance characteristics, including short charging time, high power density, safety, easy fabrication procedures, and long operational life. An SC consists of two foremost components, namely electrode materials, and electrolyte. The selection of appropriate electrode materials with rational nanostructured designs has resulted in improved electrochemical properties for high performance and has reduced the cost of SCs. In this review, we mainly spotlight the non-metallic oxide, especially metal chalcogenides (MX; X = S, Se) based nanostructured electrode materials for electrochemical SCs. Different non-metallic oxide materials are highlighted in various categories, such as transition metal sulfides and selenides materials. Finally, the designing strategy and future improvements on metal chalcogenide materials for the application of electrochemical SCs are also discussed. PMID:29671823

Reversible mechano-electrochemical writing of metallic nanostructures with the tip of an atomic force microscope.

PubMed

Obermair, Christian; Kress, Marina; Wagner, Andreas; Schimmel, Thomas

2012-01-01

We recently introduced a method that allows the controlled deposition of nanoscale metallic patterns at defined locations using the tip of an atomic force microscope (AFM) as a "mechano-electrochemical pen", locally activating a passivated substrate surface for site-selective electrochemical deposition. Here, we demonstrate the reversibility of this process and study the long-term stability of the resulting metallic structures. The remarkable stability for more than 1.5 years under ambient air without any observable changes can be attributed to self-passivation. After AFM-activated electrochemical deposition of copper nanostructures on a polycrystalline gold film and subsequent AFM imaging, the copper nanostructures could be dissolved by reversing the electrochemical potential. Subsequent AFM-tip-activated deposition of different copper nanostructures at the same location where the previous structures were deleted, shows that there is no observable memory effect, i.e., no effect of the previous writing process on the subsequent writing process. Thus, the four processes required for reversible information storage, "write", "read", "delete" and "re-write", were successfully demonstrated on the nanometer scale.

Reversible mechano-electrochemical writing of metallic nanostructures with the tip of an atomic force microscope

PubMed Central

Kress, Marina; Wagner, Andreas; Schimmel, Thomas

2012-01-01

Summary We recently introduced a method that allows the controlled deposition of nanoscale metallic patterns at defined locations using the tip of an atomic force microscope (AFM) as a “mechano-electrochemical pen”, locally activating a passivated substrate surface for site-selective electrochemical deposition. Here, we demonstrate the reversibility of this process and study the long-term stability of the resulting metallic structures. The remarkable stability for more than 1.5 years under ambient air without any observable changes can be attributed to self-passivation. After AFM-activated electrochemical deposition of copper nanostructures on a polycrystalline gold film and subsequent AFM imaging, the copper nanostructures could be dissolved by reversing the electrochemical potential. Subsequent AFM-tip-activated deposition of different copper nanostructures at the same location where the previous structures were deleted, shows that there is no observable memory effect, i.e., no effect of the previous writing process on the subsequent writing process. Thus, the four processes required for reversible information storage, “write”, “read”, “delete” and “re-write”, were successfully demonstrated on the nanometer scale. PMID:23365795

One-Dimensional Metal-Oxide Nanostructures for Solar Photocatalytic Water-Splitting

NASA Astrophysics Data System (ADS)

Wang, Fengyun; Song, Longfei; Zhang, Hongchao; Luo, Linqu; Wang, Dong; Tang, Jie

2017-08-01

Because of their unique physical and chemical properties, one-dimensional (1-D) metal-oxide nanostructures have been extensively applied in the areas of gas sensors, electrochromic devices, nanogenerators, and so on. Solar water-splitting has attracted extensive research interest because hydrogen generated from solar-driven water splitting is a clean, sustainable, and abundant energy source that not only solves the energy crisis, but also protects the environment. In this comprehensive review, the main synthesis methods, properties, and especially prominent applications in solar water splitting of 1-D metal-oxides, including titanium dioxide (TiO2), zinc oxide (ZnO), tungsten trioxide (WO3), iron oxide (Fe2O3), and copper oxide (CuO) are fully discussed.

One-step direct-laser metal writing of sub-100 nm 3D silver nanostructures in a gelatin matrix

NASA Astrophysics Data System (ADS)

Kang, SeungYeon; Vora, Kevin; Mazur, Eric

2015-03-01

Developing an ability to fabricate high-resolution, 3D metal nanostructures in a stretchable 3D matrix is a critical step to realizing novel optoelectronic devices such as tunable bulk metal-dielectric optical devices and THz metamaterial devices that are not feasible with alternative techniques. We report a new chemistry method to fabricate high-resolution, 3D silver nanostructures using a femtosecond-laser direct metal writing technique. Previously, only fabrication of 3D polymeric structures or single-/few-layer metal structures was possible. Our method takes advantage of unique gelatin properties to overcome such previous limitations as limited freedom in 3D material design and short sample lifetime. We fabricate more than 15 layers of 3D silver nanostructures with a resolution of less than 100 nm in a stable dielectric matrix that is flexible and has high large transparency that is well-matched for potential applications in the optical and THz metamaterial regimes. This is a single-step process that does not require any further processing. This work will be of interest to those interested in fabrication methods that utilize nonlinear light-matter interactions and the realization of future metamaterials.

Plasmonic nanostructures through DNA-assisted lithography

PubMed Central

Shen, Boxuan; Linko, Veikko; Tapio, Kosti; Pikker, Siim; Lemma, Tibebe; Gopinath, Ashwin; Gothelf, Kurt V.; Kostiainen, Mauri A.; Toppari, J. Jussi

2018-01-01

Programmable self-assembly of nucleic acids enables the fabrication of custom, precise objects with nanoscale dimensions. These structures can be further harnessed as templates to build novel materials such as metallic nanostructures, which are widely used and explored because of their unique optical properties and their potency to serve as components of novel metamaterials. However, approaches to transfer the spatial information of DNA constructions to metal nanostructures remain a challenge. We report a DNA-assisted lithography (DALI) method that combines the structural versatility of DNA origami with conventional lithography techniques to create discrete, well-defined, and entirely metallic nanostructures with designed plasmonic properties. DALI is a parallel, high-throughput fabrication method compatible with transparent substrates, thus providing an additional advantage for optical measurements, and yields structures with a feature size of ~10 nm. We demonstrate its feasibility by producing metal nanostructures with a chiral plasmonic response and bowtie-shaped nanoantennas for surface-enhanced Raman spectroscopy. We envisage that DALI can be generalized to large substrates, which would subsequently enable scale-up production of diverse metallic nanostructures with tailored plasmonic features. PMID:29423446

Strong, ductile, and thermally stable Cu-based metal-intermetallic nanostructured composites.

PubMed

Dusoe, Keith J; Vijayan, Sriram; Bissell, Thomas R; Chen, Jie; Morley, Jack E; Valencia, Leopolodo; Dongare, Avinash M; Aindow, Mark; Lee, Seok-Woo

2017-01-09

Bulk metallic glasses (BMGs) and nanocrystalline metals (NMs) have been extensively investigated due to their superior strengths and elastic limits. Despite these excellent mechanical properties, low ductility at room temperature and poor microstructural stability at elevated temperatures often limit their practical applications. Thus, there is a need for a metallic material system that can overcome these performance limits of BMGs and NMs. Here, we present novel Cu-based metal-intermetallic nanostructured composites (MINCs), which exhibit high ultimate compressive strengths (over 2 GPa), high compressive failure strain (over 20%), and superior microstructural stability even at temperatures above the glass transition temperature of Cu-based BMGs. Rapid solidification produces a unique ultra-fine microstructure that contains a large volume fraction of Cu 5 Zr superlattice intermetallic compound; this contributes to the high strength and superior thermal stability. Mechanical and microstructural characterizations reveal that substantial accumulation of phase boundary sliding at metal/intermetallic interfaces accounts for the extensive ductility observed.

Microcellular carbon foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1993-05-04

A microcellular carbon foam is characterized by a density in the range of about 30 to 1,000 mg/cm[sup 3], substantially uniform distribution of cell sizes of diameters less than 100 [mu]m with a majority of the cells being of a diameter of less than about 10 [mu]m. The foam has a well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.

Manipulating Energy Flow at the Nanoscale by Coupling Plasmons of Metal Nanostructures to Resonant Molecules

NASA Astrophysics Data System (ADS)

Wiederrecht, Gary

2014-03-01

Collective hybrid excitations resulting from the coupling of metal nanostructures with organic molecules present unique opportunities for manipulating light-matter interactions at the nanoscale. In this talk, I discuss recent studies that are examples of the breadth of phenomena that are possible. First, the interactions of coupled plasmonic nanostructures with azobenzene-based polymers are described, in which the spatial features of the plasmonic near-field can be used to manipulate molecular motion. The directional molecular transport that results is shown to be useful for imaging the spatial and polarization features of the optical near-field. The modeling of this effect is described. Second, the coupling of excitonic molecular aggregates to metal nanostructures produces coherent coupling that provides added structure to the optical extinction spectra of metal nanoparticles, thereby by providing a photonic handle with which to manipulate energy flow on an ultrafast timescale. Monitoring the rate of energy flow as a function of photon energy reveals important information about the energy dissipation channels and the structural interactions between molecule and metal. Third, the strongly enhanced optical nonlinearity resulting from coupled plasmonic nanorods is described. The closely spaced nanorod material exhibits nonlocality of the optical response that has an unusually strong nonlinear dependence on incident light intensity. Electromagnetic modeling confirms the nonlocal response of the plasmonic metamaterial. The broader impact of collective hybrid excitations on nanophotonics applications is described. Use of the Center for Nanoscale Materials was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

Silicon-embedded copper nanostructure network for high energy storage

DOEpatents

Yu, Tianyue

2016-03-15

Provided herein are nanostructure networks having high energy storage, electrochemically active electrode materials including nanostructure networks having high energy storage, as well as electrodes and batteries including the nanostructure networks having high energy storage. According to various implementations, the nanostructure networks have high energy density as well as long cycle life. In some implementations, the nanostructure networks include a conductive network embedded with electrochemically active material. In some implementations, silicon is used as the electrochemically active material. The conductive network may be a metal network such as a copper nanostructure network. Methods of manufacturing the nanostructure networks and electrodes are provided. In some implementations, metal nanostructures can be synthesized in a solution that contains silicon powder to make a composite network structure that contains both. The metal nanostructure growth can nucleate in solution and on silicon nanostructure surfaces.

Silicon-embedded copper nanostructure network for high energy storage

DOEpatents

Yu, Tianyue

2018-01-23

Provided herein are nanostructure networks having high energy storage, electrochemically active electrode materials including nanostructure networks having high energy storage, as well as electrodes and batteries including the nanostructure networks having high energy storage. According to various implementations, the nanostructure networks have high energy density as well as long cycle life. In some implementations, the nanostructure networks include a conductive network embedded with electrochemically active material. In some implementations, silicon is used as the electrochemically active material. The conductive network may be a metal network such as a copper nanostructure network. Methods of manufacturing the nanostructure networks and electrodes are provided. In some implementations, metal nanostructures can be synthesized in a solution that contains silicon powder to make a composite network structure that contains both. The metal nanostructure growth can nucleate in solution and on silicon nanostructure surfaces.

Washing Off Polyurethane Foam Insulation

NASA Technical Reports Server (NTRS)

Burley, Richard K.; Fogel, Irving

1990-01-01

Jet of hot water removes material quickly and safely. Simple, environmentally sound technique found to remove polyurethane foam insulation from metal parts. Developed for (but not limited to) use during rebuilding of fuel system of Space Shuttle main engine, during which insulation must be removed for penetrant inspection of metal parts.

Porous Polyurethane Foam for Use as a Particle Collection Substrate in a Nanoparticle Respiratory Deposition Sampler

PubMed Central

Mines, Levi W. D.; Park, Jae Hong; Mudunkotuwa, Imali A.; Anthony, T. Renée; Grassian, Vicki H.; Peters, Thomas M.

2017-01-01

Porous polyurethane foam was evaluated to replace the eight nylon meshes used as a substrate to collect nanoparticles in the Nanoparticle Respiratory Deposition (NRD) sampler. Cylindrical (25-mm diameter by 40-mm deep) foam with 110 pores per inch was housed in a 25-mm-diameter conductive polypropylene cassette cowl compatible with the NRD sampler. Pristine foam and nylon meshes were evaluated for metals content via elemental analysis. The size-selective collection efficiency of the foam was evaluated using salt (NaCl) and metal fume aerosols in independent tests. Collection efficiencies were compared to the nanoparticulate matter (NPM) criterion and a semi-empirical model for foam. Changes in collection efficiency and pressure drop of the foam and nylon meshes were measured after loading with metal fume particles as measures of substrate performance. Substantially less titanium was found in the foam (0.173 μg sampler−1) compared to the nylon mesh (125 μg sampler−1), improving the detection capabilities of the NRD sampler for titanium dioxide particles. The foam collection efficiency was similar to that of the nylon meshes and the NPM criterion (R2 = 0.98, for NaCl), although the semi-empirical model underestimated the experimental efficiency (R2 = 0.38). The pressure drop across the foam was 8% that of the nylon meshes when pristine and changed minimally with metal fume loading (~ 19 mg). In contrast, the pores of the nylon meshes clogged after loading with ~ 1 mg metal fume. These results indicate that foam is a suitable substrate to collect metal (except for cadmium) nanoparticles in the NRD sampler. PMID:28867869

Hierarchically Nanostructured Transition Metal Oxides for Lithium‐Ion Batteries

PubMed Central

Zheng, Mingbo; Tang, Hao; Li, Lulu; Hu, Qin; Zhang, Li; Xue, Huaiguo

2018-01-01

Abstract Lithium‐ion batteries (LIBs) have been widely used in the field of portable electric devices because of their high energy density and long cycling life. To further improve the performance of LIBs, it is of great importance to develop new electrode materials. Various transition metal oxides (TMOs) have been extensively investigated as electrode materials for LIBs. According to the reaction mechanism, there are mainly two kinds of TMOs, one is based on conversion reaction and the other is based on intercalation/deintercalation reaction. Recently, hierarchically nanostructured TMOs have become a hot research area in the field of LIBs. Hierarchical architecture can provide numerous accessible electroactive sites for redox reactions, shorten the diffusion distance of Li‐ion during the reaction, and accommodate volume expansion during cycling. With rapid research progress in this field, a timely account of this advanced technology is highly necessary. Here, the research progress on the synthesis methods, morphological characteristics, and electrochemical performances of hierarchically nanostructured TMOs for LIBs is summarized and discussed. Some relevant prospects are also proposed. PMID:29593962

Hierarchically Nanostructured Transition Metal Oxides for Lithium-Ion Batteries.

PubMed

Zheng, Mingbo; Tang, Hao; Li, Lulu; Hu, Qin; Zhang, Li; Xue, Huaiguo; Pang, Huan

2018-03-01

Lithium-ion batteries (LIBs) have been widely used in the field of portable electric devices because of their high energy density and long cycling life. To further improve the performance of LIBs, it is of great importance to develop new electrode materials. Various transition metal oxides (TMOs) have been extensively investigated as electrode materials for LIBs. According to the reaction mechanism, there are mainly two kinds of TMOs, one is based on conversion reaction and the other is based on intercalation/deintercalation reaction. Recently, hierarchically nanostructured TMOs have become a hot research area in the field of LIBs. Hierarchical architecture can provide numerous accessible electroactive sites for redox reactions, shorten the diffusion distance of Li-ion during the reaction, and accommodate volume expansion during cycling. With rapid research progress in this field, a timely account of this advanced technology is highly necessary. Here, the research progress on the synthesis methods, morphological characteristics, and electrochemical performances of hierarchically nanostructured TMOs for LIBs is summarized and discussed. Some relevant prospects are also proposed.

Hydrogen storage properties of nano-structural carbon and metal hydrides composites

NASA Astrophysics Data System (ADS)

Miyaoka, Hiroki; Ichikawa, Takayuki; Isobe, Shigehito; Fujii, Hironobu

2006-08-01

Thermodynamic and structural properties of some ball-milled mixtures composed of the hydrogenated nanostructural carbon (C nanoH x) and metal hydride (MH; M=Li, Na, Mg and Ca) were examined from thermal desoroption mass spectroscopy and powder X-ray diffraction, respectively. The results showed that the hydrogen desorption temperatures are significantly lowered from those of each hydride (C nanoH x, MH) in the composites. This indicates that a new type of interaction exists between C nanoH x and MH, which destabilizes C-H and/or M-H bonding as well. Therefore, the above Metal-C-H system would be recognized as a new family of hydrogen storage materials.

Feature Article: Fast scanning tunnelling microscopy as a tool to understand changes on metal surfaces: from nanostructures to single atoms

NASA Astrophysics Data System (ADS)

Morgenstern, Karina

2005-03-01

The Feature Article [1] describes how structural changes in metallic nanostructures can be followed with fast scanning tunneling microscopy (STM). The title page shows the same spot of a Ag(111) surface at room temperature, imaged with STM approximately one hour apart. Intrinsic changes to prepared nano-structures are marked as Brownian motion of vacancy islands (rectangle), coalescence of two vacancy islands (hexagon), and decay of an adatom island (circle).Karina Morgenstern is now professor at the University of Hannover. Her research is placed within the field of nanoscience and is in particular devoted to thermally activated processes of metallic nanostructures, electronically activated reactions of molecules on metallic surfaces, and water-metal interactions.The present issue of physica status solidi (b) also contains the article Apperance of copper d9 defect centres in wide-gap CdSe nanoparticles: A high-fequency EPR study by N. R. J. Poolton et al. as Editor's Choice [2] as well as several papers on electrical and nonlinear optical properties from the European Conference on Organised Films (ECOF 2004) chaired by José Antonio de Saja, Valladolid.

Stochastic metallic-glass cellular structures exhibiting benchmark strength.

PubMed

Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

2008-10-03

By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors.

PubMed

Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

2017-02-16

Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 μM and 8.0 μA/μM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications.

Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors

PubMed Central

Han, Tao; Jin, Jianli; Wang, Congxu; Sun, Youyi; Zhang, Yinghe; Liu, Yaqing

2017-01-01

Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 µM and 8.0 µA/µM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications. PMID:28336878

Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-05-16

In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd 150 nm /Ag 80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks (~ 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from ~ 510 to ~ 475 nm along with the decreased average size of alloy nanostructures.

Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures

NASA Astrophysics Data System (ADS)

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-05-01

In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd150 nm/Ag80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks ( 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from 510 to 475 nm along with the decreased average size of alloy nanostructures.

Structure and Compressive Properties of Invar-Cenosphere Syntactic Foams.

