Thermal properties of alkali-activated aluminosilicates with CNT admixture

NASA Astrophysics Data System (ADS)

Zmeskal, Oldrich; Trhlikova, Lucie; Fiala, Lukas; Florian, Pavel; Cerny, Robert

2017-07-01

Material properties of electrically conductive cement-based materials with increased attention paid on electric and thermal properties were often studied in the last years. Both electric and thermal properties play an important role thanks to their possible utilization in various practical applications (e.g. snow-melting systems or building structures monitoring systems without the need of an external monitoring system). The DC/AC characteristics depend significantly on the electrical resistivity and the electrical capacity of bulk materials. With respect to the DC/AC characteristics of cement-based materials, such materials can be basically classified as electric insulators. In order to enhance them, various conductive admixtures such as those based on different forms of carbon, can be used. Typical representatives of carbon-based admixtures are carbon nanotubes (CNT), carbon fibers (CF), graphite powder (GP) and carbon black (CB). With an adequate amount of such admixtures, electric properties significantly change and new materials with higher added value can be prepared. However, other types of materials can be enhanced in the same way. Alkali-activated aluminosilicates (AAA) based on blast furnace slag are materials with high compressive strength comparable with cement-based materials. Moreover, the price of slag is lower than of Portland cement. Therefore, this paper deals with the study of thermal properties of this promising material with different concentrations of CNT. Within the paper a simple method of basic thermal parameters determination based on the thermal transient response to a heat power step is presented.

Deconvoluting the Photonic and Electronic Response of 2D Materials: The Case of MoS2.

PubMed

Zhang, Kehao; Borys, Nicholas J; Bersch, Brian M; Bhimanapati, Ganesh R; Xu, Ke; Wang, Baoming; Wang, Ke; Labella, Michael; Williams, Teague A; Haque, Md Amanul; Barnard, Edward S; Fullerton-Shirey, Susan; Schuck, P James; Robinson, Joshua A

2017-12-05

Evaluating and tuning the properties of two-dimensional (2D) materials is a major focus of advancing 2D science and technology. While many claim that the photonic properties of a 2D layer provide evidence that the material is "high quality", this may not be true for electronic performance. In this work, we deconvolute the photonic and electronic response of synthetic monolayer molybdenum disulfide. We demonstrate that enhanced photoluminescence can be robustly engineered via the proper choice of substrate, where growth of MoS 2 on r-plane sapphire can yield >100x enhancement in PL and carrier lifetime due to increased molybdenum-oxygen bonding compared to that of traditionally grown MoS 2 on c-plane sapphire. These dramatic enhancements in optical properties are similar to those of super-acid treated MoS 2 , and suggest that the electronic properties of the MoS 2 are also superior. However, a direct comparison of the charge transport properties indicates that the enhanced PL due to increased Mo-O bonding leads to p-type compensation doping, and is accompanied by a 2x degradation in transport properties compared to MoS 2 grown on c-plane sapphire. This work provides a foundation for understanding the link between photonic and electronic performance of 2D semiconducting layers, and demonstrates that they are not always correlated.

Deconvoluting the Photonic and Electronic Response of 2D Materials: The Case of MoS 2

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

Zhang, Kehao; Borys, Nicholas J.; Bersch, Brian M.

Evaluating and tuning the properties of two-dimensional (2D) materials is a major focus of advancing 2D science and technology. While many claim that the photonic properties of a 2D layer provide evidence that the material is "high quality", this may not be true for electronic performance. In this work, we deconvolute the photonic and electronic response of synthetic monolayer molybdenum disulfide. We demonstrate that enhanced photoluminescence can be robustly engineered via the proper choice of substrate, where growth of MoS 2 on r-plane sapphire can yield > 100x enhancement in PL and carrier lifetime due to increased molybdenum-oxygen bonding comparedmore » to that of traditionally grown MoS 2 on c-plane sapphire. These dramatic enhancements in optical properties are similar to those of super-acid treated MoS 2 , and suggest that the electronic properties of the MoS 2 are also superior. However, a direct comparison of the charge transport properties indicates that the enhanced PL due to increased Mo-O bonding leads to p-type compensation doping, and is accompanied by a 2x degradation in transport properties compared to MoS 2 grown on c-plane sapphire. This work provides a foundation for understanding the link between photonic and electronic performance of 2D semiconducting layers, and demonstrates that they are not always correlated.« less

Deconvoluting the Photonic and Electronic Response of 2D Materials: The Case of MoS 2

DOE PAGES

Zhang, Kehao; Borys, Nicholas J.; Bersch, Brian M.; ...

2017-12-05

Evaluating and tuning the properties of two-dimensional (2D) materials is a major focus of advancing 2D science and technology. While many claim that the photonic properties of a 2D layer provide evidence that the material is "high quality", this may not be true for electronic performance. In this work, we deconvolute the photonic and electronic response of synthetic monolayer molybdenum disulfide. We demonstrate that enhanced photoluminescence can be robustly engineered via the proper choice of substrate, where growth of MoS 2 on r-plane sapphire can yield > 100x enhancement in PL and carrier lifetime due to increased molybdenum-oxygen bonding comparedmore » to that of traditionally grown MoS 2 on c-plane sapphire. These dramatic enhancements in optical properties are similar to those of super-acid treated MoS 2 , and suggest that the electronic properties of the MoS 2 are also superior. However, a direct comparison of the charge transport properties indicates that the enhanced PL due to increased Mo-O bonding leads to p-type compensation doping, and is accompanied by a 2x degradation in transport properties compared to MoS 2 grown on c-plane sapphire. This work provides a foundation for understanding the link between photonic and electronic performance of 2D semiconducting layers, and demonstrates that they are not always correlated.« less

Metallurgy and properties of plasma spray formed materials

NASA Technical Reports Server (NTRS)

Mckechnie, T. N.; Liaw, Y. K.; Zimmerman, F. R.; Poorman, R. M.

1992-01-01

Understanding the fundamental metallurgy of vacuum plasma spray formed materials is the key to enhancing and developing full material properties. Investigations have shown that the microstructure of plasma sprayed materials must evolve from a powder splat morphology to a recrystallized grain structure to assure high strength and ductility. A fully, or near fully, dense material that exhibits a powder splat morphology will perform as a brittle material compared to a recrystallized grain structure for the same amount of porosity. Metallurgy and material properties of nickel, iron, and copper base alloys will be presented and correlated to microstructure.

Improvement of Polylactide Properties through Cellulose Nanocrystals Embedded in Poly(Vinyl Alcohol) Electrospun Nanofibers.

PubMed

López de Dicastillo, Carol; Garrido, Luan; Alvarado, Nancy; Romero, Julio; Palma, Juan Luis; Galotto, Maria Jose

2017-05-11

Electrospun nanofibers of poly (vinyl alcohol) (PV) were obtained to improve dispersion of cellulose nanocrystals (CNC) within hydrophobic biopolymeric matrices, such as poly(lactic acid) (PLA). Electrospun nanofibers (PV/CNC) n were successfully obtained with a final concentration of 23% ( w / w ) of CNC. Morphological, structural and thermal properties of developed CNC and electrospun nanofibers were characterized. X-ray diffraction and thermal analysis revealed that the crystallinity of PV was reduced by the electrospinning process, and the incorporation of CNC increased the thermal stability of biodegradable nanofibers. Interactions between CNC and PV polymer also enhanced the thermal stability of CNC and improved the dispersion of CNC within the PLA matrix. PLA materials with CNC lyophilized were also casted in order to compare the properties with materials based on CNC containing nanofibers. Nanofibers and CNC were incorporated into PLA at three concentrations: 0.5%, 1% and 3% (CNC respect to polymer weight) and nanocomposites were fully characterized. Overall, nanofibers containing CNC positively modified the physical properties of PLA materials, such as the crystallinity degree of PLA which was greatly enhanced. Specifically, materials with 1% nanofiber 1PLA(PV/CNC) n presented highest improvements related to mechanical and barrier properties; elongation at break was enhanced almost four times and the permeation of oxygen was reduced by approximately 30%.

Understanding gas adsorption in MOF-5/graphene oxide composite materials.

PubMed

Lin, Li-Chiang; Paik, Dooam; Kim, Jihan

2017-05-10

Metal-organic framework (MOF) and graphene oxide (GO) composite materials (MOF/GO) have been regarded as promising for separation applications due to their synergistically enhanced adsorption properties. Molecular-level understandings of these materials, however, remain unknown to date. In this study, molecular simulations were used, for the first time, to model these composite materials. Specifically, the composite MOF-5/GO material was modeled as stacks of sandwich-like layers on top of one another, consistent with experimental observations inferred from XRD and the SEM images. Simulations indicate that CO 2 and CH 4 bind strongly in the MOF/GO interface region, resulting in synergistically enhanced adsorption properties. To exploit the interface region, we found that in simulating linear alkanes, larger guest molecules show substantially improved adsorption properties in composites compared to the parent MOF-5 structure, illustrating that the performance of adsorption in these molecules will benefit the most from the MOF/GO composites.

Mechanical properties of atomic layer deposition-reinforced nanoparticle thin films.

PubMed

Zhang, Lei; Prosser, Jacob H; Feng, Gang; Lee, Daeyeon

2012-10-21

Nanoparticle thin films (NTFs) exhibit multifunctionality, making them useful for numerous advanced applications including energy storage and conversion, biosensing and photonics. Poor mechanical reliability and durability of NTFs, however, limit their industrial and commercial applications. Atomic layer deposition (ALD) represents a unique opportunity to enhance the mechanical properties of NTFs at a relatively low temperature without drastically changing their original structure and functionality. In this work, we study how ALD of different materials, Al(2)O(3), TiO(2), and SiO(2), affects the mechanical properties of TiO(2) and SiO(2) NTFs. Our results demonstrate that the mechanical properties of ALD-reinforced NTFs are dominantly influenced by the mechanical properties of the ALD materials rather than by the compositional matching between ALD and nanoparticle materials. Among the three ALD materials, Al(2)O(3) ALD provides the best enhancement in the modulus and hardness of the NTFs. Interestingly, Al(2)O(3) ALD is able to enhance not only the modulus and hardness but also the toughness of NTFs. Our study presents an additional benefit of depositing nanometer scale ALD layers in NTFs; that is, we find that the hardness and modulus of ultrathin ALD layers (<5 nm) can be estimated from the mechanical properties of ALD-reinforced NTFs using a simple mixing rule. This investigation also provides insight into the use of nanoindentation for testing the mechanical properties of ultrathin ALD-reinforced NTFs.

Membranes with Surface-Enhanced Antifouling Properties for Water Purification

PubMed Central

Shahkaramipour, Nima; Tran, Thien N.; Ramanan, Sankara; Lin, Haiqing

2017-01-01

Membrane technology has emerged as an attractive approach for water purification, while mitigation of fouling is key to lower membrane operating costs. This article reviews various materials with antifouling properties that can be coated or grafted onto the membrane surface to improve the antifouling properties of the membranes and thus, retain high water permeance. These materials can be separated into three categories, hydrophilic materials, such as poly(ethylene glycol), polydopamine and zwitterions, hydrophobic materials, such as fluoropolymers, and amphiphilic materials. The states of water in these materials and the mechanisms for the antifouling properties are discussed. The corresponding approaches to coat or graft these materials on the membrane surface are reviewed, and the materials with promising performance are highlighted. PMID:28273869

Membranes with Surface-Enhanced Antifouling Properties for Water Purification.

PubMed

Shahkaramipour, Nima; Tran, Thien N; Ramanan, Sankara; Lin, Haiqing

2017-03-05

Membrane technology has emerged as an attractive approach for water purification, while mitigation of fouling is key to lower membrane operating costs. This article reviews various materials with antifouling properties that can be coated or grafted onto the membrane surface to improve the antifouling properties of the membranes and thus, retain high water permeance. These materials can be separated into three categories, hydrophilic materials, such as poly(ethylene glycol), polydopamine and zwitterions, hydrophobic materials, such as fluoropolymers, and amphiphilic materials. The states of water in these materials and the mechanisms for the antifouling properties are discussed. The corresponding approaches to coat or graft these materials on the membrane surface are reviewed, and the materials with promising performance are highlighted.

Advanced composite structural concepts and materials technologies for primary aircraft structures: Advanced material concepts

NASA Technical Reports Server (NTRS)

Lau, Kreisler S. Y.; Landis, Abraham L.; Chow, Andrea W.; Hamlin, Richard D.

1993-01-01

To achieve acceptable performance and long-term durability at elevated temperatures (350 to 600 F) for high-speed transport systems, further improvements of the high-performance matrix materials will be necessary to achieve very long-term (60,000-120,000 service hours) retention of mechanical properties and damage tolerance. This report emphasizes isoimide modification as a complementary technique to semi-interpenetrating polymer networks (SIPN's) to achieve greater processibility, better curing dynamics, and possibly enhanced thermo-mechanical properties in composites. A key result is the demonstration of enhanced processibility of isoimide-modified linear and thermo-setting polyimide systems.

Study of nano mechanical properties polydimethylsiloxane (PDMS)/MWCNT composites

NASA Astrophysics Data System (ADS)

Murudkar, Vrishali; Gaonkar, Amita; Deshpande, V. D.; Mhaske, S. T.

2018-05-01

Polydimethylsiloxane (PDMS), a clear elastomer, is a common material used in many applications; but has poor mechanical properties. Carbon nano tubes (CNT) exhibit excellent mechanical properties & hence are used as filler in PDMS. It was found that the elastic modulus and strength of the PDMS/MWCNT nano composites were enhanced by adding MWCNT [1]. Through the nano indentation experiment, the hardness (H), the elastic modulus (E), and other mechanical properties can be determined from very small volumes of materials [2]; hence nano indentation is widely used to study mechanical properties. PDMS/MWCNT composites have enhanced mechanical properties over neat PDMS. FTIR analysis shows bonding between MWCNT and PDMS; which affects the mechanical properties. From AFM study it shows decreasing roughness for increasing MWCNT concentration. Surface morphology (SEM) study shows well dispersion of MWCNT into PDMS matrix.

Properties and Performance Attributes of Novel Co-extruded Polyolefin Battery Separator Materials. Part 2; Electrical Properties

NASA Technical Reports Server (NTRS)

Baldwin, Richard S.

2013-01-01

As NASA prepares for its next era of manned spaceflight missions, advanced energy storage technologies are being developed and evaluated to address and enhance future mission needs and technical requirements. Cell-level components for advanced lithium-ion batteries possessing higher energy, more reliable performance and enhanced, inherent safety characteristics have been under development within the NASA infrastructure. A key component for safe and reliable cell performance is the cell separator, which separates the two energetic electrodes and functions to inhibit the occurrence of an internal short circuit but preserves an ionic current. Recently, a new generation of co-extruded separator films has been developed by ExxonMobil Chemical and introduced into their battery separator product portfolio. Several grades of this new separator material were evaluated with respect to dynamic mechanical properties and safety-related performance attributes, and the results of these evaluations were previously reported in "Part 1: Mechanical Properties" of this publication. This current paper presents safety-related performance results for these novel materials obtained by employing a complementary experimental methodology, which involved the analysis of separator impedance characteristics as a function of temperature. The experimental results from this study are discussed with respect to potential cell safety enhancement for future aerospace as well as for terrestrial energy storage needs, and they are compared with pertinent mechanical properties of these materials, as well as with current state-of-the practice separator materials.

Data analytics and parallel-coordinate materials property charts

NASA Astrophysics Data System (ADS)

Rickman, Jeffrey M.

2018-01-01

It is often advantageous to display material properties relationships in the form of charts that highlight important correlations and thereby enhance our understanding of materials behavior and facilitate materials selection. Unfortunately, in many cases, these correlations are highly multidimensional in nature, and one typically employs low-dimensional cross-sections of the property space to convey some aspects of these relationships. To overcome some of these difficulties, in this work we employ methods of data analytics in conjunction with a visualization strategy, known as parallel coordinates, to represent better multidimensional materials data and to extract useful relationships among properties. We illustrate the utility of this approach by the construction and systematic analysis of multidimensional materials properties charts for metallic and ceramic systems. These charts simplify the description of high-dimensional geometry, enable dimensional reduction and the identification of significant property correlations and underline distinctions among different materials classes.

Functional conjugated pyridines via main-group element tuning.

PubMed

Stolar, Monika; Baumgartner, Thomas

2018-03-29

Pyridine-based materials have seen widespread attention for the development of n-type organic materials. In recent years, the incorporation of main-group elements has also explored significant advantages for the development and tunability of organic conjugated materials. The unique chemical and electronic structure of main-group elements has led to several enhancements in conventional organic materials. This Feature article highlights recent main-group based pyridine materials by discussing property enhancements and application in organic electronics.

Enhancing thermoelectric properties of organic composites through hierarchical nanostructures

PubMed Central

Zhang, Kun; Zhang, Yue; Wang, Shiren

2013-01-01

Organic thermoelectric (TE) materials are very attractive due to easy processing, material abundance, and environmentally-benign characteristics, but their potential is significantly restricted by the inferior thermoelectric properties. In this work, noncovalently functionalized graphene with fullerene by π-π stacking in a liquid-liquid interface was integrated into poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate). Graphene helps to improve electrical conductivity while fullerene enhances the Seebeck coefficient and hinders thermal conductivity, resulting in the synergistic effect on enhancing thermoelectric properties. With the integration of nanohybrids, the electrical conductivity increased from ~10000 to ~70000 S/m, the thermal conductivity changed from 0.2 to 2 W·K−1m−1 while the Seebeck coefficient was enhanced by around 4-fold. As a result, nanohybrids-based polymer composites demonstrated the figure of merit (ZT) as high as 6.7 × 10−2, indicating an enhancement of more than one order of magnitude in comparison to single-phase filler-based polymer composites with ZT at the level of 10−3. PMID:24336319

Explorations in the application of nanotechnology to improve the mechanical properties of composite materials

NASA Astrophysics Data System (ADS)

Yang, Cheng

2007-12-01

This thesis presents the research achievements on the design, preparation, characterization, and analysis of a series of composite materials. By studying the interface interaction of the composite materials using nanotechnology, we developed composite materials that achieve satisfactory mechanical properties in two classes of materials. Durable press (DP) natural textiles are important consumer products usually achieved by erosslinking the molecules in the textiles to achieve long-term wrinkle resistance, which, however, also leads to the simultaneous significant drop of mechanical properties. Herein, a series of polymeric nanoparticl es were investigated, the application of as little as ˜0.14 wt% addition of the nanoparticles improved the mechanical property of the DP cotton fabric by 56% in tearing resistance and 100% in abrasion resistance; the loss in recovery angle is negligible. The author also studied the enzyme-triggered DP treatments of silk fabrics, as a green process method. After the treatment of enzymes, excellent DP property was achieved with improved strain property. Injectable calcium phosphate powder containing acrylic bone cements are widely used in orthopedic surgery to fix artificial prostheses. However, the bending strength is still unsatisfactory. The author modified the surface of the strontium (Sr) containing hydroxyapatite (HA) filler powders with acrylolpamidronate in order to improve the overall mechanical performance of the bone cement composites. By adding 0.25 wt% of acrylolpamidronate to the Sr-HA nanopowders, more than 19% of the bending strength and more than 23% compression strength of the Sr-HA bone cement were improved. Biological evaluations revealed that these bone cement composites were biocompatible and bioactive in cell culture. The results obtained in this thesis work show an effective method to significantly enhance the mechanical properties of composite materials. Different from other available methods, by developing a new series of chemical compounds and nanoparticles, we successfully bound them to the surface or to the constitutional components of the materials through covalent bond. The treatment can enhance and modulate the interface-bonding of the filler materials and enhances the mechanical property of the surface through grafting a thin nano-layer. Since only surface reaction is involved, very small amount of the new material is needed, and the treatment can be readily integrated to the existing processes. The work is instructive in modifying available composite materials to acquire ultra-high mechanical performance.

A novel high-strength and highly corrosive biodegradable Fe-Pd alloy: Structural, mechanical and in vitro corrosion and cytotoxicity study.

PubMed

Čapek, Jaroslav; Msallamová, Šárka; Jablonská, Eva; Lipov, Jan; Vojtěch, Dalibor

2017-10-01

Recently, iron-based materials have been considered as candidates for the fabrication of biodegradable load-bearing implants. Alloying with palladium has been found to be a suitable approach to enhance the insufficient corrosion rate of iron-based alloys. In this work, we have extensively compared the microstructure, the mechanical and corrosion properties, and the cytotoxicity of an FePd2 (wt%) alloy prepared by three different routes - casting, mechanical alloying and spark plasma sintering (SPS), and mechanical alloying and the space holder technique (SHT). The properties of the FePd2 (wt%) were compared with pure Fe prepared in the same processes. The preparation route significantly influenced the material properties. Materials prepared by SPS possessed the highest values of mechanical properties (CYS~750-850MPa) and higher corrosion rates than the casted materials. Materials prepared by SHT contained approximately 60% porosity; therefore, their mechanical properties reached the lowest values, and they had the highest corrosion rates, approximately 0.7-1.2mm/a. Highly porous FePd2 was tested in vitro according to the ISO 10993-5 standard using L929 cells, and two-fold diluted extracts showed acceptable cytocompatibility. In general, alloying with Pd enhanced both mechanical properties and corrosion rates and did not decrease the cytocompatibility of the studied materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Improvement of Polylactide Properties through Cellulose Nanocrystals Embedded in Poly(Vinyl Alcohol) Electrospun Nanofibers

PubMed Central

López de Dicastillo, Carol; Garrido, Luan; Alvarado, Nancy; Romero, Julio; Palma, Juan Luis; Galotto, Maria Jose

2017-01-01

Electrospun nanofibers of poly (vinyl alcohol) (PV) were obtained to improve dispersion of cellulose nanocrystals (CNC) within hydrophobic biopolymeric matrices, such as poly(lactic acid) (PLA). Electrospun nanofibers (PV/CNC)n were successfully obtained with a final concentration of 23% (w/w) of CNC. Morphological, structural and thermal properties of developed CNC and electrospun nanofibers were characterized. X-ray diffraction and thermal analysis revealed that the crystallinity of PV was reduced by the electrospinning process, and the incorporation of CNC increased the thermal stability of biodegradable nanofibers. Interactions between CNC and PV polymer also enhanced the thermal stability of CNC and improved the dispersion of CNC within the PLA matrix. PLA materials with CNC lyophilized were also casted in order to compare the properties with materials based on CNC containing nanofibers. Nanofibers and CNC were incorporated into PLA at three concentrations: 0.5%, 1% and 3% (CNC respect to polymer weight) and nanocomposites were fully characterized. Overall, nanofibers containing CNC positively modified the physical properties of PLA materials, such as the crystallinity degree of PLA which was greatly enhanced. Specifically, materials with 1% nanofiber 1PLA(PV/CNC)n presented highest improvements related to mechanical and barrier properties; elongation at break was enhanced almost four times and the permeation of oxygen was reduced by approximately 30%. PMID:28492470

Effect of polarization field on mean free path of phonons in indium nitride

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

Sahoo, Sushant Kumar

2016-05-06

The effect of built-in-polarization field on mean free path of acoustic phonons in bulk wurtzite indium nitride (InN) has been theoretically investigated. The elastic constant of the material gets modified due to the existence of polarization field. As a result velocity and Debye frequency of phonons get enhanced. The various scattering rates of phonons are suppressed by the effect of polarization field, which implies an enhanced combined relaxation time. Thus phonons travel freely for a longer distance between two successive scatterings. This would enhance the thermal transport properties of the material when built-in-polarization field taken into account. Hence by themore » application of electric field the transport properties of such materials can be controlled as and when desired.« less

Polymer Layered Silicate Nanocomposites: A Review

PubMed Central

Mittal, Vikas

2009-01-01

This review aims to present recent advances in the synthesis and structure characterization as well as the properties of polymer layered silicate nanocomposites. The advent of polymer layered silicate nanocomposites has revolutionized research into polymer composite materials. Nanocomposites are organic-inorganic hybrid materials in which at least one dimension of the filler is less than 100 nm. A number of synthesis routes have been developed in the recent years to prepare these materials, which include intercalation of polymers or pre-polymers from solution, in-situ polymerization, melt intercalation etc. The nanocomposites where the filler platelets can be dispersed in the polymer at the nanometer scale owing to the specific filler surface modifications, exhibit significant improvement in the composite properties, which include enhanced mechanical strength, gas barrier, thermal stability, flame retardancy etc. Only a small amount of filler is generally required for the enhancement in the properties, which helps the composite materials retain transparency and low density.

Enhanced spin-phonon-electronic coupling in a 5d oxide

DOE PAGES

Calder, Stuart A.; Yamaura, K.; Tsujimoto, Y.; ...

2015-11-26

Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO 3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm 1, the largest measured in any material. The anomalous modes are shown to involve solely Os O interactions and magnetism is revealed as the driving microscopic mechanismmore » for the phonon renormalization. The magnitude of the coupling in NaOsO 3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.« less

Fundamental and progress of Bi2Te3-based thermoelectric materials

NASA Astrophysics Data System (ADS)

Hong, Min; Chen, Zhi-Gang; Zou, Jin

2018-04-01

Thermoelectric materials, enabling the directing conversion between heat and electricity, are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels. Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature. Due to the intensive theoretical investigations and experimental demonstrations, significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials. In this review, we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties. On this basis, we studied the effect of material parameters on thermoelectric properties. Then, we analyzed the features of Bi2Te3-based thermoelectric materials, including the lattice defects, anisotropic behavior and the strong bipolar conduction at relatively high temperature. Then we accordingly summarized the strategies for enhancing the thermoelectric performance, including point defect engineering, texture alignment, and band gap enlargement. Moreover, we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method, ball milling, and melt spinning. Lastly, we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3, which will enlighten the enhancement of thermoelectric performance in broader materials.

Method and apparatus of spectro-acoustically enhanced ultrasonic detection for diagnostics

DOEpatents

Vo-Dinh, Tuan; Norton, Stephen J.

2001-01-01

An apparatus for detecting a discontinuity in a material includes a source of electromagnetic radiation has a wavelength and an intensity sufficient to induce an enhancement in contrast between a manifestation of an acoustic property in the material and of the acoustic property in the discontinuity, as compared to when the material is not irradiated by the electromagnetic radiation. An acoustic emitter directs acoustic waves to the discontinuity in the material. The acoustic waves have a sensitivity to the acoustic property. An acoustic receiver receives the acoustic waves generated by the acoustic emitter after the acoustic waves have interacted with the material and the discontinuity. The acoustic receiver also generates a signal representative of the acoustic waves received by the acoustic receiver. A processor, in communication with the acoustic receiver and responsive to the signal generated by the acoustic receiver, is programmed to generate informational output about the discontinuity based on the signal generated by the acoustic receiver.

Advanced thermoelectric materials with enhanced crystal lattice structure and methods of preparation

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

1998-01-01

New skutterudite phases including Ru.sub.0.5 Pd.sub.0.5 Sb.sub.3, RuSb.sub.2 Te, and FeSb.sub.2 Te, have been prepared having desirable thermoelectric properties. In addition, a novel thermoelectric device has been prepared using skutterudite phase Fe.sub.0.5 Ni.sub.0.5 Sb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using powder metallurgy techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities and good Seebeck coefficients. These materials have low thermal conductivity and relatively low electrical resistivity, and are good candidates for low temperature thermoelectric applications.

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

Yago, G.I.; Vasil`ev, V.M.; Panasyuk, O.A.

The structure of the initial iron powders, the type of alloying impurities, and the conditions of compaction and heat treatment of materials have been studied from the standpoint of their effect on the magnetic properties. Ways of enhancing the properties of magnetically-soft iron-based powder materials are recommended and methods of studying them are suggested.

1D Piezoelectric Material Based Nanogenerators: Methods, Materials and Property Optimization

PubMed Central

Li, Xing; Sun, Mei; Wei, Xianlong; Shan, Chongxin

2018-01-01

Due to the enhanced piezoelectric properties, excellent mechanical properties and tunable electric properties, one-dimensional (1D) piezoelectric materials have shown their promising applications in nanogenerators (NG), sensors, actuators, electronic devices etc. To present a clear view about 1D piezoelectric materials, this review mainly focuses on the characterization and optimization of the piezoelectric properties of 1D nanomaterials, including semiconducting nanowires (NWs) with wurtzite and/or zinc blend phases, perovskite NWs and 1D polymers. Specifically, the piezoelectric coefficients, performance of single NW-based NG and structure-dependent electromechanical properties of 1D nanostructured materials can be respectively investigated through piezoresponse force microscopy, atomic force microscopy and the in-situ scanning/transmission electron microcopy. Along with the introduction of the mechanism and piezoelectric properties of 1D semiconductor, perovskite materials and polymers, their performance improvement strategies are summarized from the view of microstructures, including size-effect, crystal structure, orientation and defects. Finally, the extension of 1D piezoelectric materials in field effect transistors and optoelectronic devices are simply introduced. PMID:29570639

A review of nanoclay applications in the pervious concrete pavement

NASA Astrophysics Data System (ADS)

Shakrani, Shahrul Azwan; Ayob, Afizah; Rahim, Mohd Asri Ab

2017-09-01

In recent years, the use of nanoclay has received various interests in order to enhance the properties of construction materials which can also be eligible for pavement technology and engineering application. This review paper summarizes the effect of nanoclay as cement replacement and additive to the performance of pervious concrete pavement. The addition of nanoclay to pervious concrete has demonstrated improvements in strength properties such as compressive and flexural strength, durability such as freeze-thaw and chloride penetration resistance, shrinkage, and denser microstructure but at the same time reduced the porosity, permeability and water absorption properties. This enhancement is due to the roles of nanoclay as nanoreinforcements, nanofillers, nucleation site, and reactive pozzolans in order to promote hydration and improve material properties.

Material Property Characterization of Potential Nanocarbon Metal-Matrix Composite: An Investigational Study

NASA Astrophysics Data System (ADS)

Zavala, Mitchel

Metal-matrix composites (MMCs) are engineered combinations of two or more materials. Tailored properties are achieved by systematic combinations of different constituents. Specialized design and synthesis procedures allow unique sets of material properties in composites. Covetics are a new type of metal-matrix nano-composite (MMnC) material. These materials are formed from FCC metals which are super-saturated with up to 10 wt. % of activated nano-carbon powder. The idea is that the nano-carbon particles will enhance the material properties of the base metal matrix, however most of the physical and mechanical properties of covetics have not been well characterized. The foci of this study are to optimize the covetic casting synthesis process under controlled conditions, to understand and analyze the microstructures of the synthesized copper and aluminum covetic, to provide a thorough analysis of the chemical composition of the synthesized covetic materials, and to characterize physical and mechanical properties of both of these materials using meticulously prepared samples and test procedures.

Enhancing Aluminum Reactivity by Exploiting Surface Chemistry and Mechanical Properties

DTIC Science & Technology

2015-06-01

alter its mechanical properties . In bulk material processing , annealing and quenching metals such as Al can relieve residual stress and improve...increasing  Al  reactivity is to alter its mechanical  properties .  In bulk material  processing , annealing and quenching metals such as  Al  can relieve...mechanical properties . On a single particle level, affecting mechanical properties may also affect Al particle reactivity. Aluminum particles underwent

Cooperative enhancement of the nonlinear optical response in conjugated energetic materials: A TD-DFT study

DOE PAGES

Sifain, Andrew E.; Tadesse, Loza F.; Bjorgaard, Josiah August; ...

2017-03-21

Conjugated energetic molecules (CEMs) are a class of explosives with high nitrogen content that posses both enhanced safety and energetic performance properties and are ideal for direct optical initiation. As isolated molecules, they absorb within the range of conventional lasers. Crystalline CEMs are used in practice, however, and their properties can differ due to intermolecular interaction. Herein, time-dependent density functional theory was used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) of monomers and dimers obtained from experimentally determined crystal structures of CEMs. OPA scales linearly with the number of chromophore units, while TPA scales nonlinearly, where a moremore » than 3-fold enhancement in peak intensity, per chromophore unit, is calculated. Cooperative enhancement depends on electronic delocalization spanning both chromophore units. An increase in sensitivity to nonlinear laser initiation makes these materials suitable for practical use. This is the first study predicting a cooperative enhancement of the nonlinear optical response in energetic materials composed of relatively small molecules. Finally, the proposed model quantum chemistry is validated by comparison to crystal structure geometries and the optical absorption of these materials dissolved in solution.« less

Hydrothermal synthesis of novel Mn3O4 nano-octahedrons with enhanced supercapacitors performances

NASA Astrophysics Data System (ADS)

Jiang, Hao; Zhao, Ting; Yan, Chaoyi; Ma, Jan; Li, Chunzhong

2010-10-01

Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors.Uniform and single-crystalline Mn3O4 nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ~160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a ``dissolution-recrystallization'' which is followed by an ``Ostwald ripening'' mechanism. The Mn3O4 nano-octahedrons exhibited an enhanced specific capacitance of 322 F g-1 compared with the truncated octahedrons with specific capacitances of 244 F g-1, making them a promising electrode material for supercapacitors. Electronic supplementary information (ESI) available: TEM images; EDTA-2Na reaction details. See DOI: 10.1039/c0nr00257g

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.

On the vibration properties of composite materials and structures

NASA Astrophysics Data System (ADS)

Lu, Y. P.; Neilson, H. C.; Roscoe, A. J.

1993-01-01

In recent years, there has been a widespread assumption that composite materials and structures offer enhanced vibration and acoustic properties. This assumption has to be evaluated or validated. The objective of this article is to address the subject of vibration characteristics and the related force transmissibility properties of composite structures. For a given composite beam made of Hercules AS4/3501-6 graphite/epoxy with a layered structure sequence of (0,0,30,-30)(sub 6S), resonance frequencies, structural damping, responses, impedances, and force transmissibility properties are determined, discussed, and compared with those of a steel beam. This article proposes a procedure to evaluate the vibration properties of individual composites. The criterion defined for performance comparison between composite materials and conventional materials is also discussed.

Thermal properties of alkali-activated aluminosilicates

NASA Astrophysics Data System (ADS)

Florian, Pavel; Valentova, Katerina; Fiala, Lukas; Zmeskal, Oldrich

2017-07-01

The paper is focused on measurements and evaluation of thermal properties of alkali-activated aluminosilicates (AAA) with various carbon admixtures. Such composites consisting of blast-furnace slag, quartz sand, water glass as alkali activator and small amount of electrically conductive carbon admixture exhibit better electric and thermal properties than the reference material. Such enhancement opens up new practical applications, such as designing of snow-melting, de-icing or self-sensing systems that do not need any external sensors to detect current condition of building material. Thermal properties of the studied materials were measured by the step-wise transient method and mutually compared.

Ag-protein plasmonic architectures for surface plasmon-coupled emission enhancements and Fabry-Perot mode-coupled directional fluorescence emission

NASA Astrophysics Data System (ADS)

Badiya, Pradeep Kumar; Patnaik, Sai Gourang; Srinivasan, Venkatesh; Reddy, Narendra; Manohar, Chelli Sai; Vedarajan, Raman; Mastumi, Noriyoshi; Belliraj, Siva Kumar; Ramamurthy, Sai Sathish

2017-10-01

We report the use of silver decorated plant proteins as spacer material for augmented surface plasmon-coupled emission (120-fold enhancement) and plasmon-enhanced Raman scattering. We extracted several proteins from different plant sources [Triticum aestivum (TA), Aegle marmelos (AM), Ricinus communis (RC), Jatropha curcas (JC) and Simarouba glauca (SG)] followed by evaluation of their optical properties and simulations to rationalize observed surface plasmon resonance. Since the properties exhibited by protein thin films is currently gaining research interest, we have also carried out simulation studies with Ag-protein biocomposites as spacer materials in metal-dielectric-metal planar microcavity architecture for guided emission of Fabry-Perot mode-coupled fluorescence.

A review of catalyst-enhanced magnesium hydride as a hydrogen storage material

NASA Astrophysics Data System (ADS)

Webb, C. J.

2015-09-01

Magnesium hydride remains an attractive hydrogen storage material due to the high hydrogen capacity and low cost of production. A high activation energy and poor kinetics at practical temperatures for the pure material have driven research into different additives to improve the sorption properties. This review details the development of catalytic additives and their effect on the activation energy, kinetics and thermodynamic properties of magnesium hydride.

Realization of New and Enhanced Materials Properties Through Nanostructural Control

DTIC Science & Technology

2007-06-11

methods have been used to guide the design of novel new organic electroactive materials (e.g., electro - optic binary chromophore organic glasses...These new materials have yielded electro - optic coefficients as high as 450 pm/V (15 times lithium niobate) with auxiliary properties of modest optical... electro - optic activity has been achieved for the first time and theoretical conclusions have been verified by a number of new measurement techniques

Synthesis and properties of nanocrystalline Bi-Te based thermoelectric materials for energy application

NASA Astrophysics Data System (ADS)

Almohaimeed, Sulaiman

Thermoelectric phenomenon is the science associated with converting thermal energy into electricity based on the Seebeck effect. Bismuth telluride Bi 2Te3 is currently considered to be the state-of-the art thermoelectric material with high efficiency for low temperature applications and is therefore attractive for energy harvesting processes. Nanostructures thermoelectric materials provide a novel way to enhance thermoelectric properties and are considered to be the efficient building blocks for thermoelectric devices. In this work, n- and p-type bulk nanocrystalline Bismuth telluride thermoelectric materials were prepared by mechanical alloying / ball milling technique. The produced nano-crystalline powder were then consolidated using hot compaction under inert atmosphere. The novel processing of these materials maintained the nanostructure in both n- and p-type. Structural properties of the n- and p-types were characterized using X ray diffraction, scanning electron microscopy and transmission electron microscope. These techniques proved that the average grian size of the milled thermoelectric materials was about 20 nm. Accordingly, a Significant improvement in the figure of merit (ZT) is achieved through significant lattice thermal conductivity reduction and Seebeck coefficient improvement. The maximum ZT value for the n-type nanocrystalline thermoelectric was 1.67 at 373 K while the maximum ZT value for the p-type was 1.78 at the same temperature. These values are considered to be the highest values reported for similar materials. Evaluation of the mechanical properties was also performed through microhardness measurement using Vickers micro-hardness test, which shows an enhancement in mechanical properties for the produced materials.

Interfacial effects in ZnO nanotubes/needle-structured graphitic diamond nanohybrid for detecting dissolved acetone at room temperature

NASA Astrophysics Data System (ADS)

Kathiravan, Deepa; Huang, Bohr-Ran; Saravanan, Adhimoorthy; Yeh, Chien-Jui; Leou, Keh-Chyang; Lin, I.-Nan

2017-12-01

A high-performance ZnO nanotubes (ZNTs)/needle-structured graphitic diamond (NGD) nanohybrid material was prepared and observed the electrochemical sensing properties of liquid acetone in water. Initially, we synthesized NGD film using bias-enhanced growth (BEG) process. Afterwards, a well-etched ZNTs were spatially grown on the NGD film using simple hydrothermal method, and utilized as sensing material for assemble an electrochemical sensor (via EGFET configuration) operating at room temperature. The systematic investigations depict the ultra-high sensing properties attained from ZNTs grown on NGD film. The NGD film mostly have needle or wire shaped diamond grains, which contributes extremely high electrical conductivity. Furthermore, needle shaped diamond grains cover with multi-layer graphitic material generates conduction channels for ZNTs and leads to enhance the oxygen residuals and species. The material stability and conductivity of NGD as well the defects exist with oxygen vacancies in ZNTs offers superior sensing properties. Thus, the interesting combination of these wide band gap semiconductor materials exhibit high sensor response (89 mV/mL), high stability and long-term reliability (tested after 60 days).

Maleic anhydride polypropylene modified cellulose nanofibril polypropylene nanocomposites with enhanced impact strength

Treesearch

Yucheng Peng; Sergio A. Gallegos; Douglas J. Gardner; Yousoo Han; Zhiyong Cai

2014-01-01

The unique aspect of polymer composites reinforced by various fillers or additives is that the mechanical properties of the material can be tailored to fit a variety of uses: construction, transportation, industrial, and consumer applications. By selecting a specific reinforcement or designing a particular manufacturing process a material with desired properties can be...

Design, crystal growth, and physical properties of low-temperature thermoelectric materials

NASA Astrophysics Data System (ADS)

Fuccillo, Michael K.

Thermoelectric materials serve as the foundation for two important modern technologies, namely 1) solid-state cooling, which enables small-area refrigeration without vibrations or moving parts, and 2) thermoelectric power generation, which has important implications for waste heat recovery and improved sources of alternative energy. Although the overall field of thermoelectrics research has been active for decades, and several consumer and industrial products have already been commercialized, the design and synthesis of new thermoelectrics that outperform long-standing state of the art materials has proven extremely challenging. This is particularly true for low-temperature refrigeration applications, which is the focus of this work; however, scientific advances in this area generally support power generation as well. In order to achieve more efficient materials for virtually all thermoelectric applications, improved materials design principles must be developed and synthetic procedures must be better understood. We aim to contribute to these goals by studying two classes of materials, namely 1) the tetradymites Bi2TeSe 2 and Bi2Te2Se, which are close relatives of state of the art thermoelectric cooling materials, and 2) Kondo insulating (-like) FeSb2 and FeSi, which possess anomalously enhanced low-temperature thermoelectric properties that arise from exotic electronic and magnetic properties. The organization of this dissertation is as follows: Chapter 1 is a brief perspective on solid-state chemistry. Chapter 2 presents experimental methods for synthesizing and characterizing thermoelectric materials. In Chapter 3, two original research projects are discussed: first, work on the tetradymite Bi2TeSe2 doped with Sb to achieve an n- to p-type transition, and second, the tetradymite Bi2Te2Se with chemical defects through two different methods. Chapter 4 gives the magnetic and transport properties of FeSb 2--RuSb2 alloys, a family of compounds exemplifying what we consider to be the next generation of thermoelectric materials for low-temperature cooling due to their anomalously enhanced low-temperature thermoelectric properties, along with an outlook for seeking additional materials with similarly enhanced properties. Lastly, in Chapter 5, a brief outlook on the future of thermoelectrics is discussed, along with our current and future work on FeSi-RuSi alloys.

High Temperature Properties of an Alumina Enhanced Thermal Barrier

NASA Technical Reports Server (NTRS)

Leiser, Daniel B.; Smith, Marnell; Keating, Elizabeth A.

1987-01-01

The heatshield material requirements for future space vehicles (Aerobraking Orbital Transfer Vehicle & National Aerospace Plane) will depend upon the desired flight capability, configuration and location on the vehicle. These requirements will be more demanding and different from those derived for the materials used in the Shuttle Orbiter thermal protection system. Research was therefore initiated into improving the thermal efficiency of this class of materials by first characterizing their thermal and structural capabilities. Alternate material systems have been developed, tested, and compared with the baseline Shuttle system. This research resulted in the development of several very low density, high porosity (80-90%) materials with enhanced durability and temperature capability. One of the developments was a family of materials referred to as Fibrous Refractory Composite Insulation (FRCI) utilizing a mixture of fibers, each serving a unique purpose. One composition of the FRCI family with two fibers was adopted as a baseline material for use on the third and fourth Orbiters in selected areas due to its strength at a lower density compared to earlier materials. A further improvement in the FRCI family of materials is the Alumina Enhanced Thermal Barrier (AETB), a three-fiber composite. It has a higher temperature capability (composition dependent) than the baseline FRCI as proven by convective heating tests of one composition. AETB was studied to better characterize its performance at high temperature and the mechanisms by which its properties change. In conclusion, the shrinkage of AETB is a factor of six better than baseline FRCI at 1260 C (2300 F) with about a 20% improvement in mechanical properties. This improvement could translate into a 110 C (200 F) higher temperature capability in use as a heat shield material, but further testing in a convective heating environment is required to determine the actual improvement attainable.

Considerations Concerning the Development and Testing of In-situ Materials for Martian Exploration

NASA Technical Reports Server (NTRS)

Kim, M.-H. Y.; Heilbronn, L.; Thibeault, S. A.; Simonsen, L. C.; Wilson, J. W.; Chang, K.; Kiefer, R. L.; Maahs, H. G.

2000-01-01

Natural Martian surface materials are evaluated for their potential use as radiation shields for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley s HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To make structural shielding composite materials from constituents of the Mars atmosphere and from Martian regolith for Martian surface habitats, schemes for synthesizing polyimide from the Mars atmosphere and for processing Martian regolith/polyimide composites are proposed. Theoretical predictions of the shielding properties of these composites are computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties enhances the shielding properties of these composites because of the added hydrogenous constituents. Laboratory testing of regolith simulant/polyimide composites is planned to validate this prediction.

Development of Perovskite-Type Materials for Thermoelectric Application.

PubMed

Wu, Tingjun; Gao, Peng

2018-06-12

Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

Computational Screening of 2D Materials for Photocatalysis.

PubMed

Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

2015-03-19

Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

Pressure-induced dramatic changes in organic–inorganic halide perovskites

PubMed Central

Yang, Wenge

2017-01-01

Organic–inorganic halide perovskites have emerged as a promising family of functional materials for advanced photovoltaic and optoelectronic applications with high performances and low costs. Various chemical methods and processing approaches have been employed to modify the compositions, structures, morphologies, and electronic properties of hybrid perovskites. However, challenges still remain in terms of their stability, the use of environmentally unfriendly chemicals, and the lack of an insightful understanding into structure–property relationships. Alternatively, pressure, a fundamental thermodynamic parameter that can significantly alter the atomic and electronic structures of functional materials, has been widely utilized to further our understanding of structure–property relationships, and also to enable emergent or enhanced properties of given materials. In this perspective, we describe the recent progress of high-pressure research on hybrid perovskites, particularly regarding pressure-induced novel phenomena and pressure-enhanced properties. We discuss the effect of pressure on structures and properties, their relationships and the underlying mechanisms. Finally, we give an outlook on future research avenues in which high pressure and related alternative methods such as chemical tailoring and interfacial engineering may lead to novel hybrid perovskites uniquely suited for high-performance energy applications. PMID:29147500

Reinforcement of nylon 6,6/nylon 6,6 grafted nanodiamond composites by in situ reactive extrusion.

PubMed

Choi, Eun-Yeob; Kim, Kiho; Kim, Chang-Keun; Kang, Eunah

2016-11-14

Nanodiamond (ND), an emerging new carbon material, was exploited to reinforce nylon 6,6 (PA66) polymer composites. Surface modified nanodiamonds with acyl chloride end groups were employed to chemically graft into PA66, enhancing the interfacial adhesion and thus the mechanical properties. The ND grafted PA66 (PA66-g-ND) reinforced PA66 composite prepared by in situ reactive extrusion exhibited increased tensile strength and modulus. The tensile strength and modulus of PA66/3 wt.% PA66-g-ND composites were enhanced by 11.6 and 20.8%, respectively when compared to those of the bare PA66 matrix. Even the PA66/pristine ND composites exhibited enhanced mechanical properties. The PA66-g-ND and the homogeneously dispersed PA66-g-ND in PA66 matrix were examined using X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy techniques. The mechanical properties and thermal conductivities of the nanodiamond incorporated PA66 composites were also explored. The enhanced mechanical properties and thermal conductivities of the PA66-g-ND/PA66 composites make them potential materials for new applications as functional engineered thermoplastics.

Reinforcement of nylon 6,6/nylon 6,6 grafted nanodiamond composites by in situ reactive extrusion

NASA Astrophysics Data System (ADS)

Choi, Eun-Yeob; Kim, Kiho; Kim, Chang-Keun; Kang, Eunah

2016-11-01

Nanodiamond (ND), an emerging new carbon material, was exploited to reinforce nylon 6,6 (PA66) polymer composites. Surface modified nanodiamonds with acyl chloride end groups were employed to chemically graft into PA66, enhancing the interfacial adhesion and thus the mechanical properties. The ND grafted PA66 (PA66-g-ND) reinforced PA66 composite prepared by in situ reactive extrusion exhibited increased tensile strength and modulus. The tensile strength and modulus of PA66/3 wt.% PA66-g-ND composites were enhanced by 11.6 and 20.8%, respectively when compared to those of the bare PA66 matrix. Even the PA66/pristine ND composites exhibited enhanced mechanical properties. The PA66-g-ND and the homogeneously dispersed PA66-g-ND in PA66 matrix were examined using X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy techniques. The mechanical properties and thermal conductivities of the nanodiamond incorporated PA66 composites were also explored. The enhanced mechanical properties and thermal conductivities of the PA66-g-ND/PA66 composites make them potential materials for new applications as functional engineered thermoplastics.

Reinforcement of nylon 6,6/nylon 6,6 grafted nanodiamond composites by in situ reactive extrusion

PubMed Central

Choi, Eun-Yeob; Kim, Kiho; Kim, Chang-Keun; Kang, Eunah

2016-01-01

Nanodiamond (ND), an emerging new carbon material, was exploited to reinforce nylon 6,6 (PA66) polymer composites. Surface modified nanodiamonds with acyl chloride end groups were employed to chemically graft into PA66, enhancing the interfacial adhesion and thus the mechanical properties. The ND grafted PA66 (PA66-g-ND) reinforced PA66 composite prepared by in situ reactive extrusion exhibited increased tensile strength and modulus. The tensile strength and modulus of PA66/3 wt.% PA66-g-ND composites were enhanced by 11.6 and 20.8%, respectively when compared to those of the bare PA66 matrix. Even the PA66/pristine ND composites exhibited enhanced mechanical properties. The PA66-g-ND and the homogeneously dispersed PA66-g-ND in PA66 matrix were examined using X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy techniques. The mechanical properties and thermal conductivities of the nanodiamond incorporated PA66 composites were also explored. The enhanced mechanical properties and thermal conductivities of the PA66-g-ND/PA66 composites make them potential materials for new applications as functional engineered thermoplastics. PMID:27841314

Design, Fabrication, Characterization and Modeling of Integrated Functional Materials

DTIC Science & Technology

2013-10-01

coated microwire to change the temperature of an FBG. We show below that the proposed sensor probe, with a relatively poor thermal coupling with FBG...Seebeck coefficient and decreased thermal conductivity due to the phenomenological properties of nanometer length scales, including enhanced...nanocomposites as compared to bulk polycrystalline materials, in addition to similar thermal conductivities , results in enhanced room temperature ZT as

Optical properties of MgF2 nano-composite films dispersed with noble metal nanoparticles synthesized by sol-gel method

NASA Astrophysics Data System (ADS)

Wakaki, Moriaki; Soujima, Nobuaki; Shibuya, Takehisa

2015-03-01

Porous MgF2 films synthesized by a sol-gel method exhibit the lowest refractive index among the dielectric optical materials and are the most useful materials for the anti-reflection coatings. On the other hand, surface plasmon resonance (SPR) absorptions of noble metal nanoparticles in various solid matrices have been extensively studied. New functional materials like a SERS (Surface Enhanced Raman Spectroscopy) tips are expected by synthesizing composite materials between porous MgF2 films featured by the network of MgF2 nanoparticles and noble metal nanoparticles introduced within the network. In this study, fundamental physical properties including morphology and optical properties are characterized for these materials to make clear the potential of the composite system. Composite materials of MgF2 films dispersed with noble metal (Ag, Au) nanoparticles were prepared using the sol-gel technique with various annealing temperatures and densities of noble metal nanoparticles. The structural morphology was analyzed by an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The size and shape distributions of the metal nanoparticles were observed using a transmission electron microscope (TEM). The optical properties of fabricated composite films were characterized by UV-Vis-NIR and FT-IR spectrophotometers. The absorption spectra due to the surface plasmon resonance (SPR) of the metal nanoparticles were analyzed using the dielectric function considering the effective medium approximation, typically Maxwell-Garnett model. The Raman scattering spectra were also studied to check the enhancement effect of specimen dropped on the MgF2: Ag nano-composite films deposited on Si substrate. Enhancement of the Raman intensity of pyridine solution specimen was observed.

In silico optimization of phase-change materials for digital memories: a survey of first-row transition-metal dopants for Ge₂Sb₂Te₅.

PubMed

Skelton, J M; Elliott, S R

2013-05-22

Phase-change materials are the alloys at the heart of an emerging class of next-generation, non-volatile digital memory technologies. However, the widely studied Ge-Sb-Te system possesses several undesirable properties, and enhancing its properties, e.g. by doping, is an area of active research. Various first-row transition-metal dopants have been shown to impart useful property enhancements, but a systematic study of the entire period has yet to be undertaken, and little has been done to investigate their interaction with the host material at the atomic level. We have carried out first-principles computer simulations of the complete phase-change cycle in Ge2Sb2Te5 doped with each of the ten first-row transition metals. In this article, we present a comprehensive survey of the electronic, magnetic and optical properties of these doped materials. We discuss in detail their atomic-level structure, and relate the microscopic behaviours of the dopant atoms to their influence on the Ge2Sb2Te5 host. By considering an entire family of similar materials, we identify trends and patterns which might be used to predict suitable dopants for optimizing materials for specific phase-change applications. The computational method employed here is general, and this materials-discovery approach could be applied in the future to study other families of potential dopants for such materials.

The development and characterization of degradable poly(vinyl ester) and poly(vinyl ester)/PEO block copolymers

NASA Astrophysics Data System (ADS)

Lipscomb, Corinne Elizabeth

The development of biodegradable materials is a challenging and important problem in polymer science. A review of the state of the art in degradable materials is presented, which reveals that current biodegradable materials do not exhibit the thermal or mechanical properties necessary for widespread applications. One strategy for toughening polymeric materials, which has previously been applied to non-degradable thermoplastics and thermoplastic elastomers, is the formation of block copolymers. Poly(vinyl esters) (PVE) homopolymers are known to have a wide range of properties, but PVE block copolymers comprise a class of inexpensive and (bio)degradable materials that were previously unknown. Therefore, the synthesis and properties of these block copolymers were explored in an effort to develop robust degradable materials. This thesis research probes the reaction conditions necessary for the reversible-addition fragmentation chain transfer (RAFT) polymerization and chain extension reactions of vinyl ester monomers. PVE di- and triblock copolymers are synthesized and studied, and the triblock copolymers display extremely poor toughness due to their relatively low molecular weights in light of the high entanglement molecular weight of the poly(vinyl acetate) center block. Attempts to improve the mechanical properties of these materials focus on the incorporation of poly(ethylene oxide) (PEO) as a low entanglement molecular weight and biocompatible center block in PVE-containing triblock copolymers. Depending on the choice of PVE endblocks and the overall polymer composition, crystallization of the PEO block can be controlled, confined, or inhibited. Polymers in which PEO crystallization is completely inhibited exhibit enhanced mechanical properties and behave as weak thermoplastics. In order to understand the relationship between the inhibition of PEO crystallization and the mechanical properties of PVE/PEO materials, these polymers were studied using dynamic mechanical spectroscopy, wide angle X-ray scattering, small angle X-ray scattering, differential scanning calorimetry, and uniaxial tensile tests. By combining insights gained from these techniques, a complex picture emerges that explains the enhanced mechanical properties of these materials based on the type and location of thermal transitions, amorphous PEO entanglements, and the strain-induced crystallization of PEO. This work represents an important step toward developing robust materials with tunable properties containing (bio)degradable components.

Electrically Addressable Optical Devices Using A System Of Composite Layered Flakes Suspended In A Fluid Host To Obtain Angularly Depende

DOEpatents

Kosc, Tanya Z.; Marshall, Kenneth L.; Jacobs, Stephen D.

2004-12-07

Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/or altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.

PMMA denture base material enhancement: a review of fiber, filler, and nanofiller addition

PubMed Central

Gad, Mohammed M; Fouda, Shaimaa M; Al-Harbi, Fahad A; Näpänkangas, Ritva; Raustia, Aune

2017-01-01

This paper reviews acrylic denture base resin enhancement during the past few decades. Specific attention is given to the effect of fiber, filler, and nanofiller addition on poly(methyl methacrylate) (PMMA) properties. The review is based on scientific reviews, papers, and abstracts, as well as studies concerning the effect of additives, fibers, fillers, and reinforcement materials on PMMA, published between 1974 and 2016. Many studies have reported improvement of PMMA denture base material with the addition of fillers, fibers, nanofiller, and hybrid reinforcement. However, most of the studies were limited to in vitro investigations without bioactivity and clinical implications. Considering the findings of the review, there is no ideal denture base material, but the properties of PMMA could be improved with some modifications, especially with silanized nanoparticle addition and a hybrid reinforcement system. PMID:28553115

Cardiovascular application of polyhedral oligomeric silsesquioxane nanomaterials: a glimpse into prospective horizons

PubMed Central

Ghanbari, Hossein; de Mel, Achala; Seifalian, Alexander M

2011-01-01

Revolutionary advances in nanotechnology propose novel materials with superior properties for biomedical application. One of the most promising nanomaterials for biomedical application is polyhedral oligomeric silsesquioxane (POSS), an amazing nanocage consisting of an inner inorganic framework of silicon and oxygen atoms and an outer shell of organic groups. The unique properties of this nanoparticle has led to the development of a wide range of nanostructured copolymers with significantly enhanced properties including improved mechanical, chemical, and physical characteristics. Since POSS nanomaterials are highly biocompatible, biomedical application of POSS nanostructures has been intensely explored. One of the most promising areas of application of POSS nanomaterials is the development of cardiovascular implants. The incorporation of POSS into biocompatible polymers has resulted in advanced nanocomposite materials with improved hemocompatibility, antithrombogenicity, enhanced mechanical and surface properties, calcification resistance, and reduced inflammatory response, which make these materials the material of choice for cardiovascular implants. These highly versatile POSS derivatives have opened new horizons to the field of cardiovascular implant. Currently, application of POSS containing polymers in the development of new generation cardiovascular implants including heart valve prostheses, bypass grafts, and coronary stents is under intensive investigation, with encouraging outcomes. PMID:21589645

The Fano-type transmission and field enhancement in heterostructures composed of epsilon-near-zero materials and truncated photonic crystals

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

Zhang, Zhi-fang; Jiang, Hai-tao, E-mail: davies2000@163.com, E-mail: jiang-haitao@tongji.edu.cn; Li, Yun-hui

2013-11-11

The Fano-type interference effect is studied in the heterostructure composed of an epsilon-near-zero (ENZ) material and a truncated photonic crystal for transverse magnetic polarized light. In the Fano-type interference effect, the ENZ material provides narrow reflection pathway and the photonic crystal provides broadband reflection pathway. The boundary condition across the ENZ interface and the confinement effect provided by the photonic crystal can enhance the electric fields in the ENZ material greatly. The field enhancements, together with the asymmetric property of Fano-type spectrum, possess potential applications for significantly lowering the threshold of nonlinear processes such as optical switching and bistability.

Designing with non-linear viscoelastic fluids

NASA Astrophysics Data System (ADS)

Schuh, Jonathon; Lee, Yong Hoon; Allison, James; Ewoldt, Randy

2017-11-01

Material design is typically limited to hard materials or simple fluids; however, design with more complex materials can provide ways to enhance performance. Using the Criminale-Ericksen-Filbey (CEF) constitutive model in the thin film lubrication limit, we derive a modified Reynolds Equation (based on asymptotic analysis) that includes shear thinning, first normal stress, and terminal regime viscoelastic effects. This allows for designing non-linear viscoelastic fluids in thin-film creeping flow scenarios, i.e. optimizing the shape of rheological material properties to achieve different design objectives. We solve the modified Reynolds equation using the pseudo-spectral method, and describe a case study in full-film lubricated sliding where optimal fluid properties are identified. These material-agnostic property targets can then guide formulation of complex fluids which may use polymeric, colloidal, or other creative approaches to achieve the desired non-Newtonian properties.

Broadband High Efficiency Fractal-Like and Diverse Geometry Silicon Nanowire Arrays for Photovoltaic Applications

NASA Astrophysics Data System (ADS)

AL-Zoubi, Omar H.

Solar energy has many advantages over conventional sources of energy. It is abundant, clean and sustainable. One way to convert solar energy directly into electrical energy is by using the photovoltaic solar cells (PVSC). Despite PVSC are becoming economically competitive, they still have high cost and low light to electricity conversion efficiency. Therefore, increasing the efficiency and reducing the cost are key elements for producing economically more competitive PVSC that would have significant impact on energy market and saving environment. A significant percentage of the PVSC cost is due to the materials cost. For that, thin films PVSC have been proposed which offer the benefits of the low amount of material and fabrication costs. Regrettably, thin film PVSC show poor light to electricity conversion efficiency because of many factors especially the high optical losses. To enhance conversion efficiency, numerous techniques have been proposed to reduce the optical losses and to enhance the absorption of light in thin film PVSC. One promising technique is the nanowire (NW) arrays in general and the silicon nanowire (SiNW) arrays in particular. The purpose of this research is to introduce vertically aligned SiNW arrays with enhanced and broadband absorption covering the entire solar spectrum while simultaneously reducing the amount of material used. To this end, we apply new concept for designing SiNW arrays based on employing diversity of physical dimensions, especially radial diversity within certain lattice configurations. In order to study the interaction of light with SiNW arrays and compute their optical properties, electromagnetic numerical modeling is used. A commercial numerical electromagnetic solver software package, high frequency structure simulation (HFSS), is utilized to model the SiNW arrays and to study their optical properties. We studied different geometries factors that affect the optical properties of SiNW arrays. Based on this study, we found that the optical properties of SiNW arrays are strongly affected by the radial diversity, the arrangement of SiNW in a lattice, and the configuration of such lattice. The proper selection of these parameters leads to broaden and enhance the light absorption of the SiNW arrays. Inspired by natural configurations, fractal geometry and diamond lattice structures, we introduced two lattice configurations: fractal-like array (FLA) that is inspired by fractal geometry, and diamond-like array (DLA) that is inspired by diamond crystal lattice structure. Optimization, using parametric analysis, of the introduced arrays parameters for the light absorption level and the amount of used material has been performed. Both of the introduced SiNW arrays show broadband, strong light absorption coupled with reduction of the amount of the used material. DLA in specific showed significantly enhanced absorption covering the entire solar spectrum of interest, where near-unity absorption spectrum could be achieved. We studied the optical properties of complete PVSC devices that are based on SiNW array. Moreover, the performance of PVSC device that is based on SiNW has been investigated by using numerical modeling. SILVACO software package is used for performing the numerical simulation of the PVSC device performance, which can simultaneously handle the different coupled physical mechanisms contributing to the photovoltaic effect. The effect of the geometry of PVSC device that is based on SiNW is investigated, which shows that the geometry of such PVSC has a role in enhancing its electrical properties. The outcome of this study introduces new SiNW array configurations that have enhanced optical properties using a low amount of material that can be utilized for producing higher efficiency thin film PVCS. The overall conclusion of this work is that a weak absorption indirect band gap material, silicon, in the form of properly designed SiNW and SiNC arrays has the potentials to achieve near-unity ideal absorption spectrum using reduced amount of material, which can lead to produce new generation of lower cost and enhanced efficiency thin film PVSC.