PubMed

Luong, Dung; Lehmhus, Dirk; Gupta, Nikhil; Weise, Joerg; Bayoumi, Mohamed

2016-02-18

The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately 41.6 and 60.0 vol.% in relation to the metal content and at 0.6 g/cm³ hollow particle density. The synthesis process results in survival of cenospheres and provides low density syntactic foams. The microstructure of the materials is investigated as well as the mechanical performance under quasi-static and high strain rate compressive loads. The compressive stress-strain curves of syntactic foams reveal a continuous strain hardening behavior in the plastic region, followed by a densification region. The results reveal a strain rate sensitivity in cenosphere-based Invar matrix syntactic foams. Differences in properties between cenosphere- and glass microsphere-based materials are discussed in relation to the findings of microstructural investigations. Cenospheres present a viable choice as filler material in iron-based syntactic foams due to their higher thermal stability compared to glass microspheres.

Recent Progress in Metal-Organic Frameworks and Their Derived Nanostructures for Energy and Environmental Applications.

PubMed

Xie, Zhiqiang; Xu, Wangwang; Cui, Xiaodan; Wang, Ying

2017-04-22

Metal-organic frameworks (MOFs), as a very promising category of porous materials, have attracted increasing interest from research communities due to their extremely high surface areas, diverse nanostructures, and unique properties. In recent years, there is a growing body of evidence to indicate that MOFs can function as ideal templates to prepare various nanostructured materials for energy and environmental cleaning applications. Recent progress in the design and synthesis of MOFs and MOF-derived nanomaterials for particular applications in lithium-ion batteries, sodium-ion batteries, supercapacitors, dye-sensitized solar cells, and heavy-metal-ion detection and removal is reviewed herein. In addition, the remaining major challenges in the above fields are discussed and some perspectives for future research efforts in the development of MOFs are also provided. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Corrigendum to "Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams"

NASA Technical Reports Server (NTRS)

Raj. Sai V.

2011-01-01

Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use an idealized three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15% and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50-57% of the cell faces were pentagonal while 24-28% were quadrilateral and 15-22% were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with 3 quadrilateral, 6 pentagonal faces and 2 hexagonal faces consistent with the 3-6-2 Matzke cell

Nanostructured GaAs solar cells via metal-assisted chemical etching of emitter layers.

PubMed

Song, Yunwon; Choi, Keorock; Jun, Dong-Hwan; Oh, Jungwoo

2017-10-02

GaAs solar cells with nanostructured emitter layers were fabricated via metal-assisted chemical etching. Au nanoparticles produced via thermal treatment of Au thin films were used as etch catalysts to texture an emitter surface with nanohole structures. Epi-wafers with emitter layers 0.5, 1.0, and 1.5 um in thickness were directly textured and a window layer removal process was performed before metal catalyst deposition. A nanohole-textured emitter layer provides effective light trapping capabilities, reducing the surface reflection of a textured solar cell by 11.0%. However, because the nanostructures have high surface area to volume ratios and large numbers of defects, various photovoltaic properties were diminished by high recombination losses. Thus, we have studied the application of nanohole structures to GaAs emitter solar cells and investigated the cells' antireflection and photovoltaic properties as a function of the nanohole structure and emitter thickness. Due to decreased surface reflection and improved shunt resistance, the solar cell efficiency increased from 4.25% for non-textured solar cells to 7.15% for solar cells textured for 5 min.

Magnetic Binary Silicide Nanostructures.

PubMed

Goldfarb, Ilan; Cesura, Federico; Dascalu, Matan

2018-05-02

In spite of numerous advantageous properties of silicides, magnetic properties are not among them. Here, the magnetic properties of epitaxial binary silicide nanostructures are discussed. The vast majority of binary transition-metal silicides lack ferromagnetic order in their bulk-size crystals. Silicides based on rare-earth metals are usually weak ferromagnets or antiferromagnets, yet both groups tend to exhibit increased magnetic ordering in low-dimensional nanostructures, in particular at low temperatures. The origin of this surprising phenomenon lies in undercoordinated atoms at the nanostructure extremities, such as 2D (surfaces/interfaces), 1D (edges), and 0D (corners) boundaries. Uncompensated superspins of edge atoms increase the nanostructure magnetic shape anisotropy to the extent where it prevails over its magnetocrystalline counterpart, thus providing a plausible route toward the design of a magnetic response from nanostructure arrays in Si-based devices, such as bit-patterned magnetic recording media and spin injectors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Morphological and physical - chemical issues of metal nanostructures used in medical field

NASA Astrophysics Data System (ADS)

Duceac, L. D.; Velenciuc, N.; Dobre, E. C.

2016-06-01

In recent years applications of nanotechnology integrated into nanomedicine and bio-nanotechnology have attracted the attention of many researchers from different fields. Processes from chemical engineering especially nanostructured materials play an important role in medical and pharmaceutical development. Fundamental researches focused on finding simple, easily accomplished synthesis methods, morphological aspects and physico-chemical advanced characterization of nanomaterials. More over, by controlling synthesis conditions textural characteristics and physicochemical properties such as particle size, shape, surface, porosity, aggregation degree and composition can be tailored. Low cytotoxicity and antimicrobial effects of these nanostructured materials makes them be applied in medicine field. The major advantage of metal based nanoparticles is the use either for their antimicrobial properties or as drug-carriers having the potential to be active at low concentrations against infectious agents.

Experimental study of a passive thermal management system for high-powered lithium ion batteries using porous metal foam saturated with phase change materials

NASA Astrophysics Data System (ADS)

Li, W. Q.; Qu, Z. G.; He, Y. L.; Tao, Y. B.

2014-06-01

A highly efficient thermal strategy to manage a high-powered Li-ion battery package within the required safe temperature range is of great demand for electric vehicles (EVs) applications. A sandwiched cooling structure using copper metal foam saturated with phase change materials was designed. The thermal efficiency of the system was experimentally evaluated and compared with two control cases: a cooling mode with pure phase change materials and an air-cooling mode. The results showed that the thermal management with air natural convection cannot fulfill the safety demand of the Li-ion battery. The use of pure PCM can dramatically reduce the surface temperature and maintain the temperature within an allowable range due to the latent heat absorption and the natural convection of the melted PCM during the melting process. The foam-paraffin composite further reduced the battery's surface temperature and improved the uniformity of the temperature distribution caused by the improvement of the effective thermal conductivity. Additionally, the battery surface temperature increased with an increase in the porosity and the pore density of the metal foam.

Band structure engineering strategies of metal oxide semiconductor nanowires and related nanostructures: A review

NASA Astrophysics Data System (ADS)

Piyadasa, Adimali; Wang, Sibo; Gao, Pu-Xian

2017-07-01

The electronic band structure of a solid state semiconductor determines many of its physical and chemical characteristics such as electrical, optical, physicochemical, and catalytic activity. Alteration or modification of the band structure could lead to significant changes in these physical and chemical characteristics, therefore we introduce new mechanisms of creating novel solid state materials with interesting properties. Over the past three decades, research on band structure engineering has allowed development of various methods to modify the band structure of engineered materials. Compared to bulk counterparts, nanostructures generally exhibit higher band structure modulation capabilities due to the quantum confinement effect, prominent surface effect, and higher strain limit. In this review we will discuss various band structure engineering strategies in semiconductor nanowires and other related nanostructures, mostly focusing on metal oxide systems. Several important strategies of band structure modulation are discussed in detail, such as doping, alloying, straining, interface and core-shell nanostructuring.

Single attosecond pulse generation by using plasmon-driven double optical gating technology in crossed metal nanostructures

NASA Astrophysics Data System (ADS)

Feng, Liqiang; Liu, Katheryn

2018-05-01

An effective method to obtain the single attosecond pulses (SAPs) by using the multi-cycle plasmon-driven double optical gating (DOG) technology in the specifically designed metal nanostructures has been proposed and investigated. It is found that with the introduction of the crossed metal nanostructures along the driven and the gating polarization directions, not only the harmonic cutoff can be extended, but also the efficient high-order harmonic generation (HHG) at the very highest orders occurs only at one side of the region inside the nanostructure. As a result, a 93 eV supercontinuum with the near stable phase can be found. Further, by properly introducing an ultraviolet (UV) pulse into the driven laser polarization direction (which is defined as the DOG), the harmonic yield can be enhanced by two orders of magnitude in comparison with the singe polarization gating (PG) technology. However, as the polarized angle or the ellipticity of the UV pulse increase, the enhancement of the harmonic yield is slightly reduced. Finally, by superposing the selected harmonics from the DOG scheme, a 30 as SAP with intensity enhancement of two orders of magnitude can be obtained.

Porous CoO nanostructures grown on three-dimension graphene foams for supercapacitors electrodes

NASA Astrophysics Data System (ADS)

Deng, Wei; Lan, Wei; Sun, Yaru; Su, Qing; Xie, Erqing

2014-06-01

Three-dimensional graphene foams with good conductivity, light weight and chemical stability were produced by chemical vapor deposition. Then porous CoO nanowalls were deposited on graphene foam by a simple hydrothermal process and subsequent thermal treatment. This hybrid structures possessing large surface area in which the CoO nanowalls are separated by graphene foam with robust adhesion can directly serve as supercapacitor electrode including current collector without the need of any other binder materials and conductive agents. Electrochemical tests manifest a high specific capacitance of 231.87 F/g scaled to the mass of CoO (139.47 F/g for total mass of electrodes) at 1 A/g current, good rate capability and excellent cycling performance of >98% capacitance retention over 1000 cycles at 7 A/g current. The high conductivity, light weight and rational architectures, which provide fast electron pathway and the low diffusion resistance of ions, are responsible for the high performance of the electrodes.

Organic nanostructures of thermally activated delayed fluorescent emitters with enhanced intersystem crossing as novel metal-free photosensitizers.

PubMed

Zhang, Jinfeng; Chen, Wencheng; Chen, Rui; Liu, Xiao-Ke; Xiong, Yuan; Kershaw, Stephen V; Rogach, Andrey L; Adachi, Chihaya; Zhang, Xiaohong; Lee, Chun-Sing

2016-09-27

We applied organic nanostructures based on thermally activated delayed fluorescent (TADF) emitters for singlet oxygen generation. Due to the extremely small energy gaps between the excited singlet states (S 1 ) and triplet states (T 1 ) of these heavy-metal-free organic nanostructures, intersystem conversion between S 1 and T 1 can occur easily. This strategy also works well for exciplex-type TADF emitters prepared by mixing suitable donors and acceptors which have no TADF characteristics themselves.

M13 Virus-Incorporated Biotemplates on Electrode Surfaces To Nucleate Metal Nanostructures by Electrodeposition.

PubMed

Manivannan, Shanmugam; Kang, Inhak; Seo, Yeji; Jin, Hyo-Eon; Lee, Seung-Wuk; Kim, Kyuwon

2017-09-27

We report a virus-incorporated biological template (biotemplate) on electrode surfaces and its use in electrochemical nucleation of metal nanocomposites as an electrocatalytic material for energy applications. The biotemplate was developed with M13 virus (M13) incorporated in a silicate sol-gel matrix as a scaffold to nucleate Au-Pt alloy nanostructures by electrodeposition, together with reduced graphene oxide (rGO). The phage when engineered with Y3E peptides could nucleate Au-Pt alloy nanostructures, which ensured adequate packing density, simultaneous stabilization of rGO, and a significantly increased electrochemically active surface area. Investigation of the electrocatalytic activity of the resulting sol-gel composite catalyst toward methanol oxidation in an alkaline medium showed that this catalyst had mass activity greater than that of the biotemplate containing wild-type M13 and that of monometallic Pt and other Au-Pt nanostructures with different compositions and supports. M13 in the nanocomposite materials provided a close contact between the Au-Pt alloy nanostructures and rGO. In addition, it facilitated the availability of an OH - -rich environment to the catalyst. As a result, efficient electron transfer and a synergistic catalytic effect of the Au and Pt in the alloy nanostructures toward methanol oxidation were observed. Our nanocomposite synthesis on the novel biotemplate and its application might be useful for developing novel clean and green energy-generating and energy-storage materials.

Silicon nanostructure arrays prepared by single step metal assisted chemical etching from single crystal wafer

NASA Astrophysics Data System (ADS)

Sarkar, Kalyan; Das, Debajyoti

2018-04-01

Arrays of silicon nanostructures have been produced by single step Metal Assisted Chemical Etching (MACE) of single crystal Si-wafers at room temp and normal atmospheric condition. By studying optical and structural properties of the silicon nanowire like structures synthesized by Ag catalyst assisted chemical etching, a significant change in the reflectance spectra has been obtained leading to a gross reduction in reflectance from ˜31% to less than 1%. In comparison with bulk c-Si, the surface areas of the nanostructured samples have been increased significantly with the etching time, leading to an efficient absorption of light, favorable for photovoltaic applications.

A New Type of Carbon Nanostructure Formed Within a Metal-Matrix

DTIC Science & Technology

2012-06-01

A New Type of Carbon Nanostructure Formed Within a Metal-Matrix 1 Lourdes Salamanca-Riba, 1 Romaine Isaacs, 2 Azzam N. Mansour, 3 Adam Hall, 2...HAADF imaging. REFERENCES [1] D.A. Muller, Y. Tzou, R. Raj, and J . Silcox, Nature 366, 725 (1993). [2] R.R. Schlittler, J.W. Seo, J.K...Gimzewiski, C. Durkan, M.S.M. Saifullah, M.E. Welland, Science 292, 1136 (2001). [3] A.C. Ferrari, and J . Robertson, Phys. Rev. B 61, 14095 (2000). [4

Nanostructuring of Palladium with Low-Temperature Helium Plasma

PubMed Central

Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N.

2015-01-01

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. PMID:28347109

Nanostructuring of Palladium with Low-Temperature Helium Plasma.

PubMed

Fiflis, P; Christenson, M P; Connolly, N; Ruzic, D N

2015-11-25

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

High-energy redox-flow batteries with hybrid metal foam electrodes.

PubMed

Park, Min-Sik; Lee, Nam-Jin; Lee, Seung-Wook; Kim, Ki Jae; Oh, Duk-Jin; Kim, Young-Jun

2014-07-09

A nonaqueous redox-flow battery employing [Co(bpy)3](+/2+) and [Fe(bpy)3](2+/3+) redox couples is proposed for use in large-scale energy-storage applications. We successfully demonstrate a redox-flow battery with a practical operating voltage of over 2.1 V and an energy efficiency of 85% through a rational cell design. By utilizing carbon-coated Ni-FeCrAl and Cu metal foam electrodes, the electrochemical reactivity and stability of the nonaqueous redox-flow battery can be considerably enhanced. Our approach intoduces a more efficient conversion of chemical energy into electrical energy and enhances long-term cell durability. The cell exhibits an outstanding cyclic performance of more than 300 cycles without any significant loss of energy efficiency. Considering the increasing demands for efficient energy storage, our achievement provides insight into a possible development pathway for nonaqueous redox-flow batteries with high energy densities.

Dynamic creation and evolution of gradient nanostructure in single-crystal metallic microcubes

NASA Astrophysics Data System (ADS)

Thevamaran, Ramathasan; Lawal, Olawale; Yazdi, Sadegh; Jeon, Seog-Jin; Lee, Jae-Hwang; Thomas, Edwin L.

2016-10-01

We demonstrate the dynamic creation and subsequent static evolution of extreme gradient nanograined structures in initially near-defect-free single-crystal silver microcubes. Extreme nanostructural transformations are imposed by high strain rates, strain gradients, and recrystallization in high-velocity impacts of the microcubes against an impenetrable substrate. We synthesized the silver microcubes in a bottom-up seed-growth process and use an advanced laser-induced projectile impact testing apparatus to selectively launch them at supersonic velocities (~400 meters per second). Our study provides new insights into the fundamental deformation mechanisms and the effects of crystal and sample-shape symmetries resulting from high-velocity impacts. The nanostructural transformations produced in our experiments show promising pathways to developing gradient nanograined metals for engineering applications requiring both high strength and high toughness—for example, in structural components of aircraft and spacecraft.

Hierarchical concave layered triangular PtCu alloy nanostructures: rational integration of dendritic nanostructures for efficient formic acid electrooxidation.

PubMed

Wu, Fengxia; Lai, Jianping; Zhang, Ling; Niu, Wenxin; Lou, Baohua; Luque, Rafael; Xu, Guobao

2018-05-08

The rational construction of multi-dimensional layered noble metal nanostructures is a great challenge since noble metals are not layer-structured materials. Herein, we report a one-pot hydrothermal synthetic method for PtCu hierarchical concave layered triangular (HCLT) nanostructures using dl-carnitine, KI, poly(vinylpyrrolidone), CuCl2, and H2PtCl6. The PtCu HCLT nanostructure is comprised of multilayered triangular dendrites. Its layer number is tunable by changing dl-carnitine concentrations, and the concavity/convexity of the PtCu triangle nanostructures is tunable by changing the H2PtCl6/CuCl2 ratio or KI concentrations. Hierarchical trigonal bipyramid nanoframes are also obtained under certain conditions. Because of its advantageous nanostructure and bimetallic synergetic effect, the obtained PtCu HCLT nanostructure exhibits enhanced electrocatalytic activity and prolonged stability to formic acid oxidation compared to commercial Pt black, Pd/C and some other nanostructures.

Ultrafine and Smooth Full Metal Nanostructures for Plasmonics

NASA Astrophysics Data System (ADS)

Zhu, Xinli; Zhang, Jaseng; Xu, Jun; Liao, Zhimin; Wu, Xiaosong; Yu, Dapeng

2013-03-01

Surface plasmon polaritons (SPPs), which are coupled excitations of electrons bound to a metal-dielectric interface, show great potential for application in future nanoscale photonic systems due to the strong field confinement at the nanoscale, intensive local field enhancement, and interplay between strongly localized and propagating SPPs. The fabrication of sufficiently smooth metal surface with nanoscale feature size is crucial for SPPs to have practical applications. A template stripping (ST) method combined with PMMA as a template was successfully developed to create extraordinarily smooth metal nanostructures with a desirable feature size and morphology for plasmonics and metamaterials. The advantages of this method, including the high resolution, precipitous top-to bottom profile with a high aspect ratio, and three-dimensional characteristics, make it very suitable for the fabrication of plasmonic structures. By using this ST method, boxing ring-shaped nanocavities have been fabricated and the confined modes of surface plasmon polaritons in these nanocavities have been investigated and imaged by using cathodoluminescence spectroscopy. The mode of the out-of-plane field components of surface plasmon polaritons dominates the experimental mode patterns, indicating that the electron beam locally excites the out-of-plane field component of surface plasmon polaritons, and quality factors can be directly acquired. Numerous applications, such as plasmonic filter, nanolaser, and efficient light-emitting devices, can be expected to arise from these developments.

Scientific and Technological Foundations for Scaling Production of Nanostructured Metals

NASA Astrophysics Data System (ADS)

Lowe, Terry C.; Davis, Casey F.; Rovira, Peter M.; Hayne, Mathew L.; Campbell, Gordon S.; Grzenia, Joel E.; Stock, Paige J.; Meagher, Rilee C.; Rack, Henry J.

2017-05-01

Severe Plastic Deformation (SPD) has been explored in a wide range of metals and alloys. However, there are only a few industrial scale implementations of SPD for commercial alloys. To demonstrate and evolve technology for producing ultrafine grain metals by SPD, a Nanostructured Metals Manufacturing Testbed (NMMT) has been established in Golden, Colorado. Machines for research scale and pilot scale Equal Channel Angular Pressing-Conform (ECAP-C) technology have been configured in the NMMT to systematically evaluate and evolve SPD processing and advance the foundational science and technology for manufacturing. We highlight the scientific and technological areas that are critical for scale up of continuous SPD of aluminum, copper, magnesium, titanium, and iron-based alloys. Key areas that we will address in this presentation include the need for comprehensive analysis of starting microstructures, data on operating deformation mechanisms, high pressure thermodynamics and phase transformation kinetics, tribological behaviors, temperature dependence of lubricant properties, adaptation of tolerances and shear intensity to match viscoplastic behaviors, real-time process monitoring, and mechanics of billet/tooling interactions.

Sub-parts per million NO2 chemi-transistor sensors based on composite porous silicon/gold nanostructures prepared by metal-assisted etching.

PubMed

Sainato, Michela; Strambini, Lucanos Marsilio; Rella, Simona; Mazzotta, Elisabetta; Barillaro, Giuseppe

2015-04-08

Surface doping of nano/mesostructured materials with metal nanoparticles to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing. In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semiconductor (CMOS) technology. Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate. In particular, we investigate the integration of cSiAuNs synthesized by metal-assisted etching (MAE), using gold nanoparticles (NPs) as catalyst, in solid-state junction-field-effect transistors (JFETs), aimed at the detection of NO2 down to 100 parts per billion (ppb). The chemi-transistor sensors, namely cSiAuJFETs, are CMOS compatible, operate at room temperature, and are reliable, sensitive, and fully recoverable for the detection of NO2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.

Modes of interaction between nanostructured metal and a conducting mirror as a function of separation and incident polarization

NASA Astrophysics Data System (ADS)

Bonnie, F.; Arnold, M. D.; Smith, G. B.; Gentle, A. R.

2013-09-01

The optical resonances that occur in nanostructured metal layers are modulated in thin film stacks if the nanostructured layer is separated from a reflecting conducting layer by various thicknesses of thin dielectric. We have measured and modeled the optical response of interacting silver layers, with alumina spacer thickness ranging from a few nm to 50 nm, for s- and p-polarized incident light, and a range of incident angles. Standard thin film models, including standard effective medium models for the nanostructured layer, will break down for spacer thickness below a critical threshold. For example, with polarisation in the film plane and some nano-islands, it may occur at around 10 nm depending on spacer refractive index. Of particular interest here are novel effects observed with the onset of percolation in the nanolayer. Hot spot effects can be modified by nearby mirrors. Other modes to consider include (a) a two-particle mode involving a particle and its mirror image (b) A Fano resonance from hybridisation of localized and de-localised plasmon modes (c) a Babinet's core-(partial) shell particle with metal core-dielectric shell in metal (d) spacing dependent phase modulation (e) the impact of field gradients induced by the mirror at the nano-layer.

Pore Size Control in Aluminium Foam by Standardizing Bubble Rise Velocity and Melt Viscosity

NASA Astrophysics Data System (ADS)

Avinash, G.; Harika, V.; Sandeepika, Ch; Gupta, N.

2018-03-01

In recent years, aluminium foams have found use in a wide range of applications. The properties of these foams, as good structural strength with light weight have made them as a promising structural material for aerospace industry. Foaming techniques (direct and indirect) are used to produce these foams. Direct foaming involves blowing of gas to create gas bubbles in the melt whereas indirect foaming technique uses blowing agents as metallic hydrides, which create hydrogen bubbles. Porosity and its distribution in foams directly affect its properties. This demands for more theoretical studies, to control such cellular structure and hence properties. In present work, we have studied the effect of gas bubble rise velocity and melt viscosity, on pore size and its distribution in aluminium foam. A 15 PPI aluminium foam, prepared using indirect foaming technique having porosity ~86 % was used for study. In order to obtain metal foam, the bubble must not escape from the melt and should get entrapped during solidification. Our calculations suggest that bubble rise velocity and melt viscosity are responsible for vertical displacement of bubble in the melt. It is observed that melt viscosity opposes bubble rise velocity and help the bubbles to stay in the melt, resulting in porous structure.

Structural Continuum Modeling of Space Shuttle External Tank Foam Insulation

NASA Technical Reports Server (NTRS)

Steeve, Brian; Ayala, Sam; Purlee, T. Eric; Shaw, Phillip

2006-01-01

The Space Shuttle External Tank is covered with rigid polymeric closed-cell foam insulation to prevent ice formation, protect the metallic tank from aerodynamic heating, and control the breakup of the tank during re-entry. The cryogenic state of the tank, as well as the ascent into a vacuum environment, places this foam under significant stress. Because the loss of the foam during ascent poses a critical risk to the shuttle orbiter, there is much interest in understanding the stress state in the foam insulation and how it may contribute to fracture and debris loss. Several foam applications on the external tank have been analyzed using finite element methods. This presentation describes the approach used to model the foam material behavior and compares analytical results to experiments.

Mechanical Properties of 17-4PH Stainless Steel Foam Panels

NASA Technical Reports Server (NTRS)

Raj, S. V.; Ghosn, L. J.; Lerch, B. a.; Hebsur, M.; Cosgriff, L. M.; Fedor, J.

2007-01-01

Rectangular 17-4PH stainless steel sandwiched foam panels were fabricated using a commercial manufacturing technique by brazing two sheets to a foam core. Microstructural observations and ultrasonic nondestructive evaluation of the panels revealed large variations in the quality of the brazed areas from one panel to the next as well as within the same panel. Shear tests conducted on specimens machined from the panels exhibited failures either in the brazed region or in the foam core for the poorly brazed and well-brazed samples, respectively. Compression tests were conducted on the foam cores to evaluate their elastic and plastic deformation behavior. These data were compared with published data on polymeric and metallic foams, and with theoretical deformation models proposed for open cell foams.

Experimental and Numerical Study of Ceramic Foam Filtration

NASA Astrophysics Data System (ADS)

Laé, E.; Duval, H.; Rivière, C.; Le Brun, P.; Guillot, J.-B.

Ceramic foam filtration is widely used to enable removal of non metallic inclusions from liquid aluminium. Its performances have been largely studied in the literature and some discrepancies remain amongst the published results. Consequently, a research program was deployed to evaluate the performances of a range of ceramic foam filters used under various conditions and to understand the inclusions capture mechanisms.

Nanostructure Neutron Converter Layer Development

NASA Technical Reports Server (NTRS)

Park, Cheol (Inventor); Lowther, Sharon E. (Inventor); Kang, Jin Ho (Inventor); Thibeault, Sheila A. (Inventor); Sauti, Godfrey (Inventor); Bryant, Robert G. (Inventor)

2016-01-01

Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

Functional Performances of CuZnAl Shape Memory Alloy Open-Cell Foams

NASA Astrophysics Data System (ADS)

Biffi, C. A.; Casati, R.; Bassani, P.; Tuissi, A.

2018-01-01

Shape memory alloys (SMAs) with cellular structure offer a unique mixture of thermo-physical-mechanical properties. These characteristics can be tuned by changing the pore size and make the shape memory metallic foams very attractive for developing new devices for structural and functional applications. In this work, CuZnAl SMA foams were produced through the liquid infiltration of space holder method. In comparison, a conventional CuZn brass alloy was foamed trough the same method. Functional performances were studied on both bulk and foamed SMA specimens. Calorimetric response shows similar martensitic transformation (MT) below 0 °C. Compressive response of CuZnAl revealed that mechanical behavior is strongly affected by sample morphology and that damping capacity of metallic foam is increased above the MT temperatures. The shape memory effect was detected in the CuZnAl foams. The conventional brass shows a compressive response similar to that of the martensitic CuZnAl, in which plastic deformation accumulation occurs up to the cellular structure densification after few thermal cycles.

Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams. Revision 1

NASA Technical Reports Server (NTRS)

Raj, S. V.

2011-01-01

Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use an idealized three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15 percent and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50 to 57 percent of the cell faces were pentagonal while 24 to 28 percent were quadrilateral and 15 to 22 percent were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with three quadrilateral, six pentagonal faces and two hexagonal faces consistent with the 3-6-2 Matzke cell. A compilation of 90 years of experimental data reveals that the average number of cell faces decreases linearly with the increasing ratio of quadrilateral to pentagonal faces. It is concluded that the Kelvin model is not supported by these experimental data.

Ultra-sensitive molecular detection using surface-enhanced Raman scattering on periodic metal-dielectric nanostructures

NASA Astrophysics Data System (ADS)

Nien, Chun; Li, Yi-Hsuan; Su, Vin-Cent; Kuan, Chieh-Hsiung

2017-02-01

Surface-enhanced Raman scattering (SERS) is a powerful technique for trace chemical analysis and single molecule detection in the application of biochemical monitoring and food safety due to its ability to enhance the Raman scattering of molecules near the metallic surface or nanostructures. Here, we present a comprehensive study of the SERS enhancement by the periodically nanostructured surface, where the thin film of silver is deposited onto the surface, except the sidewall of posts, of 1-D lamellar gratings with varying pitch to forming metal-dielectric composite nanostructures. By enhancing the localized and surface-propagating mode in the vicinity of the concaves, the SERS signal can be improved by amplifying the intensity of electric field and increasing the optical path length of the incident light. Experimental investigations show that the enhancement factor can be manipulated by varying the polarization of incident light and the pitch size of gratings. To demonstrate the SERS effects of the proposed structures, thin layers of benzoic acid, which is commonly used as a food preservative, are deposited on the SERS substrates by spin-coating a solution of benzoic acid and dried at room temperature. A Confocal Raman microscope with a 532 nm laser source is used to illuminate light and measure the Raman spectrum of benzoic acid. We demonstrate the Raman signal of benzoic acid can be enhanced on the order of 102 on the SERS substrates.

Fiber glass prevents cracking of polyurethane foam insulation on cryogenic vessels

NASA Technical Reports Server (NTRS)

Forge, D. A.

1968-01-01

Fiber glass material, placed between polyurethane foam insulation and the outer surfaces of cryogenic vessels, retains its resilience at cryogenic temperatures and provides an expansion layer between the metal surfaces and the polyurethane foam, preventing cracking of the latter.

Platinum-based electrocatalysts synthesized by depositing contiguous adlayers on carbon nanostructures

DOEpatents

Adzic, Radoslav R.; Harris, Alexander

2015-10-06

High-surface-area carbon nanostructures coated with a smooth and conformal submonolayer-to-multilayer thin metal films and their method of manufacture are described. The manufacturing process may involve initial oxidation of the carbon nanostructures followed by immersion in a solution with the desired pH to create negative surface dipoles. The nanostructures are subsequently immersed in an alkaline solution containing non-noble metal ions which adsorb at surface reaction sites. The metal ions are then reduced via chemical or electrical means and the nanostructures are exposed to a solution containing a salt of one or more noble metals which replace adsorbed non-noble surface metal atoms by galvanic displacement. Subsequent film growth may be performed via the initial quasi-underpotential deposition of a non-noble metal followed by immersion in a solution comprising a more noble metal. The resulting coated nanostructures may be used, for example, as high-performance electrodes in supercapacitors, batteries, or other electric storage devices.

Platinum-based electrocatalysts synthesized by depositing contiguous adlayers on carbon nanostructures

DOEpatents

Adzic, Radoslav; Harris, Alexander

2013-03-26

High-surface-area carbon nanostructures coated with a smooth and conformal submonolayer-to-multilayer thin metal films and their method of manufacture are described. The preferred manufacturing process involves the initial oxidation of the carbon nanostructures followed by immersion in a solution with the desired pH to create negative surface dipoles. The nanostructures are subsequently immersed in an alkaline solution containing non-noble metal ions which adsorb at surface reaction sites. The metal ions are then reduced via chemical or electrical means and the nanostructures are exposed to a solution containing a salt of one or more noble metals which replace adsorbed non-noble surface metal atoms by galvanic displacement. Subsequent film growth may be performed via the initial quasi-underpotential deposition of a non-noble metal followed by immersion in a solution comprising a more noble metal. The resulting coated nanostructures may be used, for example, as high-performance electrodes in supercapacitors, batteries, or other electric storage devices.

High-rate production of micro- and nanostructured surfaces: Injection molding and novel process for metal tooling manufacturing

NASA Astrophysics Data System (ADS)

De Jesus Vega, Marisely

Devices containing micro and nanostructured surfaces are developing and constantly finding new applications, especially for medical diagnostics, point-of-care applications, and microneedles. They are also employed in the functionalization of surfaces for superhydrophobicity, drag reduction, or reversible adhesion by mimicking bio-inspired surfaces. This research provides a thorough investigation on the effects of different polymeric materials and processing conditions on the replication of micro and nanostructured surfaces via injection molding. In addition, this dissertation also presents a novel approach for the production of durable microstructured metal tooling to be used for the production of surfaces with microchannels via injection molding. Materials such as thermoplastic vulcanizates are substituting regular thermoplastic materials and vulcanized elastomers in many applications due to their outstanding properties and ease of processability. These material properties broaden the scope of applications for microstructured surfaces. However, there is a need for understanding how these materials behave in microinjection molding since thermoplastic elastomers' behavior during injection molding have been shown to differ from that of the widely understood behavior of thermoplastics. Replication of microstructured surfaces using thermoplastic vulcanizates (TPV) was studied in the first part of this thesis. TPVs with different hardness's were molded using microinjection molding with various processing conditions and the replication and surface details of 20 microm pillars (aspect ratio of 1:1) were characterized. In the second part of this research liquid silicone rubber (LSR) was studied as a material for the production of micro and nanostructured surfaces. LSR is a silicone based material such as polydimethylsiloxane (PDMS), which is widely used for research and development of micro and nanostructured devices, and thus provides all the benefits of PDMS but can be

Foaming volume and foam stability

NASA Technical Reports Server (NTRS)

Ross, Sydney

1947-01-01

A method of measuring foaming volume is described and investigated to establish the critical factors in its operation. Data on foaming volumes and foam stabilities are given for a series of hydrocarbons and for a range of concentrations of aqueous ethylene-glycol solutions. It is shown that the amount of foam formed depends on the machinery of its production as well as on properties of the liquid, whereas the stability of the foam produced, within specified mechanical limitations, is primarily a function of the liquid.

Crack Initiation and Growth in Rigid Polymeric Closed-Cell Foam Cryogenic Applications

NASA Technical Reports Server (NTRS)

Sayyah, Tarek; Steeve, Brian; Wells, Doug

2006-01-01

Cryogenic vessels, such as the Space Shuttle External Tank, are often insulated with closed-cell foam because of its low thermal conductivity. The coefficient of thermal expansion mismatch between the foam and metallic substrate places the foam under a biaxial tension gradient through the foam thickness. The total foam thickness affects the slope of the stress gradient and is considered a significant contributor to the initiation of subsurface cracks. Rigid polymeric foams are brittle in nature and any subsurface cracks tend to propagate a finite distance toward the surface. This presentation investigates the relationship between foam thickness and crack initiation and subsequent crack growth, using linear elastic fracture mechanics, in a rigid polymeric closed-cell foam through analysis and comparison with experimental results.

Dynamic creation and evolution of gradient nanostructure in single-crystal metallic microcubes.

PubMed

Thevamaran, Ramathasan; Lawal, Olawale; Yazdi, Sadegh; Jeon, Seog-Jin; Lee, Jae-Hwang; Thomas, Edwin L

2016-10-21

We demonstrate the dynamic creation and subsequent static evolution of extreme gradient nanograined structures in initially near-defect-free single-crystal silver microcubes. Extreme nanostructural transformations are imposed by high strain rates, strain gradients, and recrystallization in high-velocity impacts of the microcubes against an impenetrable substrate. We synthesized the silver microcubes in a bottom-up seed-growth process and use an advanced laser-induced projectile impact testing apparatus to selectively launch them at supersonic velocities (~400 meters per second). Our study provides new insights into the fundamental deformation mechanisms and the effects of crystal and sample-shape symmetries resulting from high-velocity impacts. The nanostructural transformations produced in our experiments show promising pathways to developing gradient nanograined metals for engineering applications requiring both high strength and high toughness-for example, in structural components of aircraft and spacecraft. Copyright © 2016, American Association for the Advancement of Science.

Fabrication of ultra-high aspect ratio (>160:1) silicon nanostructures by using Au metal assisted chemical etching

NASA Astrophysics Data System (ADS)

Li, Hailiang; Ye, Tianchun; Shi, Lina; Xie, Changqing

2017-12-01

We present a facile and effective approach for fabricating high aspect ratio, dense and vertical silicon nanopillar arrays, using a combination of metal etching following electron-beam lithography and Au metal assisted chemical etching (MacEtch). Ti/Au nanostructures used as catalysts in MacEtch are formed by single layer resist-based electron-beam exposure followed by ion beam etching. The effects of MacEtch process parameters, including half period, etching time, the concentrations of H2O2 and HF, etching temperature and drying method are systematically investigated. Especially, we demonstrate an enhancement of etching quality by employing cold MacEtch process, and an enhancement in preventing the collapse of high aspect ratio nanostructures by employing low surface tension rinse liquid and natural evaporation in the drying stage. Using an optimized MacEtch process, vertical silicon nanopillar arrays with a period of 250 nm and aspect ratio up to 160:1 are realized. Our results should be instructive for exploring the achievable aspect ratio limit in silicon nanostructures and may find potential applications in photovoltaic devices, thermoelectric devices and x-ray diffractive optics.

Cell Structure Evolution of Aluminum Foams Under Reduced Pressure Foaming

NASA Astrophysics Data System (ADS)

Cao, Zhuokun; Yu, Yang; Li, Min; Luo, Hongjie

2016-09-01

Ti-H particles are used to increase the gas content in aluminum melts for reduced pressure foaming. This paper reports on the RPF process of AlCa alloy by adding TiH2, but in smaller amounts compared to traditional process. TiH2 is completely decomposed by stirring the melt, following which reduced pressure is applied. TiH2 is not added as the blowing agent; instead, it is added for increasing the H2 concentration in the liquid AlCa melt. It is shown that pressure change induces further release of hydrogen from Ti phase. It is also found that foam collapse is caused by the fast bubble coalescing during pressure reducing procedure, and the instability of liquid film is related to the significant increase in critical thickness of film rupture. A combination of lower amounts of TiH2, coupled with reduced pressure, is another way of increasing hydrogen content in the liquid aluminum. A key benefit of this process is that it provides time to transfer the molten metal to a mold and then apply the reduced pressure to produce net shape foam parts.

Coated foams, preparation, uses and articles

DOEpatents

Duchane, D.V.; Barthell, B.L.

1982-10-21

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tension of the polymer solution used to coat are all very important to the coating.

Doping of carbon foams for use in energy storage devices

DOEpatents

Mayer, Steven T.; Pekala, Richard W.; Morrison, Robert L.; Kaschmitter, James L.