Biomimetic Materials by Freeze Casting

NASA Astrophysics Data System (ADS)

Porter, Michael M.; Mckittrick, Joanna; Meyers, Marc A.

2013-06-01

Natural materials, such as bone and abalone nacre, exhibit exceptional mechanical properties, a product of their intricate microstructural organization. Freeze casting is a relatively simple, inexpensive, and adaptable materials processing method to form porous ceramic scaffolds with controllable microstructural features. After infiltration of a second polymeric phase, hybrid ceramic-polymer composites can be fabricated that closely resemble the architecture and mechanical performance of natural bone and nacre. Inspired by the narwhal tusk, magnetic fields applied during freeze casting can be used to further control architectural alignment, resulting in freeze-cast materials with enhanced mechanical properties.

Optimizing laser crater enhanced Raman scattering spectroscopy

NASA Astrophysics Data System (ADS)

Lednev, V. N.; Sdvizhenskii, P. A.; Grishin, M. Ya.; Fedorov, A. N.; Khokhlova, O. V.; Oshurko, V. B.; Pershin, S. M.

2018-05-01

The laser crater enhanced Raman scattering (LCERS) spectroscopy technique has been systematically studied for chosen sampling strategy and influence of powder material properties on spectra intensity enhancement. The same nanosecond pulsed solid state Nd:YAG laser (532 nm, 10 ns, 0.1-1.5 mJ/pulse) was used for laser crater production and Raman scattering experiments for L-aspartic acid powder. Increased sampling area inside crater cavity is the key factor for Raman signal improvement for the LCERS technique, thus Raman signal enhancement was studied as a function of numerous experimental parameters including lens-to-sample distance, wavelength (532 and 1064 nm) and laser pulse energy utilized for crater production. Combining laser pulses of 1064 and 532 nm wavelengths for crater ablation was shown to be an effective way for additional LCERS signal improvement. Powder material properties (particle size distribution, powder compactness) were demonstrated to affect LCERS measurements with better results achieved for smaller particles and lower compactness.

Shock enhancement of cellular materials subjected to intensive pulse loading

NASA Astrophysics Data System (ADS)

Zhang, J.; Fan, J.; Wang, Z.; Zhao, L.; Li, Z.

2018-03-01

Cellular materials can dissipate a large amount of energy due to their considerable stress plateau, which contributes to their extensive applications in structural design for crashworthiness. However, in some experiments with specimens subjected to intense impact loads, transmitted stress enhancement has been observed, leading to severe damage to the objects protected. Transmitted stress through two-dimensional Voronoi cellular materials as a protective device is qualitatively studied in this paper. Dimensionless parameters of material properties and loading parameters are defined to give critical conditions for shock enhancement and clarify the correlation between the deformations and stress enhancement. The effect of relative density on this amplifying phenomenon is investigated as well. In addition, local strain fields are calculated by using the optimal local deformation gradient, which gives a clear presentation of deformations and possible local non-uniformity in the crushing process. This research provides valuable insight into the reliability of cellular materials as protective structures.

Halogenation of microcapsule walls

NASA Technical Reports Server (NTRS)

Davis, T. R.; Schaab, C. K.; Scott, J. C.

1972-01-01

Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

Two-dimensional magnesium oxide nanosheets reinforced epoxy nanocomposites for enhanced fracture toughness

NASA Astrophysics Data System (ADS)

Balguri, Praveen Kumar; Harris Samuel, D. G.; Guruvishnu, T.; Aditya, D. B.; Mahadevan, S. M.; Thumu, Udayabhaskararao

2018-01-01

Metal oxide nanoparticles have been used as excellent reinforcements to enhance mechanical properties of polymers, natural composites, and ceramics. To date, a major portion of metal oxides used as nanofillers is three dimensional spherical nanoparticles. In the last decade, two-dimensional (2D) materials such as graphene have been widely investigated to improve the mechanical and electrical properties of polymer materials. In this paper, 2D Magnesium oxide (MgO) nanosheets reinforced epoxy composites (0.1, 0.2 and 0.4 wt%) are fabricated and studied for their ability to resist the propagation of preexisting flaw by conducting fracture toughness test for K IC, critical stress intensity factor. This property is an important mechanical property for designing applications in various engineering technologies. Our results show that the MgO with 0.2 wt% is the optimized level to improve the fracture toughness of the epoxy polymer by 47%.

Properties of lightweight cement-based composites containing waste polypropylene

NASA Astrophysics Data System (ADS)

Záleská, Martina; Pavlíková, Milena; Pavlík, Zbyšek

2016-07-01

Improvement of buildings thermal stability represents an increasingly important trend of the construction industry. This work aims to study the possible use of two types of waste polypropylene (PP) for the development of lightweight cement-based composites with enhanced thermal insulation function. Crushed PP waste originating from the PP tubes production is used for the partial replacement of silica sand by 10, 20, 30, 40 and 50 mass%, whereas a reference mixture without plastic waste is studied as well. First, basic physical and thermal properties of granular PP random copolymer (PPR) and glass fiber reinforced PP (PPGF) aggregate are studied. For the developed composite mixtures, basic physical, mechanical, heat transport and storage properties are accessed. The obtained results show that the composites with incorporated PP aggregate exhibit an improved thermal insulation properties and acceptable mechanical resistivity. This new composite materials with enhanced thermal insulation function are found to be promising materials for buildings subsoil or floor structures.

Synthesis and Characterization of Manganese Sponge doped with TiO2

NASA Astrophysics Data System (ADS)

Mallikarjun, patil

2017-06-01

The aviation and mechanical industry has seen tremendous growth in recent years. While these trends only continue, the materials on development of better fabrication technologies. Spongy materials are projected as favourable materials for the future as porous in nature. The current paper devotes to enhance mechanical properties by the use of Manganese sponge doped with TiO2 possess an outstanding array of properties not readily achievable with other materials. Samples were synthesized by Kroll process and solid-state reaction. The specified materials compares well with the presently used aeromechanical materials in all terms. The scope for further research work in this area will be outlined.

Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

NASA Astrophysics Data System (ADS)

Nikolaev, A. G.; Yushkov, G. Yu.; Oks, E. M.; Oztarhan, A.; Akpek, A.; Hames-Kocabas, E.; Urkac, E. S.; Brown, I. G.

2014-08-01

Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal-gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the "inverse" concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

Integrated Computational Materials Engineering Development of Alternative Cu-Be Alloys

DTIC Science & Technology

2012-08-01

Be alloy replacement in highly loaded wear applications . ● Development bushing designs for the enhancement of dynamic wear performance...Material Properties and Tribological Characterization Cu-Based and Co- Based Alloy Concept Selection Requirements Definition Bushing Design and...properties and cost for highly loaded bushing applications ● QuesTek’s NAVAIR-funded SBIR Phase II program demonstrated the feasibility of designing Be-free

Nonlinear optical properties of rigid-rod polymers

NASA Technical Reports Server (NTRS)

Trimmer, Mark S.; Wang, Ying

1992-01-01

The purpose of this research project was to integrate enhanced third order nonlinear optical (NLO) properties, especially high x(exp (3)) (greater than 10(exp -8) esu), into Maxdem's novel conjugated rigid-rod polymers while retaining their desirable processing, mechanical, and thermal properties. This work primarily involved synthetic approaches to optimized materials.

Wood plastic composites from agro-waste materials: Analysis of mechanical properties.

PubMed

Nourbakhsh, Amir; Ashori, Alireza

2010-04-01

This article presents the application of agro-waste materials (i.e., corn stalk, reed stalk, and oilseed stalk) in order to evaluate and compare their suitability as reinforcement for thermoplastics as an alternative to wood fibers. The effects of fiber loading and CaCO(3) content on the mechanical properties were also studied. Overall trend shows that with addition of agro-waste materials, tensile and flexural properties of the composites are significantly enhanced. Oilseed fibers showed superior mechanical properties due to their high aspect ratio and chemical characteristics. The order of increment in the mechanical properties of the composites is oilseed stalk >corn stalk>reed stalk at all fiber loadings. The tensile and flexural properties of the composite significantly decreased with increasing CaCO(3) content, due to the reduction of interface bond between the fiber and matrix. It can be concluded from this study that the used agro-waste materials are attractive reinforcements from the standpoint of their mechanical properties. Copyright 2009 Elsevier Ltd. All rights reserved.

Phase-Defined van der Waals Schottky Junctions with Significantly Enhanced Thermoelectric Properties.

PubMed

Wang, Qiaoming; Yang, Liangliang; Zhou, Shengwen; Ye, Xianjun; Wang, Zhe; Zhu, Wenguang; McCluskey, Matthew D; Gu, Yi

2017-07-06

We demonstrate a van der Waals Schottky junction defined by crystalline phases of multilayer In 2 Se 3 . Besides ideal diode behaviors and the gate-tunable current rectification, the thermoelectric power is significantly enhanced in these junctions by more than three orders of magnitude compared with single-phase multilayer In 2 Se 3 , with the thermoelectric figure-of-merit approaching ∼1 at room temperature. Our results suggest that these significantly improved thermoelectric properties are not due to the 2D quantum confinement effects but instead are a consequence of the Schottky barrier at the junction interface, which leads to hot carrier transport and shifts the balance between thermally and field-driven currents. This "bulk" effect extends the advantages of van der Waals materials beyond the few-layer limit. Adopting such an approach of using energy barriers between van der Waals materials, where the interface states are minimal, is expected to enhance the thermoelectric performance in other 2D materials as well.

Enhanced Locomotion Efficiency of a Bio-inspired Walking Robot using Contact Surfaces with Frictional Anisotropy

NASA Astrophysics Data System (ADS)

Manoonpong, Poramate; Petersen, Dennis; Kovalev, Alexander; Wörgötter, Florentin; Gorb, Stanislav N.; Spinner, Marlene; Heepe, Lars

2016-12-01

Based on the principles of morphological computation, we propose a novel approach that exploits the interaction between a passive anisotropic scale-like material (e.g., shark skin) and a non-smooth substrate to enhance locomotion efficiency of a robot walking on inclines. Real robot experiments show that passive tribologically-enhanced surfaces of the robot belly or foot allow the robot to grip on specific surfaces and move effectively with reduced energy consumption. Supplementing the robot experiments, we investigated tribological properties of the shark skin as well as its mechanical stability. It shows high frictional anisotropy due to an array of sloped denticles. The orientation of the denticles to the underlying collagenous material also strongly influences their mechanical interlocking with the substrate. This study not only opens up a new way of achieving energy-efficient legged robot locomotion but also provides a better understanding of the functionalities and mechanical properties of anisotropic surfaces. That understanding will assist developing new types of material for other real-world applications.

Enhanced Locomotion Efficiency of a Bio-inspired Walking Robot using Contact Surfaces with Frictional Anisotropy

PubMed Central

Manoonpong, Poramate; Petersen, Dennis; Kovalev, Alexander; Wörgötter, Florentin; Gorb, Stanislav N.; Spinner, Marlene; Heepe, Lars

2016-01-01

Based on the principles of morphological computation, we propose a novel approach that exploits the interaction between a passive anisotropic scale-like material (e.g., shark skin) and a non-smooth substrate to enhance locomotion efficiency of a robot walking on inclines. Real robot experiments show that passive tribologically-enhanced surfaces of the robot belly or foot allow the robot to grip on specific surfaces and move effectively with reduced energy consumption. Supplementing the robot experiments, we investigated tribological properties of the shark skin as well as its mechanical stability. It shows high frictional anisotropy due to an array of sloped denticles. The orientation of the denticles to the underlying collagenous material also strongly influences their mechanical interlocking with the substrate. This study not only opens up a new way of achieving energy-efficient legged robot locomotion but also provides a better understanding of the functionalities and mechanical properties of anisotropic surfaces. That understanding will assist developing new types of material for other real-world applications. PMID:28008936

Enhanced superconductivity in atomically thin TaS2

PubMed Central

Navarro-Moratalla, Efrén; Island, Joshua O.; Mañas-Valero, Samuel; Pinilla-Cienfuegos, Elena; Castellanos-Gomez, Andres; Quereda, Jorge; Rubio-Bollinger, Gabino; Chirolli, Luca; Silva-Guillén, Jose Angel; Agraït, Nicolás; Steele, Gary A.; Guinea, Francisco; van der Zant, Herre S. J.; Coronado, Eugenio

2016-01-01

The ability to exfoliate layered materials down to the single layer limit has presented the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top–down approach to address the problem of superconductivity in the two-dimensional limit. The transport properties of electronic devices based on 2H tantalum disulfide flakes of different thicknesses are presented. We observe that superconductivity persists down to the thinnest layer investigated (3.5 nm), and interestingly, we find a pronounced enhancement in the critical temperature from 0.5 to 2.2 K as the layers are thinned down. In addition, we propose a tight-binding model, which allows us to attribute this phenomenon to an enhancement of the effective electron–phonon coupling constant. This work provides evidence that reducing the dimensionality can strengthen superconductivity as opposed to the weakening effect that has been reported in other 2D materials so far. PMID:26984768

WSe2 nanoribbons: new high-performance thermoelectric materials.

PubMed

Chen, Kai-Xuan; Luo, Zhi-Yong; Mo, Dong-Chuan; Lyu, Shu-Shen

2016-06-28

In this work, for the first time, we systematically investigate the ballistic transport properties of WSe2 nanoribbons using first-principles methods. Armchair nanoribbons with narrow ribbon width are mostly semiconductive but the zigzag nanoribbons are metallic. Surprisingly, an enhancement in thermoelectric performance is discovered moving from monolayers to nanoribbons, especially armchair ones. The maximum room-temperature thermoelectric figure of merit of 2.2 for an armchair nanoribbon is discovered. This may be contributed to by the effects of the disordered edges, owing to the existence of dangling bonds at the ribbon edge. H-passivation has turned out to be an effective way to stabilize the edge atoms, which enhances the thermodynamic stability of the nanoribbons. In addition, after H-passivation, all of the armchair nanoribbons exhibit semiconductive properties with similar band gaps (∼1.3 eV). Our work provides instructional theoretical evidence for the application of armchair WSe2 nanoribbons as promising thermoelectric materials. The enhancement mechanism of the disordered edge effect can also encourage further exploration to achieve outstanding thermoelectric materials.

Lower Length Scale Characterization and Validation of Formation and Stability of Helium Bubbles in Nano-structured Ferritic Alloys under Irradiation

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

Zhao, Huijuan; Yun, Di; Hoelzer, David

In order to extend the operating license of current light water reactors (LWRs) in the United States and other countries to as many as 80 years or longer, it is demanding to identify potential materials for many of the internal structural components and fasteners. We proposed that 14YWT iron alloy can be adopted in such applications with its excellent material properties, such as high-temperature strength, low creep rate, and high irradiation resistance. Application with 14YWT would improve the void/helium swelling characteristics of the LWR fuels, extend the burn-up limits with the tolerant temperature up to 800oC and reduce the hydrogenmore » production. One key feature of 14YWT material property enhancement is the ultrafine high density of 2-4nm Y-Ti-O enriched nanoclusters (NCs) within the 14YWT iron matrix. The NCs can effectively pin the ultra-fine grain boundaries and dislocations, which significantly enhance mechanical properties of the alloy. Moreover, these nanoclusters remain stable with no coarsening after a large dose of ion irradiation. After ion irradiation, the helium bubbles are observed extremely uniform in size (1nm) and quite homogeneously distributed within the 14YWT matrix, which indicates that the microstructure of 14YWT remains remarkably tolerance to radiation damage. However, there is a lack of understanding of 14YWT both theoretically and experimentally in order to understand the mechanism behind the material property enhancement and to further develop and design a new generation of advanced structural material for current LWR applications and future fusion applications.« less

Evaluation of mechanical properties in metal wire mesh supported selective catalytic reduction (SCR) catalyst structures

NASA Astrophysics Data System (ADS)

Rajath, S.; Siddaraju, C.; Nandakishora, Y.; Roy, Sukumar

2018-04-01

The objective of this research is to evaluate certain specific mechanical properties of certain stainless steel wire mesh supported Selective catalytic reduction catalysts structures wherein the physical properties of the metal wire mesh and also its surface treatments played vital role thereby influencing the mechanical properties. As the adhesion between the stainless steel wire mesh and the catalyst material determines the bond strength and the erosion resistance of catalyst structures, surface modifications of the metal- wire mesh structure in order to facilitate the interface bonding is therefore very important to realize enhanced level of mechanical properties. One way to enhance such adhesion properties, the stainless steel wire mesh is treated with the various acids, i.e., chromic acid, phosphoric acid including certain mineral acids and combination of all those in various molar ratios that could generate surface active groups on metal surface that promotes good interface structure between the metal- wire mesh and metal oxide-based catalyst material and then the stainless steel wire mesh is dipped in the glass powder slurry containing some amount of organic binder. As a result of which the said catalyst material adheres to the metal-wire mesh surface more effectively that improves the erosion profile of supported catalysts structure including bond strength.

Mechanical enhancement and in vitro biocompatibility of nanofibrous collagen-chitosan scaffolds for tissue engineering.

PubMed

Zou, Fengjuan; Li, Runrun; Jiang, Jianjun; Mo, Xiumei; Gu, Guofeng; Guo, Zhongwu; Chen, Zonggang

2017-12-01

The collagen-chitosan complex with a three-dimensional nanofiber structure was fabricated to mimic native ECM for tissue repair and biomedical applications. Though the three-dimensional hierarchical fibrous structures of collagen-chitosan composites could provide more adequate stimulus to facilitate cell adhesion, migrate and proliferation, and thus have the potential as tissue engineering scaffolding, there are still limitations in their applications due to the insufficient mechanical properties of natural materials. Because poly (vinyl alcohol) (PVA) and thermoplastic polyurethane (TPU) as biocompatible synthetic polymers can offer excellent mechanical properties, they were introduced into the collagen-chitosan composites to fabricate the mixed collagen/chitosan/PVA fibers and a sandwich structure (collagen/chitosan-TPU-collagen/chitosan) of nanofiber in order to enhance the mechanical properties of the nanofibrous collagen-chitosan scaffold. The results showed that the tensile behavior of materials was enhanced to different degrees with the difference of collagen content in the fibers. Besides the Young's modulus had no obvious changes, both the break strength and the break elongation of materials were heightened after reinforced by PVA. For the collagen-chitosan nanofiber reinforced by TPU, both the break strength and the Young's modulus of materials were heightened in different degrees with the variety of collagen content in the fibers despite the decrease of the break elongation of materials to some extent. In vitro cell test demonstrated that the materials could provide adequate environment for cell adhesion and proliferation. All these indicated that the reinforced collagen-chitosan nanofiber could be as potential scaffold for tissue engineering according to the different mechanical requirements in clinic.

Damage Tolerance Enhancement of Carbon Fiber Reinforced Polymer Composites by Nanoreinforcement of Matrix

NASA Astrophysics Data System (ADS)

Fenner, Joel Stewart

Nanocomposites are a relatively new class of materials which incorporate exotic, engineered nanoparticles to achieve superior material properties. Because of their extremely small size and well-ordered structure, many nanoparticles possess properties that exceed those offered by a wide range of other known materials, making them attractive candidates for novel materials engineering development. Their small size is also an impediment to their practical use, as they typically cannot be employed by themselves to realize those properties in large structures. Furthermore, nanoparticles typically possess strong self-affinity, rendering them difficult to disperse uniformly into a composite. However, contemporary research has shown that, if well-dispersed, nanoparticles have great capacity to improve the mechanical properties of composites, especially damage tolerance, in the form of fracture toughness, fatigue life, and impact damage mitigation. This research focuses on the development, manufacturing, and testing of hybrid micro/nanocomposites comprised of woven carbon fibers with a carbon nanotube reinforced epoxy matrix. Material processing consisted of dispersant-and-sonication based methods to disperse nanotubes into the matrix, and a vacuum-assisted wet lay-up process to prepare the hybrid composite laminates. Various damage tolerance properties of the hybrid composite were examined, including static strength, fracture toughness, fatigue life, fatigue crack growth rate, and impact damage behavior, and compared with similarly-processed reference material produced without nanoreinforcement. Significant improvements were obtained in interlaminar shear strength (15%), Mode-I fracture toughness (180%), shear fatigue life (order of magnitude), Mode-I fatigue crack growth rate (factor of 2), and effective impact damage toughness (40%). Observations by optical microscopy, scanning electron microscopy, and ultrasonic imaging showed significant differences in failure behavior and fracture morphology between the two materials, related to the differences in properties. Altogether these results provided a means for proposing an explanation of the mechanism of reinforcement (and damage tolerance enhancement) provided by carbon nanotubes in hybrid composite materials.

Enhancement of Spartium junceum L. fibres properties

NASA Astrophysics Data System (ADS)

Kovačević, Z.; Bischof, S.; Antonović, A.

2017-10-01

Properties of lignocellulosic Spartium junceum L. (SJL) fibres were investigated in order to use them as reinforcement in composite material production. The fibres were obtained by microwave maceration process and additionally modified with NaOH, nanoclay and citric acid with the aim to improve their mechanical, thermal and other physical-chemical properties. Tensile and thermal properties of these natural fibres were enhanced by the different modification treatment which is investigated by the Vibrodyn/Vibroskop method and thermogravimetric analysis (TGA), whilst determination of chemical composition and fibre’s surface properties were explored using scanning electron microscope (SEM), electron dispersive spectroscopy (EDS) and elektrokinetic analyser. All the results show great improvement of nanoclay/citric acid modified SJL properties.

Dual-carbon enhanced silicon-based composite as superior anode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Wang, Jie; Liu, Dai-Huo; Wang, Ying-Ying; Hou, Bao-Hua; Zhang, Jing-Ping; Wang, Rong-Shun; Wu, Xing-Long

2016-03-01

Dual-carbon enhanced Si-based composite (Si/C/G) has been prepared via employing the widely distributed, low-cost and environmentally friendly Diatomite mineral as silicon raw material. The preparation processes are very simple, non-toxic and easy to scale up. Electrochemical tests as anode material for lithium ion batteries (LIBs) demonstrate that this Si/C/G composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pristine Si material as well as both single-carbon modified composites. Specifically for the Si/C/G composite, it can still deliver a high specific capacity of about 470 mAh g-1 at an ultrahigh current density of 5 A g-1, and exhibit a high capacity of 938 mAh g-1 at 0.1 A g-1 with excellent capacity retention in the following 300 cycles. The significantly enhanced Li-storage properties should be attributed to the co-existence of both highly conductive graphite and amorphous carbon in the Si/C/G composite. While the former can enhance the electrical conductivity of the obtained composite, the latter acts as the adhesives to connect the porous Si particulates and conductive graphite flakes to form robust and stable conductive network.

Graphene-magnesium nanocomposite: An advanced material for aerospace application

NASA Astrophysics Data System (ADS)

Das, D. K.; Sarkar, Jit

2018-02-01

This work focuses on the analytical study of mechanical and thermal properties of a nanocomposite that can be obtained by reinforcing graphene in magnesium. The estimated mechanical and thermal properties of graphene-magnesium nanocomposite are much higher than magnesium and other existing alloys used in aerospace materials. We also altered the weight percentage of graphene in the composite and observed mechanical and thermal properties of the composite increase with increase in concentration of graphene reinforcement. The Young’s modulus and thermal conductivity of graphene-magnesium nanocomposite are found to be ≥165 GPa and ≥175 W/mK, respectively. Nanocomposite material with desired properties for targeted applications can also be designed by our analytical modeling technique. This graphene-magnesium nanocomposite can be used for designing improved aerospace structure systems with enhanced properties.

Point Defects in Oxides: Tailoring Materials Through Defect Engineering

NASA Astrophysics Data System (ADS)

Tuller, Harry L.; Bishop, Sean R.

2011-08-01

Optimization of electrical, optical, mechanical, and other properties of many advanced, functional materials today relies on precise control of point defects. This article illustrates the progress that has been made in elucidating the often complex equilibria exhibited by many materials by examining two recently well-characterized model systems, TlBr for radiation detection and PrxCe1-xO2-δ, of potential interest in solid-oxide fuel cells. The interplay between material composition, electrical conductivity, and mechanical properties (electrochemomechanics) is discussed, and implications in these relations, for example, enhancing electrical properties through large mechanical strains, are described. The impact of space charge and strain fields at interfaces, particularly important in nanostructure materials, is also emphasized. Key experimental techniques useful in characterizing bulk and surface defects are summarized and reviewed.

Method and apparatus for implementing material thermal property measurement by flash thermal imaging

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

Sun, Jiangang

A method and apparatus are provided for implementing measurement of material thermal properties including measurement of thermal effusivity of a coating and/or film or a bulk material of uniform property. The test apparatus includes an infrared camera, a data acquisition and processing computer coupled to the infrared camera for acquiring and processing thermal image data, a flash lamp providing an input of heat onto the surface of a two-layer sample with an enhanced optical filter covering the flash lamp attenuating an entire infrared wavelength range with a series of thermal images is taken of the surface of the two-layer sample.

Shell-binary nanoparticle materials with variable electrical and electro-mechanical properties.

PubMed

Zhang, P; Bousack, H; Dai, Y; Offenhäusser, A; Mayer, D

2018-01-18

Nanoparticle (NP) materials with the capability to adjust their electrical and electro-mechanical properties facilitate applications in strain sensing technology. Traditional NP materials based on single component NPs lack a systematic and effective means of tuning their electrical and electro-mechanical properties. Here, we report on a new type of shell-binary NP material fabricated by self-assembly with either homogeneous or heterogeneous arrangements of NPs. Variable electrical and electro-mechanical properties were obtained for both materials. We show that the electrical and electro-mechanical properties of these shell-binary NP materials are highly tunable and strongly affected by the NP species as well as their corresponding volume fraction ratio. The conductivity and the gauge factor of these shell-binary NP materials can be altered by about five and two orders of magnitude, respectively. These shell-binary NP materials with different arrangements of NPs also demonstrate different volume fraction dependent electro-mechanical properties. The shell-binary NP materials with a heterogeneous arrangement of NPs exhibit a peaking of the sensitivity at medium mixing ratios, which arises from the aggregation induced local strain enhancement. Studies on the electron transport regimes and micro-morphologies of these shell-binary NP materials revealed the different mechanisms accounting for the variable electrical and electro-mechanical properties. A model based on effective medium theory is used to describe the electrical and electro-mechanical properties of such shell-binary nanomaterials and shows an excellent match with experiment data. These shell-binary NP materials possess great potential applications in high-performance strain sensing technology due to their variable electrical and electro-mechanical properties.

Investigation on the effect of friction stir processing on tribological and mechanical properties of Al 7075-T651 alloy

NASA Astrophysics Data System (ADS)

Murthy, Veeresh; Rajaprakash, B. M.

2018-04-01

Friction Stir Processing (FSP) is generally used as a novel method for surface properties enhancement. The surface developed through FSP alters the tribological and mechanical properties of the material in a single step. This commendable enhancement in the properties by recrystallized equiaxed microstructure attained by dynamic recrystallization can be achieved in just one step there by increasing the performance. In this study, the effect of the FSP passes on the tribological & mechanical properties such as hardness, wear resistance and tensile strength for commercially available AA7075-T651 of 6mm thick sheet was studied. Properties in terms of hardness, wear rate and tensile strength were compared with the base alloy and Friction Stir Processed (FSPed) alloy. It was observed that the hardness, wear rate of the FSPed FSP3 was enhanced by 44% and 60% as compared to that of the unprocessed sample.

Processing and Properties Of Refractory Zirconium Diboride Composites For Use In High Temperature Applications

NASA Technical Reports Server (NTRS)

Stackpoole, Margaret; Gusman, M.; Ellerby, D.; Johnson, S. M.; Arnold, Jim (Technical Monitor)

2001-01-01

The Thermal Protection Materials and Systems Branch at NASA Ames Research Center is involved in the development of a class of refractory oxidation-resistant diboride composites termed Ultra High Temperature Ceramics or UHTCs. These composites have good high temperature properties making them candidate materials for thermal protection system (TPS) applications. The current research focuses on improving processing methods to develop more reliable composites with enhanced thermal and mechanical properties. This presentation will concentrate on the processing of ZrB2/SiC composites. Some preliminary mechanical properties and oxidation data will also be presented.

Assessment of Technologies for the Space Shuttle External Tank Thermal Protection System and Recommendations for Technology Improvement - Part III: Material Property Characterization, Analysis, and Test Methods

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Johnson, Theodore F.; Whitley, Karen S.

2005-01-01

The objective of this report is to contribute to the independent assessment of the Space Shuttle External Tank Foam Material. This report specifically addresses material modeling, characterization testing, data reduction methods, and data pedigree. A brief description of the External Tank foam materials, locations, and standard failure modes is provided to develop suitable background information. A review of mechanics based analysis methods from the open literature is used to provide an assessment of the state-of-the-art in material modeling of closed cell foams. Further, this report assesses the existing material property database and investigates sources of material property variability. The report presents identified deficiencies in testing methods and procedures, recommendations for additional testing as required, identification of near-term improvements that should be pursued, and long-term capabilities or enhancements that should be developed.

Controlling material birefringence in sapphire via self-assembled, sub-wavelength defects

NASA Astrophysics Data System (ADS)

Singh, Astha; Sharma, Geeta; Ranjan, Neeraj; Mittholiya, Kshitij; Bhatnagar, Anuj; Singh, B. P.; Mathur, Deepak; Vasa, Parinda

2018-02-01

Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. Generally, this is an intrinsic optical property of a material and cannot be altered. Here, we report a novel technique—direct laser writing—that enables us to control the natural, material birefringence of sapphire over a broad range of wavelengths. The broadband form birefringence originating from self-assembled, periodic array of sub-wavelength (˜ 50-200 nm) defects created by laser writing, can enhance, suppress or maintain the material birefringence of sapphire without affecting its transparency range in visible or its surface quality.

Multifaceted prospects of nanocomposites for cardiovascular grafts and stents

PubMed Central

Vellayappan, Muthu Vignesh; Balaji, Arunpandian; Subramanian, Aruna Priyadarshini; John, Agnes Aruna; Jaganathan, Saravana Kumar; Murugesan, Selvakumar; Supriyanto, Eko; Yusof, Mustafa

2015-01-01

Cardiovascular disease is the leading cause of death across the globe. The use of synthetic materials is indispensable in the treatment of cardiovascular disease. Major drawbacks related to the use of biomaterials are their mechanical properties and biocompatibility, and these have to be circumvented before promoting the material to the market or clinical setting. Revolutionary advancements in nanotechnology have introduced a novel class of materials called nanocomposites which have superior properties for biomedical applications. Recently, there has been a widespread recognition of the nanocomposites utilizing polyhedral oligomeric silsesquioxane, bacterial cellulose, silk fibroin, iron oxide magnetic nanoparticles, and carbon nanotubes in cardiovascular grafts and stents. The unique characteristics of these nanocomposites have led to the development of a wide range of nanostructured copolymers with appreciably enhanced properties, such as improved mechanical, chemical, and physical characteristics suitable for cardiovascular implants. The incorporation of advanced nanocomposite materials in cardiovascular grafts and stents improves hemocompatibility, enhances antithrombogenicity, improves mechanical and surface properties, and decreases the microbial response to the cardiovascular implants. A thorough attempt is made to summarize the various applications of nanocomposites for cardiovascular graft and stent applications. This review will highlight the recent advances in nanocomposites and also address the need of future research in promoting nanocomposites as plausible candidates in a campaign against cardiovascular disease. PMID:25897223

How Molecular Structure Affects Mechanical Properties of an Advanced Polymer

NASA Technical Reports Server (NTRS)

Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

2000-01-01

density was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength all as a function of molecular weight and test temperature were determined. For the uncrosslinked SI material, it was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. For the crosslinked PETI-SI material, it was shown that the effect of crosslinking significantly enhances the mechanical performance of the low molecular weight material; comparable to that exhibited by the high molecular weight material.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

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

Luk, Ting S.; De Ceglia, Domenico; Liu, Sheng

We demonstrate, through our experimentation, efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10 -6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. Furthermore, this nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

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

Luk, Ting S., E-mail: tsluk@sandia.gov; Liu, Sheng; Campione, Salvatore

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10{sup −6} is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Extrinsic polarization-controlled optical anisotropy in plasmon-black phosphorus coupled system

NASA Astrophysics Data System (ADS)

Liu, Zizhuo; Wells, Spencer A.; Butun, Serkan; Palacios, Edgar; Hersam, Mark C.; Aydin, Koray

2018-07-01

Two-dimensional black phosphorus (BP) has drawn extensive research interest due to its promising anisotropic photonic and electronic properties. Here, we study anisotropic optical absorption and photoresponse of exfoliated BP flakes at visible frequencies. We enhance this intrinsic optical anisotropy in BP flakes by coupling plasmonic rectangular nanopatch arrays that support localized surface plasmon resonances. In particular, by combining extrinsic anisotropic plasmonic nanostructures lithographically aligned with intrinsically anisotropic BP flakes, we demonstrate for the first time a combined anisotropic plasmonic-semiconductor coupling that provides significant control over the polarization-dependent optical properties of the plasmon-BP hybrid material system, enhancing polarization-sensitive responses to a larger degree. This hybrid material system not only unveils the plasmon-enhanced mechanisms in BP, but also provides novel controllable functionalities in optoelectronic device applications involving polarization-sensitive optical and electrical responses.

Hydrothermal synthesis of novel Mn(3)O(4) nano-octahedrons with enhanced supercapacitors performances.

PubMed

Jiang, Hao; Zhao, Ting; Yan, Chaoyi; Ma, Jan; Li, Chunzhong

2010-10-01

Uniform and single-crystalline Mn(3)O(4) nano-octahedrons have been successfully synthesized by a simple ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal route. The octahedron structures exhibit a high geometric symmetry with smooth surfaces and the mean side length of square base of octahedrons is ∼160 nm. The structure is reckoned to provide superior functional properties and the nano-size achieved in the present work is noted to further facilitate the material property enhancement. The formation process was proposed to begin with a "dissolution-recrystallization" which is followed by an "Ostwald ripening" mechanism. The Mn(3)O(4) nano-octahedrons exhibited an enhanced specific capacitance of 322 F g(-1) compared with the truncated octahedrons with specific capacitances of 244 F g(-1), making them a promising electrode material for supercapacitors.

Extrinsic polarization-controlled optical anisotropy in plasmon-black phosphorus coupled system.

PubMed

Liu, Zizhuo; Wells, Spencer A; Butun, Serkan; Palacios, Edgar; Hersam, Mark C; Aydin, Koray

2018-07-13

Two-dimensional black phosphorus (BP) has drawn extensive research interest due to its promising anisotropic photonic and electronic properties. Here, we study anisotropic optical absorption and photoresponse of exfoliated BP flakes at visible frequencies. We enhance this intrinsic optical anisotropy in BP flakes by coupling plasmonic rectangular nanopatch arrays that support localized surface plasmon resonances. In particular, by combining extrinsic anisotropic plasmonic nanostructures lithographically aligned with intrinsically anisotropic BP flakes, we demonstrate for the first time a combined anisotropic plasmonic-semiconductor coupling that provides significant control over the polarization-dependent optical properties of the plasmon-BP hybrid material system, enhancing polarization-sensitive responses to a larger degree. This hybrid material system not only unveils the plasmon-enhanced mechanisms in BP, but also provides novel controllable functionalities in optoelectronic device applications involving polarization-sensitive optical and electrical responses.

The Physics and Chemistry of Materials

NASA Astrophysics Data System (ADS)

Gersten, Joel I.; Smith, Frederick W.

2001-06-01

A comprehensive introduction to the structure, properties, and applications of materials This title provides the first unified treatment for the broad subject of materials. Authors Gersten and Smith use a fundamental approach to define the structure and properties of a wide range of solids on the basis of the local chemical bonding and atomic order present in the material. Emphasizing the physical and chemical origins of material properties, the book focuses on the most technologically important materials being utilized and developed by scientists and engineers. Appropriate for use in advanced materials courses, The Physics and Chemistry of Materials provides the background information necessary to assimilate the current academic and patent literature on materials and their applications. Problem sets, illustrations, and helpful tables complete this well-rounded new treatment. Five sections cover these important topics: * Structure of materials, including crystal structure, bonding in solids, diffraction and the reciprocal lattice, and order and disorder in solids * Physical properties of materials, including electrical, thermal, optical, magnetic, and mechanical properties * Classes of materials, including semiconductors, superconductors, magnetic materials, and optical materials in addition to metals, ceramics, polymers, dielectrics, and ferroelectrics * A section on surfaces, thin films, interfaces, and multilayers discusses the effects of spatial discontinuities in the physical and chemical structure of materials * A section on synthesis and processing examines the effects of synthesis on the structure and properties of various materials This book is enhanced by a Web-based supplement that offers advanced material together with an entire electronic chapter on the characterization of materials. The Physics and Chemistry of Materials is a complete introduction to the structure and properties of materials for students and an excellent reference for scientists and engineers.

Bond Strength Mechanism of Fly Ash Based Geopolymer Mortars: A Review

NASA Astrophysics Data System (ADS)

Zailani, W. W. A.; Abdullah, M. M. A. B.; Razak, R. A.; Zainol, M. R. R. M. A.; Tahir, M. F. M.

2017-11-01

Geopolymer possess many excellent properties such as high compressive and bond strength, long term durability, better acid resistance and also known as a “Sustainable Material” due to its low carbon emission and low energy consumption. Thus, it is a good opportunity to develop and explore not only for cement and concrete but also as geopolymeric repair materials. This reviews showed that good bonding properties between geopolymeric repair material and concrete substrate is important in order to acquire an enhanced resistance against penetration of harmful substances and avoiding respalling of the repair material by understanding the bonding behaviour. Bond strength depends to the properties of the repair materials itself and also the surface preparations of concrete substrate.

Engineering Biomaterial Properties for Central Nervous System Applications

NASA Astrophysics Data System (ADS)

Rivet, Christopher John

Biomaterials offer unique properties that are intrinsic to the chemistry of the material itself or occur as a result of the fabrication process; iron oxide nanoparticles are superparamagnetic, which enables controlled heating in the presence of an alternating magnetic field, and a hydrogel and electrospun fiber hybrid material provides minimally invasive placement of a fibrous, artificial extracellular matrix for tissue regeneration. Utilization of these unique properties towards central nervous system disease and dysfunction requires a thorough definition of the properties in concert with full biological assessment. This enables development of material-specific features to elicit unique cellular responses. Iron oxide nanoparticles are first investigated for material-dependent, cortical neuron cytotoxicity in vitro and subsequently evaluated for alternating magnetic field stimulation induced hyperthermia, emulating the clinical application for enhanced chemotherapy efficacy in glioblastoma treatment. A hydrogel and electrospun fiber hybrid material is first applied to a rat brain to evaluate biomaterial interface astrocyte accumulation as a function of hybrid material composition. The hybrid material is then utilized towards increasing functional engraftment of dopaminergic progenitor neural stem cells in a mouse model of Parkinson's disease. Taken together, these two scenarios display the role of material property characterization in development of biomaterial strategies for central nervous system repair and regeneration.

Bioprosthetic Mesh in Abdominal Wall Reconstruction

PubMed Central

Baumann, Donald P.; Butler, Charles E.

2012-01-01

Mesh materials have undergone a considerable evolution over the last several decades. There has been enhancement of biomechanical properties, improvement in manufacturing processes, and development of antiadhesive laminate synthetic meshes. The evolution of bioprosthetic mesh materials has markedly changed our indications and methods for complex abdominal wall reconstruction. The authors review the optimal properties of bioprosthetic mesh materials, their evolution over time, and their indications for use. The techniques to optimize outcomes are described using bioprosthetic mesh for complex abdominal wall reconstruction. Bioprosthetic mesh materials clearly have certain advantages over other implantable mesh materials in select indications. Appropriate patient selection and surgical technique are critical to the successful use of bioprosthetic materials for abdominal wall repair. PMID:23372454

Stainless steel valves with enhanced performance through microstructure optimization

NASA Astrophysics Data System (ADS)

Barani, A. A.; Boukhattam, M.; Haggeney, M.; Güler, S.

2017-08-01

Compressor valves are made of hardened and tempered martensitic steels. The main design criterion for the material selection is the fatigue performance of the material under bending loads. In some cases impact loads and corrosive atmospheres additionally act on the part. For the first time, the microstructure of the most commonly used stainless steel and its influence on the properties relevant for flapper valves is presented and described in this paper. It is demonstrated how the tensile properties of a martensitic stainless steel can be enhanced by tailoring the microstructure. Electron back scatter diffraction method is carried out to explain the changes in monotonic mechanical properties. Through a modified heat treatment the martensite microstructure is refined resulting in an increase of yield and ultimate tensile strength and at the same time a significant increase of elongation.

Novel tools for accelerated materials discovery in the AFLOWLIB.ORG repository: breakthroughs and challenges in the mapping of the materials genome

NASA Astrophysics Data System (ADS)

Buongiorno Nardelli, Marco

2015-03-01

High-Throughput Quantum-Mechanics computation of materials properties by ab initio methods has become the foundation of an effective approach to materials design, discovery and characterization. This data driven approach to materials science currently presents the most promising path to the development of advanced technological materials that could solve or mitigate important social and economic challenges of the 21st century. In particular, the rapid proliferation of computational data on materials properties presents the possibility to complement and extend materials property databases where the experimental data is lacking and difficult to obtain. Enhanced repositories such as AFLOWLIB, open novel opportunities for structure discovery and optimization, including uncovering of unsuspected compounds, metastable structures and correlations between various properties. The practical realization of these opportunities depends on the the design effcient algorithms for electronic structure simulations of realistic material systems, the systematic compilation and classification of the generated data, and its presentation in easily accessed form to the materials science community, the primary mission of the AFLOW consortium. This work was supported by ONR-MURI under Contract N00014-13-1-0635 and the Duke University Center for Materials Genomics.

Enhancement of p-nitrophenol adsorption capacity through N2-thermal-based treatment of activated carbons

NASA Astrophysics Data System (ADS)

Álvarez-Torrellas, S.; Martin-Martinez, M.; Gomes, H. T.; Ovejero, G.; García, J.

2017-08-01

In this work several activated carbons showing different textural and chemical properties were obtained by chemical and physical activation methods, using a lignocellulosic material (peach stones) as precursor. The activated carbon resulting from the chemical activation, namely as CAC, revealed the best textural properties (SBET = 1521 m2 g-1, pore volume = 0.90 cm3 g-1) and an acidic character. It was found that the activated carbon obtained at 300 °C (under air atmosphere, PAC_air), and those synthesized at 750 °C in presence of N2 flow with bubbling of water/12 M H3PO4 solution (PAC_N2(H2O)/PAC_N2(H3PO4)), respectively, revealed worse textural properties, compared to CAC. Two functionalization treatments, by using sulphuric acid at boiling temperature (PACS) and nitric acid-urea-N2 heating at 800 °C (PAC-NUT), were applied to PAC_air, in order to enhance the adsorption ability of the carbon material. Several techniques were carried out to characterize the physical and chemical properties of the obtained carbon materials. The modification treatments had influence on the carbon surface properties, since the nitric acid-urea-N2 heating treatment led to a carbon material with highly-improved properties (SBET = 679 m2 g-1, pHIEP = 5.3). Accordingly, the original and modified-carbon materials were tested as adsorbents to remove 4-nitrophenol (4-NP), assessing batch and fixed-bed column adsorption tests. PAC-NUT carbon offered the best adsorption behavior (qe = 234 mg g-1), showing a high ability for the removal of 4-NP from water.

Interlaminar shear strength and thermo-mechanical properties of nano-enhanced composite materials under thermal shock

NASA Astrophysics Data System (ADS)

Gkikas, G.; Douka, D.-D.; Barkoula, N.-M.; Paipetis, A. S.

2013-04-01

The introduction of nanoscaled reinforcement in otherwise conventional fiber reinforced composite materials has opened an exciting new area in composites research. The unique properties of these materials combined with the design versatility of fibrous composites may offer both enhanced mechanical properties and multiple functionalities which has been a focus area of the aerospace technology on the last decades. Due to unique properties of carbon nanofillers such as huge aspect ratio, extremely large specific surface area as well as high electrical and thermal conductivity, Carbon Nanotubes have benn investigated as multifunvtional materials for electrical, thermal and mechanical applications. In this study, MWCNTs were incorporated in a typical epoxy system using a sonicator. The volume of the nanoreinforcement was 0.5 % by weight. Two different levels of sonication amplitude were used, 50% and 100% respectively. After the sonication, the hardener was introduced in the epoxy, and the system was cured according to the recommended cycle. For comparison purposes, specimens from neat epoxy system were prepared. The thermomechanical properties of the materials manufactured were investigated using a Dynamic Mechanical Analyser. The exposed specimens were subjected to thermal shock. Thermal cycles from +30 °C to -30 °C were carried out and each cycle lasted 24 hours. The thermomechanical properties were studied after 30 cycles . Furthermore, the epoxy systems prepared during the first stage of the study were used for the manufacturing of 16 plies quasi isotropic laminates CFRPs. The modified CFRPs were subjected to thermal shock. For comparison reasons unmodified CFRPs were manufactured and subjected to the same conditions. In addition, the interlaminar shear strength of the specimens was studied using 3-point bending tests before and after the thermal shock. The effect of the nanoreinforcement on the environmental degradation is critically assessed.

Composite Materials with Magnetically Aligned Carbon Nanoparticles and Methods of Preparation

NASA Technical Reports Server (NTRS)

Salem, David R. (Inventor); Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor)

2018-01-01

The present invention relates to magnetically aligned carbon nanoparticle composites and methods of preparing the same. The composites comprise carbon nanoparticles, host material, magnetically sensitive nanoparticles and surfactant. The composites may have enhanced mechanical, thermal, and/or electrical properties.

Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment.

PubMed

Bae, Eun Jin; Kang, Young Hun; Jang, Kwang-Suk; Cho, Song Yun

2016-01-05

The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) and tellurium- PSS (Te- PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PSS and Te- PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm(-1), respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m(-1) K(-2), respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te- PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat.

Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGa xFe 2–xO 4/BaTiO 3 composite

DOE PAGES

Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; ...

2015-03-20

Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGa xFe 2–xO 4/BaTiO 3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. Anmore » enhancement of the electrostrain with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGa xFe 2–xO 4/BaTiO 3 composites. As a result, the present work is beneficial to the practical application of composite CoFe 2O 4/BaTiO 3-based multiferroic materials.« less

Synthesis, structure, and optoelectronic properties of II-IV-V 2 materials

DOE PAGES

Martinez, Aaron D.; Fioretti, Angela N.; Toberer, Eric S.; ...

2017-03-07

II-IV-V 2 materials offer the promise of enhanced functionality in optoelectronic devices due to their rich ternary chemistry. In this review, we consider the potential for new optoelectronic devices based on nitride, phosphide, and arsenide II-IV-V 2 materials. As ternary analogs to the III-V materials, these compounds share many of the attractive features that have made the III-Vs the basis of modern optoelectronic devices (e.g. high mobility, strong optical absorption). Control of cation order parameter in the II-IV-V 2 materials can produce significant changes in optoelectronic properties at fixed chemical composition, including decoupling band gap from lattice parameter. Recent progressmore » has begun to resolve outstanding questions concerning the structure, dopability, and optical properties of the II-IV-V 2 materials. Furthermore, remaining research challenges include growth optimization and integration into heterostructures and devices.« less

A theranostic dental pulp capping agent with improved MRI and CT contrast and biological properties.

PubMed

Mastrogiacomo, S; Güvener, N; Dou, W; Alghamdi, H S; Camargo, W A; Cremers, J G O; Borm, P J A; Heerschap, A; Oosterwijk, E; Jansen, J A; Walboomers, X F

2017-10-15

Different materials have been used for vital dental pulp treatment. Preferably a pulp capping agent should show appropriate biological performance, excellent handling properties, and a good imaging contrast. These features can be delivered into a single material through the combination of therapeutic and diagnostic agents (i.e. theranostic). Calcium phosphate based composites (CPCs) are potentially ideal candidate for pulp treatment, although poor imaging contrast and poor dentino-inductive properties are limiting their clinical use. In this study, a theranostic dental pulp capping agent was developed. First, imaging properties of the CPC were improved by using a core-shell structured dual contrast agent (csDCA) consisting of superparamagnetic iron oxide (SPIO) and colloidal gold, as MRI and CT contrast agent respectively. Second, biological properties were implemented by using a dentinogenic factor (i.e. bone morphogenetic protein 2, BMP-2). The obtained CPC/csDCA/BMP-2 composite was tested in vivo, as direct pulp capping agent, in a male Habsi goat incisor model. Our outcomes showed no relevant alteration of the handling and mechanical properties (e.g. setting time, injectability, and compressive strength) by the incorporation of csDCA particles. In vivo results proved MRI contrast enhancement up to 7weeks. Incisors treated with BMP-2 showed improved tertiary dentin deposition as well as faster cement degradation as measured by µCT assessment. In conclusion, the presented theranostic agent matches the imaging and regenerative requirements for pulp capping applications. In this study, we combined diagnostic and therapeutic agents in order to developed a theranostic pulp capping agent with enhanced MRI and CT contrast and improved dentin regeneration ability. In our study we cover all the steps from material preparation, mechanical and in vitro characterization, to in vivo study in a goat dental model. To the best of our knowledge, this is the first time that a theranostic pulp capping material have been developed and tested in an in vivo animal model. Our promising results in term of imaging contrast enhancement and of induction of new dentin formation, open a new scenario in the development of innovative dental materials. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Radiofrequency Electric Field Heating of Conductive Media: Understanding Aqueous and Nanoparticle Heating Mechanisms and a Method for Heating Optimization

NASA Astrophysics Data System (ADS)

Lara, Nadia Chantal

Use of radiofrequency (RF) electric fields coupled with nanoparticles to enhance non-invasive hyperthermia in cancer cells and tumors sparked debate over the RF heating mechanisms of nanoparticles and the role of salts in heating. Under RF field exposure at 13.56 MHz, aqueous systems including electrolyte solutions, buffers, and blood, were shown to heat according to bulk material properties, regardless of composition. This universal aqueous heating behavior extended to suspensions of nanoparticles such as gold nanoparticles, full-length and ultra-short single-walled carbon nanotubes, and water-soluble fullerene derivatives. These suspensions displayed the same RF heating properties as saline solutions of the same conductivity, indicating that these nanoparticles themselves do not contribute to RF heating by any unique mechanism; rather, they modulate bulk conductivity, which in turn affects bulk RF heating. At 13.56 MHz, peak heating for an aqueous system occurs at a conductivity of 0.06 S/m, beyond which increases in conductivity result in reduced heating rates. Biologically relevant materials, such as blood, intra- and extracellular fluids, and most human tissues, exceed this peak heating conductivity, precluding the use of conductive materials for RF heating rate enhancement. Instead, kosmotropic or water-structuring materials, including sugars, glycols, zwitterionic molecules, and a water-soluble fullerene derivative, when added to blood or phosphate buffered saline reduced the bulk conductivity of these materials and enhanced their heating rates accordingly. A dielectric heating rate model taking into account the geometry of the sample under RF exposure was used to explain the experimental RF heating behavior of aqueous solutions and semi-aqueous materials, which generated distinct RF heating curves due to differences in bulk dielectric and physical properties.

Experimental Investigation of Mechanical and Thermal Properties of Silica Nanoparticle-Reinforced Poly(acrylamide) Nanocomposite Hydrogels

PubMed Central

O’Brien, Victor; Chang, Andrew; Blanco, Matthew; Zabalegui, Aitor; Lee, Hohyun; Asuri, Prashanth

2015-01-01

Current studies investigating properties of nanoparticle-reinforced polymers have shown that nanocomposites often exhibit improved properties compared to neat polymers. However, over two decades of research, using both experimental studies and modeling analyses, has not fully elucidated the mechanistic underpinnings behind these enhancements. Moreover, few studies have focused on developing an understanding among two or more polymer properties affected by incorporation of nanomaterials. In our study, we investigated the elastic and thermal properties of poly(acrylamide) hydrogels containing silica nanoparticles. Both nanoparticle concentration and size affected hydrogel properties, with similar trends in enhancements observed for elastic modulus and thermal diffusivity. We also observed significantly lower swellability for hydrogel nanocomposites relative to neat hydrogels, consistent with previous work suggesting that nanoparticles can mediate pseudo crosslinking within polymer networks. Collectively, these results indicate the ability to develop next-generation composite materials with enhanced mechanical and thermal properties by increasing the average crosslinking density using nanoparticles. PMID:26301505

Mesoporous systems for poorly soluble drugs.

PubMed

Xu, Wujun; Riikonen, Joakim; Lehto, Vesa-Pekka

2013-08-30

Utilization of inorganic mesoporous materials in formulations of poorly water-soluble drugs to enhance their dissolution and permeation behavior is a rapidly growing area in pharmaceutical materials research. The benefits of mesoporous materials in drug delivery applications stem from their large surface area and pore volume. These properties enable the materials to accommodate large amounts of payload molecules, protect them from premature degradation, and promote controlled and fast release. As carriers with various morphologies and chemical surface properties can be produced, these materials may even promote adsorption from the gastrointestinal tract to the systemic circulation. The main concern regarding their clinical applications is still the safety aspect even though most of them have been reported to be safely excreted, and a rather extensive toxicity screening has already been conducted with the most frequently studied mesoporous materials. In addition, the production of the materials on a large scale and at a reasonable cost may be a challenge when considering the utilization of the materials in industrial processes. However, if mesoporous materials could be employed in the industrial crystallization processes to produce hybrid materials with poorly soluble compounds, and hence to enhance their oral bioavailability, this might open new avenues for the pharmaceutical industry to employ nanotechnology in their processes. Copyright © 2012 Elsevier B.V. All rights reserved.

High-pressure torsion for new hydrogen storage materials.

PubMed

Edalati, Kaveh; Akiba, Etsuo; Horita, Zenji

2018-01-01

High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Since 2007, the method has been employed to enhance the hydrogenation kinetics in different Mg-based hydrogen storage materials. Recent studies showed that the method is effective not only for increasing the hydrogenation kinetics but also for improving the hydrogenation activity, for enhancing the air resistivity and more importantly for synthesizing new nanostructured hydrogen storage materials with high densities of lattice defects. This manuscript reviews some major findings on the impact of HPT process on the hydrogen storage performance of different titanium-based and magnesium-based materials.

Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles.

PubMed

Fang, Teng; Zhao, Xinbing; Zhu, Tiejun

2018-05-19

Half-Heusler (HH) compounds, with a valence electron count of 8 or 18, have gained popularity as promising high-temperature thermoelectric (TE) materials due to their excellent electrical properties, robust mechanical capabilities, and good high-temperature thermal stability. With the help of first-principles calculations, great progress has been made in half-Heusler thermoelectric materials. In this review, we summarize some representative theoretical work on band structures and transport properties of HH compounds. We introduce how basic band-structure calculations are used to investigate the atomic disorder in n-type M NiSb ( M = Ti, Zr, Hf) compounds and guide the band engineering to enhance TE performance in p-type Fe R Sb ( R = V, Nb) based systems. The calculations on electrical transport properties, especially the scattering time, and lattice thermal conductivities are also demonstrated. The outlook for future research directions of first-principles calculations on HH TE materials is also discussed.

Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles

PubMed Central

Fang, Teng; Zhao, Xinbing

2018-01-01

Half-Heusler (HH) compounds, with a valence electron count of 8 or 18, have gained popularity as promising high-temperature thermoelectric (TE) materials due to their excellent electrical properties, robust mechanical capabilities, and good high-temperature thermal stability. With the help of first-principles calculations, great progress has been made in half-Heusler thermoelectric materials. In this review, we summarize some representative theoretical work on band structures and transport properties of HH compounds. We introduce how basic band-structure calculations are used to investigate the atomic disorder in n-type MNiSb (M = Ti, Zr, Hf) compounds and guide the band engineering to enhance TE performance in p-type FeRSb (R = V, Nb) based systems. The calculations on electrical transport properties, especially the scattering time, and lattice thermal conductivities are also demonstrated. The outlook for future research directions of first-principles calculations on HH TE materials is also discussed. PMID:29783759

Polymer Nanocomposite Materials with High Dielectric Permittivity and Low Dielectric Loss Properties

NASA Astrophysics Data System (ADS)

Toor, Anju

Materials with high dielectric permittivity have drawn increasing interests in recent years for their important applications in capacitors, actuators, and high energy density pulsed power. Particularly, polymer-based dielectrics are excellent candidates, owing to their properties such as high breakdown strength, low dielectric loss, flexibility and easy processing. To enhance the dielectric permittivity of polymer materials, typically, high dielectric constant filler materials are added to the polymer. Previously, ferroelectric and conductive fillers have been mainly used. However, such systems suffered from various limitations. For example, composites based on ferroelectric materials like barium titanate, exhibited high dielectric loss, and poor saturation voltages. Conductive fillers are used in the form of powder aggregates, and they may show 10-100 times enhancement in dielectric constant, however these nanoparticle aggregates cause the dielectric loss to be significant. Also, agglomerates limit the volume fraction of fillers in polymer and hence, the ability to achieve superior dielectric constants. Thus, the aggregation of nanoparticles is a significant challenge to their use to improve the dielectric permittivity. We propose the use of ligand-coated metal nanoparticle fillers to enhance the dielectric properties of the host polymer while minimizing dielectric loss by preventing nanoparticle agglomeration. The focus is on obtaining uniform dispersion of nanoparticles with no agglomeration by utilizing appropriate ligands/surface functionalizations on the gold nanoparticle surface. Use of ligand coated metal nanoparticles will enhance the dielectric constant while minimizing dielectric loss, even with the particles closely packed in the polymer matrix. Novel combinations of materials, which use 5 nm diameter metal nanoparticles embedded inside high breakdown strength polymer materials are evaluated. High breakdown strength polymer materials are chosen to allow further exploration of these materials for energy storage applications. In summary, two novel nanocomposite materials are designed and synthesized, one involving polyvinylidene fluoride (PVDF) as the host polymer for potential applications in energy storage and the other with SU-8 for microelectronic applications. Scanning elec- tron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and ultramicrotoming techniques were used for the material characterization of the nanocomposite materials. A homogeneous dispersion of gold nanoparticles with low particle agglomeration has been achieved. Fabricated nanoparticle polymer composite films showed the absence of voids and cracks. Also, no evidence of macro-phase separation of nanoparticles from the polymer phase was observed. This is important because nanoparticle agglomeration and phase separation from the polymer usually results in poor processability of films and a high defect density. Dielectric characterization of the nanocomposite materials showed enhancement in the dielectric constant over the base polymer values and low dielectric loss values were observed.

Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film.

PubMed

Lee, Ka-Yeon; Song, Kyung Bin

2017-03-01

Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG-PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10 -9 g·m/m 2 ·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG-PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG-PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material. © 2017 Institute of Food Technologists®.

Enhancement of the bentonite sorption properties.

PubMed

Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

2010-08-15

The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. Copyright 2010 Elsevier B.V. All rights reserved.

Evaluation of the Effects of Crushed and Expanded Waste Glass Aggregates on the Material Properties of Lightweight Concrete Using Image-Based Approaches

PubMed Central

Abd Elrahman, Mohamed; Sikora, Pawel; Rucinska, Teresa; Horszczaruk, Elzbieta

2017-01-01

Recently, the recycling of waste glass has become a worldwide issue in the reduction of waste and energy consumption. Waste glass can be utilized in construction materials, and understanding its effects on material properties is crucial in developing advanced materials. In this study, recycled crushed and expanded glasses are used as lightweight aggregates for concrete, and their relation to the material characteristics and properties is investigated using several approaches. Lightweight concrete specimens containing only crushed and expanded waste glass as fine aggregates are produced, and their pore and structural characteristics are examined using image-based methods, such as scanning electron microscopy (SEM), X-ray computed tomography (CT), and automated image analysis (RapidAir). The thermal properties of the materials are measured using both Hot Disk and ISOMET devices to enhance measurement accuracy. Mechanical properties are also evaluated, and the correlation between material characteristics and properties is evaluated. As a control group, a concrete specimen with natural fine sand is prepared, and its characteristics are compared with those of the specimens containing crushed and expanded waste glass aggregates. The obtained results support the usability of crushed and expanded waste glass aggregates as alternative lightweight aggregates. PMID:29186854

Evaluation of the Effects of Crushed and Expanded Waste Glass Aggregates on the Material Properties of Lightweight Concrete Using Image-Based Approaches.

PubMed

Chung, Sang-Yeop; Abd Elrahman, Mohamed; Sikora, Pawel; Rucinska, Teresa; Horszczaruk, Elzbieta; Stephan, Dietmar

2017-11-25

Recently, the recycling of waste glass has become a worldwide issue in the reduction of waste and energy consumption. Waste glass can be utilized in construction materials, and understanding its effects on material properties is crucial in developing advanced materials. In this study, recycled crushed and expanded glasses are used as lightweight aggregates for concrete, and their relation to the material characteristics and properties is investigated using several approaches. Lightweight concrete specimens containing only crushed and expanded waste glass as fine aggregates are produced, and their pore and structural characteristics are examined using image-based methods, such as scanning electron microscopy (SEM), X-ray computed tomography (CT), and automated image analysis (RapidAir). The thermal properties of the materials are measured using both Hot Disk and ISOMET devices to enhance measurement accuracy. Mechanical properties are also evaluated, and the correlation between material characteristics and properties is evaluated. As a control group, a concrete specimen with natural fine sand is prepared, and its characteristics are compared with those of the specimens containing crushed and expanded waste glass aggregates. The obtained results support the usability of crushed and expanded waste glass aggregates as alternative lightweight aggregates.

Strong enhancement effect of silver nanowires on fluorescent property of Eu3+-ligand complexes and desired fluorescent iPP composite materials

NASA Astrophysics Data System (ADS)

Zhang, Yu; Wang, Xinzhi; Tang, Jianguo; Wang, Wei; Wang, Jinping; Belfiore, Laurence A.

2017-04-01

In this contribution, we obtained the strong enhancement effect of silver nanowires(AgNWs) on fluorescent property of Eu3+-antenna complexes through the function of the surface plasmon resonance(SPR) effect. The key structural characteristics are: (1) AgNWs are covered by the Eu3+-ligand complex and spaced by SiO2 nano-layer between AgNWs and Eu3+-ligand complex (this structure is marked as AgNWs@SiO2@EuTP), and (2) AgNWs as nano-material with large ratio of length to diameter show their good dispersion and processability in isotactic polypropylene (iPP). We obtained the important data about the optimal spacer thickness of SiO2 is 15 nm that was not found in previous publications. The enhanced intensity of fluorescence of EuTP by AgNWs in AgNWs@SiO2@EuTP is 9 times compared with that of EuTP. All of these outstanding properties and fine structures were characterized by TEM, FT-IR, XRD, and fluorescence spectrophotometer. On the other hand, the desired fluorescent iPP composite material was obtained through blending AgNWs@SiO2@EuTP into iPP host. Very importantly, the enhancement effect of AgNWs on EuTP fluorescence in AgNWs@SiO2@EuTP is refrained from the quenching caused by host polymer of iPP.