1994-01-01

A polymeric foam precursor, wetted with phosphoric acid, is pyrolyzed in an inert atmosphere to produce an open-cell doped carbon foam, which is utilized as a lithium intercalation anode in a secondary, organic electrolyte battery. Tests were conducted in a cell containing an organic electrolyte and using lithium metal counter and reference electrodes, with the anode located therebetween. Results after charge and discharge cycling, for a total of 6 cycles, indicated a substantial increase in the energy storage capability of the phosphorus doped carbon foam relative to the undoped carbon foam, when used as a rechargeable lithium ion battery.

Doping of carbon foams for use in energy storage devices

DOEpatents

Mayer, S.T.; Pekala, R.W.; Morrison, R.L.; Kaschmitter, J.L.

1994-10-25

A polymeric foam precursor, wetted with phosphoric acid, is pyrolyzed in an inert atmosphere to produce an open-cell doped carbon foam, which is utilized as a lithium intercalation anode in a secondary, organic electrolyte battery. Tests were conducted in a cell containing an organic electrolyte and using lithium metal counter and reference electrodes, with the anode located there between. Results after charge and discharge cycling, for a total of 6 cycles, indicated a substantial increase in the energy storage capability of the phosphorus doped carbon foam relative to the undoped carbon foam, when used as a rechargeable lithium ion battery. 3 figs.

Acquisition of a Modified Suction Casting Instrument for the Fabrication of Radiation Tolerant Bulk nNanostructured Metallic Materials

DTIC Science & Technology

2015-01-13

Cu/ Nb films”, Philos. Mag., 84, 1021-1028, (2004). [23] D. H. Ryan, J. M. D. Coey, “Magnetic properties of iron-rich Fe- Zr glasses”, Phys. Rev. B...2226, (1982). [26] K. Fukamichi, R. J. Gambino, T. R. McGuire, “ Electrical resistivity and Hall effect in FeZr amorphous sputtered films”, J. Appl...fabricate several bulk nanostructured metallic materials. In particular we fabricated bulk nanostructured Fe- Zr alloys via suction casting technique. The as

Plasmon hybridization in complex metallic nanostructures

NASA Astrophysics Data System (ADS)

Hao, Feng

With Plasmon Hybridization (PH) and Finite-Difference Time-Domain (FDTD) method, we theoretically investigated the optical properties of some complex metallic nanostructures (coupled nanoparticle/wire, nanostars, nanorings and combined ring/disk nanocavity systems). We applied the analytical formulism of PH studying the plasmonic coupling of a spherical metallic nanoparticle and an infinite long cylindrical nanowire. The plasmon resonance of the coupled system is shown shifted in frequency, which highly depends on the polarization of incident light relative to the geometry of the structure. We also showed the nanoparticle serves as an efficient antenna coupling the electromagnetic radiation into the low-energy propagating wire plasmons. We performed an experimental and theoretical analysis of the optical properties of gold nanorings with different sizes and cross sections. For light polarized parallel to the ring, the optical spectrum sensitively depends on the incident angle. When light incidence is normal to the ring, two dipolar resonance is observed. As the incident light is titled, some previously dark mulipolar plasmon resonances will be excited as a consequence of the retardation. The concept of plasmon hybridization is combined with the power of brute-force numerical methods to understand the plasmonic properties of some very complicated nanostructures. We showed the plasmons of a gold nanostar are a result of hybridization of the plasmons of the core and the tips of the particle. The core serves as a nanoantenna, dramatically enhanced the optical spectrum and the field enhancement of the nanostar. We also applied this method analyzing the plasmonic modes of a nanocavity structure composed of a nanodisk with a surrounding minoring. For the concentric combination, we showed the nature of the plasmon modes can be understood as the plasmon hybrization of an individual ring and disk. The interation results in a blueshifted and broadened superradiant antibonding

Enhanced Amendment Delivery to Subsurface Using Shear Thinning Fluid and Aqueous Foam for Metal, Radionuclide, and NAPL Remediation

NASA Astrophysics Data System (ADS)

Zhong, L.; Szecsody, J.; Li, X.; Oostrom, M.; Truex, M.

2010-12-01

In many contamination sites, removal of contaminants by any active remediation efforts is not practical due to the high cost and technological limitations. Alternatively, in situ remediation is expected to be the most important remediation strategy. Delivery of reactive amendment to the contamination zone is essential for the reactions between the contaminants and remedial amendments to proceed in situ. It is a challenge to effectively deliver remedial amendment to the subsurface contamination source areas in both aquifer and vadose zone. In aquifer, heterogeneity induces fluid bypassing the low-permeability zones, resulting in certain contaminated areas inaccessible to the remedial amendment delivered by water injection, thus inhibiting the success of remedial operations. In vadose zone in situ remediation, conventional solution injection and infiltration for amendment delivery have difficulties to achieve successful lateral spreading and uniform distribution of the reactive media. These approaches also tend to displace highly mobile metal and radionuclide contaminants such as hexavalent chromium [Cr(VI)] and technetium (Tc-99), causing spreading of contaminations. Shear thinning fluid and aqueous foam can be applied to enhance the amendment delivery and improve in situ subsurface remediation efficiency under aquifer and vadose zone conditions, respectively. Column and 2-D flow cell experiments were conducted to demonstrate the enhanced delivery and improved remediation achieved by the application of shear thinning fluid and foam injection at the laboratory scale. Solutions of biopolymer xanthan gum were used as the shear thinning delivering fluids. Surfactant sodium lauryl ether sulfate (STEOL CS-330) was the foaming agent. The shear thinning fluid delivery (STFD) considerably improved the sweeping efficiency over a heterogeneous system and enhanced the non-aqueous liquid phase (NAPL) removal. The delivery of amendment into low-perm zones (LPZs) by STFD also

Reactor and method for production of nanostructures

DOEpatents

Sunkara, Mahendra Kumar; Kim, Jeong H.; Kumar, Vivekanand

2017-04-25

A reactor and method for production of nanostructures, including metal oxide nanowires or nanoparticles, are provided. The reactor includes a regulated metal powder delivery system in communication with a dielectric tube; a plasma-forming gas inlet, whereby a plasma-forming gas is delivered substantially longitudinally into the dielectric tube; a sheath gas inlet, whereby a sheath gas is delivered into the dielectric tube; and a microwave energy generator coupled to the dielectric tube, whereby microwave energy is delivered into a plasma-forming gas. The method for producing nanostructures includes providing a reactor to form nanostructures and collecting the formed nanostructures, optionally from a filter located downstream of the dielectric tube.

Fabrication of highly ordered 2D metallic arrays with disc-in-hole binary nanostructures via a newly developed nanosphere lithography

NASA Astrophysics Data System (ADS)

Yang, Xi; Guo, Wei; Wang, Xixi; Liao, Mingdun; Gao, Pingqi; Ye, Jichun

2017-11-01

2D metallic arrays with binary nanostructures derived from a nanosphere lithography (NSL) method have been rarely reported. Here, we demonstrate a novel NSL strategy to fabricate highly ordered 2D gold arrays with disc-in-hole binary (DIHB) nanostructures in large scale by employing a sacrificing layer combined with a three-step lift-off process. The structural parameters of the resultant DIHB arrays, such as periodicity, hole diameter, disc diameter and thicknesses can be facilely controlled by tuning the nanospheres size, etching condition, deposition angle and duration, respectively. Due to the intimate interactions between two subcomponents, the DIHB arrays exhibit both an extraordinary high surface-enhanced Raman scattering enhancement factor up to 5 × 108 and a low sheet resistance down to 1.7 Ω/sq. Moreover, the DIHB array can also be used as a metal catalyzed chemical etching catalytic pattern to create vertically-aligned Si nano-tube arrays for anti-reflectance application. This strategy provides a universal route for synthesizing other diverse binary nanostructures with controlled morphology, and thus expands the applications of the NSL to prepare ordered nanostructures with multi-function.

Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures.

PubMed

Bigdeli, Fahime; Ghasempour, Hosein; Azhdari Tehrani, Alireza; Morsali, Ali; Hosseini-Monfared, Hassan

2017-07-01

A 3D, porous Zn(II)-based metal-organic framework {[Zn 2 (oba) 2 (4-bpmn)]·(DMF) 1.5 } n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H 2 oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn 2 (oba) 2 (4-bpmn)] (TMU-21) and {[Zn 2 (oba) 2 (4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

NASA Astrophysics Data System (ADS)

Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

2018-03-01

Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

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

NASA Astrophysics Data System (ADS)

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

2016-08-01

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

Metallic nano-structures for polarization-independent multi-spectral filters

NASA Astrophysics Data System (ADS)

Tang, Yongan; Vlahovic, Branislav; Brady, David Jones

2011-05-01

Cross-shaped-hole arrays (CSHAs) are selected for diminishing the polarization-dependent transmission differences of incident plane waves. We investigate the light transmission spectrum of the CSHAs in a thin gold film over a wide range of features. It is observed that two well-separated and high transmission efficiency peaks could be obtained by designing the parameters in the CSHAs for both p-polarized and s-polarized waves; and a nice transmission band-pass is also observed by specific parameters of a CSHA too. It implicates the possibility to obtain a desired polarization-independent transmission spectrum from the CSHAs by designing their parameters. These findings provide potential applications of the metallic nano-structures in optical filters, optical band-pass, optical imaging, optical sensing, and biosensors.

Transition metal ions mediated tyrosine based short peptide amphiphile nanostructures inhibit bacterial growth.

PubMed

Joshi, Khashti Ballabh; Singh, Ramesh; Mishra, Narendra Kumar; Kumar, Vikas; Vinayak, Vandana

2018-05-17

We report the design and synthesis of biocompatible small peptide based molecule for the controlled and targeted delivery of the encapsulated bioactive metal ions via transforming their internal nanostructures. Tyrosine based short peptide amphiphile (sPA) was synthesized which self-assembled into β-sheet like secondary structures. The self assembly of the designed sPA was modulated by using different bioactive transition metal ions which is confirmed by spectroscopic and microscopic techniques. These bioactive metal ions conjugated sPA hybrid structures are further used to develop antibacterial materials. It is due to the excellent antibacterial activity of zinc ions that the growth of clinically relevant bacteria such as E. Coli was inhibited in the presence of zinc-sPA conjugate. The bacterial test demonstrated that owing to high biocompatibility with bacterial cell, the designed sPA worked as metal ions delivery agent and therefore it can show great potential in locally addressing bacterial infections. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Foaming Volume and Foam Stability

DTIC Science & Technology

1947-02-01

for a series of hydrocarbons and for a range of concentrations of aqueous ethylene-glycol solutions. It is shown that the amount of foam formed depends...methodofmeasuringfoamingvolumeisdescribedandinvestigated to establishthecriticalfactorsin itsoperation.Dataon foaming ...zethatfoamstabll. # itymeasurementsshouldbe takenipcon@.n@ionwithmeasurementsof foam density.It iseasilyrecognizedthatinitialfoamdensities,asmeasured by

Recycling of Aluminum Alloy with Dimox and Rheocasting Functionalize High Performance Structural Foam Composite

NASA Astrophysics Data System (ADS)

Rabeeh, Bakr Mohamed

Great efforts aiming towards the synthesis and the development of structural composite materials. Direct metal oxidation, DIMOX introduced for hybrid composite processing. However, oxidation temperatures around 1100°C lead to the formation of porous ceramic materials. To utilize this porosity intentionally for foam production, a new approach based on synergetic effect of alloying elements, DIMOX and semisolid (rheocsting) processing is developed. A semisolid reaction, rheocasting is introduced to control porosity shape and size. Aluminum alloy 6xxx (automobile scrap pistons) is recycled for this objective and DIMOX at 1100°C for 30 min, then rheocasting, at 750°C for 30 minutes. The effect of α-Fe powder, Mg powder, and Boric acid powder established for the objective of a hybrid structural metal matrix composite in bulk foam matrix. The kinetic of formation of hybrid metal matrix foam composite is introduced. Microstructural and mechanical characterization established for high performance Aluminum foam hybrid composite materials.

Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

DOEpatents

Gardner, Todd H.

2015-09-15

Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

Microcellular carbon foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1993-12-07

A microcellular carbon foam is characterized by a density in the range of about 30 to 1000 mg/cm[sup 3], substantially uniform distribution of cell sizes of diameters less than 100 [mu]m with a majority of the cells being of a diameter of less than about 10 [mu]m, well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.

Microcellular carbon foam and method

DOEpatents

Simandl, Ronald F.; Brown, John D.

1994-01-01

A microcellular carbon foam characterized by a density in the range of about 30 to 1000 mg/cm.sup.3, substantially uniform distribution of cell sizes of diameters less than 100 .mu.m with a majority of the cells being of a diameter of less than about 10 .mu.m, well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.

Microcellular carbon foam and method

DOEpatents

Simandl, Ronald F.; Brown, John D.

1993-01-01

A microcellular carbon foam characterized by a density in the range of about 30 to 1000 mg/cm.sup.3, substantially uniform distribution of cell sizes of diameters less than 100 .mu.m with a majority of the cells being of a diameter of less than about 10 .mu.m, well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.

Microcellular carbon foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1994-04-05

A microcellular carbon foam is described which is characterized by a density in the range of about 30 to 1000 mg/cm[sup 3], substantially uniform distribution of cell sizes of diameters less than 100 [mu]m with a majority of the cells being of a diameter of less than about 10 [mu]m, well interconnected strut morphology providing open porosity, and an expanded d(002) X-ray turbostatic spacing greater than 3.50 angstroms. The precursor for the carbon foam is prepared by the phase inversion of polyacrylonitrile in a solution consisting essentially of at least one alkali metal halide and a phase inversion solvent for the polyacrylonitrile.

Synthesis and Antibacterial Activity of Metal(loid) Nanostructures by Environmental Multi-Metal(loid) Resistant Bacteria and Metal(loid)-Reducing Flavoproteins.

PubMed

Figueroa, Maximiliano; Fernandez, Valentina; Arenas-Salinas, Mauricio; Ahumada, Diego; Muñoz-Villagrán, Claudia; Cornejo, Fabián; Vargas, Esteban; Latorre, Mauricio; Morales, Eduardo; Vásquez, Claudio; Arenas, Felipe

2018-01-01

Microbes are suitable candidates to recover and decontaminate different environments from soluble metal ions, either via reduction or precipitation to generate insoluble, non-toxic derivatives. In general, microorganisms reduce toxic metal ions generating nanostructures (NS), which display great applicability in biotechnological processes. Since the molecular bases of bacterial reduction are still unknown, the search for new -environmentally safe and less expensive- methods to synthesize NS have made biological systems attractive candidates. Here, 47 microorganisms isolated from a number of environmental samples were analyzed for their tolerance or sensitivity to 19 metal(loid)s. Ten of them were highly tolerant to some of them and were assessed for their ability to reduce these toxicants in vitro . All isolates were analyzed by 16S rRNA gene sequencing, fatty acids composition, biochemical tests and electron microscopy. Results showed that they belong to the Enterobacter, Staphylococcus, Acinetobacter , and Exiguobacterium genera. Most strains displayed metal(loid)-reducing activity using either NADH or NADPH as cofactor. While Acinetobacter schindleri showed the highest tellurite ( TeO 3 2 - ) and tetrachloro aurate ( AuCl 4 - ) reducing activity, Staphylococcus sciuri and Exiguobacterium acetylicum exhibited selenite ( SeO 3 2 - ) and silver (Ag + ) reducing activity, respectively. Based on these results, we used these bacteria to synthetize, in vivo and in vitro Te, Se, Au, and Ag-containing nanostructures. On the other hand, we also used purified E. cloacae glutathione reductase to synthesize in vitro Te-, Ag-, and Se-containing NS, whose morphology, size, composition, and chemical composition were evaluated. Finally, we assessed the putative anti-bacterial activity exhibited by the in vitro synthesized NS: Te-containing NS were more effective than Au-NS in inhibiting Escherichia coli and Listeria monocytogenes growth. Aerobically synthesized TeNS using MF09

Synthesis and Antibacterial Activity of Metal(loid) Nanostructures by Environmental Multi-Metal(loid) Resistant Bacteria and Metal(loid)-Reducing Flavoproteins

PubMed Central

Figueroa, Maximiliano; Fernandez, Valentina; Arenas-Salinas, Mauricio; Ahumada, Diego; Muñoz-Villagrán, Claudia; Cornejo, Fabián; Vargas, Esteban; Latorre, Mauricio; Morales, Eduardo; Vásquez, Claudio; Arenas, Felipe

2018-01-01

Microbes are suitable candidates to recover and decontaminate different environments from soluble metal ions, either via reduction or precipitation to generate insoluble, non-toxic derivatives. In general, microorganisms reduce toxic metal ions generating nanostructures (NS), which display great applicability in biotechnological processes. Since the molecular bases of bacterial reduction are still unknown, the search for new -environmentally safe and less expensive- methods to synthesize NS have made biological systems attractive candidates. Here, 47 microorganisms isolated from a number of environmental samples were analyzed for their tolerance or sensitivity to 19 metal(loid)s. Ten of them were highly tolerant to some of them and were assessed for their ability to reduce these toxicants in vitro. All isolates were analyzed by 16S rRNA gene sequencing, fatty acids composition, biochemical tests and electron microscopy. Results showed that they belong to the Enterobacter, Staphylococcus, Acinetobacter, and Exiguobacterium genera. Most strains displayed metal(loid)-reducing activity using either NADH or NADPH as cofactor. While Acinetobacter schindleri showed the highest tellurite (TeO32-) and tetrachloro aurate (AuCl4-) reducing activity, Staphylococcus sciuri and Exiguobacterium acetylicum exhibited selenite (SeO32-) and silver (Ag+) reducing activity, respectively. Based on these results, we used these bacteria to synthetize, in vivo and in vitro Te, Se, Au, and Ag-containing nanostructures. On the other hand, we also used purified E. cloacae glutathione reductase to synthesize in vitro Te-, Ag-, and Se-containing NS, whose morphology, size, composition, and chemical composition were evaluated. Finally, we assessed the putative anti-bacterial activity exhibited by the in vitro synthesized NS: Te-containing NS were more effective than Au-NS in inhibiting Escherichia coli and Listeria monocytogenes growth. Aerobically synthesized TeNS using MF09 crude extracts

Phase structuring in metal alloys: Ultrasound-assisted top-down approach to engineering of nanostructured catalytic materials.

PubMed

Cherepanov, Pavel V; Andreeva, Daria V

2017-03-01

High intensity ultrasound (HIUS) is a novel and efficient tool for top-down nanostructuring of multi-phase metal systems. Ultrasound-assisted structuring of the phase in metal alloys relies on two main mechanisms including interfacial red/ox reactions and temperature driven solid state phase transformations which affect surface composition and morphology of metals. Physical and chemical properties of sonication medium strongly affects the structuring pathways as well as morphology and composition of catalysts. HIUS can serve as a simple, fast, and effective approach for the tuning of structure and surface properties of metal particles, opening the new perspectives in design of robust and efficient catalysts. Copyright © 2016 Elsevier B.V. All rights reserved.

Improved functionality of graphene and carbon nanotube hybrid foam architecture by UV-ozone treatment

NASA Astrophysics Data System (ADS)

Wang, Wei; Ruiz, Isaac; Lee, Ilkeun; Zaera, Francisco; Ozkan, Mihrimah; Ozkan, Cengiz S.

2015-04-01

Optimization of the electrode/electrolyte double-layer interface is a key factor for improving electrode performance of aqueous electrolyte based supercapacitors (SCs). Here, we report the improved functionality of carbon materials via a non-invasive, high-throughput, and inexpensive UV generated ozone (UV-ozone) treatment. This process allows precise tuning of the graphene and carbon nanotube hybrid foam (GM) transitionally from ultrahydrophobic to hydrophilic within 60 s. The continuous tuning of surface energy can be controlled by simply varying the UV-ozone exposure time, while the ozone-oxidized carbon nanostructure maintains its integrity. Symmetric SCs based on the UV-ozone treated GM foam demonstrated enhanced rate performance. This technique can be readily applied to other CVD-grown carbonaceous materials by taking advantage of its ease of processing, low cost, scalability, and controllability.Optimization of the electrode/electrolyte double-layer interface is a key factor for improving electrode performance of aqueous electrolyte based supercapacitors (SCs). Here, we report the improved functionality of carbon materials via a non-invasive, high-throughput, and inexpensive UV generated ozone (UV-ozone) treatment. This process allows precise tuning of the graphene and carbon nanotube hybrid foam (GM) transitionally from ultrahydrophobic to hydrophilic within 60 s. The continuous tuning of surface energy can be controlled by simply varying the UV-ozone exposure time, while the ozone-oxidized carbon nanostructure maintains its integrity. Symmetric SCs based on the UV-ozone treated GM foam demonstrated enhanced rate performance. This technique can be readily applied to other CVD-grown carbonaceous materials by taking advantage of its ease of processing, low cost, scalability, and controllability. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06795a

Analysis of compressive strength in flatwise and edgewise direction to characterize Al-7000 aluminium foam

NASA Astrophysics Data System (ADS)

Sutarno, Soepriyanto, Syoni; Korda, Akhmad A.; Dirgantara, Tatacipta

2015-09-01

The physical mechanical properties of Al-7000 aluminium foam product and processing has been evaluated in this study. The characterization through the compressive testing refers to flatwise direction provided more confident result than edgewise direction. This experiment may correlate with formation of side products of calcia alumina and alumina silica that involved in metal mixture of aluminium foam. These compounds are formed from additional calcium carbonate and silica in the mixture. Calcium carbonate (CaCO3) roles as a blowing agent source of carbon dioxide (CO2). The formation of calcia alumina (CaO.Al2O3) may role to strengthen of cell wall of aluminium foam and to improve the viscosity of melting metal. The Al-7000 aluminium foam indicated a decrease of compressive strength probably due to existence of alumina silica (3Al2O3.SiO2) in the metal mixture.

Catalysts for polyimide foams from aromatic isocyanates and aromatic dianhydrides. [flame retardant foams

NASA Technical Reports Server (NTRS)

Riccitiello, S. R.; Sawko, P. M.; Estrella, C. A. (Inventor)

1979-01-01

Polyimide foam products having greatly improved burn-through and flame-spread resistance are prepared by the reaction of aromatic polyisocyanates with aromatic dianhydrides in the presence of metallic salts of octoic acid. The salts, for example stannous octoate, ferric octoate and aluminum octoate, favor the formation of imide linkages at the expense of other possible reactions.

Spontaneous formation of nanostructures inside inkjet-printed colloidal drops

NASA Astrophysics Data System (ADS)

Yang, Xin; Thorne, Nathaniel; Sun, Ying

2013-11-01

Nanostructures formed in inkjet-printed colloidal drops are systematically examined with different substrates and ink formulations. Various deposition patterns from multi-ring, radial spoke, firework to spider web, foam and island structures are observed. With a high particle loading, deposition transitions from multi-ring near the drop edge to spider web and finally to foam and islands in the center of the drop with 20 nm sulfate-modified polystyrene particles. At the same particle loading, 200 nm particles self-assemble into radial spokes at the drop edge and islands in the center, due to reduced contact line pinning resulted from less particles. In drops with a low particle concentration, due to fingering instability of the contact line, 20 nm particles form radial spokes enclosed by a ring, while 200 nm particles assemble into firework-like structures without a ring. Moreover, at a high particle loading, ruptures are observed on the multi-ring structure formed by 20 nm carboxylic-modified particles, due to stronger capillary forces from the contact line. Furthermore, for a drop printed on a less hydrophilic substrate, the interparticle interactions enable a more uniform deposition rather than complex nanostructures.

Foam, Foam-resin composite and method of making a foam-resin composite

NASA Technical Reports Server (NTRS)

MacArthur, Doug E. (Inventor); Cranston, John A. (Inventor)

1995-01-01

This invention relates to a foam, a foam-resin composite and a method of making foam-resin composites. The foam set forth in this invention comprises a urethane modified polyisocyanurate derived from an aromatic amino polyol and a polyether polyol. In addition to the polyisocyanurate foam, the composite of this invention further contains a resin layer, wherein the resin may be epoxy, bismaleimide, or phenolic resin. Such resins generally require cure or post-cure temperatures of at least 350.degree. F.

Micro- and Nanostructured Metal Oxide Chemical Sensors for Volatile Organic Compounds

NASA Technical Reports Server (NTRS)

Alim, M. A.; Penn, B. G.; Currie, J. R., Jr.; Batra, A. K.; Aggarwal, M. D.

2008-01-01

Aeronautic and space applications warrant the development of chemical sensors which operate in a variety of environments. This technical memorandum incorporates various kinds of chemical sensors and ways to improve their performance. The results of exploratory investigation of the binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. A short review of the present status of the new types of nanostructured sensors such as nanobelts, nanorods, nanotube, etc. based on metal oxides is presented.

Metal Surface Modification for Obtaining Nano- and Sub-Nanostructured Protective Layers.

PubMed

Ledovskykh, Volodymyr; Vyshnevska, Yuliya; Brazhnyk, Igor; Levchenko, Sergiy

2017-12-01

Regularities of the phase protective layer formation in multicomponent systems involving inhibitors with different mechanism of protective action have been investigated. It was shown that optimization of the composition of the inhibition mixture allows to obtain higher protective efficiency owing to improved microstructure of the phase layer. It was found that mechanism of the film formation in the presence of NaNO 2 -PHMG is due to deposition of slightly soluble PHMG-Fe complexes on the metal surface. On the basis of the proposed mechanism, the advanced surface engineering methods for obtaining nanoscaled and sub-nanostructured functional coatings may be developed.

Metal Surface Modification for Obtaining Nano- and Sub-Nanostructured Protective Layers

NASA Astrophysics Data System (ADS)

Ledovskykh, Volodymyr; Vyshnevska, Yuliya; Brazhnyk, Igor; Levchenko, Sergiy

2017-03-01

Regularities of the phase protective layer formation in multicomponent systems involving inhibitors with different mechanism of protective action have been investigated. It was shown that optimization of the composition of the inhibition mixture allows to obtain higher protective efficiency owing to improved microstructure of the phase layer. It was found that mechanism of the film formation in the presence of NaNO2-PHMG is due to deposition of slightly soluble PHMG-Fe complexes on the metal surface. On the basis of the proposed mechanism, the advanced surface engineering methods for obtaining nanoscaled and sub-nanostructured functional coatings may be developed.

The Corrosion of Metals in Aqueous Film-Forming Foams.

DTIC Science & Technology

CORROSION), (*FIRE EXTINGUISHERS, STAINLESS STEEL), (*STAINLESS STEEL, (* FOAM , CORROSION), PH FACTOR, CHLORIDES, FLUORIDES, STEEL, NICKEL ALLOYS, COPPER ALLOYS, NAVAL EQUIPMENT, AIRCRAFT CARRIERS, SEA WATER, COMPATIBILITY.

Metal/Carbon Hybrid Nanostructures Produced from Plasma-Enhanced Chemical Vapor Deposition over Nafion-Supported Electrochemically Deposited Cobalt Nanoparticles

PubMed Central

Achour, Amine; Saeed, Khalid; Djouadi, Mohamed Abdou

2018-01-01

In this work, we report development of hybrid nanostructures of metal nanoparticles (NP) and carbon nanostructures with strong potential for catalysis, sensing, and energy applications. First, the etched silicon wafer substrates were passivated for subsequent electrochemical (EC) processing through grafting of nitro phenyl groups using para-nitrobenzene diazonium (PNBT). The X-ray photoelectron spectroscope (XPS) and atomic force microscope (AFM) studies confirmed presence of few layers. Cobalt-based nanoparticles were produced over dip or spin coated Nafion films under different EC reduction conditions, namely CoSO4 salt concentration (0.1 M, 1 mM), reduction time (5, 20 s), and indirect or direct EC reduction route. Extensive AFM examination revealed NP formation with different attributes (size, distribution) depending on electrochemistry conditions. While relatively large NP with >100 nm size and bimodal distribution were obtained after 20 s EC reduction in H3BO3 following Co2+ ion uptake, ultrafine NP (<10 nm) could be produced from EC reduction in CoSO4 and H3BO3 mixed solution with some tendency to form oxides. Different carbon nanostructures including few-walled or multiwalled carbon nanotubes (CNT) and carbon nanosheets were grown in a C2H2/NH3 plasma using the plasma-enhanced chemical vapor deposition technique. The devised processing routes enable size controlled synthesis of cobalt nanoparticles and metal/carbon hybrid nanostructures with unique microstructural features. PMID:29702583

Low temperature scanning tunneling microscopy of metallic and organic nanostructures

NASA Astrophysics Data System (ADS)

Fölsch, Stefan

2006-03-01

Low temperature scanning tunneling microscopy (LT-STM) is capable of both characterizing and manipulating atomic-scale structures at surfaces. It thus provides a powerful experimental tool to gain fundamental insight into how electronic properties evolve when controlling size, geometry, and composition of nanometric model systems at the level of single atoms and molecules. The experiments discussed in this talk employ a Cu(111) surface onto which perfect nanostructures are assembled from native adatoms and organic molecules. Using single Cu adatoms as building blocks, we obtain zero-, one-, and two-dimensional quantum objects (corresponding to the discrete adatom, monatomic adatom chains, and compact adatom assemblies) with intriguing electronic properties. Depending on the structure shape and the number of incorporated atoms we observe the formation of characteristic quantum levels which merge into the sp-derived Shockley surface state in the limit of extended 2D islands; this state exists on many surfaces, such as Cu(111). Our results reveal the natural linkage between this traditional surface property, the quantum confinement in compact adatom structures, and the quasi-atomic state associated with the single adatom. In a second step, we study the interaction of pentacene (C22H14) with Cu adatom chains serving as model quantum wires. We find that STM-based manipulation is capable of connecting single molecules to the chain ends in a defined way, and that the molecule-chain interaction shifts the chain-localized quantum states to higher binding energies. The present system provides an instructive model case to study single organic molecules interacting with metallic nanostructures. The microscopic nature of such composite structures is of importance for any future molecular-based device realization since it determines the contact conductance between the molecular unit and its metal ''contact pad''.

Hierarchical Co(OH)2 nanostructures/glassy carbon electrode derived from Co(BTC) metal-organic frameworks for glucose sensing

NASA Astrophysics Data System (ADS)

He, Juan; Lu, Xingping; Yu, Jie; Wang, Li; Song, Yonghai

2016-07-01

A novel Co(OH)2/glassy carbon electrode (GCE) has been fabricated via metal-organic framework (MOF)-directed method. In the strategy, the Co(BTC, 1,3,5-benzentricarboxylic acid) MOFs/GCE was firstly prepared by alternately immersing GCE in Co2+ and BTC solution based on a layer-by-layer method. And then, the Co(OH)2 with hierarchical flake nanostructure/GCE was constructed by immersing Co(BTC) MOFs/GCE into 0.1 M NaOH solution at room temperature. Such strategy improves the distribution of hierarchical Co(OH)2 nanostructures on electrode surface greatly, enhances the stability of nanomaterials on the electrode surface, and increases the use efficiency of the Co(OH)2 nanostructures. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and Raman spectra were used to characterize the Co(BTC) MOFs/GCE and Co(OH)2/GCE. Based on the hierarchical Co(OH)2 nanostructures/GCE, a novel and sensitive nonenzymatic glucose sensor was developed. The good performance of the resulted sensor toward the detection of glucose was ascribed to hierarchical flake nanostructures, good mechanical stability, excellent distribution, and large specific surface area of Co(OH)2 nanostructures. The proposed preparation method is simple, efficient, and cheap .

Recycling of Exhaust Batteries in Lead-Foam Electrodes

NASA Astrophysics Data System (ADS)

Costanza, Girolamo; Tata, Maria Elisa

Lead and lead-alloy foams have been investigated in this research. In particular low-cost techniques for the direct production of lead-based electrodes have been analyzed and discussed in this work. The relevance of the main process parameters (powder compacting pressure, granulometry, base metal composition, sintering temperature and time) have been focused and the effect on foam morphology has been discussed too. In particular "Sintering and Dissolution Process" (SDP) and "Replication Process" (RP) have been employed and suitable modified. Both spherical urea and NaCl have been adopted in the SDP method. In the replication process it has been evidenced that the viscosity of the melt is fundamental. Furthermore the research examines lead recovery and recycling of exhaust batteries into foam-based electrodes. A novel method for the direct conversion of Pb scrap into lead foam is discussed too.

mdFoam+: Advanced molecular dynamics in OpenFOAM

NASA Astrophysics Data System (ADS)

Longshaw, S. M.; Borg, M. K.; Ramisetti, S. B.; Zhang, J.; Lockerby, D. A.; Emerson, D. R.; Reese, J. M.

2018-03-01

This paper introduces mdFoam+, which is an MPI parallelised molecular dynamics (MD) solver implemented entirely within the OpenFOAM software framework. It is open-source and released under the same GNU General Public License (GPL) as OpenFOAM. The source code is released as a publicly open software repository that includes detailed documentation and tutorial cases. Since mdFoam+ is designed entirely within the OpenFOAM C++ object-oriented framework, it inherits a number of key features. The code is designed for extensibility and flexibility, so it is aimed first and foremost as an MD research tool, in which new models and test cases can be developed and tested rapidly. Implementing mdFoam+ in OpenFOAM also enables easier development of hybrid methods that couple MD with continuum-based solvers. Setting up MD cases follows the standard OpenFOAM format, as mdFoam+ also relies upon the OpenFOAM dictionary-based directory structure. This ensures that useful pre- and post-processing capabilities provided by OpenFOAM remain available even though the fully Lagrangian nature of an MD simulation is not typical of most OpenFOAM applications. Results show that mdFoam+ compares well to another well-known MD code (e.g. LAMMPS) in terms of benchmark problems, although it also has additional functionality that does not exist in other open-source MD codes.

Study of Microstructure and Mechanical Properties of Particulate Reinforced Aluminum Matrix Composite Foam

NASA Astrophysics Data System (ADS)

Kumar, Suresh; Pandey, O. P.

Metal foams cellular metals have gained an important role in the field of metallurgy, though barely a few decades old. Aluminum composite foam exhibit unique properties such as light weight, blast palliation, sound absorption, high energy absorption, and flame resistance. In the present investigation the effect of variation in the amount of CaCO3 as blowing agent on the microstructure and wear behavior of LM13 alloy foams has been studied. The blowing agent was blended in highly viscous semi-solid melt by stirring process. The process parameters that influence the formation of bubbles like the melt temperature, size and amount of blowing agent and its distribution has been optimized to get uniform size foams. The distribution behavior of blowing agent is influenced by the melt viscosity and stirring speed. For packaging application, the dry sliding wear behavior of the prepared foam was investigated by using a pin on disc method at applied loads of 9.8, 19.6 and 29.4 N at room temperature. The results indicate that the wear rate is dependent on the cell size and cell wall thickness of the foam.

A CuNi bimetallic cathode with nanostructured copper array for enhanced hydrodechlorination of trichloroethylene (TCE).

PubMed

Liu, Bo; Zhang, Hao; Lu, Qi; Li, Guanghe; Zhang, Fang

2018-09-01

To address the challenges of low hydrodechlorination efficiency by non-noble metals, a CuNi bimetallic cathode with nanostructured copper array film was fabricated for effective electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution. The CuNi bimetallic cathodes were prepared by a simple one-step electrodeposition of copper onto the Ni foam substrate, with various electrodeposition time of 5/10/15/20 min. The optimum electrodeposition time was 10 min when copper was coated as a uniform nanosheet array on the nickel foam substrate surface. This cathode exhibited the highest TCE removal, which was twice higher compared to that of the nickel foam cathode. At the same passed charge of 1080C, TCE removal increased from 33.9 ± 3.3% to 99.7 ± 0.1% with the increasing operation current from 5 to 20 mA cm -2 , while the normalized energy consumption decreased from 15.1 ± 1.0 to 2.6 ± 0.01 kWh log -1  m -3 . The decreased normalized energy consumption at a higher current density was due to the much higher removal efficiency at a higher current. These results suggest that CuNi cathodes prepared by simple electrodeposition method represent a promising and cost-effective approach for enhanced electrochemical dechlorination. Copyright © 2018 Elsevier B.V. All rights reserved.

Modeling nanostructural surface modifications in metal cutting by an approach of thermodynamic irreversibility: Derivation and experimental validation

NASA Astrophysics Data System (ADS)

Buchkremer, S.; Klocke, F.

2017-01-01

Performance and operational safety of many metal parts in engineering depend on their surface integrity. During metal cutting, large thermomechanical loads and high gradients of the loads concerning time and location act on the surfaces and may yield significant structural material modifications, which alter the surface integrity. In this work, the derivation and validation of a model of nanostructural surface modifications in metal cutting are presented. For the first time in process modeling, initiation and kinetics of these modifications are predicted using a thermodynamic potential, which considers the interdependent developments of plastic work, dissipation, heat conduction and interface energy as well as the associated productions and flows of entropy. The potential is expressed based on the free Helmholtz energy. The irreversible thermodynamic state changes in the workpiece surface are homogenized over the volume in order to bridge the gap between discrete phenomena involved with the initiation and kinetics of dynamic recrystallization and its macroscopic implications for surface integrity. The formulation of the thermodynamic potential is implemented into a finite element model of orthogonal cutting of steel AISI 4140. Close agreement is achieved between predicted nanostructures and those obtained in transmission electron microscopical investigations of specimen produced in cutting experiments.