Giant thermally-enhanced electrostriction and polar surface phase in L a2M o2O9 oxygen ion conductors

NASA Astrophysics Data System (ADS)

Li, Qian; Lu, Teng; Schiemer, Jason; Laanait, Nouamane; Balke, Nina; Zhang, Zhan; Ren, Yang; Carpenter, Michael A.; Wen, Haidan; Li, Jiangyu; Kalinin, Sergei V.; Liu, Yun

2018-04-01

Ferroelectrics possess spontaneous electric polarization at macroscopic scales which nonetheless imposes strict limitations on the material classes. Recent discoveries of untraditional symmetry-breaking phenomena in reduced material dimensions have indicated feasibilities to extend polar properties to broader types of materials, potentially opening up the freedom for designing materials with hybrid functionalities. Here, we report the unusual electromechanical properties of L a2M o2O9 (LAMOX) oxygen ion conductors, systematically investigated at both bulk and surface length levels. We first observed giant electrostriction effects in L a2M o2O9 bulk ceramics that are thermally enhanced in concert with their low-energy oxygen-vacancy hopping dynamics. Moreover, while no clear bulk polarization was detected, the surface phases of LAMOX were found to be manifestly polar, likely originating from the coupling between the intrinsic structural flexibilities with strain gradients (i.e., flexoelectricity) and/or chemical heterogeneities present in the materials. These findings identify L a2M o2O9 as a promising electromechanical material system and suggest that the flexible structural and chemical configurations in ionically active materials could enable fundamentally different venues to accommodate electric polarization.

Enhancing heat capacity of colloidal suspension using nanoscale encapsulated phase-change materials for heat transfer.

PubMed

Hong, Yan; Ding, Shujiang; Wu, Wei; Hu, Jianjun; Voevodin, Andrey A; Gschwender, Lois; Snyder, Ed; Chow, Louis; Su, Ming

2010-06-01

This paper describes a new method to enhance the heat-transfer property of a single-phase liquid by adding encapsulated phase-change nanoparticles (nano-PCMs), which absorb thermal energy during solid-liquid phase changes. Silica-encapsulated indium nanoparticles and polymer-encapsulated paraffin (wax) nanoparticles have been made using colloid method, and suspended into poly-alpha-olefin (PAO) and water for potential high- and low-temperature applications, respectively. The shells prevent leakage and agglomeration of molten phase-change materials, and enhance the dielectric properties of indium nanoparticles. The heat-transfer coefficients of PAO containing indium nanoparticles (30% by mass) and water containing paraffin nanoparticles (10% by mass) are 1.6 and 1.75 times higher than those of corresponding single-phase fluids. The structural integrity of encapsulation allows repeated use of such nanoparticles for many cycles in high heat generating devices.

AN EVALUATION OF FACTORS AFFECTING THE SOLIDIFICATION/STABILIZATION OF HEAVY METAL SLUDGE

EPA Science Inventory

Solidification/stabilization (SIS) of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are know...

MoS 2-on-MXene Heterostructures as Highly Reversible Anode Materials for Lithium-Ion Batteries

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

Chen, Chi; Xie, Xiuqiang; Anasori, Babak

Two-dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in materials science. The family of 2D transition-metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS 2-on-MXene heterostructures through in situ sulfidation of Mo 2TiC 2Tx MXene. The computational results show that MoS 2-on-MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li2S adsorption during the intercalation and conversion reactions. These characteristics render themore » as-prepared MoS 2-on-MXene heterostructures stable Li-ion storage performance. In conclusion, this work paves the way to use MXene to construct 2D heterostructures for energy storage applications.« less

MoS 2-on-MXene Heterostructures as Highly Reversible Anode Materials for Lithium-Ion Batteries

DOE PAGES

Chen, Chi; Xie, Xiuqiang; Anasori, Babak; ...

2018-01-02

Two-dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in materials science. The family of 2D transition-metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS 2-on-MXene heterostructures through in situ sulfidation of Mo 2TiC 2Tx MXene. The computational results show that MoS 2-on-MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li2S adsorption during the intercalation and conversion reactions. These characteristics render themore » as-prepared MoS 2-on-MXene heterostructures stable Li-ion storage performance. In conclusion, this work paves the way to use MXene to construct 2D heterostructures for energy storage applications.« less

The effect of fibre loading and graphene on the mechanical properties of goat hair fibre epoxy composite

NASA Astrophysics Data System (ADS)

Jayaseelan, J.; Vijayakumar, K. R.; Ethiraj, N.; Sivabalan, T.; nallayan, W. Andrew

2017-12-01

Composite materials are heterogenous materials containing one or more solid phases. In recent years cost-effective composite making is an ideal task. Hence we have come out with a natural fibre composite, which contains goat hair and epoxy as a binding element, with the combination of Graphene as a main source of enhanced mechanical property. Fabrication of natural composite consists of five layers of goat hair sandwiched in epoxy matrix. These composites made are tested for mechanical properties including Tensile strength, Flexural strength, Inter laminar shear and Impact strength. The mechanical properties of the six composite sets are analyzed and reported.

Suppression and enhancement of deep level emission of ZnO on Si4+ & V5+ substitution

NASA Astrophysics Data System (ADS)

Srivastava, T.; Bajpai, G.; Sen, S.

2018-03-01

ZnO possess a wide range of tunable properties depending on the type and concentration of dopant. Defects in ZnO due to doped aliovalent ions can generate certain functionalities. Such defects in the lattice do not deteriorate the material properties but actually modifies the material towards infinite number of possibilities. Defects like oxygen vacancies play a significant role in photocatalytic and sensing applications. Depending upon the functionality, defect state of ZnO can be modified by suitable doping. Amount and nature of different dopant has different effect on defect state of ZnO. It depends upon the ionic radii, valence state, chemical stability etc. of the ion doped. Two samples with two different dopants i.e., silicon and vanadium, Zn1-xSixO and Zn1-xVxO, for x=0 & 0.020, were synthesized using solgel method (a citric acid-glycerol route) followed by solid state sintering. A comparison of their optical properties, photoluminescence and UV-Vis spectroscopy, with pure ZnO was studied at room temperature. Silicon doping drastically reduces whereas vanadium doping enhances the green emission as compared with pure ZnO. Suppression and enhancement of defect levels (DLE) is rationalized by the effects of extra charge present on Si4+ & V5+ (in comparison to Zn2+) and formation of new hybrid state (V3d O2p) within bandgap. Reduction of defects in Zn1-xSixO makes it suitable material for opto-electronics application whereas enhancement in defects in Zn1-xVxO makes it suitable material for photocatalytic as well as gas sensing application.

Open framework metal chalcogenides as efficient photocatalysts for reduction of CO2 into renewable hydrocarbon fuel.

PubMed

Sasan, Koroush; Lin, Qipu; Mao, Chengyu; Feng, Pingyun

2016-06-07

Open framework metal chalcogenides are a family of porous semiconducting materials with diverse chemical compositions. Here we show that these materials containing covalent three-dimensional superlattices of nanosized supertetrahedral clusters can function as efficient photocatalysts for the reduction of CO2 to CH4. Unlike dense semiconductors, metal cations are successfully incorporated into the channels of the porous semiconducting materials to further tune the physical properties of the materials such as electrical conductivity and band gaps. In terms of the photocatalytic properties, the metal-incorporated porous chalcogenides demonstrated enhanced solar energy absorption and higher electrical conductivity and improved photocatalytic activity.

Mesoporous CdS via Network of Self-Assembled Nanocrystals: Synthesis, Characterization and Enhanced Photoconducting Property.

PubMed

Patra, Astam K; Banerjee, Biplab; Bhaumik, Asim

2018-01-01

Semiconduction nanoparticles are intensively studied due to their huge potential in optoelctronic applications. Here we report an efficient chemical route for hydrothermal synthesis of aggregated mesoporous cadmium sulfide (CdS) nanoparticles using supramolecular-assembly of ionic and water soluble sodium salicylate as the capping agent. The nanostructure, mesophase, optical property and photoconductivity of these mesoporous CdS materials have been characterized by using small and wide angle powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2-sorption, Raman analysis, Fourier transformed infrared (FT-IR), UV-Visible DSR spectroscopy, and photoconductivity measurement. Wide angle XRD pattern and high resolution TEM image analysis suggested that the particle size of the materials is within 10 nm and the nanoparticles are in well-crystallized cubic phase. Mesoporous CdS nanoparticles showed drastically enhanced photoelectrochemical response under visible light irradiation on entrapping a photosensitizer (dye) molecule in the interparticle spaces. Efficient synthesis strategy and the enhanced photo response in the mesoporous CdS material could facilitate the designing of other porous semiconductor oxide/sulfide and their applications in photon-to-electron conversion processes.

Enhanced thermoelectric properties of graphene oxide patterned by nanoroads.

PubMed

Zhou, Si; Guo, Yu; Zhao, Jijun

2016-04-21

The thermoelectric properties of two-dimensional (2D) materials are of great interest for both fundamental science and device applications. Graphene oxide (GO), whose physical properties are highly tailorable by chemical and structural modifications, is a potential 2D thermoelectric material. In this report, we pattern nanoroads on GO sheets with epoxide functionalization, and investigate their ballistic thermoelectric transport properties based on density functional theory and the nonequilibrium Green's function method. These graphene oxide nanoroads (GONRDs) are all semiconductors with their band gaps tunable by the road width, edge orientation, and the structure of the GO matrix. These nanostructures show appreciable electrical conductance at certain doping levels and enhanced thermopower of 127-287 μV K(-1), yielding a power factor 4-22 times of the graphene value; meanwhile, the lattice thermal conductance is remarkably reduced to 15-22% of the graphene value; consequently, attaining the figure of merit of 0.05-0.75. Our theoretical results are not only helpful for understanding the thermoelectric properties of graphene and its derivatives, but also would guide the theoretical design and experimental fabrication of graphene-based thermoelectric devices of high performance.

The TiAl channel mechanism for enhanced (de)hydrogenation kinetics in Mg-based films

NASA Astrophysics Data System (ADS)

Hao, Shiqiang

2010-09-01

The transport properties of hydrogen in metal additives are very important for understanding the enhanced kinetic processes of (de)hydrogenation in metal hydrides. Based on the first-principles calculations, we found that the H2 dissociation rates on TiAl surfaces are very facile and the dissociated H diffusion in TiAl lattice is much faster than that in host material MgH2. We propose that the "catalytic" effect of additives Ti and Al is the H transport channel within the Mg and MgH2 host materials for the enhanced reaction kinetics.

Metallic multilayers at the nanoscale

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

Jankowski, A.F.

1994-11-01

The development of multilayer structures has been driven by a wide range of commercial applications requiring enhanced material behaviors. Innovations in physical vapor deposition technologies, in particular magnetron sputtering, have enabled the synthesis of metallic-based structures with nanoscaled layer dimensions as small as one-to-two monolayers. Parameters used in the deposition process are paramount to the Formation of these small layer dimensions and the stability of the structure. Therefore, optimization of the desired material properties must be related to assessment of the actual microstructure. Characterization techniques as x-ray diffraction and high resolution microscopy are useful to reveal the interface and layermore » structure-whether ordered or disordered crystalline, amorphous, compositionally abrupt or graded, and/or lattice strained Techniques for the synthesis of metallic multilayers with subnanometric layers will be reviewed with applications based on enhancing material behaviors as reflectivity and magnetic anisotropy but with emphasis on experimental studies of mechanical properties.« less

Mesoporous Silica Molecular Sieve based Nanocarriers: Transpiring Drug Dissolution Research.

PubMed

Pattnaik, Satyanarayan; Pathak, Kamla

2017-01-01

Improvement of oral bioavailability through enhancement of dissolution for poorly soluble drugs has been a very promising approach. Recently, mesoporous silica based molecular sieves have demonstrated excellent properties to enhance the dissolution velocity of poorly water-soluble drugs. Current research in this area is focused on investigating the factors influencing the drug release from these carriers, the kinetics of drug release and manufacturing approaches to scale-up production for commercial manufacture. This comprehensive review provides an overview of different methods adopted for synthesis of mesoporous materials, influence of processing factors on properties of these materials and drug loading methods. The drug release kinetics from mesoporous silica systems, the manufacturability and stability of these formulations are reviewed. Finally, the safety and biocompatibility issues related to these silica based materials are discussed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Biosmart Materials: Breaking New Ground in Dentistry

PubMed Central

Badami, Vijetha; Ahuja, Bharat

2014-01-01

By definition and general agreement, smart materials are materials that have properties which may be altered in a controlled fashion by stimuli, such as stress, temperature, moisture, pH, and electric or magnetic fields. There are numerous types of smart materials, some of which are already common. Examples include piezoelectric materials, which produce a voltage when stress is applied or vice versa, shape memory alloys or shape memory polymers which are thermoresponsive, and pH sensitive polymers which swell or shrink as a response to change in pH. Thus, smart materials respond to stimuli by altering one or more of their properties. Smart behaviour occurs when a material can sense some stimulus from its environment and react to it in a useful, reliable, reproducible, and usually reversible manner. These properties have a beneficial application in various fields including dentistry. Shape memory alloys, zirconia, and smartseal are examples of materials exhibiting a smart behavior in dentistry. There is a strong trend in material science to develop and apply these intelligent materials. These materials would potentially allow new and groundbreaking dental therapies with a significantly enhanced clinical outcome of treatments. PMID:24672407

Properties and Performance Attributes of Novel Co-Extruded Polyolefin Battery Separator Materials. Part 1; Mechanical Properties

NASA Technical Reports Server (NTRS)

Baldwin, Richard S.; Guzik, Monica; Skierski, Michael

2011-01-01

As NASA prepares for its next era of manned spaceflight missions, advanced energy storage technologies are being developed and evaluated to address future mission needs and technical requirements and to provide new mission-enabling technologies. Cell-level components for advanced lithium-ion batteries possessing higher energy, more reliable performance and enhanced, inherent safety characteristics are actively under development within the NASA infrastructure. A key component for safe and reliable cell performance is the cell separator, which separates the two energetic electrodes and functions to prevent the occurrence of an internal short-circuit while enabling ionic transport. Recently, a new generation of co-extruded separator films has been developed by ExxonMobil Chemical and introduced into their battery separator product portfolio. Several grades of this new separator material have been evaluated with respect to dynamic mechanical properties and safety-related performance attributes. This paper presents the results of these evaluations in comparison to a current state-ofthe-practice separator material. The results are discussed with respect to potential opportunities to enhance the inherent safety characteristics and reliability of future, advanced lithium-ion cell chemistries.

Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance

PubMed Central

Qin, Guangzhao; Yan, Qing-Bo; Qin, Zhenzhen; Yue, Sheng-Ying; Cui, Hui-Juan; Zheng, Qing-Rong; Su, Gang

2014-01-01

We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit ZT of BP is found to be 0.72 at 800 K that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials. PMID:25374306

Long Distance Enhancement of Nonlinear Optical Properties Using Low Concentration of Plasmonic Nanostructures in Dye Doped Monolithic SolGel Materials (Postprint)

DTIC Science & Technology

2016-05-31

www.MaterialsViews.com Synthesis of the Gold Nanoparticles : The Au nanospheres were prepared according to previously reported procedure using the...Au Nanoparticles Using Specifi c Silicone : The synthesis of the functional silicone was previously reported as well as the surface modifi cation of...types of gold nanoparticles (AuNPs) are prepared and polished to high optical quality. Their photophysical properties are investigated. The glass

Application of High-Density Electropulsing to Improve the Performance of Metallic Materials: Mechanisms, Microstructure and Properties

PubMed Central

Sheng, Yinying; Hua, Youlu; Zhao, Xueyang; Chen, Lianxi; Zhou, Hanyu; Wang, James; Berndt, Christopher C.; Li, Wei

2018-01-01

The technology of high-density electropulsing has been applied to increase the performance of metallic materials since the 1990s and has shown significant advantages over traditional heat treatment in many aspects. However, the microstructure changes in electropulsing treatment (EPT) metals and alloys have not been fully explored, and the effects vary significantly on different material. When high-density electrical pulses are applied to metals and alloys, the input of electric energy and thermal energy generally leads to structural rearrangements, such as dynamic recrystallization, dislocation movements and grain refinement. The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation. As a result, this technology holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals. This review summarizes the effect of high-density electropulsing treatment on microstructural properties and, thus, the enhancement in mechanical strength, hardness and corrosion performance of metallic materials. It is noteworthy that the change of some properties can be related to the structure state before EPT (quenched, annealed, deformed or others). The mechanisms for the microstructural evolution, grain refinement and formation of oriented microstructures of different metals and alloys are presented. Future research trends of high-density electrical pulse technology for specific metals and alloys are highlighted. PMID:29364844

Flammability of self-extinguishing kenaf/ABS nanoclays composite for aircraft secondary structure

NASA Astrophysics Data System (ADS)

Karunakaran, S.; Majid, D. L.; Mohd Tawil, M. L.

2016-10-01

This study investigates the flammability properties of kenaf fiber reinforced acrylonitrile butadiene styrene (ABS) with nanoclays composites. Natural fiber is one of the potential materials to be used with thermoplastic as a composite due to its attractive properties such as lightweight and strong. In this paper, flammability properties of this material are evaluated through Underwriters Laboratory 94 Horizontal Burning (UL94 HB), which has been conducted for both controlled and uncontrolled conditions, smoke density and limiting oxygen index tests (LOI). These flammability tests are in compliance with the Federal Aviation Regulation (FAR) requirement. The results from UL94 HB and smoke density tests show that the presence of nanoclays with effective composition of kenaf fiber reinforced ABS has enhanced the burning characteristics of the material by hindering propagation of flame spread over the surface of the material through char formation. Consequently, this decreases the burning rate and produces low amount of smoke during burning. On contrary, through LOI test, this material requires less oxygen to burn when exposed to fire, which hinders the enhancement of burning characteristics. This is due to burning mechanism exhibited by nanoclays that catalyzes barrier formation and flame propagation rate over the surface of the biocomposite material. Overall, these experimental results suggest that this biocomposite material is capable of self-extinguishing and possesses effective fire extinction. The observed novel synergism from the result obtained is promising to be implemented in secondary structures of aircraft with significant benefits such as cost-effective, lightweight and biodegradable self-extinguishing biocomposite.

PCM-enhanced lime plasters for vernacular and contemporary architecture

NASA Astrophysics Data System (ADS)

Theodoridou, Magdalini; Kyriakou, Loucas; Ioannou, Ioannis

2016-04-01

In 1997, the European Union (EU) pledged to reduce the amount of greenhouse gas emissions by 20% below the levels of 1990 by the end of 2020. In recent years it has become evident that, in order to reach that goal, EU Member States must take measures to encourage sustainability in the building industry, which is a major energy consumer. Such measures should involve the use of innovative, environmentally friendly materials and methods in new constructions, as well as the renovation of existing properties by upgrading their current state of energy efficiency. Phase Change Materials (PCMs) have the ability to absorb and release thermal energy, in the form of latent heat, during the melting or solidifying processes respectively. Thus, they may be used as additives in the production of thermally efficient composite building materials. A PCM-enhanced plaster is a heat storage medium combining an appropriate PCM with a cementitious or non-cementitious matrix to produce a low-cost thermal storage material with structural and thermostatic properties. Although innovative technologies, such as PCMs, have certainly contributed to the boost in the evolution of the building materials industry in recent years, a significant proportion of these technologies and practices have not yet been fully exploited in materials based on traditional principles. This paper focuses on the design and production of novel cementless PCM-enhanced lime plasters, in line with the traditional production technology of lime composites. The new plasters are produced using either hydrated or natural hydraulic lime binder, crushed calcarenite sand (0-2 mm) and commercial microencapsulated PCM in powder form (5% w/w of solids). Results from comparative tests between reference mixtures and mixtures with the addition of PCM, carried out 28, 56 and 90 days after laboratory production, prove the potential of PCMs in enhancing the thermal performance of traditional lime-based composites. The modified composites have significantly lower (by 55%) thermal conductivity and increased (by almost 20%) specific heat capacity at 90 days after laboratory production. At the same time, even though porosity values are higher for the PCM-enhanced renders, compared to the reference mixtures, their capillary absorption coefficient is significantly reduced (up to 60%). This is of great importance in the case of renders and may well be an indication for better expected durability in the long-term. Regarding the mechanical properties of the laboratory composites, PCM addition seems to have a negative effect on the hydraulic plasters. In contrast, when PCM is added to the hydrated lime-based plaster, no change is observed for the flexural strength, while the compressive strength is notably improved (up to 36%). The apparently improved properties of the PCM-enhanced plasters render them particularly appropriate for application in southern European climatic conditions. Due to their compatibility with traditional substrate materials (e.g. natural stone), the aforementioned composites may be used not only in new contemporary structures, but also for the renovation and retrofitting of existing buildings. The lime-based nature of their matrix and their physico-mechanical properties further extend their applicability to listed and monumental buildings.

Graphics and composite material computer program enhancements for SPAR

NASA Technical Reports Server (NTRS)

Farley, G. L.; Baker, D. J.

1980-01-01

User documentation is provided for additional computer programs developed for use in conjunction with SPAR. These programs plot digital data, simplify input for composite material section properties, and compute lamina stresses and strains. Sample problems are presented including execution procedures, program input, and graphical output.

Emergent Properties and Toxicological Considerations for Nanohybrid Materials in Aquatic Systems

PubMed Central

Saleh, Navid B.; Afrooz, A. R. M. Nabiul; Bisesi, Joseph H.; Aich, Nirupam; Plazas-Tuttle, Jaime; Sabo-Attwood, Tara

2014-01-01

Conjugation of multiple nanomaterials has become the focus of recent materials development. This new material class is commonly known as nanohybrids or “horizon nanomaterials”. Conjugation of metal/metal oxides with carbonaceous nanomaterials and overcoating or doping of one metal with another have been pursued to enhance material performance and/or incorporate multifunctionality into nano-enabled devices and processes. Nanohybrids are already at use in commercialized energy, electronics and medical products, which warrant immediate attention for their safety evaluation. These conjugated ensembles likely present a new set of physicochemical properties that are unique to their individual component attributes, hence increasing uncertainty in their risk evaluation. Established toxicological testing strategies and enumerated underlying mechanisms will thus need to be re-evaluated for the assessment of these horizon materials. This review will present a critical discussion on the altered physicochemical properties of nanohybrids and analyze the validity of existing nanotoxicology data against these unique properties. The article will also propose strategies to evaluate the conjugate materials’ safety to help undertake future toxicological research on the nanohybrid material class. PMID:28344229

Graphene-based materials: fabrication and application for adsorption in analytical chemistry.

PubMed

Wang, Xin; Liu, Bo; Lu, Qipeng; Qu, Qishu

2014-10-03

Graphene, a single layer of carbon atoms densely packed into a honeycomb crystal lattice with unique electronic, chemical, and mechanical properties, is the 2D allotrope of carbon. Owing to the remarkable properties, graphene and graphene-based materials are likely to find potential applications as a sorbent in analytical chemistry. The current review focuses predominantly on the recent development of graphene-based materials and demonstrates their enhanced performance in adsorption of organic compounds, metal ions, and solid phase extraction as well as in separation science since mostly 2012. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced mechanical and thermal properties of regenerated cellulose/graphene composite fibers.

PubMed

Tian, Mingwei; Qu, Lijun; Zhang, Xiansheng; Zhang, Kun; Zhu, Shifeng; Guo, Xiaoqing; Han, Guangting; Tang, Xiaoning; Sun, Yaning

2014-10-13

In this study, a wet spinning method was applied to fabricate regenerated cellulose fibers filled with low graphene loading which was systematically characterized by SEM, TEM, FTIR and XRD techniques. Subsequently, the mechanical and thermal properties of the resulting fibers were investigated. With only 0.2 wt% loading of graphene, a ∼ 50% improvement of tensile strength and 25% enhancement of Young's modulus were obtained and the modified Halpin-Tsai model was built to predict the mechanical properties of composite fibers. Thermal analysis of the composite fibers showed remarkably enhanced thermal stability and dynamic heat transfer performance of graphene-filled cellulose composite fiber, also, the presence of graphene oxide can significantly enhance the thermal conductivity of the composite fiber. This work provided a facile way to improve mechanical and thermal properties of regenerated cellulose fibers. The resultant composite fibers have potential application in thermal insulation and reinforced fibrous materials. Copyright © 2014 Elsevier Ltd. All rights reserved.

Putting Nano-Tex to the Test

ERIC Educational Resources Information Center

Kao,Yvonne S; Zenner, Greta M.; Gimm, J. Aura

2005-01-01

Nanotechnology deals with machines, materials, and structures and their behaviors at the scale of atoms and molecules, or the nanoscale. By working on this scale, scientists are able to create enhanced materials with desirable properties, such as stain-resistance. The authors developed the activity described in this article to introduce middle…

High-pressure torsion for new hydrogen storage materials

PubMed Central

Edalati, Kaveh; Akiba, Etsuo; Horita, Zenji

2018-01-01

Abstract High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Since 2007, the method has been employed to enhance the hydrogenation kinetics in different Mg-based hydrogen storage materials. Recent studies showed that the method is effective not only for increasing the hydrogenation kinetics but also for improving the hydrogenation activity, for enhancing the air resistivity and more importantly for synthesizing new nanostructured hydrogen storage materials with high densities of lattice defects. This manuscript reviews some major findings on the impact of HPT process on the hydrogen storage performance of different titanium-based and magnesium-based materials. PMID:29511396

Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials.

PubMed

Peinado, Víctor; Castell, Pere; García, Lidia; Fernández, Ángel

2015-10-19

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript.

The Application of Fiber-Reinforced Materials in Disc Repair

PubMed Central

Pei, Bao-Qing; Li, Hui; Zhu, Gang; Li, De-Yu; Fan, Yu-Bo; Wu, Shu-Qin

2013-01-01

The intervertebral disc degeneration and injury are the most common spinal diseases with tremendous financial and social implications. Regenerative therapies for disc repair are promising treatments. Fiber-reinforced materials (FRMs) are a kind of composites by embedding the fibers into the matrix materials. FRMs can maintain the original properties of the matrix and enhance the mechanical properties. By now, there are still some problems for disc repair such as the unsatisfied static strength and dynamic properties for disc implants. The application of FRMs may resolve these problems to some extent. In this review, six parts such as background of FRMs in tissue repair, the comparison of mechanical properties between natural disc and some typical FRMs, the repair standard and FRMs applications in disc repair, and the possible research directions for FRMs' in the future are stated. PMID:24383057

High efficiency and non-Richardson thermionics in three dimensional Dirac materials

NASA Astrophysics Data System (ADS)

Huang, Sunchao; Sanderson, Matthew; Zhang, Yan; Zhang, Chao

2017-10-01

Three dimensional (3D) topological materials have a linear energy dispersion and exhibit many electronic properties superior to conventional materials such as fast response times, high mobility, and chiral transport. In this work, we demonstrate that 3D Dirac materials also have advantages over conventional semiconductors and graphene in thermionic applications. The low emission current suffered in graphene due to the vanishing density of states is enhanced by an increased group velocity in 3D Dirac materials. Furthermore, the thermal energy carried by electrons in 3D Dirac materials is twice of that in conventional materials with a parabolic electron energy dispersion. As a result, 3D Dirac materials have the best thermal efficiency or coefficient of performance when compared to conventional semiconductors and graphene. The generalized Richardson-Dushman law in 3D Dirac materials is derived. The law exhibits the interplay of the reduced density of states and enhanced emission velocity.

Surface-enhanced Raman scattering (SERS) dosimeter and probe

DOEpatents

Vo-Dinh, Tuan

1995-01-01

A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devises, in probe array devices.

Cement and Concrete Nanoscience and Nanotechnology

PubMed Central

Raki, Laila; Beaudoin, James; Alizadeh, Rouhollah; Makar, Jon; Sato, Taijiro

2010-01-01

Concrete science is a multidisciplinary area of research where nanotechnology potentially offers the opportunity to enhance the understanding of concrete behavior, to engineer its properties and to lower production and ecological cost of construction materials. Recent work at the National Research Council Canada in the area of concrete materials research has shown the potential of improving concrete properties by modifying the structure of cement hydrates, addition of nanoparticles and nanotubes and controlling the delivery of admixtures. This article will focus on a review of these innovative achievements.

Fabrication and durable antibacterial properties of 3D porous wet electrospun RCSC/PCL nanofibrous scaffold with silver nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Mei; Lin, Han; Wang, Yilong; Yang, Guang; Zhao, He; Sun, Dahui

2017-08-01

Electrospunnanofibers are used as three-dimensional (3D) scaffold materials that can alter cell attachment and cell proliferation, change the antibacterial properties of materials, and can be used as wound dressings. But the fabrication of porous 3D scaffold structure and the antibacterial properties enhancing are challenges remained to improve. With the states here, a Ranachensinensis skin collagen (RCSC)/poly(ɛ-caprolactone) (PCL)AgNP-loaded3D nanofiber scaffold is fabricated as a wound dressing material by using an improved wet electrospinning method (blending). The nanoscale of the AgNPs is proved. The 3D porous morphologies of the materials with different AgNP loadings, are determined with field emission scanning electron microscopy (FESEM) and the presence and uniformity distribution of AgNPs is confirmed by Energy dispersive X-ray (EDX) spectroscopy. The silver-ion release rates, antibacterial properties, and cytotoxicities of dressing materials with different AgNP contents are evaluated using ICP-AES, the zone inhibition method, and MTT testing. These results showed that the improved wet electrospun is an effective way to fabricate AgNP loaded 3D scaffold materials with porous structure and nearly 90% porosity and the presence of AgNPs in dressing materials strengthen the antibacterial properties. The RCSC/PCL 3D scaffold materials containing 2.0%AgNP would be promising for dressing materials application nearly without cytotoxicities.

Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment

PubMed Central

Jin Bae, Eun; Hun Kang, Young; Jang, Kwang-Suk; Yun Cho, Song

2016-01-01

The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tellurium-PEDOT:PSS (Te-PEDOT:PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PEDOT:PSS and Te-PEDOT:PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm−1, respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m−1 K−2, respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te-PEDOT:PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat. PMID:26728992

A gigantically increased ratio of electrical to thermal conductivity and synergistically enhanced thermoelectric properties in interface-controlled TiO2-RGO nanocomposites.

PubMed

Nam, Woo Hyun; Lim, Young Soo; Kim, Woochul; Seo, Hyeon Kook; Dae, Kyun Seong; Lee, Soonil; Seo, Won-Seon; Lee, Jeong Yong

2017-06-14

We report synergistically enhanced thermoelectric properties through the independently controlled charge and thermal transport properties in a TiO 2 -reduced graphene oxide (RGO) nanocomposite. By the consolidation of TiO 2 -RGO hybrid powder using spark plasma sintering, we prepared an interface-controlled TiO 2 -RGO nanocomposite where its grain boundaries are covered with the RGO network. Both the enhancement in electrical conductivity and the reduction in thermal conductivity were simultaneously achieved thanks to the beneficial effects of the RGO network, and detailed mechanisms are discussed. This led to the gigantic increase in the ratio of electrical to thermal conductivity by six orders of magnitude and also the synergistic enhancement in the thermoelectric figure of merit by two orders. Our results present a strategy for the realization of 'phonon-glass electron-crystals' through interface control using graphene in graphene hybrid thermoelectric materials.

Enhanced exchange bias and improved ferromagnetic properties in Permalloy-BiFe0.95Co0.05O3 core-shell nanostructures.

PubMed

Javed, K; Li, W J; Ali, S S; Shi, D W; Khan, U; Riaz, S; Han, X F

2015-12-14

Hybrid core-shell nanostructures consisting of permalloy (Ni80Fe20) and multiferroic(BiFeO3, BFO/BiFe0.95Co0.05O3, BFC) materials were synthesized by a two-step method, based on wet chemical impregnation and subsequent electrodeposition within porous alumina membranes. Structural and magnetic characterizations have been done to investigate doping effect on magnetic properties and exchange bias. The magnetometry analysis revealed significant enhancements of the exchange bias and coercivity in NiFe-BFC core-shell nanostructures as compared with NiFe-BFO core-shell nanostructures. The enhancements can be attributed to the effective reduction of ferromagnet domain sizes between adjacent layers of core-shell structure. It indicates that it is possible to improve properties of multiferroic composites by site-engineering method. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties.

Enhanced exchange bias and improved ferromagnetic properties in Permalloy–BiFe0.95Co0.05O3 core–shell nanostructures

PubMed Central

Javed, K.; Li, W. J.; Ali, S. S.; Shi, D. W.; Khan, U.; Riaz, S.; Han, X. F.

2015-01-01

Hybrid core–shell nanostructures consisting of permalloy (Ni80Fe20) and multiferroic(BiFeO3, BFO/BiFe0.95Co0.05O3, BFC) materials were synthesized by a two-step method, based on wet chemical impregnation and subsequent electrodeposition within porous alumina membranes. Structural and magnetic characterizations have been done to investigate doping effect on magnetic properties and exchange bias. The magnetometry analysis revealed significant enhancements of the exchange bias and coercivity in NiFe-BFC core-shell nanostructures as compared with NiFe-BFO core-shell nanostructures. The enhancements can be attributed to the effective reduction of ferromagnet domain sizes between adjacent layers of core-shell structure. It indicates that it is possible to improve properties of multiferroic composites by site-engineering method. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties. PMID:26658956

Synergistic Impacts of Electrolyte Adsorption on the Thermoelectric Properties of Single-Walled Carbon Nanotubes.

PubMed

Nakano, Motohiro; Nakashima, Takuya; Kawai, Tsuyoshi; Nonoguchi, Yoshiyuki

2017-08-01

Single-walled carbon nanotubes are promising candidates for light-weight and flexible energy materials. Recently, the thermoelectric properties of single-walled carbon nanotubes have been dramatically improved by ionic liquid addition; however, controlling factors remain unsolved. Here the thermoelectric properties of single-walled carbon nanotubes enhanced by electrolytes are investigated. Complementary characterization with absorption, Raman, and X-ray photoelectron spectroscopy reveals that shallow hole doping plays a partial role in the enhanced electrical conductivity. The molecular factors controlling the thermoelectric properties of carbon nanotubes are systematically investigated in terms of the ionic functionalities of ionic liquids. It is revealed that appropriate ionic liquids show a synergistic enhancement in conductivity and the Seebeck coefficient. The discovery of significantly precise doping enables the generation of thermoelectric power factor exceeding 460 µW m - 1 K -2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High efficiency and enhanced ESD properties of UV LEDs by inserting p-GaN/p-AlGaN superlattice

NASA Astrophysics Data System (ADS)

Huang, Yong; Li, PeiXian; Yang, Zhuo; Hao, Yue; Wang, XiaoBo

2014-05-01

Significantly improved electrostatic discharge (ESD) properties of InGaN/GaN-based UV light-emitting diode (LED) with inserting p-GaN/p-AlGaN superlattice (p-SLs) layers (instead of p-AlGaN single layer) between multiple quantum wells and Mg-doped GaN layer are reported. The pass yield of the LEDs increased from 73.53% to 93.81% under negative 2000 V ESD pulses. In addition, the light output power (LOP) and efficiency droop at high injection current were also improved. The mechanism of the enhanced ESD properties was then investigated. After excluding the effect of capacitance modulation, high-resolution X-ray diffraction (XRD) and atomic force microscope (AFM) measurements demonstrated that the dominant mechanism of the enhanced ESD properties is the material quality improved by p-SLs, which indicated less leakage paths, rather than the current spreading improved by p-SLs.

Thermal properties variations in unconsolidated material for very shallow geothermal application (ITER project)

NASA Astrophysics Data System (ADS)

Sipio, Eloisa Di; Bertermann, David

2018-04-01

In engineering, agricultural and meteorological project design, sediment thermal properties are highly important parameters, and thermal conductivity plays a fundamental role when dimensioning ground heat exchangers, especially in very shallow geothermal systems. Herein, the first 2 m of depth from surface is of critical importance. However, the heat transfer determination in unconsolidated material is difficult to estimate, as it depends on several factors, including particle size, bulk density, water content, mineralogy composition and ground temperature. The performance of a very shallow geothermal system, as a horizontal collector or heat basket, is strongly correlated to the type of sediment at disposal and rapidly decreases in the case of dry-unsaturated conditions. The available experimental data are often scattered, incomplete and do not fully support thermo-active ground structure modeling. The ITER project, funded by the European Union, contributes to a better knowledge of the relationship between thermal conductivity and water content, required for understanding the very shallow geothermal systems behaviour in saturated and unsaturated conditions. So as to enhance the performance of horizontal geothermal heat exchangers, thermally enhanced backfilling material were tested in the laboratory, and an overview of physical-thermal properties variations under several moisture and load conditions for different mixtures of natural material was here presented.

Potential of Electrospun Nanofibers for Biomedical and Dental Applications

PubMed Central

Zafar, Muhammad; Najeeb, Shariq; Khurshid, Zohaib; Vazirzadeh, Masoud; Zohaib, Sana; Najeeb, Bilal; Sefat, Farshid

2016-01-01

Electrospinning is a versatile technique that has gained popularity for various biomedical applications in recent years. Electrospinning is being used for fabricating nanofibers for various biomedical and dental applications such as tooth regeneration, wound healing and prevention of dental caries. Electrospun materials have the benefits of unique properties for instance, high surface area to volume ratio, enhanced cellular interactions, protein absorption to facilitate binding sites for cell receptors. Extensive research has been conducted to explore the potential of electrospun nanofibers for repair and regeneration of various dental and oral tissues including dental pulp, dentin, periodontal tissues, oral mucosa and skeletal tissues. However, there are a few limitations of electrospinning hindering the progress of these materials to practical or clinical applications. In terms of biomaterials aspects, the better understanding of controlled fabrication, properties and functioning of electrospun materials is required to overcome the limitations. More in vivo studies are definitely required to evaluate the biocompatibility of electrospun scaffolds. Furthermore, mechanical properties of such scaffolds should be enhanced so that they resist mechanical stresses during tissue regeneration applications. The objective of this article is to review the current progress of electrospun nanofibers for biomedical and dental applications. In addition, various aspects of electrospun materials in relation to potential dental applications have been discussed. PMID:28787871

Mechanical properties of nanostructure of biological materials

NASA Astrophysics Data System (ADS)

Ji, Baohua; Gao, Huajian

2004-09-01

Natural biological materials such as bone, teeth and nacre are nanocomposites of protein and mineral with superior strength. It is quite a marvel that nature produces hard and tough materials out of protein as soft as human skin and mineral as brittle as classroom chalk. What are the secrets of nature? Can we learn from this to produce bio-inspired materials in the laboratory? These questions have motivated us to investigate the mechanics of protein-mineral nanocomposite structure. Large aspect ratios and a staggered alignment of mineral platelets are found to be the key factors contributing to the large stiffness of biomaterials. A tension-shear chain (TSC) model of biological nanostructure reveals that the strength of biomaterials hinges upon optimizing the tensile strength of the mineral crystals. As the size of the mineral crystals is reduced to nanoscale, they become insensitive to flaws with strength approaching the theoretical strength of atomic bonds. The optimized tensile strength of mineral crystals thus allows a large amount of fracture energy to be dissipated in protein via shear deformation and consequently enhances the fracture toughness of biocomposites. We derive viscoelastic properties of the protein-mineral nanostructure and show that the toughness of biocomposite can be further enhanced by the viscoelastic properties of protein.

Impact response of composite materials

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Srinivasan, K.

1991-01-01

Composite materials composed of carbon fibers and resin matrices offer great promise in reducing the weight of aerospace structures. However they remain extremely vulnerable to out of plane impact loads, which lead to severe losses in strength and stiffness. The results of an experimental program, undertaken to investigate the low velocity impact damage tolerance of composite materials is presented. The objectives were to identify key neat resin/composite properties that lead to enhancement of composite impact damage tolerance and to find a small scale test that predicts compression after impact properties of panels. Five materials were selected for evaluation. These systems represented different classes of material behavior such as brittle epoxy, modified epoxies, and amorphous and semicrystalling thermoplastics. The influence of fiber properties on the impact performance was also studied in one material, i.e., in polyether ether ketone (PEEK). Several 24 and 48 ply quasi-isotropic and 24 ply orthotropic laminates were examined using an instrumented drop weight impactor. Correlations with post impact compression behavior were made.

Ion beam irradiation effect on thermoelectric properties of Bi2Te3 and Sb2Te3 thin films

NASA Astrophysics Data System (ADS)

Fu, Gaosheng; Zuo, Lei; Lian, Jie; Wang, Yongqiang; Chen, Jie; Longtin, Jon; Xiao, Zhigang

2015-09-01

Thermoelectric energy harvesting is a very promising application in nuclear power plants for self-maintained wireless sensors. However, the effects of intensive radiation on the performance of thermoelectric materials under relevant reactor environments such as energetic neutrons are not fully understood. In this work, radiation effects of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thermoelectric thin film samples prepared by E-beam evaporation are investigated using Ne2+ ion irradiations at different fluences of 5 × 1014, 1015, 5 × 1015 and 1016 ions/cm2 with the focus on the transport and structural properties. Electrical conductivities, Seebeck coefficients and power factors are characterized as ion fluence changes. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of the samples are obtained to assess how phase and microstructure influence the transport properties. Carrier concentration and Hall mobility are obtained from Hall effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Positive effects of ion irradiations from Ne2+ on thermoelectric material property are observed to increase the power factor to 208% for Bi2Te3 and 337% for Sb2Te3 materials between fluence of 1 and 5 × 1015 cm2, due to the increasing of the electrical conductivity as a result of ionization radiation-enhanced crystallinity. However, under a higher fluence, 5 × 1015 cm2 in this case, the power factor starts to decrease accordingly, limiting the enhancements of thermoelectric materials properties under intensive radiation environment.

Microstructure characterization of multi-phase composites and utilization of phase change materials and recycled rubbers in cementitious materials

NASA Astrophysics Data System (ADS)

Meshgin, Pania

2011-12-01

This research focuses on two important subjects: (1) Characterization of heterogeneous microstructure of multi-phase composites and the effect of microstructural features on effective properties of the material. (2) Utilizations of phase change materials and recycled rubber particles from waste tires to improve thermal properties of insulation materials used in building envelopes. Spatial pattern of multi-phase and multidimensional internal structures of most composite materials are highly random. Quantitative description of the spatial distribution should be developed based on proper statistical models, which characterize the morphological features. For a composite material with multi-phases, the volume fraction of the phases as well as the morphological parameters of the phases have very strong influences on the effective property of the composite. These morphological parameters depend on the microstructure of each phase. This study intends to include the effect of higher order morphological details of the microstructure in the composite models. The higher order statistics, called two-point correlation functions characterize various behaviors of the composite at any two points in a stochastic field. Specifically, correlation functions of mosaic patterns are used in the study for characterizing transport properties of composite materials. One of the most effective methods to improve energy efficiency of buildings is to enhance thermal properties of insulation materials. The idea of using phase change materials and recycled rubber particles such as scrap tires in insulation materials for building envelopes has been studied.

Enhanced graphitization of carbon around carbon nanotubes during the formation of carbon nanotube/graphite composites by pyrolysis of carbon nanotube/polyaniline composites.

PubMed

Nam, Dong Hoon; Cha, Seung Il; Jeong, Yong Jin; Hong, Soon Hyung

2013-11-01

The carbon nanotubes (CNTs) are actively applied to the reinforcements for composite materials during last decade. One of the attempts is development of CNT/Carbon composites. Although there are some reports on the enhancement of mechanical properties by addition of CNTs in carbon or carbon fiber, it is far below the expectation. Considering the microstructure of carbon materials such as carbon fiber, the properties of them can be modified and enhanced by control of graphitization and alignment of graphene planes. In this study, enhanced graphitization of carbon has been observed the vicinity of CNTs during the pyrolysis of CNT/Polyaniline composites. As a result, novel types of composite, consisting of treading CNTs and coated graphite, can be fabricated. High-resolution transmission electron microscopy revealed a specific orientation relationship between the graphene layers and the CNTs, with an angle of 110 degrees between the layers and the CNT axis. The possibility of graphene alignment control in the carbon by the addition of CNTs is demonstrated.

Surface Texture-Induced Enhancement of Optical and Photoelectrochemical Activity of Cu2ZnSnS4 Photocathodes

NASA Astrophysics Data System (ADS)

Sarswat, Prashant K.; Deka, Nipon; Jagan Mohan Rao, S.; Free, Michael L.; Kumar, Gagan

2017-08-01

The objective of this work is to understand and improve the photocatalytic activity of Cu2ZnSnS4 (CZTS) through postgrowth modification techniques to create surface textures. This objective can be achieved using a combination of solvents, etching agents, and anodization techniques. One of the most effective surface treatments for enhancing the surface properties of photovoltaic materials is formation of nanoscale flakes, although other surface modifications were also evaluated. The superior performance of textured films can be attributed to enhanced surface area of absorber material exposed to electrolyte, ZnS deficiency, and high catalytic activity due to reduced charge-transfer resistance. Fine-tuning of ion flux and electrolyte stoichiometry can be used to create a controlled growth algorithm for CZTS thin films. The resulting information can be utilized to optimize film properties. The utility of nanostructured or engineered surfaces was evaluated using photoelectrochemical measurements. Finite-difference time-domain (FDTD)-assisted simulations were conducted for selected texturing, revealing enhanced surface area of absorbing medium that ultimately resulted in greater power loss of light in the medium.

Bioinspired Design: Magnetic Freeze Casting

NASA Astrophysics Data System (ADS)

Porter, Michael Martin

Nature is the ultimate experimental scientist, having billions of years of evolution to design, test, and adapt a variety of multifunctional systems for a plethora of diverse applications. Next-generation materials that draw inspiration from the structure-property-function relationships of natural biological materials have led to many high-performance structural materials with hybrid, hierarchical architectures that fit form to function. In this dissertation, a novel materials processing method, magnetic freeze casting, is introduced to develop porous scaffolds and hybrid composites with micro-architectures that emulate bone, abalone nacre, and other hard biological materials. This method uses ice as a template to form ceramic-based materials with continuously, interconnected microstructures and magnetic fields to control the alignment of these structures in multiple directions. The resulting materials have anisotropic properties with enhanced mechanical performance that have potential applications as bone implants or lightweight structural composites, among others.

Tailoring Thermal Radiative Properties with Doped-Silicon Nanowires

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

Zhang, Zhuomin

Aligned doped-silicon nanowire (D-SiNW) arrays form a hyperbolic metamaterial in the mid-infrared and have unique thermal radiative properties, such as broadband omnidirectional absorption, low-loss negative refraction, etc. A combined theoretical and experimental investigation will be performed to characterize D-SiNW arrays and other metamaterials for tailoring thermal radiative properties. Near-field thermal radiation between anisotropic materials with hyperbolic dispersions will also be predicted for potential application in energy harvesting. A new kind of anisotropic metamaterial with a hyperbolic dispersion in a broad infrared region has been proposed and demonstrated based on aligned doped-silicon nanowire (D-SiNW) arrays. D-SiNW-based metamaterials have unique thermal radiativemore » properties, such as broadband omnidirectional absorption whose width and location can be tuned by varying the filling ratio and/or doping level. Furthermore, high figure of merit (FOM) can be achieved in a wide spectral region, suggesting that D-SiNW arrays may be used as a negative refraction material with much less loss than other structured materials, such as layered semiconductor materials. We have also shown that D-SiNWs and other nanostructures can significantly enhance near-field thermal radiation. The study of near-field radiative heat transfer between closely spaced objects and the electromagnetic wave interactions with micro/nanostructured materials has become an emerging multidisciplinary field due to its importance in advanced energy systems, manufacturing, local thermal management, and high spatial resolution thermal sensing and mapping. We have performed extensive study on the energy streamlines involving anisotropic metamaterials and the applicability of the effective medium theory for near-field thermal radiation. Graphene as a 2D material has attracted great attention in nanoelectronics, plasmonics, and energy harvesting. We have shown that graphene can be used to tailor the transmittance, reflectance, and absorptance of nanostructured materials. Furthermore, graphene can be used to enhance near-field coupling to increase the phonon tunneling probability. We have performed analysis of near-field thermophotovoltaic devices with backside reflecting mirror and with tungsten gratings. We have predicted a large enhancement of electroluminescent refrigeration at a separation distance down to 10 nm due to near-field thermal radiation effect. A heat flux measurement system is developed to measure the near-field radiation in vacuum. We have fabricated doped Si plates separated by sparsely distributed posts to create a 200-800 nm vacuum gap. Our measurement results demonstrate that 11 times enhancement of near-field thermal radiation between parallel doped-Si plates with a lateral dimension 1 cm by 1 cm.« less

Nanostructured BN-Mg composites: features of interface bonding and mechanical properties.

PubMed

Kvashnin, Dmitry G; Krasheninnikov, Arkady V; Shtansky, Dmitry; Sorokin, Pavel B; Golberg, Dmitri

2016-01-14

Magnesium (Mg) is one of the lightest industrially used metals. However, wide applications of Mg-based components require a substantial enhancement of their mechanical characteristics. This can be achieved by introducing small particles or fibers into the metal matrix. Using first-principles calculations, we investigate the stability and mechanical properties of a nanocomposite made of magnesium reinforced with boron nitride (BN) nanostructures (BN nanotubes and BN monolayers). We show that boron vacancies at the BN/Mg interface lead to a substantial increase in BN/Mg bonding establishing an efficient route towards the development of BN/Mg composite materials with enhanced mechanical properties.

Synthetic octacalcium phosphate: a possible carrier for mesenchymal stem cells in bone regeneration.

PubMed

Suzuki, Osamu; Anada, Takahisa

2013-01-01

The present paper reviews biomaterial studies of synthetic octacalcium phosphate (OCP) as a scaffold of osteoblastic cells. OCP crystals have been suggested to be one of precursor phases in hydroxyapatite (HA) crystal formation in bone and tooth. The recent intensive biomaterials and tissue engineering studies using synthetic OCP disclosed the potential function of OCP as a bioactive material as well as synthetic HA materials due to its highly osteoconductive and biodegradable properties. In vitro studies showed that OCP crystals exhibit a positive effect on osteoblastic cell differentiation. In vivo studies confirmed that the materials of OCP in a granule forms and OCP-based composite materials with natural polymers, such as gelatin and collagen, enhance bone regeneration if implanted in various model bone defects with critical-sized diameters, defined as a defect which does not heal spontaneously throughout the lifetime of the animals. One of particular characteristics of OCP, found as a mechanism to enhance bone regeneration in vivo, is a process of progressive conversion from OCP to HA at physiological conditions. The OCP-HA conversion is accompanied by progressive physicochemical changes of the material properties, which affects the tissue reaction around the crystals where osteoblastic cells are encountered. Mesenchymal stem cells (MSCs) seeded in an OCP-based material enhanced bone regeneration in the rat critical-sized calvaria defect more than that by the material alone. The overall results reveal that OCP crystals have an effect on osteoblastic cell differentiation including the differentiation of MSCs in vivo. The evidence collected experimentally in the laboratory was presented.

UHTC Research at NASA Ames

NASA Technical Reports Server (NTRS)

Johnson, Sylvia M.

2011-01-01

For enhanced aerodynamic performance. Materials for sharp leading edges can be reusable but need different properties because of geometry and very high temperatures. Require materials with significantly higher temperature capabilities, but for short duration. Current shuttle RCC leading edge materials: T approx. 1650 C. Materials for vehicles with sharp leading edges: T>2000 C. >% Figure depicts: High Temperature at Tip and Steep Temperature Gradient. Passive cooling is simplest option to manage the intense heating on sharp leading edges.

Tip-Enhanced Raman Scattering Microscopy: A Step toward Nanoscale Control of Intrinsic Molecular Properties

NASA Astrophysics Data System (ADS)

Yano, Taka-aki; Hara, Masahiko

2018-06-01

Tip-enhanced Raman scattering microscopy, a family of scanning probe microscopy techniques, has been recognized as a powerful surface analytical technique with both single-molecule sensitivity and angstrom-scale spatial resolution. This review covers the current status of tip-enhanced Raman scattering microscopy in surface and material nanosciences, including a brief history, the basic principles, and applications for the nanoscale characterization of a variety of nanomaterials. The focus is on the recent trend of combining tip-enhanced Raman scattering microscopy with various external stimuli such as pressure, voltage, light, and temperature, which enables the local control of the molecular properties and functions and also enables chemical reactions to be induced on a nanometer scale.

Recycling of asbestos tailings used as reinforcing fillers in polypropylene based composites.

PubMed

Zhai, Wensi; Wang, Yao; Deng, Yuan; Gao, Hongli; Lin, Zhen; Li, Mao

2014-04-15

In this work, asbestos tailings were recycled and used as reinforcing fillers to enhance the mechanical properties of polypropylene (PP). A silane coupling agent was used to chemically modify the asbestos tailings to increase the compatibility between asbestos tailings and polypropylene matrix. Both raw and chemically treated asbestos tailings with different loading levels (from 3 to 30 wt%) were utilized to fabricate composites. Mechanical properties of these composites have been investigated by dynamic mechanical analysis, tensile test and notched impact test. Results showed that hybridization of asbestos tailings in the composites enhanced the mechanical properties of neat PP evidently, and treated asbestos tailings/PP composites yielded even better mechanical properties compared with those of raw asbestos tailings/PP composites. This recycling method of asbestos tailings not only reduces disposal costs and avoids secondary pollution but also produces a new PP-based composite material with enhanced mechanical properties. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced mechanical properties of epoxy nanocomposites by mixing noncovalently functionalized boron nitride nanoflakes.

PubMed

Lee, Dongju; Song, Sung Ho; Hwang, Jaewon; Jin, Sung Hwan; Park, Kwang Hyun; Kim, Bo Hyun; Hong, Soon Hyung; Jeon, Seokwoo

2013-08-12

The influence of surface modifications on the mechanical properties of epoxy-hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. Homogeneous distributions of boron nitride nanoflakes in a polymer matrix, preserving intrinsic material properties of boron nitride nanoflakes, is the key to successful composite applications. Here, a method is suggested to obtain noncovalently functionalized BNNFs with 1-pyrenebutyric acid (PBA) molecules and to synthesize epoxy-BNNF nanocomposites with enhanced mechanical properties. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields an elastic modulus of 3.34 GPa, and 71.9 MPa ultimate tensile strength at 0.3 wt%. The toughening enhancement is as high as 107% compared to the value of neat epoxy. The creep strain and the creep compliance of the noncovalently functionalized BNNF nanocomposite is significantly less than the neat epoxy and the nonfunctionalized BNNF nanocomposite. Noncovalent functionalization of BNNFs is effective to increase mechanical properties by strong affinity between the fillers and the matrix. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High performance p-type thermoelectric materials and methods of preparation

NASA Technical Reports Server (NTRS)

Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

2005-01-01

The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn4-xAxSb3-yBy wherein 0?x?4, A is a transition metal, B is a pnicogen, and 0?y?3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn4Sb3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

Photon energy conversion by near-zero permittivity nonlinear materials

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

Luk, Ting S.; Sinclair, Michael B.; Campione, Salvatore

Efficient harmonic light generation can be achieved with ultrathin films by coupling an incident pump wave to an epsilon-near-zero (ENZ) mode of the thin film. As an example, efficient third harmonic generation from an indium tin oxide nanofilm (.lamda./42 thick) on a glass substrate for a pump wavelength of 1.4 .mu.m was demonstrated. A conversion efficiency of 3.3.times.10.sup.-6 was achieved by exploiting the field enhancement properties of the ENZ mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Enhancement in biological response of Ag-nano composite polymer membranes using plasma treatment for fabrication of efficient bio materials

NASA Astrophysics Data System (ADS)

Agrawal, Narendra Kumar; Sharma, Tamanna Kumari; Chauhan, Manish; Agarwal, Ravi; Vijay, Y. K.; Swami, K. C.

2016-05-01

Biomaterials are nonviable material used in medical devices, intended to interact with biological systems, which are becoming necessary for the development of artificial material for biological systems such as artificial skin diaphragm, valves for heart and kidney, lenses for eye etc. Polymers having novel properties like antibacterial, antimicrobial, high adhesion, blood compatibility and wettability are most suitable for synthesis of biomaterial, but all of these properties does not exist in any natural or artificial polymeric material. Nano particles and plasma treatment can offer these properties to the polymers. Hence a new nano-biomaterial has been developed by modifying the surface and chemical properties of Ag nanocomposite polymer membranes (NCPM) by Argon ion plasma treatment. These membranes were characterized using different techniques for surface and chemical modifications occurred. Bacterial adhesion and wettability were also tested for these membranes, to show direct use of this new class of nano-biomaterial for biomedical applications.

Enhancement of healing in osteochondral defects by collagen sponge implants.

PubMed

Speer, D P; Chvapil, M; Volz, R G; Holmes, M D

1979-10-01

Implants of porous, highly cross-linked collagen sponge (CS) were tested for their capacity to enhance the healing of osteochondral defects in rabbits. Comparison was made to the healing of similar defects with polyvinyl alcohol sponge (PVAS) implants and with no implants (CONT). Evaluation was carried out up to 44 weeks following implantation and included observation of host cellular response, biodegradability of implant, gross appearance of restored joint surface, collagenous architecture of repair tissue, and properties of the junctions of implants and host articular cartilage, subchondral bone, and medullary bone. Collagen sponge proved most effective in promoting healing of osteochondral defects with fibrous and fibrocartilaginous tissue over restored subchondral bone. Collagen sponge showed many desirable properties as a potential material for biologic resurfacing of damaged joints. These properties included porosity, biodegradability, biocompatability, ability to mechanically protect cells and matrix while directing cell ingrowth, and an available chemical technology for modifying its biomechanical and biological properties. Comparative analysis of results of healing of CS, PVAS, and CONT osteochondral defects suggest rational design criteria for implant materials to improve their effectiveness in restoration of articular surfaces.

Effect of equal channel angular pressing on the microstructure and mechanical properties of Al-10Zn-2Mg alloy

NASA Astrophysics Data System (ADS)

Manjunath, G. K.; Kumar, G. V. Preetham; Bhat, K. Udaya

2018-04-01

The current investigation is focused on evaluating the mechanical properties and the microstructure of cast Al-10Zn-2Mg alloy processed through equal channel angular pressing (ECAP). The ECAP processing was attempted at minimum possible processing temperature. Microstructural characterization was carried out in optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Hardness measurement and tensile tests were employed to estimate the mechanical properties. Experimental results showed that, ECAP processing leads to noticeable grain refinement in the alloy. Reasonable amount of dislocations were observed in the ECAP processed material. After ECAP processing, precipitates nucleation in the material was detected in the XRD analysis. ECAP leads to considerable enhancement in the mechanical properties of the material. After ECAP processing, microhardness of the material is increased from 144 Hv to 216 Hv. Also, after ECAP processing the UTS of the material is increased from 140 MPa to 302 MPa. The increase in the mechanical properties of the alloy after ECAP processing is due to the dislocation strengthening and grain refinement strengthening. Finally, fracture surface morphology of the tensile test samples also studied.

Advances in UV-Plasmonics: A Detailed Analysis of Metallic Materials as Candidates for New Applications in Nanothecnology

DTIC Science & Technology

2014-08-26

Indium, Rhodium, Ruthenium, Tungsten, Titanium, Chromium, Palladium, Copper, Platinum and Magnesium . These have been chosen because all of them...performance. vii. Considering that the observed behaviors occur precisely where UV surface-enhanced Raman spectra indicated strong local field...research objective was centered on the UV plasmonic properties of Rh NPs by means of surface-enhanced Raman spectroscopy, surface-enhanced

Surface-enhanced Raman scattering (SERS) dosimeter and probe

DOEpatents

Vo-Dinh, T.

1995-03-21

A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devices, in probe array devices. 10 figures.

Development of sodium acetate trihydrate-ethylene glycol composite phase change materials with enhanced thermophysical properties for thermal comfort and therapeutic applications.

PubMed

Kumar, Rohitash; Vyas, Sumita; Kumar, Ravindra; Dixit, Ambesh

2017-07-12

The heat packs using phase change materials (PCMs) are designed for possible applications such as body comfort and medical applications under adverse situations. The development and performance of such heat packs rely on thermophysical properties of PCMs such as latent heat, suitable heat releasing temperature, degree of supercooling, effective heat releasing time, crystallite size, stability against spontaneous nucleation in metastable supercooled liquid state and thermal stability during heating and cooling cycles. Such PCMs are rare and the available PCMs do not exhibit such properties simultaneously to meet the desired requirements. The present work reports a facile approach for the design and development of ethylene glycol (EG) and aqueous sodium acetate trihydrate (SAT) based composite phase change materials, showing these properties simultaneously. The addition of 2-3 wt% EG in aqueous SAT enhances the softness of SAT crystallites, its degree of supercooling and most importantly the effective heat releasing time by ~10% with respect to aqueous SAT material. In addition, the maximum heat releasing temperature of aqueous SAT has been tailored from 56.5 °C to 55 °C, 54.9 °C, 53.5 °C, 51.8 °C and 43.2 °C using 2%, 3%, 5%, 7% and 10 wt% EG respectively, making the aqueous SAT-EG composite PCMs suitable for desired thermal applications.

Engineered Polymer Composites Through Electrospun Nanofiber Coating of Fiber Tows

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.

2013-01-01

Toughening and other property enhancements of composite materials are typically implemented by-modifying the bulk properties of the constituents, either the fiber or matrix materials. This often leads to difficulties in processing and higher material costs. Many composites consist of tows or yarns (thousands of individual fibers) that are either filament wound or processed into a fabric by weaving or braiding. The matrix material can be added to the tow or fabric before final processing, resulting in a prepreg material, or infused into the fiber material during final processing by a variety of methods. By using a direct electrospun deposition method to apply thermoplastic nanofiber to the surface of the tows, the tow-tow interface in the resulting composite can be modified while using otherwise conventional materials and handling processes. Other materials of interest could also be incorporated into the electrospun precursor.

Applications of graphite-enabled phase change material composites to improve thermal performance of cementitious materials

NASA Astrophysics Data System (ADS)

Li, Mingli; Lin, Zhibin; Wu, Lili; Wang, Jinhui; Gong, Na

2017-11-01

Enhancing the thermal efficiency to decrease the energy consumption of structures has been the topic of much research. In this study, a graphite-enabled microencapsulated phase change material (GE-MEPCM) was used in the production of a novel thermal energy storage engineered cementitious composite feathering high heat storage capacity and enhanced thermal conductivity. The surface morphology and particle size of the microencapsulated phase change material (MEPCM) were investigated by scanning electron microscopy (SEM). Thermal properties of MEPCM was determined using differential scanning calorimetry (DSC). In addition, thermal and mechanical properties of the cementitious mortar with different admixtures were explored and compared with those of a cementitious composite. It was shown that the latent heat of MEPCM was 162 J/g, offering much better thermal energy storage capacity to the cementitious composite. However, MEPCM was found to decrease the thermal conductivity of the composite, which can be effectively solved by adding natural graphite (NG). Moreover, the incorporation of MEPCM has a certain decrease in the compressive strength, mainly due to the weak interfaces between MEPCM and cement matrix.

Investigation on the feasibility of coffee husk (endocarp) as efficient filler material for enhancing physical and mechanical properties of styrofoam based particleboard

NASA Astrophysics Data System (ADS)

Milawarni; Nurlaili; Ernayusnianti

2018-03-01

This research focuses on introducing a coffee husk as viable and efficient filler for enhancing physical and mechanical properties of Styrofoam based particleboard. Heat treatment method was adopted to produce the particleboard from the mixture of coffee husk (CH) with Styrofoam (PS). Styrofoam is material derived from polystyrene. The aim of this research is to get the appropriate weight composition between coffee husks with PS and to identify the physical and mechanical properties of the produced particleboard. The composition of coffee husk varies between 0-90%wt. The manufacture of particleboard i.e. coffee husk milled with size 20/10 mesh then soak with 10% NaOH for 2 hours, rinsed with clean water and dried and weight according to the composition. The mixture of CH and PS is inserted into mold and put into hot-press. The result shows from physical properties that density, water absorption and thick development test corresponding with SNI 03-2105-2006 standard, the mechanical properties shows MOR test meets the standard on the addition of CH 10-50%, while the MOE test has not meet the standard.

Intrinsic space charge layers and field enhancement in ferroelectric nanojunctions

DOE PAGES

Cao, Ye; Ievlev, Anton V.; Morozovska, Anna N.; ...

2015-07-13

The conducting characteristics of topological defects in the ferroelectric materials, such as charged domain walls in ferroelectric materials, engendered broad interest and extensive study on their scientific merit and the possibility of novel applications utilizing domain engineering. At the same time, the problem of electron transport in ferroelectrics themselves still remains full of unanswered questions, and becomes still more relevant over the impending revival of interest in ferroelectric semiconductors and new improper ferroelectric materials. We have employed self-consistent phase-field modeling to investigate the physical properties of a local metal-ferroelectric (Pb(Zr 0.2Ti 0.8)O3) junction in applied electric field. We revealed anmore » up to 10-fold local field enhancement realized by large polarization gradient and over-polarization effects once the inherent non-linear dielectric properties of PZT are considered. The effect is independent of bias polarity and maintains its strength prior, during and after ferroelectric switching. The local field enhancement can be considered equivalent to increase of doping level, which will give rise to reduction of the switching bias and significantly smaller voltages to charge injection and electronic injection, electrochemical and photoelectrochemical processes.« less

Strain Modulation of Electronic and Heat Transport Properties of Bilayer Boronitrene

NASA Astrophysics Data System (ADS)

Yang, Ming; Sun, Fang-Yuan; Wang, Rui-Ning; Zhang, Hang; Tang, Da-Wei

2017-10-01

Strain engineering has been proven as an effective approach to modify electronic and thermal properties of materials. Recently, strain effects on two-dimensional materials have become important relevant topics in this field. We performed density functional theory studies on the electronic and heat transport properties of bilayer boronitrene samples under an isotropic strain. We demonstrate that the strain will reduce the band gap width but keep the band gap type robust and direct. The strain will enhance the thermal conductivity of the system because of the increase in specific heat. The thermal conductivity was studied as a function of the phonon mean-free path.

Tensile properties of textile composites

NASA Technical Reports Server (NTRS)

Avva, V. Sarma; Sadler, Robert L.; Lyon, Malcolm

1992-01-01

The importance of textile composite materials in aerospace structural applications has been gaining momentum in recent years. With a view to better understand the suitability of these materials in aerospace applications, an experimental program was undertaken to assess the mechanical properties of these materials. Specifically, the braided textile preforms were infiltrated with suitable polymeric matrices leading to the fabrication of composite test coupons. Evaluation of the tensile properties and the analyses of the results in the form of strength moduli, Poisson's ratio, etc., for the braided composites are presented. Based on our past experience with the textile coupons, the fabrication techniques have been modified (by incorporating glass microballoons in the matrix and/or by stabilizing the braid angle along the length of the specimen with axial fibers) to achieve enhanced mechanical properties of the textile composites. This paper outlines the preliminary experimental results obtained from testing these composites.

Understanding the Effect of Ni on Mechanical and Wear Properties of Low-Carbon Steel from a View-Point of Electron Work Function

NASA Astrophysics Data System (ADS)

Lu, Hao; Huang, Xiaochen; Hou, Runfang; Li, D. Y.

2018-07-01

Electron work function (EWF) is correlated to intrinsic properties of metallic materials and can be an alternative parameter to obtain supplementary clues for guiding material design and modification. A higher EWF corresponds to a more stable electronic state, leading to higher resistance to any attempt to change the material structure and properties. In this study, effects of Ni as a solute with a higher EWF on mechanical, electrochemical, and tribological properties of low-carbon steel were investigated. Added Ni, which has more valence electrons, enhanced the electrons-nuclei interaction in the steel, corresponding to higher EWF. As a result, the Ni-added steel showed increased mechanical strength and corrosion resistance, resulting in higher resistances to wear and corrosive wear. Mechanism for the improvements is elucidated through analyzing EWF-related variations in Young's modulus, hardness, corrosion potential, and tribological behavior.

Laser diode package with enhanced cooling

DOEpatents

Deri, Robert J; Kotovsky, Jack; Spadaccini, Christopher M

2012-06-26

This invention provides a new method for rapidly analyzing single bioparticles to assess their material condition and state of health. The method is enabled by use of a resonant cavity apparatus to measure an optical property related to the bioparticle size and refractive index. Measuring the refractive index is useful for determining material properties of the bioparticle. The material properties depend on the biomolecular composition of the bioparticle. The biomolecular composition is, in turn, dependent on the state of health of the bioparticle. Thus, measured optical properties can be used to differentiate normal (healthy) and abnormal (diseased) states of bioparticles derived from cells or tissues. The method is illustrated with data obtained from a resonator with a gain medium. The invention also provides new methods for making multiple measurements in a single device and detecting, analyzing, and manipulating bioparticles that are much smaller than the wavelength of light.

Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials

PubMed Central

Peinado, Víctor; Castell, Pere; García, Lidia; Fernández, Ángel

2015-01-01

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript. PMID:28793622

CEMCAN Software Enhanced for Predicting the Properties of Woven Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; DiCarlo, James A.

2000-01-01

Major advancements are needed in current high-temperature materials to meet the requirements of future space and aeropropulsion structural components. Ceramic matrix composites (CMC's) are one class of materials that are being evaluated as candidate materials for many high-temperature applications. Past efforts to improve the performance of CMC's focused primarily on improving the properties of the fiber, interfacial coatings, and matrix constituents as individual phases. Design and analysis tools must take into consideration the complex geometries, microstructures, and fabrication processes involved in these composites and must allow the composite properties to be tailored for optimum performance. Major accomplishments during the past year include the development and inclusion of woven CMC micromechanics methodology into the CEMCAN (Ceramic Matrix Composites Analyzer) computer code. The code enables one to calibrate a consistent set of constituent properties as a function of temperature with the aid of experimentally measured data.

Understanding the Effect of Ni on Mechanical and Wear Properties of Low-Carbon Steel from a View-Point of Electron Work Function

NASA Astrophysics Data System (ADS)

Lu, Hao; Huang, Xiaochen; Hou, Runfang; Li, D. Y.

2018-04-01

Electron work function (EWF) is correlated to intrinsic properties of metallic materials and can be an alternative parameter to obtain supplementary clues for guiding material design and modification. A higher EWF corresponds to a more stable electronic state, leading to higher resistance to any attempt to change the material structure and properties. In this study, effects of Ni as a solute with a higher EWF on mechanical, electrochemical, and tribological properties of low-carbon steel were investigated. Added Ni, which has more valence electrons, enhanced the electrons-nuclei interaction in the steel, corresponding to higher EWF. As a result, the Ni-added steel showed increased mechanical strength and corrosion resistance, resulting in higher resistances to wear and corrosive wear. Mechanism for the improvements is elucidated through analyzing EWF-related variations in Young's modulus, hardness, corrosion potential, and tribological behavior.

High Fidelity Ion Beam Simulation of High Dose Neutron Irradiation

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

Was, Gary; Wirth, Brian; Motta, Athur

The objective of this proposal is to demonstrate the capability to predict the evolution of microstructure and properties of structural materials in-reactor and at high doses, using ion irradiation as a surrogate for reactor irradiations. “Properties” includes both physical properties (irradiated microstructure) and the mechanical properties of the material. Demonstration of the capability to predict properties has two components. One is ion irradiation of a set of alloys to yield an irradiated microstructure and corresponding mechanical behavior that are substantially the same as results from neutron exposure in the appropriate reactor environment. Second is the capability to predict the irradiatedmore » microstructure and corresponding mechanical behavior on the basis of improved models, validated against both ion and reactor irradiations and verified against ion irradiations. Taken together, achievement of these objectives will yield an enhanced capability for simulating the behavior of materials in reactor irradiations.« less

Enhanced absorption in two-dimensional materials via Fano-resonant photonic crystals

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

Wang, Wenyi; Klots, Andrey; Bolotin, Kirill I.

2015-05-04

The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and near-infrared regimes monolayer MoS{sub 2} and graphene absorb only ∼10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77%more » within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ∼0.2 μm adjacent to the graphene/electrode interface.« less

Dynamic shear-lag model for understanding the role of matrix in energy dissipation in fiber-reinforced composites.

PubMed

Liu, Junjie; Zhu, Wenqing; Yu, Zhongliang; Wei, Xiaoding

2018-07-01

Lightweight and high impact performance composite design is a big challenge for scientists and engineers. Inspired from well-known biological materials, e.g., the bones, spider silk, and claws of mantis shrimp, artificial composites have been synthesized for engineering applications. Presently, the design of ballistic resistant composites mainly emphasizes the utilization of light and high-strength fibers, whereas the contribution from matrix materials receives less attention. However, recent ballistic experiments on fiber-reinforced composites challenge our common sense. The use of matrix with "low-grade" properties enhances effectively the impact performance. In this study, we establish a dynamic shear-lag model to explore the energy dissipation through viscous matrix materials in fiber-reinforced composites and the associations of energy dissipation characteristics with the properties and geometries of constituents. The model suggests that an enhancement in energy dissipation before the material integrity is lost can be achieved by tuning the shear modulus and viscosity of a matrix. Furthermore, our model implies that an appropriately designed staggered microstructure, adopted by many natural composites, can repeatedly activate the energy dissipation process and thus improve dramatically the impact performance. This model demonstrates the role of matrix in energy dissipation, and stimulates new advanced material design concepts for ballistic applications. Biological composites found in nature often possess exceptional mechanical properties that man-made materials haven't be able to achieve. For example, it is predicted that a pencil thick spider silk thread can stop a flying Boeing airplane. Here, by proposing a dynamic shear-lag model, we investigate the relationships between the impact performance of a composite with the dimensions and properties of its constituents. Our analysis suggests that the impact performance of fiber-reinforced composites could improve surprisingly with "low-grade" matrix materials, and discontinuities (often regarded as "defects") may play an important role in energy dissipation. Counter-intuitive as it may seem, our work helps understanding the secrets of the outstanding dynamic properties of some biological materials, and inspire novel ideas for man-made composites. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics.

PubMed

Madéo, Julien; Margiolakis, Athanasios; Zhao, Zhen-Yu; Hale, Peter J; Man, Michael K L; Zhao, Quan-Zhong; Peng, Wei; Shi, Wang-Zhou; Dani, Keshav M

2015-07-15

We report on the first terahertz (THz) emitter based on femtosecond-laser-ablated gallium arsenide (GaAs), demonstrating a 65% enhancement in THz emission at high optical power compared to the nonablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime, and enhanced photoabsorption arising from the ablation process. Our results show that laser ablation allows for efficient and cost-effective optoelectronic THz devices via the manipulation of fundamental properties of materials.

Physical property control in core/shell inorganic nanostructures for fluorescence and magnetic targeting applications

NASA Astrophysics Data System (ADS)

Roberts, Stephen K.

Nanomaterials show immense promise for the future in numerous areas of application. Properties that are unique from the bulk material and are tunable allow for innovation in material design. This thesis will focus on controlling the physical properties of core/shell nanostructures to enhance the utility of the materials. The first focus is on the impact of different solvent mixtures during the shell growth phase of SILAR based core/shell quantum dot synthesis is studied. Gaining insight into the mechanism for SILAR growth of core/shell nanoparticles allows improved synthetic yields and precursor binding, providing enhanced control to synthesis of core/shell nanoparticles. The second focus of this thesis is exploring the use of magnetic nanoparticles for magnetic drug targeting for cardiovascular conditions. Magnetic targeting for drug delivery enables increased local drug concentration, while minimizing non-specific interactions. In order to be effective for magnetic targeting, it must be shown that low magnetic strength is sufficient to capture flowing nanoparticles. By demonstrating the binding of a therapeutic agent to the surface at medicinal levels, the viability for use as a nanoparticle drug delivery system is improved.

Hybrid Al/steel-joints manufactured by ultrasound enhanced friction stir welding (USE-FSW): Process comparison, nondestructive testing and microscopic analysis

NASA Astrophysics Data System (ADS)

Thomä, M.; Wagner, G.; Straß, B.; Wolter, B.; Benfer, S.; Fürbeth, W.

2017-03-01

The process of friction stir welding (FSW) is an innovative joining technique, which proved its potential in joining dissimilar metals that are poorly fusion weldable. This ability opens a wide range for applications in industrial fields, where weight reduction by partial substitution of conventional materials through lightweight materials is a current central aim. As a consequence of this, the realization of aluminum / steel-joints is of great interest. For this material compound, several friction stir welds were carried out by different researchers for varying Al/steel-joints, whereas the definition of optimal process parameters as well as the increase of mechanical properties was in the focus of the studies. To achieve further improved properties for this dissimilar joint a newly developed hybrid process named “ultrasound enhanced friction stir welding (USE-FSW)” was applied. In this paper the resulting properties of Al/steel-joints using FSW and USE-FSW will be presented and compared. Furthermore, first results by using the nondestructive testing method “computer laminography” to analyze the developed joining area will be shown supplemented by detailed light-microscopic investigations, scanning electron microscopic analysis, and EDX.

Fracture surface analysis in composite and titanium bonding

NASA Technical Reports Server (NTRS)

Devilbiss, T. A.; Wightman, J. P.

1985-01-01

To understand the mechanical properties of fiber-reinforced composite materials, it is necessary to understand the mechanical properties of the matrix materials and of the reinforcing fibers. Another factor that can affect the mechanical properties of a composite material is the interaction between the fiber and the matrix. In general, composites with strong fiber matrix bonding will give higher modulus, lower toughness composites. Composites with weak bonding will have a lower modulus and more ductility. The situation becomes a bit more complex when all possibilities are examined. To be considered are the following: the properties of the surface layer on the fiber, the interactive forces between polymer and matrix, the surface roughness and porosity of the fiber, and the morphology of the matrix polymer at the fiber surface. In practice, the surface of the fibers is treated to enhance the mechanical properties of a composite. These treatments include anodization, acid etching, high temperature oxidation, and plasma oxidation, to name a few. The goal is to be able to predict the surface properties of carbon fibers treated in various ways, and then to relate surface properties to fiber matrix bonding.

The development of all-polymer-based piezoelectrically active photocurable resin for 3D printing process (Conference Presentation)

NASA Astrophysics Data System (ADS)

Baker, Evan; Chu, Weishen; Ware, Henry Oliver T.; Farsheed, Adam C.; Sun, Cheng

2017-02-01

We present in this work the development and experimental validation of a new piezoelectric material (V-Ink) designed for compatibility with projection stereolithography additive manufacturing techniques. Piezoelectric materials generate a voltage output when a stress is applied to the material, and also can be actuated by using an external voltage and power source. This new material opens up new opportunities for functional devices to be developed and rapidly produced at low cost using emerging 3D printing techniques. The new piezoelectric material was able to generate 115mV under 1N of strain after being polled at 80°C for 40 minutes and the optimal results had a piezoelectric coefficient of 105x10^(-3)V.m/N. The current iteration of the material is a suspension, although further work is ongoing to make the resin a true solution. The nature of the suspension was characterized by a time-lapse monitoring and through viscosity testing. The potential exists to further increase the piezoelectric properties of this material by integrating a mechanical to electrical enhancer such as carbon nanotubes or barium titanate into the material. Such materials need to be functionalized to be integrated within the material, which is currently being explored. Printing with this material on a "continuous SLA" printer that we have developed will reduce build times by an order of magnitude to allow for mass manufacturing. Pairing those two advancements will enable faster printing and enhanced piezoelectric properties.

Life prediction of l6 steel using strain-life curve and cyclic stress-strain curve by means of low cycle fatigue testing

NASA Astrophysics Data System (ADS)

Inamdar, Sanket; Ukhande, Manoj; Date, Prashant; Lomate, Dattaprasad; Takale, Shyam; Singh, RKP

2017-05-01

L6 Steel is used as die material in closed die hot forging process. This material is having some unique properties. These properties are due to its composition. Strain softening is the noticeable property of this material. Due to this in spite of cracking at high stress this material gets plastically deformed and encounters loss in time as well as money. Studies of these properties are necessary to nurture this material at fullest extent. In this paper, numerous experiments have been carried on L6 material to evaluate cyclic Stress - strain behavior as swell as strain-life behavior of the material. Low cycle fatigue test is carried out on MTS fatigue test machine at fully reverse loading condition R=-1. Also strain softening effect on forging metal forming process is explained in detail. The failed samples during low cycle fatigue test further investigated metallurgically on scanning electron microscopy. Based on this study, life estimation of hot forging die is carried out and it’s correlation with actual shop floor data is found out. This work also concludes about effect of pre-treatments like nitro-carburizing and surface coating on L6 steel material, to enhance its fatigue life to certain extent.

Synthesis and gas sensing properties of α-Fe(2)O(3)@ZnO core-shell nanospindles.

PubMed

Zhang, Jun; Liu, Xianghong; Wang, Liwei; Yang, Taili; Guo, Xianzhi; Wu, Shihua; Wang, Shurong; Zhang, Shoumin

2011-05-06

α-Fe(2)O(3)@ZnO core-shell nanospindles were synthesized via a two-step hydrothermal approach, and characterized by means of SEM/TEM/XRD/XPS. The ZnO shell coated on the nanospindles has a thickness of 10-15 nm. Considering that both α-Fe(2)O(3) and ZnO are good sensing materials, we have investigated the gas sensing performances of the core-shell nanocomposite using ethanol as the main probe gas. It is interesting to find that the gas sensor properties of the core-shell nanospindles are significantly enhanced compared with pristine α-Fe(2)O(3). The enhanced sensor properties are attributed to the unique core-shell nanostructure. The detailed sensing mechanism is discussed with respect to the energy band structure and the electron depletion theory. The core-shell nanostructure reported in this work provides a new path to fabricate highly sensitive materials for gas sensing applications.

Use of Nanoparticles for Enhancing the Interlaminar Properties of Fiber-Reinforced Composites and Adhesively Bonded Joints—A Review

PubMed Central

De Cicco, Davide; Asaee, Zohreh; Taheri, Farid

2017-01-01

This review paper aims at reporting some of the notable works carried out concerning the use of nanoparticles (NPs) as a means of improving the resistance of fiber-reinforced polymer composite materials (FRPs) and adhesively bonded joints (ABJs) to delamination initiation and propagation. Applications of various nanoparticles, such as carbon-based, ceramic-based and mineral-based are discussed. The main properties that have been considered for improving the delamination and fatigue resistance of FRPs are the interlaminar shear strength, fracture toughness, and fracture energy. On the other hand, cohesive and interfacial strengths have been the focused parameters in the works that considered enhancement of ABJs. The reported results indicate that inclusion of NPs in polymeric matrices leads to improvement of various material properties, even though some discrepancies in the results have been noted. Notwithstanding, additional research is required to address some of the issues that have not yet been tackled, some of which will be identified throughout this review article. PMID:29104278

Thermoelectric silicides: A review

NASA Astrophysics Data System (ADS)

Nozariasbmarz, Amin; Agarwal, Aditi; Coutant, Zachary A.; Hall, Michael J.; Liu, Jie; Liu, Runze; Malhotra, Abhishek; Norouzzadeh, Payam; Öztürk, Mehmet C.; Ramesh, Viswanath P.; Sargolzaeiaval, Yasaman; Suarez, Francisco; Vashaee, Daryoosh

2017-05-01

Traditional research on thermoelectric materials focused on improving the figure-of-merit z T to enhance the energy conversion efficiency. With further growth and commercialization of thermoelectric technology beyond niche applications, other factors such as materials availability, toxicity, cost, recyclability, thermal stability, chemical and mechanical properties, and ease of fabrication become important for making viable technologies. Several silicide alloys were identified that have the potential to fulfill these requirements. These materials are of interest due to their abundancy in earth’s crust (e.g., silicon), non-toxicity, and good physical and chemical properties. In this paper, an overview of the silicide thermoelectrics from traditional alloys to advanced material structures is presented. In addition, some of the most effective approaches as well as fundamental physical concepts for designing and developing efficient thermoelectric materials are presented and future perspectives are discussed.

New directions for nanoscale thermoelectric materials research

NASA Technical Reports Server (NTRS)

Dresselhaus, M. S.; Chen, G.; Tang, M. Y.; Yang, R. G.; Lee, H.; Wang, D. Z.; Ren, F.; Fleurial, J. P.; Gogna, P.

2005-01-01

Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena with both bulk samples containing nanoscale constituents and nanoscale materials exhibiting enhanced thermoelectric performance in their own right. Prior theoretical and experimental proof of principle studies on isolated quantum well and quantum wire samples have now evolved into studies on bulk samples containing nanostructured constituents. In this review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications. A review of some of the results obtained to date are presented.

Study on the light-color mixing of rare earth luminescent materials for anti-counterfeiting application

NASA Astrophysics Data System (ADS)

Zhang, Jishu; Zhang, Yingzi; Tao, Jin; Zhu, Yanan

2018-04-01

In order to find out the light color mixing mechanism of rare earth luminescent materials used in anti-counterfeiting fibers, we prepared three kinds of rare earth luminescent materials according to RGB tri-primary color, and mixed it together to form different mixtures in certain proportion. The phase structures of the luminescent material monomers were measured by x-ray diffractometer. The photochromic properties of the luminescent materials were tested and analyzed by fluorescence spectrophotometer. The results show that the light color mixing was consistent with the blending principle of additive color, but not the same because of the photochromic properties of rare earth luminescent materials, and we explored the reasons in the light wavelength and intensity. It was found that the enhancement of the luminescence intensity of the mixture on account of the superimposing of luminescence.

Nano-Particle Enhanced Polymer Materials for Space Flight Applications

NASA Technical Reports Server (NTRS)

Criss, Jim M., Jr.; Powell, William D.; Connell, John W.; Stallworth-Bordain, Yemaya; Brown, Tracy R.; Mintz, Eric A.; Schlea, Michelle R.; Shofne, Meisha L.

2009-01-01

Recent advances in materials technology both in polymer chemistry and nano-materials warrant development of enhanced structures for space flight applications. This work aims to develop spacecraft structures based on polymer matrix composites (PMCs) that utilize these advancements.. Multi-wall carbon nano-tubes (MWCNTs) are expected ·to increase mechanical performance, lower coefficient of thermal expansion (CTE), increase electrical conductivity (mitigate electrostatic charge), increase thermal conductivity, and reduce moisture absorption of the resultant space structures. In this work, blends of MWCNTs with PETI-330 were prepared and characterized. The nano-reinforced resins were then resin transfer molded (RTM) into composite panels using M55J carbon fabric and compared to baseline panels fabricated from a cyanate ester (RS-3) or a polyimide (PETI-330) resin containing no MWCNTs. In addition, methods of pre-loading the fabric with the MWCNTs were also investigated. The effects of the MWCNTs on the resin processing properties and on the composite end-use properties were also determined.

Ultralow refractive index optical films with enhanced mechanical performance obtained by hybrid glancing angle deposition.

PubMed

Trottier-Lapointe, W; Zabeida, O; Schmitt, T; Martinu, L

2016-11-01

Ultralow refractive index materials (n less than 1.38 at 550 nm) are of particular interest in the context of antireflective coatings, allowing one to enhance their overall optical performance. However, application of such materials is typically limited by their mechanical properties. In this study, we explore the characteristics of a new category of hybrid (organic/inorganic) SiOCH thin films prepared by glancing angle deposition (GLAD) using electron beam evaporation of SiO₂ in the presence of an organosilicon precursor. The resulting layers exhibited n as low as 1.2, showed high elastic rebound, and generally better mechanical properties than their inorganic counterparts. In addition, hybrid GLAD films were found to be highly hydrophobic. The performance of the films is discussed in terms of their hybridicity (organic/inorganic) ratio determined by infrared spectroscopic ellipsometry as well as the presence of anisotropy assessed by the nanostructure-based spectroscopic ellipsometry model. Finally, we demonstrate successful implementation of the ultralow-index material in a complete antireflective stack.

Antimicrobial graphene family materials: Progress, advances, hopes and fears.

PubMed

Lukowiak, Anna; Kedziora, Anna; Strek, Wieslaw

2016-10-01

Graphene-based materials have become very popular bionanotechnological instruments in the last few years. Since 2010, the graphene family materials have been recognized as worthy of attention due to its antimicrobial properties. Functionalization of graphene (or rather graphene oxide) surface creates the possibilities to obtain efficient antimicrobial agents. In this review, progress and advances in this field in the last few years are described and discussed. Special attention is devoted to materials based on graphene oxide in which specifically selected components significantly modify biological activity of this carbon structure. Short introduction concerns the physicochemical properties of the graphene family materials. In the section on antimicrobial properties, proposed mechanisms of activity against microorganisms are given showing enhanced action of nanocomposites also under light irradiation (photoinduced activity). Another important feature, i.e. toxicity against eukaryotic cells, is presented with up-to-date data. Taking into account all the information on the properties of the described materials and usefulness of the graphene family as antimicrobial agents, hopes and fears concerning their application are discussed. Finally, some examples of promising usage in medicine and other fields, e.g. in phytobiology and water remediation, are shown. Copyright © 2016 Elsevier B.V. All rights reserved.

Tribological Properties of Water-lubricated Rubber Materials after Modification by MoS2 Nanoparticles

PubMed Central

Dong, Conglin; Yuan, Chengqing; Wang, Lei; Liu, Wei; Bai, Xiuqin; Yan, Xinping

2016-01-01

Frictional vibration and noise caused by water-lubricated rubber stern tube bearings, which are generated under extreme conditions, severely threaten underwater vehicles’ survivability and concealment performance. This study investigates the effect of flaky and spherical MoS2 nanoparticles on tribological properties and damping capacity of water-lubricated rubber materials, with the aim of decreasing frictional noise. A CBZ-1 tribo-tester was used to conduct the sliding tests between rubber ring-discs and ZCuSn10Zn2 ring-discs with water lubrication. These materials’ typical mechanical properties were analysed and compared. Coefficients of friction (COFs), wear rates, and surface morphologies were evaluated. Frictional noise and critical velocities of generating friction vibration were examined to corroborate above analysis. Results showed that spherical MoS2 nanoparticles enhanced rubber material’s mechanical and tribological properties and, in turn, reduced the friction noise and critical velocity. Flaky MoS2 nanoparticles reduced COF but did not enhance their mechanical properties, i.e., the damping capacity, wear resistance property; thus, these nanoparticles did not reduce the critical velocity obviously, even though increased the frictional noise at high load. The knowledge gained in the present work will be useful for optimizing friction pairs under extreme conditions to decrease frictional noise of water-lubricated rubber stern tube bearings. PMID:27713573

Characterization of basic physical properties of Sb 2Se 3 and its relevance for photovoltaics

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

Chen, Chao; Bobela, David C.; Yang, Ye

Antimony selenide (Sb 2Se 3) is a promising absorber material for thin film photovoltaics because of its attractive material, optical and electrical properties. In recent years, the power conversion efficiency (PCE) of Sb 2Se 3 thin film solar cells has gradually enhanced to 5.6%. In this article, we systematically studied the basic physical properties of Sb 2Se 3 such as dielectric constant, anisotropic mobility, carrier lifetime, diffusion length, defect depth, defect density and optical band tail states. Here, we believe such a comprehensive characterization of the basic physical properties of Sb 2Se 3 lays a solid foundation for further optimizationmore » of solar device performance.« less

Characterization of basic physical properties of Sb 2Se 3 and its relevance for photovoltaics

DOE PAGES

Chen, Chao; Bobela, David C.; Yang, Ye; ...

2017-03-17

Antimony selenide (Sb 2Se 3) is a promising absorber material for thin film photovoltaics because of its attractive material, optical and electrical properties. In recent years, the power conversion efficiency (PCE) of Sb 2Se 3 thin film solar cells has gradually enhanced to 5.6%. In this article, we systematically studied the basic physical properties of Sb 2Se 3 such as dielectric constant, anisotropic mobility, carrier lifetime, diffusion length, defect depth, defect density and optical band tail states. Here, we believe such a comprehensive characterization of the basic physical properties of Sb 2Se 3 lays a solid foundation for further optimizationmore » of solar device performance.« less

Functionalized Poly(3,4-ethylenedioxy bithiophene) Films for Tuning Electrochromic and Thermoelectric Properties.

PubMed

Hu, Yongjing; Liu, Xiaofang; Jiang, Fengxing; Zhou, Weiqiang; Liu, Congcong; Duan, Xuemin; Xu, Jingkun

2017-10-05

Conductive thiophene-based polymers have garnered great attention for use in organic electron materials such as electrochromic and thermoelectric materials. However, they suffer from poor electron transport properties and long-term stability, leading to limited development eventually. Here, we proposed a strategy of functionalized thiophene-based polymers with oligo(ethylene glycol) or alkyl side chains and synthesized a series of poly(3,4-ethylenedioxy bithiophene)s (PEDTs) to tune their electrochromic and thermoelectric properties. An alkyl group bearing electronic ability at the thiophene ring effectively achieved a large increase in the electrical conductivity with nearly invariable Seebeck coefficient, resulting in an enhancement by 1 order of magnitude for the thermoelectric power factor. Moreover, the electrochromic properties of functionalized PEDTs gained an effective improvement in the optical contrast and coloration efficiency as well as stability with multicolor changes between neutral and oxidized states. The functionalized PEDTs can be proposed as an alternative strategy to tune the electrochromic and thermoelectric properties for organic polymer materials.

Properties of PMR Polyimides Improved by Preparation of Polyhedral Oligomeric Silsesquioxane (POSS) Nanocomposites

NASA Technical Reports Server (NTRS)

Campbell, Sandi G.; Lee, Andre

2005-01-01

The field of hybrid organic-inorganic materials has grown drastically over the last several years. This interest stems from our ever-increasing ability to custom-build and control molecular structure at several length scales. This ability to control both the composition and structure of hybrid materials is sometimes broadly referred to as nanocomposite systems. One class of hybrid (organic-inorganic) nanostructured material is polyhedral oligomeric silsesquioxane (POSS), shown in the preceding diagram. The hybrid composition gives POSS materials dramatically enhanced properties relative to traditional hydrocarbons and inorganics. An important benefit of this technology is that it makes possible the formulations of nanostructured chemicals with excellent thermal and oxidative stability. This is largely due to the inorganic component.

Development of construction materials like concrete from lunar soils without water

NASA Technical Reports Server (NTRS)

Desai, Chandra S.; Saadatmanesh, H.; Frantziskonis, G.

1989-01-01

The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. A unique approach is attempted that utilizes factors such as initial vacuum and then cyclic loading to enhance the mechanical properties of dry materials similar to those available on the moon. The application of such factors is expected to allow reorientation, and coming together, of particles of the materials toward the maximum theoretical density. If such a density can provide deformation and strength properties for even a limited type of construction, the approach can have significant application potential, although other factors such as heat and chemicals may be needed for specific construction objectives.

Study of the production of some superconducting and magnetic materials by solidification in the drop tube and drop tower

NASA Technical Reports Server (NTRS)

Wu, M. K.

1987-01-01

A systematic study on the relationship between the microstructure and physical properties of several superconducting materials prepared by solidification in low gravity was conducted. Further study of the materials, such as the applications of hydrostatic pressure which is known to be an effective mean to vary the electronic structure of materials, in conjunction with the detailed microstructure analysis of the samples was also performed to better understand the low gravity effects on the enhancement of the electronic properties. Results of the studies on the directionally solidified AlInSn alloys processed in the KC-135 aircraft and immiscible GaBi alloy prepared during free fall in the Marshall Space Flight Center Drop Tower are presented.

Material condition assessment with eddy current sensors

NASA Technical Reports Server (NTRS)

Goldfine, Neil J. (Inventor); Washabaugh, Andrew P. (Inventor); Sheiretov, Yanko K. (Inventor); Schlicker, Darrell E. (Inventor); Lyons, Robert J. (Inventor); Windoloski, Mark D. (Inventor); Craven, Christopher A. (Inventor); Tsukernik, Vladimir B. (Inventor); Grundy, David C. (Inventor)

2010-01-01

Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges.

Method of making carbon nanotube composite materials

DOEpatents

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2014-05-20

The present invention is a method of making a composite polymeric material by dissolving a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes and optionally additives in a solvent to make a solution and removing at least a portion of the solvent after casting onto a substrate to make thin films. The material has enhanced conductivity properties due to the blending of the un-functionalized and hydroxylated carbon nanotubes.

Laser-assisted manufacturing of super-insulation materials

NASA Astrophysics Data System (ADS)

Wang, Zhen; Zhang, Tao; Park, Byung Kyu; Lee, Woo Il; Hwang, David

2017-02-01

Being lightweight materials with good mechanical and thermal properties, hollow glass micro-particles (HGMPs) have been widely studied for multiple applications. In this study, it is shown that by using reduced binder fraction diluted in solvent, enables minimal contacts among the HGMPs assisted by a natural capillary trend, as confirmed by optical and electron microscope imaging. Such material architecture fabricated in a composite level proves to have enhanced thermal insulation performance through quantitative thermal conductivity measurement. Mechanical strength has also been evaluated in terms of particle-binder bonding by tensile test via in-situ microscope inspection. Effect of laser treatment was examined for further improvement of thermal and mechanical properties by selective binder removal and efficient redistribution of remaining binder components. The fabricated composite materials have potential applications to building insulation materials for their scalable manufacturing nature, improved thermal insulation performance and reasonable mechanical strength. Further studies are needed to understand mechanical and thermal properties of the resulting composites, and key fabrication mechanisms involved with laser treatment of complex multi-component and multi-phase systems.

Effects of catalyst pore structure and acid properties on the dehydration of glycerol.

PubMed

Choi, Youngbo; Park, Hongseok; Yun, Yang Sik; Yi, Jongheop

2015-03-01

Hierarchical porous catalysts have recently attracted increasing interest because of the enhanced accessibility to active sites on such materials. In this context, previously reported hierarchically mesoporous ASN and ASPN materials are evaluated by applying them to the dehydration of glycerol, and demonstrate excellent catalytic performance. In addition, a comprehensive understanding of the effects of pore structures and the acid properties on the reaction through comparative studies with microporous HZSM-5 and mesoporous AlMCM-41 is provided. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Confine Clay in an Alternating Multilayered Structure through Injection Molding: A Simple and Efficient Route to Improve Barrier Performance of Polymeric Materials.

PubMed

Yu, Feilong; Deng, Hua; Bai, Hongwei; Zhang, Qin; Wang, Ke; Chen, Feng; Fu, Qiang

2015-05-20

Various methods have been devoted to trigger the formation of multilayered structure for wide range of applications. These methods are often complicated with low production efficiency or require complex equipment. Herein, we demonstrate a simple and efficient method for the fabrication of polymeric sheets containing multilayered structure with enhanced barrier property through high speed thin-wall injection molding (HSIM). To achieve this, montmorillonite (MMT) is added into PE first, then blended with PP to fabricate PE-MMT/PP ternary composites. It is demonstrated that alternating multilayer structure could be obtained in the ternary composites because of low interfacial tension and good viscosity match between different polymer components. MMT is selectively dispersed in PE phase with partial exfoliated/partial intercalated microstructure. 2D-WAXD analysis indicates that the clay tactoids in PE-MMT/PP exhibits an uniplanar-axial orientation with their surface parallel to the molded part surface, while the tactoids in binary PE-MMT composites with the same overall MMT contents illustrate less orientation. The enhanced orientation of nanoclay in PE-MMT/PP could be attributed to the confinement of alternating multilayer structure, which prohibits the tumbling and rotation of nanoplatelets. Therefore, the oxygen barrier property of PE-MMT/PP is superior to that of PE-MMT because of increased gas permeation pathway. Comparing with the results obtained for PE based composites in literature, outstanding barrier property performance (45.7% and 58.2% improvement with 1.5 and 2.5 wt % MMT content, respectively) is achieved in current study. Two issues are considered responsible for such improvement: enhanced MMT orientation caused by the confinement in layered structure, and higher local density of MMT in layered structure induced denser assembly. Finally, enhancement in barrier property by confining impermeable filler into alternating multilayer structure through such simple and efficient method could provide a novel route toward high-performance packaging materials and other functional materials require layered structure.

Photonic crystal light source

DOEpatents

Fleming, James G [Albuquerque, NM; Lin, Shawn-Yu [Albuquerque, NM; Bur, James A [Corrales, NM

2004-07-27

A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

Broadband giant-refractive-index material based on mesoscopic space-filling curves

NASA Astrophysics Data System (ADS)

Chang, Taeyong; Kim, Jong Uk; Kang, Seung Kyu; Kim, Hyowook; Kim, Do Kyung; Lee, Yong-Hee; Shin, Jonghwa

2016-08-01

The refractive index is the fundamental property of all optical materials and dictates Snell's law, propagation speed, wavelength, diffraction, energy density, absorption and emission of light in materials. Experimentally realized broadband refractive indices remain <40, even with intricately designed artificial media. Herein, we demonstrate a measured index >1,800 resulting from a mesoscopic crystal with a dielectric constant greater than three million. This gigantic enhancement effect originates from the space-filling curve concept from mathematics. The principle is inherently very broad band, the enhancement being nearly constant from zero up to the frequency of interest. This broadband giant-refractive-index medium promises not only enhanced resolution in imaging and raised fundamental absorption limits in solar energy devices, but also compact, power-efficient components for optical communication and increased performance in many other applications.

Trade-off between the Mechanical Strength and Microwave Electrical Properties of Functionalized and Irradiated Carbon Nanotube Sheets.

PubMed

Williams, Tiffany S; Orloff, Nathan D; Baker, James S; Miller, Sandi G; Natarajan, Bharath; Obrzut, Jan; McCorkle, Linda S; Lebron-Colón, Marisabel; Gaier, James; Meador, Michael A; Liddle, J Alexander

2016-04-13

Carbon nanotube (CNT) sheets represent a novel implementation of CNTs that enable the tailoring of electrical and mechanical properties for applications in the automotive and aerospace industries. Small molecule functionalization and postprocessing techniques, such as irradiation with high-energy particles, are methods that can enhance the mechanical properties of CNTs. However, the effect that these modifications have on the electrical conduction mechanisms has not been extensively explored. By characterizing the mechanical and electrical properties of multiwalled carbon nanotube (MWCNT) sheets with different functional groups and irradiation doses, we can expand our insights into the extent of the trade-off that exists between mechanical strength and electrical conductivity for commercially available CNT sheets. Such insights allow for the optimization of design pathways for engineering applications that require a balance of material property enhancements.

Preparation and characterization of adefovir dipivoxil-stearic acid cocrystal with enhanced physicochemical properties.

PubMed

Seo, Jeong-Woong; Hwang, Kyu-Min; Lee, Sung-Hoon; Kim, Dong-Wook; Park, Eun-Seok

2017-06-11

The objectives of this study were to prepare cocrystal composed of adefovir dipivoxil (AD) and stearic acid (SA) and to investigate the enhanced properties of the cocrystal. The cocrystal was prepared by antisolvent precipitation and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). The enhanced properties were evaluated by dissolution testing, permeability studies, and powder rheology analysis. The AD raw material has a cuboid-like crystal and the cocrystal has a needle shape. In the FT-IR study, there were bathochromic shifts caused by the hydrogen bonding. The melting point of the cocrystal was 52.9 °C, which was lower than that of AD. The XRPD pattern also had distinct differences, supporting the formation of a new crystalline form. The cocrystal showed changes in the lattice energy and the solvation strength, which caused an enhanced dissolution. The permeability was increased due to the SA, which acts as a P-gp inhibitor. The tabletability was enhanced due to the altered crystal habit. In conclusion, cocrystal containing AD and SA was successfully prepared, presenting advantages such as enhanced solubility, tabletability, and permeability. The use of the cocrystal is a desirable approach for the improved physicochemical properties.

Design of SERS nanoprobes for Raman imaging: materials, critical factors and architectures.

PubMed

Li, Mingwang; Qiu, Yuanyuan; Fan, Chenchen; Cui, Kai; Zhang, Yongming; Xiao, Zeyu

2018-05-01

Raman imaging yields high specificity and sensitivity when compared to other imaging modalities, mainly due to its fingerprint signature. However, intrinsic Raman signals are weak, thus limiting medical applications of Raman imaging. By adsorbing Raman molecules onto specific nanostructures such as noble metals, Raman signals can be significantly enhanced, termed surface-enhanced Raman scattering (SERS). Recent years have witnessed great interest in the development of SERS nanoprobes for Raman imaging. Rationally designed SERS nanoprobes have greatly enhanced Raman signals by several orders of magnitude, thus showing great potential for biomedical applications. In this review we elaborate on recent progress in design strategies with emphasis on material properties, modifying factors, and structural parameters.

Protonated graphitic carbon nitride coated metal-organic frameworks with enhanced visible-light photocatalytic activity for contaminants degradation

NASA Astrophysics Data System (ADS)

Huang, Jie; Zhang, Xibiao; Song, Haiyan; Chen, Chunxia; Han, Fuqin; Wen, Congcong

2018-05-01

Most of the reported composites of g-C3N4/metal-organic frameworks (MOFs) were obtained via exfoliation of g-C3N4 and wrapping the nanosheets on MOFs with weak interaction. In this work, chemical protonation of g-C3N4 and dip-coating was adopted as a feasible pathway to achieve the real combination of g-C3N4 derivatives with a familiar MOF material MIL-100(Fe). Structural, chemical and photophysical properties of the novel hybrid photocatalysts were characterized and compared to those of the parent materials. It was verified that the protonated g-C3N4 species of appropriate content were uniformly coated along the frameworks of MIL-100(Fe) with strong interaction. The optimal materials maintained the intact framework structure, surface property and porosity of MIL-100(Fe), as well as the inherent structural units and physicochemical properties of C3N4. In comparison to the parent materials, the protonated g-C3N4 coated MIL-100(Fe) materials exhibited enhanced photocatalytic activity in degradation of rhodamine B or methylene blue dye, as well as in oxidative denitrogenation for pyridine by molecular oxygen under visible light. Introduction of protonated g-C3N4 on MOFs improved the adsorption ability for contaminant molecules. Furthermore, coating effect provided a platform for rapid photoexcited electrons transfer and superior separation of photogenerated electron-hole pairs. Photocatalytic conversion of the three contaminants followed different mechanisms.

Ferroelectrics: A pathway to switchable surface chemistry and catalysis

NASA Astrophysics Data System (ADS)

Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

2016-08-01

It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

Exceeding the filling fraction limit: An approach to enhancement of thermoelectric properties of filled - Co4Sb12 skutterudite

NASA Astrophysics Data System (ADS)

Graff, Jennifer Whitney

Currently the world energy usage has nearly tripled since 1950 and is projected to grow at a rate of 1.5% per year and predicted to at least double from the beginning of the millennium to 2050. The United States alone is currently consuming more energy than it can produce (≈ 97 Quadrillion BTU's consumed in 2011).(1) Presently, fossil fuels make up over 85% of our energy landscape, including both the stationary grid (like coal and nuclear power plants) and the mobile grid (automobiles using gas and oil). This presents a major demand for developing methods of saving, storing, and renewing energy. Answers to these existing energy demands must come from a variety of renewable sources including: solar, wind, biomass, geothermal and others. But currently, most renewable sources are only a small part of the big energy picture. One approach to this exponentially growing problem, lies within high efficiency (15%-20%) thermoelectric (TE) materials which address small, yet very important and specific, parts of a bigger problem. Specifically, Co4Sb12-based skutterudites, an increasingly favorable thermoelectric material for mid to high temperature applications (currently used in General Motors TE Generator devices). These materials have the ability to be 'tuned' or controlled thermally and electrically through doping and filling mechanisms, as you will see in this dissertation. However, one of the major drawbacks of TE materials is the difficulty in optimizing both electrical and thermal properties simultaneously. Typically, different control parameters are used in order to enhance the electrical and thermal properties individually. It is very rare to observe optimization of both in a TE material via one control parameter. However, the work presented herein successfully augments all TE properties, with one control variable, by using an approach that can be applied to all doped skutterudites and clathrate materials. Skutterudites are novel materials in that they are a binary system with a crystalline framework and a narrow band gap, so they naturally possess relatively good electrical properties. This dissertation seeks to answer the question: Can we continue to improve the efficiency of one of the leading TE materials in power generation applications -- skutterudites? In trying to answer this question we discovered a material that had never been tested for its TE properties and found that it exhibits behavior not typically observed in these materials as well as showing improvements in all TE properties (electrical and thermal) via one control parameter. We also successfully improved the TE efficiencies of several different filled skutterudites by a single approach which can be applied to other skutterudite and cage-like materials.

Air Force Research Laboratory Technology Milestones 2008

DTIC Science & Technology

2008-01-01

futuristic ‘bots will possess self - healing properties as well, enhancing their resiliency to damage sustained during such missions. Leading the SuperBot...Matrix Composites Pollution Prevention Materials Polymeric Materials Power and Chemical Processes Quantitative Defect Characterization Robotics ...advanced self -sealing CMC manufactured by French company Snecma Propulsion Solide (SPS). Thus far, the seals have performed extremely well, and a

Carbon nanotube composite materials

DOEpatents

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2015-03-24

A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

Enhancing the soil organic matter pool through biomass incorporation

Treesearch

Felipe G. Sanchez; Emily A. Carter; John F. Klepac

2003-01-01

A study was installed in the Upper Coastal Plain of South Carolina, USA that sought to examine the impact of incorporating downed slash materials into subsoil layers on soil chemical and physical properties as compared with the effect of slash materials left on the soil surface. Baseline levels of slash were estimated by establishing transects within harvested stands...

Modification of lignocellulosic materials by laccase

Treesearch

William Kenealy; John Klungness; Mandla Tshabalala; Roland Gleisner; Eric Horn; Masood Akhtar; Hilda Zulaica-Villagomez; Gisela Buschle-Diller

2003-01-01

Altering the surface properties of pulp can enhance binding, increase paper strength, and decrease the cost of fiber. In this study, we modified lignocellulosic materials (bark and pulp) with laccase and selected substrates to change the nature of the pulp surface. Modified pulps were evaluated by the amount of methylene blue (a cationic dye) that would bind to the...

Dilatant effect enhancers for silica dispersions in poly(propylene glycols).

PubMed

Orawiec, Marcin; Kaczorowski, Marcin; Rokicki, Gabriel

2018-05-29

Shear thickening fluids have found many applications in energy damping materials such as sports guards and liquid body armors. Therefore, an additive which could tailor the dilatant properties of such fluids without significantly affecting other properties, especially zero shear viscosity, could significantly increase the versatility of protective materials based on shear thickening fluids. In this paper, poly(propylene glycols) (PPGs) diacetates are investigated as dilatant effect enhancers for nano-silica dispersions in poly(propylene glycols). The influence of the modifiers on rheological properties of the dispersion is studied and discussed. Additionally, FTIR and rheological properties measurements are conducted in order to determine relative interactions strength between hydroxyl groups of PPGs and silica and carbonyl groups of PPG diacetates. Our findings suggest that the relative attractive interaction strength in studied systems can be arranged in the following order: COCO < COOH < OHOH. Therefore, the addition of PPG diacetate hinders the attractive interactions between liquid and solid. We report that the addition of diacetates can lead both to enhancement and deterioration of dilatant effect depending on the concentration of the modifier and its chain length. Based on conducted measurements and literature data, mechanism explaining that phenomenon is suggested. As a result, we propose an easy to make and cheap dilatant effect enhancer for widely used shear thickening fluids which, when used in small amounts (1-2.5%), raises the viscosity jump drastically. Additionally, the presence of the modifier does not significantly affect the zero shear viscosity of the shear thickening fluid. Copyright © 2018 Elsevier Inc. All rights reserved.

Extreme mechanical properties of materials under extreme pressure and temperature conditions (Invited)

NASA Astrophysics Data System (ADS)

Kavner, A.; Armentrout, M. M.; Xie, M.; Weinberger, M.; Kaner, R. B.; Tolbert, S. H.

2010-12-01

A strong synergy ties together the high-pressure subfields of mineral physics, solid-state physics, and materials engineering. The catalog of studies measuring the mechanical properties of materials subjected to large differential stresses in the diamond anvil cell demonstrates a significant pressure-enhancement of strength across many classes of materials, including elemental solids, salts, oxides, silicates, and borides and nitrides. High pressure techniques—both radial diffraction and laser heating in the diamond anvil cell—can be used to characterize the behavior of ultrahard materials under extreme conditions, and help test hypotheses about how composition, structure, and bonding work together to govern the mechanical properties of materials. The principles that are elucidated by these studies can then be used to help design engineering materials to encourage desired properties. Understanding Earth and planetary interiors requires measuring equations of state of relevant materials, including oxides, silicates, and metals under extreme conditions. If these minerals in the diamond anvil cell have any ability to support a differential stress, the assumption of quasi-hydrostaticity no longer applies, with a resulting non-salubrious effect on attempts to measure equation of state. We illustrate these applications with the results of variety of studies from our laboratory and others’ that have used high-pressure radial diffraction techniques and also laser heating in the diamond anvil cell to characterize the mechanical properties of a variety of ultrahard materials, especially osmium metal, osmium diboride, rhenium diboride, and tungsten tetraboride. We compare ambient condition strength studies such as hardness testing with high-pressure studies, especially radial diffraction under differential stress. In addition, we outline criteria for evaluating mechanical properties of materials at combination high pressures and temperatures. Finally, we synthesize our understanding of mechanical properties and composite behavior to suggest new approaches to designing high-pressure experiments to target specific measurements of a wide variety of mechanical properties.

Stretchable conducting materials with multi-scale hierarchical structures for biomedical applications

NASA Astrophysics Data System (ADS)

Kim, Hyun; Shim, Bong Sup

2014-08-01

Electrogenetic tissues in human body such as central and peripheral nerve systems, muscular and cardiomuscular systems are soft and stretchable materials. However, most of the artificial materials, interfacing with those conductive tissues, such as neural electrodes and cardiac pacemakers, have stiff mechanical properties. The rather contradictory properties between natural and artificial materials usually cause critical incompatibility problems in implanting bodymachine interfaces for wide ranges of biomedical devices. Thus, we developed a stretchable and electrically conductive material with complex hierarchical structures; multi-scale microstructures and nanostructural electrical pathways. For biomedical purposes, an implantable polycaprolactone (PCL) membrane was coated by molecularly controlled layer-bylayer (LBL) assembly of single-walled carbon nanotubes (SWNTs) or poly(3,4-ethylenedioxythiophene) (PEDOT). The soft PCL membrane with asymmetric micro- and nano-pores provides elastic properties, while conductive SWNT or PEDOT coating preserves stable electrical conductivity even in a fully stretched state. This electrical conductivity enhanced ionic cell transmission and cell-to-cell interactions as well as electrical cellular stimulation on the membrane. Our novel stretchable conducting materials will overcome long-lasting challenges for bioelectronic applications by significantly reducing mechanical property gaps between tissues and artificial materials and by providing 3D interconnected electro-active pathways which can be available even at a fully stretched state.

Multimodal and self-healable interfaces enable strong and tough graphene-derived materials

NASA Astrophysics Data System (ADS)

Liu, Yilun; Xu, Zhiping

2014-10-01

Recent studies have shown that graphene-derived materials not only feature outstanding multifunctional properties, but also act as model materials to implant nanoscale structural engineering insights into their macroscopic performance optimization. In this work, we explore strengthening and toughening strategies of this class of materials by introducing multimodal crosslinks, including long, strong and short, self-healable ones. We identify two failure modes by fracturing functionalized graphene sheets or their crosslinks, and the role of brick-and-mortar hierarchy in mechanical enhancement. Theoretical analysis and atomistic simulation results show that multimodal crosslinks synergistically transfer tensile load to enhance the strength, whereas reversible rupture and formation of healable crosslinks improve the toughness. These findings lay the ground for future development of high-performance paper-, fiber- or film-like macroscopic materials from low-dimensional structures with engineerable interfaces.

Pulsed Laser Deposition Processing of Improved Titanium Nitride Coatings for Implant Applications

NASA Astrophysics Data System (ADS)

Haywood, Talisha M.

Recently surface coating technology has attracted considerable attention of researchers to develop novel coatings with enhanced functional properties such as hardness, biocompatibility, wear and corrosion resistance for medical devices and surgical tools. The materials currently being used for surgical implants include predominantly stainless steel (316L), cobalt chromium (Co-Cr), titanium and its alloys. Some of the limitations of these implants include improper mechanical properties, corrosion resistance, cytotoxicity and bonding with bone. One of the ways to improve the performance and biocompatibility of these implants is to coat their surfaces with biocompatible materials. Among the various coating materials, titanium nitride (TiN) shows excellent mechanical properties, corrosion resistance and low cytotoxicity. In the present work, a systematic study of pulsed laser ablation processing of TiN coatings was conducted. TiN thin film coatings were grown on commercially pure titanium (Ti) and stainless steel (316L) substrates at different substrate temperatures and different nitrogen partial pressures using the pulsed laser deposition (PLD) technique. Microstructural, surface, mechanical, chemical, corrosion and biological analysis techniques were applied to characterize the TiN thin film coatings. The PLD processed TiN thin film coatings showed improvements in mechanical strength, corrosion resistance and biocompatibility when compared to the bare substrates. The enhanced performance properties of the TiN thin film coatings were a result of the changing and varying of the deposition parameters.

Properties of Extruded PS-212 Type Self-Lubricating Materials

NASA Technical Reports Server (NTRS)

Waters, W. J.; Sliney, H. E.; Soltis, R. F.

1993-01-01

Research has been underway at the NASA Lewis Research Center since the 1960's to develop high temperature, self-lubricating materials. The bulk of the research has been done in-house by a team of researchers from the Materials Division. A series of self-lubricating solid material systems has been developed over the years. One of the most promising is the composite material system referred to as PS-212 or PM-212. This material is a powder metallurgy product composed of metal bonded chromium carbide and two solid lubricating materials known to be self-lubricating over a wide temperature range. NASA feels this material has a wide potential in industrial applications. Simplified processing of this material would enhance its commercial potential. Processing changes have the potential to reduce processing costs, but tribological and physical properties must not be adversely affected. Extrusion processing has been employed in this investigation as a consolidation process for PM-212/PS-212. It has been successful in that high density bars of EX-212 (extruded PM-212) can readily be fabricated. Friction and strength data indicate these properties have been maintained or improved over the P.M. version. A range of extrusion temperatures have been investigated and tensile, friction, wear, and microstructural data have been obtained. Results indicate extrusion temperatures are not critical from a densification standpoint, but other properties are temperature dependent.

High performance P-type thermoelectric materials and methods of preparation

NASA Technical Reports Server (NTRS)

Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

2002-01-01

The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn.sub.4-x A.sub.x Sb.sub.3-y B.sub.y wherein 0.ltoreq.x.ltoreq.4, A is a transition metal, B is a pnicogen, and 0.ltoreq.y.ltoreq.3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn.sub.4 Sb.sub.3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

Controlled surface functionality of magnetic nanoparticles by layer-by-layer assembled nano-films

NASA Astrophysics Data System (ADS)

Choi, Daheui; Son, Boram; Park, Tai Hyun; Hong, Jinkee

2015-04-01

Over the past several years, the preparation of functionalized nanoparticles has been aggressively pursued in order to develop desired structures, compositions, and structural order. Among the various nanoparticles, iron oxide magnetic nanoparticles (MNPs) have shown great promise because the material generated using these MNPs can be used in a variety of biomedical applications and possible bioactive functionalities. In this study, we report the development of various functionalized MNPs (F-MNPs) generated using the layer-by-layer (LbL) self-assembly method. To provide broad functional opportunities, we fabricated F-MNP bio-toolbox by using three different materials: synthetic polymers, natural polymers, and carbon materials. Each of these F-MNPs displays distinct properties, such as enhanced thickness or unique morphologies. In an effort to explore their biomedical applications, we generated basic fibroblast growth factor (bFGF)-loaded F-MNPs. The bFGF-loaded F-MNPs exhibited different release mechanisms and loading amounts, depending on the film material and composition order. Moreover, bFGF-loaded F-MNPs displayed higher biocompatibility and possessed superior proliferation properties than the bare MNPs and pure bFGF, respectively. We conclude that by simply optimizing the building materials and the nanoparticle's film composition, MNPs exhibiting various bioactive properties can be generated.Over the past several years, the preparation of functionalized nanoparticles has been aggressively pursued in order to develop desired structures, compositions, and structural order. Among the various nanoparticles, iron oxide magnetic nanoparticles (MNPs) have shown great promise because the material generated using these MNPs can be used in a variety of biomedical applications and possible bioactive functionalities. In this study, we report the development of various functionalized MNPs (F-MNPs) generated using the layer-by-layer (LbL) self-assembly method. To provide broad functional opportunities, we fabricated F-MNP bio-toolbox by using three different materials: synthetic polymers, natural polymers, and carbon materials. Each of these F-MNPs displays distinct properties, such as enhanced thickness or unique morphologies. In an effort to explore their biomedical applications, we generated basic fibroblast growth factor (bFGF)-loaded F-MNPs. The bFGF-loaded F-MNPs exhibited different release mechanisms and loading amounts, depending on the film material and composition order. Moreover, bFGF-loaded F-MNPs displayed higher biocompatibility and possessed superior proliferation properties than the bare MNPs and pure bFGF, respectively. We conclude that by simply optimizing the building materials and the nanoparticle's film composition, MNPs exhibiting various bioactive properties can be generated. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07373h

Enhancing the antibacterial performance of orthopaedic implant materials by fibre laser surface engineering

NASA Astrophysics Data System (ADS)

Chan, Chi-Wai; Carson, Louise; Smith, Graham C.; Morelli, Alessio; Lee, Seunghwan

2017-05-01

Implant failure caused by bacterial infection is extremely difficult to treat and usually requires the removal of the infected components. Despite the severe consequence of bacterial infection, research into bacterial infection of orthopaedic implants is still at an early stage compared to the effort on enhancing osseointegration, wear and corrosion resistance of implant materials. In this study, the effects of laser surface treatment on enhancing the antibacterial properties of commercially pure (CP) Ti (Grade 2), Ti6Al4V (Grade 5) and CoCrMo alloy implant materials were studied and compared for the first time. Laser surface treatment was performed by a continuous wave (CW) fibre laser with a near-infrared wavelength of 1064 nm in a nitrogen-containing environment. Staphylococcus aureus, commonly implicated in infection associated with orthopaedic implants, was used to investigate the antibacterial properties of the laser-treated surfaces. The surface roughness and topography of the laser-treated materials were analysed by a 2D roughness testing and by AFM. The surface morphologies before and after 24 h of bacterial cell culture were captured by SEM, and bacterial viability was determined using live/dead staining. Surface chemistry was analysed by XPS and surface wettability was measured using the sessile drop method. The findings of this study indicated that the laser-treated CP Ti and Ti6Al4V surfaces exhibited a noticeable reduction in bacterial adhesion and possessed a bactericidal effect. Such properties were attributable to the combined effects of reduced hydrophobicity, thicker and stable oxide films and presence of laser-induced nano-features. No similar antibacterial effect was observed in the laser-treated CoCrMo.

Green materials for sustainable development

NASA Astrophysics Data System (ADS)

Purwasasmita, B. S.

2017-03-01

Sustainable development is an integrity of multidiscipline concept combining ecological, social and economic aspects to construct a liveable human living system. The sustainable development can be support through the development of green materials. Green materials offers a unique characteristic and properties including abundant in nature, less toxic, economically affordable and versatility in term of physical and chemical properties. Green materials can be applied for a numerous field in science and technology applications including for energy, building, construction and infrastructures, materials science and engineering applications and pollution management and technology. For instance, green materials can be developed as a source for energy production. Green materials including biomass-based source can be developed as a source for biodiesel and bioethanol production. Biomass-based materials also can be transformed into advanced functionalized materials for advanced bio-applications such as the transformation of chitin into chitosan which further used for biomedicine, biomaterials and tissue engineering applications. Recently, cellulose-based material and lignocellulose-based materials as a source for the developing functional materials attracted the potential prospect for biomaterials, reinforcing materials and nanotechnology. Furthermore, the development of pigment materials has gaining interest by using the green materials as a source due to their unique properties. Eventually, Indonesia as a large country with a large biodiversity can enhance the development of green material to strengthen our nation competitiveness and develop the materials technology for the future.

Food structure: Its formation and relationships with other properties.

PubMed

Joardder, Mohammad U H; Kumar, Chandan; Karim, M A

2017-04-13

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food.