Mechanism of Zn Insertion into Nanostructured δ-MnO 2 : A Nonaqueous Rechargeable Zn Metal Battery

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

Han, Sang-Don; Kim, Soojeong; Li, Dongguo

2017-05-19

Unlike the more established lithium-ion based energy storage chemistries, the complex intercalation chemistry of multivalent cations in a host lattice is not well understood, especially the relationship between the intercalating species solution chemistry and the prevalence and type of side reactions. Among multivalent metals, a promising model system can be based on nonaqueous Zn2+ ion chemistry. Several examples of these systems support the use of a Zn metal anode, and reversible intercalation cathodes have been reported. This study utilizes a combination of analytical tools to probe the chemistry of a nanostructured delta-MnO2 cathode in association with a nonaqueous acetonitrile-Zn(TFSI)(2) electrolytemore » and a Zn metal anode. As many of the issues related to understanding a multivalent battery relate to the electrolyte electrode interface, the high surface area of a nanostructured cathode provides a significant interface between the electrolyte and cathode host that maximizes the spectroscopic signal of any side reactions or minor mechanistic pathways. Numerous factors affecting capacity fade and issues associated with the second phase formation including Mn dissolution in heavily cycled Zn/delta-MnO2 cells are presented including dramatic mechanistic differences in the storage mechanism of this couple when compared to similar aqueous electrolytes are noted.« less

Polymer-Derived Silicoboron Carbonitride Foams for CO2 Capture: From Design to Application as Scaffolds for the in Situ Growth of Metal-Organic Frameworks.

PubMed

Sandra, Fabien; Depardieu, Martin; Mouline, Zineb; Vignoles, Gérard L; Iwamoto, Yuji; Miele, Philippe; Backov, Rénal; Bernard, Samuel

2016-06-06

A template-assisted polymer-derived ceramic route is investigated for preparing a series of silicoboron carbonitride (Si/B/C/N) foams with a hierarchical pore size distribution and tailorable interconnected porosity. A boron-modified polycarbosilazane was selected to impregnate monolithic silica and carbonaceous templates and form after pyrolysis and template removal Si/B/C/N foams. By changing the hard template nature and controlling the quantity of polymer to be impregnated, controlled micropore/macropore distributions with mesoscopic cell windows are generated. Specific surface areas from 29 to 239 m(2)  g(-1) and porosities from 51 to 77 % are achieved. These foams combine a low density with a thermal insulation and a relatively good thermostructural stability. Their particular structure allowed the in situ growth of metal-organic frameworks (MOFs) directly within the open-cell structure. MOFs offered a microporosity feature to the resulting Si/B/C/N@MOF composite foams that allowed increasing the specific surface area to provide CO2 uptake of 2.2 %. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and characterisation of embedded metal nanostructures by ion implantation with nanoporous anodic alumina masks

NASA Astrophysics Data System (ADS)

Guan, Wei; Peng, Nianhua; Jeynes, Christopher; Ghatak, Jay; Peng, Yong; Ross, Ian M.; Bhatta, Umananda M.; Inkson, Beverley J.; Möbus, Günter

2013-07-01

Lateral ordered Co, Pt and Co/Pt nanostructures were fabricated in SiO2 and Si3N4 substrates by high fluence metal ion implantation through periodic nanochannel membrane masks based on anodic aluminium oxides (AAO). The quality of nanopatterning transfer defined by various AAO masks in different substrates was examined by transmission electron microscopy (TEM) in both imaging and spectroscopy modes.

Guided evolution of bulk metallic glass nanostructures: A platform for designing three-dimensional electrocatalytic surfaces

DOE PAGES

Doubek, Gustavo; Sekol, Ryan C.; Li, Jinyang; ...

2015-12-22

Precise control over catalyst surface composition and structure is necessary to improve the function of electrochemical systems. To that end, bulk metallic glass (BMG) alloys with atomically dispersed elements provide a highly processable, nanoscale platform for electrocatalysis and surface modification. Here we report on nanostructures of Pt-based BMGs that are modified with various subtractive and additive processes to improve their electrochemical performance.

Complex Nanostructures from Materials based on Metal-Organic Frameworks for Electrochemical Energy Storage and Conversion.

PubMed

Guan, Bu Yuan; Yu, Xin Yao; Wu, Hao Bin; Lou, Xiong Wen David

2017-12-01

Metal-organic frameworks (MOFs) have drawn tremendous attention because of their abundant diversity in structure and composition. Recently, there has been growing research interest in deriving advanced nanomaterials with complex architectures and tailored chemical compositions from MOF-based precursors for electrochemical energy storage and conversion. Here, a comprehensive overview of the synthesis and energy-related applications of complex nanostructures derived from MOF-based precursors is provided. After a brief summary of synthetic methods of MOF-based templates and their conversion to desirable nanostructures, delicate designs and preparation of complex architectures from MOFs or their composites are described in detail, including porous structures, single-shelled hollow structures, and multishelled hollow structures, as well as other unusual complex structures. Afterward, their applications are discussed as electrode materials or catalysts for lithium-ion batteries, hybrid supercapacitors, water-splitting devices, and fuel cells. Lastly, the research challenges and possible development directions of complex nanostructures derived from MOF-based-templates for electrochemical energy storage and conversion applications are outlined. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Programmable nanometer-scale electrolytic metal deposition and depletion

DOEpatents

Lee, James Weifu [Oak Ridge, TN; Greenbaum, Elias [Oak Ridge, TN

2002-09-10

A method of nanometer-scale deposition of a metal onto a nanostructure includes the steps of: providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 .mu.m apart; and depositing metal on at least one of the nanostructures by electric field-directed, programmable, pulsed electrolytic metal deposition. Moreover, a method of nanometer-scale depletion of a metal from a nanostructure includes the steps of providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 .mu.m apart, at least one of the nanostructures having a metal disposed thereon; and depleting at least a portion of the metal from the nanostructure by electric field-directed, programmable, pulsed electrolytic metal depletion. A bypass circuit enables ultra-finely controlled deposition.

Nanostructured core-shell electrode materials for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Jiang, Long-bo; Yuan, Xing-zhong; Liang, Jie; Zhang, Jin; Wang, Hou; Zeng, Guang-ming

2016-11-01

Core-shell nanostructure represents a unique system for applications in electrochemical energy storage devices. Owing to the unique characteristics featuring high power delivery and long-term cycling stability, electrochemical capacitors (ECs) have emerged as one of the most attractive electrochemical storage systems since they can complement or even replace batteries in the energy storage field, especially when high power delivery or uptake is needed. This review aims to summarize recent progress on core-shell nanostructures for advanced supercapacitor applications in view of their hierarchical architecture which not only create the desired hierarchical porous channels, but also possess higher electrical conductivity and better structural mechanical stability. The core-shell nanostructures include carbon/carbon, carbon/metal oxide, carbon/conducting polymer, metal oxide/metal oxide, metal oxide/conducting polymer, conducting polymer/conducting polymer, and even more complex ternary core-shell nanoparticles. The preparation strategies, electrochemical performances, and structural stabilities of core-shell materials for ECs are summarized. The relationship between core-shell nanostructure and electrochemical performance is discussed in detail. In addition, the challenges and new trends in core-shell nanomaterials development have also been proposed.

Development of a Hopkinson Bar Apparatus for Testing Soft Materials: Application to a Closed-Cell Aluminum Foam.

PubMed

Peroni, Marco; Solomos, George; Babcsan, Norbert

2016-01-05

An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general "soft" materials exhibit a series of peculiarities that make difficult the adoption of standard testing techniques for their high strain-rate characterization. This paper presents an innovative apparatus, where high strain-rate tests of metal foams or other soft materials can be performed by exploiting the operating principle of the Hopkinson bar methods. Using the pre-stress method to generate directly a long compression pulse (compared with traditional SHPB), a displacement of about 20 mm can be applied to the specimen with a single propagating wave, suitable for evaluating the whole stress-strain curve of medium-sized cell foams (pores of about 1-2 mm). The potential of this testing rig is shown in the characterization of a closed-cell aluminum foam, where all the above features are amply demonstrated.

Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

NASA Astrophysics Data System (ADS)

Baştürk, S. B.; Tanoğlu, M.

2013-10-01

In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.

Plasmonic nanostructures for surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Jiang, Ruiqian

In the last three decades, a large number of different plasmonic nanostructures have attracted much attention due to their unique optical properties. Those plasmonic nanostructures include nanoparticles, nanoholes and metal nanovoids. They have been widely utilized in optical devices and sensors. When the plasmonic nanostructures interact with the electromagnetic wave and their surface plasmon frequency match with the light frequency, the electrons in plasmonic nanostructures will resonate with the same oscillation as incident light. In this case, the plasmonic nanostructures can absorb light and enhance the light scattering. Therefore, the plasmonic nanostructures can be used as substrate for surface-enhanced Raman spectroscopy to enhance the Raman signal. Using plasmonic nanostructures can significantly enhance Raman scattering of molecules with very low concentrations. In this thesis, two different plasmonic nanostructures Ag dendrites and Au/Ag core-shell nanoparticles are investigated. Simple methods were used to produce these two plasmonic nanostructures. Then, their applications in surface enhanced Raman scattering have been explored. Ag dendrites were produced by galvanic replacement reaction, which was conducted using Ag nitrate aqueous solution and copper metal. Metal copper layer was deposited at the bottom side of anodic aluminum oxide (AAO) membrane. Silver wires formed inside AAO channels connected Ag nitrate on the top of AAO membrane and copper layer at the bottom side of AAO. Silver dendrites were formed on the top side of AAO. The second plasmonic nanostructure is Au/Ag core-shell nanoparticles. They were fabricated by electroless plating (galvanic replacement) reaction in a silver plating solution. First, electrochemically evolved hydrogen bubbles were used as template through electroless deposition to produce hollow Au nanoparticles. Then, the Au nanoparticles were coated with Cu shells in a Cu plating solution. In the following step, a Ag

Inherent health and environmental risk assessment of nanostructured metal oxide production processes.

PubMed

Torabifard, Mina; Arjmandi, Reza; Rashidi, Alimorad; Nouri, Jafar; Mohammadfam, Iraj

2018-01-10

The health and environmental effects of chemical processes can be assessed during the initial stage of their production. In this paper, the Chemical Screening Tool for Exposure and Environmental Release (ChemSTEER) software was used to compare the health and environmental risks of spray pyrolysis and wet chemical techniques for the fabrication of nanostructured metal oxide on a semi-industrial scale with a capacity of 300 kg/day in Iran. The pollution sources identified in each production process were pairwise compared in Expert Choice software using indicators including respiratory damage, skin damage, and environmental damages including air, water, and soil pollution. The synthesis of nanostructured zinc oxide using the wet chemical technique (with 0.523 wt%) leads to lower health and environmental risks compared to when spray pyrolysis is used (with 0.477 wt%). The health and environmental risk assessment of nanomaterial production processes can help select safer processes, modify the operation conditions, and select or modify raw materials that can help eliminate the risks.

Characterization of 17-4 PH stainless steel foam for biomedical applications in simulated body fluid and artificial saliva environments.

PubMed

Mutlu, Ilven; Oktay, Enver

2013-04-01

Highly porous 17-4 PH stainless steel foam for biomedical applications was produced by space holder technique. Metal release and weight loss from 17-4 PH stainless steel foams was investigated in simulated body fluid and artificial saliva environments by static immersion tests. Inductively coupled plasma-mass spectrometer was employed to measure the concentrations of various metal ions released from the 17-4 PH stainless steel foams into simulated body fluids and artificial saliva. Effect of immersion time and pH value on metal release and weight loss in simulated body fluid and artificial saliva were determined. Pore morphology, pore size and mechanical properties of the 17-4 PH stainless steel foams were close to human cancellous bone. Copyright © 2012 Elsevier B.V. All rights reserved.

Biomarker sensing using nanostructured metal oxide sensors

NASA Astrophysics Data System (ADS)

Kalyanasundaram, Krithika

Resistive Chemical sensors are those gas sensitive materials, typically semiconducting metal oxides, that change their electrical properties in response to a change in the ambient. The key features of a chemosensor are sensitivity, selectivity, response time and sensor stability. The hypothesis of this work is that, since metal oxides are polymorphic compounds, the crystal structure of the specific polymorph determines the relative gas selectivity of the material; also that the morphology of the sensing element determines the gas sensitivity limit. This work focuses on the synthesis of nanostructured metal oxides for chemosensors used in selective 'biomarker' detection. Biomarkers are chemical compounds, products of human metabolism which act as specific disease markers. The biomarkers studied in this work include NO, isoprene, NH3, ethanol and acetone which can all be found in exhaled human breath and which allow the non-invasive detection of a range of diseases. Sensors based on three different metal oxides-MoO3, WO 3, and TiO2 were fabricated using sol-gel, electrospinning and spray pyrolysis techniques and tested both as single elements and in an array configuration (electronic nose). The effects of the processing method used, grain size and shape and crystal phase of the material produced, and temperature effects of postsynthesis processing and sensing have been evaluated. Structural characterization has been carried out using X-Ray Diffraction, Scanning and High Resolution Transmission Electron Microscopy, while spectroscopic measurements using XPS, Raman and In-situ FTIR provide valuable information about the surface-analyte interactions. This work has shown that the use of monoclinic polymorph of WO3 yields a selective response to NO, while the other phase of the same oxide give a non-selective chemical response. The orthorhombic phase of MoO 3 exhibits specificity to NH3. An explanation for the variable sensing properties is given based on the gas

Readily available titania nanostructuring routines based on mobility and polarity controlled phase separation of an amphiphilic diblock copolymer.

PubMed

Hohn, Nuri; Schlosser, Steffen J; Bießmann, Lorenz; Grott, Sebastian; Xia, Senlin; Wang, Kun; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter

2018-03-15

The amphiphilic diblock copolymer polystyrene-block-polyethylene oxide is combined with sol-gel chemistry to control the structure formation of blade-coated foam-like titania thin films. The influence of evaporation time before immersion into a poor solvent bath and polarity of the poor solvent bath are studied. Resulting morphological changes are quantified by scanning electron microscopy (SEM) and grazing incidence small angle X-ray scattering (GISAXS) measurements. SEM images surface structures while GISAXS accesses inner film structures. Due to the correlation of evaporation time and mobility of the polymer template during the phase separation process, a decrease in the distances of neighboring titania nanostructures from 50 nm to 22 nm is achieved. Furthermore, through an increase of polarity of an immersion bath the energetic incompatibility of the hydrophobic block and the solvent can be enhanced, leading to an increase of titania nanostructure distances from 35 nm to 55 nm. Thus, a simple approach is presented to control titania nanostructure in foam-like films prepared via blade coating, which enables an easy upscaling of film preparation.

Foam Transport in Porous Media - A Review

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

Zhang, Z. F.; Freedman, Vicky L.; Zhong, Lirong

2009-11-11

Amendment solutions with or without surfactants have been used to remove contaminants from soil. However, it has drawbacks such that the amendment solution often mobilizes the plume, and its movement is controlled by gravity and preferential flow paths. Foam is an emulsion-like, two-phase system in which gas cells are dispersed in a liquid and separated by thin liquid films called lamellae. Potential advantages of using foams in sub-surface remediation include providing better control on the volume of fluids injected, uniformity of contact, and the ability to contain the migration of contaminant laden liquids. It is expected that foam can servemore » as a carrier of amendments for vadose zone remediation, e.g., at the Hanford Site. As part of the U.S. Department of Energy’s EM-20 program, a numerical simulation capability will be added to the Subsurface Transport Over Multiple Phases (STOMP) flow simulator. The primary purpose of this document is to review the modeling approaches of foam transport in porous media. However, as an aid to understanding the simulation approaches, some experiments under unsaturated conditions and the processes of foam transport are also reviewed. Foam may be formed when the surfactant concentration is above the critical micelle concentration. There are two main types of foams – the ball foam (microfoam) and the polyhedral foam. The characteristics of bulk foam are described by the properties such as foam quality, texture, stability, density, surface tension, disjoining pressure, etc. Foam has been used to flush contaminants such as metals, organics, and nonaqueous phase liquids from unsaturated soil. Ball foam, or colloidal gas aphrons, reportedly have been used for soil flushing in contaminated site remediation and was found to be more efficient than surfactant solutions on the basis of weight of contaminant removed per gram of surfactant. Experiments also indicate that the polyhedral foam can be used to enhance soil remediation

Praseodymium sorption on Laminaria digitata algal beads and foams.

PubMed

Wang, Shengye; Hamza, Mohammed F; Vincent, Thierry; Faur, Catherine; Guibal, Eric

2017-10-15

Algal (Laminaria digitata) beads and algal foams have been prepared by a new synthesis mode and the sorbents were tested for praseodymium sorption in batch and fixed-bed like systems (recirculation or one-pass modes), respectively. Metal binding occurs through ion-exchange with Ca(II) ions used for ionotropic gelation of alginate contained in the algal biomass and eventually with protons. Sorption isotherms at pH 4 are described by the Langmuir and the Sips equations with maximum sorption capacities close to 110-120mgPrg -1 . Uptake kinetics are fitted by the pseudo-second order reaction rate equation for both beads and foams; in the case of beads the Crank equation also gives good fit of experimental data. Metal is successfully desorbed using 2M HCl/0.05M CaCl 2 solutions and the sorbent can be efficiently re-used for a minimum of 5 cycles with negligible decrease in sorption/desorption properties and appreciable concentrating effect (around 8-10 times the initial metal concentration). Tested in continuous mode, the algal foam shows typical breakthrough curves that are fitted by the Yan method; desorption is also efficient and allows under the best conditions to achieve a concentration factor close to 8. Copyright © 2017 Elsevier Inc. All rights reserved.

Low-Cost and Rapid Fabrication of Metallic Nanostructures for Sensitive Biosensors Using Hot-Embossing and Dielectric-Heating Nanoimprint Methods.

PubMed

Lee, Kuang-Li; Wu, Tsung-Yeh; Hsu, Hsuan-Yeh; Yang, Sen-Yeu; Wei, Pei-Kuen

2017-07-02

We propose two approaches-hot-embossing and dielectric-heating nanoimprinting methods-for low-cost and rapid fabrication of periodic nanostructures. Each nanofabrication process for the imprinted plastic nanostructures is completed within several seconds without the use of release agents and epoxy. Low-cost, large-area, and highly sensitive aluminum nanostructures on A4 size plastic films are fabricated by evaporating aluminum film on hot-embossing nanostructures. The narrowest bandwidth of the Fano resonance is only 2.7 nm in the visible light region. The periodic aluminum nanostructure achieves a figure of merit of 150, and an intensity sensitivity of 29,345%/RIU (refractive index unit). The rapid fabrication is also achieved by using radio-frequency (RF) sensitive plastic films and a commercial RF welding machine. The dielectric-heating, using RF power, takes advantage of the rapid heating/cooling process and lower electric power consumption. The fabricated capped aluminum nanoslit array has a 5 nm Fano linewidth and 490.46 nm/RIU wavelength sensitivity. The biosensing capabilities of the metallic nanostructures are further verified by measuring antigen-antibody interactions using bovine serum albumin (BSA) and anti-BSA. These rapid and high-throughput fabrication methods can benefit low-cost, highly sensitive biosensors and other sensing applications.