Viscoelasticity of new generation thermoplastic polyurethane vibration isolators

NASA Astrophysics Data System (ADS)

Bek, Marko; Betjes, Joris; von Bernstorff, Bernd-Steffen; Emri, Igor

2017-12-01

This paper presents the analysis of pressure dependence of three thermoplastic polyurethane (TPU) materials on vibration isolation. The three TPU Elastollan® materials are 1190A, 1175A, and 1195D. The aim of this investigation was to analyze how much the performance of isolation can be enhanced using patented Dissipative bulk and granular systems technology. The technology uses granular polymeric materials to enhance materials properties (without changing its chemical or molecular composition) by exposing them to "self-pressurization," which shifts material energy absorption maxima toward lower frequencies, to match the excitation frequency of dynamic loading to which a mechanical system is exposed. Relaxation experiments on materials were performed at different isobaric and isothermal states to construct mastercurves, the time-temperature-pressure interrelation was modeled using the Fillers-Moonan-Tschoegl model. Dynamic material functions, related to isolation stiffness and energy absorption, were determined with the Schwarzl approximation. An increase in stiffness and energy absorption at selected hydrostatic pressure, compared to its stiffness and energy absorption at ambient conditions, is represented with κk(p, ω), defining the increase in stiffness and κd(p, ω), defining the increase in energy absorption. The study showed that close to the glassy state, moduli of 1190A and 1195D are about 6-9 times higher compared to 1175A, whereas their properties at ambient conditions are, for all practical purposes, the same. TPU 1190A turns out to be most sensitive to pressure: at 300 MPa its properties are shifted for 5.5 decades, while for 1195D and 1175A this shift is only 3.5 and 1.5 decades, respectively. In conclusion, the stiffness and energy absorption of isolation may be increased with pressure for about 100 times for 1190A and 1195D and for about 10 times for 1175A.

Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

NASA Astrophysics Data System (ADS)

Song, Meng; Xu, Peng; Song, Yenan; Wang, Xu; Li, Zhenhua; Shang, Xuefu; Wu, Huizhen; Zhao, Pei; Wang, Miao

2015-09-01

Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm2, and field enhancement factor of ˜1.3 × 104. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

Tuning the piezoelectric and mechanical properties of the AlN system via alloying with YN and BN

NASA Astrophysics Data System (ADS)

Manna, Sukriti; Brennecka, Geoff L.; Stevanović, Vladan; Ciobanu, Cristian V.

2017-09-01

Recent advances in microelectromechanical systems often require multifunctional materials, which are designed so as to optimize more than one property. Using density functional theory calculations for alloyed nitride systems, we illustrate how co-alloying a piezoelectric material (AlN) with different nitrides helps tune both its piezoelectric and mechanical properties simultaneously. Wurtzite AlN-YN alloys display increased piezoelectric response with YN concentration, accompanied by mechanical softening along the crystallographic c direction. Both effects increase the electromechanical coupling coefficients relevant for transducers and actuators. Resonator applications, however, require superior stiffness, thus leading to the need to decouple the increased piezoelectric response from the softened lattice. We show that co-alloying of AlN with YN and BN results in improved elastic properties while retaining some of the piezoelectric enhancements from YN alloying. This finding may lead to new avenues for tuning the design properties of piezoelectrics through composition-property maps.

Exploring Anomalous Polarization Dynamics in Organometallic Halide Perovskites

DOE PAGES

Ahmadi, Mahshid; Collins, Liam; Puretzky, Alexander; ...

2018-01-22

Organometallic halide perovskites (OMHPs) have attracted broad attention as prospective materials for optoelectronic applications. Among the many anomalous properties of these materials, of special interest are the ferroelectric properties including both classical and relaxor-like components, as a potential origin of slow dynamics, field enhancement, and anomalous mobilities. Here, ferroelectric properties of the three representative OMHPs are explored, including FAPb xSn 1–xI 3 (x = 0, x = 0.85) and FA 0.85MA 0.15PbI 3 using band excitation piezoresponse force microscopy and contact mode Kelvin probe force microscopy, providing insight into long- and short-range dipole and charge dynamics in these materials andmore » probing ferroelectric density of states. Furthermore, second-harmonic generation in thin films of OMHPs is observed, providing a direct information on the noncentrosymmetric polarization in such materials. Overall, the data provide strong evidence for the presence of ferroelectric domains in these systems; however, the domain dynamics is suppressed by fast ion dynamics. These materials hence present the limit of ferroelectric materials with spontaneous polarization dynamically screened by ionic and electronic carriers.« less

Exploring Anomalous Polarization Dynamics in Organometallic Halide Perovskites

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

Ahmadi, Mahshid; Collins, Liam; Puretzky, Alexander

Organometallic halide perovskites (OMHPs) have attracted broad attention as prospective materials for optoelectronic applications. Among the many anomalous properties of these materials, of special interest are the ferroelectric properties including both classical and relaxor-like components, as a potential origin of slow dynamics, field enhancement, and anomalous mobilities. Here, ferroelectric properties of the three representative OMHPs are explored, including FAPb xSn 1–xI 3 (x = 0, x = 0.85) and FA 0.85MA 0.15PbI 3 using band excitation piezoresponse force microscopy and contact mode Kelvin probe force microscopy, providing insight into long- and short-range dipole and charge dynamics in these materials andmore » probing ferroelectric density of states. Furthermore, second-harmonic generation in thin films of OMHPs is observed, providing a direct information on the noncentrosymmetric polarization in such materials. Overall, the data provide strong evidence for the presence of ferroelectric domains in these systems; however, the domain dynamics is suppressed by fast ion dynamics. These materials hence present the limit of ferroelectric materials with spontaneous polarization dynamically screened by ionic and electronic carriers.« less

Surface Tension Components Based Selection of Cosolvents for Efficient Liquid Phase Exfoliation of 2D Materials.

PubMed

Shen, Jianfeng; Wu, Jingjie; Wang, Man; Dong, Pei; Xu, Jingxuan; Li, Xiaoguang; Zhang, Xiang; Yuan, Junhua; Wang, Xifan; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

2016-05-01

A proper design of direct liquid phase exfoliation (LPE) for 2D materials as graphene, MoS2 , WS2 , h-BN, Bi2 Se3 , MoSe2 , SnS2 , and TaS2 with common cosolvents is carried out based on considering the polar and dispersive components of surface tensions of various cosolvents and 2D materials. It has been found that the exfoliation efficiency is enhanced by matching the ratio of surface tension components of cosolvents to that of the targeted 2D materials, based on which common cosolvents composed of IPA/water, THF/water, and acetone/water can be designed for sufficient LPE process. In this context, the library of low-toxic and low-cost solvents with low boiling points for LPE is infinitely enlarged when extending to common cosolvents. Polymer-based composites reinforced with a series of different 2D materials are compared with each other. It is demonstrated that the incorporation of cosolvents-exfoliated 2D materials can substantially improve the mechanical and thermal properties of polymer matrices. Typically, with the addition of 0.5 wt% of such 2D material as MoS2 nanosheets, the tensile strength and Young's modulus increased up to 74.85% and 136.97%, respectively. The different enhancement effect of 2D materials is corresponded to the intrinsic properties and LPE capacity of 2D materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biosensing with Förster Resonance Energy Transfer Coupling between Fluorophores and Nanocarbon Allotropes

PubMed Central

Ding, Shaowei; Cargill, Allison A.; Das, Suprem R.; Medintz, Igor L.; Claussen, Jonathan C.

2015-01-01

Nanocarbon allotropes (NCAs), including zero-dimensional carbon dots (CDs), one-dimensional carbon nanotubes (CNTs) and two-dimensional graphene, exhibit exceptional material properties, such as unique electrical/thermal conductivity, biocompatibility and high quenching efficiency, that make them well suited for both electrical/electrochemical and optical sensors/biosensors alike. In particular, these material properties have been exploited to significantly enhance the transduction of biorecognition events in fluorescence-based biosensing involving Förster resonant energy transfer (FRET). This review analyzes current advances in sensors and biosensors that utilize graphene, CNTs or CDs as the platform in optical sensors and biosensors. Widely utilized synthesis/fabrication techniques, intrinsic material properties and current research examples of such nanocarbon, FRET-based sensors/biosensors are illustrated. The future outlook and challenges for the research field are also detailed. PMID:26110411

Predicting the structure of screw dislocations in nanoporous materials

NASA Astrophysics Data System (ADS)

Walker, Andrew M.; Slater, Ben; Gale, Julian D.; Wright, Kate

2004-10-01

Extended microscale crystal defects, including dislocations and stacking faults, can radically alter the properties of technologically important materials. Determining the atomic structure and the influence of defects on properties remains a major experimental and computational challenge. Using a newly developed simulation technique, the structure of the 1/2a <100> screw dislocation in nanoporous zeolite A has been modelled. The predicted channel structure has a spiral form that resembles a nanoscale corkscrew. Our findings suggest that the dislocation will enhance the transport of molecules from the surface to the interior of the crystal while retarding transport parallel to the surface. Crucially, the dislocation creates an activated, locally chiral environment that may have enantioselective applications. These predictions highlight the influence that microscale defects have on the properties of structurally complex materials, in addition to their pivotal role in crystal growth.

Peculiarities of hydration of Portland cement with synthetic nano-silica

NASA Astrophysics Data System (ADS)

Kotsay, Galyna

2017-12-01

Application of nano-materials in cement products significantly, improves their properties. Of course, the effectiveness of the materials depends on their quantity and the way they are introduced into the system. So far, amongst nano-materials used in construction, the most preferred was nano-silica. This research investigated the effect of synthetic precipitated nano-silica on the cement hydration as well as, on the physical and mechanical properties of pastes and mortars. Obtained results showed that admixture of nano-silica enhanced flexural and compressive strength of cement after 2 and 28 days, however, only when admixture made up 0.5% and 1.0%. On the other hand, the use of nano-silica in the amount 2% had some limitations, due to its ability to agglomerate, which resulted in deterioration of the rheological and mechanical properties.

Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

NASA Technical Reports Server (NTRS)

Park, Junhong; Palumbo, Daniel L.

2004-01-01

For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

Superparamagnetic enhancement of thermoelectric performance.

PubMed

Zhao, Wenyu; Liu, Zhiyuan; Sun, Zhigang; Zhang, Qingjie; Wei, Ping; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; He, Danqi; Ji, Pengxia; Zhu, Wanting; Nie, Xiaolei; Su, Xianli; Tang, Xinfeng; Shen, Baogen; Dong, Xiaoli; Yang, Jihui; Liu, Yong; Shi, Jing

2017-09-13

The ability to control chemical and physical structuring at the nanometre scale is important for developing high-performance thermoelectric materials. Progress in this area has been achieved mainly by enhancing phonon scattering and consequently decreasing the thermal conductivity of the lattice through the design of either interface structures at nanometre or mesoscopic length scales or multiscale hierarchical architectures. A nanostructuring approach that enables electron transport as well as phonon transport to be manipulated could potentially lead to further enhancements in thermoelectric performance. Here we show that by embedding nanoparticles of a soft magnetic material in a thermoelectric matrix we achieve dual control of phonon- and electron-transport properties. The properties of the nanoparticles-in particular, their superparamagnetic behaviour (in which the nanoparticles can be magnetized similarly to a paramagnet under an external magnetic field)-lead to three kinds of thermoelectromagnetic effect: charge transfer from the magnetic inclusions to the matrix; multiple scattering of electrons by superparamagnetic fluctuations; and enhanced phonon scattering as a result of both the magnetic fluctuations and the nanostructures themselves. We show that together these effects can effectively manipulate electron and phonon transport at nanometre and mesoscopic length scales and thereby improve the thermoelectric performance of the resulting nanocomposites.

Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes

NASA Technical Reports Server (NTRS)

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

2000-01-01

Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

Cleaning Spectralon(TM) To Maintain Reflectance Properties

NASA Technical Reports Server (NTRS)

Stiegman, Albert; Bruegge, Carl; Plett, Gary

1996-01-01

Hydrocarbon impurities removed and stability of Spectralon(TM) towards ultraviolet and vacuum-ultraviolet radiation greatly enhanced by baking material at 90 degrees C for 24 h in vacuum of 10 to negative 5th power torr. After vacuum bake, material handled with white cotton, lint-free gloves in clean environment (preferably cleanroom). As material has tendency to reabsorb volatile organic compounds, stored and transported only in clean, air-tight (preferably glass or oil-free metal) containers.

Thermoelectric properties of hot-pressed fine particulate powder SiGe alloys

NASA Technical Reports Server (NTRS)

Beaty, John S.; Rolfe, Jonathan; Vandersande, Jan

1991-01-01

A novel material system and its fabrication technique have been defined and applied to the production of SiGe thermoelectric material through the hot pressing of 50-100 A ultrafine particulates into 80/20 SiGe. Relative to conventionally processed SiGe, a reduction of thermal conductivity of up to 40 percent is achieved in conjunction with an enhancement of material figure-of-merit of the order of 10-15 percent.

Applications of mass spectrometry techniques to autoclave curing of materials

NASA Technical Reports Server (NTRS)

Smith, A. C.

1983-01-01

Mass spectrometer analysis of gases evolved from polymer materials during a cure cycle can provide a wealth of information useful for studying cure properties and procedures. In this paper data is presented for two materials to support the feasibility of using mass spectrometer gas analysis techniques to enhance the knowledge of autoclave curing of composite materials and provide additional information for process control evaluation. It is expected that this technique will also be useful in working out the details involved in determining the proper cure cycle for new or experimental materials.

Nanostructuring superconductors by ion beams: A path towards materials engineering

NASA Astrophysics Data System (ADS)

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

2013-07-01

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

First-Principles Modeling of Hydrogen Storage in Metal Hydride Systems

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

J. Karl Johnson

The objective of this project is to complement experimental efforts of MHoCE partners by using state-of-the-art theory and modeling to study the structure, thermodynamics, and kinetics of hydrogen storage materials. Specific goals include prediction of the heats of formation and other thermodynamic properties of alloys from first principles methods, identification of new alloys that can be tested experimentally, calculation of surface and energetic properties of nanoparticles, and calculation of kinetics involved with hydrogenation and dehydrogenation processes. Discovery of new metal hydrides with enhanced properties compared with existing materials is a critical need for the Metal Hydride Center of Excellence. Newmore » materials discovery can be aided by the use of first principles (ab initio) computational modeling in two ways: (1) The properties, including mechanisms, of existing materials can be better elucidated through a combined modeling/experimental approach. (2) The thermodynamic properties of novel materials that have not been made can, in many cases, be quickly screened with ab initio methods. We have used state-of-the-art computational techniques to explore millions of possible reaction conditions consisting of different element spaces, compositions, and temperatures. We have identified potentially promising single- and multi-step reactions that can be explored experimentally.« less

Bottom-up design of de novo thermoelectric hybrid materials using chalcogenide resurfacing

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

Sahu, Ayaskanta; Russ, Boris; Su, Norman C.

Hybrid organic/inorganic thermoelectric materials based on conducting polymers and inorganic nanostructures have been demonstrated to combine both the inherently low thermal conductivity of the polymer and the superior charge transport properties (high power factors) of the inorganic component. While their performance today still lags behind that of conventional inorganic thermoelectric materials, solution-processable hybrids have made rapid progress and also offer unique advantages not available to conventional rigid inorganic thermoelectrics, namely: (1) low cost fabrication on rigid and flexible substrates, as well as (2) engineering complex conformal geometries for energy harvesting/cooling. While the number of reports of new classes of viablemore » hybrid thermoelectric materials is growing, no group has reported a general approach for bottom-up design of both p- and n-type materials from one common base. Thus, unfortunately, the literature comprises mostly of disconnected discoveries, which limits development and calls for a first-principles approach for property manipulation analogous to doping in traditional semiconductor thermoelectrics. Here, molecular engineering at the organic/inorganic interface and simple processing techniques are combined to demonstrate a modular approach enabling de novo design of complex hybrid thermoelectric systems. Here, we chemically modify the surfaces of inorganic nanostructures and graft conductive polymers to yield robust solution processable p- and n-type inorganic/organic hybrid nanostructures. Our new modular approach not only offers researchers new tools to perform true bottom-up design of thermoelectric hybrids, but also strong performance advantages as well due to the quality of the designed interfaces. For example, we obtain enhanced power factors in existing (by up to 500% in Te/PEDOT:PSS) and novel (Bi 2S 3/PEDOT:PSS) p-type systems, and also generate water-processable and air-stable high performing n-type hybrid systems (Bi 2Te 3/PEDOT:PSS), thus highlighting the potency of our ex situ strategy in opening up new material options for thermoelectric applications. Finally, this strategy establishes a unique platform with broad handles for custom tailoring of thermal and electrical properties through hybrid material tunability and enables independent control over inorganic material chemistry, nanostructure geometry, and organic material properties, thus providing a robust pathway to major performance enhancements.« less

Bottom-up design of de novo thermoelectric hybrid materials using chalcogenide resurfacing

DOE PAGES

Sahu, Ayaskanta; Russ, Boris; Su, Norman C.; ...

2017-01-01

Hybrid organic/inorganic thermoelectric materials based on conducting polymers and inorganic nanostructures have been demonstrated to combine both the inherently low thermal conductivity of the polymer and the superior charge transport properties (high power factors) of the inorganic component. While their performance today still lags behind that of conventional inorganic thermoelectric materials, solution-processable hybrids have made rapid progress and also offer unique advantages not available to conventional rigid inorganic thermoelectrics, namely: (1) low cost fabrication on rigid and flexible substrates, as well as (2) engineering complex conformal geometries for energy harvesting/cooling. While the number of reports of new classes of viablemore » hybrid thermoelectric materials is growing, no group has reported a general approach for bottom-up design of both p- and n-type materials from one common base. Thus, unfortunately, the literature comprises mostly of disconnected discoveries, which limits development and calls for a first-principles approach for property manipulation analogous to doping in traditional semiconductor thermoelectrics. Here, molecular engineering at the organic/inorganic interface and simple processing techniques are combined to demonstrate a modular approach enabling de novo design of complex hybrid thermoelectric systems. Here, we chemically modify the surfaces of inorganic nanostructures and graft conductive polymers to yield robust solution processable p- and n-type inorganic/organic hybrid nanostructures. Our new modular approach not only offers researchers new tools to perform true bottom-up design of thermoelectric hybrids, but also strong performance advantages as well due to the quality of the designed interfaces. For example, we obtain enhanced power factors in existing (by up to 500% in Te/PEDOT:PSS) and novel (Bi 2S 3/PEDOT:PSS) p-type systems, and also generate water-processable and air-stable high performing n-type hybrid systems (Bi 2Te 3/PEDOT:PSS), thus highlighting the potency of our ex situ strategy in opening up new material options for thermoelectric applications. Finally, this strategy establishes a unique platform with broad handles for custom tailoring of thermal and electrical properties through hybrid material tunability and enables independent control over inorganic material chemistry, nanostructure geometry, and organic material properties, thus providing a robust pathway to major performance enhancements.« less

Preparation and microwave absorption properties of honeycomb core structures coated with composite absorber

NASA Astrophysics Data System (ADS)

Luo, Hui; Chen, Fu; Wang, Fang; Wang, Xian; Dai, Weiyong; Hu, Sheng; Gong, Rongzhou

2018-05-01

Honeycomb structure coated with paraffin filled with composite of graphene and flaky carbonyl iron powder (FCIP) as lossy filler have been studied. The composite of graphene/FCIP with different weight ratio were synthesized via mechanical milling, the electromagnetic properties of the samples were measured by transmission/reflection method in the frequency range of 8-12 GHz. The microwave absorbing properties of the microwave absorbing honeycomb structure (MAHS) and microwave absorbing honeycomb sandwich structure (MAHSS) were studied based on the Finite Element Method with periodical boundary conditions. The matching layer on the top of the honeycomb sandwich structure can enhanced the microwave absorption properties. It was shown that a light weight and broadband MAHSS could be implemented with the use of the magnetic material and dielectric material.

Improvement of the mechanical properties of reinforced aluminum foam samples

NASA Astrophysics Data System (ADS)

Formisano, A.; Barone, A.; Carrino, L.; De Fazio, D.; Langella, A.; Viscusi, A.; Durante, M.

2018-05-01

Closed-cell aluminum foam has attracted increasing attention due to its very interesting properties, thanks to which it is expected to be used as both structural and functional material. A research challenge is the improvement of the mechanical properties of foam-based structures adopting a reinforced approach that does not compromise their lightness. Consequently, the aim of this research is the fabrication of enhanced aluminum foam samples without significantly increasing their original weight. In this regard, cylindrical samples with a core of closed-cell aluminum foam and a skin of fabrics and grids of different materials were fabricated in a one step process and were mechanically characterized, in order to investigate their behaviour and to compare their mechanical properties to the ones of the traditional foam.

Enhancement mechanism of field electron emission properties in hybrid carbon nanotubes with tree- and wing-like features

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

Yang, G.M.; School of Materials Science and Engineering, The University of New South Wales, NSW 2052; Yang, C.C., E-mail: ccyang@unsw.edu.a

2009-12-15

In this work, the tree-like carbon nanotubes (CNTs) with branches of different diameters and the wing-like CNTs with graphitic-sheets of different densities were synthesized by using plasma enhanced chemical vapor deposition. The nanostructures of the as-prepared hybrid carbon materials were characterized by scanning electron microscopy and transmission electron microscopy. The structural dependence of field electron emission (FEE) property was also investigated. It is found that both of the tree- and wing-like CNTs exhibit a lower turn-on field and higher emission current density than the pristine CNTs, which can be ascribed to the effects of branch size, crystal orientation, and graphitic-sheetmore » density. - Graphical abstract: Tree-like carbon nanotubes (CNTs) with branches and the wing-like CNTs with graphitic-sheets were synthesized by using plasma enhanced chemical vapor deposition. The structural dependence of field electron emission property was also investigated.« less

Magnetorheological technology for fabricating tunable solid electrolyte with enhanced conductivity and mechanical property

NASA Astrophysics Data System (ADS)

Peng, Gangrou; Ge, Yu; Ding, Jie; Wang, Caiyun; Wallace, Gordon G.; Li, Weihua

2018-03-01

Ionogels are a new class of hybrid materials where ionic liquids are immobilized by macromolecular support. The excessive amount of crosslinking polymer enhances the mechanical strength but compromises the conductivity. Here, we report an elastomeric magnetorheological (MR) ionogel with an enhanced conductivity and mechanical strength as well. Following the application of magnetic nanoparticles into an ionic liquid containing minimum cross-linking agent, the formation, thus physical properties, of MR ionogels are co-controlled by simultaneously applied UV light and external magnetic field. The application of MR ionogels as solid electrolytes in supercapacitors is also demonstrated to study electrochemical performance. This work opens a new avenue to synthesize robust ionogels with the desired conductivity and controllable mechanical properties for soft flexible electronic devices. Besides, as a new class of conductive MR elastomers, the proposed MR ionogel also possesses the potential for engineering applications, such as sensors and actuators.

Influence of raw material properties upon critical quality attributes of continuously produced granules and tablets.

PubMed

Fonteyne, Margot; Wickström, Henrika; Peeters, Elisabeth; Vercruysse, Jurgen; Ehlers, Henrik; Peters, Björn-Hendrik; Remon, Jean Paul; Vervaet, Chris; Ketolainen, Jarkko; Sandler, Niklas; Rantanen, Jukka; Naelapää, Kaisa; De Beer, Thomas

2014-07-01

Continuous manufacturing gains more and more interest within the pharmaceutical industry. The International Conference of Harmonisation (ICH) states in its Q8 'Pharmaceutical Development' guideline that the manufacturer of pharmaceuticals should have an enhanced knowledge of the product performance over a range of raw material attributes, manufacturing process options and process parameters. This fits further into the Process Analytical Technology (PAT) and Quality by Design (QbD) framework. The present study evaluates the effect of variation in critical raw material properties on the critical quality attributes of granules and tablets, produced by a continuous from-powder-to-tablet wet granulation line. The granulation process parameters were kept constant to examine the differences in the end product quality caused by the variability of the raw materials properties only. Theophylline-Lactose-PVP (30-67.5-2.5%) was used as model formulation. Seven different grades of theophylline were granulated. Afterward, the obtained granules were tableted. Both the characteristics of granules and tablets were determined. The results show that differences in raw material properties both affect their processability and several critical quality attributes of the resulting granules and tablets. Copyright © 2014 Elsevier B.V. All rights reserved.

Self-sensing and thermal energy experimental characterization of multifunctional cement-matrix composites with carbon nano-inclusions

NASA Astrophysics Data System (ADS)

D'Alessandro, A.; Pisello, A. L.; Sambuco, Sara; Ubertini, F.; Asdrubali, F.; Materazzi, A. L.; Cotana, F.

2016-04-01

The recent progress of Nanotechnology allowed the development of new smart materials in several fields of engineering. In particular, innovative construction materials with multifunctional enhanced properties can be produced. The paper presents an experimental characterization on cement-matrix pastes doped with Carbon Nanotubes, Carbon Nano-fibers, Carbon Black and Graphene Nano-platelets. Both electro-mechanical and thermo-physical investigations have been carried out. The conductive nano-inclusions provide the cementitious matrix with piezo-resistive properties allowing the detection of external strain and stress changes. Thereby, traditional building materials, such as concrete and cementitious materials in general, would be capable of self-monitoring the state of deformation they are subject to, giving rise to diffuse sensing systems of structural integrity. Besides supplying self-sensing abilities, carbon nano-fillers may change mechanical, physical and thermal properties of cementitious composites. The experimental tests of the research have been mainly concentrated on the thermal conductivity and the optical properties of the different nano-modified materials, in order to make a critical comparison between them. The aim of the work is the characterization of an innovative multifunctional composite capable of combining self-monitoring properties with proper mechanical and thermal-energy efficiency characteristics. The potential applications of these nano-modified materials cover a wide range of possibilities, such as structural elements, floors, geothermal piles, radiant systems and more.

A General Bioinspired, Metals-Based Synergic Cross-Linking Strategy toward Mechanically Enhanced Materials.

PubMed

Chen, Ke; Ding, Jin; Zhang, Shuhao; Tang, Xuke; Yue, Yonghai; Guo, Lin

2017-03-28

Creating lightweight engineering materials combining high strength and great toughness remains a significant challenge. Despite possessing-enhanced strength and stiffness, bioinspired/polymeric materials usually suffer from clearly reduced extensibility and toughness when compared to corresponding bulk polymer materials. Herein, inspired by tiny amounts of various inorganic impurities for mechanical improvement in natural materials, we present a versatile and effective metal ion (M n+ )-based synergic cross-linking (MSC) strategy incorporating eight types of metal ions into material bulks that can drastically enhance the tensile strength (∼24.1-70.8%), toughness (∼18.6-110.1%), modulus (∼21.6-66.7%), and hardness (∼6.4-176.5%) of multiple types of pristine materials (from hydrophilic to hydrophobic and from unary to binary). More importantly, we also explore the primarily elastic-plastic deformation mechanism and brittle fracture behavior (indentation strain of >5%) of the synergic cross-linked graphene oxide (Syn-GO) paper by means of in situ nanoindentation SEM. The MSC strategy for mechanically enhanced integration can be readily attributed to the formation of the complicated metals-based cross-linking/complex networks in the interfaces and intermolecules between functional groups of materials and various metal ions that give rise to efficient energy dissipation. This work suggests a promising MSC strategy for designing advanced materials with outstanding mechanical properties by adding low amounts (<1.0 wt %) of synergic metal ions serving as synergic ion-bonding cross-linkers.

Dynamic characterization of high damping viscoelastic materials from vibration test data

NASA Astrophysics Data System (ADS)

Martinez-Agirre, Manex; Elejabarrieta, María Jesús

2011-08-01

The numerical analysis and design of structural systems involving viscoelastic damping materials require knowledge of material properties and proper mathematical models. A new inverse method for the dynamic characterization of high damping and strong frequency-dependent viscoelastic materials from vibration test data measured by forced vibration tests with resonance is presented. Classical material parameter extraction methods are reviewed; their accuracy for characterizing high damping materials is discussed; and the bases of the new analysis method are detailed. The proposed inverse method minimizes the residue between the experimental and theoretical dynamic response at certain discrete frequencies selected by the user in order to identify the parameters of the material constitutive model. Thus, the material properties are identified in the whole bandwidth under study and not just at resonances. Moreover, the use of control frequencies makes the method insensitive to experimental noise and the efficiency is notably enhanced. Therefore, the number of tests required is drastically reduced and the overall process is carried out faster and more accurately. The effectiveness of the proposed method is demonstrated with the characterization of a CLD (constrained layer damping) cantilever beam. First, the elastic properties of the constraining layers are identified from the dynamic response of a metallic cantilever beam. Then, the viscoelastic properties of the core, represented by a four-parameter fractional derivative model, are identified from the dynamic response of a CLD cantilever beam.

Applications of fibrous substrates containing insolubilized phase change polymers

NASA Technical Reports Server (NTRS)

Vigo, Tyrone L.; Bruno, Joseph S.

1993-01-01

Incorporation of polyethylene glycols into fibrous substrates produces several improved functional properties when they are insolubilized by crosslinking with a methylolamide resin or by polyacetal formation by their reaction with glyoxal. The range of molecular weights of polyols that may be insolubilized is broad as are the curing conditions (0.25-10 min at 80-200C). Most representative fiber types and blends (natural and synthetic) and all types of fabric constructions (woven, nonwoven and knit) have been modified by incorporation of the bound polyols. The most novel property is the thermal adaptability of the modified substrates to many climatic conditions. This adaptability is due to the high latent heat of the crosslinked polyols that function as phase change materials, the hydrophilic nature of the crosslinked polymer and its enhanced thermal conductivity. Other enhanced properties imparted to fabrics include flex and flat abrasion, antimicrobial activity, reduced static charge, resistance to oily soils, resiliency, wind resistance and reduced lint loss. Applications commercialized in the U.S. and Japan include sportswear and skiwear. Several examples of electric sets of properties useful for specific end uses are given. In addition, other uses are biomedical horticultural, aerospace, indoor insulation, automotive interiors and components and packaging material.

Applications of fibrous substrates containing insolubilized phase change polymers

NASA Astrophysics Data System (ADS)

Vigo, Tyrone L.; Bruno, Joseph S.

1993-02-01

Incorporation of polyethylene glycols into fibrous substrates produces several improved functional properties when they are insolubilized by crosslinking with a methylolamide resin or by polyacetal formation by their reaction with glyoxal. The range of molecular weights of polyols that may be insolubilized is broad as are the curing conditions (0.25-10 min at 80-200C). Most representative fiber types and blends (natural and synthetic) and all types of fabric constructions (woven, nonwoven and knit) have been modified by incorporation of the bound polyols. The most novel property is the thermal adaptability of the modified substrates to many climatic conditions. This adaptability is due to the high latent heat of the crosslinked polyols that function as phase change materials, the hydrophilic nature of the crosslinked polymer and its enhanced thermal conductivity. Other enhanced properties imparted to fabrics include flex and flat abrasion, antimicrobial activity, reduced static charge, resistance to oily soils, resiliency, wind resistance and reduced lint loss. Applications commercialized in the U.S. and Japan include sportswear and skiwear. Several examples of electric sets of properties useful for specific end uses are given. In addition, other uses are biomedical horticultural, aerospace, indoor insulation, automotive interiors and components and packaging material.

Review on the Processing and Properties of Polymer Nanocomposites and Nanocoatings and Their Applications in the Packaging, Automotive and Solar Energy Fields

PubMed Central

Müller, Kerstin; Bugnicourt, Elodie; Latorre, Marcos; Jorda, Maria; Echegoyen Sanz, Yolanda; Lagaron, José M.; Miesbauer, Oliver; Bianchin, Alvise; Hankin, Steve; Bölz, Uwe; Pérez, Germán; Jesdinszki, Marius; Lindner, Martina; Scheuerer, Zuzana; Castelló, Sara; Schmid, Markus

2017-01-01

For the last decades, nanocomposites materials have been widely studied in the scientific literature as they provide substantial properties enhancements, even at low nanoparticles content. Their performance depends on a number of parameters but the nanoparticles dispersion and distribution state remains the key challenge in order to obtain the full nanocomposites’ potential in terms of, e.g., flame retardance, mechanical, barrier and thermal properties, etc., that would allow extending their use in the industry. While the amount of existing research and indeed review papers regarding the formulation of nanocomposites is already significant, after listing the most common applications, this review focuses more in-depth on the properties and materials of relevance in three target sectors: packaging, solar energy and automotive. In terms of advances in the processing of nanocomposites, this review discusses various enhancement technologies such as the use of ultrasounds for in-process nanoparticles dispersion. In the case of nanocoatings, it describes the different conventionally used processes as well as nanoparticles deposition by electro-hydrodynamic processing. All in all, this review gives the basics both in terms of composition and of processing aspects to reach optimal properties for using nanocomposites in the selected applications. As an outlook, up-to-date nanosafety issues are discussed. PMID:28362331

Review on the Processing and Properties of Polymer Nanocomposites and Nanocoatings and Their Applications in the Packaging, Automotive and Solar Energy Fields.

PubMed

Müller, Kerstin; Bugnicourt, Elodie; Latorre, Marcos; Jorda, Maria; Echegoyen Sanz, Yolanda; Lagaron, José M; Miesbauer, Oliver; Bianchin, Alvise; Hankin, Steve; Bölz, Uwe; Pérez, Germán; Jesdinszki, Marius; Lindner, Martina; Scheuerer, Zuzana; Castelló, Sara; Schmid, Markus

2017-03-31

For the last decades, nanocomposites materials have been widely studied in the scientific literature as they provide substantial properties enhancements, even at low nanoparticles content. Their performance depends on a number of parameters but the nanoparticles dispersion and distribution state remains the key challenge in order to obtain the full nanocomposites' potential in terms of, e.g., flame retardance, mechanical, barrier and thermal properties, etc., that would allow extending their use in the industry. While the amount of existing research and indeed review papers regarding the formulation of nanocomposites is already significant, after listing the most common applications, this review focuses more in-depth on the properties and materials of relevance in three target sectors: packaging, solar energy and automotive. In terms of advances in the processing of nanocomposites, this review discusses various enhancement technologies such as the use of ultrasounds for in-process nanoparticles dispersion. In the case of nanocoatings, it describes the different conventionally used processes as well as nanoparticles deposition by electro-hydrodynamic processing. All in all, this review gives the basics both in terms of composition and of processing aspects to reach optimal properties for using nanocomposites in the selected applications. As an outlook, up-to-date nanosafety issues are discussed.

The Effect of Water Molecules on Mechanical Properties of Cell Walls

NASA Astrophysics Data System (ADS)

Rahbar, Nima; Youssefian, Sina

The unique properties of bamboo fibers come from their natural composite structures that comprise mainly cellulose nanofibrils in a matrix of intertwined hemicellulose and lignin called lignin-carbohydrate complex (LCC). Here, we have utilized atomistic simulations to investigate the mechanical properties and mechanisms of interactions between these materials, in the presence of water molecules. The role of hemicellulose found to be enhancing the mechanical properties and lignin found to be providing the strength of bamboo fibers. The abundance of Hbonds in hemicellulose chains is responsible for improving the mechanical behavior of LCC. The strong van der Waals forces between lignin molecules and cellulose nanofibrils are responsible for higher adhesion energy between LCC/cellulose nanofibrils. We also found out that the amorphous regions of cellulose nanofibrils is the weakest interface in bamboo Microfibrils. In presence of water, the elastic modulus of lignin increases at low water content and decreases in higher water content, whereas the hemicellulose elastic modulus constantly decreases. The variations of Radial Distribution Function and Free Fractional Volume of these materials with water suggest that water molecules enhance the mechanical properties of lignin by filling voids in the system and creating Hbond bridges between polymer chains. For hemicellulose, however, the effect is always regressive due to the destructive effect of water molecules on the Hbond of its dense structure.

Polymer photovoltaics with alternating copolymer/fullerene blends and novel device architectures.

PubMed

Inganäs, Olle; Zhang, Fengling; Tvingstedt, Kristofer; Andersson, Lars Mattias; Hellström, Stefan; Andersson, Mats R

2010-05-25

The synthesis of novel conjugated polymers, designed for the purpose of photovoltaic energy conversion, and their properties in polymer/fullerene materials and photovoltaic devices are reviewed. Two families of main-chain polymer donors, based on fluorene or phenylene and donor-acceptor-donor comonomers in alternating copolymers, are used to absorb the high-energy parts of the solar spectrum and to give high photovoltages in combinations with fullerene acceptors in devices. These materials are used in alternative photovoltaic device geometries with enhanced light incoupling to collect larger photocurrents or to enable tandem devices and enhance photovoltage.

Composite scintillators for detection of ionizing radiation

DOEpatents

Dai, Sheng [Knoxville, TN; Stephan, Andrew Curtis [Knoxville, TN; Brown, Suree S [Knoxville, TN; Wallace, Steven A [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

2010-12-28

Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

Enhanced microwave absorption properties of CTAB assisted Pr-Cu substituted nanomaterial

NASA Astrophysics Data System (ADS)

Sadiq, Imran; Naseem, Shahzad; Riaz, Saira; Khan, Hasan M.; Ashiq, Muhammad Naeem; Hussain, S. Sajjad; Rana, Mazhar

2016-09-01

In this study, the rare earth Pr3+and divalent Cu2+ elements substituted Sr1-xPrxMn2Fe16-yCuyO27 (x=0, 0.02, 0.06, 0.1 and y=0, 0.1, 0.3, 0.5) W-type hexagonal ferrites were prepared by Sol-Gel method. TGA and DSC analysis of as prepared material was carried out to confirm the temperature at which required phase can be obtained. The XRD patterns exhibit the single phase for all the samples and the lattice parameters were changed with the additives. The absorption bands at wave number 636 and 554 cm-1 in FTIR spectrum indicate the stretching vibration of metal-oxygen ions which also ratifies the single phase for the prepared material. Microstructural analysis confirms the agglomeration of nanograins which leads to formation of platelet like structure which cause in the enhancement of the microwave absorption properties of material. The minimum reflection loss of -59.8 dB at 9.34 GHz frequency was observed makes the prepared material good candidate to be used in super high frequency application. The attenuation constant and reflectivity results are also in good agreement with minimum reflection losses results.

Electrostatic Assembly of Nanomaterials for Hybrid Electrodes and Supercapacitors

NASA Astrophysics Data System (ADS)

Hammond, Paula

2015-03-01

Electrostatic assembly methods have been used to generate a range of new materials systems of interest for electrochemical energy and storage applications. Over the past several years, it has been demonstrated that carbon nanotubes, metals, metal oxides, polymeric nanomaterials, and biotemplated materials systems can be incorporated into ultrathin films to generate supercapacitors and battery electrodes that illustrate significant energy density and power. The unique ability to control the incorporation of such a broad range of materials at the nanometer length scale allows tailoring of the final properties of these unique composite systems, as well as the capability of creating complex micron-scale to nanoporous morphologies based on the scale of the nanomaterial that is absorbed within the structure, or the conditions of self-assembly. Recently we have expanded these capabilities to achieve new electrodes that are templated atop electrospun polmer fiber scaffolds, in which the polymer can be selectively removed to achieve highly porous materials. Spray-layer-by-layer and filtration methods of functionalized multiwall carbon nanotubes and polyaniline nanofibers enable the generation of electrode systems with unusually high surface. Incorporation of psuedocapacitive nanoparticles can enhance capacitive properties, and other catalytic or metallic nanoparticles can be implemented to enhance electrochemical or catalytic function.

Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

DOE PAGES

Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; ...

2015-05-01

The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS 2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonantmore » photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.« less

Nanocomposites biodegradable coating on BOPET films to enhance hot seal strength properties

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

Barbaro, G., E-mail: giovannibarbaro@email.it; Galdi, M. R., E-mail: mrgaldi@unisa.it; Di Maio, L., E-mail: ldimaio@unisa.it

2015-12-17

The coating technology is a strategic solution to improve the properties of flexible packaging films. Indeed, additional functional layers are often designed and added as coating on the substrate, in order to improve the characteristic of the flexible packaging and to meet the requirements for the desired gas or vapour barrier, for adhesion and sealing, or for improving the film printability, its aesthetics and durability. Moreover, this technology allows to functionalize a polymeric substrate applying materials with different chemistry, rheology, thermal and structural characteristics. BOPET films are widely used for food packaging applications thanks to their good gas barrier andmore » mechanical properties, high transparency and for the excellent printability. In regard to sealing performance, BOPET films show poor sealing properties so they are mostly submitted to lamination processes with polyethylene. Nevertheless, this solution compromises the PET recyclability and influences the gas permeability of the multilayer PET based structures. The aim of this work is to investigate on the effect of nanocomposite biodegradable coatings for BOPET substrates in enhancing the heat sealing strength of eco-compatible PET/PLA films. At this regards, different percentages of Cloisite C30B (0%, 2% and 4%{sub wt/wt}) have been added to PLA by solution intercalation technique and the nanocomposite biodegradable materials produced have been applied on BOPET commercial films by casting. The BOPET coated films have been characterized in order to evaluate the heat sealing strength and the mechanical, gas permeability and surface properties. The results have shown that the addition of nanoclay in PLA coating significantly enhance the hot tack properties of the PET/PLA system produced, while the oxygen and water vapour permeability are slightly increased if compared to pure BOPET films.« less

Nanocomposites biodegradable coating on BOPET films to enhance hot seal strength properties

NASA Astrophysics Data System (ADS)

Barbaro, G.; Galdi, M. R.; Di Maio, L.; Incarnato, L.

2015-12-01

The coating technology is a strategic solution to improve the properties of flexible packaging films. Indeed, additional functional layers are often designed and added as coating on the substrate, in order to improve the characteristic of the flexible packaging and to meet the requirements for the desired gas or vapour barrier, for adhesion and sealing, or for improving the film printability, its aesthetics and durability. Moreover, this technology allows to functionalize a polymeric substrate applying materials with different chemistry, rheology, thermal and structural characteristics. BOPET films are widely used for food packaging applications thanks to their good gas barrier and mechanical properties, high transparency and for the excellent printability. In regard to sealing performance, BOPET films show poor sealing properties so they are mostly submitted to lamination processes with polyethylene. Nevertheless, this solution compromises the PET recyclability and influences the gas permeability of the multilayer PET based structures. The aim of this work is to investigate on the effect of nanocomposite biodegradable coatings for BOPET substrates in enhancing the heat sealing strength of eco-compatible PET/PLA films. At this regards, different percentages of Cloisite C30B (0%, 2% and 4%wt/wt) have been added to PLA by solution intercalation technique and the nanocomposite biodegradable materials produced have been applied on BOPET commercial films by casting. The BOPET coated films have been characterized in order to evaluate the heat sealing strength and the mechanical, gas permeability and surface properties. The results have shown that the addition of nanoclay in PLA coating significantly enhance the hot tack properties of the PET/PLA system produced, while the oxygen and water vapour permeability are slightly increased if compared to pure BOPET films.

Towards Rational Design of Functional Fluoride and Oxyfluoride Materials from First Principles

NASA Astrophysics Data System (ADS)

Charles, Nenian

Complex transition metal compounds (TMCs) research has produced functional materials with a range of properties, including ferroelectricity, colossal magnetoresistance, nonlinear optical activity and high-temperature superconductivity. Conventional routes to tune properties in transition metal oxides, for example, have relied primarily on cation chemical substitution and interfacial effects in thin film heterostructures. In heteroanionic TMCs, exhibiting two chemically distinct anions coordinating the same or different cations, engineering of the anion sub-lattice for property control is a promising alternative approach. The presence of multiple anions provides additional design variables, such as anion order, that are absent in homoanionic counterparts. The more complex structural and chemical phase space of heteroanionic materials provides a unique opportunity to realize enhanced or unanticipated electronic, optical, and magnetic responses. Although there is growing interest in heteroanionic materials, and synthetic and characterization advances are occurring for these materials, the crystal-chemistry principles for realizing structural and property control are only slowing emerging. This dissertation employs anion engineering to investigate phenomena in transition metal fluorides and oxyfluorides compounds using first principles density functional theory calculations. Oxyfluorides are particularly intriguing owing their tendency to stabilize highly ordered anion sublattices as well as the potential to combine the advantageous properties of transition metal oxides and fluorides. This work 1) addresses the challenges of studying fluorides and oxyfluorides using first principles calculations; 2) evaluates the feasibility of using external stimuli, such as epitaxial strain and hydrostatic pressure, to control properties of fluorides and oxyfluorides; and 3) formulates a computational workflow based on multiple levels of theory and computation to elucidate structure-property relationships and anion-order descriptors. The insights gained in this work advance the understanding of oxide-fluoride anion engineered materials and we anticipate that it will motivate novel experimental efforts and materials by design in the future.

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

Takaki, Hirokazu; Kobayashi, Kazuaki; Shimono, Masato

We present the thermoelectric properties of TiN/MgO superlattices employing first-principles calculation techniques. The Seebeck coefficients, the electrical conductances, the thermal conductances, and the figure of merit are investigated employing electrical and thermal transport calculations based on density functional theory combined with the nonequilibrium Green's function and nonequilibrium molecular dynamics simulation methods. The TiN/MgO superlattices with a small lattice mismatch at the interfaces are ideal systems to study the way for an enhancement of thermoelectric properties in artificial nanostructures. We find that the interfacial scattering between the two materials in the metal/insulator superlattices causes the electrical conductance to change rapidly, whichmore » enhances the Seebeck coefficient significantly. We show that the figure of merit for the artificial superlattice nanostructures has a much larger value compared with that of the bulk material and changes drastically with the superlattice configurations at the atomistic level.« less

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

DOE PAGES

Garg, Aaron; Milina, Maria; Ball, Madelyn; ...

2017-05-25

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

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

Garg, Aaron; Milina, Maria; Ball, Madelyn

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Theory and design of nonlinear metamaterials

NASA Astrophysics Data System (ADS)

Rose, Alec Daniel

If electronics are ever to be completely replaced by optics, a significant possibility in the wake of the fiber revolution, it is likely that nonlinear materials will play a central and enabling role. Indeed, nonlinear optics is the study of the mechanisms through which light can change the nature and properties of matter and, as a corollary, how one beam or color of light can manipulate another or even itself within such a material. However, of the many barriers preventing such a lofty goal, the narrow and limited range of properties supported by nonlinear materials, and natural materials in general, stands at the forefront. Many industries have turned instead to artificial and composite materials, with homogenizable metamaterials representing a recent extension of such composites into the electromagnetic domain. In particular, the inclusion of nonlinear elements has caused metamaterials research to spill over into the field of nonlinear optics. Through careful design of their constituent elements, nonlinear metamaterials are capable of supporting an unprecedented range of interactions, promising nonlinear devices of novel design and scale. In this context, I cast the basic properties of nonlinear metamaterials in the conventional formalism of nonlinear optics. Using alternately transfer matrices and coupled mode theory, I develop two complementary methods for characterizing and designing metamaterials with arbitrary nonlinear properties. Subsequently, I apply these methods in numerical studies of several canonical metamaterials, demonstrating enhanced electric and magnetic nonlinearities, as well as predicting the existence of nonlinear magnetoelectric and off-diagonal nonlinear tensors. I then introduce simultaneous design of the linear and nonlinear properties in the context of phase matching, outlining five different metamaterial phase matching methods, with special emphasis on the phase matching of counter propagating waves in mirrorless parametric amplifiers and oscillators. By applying this set of tools and knowledge to microwave metamaterials, I experimentally confirm several novel nonlinear phenomena. Most notably, I construct a backward wave nonlinear medium from varactor-loaded split ring resonators loaded in a rectangular waveguide, capable of generating second-harmonic opposite to conventional nonlinear materials with a conversion efficiency as high as 1.5%. In addition, I confirm nonlinear magnetoelectric coupling in two dual gap varactor-loaded split ring resonator metamaterials through measurement of the amplitude and phase of the second-harmonic generated in the forward and backward directions from a thin slab. I then use the presence of simultaneous nonlinearities in such metamaterials to observe nonlinear interference, manifest as unidirectional difference frequency generation with contrasts of 6 and 12 dB in the forward and backward directions, respectively. Finally, I apply these principles and intuition to several plasmonic platforms with the goal of achieving similar enhancements and configurations at optical frequencies. Using the example of fluorescence enhancement in optical patch antennas, I develop a semi-classical numerical model for the calculation of field-induced enhancements to both excitation and spontaneous emission rates of an embedded fluorophore, showing qualitative agreement with experimental results, with enhancement factors of more than 30,000. Throughout these series of works, I emphasize the indispensability of effective design and retrieval tools in understanding and optimizing both metamaterials and plasmonic systems. Ultimately, when weighed against the disadvantages in fabrication and optical losses, the results presented here provide a context for the application of nonlinear metamaterials within three distinct areas where a competitive advantage over conventional materials might be obtained: fundamental science demonstrations, linear and nonlinear anisotropy engineering, and extremely compact resonant all-optical devices.

Developing a Sealing Material: Effect of Epoxy Modification on Specific Physical and Mechanical Properties

PubMed Central

Schoberleitner, Christoph; Archodoulaki, Vasiliki-Maria; Koch, Thomas; Lüftl, Sigrid; Werderitsch, Markus; Kuschnig, Gerhard

2013-01-01

To develop a matched sealing material for socket rehabilitation of grey cast iron pipes, an epoxy resin is modified by the addition of different components to improve the flexibility. Three different modifications are made by adding ethylene-propylene diene monomer (EPDM) rubber powder, reactive liquid polymer (ATBN) and epoxidized modifier. In this paper the effect of the modification method as well as the influence of absorption of water on the mechanical and physical properties are analyzed in terms of: tensile strength, modulus of elasticity, adhesion performance, pressure resistance, glass transition temperature and water content. A comparison with neat epoxy shows for all materials that the modulus of elasticity and strength decrease. Unlike other tested modification methods, the modification with rubber powder did not enhance the flexibility. All materials absorb water and a plasticization effect arises with further changes of mechanical and physical properties. The application of the sealant on the grey cast iron leads to a reduction of the strain at break (in comparison to the common tensile test of the pure materials) and has to be evaluated. The main requirement of pressure resistance up to 1 MPa was tested on two chosen materials. Both materials fulfill this requirement. PMID:28788404

Developing a Sealing Material: Effect of Epoxy Modification on Specific Physical and Mechanical Properties.

PubMed

Schoberleitner, Christoph; Archodoulaki, Vasiliki-Maria; Koch, Thomas; Lüftl, Sigrid; Werderitsch, Markus; Kuschnig, Gerhard

2013-11-27

To develop a matched sealing material for socket rehabilitation of grey cast iron pipes, an epoxy resin is modified by the addition of different components to improve the flexibility. Three different modifications are made by adding ethylene-propylene diene monomer (EPDM) rubber powder, reactive liquid polymer (ATBN) and epoxidized modifier. In this paper the effect of the modification method as well as the influence of absorption of water on the mechanical and physical properties are analyzed in terms of: tensile strength, modulus of elasticity, adhesion performance, pressure resistance, glass transition temperature and water content. A comparison with neat epoxy shows for all materials that the modulus of elasticity and strength decrease. Unlike other tested modification methods, the modification with rubber powder did not enhance the flexibility. All materials absorb water and a plasticization effect arises with further changes of mechanical and physical properties. The application of the sealant on the grey cast iron leads to a reduction of the strain at break (in comparison to the common tensile test of the pure materials) and has to be evaluated. The main requirement of pressure resistance up to 1 MPa was tested on two chosen materials. Both materials fulfill this requirement.

Acousto-Optic and Linear Electro-Optic Properties of Organic Polymeric Materials

DTIC Science & Technology

1989-04-27

Naval Research Laboratory Washington, DC 20375-5000 NRL Memorandum Report 6454 od I3 Acousto - Optic and Linear Electro-Optic Properties of Organic...PROGRAM P1RC;EC7 ASK Arlington, VA 22217-5000 ELEMENT NO NO1 I1I TITLE (Include Security Classification) Acousto - Optic and Linear Electro-Optic...briefly discussing the important molecular properties for enhanced acousto ~ optic and electro-Ooptic ef fects and then relating these to "current

Enhancement of Local Piezoresponse in Polymer Ferroelectrics via Nanoscale Control of Microstructure

DOE PAGES

Choi, Yoon-Young; Sharma, Pankaj; Phatak, Charudatta; ...

2015-02-01

Polymer ferroelectrics are flexible and lightweight electromechanical materials that are widely studied due to their potential application as sensors, actuators, and energy harvesters. However, one of the biggest challenges is their low piezoelectric coefficient. Here, we report a mechanical annealing effect based on local pressure induced by a nanoscale tip that enhances the local piezoresponse. This process can control the nanoscale material properties over a microscale area at room temperature. We attribute this improvement to the formation and growth of beta-phase extended chain crystals via sliding diffusion and crystal alignment along the scan axis under high mechanical stress. We believemore » that this technique can be useful for local enhancement of piezoresponse in ferroelectric polymer thin films.« less

Experimental and numerical investigation on cladding of corrosion-erosion resistant materials by a high power direct diode laser

NASA Astrophysics Data System (ADS)

Farahmand, Parisa

In oil and gas industry, soil particles, crude oil, natural gas, particle-laden liquids, and seawater can carry various highly aggressive elements, which accelerate the material degradation of component surfaces by combination of slurry erosion, corrosion, and wear mechanisms. This material degradation results into the loss of mechanical properties such as strength, ductility, and impact strength; leading to detachment, delamination, cracking, and ultimately premature failure of components. Since the failure of high valued equipment needs considerable cost and time to be repaired or replaced, minimizing the tribological failure of equipment under aggressive environment has been gaining increased interest. It is widely recognized that effective management of degradation mechanisms will contribute towards the optimization of maintenance, monitoring, and inspection costs. The hardfacing techniques have been widely used to enhance the resistance of surfaces against degradation mechanisms. Applying a surface coating improves wear and corrosion resistance and ensures reliability and long-term performance of coated parts. A protective layer or barrier on the components avoids the direct mechanical and chemical contacts of tool surfaces with process media and will reduce the material loss and ultimately its failure. Laser cladding as an advanced hardfacing technique has been widely used for industrial applications in order to develop a protective coating with desired material properties. During the laser cladding, coating material is fused into the base material by means of a laser beam in order to rebuild a damaged part's surface or to enhance its surface function. In the hardfacing techniques such as atmospheric plasma spraying (APS), high velocity oxygen-fuel (HVOF), and laser cladding, mixing of coating materials with underneath surface has to be minimized in order to utilize the properties of the coating material most effectively. In this regard, laser cladding offers advantages due to creating coating layers with superior properties in terms of purity, homogeneity, low dilution, hardness, bonding, and microstructure. In the development of modern materials for hardfacing applications, the functionality is often improved by combining materials with different properties into composites. Metal Matrix Composite (MMC) coating is a composite material with two constituent parts, i.e., matrix and the reinforcement. This class of composites are addressing improved mechanical properties such as stiffness, strength, toughness, and tribological and chemical resistance. Fabrication of MMCs is to achieve a combination of properties not achievable by any of the materials acting alone. MMCs have attracted significant attention for decades due to their combination of wear-resistivity, corrosion-resistivity, thermal, electrical and magnetic properties. Presently, there is a strong emphasis on the development of advanced functional coatings for corrosion, erosion, and wear protection for different industrial applications. In this research, a laser cladding system equipped with a high power direct diode laser associated with gas driven metal powder delivery system was used to develop advanced MMC coatings. The high power direct diode laser used in this study offers wider beam spot, shorter wavelength and uniform power distribution. These properties make the cladding set-up ideal for coating due to fewer cladding tracks, lower operation cost, higher laser absorption, and improved coating qualities. In order to prevent crack propagation, porosity, and uniform dispersion of carbides in MMC coating, cladding procedure was assisted by an induction heater as a second heat source. The developed defect free MMC coatings were combined with nano-size particles of WC, rare earth (RE) element (La2O3), and Mo as a refractory metal to enhance mechanical properties, chemical composition, and subsequently improve the tribological performance of the coatings. The resistance of developed MMC coatings were examined under highly accelerated slurry erosion, corrosion, and wear as the most frequently encountered failure modes of mechanical components. The microstructure, mechanical properties, and the level of induced residual stress on the coating after cladding procedure are closely related to cladding process variables. Study about the effect of processing parameters on clad quality and experienced thermal history and thermally-induced stress evolution requires both theoretical and experimental understanding of the associated physical phenomena. Numerical modeling offers a cost-efficient way to better understand the related complex physics in laser cladding process. It helps to reveal the effects and significance of each processing parameters on the desired characteristics of clad parts. Successful numerical simulation can provide unique insight into complex laser cladding process, efficiently calculate the complex procedure, and help to obtain coating parts with quality integrity. Therefore, current study develops a three-dimensional (3D) transient and uncoupled thermo-elastic-plastic model to study thermal history, molten pool evolution, thermally induced residual stress, and the effect of utilizing an induction heater as a second heat source on the mechanical properties and microstructural properties of final cladded coating.

Recent Prospects in the Inline Monitoring of Nanocomposites and Nanocoatings by Optical Technologies.

PubMed

Bugnicourt, Elodie; Kehoe, Timothy; Latorre, Marcos; Serrano, Cristina; Philippe, Séverine; Schmid, Markus

2016-08-19

Nanostructured materials have emerged as a key research field in order to confer materials with unique or enhanced properties. The performance of nanocomposites depends on a number of parameters, but the suitable dispersion of nanoparticles remains the key in order to obtain the full nanocomposites' potential in terms of, e.g., flame retardance, mechanical, barrier, thermal properties, etc. Likewise, the performance of nanocoatings to obtain, for example, tailored surface affinity with selected liquids (e.g., for self-cleaning ability or anti-fog properties), protective effects against flame propagation, ultra violet (UV) radiation or gas permeation, is highly dependent on the nanocoating's thickness and homogeneity. In terms of recent advances in the monitoring of nanocomposites and nanocoatings, this review discusses commonly-used offline characterization approaches, as well as promising inline systems. All in all, having good control over both the dispersion and thickness of these materials would help with reaching optimal and consistent properties to allow nanocomposites to extend their use.

Recent Prospects in the Inline Monitoring of Nanocomposites and Nanocoatings by Optical Technologies

PubMed Central

Bugnicourt, Elodie; Kehoe, Timothy; Latorre, Marcos; Serrano, Cristina; Philippe, Séverine; Schmid, Markus

2016-01-01

Nanostructured materials have emerged as a key research field in order to confer materials with unique or enhanced properties. The performance of nanocomposites depends on a number of parameters, but the suitable dispersion of nanoparticles remains the key in order to obtain the full nanocomposites’ potential in terms of, e.g., flame retardance, mechanical, barrier, thermal properties, etc. Likewise, the performance of nanocoatings to obtain, for example, tailored surface affinity with selected liquids (e.g., for self-cleaning ability or anti-fog properties), protective effects against flame propagation, ultra violet (UV) radiation or gas permeation, is highly dependent on the nanocoating’s thickness and homogeneity. In terms of recent advances in the monitoring of nanocomposites and nanocoatings, this review discusses commonly-used offline characterization approaches, as well as promising inline systems. All in all, having good control over both the dispersion and thickness of these materials would help with reaching optimal and consistent properties to allow nanocomposites to extend their use. PMID:28335278

Superconductivity Devices: Commercial Use of Space

NASA Technical Reports Server (NTRS)

Haertling, Gene (Principal Investigator); Furman, Eugene; Li, Guang

1996-01-01

The work described in this report covers various aspects of the Rainbow solid-state actuator and sensor technologies. It is presented in five parts dealing with sensor applications, nonlinear properties, stress-optic and electrooptic properties, stacks and arrays, and publications. The Rainbow actuator technology is a relatively new materials development which had its inception in 1992. It involves a new processing technique for preparing pre-stressed, high lead containing piezoelectric and electrostrictive ceramic materials. Ceramics fabricated by this method produce bending-mode actuator devices which possess several times more displacement and load bearing capacity than present-day benders. Since they can also be used in sensor applications, Rainbows are part of the family of materials known as smart ceramics. During this period, PLZT Rainbow ceramics were characterized with respect to their piezoelectric properties for potential use in stress sensor applications. Studies of the nonlinear and stress-optic/electrooptic birefringent properties were also initiated during this period. Various means for increasing the utility of stress-enhanced Rainbow actuators are presently under investigation.

Surface Preparation Methods to Enhance Dynamic Surface Property Measurements of Shocked Metal Surfaces

NASA Astrophysics Data System (ADS)

Zellner, Michael; McNeil, Wendy; Gray, George, III; Huerta, David; King, Nicholas; Neal, George; Payton, Jeremy; Rubin, Jim; Stevens, Gerald; Turley, William; Buttler, William

2008-03-01

This effort investigates surface-preparation methods to enhance dynamic surface-property measurements of shocked metal surfaces. To assess the ability of making reliable and consistent dynamic surface-property measurements, the amount of material ejected from the free-surface upon shock release to vacuum (ejecta) was monitored for shocked Al-1100 and Sn targets. Four surface preparation methods were considered: fly-cut machined finish, diamond-turned machine finish, polished finish, and ball-rolled. The samples were shock loaded by in-contact detonation of HE PBX-9501 on the front-side of the metal coupons. Ejecta production at the back-side or free-side of the metal coupons was monitored using piezoelectric pins, optical shadowgraphy, and x-ray attenuation radiography.

Surface preparation methods to enhance dynamic surface property measurements of shocked metal surfaces

NASA Astrophysics Data System (ADS)

Zellner, M. B.; Vogan McNeil, W.; Gray, G. T.; Huerta, D. C.; King, N. S. P.; Neal, G. E.; Valentine, S. J.; Payton, J. R.; Rubin, J.; Stevens, G. D.; Turley, W. D.; Buttler, W. T.

2008-04-01

This effort investigates surface-preparation methods to enhance dynamic surface-property measurements of shocked metal surfaces. To assess the ability of making reliable and consistent dynamic surface-property measurements, the amount of material ejected from the free surface upon shock release to vacuum (ejecta) was monitored for shocked Al-1100 and Sn targets. Four surface-preparation methods were considered: Fly-cut machine finish, diamond-turned machine finish, polished finish, and ball rolled. The samples were shock loaded by in-contact detonation of HE PBX-9501 on the front side of the metal coupons. Ejecta production at the back side or free side of the metal coupons was monitored using piezoelectric pins, optical shadowgraphy, and x-ray attenuation radiography.

Giant Ferroelectric Polarization in Ultrathin Ferroelectrics via Boundary-Condition Engineering.

PubMed

Xie, Lin; Li, Linze; Heikes, Colin A; Zhang, Yi; Hong, Zijian; Gao, Peng; Nelson, Christopher T; Xue, Fei; Kioupakis, Emmanouil; Chen, Longqing; Schlom, Darrel G; Wang, Peng; Pan, Xiaoqing

2017-08-01

Tailoring and enhancing the functional properties of materials at reduced dimension is critical for continuous advancement of modern electronic devices. Here, the discovery of local surface induced giant spontaneous polarization in ultrathin BiFeO 3 ferroelectric films is reported. Using aberration-corrected scanning transmission electron microscopy, it is found that the spontaneous polarization in a 2 nm-thick ultrathin BiFeO 3 film is abnormally increased up to ≈90-100 µC cm -2 in the out-of-plane direction and a peculiar rumpled nanodomain structure with very large variation in c/a ratios, which is analogous to morphotropic phase boundaries (MPBs), is formed. By a combination of density functional theory and phase-field calculations, it is shown that it is the unique single atomic Bi 2 O 3 - x layer at the surface that leads to the enhanced polarization and appearance of the MPB-like nanodomain structure. This finding clearly demonstrates a novel route to the enhanced functional properties in the material system with reduced dimension via engineering the surface boundary conditions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant halide perovskite nanoparticles

NASA Astrophysics Data System (ADS)

Tiguntseva, Ekaterina Y.; Ishteev, Arthur R.; Komissarenko, Filipp E.; Zuev, Dmitry A.; Ushakova, Elena V.; Milichko, Valentin A.; Nesterov-Mueller, Alexander; Makarov, Sergey V.; Zakhidov, Anvar A.

2017-09-01

The hybrid halide perovskites is a prospective material for fabrication of cost-effective optical devices. Unique perovskites properties are used for solar cells and different photonic applications. Recently, perovskite-based nanophotonics has emerged. Here, we consider perovskite like a high-refractive index dielectric material, which can be considered to be a basis for nanoparticles fabrication with Mie resonances. As a result, we fabricate and study resonant perovskite nanoparticles with different sizes. We reveal, that spherical nanoparticles show enhanced photoluminescence signal. The achieved results lay a cornerstone in the field of novel types of organic-inorganic nanophotonics devices with optical properties improved by Mie resonances.

Role of Alloying Additions in Glass Formation and Properties of Bulk Metallic Glasses

PubMed Central

Chen, Na; Martin, Laura; Luzguine-Luzgin, Dmitri V.; Inoue, Akihisa

2010-01-01

Alloying addition, as a means of improving mechanical properties and saving on costs of materials, has been applied to a broad range of uses and products in the metallurgical fields. In the field of bulk metallic glasses (BMGs), alloying additions have also proven to play effective and important roles in promoting glass formation, enhancing thermal stability and improving plasticity of the materials. Here, we review the work on the role of alloying additions in glass formation and performance improvement of BMGs, with focus on our recent results of alloying additions in Pd-based BMGs. PMID:28883386

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

NASA Astrophysics Data System (ADS)

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

2010-04-01

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

APPLICATIONS OF BIOTECHNOLOGY IN DEVELOPMENT OF BIOMATERIALS: NANOTECHNOLOGY AND BIOFILMS

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

Brigmon, R.; Berry, T.; Narayan, R.

2010-11-29

Biotechnology is the application of biological techniques to develop new tools and products for medicine and industry. Due to various properties including chemical stability, biocompatibility, and specific activity, e.g. antimicrobial properties, many new and novel materials are being investigated for use in biosensing, drug delivery, hemodialysis, and other medical applications. Many of these materials are less than 100 nanometers in size. Nanotechnology is the engineering discipline encompassing designing, producing, testing, and using structures and devices less than 100 nanometers. One of the challenges associated with biomaterials is microbial contamination that can lead to infections. In recent work we have examinedmore » the functionalization of nanoporous biomaterials and antimicrobial activities of nanocrystalline diamond materials. In vitro testing has revealed little antimicrobial activity against Pseudomonas fluorescens bacteria and associated biofilm formation that enhances recalcitrance to antimicrobial agents including disinfectants and antibiotics. Laser scanning confocal microscopy studies further demonstrated properties and characteristics of the material with regard to biofilm formation.« less

Contribution of tin in electrochemical properties of zinc antimonate nanostructures: An electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Balasubramaniam, M.; Balakumar, S.

2018-04-01

Tin (Sn) doped ZnSb2O6 nanostructures was synthesized by chemical precipitation method and was used as an electrode material for supercapacitors to explore its electrochemical stability and potentiality as energy storage materials. Their characteristic structural, morphological and compositional features were investigated through XRD, FESEM and XPS analysis. Results showed that the nanostructures have well ordered crystalline features with spherical particle morphology. As the size and morphology are the vital parameters in exhibiting better electrochemical properties, the prepared nanostructures exhibited a significant specific capacitance of 222 F/g at a current density of 0.5 A/g respectively. While charging and discharging for 1000 cycles, the capacitance retention was enhanced to 105.0% which depicts the stability and activeness of electrochemical sites present in the Sn doped ZnSb2O6 nanostructures even after cycling. Hence, the inclusion of Sn into ZnSb2O6 has contributed in improving the electrochemical properties thereby it represents itself as a potential electrode material for supercapacitors.

Opportunities for Fluorochlorozirconate and Other Glass-Ceramic Detectors in Medical Imaging Devices

PubMed Central

Johnson, Jacqueline A.; Leonard, Russell L.; Lubinsky, AR; Schweizer, Stefan

2017-01-01

This article gives an overview of fluorochlorozirconate glass-ceramic scintillators and storage phosphor materials: how they are synthesized, what their properties are, and how they can be used in medical imaging. Such materials can enhance imaging in x-ray radiography, especially mammography and dental imaging, computed tomography, and positron emission tomography. Although focusing on fluorochlorozirconate materials, the reader will find the discussion is relevant to other luminescent glass and glass-ceramic systems. PMID:28890955

Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin.

PubMed

Dudás, Zoltán; Fagadar-Cosma, Eugenia; Len, Adél; Románszki, Loránd; Almásy, László; Vlad-Oros, Beatrice; Dascălu, Daniela; Krajnc, Andraž; Kriechbaum, Manfred; Kuncser, Andrei

2018-04-06

This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis( N -methyl-4-pyridyl)porphyrin-Zn(II) tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR), absorption spectroscopy (UV-Vis) and photoluminescence, nuclear magnetic resonance spectroscopy ( 29 Si-MAS-NMR) transmission and scanning electron microscopy (TEM and SEM), nitrogen absorption (BET), contact angle (CA), small angle X ray and neutron scattering (SAXS and SANS). All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands) in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications.

Enhancing Post-Expansion Chondrogenic Potential of Costochondral Cells in Self-Assembled Neocartilage

PubMed Central

Murphy, Meghan K.; Huey, Daniel J.; Reimer, Andrew J.; Hu, Jerry C.; Athanasiou, Kyriacos A.

2013-01-01

The insufficient healing capacity of articular cartilage necessitates mechanically functional biologic tissue replacements. Using cells to form biomimetic cartilage implants is met with the challenges of cell scarcity and donor site morbidity, requiring expanded cells that possess the ability to generate robust neocartilage. To address this, this study assesses the effects of expansion medium supplementation (bFGF, TFP, FBS) and self-assembled construct seeding density (2, 3, 4 million cells/5 mm dia. construct) on the ability of costochondral cells to generate biochemically and biomechanically robust neocartilage. Results show TFP (1 ng/mL TGF-β1, 5 ng/mL bFGF, 10 ng/mL PDGF) supplementation of serum-free chondrogenic expansion medium enhances the post-expansion chondrogenic potential of costochondral cells, evidenced by increased glycosaminoglycan content, decreased type I/II collagen ratio, and enhanced compressive properties. Low density (2 million cells/construct) enhances matrix synthesis and tensile and compressive mechanical properties. Combined, TFP and Low density interact to further enhance construct properties. That is, with TFP, Low density increases type II collagen content by over 100%, tensile stiffness by over 300%, and compressive moduli by over 140%, compared with High density. In conclusion, the interaction of TFP and Low density seeding enhances construct material properties, allowing for a mechanically functional, biomimetic cartilage to be formed using clinically relevant costochondral cells. PMID:23437288

Shockwave-Loading-Induced Enhancement of T c in Superconducting Bi 2Sr 2CaCu 2O 8+δ

DOE PAGES

Liu, Tiansheng; He, Chao; Wang, Fengying; ...

2017-07-27

Here, we report a shockwave method for altering the properties of the superconductor material Bi 2Sr 2CaCu 2O 8+δ (Bi2212). We find that the superconducting transition temperature (T c) increases from 84 K for the pristine sample to 94 K for the sample treated at a temperature and pressure of ~1200 K and ~31 GPa, respectively. X-ray diffraction and transmission electron microscopy characterizations indicate that this T c enhancement arises from a phase transition from pristine Bi2212 to a mixture of superconducting Bi2212 and semiconducting Bi 2Sr 2CuO 6+δ (Bi2201) during the shockwave treatment. The shockwave-treated sample exhibits n-type semiconductormore » properties (with an on-off ratio ~5), in contrast to the pure metallic pristine sample. This study offers an alternative route for modifying the superconducting properties via a shockwave treatment. Furthermore, this method may provide a new approach for studying other temperature- and pressure-sensitive materials.« less

Shaping Nanoparticles with Hydrophilic Compositions and Hydrophobic Properties as Nanocarriers for Antibiotic Delivery

PubMed Central

2015-01-01

Inspired by the lotus effect in nature, surface roughness engineering has led to novel materials and applications in many fields. Despite the rapid progress in superhydrophobic and superoleophobic materials, this concept of Mother Nature’s choice is yet to be applied in the design of advanced nanocarriers for drug delivery. Pioneering work has emerged in the development of nanoparticles with rough surfaces for gene delivery; however, the preparation of nanoparticles with hydrophilic compositions but with enhanced hydrophobic property at the nanoscale level employing surface topology engineering remains a challenge. Herein we report for the first time the unique properties of mesoporous hollow silica (MHS) nanospheres with controlled surface roughness. Compared to MHS with a smooth surface, rough mesoporous hollow silica (RMHS) nanoparticles with the same hydrophilic composition show unusual hydrophobicity, leading to higher adsorption of a range of hydrophobic molecules and controlled release of hydrophilic molecules. RMHS loaded with vancomycin exhibits an enhanced antibacterial effect. Our strategy provides a new pathway in the design of novel nanocarriers for diverse bioapplications. PMID:27162988

Sustainable Hydrogels Based on Lignin-Methacrylate Copolymers with Enhanced Water Retention and Tunable Material Properties.

PubMed

Rajan, Kalavathy; Mann, Jeffrey K; English, Eldon; Harper, David P; Carrier, Danielle Julie; Rials, Timothy G; Labbé, Nicole; Chmely, Stephen C

2018-04-12

Synthesizing lignin-based copolymers would valorize a major coproduct stream from pulp and paper mills and biorefineries as well as reduce the dependence on petrochemical-based consumer goods. In this study, we used organosolv lignin isolated from hybrid poplar ( Populus trichocarpa × P. deltoides) to generate lignin-containing methacrylate hydrogels. The copolymer hydrogels were synthesized by first grafting 2-hydroxyethyl methacrylate (HEMA) onto lignin (OSLH) via esterification and then by free radical polymerization of OSLH with excess HEMA. The copolymer hydrogels were prepared with different stoichiometric ratios of OSLH (e.g., 0, 10, 20, and 40 wt %) with respect to HEMA. Copolymerization with OSLH led to an increase in cross-linking density, which in turn enhanced the hydrogel's material properties; we report up to 39% improvement in water retention, 20% increase in thermostability, and up to a 3 order increase in magnitude of the storage modulus ( G'). The copolymer's properties, such as water retention and glass transition temperature, could be tuned by altering the percent functionalization of lignin OH groups and the ratio of OSLH to HEMA.

Fabrication of Cellulose Film with Enhanced Mechanical Properties in Ionic Liquid 1-Allyl-3-methylimidaxolium Chloride (AmimCl)

PubMed Central

Pang, Jinhui; Liu, Xin; Zhang, Xueming; Wu, Yuying; Sun, Runcang

2013-01-01

More and more attention has been paid to environmentally friendly bio-based renewable materials as the substitution of fossil-based materials, due to the increasing environmental concerns. In this study, regenerated cellulose films with enhanced mechanical property were prepared via incorporating different plasticizers using ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as the solvent. The characteristics of the cellulose films were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis (TG), X-ray diffraction (XRD), 13C Solid-state cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and tensile testing. The results showed that the cellulose films exhibited a homogeneous and smooth surface structure. It was noted that the thermal stability of the regenerated cellulose film plasticized with glycerol was increased compared with other regenerated cellulose films. Furthermore, the incorporation of plasticizers dramatically strengthened the tensile strength and improved the hydrophobicity of cellulose films, as compared to the control sample. Therefore, these notable results exhibited the potential utilization in producing environmentally friendly cellulose films with high performance properties. PMID:28809209

Direct deposit laminate nanocomposites with enhanced propellent properties.

PubMed

Li, Xiangyu; Guerieri, Philip; Zhou, Wenbo; Huang, Chuan; Zachariah, Michael R

2015-05-06

One of the challenges in the use of energetic nanoparticles within a polymer matrix for propellant applications is obtaining high particle loading (high energy density) while maintaining mechanical integrity and reactivity. In this study, we explore a new strategy that utilizes laminate structures. Here, a laminate of alternating layers of aluminum nanoparticle (Al-NPs)/copper oxide nanoparticle (CuO-NPs) thermites in a polyvinylidene fluoride (PVDF) reactive binder, with a spacer layer of PVDF was fabricated by a electrospray layer-by-layer deposition method. The deposited layers containing up to 60 wt % Al-NPs/CuO-NPs thermite are found to be uniform and mechanically flexible. Both the reactive and mechanical properties of laminate significantly outperformed the single-layer structure with the same material composition. These results suggest that deploying a multilayer laminate structure enables the incorporation of high loadings of energetic materials and, in some cases, enhances the reactive properties over the corresponding homogeneous structure. These results imply that an additive manufacturing approach may yield significant advantages in developing a tailored architecture for advanced propulsion systems.

Engineering the Structure and Properties of DNA-Nanoparticle Superstructures Using Polyvalent Counterions.

PubMed

Chou, Leo Y T; Song, Fayi; Chan, Warren C W

2016-04-06

DNA assembly of nanoparticles is a powerful approach to control their properties and prototype new materials. However, the structure and properties of DNA-assembled nanoparticles are labile and sensitive to interactions with counterions, which vary with processing and application environment. Here we show that substituting polyamines in place of elemental counterions significantly enhanced the structural rigidity and plasmonic properties of DNA-assembled metal nanoparticles. These effects arose from the ability of polyamines to condense DNA and cross-link DNA-coated nanoparticles. We further used polyamine wrapped DNA nanostructures as structural templates to seed the growth of polymer multilayers via layer-by-layer assembly, and controlled the degree of DNA condensation, plasmon coupling efficiency, and material responsiveness to environmental stimuli by varying polyelectrolyte composition. These results highlight counterion engineering as a versatile strategy to tailor the properties of DNA-nanoparticle assemblies for various applications, and should be applicable to other classes of DNA nanostructures.

Investigating the effectiveness of using agricultural wastes from empty fruit bunch (EFB), coconut fibre (CF) and sugarcane baggasse (SB) to produce low thermal conductivity clay bricks

NASA Astrophysics Data System (ADS)

Hamzah, Mohamad Hazmi; Deraman, Rafikullah; Saman, Nor Sarwani Mat

2017-12-01

In Malaysia, 45% of the average household electricity was consumed by air conditioners to create an acceptable indoor environment. This high energy consumption was mostly related to poor thermal performance of the building envelope. Therefore, selecting a low thermal conductivity of brick wall was of considerable importance in creating energy efficient buildings. Previously, numerous researchers reported the potential used of agricultural waste as an additive in building materials to enhance their thermal properties. The aim of this study is to examine how agricultural wastes from empty fruit bunch (EFB), coconut fibre (CF) and sugarcane bagasse (SB) can act as additive agents in a fired clay brick manufacturing process to produce a low thermal conductivity clay brick. In this study, these agricultural wastes were individually mixed with clay soil in different proportions ranging from 0%, 2.5%, 5%, 7.5% and 10% by weight. Physical and mechanical properties including soil physical properties, as well as thermal conductivity were performed in accordance with BS 1377: Part 2: 1990, BS 3921: 1985 and ASTM C518. The results reveal that incorporating 5% of EFB as an additive component into the brick making process significantly enhances the production of a low thermal conductivity clay brick as compared to other waste alternatives tested. This finding suggests that EFB waste was a potential additive material to be used for the thermal property enhancement of the building envelope.

Adhesion properties of an elastomer enhanced by the presence of liquid drops in its structure

NASA Astrophysics Data System (ADS)

Giustiniani, Anais; Drenckhan, Wiebke; Poulard, Christophe

Macro-cellular polymers present rich mechanical properties due to the internal structuration of the material, in which discrete cells are tightly packed within a continuous polymeric solid matrix. The size, shape, organisation and volume fraction of these cells have an important influence on the overall material properties. Here, we study a solid emulsion which consist of liquid polyethylene glycol drops in a crosslinked PDMS (polydimethylsiloxane). These present novel rheological and adhesive properties. Results show an important hysteresis of the normal stress in a compression/decompression cycle with a significant force at rupture when this force is close to zero for the bare PDMS. This was reported for 2D systems, and in this work we study the influence of the drop sizes inside the matrix, their density and the viscosity of the liquid on the adhesion energy of the 3D material. The overall motivation of this system is to allow to independently control the elastic and viscous properties of the matrix and the drops respectively, in opposition to the viscoelastic fluids commonly used as adhesives such as PSA and gels.

Study of physical and sound absorbing property of epoxy blended coir dust biocomposite

NASA Astrophysics Data System (ADS)

Nath, G.; Mishra, S. P.

2016-09-01

Reinforcement biocomposite has gained more attention recently due to its low cost, abundantly availability, low density, specific properties, easy method of separation, enhanced energy recovery, CO2 neutrality, biodegradability and recyclable in nature. As a waste product of coconut fruit, the coconut coir dust (CCD) obtained from the coconut husk. The biocomposite material prepared from the CCD modified with the proper blended solution with the help of ultrasonic technique. The study of adiabatic compressibility of acetone / water (70/30) worth its blending property for bleaching of CCD. The biocomposite material of CCD was prepared with epoxy resin. The different physical properties such as sound absorption coefficient, thermal conductivity and electrical conductivity were measured. The morphological study of biocomposite and measurement of sound absorption coefficient shows good evidence of sound absorbing characteristics of biocomposite of CCD. The sound absorption property of composite material shows a significant result where as the thermal conductivity and electrical conductivity executes a weak result. Thus biocomposite of CCD can acts as a good sound absorber and band conductor of heat and electric current.

Structurally Driven Enhancement of Resonant Tunneling and Nanomechanical Properties in Diamond-like Carbon Superlattices.

PubMed

Dwivedi, Neeraj; McIntosh, Ross; Dhand, Chetna; Kumar, Sushil; Malik, Hitendra K; Bhattacharyya, Somnath

2015-09-23

We report nitrogen-induced enhanced electron tunnel transport and improved nanomechanical properties in band gap-modulated nitrogen doped DLC (N-DLC) quantum superlattice (QSL) structures. The electrical characteristics of such superlattice devices revealed negative differential resistance (NDR) behavior. The interpretation of these measurements is supported by 1D tight binding calculations of disordered superlattice structures (chains), which include bond alternation in sp(3)-hybridized regions. Tandem theoretical and experimental analysis shows improved tunnel transport, which can be ascribed to nitrogen-driven structural modification of the N-DLC QSL structures, especially the increased sp(2) clustering that provides additional conduction paths throughout the network. The introduction of nitrogen also improved the nanomechanical properties, resulting in enhanced elastic recovery, hardness, and elastic modulus, which is unusual but is most likely due to the onset of cross-linking of the network. Moreover, the materials' stress of N-DLC QSL structures was reduced with the nitrogen doping. In general, the combination of enhanced electron tunnel transport and nanomechanical properties in N-DLC QSL structures/devices can open a platform for the development of a new class of cost-effective and mechanically robust advanced electronic devices for a wide range of applications.

Durable pectin/chitosan membranes with self-assembling, water resistance and enhanced mechanical properties.

PubMed

Martins, Jéssica G; de Oliveira, Ariel C; Garcia, Patrícia S; Kipper, Matt J; Martins, Alessandro F

2018-05-15

Processing water-soluble polysaccharides, like pectin (PT), into materials with desirable stability and mechanical properties has been challenging. Here we report a new method to create water stable and mechanical resistant polyelectrolyte complex (PEC) membranes from PT and chitosan (CS) assemblies, without covalent crosslinking. This new method overcomes challenges of obtaining stable and durable complexes, by performing the complexation at low pH, enabling complex formation even when using an excess of PT, and when using PT with high degree of O-methoxylation. By performing the complexation at low pH, the complexes form with a high degree of intermolecular association, instead of forming by electrostatic complexation. This method avoids precipitation, and overcomes the aqueous instability typical of PT/CS complexes. After neutralization, the PEC membranes display features characteristic of a high degree of intermolecular association because of the self-assembling of polymer chains. The PT/CS ratio can be tuned to enhance the mechanical strength (σ = 39 MPa) of the membranes. These polysaccharide-based materials can demonstrate advantages over synthetic materials for technological applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

Analysis of Viking infrared thermal mapping data of Mars. The effects of non-ideal surfaces on the derived thermal properties of Mars

NASA Technical Reports Server (NTRS)

Muhleman, D. O.; Jakosky, B. M.

1979-01-01

The thermal interia of the surface of Mars varies spatially by a factor of eight. This is attributable to changes in the average particle size of the fine material, the surface elevation, the atmospheric opacity due to dust, and the fraction of the surface covered by rocks and fine material. The effects of these non-ideal properties on the surface temperatures and derived thermal inertias are modeled, along with the the effects of slopes, CO2 condensed onto the surface, and layering of fine material upon solid rock. The non-ideal models are capable of producing thermal behavior similar to that observed by the Viking Infrared Thermal Mapper, including a morning delay in the post-dawn temperature rise and an enhanced cooling in the afternoon relative to any ideal, homogeneous model. The enhanced afternoon cooling observed at the Viking-1 landing site is reproduced by the non-ideal models while that atop Arsia Mons volcano is not, but may be attributed to the observing geometry.

Chemically Driven Printed Textile Sensors Based on Graphene and Carbon Nanotubes

PubMed Central

Skrzetuska, Ewa; Puchalski, Michał; Krucińska, Izabella

2014-01-01

The unique properties of graphene, such as the high elasticity, mechanical strength, thermal conductivity, very high electrical conductivity and transparency, make them it an interesting material for stretchable electronic applications. In the work presented herein, the authors used graphene and carbon nanotubes to introduce chemical sensing properties into textile materials by means of a screen printing method. Carbon nanotubes and graphene pellets were dispersed in water and used as a printing paste in the screen printing process. Three printing paste compositions were prepared—0%, 1% and 3% graphene pellet content with a constant 3% carbon nanotube mass content. Commercially available materials were used in this process. As a substrate, a twill woven cotton fabric was utilized. It has been found that the addition of graphene to printing paste that contains carbon nanotubes significantly enhances the electrical conductivity and sensing properties of the final product. PMID:25211197

TOPICAL REVIEW: Progress in engineering high strain lead-free piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Leontsev, Serhiy O.; Eitel, Richard E.

2010-08-01

Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The 'structural engineering' approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications.

Progress in engineering high strain lead-free piezoelectric ceramics

PubMed Central

Leontsev, Serhiy O; Eitel, Richard E

2010-01-01

Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The ‘structural engineering’ approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications. PMID:27877343

Shape-memory effect of nanocomposites based on liquid-crystalline elastomers

NASA Astrophysics Data System (ADS)

Marotta, A.; Lama, G. C.; Gentile, G.; Cerruti, P.; Carfagna, C.; Ambrogi, V.

2016-05-01

In this work, nanocomposites based on liquid crystalline (LC) elastomers were prepared and characterized in their shape memory properties. For the synthesis of materials, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was used as mesogenic epoxy monomer, sebacic acid (SA) as curing agent and multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO) as fillers. First, an effective compatibilization methodology was set up to improve the interfacial adhesion between the matrix and the carbonaceous nanofillers, thus obtaining homogeneous distribution and dispersion of the nanofillers within the polymer phase. Then, the obtained nanocomposite films were characterized in their morphological and thermal properties. In particular, the effect of the addition of the nanofillers on liquid crystalline behavior, as well as on shape-memory properties of the realized materials was investigated. It was found that both fillers were able to enhance the thermomechanical response of the LC elastomers, making them good candidates as shape memory materials.

Transition from poor ductility to room-temperature superplasticity in a nanostructured aluminum alloy.

PubMed

Edalati, Kaveh; Horita, Zenji; Valiev, Ruslan Z

2018-04-30

Recent developments of nanostructured materials with grain sizes in the nanometer to submicrometer range have provided ground for numerous functional properties and new applications. However, in terms of mechanical properties, bulk nanostructured materials typically show poor ductility despite their high strength, which limits their use for structural applications. The present article shows that the poor ductility of nanostructured alloys can be changed to room-temperature superplastisity by a transition in the deformation mechanism from dislocation activity to grain-boundary sliding. We report the first observation of room-temperature superplasticity (over 400% tensile elongations) in a nanostructured Al alloy by enhanced grain-boundary sliding. The room-temperature grain-boundary sliding and superplasticity was realized by engineering the Zn segregation along the Al/Al boundaries through severe plastic deformation. This work introduces a new boundary-based strategy to improve the mechanical properties of nanostructured materials for structural applications, where high deformability is a requirement.

Semiconductor apparatus utilizing gradient freeze and liquid-solid techniques

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

1998-01-01

Transition metals of Group VIII (Co, Rh and Ir) have been prepared as semiconductor compounds with the general formula TSb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freezing techniques and/or liquid phase sintering techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 1200 cm.sup.2.V.sup.-1.s.sup.-1) and good Seebeck coefficients (up to 150 .mu.VK.sup.-1 between 300.degree. C. and 700.degree. C.). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a substantial increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400.degree. C. for thermoelectric elements fabricated from such semiconductor materials.

Steady State Structural Analysis of High Pressure Gas Turbine Blade using Finite Element Analysis

NASA Astrophysics Data System (ADS)

Mazarbhuiya, Hussain Mahamed Sahed Mostafa; Murari Pandey, Krishna

2017-08-01

In gas turbines the major portion of performance dependency lies upon turbine blade design. Turbine blades experience very high centrifugal, axial and tangential force during power generation. While withstanding these forces blades undergo elongation. Different methods have proposed for better enhancement of the mechanical properties of blade to withstand in extreme condition. Present paper describes the stress and elongation for blades having properties of different materials. Steady state structural analysis have performed in the present work for different materials (In 625, In 718, In 738, In 738 LC, MAR M246, Ni-Cr, Ti-alloy, Ti-Al, Ti-T6, U500). Remarkable finding is that the root of the blade is subjected to maximum stress for all blade materials and the blade made of MAR M246 has less stress and deformation among all other blade materials which can be selected as a suitable material for gas turbine blade.

Making ultrafine and highly-dispersive multimetallic nanoparticles in three-dimensional graphene with supercritical fluid as excellent electrocatalyst for oxygen reduction reaction

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

Zhou, Yazhou; Yen, Clive H.; Hu, Yun Hang

2016-01-01

Three-dimensional (3D) graphene showed an advanced support for designing porous electrode materials due to its high specific surface area, large pore volume, and excellent electronic property. However, the electrochemical properties of reported porous electrode materials still need to be improved further. The current challenge is how to deposit desirable nanoparticles (NPs) with controllable structure, loading and composition in 3D graphene while maintaining the high dispersion. Herein, we demonstrate a modified supercritical fluid (SCF) technique to address this issue by controlling the SCF system. Using this superior method, a series of Pt-based/3D graphene materials with the ultrafine-sized, highly dispersive and controllablemore » composition multimetallic NPs were successfully synthesized. Specifically, the resultant Pt40Fe60/3D graphene showed a significant enhancement in electrocatalytic performance for the oxygen reduction reaction (ORR), including a factor of 14.2 enhancement in mass activity (1.70 A mgPt 1), a factor of 11.9 enhancement in specific activity (1.55 mA cm 2), and higher durability compared with that of Pt/C catalyst. After careful comparison, the Pt40Fe60/3D graphene catalyst shows the higher ORR activity than most of the reported similar 3D graphene-based catalysts. The successful synthesis of such attractive materials by this method also paves the way to develop 3D graphene in widespread applications.« less

Thermal conductivity of 2D nano-structured graphitic materials and their composites with epoxy resins

NASA Astrophysics Data System (ADS)

Mu, Mulan; Wan, Chaoying; McNally, Tony

2017-12-01

The outstanding thermal conductivity (λ) of graphene and its derivatives offers a potential route to enhance the thermal conductivity of epoxy resins. Key challenges still need to be overcome to ensure effective dispersion and distribution of 2D graphitic fillers throughout the epoxy matrix. 2D filler type, morphology, surface chemistry and dimensions are all important factors in determining filler thermal conductivity and de facto the thermal conductivity of the composite material. To achieve significant enhancement in the thermal conductivity of epoxy composites, different strategies are required to minimise phonon scattering at the interface between the nano-filler and epoxy matrix, including chemical functionalisation of the filler surfaces such that interactions between filler and matrix are promoted and interfacial thermal resistance (ITR) reduced. The combination of graphitic fillers with dimensions on different length scales can potentially form an interconnected multi-dimensional filler network and, thus contribute to enhanced thermal conduction. In this review, we describe the relevant properties of different 2D nano-structured graphitic materials and the factors which determine the translation of the intrinsic thermal conductivity of these 2D materials to epoxy resins. The key challenges and perspectives with regard achieving epoxy composites with significantly enhanced thermal conductivity on addition of 2D graphitic materials are presented.

Neuronal Differentiation Modulated by Polymeric Membrane Properties.

PubMed

Morelli, Sabrina; Piscioneri, Antonella; Drioli, Enrico; De Bartolo, Loredana

2017-01-01

In this study, different collagen-blend membranes were successfully constructed by blending collagen with chitosan (CHT) or poly(lactic-co-glycolic acid) (PLGA) to enhance their properties and thus create new biofunctional materials with great potential use for neuronal tissue engineering and regeneration. Collagen blending strongly affected membrane properties in the following ways: (i) it improved the surface hydrophilicity of both pure CHT and PLGA membranes, (ii) it reduced the stiffness of CHT membranes, but (iii) it did not modify the good mechanical properties of PLGA membranes. Then, we investigated the effect of the different collagen concentrations on the neuronal behavior of the membranes developed. Morphological observations, immunocytochemistry, and morphometric measures demonstrated that the membranes developed, especially CHT/Col30, PLGA, and PLGA/Col1, provided suitable microenvironments for neuronal growth owing to their enhanced properties. The most consistent neuronal differentiation was obtained in neurons cultured on PLGA-based membranes, where a well-developed neuronal network was achieved due to their improved mechanical properties. Our findings suggest that tensile strength and elongation at break are key material parameters that have potential influence on both axonal elongation and neuronal structure and organization, which are of fundamental importance for the maintenance of efficient neuronal growth. Hence, our study has provided new insights regarding the effects of membrane mechanical properties on neuronal behavior, and thus it may help to design and improve novel instructive biomaterials for neuronal tissue engineering. © 2017 S. Karger AG, Basel.

Effect of surface etching and electrodeposition of copper on nitinol

NASA Astrophysics Data System (ADS)

Ramos-Moore, E.; Rosenkranz, A.; Matamala, L. F.; Videla, A.; Durán, A.; Ramos-Grez, J.

2017-10-01

Nitinol-based materials are very promising for medical and dental applications since those materials can combine shape memory, corrosion resistance, biocompatibility and antibacterial properties. In particular, surface modifications and coating deposition can be used to tailor and to unify those properties. We report preliminary results on the study of the effect of surface etching and electrodeposition of Copper on Nitinol using optical, chemical and thermal techniques. The results show that surface etching enhances the surface roughness of Nitinol, induces the formation of Copper-based compounds at the Nitinol-Copper interface, reduces the austenitic-martensitic transformations enthalpies and reduces the Copper coating roughness. Further studies are needed in order to highlight the influence of the electrodeposited Copper on the memory shape properties of NiTi.

Evaluation of Mechanical Properties of MWCNT / Nanoclay Reinforced Aluminium alloy Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Ratna Kumar, P. S. Samuel; Robinson Smart, D. S.; Alexis, S. John

2018-04-01

Aluminium alloy 5083 (AA5083) is a widely used material in aerospace, marine, defence and structural applications were mechanical and corrosion resistance property plays a vital role. For the present work, MWCNT / Nanoclay (montmorillonite (MMT) K10) mixed with AA5083 for different composition in weight percentage to enhance the mechanical property. Semi-solid state casting method (Compo-casting) was used to fabricate the composite materials. By using Field-emission scanning electron microscope (FESEM) the uniform dispersion of the reinforcement and microstructure were studied. Finally, the addition of Nanoclay shows decrease in tensile strength compared to the AA5083 / MWCNT composites and hardness value of the composites (AA5083 / MWCNT and AA5083 / Nanoclay) was found to increase significantly.

Fabrication of p-n heterostructure ZnO/Si moth-eye structures: Antireflection, enhanced charge separation and photocatalytic properties

NASA Astrophysics Data System (ADS)

Zeng, Yu; Chen, XiFang; Yi, Zao; Yi, Yougen; Xu, Xibin

2018-05-01

The pyramidal silicon substrate is formed by wet etching, then ZnO nanorods are grown on the surface of the pyramidal microstructure by a hydrothermal method to form a moth-eye composite heterostructure. The composite heterostructure of this material determines its excellent anti-reflection properties and ability to absorb light from all angles. In addition, due to the effective heterojunction binding area, the composite micro/nano structure has excellent photoelectric conversion performance. Its surface structure and the large specific surface area gives the material super hydrophilicity, excellent gas sensing characteristic, and photocatalytic properties. Based on the above characteristics, the micro/nano heterostructure can be used in solar cells, sensors, light-emitting devices, and photocatalytic fields.

Sensing Structures Inspired by Blind Cave Fish

NASA Astrophysics Data System (ADS)

McConney, Michael E.; Chen, Nannan; Lu, David; Anderson, Kyle D.; Hu, Huan; Liu, Chang; Tsukruk, Vladimir V.

2009-03-01

Blind cave fish, with degenerated non-functioning eyes, have evolved to ``see'' their hydrodynamic environment by using the flow receptors of the lateral line system. The hair-cell receptors are encapsulated in a hydrogel-like material, called a cupula, which increases the sensitivity of the hair-cell receptors by coupling their motion to the surrounding flowing media. We characterized the viscoelastic properties and of blind cave fish cupulae by using colloidal-probe spectroscopy in fluid. A photo-patternable hydrogel with similar properties was developed to mimic the fish receptor coupling structure. Flow-based measurements indicated that the hydrogels enhance drag through increased surface area, but also inherent material properties. These bio-inspired structures endowed micro-fabricated flow sensors with sensitivities rivaling that of fish.

FY2016 Propulsion Materials Annual Progress Report

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

None, None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines and Fuels) teams to develop strategies thatmore » overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

Computational materials chemistry for carbon capture using porous materials

NASA Astrophysics Data System (ADS)

Sharma, Abhishek; Huang, Runhong; Malani, Ateeque; Babarao, Ravichandar

2017-11-01

Control over carbon dioxide (CO2) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO2 capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO2 separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO2 capture are discussed.

Hyaluronan–Itaconic Acid–Glutaraldehyde Films for Biomedical Applications: Preliminary Studies

PubMed Central

Calles, Javier Adrián; Ressia, Jorge Aníbal; Llabot, Juan Manuel; Vallés, Enrique Marcelo; Palma, Santiago Daniel

2016-01-01

New hyaluronic acid–itaconic acid films were synthesized as potential materials with biomedical applications. In this work, we explored the homogeneous cross-linking reactions of hyaluronic acid using glutaraldehyde in the presence of itaconic acid and triacetin as plasticizers. Biomechanical properties were assessed in terms of stability by measuring swelling in aqueous environments, investigating wettability using contact angle tests, and evaluating bioadhesive performance. The ductility of the materials was evaluated through stress-strain measurements and the morphology was explored by scanning electron microscopy. The results show that the incorporation of itaconic acid improved most of the desirable properties, increasing adhesiveness and reducing wettability and swelling. The use of triacetin enhanced the strength, bioadhesiveness, and ductility of the material. PMID:27110498

Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

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

Narducci, Dario, E-mail: dario.narducci@unimib.it; Consorzio DeltaTi Research; Selezneva, Ekaterina

2012-09-15

Energy filtering has been widely considered as a suitable tool to increase the thermoelectric performances of several classes of materials. In its essence, energy filtering provides a way to increase the Seebeck coefficient by introducing a strongly energy-dependent scattering mechanism. Under certain conditions, however, potential barriers may lead to carrier localization, that may also affect the thermoelectric properties of a material. A model is proposed, actually showing that randomly distributed potential barriers (as those found, e.g., in polycrystalline films) may lead to the simultaneous occurrence of energy filtering and carrier localization. Localization is shown to cause a decrease of themore » actual carrier density that, along with the quantum tunneling of carriers, may result in an unexpected increase of the power factor with the doping level. The model is corroborated toward experimental data gathered by several authors on degenerate polycrystalline silicon and lead telluride. - Graphical abstract: In heavily doped semiconductors potential barriers may lead to both carrier energy filtering and localization. This may lead to an enhancement of the thermoelectric properties of the material, resulting in an unexpected increase of the power factor with the doping level. Highlights: Black-Right-Pointing-Pointer Potential barriers are shown to lead to carrier localization in thermoelectric materials. Black-Right-Pointing-Pointer Evidence is put forward of the formation of a mobility edge. Black-Right-Pointing-Pointer Energy filtering and localization may explain the enhancement of power factor in degenerate semiconductors.« less

Mechanical properties of nanodiamond-reinforced hydroxyapatite composite coatings deposited by suspension plasma spraying

NASA Astrophysics Data System (ADS)

Chen, Xiuyong; Zhang, Botao; Gong, Yongfeng; Zhou, Ping; Li, Hua

2018-05-01

Hydroxyapatite (HA) coatings suffer from poor mechanical properties, which can be enhanced via incorporation of secondary bioinert reinforcement material. Nanodiamond (ND) possesses excellent mechanical properties to play the role as reinforcement for improving the mechanical properties of brittle HA bioceramic coatings. The major persistent challenge yet is the development of proper deposition techniques for fabricating the ND reinforced HA coatings. In this study, we present a novel deposition approach by plasma spraying the mixtures of ND suspension and micron-sized HA powder feedstock. The effect of ND reinforcement on the microstructure and the mechanical properties of the coatings such as hardness, adhesive strength and friction coefficient were examined. The results showed that the ND-reinforced HA coatings display lower porosity, fewer unmelted particles and uniform microstructure, in turn leading to significantly enhanced mechanical properties. The study presented a promising approach to fabricate ND-reinforced HA composite coatings on metal-based medical implants for potential clinical application.

Carbon-based sputtered coatings for enhanced chitosan-based films properties

NASA Astrophysics Data System (ADS)

Fernandes, C.; Calderon V., S.; Ballesteros, Lina F.; Cerqueira, Miguel A.; Pastrana, L. M.; Teixeira, José A.; Ferreira, P. J.; Carvalho, S.

2018-03-01

In order to make bio-based packaging materials competitive in comparison to petroleum-based one, some of their properties need to be improved, among which gas permeability is of crucial importance. Thus, in this work, carbon-based coatings were applied on chitosan-based films by radiofrequency reactive magnetron sputtering aiming to improve their barrier properties. Chemical and morphological properties were evaluated in order to determine the effect of the coatings on the chemical structure, surface hydrophobicity and barrier properties of the system. Chemical analysis, performed by electron energy loss spectroscopy and Fourier transform infrared spectroscopy, suggests similar chemical characteristics among all coatings although higher incorporation of hydrogen as the acetylene flux increases was observed. On the other hand, scanning transmission electron microscopy revealed that the porosity of the carbon layer can be tailored by the acetylene flux. More importantly, the chitosan oxygen permeability showed a monotonic reduction as a function of the acetylene flux. This study opens up new opportunities to apply nanostructured coatings on bio-based polymer for enhanced oxygen barrier properties.

Biominerals- hierarchical nanocomposites: the example of bone

PubMed Central

Beniash, Elia

2010-01-01

Many organisms incorporate inorganic solids in their tissues to enhance their functional, primarily mechanical, properties. These mineralized tissues, also called biominerals, are unique organo-mineral nanocomposites, organized at several hierarchical levels, from nano- to macroscale. Unlike man made composite materials, which often are simple physical blends of their components, the organic and inorganic phases in biominerals interface at the molecular level. Although these tissues are made of relatively weak components at ambient conditions, their hierarchical structural organization and intimate interactions between different elements lead to superior mechanical properties. Understanding basic principles of formation, structure and functional properties of these tissues might lead to novel bioinspired strategies for material design and better treatments for diseases of the mineralized tissues. This review focuses on general principles of structural organization, formation and functional properties of biominerals on the example the bone tissues. PMID:20827739

Preparation of poly(vinyl alcohol)/chitosan/starch blends and studies on thermal and surface properties

NASA Astrophysics Data System (ADS)

Nasalapure, Anand V.; Chalannavar, Raju K.; Malabadi, Ravindra B.

2018-05-01

Biopolymers are abundantly available from its natural sources of extraction. Chitosan(CH) is one of the widely used natural polymer which is perspective natural polysaccharide. Natural polymer blend with synthetic polymer enhances property of the material such as polyvinyl alcohol (PVA). PVA is nontoxic degradable synthetic polymer and very good film forming polymer. In this study prepared hybrid based film by adding starch into Chitosan/PVA which slighlty increased the surface and thermal property of ternary blend film.

Application of the Materials-by-Design Methodology to Redesign a New Grade of the High-Strength Low-Alloy Class of Steels with Improved Mechanical Properties and Processability

NASA Astrophysics Data System (ADS)

Grujicic, M.; Snipes, J. S.; Ramaswami, S.

2016-01-01

An alternative to the traditional trial-and-error empirical approach for the development of new materials is the so-called materials-by-design approach. Within the latter approach, a material is treated as a complex system and its design and optimization is carried out by employing computer-aided engineering analyses, predictive tools, and available material databases. In the present work, the materials-by-design approach is utilized to redesign a grade of high-strength low-alloy (HSLA) class of steels with improved mechanical properties (primarily strength and fracture toughness), processability (e.g., castability, hot formability, and weldability), and corrosion resistance. Toward that end, a number of material thermodynamics, kinetics of phase transformations, and physics of deformation and fracture computational models and databases have been developed/assembled and utilized within a multi-disciplinary, two-level material-by-design optimization scheme. To validate the models, their prediction is compared against the experimental results for the related steel HSLA100. Then the optimization procedure is employed to determine the optimal chemical composition and the tempering schedule for a newly designed grade of the HSLA class of steels with enhanced mechanical properties, processability, and corrosion resistance.

Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

PubMed Central

Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

2015-01-01

Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films. PMID:26156001

Antibacterial property of Ag nanoparticle-impregnated N-doped titania films under visible light

NASA Astrophysics Data System (ADS)

Wong, Ming-Show; Chen, Chun-Wei; Hsieh, Chia-Chun; Hung, Shih-Che; Sun, Der-Shan; Chang, Hsin-Hou

2015-07-01

Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet-visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.

Some considerations for various positioning systems and their science capabilities

NASA Technical Reports Server (NTRS)

Rey, Charles A.; Merkley, D. R.; Danley, T. J.

1990-01-01

Containerless processing of materials at elevated temperatures is discussed with emphasis on high temperature chemistry, thermophysical properties, materials science, and materials processing. Acoustic and electromagnetic positioning of high temperature melts are discussed. Results from recent ground based experiments, including KC-135 testing of an acoustic levitator, are presented. Some current positioning technologies and the potential for enhancing them are considered. Further, a summary of these technologies and their science capabilities for the development of future experiments is given.

Application of Nanostructures in Electrochromic Materials and Devices: Recent Progress.

PubMed

Wang, Jin Min; Sun, Xiao Wei; Jiao, Zhihui

2010-11-26

The recent progress in application of nanostructures in electrochromic materials and devices is reviewed. ZnO nanowire array modified by viologen and WO₃, crystalline WO₃ nanoparticles and nanorods, mesoporous WO₃ and TiO₂, poly(3,4-ethylenedioxythiophene) nanotubes, Prussian blue nanoinks and nanostructures in switchable mirrors are reviewed. The electrochromic properties were significantly enhanced by applying nanostructures, resulting in faster switching responses, higher stability and higher optical contrast. A perspective on the development trends in electrochromic materials and devices is also proposed.

Tip-Enhanced Nano-Spectroscopy, Imaging, and Control: From Single Molecules to van der Waals Materials

NASA Astrophysics Data System (ADS)

Park, Kyoung-Duck

Photon-induced phenomena in molecules and other materials play a significant role in device applications as well as understanding their physical properties. While a range of device applications using organic and inorganic molecules and soft and hard materials have led striking developments in modern technologies, using bulk systems has reached the limit in their functions, performance, and regarding application range. Recently, low-dimensional systems have emerged as appealing resources for the advanced technologies based on their significantly improved functions and properties. Hence, understanding light-matter interactions at their natural length scale is of fundamental significance, in addition to the next generation device applications. This thesis demonstrates a range of new functions and behaviors of low-dimensional materials revealed and controlled by the advanced tip-enhanced near-field spectroscopy and imaging techniques exceeding the current instrumental limits. To understand the behaviors of zero-dimensional (0D) molecular systems in interacting environments, we explore new regimes in tip-enhanced Raman spectroscopy (TERS) and scanning near-field optical microscopy (SNOM), revealing the fundamental nature of single-molecule dynamics and nanoscale spatial heterogeneity of biomolecules on the cell membranes. To gain insight into intramolecular properties and dynamic processes of single molecules, we use TERS at cryogenic temperatures. From temperature-dependent line narrowing and splitting, we investigate and quantify ultrafast vibrational dephasing, intramolecular coupling, and conformational heterogeneity. Through correlation analysis of fluctuations of individual modes, we observe rotational motion and spectral fluctuations of single-molecule. We extend single-molecule spectroscopy study into in situ nano-biomolecular imaging of cancer cells by developing in-liquid SNOM. We use a new mechanical resonance control, achieving a high-Q force sensing of the near-field probe. We reveal nanoscale correlations between surface biomolecules and intracellular organelle structures through near-field imaging of the spatial distribution of EGFRs on the membrane of A431 cancer cells. In addition, to understand modified spontaneous emission properties of single quantum dots coupled strongly with localized plasmon, we perform tip-enhanced photoluminescence (TEPL) spectroscopy of the single CdSe/ZnS quantum dots on gold film. We probe and control nanoscale processes in van der Waals two-dimensional (2D) materials. To understand lattice and electronic structure as well as elastic and phonon scattering properties of grain boundaries (GBs) in large-area graphene, we perform TERS imaging. Through correlated analysis of multispectral TERS images with corresponding topography and near-field scattering image, we reveal bilayer structure of GBs in the form of twisted stacking. In addition, we determine the misorientation angles of the bilayer GBs from a detailed quantitative investigation of the Raman modes. In addition, we present a new hybrid nano-optomechanical tip-enhanced spectroscopy and imaging approach combining TERS, TEPL, and atomic force local strain manipulation to probe the heterogeneous PL responses at nanoscale defects and control the local bandgap in transition metal dichalcogenide (TMD) monolayer. We further extend this approach to probe and control the radiative emission of dark excitons and localized excitons. Based on nano-tip enhanced spectroscopy with 600,000-fold PL enhancement induced by the plasmonic Purcell effect and few-fs radiative dynamics of the optical antenna tip, we can directly probe and actively modulate the dark exciton and localized exciton emissions in time ( ms) and space (<15 nm) at room temperature. Lastly, to extend the range of tip-enhanced microscopy applications to nano-crystallography and nonlinear optics, we present a generalizable approach controlling the excitation polarizability for both in-plane and out-of-plane vector fields by breaking the axial symmetry of a conventional Au tip. This vector field control with the tip enables probing of nonlinear optical second harmonic generation (SHG) responses from a range of ferroic materials as well as van der Waals 2D materials. Specifically, we demonstrate SHG nano-crystallography results for MoS2 monolayer film, ferroelectric YMnO3, BaTiO3-BiFeO3 multiferroics, and PbTiO3/SrTiO 3 superlattices.

Growth of multiwalled-carbon nanotubes using vertically aligned carbon nanofibers as templates/scaffolds and improved field-emission properties

NASA Astrophysics Data System (ADS)

Cui, H.; Yang, X.; Baylor, L. R.; Lowndes, D. H.

2005-01-01

Multiwalled-carbon nanotubes (MWCNTs) are grown on top of vertically aligned carbon nanofibers (VACNFs) via microwave plasma-enhanced chemical vapor deposition (MPECVD). The VACNFs are first grown in a direct-current plasma-enhanced chemical vapor deposition reactor using nickel catalyst. A layer of carbon-silicon materials is then deposited on the VACNFs and the nickel catalyst particle is broken down into smaller nanoparticles during an intermediate reactive-ion-plasma deposition step. These nickel nanoparticles nucleate and grow MWCNTs in the following MPECVD process. Movable-probe measurements show that the MWCNTs have greatly improved field-emission properties relative to the VACNFs.

Indentation versus Rolling: Dependence of Adhesion on Contact Geometry for Biomimetic Structures.

PubMed

Moyle, Nichole; He, Zhenping; Wu, Haibin; Hui, Chung-Yuen; Jagota, Anand

2018-04-03

Numerous biomimetic structures made from elastomeric materials have been developed to produce enhancement in properties such as adhesion, static friction, and sliding friction. As a property, one expects adhesion to be represented by an energy per unit area that is usually sensitive to the combination of shear and normal stresses at the crack front but is otherwise dependent only on the two elastic materials that meet at the interface. More specifically, one would expect that adhesion measured by indentation (a popular and convenient technique) could be used to predict adhesion hysteresis in the more practically important rolling geometry. Previously, a structure with a film-terminated fibrillar geometry exhibited dramatic enhancement of adhesion by a crack-trapping mechanism during indentation with a rigid sphere. Roughly isotropic structures such as the fibrillar geometry show a strong correlation between adhesion enhancement in indentation versus adhesion hysteresis in rolling. However, anisotropic structures, such as a film-terminated ridge-channel geometry, surprisingly show a dramatic divergence between adhesion measured by indentation versus rolling. We study this experimentally and theoretically, first comparing the adhesion of the anisotropic ridge-channel structure to the roughly isotropic fibrillar structure during indentation with a rigid sphere, where only the isotropic structure shows adhesion enhancement. Second, we examine in more detail the anomalous anisotropic film-terminated ridge-channel structure during indentation with a rigid sphere versus rolling to show why these structures show a dramatic adhesion enhancement for the rolling case and no adhesion enhancement for indentation.

High-throughput materials discovery and development: breakthroughs and challenges in the mapping of the materials genome

NASA Astrophysics Data System (ADS)

Buongiorno Nardelli, Marco

High-Throughput Quantum-Mechanics computation of materials properties by ab initio methods has become the foundation of an effective approach to materials design, discovery and characterization. This data driven approach to materials science currently presents the most promising path to the development of advanced technological materials that could solve or mitigate important social and economic challenges of the 21st century. In particular, the rapid proliferation of computational data on materials properties presents the possibility to complement and extend materials property databases where the experimental data is lacking and difficult to obtain. Enhanced repositories such as AFLOWLIB open novel opportunities for structure discovery and optimization, including uncovering of unsuspected compounds, metastable structures and correlations between various properties. The practical realization of these opportunities depends almost exclusively on the the design of efficient algorithms for electronic structure simulations of realistic material systems beyond the limitations of the current standard theories. In this talk, I will review recent progress in theoretical and computational tools, and in particular, discuss the development and validation of novel functionals within Density Functional Theory and of local basis representations for effective ab-initio tight-binding schemes. Marco Buongiorno Nardelli is a pioneer in the development of computational platforms for theory/data/applications integration rooted in his profound and extensive expertise in the design of electronic structure codes and in his vision for sustainable and innovative software development for high-performance materials simulations. His research activities range from the design and discovery of novel materials for 21st century applications in renewable energy, environment, nano-electronics and devices, the development of advanced electronic structure theories and high-throughput techniques in materials genomics and computational materials design, to an active role as community scientific software developer (QUANTUM ESPRESSO, WanT, AFLOWpi)

Enhanced antibacterial properties, biocompatibility, and corrosion resistance of degradable Mg-Nd-Zn-Zr alloy.

PubMed

Qin, Hui; Zhao, Yaochao; An, Zhiquan; Cheng, Mengqi; Wang, Qi; Cheng, Tao; Wang, Qiaojie; Wang, Jiaxing; Jiang, Yao; Zhang, Xianlong; Yuan, Guangyin

2015-06-01

Magnesium (Mg), a potential biodegradable material, has recently received increasing attention due to its unique antibacterial property. However, rapid corrosion in the physiological environment and potential toxicity limit clinical applications. In order to improve the corrosion resistance meanwhile not compromise the antibacterial activity, a novel Mg alloy, Mg-Nd-Zn-Zr (Hereafter, denoted as JDBM), is fabricated by alloying with neodymium (Nd), zinc (Zn), zirconium (Zr). pH value, Mg ion concentration, corrosion rate and electrochemical test show that the corrosion resistance of JDBM is enhanced. A systematic investigation of the in vitro and in vivo antibacterial capability of JDBM is performed. The results of microbiological counting, CLSM, SEM in vitro, and microbiological cultures, histopathology in vivo consistently show JDBM enhanced the antibacterial activity. In addition, the significantly improved cytocompatibility is observed from JDBM. The results suggest that JDBM effectively enhances the corrosion resistance, biocompatibility and antimicrobial properties of Mg by alloying with the proper amount of Zn, Zr and Nd. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mesoporous silica formulation strategies for drug dissolution enhancement: a review.

PubMed

McCarthy, Carol A; Ahern, Robert J; Dontireddy, Rakesh; Ryan, Katie B; Crean, Abina M

2016-01-01

Silica materials, in particular mesoporous silicas, have demonstrated excellent properties to enhance the oral bioavailability of poorly water-soluble drugs. Current research in this area is focused on investigating the kinetic profile of drug release from these carriers and manufacturing approaches to scale-up production for commercial manufacture. This review provides an overview of different methods utilized to load drugs onto mesoporous silica carriers. The influence of silica properties and silica pore architecture on drug loading and release are discussed. The kinetics of drug release from mesoporous silica systems is examined and the manufacturability and stability of these formulations are reviewed. Finally, the future prospects of mesoporous silica drug delivery systems are considered. Substantial progress has been made in the characterization and development of mesoporous drug delivery systems for drug dissolution enhancement. However, more research is required to fully understand the drug release kinetic profile from mesoporous silica materials. Incomplete drug release from the carrier and the possibility of drug re-adsorption onto the silica surface need to be investigated. Issues to be addressed include the manufacturability and regulation status of formulation approaches employing mesoporous silica to enhance drug dissolution. While more research is needed to support the move of this technology from the bench to a commercial medicinal product, it is a realistic prospect for the near future.

Remembering the snake in the grass: Threat enhances recognition but not source memory.

PubMed

Meyer, Miriam Magdalena; Bell, Raoul; Buchner, Axel

2015-12-01

Research on the influence of emotion on source memory has yielded inconsistent findings. The object-based framework (Mather, 2007) predicts that negatively arousing stimuli attract attention, resulting in enhanced within-object binding, and, thereby, enhanced source memory for intrinsic context features of emotional stimuli. To test this prediction, we presented pictures of threatening and harmless animals, the color of which had been experimentally manipulated. In a memory test, old-new recognition for the animals and source memory for their color was assessed. In all 3 experiments, old-new recognition was better for the more threatening material, which supports previous reports of an emotional memory enhancement. This recognition advantage was due to the emotional properties of the stimulus material, and not specific for snake stimuli. However, inconsistent with the prediction of the object-based framework, intrinsic source memory was not affected by emotion. (c) 2015 APA, all rights reserved).

Zr-doped TiO2 as a thermostabilizer in plasmon-enhanced dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Pasche, Anastasia; Grohe, Bernd; Mittler, Silvia; Charpentier, Paul A.

2017-07-01

Harvesting solar energy is a promising solution toward meeting the world's ever-growing energy demand. Dye-sensitized solar cells (DSSCs) are hybrid organic-inorganic solar cells with tremendous potential for commercial application, but they are plagued by inefficiency due to their poor sunlight absorption. Plasmonic silver nanoparticles (AgNPs) have been shown to enhance the absorptive properties of DSSCs, but their plasmonic resonance can cause thermal damage resulting in cell deterioration. Hence, the influence of Zr-doped TiO2 on the efficiency of plasmon-enhanced DSSCs was studied, showing that 5 mol.% Zr-doping of the photoactive TiO2 material can improve the photovoltaic performance of DSSCs by 44%. By examining three different DSSC designs, it became clear that the efficiency enhancing effect of Zr strongly depends on the proximity of the Zr-doped material to the plasmonic AgNPs.

Enhanced performance and interfacial investigation of mineral-based composite phase change materials for thermal energy storage.

PubMed

Li, Chuanchang; Fu, Liangjie; Ouyang, Jing; Yang, Huaming

2013-01-01

A novel mineral-based composite phase change materials (PCMs) was prepared via vacuum impregnation method assisted with microwave-acid treatment of the graphite (G) and bentonite (B) mixture. Graphite and microwave-acid treated bentonite mixture (GBm) had more loading capacity and higher crystallinity of stearic acid (SA) in the SA/GBm composite. The SA/GBm composite showed an enhanced thermal storage capacity, latent heats for melting and freezing (84.64 and 84.14 J/g) was higher than those of SA/B sample (48.43 and 47.13 J/g, respectively). Addition of graphite was beneficial to the enhancement in thermal conductivity of the SA/GBm composite, which could reach 0.77 W/m K, 31% higher than SA/B and 196% than pure SA. Furthermore, atomic-level interfaces between SA and support surfaces were depicted, and the mechanism of enhanced thermal storage properties was in detail investigated.

Strongly Modulated Friction of a Film-Terminated Ridge-Channel Structure.

PubMed

He, Zhenping; Hui, Chung-Yuen; Levrard, Benjamin; Bai, Ying; Jagota, Anand

2016-05-26

Natural contacting surfaces have remarkable surface mechanical properties, which has led to the development of bioinspired surface structures using rubbery materials with strongly enhanced adhesion and static friction. However, sliding friction of structured rubbery surfaces is almost always significantly lower than that of a flat control, often due to significant loss of contact. Here we show that a film-terminated ridge-channel structure can strongly enhance sliding friction. We show that with properly chosen materials and geometrical parameters the near surface structure undergoes mechanical instabilities along with complex folding and sliding of internal interfaces, which is responsible for the enhancement of sliding friction. Because this structure shows no enhancement of adhesion under normal indentation by a sphere, it breaks the connection between energy loss during normal and shear loading. This makes it potentially interesting in many applications, for instance in tires, where one wishes to minimize rolling resistance (normal loading) while maximizing sliding friction (shear loading).

Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys

NASA Astrophysics Data System (ADS)

Lu, Chenyang; Niu, Liangliang; Chen, Nanjun; Jin, Ke; Yang, Taini; Xiu, Pengyuan; Zhang, Yanwen; Gao, Fei; Bei, Hongbin; Shi, Shi; He, Mo-Rigen; Robertson, Ian M.; Weber, William J.; Wang, Lumin

2016-12-01

A grand challenge in material science is to understand the correlation between intrinsic properties and defect dynamics. Radiation tolerant materials are in great demand for safe operation and advancement of nuclear and aerospace systems. Unlike traditional approaches that rely on microstructural and nanoscale features to mitigate radiation damage, this study demonstrates enhancement of radiation tolerance with the suppression of void formation by two orders magnitude at elevated temperatures in equiatomic single-phase concentrated solid solution alloys, and more importantly, reveals its controlling mechanism through a detailed analysis of the depth distribution of defect clusters and an atomistic computer simulation. The enhanced swelling resistance is attributed to the tailored interstitial defect cluster motion in the alloys from a long-range one-dimensional mode to a short-range three-dimensional mode, which leads to enhanced point defect recombination. The results suggest design criteria for next generation radiation tolerant structural alloys.

The role of the non-magnetic material in spin pumping and magnetization dynamics in NiFe and CoFeB multilayer systems

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

Ruiz-Calaforra, A., E-mail: ruiz@physik.uni-kl.de; Brächer, T.; Lauer, V.

2015-04-28

We present a study of the effective magnetization M{sub eff} and the effective damping parameter α{sub eff} by means of ferromagnetic resonance spectroscopy on the ferromagnetic (FM) materials Ni{sub 81}Fe{sub 19} (NiFe) and Co{sub 40}Fe{sub 40}B{sub 20} (CoFeB) in FM/Pt, FM/NM, and FM/NM/Pt systems with the non-magnetic (NM) materials Ru, Cr, Al, and MgO. Moreover, for NiFe layer systems, the influence of interface effects is studied by way of thickness dependent measurements of M{sub eff} and α{sub eff}. Additionally, spin pumping in NiFe/NM/Pt is investigated by means of inverse spin Hall effect (ISHE) measurements. We observe a large dependence ofmore » M{sub eff} and α{sub eff} of the NiFe films on the adjacent NM layer. While Cr and Al do not induce a large change in the magnetic properties, Ru, Pt, and MgO affect M{sub eff} and α{sub eff} in different degrees. In particular, NiFe/Ru and NiFe/Ru/Pt systems show a large perpendicular surface anisotropy and a significant enhancement of the damping. In contrast, the magnetic properties of CoFeB films do not have a large influence of the NM adjacent material and only CoFeB/Pt systems present an enhancement of α{sub eff}. However, this enhancement is much more pronounced in NiFe/Pt. By the introduction of the NM spacer material, this enhancement is reduced. Furthermore, a difference in symmetry between NiFe/NM/Pt and NiFe/NM systems in the output voltage signal from the ISHE measurements reveals the presence of spin pumping into the Pt layer in all-metallic NiFe/NM/Pt and NiFe/Pt systems.« less

Dual-functional composite with anticoagulant and antibacterial properties based on heparinized silk fibroin and chitosan.

PubMed

Wang, Jianglin; Hu, Wei; Liu, Qun; Zhang, Shengmin

2011-07-01

Heparinized biomaterials exhibit great anticoagulant properties. However, they promote proliferation of Staphylococcus aureus (S. aureus) and therefore cause infection within the bloodstream upon implantation in vivo. In the present study, an interesting dual-functional composite with anticoagulant and antibacterial properties based on heparinized silk fibroin and chitosan was synthesized. First, heparin was grafted onto the silk fibroin by covalent immobilization with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS). All data gathered from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and elemental analysis (EA) indicated that the heparin was successfully immobilized onto the silk fibroin. The dual-functional composite of heparinized silk fibroin and chitosan was then fabricated by a blending method. The anticoagulant activity of the heparinized materials was evaluated using the prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT). The results showed that both heparinized silk fibroin and the composite material exhibited better hemocompatibility in comparison with single silk fibroin or chitosan. The antibacterial property of the materials was investigated by the pour-plate method. Results further suggested that the composite antibacterial property with respect to S. aureus was significantly enhanced. The dual-functionality of the composite material may supply a potential choice in blood contact devices. Copyright © 2011 Elsevier B.V. All rights reserved.

Sorbent Material Property Requirements for On-Board Hydrogen Storage for Automotive Fuel Cell Systems.

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

Ahluwalia, R. K.; Peng, J-K; Hua, T. Q.

2015-05-25

Material properties required for on-board hydrogen storage in cryogenic sorbents for use with automotive polymer electrolyte membrane (PEM) fuel cell systems are discussed. Models are formulated for physical, thermodynamic and transport properties, and for the dynamics of H-2 refueling and discharge from a sorbent bed. A conceptual storage configuration with in-bed heat exchanger tubes, a Type-3 containment vessel, vacuum insulation and requisite balance-of-plant components is developed to determine the peak excess sorption capacity and differential enthalpy of adsorption for 5.5 wt% system gravimetric capacity and 55% well-to-tank (WTT) efficiency. The analysis also determines the bulk density to which the materialmore » must be compacted for the storage system to reach 40 g.L-1 volumetric capacity. Thermal transport properties and heat transfer enhancement methods are analyzed to estimate the material thermal conductivity needed to achieve 1.5 kg.min(-1) H-2 refueling rate. Operating temperatures and pressures are determined for 55% WTT efficiency and 95% usable H-2. Needs for further improvements in material properties are analyzed that would allow reduction of storage pressure to 50 bar from 100 bar, elevation of storage temperature to 175-200 K from 150 K, and increase of WTT efficiency to 57.5% or higher.« less

Cellulose Acetate/N-TiO2 Biocomposite Flexible Films with Enhanced Solar Photochromic Properties

NASA Astrophysics Data System (ADS)

Radhika, T.; Anju, K. R.; Silpa, M. S.; Ramalingam, R. Jothi; Al-Lohedan, Hamad A.

2017-07-01

Flexible cellulose acetate/N-TiO2 nanocomposite films containing various concentrations of nanosized N-TiO2 and an intelligent methylene blue ink have been prepared by solution casting. The hydrothermally prepared nitrogen-doped titania (N-TiO2) and the films were characterized in detail. The photochromic properties of the prepared films were investigated under ultraviolet (UV), visible light, and simulated solar irradiation by UV-Vis spectrophotometry. Upon irradiation, the films exhibited rapid photochromic response that was reversible at room temperature. Films with higher content of nano N-TiO2 showed enhanced decoloration/recoloration under all irradiation conditions, with fast decoloration/recoloration under simulated solar irradiation. These results suggest that the amount of nano N-TiO2 in the composite, the concentration of methylene blue, and the solvent greatly influence the photochromic properties of the films. Such flexible and transparent cellulose acetate/N-TiO2 films with enhanced decoloration/recoloration properties under solar irradiation are promising smart materials for use in photoreversible printed electronics applications.

Micromechanics and Piezo Enhancements of HyperSizer

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Bednarcyk, Brett A.; Yarrington, Phillip; Collier, Craig S.

2006-01-01

The commercial HyperSizer aerospace-composite-material-structure-sizing software has been enhanced by incorporating capabilities for representing coupled thermal, piezoelectric, and piezomagnetic effects on the levels of plies, laminates, and stiffened panels. This enhancement is based on a formulation similar to that of the pre-existing HyperSizer capability for representing thermal effects. As a result of this enhancement, the electric and/or magnetic response of a material or structure to a mechanical or thermal load, or its mechanical response to an applied electric or magnetic field can be predicted. In another major enhancement, a capability for representing micromechanical effects has been added by establishment of a linkage between HyperSizer and Glenn Research Center s Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC) computer program, which was described in several prior NASA Tech Briefs articles. The linkage enables Hyper- Sizer to localize to the fiber and matrix level rather than only to the ply level, making it possible to predict local failures and to predict properties of plies from those of the component fiber and matrix materials. Advanced graphical user interfaces and database structures have been developed to support the new HyperSizer micromechanics capabilities.

Surface-Enhanced Raman Spectroscopy as a Probe of the Surface Chemistry of Nanostructured Materials.

PubMed

Dick, Susan; Konrad, Magdalena P; Lee, Wendy W Y; McCabe, Hannah; McCracken, John N; Rahman, Taifur M D; Stewart, Alan; Xu, Yikai; Bell, Steven E J

2016-07-01

Surface-enhanced Raman spectroscopy (SERS) is now widely used as a rapid and inexpensive tool for chemical/biochemical analysis. The method can give enormous increases in the intensities of the Raman signals of low-concentration molecular targets if they are adsorbed on suitable enhancing substrates, which are typically composed of nanostructured Ag or Au. However, the features of SERS that allow it to be used as a chemical sensor also mean that it can be used as a powerful probe of the surface chemistry of any nanostructured material that can provide SERS enhancement. This is important because it is the surface chemistry that controls how these materials interact with their local environment and, in real applications, this interaction can be more important than more commonly measured properties such as morphology or plasmonic absorption. Here, the opportunity that this approach to SERS provides is illustrated with examples where the surface chemistry is both characterized and controlled in order to create functional nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pressure-induced structural and electronic transitions, metallization, and enhanced visible-light responsiveness in layered rhenium disulphide

NASA Astrophysics Data System (ADS)

Wang, Pei; Wang, Yonggang; Qu, Jingyu; Zhu, Qiang; Yang, Wenge; Zhu, Jinlong; Wang, Liping; Zhang, Weiwei; He, Duanwei; Zhao, Yusheng

2018-06-01

Triclinic rhenium disulphide (Re S2 ) is a promising candidate for postsilicon electronics because of its unique optic-electronic properties. The electrical and optical properties of Re S2 under high pressure, however, remain unclear. Here we present a joint experimental and theoretical study on the structure, electronic, and vibrational properties, and visible-light responses of Re S2 up to 50 GPa. There is a direct-to-indirect band-gap transition in 1 T -Re S2 under low-pressure regime up to 5 GPa. Upon further compression, 1 T -Re S2 undergoes a structural transition to distorted-1 T' phase at 7.7 GPa, followed by the isostructural metallization at 38.5 GPa. Both in situ Raman spectrum and electronic structure analysis reveal that interlayer sulfur-sulfur interaction is greatly enhanced during compression, leading to the remarkable modifications on the electronic properties observed in our subsequent experimental measurements, such as band-gap closure and enhanced photoresponsiveness. This study demonstrates the critical role of pressure in tuning materials properties and the potential usage of layered Re S2 for pressure-responsive optoelectronic applications.

Nanoparticles Incorporated inside Single-Crystals: Enhanced Fluorescent Properties

DOE PAGES

Liu, Yujing; Zang, Huidong; Wang, Ling; ...

2016-09-25

Incorporation of guest materials inside single-crystalline hosts leads to single-crystal composites that have become more and more frequently seen in both biogenic and synthetic crystals. The unique composite structure together with long-range ordering promises special properties that are, however, less often demonstrated. In this study, we examine the fluorescent properties of quantum dots (QDs) and polymer dots (Pdots) encapsulated inside the hosts of calcite single-crystals. Two CdTe QDs and two Pdots are incorporated into growing calcite crystals, as the QDs and Pdots are dispersed in the crystallization media of agarose gels. As a result, enhanced fluorescent properties are obtained frommore » the QDs and Pdots inside calcite single-crystals with greatly improved photostability and significantly prolonged fluorescence lifetime, compared to those in solutions and gels. Particularly, the fluorescence lifetime increases by 0.5-1.6 times after the QDs or Pdots are incorporated. The enhanced fluorescent properties indicate the advantages of encapsulation by single-crystal hosts that provide dense shells to isolate the fluorescent nanoparticles from atmosphere. As such, this work has implications for advancing the research of single-crystal composites toward their functional design.« less

Etched Polymer Fibre Bragg Gratings and Their Biomedical Sensing Applications

PubMed Central

Rajan, Ginu; Bhowmik, Kishore; Xi, Jiangtao; Peng, Gang-Ding

2017-01-01

Bragg gratings in etched polymer fibres and their unique properties and characteristics are discussed in this paper. Due to the change in material and mechanical properties of the polymer fibre through etching, Bragg gratings inscribed in such fibres show high reflectivity and enhanced intrinsic sensitivity towards strain, temperature, and pressure. The short-term and long-term stability of the gratings and the effect of hysteresis on the dynamic characteristics are also discussed. The unique properties and enhanced intrinsic sensitivity of etched polymer fibre Bragg grating are ideal for the development of high-sensitivity sensors for biomedical applications. To demonstrate their biomedical sensing capabilities, a high-sensitivity pressure transducer that operates in the blood pressure range, and a breathing rate monitoring device are developed and presented. PMID:29027945

Dimethacrylate network formation and polymer property evolution as determined by the selection of monomers and curing conditions

PubMed Central

Stansbury, Jeffrey W.

2011-01-01

Objectives This overview is intended to highlight connections between monomer structure and the development of highly crosslinked photopolymer networks including the conversion dependent properties of shrinkage, modulus and stress. Methods A review is provided that combines the polymer science and dental materials literature along with examples of relevant experimental results, which include measurements of reaction kinetics, photorheology as well as polymerization shrinkage and stress. Results While new monomers are continually under development for dental materials applications, mixtures of dimethacrylate monomers persist as the most common form of dental resins used on composite restorative materials. Monomer viscosity and reaction potential is derived from molecular structure and by employing real-time near-infrared spectroscopic techniques, the development of macromolecular networks is linked to the evolution of polymerization shrinkage (measured by linometer), modulus (measured by photorheometer), and stress (measured by tensometer). Relationships between the respective polymer properties are examined. Significance Through a better understanding of the polymer network formation and property development processes using conventional dimethacrylate monomer formulations, the rational design of improved materials is facilitated with the ultimate goal of achieving dental polymers that deliver enhanced clinical outcomes. PMID:22192248

Polymorphism in Bacterial Flagella Suspensions

NASA Astrophysics Data System (ADS)

Schwenger, Walter J.

Bacterial flagella are a type of biological polymer studied for its role in bacterial motility and the polymorphic transitions undertaken to facilitate the run and tumble behavior. The naturally rigid, helical shape of flagella gives rise to novel colloidal dynamics and material properties. This thesis studies methods in which the shape of bacterial flagella can be controlled using in vitro methods and the changes the shape of the flagella have on both single particle dynamics and bulk material properties. We observe individual flagellum in both the dilute and semidilute regimes to observe the effects of solvent condition on the shape of the filament as well as the effect the filament morphology has on reptation through a network of flagella. In addition, we present rheological measurements showing how the shape of filaments effects the bulk material properties of flagellar suspensions. We find that the individual particle dynamics in suspensions of flagella can vary with geometry from needing to reptate linearly via rotation for helical filaments to the prevention of long range diffusion for block copolymer filaments. Similarly, for bulk material properties of flagella suspensions, helical geometries show a dramatic enhancement in elasticity over straight filaments while block copolymers form an elastic gel without the aid of crosslinking agents.

Enhancement of porous silicon photoluminescence property by lithium chloride treatment

NASA Astrophysics Data System (ADS)

Azaiez, Khawla; Zaghouani, Rabia Benabderrahmane; Khamlich, Saleh; Meddeb, Hosny; Dimassi, Wissem

2018-05-01

Porous silicon (PS) decorated by several nanostructured metal elements has still aroused interests as promising composites in many industrial applications. With the focus mainly on the synthesis, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work focuses primarily on the influence of lithium chloride solution (LiCl) treatment on the physical properties of PS. Variations in the structural and optoelectronic properties of PS were observed after immersion in (LiCl), as revealed by the obtained analyses. Moreover, enhanced photoluminescence (PL) property of the PS after passivation by lithium particles was clearly shown, and their presence on the surface of the microporous silicon was confirmed by FTIR spectroscopy and atomic force microscopy. An improvement of the minority carrier lifetime was also obtained, which was attributed to the decrease of the surface recombination velocity after LiCl treatment.

Microstructure and antibacterial properties of microwave plasma nitrided layers on biomedical stainless steels

NASA Astrophysics Data System (ADS)

Lin, Li-Hsiang; Chen, Shih-Chung; Wu, Ching-Zong; Hung, Jing-Ming; Ou, Keng-Liang

2011-06-01

Nitriding of AISI 303 austenitic stainless steel using microwave plasma system at various temperatures was conducted in the present study. The nitrided layers were characterized via scanning electron microscopy, glancing angle X-ray diffraction, transmission electron microscopy and Vickers microhardness tester. The antibacterial properties of this nitrided layer were evaluated. During nitriding treatment between 350 °C and 550 °C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ → (γ + γ N) → (γ + α + CrN). The analytical results revealed that the surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ N phase in nitriding process. Antibacterial test also demonstrated the nitrided layer processed the excellent antibacterial properties. The enhanced surface hardness and antibacterial properties make the nitrided AISI 303 austenitic stainless steel to be one of the essential materials in the biomedical applications.

Application of far infrared rare earth mineral composite materials to liquefied petroleum gas.

PubMed

Zhu, Dongbin; Liang, Jinsheng; Ding, Yan; Xu, Anping

2010-03-01

Far infrared rare earth mineral composite materials were prepared by the coprecipitation method using tourmaline, cerium acetate, and lanthanum acetate as raw materials. The results of Fourier transform infrared spectroscopy show that tourmaline modified with the rare earths La and Ce has a better far infrared emitting performance. Through XRD analysis, we attribute the improved far infrared emission properties of the tourmaline to the unit cell shrinkage of the tourmaline arising from La enhancing the redox properties of nano-CeO2. The effect of the composite materials on the combustion of liquefied petroleum gas (LPG) was studied by the flue gas analysis and water boiling test. Based on the results, it was found that the composite materials could accelerate the combustion of LPG, and that the higher the emissivity of the rare earth mineral composite materials, the better the effects on combustion of LPG. In all activation styles, both air and LPG to be activated has a best effect, indicating the activations having a cumulative effect.

Glass Fiber Reinforced Polypropylene Mechanical Properties Enhancement by Adhesion Improvement

PubMed Central

Etcheverry, Mariana; Barbosa, Silvia E.

2012-01-01

Glass fibers (GF) are the reinforcement agent most used in polypropylene (PP) based composites, as they have good balance between properties and costs. However, their final properties are mainly determined by the strength and stability of the polymer-fiber interphase. Fibers do not act as an effective reinforcing material when the adhesion is weak. Also, the adhesion between phases can be easily degraded in aggressive environmental conditions such as high temperatures and/or elevated moisture, and by the stress fields to which the material may be exposed. Many efforts have been done to improve polymer-glass fiber adhesion by compatibility enhancement. The most used techniques include modifications in glass surface, polymer matrix and/or both. However, the results obtained do not show a good costs/properties improvement relationship. The aim of this work is to perform an accurate analysis regarding methods for GF/PP adhesion improvement and to propose a new route based on PP in-situ polymerization onto fibers. This route involves the modification of fibers with an aluminum alkyl and hydroxy-α-olefin and from there to enable the growth of the PP chains using direct metallocenic copolymerization. The adhesion improvements were further proved by fragmentation test, as well as by mechanical properties measurements. The strength and toughness increases three times and the interfacial strength duplicates in PP/GF composites prepared with in-situ polymerized fibers. PMID:28817025

Tunable plasmonic properties of Ag-Fe nanoparticles

NASA Astrophysics Data System (ADS)

Bhatia, Pradeep; Verma, S. S.; Sinha, M. M.

2018-05-01

Compatibility problems with electronic processes, limited availability and the high cost of noble metals motivate towards the search of alternative materials to enhance the suitability and efficiency of plasmonic based devices. Alloy or coated bimetallic material configuration is an attractive way to engineer a system possessing tuneable plasmonic properties. Magneto-plasmonic nanoparticles (MPNPs) present the possibility to exhibit their tuneable magnetic and optical properties with extensive applications. We studied the optical properties of Ag-Fe alloy for different compositions. The Localised Surface Plasmon Resonance (LSPR) tunability of Agx-Fe1-x (x = 0.25, 0.50 and 0.75) alloy for nanospheres has been calculated by using Discrete Dipole Approximation (DDA) simulation technique. It is found that absorption and scattering efficiencies of Ag-Fe alloy are found in near ultra violet and visible region of electromagnetic spectrum. Large LSPR shift has been observed in absorption and scattering efficiencies peak for 40 nm and 80 nm size of nanospheres alloys. It is concluded that the LSPR can be tuned by changing nanoparticle size and the alloy composition. Results of the plasmonics properties for Ag-Fe alloy at wavelength 330-545nm (absorption) and 331-507nm (scattering) will open the avenues for new applications in optical imaging, biomedical fields particularly in (calorimetric)-DNA, pentose's, proteins (absorption) and plasmonic-enhanced spectroscopies/spectrometer devices (scattering) for determination of optical densities of cell cultures.

Chitosan membranes for tissue engineering: comparison of different crosslinkers.

PubMed

Ruini, F; Tonda-Turo, C; Chiono, V; Ciardelli, G

2015-11-03

Chitosan (CS), a derivative of the naturally occurring biopolymer chitin, is an attractive material for biomedical applications thanks to its biocompatibility, biodegradability, antibacterial properties and ability to enhance cell adhesion and growth compared to other biopolymers. However, the physical and mechanical stability of CS based materials in aqueous solutions is limited and crosslinking agents are required to increase CS performances in a biological environment. In this work, the effect of three highly-biocompatible crosslinkers as genipin (GP), γ-glycidoxypropyltrimethoxysilane (GPTMS), dibasic sodium phosphate (DSP) and a combination of GPTMS and DSP (GPTMS_DSP) on CS physicochemical, thermal, morphological, mechanical properties, swelling and degradation behavior was investigated. Infrared spectroscopy and thermogravimetric analyses confirmed the chemical reaction between CS and the different crosslinkers. CS wettability was enhanced when CS was DSP ionically crosslinked showing contact angle values of about 65° and exhibiting a higher swelling behavior compared to covalently crosslinked films. Moreover, all the crosslinking methods analyzed improved the stability of CS in aqueous media, showed model molecule permeation in time and increased the mechanical properties when compared with non-crosslinked films. The possibility to tailor the final properties of CS scaffolds through crosslinking is a key strategy in applying CS in different biomedical and tissue engineering applications. The obtained results reveal that the optimization of the crosslinking mechanism provides CS membrane properties required in different biomedical applications.

Progress in piezo-phototronic effect modulated photovoltaics.

PubMed

Que, Miaoling; Zhou, Ranran; Wang, Xiandi; Yuan, Zuqing; Hu, Guofeng; Pan, Caofeng

2016-11-02

Wurtzite structured materials, like ZnO, GaN, CdS, and InN, simultaneously possess semiconductor and piezoelectric properties. The inner-crystal piezopotential induced by external strain can effectively tune/control the carrier generation, transport and separation/combination processes at the metal-semiconductor contact or p-n junction, which is called the piezo-phototronic effect. This effect can efficiently enhance the performance of photovoltaic devices based on piezoelectric semiconductor materials by utilizing the piezo-polarization charges at the junction induced by straining, which can modulate the energy band of the piezoelectric material and then accelerate or prevent the separation process of the photon-generated electrons and vacancies. This paper introduces the fundamental physics principles of the piezo-phototronic effect, and reviews recent progress in piezo-phototronic effect enhanced solar cells, including solar cells based on semiconductor nanowire, organic/inorganic materials, quantum dots, and perovskite. The piezo-phototronic effect is suggested as a suitable basis for the development of an innovative method to enhance the performance of solar cells based on piezoelectric semiconductors by applied extrinsic strains, which might be appropriate for fundamental research and potential applications in various areas of optoelectronics.

Progress in piezo-phototronic effect modulated photovoltaics

NASA Astrophysics Data System (ADS)

Que, Miaoling; Zhou, Ranran; Wang, Xiandi; Yuan, Zuqing; Hu, Guofeng; Pan, Caofeng

2016-11-01

Wurtzite structured materials, like ZnO, GaN, CdS, and InN, simultaneously possess semiconductor and piezoelectric properties. The inner-crystal piezopotential induced by external strain can effectively tune/control the carrier generation, transport and separation/combination processes at the metal-semiconductor contact or p-n junction, which is called the piezo-phototronic effect. This effect can efficiently enhance the performance of photovoltaic devices based on piezoelectric semiconductor materials by utilizing the piezo-polarization charges at the junction induced by straining, which can modulate the energy band of the piezoelectric material and then accelerate or prevent the separation process of the photon-generated electrons and vacancies. This paper introduces the fundamental physics principles of the piezo-phototronic effect, and reviews recent progress in piezo-phototronic effect enhanced solar cells, including solar cells based on semiconductor nanowire, organic/inorganic materials, quantum dots, and perovskite. The piezo-phototronic effect is suggested as a suitable basis for the development of an innovative method to enhance the performance of solar cells based on piezoelectric semiconductors by applied extrinsic strains, which might be appropriate for fundamental research and potential applications in various areas of optoelectronics.

The novel solution for negative impact of out-of-band and outgassing by top coat materials in EUVL

NASA Astrophysics Data System (ADS)

Fujitani, Noriaki; Sakamoto, Rikimaru; Endo, Takafumi; Onishi, Ryuji; Nishita, Tokio; Yaguchi, Hiroaki; Ho, Bang-Ching

2013-03-01

EUV lithography (EUVL) is the most promising candidate of next generation technology for hp20nm node device manufacturing and beyond. However, the power of light source, masks and photo resists are the most critical issues for driving the EUVL. Especially, concerning about deterioration of the patterning performance by Out-of-Band (OoB) light existing in the EUV light, and contamination problem of exposure tool due to the resist outgassing are the key issues which have to be resolved in the material view point toward the high volume manufacturing by EUVL. This paper proposes the solution for these critical issues by applying the top coat material. The key characteristics for top coat material are the protection of the OoB effect, the prevention of the outgassing from resist as a barrier layer and enhancement of photo resist performance, like resist profile and process window. This paper describes the material design and performance. The optical property needs having the high absorbance of DUV light in OoB range and high transmittance for 13.5nm wavelength. Outgassing barrier property needs high broking property against non contamination chemical species from photo resist outgassing. The study of TOF-SIMS analysis indicates how much the polymer chemistry can impact for outgassing barrier property. The dependency of material design and lithography performance is also discussed.

Zinc alloy enhances strength and creep resistance

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

Machler, M.

1996-10-01

A family of high-performance ternary zinc-copper-aluminum alloys has been developed that provides higher strength, hardness, and creep resistance than the traditional zinc-aluminum alloys Zamak 3, Zamak 5, and ZA-8. Designated ACuZinc, mechanical properties comparable to those of more expensive materials make it suitable for high-load applications and those at elevated temperatures. This article describes the alloy`s composition, properties, and historical development.

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

Datta, Kaustuv; Neder, Reinhard B.; Chen, Jun

Revelation of unequivocal structural information at the atomic level for complex systems is uniquely important for deeper and generic understanding of the structure property connections and a key challenge in materials science. Here in this paper we report an experimental study of the local structure by applying total elastic scattering and Raman scattering analyses to an important non-relaxor ferroelectric solid solution exhibiting the so-called composition-induced morphotropic phase boundary (MPB), where concomitant enhancement of physical properties have been detected. The powerful combination of static and dynamic structural probes enabled us to derive direct correspondence between the atomic-level structural correlations and reportedmore » properties. The atomic pair distribution functions obtained from the neutron total scattering experiments were analysed through big-box atom-modelling implementing reverse Monte Carlo method, from which distributions of magnitudes and directions of off-centred cationic displacements were extracted. We found that an enhanced randomness of the displacement-directions for all ferroelectrically active cations combined with a strong dynamical coupling between the A- and B-site cations of the perovskite structure, can explain the abrupt amplification of piezoelectric response of the system near MPB. Finally, altogether this provides a more fundamental basis in inferring structure-property connections in similar systems including important implications in designing novel and bespoke materials.« less

Photo-induced conductivity in 2, 6-diaminopyridine functionalized graphene oxide containing Eu2+ for optoelectronic applications

NASA Astrophysics Data System (ADS)

Mondal, Supriya; Gupta, Abhisek; Shaw, Bikash Kumar; Saha, Shyamal K.

2017-11-01

Although, graphene is a unique electronic material, its optical property especially photoluminescence behavior is very poor. Several techniques have been developed to invoke optical property in graphene. Among these, functionalization is the most powerful technique to introduce optical property in graphene. In the present work, graphene oxide is functionalized by Diaminopyridine to achieve bright blue-green emission and subsequently Eu2+ ions are attached to the nitrogen due to electrostatic interaction between Eu2+ and the loan pair electrons of pyridinic nitrogen to tune the photoluminescence peak more broaden (extended upto green) and intense. This enhancement of photoluminescence property has been used to achieve superior photocurrent. By inducing photons, the conductivity of the device structure ITO/PEDOT: PSS/RGO-Amino-Pyridine-Eu2+/Al is better changed than that of the dark condition. It is also investigated the concentration of Eu2+ and thickness dependent photocurrent to optimize the photocurrent. Time correlated Single Photon Counting (TCSPC) spectra, Density Functional Theory (DFT) and Band structure have been used to explain this enhancement in photoluminescence and photocurrent. The formation of layered type materials with Eu2+ attached to pyridine moiety has also been confirmed by FTIR, Raman spectroscopy, AFM, XPS, TEM, and FESEM.

Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

NASA Astrophysics Data System (ADS)

Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

2018-03-01

When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

Transformation of bulk alloys to oxide nanowires

NASA Astrophysics Data System (ADS)

Lei, Danni; Benson, Jim; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

2017-01-01

One dimensional (1D) nanostructures offer prospects for enhancing the electrical, thermal, and mechanical properties of a broad range of functional materials and composites, but their synthesis methods are typically elaborate and expensive. We demonstrate a direct transformation of bulk materials into nanowires under ambient conditions without the use of catalysts or any external stimuli. The nanowires form via minimization of strain energy at the boundary of a chemical reaction front. We show the transformation of multimicrometer-sized particles of aluminum or magnesium alloys into alkoxide nanowires of tunable dimensions, which are converted into oxide nanowires upon heating in air. Fabricated separators based on aluminum oxide nanowires enhanced the safety and rate capabilities of lithium-ion batteries. The reported approach allows ultralow-cost scalable synthesis of 1D materials and membranes.

Enhancing Energy in Future Conventional Munition

NASA Astrophysics Data System (ADS)

Peiris, Suhithi

2017-06-01

Future conventional weapons are envisioned to contain more energy per volume than current weapons. Current weapons comprise of inert steel outer case, with inner volume for energetic materials, fuzing, sensor package, propulsion system, etc. Recent research on reactive materials (RM) & new energetics, and exploiting additive manufacturing can optimize the use of both mass and volume to achieve much higher energy in future weapons. For instance, replacing inert steel with RM of similar strength, additively manufacturing fuzing packages within the weapon form factor, and combing the whole with new energetics, will enable the same lethality effects from smaller weapons as obtained from today's larger weapons. This paper will elaborate on reactive materials and properties necessary for optimal utilization in various weapon features, and touch on other aspects of enhancing energy in future conventional munition.

Observation of Enhanced Hole Extraction in Br Concentration Gradient Perovskite Materials.

PubMed

Kim, Min-Cheol; Kim, Byeong Jo; Son, Dae-Yong; Park, Nam-Gyu; Jung, Hyun Suk; Choi, Mansoo

2016-09-14

Enhancing hole extraction inside the perovskite layer is the key factor for boosting photovoltaic performance. Realization of halide concentration gradient perovskite materials has been expected to exhibit rapid hole extraction due to the precise bandgap tuning. Moreover, a formation of Br-rich region on the tri-iodide perovskite layer is expected to enhance moisture stability without a loss of current density. However, conventional synthetic techniques of perovskite materials such as the solution process have not achieved the realization of halide concentration gradient perovskite materials. In this report, we demonstrate the fabrication of Br concentration gradient mixed halide perovskite materials using a novel and facile halide conversion method based on vaporized hydrobromic acid. Accelerated hole extraction and enhanced lifetime due to Br gradient was verified by observing photoluminescence properties. Through the combination of secondary ion mass spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy analysis, the diffusion behavior of Br ions in perovskite materials was investigated. The Br-gradient was found to be eventually converted into a homogeneous mixed halide layer after undergoing an intermixing process. Br-substituted perovskite solar cells exhibited a power conversion efficiency of 18.94% due to an increase in open circuit voltage from 1.08 to 1.11 V and an advance in fill-factor from 0.71 to 0.74. Long-term stability was also dramatically enhanced after the conversion process, i.e., the power conversion efficiency of the post-treated device has remained over 97% of the initial value under high humid conditions (40-90%) without any encapsulation for 4 weeks.

Binder free MnO2/PIn electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Purty, B.; Choudhary, R. B.; Kandulna, R.; Singh, R.

2018-05-01

Electrochemically stable MnO2/PIn nanocomposite was synthesized via in-situ chemical oxidative polymerization process. The structural and morphological properties were studied through FTIR and FESEM characterizing techniques. Sphere like PIn and MnO2 nanorods offers interacting surface for charge transfer action. The electrochemical properties were investigated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopic (EIS) techniques. The significant enhancement in capacitance value with 95% coulombic efficiency and relatively low equivalent series resistance (ESR)˜0.4 Ω proved that MnO2/PIn nanocomposite is an excellent performer as an electrode material in the spectrum of supercapcitors and optoelectronic devices.

Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

PubMed

Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

2012-12-21

In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

NASA Astrophysics Data System (ADS)

Drake, Christina Hartsell

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature gas sensor behavior of nanocrystalline oxide is presented that can be generalized to other nano-oxide systems and be useful in specific engineering of other nanomaterials. Deeper understanding of how nano-oxides react chemically and electronically would be extremely beneficial to issues present in current low cost, low temperature sensor technology. Ability to exactly monitor and then engineer the chemistry of nanostructures in the space charge region as well as the surface is also of great significance. Knowledge of the mechanisms responsible for enhanced sensor response in this material system could viably be applied to other material systems for sensor applications.

Perspectives: Nanofibers and nanowires for disordered photonics

NASA Astrophysics Data System (ADS)

Pisignano, Dario; Persano, Luana; Camposeo, Andrea

2017-03-01

As building blocks of microscopically non-homogeneous materials, semiconductor nanowires and polymer nanofibers are emerging component materials for disordered photonics, with unique properties of light emission and scattering. Effects found in assemblies of nanowires and nanofibers include broadband reflection, significant localization of light, strong and collective multiple scattering, enhanced absorption of incident photons, synergistic effects with plasmonic particles, and random lasing. We highlight recent related discoveries, with a focus on material aspects. The control of spatial correlations in complex assemblies during deposition, the coupling of modes with efficient transmission channels provided by nanofiber waveguides, and the embedment of random architectures into individually coded nanowires will allow the potential of these photonic materials to be fully exploited, unconventional physics to be highlighted, and next-generation optical devices to be achieved. The prospects opened by this technology include enhanced random lasing and mode-locking, multi-directionally guided coupling to sensors and receivers, and low-cost encrypting miniatures for encoders and labels.

Hierarchical Graphene Foam for Efficient Omnidirectional Solar-Thermal Energy Conversion.

PubMed

Ren, Huaying; Tang, Miao; Guan, Baolu; Wang, Kexin; Yang, Jiawei; Wang, Feifan; Wang, Mingzhan; Shan, Jingyuan; Chen, Zhaolong; Wei, Di; Peng, Hailin; Liu, Zhongfan

2017-10-01

Efficient solar-thermal energy conversion is essential for the harvesting and transformation of abundant solar energy, leading to the exploration and design of efficient solar-thermal materials. Carbon-based materials, especially graphene, have the advantages of broadband absorption and excellent photothermal properties, and hold promise for solar-thermal energy conversion. However, to date, graphene-based solar-thermal materials with superior omnidirectional light harvesting performances remain elusive. Herein, hierarchical graphene foam (h-G foam) with continuous porosity grown via plasma-enhanced chemical vapor deposition is reported, showing dramatic enhancement of broadband and omnidirectional absorption of sunlight, which thereby can enable a considerable elevation of temperature. Used as a heating material, the external solar-thermal energy conversion efficiency of the h-G foam impressively reaches up to ≈93.4%, and the solar-vapor conversion efficiency exceeds 90% for seawater desalination with high endurance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

2016-04-01

A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

Amine-Based Passivating Materials for Enhanced Optical Properties and Performance of Organic-Inorganic Perovskites in Light-Emitting Diodes.

PubMed

Lee, Seungjin; Park, Jong Hyun; Lee, Bo Ram; Jung, Eui Dae; Yu, Jae Choul; Di Nuzzo, Daniele; Friend, Richard H; Song, Myoung Hoon

2017-04-20

The use of hybrid organic-inorganic perovskites in optoelectronic applications are attracting an interest because of their outstanding characteristics, which enable a remarkable enhancement of device efficiency. However, solution-processed perovskite crystals unavoidably contain defect sites that cause hysteresis in perovskite solar cells (PeSCs) and blinking in perovskite light-emitting diodes (PeLEDs). Here, we report significant beneficial effects using a new treatment based on amine-based passivating materials (APMs) to passivate the defect sites of methylammonium lead tribromide (MAPbBr 3 ) through coordinate bonding between the nitrogen atoms and undercoordinated lead ions. This treatment greatly enhanced the PeLED's efficiency, with an external quantum efficiency (EQE) of 6.2%, enhanced photoluminescence (PL), a lower threshold for amplified spontaneous emission (ASE), a longer PL lifetime, and enhanced device stability. Using confocal microscopy, we observed the cessation of PL blinking in perovskite films treated with ethylenediamine (EDA) due to passivation of the defect sites in the MAPbBr 3 .

Tensile Characterization of Injection-Molded Fuzzy Glass Fiber/Nylon Composite Material

DTIC Science & Technology

2016-05-01

enhanced reinforcement ( CER ) in a nylon matrix. A majority of the masterbatch CER material research is focused on electromagnetic shielding applications...however, the CER system, with the CNT network fixed to the host fiber, provides a novel approach of minimizing CNT agglomeration. Tensile specimens are...injection molded with varying weight percentages of CER to evaluate effect of the reinforcement on the mechanical properties. Tension testing showed

The physical and mechanical properties of treated and untreated Gigantochloa Scortechinii bamboo

NASA Astrophysics Data System (ADS)

Daud, Norhasliya Mohd; Nor, Norazman Mohamad; Yusof, Mohammed Alias; Bakhri, Azrul Affandhi Mustaffa Al; Shaari, Amalina Aisyah

2018-02-01

Bamboo's advantages such as fast growing, renewable and easily available raw material meets the demand of sustainable material in construction. Bamboo act as reinforcement to enhance strength in structural members. This paper investigated on the properties of Gigantochloa Scortechinii bamboo (moisture content, density, compression, shear and bending) by referring to ISO 22157. Moisture content for both untreated and treated bamboo high at the bottom section while density is high at the top section. Compression strength for untreated bamboo were between 19.96 to 23.80 MPa and treated bamboo were between 31.74 to 36.60 MPa. High compression was at the top section which have the greatest wall thickness. Shear strength recorded between 4.28 to 5.69 MPa for untreated bamboo with node and 3.67 to 5.21 MPa for treated bamboo with node. The shear strength of samples with node recorded high strength compared to internode. Untreated bamboo recorded the MOR between 53.64 to 73.66 MPa and 58.23 to 62.86 MPa for treated bamboo. MOE of untreated bamboo were between 26.70 GPa to 36.31 GPa while treated bamboo were between 28.83 to 33.41 GPa. By replacing bamboo to the conventional building material, cost of materials will be reduced and sustainability will be enhanced.

Microplasma device architectures with various diamond nanostructures

NASA Astrophysics Data System (ADS)

Kunuku, Srinivasu; Jothiramalingam Sankaran, Kamatchi; Leou, Keh-Chyang; Lin, I.-Nan

2017-02-01

Diamond nanostructures (DNSs) were fabricated from three different morphological diamonds, microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films, using a reactive ion etching method. The plasma illumination (PI) behavior of microplasma devices using the DNSs and the diamond films as cathode were investigated. The Paschen curve approach revealed that the secondary electron emission coefficient (γ value) of diamond materials is similar irrespective of the microstructure (MCD, NCD, and UNCD) and geometry of the materials (DNSs and diamond films). The diamond materials show markedly larger γ-coefficient than conventional metallic cathode materials such as Mo that resulted in markedly better PI behavior for the corresponding microplasma devices. Moreover, the PI behavior, i.e. the voltage dependence of plasma current density (J pl-V), plasma density (n e-V), and the robustness of the devices, varied markedly with the microstructure and geometry of the cathode materials that was closely correlated to the electron field emission (EFE) properties of the cathode materials. The UNCD nanopillars, possessing good EFE properties, resulted in superior PI behavior, whereas the MCD diamond films with insufficient EFE properties led to inferior PI behavior. Consequently, enhancement of plasma characteristics is the collective effects of EFE behavior and secondary electron emission characteristics of diamond-based cathode materials.

Synthesis and hydrophobic adsorption properties of microporous/mesoporous hybrid materials.

PubMed

Hu, Qin; Li, Jinjun; Qiao, Shizhang; Hao, Zhengping; Tian, Hua; Ma, Chunyan; He, Chi

2009-05-30

Hybrid materials of silicalite-1 (Sil-1)-coated SBA-15 particles (MSs) have been successfully synthesized by crystallization process under hydrothermal conditions. These MSs materials were characterized by X-ray diffraction, nitrogen adsorption/desorption and TEM techniques, which illustrated that the silicalite-1-coated SBA-15 particles were successfully prepared and had large pore volume and hierarchical pore size distribution. Further experimental studies indicated that longer crystallization time under basic condition caused the mesostructure of SBA-15 materials to collapse destructively and higher calcination temperature tended to disrupt the long-range mesoscopic order while they had little influence on the phase of microcrystalline silicalite-1 zeolite. The resultant MSs materials were investigated by estimating dynamic adsorption capacity under dry and wet conditions to evaluate their adsorptive and hydrophobic properties. The hydrophobicity index (HI) value followed the sequence of silicalite-1>MSs>SBA-15, which revealed that the SBA-15 particles coated with the silicalite-1 seeds enhanced the surface hydrophobicity, and also were consistent with FTIR results. Our studies show that MSs materials combined the advantages of the ordered mesoporous material (high adsorptive capacity, large pore volume) and silicalite-1 zeolite (super-hydrophobic property, high hydrothermal stability), and the presence of micropores directly led to an increase in the dynamic adsorption capacity of benzene under dry and wet conditions.

Computationally guided discovery of thermoelectric materials

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

Gorai, Prashun; Stevanović, Vladan; Toberer, Eric S.

The potential for advances in thermoelectric materials, and thus solid-state refrigeration and power generation, is immense. Progress so far has been limited by both the breadth and diversity of the chemical space and the serial nature of experimental work. In this Review, we discuss how recent computational advances are revolutionizing our ability to predict electron and phonon transport and scattering, as well as materials dopability, and we examine efficient approaches to calculating critical transport properties across large chemical spaces. When coupled with experimental feedback, these high-throughput approaches can stimulate the discovery of new classes of thermoelectric materials. Within smaller materialsmore » subsets, computations can guide the optimal chemical and structural tailoring to enhance materials performance and provide insight into the underlying transport physics. Beyond perfect materials, computations can be used for the rational design of structural and chemical modifications (such as defects, interfaces, dopants and alloys) to provide additional control on transport properties to optimize performance. Through computational predictions for both materials searches and design, a new paradigm in thermoelectric materials discovery is emerging.« less

Metallic materials for mechanical damping capacity applications

NASA Astrophysics Data System (ADS)

Crăciun, R. C.; Stanciu, S.; Cimpoeșu, R.; (Dragoș Ursanu, A. I.; Manole, V.; Paraschiv, P.; Chicet, D. L.

2016-08-01

Some metallic materials exhibit good damping capacity of mechanical energy into thermal energy. This property along with the others metallic characteristics make this materials interesting for a big number of applications. These materials can be used as bumpers in different applications including automotive field. Beside grey cast iron and shape memory alloys few new metallic materials are presented for the supposition of high damping capacity. We analyze the causes that increase the internal friction of some metallic materials and possibilities to enhance this property through different mechanical, physical or chemical methods. Shape memory alloys, especially those based on copper, present a different damping capacity on martensite, austenite or transition state. In the transformation range M ↔A, which in case of copper base shape memory alloys is quite large, the metallic intelligent materials present a high internal friction, almost comparable with natural rubber behavior that can transform mechanical energy into thermal energy till a certain value of the external solicitation. These materials can be used as noise or small vibrations bumpers or even as shock absorbers in automotive industry.

Computationally guided discovery of thermoelectric materials

DOE PAGES

Gorai, Prashun; Stevanović, Vladan; Toberer, Eric S.

2017-08-22

The potential for advances in thermoelectric materials, and thus solid-state refrigeration and power generation, is immense. Progress so far has been limited by both the breadth and diversity of the chemical space and the serial nature of experimental work. In this Review, we discuss how recent computational advances are revolutionizing our ability to predict electron and phonon transport and scattering, as well as materials dopability, and we examine efficient approaches to calculating critical transport properties across large chemical spaces. When coupled with experimental feedback, these high-throughput approaches can stimulate the discovery of new classes of thermoelectric materials. Within smaller materialsmore » subsets, computations can guide the optimal chemical and structural tailoring to enhance materials performance and provide insight into the underlying transport physics. Beyond perfect materials, computations can be used for the rational design of structural and chemical modifications (such as defects, interfaces, dopants and alloys) to provide additional control on transport properties to optimize performance. Through computational predictions for both materials searches and design, a new paradigm in thermoelectric materials discovery is emerging.« less

Low cycle fatigue and creep-fatigue behavior of Ni-based alloy 230 at 850 C

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

Chen, Xiang; Yang, Zhiqing; Sokolov, Mikhail A

Strain-controlled low cycle fatigue (LCF) and creep-fatigue testing of Ni-based alloy 230 were carried out at 850 C. The material creep-fatigue life decreased compared with its low cycle fatigue life at the same total strain range. Longer hold time at peak tensile strain further reduced the material creep-fatigue life. Based on the electron backscatter diffraction, a novel material deformation characterization method was applied, which revealed that in low cycle fatigue testing as the total strain range increased, the deformation was segregated to grain boundaries since the test temperature was higher than the material equicohesive temperature and grain boundaries became weakermore » regions compared with grains. Creep-fatigue tests enhanced the localized deformation, resulting in material interior intergranular cracking, and accelerated material damage. Precipitation in alloy 230 helped slip dispersion, favorable for fatigue property, but grain boundary cellular precipitates formed after material exposure to the elevated temperature had a deleterious effect on the material low cycle fatigue and creep-fatigue property.« less

Nanotechnology and clean energy: sustainable utilization and supply of critical materials

NASA Astrophysics Data System (ADS)

Fromer, Neil A.; Diallo, Mamadou S.

2013-11-01

Advances in nanoscale science and engineering suggest that many of the current problems involving the sustainable utilization and supply of critical materials in clean and renewable energy technologies could be addressed using (i) nanostructured materials with enhanced electronic, optical, magnetic and catalytic properties and (ii) nanotechnology-based separation materials and systems that can recover critical materials from non-traditional sources including mine tailings, industrial wastewater and electronic wastes with minimum environmental impact. This article discusses the utilization of nanotechnology to improve or achieve materials sustainability for energy generation, conversion and storage. We highlight recent advances and discuss opportunities of utilizing nanotechnology to address materials sustainability for clean and renewable energy technologies.

Mechanical characteristic and biological behaviour of implanted and restorative bioglasses used in medicine and dentistry: A systematic review.

PubMed

Lizzi, F; Villat, C; Attik, N; Jackson, P; Grosgogeat, B; Goutaudier, C

2017-06-01

Nowadays bioactive glasses are finding increasing applications in medical practice due to their ability to stimulate re-mineralisation. However, they are intrinsically brittle materials and the study of new compositions will open up new scenarios enhancing their mechanical properties and maintaining the high bioactivity for a broader range of applications. This systematic review aims to identify the relationship between the composition of bioactive glasses used in medical applications and their influence on the mechanical and biological properties. Various electronic databases (PubMed, Science Direct) were used for collecting articles on this subject. This research includes papers from January 2011 to March 2016. PRISMA guidelines for systematic review and meta-analysis have been used. 109 abstracts were collected and screened, 68 articles were read as relevant articles and a total of 22 papers were finally selected for this study. Most of the studies obtained enhanced mechanical properties and the conservation of bioactivity behaviours; although a lack of homogeneity in the characterization methods makes it difficult to compare data. New compositions of bioactive glasses incorporating specific ions and the addition in polymers will be the most important direction for future researches in developing new materials for medical applications and especially for dentistry. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Structural evolution and electronic properties of n-type doped hydrogenated amorphous silicon thin films

NASA Astrophysics Data System (ADS)

He, Jian; Li, Wei; Xu, Rui; Qi, Kang-Cheng; Jiang, Ya-Dong

2011-12-01

The relationship between structure and electronic properties of n-type doped hydrogenated amorphous silicon (a-Si:H) thin films was investigated. Samples with different features were prepared by plasma enhanced chemical vapor deposition (PECVD) at various substrate temperatures. Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to evaluate the structural evolution, meanwhile, electronic-spin resonance (ESR) and optical measurement were applied to explore the electronic properties of P-doped a-Si:H thin films. Results reveal that the changes in materials structure affect directly the electronic properties and the doping efficiency of dopant.

Effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material

NASA Astrophysics Data System (ADS)

Zhu, J.; Zheng, W. Z.; Qin, C. Z.; Xu, Z. Z.; Wu, Y. Q.

2018-01-01

The effect of different fibers on mechanical properties and ductility of alkali-activated slag cementitious material (AASCM) is studied. The research contents include: fiber type (plant fiber, polypropylene fiber), fiber content, mechanical property index, tensile stress-strain relationship curve, treating time. The test results showed that the compressive strength of two fibers reinforced AASCM was about 90 ~ 110MPa, and the tensile strength was about 3 ~ 5MPa. The reinforcement effect of polypropylene fiber is superior to that of plant fiber, and the mechanical properties of polypropylene fiber reinforced AASCM are superior to those of plant fiber, According to the comparison of SEM pictures, the plant fiber and polypropylene fiber are both closely bound with the matrix, and the transition zones are complete and close. Thus, it is proved that plant fiber and polypropylene fiber delay the crack extension and enhance the ductility of AASCM.

Achieving Optimal Self-Adaptivity for Dynamic Tuning of Organic Semiconductors through Resonance Engineering.

PubMed

Tao, Ye; Xu, Lijia; Zhang, Zhen; Chen, Runfeng; Li, Huanhuan; Xu, Hui; Zheng, Chao; Huang, Wei

2016-08-03

Current static-state explorations of organic semiconductors for optimal material properties and device performance are hindered by limited insights into the dynamically changed molecular states and charge transport and energy transfer processes upon device operation. Here, we propose a simple yet successful strategy, resonance variation-based dynamic adaptation (RVDA), to realize optimized self-adaptive properties in donor-resonance-acceptor molecules by engineering the resonance variation for dynamic tuning of organic semiconductors. Organic light-emitting diodes hosted by these RVDA materials exhibit remarkably high performance, with external quantum efficiencies up to 21.7% and favorable device stability. Our approach, which supports simultaneous realization of dynamically adapted and selectively enhanced properties via resonance engineering, illustrates a feasible design map for the preparation of smart organic semiconductors capable of dynamic structure and property modulations, promoting the studies of organic electronics from static to dynamic.

A gelatin composite scaffold strengthened by drug-loaded halloysite nanotubes.

PubMed

Ji, Lijun; Qiao, Wei; Zhang, Yuheng; Wu, Huayu; Miao, Shiyong; Cheng, Zhilin; Gong, Qianming; Liang, Ji; Zhu, Aiping

2017-09-01

Mechanical properties and anti-infection are two of the most concerned issues for artificial bone grafting materials. Bone regeneration porous scaffolds with sustained drug release were developed by freeze-drying the mixture of nanosized drug-loaded halloysite nanotubes (HNTs) and gelatin. The scaffolds showed porous structure and excellent biocompatibility. The mechanical properties of the obtained composite scaffolds were enhanced significantly by HNTs to >300%, comparing to those of gelatin scaffold, and match to those of natural cancellous bones. The ibuprofen-loaded HNTs incorporated in the scaffolds allowed extended drug release over 100h, comparing to 8h when directly mixed the drug into the gelatin scaffold. The biological properties of the composite scaffolds were investigated by culturing MG63 cells on them. The HNTs/gelatin scaffolds with excellent mechanical properties and sustained drug release could be a promising artificial bone grating material. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhancement of interfacial adhesion between starch and grafted poly(ε-caprolactone).

PubMed

Ortega-Toro, Rodrigo; Santagata, Gabriella; Gomez d'Ayala, Giovanna; Cerruti, Pierfrancesco; Talens Oliag, Pau; Chiralt Boix, M Amparo; Malinconico, Mario

2016-08-20

The use of a modified poly(ε-caprolactone) (gPCL) to enhance polymer miscibility in films based on thermoplastic starch (S) and poly(ε-caprolactone) is reported. PCL was functionalized by grafting with maleic anyhdride (MA) and/or glycidyl methacrylate (GMA) by reactive blending in a batch mixer. gPCL based materials were analysed in terms of their grafting degree, structural and thermal properties. Blends based on starch and PCL (wt. ratio 80:20) with including gPCL (0, 2.5 and 5wt.%), as a compatibilizer, were obtained by extrusion and compression moulding, and their structural, thermal, mechanical and barrier properties were investigated. Blends containing gPCL evidenced better interfacial adhesion between starch and PCL domains, as deduced from both structural (XRD, FTIR, SEM) and bulk properties (DSC, TGA). Moreover, grafted PCL-based compatibilizers greatly improved functional properties of S-PCL blend films, as pointed out from mechanical performance and higher barrier properties, valuable to meet the food packaging requirements. Copyright © 2016 Elsevier Ltd. All rights reserved.

Improved magnetic properties of barium hexaferrite by CoFe2O4 nanoparticles prepared by ultrasonic irradiation

NASA Astrophysics Data System (ADS)

Nastiti, G.; Manaf, A.

2017-07-01

Magnetic properties of composite magnets made of nanoparticles of Barium Hexaferrite (BHF) and CoFe2O4 were reported in this paper. The two types of magnetic particles have a high total magnetization value which was required for permanent magnet applications. Both CoFe2O4 and BHF were synthesized through mechanical alloying coupled with high-frequency ultrasonic irradiation. In this respect, mechanically milled BHF precursors was sintered at a temperature of 1250 °C for 2 hours leading to single-phase powders. A similar method was also employed in the preparation of CoFe2O4 materials, but this required a relatively longer sintering time up to 12 hours at a sintering temperature of 900 °C. Composite magnets were obtained after sintering the mechanically mixed the two types of nanoparticles as constituted components of the composite. The hysteresis loop of CoFe2O4 materials as evaluated by Vibrating Sample Magnetometer (VSM) showing soft magnetic phase with a total magnetization value of 0.47 T and a coercivity of 47.37 kA/m. It is shown that the magnetic properties of composite magnets are a composition dependent in which the remanent was enhanced above the value of an isotropic single phase BHF magnet. The enhancement in remanent magnetization raised the effect of grain exchange interaction between hard and soft magnetic phases. The microstructure studied by X-Ray diffraction (XRD), Particle Size Analyzer (PSA) and their respective enhancement in magnetic properties are discussed in detail in term of grain exchange interactions.

Natural stiffening increases flaw tolerance of biological fibers

NASA Astrophysics Data System (ADS)

Giesa, Tristan; Pugno, Nicola M.; Buehler, Markus J.

2012-10-01

Many fibers in biomaterials such as tendon, elastin, or silk feature a nonlinear stiffening behavior of the stress-strain relationship, where the rigidity of the material increases severely as the material is being stretched. Here we show that such nonlinear stiffening is beneficial for a fiber's ability to withstand cracks, leading to a flaw tolerant state in which stress concentrations around cracks are diminished. Our findings, established by molecular mechanics and the derivation of a theoretical scaling law, explain experimentally observed fiber sizes in a range of biomaterials and point to the importance of nonlinear stiffening to enhance their fracture properties. Our study suggests that nonlinear stiffening provides a mechanism by which nanoscale mechanical properties can be scaled up, providing a means towards bioinspired fibrous material and structural design.

Polythiophene-carbon nanotubes composites as energy storage materials for supercapacitor application

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

Thakur, A. K., E-mail: anukulphyism@gmail.com; Choudhary, R. B.; Sartale, S. D.

Polythiophene incorporated carbon materials have sought huge attention due to various improved electrochemical properties including enhanced electrical conductivity. Our work includes the synthesis of polythiophene (PTP)-multi-wallcarbon nanotubes (MWCNTs) via in-situ polymerization method. The homogeneous distribution of MWCNT in PTP was confirmed by Field Emission Scanning Electron Microscope (FESEM). Examination of the specimen using X-Ray diffraction (XRD), Fourier Transform-Infrared (FTIR) and Raman spectroscopy confirmed the composite formation. Other electrochemical characterizations like electrochemical impendence spectroscopy (EIS) and cyclic voltammetry (CV)of the PTP-MWCNT composite affirmed that incorporation of MWCNT improves the electrochemical properties of neat PTP including a significant increase in the capacitance.more » Hence making PTP-MWCNT isa better material for supercapacitor application than neat PTP.« less

Design of materials configurations for enhanced phononic and electronic properties

NASA Astrophysics Data System (ADS)

Daraio, Chiara

The discovery of novel nonlinear dynamic and electronic phenomena is presented for the specific cases of granular materials and carbon nanotubes. This research was conducted for designing and constructing optimized macro-, micro- and nano-scale structural configurations of materials, and for studying their phononic and electronic behavior. Variation of composite arrangements of granular elements with different elastic properties in a linear chain-of-sphere, Y-junction or 3-D configurations led to a variety of novel phononic phenomena and interesting physical properties, which can be potentially useful for security, communications, mechanical and biomedical engineering applications. Mechanical and electronic properties of carbon nanotubes with different atomic arrangements and microstructures were also investigated. Electronic properties of Y-junction configured carbon nanotubes exhibit an exciting transistor switch behavior which is not seen in linear configuration nanotubes. Strongly nonlinear materials were designed and fabricated using novel and innovative concepts. Due to their unique strongly nonlinear and anisotropic nature, novel wave phenomena have been discovered. Specifically, violations of Snell's law were detected and a new mechanism of wave interaction with interfaces between NTPCs (Nonlinear Tunable Phononic Crystals) was established. Polymer-based systems were tested for the first time, and the tunability of the solitary waves speed was demonstrated. New materials with transformed signal propagation speed in the manageable range of 10-100 m/s and signal amplitude typical for audible speech have been developed. The enhancing of the mitigation of solitary and shock waves in 1-D chains were demonstrated and a new protective medium was designed for practical applications. 1-D, 2-D and 3-D strongly nonlinear system have been investigated providing a broad impact on the whole area of strongly nonlinear wave dynamics and creating experimental basis for new theories and models. Potential applications include (1) designing of a sound scrambler/decoder for secure voice communications, (2) improving invisibility of submarine to acoustic detection signal, (3) noise and shock wave mitigation for protection of vibration sensitive devices such as head mounted vision devices, (4) drastic compression of acoustic signals into centimeter regime impulses for artificial ear implants, hearing aid and devices for ease of conversion to electronic signals and processing, and acoustic delay lines for communication applications.

Highly tensile-strained Ge/InAlAs nanocomposites

NASA Astrophysics Data System (ADS)

Jung, Daehwan; Faucher, Joseph; Mukherjee, Samik; Akey, Austin; Ironside, Daniel J.; Cabral, Matthew; Sang, Xiahan; Lebeau, James; Bank, Seth R.; Buonassisi, Tonio; Moutanabbir, Oussama; Lee, Minjoo Larry

2017-01-01

Self-assembled nanocomposites have been extensively investigated due to the novel properties that can emerge when multiple material phases are combined. Growth of epitaxial nanocomposites using lattice-mismatched constituents also enables strain-engineering, which can be used to further enhance material properties. Here, we report self-assembled growth of highly tensile-strained Ge/In0.52Al0.48As (InAlAs) nanocomposites by using spontaneous phase separation. Transmission electron microscopy shows a high density of single-crystalline germanium nanostructures coherently embedded in InAlAs without extended defects, and Raman spectroscopy reveals a 3.8% biaxial tensile strain in the germanium nanostructures. We also show that the strain in the germanium nanostructures can be tuned to 5.3% by altering the lattice constant of the matrix material, illustrating the versatility of epitaxial nanocomposites for strain engineering. Photoluminescence and electroluminescence results are then discussed to illustrate the potential for realizing devices based on this nanocomposite material.

A Stable Polymer Burnable Poison Material With Special Attributes

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

Tulenko, James S.; Baney, Ronald H.; Pressley, Linda

2002-07-01

The University of Florida (UF) is carrying out basic research on a new class of thermally stable boron containing materials which appear to have special properties that will greatly enhance the performance of Burnable Poison Rod Assemblies (BPRA) and also Spent Fuel Containers (SFC). This new material ('Carborane') has the special properties of containing a tailored amount of boron, an extremely high hydrogen content, and being extremely stable to high temperatures. 'Carborane' reduces the water displacement penalty by 59% by the hydrogen present in the 'Carborane'. In addition to increasing safety margins, a cost benefit of approximately $500,000 per two-yearmore » cycle is projected from reduced enrichments, resulting from the use of this burnable poison material, making it no longer necessary to offset the water displacement reactivity penalty. This research program is supported by a Department of Energy NEER grant. (authors)« less

Highly tensile-strained Ge/InAlAs nanocomposites

PubMed Central

Jung, Daehwan; Faucher, Joseph; Mukherjee, Samik; Akey, Austin; Ironside, Daniel J.; Cabral, Matthew; Sang, Xiahan; Lebeau, James; Bank, Seth R.; Buonassisi, Tonio; Moutanabbir, Oussama; Lee, Minjoo Larry

2017-01-01

Self-assembled nanocomposites have been extensively investigated due to the novel properties that can emerge when multiple material phases are combined. Growth of epitaxial nanocomposites using lattice-mismatched constituents also enables strain-engineering, which can be used to further enhance material properties. Here, we report self-assembled growth of highly tensile-strained Ge/In0.52Al0.48As (InAlAs) nanocomposites by using spontaneous phase separation. Transmission electron microscopy shows a high density of single-crystalline germanium nanostructures coherently embedded in InAlAs without extended defects, and Raman spectroscopy reveals a 3.8% biaxial tensile strain in the germanium nanostructures. We also show that the strain in the germanium nanostructures can be tuned to 5.3% by altering the lattice constant of the matrix material, illustrating the versatility of epitaxial nanocomposites for strain engineering. Photoluminescence and electroluminescence results are then discussed to illustrate the potential for realizing devices based on this nanocomposite material. PMID:28128282

Low temperature synthesis of diamond-based nano-carbon composite materials with high electron field emission properties

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

Saravanan, A.; Huang, B. R.; Yeh, C. J.

2015-06-08

A diamond-based nano-carbon composite (d/NCC) material, which contains needle-like diamond grains encased with the nano-graphite layers, was synthesized at low substrate temperature via a bias enhanced growth process using CH{sub 4}/N{sub 2} plasma. Such a unique granular structure renders the d/NCC material very conductive (σ = 714.8 S/cm), along with superior electron field emission (EFE) properties (E{sub 0} = 4.06 V/μm and J{sub e} = 3.18 mA/cm{sup 2}) and long lifetime (τ = 842 min at 2.41 mA/cm{sup 2}). Moreover, the electrical conductivity and EFE behavior of d/NCC material can be tuned in a wide range that is especially useful for different kind of applications.

Integration of textile fabric and coconut shell in particleboard

NASA Astrophysics Data System (ADS)

Misnon, M. I.; Bahari, S. A.; Islam, M. M.; Epaarachchi, J. A.

2013-08-01

In this study, cotton fabric and coconut shell were integrated in particleboard to reduce the use of wood. Particleboards containing mixed rubberwood and coconut shell with an equal weight ratio have been integrated with various layers of cotton fabric. These materials were bonded by urea formaldehyde with a content level of 12% by weight. Flexural and water absorption tests were conducted to analyze its mechanical properties and dimensional stability. Results of flexural test showed an increment at least double strength values in fabricated materials as compared to control sample. The existence of fabric in the particleboard system also improved the dimensional stability of the produced material. Enhancement of at least 39% of water absorption could help the dimensional stability of the produced material. Overall, these new particleboards showed better results with the incorporation of cotton fabric layers and this study provided better understanding on mechanical and physical properties of the fabricated particleboard.

Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials

NASA Astrophysics Data System (ADS)

Hübener, Hannes; Sentef, Michael A.; de Giovannini, Umberto; Kemper, Alexander F.; Rubio, Angel

2017-01-01

Tuning and stabilizing topological states, such as Weyl semimetals, Dirac semimetals or topological insulators, is emerging as one of the major topics in materials science. Periodic driving of many-body systems offers a platform to design Floquet states of matter with tunable electronic properties on ultrafast timescales. Here we show by first principles calculations how femtosecond laser pulses with circularly polarized light can be used to switch between Weyl semimetal, Dirac semimetal and topological insulator states in a prototypical three-dimensional (3D) Dirac material, Na3Bi. Our findings are general and apply to any 3D Dirac semimetal. We discuss the concept of time-dependent bands and steering of Floquet-Weyl points and demonstrate how light can enhance topological protection against lattice perturbations. This work has potential practical implications for the ultrafast switching of materials properties, such as optical band gaps or anomalous magnetoresistance.

Creating stable Floquet-Weyl semimetals by laser-driving of 3D Dirac materials.

PubMed

Hübener, Hannes; Sentef, Michael A; De Giovannini, Umberto; Kemper, Alexander F; Rubio, Angel

2017-01-17

Tuning and stabilizing topological states, such as Weyl semimetals, Dirac semimetals or topological insulators, is emerging as one of the major topics in materials science. Periodic driving of many-body systems offers a platform to design Floquet states of matter with tunable electronic properties on ultrafast timescales. Here we show by first principles calculations how femtosecond laser pulses with circularly polarized light can be used to switch between Weyl semimetal, Dirac semimetal and topological insulator states in a prototypical three-dimensional (3D) Dirac material, Na 3 Bi. Our findings are general and apply to any 3D Dirac semimetal. We discuss the concept of time-dependent bands and steering of Floquet-Weyl points and demonstrate how light can enhance topological protection against lattice perturbations. This work has potential practical implications for the ultrafast switching of materials properties, such as optical band gaps or anomalous magnetoresistance.

Creating stable Floquet–Weyl semimetals by laser-driving of 3D Dirac materials

PubMed Central

Hübener, Hannes; Sentef, Michael A.; De Giovannini, Umberto; Kemper, Alexander F.; Rubio, Angel

2017-01-01

Tuning and stabilizing topological states, such as Weyl semimetals, Dirac semimetals or topological insulators, is emerging as one of the major topics in materials science. Periodic driving of many-body systems offers a platform to design Floquet states of matter with tunable electronic properties on ultrafast timescales. Here we show by first principles calculations how femtosecond laser pulses with circularly polarized light can be used to switch between Weyl semimetal, Dirac semimetal and topological insulator states in a prototypical three-dimensional (3D) Dirac material, Na3Bi. Our findings are general and apply to any 3D Dirac semimetal. We discuss the concept of time-dependent bands and steering of Floquet–Weyl points and demonstrate how light can enhance topological protection against lattice perturbations. This work has potential practical implications for the ultrafast switching of materials properties, such as optical band gaps or anomalous magnetoresistance. PMID:28094286

A universal cooperative assembly-directed method for coating of mesoporous TiO2 nanoshells with enhanced lithium storage properties

PubMed Central

Guan, Bu Yuan; Yu, Le; Li, Ju; Lou, Xiong Wen (David)

2016-01-01

TiO2 is exceptionally useful, but it remains a great challenge to develop a universal method to coat TiO2 nanoshells on different functional materials. We report a one-pot, low-temperature, and facile method that can rapidly form mesoporous TiO2 shells on various inorganic, organic, and inorganic-organic composite materials, including silica-based, metal, metal oxide, organic polymer, carbon-based, and metal-organic framework nanomaterials via a cooperative assembly-directed strategy. In constructing hollow, core-shell, and yolk-shell geometries, both amorphous and crystalline TiO2 nanoshells are demonstrated with excellent control. When used as electrode materials for lithium ion batteries, these crystalline TiO2 nanoshells composed of very small nanocrystals exhibit remarkably long-term cycling stability over 1000 cycles. The electrochemical properties demonstrate that these TiO2 nanoshells are promising anode materials. PMID:26973879

Recent Advances in Thermoplastic Puncture-Healing Polymers

NASA Technical Reports Server (NTRS)

Gordon, K. L.; Working, D. C.; Wise, K. E.; Bogert, P. B.; Britton, S. M.; Topping, C.C.; Smith, J. Y.; Siochi, E. J.

2009-01-01

Self-healing materials provide a route for enhanced damage tolerance in materials for aerospace applications. In particular, puncture-healing upon impact has the potential to mitigate significant damage caused by high velocity micrometeoroid impacts. This type of material also has the potential to improve damage tolerance in load bearing structures to enhance vehicle health and aircraft durability. The materials being studied are those capable of instantaneous puncture healing, providing a mechanism for mechanical property retention in lightweight structures. These systems have demonstrated healing capability following penetration of fast moving projectiles -- velocities that range from 9 mm bullets shot from a gun (approx.330 m/sec) to close to micrometeoroid debris velocities of 4800 m/sec. In this presentation, we report on a suite of polymeric materials possessing this characteristic. Figure 1 illustrates the puncture healing concept. Puncture healing in these materials is dependent upon how the combination of a polymer's viscoelastic properties responds to the energy input resulting from the puncture event. Projectile penetration increases the temperature in the vicinity of the impact. Self-healing behavior occurs following puncture, whereby energy must be transferred to the material during impact both elastically and inelastically, thus establishing two requirements for puncture healing to occur: a.) The need for the puncture event to produce a local melt state in the polymer material and b.) The molten material has to have sufficient melt elasticity to snap back and close the hole. 1,2 Previous ballistic testing studies revealed that Surlyn materials warmed up to a temperature approx.98 C during projectile puncture (3 C higher than it s melting temperature). 1,2 The temperature increase produces a localized flow state and the melt elasticity to snap back thus sealing the hole. Table 1 lists the commercially polymers studied here, together with their physical properties. The polymers were selected based on chemical structure, tensile strengths, tensile moduli, glass transition temperature, melting temperatures, and impact strength. The thermal properties of the polymers were characterized by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). Mechanical properties were assessed by a Sintech 2W instron according to ASTM D1708 or D638 at crosshead speeds of 5.08 cm/min. 7.6 cm x 7.6 cm panels of the different materials were prepared and ballistic testing was performed at various temperatures. The panels were shot with a .223 caliber semiautomatic rifle from a distance of 23 meters at various temperatures. Chronographs were used to measure initial and final bullet velocity. Temperatures at the site of impact were measured using a FLIR ThermaCAM S60 thermal camera. A Vision Research model Phantom 9 high speed video camera was used to capture high speed video footage of ballistics testing.

Dental applications of nanostructured bioactive glass and its composites

PubMed Central

Polini, Alessandro; Bai, Hao; Tomsia, Antoni P.

2013-01-01

To improve treatments for bone or dental trauma, and for diseases such as osteoporosis, cancer, and infections, scientists who perform basic research are collaborating with clinicians to design and test new biomaterials for the regeneration of lost or injured tissue. Developed some 40 years ago, bioactive glass (BG) has recently become one of the most promising biomaterials, a consequence of discoveries that its unusual properties elicit specific biological responses inside the body. Among these important properties are the capability of BG to form strong interfaces with both hard and soft tissues, and its release of ions upon dissolution. Recent developments in nanotechnology have introduced opportunities for materials sciences to advance dental and bone therapies. For example, the applications for BG expand as it becomes possible to finely control structures and physicochemical properties of materials at the molecular level. Here we review how the properties of these materials have been enhanced by the advent of nanotechnology; and how these developments are producing promising results in hard-tissue regeneration and development of innovative BG-based drug-delivery systems. PMID:23606653

Effects of Zn-In-Sn elements on the electric properties of magnesium alloy anode materials.

PubMed

Yu, Zhan; Ju, Dongying; Zhao, Hongyang; Hu, Xiaodong

2011-06-01

A new magnesium alloy anode is based on an environmentally friendly electrode that contains none of mercury, lead and chromate, but it can enhance the electric properties of alloy significantly. Magnesium alloy adding eco-friendly elements Zn-In-Sn which was developed by orthogonal design were obtained by two casting methods. The effect of additive elements on performance of electrode material was studied. The effects of elements addition and casting method on electric properties and corrosive properties of Mg-Zn-In-Sn alloys were investigated by using electrochemical measurements, corrosive tests and observation of surface structure. The results show that Mg-Zn-In-Sn alloy anode has higher electromotive force and more stable work potential than that commercial magnesium alloy AZ91. It is suitable for anode material of magnesium battery for its small hydrogen evolution, less self-corrosion rate and easy to shed corrosive offspring off. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

The influence of dynamical change of optical properties on the thermomechanical response and damage threshold of noble metals under femtosecond laser irradiation

NASA Astrophysics Data System (ADS)

Tsibidis, George D.

2018-02-01

We present a theoretical investigation of the dynamics of the dielectric constant of noble metals following heating with ultrashort pulsed laser beams and the influence of the temporal variation of the associated optical properties on the thermomechanical response of the material. The effect of the electron relaxation time on the optical properties based on the use of a critical point model is thoroughly explored for various pulse duration values (i.e., from 110 fs to 8 ps). The proposed theoretical framework correlates the dynamical change in optical parameters, relaxation processes and induced strains-stresses. Simulations are presented by choosing gold as a test material, and we demonstrate that the consideration of the aforementioned factors leads to significant thermal effect changes compared to results when static parameters are assumed. The proposed model predicts a substantially smaller damage threshold and a large increase of the stress which firstly underlines the significant role of the temporal variation of the optical properties and secondly enhances its importance with respect to the precise determination of laser specifications in material micromachining techniques.

Swollen hexagonal liquid crystals as smart nanoreactors: implementation in materials chemistry for energy applications.

PubMed

Ghosh, Srabanti; Ramos, Laurence; Remita, Hynd

2018-03-29

Materials are the key roadblocks for the commercialization of energy conversion devices in fuel cells and solar cells. Significant research has focused on tuning the intrinsic properties of materials at the nanometer scale. The soft template mediated controlled fabrication of advanced nanostructured materials is attracting considerable interest due to the promising applications of these materials in catalysis and electrocatalysis. Swollen hexagonal lyotropic liquid crystals (SLCs) consist of oil-swollen surfactant-stabilized 1D, 2D or 3D nanometric assemblies regularly arranged in an aqueous solvent. Interestingly, the characteristic size of the SLCs can be controlled by adjusting the volume ratio of oil to water. The non-polar and/or polar compartments of the SLCs can be doped with guest molecules and used as nanoreactors for the synthesis of various metals (Pt, Pd, Au, etc.), conducting polymers and composite nanostructures with controlled size and shape. 1D, 2D and 3D mono- and bimetallic nanostructures of controlled composition and porosity can also be fabricated. These materials have demonstrated impressive enhancements of their electrochemical properties as compared to their bulk counterparts and have been identified as promising for further implementation in energy harvesting applications. In this review article, recent research materials are described regarding the development of functional materials with much improved performances for catalysis applications. This review addresses a brief overview of swollen hexagonal mesophases as nanoreactors, describes examples of nanostructured materials synthesized in these nanoreactors, shows several examples of the energy conversion applications in solar light harvesting, fuel cells etc. and also summarizes the associated reaction mechanisms developed in the recent literature for enhanced catalytic activity.

The mechanical role of metal ions in biogenic protein-based materials.

PubMed

Degtyar, Elena; Harrington, Matthew J; Politi, Yael; Fratzl, Peter

2014-11-03

Protein-metal interactions--traditionally regarded for roles in metabolic processes--are now known to enhance the performance of certain biogenic materials, influencing properties such as hardness, toughness, adhesion, and self-healing. Design principles elucidated through thorough study of such materials are yielding vital insights for the design of biomimetic metallopolymers with industrial and biomedical applications. Recent advances in the understanding of the biological structure-function relationships are highlighted here with a specific focus on materials such as arthropod biting parts, mussel byssal threads, and sandcastle worm cement. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Periodic nanostructural materials for nanoplasmonics

NASA Astrophysics Data System (ADS)

Choi, Dukhyun

2017-02-01

Nanoscale periodic material design and fabrication are essentially fundamental requirement for basic scientific researches and industrial applications of nanoscience and engineering. Innovative, effective, reproducible, large-area uniform, tunable and robust nanostructure/material syntheses are still challenging. Here, I would like to introduce the novel periodic nanostructural materials particularly with uniformly ordered nanoporous or nanoflower structures, which are fabricated by simple, cost-effective, and high-throughput wet chemical methods. I also report large-area periodic plasmonic nanostructures based on template-based nanolithography. The surface morphology and optical properties are characterized by SEM and UV-vis. spectroscopy. Furthermore, their enhancement factor is evaluated by using SERS signals.

Development of Design Standards and Guidelines for Electromagnetic Compatibility and Lightning Protection for Spacecraft Utilizing Composite Materials

NASA Technical Reports Server (NTRS)

1996-01-01

Preliminary design guidelines necessary to assure electromagnetic compatibility (EMC) of spacecraft using composite materials, are presented. A database of electrical properties of composite materials which may have an effect on EMC is established. The guidelines concentrate on the composites that are conductive but may require enhancement to be adequate for EMC purposes. These composites are represented by graphite reinforced polymers. Methods for determining adequate conductivity levels for various EMC purposes are defined, along with the methods of design which increase conductivity of composite materials and joints to adequate levels.

Design, characterization and modeling of biobased acoustic foams

NASA Astrophysics Data System (ADS)

Ghaffari Mosanenzadeh, Shahrzad

Polymeric open cell foams are widely used as sound absorbers in sectors such as automobile, aerospace, transportation and building industries, yet there is a need to improve sound absorption of these foams through understanding the relation between cell morphology and acoustic properties of porous material. Due to complicated microscopic structure of open cell foams, investigating the relation between foam morphology and acoustic properties is rather intricate and still an open problem in the field. The focus of this research is to design and develop biobased open cell foams for acoustic applications to replace conventional petrochemical based foams as well as investigating the link between cell morphology and macroscopic properties of open cell porous structures. To achieve these objectives, two industrially produced biomaterials, polylactide (PLA) and polyhydroxyalkanoate (PHA) and their composites were examined and highly porous biobased foams were fabricated by particulate leaching and compression molding. Acoustic absorption capability of these foams was enhanced utilizing the effect of co-continuous blends to form a bimodal porous structure. To tailor mechanical and acoustic properties of biobased foams, blends of PLA and PHA were studied to reach the desired mechanical and viscoelastic properties. To enhance acoustic properties of porous medium for having a broad band absorption effect, cell structure must be appropriately graded. Such porous structures with microstructural gradation are called Functionally Graded Materials (FGM). A novel graded foam structure was designed with superior sound absorption to demonstrate the effect of cell arrangement on performance of acoustic fixtures. Acoustic measurements were performed in a two microphone impedance tube and acoustic theory of Johnson-Champoux-Allard was applied to the fabricated foams to determine micro cellular properties such as tortuosity, viscous and thermal lengths from sound absorption impedance tube measurements using an inverse technique. As the next step towards in depth understanding of the relation between cell morphology and sound absorption of open cell foams, a semi-analytical model was developed to account for the effect of micro cellular properties such as cell wall thickness and reticulation rate on overall macroscopic and structural properties. Developed model provides the tools to optimize the porous structure and enhance sound absorption capability.

Towards Enhanced Performance Thin-film Composite Membranes via Surface Plasma Modification

PubMed Central

Reis, Rackel; Dumée, Ludovic F.; Tardy, Blaise L.; Dagastine, Raymond; Orbell, John D.; Schutz, Jürg A.; Duke, Mikel C.

2016-01-01

Advancing the design of thin-film composite membrane surfaces is one of the most promising pathways to deal with treating varying water qualities and increase their long-term stability and permeability. Although plasma technologies have been explored for surface modification of bulk micro and ultrafiltration membrane materials, the modification of thin film composite membranes is yet to be systematically investigated. Here, the performance of commercial thin-film composite desalination membranes has been significantly enhanced by rapid and facile, low pressure, argon plasma activation. Pressure driven water desalination tests showed that at low power density, flux was improved by 22% without compromising salt rejection. Various plasma durations and excitation powers have been systematically evaluated to assess the impact of plasma glow reactions on the physico-chemical properties of these materials associated with permeability. With increasing power density, plasma treatment enhanced the hydrophilicity of the surfaces, where water contact angles decreasing by 70% were strongly correlated with increased negative charge and smooth uniform surface morphology. These results highlight a versatile chemical modification technique for post-treatment of commercial membrane products that provides uniform morphology and chemically altered surface properties. PMID:27363670

Effect of Silver-Emitting Filler on Antimicrobial and Mechanical Properties of Soft Denture Lining Material

PubMed Central

Jabłońska-Stencel, Ewa; Pakieła, Wojciech; Mertas, Anna; Bobela, Elżbieta; Kasperski, Jacek; Chladek, Grzegorz

2018-01-01

Colonization of silicone-based soft lining materials by pathogenic yeast-type fungi is a common problem associated with the use of dentures. In this study, silver sodium hydrogen zirconium phosphate (SSHZP) was introduced into polydimethylsiloxane-based material as an antimicrobial filler at concentrations of 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 14% (w/w). The in vitro antimicrobial efficacy was investigated. Candida albicans was used as a characteristic representative of pathogenic oral microflora. Staphylococcus aureus and Escherichia coli were used as the typical Gram-positive and Gram-negative bacterial strains, respectively. The effect of filler addition on the Shore A hardness, tensile strength, tensile bond strength, sorption, and solubility was investigated. An increase in the filler concentration resulted in an increase in hardness, sorption, and solubility, and for the highest concentration, a decrease in bond strength. The favorable combination of antimicrobial efficacy with other properties was achieved at filler concentrations ranging from 2% to 10%. These composites exhibited mechanical properties similar to the material without the antimicrobial filler and enhanced in vitro antimicrobial efficiency. PMID:29470441

Synthesis, structure stability and magnetic properties of nanocrystalline Ag-Ni alloy

NASA Astrophysics Data System (ADS)

Santhi, Kalavathy; Thirumal, E.; Karthick, S. N.; Kim, Hee-Je; Nidhin, Marimuthu; Narayanan, V.; Stephen, A.

2012-05-01

Silver-nickel alloy nanoparticles with an average size of 30-40 nm were synthesized by chemically reducing the mixture of silver and nickel salts using sodium borohydride. The structure and the magnetic properties of the alloy samples with different compositions were investigated. The phase stability of the material was analysed after annealing the sample in vacuum at various temperatures. The material exhibits single fcc phase which is stable up to 400 °C and Ni precipitation sets in when the sample is annealed to 500 °C. The thermal analysis using DSC was carried out to confirm the same. The alloy compositions are found to be in close correlation with the metal salt ratios in the precursors. The synthesized samples exhibit weak paramagnetic to ferromagnetic behaviour. The magnetic measurements reveal that by adjusting the precursor ratio, the Ni content in the material can be altered and hence its magnetic properties tailored to suit specific requirements. The formation of Ag-Ni alloy is confirmed by the observed Curie temperature from the magneto thermogram. Annealing the sample helps to produce significant enhancement in the magnetization of the material.

Progress towards Growth and Characterization of Rare-Earth Nanoparticles using the Inverse Micelle Method

NASA Astrophysics Data System (ADS)

Romero, Dulce G.; Ho, Pei-Chun

2008-03-01

Nano-sized particles and clusters have promising electrical, chemical, and magnetic properties as compared to the bulk materials. Due to their reduced dimensionality, it makes their physical properties significantly different from the bulk material. The nano-sized materials have great potential for technical applications, such as, magnetic information storage, imaging, medical devices, and magnetic refrigeration. In this report, we will present the preliminary results on the growth and characterization of rare-earth metallic nanoparticles of Gd and Nd synthesized by the inverse micelle method [1]. These results will be compared to the bulk properties of Gd and Nd, as well as, to those exhibited by metallic nanoparticles, such as Co (by inverse micelle), and Gd (by laser evaporation cluster source), which have been found to show superparamagnetic behavior, enhanced magnetization, and self-organization [2-4]. [1] X.M. Lin, et al. Langmuir. 14, 7140 (1998). [2] D.C. Douglass, et al. Phys. Rev. B. 47, 19 (1993). [3] C. Petit, et al. Advanced Materials. 10, 259 (1998). [4] J.P. Chen, et al. Phys. Rev. B. 51, 11527 (1995).

The Materials Genome Project

NASA Astrophysics Data System (ADS)

Aourag, H.

2008-09-01

In the past, the search for new and improved materials was characterized mostly by the use of empirical, trial- and-error methods. This picture of materials science has been changing as the knowledge and understanding of fundamental processes governing a material's properties and performance (namely, composition, structure, history, and environment) have increased. In a number of cases, it is now possible to predict a material's properties before it has even been manufactured thus greatly reducing the time spent on testing and development. The objective of modern materials science is to tailor a material (starting with its chemical composition, constituent phases, and microstructure) in order to obtain a desired set of properties suitable for a given application. In the short term, the traditional "empirical" methods for developing new materials will be complemented to a greater degree by theoretical predictions. In some areas, computer simulation is already used by industry to weed out costly or improbable synthesis routes. Can novel materials with optimized properties be designed by computers? Advances in modelling methods at the atomic level coupled with rapid increases in computer capabilities over the last decade have led scientists to answer this question with a resounding "yes'. The ability to design new materials from quantum mechanical principles with computers is currently one of the fastest growing and most exciting areas of theoretical research in the world. The methods allow scientists to evaluate and prescreen new materials "in silico" (in vitro), rather than through time consuming experimentation. The Materials Genome Project is to pursue the theory of large scale modeling as well as powerful methods to construct new materials, with optimized properties. Indeed, it is the intimate synergy between our ability to predict accurately from quantum theory how atoms can be assembled to form new materials and our capacity to synthesize novel materials atom-by-atom that gives to the Materials Genome Project its extraordinary intellectual vitality. Consequently, in designing new materials through computer simulation, our primary objective is to rapidly screen possible designs to find those few that will enhance the competitiveness of industries or have positive benefits to society. Examples include screening of cancer drugs, advances in catalysis for energy production, design of new alloys and multilayers and processing of semiconductors.

Novel Nanocomposite Materials for Advanced Li-Ion Rechargeable Batteries

PubMed Central

Cai, Chuan; Wang, Ying

2009-01-01

Nanostructured materials lie at the heart of fundamental advances in efficient energy storage and/or conversion, in which surface processes and transport kinetics play determining roles. Nanocomposite materials will have a further enhancement in properties compared to their constituent phases. This Review describes some recent developments of nanocomposite materials for high-performance Li-ion rechargeable batteries, including carbon-oxide nanocomposites, polymer-oxide nanocomposites, metal-oxide nanocomposites, and silicon-based nanocomposites, etc. The major goal of this Review is to highlight some new progress in using these nanocomposite materials as electrodes to develop Li-ion rechargeable batteries with high energy density, high rate capability, and excellent cycling stability.

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

PubMed

Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

2016-04-13

Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

Modifying the Interface Edge to Control the Electrical Transport Properties of Nanocontacts to Nanowires.

PubMed

Lord, Alex M; Ramasse, Quentin M; Kepaptsoglou, Despoina M; Evans, Jonathan E; Davies, Philip R; Ward, Michael B; Wilks, Steve P

2017-02-08

Selecting the electrical properties of nanomaterials is essential if their potential as manufacturable devices is to be reached. Here, we show that the addition or removal of native semiconductor material at the edge of a nanocontact can be used to determine the electrical transport properties of metal-nanowire interfaces. While the transport properties of as-grown Au nanocatalyst contacts to semiconductor nanowires are well-studied, there are few techniques that have been explored to modify the electrical behavior. In this work, we use an iterative analytical process that directly correlates multiprobe transport measurements with subsequent aberration-corrected scanning transmission electron microscopy to study the effects of chemical processes that create structural changes at the contact interface edge. A strong metal-support interaction that encapsulates the Au nanocontacts over time, adding ZnO material to the edge region, gives rise to ohmic transport behavior due to the enhanced quantum-mechanical tunneling path. Removal of the extraneous material at the Au-nanowire interface eliminates the edge-tunneling path, producing a range of transport behavior that is dependent on the final interface quality. These results demonstrate chemically driven processes that can be factored into nanowire-device design to select the final properties.

Properties of Experimental Dental Composites Containing Antibacterial Silver-Releasing Filler.

PubMed

Stencel, Robert; Kasperski, Jacek; Pakieła, Wojciech; Mertas, Anna; Bobela, Elżbieta; Barszczewska-Rybarek, Izabela; Chladek, Grzegorz

2018-06-18

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver sodium hydrogen zirconium phosphate (SSHZP). The antibacterial filler was introduced at concentrations of 1%, 4%, 7%, 10%, 13%, and 16% ( w / w ) into model composite material consisting of methacrylate monomers and silanized glass and silica fillers. The in vitro reduction in the number of viable cariogenic bacteria Streptococcus mutans ATCC 33535 colonies, Vickers microhardness, compressive strength, diametral tensile strength, flexural strength, flexural modulus, sorption, solubility, degree of conversion, and color stability were investigated. An increase in antimicrobial filler concentration resulted in a statistically significant reduction in bacteria. There were no statistically significant differences caused by the introduction of the filler in compressive strength, diametral tensile strength, flexural modulus, and solubility. Statistically significant changes in degree of conversion, flexural strength, hardness (decrease), solubility (increase), and in color were registered. A favorable combination of antibacterial properties and other properties was achieved at SSHZP concentrations from 4% to 13%. These composites exhibited properties similar to the control material and enhanced in vitro antimicrobial efficiency.

Mulifunctional Dendritic Emitter: Aggregation-Induced Emission Enhanced, Thermally Activated Delayed Fluorescent Material for Solution-Processed Multilayered Organic Light-Emitting Diodes

PubMed Central

Matsuoka, Kenichi; Albrecht, Ken; Yamamoto, Kimihisa; Fujita, Katsuhiko

2017-01-01

Thermally activated delayed fluorescence (TADF) materials emerged as promising light sources in third generation organic light-emitting diodes (OLED). Much effort has been invested for the development of small molecular TADF materials and vacuum process-based efficient TADF-OLEDs. In contrast, a limited number of solution processable high-molecular weight TADF materials toward low cost, large area, and scalable manufacturing of solution processed TADF-OLEDs have been reported so far. In this context, we report benzophenone-core carbazole dendrimers (GnB, n = generation) showing TADF and aggregation-induced emission enhancement (AIEE) properties along with alcohol resistance enabling further solution-based lamination of organic materials. The dendritic structure was found to play an important role for both TADF and AIEE activities in the neat films. By using these multifunctional dendritic emitters as non-doped emissive layers, OLED devices with fully solution processed organic multilayers were successfully fabricated and achieved maximum external quantum efficiency of 5.7%. PMID:28139768

Mulifunctional Dendritic Emitter: Aggregation-Induced Emission Enhanced, Thermally Activated Delayed Fluorescent Material for Solution-Processed Multilayered Organic Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Matsuoka, Kenichi; Albrecht, Ken; Yamamoto, Kimihisa; Fujita, Katsuhiko

2017-01-01

Thermally activated delayed fluorescence (TADF) materials emerged as promising light sources in third generation organic light-emitting diodes (OLED). Much effort has been invested for the development of small molecular TADF materials and vacuum process-based efficient TADF-OLEDs. In contrast, a limited number of solution processable high-molecular weight TADF materials toward low cost, large area, and scalable manufacturing of solution processed TADF-OLEDs have been reported so far. In this context, we report benzophenone-core carbazole dendrimers (GnB, n = generation) showing TADF and aggregation-induced emission enhancement (AIEE) properties along with alcohol resistance enabling further solution-based lamination of organic materials. The dendritic structure was found to play an important role for both TADF and AIEE activities in the neat films. By using these multifunctional dendritic emitters as non-doped emissive layers, OLED devices with fully solution processed organic multilayers were successfully fabricated and achieved maximum external quantum efficiency of 5.7%.

Temperature dependent absorption measurement of various transition metal doped laser materials

NASA Astrophysics Data System (ADS)

Horackova, Lucie; Šulc, Jan; Jelinkova, Helena; Jambunathan, Venkatesan; Lucianetti, Antonio; Mocek, Tomás.

2015-05-01

In recent years, there has been a vast development of high energy class lasers of the order of 100 J to kJ level which have potential applications in the field of science and technology. Many such systems use the gain media cooled at cryogenic temperatures which will help in enhancing the spectroscopic and thermo-optical properties. Nevertheless, parasitic effects like amplified spontaneous emission enhance and affect the overall efficiency. The best way to suppress this effect is to use cladding element attached to the gain material. Based on these facts, this work was focused on the systematic investigation of temperature dependent absorption of several materials doped with transition metals, which can be used as cladding, as laser gain material, or as passive Q-switching element. The Ti:sapphire, Cr:YAG, V:YAG, and Co:MALO samples were measured in temperature range from 80 K to 330 K by step of 50 K. Using Beer-Lambert law we estimated the absorption coefficient of these materials.

Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials

NASA Technical Reports Server (NTRS)

Evans, R. W.

1997-01-01

These guidelines address the electrical properties of composite materials which may have an effect on electromagnetic compatibility (EMC). The main topics of the guidelines include the electrical shielding, fault current return, and lightning protection capabilities of graphite reinforced polymers, since they are somewhat conductive but may require enhancement to be adequate for EMC purposes. Shielding effectiveness depends heavily upon the conductivity of the material. Graphite epoxy can provide useful shielding against RF signals, but it is approximately 1,000 times more resistive than good conductive metals. The reduced shielding effectiveness is significant but is still useful in many cases. The primary concern is with gaps and seams in the material just as it is with metal. Current carrying capability of graphite epoxy is adequate for dissipation static charges, but fault currents through graphite epoxy may cause fire at the shorting contact and at joints. The effect of lightning on selected graphite epoxy material and mating surfaces is described, and protection methods are reviewed.

Sequence-Dependent Structure/Function Relationships of Catalytic Peptide-Enabled Gold Nanoparticles Generated under Ambient Synthetic Conditions.

PubMed

Bedford, Nicholas M; Hughes, Zak E; Tang, Zhenghua; Li, Yue; Briggs, Beverly D; Ren, Yang; Swihart, Mark T; Petkov, Valeri G; Naik, Rajesh R; Knecht, Marc R; Walsh, Tiffany R

2016-01-20

Peptide-enabled nanoparticle (NP) synthesis routes can create and/or assemble functional nanomaterials under environmentally friendly conditions, with properties dictated by complex interactions at the biotic/abiotic interface. Manipulation of this interface through sequence modification can provide the capability for material properties to be tailored to create enhanced materials for energy, catalysis, and sensing applications. Fully realizing the potential of these materials requires a comprehensive understanding of sequence-dependent structure/function relationships that is presently lacking. In this work, the atomic-scale structures of a series of peptide-capped Au NPs are determined using a combination of atomic pair distribution function analysis of high-energy X-ray diffraction data and advanced molecular dynamics (MD) simulations. The Au NPs produced with different peptide sequences exhibit varying degrees of catalytic activity for the exemplar reaction 4-nitrophenol reduction. The experimentally derived atomic-scale NP configurations reveal sequence-dependent differences in structural order at the NP surface. Replica exchange with solute-tempering MD simulations are then used to predict the morphology of the peptide overlayer on these Au NPs and identify factors determining the structure/catalytic properties relationship. We show that the amount of exposed Au surface, the underlying surface structural disorder, and the interaction strength of the peptide with the Au surface all influence catalytic performance. A simplified computational prediction of catalytic performance is developed that can potentially serve as a screening tool for future studies. Our approach provides a platform for broadening the analysis of catalytic peptide-enabled metallic NP systems, potentially allowing for the development of rational design rules for property enhancement.

Touchstone for success

NASA Astrophysics Data System (ADS)

Longdon, Norman; Dauphin, J.; Dunn, B. D.; Judd, M. D.; Levadou, F. G.; Zwaal, A.

1992-04-01

This booklet is addressed to the users of the Materials and Processes Laboratories of the European Space Research and Technology Centre (ESTEC). The revised edition updates the July 1988 edition featuring the enhancement of existing laboratories and the establishment of a ceramics laboratory. Information on three ESTEC laboratories is presented as well as a look into the future. The three laboratories are the Environmental Effects Laboratory, the Metallic Materials Laboratory, and the Non-metallic Laboratory. The booklet reports on the effects of the space environment on radiation effects (UV and particles), outgassing and contamination, charging-up and discharges, particulate contaminants, atomic oxygen and debris/impacts. Applications of metallic materials to space hardware are covered in the areas of mechanical properties, corrosion/stress corrosion, fracture testing and interpretation, metallurgical processes and failure analysis. Particular applications of non metallic materials to space hardware that are covered are advanced and reinforced polymers, advanced ceramics, thermal properties, manned ambiance, polymer processing, non-destructive tests (NDT), and failure analysis. Future emphasis will be on the measurement of thermo-optical properties for the Infrared Space Observatory (ISO) and other infrared telescopes, support of the Columbus program, Hermes related problems such as 'warm' composites and 'hot' reinforced ceramics for thermal insulation, materials for extravehicular activity (EVA), and NDT.

An Innovative Approach to Control Steel Reinforcement Corrosion by Self-Healing.

PubMed

Koleva, Dessi A

2018-02-20

The corrosion of reinforced steel, and subsequent reinforced concrete degradation, is a major concern for infrastructure durability. New materials with specific, tailor-made properties or the establishment of optimum construction regimes are among the many approaches to improving civil structure performance. Ideally, novel materials would carry self-repairing or self-healing capacities, triggered in the event of detrimental influence and/or damage. Controlling or altering a material's behavior at the nano-level would result in traditional materials with radically enhanced properties. Nevertheless, nanotechnology applications are still rare in construction, and would break new ground in engineering practice. An approach to controlling the corrosion-related degradation of reinforced concrete was designed as a synergetic action of electrochemistry, cement chemistry and nanotechnology. This contribution presents the concept of the approach, namely to simultaneously achieve steel corrosion resistance and improved bulk matrix properties. The technical background and challenges for the application of polymeric nanomaterials in the field are briefly outlined in view of this concept, which has the added value of self-healing. The credibility of the approach is discussed with reference to previously reported outcomes, and is illustrated via the results of the steel electrochemical responses and microscopic evaluations of the discussed materials.

Controlled Assembly of Lignocellulosic Biomass Components and Properties of Reformed Materials

DOE PAGES

Wang, Jing; Boy, Ramiz; Nguyen, Ngoc A.; ...

2017-07-25

Reforming whole lignocellulosic biomass into value-added materials has yet to be achieved mainly due to the infusible nature of biomass and its recalcitrance to dissolve in common organic solvents. Recently, the solubility of biomass in ionic liquids (ILs) has been explored to develop all-lignocellulosic materials; however, efficient dissolution and therefore production of value-added materials with desired mechanical properties remain a challenge. This article presents an approach to producing high-performance lignocellulosic films from hybrid poplar wood. An autohydrolysis step that removes ≤50% of the hemicellulose fraction is performed to enhance biomass solvation in 1-ethyl-3-methyl imidazolium acetate ([C2mim][OAc]). The resulting biomass–IL solutionmore » is then cast into free-standing films using different coagulating solvents, yet preserving the polymeric nature of the biomass constituents. Methanol coagulated films exhibit a cocontinuous 3D-network structure with dispersed domains of less than 100 nm. The consolidated films with controllable morphology and structural order demonstrate tensile properties better than those of quasi-isotropic wood. Here, the methods for producing these biomass derivatives have potential for fabricating novel green materials with superior performance from woody and grassy biomass.« less

Two-dimensional metal-organic frameworks with high thermoelectric efficiency through metal ion selection.

PubMed

He, Yuping; Spataru, Catalin D; Léonard, Francois; Jones, Reese E; Foster, Michael E; Allendorf, Mark D; Alec Talin, A

2017-07-26

Two-dimensional (2D) materials have attracted much attention due to their novel properties. An exciting new class of 2D materials based on metal-organic frameworks (MOFs) has recently emerged, displaying high electrical conductivity, a rarity among organic nanoporous materials. The emergence of these materials raises intriguing questions about their fundamental electronic, optical, and thermal properties, but few studies exist in this regard. Here we present an atomistic study of the thermoelectric properties of crystalline 2D MOFs X 3 (HITP) 2 with X = Ni, Pd or Pt, and HITP = 2,3,6,7,10,11-hexaiminotriphenylene, using both ab initio transport models and classical molecular dynamics simulations. We find that these materials have a high Seebeck coefficient and low thermal conductivity, making them promising for thermoelectric applications. Furthermore, we explore the dependence of thermoelectric transport properties on the atomic structure by comparing the calculated band structure, band alignment, and electronic density of states of the three 2D MOFs, and find that the thermoelectric transport properties strongly depend on both the interaction between the ligands and the metal ions, and the d orbital splitting of the metal ions induced by the ligands. This demonstrates that selection of the metal ion is a powerful approach to control and enhance the thermoelectric properties. Interestingly we reveal an unexpected effect where, unlike for electrons, the thermal and electrical current may not be equally carried by the holes, leading to a significant deviation from the Wiedemann-Franz law. The results of this work provide fundamental guidance to optimize the existing 2D MOFs, and to design and discover new families of MOF-like materials for thermoelectric applications.

Cross-Discipline Bio-Nanostructured Enhanced Photonic Multimode-Sensor Science

DTIC Science & Technology

2017-05-23

experimental study aimed to combine soft material science with nanotechnology and multi-physics modeling to produce adaptable bio-nanostructure based on...degradation through optical analysis and tracking programs Protein and DNA engineering . - The properties of proteins to be used in sensors were studies

Demystifying Mystery Powders.

ERIC Educational Resources Information Center

Kotar, Michael

1989-01-01

Describes science activities which use simple chemical tests to distinguish between materials and to determine some of their properties. Explains the water, iodine, heat, acid, baking soda, acid/base indicator, glucose, and sugar tests. Includes activities to enhance chemical testing and a list of suggested powders for use. (RT)

Carrot, Corn, Lettuce and Soybean Nutrient Contents are Affected by Biochar

EPA Science Inventory

Biochar, the carbon-rich material remaining after pyrolysis of cellulosic and manure feedstocks, has the potential as a soil amendment to sequester carbon and to improve soil water-holding and nutrient properties- thereby enhancing plant growth. However, biochar produced from so...

Variation in the electrical properties of ion beam irradiated cadmium selenate nanowires

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

Chauhan, R. P., E-mail: chauhanrpc@gmail.com; Narula, Chetna; Panchal, Suresh

The key feature of nanowires consists in the pronounced change in properties induced by the low dimensionality and high surface to volume ratio. The study of electrical transport properties of nanowires is important for electronic device applications. Energetic ions create changes, which may be structural or chemical, in a material along their track and these changes might alter the material’s properties. The demand of the modern technology is to understand the effect of radiation on the different properties of the material for its further applications. The present study is on the high-energy Nickel ion beam (160 MeV Ni{sup +12}) induced modificationsmore » in the electrical and structural properties of the cadmium selenate nanowires. An enhancement in the electrical conductivity of irradiated wires was observed as the ion fluence was increased especially in the forward I–V characteristics. The creation of defects by ion irradiation and the synergy of the ions during their passage in the sample with the intrinsic charge carriers may be responsible for the variation in the transport properties of the irradiated nanowires.« less

Enhanced mechanical properties of self-polymerized polydopamine-coated recycled PLA filament used in 3D printing

NASA Astrophysics Data System (ADS)

Zhao, Xing Guan; Hwang, Kyung-Jun; Lee, Dongoh; Kim, Taemin; Kim, Namsu

2018-05-01

Dopamine readily adsorbs onto almost all kinds of surfaces and develops cohesive strength through self-polymerization; hence, aqueous solutions of dopamine can be used as adhesives. These properties were used to prevent the degradation in the mechanical properties of recycled PLA fabricated by 3D printer. The mechanical properties of 3D printed PLA play a critical role in determining its applications. To reduce the manufacturing cost as well as environmental pollutants, recycling of 3D printed materials has attracted many attentions. However, recycling of polymeric materials causes the degradation of the mechanical properties. Our study is aimed at advancing the current knowledge on the adhesion behavior of polydopamine coatings on PLA pellets used in 3D printing process. Polydopamine was synthesized by oxidative polymerization and used to coat PLA specimens. The adhesion behavior and mechanical properties of the 3D printed specimens were evaluated by tensile tests. It was found that the mechanical properties of recycled specimen with polydopamine coating have been improved. Microstructural and chemical characterization of the coated specimens was carried out using FE-SEM, FTIR, and XPS analyses.

Metamaterials-based enhanced energy harvesting: A review

NASA Astrophysics Data System (ADS)

Chen, Zhongsheng; Guo, Bin; Yang, Yongmin; Cheng, Congcong

2014-04-01

Advances in low power design open the possibility to harvest ambient energies to power directly the electronics or recharge a secondary battery. The key parameter of an energy harvesting (EH) device is its efficiency, which strongly depends on the conversion medium. To address this issue, metamaterials, artificial materials and structures with exotic properties, have been introduced for EH in recent years. They possess unique properties not easily achieved using naturally occurring materials, such as negative stiffness, mass, Poisson's ratio, and refractive index. The goal of this paper is to review the fundamentals, recent progresses and future directions in the field of metamaterials-based enhanced energy harvesting. An introduction on EH followed by the classification of potential metamaterials for EH is presented. A number of theoretical and experimental studies on metamaterials-based EH are outlined, including phononic crystals, acoustic metamaterials, and electromagnetic metamaterials. Finally, we give an outlook on future directions of metamaterials-based energy harvesting research including but not limited to active metamaterials-based EH, metamaterials-based thermal EH, and metamaterials-based multifunctional EH capabilities.

Optical Relaxation Time Enhancement in Graphene-Passivated Metal Films

NASA Astrophysics Data System (ADS)

Chugh, Sunny; Mehta, Ruchit; Man, Mengren; Chen, Zhihong

2016-07-01

Due to the small skin depth in metals at optical frequencies, their plasmonic response is strongly dictated by their surface properties. Copper (Cu) is one of the standard materials of choice for plasmonic applications, because of its high conductivity and CMOS compatibility. However, being a chemically active material, it gets easily oxidized when left in ambient environment, causing an inevitable degradation in its plasmonic resonance. Here, for the first time, we report a strong enhancement in the optical relaxation time in Cu by direct growth of few-layer graphene that is shown to act as an excellent passivation layer protecting Cu surface from any deterioration. Spectroscopic ellipsometry measurements reveal a 40-50% reduction in the total scattering rate in Cu itself, which is attributed to an improvement in its surface properties. We also study the impact of graphene quality and show that high quality graphene leads to an even larger improvement in electron scattering rate. These findings are expected to provide a big push towards graphene-protected Cu plasmonics.

Recent Development of Nanomaterial-Doped Conductive Polymers

NASA Astrophysics Data System (ADS)

Asyraf, Mohammad; Anwar, Mahmood; Sheng, Law Ming; Danquah, Michael K.

2017-12-01

Conductive polymers (CPs) have received significant research attention in material engineering for applications in microelectronics, micro-scale sensors, electromagnetic shielding, and micro actuators. Numerous research efforts have been focused on enhancing the conductivity of CPs by doping. Various conductive materials, such as metal nanoparticles and carbon-based nanoparticles, and structures, such as silver nanoparticles and graphene nanosheets, have been converted into polypyrrole and polypyrrole compounds as the precursors to developing hybrids, conjugates, or crystal nodes within the matrix to enhance the various structural properties, particularly the electrical conductivity. This article reviews nanomaterial doping of conductive polymers alongside technological advancements in the development and application of nanomaterial-doped polymeric systems. Emphasis is given to conductive nanomaterials such as nano-silver particles and carbon-based nanoparticles, graphene nano-sheets, fullerene, and carbon nanotubes (CNT) as dopants for polypyrrole-based CPs. The nature of induced electrical properties including electromagnetic absorption, electrical capacitance, and conductivities of polypyrrole systems is also discussed. The prospects and challenges associated with the development and application of CPs are also presented.

Use of weathered and fresh bottom ash mix layers as a subbase in road constructions: environmental behavior enhancement by means of a retaining barrier.

PubMed

Del Valle-Zermeño, R; Chimenos, J M; Giró-Paloma, J; Formosa, J

2014-12-01

The presence of neoformed cement-like phases during the weathering of non-stabilized freshly quenched bottom ash favors the development of a bound pavement material with improved mechanical properties. Use of weathered and freshly quenched bottom ash mix layers placed one over the other allowed the retention of leached heavy metals and metalloids by means of a reactive percolation barrier. The addition of 50% of weathered bottom ash to the total subbase content diminished the release of toxic species to below environmental regulatory limits. The mechanisms of retention and the different processes and factors responsible of leaching strongly depended on the contaminant under concern as well as on the chemical and physical factors. Thus, the immediate reuse of freshly quenched bottom ash as a subbase material in road constructions is possible, as both the mechanical properties and long-term leachability are enhanced. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dopant-Modulating Mechanism of Lithium Adsorption and Diffusion at the Graphene /Li2S Interface

NASA Astrophysics Data System (ADS)

Guo, Lichao; Li, Jiajun; Wang, Huayu; Zhao, Naiqin; Shi, Chunsheng; Ma, Liying; He, Chunnian; He, Fang; Liu, Enzuo

2018-02-01

Graphene modification is one of the most effective routes to enhance the electrochemical properties of the transition-metal sulfide anode for Li-ion batteries and the Li2S cathode for Li-S batteries. Boron, nitrogen, oxygen, phosphorus, and sulfur doping greatly affect the electrochemical properties of Li2S /graphene . Here, we investigate the interfacial binding energy, lithium adsorption energy, interface diffusion barrier, and electronic structure by first-principles calculations to unveil the diverse effects of different dopants during interfacial lithiation reactions. The interfacial lithium storage follows the pseudocapacitylike mechanism with intercalation character. Two different mechanisms are revealed to enhance the interfacial lithium adsorption and diffusion, which are the electron-deficiency host doping and the vacancylike structure evolutions with bond breaking. The synergistic effect between different dopants with diverse doping effects is also proposed. The results give a theoretical basis for the materials design with doped graphene as advanced materials modification for energy storage.

Finding consistency between different views of the absorption enhancement of black carbon: An observationally constrained hybrid model to support a transition in optical properties with mass fraction

NASA Astrophysics Data System (ADS)

Coe, H.; Allan, J. D.; Whitehead, J.; Alfarra, M. R. R.; Villegas, E.; Kong, S.; Williams, P. I.; Ting, Y. C.; Haslett, S.; Taylor, J.; Morgan, W.; McFiggans, G.; Spracklen, D. V.; Reddington, C.

2015-12-01

The mixing state of black carbon is uncertain yet has a significant influence on the efficiency with which a particle absorbs light. In turn, this may make a significant contribution to the uncertainty in global model predictions of the black carbon radiative budget. Previous modelling studies that have represented this mixing state using a core-shell approach have shown that aged black carbon particles may be considerably enhanced compared to freshly emitted black carbon due to the addition of co-emitted, weakly absorbing species. However, recent field results have demonstrated that any enhancement of absorption is minor in the ambient atmosphere. Resolving these differences in absorption efficiency is important as they will have a major impact on the extent to which black carbon heats the atmospheric column. We have made morphology-independent measurements of refractory black carbon mass and associated weakly absorbing material in single particles from laboratory-generated diesel soot and black carbon particles in ambient air influenced by traffic and wood burning sources and related these to the optical properties of the particles. We compared our calculated optical properties with optical models that use varying mixing state assumptions and by characterising the behaviour in terms of the relative amounts of weakly absorbing material and black carbon in a particle we show a sharp transition in mixing occurs. We show that the majority of black carbon particles from traffic-dominated sources can be treated as externally mixed and show no absorption enhancement, whereas models assuming internal mixing tend to give the best estimate of the absorption enhancement of thickly coated black carbon particles from biofuel or biomass burning. This approach reconciles the differences in absorption enhancement previously observed and offers a systematic way of treating the differences in behaviour observed.

Properties of leaves particleboard for sheathing application

NASA Astrophysics Data System (ADS)

Nuryawan, Arif; Rahmawaty

2018-03-01

Manufacturing particleboard (PB) made of leaves was carried out to make non-structural building components, such as insulation, partition, wall, and sheathing. Raw materials used dry leaves originated from plantation (palm oil leaves) and forest plantation (magahony leaves). The adhesive used was interior type thermosetting commercial resins, namely 10% urea-formaldehyde (UF) based on oven dry leaves. Hardener used for UF resin was 1% and 3% ammonium chloride (NH4Cl) 20% (w/w), respectively. Technically, the target density of PB was 0.8 g/cm3 with the dimension’s size of (250 x 250 x 10) mm3. The pressure, temperature, and time of pressing of the hot press were 25 kgf/cm2, 120C, and 10 minutes, respectively. After conditioning for one week, the PB then was evaluated their physical and mechanical properties according to Japanese Industrial Standard (JIS) A 5908 (2003). Results of this work showed: 1) Both types of PB (palm oil and mahagony leaves) were feasible to be produced for non-structural applications; 2) Addition of hardener enhanced the physical and mechanical properties of PB; 3) It was recommended to enhance the performance of the PB by manipulation of the raw materials and the design.

The application of halloysite tubule nanoclay in drug delivery.

PubMed

Lvov, Yuri M; DeVilliers, Melgardt M; Fakhrullin, Rawil F

2016-07-01

Natural and biocompatible clay nanotubes are among the best inorganic materials for drug nanoformulations. These halloysite tubes with SiO2 on the outermost surface have diameter of ca. 50 nm, length around 1 micrometer and may be loaded with drugs at 10-30 wt. %. Narrow tube openings allow for controllable sustained drug release for hours, days or even weeks. Physical-chemical properties of these nanotubes are described followed by examples of drug-loading capabilities, release characteristics, and control of duration of release through the end tube capping with polymers. Development of halloysite-polymer composites such as tissue scaffolds and bone cement/dentist resin formulations with enhanced mechanical properties and extension of the drug release to 2-3 weeks are described. Examples of the compression properties of halloysite in tablets and capsules are also shown. We expect that clay nanotubes will be used primarily for non-injectable drug formulations, such as topical and oral dosage forms, cosmetics, as well as for composite materials with enhanced therapeutic effects. These include tissue scaffolds, bone cement and dentist resins with sustained release of antimicrobial and cell growth-promoting medicines (including proteins and DNA) as well as other formulations such as compounds for antiseptic treatment of hospitals.

Photoconductivity enhancement and charge transport properties in ruthenium-containing block copolymer/carbon nanotube hybrids.

PubMed

Lo, Kin Cheung; Hau, King In; Chan, Wai Kin

2018-04-05

Functional polymer/carbon nanotube (CNT) hybrid materials can serve as a good model for light harvesting systems based on CNTs. This paper presents the synthesis of block copolymer/CNT hybrids and the characterization of their photocurrent responses by both experimental and computational approaches. A series of functional diblock copolymers was synthesized by reversible addition-fragmentation chain transfer polymerizations for the dispersion and functionalization of CNTs. The block copolymers contain photosensitizing ruthenium complexes and modified pyrene-based anchoring units. The photocurrent responses of the polymer/CNT hybrids were measured by photoconductive atomic force microscopy (PCAFM), from which the experimental data were analyzed by vigorous statistical models. The difference in photocurrent response among different hybrids was correlated to the conformations of the hybrids, which were elucidated by molecular dynamics simulations, and the electronic properties of polymers. The photoresponse of the block copolymer/CNT hybrids can be enhanced by introducing an electron-accepting block between the photosensitizing block and the CNT. We have demonstrated that the application of a rigorous statistical methodology can unravel the charge transport properties of these hybrid materials and provide general guidelines for the design of molecular light harvesting systems.

Resonantly enhanced second-harmonic generation using III–V semiconductor all-dielectric metasurfaces

DOE PAGES

Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; ...

2016-08-08

Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using galliummore » arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 10 4 relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ~2 × 10 –5 with ~3.4 GW/cm 2 pump intensity. In conclusion, the polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.« less

Enhanced piezoelectric effect in Janus group-III chalcogenide monolayers

NASA Astrophysics Data System (ADS)

Guo, Yu; Zhou, Si; Bai, Yizhen; Zhao, Jijun

2017-04-01

Piezoelectricity is a unique material property that converts mechanical energy into electricity or vice versa. Starting from the group-III monochalcogenide monolayers, we design a series of derivative Janus structures for piezoelectric materials, including Ga2SSe, Ga2STe, Ga2SeTe, In2SSe, In2STe, In2SeTe, GaInS2, GaInSe2, and GaInTe2. Our first-principles calculations show that these Janus structures are thermodynamically and dynamically stable. They have a bandgap in the range of 0.89-2.03 eV, lower than those of the perfect monolayers, and Ga2STe, Ga2SeTe, In2STe, and In2SeTe monolayers are direct gap semiconductors. They possess piezoelectric coefficients up to 8.47 pm/V, over four times the maximum value obtained in perfect group-III monochalcogenide monolayers. Moreover, the broken mirror symmetry of these Janus structures induces out-of-plane dipolar polarization, yielding additional out-of-plane piezoelectric coefficients of 0.07-0.46 pm/V. The enhanced piezoelectric properties enable the development of these novel two-dimensional materials for piezoelectric sensors and nanogenerators.

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices.

PubMed

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J; Grant, Patrick S

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

Osteoblastic cell response to spark plasma-sintered zirconia/titanium cermets.

PubMed

Fernandez-Garcia, Elisa; Guillem-Marti, Jordi; Gutierrez-Gonzalez, Carlos F; Fernandez, Adolfo; Ginebra, Maria-Pau; Lopez-Esteban, Sonia

2015-01-01

Ceramic/metal composites, cermets, arise from the idea to combine the dissimilar properties in the pure materials. This work aims to study the biocompatibility of new micro-nanostructured 3 Y-TZP/Ti materials with 25, 50 and 75 vol.% Ti, which have been successfully obtained by spark slasma sintering technology, as well as to correlate their surface properties (roughness, wettability and chemical composition) with the osteoblastic cell response. All samples had isotropic and slightly waved microstructure, with sub-micrometric average roughness. Composites with 75 vol.% Ti had the highest surface hydrophilicity. Surface chemical composition of the cermets correlated well with the relative amounts used for their fabrication. A cell viability rate over 80% dismissed any cytotoxicity risk due to manufacturing. Cell adhesion and early differentiation were significantly enhanced on materials containing the nanostructured 3 Y-TZP phase. Proliferation and differentiation of SaOS-2 were significantly improved in their late-stage on the composite with 75 vol.% Ti that, from the osseointegration standpoint, is presented as an excellent biomaterial for bone replacement. Thus, spark plasma sintering is consolidated as a suitable technology for manufacturing nanostructured biomaterials with enhanced bioactivity. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Dielectric properties of polyhedral oligomeric silsesquioxane (POSS)-based nanocomposites at 77k

NASA Astrophysics Data System (ADS)

Pan, Ming-Jen; Gorzkowski, Edward; McAllister, Kelly

2011-10-01

The goal of this study is to develop dielectric nanocomposites for high energy density applications at liquid nitrogen temperature by utilizing a unique nano-material polyhedral oligomeric silsesquioxanes (POSS). A POSS molecule is consisted of a silica cage core with 8 silicon and 12 oxygen atoms and organic functional groups attached to the corners of the cage. In this study, we utilize POSS for the fabrication of nanocomposites both as a silica nanoparticle filler to enhance the breakdown strength and as a surfactant for effective dispersion of high permittivity ceramic nanoparticles in a polymer matrix. The matrix materials selected for the study are polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The ceramic nanoparticles are barium strontium titanate (BST 50/50) and strontium titanate. The dielectric properties of the solution-cast nanocomposites films were correlated to the composition and processing conditions. We determined that the addition of POSS did not provide enhanced dielectric performance in PVDF- and PMMA-based materials at either room temperature or 77K. In addition, we found that the dielectric breakdown strength of PMMA is lower at 77K than at room temperature, contradicting literature data.

High-harmonic generation from an atomically thin semiconductor [Observation of high harmonics from an atomically thin semiconductor

DOE PAGES

Liu, Hanzhe; Li, Yilei; You, Yong Sing; ...

2016-11-14

High-harmonic generation (HHG) in bulk solids permits the exploration of materials in a new regime of strong fields and attosecond timescales. The generation process has been discussed in the context of strongly driven electron dynamics in single-particle bands. Two-dimensional materials exhibit distinctive electronic properties compared to the bulk that could significantly modify the HHG process, including different symmetries, access to individual valleys and enhanced many-body interactions. Here we demonstrate non-perturbative HHG from a monolayer MoS 2 crystal, with even and odd harmonics extending to the 13th order. The even orders are predominantly polarized perpendicular to the pump and are compatiblemore » with the anomalous transverse intraband current arising from the material’s Berry curvature, while the weak parallel component suggests the importance of interband transitions. The odd harmonics exhibit a significant enhancement in efficiency per layer compared to the bulk, which is attributed to correlation effects. In conclusion, the combination of strong many-body Coulomb interactions and widely tunable electronic properties in two-dimensional materials offers a new platform for attosecond physics.« less

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices

NASA Astrophysics Data System (ADS)

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J.; Grant, Patrick S.

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y3Fe5O12 ferrites

PubMed Central

Chen, Fu; Wang, Xian; Nie, Yan; Li, Qifan; Ouyang, Jun; Feng, Zekun; Chen, Yajie; Harris, Vincent G.

2016-01-01

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3−xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4–8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to −5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits. PMID:27320039

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y3Fe5O12 ferrites.

PubMed

Chen, Fu; Wang, Xian; Nie, Yan; Li, Qifan; Ouyang, Jun; Feng, Zekun; Chen, Yajie; Harris, Vincent G

2016-06-20

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3-xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4-8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to -5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits.

Electrospun microcrimped fibers with nonlinear mechanical properties enhance ligament fibroblast phenotype.

PubMed

Grace Chao, Pen-hsiu; Hsu, Hsiang-Yi; Tseng, Hsiao-Yun

2014-09-01

Fiber structure and order greatly impact the mechanical behavior of fibrous materials. In biological tissues, the nonlinear mechanics of fibrous scaffolds contribute to the functionality of the material. The nonlinear mechanical properties of the wavy structure (crimp) in collagen allow tissue flexibility while preventing over-extension. A number of approaches have tried to recreate this complex mechanical functionality. We generated microcrimped fibers by briefly heating electrospun parallel fibers over the glass transition temperature or by ethanol treatment. The crimp structure is similar to those of collagen fibers found in native aorta, intestines, or ligaments. Using poly-L-lactic acid fibers, we demonstrated that the bulk materials exhibit changed stress-strain behaviors with a significant increase in the toe region in correlation to the degree of crimp, similar to those observed in collagenous tissues. In addition to mimicking the stress-strain behavior of biological tissues, the microcrimped fibers are instructive in cell morphology and promote ligament phenotypic gene expression. This effect can be further enhanced by dynamic tensile loading, a physiological perturbation in vivo. This rapid and economical approach for microcrimped fiber production provides an accessible platform to study structure-function relationships and a novel functional scaffold for tissue engineering and cell mechanobiology studies.

Incorporation of New Benzofulvene Derivatives Into Polymers to Give New NLO Materials

NASA Technical Reports Server (NTRS)

Bowens, Andrea D.; Bu, Xiu; Mintz, Eric A.; Zhang, Yue

1996-01-01

The need for fast electro-optic switches and modulators for optical communication, and laser frequency conversion has created a demand for new second-order non-linear optical materials. One approach to produce such materials is to align chromophores with large molecular hyperpolarizabilities in polymers. Recently fulvenes and benzofulvenes which contain electron donating groups have been shown to exhibit large second-order non-linear optical properties. The resonance structures shown below suggest that intramolecular charge transfer (ICT) should be favorable in omega - (hydroxyphenyl)benzofulvenes and even more favorable in omega-omega - (phenoxy)benzofulvenes because of the enhanced donor properties of the O group. This ICT should lead to enormously enhanced second-order hyperpolarizability. We have prepared all three new omega - (hydroxyphenyl)benzofulvenes by the condensation of indene with the appropriate hydroxyaryl aldehyde in MeOH or MeOH/H2O under base catalysis. In a similar fashion we have prepared substituted benzofulvenes with multipal donor groups. Preliminary studies show that some of our benzofulvene derivatives exhibit second order harmonic generation (SHG). Measurements were carried out by preparing host-guest polymers. The results of our work on benzofulvene derivatives in host-guest polymers when covalently bonded in the polymer will be described.

FY2014 Propulsion Materials R&D Annual Progress Report

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

None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines [ACE], Advanced Power Electronics and Electrical Machinesmore » [APEEM], and fuels) teams to develop strategies that overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

FY2015 Propulsion Materials Annual Report

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

None, None

The Propulsion Materials Program actively supports the energy security and reduction of greenhouse emissions goals of VTO by investigating and identifying the materials properties that are most essential for continued development of cost-effective, highly efficient, and environmentally friendly next-generation heavy and light-duty powertrains. The technical approaches available to enhance propulsion systems focus on improvements in both vehicle efficiency and fuel substitution, both of which must overcome the performance limitations of the materials currently in use. Propulsion Materials Program activities work with national laboratories, industry experts, and VTO powertrain systems (e.g., Advanced Combustion Engines [ACE], Advanced Power Electronics and Electrical Machinesmore » [APEEM], and fuels) teams to develop strategies that overcome materials limitations in future powertrain performance. The technical maturity of the portfolio of funded projects ranges from basic science to subsystem prototype validation. Projects within a Propulsion Materials Program activity address materials concerns that directly impact critical technology barriers within each of the above programs, including barriers that impact fuel efficiency, thermal management, emissions reduction, improved reliability, and reduced manufacturing costs. The program engages only the barriers that result from material property limitations and represent fundamental, high-risk materials issues.« less

Micro- and nanostructure characterization and imaging of TWIP and unalloyed steels

NASA Astrophysics Data System (ADS)

Batista, L.; Rabe, U.; Hirsekorn, S.

2012-05-01

New design concepts for constructing light-weight and crash resistant transportation systems require the development of high strength and supra-ductile steels with enhanced energy absorption and reduced specific weight. TWIP steels combine these properties, a consequence of intensive mechanical twinning. To understand the mechanisms, related microstructures and local material properties are probed by AFAM, nanoindentation, and EBSD. The morphology of a cementite phase controls the macroscopic mechanical and magnetic properties of steels. Cementite embedded in a ferrite matrix is characterized by AFAM and MFM.

Aligned Carbon Nanotube to Enhance Through Thickness Thermal Conductivity in Adhesive Joints (Preprint)

DTIC Science & Technology

2006-12-01

aligned CNT films were prepared by pyrolyzing iron (II) phthalocyanine under Ar/H2 at 900°C as described in details elsewhere16. The average diameter...zone. Keywords: thermal conductivity, carbon nanotubes The unique properties of carbon nanotubes ( CNTs ) have generated interest amongst many...structure and high aspect ratio. These 2 unique properties make CNTs the material of choice for numerous applications like sensors5, actuators6, energy

Study on preparation and microwave absorption property of the core-nanoshell composite materials doped with La.

PubMed

Wei, Liqiu; Che, Ruxin; Jiang, Yijun; Yu, Bing

2013-12-01

Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Advancements in the Quantification of the Crystal Structure of ZNS Materials Produced in Variable Gravity

NASA Astrophysics Data System (ADS)

Castillo, Martin

2016-07-01

Screens and displays consume tremendous amounts of power. Global trends to significantly consume less power and increase battery life have led to the reinvestigation of electroluminescent materials. The state of the art in ZnS materials has not been furthered in the past 30 years and there is much potential in improving electroluminescent properties of these materials with advanced processing techniques. Self-propagating high temperature synthesis (SHS) utilises a rapid exothermic process involving high energy and nonlinearity coupled with a high cooling rate to produce materials formed outside of normal equilibrium boundaries thus possessing unique properties. The elimination of gravity during this process allows capillary forces to dominate mixing of the reactants which results in a superior and enhanced homogeneity in the product materials. ZnS type materials have been previously conducted in reduced gravity and normal gravity. It has been claimed in literature that a near perfect phases of ZnS wurtzite was produced. Although, the SHS of this material is possible at high pressures, there has been no quantitative information on the actual crystal structures and lattice parameters that were produced in this work. Utilising this process with ZnS doped with Cu, Mn, or rare earth metals such as Eu and Pr leads to electroluminescence properties, thus making this an attractive electroluminescent material. The work described here will revisit the synthesis of ZnS via high pressure SHS and will re-examine the work performed in both normal gravity and in reduced gravity within the ZARM drop tower facility. Quantifications in the lattice parameters, crystal structures, and phases produced will be presented to further explore the unique structure-property performance relationships produced from the SHS of ZnS materials.