Low-Cost and Rapid Fabrication of Metallic Nanostructures for Sensitive Biosensors Using Hot-Embossing and Dielectric-Heating Nanoimprint Methods

PubMed Central

Lee, Kuang-Li; Wu, Tsung-Yeh; Hsu, Hsuan-Yeh; Yang, Sen-Yeu; Wei, Pei-Kuen

2017-01-01

We propose two approaches—hot-embossing and dielectric-heating nanoimprinting methods—for low-cost and rapid fabrication of periodic nanostructures. Each nanofabrication process for the imprinted plastic nanostructures is completed within several seconds without the use of release agents and epoxy. Low-cost, large-area, and highly sensitive aluminum nanostructures on A4 size plastic films are fabricated by evaporating aluminum film on hot-embossing nanostructures. The narrowest bandwidth of the Fano resonance is only 2.7 nm in the visible light region. The periodic aluminum nanostructure achieves a figure of merit of 150, and an intensity sensitivity of 29,345%/RIU (refractive index unit). The rapid fabrication is also achieved by using radio-frequency (RF) sensitive plastic films and a commercial RF welding machine. The dielectric-heating, using RF power, takes advantage of the rapid heating/cooling process and lower electric power consumption. The fabricated capped aluminum nanoslit array has a 5 nm Fano linewidth and 490.46 nm/RIU wavelength sensitivity. The biosensing capabilities of the metallic nanostructures are further verified by measuring antigen–antibody interactions using bovine serum albumin (BSA) and anti-BSA. These rapid and high-throughput fabrication methods can benefit low-cost, highly sensitive biosensors and other sensing applications. PMID:28671600

Cryogenic Temperature-Gradient Foam/Substrate Tensile Tester

NASA Technical Reports Server (NTRS)

Vailhe, Christophe

2003-01-01

The figure shows a fixture for measuring the tensile strength of the bond between an aluminum substrate and a thermally insulating polymeric foam. The specimen is meant to be representative of insulating foam on an aluminum tank that holds a cryogenic liquid. Prior to the development of this fixture, tensile tests of this type were performed on foam/substrate specimens immersed in cryogenic fluids. Because the specimens were cooled to cryogenic temperatures throughout their thicknesses, they tended to become brittle and to fracture at loads below true bond tensile strengths. The present fixture is equipped to provide a thermal gradient from cryogenic temperature at the foam/substrate interface to room temperature on the opposite foam surface. The fixture includes an upper aluminum block at room temperature and a lower aluminum block cooled to -423 F (approx. -253 C) by use of liquid helium. In preparation for a test, the metal outer surface (the lower surface) of a foam/substrate specimen is bonded to the lower block and the foam outer surface (the upper surface) of the specimen is bonded to the upper block. In comparison with the through-the-thickness cooling of immersion testing, the cryogenic-to-room-temperature thermal gradient that exists during testing on this fixture is a more realistic approximation of the operational thermal condition of sprayed insulating foam on a tank of cryogenic liquid. Hence, tensile tests performed on this fixture provide more accurate indications of operational bond tensile strengths. In addition, the introduction of the present fixture reduces the cost of testing by reducing the amount of cryogenic liquid consumed and the time needed to cool a specimen.

Ternary mixed metal Fe-doped NiCo2O4 nanowires as efficient electrocatalysts for oxygen evolution reaction

NASA Astrophysics Data System (ADS)

Yan, Kai-Li; Shang, Xiao; Li, Zhen; Dong, Bin; Li, Xiao; Gao, Wen-Kun; Chi, Jing-Qi; Chai, Yong-Ming; Liu, Chen-Guang

2017-09-01

Designing mixed metal oxides with unique nanostructures as efficient electrocatalysts for water electrolysis has been an attractive approach for the storage of renewable energies. The ternary mixed metal spinel oxides FexNi1-xCo2O4 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, 1) have been synthesized by a facile hydrothermal approach and calcination treatment using nickel foam as substrate. Fe/Ni ratios have been proved to affect the nanostructures of FexNi1-xCo2O, which imply different intrinsic activity for oxygen evolution reaction (OER). SEM images show that Fe0.5Ni0.5Co2O4 has the uniform nanowires morphology with about 30 nm of the diameter and 200-300 nm of the length. The OER measurements show that Fe0.5Ni0.5Co2O4 exhibits the better electrocatalytic performances with lower overpotential of 350 mV at J = 10 mA cm-2. In addition, the smaller Tafel slope of 27 mV dec-1 than other samples with different Fe/Ni ratios for Fe0.5Ni0.5Co2O4 is obtained. The improved OER activity of Fe0.5Ni0.5Co2O4 may be attributed to the synergistic effects from ternary mixed metals especially Fe-doping and the uniform nanowires supported on NF. Therefore, synthesizing Fe-doped multi-metal oxides with novel nanostructures may be a promising strategy for excellent OER electrocatalysts and it also provides a facile way for the fabrication of high-activity ternary mixed metal oxides electrocatalysts.

Mechanism of Zn Insertion into Nanostructured δ-MnO 2 : A Nonaqueous Rechargeable Zn Metal Battery

DOE PAGES

Han, Sang-Don; Kim, Soojeong; Li, Dongguo; ...

2017-05-08

Unlike the more established lithium-ion based energy storage chemistries, the complex intercalation chemistry of multivalent cations in a host lattice is not well understood, especially the relationship between the intercalating species solution chemistry and the prevalence and type of side reactions. Among multivalent metals, a promising model system can be based on nonaqueous Zn 2+ ion chemistry. There are several examples of these systems support the use of a Zn metal anode, and reversible intercalation cathodes have been reported. Our study utilizes a combination of analytical tools to probe the chemistry of a nanostructured δ-MnO 2 cathode in association withmore » a nonaqueous acetonitrile–Zn(TFSI) 2 electrolyte and a Zn metal anode. As many of the issues related to understanding a multivalent battery relate to the electrolyte–electrode interface, the high surface area of a nanostructured cathode provides a significant interface between the electrolyte and cathode host that maximizes the spectroscopic signal of any side reactions or minor mechanistic pathways. There are numerous factors affecting capacity fade and issues associated with the second phase formation including Mn dissolution in heavily cycled Zn/δ-MnO 2 cells are presented including dramatic mechanistic differences in the storage mechanism of this couple when compared to similar aqueous electrolytes are noted.« less

Superalloy Foams for Aeroshell Applications

NASA Technical Reports Server (NTRS)

Gayda, John; Padula, Santo, II

2001-01-01

Current thermal protection systems for reentry from space, such as that employed on the space shuttle, rely on ceramic tiles with ultra-low conductivity. These materials provide excellent thermal protection but are extremely fragile, easily degraded by environmental attack, and carry no structural loads. Future thermal protection systems being proposed in NASAs MITAS Program will attempt to combine thermal protection with improved durability and structural capability without significant increases in vehicle weight. This may be accomplished by combining several materials in a layered structure to obtain the desired function for aeroshell applications. One class of materials being considered for inclusion in this concept are high temperature metal foam. The objective of this paper was to fabricate low density, superalloy foams and conduct limited testing to evaluate their thermal and structural capabilities. Superalloys were chosen for evaluation as they possesses good strength and excellent environmental endurance over a wide range of temperatures. Utilizing superalloys as low density foams, with porosity contents greater than 90%, minimizes weight and thermal conductivity.

Broadband enhancement of photoluminance from colloidal metal halide perovskite nanocrystals on plasmonic nanostructured surfaces.

PubMed

Zhang, Si; Liang, Yuzhang; Jing, Qiang; Lu, Zhenda; Lu, Yanqing; Xu, Ting

2017-11-07

Metal halide perovskite nanocrystals (NCs) as a new kind of promising optoelectronic material have attracted wide attention due to their high photoluminescence (PL) quantum yield, narrow emission linewidth and wideband color tunability. Since the PL intensity always has a direct influence on the performance of optoelectronic devices, it is of vital importance to improve the perovskite NCs' fluorescence emission efficiency. Here, we synthesize three inorganic perovskite NCs and experimentally demonstrate a broadband fluorescence enhancement of perovskite NCs by exploiting plasmonic nanostructured surface consisting of nanogrooves array. The strong near-field optical localization associated with surface plasmon polariton-coupled emission effect generated by the nanogrooves array can significantly boost the absorption of perovskite NCs and tailor the fluorescence emissions. As a result, the PL intensities of perovskite NCs are broadband enhanced with a maximum factor higher than 8-fold achieved in experimental demonstration. Moreover, the high efficiency PL of perovskite NCs embedded in the polymer matrix layer on the top of plasmonic nanostructured surface can be maintained for more than three weeks. These results imply that plasmonic nanostructured surface is a good candidate to stably broadband enhance the PL intensity of perovskite NCs and further promote their potentials in the application of visible-light-emitting devices.

Design of an experiment for the production of a foamed tin sample

NASA Technical Reports Server (NTRS)

Wernimont, E.

1986-01-01

One of the major experiments in the GAS container is concerned with the experimental production of a foamed metal. A foamed metal is one that contains a significant amount of gas bubbles suspended in its solid volume. Purdue's GAS team proposes to do this with the help of a solid zinc carbonate that gives off carbon dioxide at high temperatures. Because of low energy requirements, the metal used for this experiment is tin. It is hoped that the use of near zero environment will keep the suspended bubbles more uniform than in an Earth based process, hence not depleting the physical strength of the material as greatly as is observed on Earth.

Design of a Metal Oxide-Organic Framework (MoOF) Foam Microreactor: Solar-Induced Direct Pollutant Degradation and Hydrogen Generation.

PubMed

Zhu, Liangliang; Fu Tan, Chuan; Gao, Minmin; Ho, Ghim Wei

2015-12-16

A macroporous carbon network combined with mesoporous catalyst immobilization by a template method gives a metal-oxide-organic framework (MoOF) foam microreactor that readily soaks up pollutants and localizes solar energy in itself, leading to effective degradation of water pollutants (e.g., methyl orange (MO) and also hydrogen generation. The cleaned-up water can be removed from the microreactor simply by compression, and the microreactor used repeatedly. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Springback Foam

NASA Technical Reports Server (NTRS)

1979-01-01

A decade ago, NASA's Ames Research Center developed a new foam material for protective padding of airplane seats. Now known as Temper Foam, the material has become one of the most widely-used spinoffs. Latest application is a line of Temper Foam cushioning produced by Edmont-Wilson, Coshocton, Ohio for office and medical furniture. The example pictured is the Classic Dental Stool, manufactured by Dentsply International, Inc., York, Pennsylvania, one of four models which use Edmont-Wilson Temper Foam. Temper Foam is an open-cell, flameresistant foam with unique qualities.

Fabrication routes for one-dimensional nanostructures via block copolymers

NASA Astrophysics Data System (ADS)

Tharmavaram, Maithri; Rawtani, Deepak; Pandey, Gaurav

2017-05-01

Nanotechnology is the field which deals with fabrication of materials with dimensions in the nanometer range by manipulating atoms and molecules. Various synthesis routes exist for the one, two and three dimensional nanostructures. Recent advancements in nanotechnology have enabled the usage of block copolymers for the synthesis of such nanostructures. Block copolymers are versatile polymers with unique properties and come in many types and shapes. Their properties are highly dependent on the blocks of the copolymers, thus allowing easy tunability of its properties. This review briefly focusses on the use of block copolymers for synthesizing one-dimensional nanostructures especially nanowires, nanorods, nanoribbons and nanofibers. Template based, lithographic, and solution based approaches are common approaches in the synthesis of nanowires, nanorods, nanoribbons, and nanofibers. Synthesis of metal, metal oxides, metal oxalates, polymer, and graphene one dimensional nanostructures using block copolymers have been discussed as well.

Exploring electrolyte preference of vanadium nitride supercapacitor electrodes

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

Wang, Bo; Chen, Zhaohui; Lu, Gang

Highlights: • Hierarchical VN nanostructures were prepared on graphite foam. • Electrolyte preference of VN supercapacitor electrodes was explored. • VN showed better capacitive property in organic and alkaline electrolytes than LiCl. - Abstract: Vanadium nitride hierarchical nanostructures were prepared through an ammonia annealing procedure utilizing vanadium pentoxide nanostructures grown on graphite foam. The electrochemical properties of hierarchical vanadium nitride was tested in aqueous and organic electrolytes. As a result, the vanadium nitride showed better capacitive energy storage property in organic and alkaline electrolytes. This work provides insight into the charge storage process of vanadium nitride and our findings canmore » shed light on other transition metal nitride-based electrochemical energy storage systems.« less

Microwave-Assisted Green Synthesis of Silver Nanostructures

EPA Science Inventory

This account summarizes a microwave (MW)-assisted synthetic approach for producing silver nanostructures. The rapid and in-core MW heating has received considerable attention as a promising new method for the one-pot synthesis of metallic nanostructures in solutions. Conceptually...

Holographic study of conventional and negative Poisson's ratio metallic foams - Elasticity, yield and micro-deformation

NASA Technical Reports Server (NTRS)

Chen, C. P.; Lakes, R. S.

1991-01-01

An experimental study by holographic interferometry is reported of the following material properties of conventional and negative Poisson's ratio copper foams: Young's moduli, Poisson's ratios, yield strengths and characteristic lengths associated with inhomogeneous deformation. The Young's modulus and yield strength of the conventional copper foam were comparable to those predicted by microstructural modeling on the basis of cellular rib bending. The reentrant copper foam exhibited a negative Poisson's ratio, as indicated by the elliptical contour fringes on the specimen surface in the bending tests. Inhomogeneous, non-affine deformation was observed holographically in both foam materials.

Comparison Through Image Analysis Between Al Foams Produced Using Two Different Methods

NASA Astrophysics Data System (ADS)

Boschetto, A.; Campana, F.; Pilone, D.

2014-02-01

Several methods are available for making metal foams. They allow to tailor their mechanical, thermal, acoustic, and electrical properties for specific applications by varying the relative density as well as the cell size and morphology. Foams have a very heterogeneous structure so that their properties may show a large scatter. In this paper, an aluminum foam produced by means of foaming of powder compacts and another one prepared via the infiltration process were analyzed and compared. Image analysis has been used as a useful tool to determine size, morphology, and distribution of cells in both foams and to correlate cell morphology with the considered manufacturing process. The results highlighted that cell size and morphology are strictly dependent upon the manufacturing method. This paper shows how some standard 2D morphological indicators may be usefully adopted to characterize foams whose structure derives from the specific manufacturing process.

Structure and Electronic Properties of Interface-Confined Oxide Nanostructures

DOE PAGES

Liu, Yun; Ning, Yanxiao; Yu, Liang; ...

2017-09-16

The controlled fabrication of nanostructures has often made use of a substrate template to mediate and control the growth kinetics. Electronic substrate-mediated interactions have been demonstrated to guide the assembly of organic molecules or the nucleation of metal atoms but usually at cryogenic temperatures, where the diffusion has been limited. Combining STM, STS, and DFT studies, we report that the strong electronic interaction between transition metals and oxides could indeed govern the growth of low-dimensional oxide nanostructures. As a demonstration, a series of FeO triangles, which are of the same structure and electronic properties but with different sizes (side lengthmore » >3 nm), are synthesized on Pt(111). The strong interfacial interaction confines the growth of FeO nanostructures, leading to a discrete size distribution and a uniform step structure. Given the same interfacial configuration, as-grown FeO nanostructures not only expose identical edge/surface structure but also exhibit the same electronic properties, as manifested by the local density of states and local work functions. We expect the interfacial confinement effect can be generally applied to control the growth of oxide nanostructures on transition metal surfaces. These oxide nanostructures of the same structure and electronic properties are excellent models for studies of nanoscale effects and applications.« less

Structure and Electronic Properties of Interface-Confined Oxide Nanostructures

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

Liu, Yun; Ning, Yanxiao; Yu, Liang

The controlled fabrication of nanostructures has often made use of a substrate template to mediate and control the growth kinetics. Electronic substrate-mediated interactions have been demonstrated to guide the assembly of organic molecules or the nucleation of metal atoms but usually at cryogenic temperatures, where the diffusion has been limited. Combining STM, STS, and DFT studies, we report that the strong electronic interaction between transition metals and oxides could indeed govern the growth of low-dimensional oxide nanostructures. As a demonstration, a series of FeO triangles, which are of the same structure and electronic properties but with different sizes (side lengthmore » >3 nm), are synthesized on Pt(111). The strong interfacial interaction confines the growth of FeO nanostructures, leading to a discrete size distribution and a uniform step structure. Given the same interfacial configuration, as-grown FeO nanostructures not only expose identical edge/surface structure but also exhibit the same electronic properties, as manifested by the local density of states and local work functions. We expect the interfacial confinement effect can be generally applied to control the growth of oxide nanostructures on transition metal surfaces. These oxide nanostructures of the same structure and electronic properties are excellent models for studies of nanoscale effects and applications.« less

Generation of metallic plasmon nanostructures in a thin transparent photosensitive copper oxide film by femtosecond thermochemical decomposition

NASA Astrophysics Data System (ADS)

Danilov, P. A.; Zayarny, D. A.; Ionin, A. A.; Kudryashov, S. I.; Litovko, E. P.; Mel'nik, N. N.; Rudenko, A. A.; Saraeva, I. N.; Umanskaya, S. P.; Khmelnitskii, R. A.

2017-09-01

Irradiation of optically transparent copper (I) oxide film covering a glass substrate with a tightly focused femtosecond laser pulses in the pre-ablation regime leads to film reduction to a metallic colloidal state via a single-photon absorption and its subsequent thermochemical decomposition. This effect was demonstrated by the corresponding measurement of the extinction spectrum in visible spectral range. The laser-induced formation of metallic copper nanoparticles in the focal region inside the bulk oxide film allows direct recording of individual thin-film plasmon nanostructures and optical-range metasurfaces.

Compressive Properties of Metal Matrix Syntactic Foams in Free and Constrained Compression

NASA Astrophysics Data System (ADS)

Orbulov, Imre Norbert; Májlinger, Kornél

2014-06-01

Metal matrix syntactic foam (MMSF) blocks were produced by an inert gas-assisted pressure infiltration technique. MMSFs are advanced hollow sphere reinforced-composite materials having promising application in the fields of aviation, transport, and automotive engineering, as well as in civil engineering. The produced blocks were investigated in free and constrained compression modes, and besides the characteristic mechanical properties, their deformation mechanisms and failure modes were studied. In the tests, the chemical composition of the matrix material, the size of the reinforcing ceramic hollow spheres, the applied heat treatment, and the compression mode were considered as investigation parameters. The monitored mechanical properties were the compressive strength, the fracture strain, the structural stiffness, the fracture energy, and the overall absorbed energy. These characteristics were strongly influenced by the test parameters. By the proper selection of the matrix and the reinforcement and by proper design, the mechanical properties of the MMSFs can be effectively tailored for specific and given applications.

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

NASA Technical Reports Server (NTRS)

Ryan, S.; Ordonez, E.; Christiansen, E. L.; Lear, D. M.

2010-01-01

Open cell metallic foam core sandwich panel structures are of interest for application in spacecraft micrometeoroid and orbital debris shields due to their novel form and advantageous structural and thermal performance. Repeated shocking as a result of secondary impacts upon individual foam ligaments during the penetration process acts to raise the thermal state of impacting projectiles ; resulting in fragmentation, melting, and vaporization at lower velocities than with traditional shielding configurations (e.g. Whipple shield). In order to characterize the protective capability of these structures, an extensive experimental campaign was performed by the Johnson Space Center Hypervelocity Impact Technology Facility, the results of which are reported in this paper. Although not capable of competing against the protection levels achievable with leading heavy shields in use on modern high-risk vehicles (i.e. International Space Station modules), metallic foam core sandwich panels are shown to provide a substantial improvement over comparable structural panels and traditional low weight shielding alternatives such as honeycomb sandwich panels and metallic Whipple shields. A ballistic limit equation, generalized in terms of panel geometry, is derived and presented in a form suitable for application in risk assessment codes.

Impact of foamed matrix components on foamed concrete properties

NASA Astrophysics Data System (ADS)

Tarasenko, V. N.

2018-03-01

The improvement of the matrix foam structure by means of foam stabilizing additives is aimed at solving the technology-oriented problems as well as at the further improvement of physical and mechanical properties of cellular-concrete composites. The dry foam mineralization is the mainstream of this research. Adding the concrete densifiers, foam stabilizers and mineral powders reduces the drying shrinkage, which makes the foam concrete products technologically effective.

Plasmon Mapping in Metallic Nanostructures and its Application to Single Molecule Surface Enhanced Raman Scattering: Imaging Electromagnetic Hot-Spots and Analyte Location

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

Camden, Jon P.

2013-07-12

A major component of this proposal is to elucidate the connection between optical and electron excitation of plasmon modes in metallic nanostructures. These accomplishments are reported: developed a routine protocol for obtaining spatially resolved, low energy EELS spectra, and resonance Rayleigh scattering spectra from the same nanostructures; correlated optical scattering spectra and plasmon maps obtained using STEM/EELS; and imaged electromagnetic hot spots responsible for single-molecule surface-enhanced Raman scattering (SMSERS).

Attenuation of FJ44 Turbofan Engine Noise with a Foam-Metal Liner Installed Over-the-Rotor

NASA Technical Reports Server (NTRS)

Sutliff, Daniel L.; Elliott, Dave M.; Jones, Michael G.; Hartley, Thomas C.

2009-01-01

A Williams International FJ44-3A 3000-lb thrust class turbofan engine was used as a demonstrator for a Foam-Metal Liner (FML) installed in close proximity to the fan. Two FML designs were tested and compared to the hardwall baseline. Traditional single degree-of-freedom liner designs were also evaluated to provide a comparison. Farfield acoustic levels and limited engine performance results are presented in this paper. The results show that the FML achieved up to 5 dB Acoustic Power Level (PWL) overall attenuation in the forward quadrant, equivalent to the traditional liner design. An earlier report presented the test set-up and conditions.

Nanostructuring of sapphire using time-modulated nanosecond laser pulses

NASA Astrophysics Data System (ADS)

Lorenz, P.; Zagoranskiy, I.; Ehrhardt, M.; Bayer, L.; Zimmer, K.

2017-02-01

The nanostructuring of dielectric surfaces using laser radiation is still a challenge. The IPSM-LIFE (laser-induced front side etching using in-situ pre-structured metal layer) method allows the easy, large area and fast laser nanostructuring of dielectrics. At IPSM-LIFE a metal covered dielectric is irradiated where the structuring is assisted by a self-organized molten metal layer deformation process. The IPSM-LIFE can be divided into two steps: STEP 1: The irradiation of thin metal layers on dielectric surfaces results in a melting and nanostructuring process of the metal layer and partially of the dielectric surface. STEP 2: A subsequent high laser fluence treatment of the metal nanostructures result in a structuring of the dielectric surface. At this study a sapphire substrate Al2O3(1-102) was covered with a 10 nm thin molybdenum layer and irradiated by an infrared laser with an adjustable time-dependent pulse form with a time resolution of 1 ns (wavelength λ = 1064 nm, pulse duration Δtp = 1 - 600 ns, Gaussian beam profile). The laser treatment allows the fabrication of different surface structures into the sapphire surface due to a pattern transfer process. The resultant structures were investigated by scanning electron microscopy (SEM). The process was simulated and the simulation results were compared with experimental results.

Design of an ultrabroadband visible metamaterial absorber based on three-dimensional metallic nanostructures

NASA Astrophysics Data System (ADS)

Luo, Hao; Cheng, Yong Zhi

2017-09-01

We present the design and numerical simulations of an ultrabroadband visible metamaterial absorber (MMA) with polarization-insensitive and wide-angle based on three-dimensional (3D) metallic nanostructure. Distinct from previous designs, the proposed visible MMA only consisted of structured 3D metallic film constructed with an assembly of four vertical split-rings (FVSR) structure. For the optimized design of our MMA, the absorbance of over 90% with a relative bandwidth of 94.8% can be obtained. Further simulation results indicate that our design is polarization-insensitive and also operated well in a wide range of incident angles for both TE and TM modes. In addition, the designed visible MMA design can tolerate some geometric parameters errors in fabrication. Thus, the proposed visible MMA can be potential application in the photodetectors, thermal imaging, photoelectrochemical, and solar energy harvesting devices.

Engineered carbon foam for temperature control applications

NASA Astrophysics Data System (ADS)

Almajali, Mohammad Rajab

The need for advanced thermal management materials is well recognized in the electronics and communication industries. An overall reduction in size of electronic components has lead to higher power dissipation and increased the necessity for innovative cooling designs. In response, material suppliers have developed and are continuing to develop, an increasing number of light weight thermal management materials. The new carbon foam is a low density and high thermal conductivity material which has the potential to radically improve heat transfer, thereby reducing size and weight of equipment while simultaneously increasing its efficiency and capabilities. However, carbon foam exhibits low strength and low heat capacity. The present work is intended to overcome these two main drawbacks using a combinatorial approach: (i) initially, copper coating was carried out to improve the thermo-mechanical properties of carbon foam. The thermal and mechanical properties of coated foam were measured using laser flash technique and compression test, respectively. An analytical model was developed to calculate the effective thermal conductivity. It was observed that the copper-coated carbon foam with 50% porosity can attain a thermal conductivity of 180 W/mK. The results from the analytical model were in a very good agreement with experimental results. The modulus increased from 4.5 MPa to 8.6 MPa and the plateau stress increased from 54 kPa to 171 kPa. The relationships between the measured properties and the copper weight ratio were determined. The above analyses demonstrated the significance of copper coating in tailoring carbon foam properties. (ii) Numerical and experimental studies were performed to analyze the phase change behavior of wax/foam composite encapsulated in metal casing. A two-energy equation model was solved using computational fluid dynamics software (CFD). Interfacial effects at the casing-composite junction and between the wax-foam surfaces and the capillary

One-Dimensional Oxide Nanostructures as Gas-Sensing Materials: Review and Issues

PubMed Central

Choi, Kyoung Jin; Jang, Ho Won

2010-01-01

In this article, we review gas sensor application of one-dimensional (1D) metal-oxide nanostructures with major emphases on the types of device structure and issues for realizing practical sensors. One of the most important steps in fabricating 1D-nanostructure devices is manipulation and making electrical contacts of the nanostructures. Gas sensors based on individual 1D nanostructure, which were usually fabricated using electron-beam lithography, have been a platform technology for fundamental research. Recently, gas sensors with practical applicability were proposed, which were fabricated with an array of 1D nanostructures using scalable micro-fabrication tools. In the second part of the paper, some critical issues are pointed out including long-term stability, gas selectivity, and room-temperature operation of 1D-nanostructure-based metal-oxide gas sensors. PMID:22319343

Landau damping of quantum plasmons in metal nanostructures

DOE PAGES

Li, Xiaoguang; Xiao, Di; Zhang, Zhenyu

2013-02-06

Using the random phase approximation with both real space and discrete electron–hole (e–h) pair basis sets, we study the broadening of surface plasmons in metal structures of reduced dimensionality, where Landau damping is the dominant dissipation channel and presents an intrinsic limitation to plasmonics technology. We show that for every prototypical class of systems considered, including zero-dimensional nanoshells, one-dimensional coaxial nanotubes and two-dimensional ultrathin films, Landau damping can be drastically tuned due to energy quantization of the individual electron levels and e–h pairs. Both the generic trend and oscillatory nature of the tunability are in stark contrast with the expectationsmore » of the semiclassical surface scattering picture. Our approach also allows to vividly depict the evolution of the plasmons from the quantum to the classical regime, and to elucidate the underlying physical origin of hybridization broadening of nearly degenerate plasmon modes. Lastly, these findings may serve as a guide in the future design of plasmonic nanostructures of desirable functionalities.« less

Advanced nondestructive techniques applied for the detection of discontinuities in aluminum foams

NASA Astrophysics Data System (ADS)

Katchadjian, Pablo; García, Alejandro; Brizuela, Jose; Camacho, Jorge; Chiné, Bruno; Mussi, Valerio; Britto, Ivan

2018-04-01

Metal foams are finding an increasing range of applications by their lightweight structure and physical, chemical and mechanical properties. Foams can be used to fill closed moulds for manufacturing structural foam parts of complex shape [1]; foam filled structures are expected to provide good mechanical properties and energy absorption capabilities. The complexity of the foaming process and the number of parameters to simultaneously control, demand a preliminary and hugely wide experimental activity to manufacture foamed components with a good quality. That is why there are many efforts to improve the structure of foams, in order to obtain a product with good properties. The problem is that even for seemingly identical foaming conditions, the effective foaming can vary significantly from one foaming trial to another. The variation of the foams often is related by structural imperfections, joining region (foam-foam or foam-wall mold) or difficulties in achieving a complete filling of the mould. That is, in a closed mold, the result of the mold filling and its structure or defects are not known a priori and can eventually vary significantly. These defects can cause a drastic deterioration of the mechanical properties [2] and lead to a low performance in its application. This work proposes the use of advanced nondestructive techniques for evaluating the foam distribution after filling the mold to improve the manufacturing process. To achieved this purpose ultrasonic technique (UT) and cone beam computed tomography (CT) were applied on plate and structures of different thicknesses filled with foam of different porosity. UT was carried out on transmission mode with low frequency air-coupled transducers [3], in focused and unfocused configurations.

Development of metal organic fromwork-199 immobilized zeolite foam for adsorption of common indoor VOCs.

PubMed

Saini, Vipin K; Pires, João

2017-05-01

Reticulated foam shaped adsorbents are more efficient for the removal of volatile organic compounds (VOCs), particularly from low VOC-concentration indoor air streams. In this study composite structure of zeolite and metal organic frameworks (MOFs), referred as ZMF, has been fabricated by immobilization of fine MOF-199 powder on foam shaped Zeolite Socony Mobil-5 (ZSM-5) Zeolitic structure, referred as ZF. The ZMF possess a uniform and well-dispersed coating of MOF-199 on the porous framework of ZF. It shows higher surface area, pore volume, and VOCs adsorption capacity, as compared to ZF-structure. Post-fabrication changes in selective adsorption properties of ZMF were studied with three common indoor VOCs (benzene, n-hexane, and cyclohexane), using gravimetric adsorption technique. The adsorption capacity of ZMF with different VOCs follow the order of benzene>n-hexane>cyclohexane. In comparison with MOF-199 and ZF, the composite structure ZMF shows improvement in selectivity for benzene from other two VOCs. Further, improvement in efficiency and stability of prepared ZMF was found to be associated with its high MOF loading capacity and unique morphological and structural properties. The developed composite structure with improved VOCs removal and recyclability could be a promising material for small to limited scale air pollution treatment units. Copyright © 2016. Published by Elsevier B.V.

Foam injection molding of thermoplastic elastomers: Blowing agents, foaming process and characterization of structural foams

NASA Astrophysics Data System (ADS)

Ries, S.; Spoerrer, A.; Altstaedt, V.

2014-05-01

Polymer foams play an important role caused by the steadily increasing demand to light weight design. In case of soft polymers, like thermoplastic elastomers (TPE), the haptic feeling of the surface is affected by the inner foam structure. Foam injection molding of TPEs leads to so called structural foam, consisting of two compact skin layers and a cellular core. The properties of soft structural foams like soft-touch, elastic and plastic behavior are affected by the resulting foam structure, e.g. thickness of the compact skins and the foam core or density. This inner structure can considerably be influenced by different processing parameters and the chosen blowing agent. This paper is focused on the selection and characterization of suitable blowing agents for foam injection molding of a TPE-blend. The aim was a high density reduction and a decent inner structure. Therefore DSC and TGA measurements were performed on different blowing agents to find out which one is appropriate for the used TPE. Moreover a new analyzing method for the description of processing characteristics by temperature dependent expansion measurements was developed. After choosing suitable blowing agents structural foams were molded with different types of blowing agents and combinations and with the breathing mold technology in order to get lower densities. The foam structure was analyzed to show the influence of the different blowing agents and combinations. Finally compression tests were performed to estimate the influence of the used blowing agent and the density reduction on the compression modulus.

When lithography meets self-assembly: a review of recent advances in the directed assembly of complex metal nanostructures on planar and textured surfaces

NASA Astrophysics Data System (ADS)

Hughes, Robert A.; Menumerov, Eredzhep; Neretina, Svetlana

2017-07-01

One of the foremost challenges in nanofabrication is the establishment of a processing science that integrates wafer-based materials, techniques, and devices with the extraordinary physicochemical properties accessible when materials are reduced to nanoscale dimensions. Such a merger would allow for exacting controls on nanostructure positioning, promote cooperative phenomenon between adjacent nanostructures and/or substrate materials, and allow for electrical contact to individual or groups of nanostructures. With neither self-assembly nor top-down lithographic processes being able to adequately meet this challenge, advancements have often relied on a hybrid strategy that utilizes lithographically-defined features to direct the assembly of nanostructures into organized patterns. While these so-called directed assembly techniques have proven viable, much of this effort has focused on the assembly of periodic arrays of spherical or near-spherical nanostructures comprised of a single element. Work directed toward the fabrication of more complex nanostructures, while still at a nascent stage, has nevertheless demonstrated the possibility of forming arrays of nanocubes, nanorods, nanoprisms, nanoshells, nanocages, nanoframes, core-shell structures, Janus structures, and various alloys on the substrate surface. In this topical review, we describe the progress made in the directed assembly of periodic arrays of these complex metal nanostructures on planar and textured substrates. The review is divided into three broad strategies reliant on: (i) the deterministic positioning of colloidal structures, (ii) the reorganization of deposited metal films at elevated temperatures, and (iii) liquid-phase chemistry practiced directly on the substrate surface. These strategies collectively utilize a broad range of techniques including capillary assembly, microcontact printing, chemical surface modulation, templated dewetting, nanoimprint lithography, and dip-pen nanolithography and

Surpassing the Theoretical Limit of Porosity in Conventional Solid-State Foaming: Microstructure Characterization of Length Scales in a Copper Metal Foam

DTIC Science & Technology

2014-11-01

powder metallurgy processes (e.g., using a polymer foam as a fugitive template7) can exceed 85% porosity, it is more common for powder metallurgy ...for the 0.5 GPa compact is a remarkable result from a powder metallurgy process, especially because the pore structure is not dominated by necks...strengths in bulk engineering structures produced via powder metallurgy . Completely unique to this process is the ability to create foamed powder . This

Role of foam drainage in producing protein aggregates in foam fractionation.

PubMed

Li, Rui; Zhang, Yuran; Chang, Yunkang; Wu, Zhaoliang; Wang, Yanji; Chen, Xiang'e; Wang, Tao

2017-10-01

It is essential to obtain a clear understanding of the foam-induced protein aggregation to reduce the loss of protein functionality in foam fractionation. The major effort of this work is to explore the roles of foam drainage in protein aggregation in the entire process of foam fractionation with bovine serum albumin (BSA) as a model protein. The results show that enhancing foam drainage increased the desorption of BSA molecules from the gas-liquid interface and the local concentration of desorbed molecules in foam. Therefore, it intensified the aggregation of BSA in foam fractionation. Simultaneously, it also accelerated the flow of BSA aggregates from rising foam into the residual solution along with the drained liquid. Because enhancing foam drainage increased the relative content of BSA molecules adsorbed at the gas-liquid interface, it also intensified the aggregation of BSA during both the defoaming process and the storage of the foamate. Furthermore, enhancing foam drainage more readily resulted in the formation of insoluble BSA aggregates. The results are highly important for a better understanding of foam-induced protein aggregation in foam fractionation. Copyright © 2017 Elsevier B.V. All rights reserved.

Stability of biogenic metal(loid) nanomaterials related to the colloidal stabilization theory of chemical nanostructures.

PubMed

Piacenza, Elena; Presentato, Alessandro; Turner, Raymond J

2018-02-25

In the last 15 years, the exploitation of biological systems (i.e. plants, bacteria, mycelial fungi, yeasts, and algae) to produce metal(loid) (Me)-based nanomaterials has been evaluated as eco-friendly and a cost-effective alternative to the chemical synthesis processes. Although the biological mechanisms of biogenic Me-nanomaterial (Bio-Me-nanomaterials) production are not yet completely elucidated, a key advantage of such bio-nanostructures over those chemically synthesized is related to their natural thermodynamic stability, with several studies ascribed to the presence of an organic layer surrounding these Bio-Me-nanostructures. Different macromolecules (e.g. proteins, peptides, lipids, DNA, and polysaccharides) or secondary metabolites (e.g. flavonoids, terpenoids, glycosides, organic acids, and alkaloids) naturally produced by organisms have been indicated as main contributors to the stabilization of Bio-Me-nanostructures. Nevertheless, the chemical-physical mechanisms behind the ability of these molecules in providing stability to Bio-Me-nanomaterials are unknown. In this context, transposing the stabilization theory of chemically synthesized Me-nanomaterials (Ch-Me-nanomaterials) to biogenic materials can be used towards a better comprehension of macromolecules and secondary metabolites role as stabilizing agents of Bio-Me-nanomaterials. According to this theory, nanomaterials are generally featured by high thermodynamic instability in suspension, due to their high surface area and surface energy. This feature leads to the necessity to stabilize chemical nanostructures, even during or directly after their synthesis, through the development of (i) electrostatic, (ii) steric, or (iii) electrosteric interactions occurring between molecules and nanomaterials in suspension. Based on these three mechanisms, this review is focused on parallels between the stabilization of biogenic or chemical nanomaterials, suggesting which chemical-physical mechanisms may be

Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding.

PubMed

Hangai, Yoshihiko; Nakano, Yukiko; Koyama, Shinji; Kuwazuru, Osamu; Kitahara, Soichiro; Yoshikawa, Nobuhiro

2015-10-23

Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately t H = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube.